| With the development of technology and science, with the popularization of laptop, smartphone, tablet PC, people put new requirments forward for wilesss communication, larger capacity of system, higher speed of data transmission, lower energe cost.With the development of multiple-input multiple-output (MIMO) and the emergence of massive MIMO, a way to satisfy the requirements of the burst data comes into being. At the same time it still faces many problems and challenges.Pilot contamination limits the performance of massive MIMO system severely due to the degraded channel estimation in present wireless communication system. In multi-cell multi-antenna time division duplex (TDD) wireless systems for downlink transmission, an efficient way to solve this problem is shifting the location of pilots in time frames used in neighboring cells. However, this shifted frame structure has only been studied in MIMO system with the ideal independent and identically distributed (ⅡD) channel coefficients. In reality, if the large antenna arrays are smaller in size, it would bring some drawbacks such as higher antenna correlations. In this paper, the shifted frame structure is studied in a channel for a certain class of channel fading statistics with a number of antennas. To deal with the high inter-cell interference in such a measured channel condition, the key lies in two aspects. One is the channel state information (CSI) among base stations (BSs), the other is getting sutable statistics on the second order for the desired and interference signals. In another word, the covariance information is the key to interference mitigation.This paper introduces the advantages and disadvantages of sychonized structure and shifted structure and proposes an covariance-aided estimation scenario. We analyse the parameters that influence the result of simulation. The simulations of the scenario with a covariance-aided channel estimator give a powerful result of interference rejection and achievable rate promotion. |
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