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Network Coordinated Beamforming and Feedback Mechanism for Improved Cell-Edge Performance

This proposal discusses the rationale, mechanism, and advantages of implementing network coordinated beamforming (BF) and feedback in wireless networks. It explores the measurement and recognition of user locations by the network, as well as suitable antenna configurations for network coordinated BF. The proposal also discusses the use of frequency reuse and cooperation with neighboring cells to mitigate inter-cell interference and improve cell-edge performance.

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Network Coordinated Beamforming and Feedback Mechanism for Improved Cell-Edge Performance

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  1. CONTENTS • Rationale • Mechanism of Network Coordinated BF • Measurement • Feedback • MS location recognition by network • Network coordinated BF associated with FFR • Advantages • Text Proposals

  2. Rationale • Antenna Configuration • Narrow spacing (~0.5) multiple transmit antennas (array antenna) • Wide spacing (> 4l) multiple transmit antennas • Target Channels • Downlink dedicated data channels • Downlink dedicated control channels • Purposes • To improve cell-edge performance • To reduce feedback overhead • To reduce pilot overhead

  3. Mechanism of Network Coordinated BF • Measurements & Feedback by MSs • CINR • Preferred beam index (n) • Cell ID • Coordinated BF by Network Cooperation • BSs are sharing feedback information (measurements) from MSs via network interface. • Network recognizes user (MS) locations in the network • Coordinated BF by network cooperation

  4. MS Location Recognition & Network Coordinated BF • User Location Recognition by Network using Feedback Parameters • MS1: High CINR, Preferred beam index 7, Cell ID 1 • MS2: Low CINR, Preferred beam index 6, Cell ID 3 • Network Coordinated BF • To mitigates inter-cell interference • To obtain macro diversity

  5. Suitable Antenna Configurationfor Network Coordinated BF • High CINR Users Group (Cell center region) • Multiple transmit antennas with wide spacing (AntennaSpacing > 4l) • Multiuser MIMO (MU-MIMO) • Spatial Multiplexing (SM) • Array antenna with narrow spacing (AntennaSpacing  0.5l) • Space Division Multiple Access (SDMA) • Low CINR Users Group (Cell edge region) • Narrow antenna spacing (0.5l) • BF and Macro diversity gain by Network cooperation • Inter-cell interference mitigation by arranging beams using the same spectrum from neighboring cells not to collide • Preference for Antenna Configuration • High CINR Cell Center Region • Urban: Wide space (rich scattering) • Rural: Narrow space (LOS) • Low CINR Cell Edge Region • Narrow space for both urban & rural

  6. Network Coordinated BF & FFR • FFR Group 1 for Coordinated BF (Reuse 1: spectrum fully reused) • High CINR users group (cell center region) • Cooperation with neighbor cells is not required • MU-MIMO, SM or SDMA can be implemented in terms of only serving cell point of view • FFR Group 2 for Coordinated BF (Reuse 1: spectrum fully reused) • Low CINR users group (not-clustered users in the cell edge region) • Cooperation with neighbor cells is required • Multiple single streams using the same spectrum from neighboring cells by the help of both coordinated BF and Macro diversity • FFR Group 3 for Coordinated BF (Reuse N: spectrum flexibly reused) • Low CINR users group (clustered users in the cell edge region) • Cooperation with neighbor cells is required • Common subcarrier permutation may be required

  7. Advantages • Reduced Feedback Overhead • Low Pilot Density • Cell-edge Performance • Inter-cell Interference Mitigation • Low Deployment Cost

  8. Text Proposal 11.X Downlink Network Coordinated BF In order to improve spectral efficiency of downlink dedicated data and control channels, network coordinated BF can be used. Such parameters as CINR and preferred beam index should be measured at MS and reported to the BS. Then BSs will share these feedback information. Depending on the feedback parameters from MSs, Access Service Network (ASN) can recognize the locations of MSs. MU-MIMO, SM or SDMA should be applied to MSs located at cell center regions in terms of only serving cell point of view. For MSs located at cell-edge regions and spaced apart enough to neglect inter-beam interference, network will arrange beams using the same spectrum from neighboring BSs not to collide each other as well as to obtain macro diversity. In case where users are clustered in the cell-edge regions, the network should use Reuse N to mitigate inter-cell interference.

  9. References [1] IEEE 802.16m-07/002r4, “TGm System Requirements Document (SRD)” [2] IEEE 802.16m-08/003r1, “Draft IEEE 802.16m System Description Document” [3] IEEE 802.16m-08/004r1, “TGm Evaluation Methodology Document” [4] IEEE C802.16m-08/017, “Frame Structure to Support Inter-cell Interference Mitigation for Downlink Traffic Channel using Co-MIMO and FFR” [5] IEEE P802.16Rev2/D3

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