TABLE OF CONTENTS In this chapter, we have presented a brief description of the UMTS system, its features, and the UTRAN network architecture. The radio interface protocol stack of the UTRAN, which is also the same as the lower-layer protocols of UE, has been presented in some detail. More specifically, we have described the physical layer, the medium access control layer, radio link control, the packet data convergence layer, the broadcast multicast protocol, and the radio resource control protocol. Procedures such as those used in synchronization, power controls, and handovers are also described.
The key features of UMTS W-CDMA may be summarized as follows:
Wider bandwidth This is a direct-spread CDMA system with a nominal bandwidth of 5 MHz. The chip rate is 3.84 Mc/s. A radio frame is usually 10 ms long and consists of 15 slots, each of duration 2,560 chips.
Asynchronous operation There is no need for cell sites to be synchronized to each other using a global timing reference. Each cell site may operate in a fully asynchronous manner. However, this requires a different scrambling code for each cell or each sector of a cell.
Channel coding Incoming data, depending upon applications, may not be encoded at all or may be encoded into either a convolutional code of rate ? or 1/2, or turbo code of rate ?.
Spreading codes Physical channels are separated at the receiver by spreading them with channel-specific OVSF codes. A spreading factor of 256 is used...
