Wireless MAN IEEE 802.16

1
Wireless MAN IEEE 802.16

• By
• Sameer Kurkure
• KReSIT
• IIT Bombay

Guide Prof. Anirudha Sahoo KReSIT IIT Bombay
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Overview

• Broadly applicable to the systems operating
  between 11-66Ghz
• Point to Multipoint
• Metropolitan Area Network
• Connection oriented
• Support difficult user environment
• High bandwidth, large number of end users
• Continuous and burst traffic
• Efficient user of spectrum
• Flexibility in offering QoS for
• CBR, rt-VBR, nrt-VBR, and BE according to their
  classes
• Supports multiple 802.16 PHYs
• LOS communication

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Basic Architecture

• Single BS (Base Station)
• Multiple fixed SS (Subscriber Stations)
  associated with one BS
• Hundreds of users in one SS

4
MAC Mechanism and Framing

• BS periodically grants transmission opportunities
• Grants are time slots on uplink channel
• Some time slots reserved for contention
• Broadcasting MAP message
• Downlink subframe contains
• DL-MAP
• UL-MAP

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Scheduling Services

• Unsolicited Grant Service (UGS)
• Fixed size data on periodic basis e.g. VoIP
• Bandwidth is separately reserved
• Real Time Polling Service (rtPS)
• Variable size data on periodic basis e.g. MPEG
  video
• By unicast requests
• Non-real Time Polling Service (nrtPS)
• Variable size data e.g. FTP service
• Requires some minimum bandwidth
• Best Effort (BE)
• Service flows like HTTP (no minimum bandwidth)
• Use contention window for requests

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Bandwidth Allocation and Request Mechanism

• Grant per Connection (GPC)
• Bandwidth allocated
• Decision made at BS for each connection
• BS may be overloaded
• Suitable for few SSs.
• Grant per Subscriber Station (GPSS)
• Fixed bandwidth for each SS
• Decision for connection made at SS
• Less burden on BS

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QoS Architectures
General
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QoS Architectures
General

• Components
• Traffic Classifier
• Contention Ratio Calculator (CRC)
• SSs upstream Scheduler
• BSs upstream scheduler
• Contention Slot Allocator (CSA)
• Contention Resolution Algorithm (CRA)
• BSs downstream scheduler

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QoS Architectures
General

• Components
• Traffic Classifier
• Contention Ratio Calculator (CRC)
• Ru Rrp Rnp Rbe 100
• SSs upstream Scheduler
• BSs upstream scheduler
• Contention Slot Allocator (CSA)
• Contention Resolution Algorithm (CRA)
• BSs downstream scheduler

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QoS Architectures
General

• Components
• Traffic Classifier
• Contention Ratio Calculator (CRC)
• SSs upstream Scheduler
• Selects traffic according to the grants from BSs
  upstream scheduler
• BSs upstream scheduler
• Contention Slot Allocator (CSA)
• Contention Resolution Algorithm (CRA)
• BSs downstream scheduler

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QoS Architectures
General

• Components
• Traffic Classifier
• Contention Ratio Calculator (CRC)
• SSs upstream Scheduler
• BSs upstream scheduler
• Decide schedules from the requests obtained
• Contention Slot Allocator (CSA)
• Contention Resolution Algorithm (CRA)
• BSs downstream scheduler

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QoS Architectures
General

• Components
• Traffic Classifier
• Contention Ratio Calculator (CRC)
• SSs upstream Scheduler
• BSs upstream scheduler
• Contention Slot Allocator (CSA)
• Maintain proper ratio between contention slots
  reservation slots
• Contention Resolution Algorithm (CRA)
• BSs downstream scheduler

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QoS Architectures
General

• Components
• Traffic Classifier
• Contention Ratio Calculator (CRC)
• SSs upstream Scheduler
• BSs upstream scheduler
• Contention Slot Allocator (CSA)
• Contention Resolution Algorithm (CRA)
• Rules to resolve contentions
• BSs downstream scheduler

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QoS Architectures
General

• Components
• Traffic Classifier
• Contention Ratio Calculator (CRC)
• SSs upstream Scheduler
• BSs upstream scheduler
• Contention Slot Allocator (CSA)
• Contention Resolution Algorithm (CRA)
• BSs downstream scheduler
• Schedule back grant along with other data.

