1. Spatial Discovery in 60 GHz
March 2010
doc.: IEEE /0245r0
March 2010
Spatial Discovery in 60 GHz
Authors:
Date:
Saad Ahmad et.al., InterDigital
Saad Ahmad et. al., InterDigital

2. March 2010
doc.: IEEE /0245r0
March 2010
Abstract
The proposal presented in this new technique presentation deals with the problem of device discovery using directional antennas in 60 GHz band. The presentation outlines the existing techniques, presents a new approach and provides a comparison
Saad Ahmad et.al., InterDigital
Saad Ahmad et. al., InterDigital

3. March 2010
Background
In , AP or devices are discovered using periodic beaconing
In 2.4/5 GHz , Omni-directional beacons are used
In 60Ghz Omni-directional beacon have limited range
Sending out directional beacon in all the directions can be problematic and time consuming
Saad Ahmad et.al., InterDigital

4. Spatial Discovery – Problem Statement
March 2010
Spatial Discovery – Problem Statement
Directional antenna makes neighbor discovery difficult
Need to efficiently discover all neighbors
Just to know that a neighbor is somewhere around you is not enough
Need to have good knowledge of the directional location of the neighbors
This can help to solve problems arising from directional communication e.g. deafness problem
We need to track devices to provide support for low mobility
Saad Ahmad et.al., InterDigital

5. Existing Techniques Low Rate PHY (LRP) Fixed Discovery Channel (FDC)
March 2010
Existing Techniques
Low Rate PHY (LRP)
Omni directional discovery using a low rate channel. The bandwidth of the channel is also smaller than the high rate channel
Fixed Discovery Channel (FDC)
Devices listen to a low rate separate and known discovery channel at scheduled time slots to receive the beacon
Out Of Band Control Channel (OOB)
Devices discover each other and their 60 GHz capabilities such as g PHY
Scanning each sector with a directed beam using brute force (BF)
Saad Ahmad et.al., InterDigital

6. Let’s see how these techniques do:
March 2010
doc.: IEEE /0245r0
March 2010
Let’s see how these techniques do:
Comparison Metrics:
Reliability : Probability of successfully discovering neighbors
Discovery Speed : How quickly neighbor devices are discovered
Device Mobility : Does the discovery procedure support mobility of stations
Single PHY : Does the procedure require multiple radios
Neighborhood Location Information : After discovery, does the procedure provide location information
LRP
FDC
OOB
Reliability  
Discovery Speed
Device Mobility
Single PHY
Neighborhood Location Information BF  
Clearly there is room for improvement…
Saad Ahmad et.al., InterDigital
Saad Ahmad et. al., InterDigital

7. Proposed Technique In a nutshell...
March 2010
Proposed Technique
In a nutshell...
Two types of beacons may be used i.e. Discovery beacon and Periodic beacon
Each of these beacons uses coarse sectors/ coarse beam
Periodic beacon may be transmitted only in discovered sectors
Data is transmitted and received using fine beam
Details are presented in the following slides
Slide 15 provides a qualitative comparison of existing techniques and the proposed technique
Saad Ahmad et.al., InterDigital

8. March 2010
Coarse Discovery (1 / 2)
The approach is to send out a coarse directional beam that carries beacons rotating in a Time Division fashion followed by a listening period
Beam for normal data transmission may be finer
Saad Ahmad et.al., InterDigital

9. March 2010
Coarse Discovery (2 / 2)
In the initial discovery phase, STA sends discovery beacons in a randomly chosen coarse sector (Discovery Beacon)
It then listens for the response for a specific duration and then moves on to the next sector
After the initial phase, the beaconing STA may focus in direction of interest i.e. the sectors where it has found STAs
Beaconing STA will exchange antenna training symbols using Beam forming protocol with discovered STAs to enable fine beam for data traffic (Fine Beam forming)
Beaconing STA will only send periodic beacons in the sectors where STAs are discovered (Periodic Beacon)
Beaconing STA may opportunistically send discovery beacons in all sectors, or only in those sectors without STAs, to check for new STAs
Saad Ahmad et.al., InterDigital

10. Infrastructure BSS Scenario – AP Operation
March 2010
Infrastructure BSS Scenario – AP Operation
In this example, AP sends out beacon in each quarter.
It finds 2 STAs in quarter 1 and 2 STAs in quarter 2
After all four STAs are associated, AP sends out periodic beacon (every Beacon Interval) only in quarter 1 & 2
AP will send out discovery beacon in all directions every ‘x’ beacon intervals or opportunistically during idle period
Saad Ahmad et.al., InterDigital

11. Infrastructure BSS – STA Operation
March 2010
Infrastructure BSS – STA Operation
STA starts scanning; looks for a discovery beacon in each sector
STA scan time for all sectors should be slightly less than the discovery beacon transmission time for the AP in each sector
Once the STA is associated to the AP it will just look for the periodic beacon in the discovered sector (e.g. quarter D in this fig.)
Saad Ahmad et.al., InterDigital

12. Infrastructure BSS – Discovery Signal Flow
March 2010
doc.: IEEE /0245r0
March 2010
Infrastructure BSS – Discovery Signal Flow
Signal flow for device discovery (management message exchange) for the network illustrated above
Saad Ahmad et.al., InterDigital
Saad Ahmad et. al., InterDigital

13. Coarse-Fine Summary March 2010 March 2010 doc.: IEEE 802.11-10/0245r0
Saad Ahmad et.al., InterDigital
Saad Ahmad et. al., InterDigital

14. March 2010
Channel Detection
STAs need to detect the channel where beacon is being sent. This can be done in several ways:
Scanning all the available frequencies
Implementing Common Mode Signaling (CMS)
Fixed/ known discovery channel
Sending beacon over multiple frequencies
Sending beacon on fixed channel(s) with a very high coding gain(Underlay approach)
Scanning Multiple frequencies at the same time (Coarse Scan)
Frequency identified by using another RAT technology or 2.4/5 GHz
Saad Ahmad et.al., InterDigital

15. Comparison Matrix      March 2010 A B C D E Reliability
doc.: IEEE /0245r0
March 2010
Comparison Matrix A B C
Reliability  
Discovery Speed
Device Mobility
Single PHY
Neighborhood Location Information D   E 
A: Low Rate PHY
B: Fixed Discovery Channel
C: Out Of Band Control Channel
D: Brute Force
E: Proposed technique
Saad Ahmad et.al., InterDigital
Saad Ahmad et. al., InterDigital

16. March 2010
Conclusion
Device discovery using directional antenna can be performed efficiently with a nominal overhead by using two beacons i.e. discovery beacon & periodic beacon
By solving the spatial discovery problem, the location of the device is known; this can assist in solving other issues e.g. deafness and hidden node problem
Saad Ahmad et.al., InterDigital

17. March 2010
Straw Poll
Do you support inclusion of the technique “Spatial Discovery in 60GHz” as described in 10/0245r0 in the TGad draft amendment?
Yes No
Abstain
Need more info
Saad Ahmad et.al., InterDigital

18. March 2010
References
[1] ECMA-387
[2] “Overview of WirelessHD Specification Version 1.0a”
[3] IEEE std c-2009
[4] c “Automatic Device Discovery for Directional Antenna Devices”
Saad Ahmad et.al., InterDigital