This paper presents performance analysis and cross-layer design approaches for hybrid ARQ (HARQ) protocols in wireless networks, which employ adaptive modulation and coding (AMC) in conjunction with adaptive cooperative diversity and are subject to time-correlated fading channels. We first consider a point-to-point scenario, i.e., non-cooperative HARQ with AMC. Utilizing a Markov channel model which accounts for the temporal correlation in the successive transmission of incremental redundancy by the HARQ protocol, we derive the system throughput and the packet loss probability based on a rate compatible punctured convolutional code family. Next, we consider a cooperative HARQ (CHARQ) scheme in which a relay node, also equipped with AMC, retransmits redundancy packets when it is able to decode the source information packet correctly. For this scenario, we also derive the throughput and packet loss performance. Finally, we present a cross-layer AMC design approach which takes into account the hybrid ARQ protocol at the link layer. The results illustrate that including AMC in the HARQ protocols leads to a substantial throughput gain. While the performance of the AMC with HARQ protocol is strongly affected by the channel correlation, the CHARQ protocol provides noticeable performance gains over correlated fading channels as well

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In a cooperative relay network, a relay node (R) facilitates data transmission to the destination node (D), when the latter is unable to decode the source node (S) data correctly. This paper considers such a system model and presents a cross-layer approach to jointly design adaptive modulation and coding (AMC) at the physical layer and cooperative truncated automatic repeat request (ARQ) protocol at the data link layer. We first derive a closed form expression for the spectral efficiency of the joint cooperative ARQ-AMC scheme. Aiming at maximizing this performance measure, we then optimize two AMC schemes for S-D and R-D links, which directly satisfy a prescribed packet loss rate constraint. As an interesting application, we also consider the problem of joint link adaptation and blockage mitigation in land mobile satellite communications (LMSC). We also present a new relay-assisted transmission protocol for LMSC, which delivers the source data to the destination via the relaying link, when the S-D channel is in outage. Numerical results indicate that the proposed schemes noticeably enhances the spectral efficiency compared to a system, which uses a conventional ARQ-AMC scheme at the S-D link, or a system which employs an optimized fixed rate cooperative-ARQ protocol.

The effective capacity (EC) for a wireless system expresses the maximum arrival source rate that the system can reliably transmit over the wireless channel while fulfilling a probabilistic delay constraint. This paper presents an EC optimization for a multiuser diversity system exploiting proportional opportunistic scheduling at the medium access control layer in conjunction with adaptive modulation and coding (AMC) at the physical layer. We consider the downlink of a time‐slotted multiuser system with two different types of channel state information (CSI) at the transmitter, that is, (i) full CSI, whereby each user feeds back its normalized signal‐to‐noise ratio to the transmitter and (ii) quantized CSI, where each user feeds back the AMC mode for transmission. For each case, we first derive the EC function of the queue service process for the individual users at the medium access control layer. We then design the AMC scheme with power control aiming at maximizing the said function subject to a target packet‐error rate constraint. Both independent and identically distributed and time‐correlated fading channels are considered. The results illustrate the superior performance of the proposed schemes, when compared with the previous systems such as opportunistic scheduling with single‐rate transmission and round‐robin scheduling with AMC. Copyright © 2012 John Wiley & Sons, Ltd.

Aiming at improving the QoS performance over fading channels, this paper presents an analysis of the effective capacity for a relay-assisted communication system which utilizes a cooperative packet retransmission protocol at the link-layer in conjunction with AMC-based multi-rate transmission at the physical layer. In the considered model, a source (S) node employs AMC to transmit delay-constrained packet traffic to the destination (D) node. To achieve adaptive cooperative diversity, a relay node, also equipped with AMC, forwards the packet received from node S to node D if it was able to decode the source packet correctly and node D requested a packet retransmission. For this protocol we derive a closed-form expression for the effective capacity of the queue service process at node S. Numerical results reveal that the proposed cooperative protocol can dramatically increase the effective capacity with respect to a direct transmission system with AMC