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Wideband CDMA For Third Generation Mobile Communications: Universal Personal Communications
Abstract
From the Publisher:Here's an in-depth, comprehensive study of the developmental trends and practical design, planning, and deployment issues associated with wideband CDMA technology. Prepared by two leading authorities in the field, this book evaluates wideband CDMA as an effective third generation technology option, and gives you a clear picture of the various wideband CDMA standardization activities currently underway worldwide. Wireless system engineers responsible for designing wideband CDMA systems will appreciate the book's depth of coverage as it compares a wide array of CDMA design techniques and examines how each affects system performance. The book also describes how third generation system applications will impact radio access system design and... Compares and contrasts major wideband CDMA standardization proposals, including FRAMES, WCDMA in 3GPP, CDMA2000, and IS-95B Identifies and describes various air interface access schemes for third and fourth generation mobile communications systems Analyzes wideband CDMA performance in varying radio environments, and presents simulation results Discusses the integration of the GSM core network with wideband CDMA 1 Examines the basic principles of CDMA, including IS-95B air interference, and includes details on EDGE/136HS
... UMTS forum[7]. The common air-interface enables, for the first time, world-wide compatibility of mobile systems as shown inFigure 2.Figure 2The information bit rate versus the user mobility for different wireless communication systems[9]. ...
... Wideband Code Division Multiple Access (WCDMA) technology has emerged as the most widely adopted 3G air interference. Its specification has been created in the 3 rd Generation Partnership Project (3GPP), which is the joint standardization project of the standardization bodies from Europe, Japan, Korea, the USA and China[9,10]. WCDMA is considered to be wideband technologies based on the direct sequence spread spectrum transmission scheme, where user information bits are spread over a wide bandwidth by multiplying the user data with quasi-random bits called chips derived from CDMA spreading codes. In order to support very high bit rates (upto 2 Mbps), the use of a variable spreading factor and multicode connection is supported. ...
... There are many areas varying from First Generation(1G)to Fourth Generation (4G). The recent trends in the Research and Development are in the cutting edge technologies such as IS95,GSM,CDMA,CDMA 2000,WCDMA,MIMO,SDR etc and the commonly employed different air interface techniques such as TDMA, FDMA ,WCDMA etc.[1,[7][8][9][10][11][12][13][14][15][16]IJCEM International Journal of Computational Engineering & Management, Vol. 12, April 2011 ISSN (Online): 2230-7893 www.IJCEM.org IJCEM www.ijcem.org ...
One of the most challenging issues facing deployment of 3G technology is how to make the network architectures compatible with each other. New signaling techniques are being designed specially to enhance today's 2G networks, deliver unprecedented functionality for 3G, and successfully derive the future generation of wireless systems, thus delivering immediate and long term benefits to subscribers. With the architecture of each generation of wireless devices addressed in the development of advance technologies, subscribers can easily evolve their systems without additional network modification, significantly reducing cost and implementing time. The present paper provide the in depth review of Data Communication using Pulse Shaping techniques in wireless signal processing approach.
... Two main mechanisms for energy conservation at the MAC layer are power control and sleep cycling. Power control loops for various cellular telephony systems have been studied extensively in the past and are used in commercially deployed systems [Ojanperä andPrasad 1998, Lee 1989]. They are especially important in ad-hoc networks due to the higher levels of interference. ...
... Power control loops for various cellular telephony systems have been studied extensively in the past and are used in commercially deployed systems [Ojanperä andPrasad 1998, Lee 1989]. The related literature is vast, and we will not attempt a complete survey. ...
... The power control loop mechanism we present is different from prior work in several ways. Our focus is on ad-hoc networks, not cellular systems as in references [Ojanperä and Prasad 1998, Lee 1989, Narendran et al. 1997, Kwon and Gerla 1999. We allow each node to choose different transmit power levels for different neighboring nodes. ...
Abstract Mobile ad-hoc networking involves peer-to-peer communication,in a network with a dynamically changing topology. Energy efficient communication,in such a network is more challenging than in cellular networks since there is no centralized arbiter such as a base station that can administer power management. In this report, we examine energy efficient networking protocols for ad-hoc networks. We propose MAC (media access control) and routing protocols that significantly impact the energy conservation and throughput of ad-hoc networks. We introduce a comprehensive,simulation infrastructure consisting of group mobility, group communication and terrain blockage models. We employ these models to evaluate a power control loop, similar to those commonly found in cellular CDMA networks, for ad-hoc wireless networks. We show that this power control loop reduces energy consumption,per transmitted byte by 10 - 20%. Furthermore, we show that it increases overall throughput by 15%. It performs significantly better in the new proposed simulation models than in simulations with random,node mobility and communication,models. We also discuss sleep cycle and low energy routing mechanisms. 1
... Owing to the rapid increase in mobile radio communications, new frequency ranges and novel radio interface techniques will be employed in the near future [2]. In Europe, the third generation mobile systems are developed in the UMTS (Universal Mobile Telecommunications System) framework [3]. UMTS will operate at around 2 GHz frequency range. ...
... Therefore, advanced wideband techniques will be employed in future radio networks. The next generation radio systems are intelligent; they adapt to the radio propagation environment by using advanced radio interface techniques, e.g. the Rake receiver in UMTS [3], OFDM (Orthogonal Frequency Division Multiplexing) [4] in HIPERLAN, and by adaptive antennas [5]. ...
... Autocorrelation of the high-speed code generator output waveform with f chip = 166.7 MHz is shown in Fig. 2-3. The waveform was sampled with a digital oscilloscope, and the autocorrelation was calculated off-line by (2)(3). The envelope of the spectrum of a signal with 53.75 MHz chip rate upconverted to 5.3 GHz is shown in Fig. 2-4. ...
This thesis discusses the development of micro- and millimeterwave wideband radio channel measurement and modeling techniques for future radio networks. Characterization of the radio channel is needed for radio system, wireless network, and antenna design. A radio channel measurement system was designed for 2.154, 5.3 GHz and 60 GHz center frequencies, and completed at the two lower frequencies. The sounder uses a pseudonoise code in the transmitter. In the receiver, first a sliding correlator, and later direct digital sampling, where the impulse response is detected by digital post processing, were realized. Certain implementation questions, like link budget, effects of phase noise on impulse response and direction of arrival estimation, and achievable performance using the designed concept, are discussed. Measurement campaigns included in this thesis were realized at 5.3 GHz frequency in micro- and picocells. A comprehensive measurement campaign performed inside different buildings was thoroughly analyzed. Propagation mechanisms were studied and empirical models for both large scale fading and multipath propagation were developed. Propagation through walls, diffraction through doorways, and propagation paths outside the building were observed. Pathloss in LOS was lower than the free space pathloss, due to wave guiding effects. In NLOS situation difference in the pathloss models in different buildings was significant. Behavior of the spatial diversity was estimated on the basis of spatial correlation functions extracted from the measurement data; an antenna separation of a fraction of a wavelength gives sufficient de-correlation for significant diversity gain in indoor environments at 5.3 GHz in NLOS. Helsinki University of Technology Radio Laboratory publications. Report S, ISSN 1456-3835; 244
... Code division multiple access (CDMA) is a radio communication technique to allow multiple users to share the same spectrum simultaneously. It is the most investigated application of spread spectrum techniques [1] . In DS-CDMA (directsequence code division multiple access), the narrowband message is multiplied by a large bandwidth signal, which is called the spreading signal. ...
