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Throughput analysis of STS-based CDMA system with variable spreading factor in non-frequency selective Rayleigh fading channel

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COMPUTERS & ELECTRICAL ENGINEERING 2009年第4期35卷 528-535页

作者： Vakil, Vahideh Aghaeinia, Hassan Amirkabir Univ Technol Dept Elect Engn Radio Commun Ctr Excellence Spread Spectrum Res Lab Tehran Iran

The throughput enhancement of space-time spreading (STS)-based code division multiple access (CDMA) system is investigated in this paper. variable spreading factor (VSF) is utilized to improve the data throughput of the system in non-frequency selective Rayleigh fading channel. In this contribution, an analytical approach is proposed to compute a new expression for the bit error rate (BER) performance of the STS-based CDMA system against pre-despreading signal-to-noise-ratio (SNR) for different values of spreading factor. The other contribution of the paper is deriving a new analytical expression for the throughput enhancement of the VSF STS-based CDMA system in non-frequency selective Rayleigh fading channel. Simulation and analytical results demonstrate that using VSF method in STS-based CDMA system improves the throughput of the system by keeping the BER performance at a target level. (C) 2008 Elsevier Ltd. All rights reserved.

关键词： CDMA Space-time spreading Throughput variable spreading factor

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Joint Physical Layer and Data Link Layer Optimization of CDMA-Based Networks

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2011年第10期10卷 3278-3287页

作者： Shojaeifard, A. Zarringhalam, F. Shikh-Bahaei, M. Kings Coll London Ctr Telecommun Res London WC2R 2LS England Quad Financial London England

In CDMA systems, outer loop power control (OLPC) determines the target value of SNR at the receiver, mostly by using look-up tables to map bit error rates (BERs) to SNR-targets. In this contribution, transmission delay and packet loss rate constraints in the data link layer (DLL) are invoked in order to determine the optimum outer loop SNRtarget setpoint analytically, according to the number of active users in cell. Optimality is, in this sense, the maximization of system throughput. Using the optimum SNR-target, the optimal spreading factor is determined. Subsequently, the joint optimization of outer loop SNR-target and variable spreading factor (VSF), at the physical(PHY)-layer, with truncated automatic repeat request (ARQ) error control mechanism at the data link layer are proposed. Hence, we show that quality of service (QoS) requirements at these layers can be simultaneously satisfied while maximizing throughput. Total and truncated channel inversion strategies are employed in the inner loop to adapt transmit power to short-time channel variations. We propose a system where the number of users in a cell is modeled by a one-dimensional discrete Markov chain, and design the adaptive continuous power and rate mechanism for the worst case packet error rate (PER) condition. The corresponding theoretical throughput, which can be regarded as upper-bound for discrete spreading factor case, is obtained numerically for various settings of system parameters. We have also provided simulation results for a practical channel condition. Our scheme is compared with 'constant SNR-target` and ` PHY-layer based variable SNR-target' cases under continuous power and rate variation to show the achievable gain through the coupling of physical and data link layers parameters.

关键词： Cross-layer optimization variable spreading factor outer/inner loop power control channel inversion truncated automatic repeat request (ARQ) one-dimensional Markov chain

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Throughput-Optimal Cross-layer Resource Allocation in DS-CDMA Systems with Nakagami Multipath Fading

Throughput-Optimal Cross-layer Resource Allocation in DS-CDM...

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22nd IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC)

作者： Shojaeifard, A. Zarringhalam, F. Shikh-Bahaei, M. Kings Coll London Ctr Telecommun Res London England

ISBN: (纸本)9781457713484

Joint optimization of outer loop power control (OLPC) signal to noise ratio-target (SNR-target) and variable spreading factor (VSF), at the physical(PHY)-layer, with truncated automatic repeat request (ARQ), at data link layer (DLL), in accordance to the number of active users in the cell is considered. This investigation is on a single cell conventional cellular DS-CDMA communication system with frequency-selective fading channels, where the number of active users is modelled through a one-dimensional discrete Markov chain. The optimally is in the sense of maximizing the sum-throughput, given a coherent RAKE receiver is employed with maximum ratio combining (MRC). We determine the optimal spreading factor using OLPC SNR-target at the PHY-layer, which satisfies the QoS imposed by packet error rate-target (PER-target) as a function of maximum number of allowed ARQ retransmissions at the DLL. The channel model considers independent paths with Nakagami fading characteristics. Total and truncated channel inversion techniques are used within the inner loop power control (ILPC) to adapt the transmission power to short time channel variations. Sum-throughput performance of the optimized system and non optimized system, where the SNR-target is assumed to be constant, under various multipath fading conditions are studied. A considerable gain in sum-throughput is achieved through coupling of PHY-layer and DLL parameters.

