| Conventionally in packet-oriented random access networks, the colliding packets are discarded and later retransmitted, resulting in decreased throughput performance. Collision resolution strategies help recover collided packets and subsequently increase network throughput. The ability to combat collisions makes DS-CDMA a promising modulation scheme to be adopted in wireless ad hoc networks. In this thesis, we will first introduce a novel spreading code scheme that is particularly adapted to decentralized random access ad hoc networks. Then we will discuss the active user identification module and multiuser detection module of the receiver, both implemented using subspace techniques. The active user identification module identifies the users trying to reach the receiver. And the multiuser detection module decodes these packets of interest by blindly rejecting unknown interferers. In addition, we will also investigate a few interesting subspace techniques that may enhance the active user identification capability when multiple receiver antennas are available. |
