IEEE Standard 802.16: A Technical Overview of the WirelessMAN Air Interface for Broadband Wireless Access

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IEEE Standard 802.16A Technical Overview of the
WirelessMAN Air Interface for Broadband Wireless
Access

• From IEEE Communications Magazine, June 2002
• Presented by Hermes Liu

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Authors

• Carl Eklund,
• Nokia Research Center
• Roger B. Marks,
• National Institute of Standards and Technology
• Kenneth L. Stanwood and Stanley Wang,
• Ensemble Communications Inc.

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Agenda

• -Introduction
• -Technology Design
• -Physical Layer Details
• -Medium Access Control Details
• -Conclusion

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Agenda

• -Introduction
• -Technology Design
• -Physical Layer Details
• -Medium Access Control Details
• -Conclusion

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Introduction

• IEEE 802.16 Wireless MAN
• -Provides network access to buildings through
  exterior antennas and substitute the cabled
  access network (fiber optic, cable modem, DSL
  etc.)
• -Wireless systems have the capacity to address
  broad geographic areas without the costly cable
  links.
• -User inside the building connect to it with
  Ethernet( 802.3) or Wireless LANs (802.11).
• -May eventually allow the Wireless MAN networking
  protocols directly to the individual user by
  exchange medium access control (MAC) protocol
  data with each other.

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(No Transcript)
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Introduction

• 802.16 1066 GHz
• -Short wavelengths introduce deployment problems.
  (line-of-sight)
• -A set of air interfaces based on a common MAC
  protocol but with PHY spec. dependent on the
  spectrum
• 802.16a 211 GHz (licensed and license-exempt)
• -Reach more customers less expensively but lower
  data rates.
• 802.16 Working Group
• -Development of IEEE 802.16
• -Included WirelessMAN air interface
• -Associates standards and amendments

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Introduction
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Agenda

• -Introduction
• -Technology Design
• -Physical Layer Details
• -Medium Access Control Details
• -Conclusion

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Technology Design

• Medium Access Control
• -Point-to-multipoint broadband wireless access
• -Very high bit rates both uplink and downlink
• -Hundreds of terminals per channel
• -Terminals be shared by multiple end users
• Services
• -Legacy time-division multiplex (TDM) data
• -Internet Protocol (IP) connectivity
• -Packetized voice over IP (VoIP)
• -Accommodate both continuous and bursty traffic
• -Also provide QoS analogous to asynchronous
  transfer mode (ATM) as well as guaranteed frame
  rate (GFR)

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Technology Design

• Medium Access Control
• -Support backhaul requirements both ATM and
  packet-based protocol (like TCP)
• -Convergence sublayers are used to map the
  transport-layer-specific traffic to a MAC, which
  make the traffic more efficient and flexible
• -Transport efficiency are addressed at the
  interface between MAC and PHY, ex the Modulation
  and coding schemes (MCS) adjustment
• -The request-grant mechanism is designed to be
  scalable, efficient, and self-correcting
  (self-correcting protocol)

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Technology Design

• Medium Access Control
• -802.16 MAC just provide Bandwidth Allocation and
  QoS Mechanisms, left the scheduling and
  reservation management unstandardized so that the
  vendors can differentiate their equipment
• -Has sublayer which provides authentication, key
  exchange and encryption
• -802.16a upgrades the MAC to provide automatic
  repeat request (ARQ) and support for mesh network
  architecture
• ?Note Transport efficiency, Request-grant,
  Bandwidth allocate, QoS, Authentication, Key
  exchange, Encryption, Error correct all in MAC

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Technology Design

• The Physical Layer (10-66 GHz)
• -Line-of-sight propagation (short wavelength)
• -Single-carrier modulation (Wireless MAN SC)
• -Multiplexing time-division multiplexing (TDM)
• -Access time-division multiple access (TDMA)
• Duplexing both TDD and FDD
• -TDD UL DL share a channel but not transmit
  simultaneously
• -FDD UL DL on separate channels, sometimes
  simultaneously
• -Both TDD FDD support adaptive burst profiles
  in which MCS can be assigned burst-by-burst

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Technology Design

• The Physical Layer (2-11 GHz) in 2002
• -Non-line-of-sight, multi-path propagation
• Three air interface specification in draft
• -WirelessMAN-SC2 single-carrier modulation
• -WirelessMAN-OFDM Orthogonal Frequency Division
  Multiplexing with 256-point transform, access by
  TDMA, only for license-exempt bands
• -WirelessMAN-OFDMA 2048-point transform,
  multiple access is provided by addressing a
  subset of the multiple carriers to individual
  receivers
• ?WirelessMAN-OFDM becomes the standard of 802.16a

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Agenda

• -Introduction
• -Technology Design
• -Physical Layer Details
• -Medium Access Control Details
• -Conclusion

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Physical Layer Details

• -The transmission parameters (modulation and
  coding schemes MCS) from a Base Station (BS) may
  be adjusted individually to each Subscriber
  Station (SS) on a frame-by-frame basis
• -Forward Error Correction (FEC) Reed-Solomon GF
  (256) with variable block size and error
  correction capabilities
• Modulation Technique
• -Quadrature Phase Shift Key (QPSK)
• -16-state Quadrature Amplitude Modulation
  (16-QAM)
• -64-state QAM (64-QAM)

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Physical Layer Details

• -The frame (0.5, 1, or 2 ms) is divided into
  physical slots for bandwidth allocation and
  identification of PHY transitions
• -TDD UL subframe follows DL subframe on the same
  carrier frequency
• -FDD UL DL subframes are in time but on
  separate frequency.

