Quantized-Non Quantized Code Tree Partitioning and Reduction in Internal-External Fragmentation

Abstract

The use of orthogonal variable spreading factor codes as channelization codes in downlink give rise to code blocking probability due to orthogonal nature of codes. This will further lead to increase in call establishment delay to locate a suitable code which can be assigned to new call request. Code blocking is mainly due to fragmentation of lower rate calls in code tree, which blocks capacity of higher rate codes and consequently blocking of higher rate call requests. In this paper, an assignment approach is proposed which addresses fragmentation due to scattered codes i.e. external fragmentation and internal fragmentation associated with non-quantized rates too. The code tree is virtually divided in two portions, one for quantized and another for non quantized rates. This will lead to reduction in number of code searches before assignment of call to a code. In addition, data calls are queued in buffer to handle voice calls. The data calls share the capacity of a assigned code, to reduce code blocking of real time calls. The data calls are handled using a code of higher capacity for most of the time which reduces their call duration. The proposed scheme is compared with existing novel schemes to show its ascendancy over them.