Estimation of spectral efficiency for MC/DS-CDMA in cellular systems (original) (raw)
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Spectral efficiency of a cellular MC/DS-CDMA system in Rayleigh fading
International Journal of Communication Systems, 2005
The spectral efficiency of a multicarrier direct-sequence code-division multiple-access (MC/DS-CDMA) cellular system, operating in a mobile radio environment with Rayleigh fading, is investigated and evaluated in terms of channel capacity (in the Shannon sense) per user, estimated in an average sense. The analysis is based on the combination of path-diversity reception, achieved by a conventional coherent maximal-ratio combining (MRC) RAKE receiver and the physical frequency diversity potential provided by orthogonal frequency division multiplexing (OFDM). As shown, a closed-form expression for the achieved spectral efficiency of the considered system's operation is derived following a recently presented general method.
Spectral efficiency of a single-cell multi-carrier DS-CDMA system in Rayleigh fading
Journal of the Franklin Institute, 2006
The spectral efficiency of a multi-carrier direct-sequence code-division multiple-access (MC/DS-CDMA) system operating in a Rayleigh fading environment is investigated and evaluated in terms of the theoretically achievable channel capacity (in the Shannon sense) per user, estimated in an average sense. This short paper covers operation of the considered system over broadcast communication randomly time-varying channels as applicable to wireless radio networks and single-cell indoor mobile systems and leads to the derivation of a closed-form expression for the achieved spectral efficiency. Furthermore, the relation between the number of the employed sub-carriers and the achieved spectral efficiency is revealed.
Spectral efficiency for a hybrid DS/FH code-division multiple-access system in cellular mobile radio
IEEE Transactions on Vehicular Technology, 2001
The spectral efficiency of a hybrid cellular direct-sequence/frequency hopping code-division multiple-access (DS/FH-CDMA) system operating in a Rayleigh-fading environment is examined. In this work, spectral efficiency is evaluated in terms of the theoretically achievable channel capacity (in the Shannon sense) per user, on the condition that this is estimated in an average sense. The analysis covers the downlink assuming a static model of operation and a direct-sequence/slow-frequency hopping (DS/SFH) as well as a direct-sequence/fast-frequency hopping (DS/FFH) scheme. As it is shown, the spectral efficiency of cellular DS/FFH-CDMA operating in a Rayleigh-fading environment is greater than that of broad-band DS-and DS/SFH-CDMA systems operating under normalized conditions. This is justified by the combination of path-diversity reception as achieved by conventional coherent RAKE receivers and the frequency diversity that is inherently present in FFH transmission.
Arabian Journal for Science and Engineering, 2018
Multicarrier code-division multiple access (MC-CDMA), multicarrier direct-sequence CDMA (MC DS-CDMA) and multitone CDMA (MT-CDMA) are three flavors of spread spectrum multicarrier communications. Multiple access interference, inter-carrier interference, self-interference and noise are the major factors that deteriorate their spectral efficiency. A novel joint analysis of spectral efficiency is presented for asynchronous MC-CDMA, MC DS-CDMA and MT-CDMA in a frequencyselective Rayleigh fading environment. This allows us to compare performance of the three schemes in indoor and outdoor environments in the presence of interferers, carrier frequency offset, multipath fading and noise.
Spectral efficiency of CDMA uplink cellular networks
2005
Abstract In this contribution, the performance of an uplink CDMA system with random spreading and multi-cell interference is analyzed. A useful framework is provided in order to determine the base station coverage for wireless flat fading channels with very dense networks (in the number of users per meter) considering different receiver structures at the base station, namely the matched filter, the Wiener filter and the optimum filter.
Performance Evaluation for Cellular CDMA
IEEE Journal on Selected Areas in Communications, 1992
In this paper, we consider the performance of a cellular radio direct-sequence code-division multiple access system. The base-to-mobile link is modeled as a flat Rayleigh fading channel, with all signals transmitted from a given base station fading in unison. For the mobile-to-base link, we use a similar model, except that the waveforms from all users are assumed to experience independent fading. Finally, we show the effects of imperfect power control.
