Proposal for Inter-cell Multiple Access Scheme in 802.16m Downlink

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Proposal for Inter-cell Multiple Access Scheme in
802.16m Downlink

• Zhou Shidong, Li Yunzhou
• Tsinghua University

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Content

• Non-orthogonal downlink resource allocation among
  adjacent cells/sectors
• Requirement of resource allocation criterion

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Physical resource allocation of downlink

• Multiuser resource allocation within each cell
• Orthogonal allocation is highly recommended,
  i.e., OFDMA,
• both in time domain and frequency domain
• In special cases, non-orthogonal allocation can
  also be included
• Superposition coding for making full use of
  near-far effect
• Multi-cell resource allocation between adjacent
  cells
• Fractional frequency reuse can be applied
• At the cell edge, when traffic is light,
  orthogonal allocation is highly recommended
• At the cell edge, when traffic is heavy,
  non-orthogonal resource allocation
  (time/frequency reusing) among adjacent cells
  will be included, e.g., CDMA, IDMA (interleaver
  divistion multiple access)

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Spectrum segmentation for downlink physical
resource allocation at the cell edge

• Different resource blocks (chunks) can be
  allocated to adjacent cells
• A separate segment of resource blocks is to be
  assigned for the use of IDMA
• This region can be further divided into subzones,
  for different kinds of resource reuse
• Benefit of IDMA
• Provide more users served at cell edge
• Provide higher data rate with joint decoding at
  cell edge.

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Requirement on non-orthogonal resource allocation

• When only single-user-decoding is applied with
  IDMA,
• no additional restriction of resource allocation
• When some of the terminals at cell edge need to
  perform joint decoding with adjacent cell users
• Resource allocation alignment is recommended
• For simple implementation

With resource alignment, joint decoding can be
local ones
Without resource alignment, joint decoding should
be global
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Proposed SDD Text (1)

• x.x Downlink and Uplink Multiple Access Schemes
• IEEE 802.16m uses OFDMA as the downlink
  intra-cell/sector multiple access scheme.
• As for downlink inter-cell/sector multiple access
  schemes, besides orthogonal(time/frequency)
  multiple access among adjacent cells/sectors
  where cell/sector edge traffic is not very heavy,
  non-orthogonal multiple access shall be included
  for heavy traffic as cell/sector edge, when
  adjacent cells/sectors can use the same
  frequency/time resource simultaneously.
• As an additional non-orthogonal multiple access
  technique, IDMA is used to support higher rate
  for users at cell/sector edge.

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Proposed SDD Text (2)

• x.x Downlink Physical Resource Allocation Unit
• When non-orthogonal downlink multiple access
  among adjacent cells/sectors is to be applied for
  downlink resource allocation, a segment for
  non-orthogonal resource allocation shall be
  defined, which is better to be aligned with
  adjacent cells/sectors. The allocation of such
  resource segment among users shall support
  resource unit alignment among users from adjacent
  cells/sectors which may share the resource.