Efficient MIMO downlink intercell interference cancellation using pre-coding
IEEE 802.16 Presentation Submission Template (Rev. 9)
Document Number: IEEE S802.16m-08/449
Date Submitted: 2008-05-11
Source:
Chris Williams, Kevin Power, Sunil Vadgama
Fujitsu Laboratories of Europe
E-mail:
{chris.williams,kevin.power,sunil.vadgama}@uk.fujitsu.com
*<http://standards.ieee.org/faqs/affiliationFAQ.html>
Re:IEEE 802.16m-08/0016 Call for Contributions on Project 802.16m SDD; Topic – DL MIMO
Purpose:
For discussion at TGm and adoption within Project 802.16m SDD
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Requirements from SRD
• IEEE 802.16m shall support MIMO, beamforming
operation or other advanced antenna techniques.
• IEEE 802.16m shall further support single-user and
multi-user MIMO techniques.IEEE 802.16m shall
enable the advanced RRM for efficient utilization of
radio resources. This may be achieved by appropriate
measurement/reporting, interference management and
flexible resource allocation mechanisms.
• IEEE 802.16m shall support interference mitigation
schemes.
MU-MIMO
• MU-MIMO schedules 2 users in the same
resource, but uses spatial discrimination to aid
separation
• Applied with in a cell to enhance system
throughput
BSA
HAA
MSA
HAB
MSB
Cooperative MIMO
• Cooperative MIMO
coordinates the
transmission of base
stations
• Where both BSs
transmit to one user, cell
edge throughput &
coverage improved, but
~ double resources are
used & BS share data
streams
BSA
HAA
MSA
HBA
BSB
Pre-coding for Interference Reduction
• Cell edge users see high levels of interference
in reuse 1 scenario
• If an interfering BS (BSA) knows the channel
response to the adjacent cell user (MSB), it can
precode its transmissions (to MSA) to reduce
interference (ZF)
BS
A
HAA
Avoid having an active
link between BSA & MSB
MSA
HAB
MSB
HBB
BSB
Antenna Requirements
• MS (on receive) sacrifice spatial modes to
enable precoding
• Interference reduction compensates for loss of
spatial modes
• BS transmit antennas NT
• MS receive antennas NR
• MSA antennas used in data transmission – NRA
• MSB antennas used in data transmission – NRB
• Require NRA + NRB ≤ NR
• BS to chose pairs of users (and matching
resource blocks) to minimise interference (zero
forcing) while not degrading performance to
wanted user (decorrelated channels)
• BSA does not need to know full channel matrix
HAB, just required precoding matrix derived
from HAB .
• Size of matrix is NT  (NR- NRB)
Example Scenario
• Practical measurements for spatial channels
• SLS for SINR distribution (19 cells)
• NT=4; NR=4; NRA=2; NRB=2
Performance
Empirical CDF
1
Probability(capacity < abscissa)
0.9
0.8
0.7
0.6
non pre-coded capacity
pre-coded capacity with
channel selection criterion
0.5
0.4
0.3
0.2
0.1
0
0
5
10
15
channel capacity sum (bits/s/Hz)
20
25
• Despite loss of spatial modes, there is a sum
capacity gain 80% of the time
Measurements
• Need to measure HAB
• If done at BSA then BSA will
need to make many
measurements of adjacent
cell users
• More efficient for MSB to
measure channel only when
interference is known to
exist from preferred set
• MS calculates precoding
vector/index and sends to
serving BSB for distribution
• BSB sends PV/PVI &
resource allocation to BSA
BSA
HAA
MSA
HAB
MSB
HBB
BSB
SDD Text Proposal
11. x Advanced multiple antenna technique
11.x.1 SU-MIMO technique
11.x.2 MU-MIMO technique
11.x.3 Cooperative MU-MIMO technique
Co-operative MIMO by precoding is to be supported in order to
reduce intercell interference. Terminals will share precoding
vectors with adjacent cell BSs. A terminal that senses having
high levels of interference will determine the required
precoding vectors to each preferred BS. The terminal will
signal these vectors along with the BS identifier to its serving
BS. The serving BS will then forward the precoding vectors to
the relevant BSs.