... In DS-CDMA (directsequence code division multiple access), the narrowband message is multiplied by a large bandwidth signal, which is called the spreading signal. The spreading signal is generated by convolving a pseudo-noise (PN) code with a chip waveform whose duration is much smaller than the symbol duration [2], [1]. By assigning different code sequences to each user, it is possible to allow many users to share the same channel and frequency simultaneously [1]. ...
... The spreading signal is generated by convolving a pseudo-noise (PN) code with a chip waveform whose duration is much smaller than the symbol duration [2], [1]. By assigning different code sequences to each user, it is possible to allow many users to share the same channel and frequency simultaneously [1]. However an approximate orthogonality constraint on the code sequence is employed to guarantee acceptable performance [2]. ...
In this paper, we present a study of the bit error rate (BER) performance of DS-CDMA system over a frequency selective multipath Rayleigh fading channel with perfect power
control. The standard Gaussian approximation (SGA) is used to evaluate the BER performance for the DS-CDMA. The performance of DS-CDMA over the frequency selective fading channel is examined with the varying numbers of multipath components, varying numbers of interfering cells, and various process gain. From the simulation results we have seen that the BER performance is affected by these parameters.
... The multiple access techniques have been widely used in mobile communications, e.g., frequency division multiple access (FDMA) [1], time division multiple access (TDMA) [2], code division multiple access (CDMA) [3] and orthogonal frequency division multiple access (OFDMA) [4]. All these multiple access schemes allocate the data of different users to orthogonal resources in order to avoid multiuser interference. ...
... Consequently, users only broadcast θ p k to neighboring users. 3 For a connected graph that each user has at least one neighbor, after running several consensus iterations, all users reach consensus on the global message, i.e., ρ Np k (s n j ) = µ s n j →φ n j (s n j ) 1/K , ∀k [38]. However, when exchanging packets between users, inter-user links may suffer from additive noise, which causes the variance of θ k growing unbounded. ...
The rapid development of the mobile communications requires ever higher spectral efficiency. The non-orthogonal multiple access (NOMA) has emerged as a promising technology to further increase the access efficiency of wireless networks. Amongst several NOMA schemes, the sparse code multiple access (SCMA) has been shown to be able to achieve better performance. In this paper, we consider a downlink MIMO-SCMA system over frequency selective fading channels. For optimal detection, the complexity increases exponentially with the product of the number of users, the number of antennas and the channel length. To tackle this challenge, we propose near optimal low-complexity iterative receivers based on factor graph. By introducing auxiliary variables, a stretched factor graph is constructed and a hybrid belief propagation (BP) and expectation propagation (EP) receiver, named as `Stretch-BP-EP', is proposed. Considering the convergence problem of BP algorithm on loopy factor graph, we convexify the Bethe free energy and propose a convergence-guaranteed BP-EP receiver, named as `Conv-BP-EP'. We further consider cooperative network and propose two distributed cooperative detection schemes to exploit the diversity gain, namely, belief consensus-based algorithm and Bregman alternative direction method of multipliers (ADMM)-based method. Simulation results verify the superior performance of the proposed Conv-BP-EP receiver compared with other methods. The two proposed distributed cooperative detection schemes can improve the bit error rate performance by exploiting the diversity gain. Moreover, Bregman ADMM method outperforms the belief consensus-based algorithm in noisy inter-user links.
... The transmitted symbols pass through root raised cosine shaping filters with a roll-off factor of α = 0.5 and FTN packing factor of τ = 0.8. 3 The number of ISI taps imposed by FTN signaling is assumed to be L = 10. The channel obeys uncorrelated Rayleigh fading whose impulse response is generated according to Jake's model. ...
... We have compared the BER performance of the specifically designed LDPC code and of the rate-2/5 CCSDS standard LDPC code having a length of 10240 for our FTN system associated with τ = 0.8. As a result, 0.1dB performance gain can be observed for the specifically designed LDPC code, even though its code rate is higher than that of the CCSDS code.3 We assume the same shaping filter is employed for different resource elements at the transmitter side. ...
The sparse code multiple access (SCMA) is a promising candidate for bandwidth-efficient next generation wireless communications, since it can support more users than the number of resource elements. On the same note, faster-than Nyquist (FTN) signaling can also be used to improve the spectral efficiency. Hence in this paper, we consider a combined uplink FTN-SCMA system in which the data symbols corresponding to a user are further packed using FTN signaling. As a result, a higher spectral efficiency is achieved at the cost of introducing intentional inter-symbol interference (ISI). To perform joint channel estimation and detection, we design a low complexity iterative receiver based on the factor graph framework. In addition, to reduce the signaling overhead and transmission latency of our SCMA system, we intrinsically amalgamate it with grant-free scheme. Consequently, the active and inactive users should be distinguished. To address this problem, we extend the aforementioned receiver and develop a new algorithm for jointly estimating the channel state information, detecting the user activity and for performs data detection. In order to further reduce the complexity, an energy minimization based approximation is employed for restricting the user state to Gaussian. Finally, a hybrid message passing algorithm is conceived. Our Simulation results show that the FTN-SCMA system relying on the proposed receiver design has a higher throughput than conventional SCMA scheme at a negligible performance loss.
... The multiple access techniques have been widely used in mobile communications, e.g., frequency division multiple access (FDMA) [1], time division multiple access (TDMA) [2], code division multiple access (CDMA) [3] and orthogonal frequency division multiple access (OFDMA) [4]. All these multiple access schemes allocate the data of different users to orthogonal resources in order to avoid multiuser interference. ...
... Consequently, users only broadcast θ p k to neighboring users. 3 For a connected graph that each user has at least one neighbor, after running several consensus iterations, all users reach consensus on the global message, i.e., ρ Np k (s n j ) = µ s n j →φ n j (s n j ) 1/K , ∀k [38]. However, when exchanging packets between users, inter-user links may suffer from additive noise, which causes the variance of θ k growing unbounded. ...
The rapid development of the mobile communications requires ever higher spectral efficiency. The non-orthogonal multiple access (NOMA) has emerged as a promising technology to further increase the access efficiency of wireless networks. Amongst several NOMA schemes, the sparse code multiple access (SCMA) has been shown to be able to achieve better performance. In this paper, we consider a downlink MIMO-SCMA system over frequency selective fading channels. For optimal detection, the complexity increases exponentially with the product of the number of users, the number of antennas and the channel length. To tackle this challenge, we propose near optimal low-complexity iterative receivers based on factor graph. By introducing auxiliary variables, a stretched factor graph is constructed and a hybrid belief propagation (BP) and expectation propagation (EP) receiver, named as `Stretch-BP-EP', is proposed. Considering the convergence problem of BP algorithm on loopy factor graph, we convexify the Bethe free energy and propose a convergence-guaranteed BP-EP receiver, named as `Conv-BP-EP'. We further consider cooperative network and propose two distributed cooperative detection schemes to exploit the diversity gain, namely, belief consensus-based algorithm and Bregman alternative direction method of multipliers (ADMM)-based method. Simulation results verify the superior performance of the proposed Conv-BP-EP receiver compared with other methods. The two proposed distributed cooperative detection schemes can improve the bit error rate performance by exploiting the diversity gain. Moreover, Bregman ADMM method outperforms the belief consensus-based algorithm in noisy inter-user links.
... Cellular system: The cellular system is categorized according to the multiple access scheme or frequency gain process [6][7][8]. Frequency division multiple access (FDMA) and time division multiple access (TDMA) are used in GSM-based systems, e.g., UMTS, in a mixed form. In FDMA, frequencies are assigned to users, and therefore, the larger the number of users in the FDMA system, the larger the number of available frequencies must be. ...
