Spectrum pool reassignment for wireless multi-hop relay systems

We consider a wireless multi-hop relay system that operates on secondary sharing basis in licensed spectrum. The system employs OFDM-based spectrum pooling to avoid harmful interference to licensed systems. An OFDM-based spectrum pool comprises of a set of OFDM subchannels that correspond to white space spectrum regions. The proposed relay system comprises of a source node that transmits data to a destination node in multi-hops using multiple relay nodes. Communication over node pairs occurs on an available spectrum pool. At each receiving intermediate node, received data symbols are amplified, permuted and then forwarded on. Spectrum pool reassignment comprises determination of the permutation mapping at each intermediate node. We consider the problem of maximizing the system capacity by determining the optimum spectrum pool reassignment. We show that each relay can determine the optimum permutation mapping based on the effective signal to noise ratios in the previous hops and the signal to noise ratio in the next hop, while preserving system optimality.