Transcript Emerging Broadband Wireless Standards

Emerging Broadband Wireless Standards
MC-CDMA
OFDMA–VSF
SC-WRF
Hybrid MAC/ MIMO
OFDMA/ MIMO
HSDPA/ HSUPA
Super 3G
802.16e
WAN
IEEE 802.16d
MAN
IEEE 802.11nWireless LAN
OFDM/ MIMO
IEEE 802.15 Bluetooth
LAN
PAN
The Electromagnetic Spectrum
Frequency Spectrum
Gamma Rays
TeraHz
XRays
Microwave
GigaHz
Television
Cellular Phone
MegaHz
Radio
KHz
Human Voice
Piano
Hz
Light Spectrum
Infrared
Visible
Ultraviolet
Agenda
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What is a Wireless LAN (WLAN)
WLAN technology overview
Components of a WLAN
WLAN specifications
IEEE 802.11
Nortel Networks WLAN Product Overview
What is a Wireless Local Area Network (“WLAN”)?
Over the air method of communicating with other wireless
clients as well as wired network resources such as e-mail, file
servers, databases, printers, intranets, and the Internet. A
WLAN is a fully functional, high speed network connection
without cables. All the advantages of a wired LAN connection
are available without being tethered to a wire.
• Spread Spectrum RF Radios
• 2.4 Ghz frequency range ISM band (Industrial Science Medical)
• Wireless Standards (Interoperability)
• IEEE 802.11
• RF Coverage Area
• Max supported Distances
• Maximum support speed
• Wireless client Roaming capabilities
• Load Balancing capabilities
• Security
• Network Protocol Independent
• Scalability
Wireless Access Point (“AP”)
• Wireless Hub/Bridge functionality
• Connection point for multiple wireless clients
• Bridges wireless NICS traffic to wired Ethernet
• Serves as a gateway to the wired Ethernet backbone
• Connects to wired infrastructure via 10BaseT or 10Base2 data port
WLAN Access Points
• Act as wireless shared media hub
• Create separate independent WLAN segments
• Separate wireless traffic from wired traffic
• Support overlapping coverage area to reduce contention and load balancing
AP Contention Reduction
&
Load Balancing
• Multiple Overlapped APs for high density areas
– Clients dynamically choose which AP to connect to based on AP
load and signal strength
– Increased system capacity and throughput
– Aggregate system bandwidth up to 10 Mb/s
WLAN Cellular Architecture
• Access Points create zones of wireless coverage called cells
• Multiple Access Points can be deployed to provide large contiguous
coverage areas
• Coverage area not limited by range of single AP
• Coverage areas do not have to be contiguous
• Deploy Access Point where coverage is desired
WLAN Client Roaming
Unlimited Range
– Network connection is maintained as users
move about the building/campus (from one AP
coverage area to another)
– Handoff is automatic and seamless to user
– DHCP for “cross IP segment” roaming
Dead Zone
WLAN Performance
• Most Ethernet (10Mbps) clients share bandwidth with large numbers of users
• Real-world performance - most shared Ethernet clients realize throughput
below 1 Mbps
• WLAN Performance similar to WAN performance
•WLAN performance exceeds performance of remote access solutions used by
most remote users
What is Spread Spectrum?
The term spread spectrum describes a modulation technique used to spread a
transmitted signal over a frequency wider than the minimum bandwidth
required to send the signal. Spread spectrum signals are wide band and
noise-like making them very difficult to intercept or jam. During World War
II the military used spread spectrum technology for “Secret” military
communications and radar counter measures. Now Spread Spectrum
technology is being exploited for commercial and industrial purposes.