... In other words, in order for a new cluster head to achieve the desirable SN IR, the system has to consider both the load of the used base station and the load of the neighboring cells whose load plays an externality role for the used base station. In a multi-cell CDMA system, the received SN IR for cluster head i at base station k equals (see [9], Chapter 8): (8) where N c is the number of sectors in each cell, P 0 is the received power of each cluster head at the used base station (due to the power control mechanism), G 0 is the spreading gain, η is the background additive noise in the spread bandwidth and P r in (k) and P r ex (k) are the internal (cluster heads connected to base station k) and external (all other cluster heads) interference terms received at the base station k, respectively. A cell is typically sectorized into three sectors to achieve rapid frequency reuse (see [14] for optimum sectorization for the CDMA system). ...
For practical deployment of wireless sensor networks (WSN), WSNs construct clusters, where a sensor node communicates with other nodes in its cluster, and a cluster head support connectivity between the sensor nodes and a sink node. In hybrid WSNs, cluster heads have cellular network interfaces for global connectivity. However, when WSNs are active and the load of cellular networks is high, the optimal assignment of cluster heads to base stations becomes critical. Therefore, in this paper, we propose a game theoretic model to find the optimal assignment of base stations for hybrid WSNs. Since the communication and energy cost is different according to cellular systems, we devise two game models for TDMA/FDMA and CDMA systems employing power prices to adapt to the varying efficiency of recent wireless technologies. The proposed model is defined on the assumptions of the ideal sensing field, but our evaluation shows that the proposed model is more adaptive and energy efficient than local selections.
... The last section gives a perspective of future trends in transceiver front-end design for 3G systems. In 1985 the ITU (International Telecommunications Union) started work on 3G systems unter the acronym FPLMTS (Future Public Land Mobile Telephone System ) which was later renamed to IMT-2000 (International Mobile Telecommunications) [1]. The key factors and main objectives for 3G systems include worldwide coverage and roaming incorporating a satellite component, capacity and capability to serve more than 50% of the population [2] , multimedia service capability, high-speed access, low-cost operation, and integration of residential, office, and cellular services into a single system based on one piece of user equipment. ...
... From the above mentioned items the basic demands for data throughput over the air interface were identified as 144 kbps (preferably 384 kbps) with full coverage and high mobility of the user equipment (UE) and up to 2 Mbps for low mobility and coverage limited to high traffic areas. These bit rates were harmonized to the ISDN (Integrated Services Digital Network) 2B+D (144 kbps), H0 (384 kbps), and H12 (1920 kbps) chan- nels [1]. The general vision of 3G systems, is that they should basically ensure communications from anywhere to anybody at any time. ...
The standardization phase for wideband CDMA systems like UMTS is running towards its final-ization. As is typical for mobile communication systems standardizing, sufficient RF performance has been as-sumed and most efforts have been put to baseband issues. This is especially true for the pocket phone transceivers the RF part of which is, although its baseband part is much more complex in terms of number of devices, still the bottleneck of the entire system. In the RF concept engineering of today's commercial products with their short time-to-market requirements, a prediction of the needed RF performance by using RF system simulation is meanwhile indispensable. This is in particular the case with third generation (3G) wireless systems which, from the RF design point of view, are quite different from 2G TDMA/FDMA systems due to the fact that the users are now separated in the power domain (using codes) rather than being separated in the time and/or frequency do-main. The present work gives an insight how to derive the transceiver requirements of 3G mobiles in terms rec-ognizable by RF designers.
... A RAKE receiver (seeFigure 1) is used for wideband code division multiple access systems (WCDMA) [6]. In a WCDMA system all the users transmit in the same band simultaneously. ...
... This basic principle of a RAKE receiver is shown inFigure 1. For a more detailed description, see [6], ...
An energy-efficient architecture is vital for the next generation of mobile phones. The battery operated nature of these systems requires them to be designed and operated in a highly energy-efficient manner to maximize the battery lifetime. In this paper the characteristics (in terms of power consumption and quality) of a RAKE receiver in combination with a turbo decoder are considered. Important parameters are selected and their influences on the energy consumption and quality are investigated by means of simulations.
... Code Division Multiple Access (CDMA) has become the standard for the third generation of Global System for Mobile (GSM) communications and American cellular systems [1]. Also, optical CDMA systems have become an alternative multiple access for fiber optics and optical wireless systems [2]- [4]. ...
... In addition, in [14], we developed lower and upper bounds for the sum capacity of a binary synchronous 1 Codes for Overloaded Wireless systems 2 Codes for Overloaded Optical systems 3 CDMA under noiseless environment conditions and the assumption that users are jointly dependent. These sum capacity bounds suggest that there exists a linear region with respect to the number of users far beyond the orthogonal Walsh codes (n = m where m is the chip rate), i.e., errorless overloaded (n ≫ m) codes do exist. ...
In this paper, we explore the mystery of synchronous CDMA as applied to wireless and optical communication systems under very general settings for the user symbols and the signature matrix entries. The channel is modeled with real/complex additive noise of arbitrary distribution. Two problems are addressed. The first problem concerns whether overloaded error free codes exist in the absence of additive noise under these general settings, and if so whether there are any practical optimum decoding algorithms. The second one is about the bounds for the sum channel capacity when user data and signature codes employ any real or complex alphabets (finite or infinite). In response to the first problem, we have developed practical Maximum Likelihood (ML) decoding algorithms for overloaded CDMA systems for a large class of alphabets. In response to the second problem, a general theorem has been developed in which the sum capacity lower bounds with respect to the number of users and spreading gain and Signal-to-Noise Ratio (SNR) can be derived as special cases for a given CDMA system. To show the power and utility of the main theorem, a number of sum capacity bounds for special cases are simulated. An important conclusion of this paper is that the lower and upper bounds of the sum capacity for small/medium size CDMA systems depend on both the input and the signature symbols; this is contrary to the asymptotic results for large scale systems reported in the literature (also confirmed in this paper) where the signature symbols and statistics disappear in the asymptotic sum capacity. Moreover, these questions are investigated for the case when not all users are active. Furthermore, upper and asymptotic bounds are derived and numerically evaluated and compared to other derivations. Comment: 71 pages, submitted to IEEE Trans. on Information Theory
... The information is spread over a band of approximately 5 MHz. This wide bandwidth has given rise to the name Wideband CDMA or WCDMA.[8][9]The future mobile systems should support multimedia services. ...
... In a physical channel, these transitions can be smoothed, depending on the filters implemented in transmission. In fact, the use of a filter plays an important part in a communications channel because it is effective at eliminating spectral leakage, reducing channel width, and eliminating interference from adjacent symbols (Inter Symbol Interference, ISI)[1][2][3][4][5][6][7][8][9].Transmitting a signal at high modulation rate through a band-limited channel can create intersymbol interference. As the modulation rate increases, the signal's bandwidth increases. ...
The goal for the Third Generation (3G) of mobile communications system is to seamlessly integrate a wide variety of communication services. The rapidly increasing popularity of mobile radio services has created a series of technological challenges. One of this is the need for power and spectrally efficient modulation schemes to meet the spectral requirements of mobile communications. Pulse shaping plays a crucial role in spectral shaping in the modern wireless communication to reduce the spectral bandwidth. Pulse shaping is a spectral processing technique by which fractional out of band power is reduced for low cost, reliable , power and spectrally efficient mobile radio communication systems. It is clear that the pulse shaping filter not only reduces inter-symbol interference (ISI), but it also reduces adjacent channel interference. The present paper deals with critical analysis of pulse shaping in wireless communication.
