WiMAX Protocol

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WiMAX Protocol

• CSCE 4520/5520 Fall 2006
• Shori Fukatsu

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Contents List

• WiMAX Protocol
• About WiMAX
• Physical layer
• MAC layer
• Fixed / Mobile WiMAX
• WiMAX vs Wi-Fi
• WiMAX applications
• Reference
• Quiz

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WiMAX

• Worldwide Interoperability for Microwave Access
• a standards-based technology enabling the
  delivery of last mile wireless broadband access
  as an alternative to cable and DSL
• Metropolitan Area Network (MAN)
• Based on IEEE 802.16

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Purpose of WiMAX

• To provide point-to-multipoint wireless access to
  Internet and other networks
• To provide high data rates over 10-40km

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WiMAX Architecture
MIB Management Information Base
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802.16 protocol
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802.16 protocol stack

• 802.16 covers data link and physical layer

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IEEE 802.16 Standards

• 802.16.1 (10-66 GHz, line-of-sight, up to
  134Mbit/s)
• 802.16.2 (minimizing interference between
  coexisting WMANs.)
• 802.16a (2-11 Ghz, Mesh, non-line-of-sight)
• 802.16b (5-6 Ghz)
• 802.16c (detailed system profiles)
• 802.16e (Mobile Wireless MAN) called MobileWiMAX

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Physical layer (PHY)
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PHY cont.

• QPSK 2 bits/baud (lt 10km)
• QAM-16 4 bits/baud (6-10km)
• QAM-64 6 bits/baud (gt6km)
• Example a 25 MHz bandwidth, QPSK can deliver 50
  Mbps, QAM-16 100 Mbps, QAM-64 150 Mbps
• Baud (Bd) measure of the symbol rate the number
  of distinct symbolic changes (signalling event)
  made to the transmission medium per second in a
  digitally modulated signal
• 25 Bd means that 25 symbols are transmitted per
  second.

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PHY cont.

• TDD (time-division duplex)
• - use same bandwidth for uplink and downlink
• - controlled by timing
• FDD (frequency-division duplex)
• - use different frequency for uplink and
  downlink
• OFDM (orthogonal frequency-division multiplexing)
• - enhancement of frequency division multiplexing
  (FDM)
• - maximize use of bandwidth

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TDD and FDD
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OFDM
FDM
OFDM
OFDM uses bandwidth which is not available for
use in FDM
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MAC layer

• Protocol-Independent core (IP, ATM, etc)
• Support multiple 802.16 PHYs

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MAC cont.

• Each MAC packet contains three components
• MAC header contains frame control information
• variable length frame body contains information
  specific to the frame type
• frame check sequence (FCS) contains an IEEE
  32-bit cyclic redundancy code (CRC).

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MAC cont.

• Generic Uplink/Downlink header

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Downlink Header
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Downlink Header

• Encryption Control (EC) Indicates whether the
  payload is encrypted
• Encryption Key Sequence (EKS) An index into a
  vector of encryption key information
• Length Length in bytes of the entire MAC frame
• Connection Identifier A unidirectional, MAClayer
  address that identifies a connection to
  equivalent peers
• Header Type Indicates whether this is a generic
  or bandwidth request header
• ARQ Indicator Indicates whether the frame
  belongs to an ARQ enabled connection
• Fragment Control Used in fragmentation and
  reassembly
• Fragment Sequence Number Sequence number of the
  current fragment
• Header Check Sequence 8-bit CRC to detect errors
  in the header

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Uplink Header
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Uplink Header

• Slip indicator indicate a slip of uplink grants
  relative to the uplink queue depth
• Poll-me request a poll by the base station
• Grants per interval the number of bandwidth
  grants required in the next time interval
• Piggyback request the number of bytes of uplink
  capacity requested

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Bandwidth request and allocation

• SSs may request bandwidth in 3 ways
• Use the contention request opportunities
  interval upon being polled by the BS (multicast
  or broadcast poll).
• Send a standalone MAC message called BW request
  in an allready granted slot.
• Piggyback a BW request message on a data packet.

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Bandwidth request and allocation cont.

