Slotted DS/SSMA ALOHA with packet combining in a Rayleigh fading channel

TitleSlotted DS/SSMA ALOHA with packet combining in a Rayleigh fading channel
Publication TypeConference Paper
Year of Publication1996
AuthorsBigloo, A. M. Y., T. A. Gulliver, and V. K. Bhargava
Conference NameVehicular Technology Conference, 1996. 'Mobile Technology for the Human Race'., IEEE 46th
Pagination1710 -1714 vol.3
Date Publishedapr.
Keywordsaccess protocols, BPSK modulation, channel capacity, code division multiple access, diversity order, diversity reception, FEC, forward error correction, frequency selective channel, land mobile radio, mobile environment, multi-path intensity profile, multipath channels, packet combining, packet radio networks, phase shift keying, power control, pseudonoise codes, radio receivers, RAKE receiver, Rayleigh channels, Rayleigh fading channel, slotted ALOHA packet radio system, slotted DS/SSMA ALOHA, spread spectrum communication, throughput

A DS/SSMA slotted ALOHA packet radio system using BPSK modulation and a RAKE receiver is considered in a mobile environment. We assume a Rayleigh fading channel, with an exponential multi-path intensity profile (MIP) for all users which in conjunction with CDMA results in a frequency selective channel. Average power control is assumed, which means that on average the same power is received from each user. The receiver retains and combines all received copies of a packet, instead of discarding those which are detected in error. This effectively results in a multiplication of the diversity order at the RAKE receiver, by a factor d, where d is the number of packet copies being combined. The throughput and the average number of transmissions to transmit a packet successfully with FEC are evaluated. It is shown that combining the received copies of a packet results in a throughput which is an increasing function of the offered load (at least for a broad range of the offered load). This ensures a stable (or at least more stable) system. It is also shown that this combining results in a higher throughput and a lower average number of transmissions to successfully obtain a packet


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