Analysis and design of reliable and stable link-layer protocols for wireless communication

Wireless links are error-prone and susceptible to noise imposed by fading, interference and mobility. Therefore, current wireless networks suffer from high packet loss and poor connectivity among users. Wireless link-layer protocol embedded in Medium Access Control (MAC) has a significant role in providing robust information delivery over wireless channels. A primary focus of popular wireless link-layer protocols is to achieve some level of reliability using ARQ or Hybrid ARQ mechanisms. However, these and other leading link-layer protocols largely ignore the stability aspect of wireless communication, and rely on higher layers to provide stable traffic flow control. This thesis investigates the problem of reliable and stable transmission over wireless channels and highlights the inadequacies of the current IEEE802.11 standard link-layer which attempts to recover from losses using retransmissions.;In this thesis, we aim to tackle the critical issues associated with the inefficiencies of current wireless link-layer protocols and pursue a paradigm shift in the conventional 802.11 link-layer design. We develop a new link-layer framework to provide both the reliability and stability for point-to-point contention free wireless communication.;Using this framework, we introduced four link-layer protocols: (1) Packet Embedded Error Control (PEEC) protocol, a link-layer protocol designed to ensure reliable wireless communication by reducing the number of retransmissions which essentially leads to improving system throughput. PEEC is layer oblivious and uses the packet formats of current IEEE802.11 standard; (2) Delay Constraint PEEC (DC-PEEC), an extension of the PEEC protocol that targets the flow control of realtime video traffic (in addition to reliability) in wireless communication. DC-PEEC adjusts its parameters to provide low-latency communication to satisfy the delay constraint (required by the video application) while utilizing the channel bandwidth effectively; (3) Automatic Code Embedding (ACE) link-layer protocol, the first effort to develop a theoretical framework for analyzing and designing a wireless link-layer protocol that targets system stability in conjunction with reliable communication. The ACE protocol uses a unique and optimal code embedding rate to construct coded link-layer packets in every transmission to ensure stability, reliability and maximum throughput; (4) Prioritized ACE (PACE), the ACE based stable-and-reliable link-layer that employs a novel rate-adaptive Low Density Parity Check (LDPC) channel codes while interacting with the higher layers to provide a dynamic decoder scheduling service over varying wireless channel condition. PACE provides prioritized wireless link-layer communication that takes into consideration the level of importance/impact of each packet to improve the overall performance. Our analysis and results of various experimental scenarios show that these protocols significantly outperform all competing link-layer protocols. Our findings in this thesis indeed provide a clear evidence of the feasibility of designing stable and reliable link layer over point-to-point (single-hop) 802.11 channels; and more importantly the potential of achieving significantly improved throughput by using this type of link-layer.