WLAN RF Design Considerations

[notes]
Higher frequencies exhibit less range and are subject to greater attenuation from solid objects.

2.4Ghz
FCC = 11 channels
ETSI = 13 channels
TELEC = 14 channels (special licensing needed for Channel 14)

UNII-1

• frequency - 5.150 - 5.250
• channels - 36, 40, 44, 48

UNII-2

• frequency - 5.250 - 5.350
• channels - 52, 56, 60, 64
• required DFS/TPC

UNII-2 (new channels/2004)

• frequency - 5.470 - 5.725
• channels - 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140

UNII-3

• 5.725 - 5.825
• 149, 153, 157, 161, 165
• requires DFS/TPC

802.11A has 23 useable channels (where permitted)

IEEE 802.11 Task Group Initiatives: LINK

DSSS encodes redundant information into the RF signal chipping sequence = 11 chips per bit.
Binary Phase Shifting Keying/Quadrature Phase-Shift Keying (BPSK/QPSK) @ 1Mb/2Mb
8 chips at the 11 & 5.5MBs data rate.
At 11Mbps, 8 bits are transmitted for every one bit of data.

The chipping sequence is transmitted in parallel across the spread spectrum frequency range.

802.11g Modulation and Transmission Types: LINK