Spread Spectrum Interference Mitigation with Variable Processing Gain
Abstract
Designing a spread spectrum signal for the worst case channel conditions can be wasteful of system resources such as bandwidth and network throughput capacity. This report focuses on the performance of spread spectrum system based on multi-carrier modulation, also known as Orthogonal Frequency Division Multiplexing (OFDM), which provides variable processing gain by adjusting the redundancy in the signal in response to the channel conditions. A signal structure based on OFDM is defined and a technique for adapting the signal properties, including the data rate, in response to channel conditions and/or transmission requirements, is developed. Analytical and simulation results demonstrate that the signaling format can maintain a desired error rate performance over a wide range of channel conditions. The report also considers the impact of this variable signaling scheme on the upper layers of the network and, in particular, the data link layer. Classic throughput analysis for fixed and random access schemes is extended for this proposed adaptive packet radio network. The focus in on pure-ALOHA and non-persistent CSMA (NP-CSMA) systems. A large improvement in throughput is demonstrated for the adaptive system, as compared to a conventional fixed rate system, for various mobile user population profiles and radio propagation path loss models.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1999
- Accession Number
- ADA372117
Entities
People
- Gary J. Saulnier
- Zhong Ye
Organizations
- Rensselaer Polytechnic Institute