Zhiheng Guo

LTE In-Band Relay Prototype and Field Measurement

Relaying is a feature defined in LTE Release 10 to provide coverage in new areas and/or to improve cell-edge throughput. For the purpose of investigating relays performance in a real network, an LTE TDD in-band relay prototype was developed. Based on this prototype some field measurements were conducted using LTE Release-8 terminals. Both indoor scenarios and outdoor scenarios were tested. Measurement results show that relays (once properly deployed) provide good coverage in the coverage holes of a donor eNB. Besides coverage extension, relays can also improve data rate in the poorly-covered area of a donor eNB, i.e. cell edge. The throughput of a terminal served by this relay prototype reaches around 8 Mbps in the uplink and 20 Mbps in the downlink. Regarding latency, given uplink data is always scheduled, the measured round-trip time via the relay is around 10 ms larger than that directly via the donor eNB.

Improving outdoor to indoor coverage by use of TD-LTE in-band relay

Indoor coverage is essential to the mobile user experience, because the signal power from the remote macro base stations is seriously weakened after penetrating the walls. Traditional indoor coverage system is a good solution but it can not be deployed in all the buildings. In order to enhance the received signal power inside the building, a relay can be used in a long term evolution (LTE) system. The benefits of relay are: it can be deployed anywhere quite near to the building since it uses wireless backhaul with less position limitation, and thus it can amplify the transmitting power due to the nearby position to the building comparing to the remote macro base stations. Then even with penetration loss, the received signal power inside the building is still high enough to carry traffic. The field test results show that a TD-LTE relay can improve the indoor received signal power and traffic obviously, and thus its a good solution to enhance outdoor to indoor coverage.

Non-Line-of-Sight 2.6GHz Relay Backhaul Channel Performance: Field Test and Analysis

Relay technologies have been standardized in 3GPP long term evolution (LTE), and can be a useful tool for coverage extension in diverse deployments. The backhaul channel between the relay and its donor eNodeB is essential to the end-to-end relay performance. Recently there has been an increased interest in deployments with non-line-of-sight (NLoS) backhaul channel conditions. In this paper, the NLoS backhaul channel quality has been measured in the real field, and the results show that NLoS backhaul has obvious gain over donor-UE channel and can be good enough to support relay data forwarding. Rules of thumb for NLoS relay deployment are identified that can help to minimize the diffraction loss or to utilize the strong reflections to improve the channel quality.

Inter-Cell Interference Field Test Results and Coordination Methods with the Deployment of TD-LTE In-Band Relay

Relay is a key technique in the 3G long term evolution (LTE), it uses wireless backhaul to communicate with the donor eNodeB. Relay can be deployed to improve the cell-edge coverage and throughput. However, when relay is introduced into the network, it will also cause additional inter-cell interference for both uplink (UL) and downlink (DL). A field test is done to understand the inter-cell interference impacts of TD-LTE in-band relay. The results show that without coordination, relay may increase both UL and DL inter-cell interference to the neighbor cells, and this may impair the cell-edge user throughput of the neighbor cells. Therefore a coordination mechanism tailor made for relay is proposed, and the analyses show that it can help to reduce the inter-cell interference due to the introduction of relay.

Field Measurements of Uplink MU-MIMO

In order to identify the technology potential of uplink MU-MIMO, Ericsson developed the LTE TDD test bed according to 3GPP Release 8 specification with simplified MMSE receiver and scheduling schemes. The implemented simplified MMSE receiver can significantly reduce the computation complexity with the restriction that the dominant interference should be monitored by the receiver. This paper presents plenty of field test results of uplink MU-MIMO in single cell. The test results show that the simplified receiver can work well for uplink MU-MIMO and that majority potential throughput gain can be achieved with low complexity implementation. The results further mean that complex scheduling scheme or receiver implementation is not mandatory to achieve majority of gain from MU-MIMO in the tested cases.