Synchronization in WLAN

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Preamble Aided Packet Detection • In this approach, the known IEEE 802.11 preamble structure is incorporated into the synchronization algorithm • The IEEE 802.11 was designed to aid the detection of the incoming packet edge 10 x 0.8 = 8.0 µ s 2 x 0.8 + 2 x 3.2 = 8.0 µ s A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 CP C1 C2 Packet Detection, AGC, Diversity Selection Coarse Freq., Offset estimation, Symbol Timing Channel Estimation, Fine Frequency Offset Estimation Preamble parts: A1 A10 : short training symbols (16 samples each) CP : cyclic prefix (32 samples) that protects C1 and C2 from ISI C1 & C2 : Long training symbols (64 samples) WLAN Synchronization 16.3.2004 © Hafeth Hourani 16
Preamble Aided Detection (cont’d) • Delay and Correlate Algorithm • This algorithm utilizes the same DSW algorithm, but with taking advantage of the periodicity of the short training symbols at start of the preamble L−1 * n = ∑ n+ k n+ k+ D k = 0 c r r L−1 L−1 * n = ∑ n+ k+ D n+ k+ D = ∑ n+ k+ D k= 0 k= 0 2 cn r m n n 2 p r r r ⇒ = ( p ) n 2 2 C ÷ ( ) * p D z − P n ( ) 2 Delay and Correlate Algorithm Two sliding windows C & P The delay D = the period of the start of the preamble (e.g. D = 16 for IEEE 802.11) WLAN Synchronization 16.3.2004 © Hafeth Hourani 17 c n m n
Page 1 and 2: S-72.333 Postgraduate Course in Rad
Page 3 and 4: Next . . . •Overview • Timing E
Page 5 and 6: Synchronization in Packet-Switched
Page 7 and 8: Timing Estimation Overview Timing E
Page 9 and 10: • Packet detection test H H 0 1 :
Page 11 and 12: Packet Detection Methods Timing Est
Page 13 and 14: Received Signal Energy Detection (c
Page 15: • The result of the DSW does not
Page 19 and 20: Packet Detection Methods Timing Est
Page 21 and 22: Symbol Timing Algorithm • Symbol
Page 23 and 24: Sample Clock Synchronization • Th
Page 25 and 26: Estimating the Sampling Frequency E
Page 27 and 28: Next . . . • Overview • Timing
Page 29 and 30: Frequency Synchronization Approache
Page 31 and 32: Channel Estimation • Channel Esti
Page 33 and 34: Frequency Domain Channel Estimation
Page 35 and 36: Next . . . • Overview • Timing
Page 37 and 38: References • OFDM Wireless LANs:
Page 39: Homework • Q1. In that equation i

Synchronization in WLAN

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