... In future work, the scope will be extended to a more global view, including the possibilities at the base station.Figure 1 shows the combination of a rake receiver and a turbo decoder. The rake receiver is used for wideband code division multiple access systems (WCDMA) [8]. In a WCDMA system all the users transmit in the same band simultaneously. ...
... Each recognized path element is correlated with a code in a finger to retrieve the original signal. This basic principle of a rake receiver is shown inFigure 2. For a more detailed description, see [8], [13]. The soft output signal of the rake receiver is a signed value. ...
Energy efficiency is vital for a mobile terminal. In this paper we investigate how to choose the right parameter settings at run-time so that the energy consumption is minimized while satisfying the required level of service. To use a real world example, the energy consumption of a third generation telephone WCDMA downlink receiver with turbo decoding forward error correction is considered. A trade-off is made between the number of fingers of a rake receiver and the number of iterations of the turbo decoder. A simulation environment is constructed to simulate the system. In this paper we present graphs, with which the trade-off can be easily made.
... A RAKE receiver (seeFigure 1) is used for Wideband Code Division Multiple Access systems (WCDMA) [4]. In a WCDMA system all the users transmit in the same band simultaneously. ...
... A RAKE receiver has multiple fingers to correlate the received signals from different paths with different delays, and combines the results of the different paths to construct one output signal. For a more detailed description of a RAKE receiver, see [4, 7]. ...
This paper presents a control system that adapts a WCDMA receiver at run-time to minimize the energy consumption while providing an adequate Quality of Service (QoS). The adaptation is done at run-time, because of the dynamic environment of a mobile receiver. Simulations show that run-time adaptation to the environment decreases the energy consumption of a receiver and also improves other QoS parameters, such as a higher throughput and a lower frame error rate.
... Une comparaison entre les trois membres de la famille des étalements de spectre est présentée dans la figure (I.4). Il est construire une méthode hybride de modulation [10].Bien que ceci puisse être utile dans être avantageux ou pas. ...
qCette thèse porte sur la minimisation du taux d’erreur lors de la réception au sein d'un système de transmission de données. Des problèmes d'accès au canal dans les protocoles large bande de type WCDMA (Wideband Code Division Multiple Access) -Multiplexage à large bande par code- sont toujours présent du fait que les applications dans le domaine des communications numériques deviennent de plus en plus complexes et diversifiées dont l’apparition du terme turbo-communication en témoigne.
Techniquement, la turbo-communication consiste en une adaptation du processus de décodage itératif appelé turbocodes.
L’apparition des systèmes de turbo-communications, communément appelés turbo-récepteurs a fait preuve de sa capacité de transmettre un flux importants d’information sauf que le taux d’erreurs était d’autant plus important que le flux augmente, ainsi il est devenu indispensable d’introduire des techniques de minimisation d’erreurs pour atteindre les performances aujourd'hui exigées en terme de qualité de transmission.
Des architectures matérielles dédiées implantant ces systèmes ont étaient développées par plusieurs équipes de recherches scientifiques et avaient déjà vu le jour dans des applications industrielles.
A titre d’exemple, dans une chaîne de transmission radio mobile, le codage constitue une opération indispensable et par conséquent, des erreurs de transmission sont très probables. Ainsi, et afin de minimiser la probabilité d’erreur pour optimiser les performances du système à la réception, on applique des codes correcteurs d’erreur.
Dans ce travail nous avons appliqué le code de Hamming comme codes en blocs, le code convolutionnel et le turbocode.
Nos résultats montrent que l’application du code convolutionnel donne des résultats meilleurs qu’en appliquant le code de Hamming. La contrainte est que l’application du code convolutionnel mène l’algorithme du système à devenir de plus en plus complexe et nécessite un temps de calcul un peut plus long. Cependant, nous avons introduit les turbocodes qui nous avaient permis de minimiser le taux d’erreur sans grande complexité de l’algorithme du système surtout quand nous avons appliqué le turbocode dans une chaine de transmission de
3
l’UMTS, le taux d’erreur devient de plus en plus faible en augmentant le nombre de bit d’entré du système ou en augmentant le nombre d’itération de son décodeur itératif.
L’avantage des turbocodes est que son décodage itératif permet de casser l’enchainement séquentiel des étapes élémentaires de la réception par l’introduction d’une boucle de retour.
L’effet de retour permet de traquer les anomalies de transmission dans le récepteur et donne des taux d’erreurs plus faibles et par conséquent la réception est globalement améliorée. Ceci prouve que les turbocodes sont des codes prometteurs pour les futurs systèmes de communication filaires et non filaires.
... WCDMA requires a minimum bandwidth allocation of 5MHz, which is an important distinction from the other generation standards [4]. Packet data rates up to 2Mb/s per user in indoor or small-cell outdoor environments and at rates of up to 384 Kbit/s in wide-area coverage is supported by WCDMA [5].W-CDMA systems can employ the high order modulation (MPSK or M-QAM) to increase the transmission data rate with the link quality control. [6] . ...
The aim of this paper are to study, analyze and design software program to simulate the link performance of mobile communication system under the impairment of the multiple access schemes, down-link thermal noise and the multipath fading in the mobile channel. For this purpose, modeling and simulation has been used to study the effects of nonlinearities in mobile channel using spread spectrum for Direct Sequence Code Division Multiple-Access, with Quadrature Phase shift Keying Modulation (DS-CDMA/QPSK).
... Moreover, errors can be easily produced as the number of users is increased and the mobile terminal is subjected to mobility. Thus, it has driven many researches into the application of higher order modulations [2,8,10]. This paper focuses on the performance measurement of high data rate modulation schemes in channels which are subjected to Multipath Rayleigh Fading and Additive White Gaussian Noise (AWGN). ...
In recent times the Wideband Code Division Multiple Access (WCDMA) is one of the most used. This is because it provides higher data rates in mobile communication and it provides the users with many multimedia applications such as video streams and high resolution pictures. In other to enhance the performance of the technology a suitable modulation technique and error correcting technique is implemented.in this paper I have done performance analysis of different spread spectrum sequence with the Quadrature Phase Shift Keying (QPSK) modulation technique when the system is subjected to multipath Rayleigh fading and Additive White Gaussian Noise (AWGN). The research has been done using MATLAB for simulation and evaluation of the bit error rate for the WCDMA system models.
... WCDMA requires a minimum bandwidth allocation of 5MHz, which is an important distinction from the other generation standards [6]. Packet data rates up to 2Mb/s per user in indoor or small-cell outdoor environments and at rates of up to 384 Kbit/s in wide-area coverage is supported by WCDMA [7]. Therefore, high quality data, multimedia, streaming audio, steaming video and broadcast-type services are allowed by using WCDMA technology to consumers. ...
... Equation (1) is the signal reaching to a receiver of the standard train, under the condition that as the standard train, j in i cell is set up [3,4]. ...
