Abstract
We propose a generation scheme for a sounding reference signal (SRS) suitable for supporting a large number of users in massive multi-input multi-output (MIMO) system with a distributed antenna system (DAS) environment. The proposed SRS can alleviate the pilot contamination problem which occurs inherently in the multi-user system due to the limited number of orthogonal sequences. The proposed SRS sequence is generated by applying a well-chosen phase rotation to the conventional LTE/LTE-A SRS sequences without requiring an increased amount of resource usage. We also propose using the correlation-aided channel estimation algorithm as a supplemental scheme to obtain more reliable and refined channel estimation. It is shown that the proposed SRS sequence and the supplemental channel estimation scheme improve significantly the channel estimation performance in multi-user massive MIMO systems.
Highlights
It is expected that the amount of mobile wireless traffic in 2020 will be 1000 times higher than that of2010 [1,2,3]
We evaluate the performances of the proposed sounding reference signal (SRS) and the proposed supplemental channel estimation algorithm in terms of mean squared error (MSE) in the multi-user m-multi-input multi-output (MIMO) distributed antenna system (DAS) environment
We consider the following three types: (a) using repeatedly M orthogonal sequences generated by varying α and s without applying the p phase rotation e j2π L p m in Equation (7), j2π p m (b) using the phase rotation e L p together with varying α and s for SRS generation, but not using the supplemental correlation-aided channel estimation, (c) using the phase rotation e L p together with varying α and s for SRS generation, and the supplemental correlation-aided channel estimation as well
Summary
It is expected that the amount of mobile wireless traffic in 2020 will be 1000 times higher than that of2010 [1,2,3]. Along with the dramatic growth in the demand for wireless communications, performance requirements for data rate, spectral efficiency and energy efficiency are getting higher [4,5,6]. To meet these growing demand and performance requirements for wireless communications, massive multi-input multi-output (m-MIMO) technology was proposed as one of the key technologies for the generation cellular networks, known as fifth generation (5G) systems [7,8,9,10].
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