NON BLOCKING OVSF CODES INFLUENCE THE PERFORMANCE OF WCDMA SYSTEM

摘要

In this paper the performance of OVSF and NOVSF codes in WCDMA are evaluated by calculating their blocking probability and plotting graphs between blocking probability and new call arrival rate (request per minute) at different data rates (R, 2R, 4R and 8R where R can be either 8kbps or 16kbps). NOVSF is a new code assignment scheme which greatly reduces the code blocking problem. There are mainly three techniques of NOVSF code generation. We have implemented two of them out of one is using time multiplexing and the other is NOVSF codes having SF greater than equal to 4 and less than 512. The common purpose of all of them is to minimize the blocking probability and the reallocation codes cost so that more of new arriving call requests can be supported. The probability of code blocking due to the inappropriate resource allocation will be thus minimized. Using NOVSF code of spread factor 32, we have spreaded and then de-spreaded the randomly generated data and considering the noise factor, we have plotted the graph between input and output bit sequences, and further shown the effect of noise factor on bit error rate by plotting a graph. This paper deals with the evaluation of performance of blocking and non blocking codes in WCDMA system by calculating the blocking probability in various channelization code schemes, also we have spreaded and de-spreaded the user data with NOVSF codes and tried to find the error in output bit sequence as compared to input bit sequence considering different values of noise-factor. After analyzing the results, we may be able to conclude about the better code scheme for the third generation system.