Transcript What is WiMAX?

VISHNU
VASANT
PAVAN
ABHILASH
Contents
• Introduction
• What is WiMAX?
• IEEE 802.16 Extensions
• Architecture
• Functionality
• WiMAX Protocol
• Scenario
• Features
• Security Issues
• Benefits
• WiFi vs WiMAX
• WiMAX Applications
• Future of WiMAX
• Conclusion
• References
Introduction
• Broadband access - In your home, you have either a DSL or
cable modem At the office, your company may be using a T1
or T3 line.
• WiFi access - In your home, you may have set up a WiFi
router that lets you surf the Web while you lounge with your
laptop on the road, you can find WiFi hot spots in restaurants,
hotels, coffee shops and libraries.
• Dial-up access - If you are still using dial-up, chances are that
either broadband access is not available, or you think that
broadband access is too expensive
Contd..
• The main problems with broadband access are that it is
pretty expensive and it doesn't reach all areas.
• The main problem with WiFi access is that hot spots are
very small, so coverage is sparse.
• There is a need for a system which provides high speed of
Broadband and is wireless instead of wired.
• WiMAX(Worldwide Interoperability Microwave Access)
provides these features .Its also known as IEEE 802.16
What is WiMAX?
• WiMAX (Worldwide Interoperability for microwave access)
•
A technology based on an evolving standard for point-tomulti point wireless networking
•
The commercialization of IEEE 802.16 standard
•
Solution for Wireless Metropolitan Area Network
•
BWA (Broadband Wireless Access) Solution
•
Comply with European BWA standard
• European Telecommunications Standards Institutes's
High-performance radio metropolitan area network
(HiperMAN)
Wireless MAN (Metropolitan
Area Network)
Contd..
Coverage range up to 50km and speeds up to 70Mbps(shared
among users).
Operation of WiMAX
• WiMAX consists of two parts
• A WiMAX tower, similar in concept to a cell-phone tower A single WiMAX tower can provide coverage to a very
large area -- as big as 3,000 square miles
• A WiMAX Receiver The receiver and antenna could be a
small box or PCMCIA card, or they could be built into a
laptop the way WiFi access is today
Service Types
• Non-Line-Of-Sight
•
A Service where a small antenna on your computer
connects to the tower. In this mode, WiMAX uses a lower
frequency range -- 2 GHz to 11 GHz (similar to WiFi)
• Line-Of-Sight
•
A Service where a fixed dish antenna points straight at the
WiMAX tower from a rooftop or pole. Line-of-sight
transmissions use higher frequencies, with ranges reaching
a possible 66 GHz
IEEE 802.16
• IEEE 802.16 was completed on Oct, 2004
•
Range - 30-mile (50-km) radius from base station
•
Speed - 70 megabits per second
•
Line-of-sight not needed between user and base station
•
Frequency bands - 2 to 11 GHz and 10 to 66 GHz (licensed and
unlicensed bands)
•
Defines both the MAC and PHY layers and allows multiple PHYlayer specifications
IEEE Extensions
• 802.16a
– use the licensed and license-exempt frequencies from 2 to 11Ghz
– Support Mesh-Network
• 802.16b
– Increase spectrum to 5 and 6GHz
– Provide QoS (for real-time voice and video service)
• 802.16c
– Represents a 10 to 66GHz system profile
• 802.16d
– Improvement and fixes for 802.16a
• 802.16e
– Addresses on Mobile
– Enable high-speed signal handoffs necessary for communications with
users moving at vehicular speeds
Architecture
●
●
P2MP(Point to Multi point)
– Wireless MAN
– BS connected to Public Networks
– BS serves Subscriber Stations(SS)
– Provides SS with first mile access to Public
Networks
Mesh Architecture
– Optional architecture for WiMAX
P2MP Architecture
WiMAX Mesh Architecture
WiMAX FUNCTIONALITY
WiMAX Protocol
• Covers MAC layer and PHY layer
– PHY layer
– Transmission Convergence sublayer
– MAC layer
Reference Model
PHY Layer
• In the design of the PHY specification for 10–66 GHz, line-of-sight
propagation was deemed a practical necessity.
