OFCDM-based small femtocells embedded in OFDM-based macro cellular network

To extend indoor coverage and offload cellular network traffic, femtocell technology becomes more promising. Multi-carrier spread spectrum technology has proven to be effective in multiple access and provides robust performance in fading radio channels. In this paper, VSF-OFCDM is utilized for sub-carrier allocation with two dimensional spreading (2D) for femto users (FUEs) in small cells that are deployed within an OFDMA macro network. The performance of femto/macro hybrid network is investigated by deriving closed form expressions for the SINR for FUEs and macro users (MUEs) in uplinks, that are impacted by different types of interferers, 2D spreading factors and load conditions. We also evaluate the BER performance of FUEs and MUEs through Monte Carlo simulation in interference- and noise-limited scenarios for different parameters.