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Register a new userInter-Cell Antenna Calibration for Coherent Joint Transmission in TDD System
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Added by
Yajun Zhao
Publication date
2019
fields
Informatics Engineering
and research's language is
English
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In this work the modeling and calibration method of reciprocity error in a coherent TDD coordinated multi-point (CoMP) joint transmission (JT) system are addressed. The modeling includes parameters such as amplitude gains and phase differences of RF chains between the eNBs. The calibration method used for inter-cell antenna calibration is based on precoding matrix indicator (PMI) feedback by UE. Furthermore, we provide some simulation results for evaluating the performance of the calibration method in different cases such as varying estimation-period, cell-specific reference signals (CRS) ports configuration, signal to noise ratio (SNR), phase difference, etc. The main conclusion is that the proposed method for intercell antenna calibration has good performance for estimating the residual phase difference. Keywords-LTE-Advanced; TDD; CoMP; JT; reciprocity error; phase difference; inter-cell antenna calibration
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Dynamic time-division duplexing (TDD) is considered a promising solution to deal with fast-varying traffic often found in ultra-densely deployed networks. At the same time, it generates more interference which may degrade the performance of some user equipment (UE). When base station (BS) utilization is low, some BSs may not have an UE to serve. Rather than going into sleep mode, the idle BSs can help nearby UEs using joint transmission. To deal with BS-to-BS interference, we propose using joint transmission with dummy symbols where uplink BSs serving uplink UEs participate in the precoding. Since BSs are not aware of the uplink symbols beforehand, any symbols with zero power can be transmitted instead to null the BS-to-BS interference. Numerical results show significant performance gains for uplink and downlink at low and medium utilization. By varying the number of participating uplink BSs in the precoding, we also show that it is possible to successfully trade performance in the two directions.
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Base station (BS) cooperation is set to play a key role in managing interference in dense heterogeneous cellular networks (HCNs). Non-coherent joint transmission (JT) is particularly appealing due to its low complexity, smaller overhead, and ability for load balancing. However, a general analysis of this technique is difficult mostly due to the lack of tractable models. This paper addresses this gap and presents a tractable model for analyzing non-coherent JT in HCNs, while incorporating key system parameters such as user-centric BS clustering and channel-dependent cooperation activation. Assuming all BSs of each tier follow a stationary Poisson point process, the coverage probability for non-coherent JT is derived. Using the developed model, it is shown that for small cooperative clusters of small-cell BSs, non-coherent JT by small cells provides spectral efficiency gains without significantly increasing cell load. Further, when cooperation is aggressively triggered intra-cluster frequency reuse within small cells is favorable over intra-cluster coordinated scheduling.
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