Title :
UCHT-based complex sequences for asynchronous CDMA system
Author :
Rahardja, Susanto ; Ser, Wee ; Lin, Zinan
Author_Institution :
Inst. for Infocomm Res., Agency for Sci. Technol., & Res., Singapore, Singapore
fDate :
4/1/2003 12:00:00 AM
Abstract :
The use of orthogonal spreading codes has attracted much attention due to their ability to suppress interference from other users, compared with the nonorthogonal sequences in the synchronous case. In this paper, new sets of orthogonal sequences derived from the unified complex Hadamard transforms (UCHTs) are investigated. Various correlation properties of the sequences are mathematically derived and analyzed. It is shown that some UCHT sequences provide better autocorrelation properties than orthogonal Walsh-Hadamard sequences. Performance comparisons between UCHT sequences, Gold, small set of Kasami, and m-sequences show that some UCHT sequences outperform these well-known spreading sequences under simulation of systems in the presence of multiple access interference and additive white Gaussian noise.
Keywords :
Hadamard transforms; code division multiple access; codes; correlation methods; interference suppression; multiuser channels; radiofrequency interference; sequences; spread spectrum communication; Gold sequences; IS-95 system; Kasami sequences; UCHT sequences; UCHT-based complex sequences; additive white Gaussian noise; asynchronous CDMA system; autocorrelation properties; correlation properties; interference suppression; m-sequences; multiple access interference; nonorthogonal sequences; orthogonal Walsh-Hadamard sequences; orthogonal sequences; orthogonal spreading codes; systems simulation; unified complex Hadamard transforms; Additive white noise; Autocorrelation; Error correction; Error correction codes; Gold; Helium; Interference suppression; Multiaccess communication; Multiple access interference; Spread spectrum communication;
Journal_Title :
Communications, IEEE Transactions on
DOI :
10.1109/TCOMM.2003.810798
