Transcript Wireless Communications

Wireless Communications
Mark Blunk
Hassan Mirmotahari
Wei Min, Cheng
Wing Kai, Cheng
Group 1 CIS 585, All rights reserved.
1 - Wireless Spectrum
http://et.nmsu.edu/~etti/spring97/techtips/spectrum.html
Group 1 CIS 585, All rights reserved.
Physical Layer – Transmission Types
• Infrared light spectrum
• Radio wave spectrum
• Microwave spectrum
Infrared Light - Positive Options
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Inexpensive
Compatible with fiber-optic links
Not bandwidth limited
No licensing required (FCC)
Transmissions may be aimed (1 to 2 kilometers)
Transmissions may be omni-directional (30-60 feet)
Amplitude driven – little interference
Range of 1-2 kilometers (approximately ½ to 1 ½ miles)
Highest bandwidth and throughput
• InfraLAN – product with infrared transmission
Infrared Light – Negative Aspects
• Spectrum is shared with the sun and other lighting sources
• LAN may become “useless” with enough interference
• Signals will not permeate opaque objects (walls, dividers,etc)
Microwaves
Microwave - Positive Options
• Higher throughput without spread spectrum
• 5.8ghz band – using a narrow-band transmission
• RadioLAN - product using microwave transmission
Microwave – Negative Aspects
• Expensive to build infrastructure
• Must operate at less than 500 milliwatts (strict FCC regulations)
• Not commonly used – less available knowledge pool
Radio Waves - Spectrum
Pure tone
500.00 Hz
1500.0 Hz
http://www.heritage.org/library/categories/regulation/tp11c1.gif
Radio Waves - Positive Options
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Commonly understood technology
Not subject to interference of light waves like infrared
Less expensive than microwave
Long-range medium – several architectures exist
Commonly used – larger knowledge pool
• WaveLAN, BreezeNet pro, Proxim Rangelan2, & RadioLAN
Radio Waves – Negative Aspects
• Spread spectrum technology – high overhead
• Lower rates of data transmissions – due to overhead required
• Subject to some interference – causing delays in transmission
Radio Waves – Spread Spectrum Methods
• Direct Sequence Spread Spectrum (DSSS)
– Transmission signal is spread over an allowed band
• Frequency Hopping Spread Spectrum (FHSS)
– Splits the band into subchannels – signal then hops to transmit
Radio Waves – Direct Sequence Spread Spectrum
(DSSS)
• Spreads signal over a band (Example, 50 MHz)
• Random Binary String Modulates the Transmission Signal
• String is known as a “Spreading Code”
• Bits are mapped out as “chips” and mapped back as “bits”
• Spreading Ratio – The number of “chips” per bit
DSSS Spreading Ratios
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Higher Ratios Resist Interference Better
Lower ratios allow for use of more bandwidth
FCC dictates spreading ratios must be more than ten
IEEE 802.1 standard requires a spreading ratio of eleven
Sender & Receiver must synchronize to the spreading code
Orthogonal spreading codes allow sharing of the band between LANs
DSSS systems use wide subchannels, limiting LANs possible
Recovery is faster with DSSS due to ability to spread the signal over a
wider band
• Example Product = WaveLAN
Radio Waves – Frequency Hopping Spread
Spectrum (FHSS)
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Splits the band into many subchannels (1-2MHz)
Signal “hops” from subchannel to subchannel
Uses short bursts of data on each channel
Bursts are within a “dwell” time (very short time)
FCC requires at least 75 subchannels
FCC requires “dwell” time of no longer than 400ms
Less interference than DSSS due to hopping
Security is higher due to the hopping
Frequency Hopping Spread Spectrum (FHSS)
(Continued)
• Used by military and law enforcement
• Jamming is very difficult as the whole band must be
jammed
• Orthogonal hopping sequence allows for co-location
of multiple LANs
• Allows for more co-located LANs than DSSS
• Common new product method for wireless
• Product Example = BreezeNet
Multipath Interference
• Interference caused by signals bouncing off of physical objects
and arriving at a receiver at differing times
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Multipath is a problem for all wireless modes
DHSS resists the issue by hopping to other frequencies
Anti-Multipath algorithms exist to resist the problem
Rayleigh fading is a subset of Multipath and can completely
cancel out the signal
• Infrared resists Rayleigh fading due to small wavelengths
Wireless Types
Information Sources
Pinacor.com
http://www.fcc.gov/oet/spectrum/
e
http://www.ntia.doc.gov/
End Of Module
2 -Examples of Wireless protocols and
technologies
The two main protocols and technologies
discussed in this sections are:
•Wireless ATM
•Wireless Application protocol
Some background on ATM
• ATM ( Asynchronous Transfer Mode) has
been advocated as an important technology
for the wide area interconnection of
heterogeneous networks
• In ATM networks, the data is divided into
small, fixed length units called cells. The cell
is 53 bytes.
