Mitigation of Uplink ICI and IBI in OFDMA Two-Tier Networks

For two-tier networks using orthogonal frequency-division multiple access (OFDMA) over frequency-selective channels, macrocell-user (MU) signals generally arrive at small-cell base stations (SBSs) with different delays and can hardly be synchronized in time, causing intercarrier interference (ICI) a...

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Bibliographic Details
Published in:IEEE transactions on vehicular technology 2016-08, Vol.65 (8), p.6244-6258
Main Authors: Wang, Hong, Song, Rongfang, Leung, Shu-Hung
Format: Article
Language:English
Subjects:
Capacity
Channels
Computer architecture
Exact solutions
Fading
Indexes
interblock interference (IBI)
intercarrier interference (ICI)
Interference
Macrocell networks
Mathematical analysis
Networks
OFDM
orthogonal frequency-division multiple access (OFDMA)
Simulation
Subcarriers
Synchronization
two-tier networks
Uplink
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Summary:For two-tier networks using orthogonal frequency-division multiple access (OFDMA) over frequency-selective channels, macrocell-user (MU) signals generally arrive at small-cell base stations (SBSs) with different delays and can hardly be synchronized in time, causing intercarrier interference (ICI) and interblock interference (IBI) in OFDM demodulation. The effects on small-cell uplink capacity by ICI and IBI and their mitigation have not been well addressed in the literature. In this paper, the ICI and IBI of OFDMA two-tier networks with fractional power control (FPC) in multipath fading channels are formulated, and closed-form expressions of their covariance matrices at the SBS with random MU locations are derived. Simulation results verify the validity of the theoretical analysis. It is shown that small-cell uplink capacity is substantially degraded in the presence of ICI and IBI. A precoding method for small cells for mitigating the effects of ICI and IBI on uplink capacity is proposed. In the method, the received signals over small-cell subcarriers at the SBS are decorrelated jointly by small-cell user (SU) precoders and an equalizer at the SBS. Closed-form design procedures for precoding of different subcarrier sizes to maximize uplink capacity under different information feedback are developed. Simulation results demonstrate that the proposed method for using all the subcarriers for precoding has a large capacity gain over that of no small-cell precoding. Moreover, the method can perform very well, even if MU locations are the only information fed back from the macrocell.
ISSN:0018-9545
1939-9359
DOI:10.1109/TVT.2015.2477322