Spectral efficiency is a major concern for future 6G wireless communication systems. Thus, an appropriate scheme is needed to provide channel capacity improvement for multiple transmitters and receiver-based wireless communication systems without consuming extra resource for communication (e.g., frequency/time/code) or causing interference. Therefore, to fulfill the mentioned requirements for the future 6G wireless network, orbital angular momentum-based multiple-input-multiple-output (OAM-MIMO) multiplexing technique is incorporated with the receive antenna shift keying (RASK) technique in this study (termed as the OAM-MIMO-RASK scheme). OAM-MIMO-RASK can transfer multiple symbols from multiple transmitters to different receivers simultaneously by using multiple subchannels using the OAM and RASK techniques without any interference or additional resource (frequency/time/code). The numerical results illustrated that the proposed OAM-MIMO-RASK can achieve almost double capacity than the existing OAM-MIMO scheme and significantly higher capacity than the existing RASK-based scheme for different values of signal-to-noise ratio. Moreover, the simulation result is validated by the theoretical result which is also shown by the numerical result. In addition, due to different normalized distances from the transmitters and receivers, the proposed OAM-MIMO-RASK scheme can achieve almost double capacity than the existing OAM-MIMO scheme by using OAM-MIMO and RASK technique effectively which is also depicted by the numerical results.
Time splitting and power splitting incorporating, a hybrid Simultaneous Wireless Information and Power Transfer (SWIPT) based cooperative Non-Orthogonal Multiple Access (CNOMA) protocol is considered in this paper. Cell center user of the CNOMA system acts as a relay to enhance the reliability of the cell edge user (CEU). SWIPT is considered to empower the relay operation to avoid the battery draining issue. To enhance the system performance in terms of ergodic sum capacity (ESC) and outage probabilities (OP), an integration of CNOMA strategy and hybrid SWIPT protocol for the downlink (DL) transmission is proposed here. By utilizing the idle link of hybrid SWIPT protocol an enhanced hybrid SWIPT protocol is proposed here to enhance the performance of CNOMA DL transmission. Moreover, Maximal ratio combining is utilized as a diversity combining technique at CEU to enhance the performance as well. The performance of the proposed protocol is examined in terms of ergodic sum capacity, outage probabilities and energy efficiency. Finally, the analytical results are justified by the Monte-Carlo simulation. Numerical results demonstrate that the proposed protocol with effective CNOMA strategy achieves superior performance than HS-CNOMA with selection combining.
In this paper, joint transmission coordinated multipoint (JT-CoMP) is exploited by using virtual user pairing non-orthogonal multiple access (VP-NOMA), termed as JT-CoMP VP-NOMA. The technique combines both VP-NOMA for enhancing ergodic sum capacity (ESC) and JT-CoMP for inter-cell interference mitigation. To show the performance gains, ESC of a three-cell scenario is analyzed as a key performance metric. The analytical and simulation results of JT-CoMP VP-NOMA are compared with orthogonal multiple access (OMA), non-orthogonal multiple access (NOMA), and VP-NOMA. It is shown that the proposed JT-CoMP VP-NOMA outperforms the other schemes in the viewpoint of ESC.
In this paper, a joint transmission coordinated multi-point based non-orthogonal multiple access (JT-COMP NOMA) combined with spatial modulation (SM), termed as JT-COMP NOMA-SM, is proposed to enhance capacity. User capacity and ergodic sum capacity (ESC) of M number coordinated multi-point base stations (COMP BSs) within N number of cells are analyzed by considering imperfect successive interference cancellation (SIC) and imperfect channel state information (CSI). The performances of the proposed syatem are compared with non-orthogonal multiple access (NOMA), and joint transmission coordinated multi-point combined with virtual user pairing based non-orthogonal multiple access (JT-COMP VP-NOMA) by both simulation and analysis. The results show that the proposed system has the same cell center user (CCU) capacity compared to JT-COMP VP-NOMA and a higher cell edge user (CEU) capacity than the other schemes. ESC of the proposed system outperforms the other schemes due to enhancing CEU capacity. Imperfect SIC and imperfect CSI may degrade capacity. The proposed system can maintain CEU capacity better than the other schemes if the number of cells is increased. It happens because SM works beyond Shannon upper bounds which can mitigate inter-cell interference (ICI).
