Abstract
Random packet CDMA (RP-CDMA) is a recently proposed random transmission scheme which has been designed from the beginning as a cross-layer method to overcome the restrictive nature of the Aloha protocol. Herein, we more precisely model its performance and investigate throughput and network stability. In contrast to previous works, we adopt the spread Aloha model for header transmission, and the performance of different joint detection methods for the payload data is investigated. Furthermore, we introduce performance measures for multiple access systems based on the diagonal elements of a modified multipacket reception matrix, and show that our measures describe the upper limit of the vector of stable arrival rates for a finite number of users. Finally, we simulate queue sizes and throughput characteristics of RP-CDMA with various receiver structures and compare them to spread Aloha.
Highlights
Channel access can be performed either in a centrally controlled or distributed fashion
As a result of these specific assumptions, it was concluded that Random packet CDMA (RP-CDMA) allows to approach the capacity of the multiaccess channel, and system performance is only limited by the capabilities of the base station in terms of the number of decodeable concurrent transmissions
(2) We investigate the behavior of the matched filter, the MMSE, the decorrelation receiver, as well as partitioned spreading demodulation for the data frame of the RP-CDMA packet in a multipacket capture channel
Summary
Channel access can be performed either in a centrally controlled or distributed fashion. As has been shown in [6], RP-CDMA has the potential to greatly improve system throughput and to approach the goodput (“raw” channel capacity minus signaling overhead) of scheduled channel access This is achieved through a reduction of the probability of packet collisions combined with multiuser detection technology to resolve multiuser interference. As a result of these specific assumptions, it was concluded that RP-CDMA allows to approach the capacity of the multiaccess channel, and system performance is only limited by the capabilities of the base station in terms of the number of decodeable concurrent transmissions. It follows from those references that Λn serves as the upper limit of the stable arrival rates for n users Using those metrics, we present more detailed and realistic results for the possibilities as well as limitations of RP-CDMA header and data transmission than those derived in [6].
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