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Physical Layer Details
frame control section
Figure 1. The downlink subframe structure
DIUC Downlink Interval Usage Code
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Physical Layer Details
Figure 2. The uplink subframe structure
UIUC specified burst profile
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Physical Layer Details
Figure 3. TC PDU format.
Transmission Convergence (TC) Sublayer
-performs the transformation of variable length
MAC protocol data unit (PDUs) into fixed length
FEC blocks (padding) -Allows resynchronization
in case the previous FEC block had irrecoverable
errors
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Agenda

• -Introduction
• -Technology Design
• -Physical Layer Details
• -Medium Access Control Details
• -Conclusion

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Medium Access Control Details
Service-Specific Convergence Sublayers Interface to higher layers
Common Part Sublayer Carries out the key MAC functions
Privacy Sublayer Privacy protocol and security
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Medium Access Control Details

• Service-Specific Convergence Sublayers
• -Classify service data units (SDUs) to the proper
  MAC connection
• ex. Legacy TDM, IP, VoIP, ATM with GFR
• -Preserve or enable QoS
• -Enable bandwidth allocation
• -Payload header suppression and reconstruction
• -ATM Con. Sublayer for ATM services
• -Packet Con. Sublayer packet services (IPv4,
  IPv6, Ethernet, VLAN)

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Medium Access Control Details

• Common Part Sublayer
• General Architecture
• 802.16 point to multipoint

-DL TDM -ULTDMA -Connection-oriented all
services are mapped to a connection -Requesting
bandwidth -QOS -Traffic parameters -Transporting
routing data -Connections are referenced with
16-bit Connection identifiers (CID)
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Medium Access Control Details

• Common Part Sublayer
• Three QoS levels to SS
• -Basic connection
• short, time critical MAC and radio link control
  (RLC) message
• -Primary management connection
• longer, delay-tolerant message (ex.
  authentication, connection setup)
• -Secondary message connection
• standards-based management message (ex. DHCP,
  TFTP, SNMP)
• Transport connection (for contracted services)
• -Unidirectional, UL and DL QoS and traffic
  parameters, assigned to services in pairs.
• Reserved connections
• -Connection-based initial access, broadcast,
  multicast

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Medium Access Control Details

• MAC PDU Formats
• -Data unit exchanged between the MAC layers of
  the BS and its SS.
• Two format
• -Generic Header,
• -Bandwidth Request Header (no payload)
• -Fixed length MAC header
• -Variable length payload
• -Cyclic redundancy check (CRC) , optional

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(Generic header)
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Medium Access Control Details

• MAC PDU Formats
• Three types of MAC subheader
• -Grant management subheader
• SS use it to request bandwidth to BS
• -Fragmentation subheader
• Fragmentation is a MAC SDU is divided into one
  or more MAC SDU segment
• Indicates the presence and orientation in the
  payload of any fragments of SDUs
• -Packing subheader
• Packing is multiple MAC SDUs are packed into a
  single MAC PDU payload
• Indicate the packing of multiple SDUs into a
  single SDU

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Medium Access Control Details

• PHY support
• -The MAC builds the DL subframe starting with a
  frame control section containing the DL-MAP (PHY
  transitions) and UP-MAP (bandwidth allocations
  and burst profiles) messages.

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Medium Access Control Details

• Radio Link Control (RLC)
• -Burst profiles for the DL are tagged with
  Downlink Interval Usage Code (DIUC), for the UL
  are tagged with UIUC.
• -Ranging request (RNG-REQ) power leveling and
  ranging
• -Ranging response (RNG-RSP) power and ranging
  adjustment
• -RLC monitor and control the burst profiles. RLC
  can adapt the SSs current UL and DL burst
  profiles to a balance between robustness and
  efficiency (ex. rain fades or good weather)

RNG-REQ
SS
BS
RNG-RSP
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Medium Access Control Details
DBPC DL burst profile change
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Medium Access Control Details
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Medium Access Control Details

