Submission March 9, 2009 doc.:IEEE /0309r1 Slide 1 TGac Channel Model Addendum Highlights Greg Breit, Hemanth Sampath, Sameer Vermani, Richard Van Nee, Minho Cheong, Naoki Honma, Takatori Yasushi, Yongho Seok, Seyeong Choi, Phillipe Chambelin, John Benko, Laurent Cariou, VK Jones, Allert Van Zelst, Note: The author list will grow to reflect those providing explicit contributions and review comments

SubmissionSlide 2 Introduction The TGn task group has developed a comprehensive MIMO broadband channel models, with support for 40 MHz channelization and 4 antennas. The TGac task group is targeting > 1 Gbps MAC SAP throughput using one or more of the following technologies: –Higher order MIMO (> 4x4) –Multi-User MIMO with > 4 AP antennas –Higher Bandwidth (> 40 MHz) –OFDMA We propose some simple modifications to TGn channel models to enable their use for TGac. March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 3 Modifications to Handle Large System BW TGn systems handled 40 MHz systems BW, assuming tap-spacing of 10 nsec. For TGac systems with larger overall system bandwidth (W), we propose to decrease channel tap spacing by a factor of The calculation of W and tap spacing is illustrated in the below examples: –Example : A TGac modem can have 2 channels of 40 MHz each that are spaced by 60 MHz for sufficient isolation. W = 40*2+60 = 140 MHz. Channel tap spacing = 2.5 nsec. The reduced channel tap-spacing is modeled by linearly interpolating the Cluster channel tap power values, on a cluster by cluster basis. March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 4 Higher Order MIMO Propose to extend Kronecker models of TGn for higher order MIMO. It has shown by measurements [1] that –TGn channel models tightly bound and sweep the range of MIMO performance observed in real environments. –Randomly rotating the TGn defined cluster AoA and AoDs is sufficient to emulate the case-by-case variation expected in real- world environments. Random AoA offsets were distributed uniformly between ±180° Random AoD offsets were distributed uniformly between ±30°. For each case, the same offset was applied to all clusters. March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 5 Higher Order MIMO Measured Capacity CDFs in Office Environment [1] Channel Model B Capacity CDFs (Random AoA/AoD) Channel Model D Capacity CDFs (Random AoA/AoD) Randomly rotating the TGn defined cluster AoA and AoDs is sufficient to emulate the case-by-case variation expected in real-world environments. In this figure, capacity calculated assuming SNR = 24 dB and March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 6 Multi-User MIMO Extensions Literature Search: –J-G. Wang, A.S. Mohan, and T.A. Aubrey,” Angles-of-arrival of multipath signals in indoor environments,” in proc. IEEE Veh. Technol. Conf., 1996, pp For the same RX location, cluster AoA from 2 different TX locations vary up to 20 degrees in classroom and up to 60 degrees in large halls. In Hall, clusters that are relevant for one TX location were absent for another TX location. Results directly applicable to MU-MIMO March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 7 Multi-User MIMO Extension AoD/AoA vs. Physical Geometry From Physics: AP has a different AoD to STA-1 and STA-2. Also, each STA has a different AoA from AP.  The LOS steering vectors to STA-1 and STA-2 are different. Scenario 1: Pure LOS channel March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 8 Multi-User MIMO Extension AoD/AoA vs. Physical Geometry Different scatterers may be relevant to different STAs. AP may have a completely independent AoD for clusters corresponding to STA-1 and STA-2 STAs may have completely independent AoA depending on location and device orientation Scenario 2: NLOS channel with scatterers far away from AP March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 9 Multi-User MIMO Extension AoD/AoA vs. Physical Geometry AP may have a similar AoDs for clusters regardless of transmission to STA-1 or STA-2. STAs may have independent AoAs depending on location and device orientation Scenario 3: NLOS channel with scatterers close to AP March 9, 2009 doc.:IEEE /0309r1