This paper proposes a device-to-device (D2D) enabling cellular full-duplex (FD) cooperative (DFC) protocol using non-orthogonal multiple access (NOMA) called DFC-NOMA, where an FD relay acting D2D transmitter assists in relaying a NOMA far user's signal and transmits a D2D receiver's signal simultaneously. The ergodic capacity, outage probability, and diversity order of DFC-NOMA are theoretically investigated under the assumption of both perfect and imperfect interference cancellation. The theoretical analysis is then validated by simulations. Both analysis and simulation results demonstrate the performance gain of DFC-NOMA over conventional FD cooperative NOMA and existing D2D aided FD NOMA.
This paper focuses on user pairing (UP) and power allocation (PA) by considering an uplink Non-orthogonal multiple access (NOMA) system. In NOMA, UP and PA serve as critical factors to achieve high performance gains. In this context, channel gains of paired users and their PA factors are varied to comprehensively analyze the dynamics of UP and PA in the context of individual and sum capacity of paired users. On the basis of this analysis, a look-up table is provided, which shows that efficient UP and PA can maximize the sum capacity of an uplink NOMA system, while satisfying the individual target rates of the paired users. Moreover, a mechanism to choose the best user pair and corresponding PA by using such tables is also discussed for swift UP and PA.
In this paper, an uplink scheme that exploits cooperative diversity using power domain non-orthogonal multiple access (NOMA), termed UCD-NOMA, with successive interference cancellation receivers is proposed. A two-user case is considered, where both the NOMA users can communicate with the base station directly and indirectly via a half-duplex decode-and-forward relay. Under perfect and imperfect SIC assumptions, the ergodic sum capacity, outage probability, and outage sum capacity of the considered protocol are analyzed over the Rayleigh fading channel. As a protocol with which to compare the proposed UCD-NOMA protocol, an uplink cooperative network using a conventional multiple access technique (termed UCD-OMA) is also considered and analyzed. The performance excellence of UCD-NOMA as compared to UCD-OMA is clarified through simulations and theoretical analyses.
To cope with the exponential growth of existing mobile traffic and the emergence of new wireless applications, a new wireless communications system, namely a fifth-generation of wireless networks, abbreviated 5G, is anticipated to be emerged by 2020. As a possible candidate technique to radio access of 5G, non-orthogonal multiple access (NOMA) has garnered much interest from both industry and academia, in their attempt to significantly boost system's spectral efficiency and serve a large number of users. For a single technology, it is considered not easy to meet the performance requirements of 5G and beyond. The integration of multiple technologies is expected to deal with these challenging requirements. Hence, several protocols are proposed in this thesis over independent Rayleigh fading channels, wherein NOMA is incorporated with some other promising technologies such as half-duplex/full-duplex relaying, space-time block coding, relay sharing, cooperative spectrum sharing (CSS), and energy harvesting (EH) etc. In the first part of the thesis, it is demonstrated that NOMA and half-duplex cooperative relaying scheme (CRS) can be incorporated to improve system spectral efficiency and reliability. Four different protocols are investigated along with analytical derivations. Firstly, a CRS using NOMA is proposed, where a base station (BS) communicates simultaneously with two NOMA users via the help of a half-duplex decode-and-forward (DF) relay. The outage probability (OP) and outage capacity are investigated. It is shown that the proposed cooperative NOMA can outperform non-cooperative NOMA, in terms of OP. Secondly, a coordinated direct and relay transmission scheme using uplink NOMA (termed as UP-NOMA) is proposed. In UP-NOMA, a cell-center user communicates directly with a BS, whereas a cell-edge user needs the assistance of a half-duplex DF relay to communicate with the BS. Under both perfect and imperfect successive interference cancellation (SIC), the ergodic sum capacity (E-SC) of UP-NOMA is analyzed. Through analysis and simulation, the superiority of UP-NOMA over conventional multiple access (OMA) is also demonstrated. Thirdly, the performance of a NOMA-based cooperative relay sharing network is studied, where multiple sources share a relay to communicate with their corresponding destinations simultaneously on the same frequency band. In terms of E-SC, the superiority of the proposed protocol over OMA is proved through the simulation and analysis, by considering perfect and imperfect SIC. Finally, the performance of a CRS based on Alamouti space-time block coded NOMA is investigated, in terms of E-SC, OP, and