Group 1 CIS 585, All rights

reserved.

Wireless Communications

Mark BlunkHassan Mirmotahari

Wei Min, ChengWing Kai, Cheng

Group 1 CIS 585, All rights

reserved.

1 - Wireless Spectrum

http://et.nmsu.edu/~etti/spring97/techtips/spectrum.html

Physical Layer – Transmission Types

• Infrared light spectrum

• Radio wave spectrum

• Microwave spectrum

Infrared Light - Positive Options

• 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

http://www.heritage.org/library/categories/regulation/tp11c1.gif

Pure tone 500.00 Hz

1500.0 Hz

Radio Waves - Positive Options

• 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

• 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)

• 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

• 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.comhttp://www.fcc.gov/oet/spectrum/

http://www.ntia.doc.gov/

e

End Of ModuleEnd 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:

• Job Dispatch• Remote Point Of Sale• Customer Service• Remote Monitoring Such As Meter Reading

• Vehicle Positioning • Corporate Email

Business Applications Cont..

• 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:

• Simple Person to Person Messaging • Voice and Fax Mail Notifications• Unified Messaging• Internet Email• Prepayment• Mobile Commerce• Mobile Banking• Chat • Information Services

End Of ModuleEnd 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 ModuleEnd 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 • 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.

• Microwave spectrum

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

Access Point(s) link wireless clients to the

wired network

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

• Microwave spectrum

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

• Microwave spectrum

Add-on security software

by

Products

PCMCIA slot II16-bit ISA

32-bit PCIAccess point

Aironet products

Bridge

RF Product - client adapters

• Network Architecture - Supports peer-to-peer 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 ModuleEnd Of Module

End Of PresentationEnd Of Presentation