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arXiv · 1005.2731

Cross-Band Interference Considered Harmful in OFDM Based Distributed Spectrum Sharing

Wei Hou·Lin Zhang·Lei Yang·Heather Zheng·Xiuming Shan
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Abstract

In the past few years we have witnessed the paradigm shift from static spectrum allocation to dynamic spectrum access/sharing. Orthogonal Frequency-Division Multiple Access (OFDMA) is a promising mechanism to implement the agile spectrum access. However, in wireless distributed networks where tight synchronization is infeasible, OFDMA faces the problem of cross-band interference. Subcarriers used by different users are no longer orthogonal, and transmissions operating on non-overlapping subcarriers can interfere with each other. In this paper, we explore the cause of cross-band interference and analytically quantify its strength and impact on packet transmissions. Our analysis captures three key practical artifacts: inter-link frequency offset, temporal sampling mismatch and power heterogeneity. To our best knowledge, this work is the first to systematically analyze the cause and impact of cross-band interference. Using insights from our analysis, we then build and compared three mitigating methods to combat cross-band interference. Analytical and simulation results show that placing frequency guardband at link boundaries is the most effective solution in distributed spectrum sharing, while the other two frequency-domain methods are sensitive to either temporal sampling mismatch or inter-link frequency offset. We find that the proper guardband size depends heavily on power heterogeneity. Consequently, protocol designs for dynamic spectrum access should carefully take into account the cross-band interference when configuring spectrum usage.

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Wei Hou, Lin Zhang, Lei Yang, Heather Zheng, Xiuming Shan. 2010-05-16. Cross-Band Interference Considered Harmful in OFDM Based Distributed Spectrum Sharing. https://arxiv.org/abs/1005.2731

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