Adaptive data link protocol for wireless communication networks

Abstract

In a wireless network, mobile stations experience multipath fading, severe shadowing and weather impairments, which cause burst errors to occur frequently. Therefore, in order to provide reliable transmission of packet data in such an environment, an efficient data link protocol is required, even though this could cause slight service delays. Error recovery schemes to cope with wireless channel noise have been investigated extensively. Conventional error recovery methods are based on automatic repeat request (ARQ) retransmission schemes, such as Stop-and-Wait (SAW), GO-Back-N (GBN), and Selective-Repeat (SR). Other approaches are related to the hybrid ARQ (HARQ), in which automatic repeat request scheme is combined with forward error control (FEC). In the ARQ and HARQ schemes, a fixed frame length is usually used, which is designed in the consideration of the worst channel condition and the overhead required per frame in mind. The frame length of the data link layer is an important factor that affects the throughput performance of wireless packet transmission. If the frame length could be chosen adaptively in response to the dynamically varying wireless channel, maximum throughput could be achieved in both noisy and non-noisy error conditions. In order to maximize the long-term throughput performance, the short-term performance must be optimized over the time-varying wireless channel. This short-term best performance could be achieved if the optimal frame length could be chosen almost instantaneously. Further, the optimum frame length could be obtained by proper estimation of the wireless channel characteristics. So, if the short-term channel status of the instantaneous burst error channel could be estimated, good throughput performance would be achieved continuously. However, the estimation of error channel is difficult because there are various kinds of degradation due to fading, shadowing, and propagation loss. The bit error rate(BER) and the duty cycle of n...