MAC Layer Support for Interference Mitigation using Multi-BS MIMO
IEEE 802.16 Presentation Submission Template (Rev. 9)
Document Number:
IEEE C802.16m-08/690
Date Submitted:
2008-07-07
Source:
Rajagopal Iyengar, Jungnam Yun
POSDATA America
2350 Mission College Blvd, #703
Santa Clara, Ca 95054, USA.
E-mail:
[email protected]
*<http://standards.ieee.org/faqs/affiliationFAQ.html>
Venue:
IEEE 80216m-08/024 Call for Comments and Contributions on Project 802.16m System Description Document (SDD), on the topic of
“Interference mitigation”.
Base Contribution:
Purpose:
Accept Proposed text into the SDD
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Multi-BS MIMO for Interference Mitigation
• The Multi-BS MIMO concept (in a broad
sense) was one of the main ideas to come out
of Session #55, with support and proposals
from multiple companies.
• The main aim here is the improvement of cell
edge performance
• While it was proposed as a DL-MIMO
solution, the applications to Interference
Mitigation are obvious.
High Level View of MAC features for Multi-BS
MIMO.
• The idea is to make the operation of Multi-BS MIMO
as simple as possible without losing too much of the
functionality.
• What new MAC features are required to support a
PHY that supports this feature?
– Inter-BS Communication details: if the group decides to
take this part on
– How to Schedule Users served by multiple BSes: Operation
of Multi-BS MIMO can be simplified by specifying a
framework (conceptual guidelines) for this purpose
– A scheme for ‘consensus building’ between schedulers at
different BSes, due to possible conflicts between cooperating BSes.
Concepts Related to Specifying a Framework for
Scheduling cell edge users.
• Form sets of cell edge users, each set is served
by 2 or 3 co-operating BSes
– Number of BSes is not crucial at this stage.
• Form sets of co-operating BS sectors
• The MAC function is to create these user and
BS sector sets and assign each cell edge user to
the right set of co-operating sectors.
MAC Feature Proposal
• Divide DL frame into two regions
– Co-operative transmission region (cell edge)
– Non Co-operative (single BS) transmission region (closer
to BS)
• Calculate the number of non-overlapping slots
required to schedule each set of cell edge users
– Non-overlapping  only one set scheduled at a time, all
antennas of sector in question are utilized to send data to
current edge user set.
– The choice of sectors which serves a given cell edge user
set is motivated by geometry and proximity, as described in
an example later.
Frame Partition
Diagram shows DL Subframe
at one sector of a BS
Consensus between BSes possibly
required in these regions.
Cell Edge User Set Scheduling: 3 Sector, FRF-1
Scenario
Co-operative coverage of cell-edge
users in Sector a1
This example considers sets of cell
edge users being served in some cases
by 2 sectors and in some by 3.
Served by a2, a1
Served by f3, a1, e2
8 Non-overlapping slots required to
Schedule cell edge users at Sector a1
Served by e3, a1
Some further thoughts on the Scheduling
problem.
• At the high level, each frame can be divided into co-operative and noncooperative regions
• Within the co-operative region, equal allocations can be made for each set.
• Members of each cell edge user set are associated with different sectors,
with varying requirements so conflicting scheduling decisions between
BSes must be resolved on a per frame basis.
– Example: 2 users in a cell edge set, each requiring that the entire region be
allocated to itself => conflict.
– How can such conflict be resolved?
– Simple solution: equal allocation to all members of the set, irrespective of
requirements
– More Fancy Solution: BSes exchange per frame resource allocation
information (perhaps DL-MAP for example) and ‘converge’ on a mutually
acceptable solution
• This is complicated, hence alternatives need to be considered.
Proposed Text for the SDD
• 10.x MAC Features to support Multi-BS MIMO
– DL resources may be partitioned into 2: co-operative region
(for the cell edge) and non-co-operative for the rest of the
users.
– BS allocates users to be served by one of a (maybe predefined) set of co-operating BSes.
– The co-operative region of the frame is divided into nonoverlapping portions, one for each set of cell edge users.
Multiple cell edge users can be allocated to the same set of
co-operating BSes to serve them.
– Conflicting resource allocation inside of a region allocated
to a given set of cell edge users will be resolved using a
‘consensus building’ scheme between BSes.