Collaborative uplink MIMO techniques for IEEE 802.16m
Document Number:
C80216m-08/638
Date Submitted:
7/7/2008
Source:
Mohamed Abdallah
Mohammed Nafie
Cairo University, Cairo, Egypt
Venue:
Call for contributions on project 802.16m SDD
Session #56: Denver, USA
Base Contribution:
C80216m-08/638
Purpose:
For discussion and approval by IEEE 802.16m group.
Notice:
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Collaborative MIMO
• Mobile stations (MS) can transmit at the same time in
the same frequency
– Improve system throughput by employing collaborate
spatial multiplexing (CSM)
• Rate 2 by using 2 BS ant. x 1 MS ant. configuration. (adopted by
IEEE 802.16e)
• Rate 4 by using 4 BS ant. x 2 MS ant. configuration.
– Interference mitigation can be provided at the BS by
• Proper selection of the MSs based on channel conditions.
• Applying Precoding techniques at the MS.
Open Loop CSM
• 2 (M.S) x 4 (BS) OL collaborative spatial
multiplexing (CSM) can achieve system
throughput of rate 4
• Matrix A used at each MS
s 
A 
s 
1
2
• At the BS, the 4 streams can be separated
given that the two MSs are chosen properly.
Closed Loop CSM
• Precoding techniques can be applied at the MS for the CSM.
– Improve the performance of the CSM.
• At each MS, a precoding 2x2 matrix V is chosen from a
codebook such that
H V lies in the null space of H V
1
•
1
2
2
H and H are the 4x2 channel matrices between BS and MS1
1
2
and MS2, respectively.
• Due to the limited power constraint at the MS
– The precoding matrix V should limit the power transmitted per antenna.
– The joint selection of the matrix V and the corresponding MS are
performed at the BS and fedback to the MSs.
Proposed SDD Text
• 11.x.x. MU MIMO
– For open loop CSM mode, two MS with 2 transmit
antenna can cooperate together by sending their
data using matrix A to a 4 receive antennas at the
BS.
– For closed loop CSM mode, precoding is applied
at each MS where the 2x2 matrix V is properly
selected to separate the 2 streams of each MS
efficiently at the 4 ant. BS.