Cross-layer combination of hybrid ARQ and adaptive modulation and coding for QoS provisioning in wireless data networks

In this paper, we present a cross-layer design which combines adaptive modulation and coding (AMC) at the physical layer with type-II hybrid automatic repeat request (HARQ) at the data link layer for QoS provisioning under fading channels. To maximize system spectral efficiency as well as satisfy QoS parameters such as data rate, delay and packet error rate (PER), we have proposed a new cross-layer scheme, where AMC transmits incremental redundancy for combining decoding with type-II HARQ. The proposed cross-layer scheme is designed to meet the target packet error rate within the pre-defined number of retransmissions. Since the number of retransmissions can be determined by the maximum delay bound imposed by upper layer applications, the proposed scheme will provide guaranteed QoS in terms of data rate, delay and packet error rate under fading channels. We have theoretically analyzed the system PER performance, the spectral efficiency and goodput of the proposed cross-layer design scheme. Since the application packet size is one of the most crucial factors to affect the performance of the proposed scheme, we also introduce an adaptive algorithm to derive the optimal information packet size under the current channel condition to achieve the maximum throughput. Numerical results show that the proposed scheme can achieve the maximum spectral efficiency while satisfying the target delay, packet loss rate and goodput imposed by the applications.