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Improving satellite services with cooperative communications
Abstract
This paper proposes new transmission schemes for the delivery of satellite services. In the proposed scenarios, mobile terminals are allowed to forward the signal received from the satellite. This scheme provides spatial diversity just like MIMO transmission schemes. Moreover, the coverage area is extended because masked terminals have an additional opportunity to get the service from neighboring terminals. We use the paradigm of cooperative communications to compare the advantages and limitations of several scenarios in hybrid terrestrial/satellite systems. In particular, we study the following basic transmission scheme: in a first time slot, the satellite sends its signal and, in a second time slot, mobile terrestrial terminals are relaying the satellite signal. An analysis framework is proposed and applied to this cooperation scenario at the destination terminal. The framework is modeling the cooperation process and clearly separates the control part from the data user part. The paper outlines the importance of the control part by evaluating the relay selection policy on a basic hybrid satellite/ad hoc system. Copyright © 2011 John Wiley & Sons, Ltd.
... Hybrid satellite-terrestrial relay networks (HSTRNs) play an important role in the fifth-generation (5G) communications and have attracted huge attention owing to its characteristics of providing broad coverage, seamless connectivity, and high information transmission capability in remote areas [1]. The HSTRNs fundamentally use the terrestrial cooperation into satellite systems and find potential applications in various fields such as navigation, military, broadcasting, and disaster relief [2]. Until now, a significant number of efforts have been made towards the performance investigation on HSTRNs in terms of important measures such as ergodic capacity analysis [3], symbol error rate [4], [5], and outage probability [6]- [8]. ...
... In the first time slot, S broadcasts the superposition signal x s (x s = √ α 1 P s x p + √ α 2 P s x q ) to R, consequently, the received signal at R can be 1 The considered NOMA-based HSTRN architecture can be generalized comprehensively to multiple users' scenario, where users are split to form multiple orthogonal groups and the NOMA technique is executed within each group. 2 Herein, it is assumed that E can receive the information from the relay including the relaying protocol and decoding techniques at relay R. written as ...
... with Ξ(κ) = (−1) κ (1 − m s ) κ δ κ /(κ!) 2 . Next, f γsr (·) can be derived, by simply making the transformation of variates, as ...
... However, in some cases, it is hard to achieve direct links between the satellite and the terrestrial nodes due to so-called masking effects from atmospheric conditions (i.e., clouds, rain, etc.) and ground obstructions (i.e., receivers in tunnels, etc.). To combat these negative effects, the cooperative relay-based hybrid satellite-terrestrial systems (HSTSs) were investigated in literature [20][21][22]. In [20], the future development direction of satellite-terrestrial systems was outlined. ...
... In [20], the future development direction of satellite-terrestrial systems was outlined. A service transmission scheme is proposed that mobile terminals are allowed to forward the signal received from the satellite in [21]. The performance of satellite-terrestrial systems has been analyzed for two relay protocols: i) amplify-andforward (AF) [23,24] and ii) decode-and-forward (DF) [22,25]. ...
Land mobile satellite communication and physical layer security are considered as the promising paradigms in beyond 5G networks. In this paper, we establish the multi-relay hybrid satellite-terrestrial systems (HSTSs) with artificial noise (AN) to investigate the reliability and security, in which the satellite sends signals to the terrestrial destination through multiple decode-and-forward relays and there exists an eavesdropper trying to overhear the useful information. In order to improve the overall system performance, two relay selection (RS) schemes: i) optimal relay-receiver pair selection (ORRPS) and ii) suboptimal relay selection (SRS) are considered. ORRPS selects an optimal relay-receiver pair and an AN signal to maximize the corresponding signal-to-interference-plus-noise ratios of Rk → D(Rk → E) and the SRS refers to selecting a relay that optimize the instantaneous channel gain |hRkD|2(|hRkE|2) among K relays, with the traditional round-robin selection scheme as a benchmark for comparison. Furthermore, the exact closed-form analytical expressions of outage probability (OP) and intercept probability (IP) under different RS schemes are derived for AN and non-AN conditions. To obtain more insights, the asymptotic analysis for high signal-to-noise-ratio regime is carried out. Based on the asymptotic analysis of OP, the diversity orders of the HSTSs are obtained. The numerical results and theoretical analysis shown that: i) The reliability of TRRS scheme is the worst among the three RS schemes, and the reliability of ORRPS scheme is the best; ii) The AN technology can significantly improve the security of the system, although it has a little adverse affect on the reliability; iii) Infrequent light shadowing has the best reliability, frequent heavy shadowing has the worst outage performance, and the change of security is opposite; iv) The OP of SRS and ORRP schemes decreased with the increase of K, while the IP changed on the contrary, and the reliability and security of TRRS schemes did not change obviously.
... The HSTRN architecture basically invokes the terrestrial relay cooperation into the satellite system to improve the coverage and transmission accuracy in the highly shadowed environments (e.g. shopping malls, tunnels, indoor environments etc.) [2,3]. Such networks have become popular and essential in the full realisation and development of 5G networks owing to their compatibility in different areas such as military, disaster relief, and defence services [4]. ...
... where P s is the transmit power at S, h sr = h sr (1) , h sr (2) , …, h sr (M) T be the M × 1 channel vector for S → R channel, u r ∼ CN(0, N 0 ) is AWGN at R, and w s is the M × 1 transmit weight vector, which is chosen, according to the principle of maximum ratio transmission [30], as w s = h sr / ∥ h sr ∥ F . During the second time phase, the relay R first amplifies the received signal y r by a variable gain factor G as and then forwards it to the destination D. Thus, the received signal at the destination D can be given as ...
This paper investigates the physical layer security of a downlink hybrid satellite-terrestrial relay network (HSTRN) where the satellite channel follows Shadowed-Rician fading and terrestrial channels are assumed to undergo independent and non-identically distributed (i.ni.d.) Nakagami-\emph{m} fading. Herein, we consider a multi-antenna satellite which communicates with a terrestrial user via an amplify-and-forward relay in the presence of multiple colluding eavesdroppers at the earth. We derive novel expressions of secrecy outage probability (SOP), ergodic secrecy capacity (ESC), and probability of positive secrecy capacity (PSC) for the proposed network. We further obtain the achievable secrecy diversity order of the considered HSTRN by employing asymptotic analysis of SOP expression. Finally, numerical and simulation results are provided to validate the accuracy of the proposed analysis and to highlight the impact of a multi-antenna satellite on future wireless systems.
... For instance, it could be deployed for broadcast/multicast mobile TV services ensuring indoor coverage with the aid of a low-power terrestrial repeater [8]. 2 This could be possible when the terrestrial repeater (acting as relay) lies close to other earth stations and/or to cluster of non-targeted land users. 3 For such a complicated hybrid system, we considered the outdated CSI only for terrestrial links. ...
... where P s is the transmit power at S, h sr = h (1) sr , h (2) sr , . . . , h (M ) sr T is the M × 1 channel vector for S → R link, P c ı is the transmit power of the ıth interferer, h ı r is the channel coefficient of the link between ıth interferer and relay, x ı is the unit energy signal of the ıth interferer, and n r is AWGN. ...
In this paper, we investigate the ergodic capacity (EC) of a downlink multiuser hybrid satellite-terrestrial amplify-and-forward relay network (HSTAFRN) using fixed gain relaying protocol in the presence of co-channel interference (CCI). Herein, we employ opportunistic scheduling of terrestrial users by considering outdated channel state information (CSI) over Nakagami-m fading channels of pertinent links. By deploying multiple antennas at the satellite, we derive novel and accurate analytical expression of the achievable EC by making use of complementary moment generating function transform. More importantly, we carry out the EC analysis under both uncorrelated and correlated Shadowed-Rician fading channels of satellite links. Our numerical and simulation results attest the accuracy of the proposed analysis and reveal the impact of various system/channel parameters on EC of considered HSTAFRN.
... Diversity techniques such as time, frequency, and satellite diversity techniques [5] can tackle this problem by providing ground receivers with different versions of a satellite signal. 1 In the context of hybrid satellite/terrestrial systems, cooperative communications can also enhance the service availability by allowing relay nodes to forward satellite messages to masked nodes [6] [7] [8]. ...
... the contrary, it has been shown that non masked (NoM) mobile nodes can serve as relay nodes in a dynamic environment. 2 For instance, in [6], satellite downlink (DL) communications are divided into two time-slots. During the first time-slot, the satellite is transmitting its message toward ground receivers. ...
Abstract—In this paper, we address the design of a cooperative
protocol for a hybrid satellite/terrestrial emergency system. We
want to perform energy savings compared to the case where all
the terrestrial relay nodes are forwarding satellite messages to
ground receivers. This is done via the selection of relevant relay
nodes. The parameterization of the protocol phases has been done
through simulations and takes into account the duration of the
selection process, the number of selected nodes, and the signaling
overhead. The selection process based on a node identifier (ID)
appears to provide greater energy savings compared to the
selection process based on the signal to interference and noise
ratio (SINR). The solutions have been implemented in the real
case scenario of forest fire that has been thoroughly documented
by the US administration. According to the scenario parameters,
100% of the masked nodes are reached after cooperation.
