MMSE PROTOCOL FOR A DOUBLE RELAY CHANNEL IN CELLULAR SYSTEMS

The continuous growth of demand for wireless connectivity has turned bandwidth into a scarce resource that should be carefully managed. A common solution is to assign disjoint portions of the bandwidth to different users, but the portion size decreases as the number of users grows. An alternative solution is to introduce spatial diversity through coordinated base stations, but such systems are very sensitive to timing and frequency synchronization offsets. To tackle these problems, we use principles of network coding for bandwidth management in a cellular system of two base stations and two users. We propose a three-time-slots transmission strategy and a MMSE reception strategy. It avoids the need of tight frequency or timing synchronization through a simple communication protocol without using additional bandwidth or infrastructure. By finding a balance between spatial diversity and transmission time, our approach achieves the system capacity and optimal fairness in all SNR conditions.