• BS grants/allocates bandwidth in one of two
  modes
• Grant Per Subscriber Station (GPSS)
• Grant Per Connection (GPC)
• Decision based on requested bandwidth and QoS
  requirements vs available resources.
• Grants are realized through the UL-MAP (Uplink
  message).

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Bandwidth request and allocation cont.
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Fixed and Mobile WiMAX

• Fixed WiMAX is optimized for home/office networks
• Mobile WiMAX is optimized for mobiles

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Fixed WiMAX

• IEEE 802.16d
• T1/E1 substitute
• 1BS thousands of user
• lt 50km coverage
• lt 75Mbps

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Fixed WiMAX Architecture
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Mobile WiMAX

• IEEE 802.16e
• 2-3km coverage (optimal)
• High speed hand over
• (lt 50ms latencies)
• Ensures performance at vehicular speeds greater
  than 120km/h
• lt 30Mbps for downlink
• lt 15Mbps for uplink

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WiMAX vs Wi-Fi
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WiMAX vs Wi-Fi cont.
WiMAX is designed to cover large area (multiple
homes/buildings), while Wi-Fi is to cover small
area (a home/building)
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Comparison of WiMAX, WiFi and 3G technology
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WiMAX vs Wi-Fi cont.
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WiMAX applications

• Broadband Internet
• Multimedia
• IP multimedia subsystem (IMS)
• Cellular Alternative

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Broadband Internet

• Fixed WiMAX is substitute for T1
• Mobile WiMAX has larger coverage than WiFi

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Multimedia

• Mobile TV
• IPTV (TV broadcasting via IP network)

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Traditional networks

• Different device, different network
• For example
• TV is only for watching TV
• Phone is only for call

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IMS network

• One network provides multiple things
• For example
• Watch TV and use Internet via cell phone

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WiMAX as cellular alternative

• Support IP by default
• VoIP

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Reference

• Frank Ohrtman Wimax overview
  http//www.wimax.com/education/wimax/wimax_overvie
  w
• The 802.16 WirelessMAN MAC Its Done, but What
  Is It? (2001-11-12)
• Zheng Yu Huang (2006-10-25)Considerations for
  Next Generation Telecommunications Deployments in
  China, Intel Corporation
• Michael Richardson and Patrick Ryan (2006-3-19)
  WiMAX Opportunity or Hype?
• Adaptive Modulation (2004), Intel Corporation
• Tim Sanders (2005-9-21) WiMax/802.16 Revealed,
  http//www.wi-fiplanet.com/tutorials/article.php/3
  550476
• Michael F. Finneran (2004-6-1) WiMAX versus
  Wi-Fi, dBrn Associates, Inc.

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• Israel Koffman and Vincentzio Roman (2002)
  Broadband Wireless Access Solutions Based on
  OFDM Access in IEEE 802.16, IEEE Communications
  Magazine April 2002
• WiMAX Forum (2006-8) Mobile WiMAX Part I A
  Technical Overview and Performance Evaluation
• dailywireless.org (2005-7-8) Mobile WiMAX
  Chips, http//www.dailywireless.org/2005/07/08/mo
  bile-wimax-chips/
• Carl Eklund, Roger B. Marks, Kenneth L. Stanwood
  and Stanley Wang (2002-6) IEEE Standard 802.16
  A Technical Overview of the WirelessMAN Air
  Interface for Broadband Wireless Access, IEEE
  Communications Magazine June 2002
• Robert Healey (2003)Network Architecture for
  WiMAX applications, Juniper Networks, Inc.
• Kuo-Hui Li (2006-6-5) WiMAX Network
  Architecture, Intel Mobility Group
• Technology Primer WiMAX, http//www.tektronix.co
  m/wimax

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Quiz

• How much bps can QPSK (2bits/Bd), QAM-16
  (4bits/Bd) and QAM-64 (6bits/Bd) can deliver if a
  bandwidth is 20MHz?
• What is the difference between OFDM and FDM?
• What are the differences between WiMAX and Wi-Fi?

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Answer

• QPSK - 40Mbps, QAM-16 - 80Mbps, QAM-64 -120Mbps
  (slide 11)
• See slide 14
• The main difference is that WiMAX is focused on
  MAN, while Wi-Fi is LAN technology. (slide
  30-33)