Hits:

Indexed by:期刊论文

Date of Publication:2017-09-07

Journal:IET COMMUNICATIONS

Included Journals:Scopus、SCIE、EI

Volume:11

Issue:13

Page Number:2027-2034

ISSN No.:1751-8628

Key Words:precoding; MIMO communication; channel estimation; statistical analysis; zero forcing precoding; multicell TDD massive MIMO systems; massive multiple-input multiple-output systems; uplink pilot training; channel reciprocity property; channel estimation; time division duplex operation; pilot contamination elimination scheme; orthogonal variable spreading factor code row; OVSF code row; Zadoff-Chu sequences; interference free downlink transmission; second-order statistics

Abstract:In massive multiple-input multiple-output (M-MIMO) systems, the base station (BS) estimates the downlink and uplink channels using the uplink pilot training in conjunction with channel reciprocity property of time division duplex (TDD) operation. However, this channel estimation is contaminated due to the use of non-orthogonal pilot sequences for the uplink training in neighbouring cells that results in inter-cell interference. This study proposes an effective pilot contamination elimination scheme along with zero forcing precoding for multi-cell TDD M-MIMO systems. In the proposed scheme, each BS is assigned with a specific orthogonal variable spreading factor (OVSF) code row and a set of Zadoff-Chu (ZC) sequences are used for uplink pilot training. Then, the set of ZC sequences is multiplied element-wise at each BS with its OVSF code row to generate the orthogonality among the pilot sequences across the neighbouring cells. The proposed method can promise uncontaminated channel estimation and interference free downlink transmission without requiring the knowledge of the channels' second-order statistics and without increasing the training overhead by a factor equal to the number of interfering cells. The simulation results authenticate the effectiveness and superiority of the proposed scheme over other schemes.