Downlink Optimal Power Allocation in OVSF-WCDMA Communications

Y.-Y. Yang and J.-F. Chang (Taiwan)


Downlink power allocation, WCDMAresource allocation, optimal power allocation, nonlinear programming.


In this paper the issue of optimal power allocation on the downlink channel in an orthogonal variable spreading factor wideband code division multiple access (OVSF WCDMA) system for a group of mobiles coordinated by a base station is addressed. Quality of service is measured in terms of bit error rate (BER). Optimal allocation of power to mobiles is sought subject to a constraint that the per-cell total power budget has been determined by the network controller. Power allocation can be formulated as a nonlinear programming problem (NLP) and we are able to prove that the objective function of this NLP is pseudo concave on its feasible set of solutions in an AWGN/a Rayleigh fading/ a Rayleigh fading with diversity channel. Frank-Wolfe Algorithm [1] may be employed to find the global optimum. Or since the objective function is separable, existing techniques such as the λ -method [2] in separable programming can be called to transform the original NLP into a linear programming problem and the search for an optimum has polynomial-time complexity.

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