Performance Analysis of Large CDMA Random Access Systems with Retransmission Diversity over Fading Channels

Abstract

The random access systems, with retransmission diversity (RD) employment, over large random spreading code division multiple access (CDMA) channel subject to fading is investigated, under the assumption of infinite number of users and infinite spreading gain with their ratio converging to a constant. The low bound of the signal to interference and noise ratio (SINR) is shown to converge almost surely to a constant. The throughput, spectrum efficiency and energy efficiency in the dominating systems are obtained. The analytical results are confirmed by simulations. We find that in high traffic loads the throughput with fading is higher than that without. When the energy efficiency increases, the spectrum efficiency tends to two contrary values due to SNR increases or decreases. For the ordinary stable systems, the stability region is shown to shrink as the traffic increases and enlarge with RD employment.

Throughput of Coded DS CDMA/Unslotted ALOHA Networks with Variable Length Data Traffic and Two User Classes in Rayleigh Fading FSMC Model

“…Direct-sequence code-division multiple access (DS CDMA) is a wireless transmission technology which offers random access abilities and potential for higher throughput [1][2][3][4][5][6][7]. In [8][9][10][11][12][13][14][15], the DS CDMA/slotted ALOHA system is investigated in wireless and optical channels.…”

“…-12, we use error correction code, and the number of correctable bits is 6, 8 and 10.Figs 4. 6 shows that the simulation and numerical result of the proposed model versus the various Doppler frequency shift Fd with the number of correctable bit t =6, 8 and 10, respectively.…”