outage sum capacity (O-SC). The superiority of the proposed protocol over conventional CRS using NOMA and the traditional DF relaying schemes, is demonstrated through analysis and simulation. In the second part of the thesis, it is investigated that NOMA and full-duplex CRS can be integrated to overcome the spectral efficiency loss in a half-duplex protocol. An FD NOMA protocol for a cooperative relay sharing network (termed as FD-NOMA-RS) is presented, in which two source-destination pairs share a dedicated FD relay. The E-SC, OP, and O-SC are investigated along with analytical derivations, considering both perfect and imperfect interference cancellation. Moreover, the effectiveness of FD-NOMA-RS is demonstrated through analysis and simulation and then compared with that of its counterpart, the half-duplex system. In the final part of the thesis, it is manifested that by incorporating NOMA into cognitive radio systems, system throughput and the spectrum utilization can be increased substantially. Three different protocols are investigated along with analytical derivations. Firstly, a hybrid CSS protocol is proposed by jointly considering the underlay and NOMA-based overlay models, for a multi-constraint, multi-relay scenario. It is shown that the performance of both the primary and secondary systems improve with the increasing number of secondary nodes. The efficacy of the proposed protocol than the traditional overlay and underlay models is confirmed, in terms of OP and E-SC. Secondly, a NOMA-based CSS protocol is proposed, wherein three data symbols can be transmitted during the two phases; this is unlike the traditional DF relaying where one data symbol can be transmitted and the conventional superposition coding-based overlay spectrum sharing and CRS using NOMA, where two data symbols can be transmitted, under a single relay scenario. The performance of the proposed protocol is investigated, in terms of E-SC and OP. Finally, by integrating NOMA, simultaneous wireless information and power transfer, and spectrum sharing, two novel protocols, namely CSS using time-switching based EH and CSS using power-splitting based EH at secondary transmitter, are proposed. The achievable sum data rate/ throughput of both protocols is investigated. Moreover, the optimal EH ratio that maximizes the sum data rate of both protocols is also investigated numerically. Lastly, it is expected that this thesis can be beneficial in understanding how NOMA can be incorporated with other wireless technologies to improve system performance. Various accurate, interesting and previously unknown results are demonstrated, which can be very useful to incorporate NOMA in 5G or future wireless networks.
The downlink coordinated multipoint (CoMP) transmission system with non-orthogonal multiple access (NOMA) is presented to enhance downlink capacity. Since perfect knowledge of a channel is not always available in practice, imperfect channel state information (CSI) needs to be considered in downlink CoMP with NOMA. In this paper, imperfect CSI is modeled with channel estimation error, where a priori of variance of the error estimation is known. Instead of a specific number of coordinated base stations (BSs), a downlink CoMP NOMA with coordinated BSs is proposed. Further, the ergodic capacity of the cell-center user (CCU), and the cell-edge user (CEU), as well as their sum capacity are analyzed, derived as closed forms, and validated by simulations in both perfect CSI and imperfect CSI with channel estimation error. The result shows that CoMP NOMA outperforms the CoMP orthogonal multiple access (OMA) capacity, where channel estimation error degrades the performance of both CoMP NOMA and CoMP OMA. In CoMP NOMA, it is noted that the impact of channel estimation error is less significant at CEU compared to that at CCU, due to the utilization of the incoming signals from all the coordinated BSs. Additionally , by exploiting non-orthogonal channel, the sum capacity of CoMP NOMA still can be improved with an increase in coordinated BSs. It is also demonstrated that CEU needs to be allocated with much higher power than CCU to maintain their capacity simultaneously. Finally, the performance analysis is successfully validated through the close accordance between the analytical and simulation results.
In non-orthogonal multiple access (NOMA), cell-edge users experience significantly low spectral density because only some part of the total transmit power is allocated. This leads to low spectral efficiency for the paired users in NOMA. To overcome this problem, we propose an integration of NOMA and generalized space shift keying (GSSK), called NOMA-GSSK, to improve the spectral efficiency by exploiting the spatial domain. Spectral and energy efficiency, bit error rate (BER), and computational complexity of the proposed system were analyzed and compared to those of multiple-input multiple-output NOMA (MIMO-NOMA). It is shown that NOMA-GSSK outperforms MIMO-NOMA.
