QoS mechanisms in IEEE 802

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QoS mechanisms in IEEE 802

• Bin Zhen, Huan-band Li and Ryuji Kohno
• National Institute of Information and
  Communications Technology (NICT)

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• Project IEEE P802.15 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
• Voice81 46 847 5445, E-Mail
  zhen.bin_at_nict.go.jp
• Abstract review of QoS mechanisms in IEEE 802
  framework
• Purpose for discussion in MBAN
• Notice This document has been prepared to assist
  the IEEE P802.15. 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
  P802.15.

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Motivations

• Distinguished features of MBAN from other 802.15
  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

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QoS Limitations of 802.11

• 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)

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Hybrid Coordination Function of 802.11e

• 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

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Enhanced distributed channel access
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Enhanced distributed channel access (cont.)
Priority Access Category (AC) Designation (Informative)
0 0 Best Effort
1 0 Best Effort
2 0 Best Effort
3 1 Video Probe
4 2 Video
5 2 Video
6 3 Voice
7 3 Voice
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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

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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
CAP (HCCA)
QoS CF-Poll
QoS CF-Poll
PCF



ACK
ACK

HC

PIFS
SIFS
PIFS
SIFS
DIFS
PIFS
DIFS
DATA
RTS



DATA



Stations
AIFS
SIFS
SIFS
TXOP ( Station n )
time
TXOP ( Station m )
backoff time
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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

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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

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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

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802.11k radio resource management

• Scope of 11k
• To enhance the MAC of 802.11 standards to provide
  mechanisms to higher layers for radio and network
  measurements
• Purpose of 11k
• To define measurements and develop mechanisms to
  provide 802.11 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

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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

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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-802.11 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

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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 802.11 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

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802. 11v 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

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802. 11v 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

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802.15

• Bluetooth (802.15.1)
• TDMA
• Round-robin scheduling
• 802.15.3 and 802.15.4
• Guarantee time slot (GTS)
• Polling

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Comments

• Main focus and limitation
• 802.11 and 802.15.3
• to maximize data throughout
• 802.15.4
• 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

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Conclusions

• Review of QoS mechanisms in IEEE 802
• 802.11e
• 802.11k
• 802.11v
• 802.15
• Comments on applying these mechanisms to MBAN