Load-Based Transmission Control for CDMA Cellular Packet Systems with Rayleigh Fading Channels

Kazuo MORI

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E82-A    No.7    pp.1151-1160
Publication Date: 1999/07/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Multi-dimensional Mobile Information Networks)
CDMA,  packet communication,  power control,  processing gain control,  fading channel,  

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This paper proposes an adaptive transmission control scheme for code-division multiple-access (CDMA) cellular slotted-ALOHA systems. This scheme adaptively controls the target received power and the processing gain according to both channel load and location of the mobile station. The target received power of each mobile station is controlled so that the difference between the target received powers by distance becomes large under heavy load conditions. As the distance from the base station increases, the target received power becomes smaller. The processing gain of transmitted packets is concurrently controlled with their target received powers. The packets transmitted with low signal power are spread by a large processing gain in order to reduce the unfairness in packet reception. The radio channels with distance attenuation, shadowing, slow Rayleigh fading and imperfect power control are taken into consideration in order to evaluate the performance of this scheme in the case that mobile stations transmit short massages to the base station in cellular environments. Computer simulation validates the effectiveness of this scheme: the capture effect can be achieved under heavy channel loads, and therefore, throughput performance is improved. Detailed evaluation of throughput, packet reception probability and transmission complete probability is presented. The effect of movement of mobile stations is also discussed. Calculated results show that the proposed scheme has superior characteristics and thus can expand the allowable load area in the cellular environments with slow Rayleigh fading channels.