Abstract
Cellular communication provides an efficient, flexible, long-lived, and reliable communication technology for smart grids to improve the automated analysis, demand response, adoptive control, and coordination between the generator and consumers. With the expansion of wireless networks and the increase of access devices, interference has become a major problem that limits the performance of cellular wireless communication systems for smart grids. Spatial interference alignment (IA) is an effective method to eliminate interference and improve the capacity of wireless communication networks. This paper provides the sufficient conditions of spatial interference alignment operating with limited precoding matrix feedback for a K-user MIMO interference channel. Each receiver feeds the matrix index of the transmitting precoder back to the corresponding transmitter through an interference-free and error-free link. We calculated the number of feedback bits required to achieve the maximum theoretical multiplexing gain for the spatial interference alignment schemes considered and demonstrate the feasibility of spatial interference alignment under the limited feedback constraint investigated. It is shown that in order to maintain the same spatial multiplexing gain as that of the idealized scheme relying on perfect channel state information, the number of feedback bits per receiver scales as Nd≥di(M−di)log2SNR, where M and di denote the number of transmit (receive) antennas and the number of data steams for user i. Finally, the analytical results were verified by simulations for practical interference alignment schemes relying on limited precoding matrix feedback indices.
Highlights
Since the optimal quantitative design for a given distance metric is a challenging problem, instead, we considered the performance averaged over random quantization codebooks [38], which have been applied in the single-user MIMO channel with limitedrate feedback [39–41]
This means that the proposed transmit precoding (TPC) matrix feedback strategy was capable of achieving the same spatial multiplexing gain as the interference alignment (IA) relying on the perfect channel state information (CSI), some inconsistencies still existed for some of the signal-to-noise ratio (SNR) due to the propagation of errors in the above pair of IA algorithms
We verified the feasibility of achieving accurate spatial IA, despite relying on a limited feedback for the K-user MIMO interference channel (IC), while operating without any symbol extensions in the frequency domain and time domain, when the TPC matrix index is used as the feedback information
Summary
We calculate the required feedback rate and demonstrated that the feasibility conditions of the interference alignment scheme mentioned in [36] for IA in the signal space can be satisfied even in the limited-feedback-based K-user MIMO interference channel having M antennas at each transmitter and N antennas at each receiver, if the number of bits fed back by each receiver is equal to or more than di ( M − di ) log P, where di is the number of data streams for user i and P is the total power available This implies that in order to obtain the same spatial multiplexing gain as those IA schemes operating under a perfect CSI [14], the number of precoding matrix index bits for each receiver should be increased linearly with the total available power. This manuscript addresses this issue and provides the implementation method of spatial interference alignment relying on limited precoding matrix feedback indices in multi-cell communication scenario
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