Capacity enhancements in wireless packet networks.

摘要

The last ten years have seen a tremendous increase in the development of wireless services. As these services mature, the expected large influx of new customers will stress network capacity. To solve the problem of serving more subscribers while maintaining acceptable quality of service, wireless system designers will have to either use more spectrum bands, make cells smaller and more densely distributed, or enhance the equipment technology to use bandwidth optimally.; In this thesis, we propose and quantify several possible enhancements to wireless networks. First, we study the reliability of a symmetric rectangular grid. These grids have been proposed as an enabling technology for the deployment of high capacity picocellular radio cells. For these types of networks, we address reliability and fault tolerance issues.; Second, we propose a heuristic scheduling algorithm that uses interference estimation and measurement as well as limited base station coordination to schedule segments in a power efficient way in a packet multi-code CDMA system. Our algorithm is fair in the sense that it seeks to transmit data to every user at an agreed upon QOS. The target QOS is a “delivery rate” for all terminals and a maximum segment loss rate per user. We show that in a fast flat fading environment, the number of acceptable users per cell more than doubles if complete knowledge of the multipath fade value is available a priori at the scheduler, as compared against a system where only the average shadow fading and path loss conditions are known when scheduling.; Finally, Wireless Local Loop (WLL) is a technology that is used to solve the last mile problem in countries with low wireline service penetration. A crucial issue for WLL is the system design so that the number of subscribers can be maximized while providing the required quality of service. The impact of the system parameters on the WLL performance is studied via simulation and useful insight on how to efficiently design the network is obtained.