On OFDMA Resource Allocation and Wavelength Assignment in OFDMA-Based WDM Radio-Over-Fiber Picocellular Networks

This paper addresses the orthogonal frequency-division multiple access (OFDMA) resource allocation and wavelength assignment problems in wavelength-division multiplexing (WDM) radio-over-fiber picocellular networks with OFDMA as the wireless modulation and access scheme. We consider the case that the number of WDM wavelengths is limited in which one wavelength is shared among multiple picocells. The set of picocells sharing the same wavelength is referred to as a nanocell in this paper. Since picocells in the same nanocell cannot be allocated with OFDMA resource block (RB) of the same frequency at a time, the intra-nanocell interference is eliminated. However, picocells in different nanocells may be allocated with OFDMA RBs of the same frequency at a time, thus posing interference to each other. To minimize the inter-nanocell interference, OFDMA RBs of the same frequency are assigned to picocells which pose the least interference to each other. However, this may result in some picocells being allocated with a large number of OFDMA RBs, leading to the limited power share received by each OFDMA RB because of the power constraint of the picocell. To minimize the inter-nanocell interference with consideration of the power constraints of picocells, we recast the OFDMA resource allocation and wavelength assignment problems into graph problems, and then propose corresponding solutions.