Index Terms—satellite communications; hybrid systems; emergency
communications; cooperative protocols; relay selection
... In recent times, a novel and promising network paradigm referred to as the Hybrid Satellite-Terrestrial Relay Network (HSTRN) system has emerged, as elucidated in recent publications [1][2][3][4]. This innovative system ingeniously combines the capabilities of both satellite and terrestrial networks, presenting a hybridized architecture that holds significant potential for transformative advancements in the realm of mobile communications. ...
p>The paper investigates the outage probability (OP) of a cognitive radio-based satellite-ground transmission system. In this configuration, both direct and relay links are activated to facilitate transmission from the primary satellite source to terrestrial users. The primary metric under scrutiny is the outage probability for both the primary and secondary networks. Utilizing the Shadowed-Rician fading model, commonly applied to satellite channels, for the satellite segment, and Nakagami-m fading models for terrestrial channels, we assess the OP by analyzing the expressions for both primary and secondary users. Additionally, we explore the impact of key system parameters on the OP’s performance. Indeed, the signal-to-noise ratio (SNR) and target rate are the main factors affecting the outage behavior of users on the ground. We identify certain conditions necessary to achieve improved performance by controlling key system parameters. Furthermore, this paper provides guidelines for designing cognitive radio (CR) systems in satellite configurations to meet the quality requirements of received signals on the ground. The analysis results are validated through Monte Carlo simulations implemented using MATLAB. </p
... In recent times, a novel and promising network paradigm referred to as the Hybrid Satellite-Terrestrial Relay Network (HSTRN) system has emerged, as elucidated in recent publications [1][2][3][4]. This innovative system ingeniously combines the capabilities of both satellite and terrestrial networks, presenting a hybridized architecture that holds significant potential for transformative advancements in the realm of mobile communications. ...
p>The paper investigates the outage probability (OP) of a cognitive radio-based satellite-ground transmission system. In this configuration, both direct and relay links are activated to facilitate transmission from the primary satellite source to terrestrial users. The primary metric under scrutiny is the outage probability for both the primary and secondary networks. Utilizing the Shadowed-Rician fading model, commonly applied to satellite channels, for the satellite segment, and Nakagami-m fading models for terrestrial channels, we assess the OP by analyzing the expressions for both primary and secondary users. Additionally, we explore the impact of key system parameters on the OP’s performance. Indeed, the signal-to-noise ratio (SNR) and target rate are the main factors affecting the outage behavior of users on the ground. We identify certain conditions necessary to achieve improved performance by controlling key system parameters. Furthermore, this paper provides guidelines for designing cognitive radio (CR) systems in satellite configurations to meet the quality requirements of received signals on the ground. The analysis results are validated through Monte Carlo simulations implemented using MATLAB. </p
... The integration of satellite and terrestrial communication is used to reduce masking effects and latency [3][4][5]. Cooperative communication is used to improve the performance of satellite communication systems [6][7][8][9][10]. A simple channel model is proposed in [11] Prateek Anand is with the USICT, AIACTR, GGSIPU, Delhi, India, (email:anand.prateek91@gmail.com) ...
The broadcast properties of satellites communication makes transmission less susceptible to eavesdropping or even negative obstruction. Physical Layer Security (PLS) technique prevents privacy of data sent by the sender from being intercepted by illegal hackers, which ensures the confidentiality and transmission security between the sender and authorized users. The evolution of mobile communications has brought new challenges to physical security research. Data security techniques implemented at the physical layer of satellite communication are proving to be effective on many parameters. Considering the down-link of a satellite communication system, with multiple antennas at Earth station (ES), Eavesdropper, as well as on satellite, an eavesdropper wants to hack the signal of the satellite to the ES. We propose a method by which the signal received by the eavesdropper is in a meaningless form. The proposed method uses nulling based approach, in which the signal transmitted by the satellite gets multiplied by a beamforming vector, which is selected in a manner so that no information can be received by the eavesdropper. The performance of the received data at ES is analyzed in terms of symbol error rate.
... In this case, the terrestrial mobile users can make full use of the spatial diversity gain by receiving independent multipath fading signals from satellites and terrestrial base stations. Consequently, the effectiveness and reliability of transmission will be greatly increased (Paillassa et al., 2011). ...
The integration of satellite and terrestrial communication systems plays a vital role in the fifth-generation mobile communication system (5G) for the ubiquitous coverage, reliable service and flexible networking. Moreover, the millimeter wave (mmWave) communication with large bandwidth is a key enabler for 5G intelligent rail transportation. In this paper, the satellite-terrestrial channel at 22.6 GHz is characterized for a typical high-speed railway (HSR) environment. The three-dimensional model of the railway scenario is reconstructed and imported into the Cloud Ray-Tracing (CloudRT) simulation platform. Based on extensive ray-tracing simulations, the channel for the terrestrial HSR system and the satellite-terrestrial system with two weather conditions are characterized, and the interference between them are evaluated. The results of this paper can help for the design and evaluation for the satellite-terrestrial communication system enabling future intelligent rail transportation.
... In this case, the terrestrial mobile users can make full use of the spatial diversity gain by receiving independent multipath fading signals from satellites and terrestrial base stations. Consequently, the effectiveness and reliability of transmission will be greatly increased (Paillassa et al., 2011). ...
The integration of satellite and terrestrial communication systems plays a vital role in the fifth‐generation mobile communication system (5G) for the ubiquitous coverage, reliable service, and flexible networking. Moreover, the millimeter wave (mmWave) communication with large bandwidth is a key enabler for 5G intelligent rail transportation. In this paper, the satellite‐terrestrial channel at 22.6 GHz is characterized for a typical high‐speed railway (HSR) environment. The three‐dimensional model of the railway scenario is reconstructed and imported into the Cloud Ray‐Tracing (CloudRT) simulation platform. Based on extensive ray‐tracing simulations, the channel for the terrestrial HSR system and the satellite‐terrestrial system with two weather conditions are characterized, and the interference between them are evaluated. The results of this paper can help for the design and evaluation for the satellite‐terrestrial communication system enabling future intelligent rail transportation.
... The masking effect caused IEEE INTERNET OF THINGS JOURNAL 11 by impediments becomes more severe when the angles of satellite elevation are low or the terrestrial users are the indoor users [80]. To overcome this issue, it is expected that a novel architecture termed as hybrid satellite-terrestrial relay network (HSTRN) [81]- [83] is introduced, where the satellite network can be well integrated with existing terrestrial networks by taking full advantage of the spatial diversity brought by terrestrial relay stations. In this regard, the satellite signals can be forwarded to the ground users reliably with the assistance of terrestrial relay stations. ...
Physical-layer security (PLS) has emerged as an alternative security paradigm that explores the randomness of the wireless channel to achieve confidentiality and authentication. The success story of PLS technique now spans a decade and thrives to provide a layer of defence in satellite communications. With this position, a comprehensive survey of satellite communications is conducted in this paper with an emphasis on PLS. We first briefly introduce essential background and the view of satellite Internet of Things (IoT), as well as discuss related research challenges faced by the emerging integrated network architecture. Then, we revisit the most popular satellite channel model influenced by many factors and list the commonly used secrecy performance metrics. Also, we provide an exhaustive review of state-of-the-art research activity on PLS in satellite communications, which we categorize by different architectures including land mobile satellite communication networks, hybrid satellite-terrestrial relay networks, and satellite-terrestrial integrated networks. In addition, a number of open research problems are identified as possible future research directions.
... I N present of fifth-generation (5G), satellite communication system are meant to deliver a terrestrial experience with seamless connectivity and broadband access to mobile users. Recently, an integrated system has been devised to exploit cooperative relaying techniques with satellite communication, thus satellite terrestrial relay networks (STRN) are proposed, which is capable of providing ubiquitous coverage, higher transmission rate and broadcast/multiple cast reliable service to portable and mobile users [1], [2]. Among the recent works, the symbol error rate and outage probability for the CSTRN were analyzed in [3]. ...
This paper investigates the joint effects of hardware impairments (HIs) and imperfect channel state information (CSI) on the cognitive satellite-terrestrial relay networks (CSTRN) with multiple primary users (PUs). The satellite links are assumed to follow the Shadowed-Rician (SR) fading, while the terrestrial links follow the Rayleigh fading. Specifically, we derive the closed-form expressions of the outage probability (OP) and throughout for the considered CSTRN which is interfered by the multiple adjacent terrestrial primary users' (PUs) interference. Moreover, in order to evaluate the effect of HIs and outdated CSI on the system performance at high signal-to-noise ratios (SNRs), the asymptotic analysis is also presented. Furthermore, computer simulation results are presented to validate the correctness of our analytical results.
... This model is widely adopted in literature [6], [27] for the performance analysis of hybrid satelliteterrestrial systems since it offers less computational burden as compared to other models like Loo's model [37]. 3 Herein, we assume perfect CSI acquisition with negligible Doppler spread over the satellite-relay links by considering a GEO satellite and a fixed location of the terrestrial relay. Albeit, in [38], authors have studied such problems of channel estimation and associated imperfection for a basic HSTRN, the research in this domain is in still infancy and is a topic for future investigation. ...
Satellite communication systems need to be integrated with emerging cooperative relaying techniques to provide seamless connectivity and high-speed broadband access for mobile users in future wireless networks. In this paper, we study a multi-antenna multiuser hybrid satellite-terrestrial relay network (HSTRN) employing opportunistic user scheduling with outdated channel state information (CSI) and amplify-and-forward relaying with co-channel interference (CCI). By adopting Shadowed-Rician fading for satellite links and Nakagami-m fading for terrestrial links, we derive novel and accurate expressions for outage probability and ergodic capacity of the proposed HSTRN and further examine its achievable diversity order. More importantly, we conduct the performance analysis by taking both uncorrelated and correlated Shadowed-Rician fading channels into account and show that the antenna correlation at the satellite does not affect the overall system diversity order. Our derived analytical expressions provide efficient tools to characterize the impact of CCI, outdated CSI, and antenna correlation on the system performance of HSTRN with arbitrary number of satellite antennas, number of interferers, number of users, and integer values of the per-hop fading severity parameters. Our results provide useful guidelines in the design of futuristic HSTRNs for satellite mobile communications.
... Secure transmission in cognitive satellite terrestrial networks is discussed in [30][31][32][33]. Another scheme for hybrid systems is studied in [34]; in this scheme, two time slots are used for transmission. The satellite sends its signal in first time slot and, in a second time slot, mobile terrestrial terminals are forwarding the satellite signals. ...
