Adaptive multiuser detection for mobile-centric fast handoffs in pseudocellular wireless networks

We optimize jointly the physical and medium access control layers for enabling rapid, contention-based reservations in wireless networks. Users contend by randomly choosing reservation slots for transmitting, randomly choosing the "phase" of a common periodic training sequence known to the access point, and randomly choosing short spreading sequences not known to the access point. Adaptive multiuser detection based on the differential minimum mean squared error criterion is employed, thus permitting reliable demodulation of multiple contending users in a reservation slot despite multiuser interference (and possibly a near-far problem), fading, lack of carrier synchronization, and lack of knowledge of the users\´ spreading sequences. We show that multiple reservations are successful in a reservation frame with high probability, thus drastically reducing the delay compared to reservations based on classical slotted ALOHA. These techniques are applied to achieve rapid, mobile-centric handoffs in pseudocellular networks with small, wireless LAN sized cells supporting real-time applications under vehicular mobility.