• Because of the point-to-multipoint architecture, the BS basically transmits
a TDM signal, with individual subscriber stations allocated time slots
serially.
• The PHY specification defined for 10–66 GHz uses burst single-carrier
modulation with adaptive burst profiling in which transmission
parameters, including the modulation and coding schemes, may be
adjusted individually to each subscriber station (SS) on a frame-by-frame
basis. Both TDD and burst FDD variants are defined.
• Channel bandwidths of 20 or 25 MHz (typical U.S. allocation) or 28 MHz
(typical European allocation) are specified, along with Nyquist squareroot raised-cosine pulse shaping with a roll off factor of 0.25.
Contd..
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●
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Adaptive Burst Profiles
– On DL, multiple SS's can associate the same DL burst
– On UL, SS transmits in an given time slot with a
specific burst
Allows use of directional antennas
– Improves range
Allows use of two different duplexing schemes:
– Frequency Division Duplexing (FDD)
– Time Division Duplexing (TDD)
Support for both full and half duplex stations
Adaptive PHY
FDD (Frequency Division
Duplexing)
●
●
In case of FDD both uplink and downlink channels are on
separate frequencies
The capability of downlink to be transmitted in bursts
simultaneously supports two different modulation
types
– Full Duplex SS's( which can transmit and receive
simultaneously)
– Half Duplex SS's( which cannot)
FDD Frame bursting
TDD (Time Division Duplexing)
●
●
●
In case of TDD both uplink and downlink transmissions
share the same frequency but are separated on time
A TDD frame has a fixed duration and also consists of one
uplink and one downlink frame
TDD framing is Adaptive
Time Division Duplexing
Data Rates
●
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Data rates determined by
exact modulation and
encoding schemes
Channel
Symbol BitRate BitRate BitRate
Rate
Rate
(Mb/s)
(Mb/s)
(Mb/s)
(Mhz)
(Mbd)
20
16
32
64
96
TDD and FDD supported 25
in 802.16 to accommodate28
burst profiling
802.16a adds OFDM and
OFDMA to support NLOS
multipath propagation
20
40
80
120
22.4
44.8
89.6
134.4
Medium Access Control(MAC)
●
●
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WirelessMAN: Point-to-Multipoint and optional mesh
topology
Connection-Oriented
– Connection ID(CID),Service Flows(FS)
MAC layer is further subdivided into three layers
– Convergence sub-layer (CS)
– Common part sub-layer (CPS)
– Privacy sub-layer
MAC Addressing
●
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SS has 48-bit 802.3 MAC address
BS has 48-bit base station ID
– Not a MAC address
Connection ID (CID)
– 16 bit
– Used in MAC PDU
– Connection Oriented Service
Frame Structure and PDU
• Each MAC packet consists of the three components,
– A MAC header, which contains frame control
information.
– A variable length frame body, which contains
information specific to the frame type.
– A frame check sequence (FCS), which contains an
IEEE 32-bit cyclic redundancy code (CRC).
MAC PDU
msb
MAC PDU
lsb
Generic MAC
Header
(6 bytes)
Generic MAC Header Format
(Header Type (HT) = 0)
H E
T C
Type (6 bits)
rs C EKS rs
v I
(2) v
CRC
(optional)
payload (optional)
LEN
msb
(3)
BW Req. Header Format
(Header Type (HT) =1)
H E
T C
Type (6 bits)
BW Req.
msb (8)
LEN lsb (8)
CID msb (8)
BWS Req. lsb (8)
CID msb (8)
CID lsb (8)
HCS (8)
CID lsb (8)
HCS (8)
MAC CS Sub Layer
●
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Interoperability requires convergence sub-layer to be service
specific
Separate CS layers for ATM & packet protocols
CS Layer:
– Receives data from higher layers
– Classifies data as ATM cell or packet
– Forwards frames to CPS layer
Contd..