This paper proposes time sharing (TS) based half/full-duplex (HD/FD) cooperative non-orthogonal multiple access (CRNOMA) schemes namely TS-HD-CRNOMA and TSFD- CRNOMA to efficiently utilize the spectrum of unpaired users. A scenario with more cell edge users (CEUs) than cell center users (CCUs) is considered. Both schemes pair a CCU with multiple clustered CEUs in a TS fashion via a relay, thereby efficiently utilizing the frequency bands of multiple CEUs, which may remain underused in conventional CRNOMA. Ergodic sum capacity of the schemes is analytically derived, validated through simulations, and compared with conventional multiple access schemes to show the achieved capacity gains.
Non-orthogonal multiple access (NOMA) is thought of as a challenging technique for providing the data rate and spectral efficiency requirement in the era of future wireless communication. This article studies the performance of a NOMA adopted two-cell downlink communication scenario where adjacent cells interfere into each other' s data transmission and each cell consists of two users. Then, the optimization problem with respect to power allocation between NOMA users is formulated. This optimization problem aims at maximizing the throughput of the system under two constraints. First, it considers a total transmit power constraint for distributing power among NOMA user devices. Second, it regards a quality-of-service demand constraint to meet minimum data rate requirements of the users. Two different closed-form solutions are derived based on the proposed optimization problem. The superiority of the proposed power allocation scheme is proved through simulation results.
Non-orthogonal multiple access (NOMA) is considered to be a significant multiple radio access technology for future wireless networks owing to its improved spectral efficiency. This work proposes two different cases of a downlink two phase cooperative decode-and-forward relaying scheme using multiple-input-multiple-output non-orthogonal multiple access (MIMO-NOMA) systems with the availability of statistical channel state information at the transmitter. Ergodic sum capacities of the proposed cases are provided for independent Rayleigh fading channels. It has been demonstrated that the proposed protocol exhibits superior performance gains than the existing cooperative relaying scheme (CRS) using single-input-single-output NOMA, CRS using multiple-input-single-output NOMA, and conventional CRS MIMO protocols. It is also noticed that the relay position between the transmitter and the receiver can bring a vital change in the performance of the proposed network. Index Terms-Decode-and-forward relay, ergodic sum capacity , MIMO, non-orthogonal multiple access, successive interference cancellation.
Non-orthogonal multiple access (NOMA) with successive interference cancellation receiver is considered as one of the most potent multiple access techniques to be adopted in future wireless communication networks. Data security in the NOMA transmission scheme is on much attention drawing issue. Blockchain is a distributed peer-to-peer network enables a way of protecting information from unauthorized access, tempering etc. By utilizing encryption techniques of blockchain, a secured data communication scheme using blockchain in NOMA is proposed in this paper. A two-phase encryption technique with key generation using different parameter is proposed. In the first-phase data is encrypted by imposing users’ public key and in the second phase, a private key of the base station (BS) is engaged for encryption. Finally, the superiority of the proposed scheme over existing scheme is proven through a comparative study based on the different features.
Non-orthogonal multiple access (NOMA) is considered as an effective technique for quenching the data rate demand in upcoming 5G wireless networks. This paper investigates the capacity of a multi-cell downlink network with two interfering cells over independent Rayleigh fading channels, where inter-cell interference is taken into account. Lastly, the predomination of the proposed NOMA-based scheme over conventional multiple access is observed through simulations.
Cooperative relaying strategy in Non-orthogonal multiple access (NOMA) is one of the most efficient techniques to increase the data reliability, enlarge the coverage area, and upgrade the spectral efficiency. This paper proposes amplify-and-forward (AF) relaying in cooperative systems using NOMA. The performance of AF and decode-and-forward relaying techniques in the considered system is provided through the Monte Carlo simulation results.
This paper comprehensively investigates the dynamics of user pairing and power allocation (UPPA) in non-orthogonal multiple access (NOMA). The focal point of this work is to explore the effects of UPPA on capacity and bit error rate (BER) of NOMA users, thereby understanding the tradeoffs involved when UPPA is performed. These tradeoffs facilitate the design of UPPA strategies to maximize system capacity and satisfy individual target data rates of users without exceeding their allowed BER upper bounds to meet the strict data reliability constraints. Data reliability is critical in NOMA and serves as bottleneck to its manifold capacity gains, as NOMA users are prone to significant interference. The existing UPPA strategies focusing on capacity maximization or user fairness completely neglect this extremely critical tradeoff. This paper provides extensive analysis and results of UPPA considering individual/sum capacity and BER of users. Results are summarized in the form of look-up tables, which facilitate swift selection of user pairs and power allocation factors. The process of performing UPPA by using the developed look up tables, such that both capacity and data reliability goals can be simultaneously achieved, is comprehensively explained in the end.
