1. doc.: IEEE 802.11-05/0037r1 Submission January 2005 Jie Liang, Paragon Wireless IncSlide 1 Proposal for Fast Inter-BSS Transitions Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at.http:// ieee802.org/guides/bylaws/sb-bylaws.pdfstuart.kerry@philips.compatcom@ieee.org Date: 2005-01-17 Authors:

2. doc.: IEEE 802.11-05/0037r1 Submission January 2005 Jie Liang, Paragon Wireless IncSlide 2 Executive Summary This proposal is focused on QoS aspects of fast inter-BSS transitions More specifically, this proposal deals not only with signaling protocol but also innovative methods for speeding up packet delivery of the handoff signaling protocols using TGe mechanisms (HCCA and EDCA) This proposal expedites packet delivery sequence for hand-off packets from security context transfer, to QoS traffic stream setup –HCCA based methods for bounded maxim delay –EDCA based methods for expedited hand-off related packet delivery This proposal is beneficial for various handoff scenarios (proposed faster handshake, normal 4- way handshake, full 802.1x authentication, etc), and is designed also for seamless integration with other security-focused proposals (it does not affect key hierarchy or packet exchange sequence)

3. doc.: IEEE 802.11-05/0037r1 Submission January 2005 Jie Liang, Paragon Wireless IncSlide 3 Expedited Handoff Packet Delivery - Motivation Packet delivery latency in a BSS depends heavily on the network load (number of users, traffic pattern, etc.). Handoff packets must contend for the medium just like other contention based packets. Due to the variability of the packet delivery delay, even with the proposed shortened handoff signaling protocol sequence, it is very difficult to have a bounded delay for fast BSS handoff. To reach the goal of less than 50ms handoff latency, a method for expediting the delivery of fast BSS handoff protocol packets must be provided by TGr.

4. doc.: IEEE 802.11-05/0037r1 Submission January 2005 Jie Liang, Paragon Wireless IncSlide 4 Packet Delivery Latencies AP VoIP Phone Roaming STA Regular Data Users: BE packets, 1000 bytes nominal packets High Priority AC

5. doc.: IEEE 802.11-05/0037r1 Submission January 2005 Jie Liang, Paragon Wireless IncSlide 5 Packet Delivery Latencies Assumptions: –N: number of active users, CW-BE: contention window size for BE data, FrameSize: norminal BE MPDU size, R: PHY rate, T d : packet delivery delay –CW-VO: contention window size for high priority AC, α: CW-VO/CW-BE ratio of CW-VO and CW-BE Factors considered: –Only considered packet deferment. No collision. No higher priority packets (EDCA) from other STAs. We can derive a lower bound on the average packet delivery latency T d : CW-VO/CW-BENFrameSize (bytes) Rate (mbps) Total PacketsTotal Delay (lower bound) 7/15151000111017.0ms 7/15151000110153ms Td ≧ α 2 · CW-BE/2 · min(1, N/CW-BE) · (DIFS+PreambleTime+FrameSize*8/PhyRate) +CW-VO/2 ·aSlotTime

6. doc.: IEEE 802.11-05/0037r1 Submission January 2005 Jie Liang, Paragon Wireless IncSlide 6 Expedited Delivery Sequence: HCCA based AP STA A B SIFS Ack P C T1T2 T3 D ●●● ●●● G+ A P+ F P+ X P scheduled Ack frames P QoS CF-Poll Management or 802.1x data packets QoS data+CF-Ack G+ X P+ X P+ X+ A QoS Data+CF-Poll QoS Data+CF-Ack + CF-Poll T1: fast delivery setup period T2: HCCA controlled handoff period T3: 802.1x port open, payload delivery with TSPEC setup PIFS AP Proc. delay CAP: polled access period Payload packets AP Proc. delay P E PIFS Proc. delay Proc. delay

7. doc.: IEEE 802.11-05/0037r1 Submission January 2005 Jie Liang, Paragon Wireless IncSlide 7 Fast Handoff Delivery Setup Procedure Fast handoff delivery is requested by STA through first handoff packet (e.g. open authentication request) The request is through the inclusion of a Fast Handoff Packet Delivery (FHPD) Request information element Fast handoff delivery request is granted or denied by AP in the next packet in the handoff sequence (e.g. open authentication response): handoff admission policy The AP indicates to the requesting STA, through the inclusion of Fast Handoff Packet Delivery (FHPD) Status information element, the mode and parameters to be use for the subsequent handoff packets. Modes supported: HCCA, EDCA Parameters: –TSID (Traffic Stream ID) to be used for HCCA delivery –UP (user priority) to be used for EDCA delivery

8. doc.: IEEE 802.11-05/0037r1 Submission January 2005 Jie Liang, Paragon Wireless IncSlide 8 Fast Handoff Packet Delivery (FHPD) Request Information Element FHPD control: - HCCA: HCCA mode is supported for FHPD - EDCA: EDCA mode is supported for FHPD - Preference: 10 – HCCA mode is preferred 01- EDCA mode is preferred 00 – best effort is preferred 11 – No preference Minimum Response Time (STA processing delay): -The time that will take the Station to process an incoming handoff frame -T= this field * 32us -The AP can use this information to schedule the separation between a downlink (AP-STA) packet and a uplink CAP (polled access time) Element ID LengthFHPD ControlMinimum Response Time Octects 1 1 1 2 HCCA (1 bit) EDCA (1 bit) Reserved (4 bits) Preference (2 bits) Sent by STA

