A Performance Analysis of a Joint Lmds/Satellite Communication Network

The goal of this research is to provide a performance analysis of a joint-terrestrial/satellite communication network. The systems of interest are the Local Multipoint Distribution Service (LMDS) terrestrial system and the proposed Teledesic satellite network. This analysis is performed using the OPNET network simulation tool. Simulations are run for twelve separate scenarios involving three factors which include: number of users, modulation type, and Quality of Service (QoS). The key metrics for characterizing simulation scenarios are the end-to-end delay, bit error rate, and average system throughput. The results obtained display the benefit of improved throughput, approximately 20 Mbps for the low user load and approximately 8 to 11 Mbps for the high user load, when the modulation schemes where changed. This improvement cones at the expense the bit error rate. For example, the bit error rate increased by a factor of 5 for the low user load when changing from BPSK to QPSK and by a factor of 1.5 for the QPSK to 8-PSK change. The peak end-to-end delay results, ranging from .053 seconds to .446 seconds, proved to support real-t voice communication for all but one scenario (BPSK/ high user load). The QoS proved to be a benefit for scenarios with a high user load (150 users) increasing the average throughput by 2 to 4 Mbps. The QoS also reduced the peak end-to-end delay, narrowing the range from .04 to .104 seconds. The analysis of these three main operational characteristics gives a fundamental look at the joint network's performance capabilities.