1 / 11

Evaluation of AoD/AoA for TGac Multi-User MIMO channel Model

Evaluation of AoD/AoA for TGac Multi-User MIMO channel Model. Greg Breit , gbreit@qualcomm.com Hemanth Sampath, hsampath@qualcomm.com Sameer Vermani , vermani@qualcomm.com Richard Van Nee, rvannee@qualcomm.com Minho Cheong, minho@etri.re.kr Naoki Honma , honma.naoki@lab.ntt.co.jp

abeni
Télécharger la présentation

Evaluation of AoD/AoA for TGac Multi-User MIMO channel Model

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Evaluation of AoD/AoA for TGac Multi-User MIMO channel Model Greg Breit, gbreit@qualcomm.com Hemanth Sampath, hsampath@qualcomm.com SameerVermani, vermani@qualcomm.com Richard Van Nee, rvannee@qualcomm.com Minho Cheong, minho@etri.re.kr Naoki Honma, honma.naoki@lab.ntt.co.jp YonghoSeok, yhseok@lge.com SeyeongChoi, seyeong.choi@lge.com PhillipeChambelin, philippe.chambelin@thomson.net John Benko, john.benk@orange.com Tomo Adachi, tomo.adachi@toshiba.co.jp Laurent Cariou, laurent.cariou@orange-ftgroup.com VK Jones, vkjones@qualcomm.com Allert Van Zelst, allert@qualcomm.com

  2. Background • In the LA meeting, there was discussion on whether to use identical or different AoD for MU-MIMO transmission to different clients • Ref: Doc-09/0088: • Independent AoD clusters (i.e. different RTX matrices) at the AP for transmission to each client. • Ref: doc – 09/0179: • Identical AoD clusters (i.e. same RTX matrix) at the AP for transmission to each client. • Had some offline discussions on this topic with: • Vinko Erceg (Broadcom), Eldad Perahlia(Intel), ETRI, Thomson, LG, NTT, Orange, Toshiba. • In this study: • We investigate the AoD/AoA diversity on MU-MIMO channel capacity • Propose a MU-MIMO channel model with minimal changes to TGn channel model.

  3. 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. 155-159. • AoA measurements were made in classroom and hall scenarios. • Classroom: For the same RX location, cluster AoA from 2 different TX locations vary up to 20 degrees • Hall: For the same RX location, cluster AoA from different 2 TX locations vary up to 60 degrees. Also, clusters that are relevant for one TX location were absent for another TX location. • The above observations are applicable to the DL MU-MIMO scenario, with the following substitutions: TX  STA; RX  AP and AoA  AoD.

  4. AoD/AoA vs. Physical Geometry Scenario 1: Pure LOS channel • 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.

  5. AoD/AoA vs. Physical Geometry Scenario 2: NLOS channel with scatterers far away from AP • 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

  6. AoD/AoA vs. Physical Geometry Scenario 3: NLOS channel with scatterers close to AP • 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

  7. MU-MIMO Channel Model Proposal • For Link Level simulations: • 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 random offset is added to cluster AoDs and AoAs • Pseudorandomly chosen from a pre-determined set of client offsets to allow comparison across proposals. • All cluster angles for a single client are rotated by the same offset • Retain cluster spacing from TGn • AoD offsets uniformly distributed between ±30° • Reasonable compromise across scenarios mentioned in slides 3,4,5. • AoA offsets uniformly distributed between ±180° • STAs that are not co-located will see independent AoA (see slides 3,4,5). • 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.

  8. 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 log2(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

  9. Model B Results – Capacity CDFs • Model B: 2 clusters, 0dB K factor in LOS case • Capacity CDFvaries 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.

  10. Model D Results – Capacity CDFs • Model D: 3 clusters, 3dB K factor in LOS case • Capacity CDF varies by +/-15% 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.

  11. 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. • Artifact: TGn AoA specification is optimal, especially in Model D. Any deviation tends to degrades performance. • Up to 15% capacity loss noted in channel model D. • Recommend using a pseudo-randomly selected AoDs/AoA offset across users in MU-MIMO model • AoD offsets uniformly distributed between ±30° • AoA offsets uniformly distributed between ±180°

More Related