Performance of orthogonal CDMA codes for quasi-synchronous communication systems

DaSilva, V.M.; Sousa, E.S.

doi:10.1109/icupc.1993.528528

Cited by 139 publications

(86 citation statements)

References 8 publications

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“…NONCOOPERATIVE POWER CONTROL GAME IN MULTICARRIER SYSTEMS Let us consider the uplink of a synchronous multicarrier DS-CDMA data network with users, carriers and processing gain (for each carrier). The carriers are assumed to be sufficiently far apart so that the (spread-spectrum) signal transmitted over each carrier does not interfere with the signals transmitted over other carriers [11]. We also assume that the delay spread and Doppler spread are negligible for each individual carrier.…”

Section: Withmentioning

confidence: 99%

“…Proof: We first show that is maximized when is such that . For this, we take the derivative of with respect to and equate it to zero to obtain (11) Since for all linear receivers [9], is maximized when , the (positive) solution to . It is shown in [17] that for an S-shaped function, exists and is unique.…”

Section: Withmentioning

confidence: 99%

“…In particular, in multicarrier direct-sequence CDMA (DS-CDMA), the data stream for each user is divided into multiple parallel streams. Each stream is first spread using a spreading sequence and is then transmitted on a carrier [11]. In a single-user scenario with a fixed total transmit power, the optimal power allocation strategy for maximizing the rate is waterfilling over the frequency channels [12].…”

mentioning

confidence: 99%

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A game-theoretic approach to energy-efficient power control in multicarrier CDMA systems

Meshkati

Chiang

Poor

et al. 2006

IEEE J. Select. Areas Commun.

261

283

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Abstract-A game-theoretic model for studying power control in multicarrier code-division multiple-access systems is proposed. Power control is modeled as a noncooperative game in which each user decides how much power to transmit over each carrier to maximize its own utility. The utility function considered here measures the number of reliable bits transmitted over all the carriers per joule of energy consumed and is particularly suitable for networks where energy efficiency is important. The multidimensional nature of users' strategies and the nonquasi-concavity of the utility function make the multicarrier problem much more challenging than the single-carrier or throughput-based-utility case. It is shown that, for all linear receivers including the matched filter, the decorrelator, and the minimum-mean-square-error detector, a user's utility is maximized when the user transmits only on its "best" carrier. This is the carrier that requires the least amount of power to achieve a particular target signal-to-interference-plus-noise ratio at the output of the receiver. The existence and uniqueness of Nash equilibrium for the proposed power control game are studied. In particular, conditions are given that must be satisfied by the channel gains for a Nash equilibrium to exist, and the distribution of the users among the carriers at equilibrium is characterized. In addition, an iterative and distributed algorithm for reaching the equilibrium (when it exists) is presented. It is shown that the proposed approach results in significant improvements in the total utility achieved at equilibrium compared with a single-carrier system and also to a multicarrier system in which each user maximizes its utility over each carrier independently.

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Section: Withmentioning

confidence: 99%

Section: Withmentioning

confidence: 99%

mentioning

confidence: 99%

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A game-theoretic approach to energy-efficient power control in multicarrier CDMA systems

Meshkati

Chiang

Poor

et al. 2006

IEEE J. Select. Areas Commun.

261

283

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“…Each bin with coordinate (n,q) represents the signal transmitted on the n th sub-carrier of the q th OFDM symbol. , this resumes to a MC-CDMA scheme [7] and for N F =1, to MC-DS-CDMA [8].…”

Section: System Modelmentioning

confidence: 99%

Sensitivity of OFDM-CDMA Systems to Carrier Frequency Offset

Nasser

Noes

Ros

et al. 2006

2006 IEEE International Conference on Communications

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Abstract-This paper presents the impact of a carrier frequency offset on the performance of 2 dimensional spreading OFDM-CDMA systems. This is measured by the degradation of the Signal to Interference plus Noise Ratio (SINR) obtained after despreading and equalization. Using some properties of random matrix and free probability theories, a new expression of the SINR is derived. It is independent of the actual value of the spreading codes while still accounting for the orthogonality between codes. This model is validated by means of MonteCarlo simulations. . It is also exploited to compare the sensitivities of MC-CDMA and MC-DS-CDMA systems to carrier offset in a frequency selective channel. This work is carried out for zero forcing (ZF) and minimum mean square error (MMSE) equalizers.

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“…In a channel affected only by additive white Gaussian noise (AWGN), the system. in [9] is simple to implement, and with a longer symbol time, i t offers the advantages of easier sequence synchronization and multipleaccess interference (MAI) reduction, which in turn may lead to an increase in performance over a single carrier DS-CDMA system (SC-DS-CDMA). However, in the presence of multipath fading, the MC system is disadvantageous when compared to a SC-DS-CDMA system using a RAKE receiver.…”

Section: Introductionmentioning

confidence: 99%

Multicarrier CDMA with adaptive frequency hopping for mobile radio systems

Chen

Sousa

Pasupathy

1996

IEEE J. Select. Areas Commun.

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Abstract-A modified multicarrier (MC) direct-sequence codedivision multiple-access (DS-CDMA) system has been proposed for use over slow multipath fading channels with frequency selectivity in the reverse link transmission of a cellular network. Instead of transmitting data substreams uniformly through subchannels, data substreams hop over subchannels with the hopping patterns adaptively adjusted to the channel fading characteristics. The problem of determining the optimal hopping pattern is formulated as a multiobjective optimization problem, for which an efficient algorithm, based on the water-filling (WF) principle, is designed to solve the problem practically. Simulation results show that the performance in terms of the average bit-error probability (BEP) (over all users) is better than that of single carrier RAKE receiver systems, conventional MC CDMA systems applying moderate error protection, or diversity systems with different combining techniques.

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Performance of orthogonal CDMA codes for quasi-synchronous communication systems

Cited by 139 publications

References 8 publications

A game-theoretic approach to energy-efficient power control in multicarrier CDMA systems

A game-theoretic approach to energy-efficient power control in multicarrier CDMA systems

Sensitivity of OFDM-CDMA Systems to Carrier Frequency Offset

Multicarrier CDMA with adaptive frequency hopping for mobile radio systems

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