Spread Spectrum Radio Types
• Direct Sequence Spread Spectrum
- Signal spread over a broad transmission range
• Frequency Hopping Spread Spectrum
- Signal jumps to a different 1 MHz channel at a
predetermined interval
Direct Sequence Spread Spectrum (DSSS)
• Signal is spread using an 11-bit “chipping code”
- Low power spread signal uses more spectrum but causes less interference
- “Processing gain” provides noise rejection and security
• Continuous transmission = highest performance
• Provides migration path to future higher speed (11Mbps) data rate
DSSS Chipping Code Spreading Factor
• Original data stream is multiplied by a 11-bit chipping code (spreading factor)
• Result or coded data stream is now transmitted over a wide range in the ISM band
DSSS Interference Immunity & Security
DSSS Scalability
Frequency Hopping Spread Spectrum (FHSS)
• Radios transmit and receive short bursts of data on one
frequency for a short period of time
• Signals change frequency (Hop) to another frequency
automatically
FHSS Channel Hopping
• ISM band carved into 78 separate 1 MHz channels
• Signal moves from one frequency to another every 10th of
a second
• Choice of channels based on a pseudo-random hopping
algorithm
FHSS Interference Immunity & Security
• Susceptibility to interference significantly reduced since
transmission frequency is constantly shifting; interference can
effectively be avoided
• Constant frequency shifting makes signal very difficult to intercept
or jam
FHSS Scalability
• Numerous Access Points can be placed in a coverage area
• Each AP uses one of the available “78” 1 MHz channels
• Multiple transmissions can occur simultaneously; each AP uses a different
channel
• 10, 20, or even more overlapping Access Points can be deployed to support
dense wireless user areas
• Overlapping Access Points provide capability to support larger loads
• As the wireless client population expands in particular areas, more Access
Points can be add to support growth
Wireless Networking Standards
Target
Application
Modulation
Frequency
Availability
OpenAir™
Mobile data
networking
FH
1.6 Mbps
2.4 GHz
Today
HiperLAN
HighSpeed
multimedia
wireless LANS
GPSK
24 Mbps
5 GHz
1999
SWAP
SOHO Wireless
communications
Bluetooth
Short range cable
replacement
802.11 FH
Wireless data
networking
802.11 DS
Wireless data
networking
FH
2 Mbps
2.4 GHz
FH
1 Mbps
2.4GHz
FH
2 Mbps
2.4 GHz
DS
2 Mbps
2.4 GHz
High Speed
802.11
2.4 GHz
High Speed
802.11
5 GHz
1999
1999
Late 1998
Late 1998
High speed
wireless LANs
DS
11 Mbps
2.4GHz
1999
High speed
wireless LANs
DS
10Mbps
5 GHz
1999
WLAN Specifications IEEE 802.11
• Institute of Electrical & Electronics Engineering
– The authority in networking standards
– 802.3 Ethernet, 802.5 Token Ring, etc.
• Standardization effort started in 1989
• Initial 802.11 standard was ratified June 1997
• Addresses three different wireless technologies
– Direct Sequence Spread Spectrum
– Frequency Hopping Spread Spectrum
– Infrared
• 802.11 is a complete specification that provides full network
functionality including multi-vendor roaming and true multivendor interoperability
• The standard defines PHY and MAC layer specifications
What is IEEE 802.11 Specification?
IEEE 802.11 is a wireless LAN standard developed by the Institute of Electrical
and Electronic Engineering committee. The standard specifies an over the air
interface between wireless clients and Access Points; it also addresses
communication between other wireless clients. The Physical and Media Access
Layers (Layers 1 & 2) of the Open Systems Interconnection (OSI) Model are
defined by the standard. DSSS & FHSS are two WLAN physical
characteristics defined by IEEE 802.11. Both are radio-based technologies that
operate in the ISM band. Radios in this band do not require end user licenses.
Most importantly the standard makes interoperability between wireless devices
from different manufacturers possible.
IEEE 802.11 WLAN Standard
• Media Access Control
(MAC Layer)
– Similar to 802.3 Ethernet
– CSMA/CA vs. CSMA/CD
• Physical (PHY layer)
– Defines 3 alternatives
– Diffuse Infra-Red
– DS radios
– FH radios
– DS & FH operate in the 2.4
GHz frequency range
IEEE 802.11 MAC Layer
• Assures fair and controlled access to the media
• Carrier Sense Multiple Access/Collision Avoidance
– Collision minimizing protocol
– Provides reliable communication via virtual collision
detection and enhanced error detection
• Defines security provisions (WEP) w/ RSA’s RC4 encryption
• Specifies the operation of power management
• Interfaces to the LLC through network drivers
– NDIS3 driver for WIN95, 98 and NT 4.0
CSMA/CA
• Like Ethernet’s CSMA/CD arbitrates access to a shared medium
• More efficient method of controlling access to the physical meduim
• Collision Avoidance (CA) provides superior contention management
CSMA/CA Media Access Process
WLAN Security
• Separate virtual WLAN segments via different
system SSIDs (Service Set IDs)
– e.g. PCs with SSID=BNet will not associate with AP
with SSID = ANet even if closer to ANet AP.
WLAN Application Options
• Infrastructure
• wireless clients use AP as gateway to resources on wired network
• Ad Hoc
– multiple PCs communicate directly with each other - no AP needed!
Ad Hoc Mode Applications
– Spontaneous and/or collaborative workgroups
– Small/branch offices sharing resources
– Deployment of a LAN where cabling is not readily available
– Remote control of another PC
– Field demonstrations
– Multiple PCs in home