Code Division Multiple Access (CDMA) 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 allows multiple users to "coexist"and transmit simultaneously with minimal interference (if codes are“orthogonal'" encoded signal=(original data)X(chipping sequence) decoding:inner-product of encoded signal and chipping sequence Wireless,Mobile Networks 6-16
Wireless, Mobile Networks 6-16 Code Division Multiple Access (CDMA) 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 allows multiple users to “coexist” and transmit simultaneously with minimal interference (if codes are “orthogonal”) encoded signal = (original data) X (chipping sequence) decoding: inner-product of encoded signal and chipping sequence
CDMA encode/decode channel output Zi.m Zi.m=diCm data d0=1 d1=-1 风的币风 bits sender 的 而日 1 ! slot 1 slot 0 code 内的 百的 channel channel slot 1 output output slot 0 M D= M received 日的 d=1 input 15 d1=-1 slot 1 slot 0 code 而可 百的 包5 channel channel receiver output output slot 1 slot 0 Wireless,Mobile Networks 6-17
Wireless, Mobile Networks 6-17 CDMA encode/decode slot 1 slot 0 d1 = -1 1 1 1 1 -1 -1 -1 -1 Zi,m = di . c m d0 = 1 1 1 1 1 -1 -1 -1 -1 1 1 1 1 -1 -1 -1 -1 1 1 1 1 -1 -1 -1 -1 slot 0 channel output slot 1 channel output channel output Zi,m sender code data bits slot 1 slot 0 d1 = -1 d0 = 1 1 1 1 1 -1 -1 -1 -1 1 1 1 1 -1 -1 -1 -1 1 1 1 1 -1 -1 -1 -1 1 1 1 1 -1 -1 -1 -1 slot 0 channel output slot 1 channel output receiver code received input Di = Zi,m . c m m=1 M M
CDMA:two-sender interference senders channel sums data =1 Zi.m=djcm together transmissions its d=-1 by sender 1 and 2 Sender 1 code的的 channel,Z 1.m data d=1 d6=1 Sender 2bits code 阿而币而币雨人 d s -1 using same code as slot 1 slot 0 sender 1,receiver received received recovers sender 1's input input receiver 1 original data from code匝 面 日的 summed channel data! Wireless,Mobile Networks 6-18
Wireless, Mobile Networks 6-18 CDMA: two-sender interference using same code as sender 1, receiver recovers sender 1’s original data from summed channel data! Sender 1 Sender 2 channel sums together transmissions by sender 1 and 2
Chapter 6 outline 6.1 Introduction Mobility Wireless 6.5 Principles:addressing and routing to mobile 6.2 Wireless links, users characteristics ·CDMA 6.6 Mobile IP 6.3 IEEE 802.11 wireless 6.7 Handling mobility in LANs (Wi-Fi") cellular networks 6.4 Cellular Internet 6.8 Mobility and higher-layer Access protocols ■architecture standards(e.g,GSM） 6.9 Summary Wireless,Mobile Networks 6-19
Wireless, Mobile Networks 6-19 Chapter 6 outline 6.1 Introduction Wireless 6.2 Wireless links, characteristics CDMA 6.3 IEEE 802.11 wireless LANs (“Wi-Fi”) 6.4 Cellular Internet Access architecture standards (e.g., GSM) Mobility 6.5 Principles: addressing and routing to mobile users 6.6 Mobile IP 6.7 Handling mobility in cellular networks 6.8 Mobility and higher-layer protocols 6.9 Summary
IEEE 802.11 Wireless LAN 802.11b 802.11a 2.4-5 GHz unlicensed spectrum ■5-6 GHz range ■upto54Mbps up to 11 Mbps 802.11g direct sequence spread ■2.4-5 GHz range spectrum(DSSS)in physical ■upto54Mbps layer 802.11n:multiple antennae ■all hosts use same ■2.4-5 GHz range chipping code ■upto200Mbps all use CSMA/CA for multiple access all have base-station and ad-hoc network versions Wireless,Mobile Networks 6-20
Wireless, Mobile Networks 6-20 IEEE 802.11 Wireless LAN 802.11b 2.4-5 GHz unlicensed spectrum up to 11 Mbps direct sequence spread spectrum (DSSS) in physical layer all hosts use same chipping code 802.11a 5-6 GHz range up to 54 Mbps 802.11g 2.4-5 GHz range up to 54 Mbps 802.11n: multiple antennae 2.4-5 GHz range up to 200 Mbps all use CSMA/CA for multiple access all have base-station and ad-hoc network versions