1. QoS mechanisms in IEEE 802 Bin Zhen, Huan-band Li and Ryuji Kohno
January 2007
doc.: IEEE
July/2007
QoS mechanisms in IEEE 802
Bin Zhen, Huan-band Li and Ryuji Kohno
National Institute of Information and Communications Technology (NICT)
Zhen, Li and Kohno
Carlos Cordeiro, Philips

2. Submission Title: [QoS mechanisms of IEEE 802]
January 2007
doc.: IEEE
July/2007
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [QoS mechanisms of IEEE 802]
Date Submitted: [July, 2007]
Source: [Bin Zhen, Huan-Bang Li and Ryuji Kohno]
Company [National Institute of Information and Communications Technology (NICT)]
Contact: Bin Zhen
Voice:[ ,
Abstract: [review of QoS mechanisms in IEEE 802 framework]
Purpose: [for discussion in MBAN]
Notice: This document has been prepared to assist the IEEE P 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 acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P
Zhen, Li and Kohno
Carlos Cordeiro, Philips

3. Motivations Distinguished features of MBAN from other 802.15 standards
January 2007
doc.: IEEE
July/2007
Motivations
Distinguished features of MBAN from other standards
QoS for life critical applications
Extreme low power wireless
Review of QoS mechanism of IEEE 802
802.11e: QoS enhancements
802.11k: radio resource measurement enhancements
802.11v: wireless network management
802.15
Zhen, Li and Kohno
Carlos Cordeiro, Philips

4. QoS Limitations of 802.11 Distributed Coordination Function
January 2007
doc.: IEEE
July/2007
QoS Limitations of
Distributed Coordination Function
Only support best-effort services
No guarantee in bandwidth, packet delay and jitter
Point Coordination Function
Unpredictable beacon frame delay due to incompatible cooperation between CP and CFP modes
Transmission time of the polled stations is unknown
Point Coordinator does not know the QoS requirement of traffic
Basic elements for QoS
Traffic Differentiation
Concept of Transmission Opportunity (TXOP)
Zhen, Li and Kohno
Carlos Cordeiro, Philips

5. Hybrid Coordination Function of 802.11e
January 2007
doc.: IEEE
July/2007
Hybrid Coordination Function of e
Hybrid Coordinator Function (HCF)
Enhanced distributed channel access (EDCA)
Contention-Based channel access
Provides service differentiation
8 different traffic classes
4 access categories in each station
HCF controlled channel access (HCCA)
Hybrid coordinator to coordinate contention free media
To provides Guaranteed Services with a much higher probability than EDCA
Operates in CFP and CP
Coordinates the traffic in any fashion
not just round-robin
Zhen, Li and Kohno
Carlos Cordeiro, Philips

6. Enhanced distributed channel access
January 2007
doc.: IEEE
July/2007
Enhanced distributed channel access
8 User priorities mapping to 4 Access Categories
Scheduler (resolves virtual collisions by granting TXOP to highest priority
8 User priorities per QSTA
Pri 0
Pri 1
Pri 7
Backoff
(AIFSN3)
(AIFSN2)
(AIFSN1)
(AIFSN0)
AC0
AC1
AC2
AC3
Transmission Attempt
Zhen, Li and Kohno
Carlos Cordeiro, Philips

7. Enhanced distributed channel access (cont.)
January 2007
doc.: IEEE
July/2007
Enhanced distributed channel access (cont.)
Priority
Access Category (AC)
Designation (Informative)
Best Effort 1 2 3
Video Probe 4
Video 5 6
Voice 7
Zhen, Li and Kohno
Carlos Cordeiro, Philips

8. Transmission Opportunities
January 2007
doc.: IEEE
July/2007
Transmission Opportunities
TXOP is the time interval of a QSTA to transmit frame(s)
In TXOP, frames exchange sequences are separated by SIFS
When will a QSTA get a TXOP ?
Win a contention in EDCA during CP
Receive a QoS ControlField-poll (“polled TXOP”) from hybrid coordinator
TXOPs will increase RTS/CTS use
Unlike with short, single frame, transmissions, use of RTS/CTS is efficient with TXOPs
Zhen, Li and Kohno
Carlos Cordeiro, Philips

9. HCF controlled channel access
January 2007
doc.: IEEE
July/2007
HCF controlled channel access
The time is divided into repeated Superframes
HC starts a CAP during which only polled and granted QSTAs are allowed to transmit for TXOPs
Superframe
TCA
Beacon
Frame
Beacon
Frame
EDCA
EDCA
CAP (HCCA)
CAP
QoS CF-Poll
QoS CF-Poll
PCF HC …
ACK
ACK … … … …
PIFS
SIFS
PIFS
SIFS
DIFS
PIFS
DIFS …
RTS
DATA
DATA … …
Stations … … …
AIFS
SIFS
SIFS
TXOP
( Station n )
TXOP
( Station m )
time
backoff time
Zhen, Li and Kohno
Carlos Cordeiro, Philips

10. Admission control Admission control
January 2007
doc.: IEEE
July/2007
Admission control
Admission control
To limit the level where appropriate QoS can be guaranteed for all the admitted traffic stream
Admission control can be mandated per access control
Admission control algorithm is not specified
Dynamic behavior of the radio link
To adjust operation according to changing conditions
Zhen, Li and Kohno
Carlos Cordeiro, Philips

