1. Service Coverage Extension in IEEE 802.11TGad
Month Year
doc.: IEEE /xxxxr0
July 2009
Service Coverage Extension in IEEE TGad
Date:
Authors:
Name
Affiliations
Address
Phone
Kapseok Chang
ETRI
Sunggeun Jin
Hyoungjin Kwon
Kapseok Chang (ETRI)
VInko Erceg, Broadcom

2. Outline Introduction Mesh Network Wireless Distribution System
Month Year
doc.: IEEE /xxxxr0
July 2009
Outline
Introduction
Mesh Network
Wireless Distribution System
Ad hoc Network
Exclusive relay
STA cooperation
Conclusion
Kapseok Chang (ETRI)
VInko Erceg, Broadcom

3. Introduction (1/3) Problem statement of 60 GHz channel
Month Year
doc.: IEEE /xxxxr0
July 2009
Introduction (1/3)
Problem statement of 60 GHz channel
P1: High directivity and High path loss
Large free space path loss (22 dB higher than 5GHz [1])
Resulting in shortening communication coverage (or range)
P2: High penetration loss by human or wall
60GHz ray cannot penetrate most walls and doors.
High penetration loss (e.g., human body ~18 to 36 dB [2])
Resulting in no or lower-rate communication between source and destination STAs
Kapseok Chang (ETRI)
VInko Erceg, Broadcom

4. Introduction (2/3) Current solution of P1 Current solution of P2
Month Year
doc.: IEEE /xxxxr0
July 2009
Introduction (2/3)
Current solution of P1
Beam-forming
Previous 60 GHz standards have sought for coverage up to 10 meters in some NLOS PHY channel conditions.
It is insufficient to extend coverage with maintaining required throughput.
Current solution of P2
Beam-steering
A bad link detection and then scheduling of next best beam direction
It is insufficient in case of no reflector nearby or insufficient one.
Fast session transfer (60 GHz  2.4/5 GHz) in current TGad functional requirements
Coverage extension, but throughput reduction
Kapseok Chang (ETRI)
VInko Erceg, Broadcom

5. Month Year
doc.: IEEE /xxxxr0
July 2009
Introduction (3/3)
We introduce some alternatives to complement current solutions of P1 and/or P2 as the following:
Mesh network
Wireless distribution system
Ad hoc network
Exclusive relay
STA cooperation
Kapseok Chang (ETRI)
VInko Erceg, Broadcom

6. Figure - an exemplary mesh network topology [4]
Month Year
doc.: IEEE /xxxxr0
July 2009
Mesh Network
Mesh network for IEEE WLANs
Mesh network is a candidate technology for service coverage extension since user stations scattered in a wide area can reach backhaul via relays participating in mesh network.
Technical issues are handled directly in IEEE s task group [3].
Discussions
Mesh Points (MPs) relay data frames between backhaul and user stations. The figure shows an example that data frames are transferred from A to B through a mesh network.
An MP does not need to provide the AP’s functions. However, it is no problem to do that.
Routing metrics for mesh networks are possibly designed under the assumption that MPs are nearly stationary, and hence, it may not be suitable for the MPs with mobility.
Figure - an exemplary mesh network topology [4]
Kapseok Chang (ETRI)
VInko Erceg, Broadcom

7. Wireless Distribution System (WDS)
Month Year
doc.: IEEE /xxxxr0
July 2009
Wireless Distribution System (WDS)
IEEE WDS
WDS allows APs to reach stations without wired backbone, and otherwise impossible.
Theoretically, WDS-enabled stations relay data frames irrespective of hop number in multi-hop environments.
It provides an easy and cost-effective way to extend service coverage but the standard does not specify how it works.
Figure - IEEE WDS to expand service coverage by using WDS-enabled AP.
Is this still available for TGad devices?
It could be a promising candidate for service coverage extension.
WDS-enabled stations work as a pair, and hence, it may not be suitable for TGad usage.
It is required to consider WDS-related operations not likely to basic standard due to indispensable directional transmission in 60 GHz band.
Kapseok Chang (ETRI)
VInko Erceg, Broadcom

8. Ad hoc Network IEEE 802.11 ad hoc network Considerations for TGad
Month Year
doc.: IEEE /xxxxr0
July 2009
Ad hoc Network
IEEE ad hoc network
Basically, it does not support multi-hop transmission. However, there are a lot of mechanisms to provide the multi-hop transmission with the help of Layer-3, namely, IP layer.
Considerations for TGad
TGad devices should be simple not to be equipped with IP layer. Therefore, TGad needs to provide a scheme to support multi-hop transmission in Layer-2.
Kapseok Chang (ETRI)
VInko Erceg, Broadcom

