1. Feasibility of Coordinated Transmission for HEW
Month Year
doc.: IEEE /xxxxr0
September 2013
Feasibility of Coordinated Transmission for HEW
Date:
Authors:
Yunzhou Li, Tsinghua Univ.
Yunzhou, Tsinghua

2. September 2012
doc.: IEEE /xxxxr0
September 2013
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.
Yasuhiko Inoue (NTT), et. al.

3. Background &Motivation
September 2012
doc.: IEEE /xxxxr0
September 2013
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.
Strategies
Yunzhou Li, Tsinghua Univ.
Yasuhiko Inoue (NTT), et. al.

4. The Feasibility of Coordinated Transmission
September 2012
doc.: IEEE /xxxxr0
September 2013
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
Yasuhiko Inoue (NTT), et. al.

5. The Feasibility of Coordinated Transmission
September 2012
doc.: IEEE /xxxxr0
September 2013
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.
Enterprise WiFi
wng looking-ahead-to-the-future-part-II
Yunzhou Li, Tsinghua Univ.
Yasuhiko Inoue (NTT), et. al.

6. Coordinated Multi-Point (CoMP) transmission and reception In LTE
September 2012
doc.: IEEE /xxxxr0
September 2013
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.
Joint Processing (JP): Data for a UE is available at more than one point in the CoMP cooperating set
(definition below) for a time-frequency resource
3GPP TR Coordinated multi-point operation for LTE physical layer aspects
Yunzhou Li, Tsinghua Univ.
Yasuhiko Inoue (NTT), et. al.

7. September 2012 doc.: IEEE 802.11-12/xxxxr0
Joint Processing (JP): Data for a UE is available at more than one point in the CoMP cooperating set
(definition below) for a time-frequency resource
Yasuhiko Inoue (NTT), et. al.

8. The Difference between TD-LTE and WiFi for Coordinated Transmission
September 2012
doc.: IEEE /xxxxr0
September 2013
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 itself situation and don’t take care of other adjacent AP’s TX/RX.
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.
Yasuhiko Inoue (NTT), et. al.

9. The Difference between TD-LTE and Wi-Fi for Coordination Transmission
September 2012
doc.: IEEE /xxxxr0
September 2013
The Difference between TD-LTE and Wi-Fi for Coordination Transmission
Besides, there is a significant difference in use of time and frequency block between cellular and Wi-Fi.
In each time transmit,
Yunzhou Li, Tsinghua Univ.
Yasuhiko Inoue (NTT), et. al.

10. Some Coordinated Transmission Schemes
September 2012
doc.: IEEE /xxxxr0
September 2013
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
IEEE 1588 & synchronization
Yunzhou Li, Tsinghua Univ.
Yasuhiko Inoue (NTT), et. al.

11. Some Coordinated Transmission Schemes
September 2012
doc.: IEEE /xxxxr0
September 2013
Some Coordinated Transmission Schemes
Coordinated power allocation
The scheme of AP selection is one special case of coordinated power allocation.
Take turn at
Yunzhou Li, Tsinghua Univ.
Yasuhiko Inoue (NTT), et. al.

12. Some Coordinated Transmission Schemes
September 2012
doc.: IEEE /xxxxr0
September 2013
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
IEEE 1588 & synchronization
Coordinated frequency band
Coordinated power and frequency band
Yunzhou Li, Tsinghua Univ.
Yasuhiko Inoue (NTT), et. al.

13. Some Coordinated Transmission Schemes
September 2012
doc.: IEEE /xxxxr0
September 2013
Some Coordinated Transmission Schemes
Joint Transmission based one joint precoding
like SU-MIMO / MU-MIMO in ac
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.
Coherent
IEEE 1588 & synchronization, Common Public Radio Interface
Coordinated frequency band
Coordinated power and frequency band
Yunzhou Li, Tsinghua Univ.
Yasuhiko Inoue (NTT), et. al.

14. Experiment of Multi-AP for Dense WLAN
September 2012
doc.: IEEE /xxxxr0
September 2013
Experiment of Multi-AP for Dense WLAN
Each STA can detect multiple APs within its received range.
Logic Topology figure
Coordinated frequency band
Coordinated power and frequency band
Yasuhiko Inoue (NTT), et. al.

15. Experiment of Multi-AP for Dense WLAN
September 2012
doc.: IEEE /xxxxr0
September 2013
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.
Real Topology in experiment
Coordinated frequency band
Coordinated power and frequency band
StarEast
Yasuhiko Inoue (NTT), et. al.

16. Experiment of Multi-AP for Dense WLAN
September 2012
doc.: IEEE /xxxxr0
September 2013
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. UL DL
[1] Y. Zhu, Q. Zhang, Z. Niu, J. Zhu, “On Optimal Physical Carrier Sensing: Theoretical Analysis and Protocol Design”, IEEE INFOCOM2007
[2] Y. Zhu, Q. Zhang, Z. Niu, J. Zhu, “Leveraging Multi-AP Diversity for Transmission Resilience in Wireless Networks: Architecture and Performance Analysis”, IEEE Trans. Wireless Comm.,
Yunzhou Li, Tsinghua Univ.
Yasuhiko Inoue (NTT), et. al.

17. Remarks on Coordination Gain
September 2012
doc.: IEEE /xxxxr0
September 2013
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.
IEEE 1588 & synchronization
Coordinated frequency band
Coordinated power and frequency band
Yunzhou Li, Tsinghua Univ.
Yasuhiko Inoue (NTT), et. al.

18. September 2012
doc.: IEEE /xxxxr0
September 2013
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.
IEEE 1588 & synchronization
Coordinated frequency band
Coordinated power and frequency band
Yunzhou Li, Tsinghua Univ.
Yasuhiko Inoue (NTT), et. al.