In this paper, we present the application of single user multiple input multiple output (SU-MIMO) to uplink (UL) non-orthogonal multiple access (NOMA) to enhance UL capacity. However, SU-MIMO NOMA produces inter-stream interference in addition to intra-pair interference, leading to performance degradation. Therefore, a novel UL SU-MIMO NOMA signal detection, combining minimum mean square error (MMSE) with dual-level iterative successive interference cancelation is proposed to mitigate the interference. Additionally, generalized dynamic power allocation is proposed at UL transmitters to ensure the capacity for NOMA over orthogonal multiple access (OMA) and the capability to overcome error floor phenomenon caused by fixed power allocation. A practical SIC scheme is also considered to create a more realistic scenario than the perfect SIC. The proposed system is evaluated in terms of capacity, throughput, error performance, and computational complexity. The results show that the proposed SU-MIMO based NOMA outperforms in capacity, throughput, and error performance at the same MMSE complexity order.
Non-Orthogonal Multiple Access (NOMA) is one of potential candidate multiple access technique to achieve high data rate communication in 5G cellular system. In NOMA, same non-orthogonal frequency resources are used together by exploiting channel gain differences and multiplexed the signal via superposition coding into power domain transmission. In order to perform NOMA system under uplink transmission, appropriate power allocation on user sides is mandatory. In this paper, we investigate BER performance of uplink NOMA transmission by proposing simple power allocation based on channel gain information
Non-orthogonal multiple access (NOMA) is recognized as a promising radio access technology for next generation wireless networks. In this paper, a novel full-duplex (FD) cooperative relaying scheme for a NOMA based system (termed FD-NOMA-VP) is proposed, where K similar gain near users and relay-aided N similar gain far users are distributed into different NOMA cluster. In each cluster, one near user is virtually paired (VP) with multiple far users over non-overlapping frequency bands. In FD-NOMA-VP, the near user directly communicates with the base station, whereas far users communicate via a dedicated FD relay, in each cluster. The performance of FD-NOMA-VP is studied comprehensively in terms of the ergodic sum capacity, outage probability, and outage sum capacity along with analytical derivations under both perfect and imperfect interference cancellation (IC) scenarios. The results demonstrate that FD-NOMA-VP shows significant performance gains compared to the conventional multiple access scheme under perfect IC, while the residual interference has a substantial impact on the performance gain under imperfect IC. In addition, a strong agreement between analytical and simulation results affirms the correctness of our analysis.
In this paper, a full-duplex (FD) non-orthogonal multiple access (NOMA) scheme for a cooperative relay sharing network (termed as FD-NOMA-RS) is presented, in which two source-destination pairs share a dedicated FD relay FD-R. Following the principle of uplink NOMA, both sources transmit their symbols to FD-R, forming a NOMA pair, by depending on their channel conditions with respect to FD-R. The FD-R then decodes these symbols and simultaneously transmits a superimposed composite signal to the destinations with a processing delay $\tau$ according to the principle of downlink NOMA. The ergodic sum capacity, outage probability and outage sum capacity of FD-NOMA-RS are investigated comprehensively along with analytical derivations, considering both perfect and imperfect interference cancellation. A simulation is conducted to corroborate the correctness of the analysis presented here. Moreover, the effectiveness of FD-NOMA-RS is demonstrated through analysis and simulation and then compared with that of its counterpart, the half-duplex system.
A coordinated direct and relay transmission is proposed using uplink non-orthogonal multiple access (NOMA) (termed as UP-NOMA). A two-user uplink NOMA scenario is considered, where a cell-center user directly communicates with a base station (BS), whereas a cell-edge user needs the assistance of a half-duplex decode-and-forward relay to communicate with the BS. The ergodic sum capacity of UP-NOMA is analyzed under both perfect and imperfect successive interference cancellation. The superiority of UP-NOMA over conventional multiple access is demonstrated through simulation and analysis.