The problem of relay selection in amplify-and-forward (AF)-based hybrid satellite-terrestrial cooperative communication systems is considered. A partial relay selection scheme is studied in which satellite selects a relay earth station (ES) among multiple relay ESs (situated on ground) on the basis of maximum instantaneous signal-to-noise ratio (SNR). Satellite-relay ESs are assumed to follow Shadowed-Rician fading, whereas relay ESs-destination ES links (terrestrial links) are assumed to follow Nakagami-m distribution. First, the cumulative distribution function and probability density function (PDF) of the maximum instantaneous SNR of satellite-relay ESs links are derived; then by using this PDF, the expression of moment generating function (MGF) of the received instantaneous SNR at destination ES is obtained. The average error performance of the considered system with the proposed relay ES selection is derived in terms of Meijer-G functions by using MGF approach. In order to get the diversity order of the relay ES selection-based AF scheme, the asymptotic PDF of the considered scheme is derived, and then by using this asymptotic PDF, the analytical diversity order of the system is obtained. It is demonstrated by the analysis and simulation that the performance of the AF-based hybrid satellite-terrestrial communication systems can be significantly improved by deploying more relay ES at the ground in between satellite and destination ES.
... A number of works have studied the performance of hybrid satellite-terrestrial system (HSTS) [1,2] in the presence of the masking effect, e.g., [5][6][7][8][9][10]. The average symbol error rate (SER) of the fixed gain amplify-and-forward (AF) hybrid satellite terrestrial-system with generalized fading channels was derived in [6]. ...
The transmission of signals in a hybrid satellite-terrestrial system (HSTS) in the presence of co-channel interference (CCI) is considered in this study. Specifically, we examine the problem of amplify-and-forward (AF)-based relaying in a hybrid satellite-terrestrial link, where the relay node is operating in the presence of a dominant co-channel interferer. It is assumed that direct connection between a source node (satellite) and a destination node (terrestrial receiver) is not available due to masking by obstacles in the surrounding. The destination node is only able to receive signals from the satellite with the help of a relay node located at the ground. In the proposed HSTS, the satellite-relay channel follows the shadowed Rice fading; and the channels of interferer-relay and relay-destination links experience generalized Nakagami-m fading. For the considered AF-based HSTS, we first develop the analytical expression for the moment generating function (MGF) of the overall output signal-to-interference-plus-noise ratio (SINR). Then, based on the derived exact MGF, we derive novel expressions for the average symbol error rate (SER) of the considered HSTS for the following digital modulation techniques: M-ary phase shift keying (M-PSK), M-ary quadrature amplitude modulation (M-QAM) and M-ary pulse amplitude modulation (M-PAM). To significantly reduce the computational complexity for utility in system-level simulations, simple analytical approximation for the exact SER in the high signal-to-noise ratio (SNR) regime is presented to provide key insights. Finally, numerical results and the corresponding analysis are presented to demonstrate the effectiveness of the developed performance evaluation framework and to view the impact of CCI on the considered HSTS under varying channel conditions and with different modulation schemes.
... On the other hand, the cooperation among communications and navigation systems, components, and services will be key features of future emergency systems. The integration of navigation and communication systems allows the exploitation of both navigation information for communication purposes (optimization of communication techniques, interference reduction, and location-based information services delivery) and communication support for navigation purposes (high precision localization and cooperative positioning)[4],[5]. The main goal of the Satellite-Assisted LocalIzation and Communication Systems for Emergency Services (SALICE) project was the investigation of the open issues related to this scenario, the proposal of a proper system architecture, and the establishment of a definition of the innovative solutions that have proven beneficial for emergency operators. ...
... Thus, spatial diversity is useful to provide reliable communication service. Paillassa et al. proposed cooperative transmission schemes for the delivery of satellite services; these schemes provide spatial diversity just like MIMO transmission schemes and the coverage area is extended [6]. Nasser and Helard proposed a Layered Space-Time Block Code (LSTBC) for MIMO schemes in hybrid satellite-terrestrial transmission of NGH systems; the code in ...
Channels of mobile satellite communications are affected by multipath fading and shadowing attenuation. At the same time, diversity gains are believed to improve the transmission reliability in fading channels. Considering that the traditional Space-Time Coding (STC) is not suitable for the cooperative mobile satellite communication, in this paper, a new cooperative mobile satellite communication system is proposed based on the Dynamic Space-Time Coding (D-STC). The transmitting energy of the proposed scheme is saved by avoiding forwarding erroneous signals in cooperative users. Meanwhile, this system benefits from diversity gains and the transmission is robust. Additionally, a closed-form expression of the outage probability for the proposed scheme is derived, and then it is demonstrated that this scheme is much better than the existing noncooperative scheme and schemes with traditional STCs in the outage performance. Finally, the analytical result is supported and validated by numerical simulations.
... Moreover, several private companies have developed their own standards for satellite to land mobile, maritime, and aeronautical communications. Recently, the adoption of cooperative paradigms in satellite terrestrial networks has been addressed in [7,8]. The provision of an effective and rapid assistance to people during emergency situations requires the integration of space-based and terrestrial communication capabilities into a single emergency system architecture. ...
SUMMARY This paper deals with the cooperative strategies, which can be adopted in emergency scenarios by integrating space and terrestrial segments, and communication and localization services. First, the cooperative solutions for integrated Navigation and Communication systems are reviewed and an effective software-defined radio implementation is described. Then, cooperative systems for broadcast and multicast communications in Incident Area Network are proposed and evaluated: in the broadcast scenario, low-complexity relaying techniques are adopted to overcome the propagation impairments and the performance degradation; in the multicast system, radio resources management techniques for group communications are designed to allow the efficient use of scarce resources and improve connectivity and reliability of the overall system. The technical solutions have been studied and tested in the framework of the Italian National Research Project SAtellite-assisted LocalIzation and Communication system for Emergency services [1]. Copyright © 2013 John Wiley & Sons, Ltd.
In this article, we investigate the performance of hybrid satellite–terrestrial relay networks with multiuser downlink nonorthogonal multiple access. The satellite applies Alamouti space–time block coding, and users exploit a receive antenna selection technique. Communication between the satellite and users is assumed to be established with the aid of a half-duplex terrestrial relay equipped with multiple receive antennas and operating in amplify-and-forward mode, because of the heavy masking effects attributed to environmental obstacles. Subsequently, the satellite–relay link is exposed to shadowed-Rician fading, whereas the relay–users links undergo Nakagami-
m
fading, which is a generic statistical channel model for nonterrestrial networks. To be more practical, we consider imperfect successive interference cancellation. The exact outage probability of each user and the corresponding asymptotic expression at the high signal-to-noise ratio are derived to demonstrate the system performance. The analysis indicates that the shadowing conditions do not affect the array gain when the diversity order is dominated by the multiantenna configuration of the second hop. The theoretical derivations are validated by using Monte Carlo simulations. The numerical results indicate that the proposed scheme significantly improves the performance of each user under various shadowing conditions. It also outperforms orthogonal multiple access when proper power levels are allocated to users.
This paper intends to justify why the aerospace communications is a key technology that will bring the Internet of Things (IoT) vision closer to reality. Both satellites and aerial platforms, such as High-Altitude Platforms (HAPs) and Unmanned Aerial Vehicles (UAVs), are considered. Their advantages are highlighted mainly in terms of the radio coverage and the link reliability, and their potential applications in several sectors are described. Emphasis is also given on the advanced wireless technologies that can further enhance the capabilities of aerospace communications.
Featured by broad coverage and seamless connectivity in remote areas, hybrid satellite-terrestrial relay networks (HSTRNs) have gained growing attention in fifth- and next-generation communications. However, security issues in such networks have been rapidly increasing due to the inherent openness of wireless medium. Recently, an information-theoretic approach based physical layer security (PLS) emerges as a promising technique to ensure overall security in wireless communications. Unlike conventional cryptographic methods, PLS techniques exploit physical characteristics of wireless fading channels and provide confidentiality to radio transmissions. In this chapter, we introduce the HSTRN architecture and present practical challenges to PLS in HSTRNs. Specifically, by adopting pertinent channel models for satellite and terrestrial links, we examine the secrecy outage probability (SOP) performance of a basic HSTRN in the presence of a single eavesdropper and generalized HSTRN configuration with multiple eavesdroppers. For multiple eavesdroppers, we consider two different scenarios of colluding and non-colluding eavesdroppers. Moreover, at a high signal-to-noise ratio regime, we analyze the asymptotic behavior of SOP performance and reveal the achievable diversity order of the considered HSTRNs. We further demonstrate numerical and simulation results to justify our hypothesis and illustrate the impact of various channel/system parameters on the secrecy performance of HSTRN communications.
The fifth-generation (5G) wireless systems have recently reached to the deployment stage, and research toward next-generation wireless communications has already started. The integration of Internet of things (IoT) to satellite networks is one of the key focuses in 5G and beyond systems. Since the spectrum resources are not abundant to accommodate billions of IoT devices, the cognitive satellite-terrestrial networks supporting IoT communications are of great importance. In this chapter, we present the outage performance analysis of a cognitive overlay multi-user satellite-terrestrial network (OMSTN) where a primary satellite communicates with a selected terrestrial receiver via a secondary IoT network in the presence of interference from extra-terrestrial sources (ETSs) and terrestrial sources (TSs). Hereby, we consider the following two cases for system performance analysis: (a) Case 1: when interference occurs due to TSs only; (b) Case 2: when interference occurs due to both ETSs and TSs. We specifically derive the tight closed-form outage probability (OP) expressions of both the primary satellite and secondary IoT networks. We further carry out the asymptotic high signal-to-noise ratio (SNR) analysis to obtain the diversity order of both satellite and IoT networks. For asymptotic analysis, we consider two scenarios, namely when interferers’ power is fixed and when it varies proportionally to the transmit power of satellite and IoT nodes. We further devise a scheme for the adaptive power splitting factor under a guaranteed quality-of-service (QoS) of the primary satellite network. We provide various insights on the considered OMSTN based on our analysis and numerical results.
