Abstract
Coordinated multipoint (CoMP) technology utilizes simultaneous transmission/reception from/to different access points, and it is considered as an important feature to exploit and/or mitigate intercell interference in fourth-generation mobile networks. Yet, channel power imbalance at the receiver is experienced in CoMP systems due to, e.g., spatially distributed transmissions. Traditional co-located multi-antenna systems may also experience power imbalance among antenna branches due to inaccurate antenna calibration. This paper presents a bit error rate (BER) analysis and derives asymptotic and approximate BER expressions for some practical CoMP transmission techniques under channel power imbalance. Besides the analytical results, numerical analysis is made to thoroughly capture the performance impact of channel power imbalance on the performance gain of the CoMP methods. The results demonstrate that power imbalance considerably affects BER performance and applying long-term amplitude information with fast phase feedback has insignificant benefit to effectively compensate the detrimental effect of large channel power imbalance when base stations use a single antenna. In this case, exploiting both short-term amplitude and phase information is a very good choice. On the contrary, for a large number of diversity antennas in base stations, using long-term amplitude information with a sparsely quantized phase shows BER performance close to the case where full channel state information is applied.
Highlights
The inconsistent quality of experience across mobile networks is an important challenge of contemporary mobile communications, the intercell interference being one of the main causes of the inconsistency [1]
In [16], we presented a detailed analysis for the optimal amplitude weights, signal-to-noise ratio (SNR) gain, and average capacity under channel power imbalance in the case of selected Coordinated multipoint (CoMP) techniques that are consistent with standardized limited-feedback methods
5 Conclusions We studied the impact of mean channel power imbalance on CoMP transmission
Summary
The inconsistent quality of experience across mobile networks is an important challenge of contemporary mobile communications, the intercell interference being one of the main causes of the inconsistency [1]. In [16], we presented a detailed analysis for the optimal amplitude weights, signal-to-noise ratio (SNR) gain, and average capacity under channel power imbalance in the case of selected CoMP techniques that are consistent with standardized limited-feedback methods. We derive asymptotic and approximate BER expressions for the CoMP techniques assuming single-antenna BSs. As the analytical computations are cumbersome for the multi-antenna BSs, the channel power imbalance impact study in a more general case is made through simulation. Our results illustrate how sensitive a limited-feedback technique that exploits long-term CSI feedback to maximize the SNR is to the channel power imbalance in the single-antenna case. We note that the short-term amplitude feedback is not important when a larger number of transmit antennas are employed in BSs. In terms of organization, Section 2 provides an overview of the system model and the CoMP algorithms.
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