Title :
Multiple Rake Combiners and Performance Improvement in 3G and Beyond WCDMA Systems
Author :
Saini, Davinder S. ; Upadhyay, Manoj
Author_Institution :
Dept. of Electron. & Commun., Jaypeee Univ. of Inf. Technol., Waknaghat, India
Abstract :
We propose an efficient code-assignment scheme utilizing multiple rake combiners to avoid the code-blocking problem in third-generation (3G) and beyond wideband code-division multiple-access (WCDMA) systems based upon orthogonal variable spreading factor (OVSF) channelization codes. The multiple rake combiners are required to be equipped with each base station (BS) and user equipment (UE). The major benefit of the proposed assignment scheme is in handling nonquantized data rates, making internal code fragmentation approximately zero. The task of code assignment to handle quantized data rates is divided into three steps. In the first step, the number of terms satisfying the capacity equation is found. The code combinations for all the terms in step 1 are found in step 2, which can be further subdivided into terms producing unique combinations and multiple combinations of terms. The procedure for finding the optimal code combination according to the number of rake combiners available at the UE and BS is given in step 3. Simulation results show the performance improvement in terms of reduction in blocking probability compared with existing single-code assignment schemes.
Keywords :
3G mobile communication; code division multiple access; orthogonal codes; probability; 3G mobile communication; WCDMA system; base station; blocking probability reduction; code-blocking problem; internal code fragmentation; multiple RAKE combiner; orthogonal variable spreading factor channelization code; single-code assignment schemes; user equipment; wideband code-division multiple-access system; Code (channel) assignment and reassignment; code blocking; orthogonal variable spreading factor (OVSF) codes; spreading factor (SF); wideband code-division multiple access (WCDMA);
Journal_Title :
Vehicular Technology, IEEE Transactions on
DOI :
10.1109/TVT.2009.2015143