Signal up into parts and transmitting each of the

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signal up into parts and transmitting each of the parts on a different subcarrier at a different center frequency. Thus a fast transmission is sent as many slow transmissions, simultaneously, on many different frequencies. This effective slowing of the symbol transmission rate, without slowing the actual data transmission rate, makes OFDM resistant to intersymbol interference resulting from multipath. In theory, if higher data rates are required, then the signal can just be broken up into more parts and transmitted on additional subcarriers, each part still being sent at a slow enough rate to avoid intersymbol interference. In practice, the amount of bandwidth available for additional subcarriers is limited by the FCC. These different techniques for spreading the signal’s carrier, and the different digital modulation techniques employed to put information on the carrier, are central to defining the different wireless technologies and standards, as well as putting a perspective on interference issues among 802.11 LANs and Bluetooth networks.
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12 Appendix Acronyms AP - Access Point BER - Bit Error Rate BSS – Basic Service Set CCK - Complementary Code Keying DSSS - Direct Sequence Spread Spectrum ESS – Extended Service Set FCC -Federal Communications Commission FHSS - Frequency Hopping Spread Spectrum IBSS – Independent Basic Service Set IEEE - Institute of Electrical & Electronic Engineers ISM - Industrial, Scientific, Medical IT - Information Technology MAC - Media Access Control MAN - Metropolitan Area Network Mbps - Megabits per second MBps - Megabytes per second OFDM - Orthogonal Frequency Division Multiplexing OSI - Open System Interconnection PAN - Personal Area Network PBCC - Packet Binary Convolution Coding PCMCIA - Personal Computer Memory Card International Association PHY - Physical (Layer) PN - Pseudo-random Noise QoS - Quality of Service RF - Radio Frequency S/N ratio - Signal-to-Noise Ratio SNR - Signal-to-Noise Ratio STA - Station TG - Task Group U-NII - Unlicensed National Information Infrastructure USB – Universal Serial Bus WECA – Wireless Ethernet Compatibility Alliance WG - Working Group WLAN - Wireless LAN XOR - exclusive OR (a mathematical logic operation)
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13 References on the Web 1 Wireless Ethernet Compatibility Alliance, 2 IEEE 802 LAN/MAN Standards Committee, 3 IEEE 802 standards, 4 A good explanation of the seven-layer OSI Reference Model, 5 IEEE 802.11 working group, 6 IEEE 802.15 working group, 7 FHSS, 8 DSSS, 9 OFDM, Wi-Fi™ is a trademark of the Wireless Ethernet Compatibility Alliance Wi-Fi5™ is a trademark of the Wireless Ethernet Compatibility Alliance
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  • Spring '12
  • BryanJensen
  • ........., IEEE 802.11, WLANs

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