Authors: Ju Wang, Jonathan C.L. Liu
Addresses: Department of Computer Science, Virginia Commonwealth University, Richmond, VA 23284, USA. ' Department of Computer, Information Science and Engineering, University of Florida, Gainesville, FL 32611-6250, USA
Abstract: We propose a hybrid uplink architecture that seamlessly integrates 802.11 WLAN (ad hoc mode) and WCDMA interfaces. In our scheme, mobile stations can be dynamically appointed as a Relaying Mobile Terminal (RMT) to forward uplink traffic. The RMT terminals significantly reduce the overall transmission activity and out-of-cell interference to the neighbouring cells. To find the close approximation of the optimum RMT set, we propose a two-approximation-based heuristic algorithm that is originally used to solve a minimum vertex set. The algorithm results in low out-of-cell interference, and the selected RMT terminals have good channel quality with the base stations. We further investigate the optimum uplink traffic scheduling algorithm subject to different Quality of Service (QoS) requirements (i.e. Bit-Error-Rates (BER)) and limited power budget at the RMT terminals. To provide a fair access and also have high radio efficiency (via spatial diversity), we adopt a proportional scheduling algorithm to coordinate the transmission among RMTs. Within a RMT, packets of different BER requirements are further scheduled via link-adaptive CDMA transmission scheme. We demonstrate that power/code allocation (inside the RMT scheduler) enables the reassignment of the slack power among traffics according to their BER requirements. It is thus possible that some BER-stringent traffic can be transmitted at a higher data rate. The simulation results are promising, showing at least 28% increase in overall throughput at different traffic patterns, including performance-guaranteed multimedia streams.
Keywords: 3G cellular networks; CDMA2000; uplink scheduling; relaying mobile terminals; out-cell-interference; quality-of-service; QoS; link adaption; WLANs; wireless LANS; wireless networks; local area networks; ah hoc networks; WCDMA interfaces; simulation; throughput; multimedia streams.
International Journal of Wireless and Mobile Computing, 2007 Vol.2 No.4, pp.288 - 302
Published online: 18 Jan 2008 *Full-text access for editors Access for subscribers Purchase this article Comment on this article