●
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Packet Convergence Sub-Layer
– Initial support for Ethernet, VLAN, IPv4, and IPv6
– Payload header suppression
– Full QoS support
ATM Convergence Sub-Layer
– Support for VP/VC switched connections
– Support for end-to-end signaling of dynamically
created connections
– ATM header suppression
– Full QOS support
MAC CPS Layer
●
●
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Performs typical MAC functions such as addressing
– Each SS assigned 48-bit MAC address
– Connection Identifiers used as primary address after
initialization
MAC policy determined by direction of transmission
– Uplink is DAMA-TDM
– Downlink is TDM
Data encapsulated in a common format facilitating
interoperability
– Fragment or pack frames as needed
– Changes transparent to receiver
MAC PDU Types
●
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Data MAC PDUs
– HT = 0
– Payloads are MAC SDUs/segments, i.e., data from
upper layer (CS PDUs)
– Transmitted on data connections
Management MAC PDUs
– HT =0
– Payloads are MAC management messages or IP packets
encapsulated in MAC CS PDUs
– Transmitted on management connections
BW Req. MAC PDUs
– HT =1; and no payload, i.e., just a Header
MAC PDU Transmission
●
MAC PDU’s are transmitted on PHY bursts
●
The PHY burst can contain multiple FEC blocks
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Concatenation
– Multiple MAC PDU's can be concatenated into a single
transmission in either uplink or downlink direction
Fragmentation
– Each MAC SDU can be divided into one or more MAC
PDU's
Packing
– Packs multiple MAC SDU's into a single MAC PDU
MAC Privacy Sub Layer
●
●
Provides secure communication
– Data encrypted with cipher clock chaining mode of
DES
Prevents theft of service
– SSs authenticated by BS using key management protocol
Transmission Convergence
Sublayer
• This layer performs the transformation of variable length
MAC protocol data units (PDUs) into the fixed length FEC
blocks (plus possibly a shortened block at the end) of each
burst.
• The TC layer has a PDU sized to fit in the FEC block
currently being filled. It starts with a pointer indicating
where the next MAC PDU header starts within the FEC
block. The TC PDU format allows resynchronization to the
next MAC PDU in the event that the previous FEC block
had irrecoverable errors.
WiMAX Scenario
Consider a scenario where a wimax-enabled computer is 10
miles away from the wimax base station.
•
A special encryption code is given to computer to gain
access to base station.
•
The base station would beam data from the Internet required
for computer (at speeds potentially higher than today's
cable modems)
•
Contd..
•The user would pay the provider monthly fee for using
the service. The cost for this service could be much
lower than current high-speed Internet-subscription fees
because the provider never had to run cables.
•The WiMAX protocol is designed to accommodate
several different methods of data transmission, one of
which is Voice Over Internet Protocol (VoIP).
• If WiMAX-compatible computers become very
common, the use of VoIP could increase dramatically.
Almost anyone with a laptop could make VoIP calls.
WiMAX Features
•Scalability
•Quality of service
•Range
•Coverage
Scalability
•The 802.16 standard supports flexible radio frequency
(RF)
channel
bandwidths.
•The standard supports hundreds or even thousands of
users within one RF channel.
•As the number of subscribers grow the spectrum can
be reallocated with process of sectoring.
Quality Of Service
•Primary purpose of QoS feature is to define
transmission ordering and scheduling on the air
interface.
•These features often need to work in conjunction with
mechanisms beyond the air interface in order to
provide end to end QoS or to police the behaviour or
SS.
•Standard defines several QoS related concepts.
- Service flow Qos scheduling.
- Dynamic service Establishment.
-Two Phase Activation Model.
Theory Of Operation
•All protocol mechanisms support Qos for both uplink
and downlink traffic through the SS and BS.
•Requirements for QoS :
- A configuration and registration function to pre
configure SS based QoS service flows and traffic
parameters.
- A signalling function for dynamically establishing Qos
enabled service flows and traffic parameters.
- Utilization of MAC scheduling and QoS traffic
parameters for uplink service flows.
- Utilization of QoS traffic parameters for downlink
service flows.
Service flows
•A service flow is a MAC transport service that provides
unidirectional transport of packets either to uplink
packets transmitted by the SS or to downlink packets
transmitted by the
BS.
•A service flow is characterized by a set of QoS
parameters such as latency,jitter and throughput
assurances.
