Zhou, Y.Q. and Wang, J.Z. and Ng, T.S. (2008) Downlink Transmission of Broadband OFCDM Systems-Part V: Code Assignment. IEEE Transactions on Wireless Communications, 7 (11). pp. 4546-4557. ISSN 1536-1276.
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To provide high speed mobile services, orthogonal multi-code transmission is employed in the orthogonal frequency and code division multiplexing (OFCDM) system. However, in a wireless frequency selective channel either with or without Doppler shift, code orthogonality is distorted and multi-code interference (MCI) is caused. The variance of the MCI is dependent on which codes to be used. This paper investigates the code assignment in the OFCDM system, aiming to mitigate the MCI. The code assignment can be explored in terms of the code distance defined in this paper. Generally, the codes with large code distances to each other should be assigned with high priority. Moreover, to avoid large interference from the powerful code-multiplexed pilot channel, the time spreading code adjacent to the pilot code in the code tree  is suggested not be used when the time domain spreading factor is large. The performance of the proposed non-sequential code assignment scheme is analytically evaluated. It has been shown that the system performance can be improved significantly by the non-sequential scheme under various channel conditions, especially when a low to medium system load is assumed.
|Uncontrolled keywords:||Code assignment; OFDM; two-dimensional spreading; multi-code interference; hybrid detection; Doppler shift|
|Subjects:||T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK5101 Telecommunications > TK5103.4 Broadband (inc wireless broadband)|
|Divisions:||Faculties > Science Technology and Medical Studies > School of Engineering and Digital Arts > Broadband & Wireless Communications|
|Depositing User:||Louise Dorman|
|Date Deposited:||26 Feb 2009 09:53|
|Last Modified:||24 Apr 2012 14:16|
|Resource URI:||http://kar.kent.ac.uk/id/eprint/15355 (The current URI for this page, for reference purposes)|
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