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QoS Architectures
Admission Control based on scheduling service
characteristics

• BS decides ? accept / reject of users request
• Accepting may cause QoS degradation
• Some portion of bandwidth d from is given to
  new connection
• Cannot compromise on UGS and rtPS connections
• nrtPS connection best for sacrifice
• Keep assigning BW for new connection until QoS
  parameter is safe (Lmax degradation level)

Degradation Model
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QoS Architectures
Admission Control based on scheduling service
characteristics
New Connection
Assign BW for New connection
Yes
Cut d from ongoing nrtPS connections L L 1
(initially 0)
bmax Ld gt bmin
Degradation Model
No
Reject connection
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QoS Architectures
Admission Control based on scheduling service
characteristics

• Analytical Model
• Can be expressed in state diagram
• s ( nUGS, nrtPS, nnrtPS, Ln) be the valid state
• Constraints of Validity
• nUGSbUGS nrtPSbrtPS nnrtPS(bmax Lnd gt
  bmin) lt B
• nrtPSbrtPS nnrtPS(bmax Lnd gt bmin) lt B -
  U
• Ln lt Lmax
• Transition
• At acceptance of new request
• Completion of connection

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QoS Architectures
Admission Control based on scheduling service
characteristics
State Transition Diagram
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QoS Architectures
DOCSIS (Data Over Cable Service Interface
Specification)

• Addition of high-speed data transfer to existing
  cable TV systems
• Components
• CMTS (Cable Modem Termination System)
• CM (Cable Modem)
• Works on request/grant mechanism
• Headend sends ack / data grant at each request
• Contention happens when CM doesnt receive any of
  them

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QoS Architectures
DOCSIS (Data Over Cable Service Interface
Specification)

• Variable length upstream frame is used
• Need to optimize contention mini slots j
• Adjust j such that
• Throughput of contention requests become equal to
  new data packets transmitted in max. frame
• Assigned appropriate priorities to service flows
• Allocate mini slots for that flow

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QoS Architectures
DOCSIS (Data Over Cable Service Interface
Specification)
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QoS Architectures
DOCSIS (Data Over Cable Service Interface
Specification)

• Handling priorities
• Choose set of multiplication factors, ad such
  that 0 lt ad lt 1
• where d 0,,K and a0a1 .aK 1
• Associate these number at the specific flows
• aK to highest priority
• a0 to lowest priority
• Allocate j ad number of slots to the
  corresponding service flow

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QoS Architectures
Mesh Networks IEEE 802.16d

• Area divided meshes to form a network
• Components
• Mesh Base Station (MBS)
• Mesh Subscriber Station (MSS)
• MBS periodically collects
• Channel information
• Resource request
• MBS decides on
• Routing
• Scheduling Strategy

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QoS Architectures
Mesh Networks IEEE 802.16d

• Communication
• Intra-mesh communication
• MSSs ??MSSi??MSSd
• Inter-mesh communication
• MSSs?..?MBSs?MBSd?..MSSd
• Traffic associated
• Real Time Application
• Like VoIP uses UDP
• Data Application
• Uses TCP
• QoS requirement for both are different

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QoS Architectures
Mesh Networks IEEE 802.16d
Routing
Queue Length
link(i,j) always assign ni,j slots assuming
schedule to be fixed
For queue to be stable Outgoing gt Incoming
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QoS Architectures
Mesh Networks IEEE 802.16d
Scheduling

• QoS for Real Time (UDP) Traffic
• Constant Bit Rate (CBR)
• Like VoIP
• Drop the packet when out of constraint
• E.g. delay gt 10ms
• Let Xi be constant amount of traffic generated at
  nodei
• Let ei be the end to end dropping probability
  decomposed into ei,j
• ni,j be number slots assign at nodej for flow
  from nodei then following condition must get
  satisfied

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QoS Architectures
Mesh Networks IEEE 802.16d
Scheduling

• QoS for Real Time (UDP) Traffic
• Variable Bit Rate (CBR)
• Like video conferencing
• Drop the packet when out of constraint
• E.g. delay gt 10ms
• Let there are J number of VBR flows at nodei
• Dk(i,j) be amount of data generated by jth flow
  in framek
• Let ei be the end to end dropping probability
  decomposed into eb ed
• Find Ci such that

Ci/J can be called as eqv BW of VBR for which MBS
can treat as CBR for dropping ed
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QoS Architectures
Mesh Networks IEEE 802.16d
Scheduling

• QoS for TCP Traffic
• Fixed Allocation Scheme
• Need to calculate ni,j number of slots to be
  allocated at nodej for traffic generated at nodei
• Let
• Required to satisfy two constraint

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QoS Architectures
Mesh Networks IEEE 802.16d
Scheduling

• QoS for TCP Traffic
• Fixed Allocation Scheme
• Also is directly proportional to throughput
  assigned to traffic at each nodei. Therefore,

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QoS Architectures
Mesh Networks IEEE 802.16d
Scheduling

• QoS for TCP Traffic
• Adaptive Allocation Scheme
• Classify the link as G and B
• Defer allocation of slots to links which are bad
• Assign counter ck(i) for number of slots for
  nodei compensating missed slots
• Assign channel if counter exceeds CLim(i)

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QoS Architectures
Mesh Networks IEEE 802.16d
Scheduling

• QoS for TCP Traffic
• Adaptive Allocation Scheme
• calculate,
• Now
• Here Rth(i) and CLim(i) are design parameter

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Thank You