Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/17039
Title: Sub-carrier allocation schemes for MC-DS-CDMA systems
Authors: LONG HAI
Keywords: Inter-Symbol Interference, Multicarrier CDMA, sub-carrier allocation, Multiple Access Interference, bit-error-rate, objective function
Issue Date: 30-Apr-2005
Source: LONG HAI (2005-04-30). Sub-carrier allocation schemes for MC-DS-CDMA systems. ScholarBank@NUS Repository.
Abstract: AbstractIn this thesis, we propose two algorithms to adaptively allocate sub-carriers for multi-user MC-DS-CDMA systems, with Multiple Access Interference (MAI) being taken into consideration. The optimal solution to the problem has its complexity grows exponentially when the number of users and sub-carriers grow. The first algorithm we proposed is to minimize BER of respective users rather than minimizing the overall system BER. Each user performs channel estimation, orders the sub-carrier channel gains and feeds back an index vector to the BS. BS uses these index vectors from all the users, together with the sub-carrier allocation coefficients of the previous updating stage, adaptively generates the sub-carrier allocation coefficients of the current updating stage. Our second proposed algorithm overcomes the discrepancy that may result from our first algorithm when MAI is small. The problem is formulated using Quadratic Programming (QP), and a single objective function is used to optimize the system BER. The algorithm uses the actual values of the channel gains and no sub-carrier allocation coefficients of the previous updating stage are needed. We use Kuhn-Tucker conditions to convert the formulated QP to a linear programming problem, which is easier to solve.
URI: http://scholarbank.nus.edu.sg/handle/10635/17039
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