Multi-code multicarrier CDMA: performance analysis
2004 IEEE International Conference on Communications (IEEE Cat. No.04CH37577), 2004
A novel multi-code multicarrier code division multiple access (MC-MC-CDMA) system is proposed and analyzed in a frequency selective fading channel. By allowing each user to transmit multiple orthogonal codes, the proposed MC-MC-CDMA system can support various data rates, as required by next generation standards, and achieve spreading gain in the time domain. Multicarrier CDMA provides robustness to multipath and spreading in the frequency domain. The bit error rate of the system is analytically derived in frequency selective fading, with Gaussian noise and multiple access interference. The results show that the proposed MC-MC-CDMA system clearly outperforms both single-code multicarrier CDMA (MC-CDMA) and singlecarrier multi-code CDMA in a fixed bandwidth allocation. This indicates that MC-MC-CDMA should be seriously considered for next generation cellular systems.
Asymptotic spectral efficiency of multiuser multisignature CDMA in frequency-selective channels
IEEE Transactions on Information Theory, 2000
This paper presents an asymptotic analysis of multisignature code-division multiple access (CDMA) in the presence of frequency-selective channels. We characterize the sum spectral efficiency and spectral efficiency regions for both the optimal and linear minimum mean-squared error (MMSE) multiuser receivers. Both independent and identically distributed (i.i.d). signatures and isometric signatures, which are orthogonal at each transmitter, are considered. Our results are asymptotic as the number of signatures per user and processing gain both tend to infinity with fixed ratio. The spectral efficiency of the MMSE receiver is determined from the asymptotic output signal-to-interference-plus noise ratio (SINR). For isometric signatures, our results rely on approximating certain covariance matrices with unitarily invariant matrices that are asymptotically free. This approximation is shown to be very accurate through comparison with both simulation and an "incremental-signature" analysis, which can be used to compute asymptotic moments. Also, a novel proof of the convergence of the empirical spectral distribution of the signal correlation matrix is presented. From these results, we derive the optimal coding-spreading tradeoff, which maximizes the MMSE spectral efficiency, for the case of a single user with multiple i.i.d. signatures. Simulation studies demonstrate that the asymptotic results accurately predict the performance of finite-size systems of interest. The resulting expressions are used to highlight and infer properties of the multisignature CDMA system, including the benefit of orthogonal relative to i.i.d. signatures, and the tradeoff between spectral efficiency and the versatility of providing a variable data rate service through multiple signatures.
Design and performance of multicarrier CDMA system in frequency-selective Rayleigh fading channels
Vehicular Technology, IEEE Transactions …, 1999
This paper presents the advantages and disadvantages of a multicarrier code-division multiple-access (MC-CDMA) system. The transmitter/receiver structure and the bandwidth of transmitted signal spectrum are compared with those of a conventional direct-sequence (DS) CDMA system, and an MC-CDMA design method, how to determine the number of subcarriers and the length of guard interval is discussed. The bit error rate (BER) lower bounds for DS-CDMA and MA-CDMA systems are derived and their equivalence is theoretically demonstrated. Finally, the BER performance in downlink and uplink channels with frequency-selective Rayleigh fading is shown by computer simulation.
Wireless Personal Communications
The bit-error rate (BER) for a forward-link cellular direct-sequence code-division multiple-access (DS-CDMA) system is evaluated. This analysis takes into account the effects of multi-cell interference resulting from Nakagami multipath fading, frequency selectivity, path loss and mobile user spatial distribution. Exponentially decaying multipath intensity profile (MIP) is adopted in the model to investigate its significance on the overall performance. In order to evaluate the BER performance efficiently, saddlepoint integration (SPI) is applied in the analysis. By fixing the number of resolvable multipaths and varying the number of fingers for the RAKE receiver, it can be shown that the capacity of a DS-CDMA cellular system increases almost linearly with the number of RAKE fingers.