wlan physical layer

null WLAN physical layer802.11 a/g WLAN physical layer802.11 a/g 组员：唐敬 刘凯 雷震德 Outline Outline􀂄802.11a 􀂄OFDM 􀂄Parameters 􀂄802.11g 􀂄Modulations: DSSS, CCK, PBCC, DSSS-OFDM 􀂄Wi –Fi Alliance 802.11 a 802.11 aOctober 1999 Frequency: 5.15–5.35 and 5.725–5.825 GHz ( U-NII band ) 52 subcarrier OFDM ( 4 pilot ) Data rates: 6,9, 12, 18, 24, 36, 48, 54Mbps Modulation: BPSK/QPSK , 16QAM/64QAM OFDM OFDMMulticarrier Spread Spectrum Technique High-rate serial data stream divided into numerous parallel low-rate data streams that are modulated by a set of subcarriers Subacarriers are orthogonal with overlapping spectra Pilot subcarriers for channel estimation 802.11 a/g OFDM symbol structure 802.11 a/g OFDM symbol structure 802.11 a parameters 802.11 a parameters 802.11 g 802.11 gJune 2003 Frequency: 2,4 GHz ( ISM band ) Successor to 802.11 b Backward compatibility Data rates: 1, 2, 5.5, 6, 9, 11, 12, 18, 22, 24, 33, 36, 48, 54 Mbps 802.1 g modulations 802.1 g modulations Direct Sequence Spread Spectrum Direct Sequence Spread SpectrumCreated by XOR of the signal and pseudo-random number (chipping sequence) Long chipping sequences (eg. 128 bits) result in higher bandwidth Precise power control needed Alleviates the effects of frequency selective fading Complementary Code Keying Complementary Code KeyingUsed in 802.11b􀂄 Single carrier􀂄 Complex code􀂄 PBCC PBCCSingle carrier modulation Payload encoded using 256-state packet binary convolutional code Rate 2/3 DSSS-OFDM DSSS-OFDMHybrid modulation DSSS preamble and header OFDM payload Payload data rates: 6, 9, 12, 18, 24, 36, 48, 54 Mbps Wi –Fi Alliance Wi –Fi Alliance1999 Wireless Ethernet Compatibility Alliance: 3Com, Cisco, Harris Semiconductor, Lucent, Nokiaand Symbol Technologies 2003 WECA -> Wi –Fi Alliance Testing Certify interoperability of products Promotion of technology References ReferencesIEEE standard 802.11a Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications 􀂄IEEE standard 802.11g Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications TLT-6106 Basic Course on Wireless Communications lecture slides Wireless Network CoexistenceBy Robert K. Morrow IEEE 802.11g Explained By Jim Zyren nullQuestion :Which areas do we use this technology, please give me a example. Answer:we use this technology in many areas, for example the wireless video conference, the projector uses this technology to transfer the video singals.