1. Fast Session Transfer Date: 2010-04-30 Authors: May 2010 March 2010
doc.: IEEE /0xxxr0
May 2010
Fast Session Transfer
Authors:
Date:
L. Cariou, Orange Labs
Yuichi Morioka, Sony Corporation

2. March 2010
doc.: IEEE /0xxxr0
May 2010
Abstract
Collaboration between 2.4/5 and 60 GHz bands allows the user experience to be met by seamlessly providing both the wide coverage of WLAN and the very high throughput of 60 GHz when available
A key merit of ad is that it can build on past successful standards
e.g a/n/ad system
This will provide many new market opportunities for the ad standard
In [1] and [2] we introduced several use cases dedicated to fast session transfer.
A method of fast session transfer is proposed which enables very fast transparent switching to deal with user mobility, dynamic channel conditions and to allow joint management of multiple bands
L. Cariou, Orange Labs
Yuichi Morioka, Sony Corporation

3. Use case 1: FST with a switchable interface in STA
Media server
Switchable interface
Single link either at 5 or 60
FTTH
Set-top box AP
WiFi 60GHz ( 1 Gbps)
WiFi 5GHz ( 500 Mbps)
Concurrent dual interfaces
Slide 3
presentation title 3 3

4. Use case 2: FST with concurrent dual interfaces in STA
Media server
Concurrent dual interfaces
Two links, at 5 and 60
FTTH
Flow transfer between interfaces
or bonding of the two interfaces
Set-top box AP
WiFi 60GHz ( 1 Gbps)
WiFi 5GHz ( 500 Mbps)
Concurrent dual interfaces
Slide 4
presentation title 4 4

5. Use cases 1&2: Switch from 2.4/5 to 60GHz or from 60 to 2.4/5GHz
Band selection for all flows of a station (stations with only one band active at a given time (Switchable interface) or stations with multiple bands active simultaneously at a given time)
AP-STB either in 2.4/5 GHz band or in 60 GHz band (one at a time)
Band selection for each flow of a station separately (only stations with multiple bands active simultaneously at a given time)
Multiple HD flows between AP and STB either in 2.4/5 GHz band or in 60 GHz band
Session transfer of some HD flows in case of saturation of 2.4/5GHz or 60GHz
Band selection may be based on (a) maintaining coverage with user mobility, (b) dynamically changing channel quality, (c) throughput enhancement, (d) load balancing between bands, etc
 We believe that this interface convergence will improve the overall home network
In this presentation, we only consider the case 1 with
an AP concurrent dual band
a STA with switchable interface
Case 2 is considered in [3].
Slide 5

6. Requirements on fast session transfer
Requirements for speed of fast session transfer
For video applications:
1080p 60Hz => frame every 16.6 ms
Assuming packet loss: latency between 5 and 10 ms
For VoIP applications:
Maximum acceptable BSS transfer for VoIP roaming is 50 ms
For gaming applications, distributed storage or contents sharing:
Same constraints as for video
 Session transfer should not exceed 5 to 10 ms
Quite severe constraint: needs to be better than 11r
Other requirements
Switch should be able to be initiated by either device in a link (AP or STA)
Slide 6

7. How to perform the fast session transfer
Example scenario:
One AP working at both 60 GHz and at 5 GHz
link to TV at 5GHz (red)
link to laptop at 60GHz (blue) to be switched to 5GHz
BSSID
SSID
Encryption key
AID database
BSSID
SSID
Encryption key
AID database
5 GHz
60 GHz
5GHz
5GHz
60GHz f f
AID1
BSSID
SSID
Encryption key
AID1
BSSID
SSID
Encryption key
Slide 7

8. How to perform the fast session transfer
Required functions for FST:
 Preparation phase:
Exchange of FST capabilities and FST negotiation for each link prior to transmission.
We believe the negotiation should lead to the direct acceptance of future switches, to suppress the need to provide a response when a switch is requested
Sharing of the association parameters between the two bands
To speed up the process by removing the need for disassociation/re-association during the switch
Definition in STA of a unique logical MAC address, switchable from one interface to another
 FST phase (phase during which FST can be done):
Report request/response on one band/channel of particular metrics (such as the load and SNR) of the other band/channel
Triggering of the session transfer by the transmission of a signal frame
No need for a response to the trigger frame because of the prior negotiation
No need for disassociation/re-association because of the sharing of association parameters
Slide 8

9. How to perform the fast session transfer Sharing of association parameters (1/2)
Split between association function and forwarding function
Association to an AP, independently of the current interface/band:
Negotiation of MAC parameters (security, power save, ….)
Reception of a unique AID, whatever the band/channel
Slide 9

10. How to perform the fast session transfer Sharing of association parameters (2/2)
BSSID
SSID
Encryption key
AID database
BSSID
SSID
Encryption key
BSSID
SSID
Encryption key
Trigger signal frame f f
Association parameters match
AID1
BSSID
SSID
Encryption key
AID2
BSSID
SSID
Encryption key
Slide 10

