Abstract
Relay, which enables coverage extension and throughput enhancement, is a very promising technique for future wireless communication systems. Among different types of relay, type II relay is one kind of inband relays and is hotly discussed in LTE-Advanced system for throughput enhancement. In order to support type II relay, many challenges must be overcome. In this article, we focus on relay-assisted uplink data retransmission and propose a novel joint design of reference signal and data precoding for type II relay. The proposed method not only solves the problem of channel estimation mismatch for control information, but also achieves cooperative diversity gain for data transmission. Simulation results show the effectiveness of the proposed method over existing schemes.
Highlights
Relay is a very promising technique for future wireless communication systems to extend coverage and enhance throughput, and has drawn increasing interest from both academia and industry [1-6]
We focus on an enhanced type II relay-assisted uplink data retransmission scheme in order to improve block error rate (BLER) performance while maintaining backward compatibility to legacy user equipment (UE)
A novel joint design of reference signal and data precoding at the relay are proposed, where the data precoding is conducted on the basis of the cyclic shift of the reference signal
Summary
Relay is a very promising technique for future wireless communication systems to extend coverage and enhance throughput, and has drawn increasing interest from both academia and industry [1-6]. We propose a novel retransmission method that is fully backward compatible to legacy UEs without any new signaling, does not require additional control channel resource for control information, has no HARQ failure problem, and achieves cooperative diversity gain for data retransmission. One straightforward idea is to perform puncture at the relay in order to avoid the control information collision, i.e., in the retransmission, type II relay only transmits reference signal and data while not control information. Such a transmission of the relay will lead to channel estimation mismatch for control information detection at the eNodeB. As the control information is embedded in the data channel, if eNodeB uses the estimated combined channel gain to detect control
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