1. Meeting Report Gill Aug. 24, 2010

2. Letter -- simulation Sum rate DIA-MMSE 2 DIA-MMSE: Since DIA is suboptimal, it should be operated for Tx first, then MMSE for Rx during each iteration.

3. Letter -- simulation (cont.) 4×4 3 links 3

4. Letter -- simulation (cont.) 3×3 3 links 4 Which case to choose in the letter? ‒ {3x3, 3} or/and {4x4, 3}?

5. Letter – Larry’s comments Title: A new distributed interference alignment algorithm for multiuser MIMO networks. –Should “Max SNR” be added in the title? Compared with ML- DIA, this is the main improvement of MS-DIA. One of old algorithms, named as Max-SINR or MMSE? The classification in section III (algorithm description part): 3 or 4 subsections? The contribution of the letter –Compared with ML-DIA, MS-DIA has better performance. –Compared with MMSE, MS-DIA has faster convergence. 5

6. Distributed Power Control and Interference Alignment for MIMO BC Networks

7. System model MIMO-BC Motivation Larry: use different SNRs for each link, taking path loss and errors in the channel into account. Doug: MIMO-BC and MIMO- MAC are realistic cases in 802.11ac. Power constraints of the network.

8. Downlink network (original network) –BS/AP with M antennas –K users with N k antennas and one data stream each –DL channel: –SINR of the kth stream/user: Uplink network (dual network) –SINR of the kth stream/user: Problem to solve: beamformer and power optimization. 8 System model (cont.)

9. General algorithm – BF&PC Step 1: consider downlink channel with fixed and given q k and V k –Update vector p k by a certain power control method –Optimize vector U k by beamforming method. Step 2: consider uplink channel with fixed and given p k and U k –Update q k by a power control method –Optimize vector V k by beamforming method. Step 3: test a stopping criterion Beamforming method: IA, ZF, MMSE. Power control method: waterfilling, binary power control, pricing algorithm, etc. Convergence of iterative method: monotonic increase of SINR with a bound. 9

10. Simulation Case 1: {4x4, 3} –AP with 4 Tx antennas –3 users with 4 Rx antenna each Case 2: {3x3, 2} –AP with 3 Tx antennas –2 users with 3 Rx antenna each Single SS per user in the MU-MIMO Uniform power allocation Results for 2000 channel realizations Iterative algorithms –MMSE: done to beam-form the 1 SS of each user –MS-DIA 10

11. Simulation & discussion 4×4 3 links3×3 2 links 11 As optimal filter, MMSE is widely used for BF&PC in literature. MS-DIA achieves the same performance as MMSE at high SNR. (Similar to MIMO X Channel) The difference between MIMO-BC/MAC and MIMO X Channel?