This paper investigates secure transmission of an integrated satellite‐aerial‐terrestrial network (ISATN), where multiple eavesdroppers (Eves) attempt to overhear the satellite signals cooperatively. The ISATN adopts an unmanned aerial vehicle (UAV) equipped with multiple antennas as a relay with threshold‐based decode‐and‐forward (DF) protocol. By assuming that perfect instantaneous channel state information (CSI) of the satellite‐UAV link and the statistical CSI of the UAV‐user link are available, we first propose a beamforming (BF) scheme for maximizing the achievable secrecy rate (ASR) of the considered network. Then, we derive the analytical expressions of the secrecy outage probability (SOP) and ergodic secrecy rate (ESR) of the considered system with the BF strategy under an assumption that the satellite‐UAV link undergoes the shadowed‐Rician fading, while the UAV‐user link experiences the correlated Rayleigh fading. Finally, numerical results are given to demonstrate the superiority of the proposed BF scheme against zero forcing (ZF) and maximal ratio transmission (MRT) schemes and the validity of the secrecy performance analysis. This paper investigates secure transmission of an integrated satellite‐aerial‐terrestrial network, a secure beamforming scheme is proposed and the the secrecy outage probability and ergodic secrecy rate of the consideredsystem are analyzed.
In this paper, we propose a novel decode-and-forward (DF)-based secure 3D mobile unmanned aerial vehicle (UAV) relaying for hybrid satellite-terrestrial networks (HSTNs) in the presence of an aerial eavesdropper lying around a serving UAV relay in a circular plane. Herein, we adopt a stochastic mixed mobility (MM) model for mobilizing the UAV relays in a 3D cylindrical cell with a ground user equipment (UE). We consider the deployment of eavesdropper under the cases: (a) the eavesdropper is located at certain fixed distance around a serving UAV relay; (b) the eavesdropper is located uniformly random around the relay. By considering the opportunistic closest-, uniform-, and maximum-signal-to-noise ratio (maximum-SNR) UAV relay selection (URS) strategies, we analyze the secrecy performance of the considered HSTN in terms of probability of non-zero secrecy capacity (PNZSC) and secrecy outage probability (SOP). In particular, we derive exact PNZSC and SOP for the closest-URS (CURS) and uniform-URS (UURS). While, we derive analytical lower and upper bounds on PNZSC and SOP for maximum-SNR URS (MURS). We further carry out the corresponding asymptotic SOP analysis to assess the secrecy diversity order and coding gain of aforementioned URS strategies. Simulations are performed to corroborate the analysis.
In this paper, we study the physical layer security of a downlink hybrid satellite-terrestrial relay network (HSTRN), where a multi-antenna satellite communicates with multiple terrestrial destinations via multiple cooperative relays in the presence of multiple eavesdroppers. We investigate the secrecy performance of the considered HSTRN by employing two classic cooperative protocols, namely, amplify-and-forward (AF) and decode-and-forward (DF) for two intercepting ways at eavesdroppers, i.e., non-colluding and colluding eavesdroppers scenarios. For both these cooperative protocols, we present opportunistic user-relay selection criteria and then derive novel and accurate expressions of the secrecy outage probability (SOP) by adopting Shadowed-Rician fading for satellite channels and Nakagami-m fading for terrestrial channels. Further, in order to extract useful insights on the system design, we obtain the tractable asymptotic SOP expressions at high signal-to-noise ratio regime. Finally, we provide the numerical and simulation results to validate our analysis and highlight the impact of various channel/system parameters on the secrecy performance of the considered HSTRN.
The development of next-generation wireless networks envisages the seamless integration between satellite systems and terrestrial cellular networks. The spectral resources allocated to satellite are not fully utilized, whereas terrestrial spectral resources are becoming overutilized day by day. Therefore, it is important to ascertain an efficient way to share the resources of space-based networks with the terrestrial networks. In view of different capabilities and services, the geostationary earth orbit (GEO) satellite could be the component of the space segment, while the terrestrial segment may be a 3G/4G heterogeneous network. With growing requirements of broadband services and limited availability of spectral resources, higher frequency bands (above 10 GHz), viz., Ku and Ka, may also need to be assigned for mobile satellite services. As such, it is quite challenging to transmit over such higher frequencies due to severe effects of atmospheric turbulence and scattering. Hence, it is imperative to explore cognitive spectrum sharing techniques to enhance spectrum utilization efficiency through the development of hybrid satellite-terrestrial communication systems. In this regard, this chapter studies the satellite-terrestrial communications with the emerging cooperative and cognitive radio techniques to promote the information and communication technology (ICT) sector in a more efficient and reliable manner. More specifically, the chapter addresses the hybrid satellite-terrestrial system design, planning, and resource allocation problems while exploiting cooperation among available network resources with hierarchical spectrum sharing to cope with the demands of futuristic wireless network.
This paper addresses the cooperative beamforming (BF) problem for hybrid satellite-terrestrial relay networks (HSTRNs), where a geostationary satellite transmits signals to a terrestrial mobile terminal (MT) with the help of multiple single-antenna relays. Specifically, we first formulate a constrained optimization problem to maximize the achievable rate of MT while satisfying the total power constraint of relays and the interference-to-noise ratio (INR) constraint at the earth stations (ESs). Then, based on Rayleigh-Ritz method, we propose an iterative BF algorithm to obtain the optimal analytical expressions of weight vector. Furthermore, to reduce computational complexity and transmission delay, we design MRT-based BF scheme as the suboptimal scheme. Finally, numerical results are given to confirm the validity and superiority of the proposed cooperative BF schemes.
Allowing frequency reuse between satellite and terrestrial networks, the integrated satellite-terrestrial network can spatially optimize the usage of scarce spectrum resource and is becoming one of the most promising infrastructure for future multimedia services. Taking the requirements of both efficiency and reliability in satellite communications into account, we propose an adaptive transmission scheme for the integrated network in this paper, where the satellite can communicate with the destination user either in direct mode or in cooperative mode. Specifically, we first investigate the symbol error rate (SER) performance of two transmission modes with co-channel interference under composite multipath/shadowing fading. Taking the derived SERs as constraints, we formulate the adaptive transmission scheme as an optimization problem with the objective of maximizing energy efficiency (EE) and discuss the tradeoff among EE, spectral efficiency (SE), and SER. Furthermore, economic efficiency (ECE) is also analyzed as a complementary performance measure to SE and EE. Simulation results show that the proposed scheme can increase the attainable EE of satellite communications, which indicates that we should choose the transmission mode adaptively according to different interfering scenarios and shadowing degrees, rather than adopting cooperative transmission aggressively.
In this paper, we study a hybrid satellite-terrestrial spectrum sharing system (HSTSSS) in which multiple terrestrial secondary networks cooperate with a primary satellite network for dynamic spectrum access. For complexity-aware HSTSSS design, we propose an amplify-and-forward based overlay spectrum sharing protocol using partial and opportunistic secondary network selection schemes. The secondary network selection aims to minimize the outage probability of primary satellite system, and thereby, to explore spectrum sharing opportunities. With overlay approach, the selected secondary network allocates part of its power to relay the satellite signal and utilizes the remaining power to transmit its own signal. Considering Shadowed-Rician fading for satellite links, and Nakagami-m as well as Rician fading for terrestrial links, we derive closed-form expressions for the outage probability of both primary and secondary networks, and examine their achievable diversity orders. Numerical and simulation results validate our analysis and highlight the performance gains of the proposed schemes for HSTSSS with and without a direct satellite primary communication link.
In this paper, the outage probability of the uplink is analyzed for a land mobile satellite (LMS) cooperative system, which consists of a satellite (the destination), a mobile terminal (the source) and a relay node on the ground. It is assumed that the source-satellite (S-D) link and the relay-satellite (R-D) link experience independent shadowed Rician fading, and the source-relay (S-R) link experiences Rayleigh fading. The maximal ratio combining technique is used at the destination to combine the direct signal from the source and the relayed signal from the relay with different relaying protocols, such as amplify-and-forward (AF), decode-and-forward (DF) and selection decode-and-forward (SDF). With the trapezoidal rule-based integration approximation method and the moment generating function (MGF)-based approach, the closed-form expressions of the outage probability of the uplink in the LMS cooperative system with three relaying protocols are derived. The analytical results are confirmed by Monte Carlo simulations. The results show that the outage probability of the uplink in the LMS SDF cooperative system is the smallest among three relaying protocols, and the performance of the uplink in the LMS AF cooperative system is better than that of the DF cooperative system when the transmit SNR is high. Moreover, the outage probability of the uplink in the LMS cooperative system with SDF and AF relaying protocols obviously decreases as the channel condition of the S-D link gets better. The performance of the LMS DF cooperative system depends on the channel condition of the S-R link. In addition, the performance of the LMS cooperative system is better than that of the no relay LMS system in most of cases.
In this paper we analyze the impact of cooperative satellite terminals on the link availability for a land mobile satellite (LMS) scenario. By using multiple terminals the overall probability to encounter severe fading conditions is reduced. In particular, the potential of maximal ratio combining (MRC) and selection combining (SC) is compared for different numbers of cooperative terminals and for various spatial terminal separations. The results, presented in terms of link availability, are based on the analysis of LMS channel measurements. These were conducted in different environments using a single measurement vehicle. Thus, in order to virtually increase the number of terminals, we rely on a convoy scenario using spatially shifted versions of the data. Analyzing up to four cooperative terminals with various terminal distances, a significant gain in link availability is already found for small separations.
In this paper, we consider an amplify-and-forward hybrid satellite-terrestrial co-operative network in the presence of cochannel interference (CCI). More specifically, we assume that both the satellite-destination and the satellite-relay links undergo the shadowed-Rician fading and the relay-destination link follows the Nakagami-m fading. By applying the amplify-and-forward (AF) protocol at the terrestrial relay, both the relay and the destination are corrupted by cochannel interference from the terrestrial network. Based on this setup, we first derive the approximate statistical distributions signal-to-interference-plus noise ratio (SINR) and then analyze the system performance. To obtain more insights into the system performance, some asymptotical bit-error rate (BER) results are provided. Moreover, we extend our analysis to a multiple-relay network and analyze the asymptotic performance. Finally, some numerical results are provided to verify our analysis.
