LTE MIMO www.huawei.com Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. MIMO Video Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page1 Contents 1. MIMO Feature Overview 2. UL MIMO in eNodeB 3. DL MIMO in eNodeB 4. Beamforming Overview Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page2 Introduction of MIMO(1/2) Trend : Desire of higher throughput Solution: Higher bandwidth: Now 20MHz is supported and further 100Mhz can be achieved in LTE advanced, but it will be limited Higher MCS scheme: Now 64 QAM is used and further 256 QAM will be introduced in LTE advanced, but it will be limited MIMO is technology based on spatial domain, achieve the obvious improvement of throughput Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page3 Introduce of MIMO(2/2) MIMO is developed to provide doubled and more spectral efficiency Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page4 Benefit of MIMO MIMO uses signal processing techniques to improve the transmission reliability and signal quality of radio links MIMO not only increases capacity and enhances coverage for the system but also provides higher rates and better experience for users MIMO brings power gains, multiplexing gains, diversity gains, and array gains Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page5 Power Gains Assuming that each transmit antenna has the same transmit power, M transmit antennas bring a power gain of 10 lg(M) dB compared with the scenario in which only one transmit antenna is used In noise-limited scenarios, power gains indicate larger signal to interference plus noise ratios (SINRs) at the receiver and improved receive signal quality Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page6 Multiplexing Gains Multiplexing gains are subject to the multiplexing orders of spatial channels Multiplexing gains indicate higher transmission rates Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page7 Diversity Gains Diversity gains are subject to the diversity orders of spatial channels Diversity gains indicate improved SINR stability and signal reliability at the receiver Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page8 Classifications of MIMO DL MIMO Open-Loop MIMO and Closed-Loop MIMO Transmit Diversity and Spatial Multiplexing SU-MIMO and MU-MIMO UL MIMO Receive diversity SU-MIMO and MU-MIMO Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page9 Contents 1. MIMO Feature Overview 2. UL MIMO in eNodeB 3. DL MIMO in eNodeB 4. Beamforming Overview Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page10 Principle of Receive Diversity This process maximizes the SINR, brings diversity and array gains, and improves cell capacity and coverage Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page11 MU-MIMO MU-MIMO enables multiple UEs to use the same timefrequency resources for uplink data transmission In addition to bringing diversity and array gains like uplink receive diversity, MU-MIMO also brings multiplexing gains System gains brought by MU-MIMO are subject to the SINRs of paired UEs and UE channel correlations Not recommended to UEs moving with high speed. Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page12 Principle of MU-MIMO In MU-MIMO mode, the number of UEs that use the same time-frequency resources cannot exceed the number of receive antennas employed on the eNodeB Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page13 Uplink SU-MIMO UEs that support uplink SU-MIMO have two transmit antennas and support uplink closed-loop transmission mode TM2. Common UEs have only one transmit antenna and support only TM1. Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page14 Uplink SU-MIMO PMI selection is supported in uplink TM2. When the eNodeB receives sounding reference signals (SRSs) from a UE, the eNodeB traverses all protocol-defined PMIs, selects a PMI that is suitable for channel transmission, and delivers the PMI to the UE. The UE will use this PMI for weighting during uplink data transmission. The eNodeB selects closed-loop spatial multiplexing or closed-loop transmit diversity for UEs based on their signal quality. Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page15 Contents 1. MIMO Feature Overview 2. UL MIMO in eNodeB 3. DL MIMO in eNodeB 4. Beamforming Overview Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page16 Contents 3 . DL MIMO 3.1 DL MIMO Implementation 3.2 DL MIMO Introduction 3.3 Working Mode 3.4 Configuration for CSI Reporting Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page17 Transmission Modes (FDD) Transmi 3GPP-Defined MIMO ssion Technique Mode Single antenna port TM1 (port 0) TM2 Transmit diversity Transmit diversity TM3 Description The reference signal (RS) pattern corresponding to antenna port 0 is used for transmission Open-loop transmit diversity is used If only one data block is transmitted, open-loop transmit diversity is used Large-delay CDD spatial If multiple data blocks are transmitted, open-loop spatial multiplexing is used multiplexing Transmit diversity If only one data block is transmitted without using the PMIs reported by UEs, open-loop transmit diversity is used Closed-loop spatial multiplexing If one or more data blocks are transmitted using the PMIs reported by UEs, closed-loop spatial multiplexing is used Transmit diversity If only one data block is transmitted without using the PMIs reported by UEs, open-loop transmit diversity is used TM4 Closed-loop spatial multiplexing using a If only one data block is transmitted using the PMIs reported by UEs, closed-loop transmit diversity is used single transmission Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page18 layer TM6 Transmission