1. doc.: IEEE 802.11-13/1157r3 SubmissionYunzhou Li, Tsinghua Univ.Slide 1 Feasibility of Coordinated Transmission for HEW Date: 2013-09-18 Authors: September 2013

2. doc.: IEEE 802.11-13/1157r3 SubmissionSlide 2 Abstract This presentation discuss the feasibility of using coordinated transmission between adjacent APs for future WLAN networks. As a similar technique, CoMP in LTE has been introduced briefly. The potential gain derived from coordinated transmission has been analyzed, by comparing with LTE CoMP and coordinated transmission in WiFi and referring the experiment results. Some simple coordinated schemes have been introduced. Yunzhou Li, Tsinghua Univ. September 2013

3. doc.: IEEE 802.11-13/1157r3 SubmissionSlide 3 Background &Motivation With the increase of AP density, the inter-BSS interference will be the dominant obstacle for increase of area throughput. It is very difficult to work well If there existed a good path between two adjacent APs due to DL-UL interference between the two APs. Therefore, effective technologies and strategies have been proposed to deal with inter-BSS interference in HEW. Yunzhou Li, Tsinghua Univ. September 2013

4. doc.: IEEE 802.11-13/1157r3 Submission The Feasibility of Coordinated Transmission As showed in the figure, Access Controller (AC) are widely used in operator deployed Wi-Fi networks –AC can play a role of controller of coordinated transmission between adjacent APs September 2013

5. doc.: IEEE 802.11-13/1157r3 SubmissionSlide 5 The Feasibility of Coordinated Transmission Enterprise is evolving towards a cloud-based model –No longer files and information are stored on local machines Mobile access to cloud is expected to increase with the increase of smart mobile devices. 11-13-0098-00-0wng-802-11-looking-ahead-to-the-future-part-II Yunzhou Li, Tsinghua Univ. September 2013 Enterprise WiFi

6. doc.: IEEE 802.11-13/1157r3 SubmissionSlide 6 Coordinated Multi-Point (CoMP) transmission and reception In LTE Joint Transmission (JT) –Simultaneous data transmission from multiple points (part of or entire CoMP cooperating set) to a single UE or multiple UEs in a time-frequency resource Dynamic point selection (DPS)/muting –Data transmission from one point (within the CoMP cooperating set) in a time-frequency resource Coordinated Scheduling/Beamforming (CS/CB) –Data for an UE is only available at and transmitted from one point –scheduling/beamforming decisions are made with coordination among points corresponding to the CoMP cooperating set. 3GPP TR 36.819 Coordinated multi-point operation for LTE physical layer aspects Yunzhou Li, Tsinghua Univ. September 2013

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8. doc.: IEEE 802.11-13/1157r3 SubmissionSlide 8 The Difference between TD-LTE and WiFi for Coordinated Transmission In cellular systems of TD-LTE, all the eNBs are synchronized in symbol and slot Whereas each AP in Wi-Fi systems decide to transmit/receive according to its situation and don’t take care of other adjacent AP’s TX/RX. –The AP will transmit if it can detect the channel and find the channel is idle or the adjacent AP's signal is below the CCA level. In addition, the deployment of eNB are chosen base on well-planning, which is very different from selection of AP’s position. Yunzhou Li, Tsinghua Univ. September 2013

9. doc.: IEEE 802.11-13/1157r3 Submission Besides, there is a significant difference in use of time and frequency block between cellular and Wi-Fi. Yunzhou Li, Tsinghua Univ. September 2013 The Difference between TD-LTE and Wi- Fi for Coordination Transmission

10. doc.: IEEE 802.11-13/1157r3 SubmissionSlide 10 Some Coordinated Transmission Schemes Integrated coordinated transmission mechanism with Wi- Fi networks –All the time domain resource is divided into two categories: Coordinated TX/RX Intervals(CTRI) and Non-Coordinated TX/RX Intervals(NCTRI) which is scheduled and decided by coordination controller according to the amount of STA and their distribution –CTRI is like the mechanism of DMA or Interrupt in computer system. Yunzhou Li, Tsinghua Univ. September 2013

11. doc.: IEEE 802.11-13/1157r3 Submission Some Coordinated Transmission Schemes Coordinated power allocation –The scheme of AP selection is one special case of coordinated power allocation. Yunzhou Li, Tsinghua Univ. September 2013

12. doc.: IEEE 802.11-13/1157r3 SubmissionSlide 12 Some Coordinated Transmission Schemes Coordinated frequency band allocation: similar to fractional frequency reuse in LTE Joint dynamic allocation of frequency and power –Which is the combining case of coordinated power allocation and coordinated frequency band allocation Yunzhou Li, Tsinghua Univ. September 2013

13. doc.: IEEE 802.11-13/1157r3 SubmissionSlide 13 Some Coordinated Transmission Schemes Joint Transmission based one joint precoding – like SU-MIMO / MU-MIMO in 802.11ac –The combing channel is and the precoding matrix is decided based on – MU-MIMO can be combined to the scheme –JT need high-resolution synchronization in time and frequency among the adjacent APs, which can be implemented by CPRI / IEEE 1588, etc. Yunzhou Li, Tsinghua Univ. September 2013 Coherent

14. doc.: IEEE 802.11-13/1157r3 Submission Experiment of Multi-AP for Dense WLAN Each STA can detect multiple APs within its received range. September 2013

15. doc.: IEEE 802.11-13/1157r3 Submission Experiment of Multi-AP for Dense WLAN Strategies: –In UL, multi-AP demodulate the STA’s signal simultaneously and check it by CRC. –In DL, the controller chooses one AP from multi-AP as transmit point according to channel condition and load balance. September 2013 StarEast

16. doc.: IEEE 802.11-13/1157r3 SubmissionSlide 16 Experiment of Multi-AP for Dense WLAN Combining with optimal physical carrier sensing(PCS), more 100% gain can be achieved in both UL and DL. Yunzhou Li, Tsinghua Univ. September 2013 ULDL

17. doc.: IEEE 802.11-13/1157r3 SubmissionSlide 17 Remarks on Coordination Gain Although only about 15% gain from CoMP in LTE can be achieved, considerable gain from simple coordinated scheme has been showed in our experiment. In our opinion, the possible reason is CoMP gain in LTE derived from the improved SINR for cell-edge UEs who are at low rates, so the contribution for the whole cell throughput is not considerable. However, the gain from coordinated transmission in WLAN is from the decrease of collision and resulting in the increase of transmission opportunity. Yunzhou Li, Tsinghua Univ. September 2013

18. doc.: IEEE 802.11-13/1157r3 SubmissionSlide 18 Summary It is feasible for integrating coordinated transmission in to WLAN for HEW by extending the role of AC. For analysis of potential gain, CoMP in LTE has been introduced briefly. Further, the difference between TD-LTE and WiFi for coordinated transmission has been summed up and some simple coordinated scheme has been introduced. Finally, the potential gain for HEW has been analyzed. Yunzhou Li, Tsinghua Univ. September 2013