The RF-CBTC (Radio Frequency-Communication Based Train Control) System is a communication system in railroad systems. The communication method of RF-CBTC system is the wireless between the wayside device and on-board device. The wayside device collects its location and speed from each train and transmits the distance from the forwarding train to the speed-limit position to it. The on-board device controlling device controls the speed optimum for the train. In the case of the RF-CBTC system used in Korea, transmission frequency is 2.4 [GHz]. It is the range of ISM(Industrial Scientific and Medical equipment) band and transmission of voice and data is performed by CDMA (Code Division Multiple Access) method. So noises are made in the AWGN (Additive White Gaussian Noise) and fading environment. Currently, the SNR (Signal to Noise Ratio) is about 20 [dB], so due to bit errors made by noises, transmission of reliable information to the train is not easy. Also, in the case that two tracks are put to a single direction, it is needed that two trains transmit reliable voice and data to a wayside device. But, by noises, it is not easy that just a train transmits reliable information. In this paper, we estimated the BER (Bit Error Rate) related to the SNR of voice and data transmission in the environment such as AWGN and fading from the RF-CBTC system using the CDMA method. Also, we supposed the SNR which is required to meet the BER standard for voice and data transmission. By increasing the processing gain that is a ratio of chip transmission to voice and data transmission, we made possible voice and data transmission from maximally two trains to a wayside device, and demonstrated it by using Matlab program.
... In the analysis, the number of users with a RAKE receiver is represented by and those with a MUD receiver by . The efficiency of MUD receiver also denoted by at a give is [12] ) ...
... I Introduction code-division multiple access (CDMA) has been the most important multiple access technology for the 3rd generation GSM and American Cellular systems [1]. Optical CDMA systems have become an alternative multiple access for fiber optics and optical wireless systems [2][3][4]. ...
This paper is a tutorial review on important issues related to code-division multiple-access (CDMA) systems such as channel capacity, power control, and optimum codes; specifically, we consider optimum overloaded codes that achieve errorless transmission in the absence of noise for the binary and nonbinary cases. A survey of lower and upper bounds for the sum channel capacity of such systems is given in the presence and absence of channel noise. The asymptotic results for the channel capacity are also investigated. The channel capacity, errorless transmission codes, and power estimation for near-far effects are also explored. The emphasis of this tutorial review is on the overloaded CDMA systems.
... Code division multiple access (CDMA) [1][2] constitutes an attractive multiuser scheme that allows users to transmit at the same carrier frequency in an uncoordinated manner. However, this creates multiple access interference (MAI), which-if not controlled-can seriously deteriorate the quality of reception. ...
A novel multiuser code division multiple access (CDMA) channel estimator based on genetic algorithm is considered which estimates the fading channel impulse response coefficients of all the users. Furthermore, the optimum multiuser detector, based on the maximum likelihood (ML) rule, is developed in order to identify the transmitted data sequence. As is demonstrated in simulation results, the proposed method in channel estimation is much more accurate. As a result, we can achieve a near-optimum bit error rate (BER) performance upon perfect channel estimation.
... Multipath fading and system capacity limitations are major hurdles in the delivery of 3G data rates and services as envisioned in IMT-2000 [1]- [2]. Limits on RF spectrum allocation means that there is only a finite bandwidth in which a wireless system can operate, as such, increasing data rates and system capacity by increasing bandwidth is not an option. ...
The main objective of this paper is to develop a new software testbed to aid our research on various smart antenna (SA) technologies proposed for future generation wireless communication systems. These models can be used as a platform to test the use of DSPs/FPGs in new generation CDMA-SA systems and will allow to evaluate the array pattern (AP) and the Bit Error Rate (BER) performance over a range of communication channel conditions, e.g., whether the fading is flat or frequency selective, and how much interference the user is getting from other users. This goal is achieved through modeling and simulation using the rapid prototyping environment based on Mathworks Simulink (5). BER and AP performances are evaluated for different models under various channel conditions to demonstrate the merits of the combined CDMA-SA system.
... Streaming DSP algorithms are becoming more common in portable embedded systems and require an efficient processing architecture. Typical streaming DSP examples are found in signal processing for phased array antennas (for radar and radio astronomy), wireless baseband processing (for Hiper- LAN/2, WiMax, DAB, DRM, DVB, UMTS [1, 2] ), multimedia processing (encoding/decoding), MPEG/TV, medical image processing, and sensor processing (e.g., remote surveillance cameras and automotive). Streaming DSP algorithms (sometimes modeled as synchronous dataflow programs) express computation as a dataflow graph with streams of data items (the edges) flowing between computation kernels (the nodes). ...
... This actually creates higher uncertainty to the performance than the technology evolution is able to improve in average during a life cycle of one technology generation. [12] ...
Availability of spectrum for mobile communication is an open question. The number of different players with different agendas, emerging new technologies and recently, extremely high auction prices paid by some mobile operators have made the issues more complex and also by far more public. Radio spectrum can be seen as an enabler for different businesses but it may also be considered an important factor impacting also indirectly to the overall prosperity in national or even global perspective.
... The medium access control (MAC) protocol coordinates the nodes in a network and resolves the contention among their accessing the shared medium so that the resources are shared fairly and efficiently [8]. Wireless access can be classified into three categories [9] Guaranteed access protocols are contention-free protocols with which stations access the channel via polling or scheduling. ...
In this paper, we applied an error control protocol for wireless local area network in medium access control. Hiperlan2 random access phase is taken as an example. We applied quality of service support in the random access phase. Analytical model is developed for the backoff strategy with error control protocol. The performance metrics are shown.
... the Universal Mobile Telecommunication Systems (UMTS) and American cellular systems [1]. Also, optical CDMA systems have become an alternative multiple access for fiber optics and optical wireless systems [2]- [4]. ...
In this paper, we explore some of the fundamentals of synchronous Code Division Multiple Access (CDMA) as applied to wireless and optical communication systems under very general settings (of any size) for the user symbols and the signature matrix entries. The channel is modeled by real/complex additive noise of arbitrary distribution. Two problems are addressed. The first problem concerns whether uniquely detectable overloaded matrices exist in the absence of additive noise under these general settings, and if so, whether there are any practical optimum detection algorithms. The second one is about the bounds for the sum channel capacity when user data and signature matrices employ any real or complex alphabets (finite or infinite). In response to the first problem, we have developed practical maximum likelihood detection algorithms for overloaded CDMA systems for a large class of alphabets. In response to the second problem, a general theorem has been developed in which the sum capacity lower bounds with respect to the number of users, spreading gain, and signal-to-noise ratio can be derived. To show the power and utility of the main theorem, a number of sum capacity bounds for special cases are evaluated. An important conclusion of this paper is that the lower and upper bounds of the sum capacity for small/medium-size CDMA systems depend on both the input and the signature symbols; this is contrary to the asymptotic results for large-scale systems reported in the literature (also confirmed in this paper) where the signature symbols and statistics disappear for signature matrices and input vectors with i.i.d. entries. Furthermore, upper and asymptotic bounds are derived and compared to other derivations.
... Digital tel-00280968, version 1 -20 May 2008 processing blocks ensure its shaping [34,35]. Then, data scrambling allows separating users by assigning each one a different code and thus controls confidentiality of transmitted data [36]. PN-codes are used in UMTS to generate the HPSK complex scrambling sequence [37,38]. ...
Dans le cadre de la radio logicielle, un transmetteur numérique, basé sur la modulation ΔΣ, est proposé. Son architecture est construite autour de deux modulateurs ΔΣ passe-bas suréchantillonnés du 3ème ordre qui fournissent un signal multiplexé sur 1 bit à haute cadence, qui code directement le signal RF dans le domaine numérique. La séquence de sortie peut ensuite être appliquée à l’entrée d’un amplificateur de puissance commuté ayant une bonne efficacité.
Le standard UMTS a été choisi comme exemple d’application et un générateur de signaux RF 1 bit à 7,8Géch/s a été réalisé dans une technologie 90nm CMOS. Une arithmétique redondante comprenant des signaux complémentaires, une quantification de sortie non exacte et une évaluation anticipée de la sortie ont été implémentées pour parvenir à la cadence désirée. Une logique dynamique différentielle sur 3 phases d’horloge, générées par une DLL, a été utilisée au niveau circuit.
