REAL TIME IMPLEMENTATION OF A MULTIUSER DETECTION ENABLED AD-HOC NETWORK

In contrast to the interference avoidance paradigm that conventional wireless communication systems follow, the DARPA Interference Multiple Access (DIMA) Communications program intentionally structures multiple-access interference to enable high-capacity, low-latency, spread spectrum communications. The system's adaptive multi-user detection (MUD) receiver algorithms enable the transmission of multiple data streams in the same time and frequency channel without need for centralized control of synchronization or power levels. This paper focuses on the DIMA system level implementation of the prototype radio network, along with the results from both non-real-time testing and real-time performance characterization efforts. Extensive simulations and non-real-time over-the-air testing helped to drive the design of a real-time MUD receiver implemented on a single FPGA. The Media Access Control Layer, implemented on a General Purpose Processor (GPP), facilitates intentional interference through a defined frame structure that also enables distributed synchronization and scheduling. During the real-time performance characterization period, the DIMA prototype network demonstrated 3.5 times the spectral efficiency of comparable 802.11 ad-hoc systems at low signal to noise ratios (SNRs). DIMA demonstrated up to 11x reductions in latency jitter in the same comparison. These gains can be leveraged in future military applications to provide increased capabilities and improved performance to the war fighter.