This paper considers the effect of co-channel interference on hybrid satellite-terrestrial relay network. In particular, we investigate the problem of amplify-and-forward (AF) relaying in hybrid satellite-terrestrial link, where the relay is interfered by multiple co-channel interferers. The direct link between satellite and terrestrial destination is not available due to masking by surroundings. The destination node can only receive signals from satellite with the assistance of a relay node situated at ground. The satellite-relay link is assumed to follow the shadowed Rice fading, while the channels of interferer-relay and relay-destination links experience Nakagami-m fading. For the considered AF relaying scheme, we first derive the analytical expression for the moment generating function (MGF) of the output signal-to-interference-plus-noise ratio (SINR). Then, we use the obtained MGF to derive the average symbol error rate (SER) of the considered scenario for M-ary phase shift keying (M-PSK) constellation under these generalized fading channels.
We study the problem of amplify-and-forward relaying in a hybrid satellite-terrestrial communication system with imperfect channel gains. Signals are received by masked destination earth station (ES) with the help of a relaying ES, situated at the ground with good line-of-sight. No direct transmission is possible from the satellite to the destination ES. The satellite-relay ES link is assumed to be Shadowed-Rician fading, and relay ES-destination ES (terrestrial link) is assumed to follow Nakagami-m fading. We propose a scheme for channel estimation and detection of channel gains and transmitted signal from the satellite. The estimation of terrestrial-link is performed separately, whereas, the channel estimation of cooperative hybrid link (satellite-relay ES-destination ES) and symbol detection is performed jointly. The average symbol error rate of the considered system for M-ary phase shift keying constellation is derived by using moment generating function (M.G.F.) approach. Moreover, the analytical diversity order of the considered system with estimated channel gains is also derived. It is shown by simulation and analysis that the diversity order of the system is not affected by the estimation errors. By using the expression of M.G.F., the average capacity of the system is also derived.
Diversity gains are believed to improve the transmission reliability in fading mobile satellite channels. Considering that the traditional Space-Time Coding (STC) is not suitable for the cooperative mobile satellite communication, in this paper a new cooperative mobile satellite communication system is proposed based on the Dynamic Space-Time Coding (D-STC). The transmit energy of the propose scheme is saved by avoiding forwarding erroneous signals in cooperative users. Meanwhile, the system benefits from diversity gains and the transmission is robust. Finally, the analytical result is validated by numerical simulations.
In order to improve the capacity and spectral efficiency of geostationary orbiting satellite collocation system, a cooperative transmission scheme is proposed in this paper. With the cooperative beamforming at the ground control station, a satellite spot beam can be split into virtual beams, which can support radio resources multiplexing for selected users. A cooperative gain is defined and further studied to evaluate the enhancement of cooperative and non-cooperative system. Then, according to this cooperative gain, a ground user selection criterion is derived, in which equivalent distance mismatch can be tolerated under the constraint of capacity degradation. Furthermore, the expectation of selectable ground users is analyzed to show the feasibility of our proposed scheme. Simulation results demonstrate that with the proposed cooperative transmission scheme, a high cooperative gain can be achieved.
We address the problem of amplify-and-forward (AF) relaying in a hybrid satellite-terrestrial communication system with unknown channel gains. A masked destination earth station (ES) receives the signal forwarded by a relaying ES, i.e., from a terrestrial link. There is no direct transmission from the satellite to the destination ES. The satellite-relay ES (satellite link) and relay ES-destination ES (terrestrial link) links are assumed to follow shadowed Rician fading and Nakagami-m fading, respectively. A scheme for channel estimation and detection of transmitted signal from the satellite to the destination ES is proposed. The terrestrial link is estimated separately, whereas the cooperative hybrid link (satellite-relay-destination) is estimated jointly with symbol detection. The average symbol error rates of the M-ary phase-shift keying and M-ary quadrature amplitude modulation constellations are derived for the considered hybrid communication system. Moreover, we also derive the analytical diversity order of the considered system with estimated channel gains. It is shown by simulation and analysis that the estimation error does not affect the diversity order of the system. Furthermore, the average and asymptotic capacity of the system is also derived by using the moment-generating function approach.
Cooperative communication for wireless networks has gained a lot of attention due to its ability to mitigate fading with exploration of spatial diversity. This paper studies an optimal relay selection problem which aims to select the optimal number of relay nodes for each source and destination to obtain the maximal transmission throughput. A coalitional game based relay selection algorithm is proposed to solve the problem. In order to reduce the complexity of coalition formation, a merge-andsplit rule is used in the algorithm. We have carried out extensive simulations to evaluate the performance of the proposed algorithm. The simulation results demonstrate the significant performance enhancement by using the proposed algorithm.
Next generation communication networks incorporate Land Mobile Satellite (LMS) systems in order to provide greater areas of coverage and higher throughput for specific applications. Cooperation between satellite communication networks and terrestrial relays is or increasing the system's performance and availability. In this paper, the outage performance of a cooperative hybrid satellite and terrestrial system configuration is analytically evaluated assuming that the satellite links suffer from shadowed Rician fading, while the terrestrial link suffers from the Nakagami-m fading. Two cooperative relaying strategies are examined and the final formulas for the calculation of the outage probability are given. Moreover, a block diagram for the generation of time series for the reliable simulations of the outage probability of the cooperative hybrid land mobile satellite systems is given. The theoretical results and the simulation results almost coincide. Moreover, extended numerical results investigate the impact, of different shadowing conditions and more generally of the satellite links elevation angles, on the overall cooperative LMS system performance.
In this paper, we propose an efficient cooperative diversity scheme for mobile satellite multimedia broadcasting services. The proposed scheme is a transmit diversity technique to adapt time varying channel conditions, and we do not need any channel quality information from the return link. In the proposed scheme, we utilize space-time block coding (STBC) and rate compatible turbo codes in order to realize the transmit diversity for the mobile satellite system with several repeaters. The satellite and several repeaters operate in unison to send the encoded signals, so that the receiver may realize diversity gain. The simulation results demonstrate that the proposed scheme can provide highly improved performance.
A mobile satellite broadcasting service including an ancillary terrestrial component (ATC) takes advantage of the satellite's inherent capability to provide broadcast service over global coverage. We consider the downlink transmission concept using ATC with space-time code (STC) for the mobile satellite communication. We do not regard ATC as simply a repeater but consider it as an antenna for STC. First, transmission scenarios for an application of STC are represented. Next, we apply STC in the mobile satellite system including ATC and compare the system performance in the proposed architecture of ATC to that in the conventional structure. The simulation results are compared to the conventional downlink transmission concept for the mobile satellite broadcasting service.
In this paper, a new MAC protocol supporting cooperative diversity named as CD-Maca is presented. By making use of the information carried by the handshaking frames of the Maca protocol, which has been employed in IEEE 802.11 standard, the CD-Maca protocol allows terminals in the network to transmit data frames cooperatively, resulting in more reliable retransmission and better performance. We model the CD-Maca protocol with Markov chain and derive the throughout of the protocols. It's shown by numerical results and simulations that the performance of the CD-Maca protocol depends on the packet error ratio (PER) of the handshaking frames, the PER of the cooperative transmission and the network topologies
Cooperative transmission is an emerging communication technique that takes advantage of the broadcast nature of wireless channels. However, due to low spectral efficiency and the requirement of orthogonal channels, its potential for use in future wireless networks is limited. In this paper, by making use of multiuser detection (MUD) and network coding, cooperative transmission protocols with high spectral efficiency, diversity order, and coding gain are developed. Compared with the traditional cooperative transmission protocols with singleuser detection, in which the diversity gain is only for one source user, the proposed MUD cooperative transmission protocols have the merit that the improvement of one user's link can also benefit the other users. In addition, using MUD at the relay provides an environment in which network coding can be employed. The coding gain and high diversity order can be obtained by fully utilizing the link between the relay and the destination. From the analysis and simulation results, it is seen that the proposed protocols achieve higher diversity gain, better asymptotic efficiency, and lower bit error rate, compared to traditional MUD schemes and to existing cooperative transmission protocols. From the simulation results, the performance of the proposed scheme is near optimal as the performance gap is 0.12dB for average bit error rate (BER) 10-6 and 1.04dB for average BER 10-3, compared to two performance upper bounds.
This paper evaluates the applicability of MIMO techniques to satellite networks in order to achieve diversity and multiplexing gain through dual polarized antennas. In single satellite scenarios the proposed STTC and OSTBC techniques proposed offer better BER than plain stream multiplexing along each polarizations and SISO transmissions. By adding a satellite with dual polarization antennas and performing a joint distributed OSTBC, the spectral efficiency increases as the satellites transmit in the same frequency band. Finally the hybrid satellite-terrestrial network has been considered for MIMO transmission. In this case, the spectral efficiency can be multiplied by 4 if a joint encoding of satellite and terrestrial signals is performed. In each scenario the broadcast signal follows the DVB-SH standard.
The present article carries out a review of MIMO-based techniques that have been recently proposed for satellite communications. Due to the plethora of MIMO interpretations in terrestrial systems and the particularities of satellite communications, this review is built on two pillars, namely fixed satellite and mobile satellite. Special attention is given to the characteristics of the satellite channel, which will ultimately determine the viability of MIMO over satellite. Finally, some future research directions are identified.
This paper presents a new cooperative MAC (medium access control) protocol called BRIAF (best relay based incremental amplify-and-forward). The proposed protocol presents two features: on-demand relaying and selection of the best relay terminal. "On-demand relaying" means that a cooperative transmission is implemented between a source terminal and a destination terminal only when the destination terminal fails in decoding the data transmitted by the source terminal. This feature maximizes the spatial multiplexing gain r of the transmission. "Selection of the best relay terminal" means that a selection of the best relay among a set of (m-1) relay candidates is implemented when a cooperative transmission is needed. This feature maximizes the diversity order d(r) of the transmission. Hence, an optimal DMT (diversity multiplexing tradeoff) curve is achieved with a diversity order d(r) m(1-r) for 0 ¿ r ¿ 1.
