Signal processing in wireless packet networks

Date of Completion

January 1999


Engineering, Electronics and Electrical




The independent-layer-design methodology, which is widely used in designing wireline networks, restricts signal processing to the physical layer. However, for wireless networks, such methodology does not necessarily lead to a bandwidth-efficient network design. This dissertation examines two topics concerning signal processing and bandwidth utilization in high speed wireless packet networks. ^ In the first topic, we study the equalizer design problem in wireless Asynchronous Transfer Mode (ATM) networks. We propose the Protocol-Aided Channel Equalization (PACE) approach to exploit Medium Access Control (MAC) protocol information in the equalizer design to improve the efficiency of bandwidth utilization and maintain good radio link quality. A Blind Channel Estimation-Decision Feedback Equalization (BCE-DFE) algorithm is designed for up-link data transmissions so that training symbols can be eliminated and the propagation of channel estimation errors is avoided. ^ In the second topic, we study the impact of signal processing on the network performance. Two types of slotted Aloha Code Division Multiple Access (CDMA) networks are considered: cellular and Ad-Hoc. We divide this topic into two parts. In the first part, we focus on Ad-Hoc networks and use a general Multiple Packet Reception (MPR) model to describe reception capabilities of spread spectrum receivers. The key issue of converting the single node MPR to the network MPR at the link layer is addressed and a closed-form solution is provided. A throughput bound is also derived for such Ad-Hoc networks. In the second part, we apply the results obtained in the first part to CDMA networks and quantitatively analyze the effect of spreading gain and error control coding on the network performance for cellular and Ad-Hoc systems. The efficiency of bandwidth utilization in both systems is investigated by normalizing the network performance with respect to the consumed bandwidth. In addition, we compare the performance of the cellular network with that of the Ad-Hoc network to gain insights into the relationship between the network architecture and the network performance. ^