Submission Assume TGn-defined cluster AoDs and AoAs for link level simulations. For Multi-User MIMO system simulations: –Assume TGn-defined cluster AoDs and AoAs as baseline. –For each client, a single pseudo-random offset is added to all cluster AoDs and AoAs. Pseudo-random selection allows comparison across proposals. Single offset retains TGn angular spacing between clusters. –NLOS Cluster AoD offsets uniformly distributed between ±30° Based on experimental results from Wang et al. Compromises scenarios outlined in slides 3,4,5. –NLOS Cluster AoA offsets uniformly distributed between ±180° Clients can see independent AoA depending on orientation and location. –LOS tap AoA and AoD offsets uniformly distributed between ±180°. Direct LOS path to each client can have independent AoA/AoD depending on location. Pros: –Physically realistic – Introduces statistical AoA/AoD variation across clients –Minimal change to TGn channel model –Simulation complexity increase is reasonable: TX/RX correlation matrix need to be computed only once per client, for the entire simulation run. Slide 10 MU-MIMO Channel Model Proposal March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 11 MU-MIMO Simulation Overview Assumptions: –16 TX antennas, 8 STAs, 2 RX antennas per STA –TGn channel models B, D (LOS and NLOS scenarios) used as baseline AoD and AoA as specified in the channel model document –Composite multi-user channel matrix constructed from vertical concatenation of 8 2x16 channel matrices Clients are effectively uncorrelated from each other Capacity Analysis: –For each channel model, 5 cases of random per-user AoA and AoD generated –200 channel realizations generated per case –MMSE precoder applied to each 16x16 channel instance Post-processing SINRs calculated for each stream and subcarrier PHY capacity for each stream/subcarrier calculated as log 2 (1+SINR) –For each instance, sum-average channel capacity calculated by averaging across subcarriers and summing across spatial streams –CDFs generated across all 200 channel instances March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 12 MU-MIMO Model B Results – Capacity CDFs Model B: 2 clusters, 0dB K factor in LOS case Capacity CDF varies by +20% depending on user selection and their AoA/AoD –Note #1: AoD variation in LOS channel component leads to variation of steering vectors across clients and hence improves MU-MIMO capacity. March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 13 MU-MIMO Model D Results – Capacity CDFs Model D: 3 clusters, 3dB K factor in LOS case Capacity CDF varies by +/-10% depending on user selection and their AoD/AoA. –Note #1: Artifact of TGn model: TGn AoA specification result in optimal per-user MIMO capacity. Any AoA offset tends to degrade per-user MIMO capacity. –Note #2: AoD variation in LOS channel component leads to variation of steering vectors across clients and hence improves MU-MIMO capacity. March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 14 MU-MIMO Model F Results – Capacity CDFs Model F: 6 clusters, 6 dB K factor in LOS case Capacity CDF varies by negligible amount depending on user selection and their AoD/AoA. –Note #1: 6 clusters, each with a large AS of degrees, make the capacity CDF less sensitive to AoA/AoD variations. March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 15 MU-MIMO Summary Equal AoD for all STAs is not physically realistic. –In pure LOS scenarios, such a model will “break” MU-MIMO by mandating equal steering matrices across clients. Diversity of AoD/AoA across STAs impacts MU-MIMO performance: –Capacity improves in LOS scenarios and models with small # of clusters. 20% improvement in LOS channel model B. Recommend using a pseudo-randomly selected AoDs/AoA offset across users in MU-MIMO model –NLOS Cluster AoD offsets uniformly distributed between ±30° –NLOS Cluster AoA offsets uniformly distributed between ±180° –LOS tap AoA and AoD offsets uniformly distributed between ±180°. March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 16 Incorporating Dual Polarized Antennas Dual-Pol antennas are likely to be employed in TGac devices. –Dual-polarized antennas improve MIMO channel capacity, especially in LOS channel conditions. E.g: Hallways. –Co-located dual-pol antennas minimize real estate in devices. Measurements indicate that Dual-Pol TGn channel models suggested in Erceg et al., is applicable to 8x8 MIMO. –We assumed the following, while comparing measured data with simulation results: XPD value of 10 dB for the steering matrix H F, XPD value of 3 dB for the variable matrix H v. 0.2 correlation for co-located cross-polarized antenna elements. March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 17 Incorporating Dual Polarized Antennas Measurements vs. Simulations CDFs in “light lines” indicate measured capacity CDFs in office environment [1] TGn channel models B, used as baseline with AoD and AoA as specified in the channel model document March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 18 References 1.Breit, G. et al. “802.11ac Channel Modeling.” Doc. IEEE /0088r1. 2.Erceg, V. et al. “TGn Channel Models.” Doc. IEEE /940r4. 3.Kenny, T., Perahia, E. “Reuse of TGn Channel Model for SDMA in TGac.” Doc.IEEE /0179r0. 4.Schumacher, L.; Pedersen, K.I.; Mogensen, P.E., "From antenna spacings to theoretical capacities - guidelines for simulating MIMO systems," Personal, Indoor and Mobile Radio Communications, The 13th IEEE International Symposium on, vol.2, no., pp vol.2, Sept Jian-Guo Wang; Mohan, A.S.; Aubrey, T.A., "Angles-of-arrival of multipath signals in indoor environments," Vehicular Technology Conference, 'Mobile Technology for the Human Race'., IEEE 46th, vol.1, no., pp vol.1, 28 Apr-1 May Offline discussions with Vinko Erceg (Broadcom) and Eldad Perahia (Intel). March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 19 Appendix MU-MIMO Code Changes March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 20 MU-MIMO Code Changes Channel generation by offsetting TGn-defined cluster AoAs/AoDs –IEEE_802_11_Cases.m function altered Four new function arguments defining angular offsets: Delta_AoD_LOS_deg, Delta_AoA_LOS_deg, Delta_AoD_NLOS_deg, Delta_AoA_NLOS_deg –“LOS” arguments specify offset in degrees added to steering matrix AoD and AoA –“NLOS” arguments specify common offset in degrees added to all cluster AoDs and AoAs Composite MU-MIMO channel generation –Example scenario 8 TX antenna, 2 users, 4 RX antennas per user Generate independent 4x8 channel matrices for each user, denoted as H 1 and H 2 –Each user channel formed assuming different cluster AoA and AoDs Form the composite 8x8 channel: March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 21 MU-MIMO Code Changes March 9, 2009 doc.:IEEE /0309r1

SubmissionSlide 22 MU-MIMO Code Changes March 9, 2009 doc.:IEEE /0309r1