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Rationale

Rationale. Problem Statement Universal or aggressive frequency reuse in upcoming OFDMA systems including TGm cause very severe inter-cell interference especially in the cell boundaries and limit system capacity. What should we do?

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Rationale

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  1. Rationale • Problem Statement Universal or aggressive frequency reuse in upcoming OFDMA systems including TGm cause very severe inter-cell interference especially in the cell boundaries and limit system capacity. • What should we do? In order to mitigate inter-cell interference and to improve system performance not only PHY/MAC layer but also Inter-BS coordination should be specified in SDD.

  2. Proposed ToC for Interference Management 11.x Interference Management 11.x.1 Inter-cell Coordination [FFR, power control, and Multi-cell MIMO are the key factors to mitigate inter-cell interference. Inter-BS coordination is indispensible to support these functionalities.] 11.x.2 Logical Control Channels [DL and UL control channels for resource allocation and for carrying required measurements may be necessary.] 11.x.3 Interference Randomization [Allocating subcarriers into a subchannel, the adjacent cells permute them differently in order to guarantee minimum subcarrier-hit probability. But when applying FFR where some of the subcarriers are not used to reduce inter-cell interference, the subcarrier permutation may not be necessary. With the absence of permutation in FFR, there is no subcarrier hit and therefore no inter-cell interference between neighbors. But with the permutation, there still exists inter-cell interference due to the subcarrier-hit.]

  3. 11.x.4 FFR 11.x.4.1 Hard FFR [Some of the tones can not be used to mitigate inter-cell interference.] 11.x.4.2 Soft FFR [To mitigate inter-cell interference the power of some of the tones can be adjusted (reduced) rather than not used. Uplink power control considering the neighbor cells’ overload condition falls into soft FFR.] 11.x.5 Multi-cell MIMO [Network coordinated BF, precoding, or interference nulling shall be supported to mitigate inter-cell interference. A multi-cell MIMO zone can be configured in a frame to support multi-cell MIMO transmission.]

  4. References [1] IEEE 802.16m-07/002r4, “TGm System Requirements Document (SRD)” [2] IEEE 802.16m-08/004r2, “TGm Evaluation Methodology Document” [3] IEEE 802.16m-08/003r3, “Draft IEEE 802.16m System Description Document”

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