This paper evaluates the performance of a virtual user pairing scheme that efficiently utilizes the spectrum of unpaired users in non-orthogonal multiple access (NOMA), termed as VP-NOMA. The scheme aims at utilizing the frequency bands of those users which remain unpaired due to the non-uniform distribution of users in a cellular area. We consider a case where the cell edge users are more than the cell center users, so that complete one-to-one correspondence does not exist between all cell center and cell edge users to be accommodated/paired using conventional NOMA (C-NOMA) user pairing. Thus, some cell edge users remain unpaired, and are served using conventional multiple access (OMA) schemes. In such scenario, VP-NOMA pairs a single cell center user with two or more clustered (closely located) cell edge users over non-overlapping frequency bands, thus enabling the cell center user to efficiently use the frequency bands of these previously unpaired cell edge users. Performance of VP-NOMA in terms of ergodic sum capacity (ESC), outage probability (OP), and outage sum capacity (OSC), is analyzed through comprehensive mathematical derivations and simulations for a generalized system model. Moreover, the mathematical analysis is validated through close concordance between analytical and simulation results of ESC, OP, and OSC.
We present a novel interference free dual-hop cooperative spectrum sharing protocol in cognitive radio networks exploiting spatial modulation (SM) at both primary transmitter (PT) and secondary transmitter (ST). A ST equipped with multi-antenna acts as a half-duplex decode-and-forward relay for the primary system. During phase-1, SM is invoked at PT, while ST keeps silent. The information bit stream of PT is mapped into two different sets: the M-ary phase shift keying (M-PSK)/M-ary quadrature amplitude modulation (M-QAM) bits and the antenna index. The ST then exploits iterativemaximum ratio combining (i-MRC) technique to de-map the block of information bits, transmitted by PT. During phase-2, ST forwards the primary data by activating only one antenna based on its own secondary data exploiting the concept of SM. The PT’s data is then retrieved at the primary receiver (PR) and the secondary receiver (SR) recover its own desired data by detecting only the transmit antenna indices of ST using i-MRC. As a result, mutual interference between primary and secondary systems is avoided and interference cancellation techniques at the PR and SR are no longer needed. In the proposed protocol, the primary user does not need to lease its spectrum or time slots to the secondary user in exchange for cooperation. Moreover, power of ST does not need to be distributed for primary and secondary transmission simultaneously during phase-2. The simulation and analytical results are presented to show effectiveness of the proposed protocol compared to conventional spectrum leasing and superposition coding based overlay protocols.
Non-orthogonal multiple access (NOMA) is a promising candidate to be a part of the 5G wireless communications framework. This paper proposes a generalized M-users pairing scheme for a NOMA system. The goal of the proposed scheme is to make sure that maximum possible number of users are paired in a user pair. Minimum allowed channel gain difference between any two paired users is considered as the criteria for pairing the users. It is shown through simulations that the proposed scheme can efficiently make users pairs from a set of N users.
Among the key technologies that have been developed for efficient transmission for 5G, are spatial modulation (SM) and non-orthogonal multiple access (NOMA). In SM, multiple transmission antenna is modulated as information in order to increase capacity. On the other hand, NOMA allows to share the same frequency resources at the same time. Obviously, combination of these two techniques offers a new accomplishment for wireless transmission. In this paper, we develop a new technique to combine SM and NOMA for uplink transmission. A hybrid detection scheme is introduced in order to estimate information in receiver side. In transmitter, we set maximum transmission power for near-end user (NEU) and lower transmission power for far-end user (FEU). The main idea of our proposed detection scheme is to perform maximum receive ratio combining (MRRC) to obtain antenna index and then estimate the corresponding symbol for NEU. Afterwards, we apply successive interference cancellation (SIC) to the total received signal in order to eliminate NEU's signal. Finally, maximum likelihood estimation (MLE) is applied to the remaining signal to estimate FEU's antenna index and transmitted symbol. As the result, we also present the bit error rate (BER) comparison and achievable user and system transmission bits.