关键词： Cross-layer optimization variable spreading factor outer loop power control packet error rate (PER) truncated automatic repeat request (ARQ)

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Packet Error Rate(PER)-based Cross-layer Optimization of CDMA Networks

Packet Error Rate(PER)-based Cross-layer Optimization of CDM...

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54th Annual IEEE Global Telecommunications Conference (GLOBECOM)

作者： Shojaeifard, A. Zarringhalam, F. Shikh-Bahaei, M. Kings Coll London Ctr Telecommun Res London England

ISBN: (纸本)9781424492688

关键词： Cross-layer optimization packet error rate variable spreading factor outer loop power control truncated automatic repeat request one-dimensional markov chain

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MC-CDMA HARQ with variable spreading factor

MC-CDMA HARQ with Variable Spreading Factor

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63rd IEEE Vehicular Technology Conference

作者： Takaoka, Shinsuke Gacanin, Haris Adachi, Fumiyuki Tohoku Univ Grad Sch Engn Dept Elect & Commun Engn Aoba Ku Sendai Miyagi 9808579 Japan

ISBN: (纸本)9780780393912

This paper presents a hybrid automatic repeat request (HARQ) with variable spreading factor (VSF) suitable for a multicarrer code division multiple access (MC-CDMA). We consider a HARQ based on incremental redundancy (IR) strategy. The throughput of MC-CDMA HARQ is a tradeoff among the frequency diversity gain, the coding gain and the inter-code interference (ICI). In order to effectively exploit the channel frequency-selectivity and the channel coding, the spreading factor is changed between the initial transmission and the succeeding retransmissions. The throughput performance of HARQ with VSF in a frequency-selective Rayleigh fading channel is evaluated by the computer simulation and compared with that with fixed spreading factor (FSF). It is shown that HARQ with VSF can provide better throughput performance than with FSF and is particularly useful when high-level modulation (e.g., 16QAM and 64QAM) is used. The impacts of fading correlation between packet retransmissions and the channel frequency-selectivity on achievable throughput performance are discussed.

关键词： MC-CDMA HARQ variable spreading factor

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Throughput-Optimal Cross-layer Resource Allocation in DS-CDMA Systems with Nakagami Multipath Fading

Throughput-Optimal Cross-layer Resource Allocation in DS-CDM...

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IEEE International Symposium on Personal, Indoor and Mobile Radio Communications

作者： A. Shojaeifard F. Zarringhalam M. Shikh-Bahaei Centre for Telecommunications Research King's College London

ISBN: (纸本)9781457713460

Joint optimization of outer loop power control (OLPC) signal to noise ratio-target (SNR-target) and variable spreading factor (VSF), at the physical (PHY)-layer, with truncated automatic repeat request (ARQ), at data link layer (DLL), in accordance to the number of active users in the cell is considered. This investigation is on a single cell conventional cellular DS-CDMA communication system with frequency-selective fading channels, where the number of active users is modelled through a one-dimensional discrete Markov chain. The optimally is in the sense of maximizing the sum-throughput, given a coherent RAKE receiver is employed with maximum ratio combining (MRC). We determine the optimal spreading factor using OLPC SNR-target at the PHY-layer, which satisfies the QoS imposed by packet error rate-target (PER-target) as a function of maximum number of allowed ARQ retransmissions at the DLL. The channel model considers independent paths with Nakagami fading characteristics. Total and truncated channel inversion techniques are used within the inner loop power control (ILPC) to adapt the transmission power to short time channel variations. Sum-throughput performance of the optimized system and non optimized system, where the SNR-target is assumed to be constant, under various multipath fading conditions are studied. A considerable gain in sum-throughput is achieved through coupling of PHY-layer and DLL parameters.

