Reception of Multiple Users in Reconfigurable Networks
Juan M. Velazquez-Gutierrez, Cesar Vargas-Rosales, Rafaela Villalpando-Hernandez and Ivan G. Ayala-Ezquivel
Reconfigurable wireless networks (RWNs) are temporal networks formed through opportunistic communication links such as in ad-hoc and sensor networks. RWN has important challenges due to their dynamic nature with frequent changes in topology, connectivity, and active or inactive wireless device (WD) status, that produce changes in wireless channel conditions. Multiuser channel problems such as hidden and exposed terminals are avoided through multiple access techniques that consider temporal, spectral and spatial dimensions. In this paper, we introduce a communication system that uses the attractive features of code division multiple access (CDMA), and the properties of sequences for coexistence schemes to avoid the implementation of a dynamic multiple access technique in a RWN. The system uses an origin-destination pair of sequences to encode the information, increasing the security in communication links. We compare both systems, traditional direct sequence CDMA (DS-CDMA) with different families of sequences and ours with code selection. Our results indicate that under equal conditions, the proposed system is robust to hidden terminal interference, while the traditional system is not. This is an important advantage in order to have the feature of simultaneous reception of information from multiple sources.
Keywords: Multiple users, multiple reception, orthogonal sequences