Le circuit intégré du transmetteur prototype démontre une fonctionnalité complète jusqu’à une fréquence d’horloge de 4GHz, permettant ainsi d’atteindre une bande passante de 50MHz autour d’une fréquence porteuse de 1GHz. Si la bande image est utilisée, la fréquence d’émission peut être déplacée jusqu’à 3GHz. Avec une fréquence d’horloge de 2,6GHz et un canal WCDMA de 5MHz modulé autour d’une fréquence porteuse à 650MHz, 53,6dB d’ACLR sont obtenus pour une puissance de canal en sortie de -3,9dBm. Pour la bande image (1,95GHz), l’ACPR est de 44,3dB pour une puissance maximale du canal en sortie de -15,8dBm, ce qui rentre dans les spécifications UMTS. L’aire active du circuit est de 0,15mm² et sa consommation de 69mW sous 1V à cette fréquence.
... Streaming DSP algorithms are becoming more common in portable embedded systems and require an efficient processing architecture. Typical streaming DSP examples are found in signal processing for phased array antennas (for radar and radio astronomy), wireless baseband processing (for Hiper- LAN/2, WiMax, DAB, DRM, DVB, UMTS [1, 2] ), multimedia processing (encoding/decoding), MPEG/TV, medical image processing, and sensor processing (e.g., remote surveillance cameras and automotive). Streaming DSP algorithms (sometimes modeled as synchronous dataflow programs) express computation as a dataflow graph with streams of data items (the edges) flowing between computation kernels (the nodes). ...
We focus on architectures for streaming DSP applications such as wireless baseband processing and image processing. We aim at a single generic architecture that is capable of dealing with different DSP applications. This architecture has to be energy efficient and fault tolerant. We introduce a heterogeneous tiled architecture and present the details of a domain-specific reconfigurable tile processor called Montium. This reconfigurable processor has a small footprint (1.8 mm2 in a 130 nm process), is power efficient and exploits the locality of reference principle. Reconfiguring the device is very fast, for example, loading the coefficients for a 200 tap FIR filter is done within 80 clock cycles. The tiles on the tiled architecture are connected to a Network-on-Chip (NoC) via a network interface (NI). Two NoCs have been developed: a packet-switched and a circuit-switched version. Both provide two types of services: guaranteed throughput (GT) and best effort (BE). For both NoCs estimates of power consumption are presented. The NI synchronizes data transfers, configures and starts/stops the tile processor. For dynamically mapping applications onto the tiled architecture, we introduce a run-time mapping tool.
Sparse code multiple access (SCMA) and multiple input multiple output (MIMO) are considered as two efficient techniques to provide both massive connectivity and high spectrum efficiency for future machine-type wireless networks. However, the computational complexity of the conventional message passing algorithm (MPA) for the downlink MIMO-SCMA detection increases exponentially with the degree of variable nodes (VNs). To address this issue, two novel fixed low complexity MPA detectors are proposed by utilizing the sparse feature of codewords, which are based on the serial schedule strategy in order to accelerate their convergence. First, a maximum distance MPA (MDMPA) detector is introduced to reduce the number of VNs involved in the message updating procedure in the first
iterations and fix
codewords at the
iteration, which subsequently drops the redundant codeword combinations in the remaining iterations. To further improve the bit error ratio (BER) performance, an improved MDMPA (IMDMPA) is proposed, in which, the VNs associated with the target user are always allowed to participate in the iterative propagation of message. An efficient linear squares (LS) channel estimation scheme is also derived based on block pilots by stacking all the received signals at the same subcarrier together. Simulation results illustrate that the proposed MDMPA and IMDMPA detectors significantly reduce the computational complexity of the original MPA, but with comparable decoding capabilities, and the proposed LS channel estimator can closely approach the corresponding lower bound over frequency selective channels.
La demande toujours croissante de connectivité sans fil entraine le développement de nouvelles générations de normes de communication utilisant les dernières technologies en matière de télécommunication. Pour atteindre les débits annoncés, l'utilisation de signaux de plus en plus complexes est nécessaire afin d'occuper le plus efficacement le spectre radio restreint. Cela implique notamment des contraintes de plus en plus strictes sur les emetteurs radio afin d'assurer l'intégrité des informations tranmises et une bonne qualité de service. Dans ce contexte, cette thèse a pour objectif l'amélioration des performances énergétiques et spectrales d'un amplificateur de puissance (PA) en technologie CMOS pour appareil mobile en utilisant une méthode de linéarisation. Le PA conçu dans cette thèse est basé sur la cellule MASMOS (cellule brevettée) et doit répondre à notre cahier des charges basé sur le standard 3G.L'étude des interconnexions flip-chip sur les performances de la cellule révèle que son impact doit être atténué. Pour cela, la topologie différentielle est retenue pour la conception du PA. Une structure différentielle de référence (n'incluant pas de méthode de linéarisation) est conçue et mesurée. Elle consiste en un étage de puissance terminé par un balun sur substrat stratifié synthétisant les impédances optimales de l'étage à la fréquence fondamentale et au second harmonique. Les résultats obtenus sont proches de l'état de l'art existant en PA CMOS pour la 3G sans utiliser de technique de linéarisation.Nous proposons ensuite deux méthodes de linéarisation circuit spécifiques aux structures différentielles. Nous retenons l'utilisation d'un filtre différentiel au second harmonique au sein de la cellule d'amplification. Un PA complet (étage driver + étage de puissance) est conçu. Nous proposons une méthode de conception pour le balun de sortie et du réseau d'adaptation inter-étage. Les résultats finals de simulation permettent de conclure que le PA proposé dépasse les objectifs du cahier des charges.
In this paper, the uplink multiuser code division multiple access (CDMA) communication system model is described in the form of space-time domain through antenna array and multipath fading expression. Novel suitable neural network technique is proposed as an effective signal processing method for the receiver of such an uplink multiuser CDMA system. By the appropriate choice of the channel state information for the neural network parameters, the neural network can collectively resolve the effects of both the inter-symbol interference due to the multipath fading channel and the multiple access interference in the receiver of the uplink multiuser CDMA communication system. The dynamics of the proposed neural network receiver for the uplink multiuser CDMA communication system is also studied.
The pulse shaping filter is a useful means to shape the signal spectrum and avoid interferences. The analysis and simulation of transmit and receive pulse shaping filter is an important aspect of digital wireless communication since it has a direct effect on error probabilities. Pulse shaping for wireless communication over time as well as frequency selective channels is the need of hour for 3G and 4G systems. Basically digital filters are used to modify the characteristics of signal in time and frequency domain and have been recognized as primary digital signal processing operations.The present paper deals with analysis of Flipped Secant Hyperbolic Pulse based FIR Filter for WCDMA.
Mobile world's rapid growth has spurred development of new protocols and new algorithms to meet changing operation requirements such as mobile networking, and quality-of-service support. A key requirement in the bearer capabilities is the handover. The freedom to be able to make and receive calls anywhere, at any time, creating a totally new dimension in human communications has frequently been advertised as the main advantage of new wireless systems. Handovers are a key concept in providing this mobility. It makes it possible for a user to travel from one cell to another while having a seamless connection. Network operators give emphasis to optimize handover, since it is strongly related to dropped calls, network overload and subsequently users' criticism. The ability of a cellular network to perform efficient handovers is crucial to offer attractive services as real-time applications or streaming media as planned in third generation networks. Since signal propagation and pathloss are complex in nature, we can expect unnecessary and wrong handoff executions. Both UMTS and those of the second generation (GSM) systems will require redefined handoff algorithms of active connections as the smooth mobility support and continuous connection are essential issues for obtaining high performance and increasing user satisfaction. In this paper we present a set of intelligent algorithms using the mobile terminal (MT) location information and area awareness to assist safe handoff decisions. The implemented algorithms are validated by means of cellular network simulators that clearly show the impact of these techniques to major system performance metrics.