• Each cell contain a 5 byte header which
comprises of identification, control priority
and routing information. The rest 48 bytes are
the actual data.
Background continued
• ATM does not provide any error detection
operations on the user payload inside the cell,
and also provides no retransmission services,
and only few operations are performed on the
small header
• ATM switches support two kinds of
interfaces: user-network interface (UNI) and
network-node interface (NNI).
• UNI connects ATM end systems (hosts,
routers etc.) to an ATM switch, while an NNI
may be imprecisely defined as an interface
connection of two ATM switches together
Why Wireless ATM?
• ATM provides end-to-end
communication in a WAN environment
• Companies do not have to invest in
extra equipment (i.e. routers, switches,
etc.)
• ATM reduces the complexity, improves
flexibility, while providing end-to-end
connectivity
Why ATM Cont...
• Due to the recent advancement of fiber, next
generation wireless networks should be
designed so as to easily fit and co-exist with
the Broadband ISDN (Integrated Services
Digital Network).
• In order to avoid a serious mismatch
between wireline and wireless networks, it is
now timely to begin consideration of
broadband wireless networks with similar
service capabilities
Wireless ATM Challenges
• Both wireless networks technology, and
ATM protocol are relatively new, and
there are no fixed standards being
defined for wireless ATM networks
• Still in research stage and the
technology is being developed
• Some wireless LAN’s have lower speed
and higher error rates
Modifications to ATM
• The ATM cell size (53 bytes) may be too big for some
wireless LANs ( due to lower speed and higher error
rates), therefore wireless LANs may use 16 or 24 byte
payload.
• The ATM header can also be compressed and be
expanded to standard ATM at the base station
• An example of ATM header compression is to use 2
bytes containing 12-bit VCI (virtual channel
identifier) and 4 bit control ( payload type, cell loss
priority etc.)
WAP Defined
• The Wireless Application Protocol (WAP) is
simply a protocol—a standardized way that a
mobile phone/unit communicates to a server
installed in the mobile phone network
• Many advertising agencies and “dot.coms”
have announced WAP services
• WAP takes a client-server approach. It
incorporates a relatively simple microbrowser
into the mobile phone, requiring only limited
resources on the phone.
WAP Cont..
• This makes WAP suitable for thin clients and
early smart phones
• WAP puts the intelligence in the WAP
Gateways while adding just a microbrowser
to the phones themselves
• Microbrowser-based services and
applications reside temporarily on servers,
not permanently in phones
WAP Cont..
• WAP is aimed at turning a mass-market
mobile phone into a network-based smart
phone
• A person with a WAP-compliant phone uses
the built-in microbrowser to:
1. Make a request in wireless markup language (WML), a
language derived from HTML especially for wireless network
characteristics
2. This request is passed to a WAP Gateway, which then
retrieves the information from an Internet server either in
standard HTML format or WML
3. The requested information is then sent from the WAP
Gateway to the WAP client, using whatever mobile network
bearer service is available and most appropriate
WAP Cont..
