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In this paper we analyse the performance of multiple relay channels when multiple antennas are deployed only at relays. We apply two antenna diversity techniques at relays, namely maximum ratio combining (MRC) on receive and transmit beamforming (TB). We show that for both decode-and-forward and amplify-and-forward relaying protocols, with K relays the network can be decomposed into K diversity channels each with a different channel gain, and that the signals can be effectively combined at the destination. We assume that the total number of antennas at all relays is fixed at N. With a reasonable power constraint at the relays, the network capacity will be lower bounded by that of N relay channels each with single antenna, and upper bounded by that of single relay channel with N antennas.

Summary This paper proposes a transmission-scheduling algorithm for interference management in broadband wireless access networks. The algorithm aims to minimize the cochannel interference using basestation coordination while still maintaining the other quality of service (QoS) requirements such as packet delay, throughput and packet loss. The interference reduction is achieved by avoiding (or minimizing) concurrent transmission of potential dominant interferers. Dynamic slot allocation based on traffic information in other cells/sectors is employed. In order to implement the algorithm in a distributed manner, basestations (BSs) have to exchange traffic information. Both real-time and non-real-time services are considered in this work. Results show that significant reduction in the packet error rate can be achieved without increasing the packet delay at low to medium loading values and with a higher but acceptable packet delay at high loading values. Since ARQ schemes can also be used for packet error rate reduction, we compare the performance of the proposed scheme with that of ARQ. Results indicate that although ARQ is more effective in reducing packet error rate, the proposed algorithm incurs much less packet delay particularly at medium to high loading. Copyright # 2006 John Wiley & Sons, Ltd.

It is anticipated that there will be a strong market for a rich variety of wireless internet-based multimedia devices in the not-too-distant future. It is quite difficult to predict the nature of these devices as well as the corresponding applications; but it is certain that those devices and applications will have very different QoS, rate, delay and power constraints. Arguably, effective management of radio resources (through techniques such as interference management and cancellation, dynamic resource allocation and control, packet scheduling and call admission control) is not only essential in future networks, but is also the key factor in the efficient and affordable deployment and operation of these networks. Proportional to its importance, radio resource management appears to be an immensely complex task as well in future wireless networks. However, it is not yet clear whether this task is inherently difficult or whether it only appears so due to our lack of sufficient understanding of this multidimensional problem. As deeper insight into this field is developed by researchers, it is foreseeable that very efficient and straightforward (although suboptimal) algorithms can be developed. Research activities towards 4th generation mobile communication networks have already started; in the meanwhile, the standards for the 3rd generation networks are continuously being revised for higher performance. Not surprisingly, one main area of focus in all these activities is the better management of radio resources. This Special Issue is composed of nine papers (the first three of which are invited papers from the industry) discussing various aspects of radio resource management within the framework of wireless internet. The first invited paper, authored by Shalini Periyalwar et al. (Nortel Networks, Canada), is a visionary one in which radio resource management related issues are discussed for the envisioned future mobile broadband wireless networks. In the second invited paper, Werner Mohr (Siemens, Germany) presents an analytical model for estimating the spectrum demand for beyond-3G mobile networks, based on projected data rate requirements. In the third and final invited paper, Ralph Gholmieh (Ericsson, USA) and Farideh Khaleghi discuss one important feature in the recently revised version of the IS-2000 standard, the control-hold mode, which aims to maximize the throughput in the forward link. In the paper entitled ‘Linear successive interference cancellation in DS-CDMA systems’, Fredrik Berggren and S. Ben Slimane analyze the capacity performance of a receiver with interference cancellation capability which is supported by a novel interference cancellation-aware power control algorithm. The following two papers discuss different aspects of scheduling in CDMA networks. The first paper, authored by Sonia Aissa, Amine Maaref and Paul Mermelstein, proposes a novel flow control algorithm for multi-rate networks with interference cancellation, while the second paper authored by Tao Shu and Zhisheng Niu, demonstrates the optimum method of choosing (with respect to throughput maximization) concurrently transmitting data users. The paper authored by Walid Ibrahim, John W. Chinneck and Shalini Periyalwar, proposes a novel QoS-based charging and resource allocation framework which may potentially allow the network operators to pursue a wide variety of policy options. In the paper entitled ‘Radio resource management techniques for UE-MAC in 3GPP W-CDMA systems’, Sheng-Tzong Cheng and Jian-Liang Lin investigate the adverse effects of rapid transmission rate changes on the BER and they