One of the most challenging issues facing deployment of 3G technology is how to make the network architectures compatible with each other. New signaling techniques are being designed specially to enhance today's networks, deliver unprecedented functionality for 3G, and successfully derive the future generation of wireless systems, thus delivering immediate and long term benefits to subscribers. With the architecture of each generation of wireless devices addressed in the development of advance technologies, subscribers can easily evolve their systems without additional network modification, significantly reducing cost and implementing time. The next generation systems based on the DS-CDMA, FDMA/TDMA and GSM concepts are projected to provide transmitting high speed data, video and multimedia traffic for both indoor and outdoor systems, new technologies like Wideband Code Division Multiple Access (WCDMA), already in service, are providing users with high data rate services options like they have never experienced previously. The present paper deals with DSP Implementation of pulse shaping filter for wireless communication.
This paper introduces a novel Trellis Coded Multiple Access (TCMA) technique which takes advantage of Trellis-Coded Modulation (TCM) and signalling set redundancy to differentiate transmissions from different users. The proposed TCMA scheme exploits modulation with memory principles to provide the flexibility of accommodating an increasing number of users within the fixed time-frequency resource. In the scheme, users are assigned unique, code-based trellises employing distinct subsets of generic signals. This paper focuses on the applicability of chirp signalling to TCMA, even though the proposed system can use other types of narrowband modulations, such as FSK or QAM. Specifically, the MA scheme presented in this paper features the assignment of overlapping, dissimilar signal trellises that efficiently occupy the system bandwidth and allow for (i) user identification and (ii) reliable data recovery. Careful design of a chirp signalling scheme and the trellis arches guiding the frequency hopping patterns is conducted to reduce MAI. An effective demodulation algorithm is developed using the Viterbi decoder incorporated with a parallel, iterative MAI cancellation scheme. It is demonstrated with a theoretical analysis and simulations that the proposed scheme achieves an acceptable bit error rate performance for different system configurations.
In direct sequence spread spectrum (DSSS) communication system, the pseudo-noise (PN) code sequence is used to spread the transmitted signal in frequency at the modulator and to despread the received signal at the demodulator. As a spread spectrum sequence, the PN sequence's character impacts the performance of the DSSS system directly. There are many good spread spectrum sequence that can be used in DSSS system. In this paper, we applied a new kind of spread sequence, sequence pairs in DSSS system. Simulation results show that when the sinusoid amplitude is large, the BER of the DSSS system based on sequence pairs is better than that base on other spread spectrum sequences.
This paper presents a novel dual-channel RF receiving front-end design used for 3G system. The reasonable solution to front-end is given. The performance of component is simulated by using commercial EDA software. The whole receiver is integrated on a four-layer PCB with small size, low power consumption, high accuracy, high linearity and high sensitivity. Finally, the front-end had been tested and the measured results show that it meets the 3GPP standard perfectly. The solution is also available for dual-channel RF receiver design in cdma2000 and TD-SCDMA.
The mobile communication systems services are shifting from voice conversation to data transmission through the Internet. The information transferred over the Internet is becoming increasingly rich, there will be a demand of peak data transmission rates of around 100 Mbps-1Gbps even in mobile communications systems. However, as the data transmission rate becomes higher, the peak transmit power becomes larger. To decrease the peak transmit power, a multi-hop virtual cellular network (VCN) that can significantly reduce the transmit power was proposed. This paper introduces the multi-hop maximal ratio combining (MHMRC), to the VCN in order to decrease the route total transmit power, improve the transmit power efficiency degradation caused by the carrier frequency difference between the control and the data communication channels for VCN. It was shown that the MHMRC diversity gain decreases. MHMRC diversity can reduce the number of hops in the rout.
We propose in this work, a simple method to calculate the bit error rate (BER) performance of a direct sequence code division multiple access (DS/CDMA) system over a Rayleigh multipath fading with power control error for both coherent and noncoherent reception, the RAKE structure receivers under consideration employ despreading sequences weighted (WDS) by exponential chip weighting waveforms. Numerical results show that the proposed approach reduce complexity and time of BER’s computing, then its performance does not undergo any degradation.
Mobile world’s rapid growth has spurred development of new protocols and new algorithms to meet changing operation requirements-
such as mobile networking, and quality-of-service support. Handoff is one of the most critical procedures in cellular systems.
Network operators give emphasis to optimize handover, since it is strongly related to dropped calls, network overload and
subsequently users’ criticism. Handoff can be seen as a blind procedure, if it is only based on the comparison of measurements,
without the information of location. Since signal propagation and pathloss are complex in nature, we can expect unnecessary
and wrong handoff executions. Both UMTS and those of the second generation (GSM) systems will require redefined handoff algorithms
of active connections as the smooth mobility support and continuous connection are essential issues for obtaining high performance
and increasing user satisfaction. In this paper we present a set of intelligent algorithms using the mobile terminal (MT)
location information and area awareness to assist safe handoff decisions. The implemented algorithms are validated by means
of cellular network simulators that clearly show the impact of these techniques to major system performance metrics.
Les contraintes au niveau du coût, de la consommation et du temps de mise sur le marché des applications de traitement numérique du signal exigent la mise en oeuvre de métho-dologies d'implantation automatique d'algorithmes spécifiés en virgule flottante au sein d'ar-chitectures en virgule fixe. Dans cet article, une nouvelle méthodologie d'implantation au sein des processeurs de traitement du signal (DSP) sous contrainte de précision est définie. Par rapport aux méthodologies existantes, l'architecture du processeur DSP est entièrement prise en compte pour l'optimisation du codage des données. Les justifications de la structure de cette méthodologie et les différentes étapes la composant sont détaillées. ABSTRACT. The development of methodologies for the automatic implementation of floating-point algorithms in fixed-point architectures is required for the minimization of cost, power consumption and time-to-market of digital signal processing applications. In this paper, a new methodology of implementation in Digital Signal Processors (DSP) under accuracy constraint is presented. In comparison with the existing methodologies, the DSP architecture is completely taken into account for optimizing the execution time under accuracy constraint. The justification and the different stages of our methodology are presented. MOTS-CLÉS : arithmétique à virgule fixe, précision finie, processeurs de traitement du signal, DSP, génération de code.