Non-orthogonal multiple access (NOMA) acquires capacity improvement by utilizing channel gain difference between paired users. Multiple users are multiplexed into power domain with same frequency, time, as well as spreading code therefore capacity improvement can be obtained. In NOMA system, user pairing scheme plays important role because of high association with inter-set interference and capacity improvement. Thus, we propose user pairing schemes based on Channel Quality Indicator (CQI) for sum capacity maximization over Uplink (UL) NOMA system. We also propose hybrid CQI scheme, hence interset interference toward last sequences CQI indexes of strong set users can be reduced while the extreme poor level of CQI users also can be handled in the same time. For result, we provide mathematical analysis of our proposed uplink (UL) NOMA system with two paired user for both perfect and imperfect SIC. Then, the cell capacities of proposed user pairing schemes under perfect SIC as well as imperfect SIC are analyzed and compared with orthogonal multiple access (OMA). Finally, data rate as well as inter-set interference impact of proposed user pairing schemes in strong set users are also evaluated.
In this paper, we propose a novel hybrid detection scheme for combination of spatial modulation (SM) and non-orthogonal multiple access (NOMA) in uplink transmission. We prove that combination of SM and NOMA is theoretically applicable in wireless. The main idea is to employ maximum receive ratio combining (MRRC) to decode near-end user (NEU) signal and maximum likelihood estimation (MLE) to decode far-end user (FEU) signal
Non-Orthogonal Multiple Access (NOMA) is one of potential candidate radio access for 5G cellular system. Multiple Input Multiple Output (MIMO) is widely known as a key technology for previous cellular generation. Thus, combining both MIMO and NOMA is promising solution to obtain multiple fold capacity improvement. However, combining MIMO to NOMA system will cause inter-stream interference in addition to inter-user interference for each NOMA user. Therefore, robust and low complexity decoding technique is required in order to combat MIMO-NOMA interference. In this paper, we propose to utilize MMSE as decoding technique for combating MIMO-NOMA interference in receiver. We also propose design of practical SIC for MIMO-NOMA processing instead of perfect SIC for more practical study. Finally, bit error rate (BER) result will be evaluated and compared with the other decoding techniques
For example, an uplink cellular scenario with a BS and two users UE1 and UE2. Let's say, two users transmit to the BS at the same time via orthogonal channels. Is it possible to decode signal of a user at BS without any interference from another user? Can anyone please provide an answer with appropriate references?
We propose two novel cooperative spectrum sharing (CSS) protocols by using time-switching and power-splitting based energy harvesting (EH), namely CSS-TSP and CSS-PSP respectively. The considered system consists of a set of energy constrained secondary transmitters (STs) that cooperate with the primary user (PU) to forward its symbol. All STs rely on the harvested energy from the source signal to forward the primary symbol. In exchange of cooperation, one of the STs behaving as the best EH decode-and-forward relay (ST br) gets channel access simultaneously with the PU according to the non-orthogonal multiple access. Two ST br selection strategies namely ST br selection based on harvested energy in current block of time and ST br selection based on harvested energy from current plus previous blocks of time have been proposed. The distributed nature of the ST br selection to forward the primary symbol increases the network lifetime. We have investigated the achievable sum data rate/ throughput of both CSS-TSP and CSS-PSP. Moreover, the optimal EH ratio that maximizes the sum data rate of both protocols is also investigated numerically.
Non-orthogonal multiple (NOMA) access using successive interference cancellation and cognitive radio are two promising techniques for enhancing the spectrum efficiency and utilization for future wireless communication systems. This paper presents a NOMA-based cooperative hybrid spectrum sharing protocol for cognitive radio networks. A two phase decode-and- forward (DF) relaying scheme in a multi-relay scenario is considered. Each secondary transmitter is grouped into one of the two clusters: a non-cooperative cluster (NCC) and a cooperative cluster (CC). The cluster head (CH) of the CC working as the best DF relay for the primary system is permitted to transmit its own signal superimposed on the primary signal using a NOMA approach in exchange for cooperation. On the other hand, the CH of the NCC transmits in parallel with the primary system satisfying a predefined peak transmit power and peak interference power constraints that guarantee a given primary quality of the service requirement. It is demonstrated that the performances of both the primary and secondary systems increase with the increasing number of secondary nodes. The simulation and theoretical results affirm the efficacy of the proposed protocol compared to the traditional overlay and underlay models in terms of the outage probability and the ergodic capacity. @springer nature shared link: http://rdcu.be/vbjc
This paper addresses the power allocation issue in non-orthogonal multiple access (NOMA) systems. In NOMA, multiple paired users can simultaneously utilize the frequency bands of each other such that the message signals of all these users are superimposed by the transmitter by allocating different powers to all users. As the paired users communicate over the same frequency band, high amount of interference is faced by them. Thus, some paired users perform successive interference cancellation to decode and cancel the signals of other users while some users recover their signals by simply treating signals of other users as noise. Inefficient power allocation may increase the interference significantly, which causes degradation in data recovery at the user ends. We propose a novel power allocation strategy that can optimize the system ergodic sum capacity while minimizing the mutual interference between the paired users. It is shown through simulations that the proposed scheme outperforms conventional power allocation in terms of bit error rates at the user ends with negligible effect on the system ergodic sum capacity.