Modes (FDD) Transmis 3GPP-Defined sion MIMO Technique Mode TM9 and TM10 Description If the PMIs reported by UEs are not used for signal processing at the transmitter and only one antenna port is used for the physical broadcast channel (PBCH) in non-MBSFN Transmit diversity subframes, antenna port 0 is used for transmission. Otherwise, transmit diversity is used and only one data block is transmitted Spatial multiplexing If the PMIs reported by UEs are used for signal processing at the transmitter, spatial multiplexing is used and one or more data blocks are transmitted Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page19 Transmission Modes (TDD) Transmi 3GPP-Defined MIMO ssion Technique Mode Single antenna port TM1 (port 0) TM2 Transmit diversity Transmit diversity TM3 Large-delay CDD spatial multiplexing Transmit diversity TM4 Closed-loop spatial multiplexing Transmit diversity TM6 Closed-loop spatial multiplexing using a single transmission layer Description The reference signal (RS) pattern corresponding to antenna port 0 is used for transmission Open-loop transmit diversity is used If only one data block is transmitted, open-loop transmit diversity is used If multiple data blocks are transmitted, open-loop spatial multiplexing is used If only one data block is transmitted without using the PMIs reported by UEs, open-loop transmit diversity is used If one or more data blocks are transmitted using the PMIs reported by UEs, closed-loop spatial multiplexing is used If only one data block is transmitted without using the PMIs reported by UEs, open-loop transmit diversity is used If only one data block is transmitted using the PMIs reported by UEs, closed-loop transmit diversity is used Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page20 Transmission Modes (TDD) Transmi 3GPP-Defined MIMO ssion Technique Mode TM7 Single antenna port (port 5) Description RSs are transmitted over antenna port 5 for single-stream beamforming Dual-layer transmission RSs are transmitted over ports 7 and 8 for dual-stream beamforming (ports 7 and 8) TM8 TM9 Single antenna port (port 7 or 8) In this mode, RSs are transmitted over port 7 or 8 for single-stream beamforming Transmit diversity Please refer to TM9 FDD Transmit diversity Spatial multiplexing If the PMIs reported by UEs are used for signal processing at the transmitter, spatial multiplexing is used and one or more data blocks are transmitted Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page21 Contents 3 . DL MIMO 3.1 DL MIMO Implementation 3.2 DL MIMO Introduction 3.3 Working Mode 3.4 Configuration for CSI Reporting Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page22 Transmit Diversity Open-loop transmit diversity: The transmitter uses predefined PMIs, instead of depending on the PMIs reported by UEs Closed-loop transmit diversity: The transmitter uses the PMIs reported by UEs Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page23 Close-Loop Transmit Diversity As a special closed-loop spatial multiplexing, closed-loop transmit diversity processes only one data block It maps one codeword to one layer and uses zero-delay CDD for precoding Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page24 Spatial Multiplexing Open-loop spatial multiplexing: The transmitter uses predefined PMIs, instead of depending on the PMIs reported by UEs Closed-loop spatial multiplexing: The transmitter uses the PMIs reported by UEs Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page25 Principles of Spatial Multiplexing s: data transmitted after being mapped onto different layers x: data transmitted after being precoded y: receive data H: channel matrix Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page26 Open-Loop Spatial Multiplexing Open-loop spatial multiplexing brings spatial multiplexing gains It also brings diversity gains due to its use of large-delay CDD precoding Diversity gains are brought when the copies of the same signal are transmitted using different antennas with different delays Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page28 Closed-Loop Spatial Multiplexing The precoding matrix is reported by UE Precoding provides the spatial multiplexing gain if the interval between UE reports on the precoding information (for example, precoding matrix indication (PMI) is not too long CL-SM is applicable to slowly moving UEs Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page29 Transmit Diversity and Spatial Multiplexing Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page30 Contents 1. MIMO Feature Overview 2. UL MIMO in eNodeB 3. DL MIMO in eNodeB 4. Beamforming Overview Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page31 Overview Beamforming is a downlink multipleantenna feature introduced since 3GPP Release 8 When beamforming is enabled, an eNodeB weights physical downlink shared channel (PDSCH) data to form a narrow beam towards target UEs, thereby increasing the signal-to-noise ratio (SNR) for demodulation and improving user experience at the cell edge Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page32 Benefits Power Gains, Array Gains, Diversity Gains Multiplexing Gains When signal quality is satisfactory, beamforming enables an eNodeB to transmit multiple data streams using the same timefrequency resource, thereby increasing the cell throughput and peak capacity Beamforming Gains Beamforming enables beams to be directed at target UEs, thereby increasing the signal strength of UEs, especially that of cell edge users (CEUs) Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page33 Beamforming Principles Copyright © 2017 Huawei Technologies Co., Ltd. All rights reserved. Page34
