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Wireless Networks. Wireless Technologies. Bluetooth, ZigBee & Wireless USB short range communication between devices typically controlled by a single person. WiFi, DECT, HIPERLAN WLAN. WiFi is the most widely implemented in this space. UMTS over W-CDMA, UMTS-TDD, EVDO HSPA, WiMAX

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wireless technologies
Wireless Technologies
  • Bluetooth, ZigBee & Wireless USB
    • short range communication between devices typically controlled by a single person.
  • WiFi, DECT, HIPERLAN
    • WLAN. WiFi is the most widely implemented in this space.
  • UMTS over W-CDMA, UMTS-TDD, EVDO HSPA, WiMAX
    • Wide Area
slide3
WiFi
  • Base Standard 802.11
  • Utilises unlicensed spectrum
    • 2.4 GHz ISM range
    • 5 GHz UNII range
  • Access technology
802 11 1997
802.11 (1997)
  • 1 or 2 Mbps
  • 2.4GHz Industrial, Scientific & Medical (ISM) band; or IR
  • Frequency Hopping Spread Spectrum (FHSS) or Direct-Sequence Spread Spectrum (DSSS)
  • CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance)
dsss channel
≥30 dB

≥50 dB

Centre

Frequency

-22MHz

-11MHz

+11MHz

+22MHz

DSSS Channel
dsss channel overlap
4

8

9

6

7

10

1

2

5

11

3

12

13

DSSS Channel Overlap
802 11b
802.11b
  • Operates in the 2.4GHz ISM band
  • Utilises HR-DSSS to provide speeds up to 11Mbps
  • Rates are 1M, 2M, 5.5 M 11M
802 11a 1999
UNII-1 (Low)

UNII-2 (Mid)

UNII-2 (High)

5.150GHz

5.825GHz

5.725GHz

5.350GHz

5.250GHz

802.11a (1999)
  • Operates in 5GHz UNII bands
    • Consumer equipment generally uses middle & low bands
  • 4 channels/band at 20m MHz spacing resulting in 8 non-overlapping channels
  • Utilises OFDM to produce speeds up to 54Mbps
slide10
OFDM
  • Orthogonal Frequency Division Multiplexing
  • Communications channels is made up of many sub-carriers in parallel
  • Convolution coding used for error checking.
  • Utilises Quadrature Amplitude Modulation (QAM )to achieve data rates of 24Mbps-54Mbps
802 11g
802.11g
  • Operates in the 2.4 GHz ISM band
  • Utilises OFDM and DSSS to provide speeds up to 54Mbps
    • Thus 802.11g equipment can act as 802.11b equipment
    • Presence of 802.11b equipment will reduce the throughput of an 802.11g WLAN
beyond 802 11g
Beyond 802.11g
  • 802.11e - QoS extensions
  • 802.11f - hand-off for roaming
  • 802.11i – improved security
  • 802.11s – Mesh Networks
  • 802.11n - MIMO
common issues in wifi
Common Issues in WiFi
  • Interference; other hotspots, other equipment in same band, microwave ovens.
  • Near/Far
  • Hidden Node
  • Multipath
wimax
WiMAX
  • Worldwide Interoperability for Microwave Access
  • Fixed WiMAX 802.16-2004 ('802.16d')
  • Mobile WiMAX 802.16e-2005
  • OFMD / SOFDMA
  • As with DSL & WiFi more distance / interference = less throughput.
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