It has been shown that the cooperation among nodes can improve the performance of a network under certain considerations. So far, research focus has been mainly put on cooperation and not on the coordination required to obtain this cooperation. In this paper we discuss how the MAC layer plays a key role in determining the effectiveness of a cooperative orthogonal multiple relay channel. We propose and analyze the performance of a novel MAC protocol based on the legacy IEEE 802.11 standard in a representative and general study case scenario. The main conclusion of the study is that a proper selection of the MAC protocol being used in a cooperative system is highly relevant in order to actually achieve the benefits of this kind of systems
In this paper we study simple and feasible cooperative relaying strategies which rely on the introduction of the Delay Diversity technique in a DVB-SH compliant hybrid satellite/terrestrial network. These strategies are investigated in a public emergency scenario where the adoption of a hybrid network combined with the cooperative diversity techniques guarantees the connection between the incident area and the external areas: particularly, the drawbacks of the Non-Line-Of-Sight (NLOS) propagation are mitigated. The proposed schemes are analysed and compared, highlighting the assumptions required and the simulation results with respect to the satellite-only and the terrestrial-only cases.
Cooperative diversity techniques exploit the spatial characteristics of the network to create transmit-diversity, in which the same information can be forwarded through multiple paths towards a single destination or a set of destination nodes. In this paper, we study the integration of cooperative diversity into wireless routing protocols by developing distributed cooperative MAC (C-MAC) and routing protocols. The proposed protocols employ efficient relay selection-coordination and power allocation techniques to maximize the cooperation benefits in the network. Simulation results show that the energy-saving performance of the minimum-energy routing protocols can be significantly improved when they are implemented together with the proposed C-MAC protocol (%50). We also show that the performance of the C-MAC protocol can be further enhanced when the initial path is selected using the cooperation characteristics of the network (%11 more energy-savings compared to the previous case, i.e., C-MAC with minimum-energy routing)
Practical cooperative diversity protocols often rely on low-cost radios that treat multiple in-band signals as noise and thus require strictly orthogonal transmissions. We analyze the performance of a class of opportunistic relaying protocols that employ simple packet level feedback and strictly orthogonal transmissions. It is shown that the diversity-multiplexing tradeoff of the proposed protocols either matches or outperforms the multi-input-single-output (MISO), zero-feedback performance. These gains indicate that low complexity radios and feedback could be an appealing architecture for future user cooperation protocols.
Motivated by the recent works on the relay channel and cooperative diversity, this letter introduces coded cooperation, where cooperation is achieved through channel coding methods instead of a direct relay or repetition. Each codeword is partitioned into two subsets that are transmitted from the user's and partner's antennas, respectively. Coded cooperation achieves impressive gains compared to a non-cooperative system while maintaining the same information rate, transmit power, and bandwidth. We develop bounds on BER and FER and illustrate the advantage of coded cooperation under a number of different scenarios.
When mobiles cannot support multiple antennas due to size or other constraints, conventional space-time coding cannot be used to provide uplink transmit diversity. To address this limitation, the concept of cooperation diversity has been introduced, where mobiles achieve uplink transmit diversity by relaying each other's messages. A particularly powerful variation of this principle is coded cooperation. Instead of a simple repetition relay, coded cooperation partitions the codewords of each mobile and transmits portions of each codeword through independent fading channels. This paper presents two extensions to the coded cooperation framework. First, we increase the diversity of coded cooperation in the fast-fading scenario via ideas borrowed from space-time codes. We calculate bounds for the bit- and block-error rates to demonstrate the resulting gains. Second, since cooperative coding contains two code components, it is natural to apply turbo codes to this framework. We investigate the application of turbo codes in coded cooperation and demonstrate the resulting gains via error bounds and simulations.
Cooperative diversity has been recently proposed as a way to form virtual antenna arrays that provide dramatic gains in slow fading wireless environments. However, most of the proposed solutions require distributed space-time coding algorithms, the careful design of which is left for future investigation if there is more than one cooperative relay. We propose a novel scheme that alleviates these problems and provides diversity gains on the order of the number of relays in the network. Our scheme first selects the best relay from a set of M available relays and then uses this "best" relay for cooperation between the source and the destination. We develop and analyze a distributed method to select the best relay that requires no topology information and is based on local measurements of the instantaneous channel conditions. This method also requires no explicit communication among the relays. The success (or failure) to select the best available path depends on the statistics of the wireless channel, and a methodology to evaluate performance for any kind of wireless channel statistics, is provided. Information theoretic analysis of outage probability shows that our scheme achieves the same diversity-multiplexing tradeoff as achieved by more complex protocols, where coordination and distributed space-time coding for M relay nodes is required, such as those proposed by Laneman and Wornell (2003). The simplicity of the technique allows for immediate implementation in existing radio hardware and its adoption could provide for improved flexibility, reliability, and efficiency in future 4G wireless systems.
In this paper, a statistical model for the land mobile satellite
(LMS) channel is presented. The model is capable of describing both
narrow- and wide-band conditions. The other relevant characteristic is
that it can be used to study links with geostationary as well as
nongeostationary satellites. The model is of the generative type, i.e.,
it is capable of producing time series of a large number of signal
features: amplitudes, phases, instantaneous power-delay profiles,
Doppler spectra, etc. Model parameters extracted from a comprehensive
experimental data bank are also provided for a number of environments
and elevation angles at L-, S-, and Ka-bands
We propose novel cooperative transmission protocols for delay-limited coherent fading channels consisting of N (half-duplex and single-antenna) partners and one cell site. In our work, we differentiate between the relay, cooperative broadcast (down-link), and cooperative multiple-access (CMA) (up-link) channels. The proposed protocols are evaluated using Zheng-Tse diversity-multiplexing tradeoff. For the relay channel, we investigate two classes of cooperation schemes; namely, amplify and forward (AF) protocols and decode and forward (DF) protocols. For the first class, we establish an upper bound on the achievable diversity-multiplexing tradeoff with a single relay. We then construct a new AF protocol that achieves this upper bound. The proposed algorithm is then extended to the general case with (N-1) relays where it is shown to outperform the space-time coded protocol of Laneman and Wornell without requiring decoding/encoding at the relays. For the class of DF protocols, we develop a dynamic decode and forward (DDF) protocol that achieves the optimal tradeoff for multiplexing gains 0lesrles1/N. Furthermore, with a single relay, the DDF protocol is shown to dominate the class of AF protocols for all multiplexing gains. The superiority of the DDF protocol is shown to be more significant in the cooperative broadcast channel. The situation is reversed in the CMA channel where we propose a new AF protocol that achieves the optimal tradeoff for all multiplexing gains. A distinguishing feature of the proposed protocols in the three scenarios is that they do not rely on orthogonal subspaces, allowing for a more efficient use of resources. In fact, using our results one can argue that the suboptimality of previously proposed protocols stems from their use of orthogonal subspaces rather than the half-duplex constraint.
This paper addresses digital communication in a Rayleigh fading environment when the channel characteristic is unknown at the transmitter but is known (tracked) at the receiver. Inventing a codec architecture that can realize a significant portion of the great capacity promised by information theory is essential to a standout long-term position in highly competitive arenas like fixed and indoor wireless. Use (nT, nR) to express the number of antenna elements at the transmitter and receiver. An (n, n) analysis shows that despite the n received waves interfering randomly, capacity grows linearly with n and is enormous. With n = 8 at 1% outage and 21-dB average SNR at each receiving element, 42 b/s/Hz is achieved. The capacity is more than 40 times that of a (1, 1) system at the same total radiated transmitter power and bandwidth. Moreover, in some applications, n could be much larger than 8. In striving for significant fractions of such huge capacities, the question arises: Can one construct an (n, n) system whose capacity scales linearly with n, using as building blocks n separately coded one-dimensional (1-D) subsystems of equal capacity? With the aim of leveraging the already highly developed 1-D codec technology, this paper reports just such an invention. In this new architecture, signals are layered in space and time as suggested by a tight capacity bound.
Multiple antennas can be used for increasing the amount of diversity or the number of degrees of freedom in wireless communication systems. We propose the point of view to study the tradeoff between the two types of gains. In this paper, we present the complete results on the optimal tradeoff, and give a brief discussion on the techniques used to get the results.
This is the second in a two-part series of papers on a new form of spatial diver-sity, where diversity gains are achieved through the cooperation of mobile users. PartI described the user cooperation concept and proposed a cooperation strategy for aconventional CDMA system. Part II investigates the cooperation concept further andconsiders practical issues related to its implementation. In particular, we investigatethe optimal and suboptimal receiver design, and present performance...
This paper addresses digital communication in a Rayleigh fading environment when the channel characteristic is unknown at the transmitter but is known (tracked) at the receiver. Inventing a codec architecture that can realize a significant portion of the great capacity promised by information theory is essential to a standout long-term position in highly competitive arenas like fixed and indoor wireless. Use (nT, nR) to express the number of antenna elements at the transmitter and receiver. An (n, n) analysis shows that despite the n received waves interfering randomly, capacity grows linearly with n and is enormous. With n = 8 at 1% outage and 21-dB average SNR at each receiving element, 42 b/s/Hz is achieved. The capacity is more than 40 times that of a (1, 1) system at the same total radiated transmitter power and bandwidth. Moreover, in some applications, n could be much larger than 8. In striving for significant fractions of such huge capacities, the question arises: Can one construct an (n, n) system whose capacity scales linearly with n, using as building blocks n separately coded one-dimensional (1-D) subsystems of equal capacity? With the aim of leveraging the already highly developed 1-D codec technology, this paper reports just such an invention. In this new architecture, signals are layered in space and time as suggested by a tight capacity bound.