9. doc.: IEEE 802.11-05/0037r1 Submission January 2005 Jie Liang, Paragon Wireless IncSlide 9 Fast Handoff Packet Delivery (FHPD) Status Information Element ModeDelivery Method 10HCCA 01EDCA 00Reserved 11Reserved FHPD control: QoS mode to be used for packet delivery Element ID LengthFHPD ControlFHPD Parameter Octects 1 1 1 1 HCCA (1 bit) EDCA (1 bit) Mode (2 bits) Reserved (4 bits) TID (4 bit) Reserved (4 bits) FHPD Parameter: - TID: HCCA: TSID to be used in HCCA polling EDCA: User Priority to be used by the STA for handoff packets Sent by AP

10. doc.: IEEE 802.11-05/0037r1 Submission January 2005 Jie Liang, Paragon Wireless IncSlide 10 HCCA Controlled Handoff After the initial setup period (T1), the rest of the handoff signaling protocol can be delivered using HCCA mechanism for bounded delay In HCCA controlled handoff, all downlink packets can be delivered through pre-emption by AP using PIFS after an on-air transmission All uplink packets can be delivered through polling by AP AP can schedule handoff exchange sequence around existing admitted TSPEC schedules, as well as considering minimum separation between consecutive handoff signaling frames. Handoff time can be bounded and is not related to network load The proposed methods can be applied to various handoff scenarios: –Cached PMK with accelerated handshake –Cached PMK with normal 4-way handshake –Full EAP/RADIUM authentication, 4-way handshake, TSPEC setup This proposal also applies to the other proposals before TGr (e.g. 802.11-04-1117/r0, 802.11-04-1127/r0)

11. doc.: IEEE 802.11-05/0037r1 Submission January 2005 Jie Liang, Paragon Wireless IncSlide 11 EDCA Controlled Handoff After the initial setup period (T1), the STA is assigned a Priority to use for subsequent handoff packets (management frames and data frames such as the 802.1x frames and 4-way handshake frames) The EDCA based signaling also allows the flexibility of protecting existing sessions (such as VoIP) from a flood of handoff management frames In normal cases when the highest priority Access Category (AC) has excess bandwidth left, the highest priority AC (3) will be assigned All uplink handoff packets can be delivered using this high priority queue AP can still deliver downlink packets using AP preemption if it chooses to do so. Unlike HCCA controlled handoff where delay can be bounded, EDCA based method will statistically achieve much faster handoff, but no delay bound can be guaranteed. The EDCA method also can be applied to various handoff scenarios: –Cached PMK with accelerated handshake –Cached PMK with normal 4-way handshake –Full EAP/RADIUS authentication, 4-way handshake, TSPEC setup The EDCA method also applies to the other proposals before TGr (e.g. 802.11-04/1117r0, 802.11- 04/1127r0)

12. doc.: IEEE 802.11-05/0037r1 Submission January 2005 Jie Liang, Paragon Wireless IncSlide 12 Performance: 802.11i 4-way handshake Assumptions: 11mbps/1mbps PHY rate, HCCA controlled handoff, real-time response from STA and AP All packet exchanges are done in one HCCA controlled burst sequence The results do not change with network load SequencePacketSenderLength (Bytes) Delay (ms) (11mbps/1mbps) AOpen Authentication #1STA370.24/0.61 BOpen Authentication #2AP380.27/0.65 CRe-Association RequestSTA680.44/1.25 DRe-Association ResponseAP580.28/0.81 E4-way packet #1STA1590.51/1.98 F4-way packet #2AP1770.37/1.76 G4-way packet #3STA1770.52/2.13 H4-way packet #4AP1370.34/1.44 ITSPEC requestSTA1010.46/1.52 JTSPEC responseAP1220.33/1.32 Total3.76/13.47

13. doc.: IEEE 802.11-05/0037r1 Submission January 2005 Jie Liang, Paragon Wireless IncSlide 13 FHPD Capability Announcement AP indicates its support for Fast Handoff Packet Delivery (FHPD) by including a FHPD Status Information Element in its Beacon Element ID LengthFHPD ControlFHPD Parameter Octects 1 1 1 1 HCCA (1 bit) EDCA (1 bit) Preference (2 bits) Reserved (4 bits) Reserved (4 bit) Reserved (4 bits) AP indicates its support for Fast Handoff Packet Delivery (FHPD) by including a FHPD Information Element in its Beacon HCCA and EDCA bits in FHPD control indicate the modes supported by the AP Preference bits in FHPD indicate the preferred mechanism in this BSS Mode 10HCCA 01EDCA 00Reserved 11No Preference

14. doc.: IEEE 802.11-05/0037r1 Submission January 2005 Jie Liang, Paragon Wireless IncSlide 14 Conclusions This proposal addresses a critical missing piece in Fast Inter-BSS handoff: speedy delivery of the handoff packets Using HCCA mode, a deterministic handoff delay bound can be guaranteed Using EDCA mode, significant improvement can be obtained in handoff delay when 802.1x data frames are involved. It also allows better control of the handoff process (priority of the handoff frames vs. current active high-priority sessions) This proposal achieves its benefits for various scenarios that will be encountered in real- world handoff applications: –Cached PMK exists –Full 802.1x authentication is needed This proposal can be combined naturally with other proposals which try to reduce the number of packets in a handoff process to achieve better results.