DocumentCode :
2068830
Title :
Synchronous overloaded system for the uplink of cellular CDMA with Unequal Chip Delay Spreading (UCDS)
Author :
Singh, Ashutosh ; Singh, Prashant
Author_Institution :
Electron. & Commun. Eng. Dept., NIT Rourkela, Rourkela, India
fYear :
2012
fDate :
17-19 Dec. 2012
Firstpage :
1
Lastpage :
4
Abstract :
Channel overloading in Code Division Multiple Access (CDMA) facilitates to accommodate more number of users than the assigned spreading factor N. Our proposal for a synchronous CDMA technique for the uplink of a cellular system over additive white gaussian noise (AWGN) channel achieves oversaturation by using the same set of orthogonal Walsh Hadamard codes and a receiver with lower complexity. The technique involves dividing the total number of active users into G groups, each with L users. Each user in a group is assigned the same signature sequence but with different chip duration. Users in a group can be classified as Primary and Secondary. The Primary user avails the spreading sequence with the maximum chip duration Tc. The rest L-1 (secondary) users are assigned the same code with chip duration as multiples of Tc/L. Unlike conventional Direct Sequence CDMA (DS-CDMA), all the users participate in spreading using the proposed Unequal Chip Delay Spreading (UCDS) technique. The receiver contains a switching unit to separate the received stream into L sub-streams followed by the detection process using a simple multi user detector. On the other hand, L levels of Unequal Error Protection (UEP) can be attained due to the unequal amount of multiple access interference (MAI) existing in alternate chip interval during transmission. Unequal chip delay spreading finally enables it to have a L-fold increase in the user data rate at the receiving end as compared to that of the transmission.
Keywords :
AWGN channels; Hadamard codes; cellular radio; code division multiple access; multiuser detection; orthogonal codes; radio links; radio receivers; radiofrequency interference; spread spectrum communication; AWGN channel; DS-CDMA; MAI; UCDS; UEP; additive white gaussian noise; cellular CDMA uplink; code division multiple access; direct sequence CDMA; multiple access interference; multiuser detector; orthogonal Walsh Hadamard codes; primary user; receiver; spreading sequence; synchronous overloaded system; unequal chip delay spreading; unequal error protection; Collaborative Spreading CDMA (CS-CDMA); MAI; OSIC; Overloading; Superposition Coding CDMA (SPC-CDMA); UCDS-CDMA; UEP;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Computers and Devices for Communication (CODEC), 2012 5th International Conference on
Conference_Location :
Kolkata
Print_ISBN :
978-1-4673-2619-3
Type :
conf
DOI :
10.1109/CODEC.2012.6509233
Filename :
6509233
Link To Document :
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