9. Brief Discussions about the Existing Technologies
Month Year
doc.: IEEE /xxxxr0
July 2009
Brief Discussions about the Existing Technologies
Due to the short transmission ranges in 60 GHz band, it is required to consider new strategies for coverage extension.
The existing technologies including mesh network, WDS, and ad hoc network are not exactly fit for coverage extension in case of directional transmission.
Exclusive relay and STA cooperation can be considered for the candidates for the purpose.
Kapseok Chang (ETRI)
VInko Erceg, Broadcom

10. Exclusive Relay (1/2) Usage Model [5]
Month Year
doc.: IEEE /xxxxr0
July 2009
Exclusive Relay (1/2)
Usage Model [5]
When LOS signal cannot be penetrated to wall, alternatives are
Detour via exclusive relay
A relay is utilized to transfer data and management frames to a destination device when there exist unavoidable obstacles between source and destination STAs.
Without throughput reduction
Fast session transfer (FST)
With throughput reduction
Living Room
Wall
Room
FST
(2.4/5GHz)
Relay (60 GHz)
Kapseok Chang (ETRI)
VInko Erceg, Broadcom

11. Exclusive Relay (2/2) Merit Technical Issues in Layer-1 and Layer-2
Month Year
doc.: IEEE /xxxxr0
July 2009
Exclusive Relay (2/2)
Merit
Preventing the outage of direct link by obstacles.
Maintaining the required data rates when the direct link is not enough.
Technical Issues in Layer-1 and Layer-2
Relay operation for directional communication
Relay-capable device discovery
Relay link setup including beam-forming procedure via relay
Data transfer via relay
[Configuration of a pair of devices and a relay]
Direct link
Relay link
Source
Destination
Relay
Kapseok Chang (ETRI)
VInko Erceg, Broadcom

12. STA Cooperation (1/2) Multi-hop Model [6] July 2009
An selected STA cooperates with source STA in order to enhance throughput.
Recently much attention has been paid to research how to achieve higher rates with reliability in communication [7].
Cooperated 60 GHz STA can practically operate at half-duplex (HD) mode, so that decode-and-forward (DF) rather than amplify-and-forward (AF) is preferable due to RF buffering.
Most previous works assumed omni-directional mode rather than beam-forming mode which is important in communication using 60 GHz.
Direct link
Detour link
Source
STA
Destination
Cooperated
Device
Cooperation
Kapseok Chang (ETRI)

13. STA Cooperation (2/2) Merit Technical Issues in Layer-1 and Layer-2
Month Year
doc.: IEEE /xxxxr0
July 2009
STA Cooperation (2/2)
Merit
Throughput enhancement that can be converted into Coverage extension.
It is possible to make a seamless communication due to detour link although direct link is blocked.
Technical Issues in Layer-1 and Layer-2
A hybrid of beam-forming and device cooperation should be considered.
The TGad STA should have the ability to participate in transmitting together with a source STA in order to improve transmission throughput.
A protocol that the transmission signals of Source and Cooperated STAs are synchronized at Destination STA is needed.
It is referred that TGac STA may support Multi-user MIMO operation.
Slide 13
Kapseok Chang (ETRI)
VInko Erceg, Broadcom

14. Month Year
doc.: IEEE /xxxxr0
July 2009
Conclusion
In order to efficiently deploy an WLAN operating at 60 GHz, coverage extension is needed at Layer-1, Layer-2, and/or Layer-3.
Layer-1/Layer-2 approach
Exclusive relay
STA cooperation
Layer-2/Layer-3 approach
Mesh network
WDS
Ad hoc network
Kapseok Chang (ETRI)
VInko Erceg, Broadcom

15. References July 2009 [1] IEEE 802.11-09/0572r0.
Month Year
doc.: IEEE /xxxxr0
July 2009
References
[1] IEEE /0572r0.
[2] S.K. Yong, “TG3c channel modeling sub-committee final report,” IEEE c, Nov
[3] G. R. Hiertz, S. Max, R. Zhao, D. Denteneer, and L. Berlemann, “Principles of IEEE s,” in Proc. ICCCN’07, 2007.
[4]
[5] IEEE /2988r4.
[6] A. Nosratinia, T.E. Hunter, and A. Hedayat, “Cooperative communication in wireless networks,” IEEE Commun. Mag., no. 10, pp , Oct
[7] P. Popovski and E.D. Carvalho, “Improving the rates in wireless relay systems through superposition coding,” IEEE Tr. Wirel. Commun., no. 12, pp , Dec
Kapseok Chang (ETRI)
VInko Erceg, Broadcom