• WAP has also given a significant impetus for
new players to add mobile as a new
distribution channel for their existing
products and services
• For example, CNN and Nokia teamed up to
offer CNN Mobile, and Reuters and Ericsson
teamed up to provide Reuters Wireless
Services
Business Applications
Corporate applications that are being enhanced
and enabled with a WAP interface include:
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Job Dispatch
Remote Point Of Sale
Customer Service
Remote Monitoring Such As Meter Reading
• Vehicle Positioning
• Corporate Email
Business Applications Cont..
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Remote LAN Access
File Transfer
Web Browsing
Document Sharing/Collaborative Working
Audio
Still Images
Moving Images
Home Automation
Consumer Applications
Consumer Applications that are being
enhanced and enabled with a WAP interface
include:
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Simple Person to Person Messaging
Voice and Fax Mail Notifications
Unified Messaging
Internet Email
Prepayment
Mobile Commerce
Mobile Banking
Chat
Information Services
End Of Module
3 -Wireless LAN Configurations
• A Peer-to-Peer Network
• Client and Access Point
• Multiple Access Points and Roaming
• Use of an Extension Point
• The Use of Directional Antennas
A Wireless Peer-to-Peer
Network
Client and Access Point
AP as Master
Multiple Access Points and
Roaming
Use of an Extension Point
The Use of Directional Antennas
Factors to be Considered
• Range and Coverage
• Throughput
• Integrity and Reliability
• Compatibility with the Existing Network
• Interoperability of Wireless Devices
• Interference and Coexistence
Factors to be Considered
• Licensing Issues
• Simplicity/Ease of Use
• Security
• Cost
• Scalability
• Battery Life for Mobile Platforms
• Safety
EP: EP Roles as AP
EP: Preferred Master List
EP Topology: Single EP
EP Topology: Tree
EP Topology: Multi-hop Linear
EP Topology: combination
Building Environment
Recommended Test Equipment
Roaming Test
Site Survey Sample
Recommended Test
• File Transfer
• Printing
• Loading Application over the Network
• Running Client/Server Application
Special Tests for WLAN
• Microwave Interference
• Near/Far Phenomenon
• Hidden Terminal
End Of Module
4 - Wireless LAN - Products
A flexible data communication system
implemented as an extension to, or as
an alternative for, a wired LAN
Wireless Evolution
• Ethernet - the predominant LAN technology in
the wired world
• First wireless LAN technologies operated in the
900MHz band & low speed (1-2Mbps)
• 1992, wireless LAN makers began developing
products operating in the unlicensed 2.4 GHz
frequency band
• 1997 IEEE released the 802.11 standard for
WLAN ( infrared light, FHSS, DSSS)
Geographic Scope
• SOHO - set of PCs talk to each other
(peer to peer WLAN)
• Within a building or campus
• Across buildings
Benefits
• Mobility - access to real-time information
anywhere
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Installation - Simple, fast
Flexibility - move, add, change
Connectivity - go where wire cannot go
Scalability - a few PCs to full infrastructure
networks of thousands of users that allows
roaming over a broad area.
