24-july-2007 wireless networks. wireless technologies bluetooth, zigbee & wireless usb short...

24-July-200724-July-2007

Wireless NetworksWireless Networks

Wireless TechnologiesWireless Technologies

Bluetooth, ZigBee & Wireless USB Bluetooth, ZigBee & Wireless USB short range communication between devices short range communication between devices

typically controlled by a single person. typically controlled by a single person.

WiFi, DECT, HIPERLANWiFi, DECT, HIPERLAN WLAN. WiFi is the most widely implemented WLAN. WiFi is the most widely implemented

in this space.in this space.

UMTS over W-CDMA, UMTS-TDD, UMTS over W-CDMA, UMTS-TDD, EVDO HSPA, WiMAXEVDO HSPA, WiMAX Wide AreaWide Area

WiFiWiFi

Base Standard 802.11Base Standard 802.11

Utilises unlicensed spectrumUtilises unlicensed spectrum 2.4 GHz ISM range2.4 GHz ISM range 5 GHz UNII range5 GHz UNII range

Access technologyAccess technology

802.11 (1997)802.11 (1997)

1 or 2 Mbps1 or 2 Mbps

2.4GHz Industrial, Scientific & Medical 2.4GHz Industrial, Scientific & Medical (ISM) band; or IR(ISM) band; or IR

Frequency Hopping Spread Spectrum Frequency Hopping Spread Spectrum (FHSS) or Direct-Sequence Spread (FHSS) or Direct-Sequence Spread Spectrum (DSSS)Spectrum (DSSS)

CSMA/CA (Carrier Sense Multiple CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance)Access with Collision Avoidance)

DSSS Channel FrequenciesDSSS Channel FrequenciesChannel IDChannel ID Freq. Hz)Freq. Hz) North AmericaNorth America Europe** Europe** SpainSpain FranceFrance

11 2.4122.412 YesYes YesYes









1010 2.4572.457 YesYes YesYes YesYes YesYes

1111 2.4622.462 YesYes YesYes YesYes YesYes



1414 2.4842.484

DSSS ChannelDSSS Channel

Centre Frequency

+11MHz-11MHz +22MHz-22MHz

≥30 dB

≥50 dB

7 8 9 10 12 131 2 3 4 5 6 11

DSSS Channel OverlapDSSS Channel Overlap

802.11b802.11b

Operates in the 2.4GHz ISM bandOperates in the 2.4GHz ISM band

Utilises HR-DSSS to provide speeds Utilises HR-DSSS to provide speeds up to 11Mbps up to 11Mbps

Rates are 1M, 2M, 5.5 M 11MRates are 1M, 2M, 5.5 M 11M

802.11a (1999)802.11a (1999)

Operates in 5GHz UNII bandsOperates in 5GHz UNII bands Consumer equipment generally uses Consumer equipment generally uses

middle & low bandsmiddle & low bands

4 channels/band at 20m MHz spacing 4 channels/band at 20m MHz spacing resulting in 8 resulting in 8 non-overlappingnon-overlapping channels channelsUtilises OFDM to produce speeds up to Utilises OFDM to produce speeds up to 54Mbps54Mbps

UNII-1 (Low) UNII-2 (Mid) UNII-2 (High)

5.15

0GH

z

5.25

0GH

z

5.35

0GH

z

5.72

5GH

z

5.82

5GH

z

OFDMOFDM

Orthogonal Frequency Division Orthogonal Frequency Division MultiplexingMultiplexingCommunications channels is made up Communications channels is made up of many sub-carriers in parallel of many sub-carriers in parallelConvolution coding used for error Convolution coding used for error checking.checking.Utilises Quadrature Amplitude Utilises Quadrature Amplitude Modulation (QAM )to achieve data rates Modulation (QAM )to achieve data rates of 24Mbps-54Mbpsof 24Mbps-54Mbps

802.11g802.11g

Operates in the 2.4 GHz ISM bandOperates in the 2.4 GHz ISM band

Utilises OFDM and DSSS to provide Utilises OFDM and DSSS to provide speeds up to 54Mbpsspeeds up to 54Mbps Thus 802.11g equipment can act as Thus 802.11g equipment can act as

802.11b equipment802.11b equipment Presence of 802.11b equipment will reduce Presence of 802.11b equipment will reduce

the throughput of an 802.11g WLANthe throughput of an 802.11g WLAN

Beyond 802.11gBeyond 802.11g

802.11e - QoS extensions802.11e - QoS extensions

802.11f - hand-off for roaming802.11f - hand-off for roaming

802.11i – improved security802.11i – improved security

802.11s – Mesh Networks802.11s – Mesh Networks

802.11n - MIMO802.11n - MIMO

Common Issues in WiFiCommon Issues in WiFi

Interference; other hotspots, other Interference; other hotspots, other equipment in same band, microwave equipment in same band, microwave ovens.ovens.

Near/FarNear/Far

Hidden NodeHidden Node

MultipathMultipath

WiMAXWiMAX

WWorldwide orldwide IInteroperability for nteroperability for MMicrowave icrowave AccAccess ess

Fixed WiMAX 802.16-2004 ('802.16d')Fixed WiMAX 802.16-2004 ('802.16d')

Mobile WiMAX 802.16e-2005Mobile WiMAX 802.16e-2005

OFMD / SOFDMAOFMD / SOFDMA

As with DSL & WiFi more distance / As with DSL & WiFi more distance / interference = less throughput.interference = less throughput.

Wireless MeshWireless Mesh

24-july-2007 wireless networks. wireless technologies bluetooth, zigbee & wireless usb short...

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