OVSF code assignment in UMTS networks

3G networks are designed to provide voice, data and multimedia services in an efficient way. The 3G system has to provide all of these applications with higher and multirate and different quality of service (QoS) requirements. UMTS employs wide-band code division multiple access (WCDMA) to support multi-rate applications utilizing OVSF codes. The transmission rate can be easily changed by changing the spreading factor of orthogonal spreading code. The objective of code assignment is to enhance statistical multiplexing and spectral efficiency of W-CDMA systems supporting variable user data rates. This paper compares the performance of OVSF code assignment schemes, in terms of code blocking probability. We research the problem of assigning orthogonal variable spreading factor (OVSF) codes at the download link in 3G mobile communications systems employing WCDMA.