11. How to perform the fast session transfer Forwarding (1/2)
Definition in FST STA of a unique logical MAC address, switchable from one interface to another
Definition in AP of a common MAC with a forwarding table indicating the active interface of a FST STA AP
common MAC
MAC addr
MAClog0
5GHz
MAC 5
MAC 60
MAC_ad0
60GHz
PHY 5
PHY 60
11ad STA
PHY60
MAC 60
MAC addr: MAC_ad0
FST STA
PHY 5
PHY 60
MAC 5
Physical MAC addr: MAC1
MAC 60
Physical MAC addr: MAC2
Logical MAC addr: MAClog0 IP
IP addr linked to the unique logical MAC addr: MAClog0

12. How to perform the fast session transfer Forwarding (2/2)
Definition in FST STA of a unique logical MAC address, switchable from one interface to another
Definition in AP of a common MAC with a forwarding table indicating the active interface of a FST STA AP
common MAC
MAC addr
MAClog0
60GHz
MAC 5
MAC 60
MAC_ad0
60GHz
PHY 5
PHY 60
11ad STA
PHY60
MAC 60
MAC addr: MAC_ad0
FST STA
PHY 5
PHY 60
MAC 5
Physical MAC addr: MAC1
MAC 60
Physical MAC addr: MAC2
Logical MAC addr: MAClog0 IP
IP addr linked to the unique logical MAC addr: MAClog0

13. How to perform the fast session transfer Trigger the switch by a signal frame (1/3)
The trigger signal frame should provide the information to localize the destination band and to indicate which station the switch concerns
FST signal frame needs to include
The channel number from the destination channel
The BSSID of the destination band
The AID of the station that will switch band
Slide 13

14. How to perform the fast session transfer Trigger the switch by a signal frame (2/3)
Additional information in FST signal frame to speed up the FST
Option 1: include the capabilities of the destination channel in the FST signal frame
By doing this, the station does not need to wait for the next beacon once arrived in the destination band in order to get the capabilities
This will be very efficient for destination bands/channels working with CSMA-CA (ex: from ad to n or ac): very low FST duration
However, for TDMA-based destination bands/channels like ad 60 GHz, the station will anyway need to wait for the next beacon to be informed a) of the next contention-period to request a reserved slot b) of its reserved slot, if a slot has been pre-reserved
Slide 14

15. How to perform the fast session transfer Trigger the switch by a signal frame (3/3)
Additional information in FST signal frame to speed up the FST
Option 2: use the principle of the "channel switch announcement frame" to plan the arrival in the destination band just before the beacon transmission
signaling of the destination band/channel TBTT in the FST signal frame
in addition, the switch can be planned using the "channel switch announcement element" field in the FST signal frame
By doing this, the station will directly receive the capabilities and the contention-period time in case of TDMA.
This will be very efficient for all destination band/channels working with either CSMA-CA or TDMA
Slide 15

16. Fast session transfer performance
Speed of the FST
When using option 2, the FST switch time easily satisfies the 5 to 10 ms switching requirements
FST duration only includes the time needed to perform the switch and the reception of the beacon on the destination band/channel
Trigger of the FST by the AP
Trigger by a FST signal frame
Such a decision requires a report on one band/channel of particular metrics (such as the load and SNR) of the other band/channel
Trigger of the FST by the station
The FST can be instantaneous thanks to UL data transmission in the new band
Slide 16

17. March 2010
doc.: IEEE /0xxxr0
May 2010
Conclusions
Fast session transfer is a very important feature to improve home network by allowing the joint management of multiple bands, and to open new market opportunities.
To be efficient, FST needs to be triggered by either one or the other device of a link and to be as fast as 5 to 10ms.
We proposed to share the association parameters and a new trigger frame that enable such an efficient FST.
Slide 17
Slide 17
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Yuichi Morioka, Sony Corporation

18. March 2010
doc.: IEEE /0xxxr0
May 2010
Straw polls
Do you support inclusion of Fast Session Transfer, as described in 10/491r0 in the TGad draft amendment?
Yes:
No:
Abstain:
2.4/5 assisted DLS of 60 GHz
Slide 18
Page 18
Yuichi Morioka, Sony Corporation

19. Reference [1] “5-60 GHz use cases”, 802/11-09-0835r0
March 2010
doc.: IEEE /0xxxr0
May 2010
Reference
[1] “5-60 GHz use cases”, 802/ r0
[2] “Fast Session Transfer use cases”, 802/ r0
[3] “Collaboration between 2.4/5 and 60GHz”, 802/ r0
Slide 19
Page 19
Yuichi Morioka, Sony Corporation

20. How to perform the fast session transfer Trigger the switch by a signal frame
Time
TBTT signaled in FST signal frame
Time
FST signal frame
FST switch duration << 5ms
FST Switching instant
Slide 20