Multi-carrier transmission techniques for wireless communication systems: a survey
WSEAS TRANSACTIONS on COMMUNICATIONS
WiMAX femtocell: requirements, challenges, and solutions
IEEE Communications Magazine
Spectrum allocation in tiered cellular networks
IEEE Transactions on Communications
Self-Optimization of Spectrum Assignment and Transmission Power in OFDMA Femtocells
AICT '10 Proceedings of the 2010 Sixth Advanced International Conference on Telecommunications
Femtocells: Technologies and Deployment
Femtocells: Technologies and Deployment
Open vs. closed access femtocells in the uplink
IEEE Transactions on Wireless Communications
IEEE Transactions on Wireless Communications
A microcell/macrocell cellular architecture for low- and high-mobility wireless users
IEEE Journal on Selected Areas in Communications
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Femtocells provide indoor coverage for voice and high speed data services and are self-deployed by end-users. Orthogonal frequency code division multiplexing (OFCDM) is a multi-carrier spread spectrum technique that utilizes two dimensional spreading in time and frequency domains simultaneously to improve frequency diversity and minimize multiuser access interference. In this paper, variable spreading factor (VSF)-OFCDM is employed in subcarrier allocation for femto users (FUEs) in a hybrid femto/macro network, and the effect of FUE deployment on macro users (MUEs) is studied. We evaluate the bit error rate (BER) performance of FUEs and MUEs through Monte Carlo simulation under various load conditions in noise and interference-limited scenarios. Relationship between the channel load and optimum spreading factor employed by FUEs for the given network configuration, is also analyzed. We provide various graphs showing the impact of FUE spreading factor on the MUE BER. We note that in interference-limited conditions, $$4\times 8$$ spreading $$(\text{ time}\times \text{ freq}.)$$ proves to be the best choice for macro users; and for the noise-limited case, when there are limited number of users and channel noise is dominant, $$2\times 16$$ spreading is the optimum choice for the considered hybrid network configuration. We also evaluate the effect of femto wall penetration loss on macro BER for various spreading factors. The favorable spreading factor for MUEs is tabulated for different loads and different number of subcarriers, which can be used as a deployment guide in this heterogeneous network.