Non-blocking extended OVSF codes on multi-rate CDMA systems

Wideband code division multiple access (WCDMA) systems have offered opportunities to provide variable user data rates and flexibly support applications with different bandwidth requirements. In the data channelization technology, orthogonal variable spreading factor (OVSF) code can distinguish the different data tunnels and promise the orthogonality for different customer tunnels or the same customer but different business tunnels. However, due to its distinctive feature of orthogonality, there is a limitation of the code allocation. Both intelligence and good integration mechanism are required to achieve OVSF tree's highest system utilization. This results in a major drawback of OVSF codes, called blocking property: It may have significant impact on the bandwidth utilization of the systems. This paper presents novel non-blocking extended orthogonal variable spreading factor (EOVSF) codes to support arbitrary users in multi-rate wireless CDMA system. As a result of this non-blocking property, none of the EOVSF codes blocks the assignment of any other EOVSF code. It decreases the rejection probability and the number of code rejections in the multi-rate CDMA system.