关键词： Cross-layer optimization variable spreading factor Outer loop power control Packet error rate (PER) Truncated automatic repeat request (ARQ)

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Jointly Optimized Rate and Outer Loop Power Control with Single- and Multi-User Detection

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2009年第1期8卷 186-195页

作者： Zarringhalam, F. Seyfe, B. Shikh-Bahaei, M. Charbit, G. Agrhvami, H. Kings Coll London Dept Elect Engn Strand London WC2R 2LS England Shahed Univ Dept Elect Engn Tehran Iran Nokia UK Ltd Farnborough GU14 0NG Hants England

We propose a technique for enhancing the achievable spectral efficiency of multiuser direct-sequence code-division multiple-access (DS-CDMA) fading channels in the presence of additive white Gaussian noise (AWGN) and multiple access interference (MAI). The proposed scheme involves the joint optimization of outer loop power control (OLPC) and rate control using variable spreading factors (VSFs). The optimality is in the sense of average spectral efficiency maximization. The optimum outer loop target signal-to-noise ratio (SNR-target) and the corresponding spreading factor are derived jointly, in terms of the number of active users. Along with transmit power adaptation in the inner loop, this leads to maximized average spectral efficiency. Total and truncated channel inversion strategies are used in the inner loop. The average spectral efficiency of the joint optimization scheme is derived for the conventional matched-filter and the multiuser decorrelating detectors. Average transmit power and instantaneous bit error rate (BER) constraints are considered and the performance is evaluated over Nakagami-m flat-fading channels. In low SNRs, the proposed scheme can provide a considerable gain in bits/s/Hz for either of the detectors, compared to a VSF-assisted system that does not exploit OLPC and thus the optimum SNR-target.

关键词： variable spreading factor outer loop power control optimum SNR-target spectral efficiency

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Novel CSMA scheme for DS-UWB ad-hoc network with variable spreading factor

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IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES 2004年第10期E87A卷 2615-2620页

作者： Horie, W Sanada, Y Keio Univ Dept Elect & Elect Engn Yokohama Kanagawa 2238522 Japan

In this paper, a novel carrier-sense multiple-access (CSMA) scheme for UWB ad-hoc network is proposed and evaluated. UWB is a kind of spread spectrum communication and it is possible to detect the distance between the nodes. With this positioning capability of the UWB systems: DS-CDMA (DS-UWB) scheme with variable spreading factor is used. In this paper, a novel CSMA scheme that employs the correlation of the spreading code is proposed.

关键词： WVB ad-hoc network spread spectrum CSMA variable spreading factor

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Novel CSMA scheme for DS-UWB ad-hoc network with variable spreading factor

Novel CSMA scheme for DS-UWB ad-hoc network with variable sp...

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International Workshop on Ultra Wideband Systems/Conference on Ultra Wideband Systems and Technologies

作者： Horie, W Sanada, Y Keio Univ Dept Elect & Elect Engn Yokohama Kanagawa 2238522 Japan

ISBN: (纸本)0780383737

In this paper, a novel carrie-sense multiple-access (CSMA) scheme for UWB ad-hoc network is proposed and evaluated. UWB is a kind of spread spectrum communication and it is possible to detect the distance between the nodes. With this positioning capability of the UWB systems, DS-CDMA (DS-UWB) scheme with variable spreading factor is used. In this paper, a novel CSMA scheme that employs the correlation of the spreading code is proposed.

关键词： UWB ad-hoc network spread sectrum CSMA variable spreading factor

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Adaptive power and rate transmission with single-and multi-user detection

Adaptive power and rate transmission with single-and multi-u...

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IEEE Wireless Communications and Networking Conference

作者： Zarringhalam, F. Seyfe, B. Shikh-Bahaei, M. R. Kobravi, A. Charbit, G. Kings Coll London Dept Elect Engn London WC2R 2LS England Nokia UK Ltd Farnborough GU14 0NG Hants England

ISBN: (纸本)9781424406586

We propose a technique for enhancing the achievable spectral efficiency of multiuser direct-sequence code-division multiple-access (DS-CDMA) channels in the presence of additive white Gaussian noise (AWGN) and multiple access interference (MAI). The proposed scheme is the joint optimization of outer loop power control and variable spreading factors (VSFs). The optimum SNR-target, the SNR that results in optimal spectral efficiency, is set in the outer loop. Accordingly, appropriate spreading factor is selected, and along with the transmit power adaptation in the inner loop, it leads to maximized spectral efficiency. Total and truncated channel inversion strategies are used in the inner loop. Analytical expressions are derived for the spectral efficiency of the joint optimization scheme for the conventional matched-filter and the multiuser decorrelating detectors. Average transmit power and instantaneous BER constraints are considered and the performance is evaluated over Nakagami-m flat fading channels. We show that our scheme achieves higher spectral efficiency than a system that uses VSF transmission but without outer loop optimal SNR-target. The gain is realized at no transmit power cost and without sacrificing the BER.

关键词： variable spreading factor outer / inner loop power control total / truncated channel inversion

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