Non-orthogonal multiple access (NOMA) has attracted a significant attention to the research community as a potential candidate for 5G or future radio access. This paper presents a NOMA-based cooperative network where a transmitter considered as a base station communicates simultaneously with two users treating as a far user and a near user via the help of a half-duplex decode-and-forward relay. We investigate the outage probability and the outage capacity of the proposed network over independent Rayleigh slow fading channels. Closedfrom expressions of the outage probabilities are derived for both users. Approximate outage capacity of the users are also investigated at high signal to noise ratio regime. It has been shown that the proposed cooperative NOMA can achieve superior performance compared to the non-cooperative NOMA in terms of outage probability. The tightness between the simulation and theoretical results confirms the efficiency of the proposed protocol. http://www.tandfonline.com/eprint/jpp8bzjU4hJRBSS2ZU5I/full
This paper presents an outage analysis of a cooperative relaying scheme over flat Rayleigh and Nakagami-$m$ fading channels. In the proposed scheme, secondary transmitters cooperatively relay the primary traffic. Each secondary transmitter, equipped with multiple antennas, is divided into one of the two clusters: a cooperative cluster (CC) and a non-cooperative cluster (NCC). Cluster head (CH) of the CC will be selected as a best decode-and-forward (DF) relay and will forward the primary information. Results show that the proposed scheme outperforms both non-cooperative, conventional single-antenna systems and random relay selection schemes in terms of outage probability. In each case, theoretical results are verified with Monte-Carlo simulation results.
We propose and investigate a dual-hop cooperative relaying scheme using non-orthogonal multiple (NOMA) access (termed NOMA-RS) where two sources communicate with their corresponding destinations in parallel over the same frequency band via a common relay. In this scheme, after receiving symbols transmitted in parallel by both sources with different allocated powers, the relay forwards a superposition coded composite signal using NOMA to the destinations. One of the main benefits of NOMA-RS is that multiple (two) sources can share the same relay, unlike the previous works. Through the simulations and mathematical analysis, we demonstrate the effectiveness of the proposed protocol in terms of ergodic sum capacity by considering perfect and imperfect successive interference cancellation.
In this paper, we have proposed a novel two-phase cooperative spectrum sharing protocol on the basis of Alamouti space time block coded (STBC) non-orthogonal multiple access. The network scenario comprising of a primary transmitter-receiver pair and a secondary transmitter-receiver pair. During the first two time slots, the primary transmitter transmits two STBC primary symbols to the cooperative secondary transmitter. The secondary transmitter acting as a decode-and-forward relay for the primary system is allowed to transmit its own secondary signal superposed on the STBC coded primary signal in exchange of cooperation during the next two time slots. Simulation and theoretical results demonstrate the efficacy of the proposed protocol compared to the conventional super positing coding based overlay scheme in terms of the outage probability and the ergodic capacity.
Non-orthogonal multiple access (NOMA) has attracted significant attention in the research community as a potential radio access technology for future wireless networks. In this work, we propose a two-phase cooperative decode-and-forward (DF) relaying scheme based on Alamouti (2by�1 multiple-input single-output mode) space-time block coded non-orthogonal multiple access (STBC-NOMA). Closed-form solutions for ergodic sum capacity and outage probability of the proposed scheme are analyzed over independent Rayleigh fading channels. Asymptotic approximations for ergodic sum capacity, outage probability and outage sum capacity at high signal-to-noise ratio regime are also provided. It has been pointed out that the proposed cooperative relaying system (CRS) using STBCNOMA can attain significant performance gains compared to the conventional CRS using NOMA and the traditional DF relaying schemes. It is also demonstrated that the relay position between the transmitter and receiver has significant impact on the performance of the proposed protocol. In addition, the proximity between analytical and simulation results confirms the efficiency of the proposed protocol.