3. Wireless and Mobile Networks

3. Wireless and Mobile Networks - Wireless and Mobile...

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Wireless and Mobile Networks Which layer? Layer 2 data link layer Wireless network architecture wireless hosts laptop, PDA, IP phone run applications may be stationary (non-mobile) or mobile o wireless does not always mean mobility base station typically connected to wired network relay - responsible for sending packets between wired network and wireless host(s) in its “area” o e.g., cell towers, 802.11 access points wireless link typically used to connect mobile(s) to base station also used as backbone link multiple access protocol coordinates link access various data rates, transmission distance infrastructure mode base station connects mobiles into wired network handoff: mobile changes base station providing connection into wired network ad hoc mode no base stations nodes can only transmit to other nodes within link coverage nodes organize themselves into a network: route among themselves CDMA encoding/decoding scheme Code Division Multiple Access (CDMA) used in several wireless broadcast channels (cellular, satellite, etc) standards unique “code” assigned to each user; i.e., code set partitioning all users share same frequency, but each user has own “chipping” sequence (i.e., code) to encode data encoded signal = (original data) X (chipping sequence) decoding: inner-product of encoded signal and chipping sequence allows multiple users to “coexist” and transmit simultaneously with minimal interference (if codes are “orthogonal”)
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WLAN(WiFi), 802.11 architecture (concepts)
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This note was uploaded on 02/26/2012 for the course CSC 138 taught by Professor Jingsong during the Spring '11 term at CSU Chico.

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3. Wireless and Mobile Networks - Wireless and Mobile...

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