In future packet based wireless communication systems, transmission in the downlink will often dominate the traffic load. High bit-rate applications like WWW-browsing, file transfer, and full motion video will impose strong requirements on the system capacity. An obstacle in this context is the time-variability of the channel: For mobile users, frequently occuring fading dips will cause unneces-sary, and capacity degrading, retransmissions. To achieve a high throughput also over fading channels, adaptive methods for adjustment of e.g. the modulation alphabet, and the coding complexity, can be used. The idea is to make efficient use of the bits: Whenever channel conditions are adequate, transmission of redundant bits should be avoided. In this paper we shall investigate the effect of adaptive modulation in a scenario involving one mobile and one base station.