We investigate the use of multiple transmitting and/or receiving antennas for single user communications over the additive Gaussian channel with and without fading. We derive formulas for the capacities and error exponents of such channels, and describe computational procedures to evaluate such formulas. We show that the potential gains of such multi-antenna systems over single-antenna systems is rather large under independenceassumptions for the fades and noises at different receiving antennas.
This paper is motivated by the need for fundamental understanding of ultimate limits of bandwidth efficient delivery of higher bit-rates in digital wireless communications and to also begin to look into how these limits might be approached. We examine exploitation of multi-element array (MEA) technology, that is processing the spatial dimension (not just the time dimension) to improve wireless capacities in certain applications. Specifically, we present some basic information theory results that promise great advantages of using MEAs in wireless LANs and building to building wireless communication links. We explore the important case when the channel characteristic is not available at the transmitter but the receiver knows (tracks) the characteristic which is subject to Rayleigh fading. Fixing the overall transmitted power, we express the capacity offered by MEA technology and we see how the capacity scales with increasing SNR for a large but practical number, n, of antenna elements at both transmitter and receiver. We investigate the case of independent Rayleigh faded paths between antenna elements and find that with high probability extraordinary capacity is available. Compared to the baseline n = 1 case, which by Shannon’s classical formula scales as one more bit/cycle for every 3 dB of signal-to-noise ratio (SNR) increase, remarkably with MEAs, the scaling is almost like n more bits/cycle for each 3 dB increase in SNR. To illustrate how great this capacity is, even for small n, take the cases n = 2, 4 and 16 at an average received SNR of 21 dB. For over 99%
We study selective digital relaying schemes where the relay may choose to retransmit or to remain silent based on the qualities of the links between the source, relay and the destination. We first analyze a baseline scheme, called static relaying, where the relaying decisions are based only on the average signal-to-noise ratio (SNR) values of all the links. The second scheme, dynamic relaying, allows the relay to make decisions based on the instantaneous SNR of the source-relay link and average SNRs of the relay-destination and source-destination links. We show that, in dynamic relaying the optimal strategy to minimize the average end-to-end bit error rate is a threshold rule on the instantaneous SNR of the source-relay channel. In this case, the optimal threshold value is a function of average SNR of relay-destination and source-destination channels. We derive closed-form expressions for the optimal threshold and the bit error performance achieved by this threshold. We show that dynamic relaying can provide significant performance advantage over static relaying.
In order to improve the communication efficiency without using multi-antennae terminals, cooperative communications implement one or several single antenna relays to assist the transmission between a source and a destination. The design of such a cooperative network, involves several layers of the OSI model. Transmission and multiplexing techniques are addressed at the physical layer whereas the management of the cooperative network (activation of a cooperative mode, selection of relays) is done at the Medium Access Control (MAC) layer and the layers above. After an overview of protocols that have been designed in this domain, we propose an original framework of a cooperative network, at the system level. Inspired from models of the ITU normative organization, our cooperative network model is based on two planes: a data plane and a control plane. A validation of the framework is given by modeling an existing cooperative MAC protocol.
We recall the principles of cyclic delay diversity (CDD) and discuss the properties and impact of this transmit antenna diversity technology. Different applications motivate variations of the CDD principle. This variants are briefly introduced and discussed. We show the application to several types of wireless systems, in particular terrestrial digital video broadcasting, cellular mobile radio communications systems and a wireless communications system using adaptive bit loading. Simulation results show the benefits of CDD for these kind of systems.
We develop two variants of an energy-efficient cooperative
diversity protocol that combats fading induced by multipath propagation
in wireless networks, The underlying techniques build upon the classical
relay channel and related work and exploit space diversity available at
distributed antennas through coordinated transmission and processing by
cooperating radios. While applicable to any wireless setting, these
protocols are particularly attractive in ad-hoc or peer-to-peer wireless
networks, in which radios are typically constrained to employ a single
antenna. Substantial energy-savings resulting from these protocols can
lead to reduced battery drain, longer network lifetime, and improved
network performance in terms of, e.g., capacity
Cooperative transmission can obtain spatial diversity without using multiple antennas, thus achieving more reliable transmission or consuming less power. To realize cooperative communication in a distributed wireless network, two key questions need to be answered, namely when to cooperate and whom to cooperate with. In this paper, we propose a distributed MAC protocol with automatic relay selection to address these questions. We show by theoretical analysis and simulation results that the proposed solution outperforms conventional noncooperation transmission by 8 to 10 dB, for various target outage probabilities
User-cooperation represents an effective way of introducing diversity in wireless networks. Spatial diversity gains are obtained through the cooperation of mobile users and the use of the partner's antenna. In this paper, we design channel codes that are capable of achieving the full diversity provided by user-cooperation, with the constraint that they also provide the best possible performance in the noncooperative case. The codes continue to perform well, even when the interuser channel is noisy, still offering significant improvements with respect to the noncooperative case.
Future mobile networks are expected to involve systems that are based on different technologies, such as WiFi, WiMAX, 2G/3G/3G+, LTE, and satellite. To address this scenario, ITU has defined integrated and hybrid networks in the framework of Next-Generation Networks. The interest is to exploit the cooperation of different wireless communication systems (segments) to provide service to mobile users in the most efficient way, taking into account signal quality (coverage), traffic congestion conditions, and cost issues. Integrated and hybrid networks have the potential to be an efficient and cost-effective solution to employ satellite communications for mobile users. In the view of this, our paper focuses on the design of integrated/hybrid systems taking into account physical, MAC, and network layers issues. System examples and standards are described as well. Then, cooperative diversity techniques and traffic engineering issues for overflow traffic are discussed. This paper concludes identifying some possible future trends. Copyright © 2010 John Wiley & Sons, Ltd.
This paper presents a new cooperative MAC (Medium Access Control) protocol for IEEE 802.11-based mesh networks. The protocol is characterized by two features: on-demand relaying and selection of the best relay terminal. ”On-demand relaying” means that a cooperative communication occurs only when a destination terminal fails in decoding the data transmitted by a source terminal. This approach allows minimization of bandwidth degradation due to both cooperation implementation and cooperative communications. ”Selection of the best relay terminal” means that a relay selection is implemented when cooperation is needed. This feature allows maximization of the spatial diversity order. The outage probability of the new protocol is compared to the outage probability of other cooperative MAC protocols.
Cooperative communication techniques have been proposed in order to improve the quality of the received signals at the receivers by using the diversity added by duplication of signals sent by relays situating between each transmission pair. This paper proposes a new on-demand cooperative transmission technique concerned with the interoperability issues between nodes with cooperative functionality and legacy nodes. Based on the standard IEEE 802.11, the proposed method can switch its transmission mode for each data frame between a cooperative mode and a non-cooperative mode automatically. Moreover, it can work with the IEEE medium access method in the basic mode and in the optional RTS/CTS mode. An original method is proposed, where the relay node acts as a proxy that is in charge of data retransmissions when needed. Interest of the proposition is to improve the transmission performance by decreasing the number of retransmissions due to frame errors. Moreover, the proposition avoids inappropriate routing processes that are costly in time and bandwidth. Evaluation of the proposition is done by simulation. Analysis of the results is mainly based on the Packet Delivery Ratio (PDR) and on the Number of Route Discovery and Maintenance (NRDM) per second.
Thesis (Ph. D. in Engineering-Electrical Engineering and Computer Sciences)--University of California, Berkeley, Fall 2002. Includes bibliographical references (leaves 113-115).
In this paper, we propose an efficient cooperative diversity scheme for mobile satellite multimedia broadcasting systems. The proposed scheme is a transmit diversity technique to adapt different channel environments, and thus we do not need any channel quality information from the return link. In the proposed scheme, we utilize space-time block coding (STBC) and rate compatible turbo codes in order to realize the transmit diversity for the mobile satellite system with several repeaters. The satellite and several repeaters operate in unison to send the encoded signals, so that the receiver may realize diversity gain. The simulation results demonstrate that the proposed scheme can provide highly improved performance.
Cooperative relaying is a recently developed concept that allows for providing single-antenna devices with gains from spatial diversity. So far, the performance of those schemes has mainly been investigated in comparison to conventional multiple-antenna systems and conventional relaying techniques. Yet, the cooperation of mobile terminals offers another important enhancement. Whenever other sources of diversity are scarce, the transmission over a statistically independent relay path can provide a significant amount of spatial diversity then to be exploited by error correction techniques to effectively combat fading effects. We therefore examine the performance of cooperative relaying protocols in slow and fast fading regimes, in comparison to approaches that exploit temporal diversity. Our results imply that user cooperation is a powerful means of enhancing link level performance in environments where temporal diversity is limited and delay constraints preclude the use of larger interleavers.