•In order to standardize operations between SS and BS
these attributes include details of how the SS requests
uplink bandwidth allocations and the expected behaviour
of the BS uplink scheduler.
Range
•Optimized for up to 50 Km.
•Designed to handle many users spread out over
kilometres.
•Designed to tolerate greater multi-path delay spread
(signal reflections) up to 10.0μ seconds.
•PHY and MAC designed with multi-mile range in mind.
Coverage
•Standard supports mesh network topology.
• Optimized for outdoor NLOS performance.
•Standard supports advanced antenna techniques.
Security Issues
•Security provides subscribers with privacy across the
fixes broadband wireless network.
•Security is implemented by encrypting connections
between SS and BS.
•Protection against unauthorized access to the data
transport services is done by enforcing encryption of the
associated service flows across the network.
Security Architecture
•Two component protocols:
- An encapsulation protocol for encrypting packet
data
across fixed network.
- A key management protocol (PKM) providing the
secure
distribution of keying data from BS to SS.
Packet Data Encryption
•Encryption services are defined as set of capabilities
within the MAC security sub layer.
•MAC Header information specific to encryption is
allocated in the generic MAC header format.
•Encryption is always applied to the MACPDU payload,
generic MAC is no encrypted.
•All MAC management messages shall be sent in clear
to facilitate registration,ranging and normal operation of
the MAC.
Key Management Protocol
•An SS uses the PKM protocol to obtain authorization
and traffic keying material from the BS.
•PKM protocol is also used for periodic reauthorization
and key refresh.
•PKM uses X.509 certificates and the RSA pubic -key
encryption algorithm to perform key exchanges
between SS and BS.
Contd..
•PKM protocol adheres to a client/server model.
•SS acts like PKM client and requests for keying material
and BS acts like PKM server and responds to the
requests ensuring that individual SS clients receive only
keying material for which they are authorized.
•PKM protocol uses MAC management messaging PKMRSP
messages.
•PKM protocol uses public-key cryptography to establish
a shared secret between the SS and the BS.
Security Association
•A security Association is the set of security information a
BS and one or more of its clients SS s share in order to
support secure communication across the IEEE std 802.16
network.
•Three types of SA are defined:
Primary: SS establishes a primary security
association
during the SS initialization process.
Static: Static SA are provisioned within the BS.
Dynamic: Dynamic SA are established and
eliminated
a
on fly in response to the initiation and
termination of specific service flows.
•Static and Dynamic SA can be shared by multiple SS.
Contd..
Figure conceptually depicts end-to-end Authentication,
Authorization, and Accounting (AAA) on 802.16 networks
supporting portability and fully mobile operations.
•
Encryption (security association) is established using the
PKM-EAP protocol.
•
Extensible Authentication Protocol (EAP) is carried over
RADIUS or DIAMETER to the AAA back end.
•
Contd..
• Intel recommends using an end-to-end tunnelling
protocol such as Protected EAP (PEAP) or Tunnelled TLS
(TTLS) to afford mutual authentication.
• It also recommends 128-bit or better Transport Layer
Security (TLS) encryption to further enhance end-to-end
security (especially in situations where cryptographically
weaker EAP methods may be deployed).
Benefits of WiMAX
●
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Speed
– Faster than broadband service
Wireless
– Not having to lay cables reduces cost
– Easier to extend to suburban and rural areas
Broad coverage
– Much wider coverage than WiFi hotspots
Benefits for Network Service
Providers
•Allow service providers to deliver high throughput
broadband based services like VoIP, high-speed Internet
and Video
•Facilitate equipment compatibility
•Reduce the capital expenditures required for network
expansion
•Provide improved performance and extended range
•Allow service providers to achieve rapid ROI and
maximize revenues
Benefits for consumers
●
Range of technology and service level choices from both
fixed and wireless broadband operators
●
DSL-like services at DSL prices but with portability
●
Rapidly declining fixed broadband prices
●
No more DSL “installation” fees from incumbent
WiFi Vs WiMAX
• Scalability
• Relative Performance
• Quality of Service
• Range
• Coverage
• Security
Scalability
802.11
•
•
Wide (20MHz) frequency
channels
MAC designed to support 10’s
of users
802.16a
Channel bandwidths can be
chosen by operator (e.g. for
sectorization)
•
1.5 MHz to 20 MHz width
channels. MAC designed for
scalability. independent of
channel bandwidth
•
•
MAC designed to support
thousands of users.