How WLAN works (1)
Independent (or peer-to-peer)
WLAN that connects a set of PCs
with wireless adapters
How WLAN works (2)
Access Point(s) link
wireless clients to the
wired network
Access Point
Product Considerations (1)
• Range / Coverage - 100 to 500+ ft (walls, metal)
• Throughput - 1 - 11+ Mbps (client #, range,
multipath)
• Interference - unlicensed RF band ( wireless
product)
• Coexistence - multi WLAN, multi vendor
(interference)
• Ease of use - transparent to users
• Scalability - client #, coverage
Product Considerations (2)
• Interoperability - wired & wireless infrastructure
• Network Management - add, delete, move,
troubleshoot
• Security - 40-bit keying standard not safe
Add-on security software
Station enable capability
• Battery Life - extra power for transmit/receive
• Safety - stringent government and industry
regulations
Add-on security software
by
Products
Access point
32-bit PCI
Bridge
16-bit ISA
PCMCIA slot II
Aironet products
RF Product - client adapters
• Network Architecture - Supports peer-topeer networking and communication to wired
networks via Access Points
• Range at 1Mbps 1600ft (490m) open
environment; 325ft (100m) office
Range at 11Mbps 425ft (130m) open
environment; 110ft (35m) office
• Encryption 40-bit WEP / 128-bit WEP
• Antenna Integrated Internal antenna with
diversity support, External 2dBi dipole antenna
with RP-TNC connection
RF Product - client adapters(cont)
• Device Drivers Available NDIS2, NDIS3,
NDIS4, NDIS5 ODI and Packet
• System Interface PCMCIA Type II slot, 32-bit
PCI slot, 16-bit ISA slot
• Receive Sensitivity - 90dBm @ 1Mbps, 88dBm @ 2Mbps, - 87dBm @ 5.5Mbps, 84dBm @ 11Mbps
• Output Power 30mW (US, Canada, ETSI)
• Power Consumption Transmit: 350mA,
Receive: 250mA, Sleep: under 10mA
RF Product - Access points
• Network Architecture Types Complies with
IEEE 802.3 and Ethernet Blue Book
• Range at 1Mbps 1800ft (550m) open
environment; 350ft (105m) office
Range at 11Mbps 400ft (120m) open
environment; 100ft (30m) office
• Encryption 40-bit WEP
• No. of Clients 10 - 2048
RF Product - Access points (Cont)
• Local Configuration Direct console port
(Serial EIA-232 DB-9 female)
• Remote Configuration HTTP, Telnet, FTP,
SNMP
• Automatic Configuration BOOTP and DHCP
Receive
• Sensitivity -90dBm @ 1Mbps, -88dBm @
2Mbps, -87dBm @ 5.5Mbps, -84dBm @ 11Mbps
s
• Output Power 30mW (US, Canada, ETSI)
• SNMP Compliance MIB I, MIB II
RF Product - client adapters
• Device Drivers Available NDIS2, NDIS3,
NDIS4, NDIS5 ODI and Packet
• System Interface PCMCIA Type II slot, 32-bit
PCI slot, 16-bit ISA slot
• Receive Sensitivity - 90dBm @ 1Mbps, 88dBm @ 2Mbps, - 87dBm @ 5.5Mbps, 84dBm @ 11Mbps
• Output Power 30mW (US, Canada, ETSI)
4.5mW/MHz (EIRP, Japan)
• Power Consumption Transmit: 350mA,
Receive: 250mA, Sleep: under 10mA
RF Product - Wireless bridges
• Data Rates Supported 1, 2, 5.5 and 11 Mbps
• Range* Up to 8 Miles (13km) at 11 Mbps
• Frequency Band 2400-2483.5 Mhz
• Wireless Medium Direct Sequence Spread
Spectrum
• Media Access Protocol Carrier Sense Multiple
Access with Collision Avoidance (CSMA/CA)
• Network Protocols Supported IEEE 802.3
and Ethernet Blue Book
RF Product - Wireless bridges (cont)
• Modulation DBPSK @ 1 Mbps, DQPSK @ 2
Mbps,
CCK @ 5.5 and 11 Mbps
• Operating Channels 11 channels
• Simultaneous Channels Three
• SNMP Compliance MIB I, MIB II
• Routing Protocol RIP II IP
• Bridging Protocol IEEE 802.1d Spanning Tree
support
• Wireless Bridges per LAN Unlimited
• Maximum Users per Bridge 2048 (wireless)
Future Trend
• Faster, Better and Cheaper
• IEEE 802.11b standard 11Mbps WLANs at 2.4GHz
band. With optional modulation technique within the
802.11b specification, it is possible to double the
current data rate.
• 900MHz to 2.4GHz to 5.7GHz.
• (802.11a) for equipment operating at 5.7GHz that
supports a 54Mbps data rate
• Longer key length and authentication will improve
through the use of x.509 certificates
Wireless Information Sources
• http://www.wlana.com
• http://www.dcbnet.com/apnotes.html
#wireless
• http://www.nwn.com
(NoWiresNeeded)
• http://www.aironet.com
End Of Module
End Of Presentation