Investigating Distributed RF/Microwave Wireless Relays

University Of California-Riverside, Riverside CA

Investigators

Abstract

0401310 Hua This project investigates a novel concept of wireless communications, which is based on cooperative nature of multiple wireless mobile nodes within the framework of mobile ad hoc networks. But unlike the previously explored approaches that are mostly medium access control (MAC) protocols, this project aims at improving the capacity of the most fundamental physical link via multiple distributed wireless relays. These relays that are clustered and located anywhere between a source and a destination do not perform the conventional store-and-forward operations, but rather they are programmed to perform space-time modulation on their received baseband signals that are corrupted by both fading and noise. These relays do not need to exchange symbols with each other, and no feedback of channel state information is necessary. Hence, the burden on the MAC layer is reduced, and the ability to adapt to fast time-varying environment is improved. Such an array of relays performs like an array of wireless antennas, and reduces the negative effect of small scale fading on the signals received at the destination. With the space diversity achieved by the relays, the effective channel between the source and the destination becomes virtually free of small scale fading, which resembles wireline communications. The relays to be developed in this project are a function rather than a rigid device, and this function can be embedded in all mobile nodes, and more importantly can be embedded under the MAC based cooperative schemes. This project goes beyond the traditional mode of research, and the PIs of complementary strength have laid out a vertically integrated research plan to rapidly further develop the concept of distributed wireless relays, which is already proven to be promising based on a preliminary study. Broader Impact: Wireless communication technology will continue to evolve to meet the needs of future generations of mankind. One of the desired features of wireless communications is a fully mobile wireless network where neither base-station nor pre-existing infrastructure is required. Such a communication network is desired by people working and moving in remote areas and by the general public in the events of catastrophe. Distributed wireless relays may also be a useful solution to enhance the capacity of the cellular mobile systems, and the quality of future wireless communications may become seamless from that of wireline communications. A preliminary study by the PI shows that with distributed wireless relays, the total power consumption can be reduced by more than 10 dB from the baseline of the traditional single relay system. When fully proven and implemented, this power saving may imply that all batteries used in mobile nodes in a dense mobile network could last more than ten times longer. This project is not only likely to lead to technological breakthrough, but also will help the training of graduate students and undergraduate students (especially minority students) from two campuses of the University of California, who may become the first entrepreneurs to benefit the society by using distributed wireless relays in wireless communications.