Relative Performance
Channel
Bandwidth
Maximum
Data Rate
Maximum
bps/Hz
802.11
20 MHz
54 Mbps
2.7 bps/Hz
802.16a
1.5 – 20 MHz
100 Mbps
5.0 bps/Hz
Quality Of Service (QoS)
802.11
•
•
•
•
Contention-based MAC
(CSMA/CA) => no guaranteed QoS
Standard cannot currently
guarantee latency for Voice, Video
Standard does not allow for
differentiated levels of service on a
per-user basis
802.11e (proposed) QoS is
prioritization only
802.16a
•
•
•
•
Grant-request MAC
Designed to support Voice and
Video from ground up
Supports differentiated service
levels: e.g. T1 for business
customers; best effort for
residential.
Centrally-enforced QoS
Range
802.11
802.16a
•
Optimized for ~100 meters
•
•
No “near-far” compensation
•
•
•
Designed to handle indoor multipath delay spread of 0.8μ seconds
Optimization centers around PHY
and MAC layer for 100m range
•
•
Optimized for up to 50 Km
Designed to handle many users
spread out over kilometers
Designed to tolerate greater
multi-path delay spread (signal
reflections) up to 10.0μ seconds
PHY and MAC designed with multimile range in mind
Coverage
802.11
•
Optimized for indoor
performance
802.16a
•
•
•
No mesh topology support within
ratified standards
•
Optimized for outdoor NLOS
performance
Standard supports mesh network
topology
Standard supports advanced
antenna techniques
Security
802.11
•
•
Existing standard is WPA +
WEP
802.11i in process of addressing
security
802.16a
•
Existing standard is PKM - EAP
Applications
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Fixed last-mile broadband access as a replacement or
substitute for wired DSL, cable, or T1 connections
●
Inexpensive backhaul for cell sites and WiFi hotspots
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High speed enterprise connectivity for businesses
●
Voice Over Internet Protocol (VOIP)
Future of WiMAX
•
WiMAX will be deployed in three phases
•
In the first phase WiMAX technology (based on IEEE
802.16-2004) provides fixed wireless connections
•
In the second phase WiMAX will be available as a cheap
and self-installing Subscriber Terminal (ST), linked to PC
and to antenna
•
The third phase enables portability, thus WiMAX (based
on IEEE 802.16e) will be integrated into commercial
laptops.
WiMAX Technology
WiMAX Forum
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Worldwide Interoperability for Microwave Access
WiMAX was Founded in April 01’
No Profit organization comprised of wireless access system
manufacturers, component suppliers, software developers and carriers
A wireless industry consortium that supports and promotes WiMAX’s
commercial usage
Members include Intel, AT&T, Siemens Mobile, British
Telecommunications, etc..
Comply with the WiMAX standard and focus on the interoperability
Conclusion
●
●
WiMAX is poised to be the next Big Thing
WiMAX will connect you to the internet at faster speeds and
from much longer ranges
●
WiMAX can handle last-mile access in remote areas
●
Mobility can be achieved with design into computer chips
References
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http://www.ceenet.org/workshops/lectures2004/Richard_Perlman/additi
onal_materials_(wimax)/
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www.ewh.ieee.org/r4/chicago/Yu-WiMAX.pdf
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www.WIMAXFORUM.org
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http://computer.howstuffworks.com/wimax.htm
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http://standards.ieee.org/catalog/olis/lanman.html
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http://netgroup.polito.it/Corsi/ISRG/Lucidi/Nicoletti_WiMAX.pdf
●
http://www.gartner.com/teleconferences/attributes/attr_133634_115.pdf
Questions
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What are different kinds of service WIMAX offers and what
is difference between
them?
How is interoperability achieved in
WIMAX?
How is QOS implemented in
WIMAX?
What is difference between P2MP and Mesh architectures?
List out three differences between WIMAX and WIFI?
QUESTIONS ?
THANK YOU!