Proposal for Inter-cell Multiple Access Scheme in 802.16m

Downlink

Zhou Shidong, Li YunzhouTsinghua University

Content

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

• Requirement of resource allocation criterion

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)

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.

For Cell 1 For Cell 2 For Cell 3For IDMA

Z23 Z13 Z12 Z123

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

User 1 of cel l A

User 1 of cel l B

User 2 of cel l A

User 2 cel l B

User 3 cel l B

User 1 of cel l A

User 1cel l B

User 2 of cel l A

User 2 cel l B

User 3 cel l B

With resource alignment, joint decoding can be local ones

Without resource alignment, joint decoding should be global

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.

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.