Adaptive modulation and scheduling of IP traffic over fading channels

Abstract

In future packet based wireless communication systems, transmission in the downlink will often dominate the traffic load. An obstacle in this context is the time-variability of the channel. To achieve a high throughput also over fading channels, adaptive methods for adjustment of, for example, the modulation alphabet, and the coding complexity, can be used. We investigate the effect of adaptive modulation, along with time-slot scheduling of IP-like traffic in a scenario involving several types of mobile hosts and one base station. We extend a study of the impact of adaptive modulation and scheduling on the bit error rate, to include models for packet length and packet inter-arrival, to find the queueing delay imposed by our proposed scheduling algorithm. Our scheduler keeps the bit error rate at attractively low, prespecified levels, well suited for forward error correction (FEC) codes. Moreover, the scheduler splits the bandwidth between different types of traffic in a desirable way, according to the traffic situation.