L'UMTS est un nouveau standard de radiocommunications mobiles destiné à résoudre les problèmes des actuels réseaux de deuxième génération, proches localement de la saturation et limités dans leur offre de services multimédias par les faibles débits utiles supportés. L'UMTS représente une rupture technologique importante et nécessite un effort particulier pour la réa- lisation des équipements, car la complexité des traitements à effectuer a augmenté dans des proportions considérables. Les terminaux 3G, par exemple, devront embarquer une puissance de calcul supérieure de plus d'un ordre de grandeur à celle embarquée par leurs prédécesseurs. Après avoir introduit l'UMTS et une de ses interfaces radios, le Wideband CDMA, nous avons identifié l'estimation par le terminal du canal radiomobile par lequel a transité le signal émis par la station de base comme étant une des tâches susceptibles d'entraîner le plus grand nombre d'opérations à effectuer. Une solution originale à ce problème est proposée sous la forme d'un algorithme d'estimation itérative de canal à suppression de trajets. La complexité calculatoire de cet algorithme a l'inconvénient majeur de varier avec le carré du facteur de suréchantillonnage, ce qui empêche de travailler avec une valeur élevée de celui-ci, et par consé- quent ne permet pas d'obtenir une grande précision quant à l'estimation des instants d'arrivée des trajets. Ce problème est résolu en introduisant une version optimisée de cet algorithme, dont la complexité varie linéairement avec le facteur de suréchantillonnage. Conserver une com- plexité raisonnable tout en travaillant avec des facteurs de suréchantillonnage élevés devient réaliste, ce qui permet d'accéder à coût égal à une précision plus élevée qu'avec l'algorithme origininal. De plus, cette optimisation simplifie les opérations élémentaires effectuées par l'algo- rithme, ce qui a pour conséquence de rendre son implémentation sur une architecture hybride matérielle-logicielle plus efficace que son implémentation sur un seul processeur de signal. Une méthodologie de conception au niveau système est ensuite proposée pour réaliser cette architecture hybride dans un but de prototypage rapide. Cette méthodologie, bâtie autour du logiciel N2C, de la société CoWare, utilise un langage de haut niveau, surensemble du langage C auquel ont été rajoutées les constructions nécessaires pour décrire des architectures matérielles. L'algorithme est partitionné en une partie logicielle s'exécutant sur un cœur de DSP ST100 et un coprocesseur réalisé en logique câblée. De sévères incompatibilités logicielles ont empêché la réalisation de cette architecture hybride selon la méthodologie proposée, mais des résultats intéressants ont néanmoins été obtenus à partir d'une implémentation purement logicielle de l'algorithme proposé. L'architecture obtenue avec l'application des premières étapes de la méthodologie proposée à l'algorithme d'estimation de canal est décrite, ainsi que quelques suggestions faites à la société CoWare, Inc. pour l'amélioration de leur outil. Enfin, l'adéquation de la méthodologie proposée à un environnement de prototypage rapide est discutée et des pistes pour la réalisation d'un éventuel démonstrateur sont données.
Thesis (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2002. Includes bibliographical references (p. 163-169). This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. by Maria Fuencisla Merino Artalejo. S.M.
This presentation will focus on algorithms and reconfigurable tiled architectures for streaming DSP applications. The tile concept will not only be applied on chip level but also on board-level and system-level. The tile concept has a number of advantages: (1) depending on the requirements more or less tiles can be switched on/off, (2) the tile structure fits well to future IC process technologies, more tiles will be available in advanced process technologies, but the complexity per tile stays the same, (3) the tile concept is fault tolerant, faulty tiles can be discarded and (4) tiles can be configured in parallel. Because processing and memory is combined in the tiles, tasks can be executed efficiently on tiles (locality of reference). There are a number of application domains that can be considered as streaming DSP applications: for example wireless baseband processing (for HiperLAN/2, WiMax, DAB, DRM, DVB), multimedia processing (e.g. MPEG, MP3 coding/decoding), medical image processing, color image processing, sensor processing (e.g. remote surveillance cameras) and phased array radar systems. In this presentation the key characteristics of streaming DSP applications are highlighted, and the characteristics of the processing architectures to efficiently support these types of applications are addressed. @InProceedings{smit_et_al:DSP:2006:743, author = {Gerard J.M. Smit and Andre B. J. Kokkeler and Pascal T. Wolkotte and Marcel D. van de Burgwal and Paul M. Heysters}, title = {Efficient architectures for streaming applications}, booktitle = {Dynamically Reconfigurable Architectures}, year = {2006}, editor = {Peter M. Athanas and J{"u}rgen Becker and Gordon Brebner and J{"u}rgen Teich}, number = {06141}, series = {Dagstuhl Seminar Proceedings}, ISSN = {1862-4405}, publisher = {Internationales Begegnungs- und Forschungszentrum f{"u}r Informatik (IBFI), Schloss Dagstuhl, Germany}, address = {Dagstuhl, Germany}, URL = {http://drops.dagstuhl.de/opus/volltexte/2006/743}, annote = {Keywords: Reconfigurable streaming efficient} }
This study presents an easy approach based on neural networks (NN) to facilitate the computing of the bit error rate (BER) performance of a direct sequence code division multiple access (DS/CDMA) system over a Rayleigh multipath fading with power control error for both coherent and noncoherent reception, by producing the despreading sequences weighted (WDS) by stepping chip weighting waveforms. From the simulation results for this above method, we note that the BER performance does not undergo any degradation by using the parameters producing by the proposed method. This study presents an easy approach based on neural networks (NN) to facilitate the computing of the bit error rate (BER) performance of a direct sequence code division multiple access (DS/CDMA) system over a Rayleigh multipath fading with power control error for both coherent and noncoherent reception, by producing the despreading sequences weighted (WDS) by stepping chip weighting waveforms. From the simulation results for this above method, we note that the BER performance does not undergo any degradation by using the parameters producing by the proposed method.
This paper extends the traditional orthogonal transmit diversity (OTD) analyses to the multipath intra-cell interference presented in a realistic wideband code-division multiple access (WCDMA) downlink channel. A generic OTD system model is proposed for analyses permitting maximizing the spatial and temporal diversity dimensions for multiple transmit antennas and space-time block code (STBC) respectively. Analytical expressions are derived to evaluate the Chernoff upper bounds on the bit-error rate (BER) for the OTD system under a variety of channel parameters. The expression shows that the BER upper bound can be simplified and determined using an attained signal-to-interference-plus-noise power ratio (SINK) obtained in terms of the number of transmit antennas, the phase difference between two transmit antennas, the channel orthogonality, and the relative cross-correlations of the desired signal to the intra-cell interferers power ratio when equal power allocation at each intra-cell user and perfect channel state information (CSI) are applied in the closed-loop TD system.
Improvement of the capacity of the CDMA (code division multiple access) system is a major objective. The capacity of the system is mainly limited by the signal to noise ratio, where the noise comes from the channel background and from MAI (multiple access interference). Usually, the way to improve the capacity is to decrease the MAI; this is why orthogonal codes are adopted by the IS-95 standard. One problem is that the number of orthogonal codes is constrained by the dimensionality of the signal space. So in IS-95, there are only 64 orthogonal codes available when the number chips for each sequence is 64. To solve this problem, a non-orthogonal code called WBE (Welch bound equality) sequences (Massey and Mittelholzer 1991) is used in this paper The criterion to construct the code is to minimize the MAI. Two methods are used to construct the WBE sequences: from a linear cyclic code or from a Hadamard matrix. In order to improve the performance of the WBE sequence set, an iteration receiver (Sari et al. 1999) is applied. The conclusion obtained is that when the number of users is slightly greater than the signal space dimensionality, after the first iteration, the performance is only marginally worse than the orthogonal CDMA system.
This paper proposes a new way to incorporate H.263 video into
existing voice/data code-division multiple access (CDMA) networks using
a multi-code access protocol. A channel allocation policy is proposed
that “shares” codes for larger I-frame video transmission
and allocates a fixed number of codes for P-frame transmissions. The
base station in a given cell of a CDMA network controls this allocation
method, but bandwidth access distribution is based on both mobile host
requests and base station forced requests. This scheme allows more
efficient allocation of resources in the bandwidth-limited wireless
spectrum and improves the quality of service (QoS) of video traffic over
this lossy environment
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