A wireless packet multiple access method exploiting joint detection

Abstract

A new packet-based, multiple access scheme for connectionless, uncoordinated random access is proposed using code-division multiple access (CDMA) as the physical access method. The new method uses a novel packet format with a common header with identical spreading codes for all users and packets, and random spreading codes for the data portion. The receiver operates in two stages: header detection using a conventional spread spectrum receiver and data detection using a multiuser detector to allow for decoding of overlapping active packets. The headers are spread with a large enough processing gain to allow detection even in severe interference.It is shown that this system is detector capability limited and that it can significantly outperform conventional ALOHA systems whose performance is limited by the collision mechanism. This system also experiences a much smaller packet retransmission rate and better spectral efficiency than conventional or spread ALOHA.

A MAC Method with Joint Detection for Ad Hoc Networks

“…Simulation results show that the performance of our proposed scheme is superior to that of Kota 's and Nagaraj's scheme proposed in [4] and [5].…”

“…Collision is assumed to be destroyed and a transmission not to be successful. In [4], Aloha is adopted for the Physical Layer Header (PLH) of a packet. In Aloha system, a node transmits whenever it has data to transmit.…”

“…A novel MAC scheme exploiting joint detection is proposed by Kota in [4]. Nagaraj introduce a variant of the scheme that uses Carrier Sense Multiple Access (CSMA) for the Physical Layer Header (PLH) of a packet in [5].…”

“…This flexibility introduces new challenges of developing efficient protocols for ad hoc networks. The throughput of the network depends largely upon the performance of the medium access control (MAC) algorithm [1][2][3][4][5]. Two phenomena in channel accessing schemes have major impact on the network throughput: the hidden and the exposed terminal problems.…”

“…To address these problems, a channel access method exploiting joint detection of overlapping packets is proposed by Kota in [4]]. In this paper, we propose an improvement on the method, which uses CSMA/CD medium access protocol for the RTS/CTS control packets and transmitter-based code assignment for spreading the data packets.…”