Space-time communications can help combat fading and, hence, can significantly increase the capacity of ad hoc networks. Cooperative diversity or virtual antenna arrays facilitate spatio-temporal communications without actually requiring the deployment of physical antenna arrays. Virtual MISO entails the simultaneous transmission of appropriately encoded information by multiple nodes to effectively emulate a transmission on an antenna array. We present a novel multilayer approach for exploiting virtual MISO links in ad hoc networks. The approach spans the physical, medium access control and routing layers, and provides 1) a significant improvement in the end-to-end performance in terms of throughput and delay and 2) robustness to mobility and interference-induced link failures. The key physical layer property that we exploit is an increased transmission range due to achieved diversity gain. Except for space-time signal processing capabilities, our design does not require any additional hardware. We perform extensive simulations to quantify the benefits of our approach using virtual MISO links. As compared to using only SISO links, we achieve an increase of up to 150 percent in terms of the end-to-end throughput and a decrease of up to 75 percent in the incurred end-to-end delay. Our results also demonstrate a reduction in the route discovery attempts due to link failures by up to 60 percent, a direct consequence of the robustness that our approach provides to link failures
Due to the broadcast nature of wireless signals, a wireless transmission intended for a particular destination station can be overheard by other neighboring stations. A focus of recent research activities in cooperative communications is to achieve spatial diversity gains by requiring these neighboring stations to retransmit the overheard information to the final destination. In this paper we demonstrate that such cooperation among stations in a wireless LAN (WLAN) can achieve both higher throughput and lower interference. We present the design for a medium access control protocol called CoopMAC, in which high data rate stations assist low data rate stations in their transmission by forwarding their traffic. In our proposed protocol, using the overheard transmissions, each low data rate node maintains a table, called a CoopTable, of potential helper nodes that can assist in its transmissions. During transmission, each low data rate node selects either direct transmission or transmission through a helper node in order to minimize the total transmission time. Using analysis, simulation and testbed experimentation, we quantify the increase in the total network throughput, and the reduction in delay, if such cooperative transmissions are utilized. The CoopMAC protocol is simple and backward compatible with the legacy 802.11 system. In this paper, we also demonstrate a reduction in the signal-to-interference ratio in a dense deployment of 802.11 access points, which in some cases is a more important consequence of cooperation
This paper presents an overview of progress in the area of multiple input multiple output (MIMO) space-time coded wireless systems. After some background on the research leading to the discovery of the enormous potential of MIMO wireless links, we highlight the different classes of techniques and algorithms proposed which attempt to realize the various benefits of MIMO including spatial multiplexing and space-time coding schemes. These algorithms are often derived and analyzed under ideal independent fading conditions. We present the state of the art in channel modeling and measurements, leading to a better understanding of actual MIMO gains. Finally, the paper addresses current questions regarding the integration of MIMO links in practical wireless systems and standards.
This paper presents a simple two-branch transmit diversity scheme.
Using two transmit antennas and one receive antenna the scheme provides
the same diversity order as maximal-ratio receiver combining (MRRC) with
one transmit antenna, and two receive antennas. It is also shown that
the scheme may easily be generalized to two transmit antennas and M
receive antennas to provide a diversity order of 2M. The new scheme does
not require any bandwidth expansion or any feedback from the receiver to
the transmitter and its computation complexity is similar to MRRC
Multimedia broadcast and multicast services have started to outpace simple data unicast services. A hybrid satellite-terrestrial network can provide a cooperative system in such a way as to provide high-quality seamless MBMS effectively. In this article we discuss two promising techniques that can improve the performance of a mobile satellite broadcasting system with HSTN. The objective of the first technique is to obtain diversity gain from independent signal paths; this can be achieved by using the space-time coding technique jointly operated on both the satellite and terrestrial repeaters. The goal of the second scheme is to obtain power gain by using a layered channel coding scheme with which a user terminal adapts to the channel condition. We demonstrate various simulation results for both schemes on the prescribed network structure, and the results show substantial improvements in performance.
User cooperation represents an effective way of introducing diversity in wireless networks. Spatial diversity gains are obtained through the cooperative use of antennas belonging to several nodes. We design and analyze the performance of channel codes that are capable of achieving the full diversity provided by user cooperation, with the constraint that they also provide the best possible performance in the interuser link. We show that even though the interuser channel is noisy, the codes provide substantial diversity and coding gains over the noncooperative case.
Mobile users' data rate and quality of service are limited by the fact that, within the duration of any given call, they experience severe variations in signal attenuation, thereby necessitating the use of some type of diversity. In this two-part paper, we propose a new form of spatial diversity, in which diversity gains are achieved via the cooperation of mobile users. Part I describes the user cooperation strategy, while Part II (see ibid., p.1939-48) focuses on implementation issues and performance analysis. Results show that, even though the interuser channel is noisy, cooperation leads not only to an increase in capacity for both users but also to a more robust system, where users' achievable rates are less susceptible to channel variations.
The communication channel between the MARECS satellite at 26°W
and a cruising van was measured and recorded in European areas
exhibiting satellite elevations from 13 to 43°. Different
environments and mobile antennas were tested. The results of an
extensive statistical evaluation include spectra of the fading
amplitude; probability density, and distribution of the received signal
power; and the percentage of time for fade and nonfade periods. Based on
the physical phenomena of multipath fading and signal shadowing, an
analog model of the land mobile satellite channel which can readily be
used for software and hardware fading simulation is developed. The most
important parameter of this model is the time-share of shadowing. The
Rice factor which characterizes the channel during unshadowed periods,
can vary from 3.9 to 18.1 dB. Block error probability density, error gap
distribution, and block error probability are discussed
Coding strategies that exploit node cooperation are developed for relay networks. Two basic schemes are studied: the relays decode-and-forward the source message to the destination, or they compress-and-forward their channel outputs to the destination. The decode-and-forward scheme is a variant of multihopping, but in addition to having the relays successively decode the message, the transmitters cooperate and each receiver uses several or all of its past channel output blocks to decode. For the compress-and-forward scheme, the relays take advantage of the statistical dependence between their channel outputs and the destination's channel output. The strategies are applied to wireless channels, and it is shown that decode-and-forward achieves the ergodic capacity with phase fading if phase information is available only locally, and if the relays are near the source node. The ergodic capacity coincides with the rate of a distributed antenna array with full cooperation even though the transmitting antennas are not colocated. The capacity results generalize broadly, including to multiantenna transmission with Rayleigh fading, single-bounce fading, certain quasi-static fading problems, cases where partial channel knowledge is available at the transmitters, and cases where local user cooperation is permitted. The results further extend to multisource and multidestination networks such as multiaccess and broadcast relay channels.
We develop and analyze low-complexity cooperative diversity protocols that combat fading induced by multipath propagation in wireless networks. The underlying techniques exploit space diversity available through cooperating terminals' relaying signals for one another. We outline several strategies employed by the cooperating radios, including fixed relaying schemes such as amplify-and-forward and decode-and-forward, selection relaying schemes that adapt based upon channel measurements between the cooperating terminals, and incremental relaying schemes that adapt based upon limited feedback from the destination terminal. We develop performance characterizations in terms of outage events and associated outage probabilities, which measure robustness of the transmissions to fading, focusing on the high signal-to-noise ratio (SNR) regime. Except for fixed decode-and-forward, all of our cooperative diversity protocols are efficient in the sense that they achieve full diversity (i.e., second-order diversity in the case of two terminals), and, moreover, are close to optimum (within 1.5 dB) in certain regimes. Thus, using distributed antennas, we can provide the powerful benefits of space diversity without need for physical arrays, though at a loss of spectral efficiency due to half-duplex operation and possibly at the cost of additional receive hardware. Applicable to any wireless setting, including cellular or ad hoc networks-wherever space constraints preclude the use of physical arrays-the performance characterizations reveal that large power or energy savings result from the use of these protocols.
We develop and analyze space-time coded cooperative diversity protocols for combating multipath fading across multiple protocol layers in a wireless network. The protocols exploit spatial diversity available among a collection of distributed terminals that relay messages for one another in such a manner that the destination terminal can average the fading, even though it is unknown a priori which terminals will be involved. In particular, a source initiates transmission to its destination, and many relays potentially receive the transmission. Those terminals that can fully decode the transmission utilize a space-time code to cooperatively relay to the destination. We demonstrate that these protocols achieve full spatial diversity in the number of cooperating terminals, not just the number of decoding relays, and can be used effectively for higher spectral efficiencies than repetition-based schemes. We discuss issues related to space-time code design for these protocols, emphasizing codes that readily allow for appealing distributed versions.
This work considers the achievable performance for coded systems
adapted to a multipath block-fading channel model. This is a
particularly useful model for analyzing mobile-radio systems which
employ techniques such as slow frequency-hopping under stringent
time-delay or bandwidth constraints for slowly time-varying channels. In
such systems, coded information is transmitted over a small number of
fading channels in order to achieve diversity. Bounds on the achievable
performance due to coding are derived using information-theoretic
techniques. It is shown that high diversity can be achieved using
relatively simple codes as long as very high spectral efficiency is not
required. Examples of simple block codes and carefully chosen trellis
codes are given which yield, in some cases, performances approaching the
information-theoretic bounds
This paper, tutorial in nature, describes the effort of many
investigators who have and still are conducting channel measurements and
modeling for land mobile satellite communications. Various channel
measurement results, ranging from ultrahigh frequency to Ka-band, are
given. Many statistical channel models and simplified models that have
been developed are referred to. Some of the models are applicable to
geostationary and nongeostationary communications satellites. A
statistical model developed by Loo (1985) is described in detail, as
well as its extension to modeling land mobile satellite communications
at Ka-band. This was accomplished by including a Gaussian probability
density function to account for weather conditions. Also, practical
computer-generated statistical channel models are given. These computer
models should facilitate the estimation of performance of satellite
communications systems
We investigate the use of multiple transmitting and/or receiving antennas for single user communications over the additive Gaussian channel with and without fading. We derive formulas for the capacities and error exponents of such channels, and describe computational procedures to evaluate such formulas. We show that the potential gains of such multi-antenna systems over single-antenna systems is rather large under independence assumptions for the fades and noises at different receiving antennas. 1 Introduction We will consider a single user Gaussian channel with multiple transmitting and/or receiving antennas. We will denote the number of transmitting antennas by t and the number of receiving antennas by r. We will exclusively deal with a linear model in which the received vector y 2 C r depends on the transmitted vector x 2 C t via y = Hx+ n (1) where H is a r Theta t complex matrix and n is zero-mean complex Gaussian noise with independent, equal variance real and imaginary p...
We develop energy-efficient transmission protocols for wireless networks that exploit spatial diversity created by antenna sharing: coordinated transmission and/or processing by several distributed radios. We focus on single-user transmission and examine several possibilities for the strategy employed by the assisting radio, or relay, including decoding and forwarding as well as amplifying and forwarding. In each case, we develop receivers based upon maximum-likelihood and/or maximum signal-to-noise ratio criteria, relate their structures, and compare their bit-error probability performance by means of analysis and simulations. We cast singlehop and multihop routing into our framework for comparison purposes. All of our antenna sharing protocols offer diversity gains over single- and multi-hop transmission, and our results suggest that low complexity amplifying and forwarding is energy-efficient in spite of noise amplification at the relay.