AUTOMATIC REPEAT REQUEST PROTOCOLS FOR RADIO CDMA SYSTEMS
Djoemadi, Faizal Rochmad
The Industrial, Science, and Medical USM) band has been allocated to meet the growing demand for data communications including VSAT tail circuit networks. The users are allowed to share the ISM band by using a particular transmission method known as spectrum spreading. One type of spread spectrum, which is suitable for multiple access radio, is Code Division Multiple Access (CDMA). In the CDMA system, the multiuser interference, multipath fading, and thermal noise result in transmission errors. Automatic- repeat-request (ARQ) protocols are commonly used to mitigate the effect of transmission errors. The stop-and-wait (SW) type of ARQ protocol offers simple implementation but has low throughput. In this thesis, new generalized-stop-and-wait (GSW) protocols that retain the simple implementation feature of the classical SW protocol, while reducing the transmitter's wait state time, are proposed to increase the throughput. The throughput performance of the GSW protocols over a CDMA system is analysed and verified by computer simulation. In particular, four type of GSW simulation methods termed GSW-l to GSW-4 are analyzed and compared, Both analytical and simulation results show that GSW-4 and GSW-3 protocols are superior under severe channel conditions to somewhat lower complexity protocols such as SW, GBN, GSW-1, and GSW-2. On the other hand, the GSW-1 protocol has the advantage of fairly simple protocol and no buffer. It offers the best solution when thermal noise is the limiting factor. Furthermore, the GSW-2 protocol is comparable in performance to well known GBN protocol under different delay conditions and for different buffer sizes.