Relay User Equipment Research Articles

Relaying Robust Beamforming for Device-to-Device Communication With Channel Uncertainty

In this letter, we study robust beamforming design in the scenario that user equipments (UEs) relay the messages from a base station (BS) to a destination UE out of the cellular networks, which is considered as a high-priority device-to-device (D2D) scenario in the 3rd Generation Partnership Project (3GPP) Long-Term-Evolution (LTE) standardization. We assume that another D2D UE, which receives data from another D2D transmission group, coexists in the network, and it is interfered by D2D relay UEs. Moreover, the channel links between D2D relay UEs and the interfered UE are supposed to suffer from Gaussian errors due to low accuracy of channel estimation. Our optimization objective is to minimize the total transmission power at the BS and D2D relay UEs, while satisfying the signal-to-interference-plus-noise ratio (SINR) requirement of the destination D2D receiver and keeping the probability of low SINR event of the interfered D2D receiver smaller than a predefined threshold. Finally, we present the joint BS and D2D relay UE beamforming design, the effectiveness of which is verified by computer simulations.

Radio Resource Management Scheme for Relieving Interference to MUEs in Relay-Based Cellular Networks

Relay nodes (RNs) have been recently introduced as a cost-effective solution to achieve ubiquitous high data rates in cellular networks. By providing a two-hop link between evolved nodeB (eNB) and user equipment (UE), RNs can improve the UE's signal-to-interference-plus-noise ratio (SINR) and throughput. A typical relay-based cellular network is comprised of macro UEs (MUEs) that are served directly by eNB and relay UEs (RUEs) that are served via RNs. The performance of the entire network is degraded if the interference between RNs and MUEs is not carefully managed. In this paper, we propose a radio resource management scheme that effectively exploits the advantages of RNs without causing severe interference to MUEs, which yields a better overall network and cell-edge user throughput. To improve channel quality of MUEs located nearby RNs, the proposed scheme determines a specific set of subchannels to be used by each RN. Second, the proposed scheme assigns subchannels to UEs and RNs considering channel quality, average UE data rate, and the number of required subchannels at RNs. For resource allocation, we formulate a binary integer linear programming (BILP) problem and propose a novel heuristic algorithm to reduce its computational complexity. Our simulation results show that the heuristic algorithm achieves similar performance with the BILP. In addition, we discuss a detailed procedure for control signal exchange and data transmission and analyze the lower bound of SINR gain of MUEs obtained from the proposed scheme. It has been shown that the proposed scheme improves the overall network throughput and the cell-edge user throughput compared with existing schemes.

3GPP LTE-Advanced 시스템에서 Type 1 relay의 셀 ID 검출을 위한 부분 전이중 relay 기법

In this paper, we propose a partial full duplex relay scheme for 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution)-Advanced system using a Type 1 relay. The Type 1 relay as inband relay is prohibited to transmit and receive simultaneously because of self-interference. Therefore, the Type 1 relay cannot receive synchronization signals which are transmitted to eNB. To overcoming this problem, we propose the partial full duplex relay scheme which transmits to R-UE (Relay-User Equipment) and receives from eNB (evolved NodeB) simultaneously when eNB and the Type 1 relay transmit subframes which have synchronization signals. Additionally, for solving self-interference, the Type 1 relay transmitter and receiver antennas are sufficiently sufficiently isolated and self-interference cancellation is applied for the self-interference signal from the relay transmitter. Thus, the partial full duplex relay scheme can receive synchronization signals from eNB and solve the problems of conventional solutions and we propose the partial channel estimation scheme for partial full duplex relay scheme using SCI. By extensive computer simulation, we verify that the partial full duplex relay scheme is attractive and suitable for the Type 1 relay system.