Joint AMC and Packet Fragmentation for Error Control Over Fading Channels

Error control is critical for wireless networks to combat channel fading and ensure efficient resource utilization. Adaptive modulation and coding (AMC) in the physical (PHY) layer and packet fragmentation and automatic repeat request (ARQ) in the link layer are widely used error-control mechanisms. However, how to jointly optimize them in both layers for high-rate wireless networks is still open. In this paper, using the WiMedia ultrawideband (UWB) networks as an example, we first develop a general analytical framework to quantify the link delay and loss performance considering the channel fading, the joint error-control mechanisms, and the arbitrary reservation-based media access control (MAC) protocol. Second, we introduce a cross-layer design to optimize the PHY-layer AMC and the link-layer packet fragmentation and propose a joint-adaptation mechanism that is simple to implement and has near-optimal performance. Numerical results reveal that fragmentation has a greater impact than AMC on the delay and loss performance for marginal links and that the proposed joint-adaptation strategy is efficient for high-rate wireless networks.