• Uplink scheduling services
• -Each connection in the uplink direction is
  mapped to a scheduling service.
• Unsolicited Polling Service (UGS)
• -Need constant bandwidth allocation
• Real-time polling service
• -suited for VoIP, streaming video or audio
• Non-real-time polling service
• -tolerate longer delays and are rather
  insensitive to delay jitter. Suited for Internet
  access with minimum guaranteed rate and for ATM
  GFR connections
• Best effort service
• -Neither throughput nor delay guarantees are
  provided

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Medium Access Control Details

• Bandwidth Request and Grants
• Grant per connection (GPC)
• -bandwidth is granted explicitly to a connection,
  and SS uses the grant only for that connection.
  RLC and other management protocols use bandwidth
  allocated to the management connections.
• Grant per SS (GPSS)
• -SSs are granted bandwidth aggregated into a
  single grant to the SS itself. Is the only class
  of SS allowed with the 10-66 GHz PHY.
• Request by DBPC-REQ
• -The two class of SS allow a trade-off between
  simplicity (GPC) and efficiency (GPSS)

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Medium Access Control Details

• Bandwidth Request and Grants
• Reasons for failure bandwidth request-
• -The BS/ SS did not see the request due to
  irrecoverable PHY errors or collision of a
  contention-based reservation
• -The BS did not have sufficient bandwidth
  available
• -The GPSS SS used the bandwidth for another
  purpose
• -In self-correcting protocol, these are treated
  the same. After a timeout appropriate for the QoS
  of the connection, the SS simply requests again.
• -Less bandwidth, less delay than acknowledge
  protocol

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Medium Access Control Details

• Bandwidth Request and Grants
• Ways to request bandwidth-
• -Use Poll-me bit in grant management subheader
  when have unsolicited grant service (UGS)
• -Piggyback a request for additional bandwidth
  in grant management subheader within a MAC PDU
  for the same connection (GPC)
• -Use Bandwidth Request Header in MAC PDU with no
  payload (GPSS)
• -In addition to polling individual SSs, the BS
  may issue a broadcast poll by allocating a
  request interval to the broadcast CID

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Medium Access Control Details

• Channel Acquisition
• -The MAC protocol includes initialization
  procedure, need no manual configuration. An SS
  begins scanning frequency to find an operating
  channel.
• -After decide which channel, the SS tries to
  synchronize to the downlink transmission by
  detecting the periodic frame preambles.
• -After the PHY is synchronized, the SS can learn
  the modulation and FEC (Forward Error Correction)
  schemes (MCS) used on the carrier.

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Medium Access Control Details

• Initial Ranging and Negotiation of SS
  Capabilities
• -The SS uses a truncated exponential backoff
  algorithm to determine which initial ranging
  slot it will use to send a ranging request
  message.
• -The SS will send the burst using the minimum
  power setting and will try again with higher
  power if it does not receive a ranging response.
• -The BS commands a timing advance and a power
  adjustment to the SS in the ranging response.
• -The response also provides the SS with the
  basic and primary management CIDs

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Medium Access Control Details

• SS Authentication and Registration
• -manufacturer-issued factory-installed X.509
  digital certificate
• -Certificate of the manufacturer
• These two establish a link between the 48-bit MAC
  address of the SS and its public RSA key, are
  sent to the BS in the Authorization Request and
  Authentication Information message
• The BS will respond to its request with an
  Authorization Reply containing an Authorization
  Key (AK) encrypted with the SSs public key
• After that, the SS will register with the
  network, and establish the secondary management
  connection, determine capabilities, and which
  version of IP will be used.

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Medium Access Control Details

• IP Connectivity
• Get an IP address via DHCP
• Connection Setup
• Use service flows with two-phase activation,
  setup by the BS, and can be dynamically
  established by SS.
• Privacy Sublayer
• The privacy protocol is based on the Privacy Key
  Management (PKM) protocol and provide stronger
  cryptographic methods such as Advanced Encryption
  Standard (AES)

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Medium Access Control Details

• Security Associations
• -SA is a set of cryptographic methods and the
  associated keying material, contains the
  information about which algorithms to apply,
  which key to use. Every SS establishes at least
  one SA during initialization. Each connection is
  mapped to an SA.
• Cryptographic Methods

Authentication Authorization for SS Traffic encryption Exchange of transmission encryption keys
PKM protocol uses X.509 with RSA public key Data encryption Standard (DES) in the cipher block chaining (CBC) with 56-bit keys 3DES
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Agenda

• -Introduction
• -Technology Design
• -Physical Layer Details
• -Medium Access Control Details
• -Conclusion

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Conclusion

• -IEEE 802.16 provides a platform for the
  development and deployment of metropolitan area
  networks broadband wireless access.
• -Allow for multiple vendors to produce
  interoperable equipment, meanwhile
  differentiation as well.
• -The efficiency of a transition will be optimized
  by adaptive burst profile feature and scheduling
  algorithm, and schemesetc.
• -Power consumption concern, may apply
  optimization of ranging mechanism
• -The IEEE 802.16 wirelessMAN becomes a major
  alternative for broadband access.

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The EndThanks for your patience!!