11. Other mechanisms Block Ack: by aggregating several Acks into one frame
January 2007
doc.: IEEE
July/2007
Other mechanisms
Block Ack: by aggregating several Acks into one frame
Immediate Block Ack
Delayed Block Ack
Support for higher layer synchronization
Broadcast Sync packet containing time stamp and sequence number
Direct link
Directly send frames from one QSTA to another in QBSS
Zhen, Li and Kohno
Carlos Cordeiro, Philips

12. Automatic power-save delivery
January 2007
doc.: IEEE
July/2007
Automatic power-save delivery
Automatic power-save delivery (APSD)
QAP deliver downlink frames, which belong to some specified AC, to power saving stations automatically
Unscheduled APSD (U-APSD)
Power-saving QSTA wakes up and send a “trigger” data frame belonging to “trigger-enabled” AC to QAP
After receiving “trigger” frame, a service period is started
QAP send frames belonging to “delivery-enabled” AC to QSTA
Scheduled APSD (S-APSD)
QSTA negotiate a APSD Schedule with QAP
QAP start transmitting the frames of the specified traffic stream at Service Start Time and the following periods
QSTA must wake up at Service Start Time and the following periods to receive frames
Zhen, Li and Kohno
Carlos Cordeiro, Philips

13. 802.11k: radio resource management
January 2007
doc.: IEEE
July/2007
802.11k: radio resource management
Scope of 11k
To enhance the MAC of standards to provide mechanisms to higher layers for radio and network measurements
Purpose of 11k
To define measurements and develop mechanisms to provide wireless network measurement information to higher layers and new applications
Radio measurements enable STA to understand the radio environments in which they exist
STA to observe and gather data on radio link
Local measurement or remote measurement
Standard measurement across venders and interface to upper layer
message inside a STA
Zhen, Li and Kohno
Carlos Cordeiro, Philips

14. 802.11k measurements AP related measurements
January 2007
doc.: IEEE
July/2007
802.11k measurements
AP related measurements
Beacon
Backup AP tables on a specified channel
Can be done by active mode, passive mode, or beacon table mode
Measurement pilot
a minimum set of compact beacon with a smaller interval
To reduce duty cycle of beacon and provide timely information
Neighbor report
Known neighbor AP that are candidates for handover
Traffic related measurements
Channel load
Channel utilization
Frame
Picture of all the channel traffic and a counter
Zhen, Li and Kohno
Carlos Cordeiro, Philips

15. 802.11k measurements (cont.) Channel related measurements
January 2007
doc.: IEEE
July/2007
802.11k measurements (cont.)
Channel related measurements
Link measurement
An RF ping
Link path loss and link margin
Noise histogram
A power histogram measurement of non noise power when CCA indicates idle
QoS related measurements
STA statistics
A groups of values for STA counter and for BSS average access delay
Transmit stream measurement
Transmit-side performance metrics for the measured traffic stream
Zhen, Li and Kohno
Carlos Cordeiro, Philips

16. 802.11v: wireless link management
January 2007
doc.: IEEE
July/2007
802.11v: wireless link management
Scope of 11v
“to extend prior work in radio measurement to effect a complete and coherent upper layer interface for managing device”
Purpose of 11v
“enable management of attached STA in a centralized or in a distributed fashion through a L2 mechanism”
Message format exchanged between station and AP to configure STA
Zhen, Li and Kohno
Carlos Cordeiro, Philips

17. 802. 11v mechanisms AP collaboration BSS load balancing Power saving
January 2007
doc.: IEEE
July/2007
v mechanisms
AP collaboration
Virtual AP
A logical entity that exists within a physical AP
To use a single beacon to efficiently advertise multiple BSSIDs and SSIDs
Time and power collaboration
BSS load balancing
geographically non-uniformly distributed traffic in indoor applications
Handover of STA from one AP to another AP triggered by load considerations; not by mobility
Station centric or AP centric?
Power saving
Idle and paging mode
Zhen, Li and Kohno
Carlos Cordeiro, Philips

18. 802. 11v mechanisms (cont.) Dynamic channel selection
January 2007
doc.: IEEE
July/2007
v mechanisms (cont.)
Dynamic channel selection
Change the operating channel for the entire BSS during live system operation
seamlessly with no loss of connectivity both when idle and in a session
Channel quality index
Deferral management
Control of transmission power by transmitter and energy detection threshold (EDT) by receiver
to allow for higher channel reuse and higher system capacity
Flexible broadcast/multicast service
Co-located interference reporting
Admission control
Zhen, Li and Kohno
Carlos Cordeiro, Philips

19. January 2007
doc.: IEEE
July/2007
802.15
Bluetooth ( )
TDMA
Round-robin scheduling
and
Guarantee time slot (GTS)
Polling
Zhen, Li and Kohno
Carlos Cordeiro, Philips

20. Comments Main focus and limitation Useful features
January 2007
doc.: IEEE
July/2007
Comments
Main focus and limitation
and :
to maximize data throughout
simple and battery-powered device
MBAN
life critical applications and periodical medical data
Limited power
Useful features
Measurement pilot, idle mode, power-save delivery
Dynamic channel switch, traffic priorities, block ACK
Admission control, direct link
Location indicator
Zhen, Li and Kohno
Carlos Cordeiro, Philips

21. Conclusions Review of QoS mechanisms in IEEE 802
January 2007
doc.: IEEE
July/2007
Conclusions
Review of QoS mechanisms in IEEE 802
802.11e
802.11k
802.11v
802.15
Comments on applying these mechanisms to MBAN
Zhen, Li and Kohno
Carlos Cordeiro, Philips