http://hdl.handle.net/1983/42 Mon, 13 May 2013 18:47:46 GMT 2013-05-13T18:47:46Z http://hdl.handle.net/1983/1832 Location-aided multi-user beamforming for 60 GHz WPAN systems Zhu, X; Doufexi, A; Kocak, T 60 GHz wireless personal area networks (WPANs) offer multi-Gbps throughput, which will provide for a new wave of high data rate applications. This paper exploits the use of location information to improve the performance and enhance range of 60 GHz multi-user beamforming systems. When the location information is available at the transmitter, the scheduler chooses a set of maximum angularly separated users to share wireless resources simultaneously. If additional feedback of signal-to-interference and noise ratio (SINR) is known, a location-assisted scheduler is employed to increase the system overall performance. Both numerical and simulated results show that significant enhancement can be achieved by the proposed schedulers for 60 GHz WPAN systems. Tue, 01 May 2012 00:00:00 GMT http://hdl.handle.net/1983/1832 2012-05-01T00:00:00Z http://hdl.handle.net/1983/1831 CARLA: combining Cooperative Relaying and Link Adaptation for IEEE 802.11 wireless networks Li, L; Zhong, Fan; Kaleshi, D In this paper, we present a novel design named CARLA which combines Cooperative Relaying and Link Adaptation for IEEE 802.11 wireless networks, in order to maximize spectral efficiency and hence improve the throughput of the network. Unlike previous studies assuming that accurate channel information is available for relaying and link adaptation,the novelty of our approach is to use the expected packet transmission time (ETT) and RTS/CTS exchange to estimate the quality and level of contention for the current channel. By taking into account the quality of the direct channel from source to destination and the relay channel between relay and destination, CARLA enables both source and relay terminals to adjust their transmission rates so that not only the reliability of the transmission but also the bandwidth efficiency can be improved, hence fully utilizing the diversity gain. CARLA is a simple, distributed and rate-per-link adaptation protocol requiring no modification on 802.11 PHY and MAC. Simulation results show that CARLA can achieve significant performance improvement in terms of end-to-end throughput and energy efficiency for different network conditions. Tue, 01 May 2012 00:00:00 GMT http://hdl.handle.net/1983/1831 2012-05-01T00:00:00Z http://hdl.handle.net/1983/1827 Using multiple metrics for rate adaptation algorithms in IEEE 802.11 WLANs Li, L; Fan, Zhong; Kaleshi, D IEEE 802.11 Wireless LANs (WLANs) use rate adaptation algorithms (RAAs) to dynamically switch data rates to accommodate the fluctuating wireless channel conditions. Classic RAAs such as ARF and ONOE suffer from rate poisoning and nability to distinguish between collision and packet losses caused by channel errors. Existing approaches in the literature are able to solve only one of the above two issues. In this paper we propose a novel rate adaptation protocol to address both issues for multi-rate wireless networks. The novelty of our approach is to combine the metrics of expected packet transmission time (ETT) and the average number of frozen slots (ANFS) to estimate the quality and level of contention for the current channel. A mathematical model to calculate ETT and ANFS on the fly is presented. Our protocol is simple and practical, which takes into consideration not only link quality and frame loss characteristics, but also impact of collisions during the design. Simulation results show that without the perfect knowledge of current channel condition and any signal strength information, our algorithm can achieve significant performance improvement in terms of end-toend throughput for different network conditions compared with state-of-the-art link adaptation algorithms. Sun, 01 Apr 2012 00:00:00 GMT http://hdl.handle.net/1983/1827 2012-04-01T00:00:00Z http://hdl.handle.net/1983/1826 A performance enhancement for 60 GHz wireless indoor applications Zhu, X; Doufexi, A; Kocak, T This paper studies the throughput and range of the OFDM based IEEE 802.11ad millimeter-wave WPANs. The cross layer results show that the MIMO and beamforming schemes with frame aggregation and block acknowledgement enhance the throughput and operation range compared to the case of single antenna with reasonable hardware complexity. With accompanying conference presentation Fri, 13 Jan 2012 00:00:00 GMT http://hdl.handle.net/1983/1826 2012-01-13T00:00:00Z