Transcript WiMAX Protocol

WiMAX Protocol
CSCE 4520/5520 Fall 2006
Shori Fukatsu
Contents List
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WiMAX Protocol
 About
WiMAX
 Physical layer
 MAC layer
Fixed / Mobile WiMAX
 WiMAX vs Wi-Fi
 WiMAX applications
 Reference
 Quiz
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WiMAX
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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
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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
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802.16 covers data link and physical layer
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IEEE 802.16 Standards
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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 (< 10km)
 QAM-16: 4 bits/baud (6-10km)
 QAM-64: 6 bits/baud (>6km)
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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.
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TDD (time-division duplex)
- use same bandwidth for uplink and downlink
- controlled by timing
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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
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Protocol-Independent core (IP, ATM, etc)
Support multiple 802.16 PHYs
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MAC cont.
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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.
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Generic Uplink/Downlink header
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Downlink Header
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Downlink Header
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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
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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
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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.
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BS grants/allocates bandwidth in one of two
modes:
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Grant Per Subscriber Station (GPSS)
Grant Per Connection (GPC)
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Decision based on requested bandwidth and
QoS requirements vs available resources.
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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
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Fixed WiMAX is optimized for home/office
networks
Mobile WiMAX is optimized for mobiles
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Fixed WiMAX
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IEEE 802.16d
T1/E1 substitute
1BS – thousands of user
< 50km coverage
< 75Mbps
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Fixed WiMAX Architecture
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Mobile WiMAX
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IEEE 802.16e
2-3km coverage (optimal)
High speed hand over
(< 50ms latencies)
Ensures performance at
vehicular speeds greater
than 120km/h
< 30Mbps for downlink
< 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
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Mobile TV
IPTV (TV broadcasting via IP network)
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Traditional networks
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Different device,
different network
For example:
TV is only for
watching TV
Phone is only for call
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IMS network
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One network provides
multiple things
For example:
Watch TV and use
Internet via cell phone
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WiMAX as cellular alternative
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Support IP by default
VoIP
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Reference
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Frank Ohrtman: “Wimax overview”:
http://www.wimax.com/education/wimax/wimax_overview
“The 802.16 WirelessMAN™ MAC: It’s Done, but What Is It?” (200111-12)
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.wifiplanet.com/tutorials/article.php/3550476
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/mobile-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.com/wimax
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Quiz
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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
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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)
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