Data networks
Multi-Carrier Digital Communications: Theory and Applications of Ofdm
Multi-Carrier Digital Communications: Theory and Applications of Ofdm
OFDM for Wireless Multimedia Communications
OFDM for Wireless Multimedia Communications
Spectral efficiency of CDMA with random spreading
IEEE Transactions on Information Theory
Linear multiuser receivers: effective interference, effective bandwidth and user capacity
IEEE Transactions on Information Theory
Large system performance of linear multiuser receivers in multipath fading channels
IEEE Transactions on Information Theory
Asymptotically optimal water-filling in vector multiple-access channels
IEEE Transactions on Information Theory
The impact of frequency-flat fading on the spectral efficiency of CDMA
IEEE Transactions on Information Theory
The throughput of hybrid-ARQ protocols for the Gaussian collision channel
IEEE Transactions on Information Theory
Opportunistic beamforming using dumb antennas
IEEE Transactions on Information Theory
Spectral efficiency of multicarrier CDMA
IEEE Transactions on Information Theory
How fading affects CDMA: an asymptotic analysis with linear receivers
IEEE Journal on Selected Areas in Communications
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We study uncoordinated multiple access using the orthogonal frequency division multiple access (OFDMA) technique where multiple users independently and randomly pick a sub-carrier from a set of sub-carriers for transmission in each slot. Signals transmitted on distinct sub-carriers are orthogonal to each other while signals transmitted by different users on the same sub-carrier interfere with each other. We study average throughput and outage probability performance of such a system in the asymptotic limit of large numbers of sub-carriers and users while keeping the ratio of number of users to sub-carriers fixed, for non-fading, flat fading, and frequency-selective fading additive white Gaussian noise channels. The performance is compared to that of a system in which all users spread their signal over all the sub-carriers as in a code division multiple access (CDMA) system. Our results show that at high signal-to-noise ratio (SNR), transmission without spreading results in higher throughput but requires more retransmissions on the average. At low SNRs, the throughput performance is comparable but the system with spreading requires smaller average number of retransmissions.