TABLE OF CONTENTS In this section, we provide an overview of the Universal Mobile Telecommunication System (UMTS) cellular system [14 16]. We begin by describing the elements inside the UMTS architecture as shown in Fig. 7.31. In the 2G cellular system, the terminals were called Mobile Stations (MS), and in the 3G cellular system, they are called User Equipment (UE). Also, the numerology for the BS and BSC have changed to NodeB and Radio Network Controller (RNC), respectively. Each RNC can have multiple NodeBs; the communication mechanism between them is labeled I ub. Moreover, RNCs can communicate over an interface labeled I uR, which is important if soft handoff is supported. The RNCs communicate to the UMTS core network via the I u interface.
In the UMTS architecture diagram in Fig. 7.31, we have a single UE communicating to three NodeBs. For sake of discussion, we have assumed each NodeB operates at a single RF carrier and has three sectors. These sectors are highlighted by the circular antenna patterns provided. The traffic sent to the UE is sent via the NodeBs shown; one will be called the serving NodeB. As the UE travels toward the bottom of the page, NodeBs closer to the UE will start to communicate while others further away begin to cease communication. This procedure is called handoff. We have also shown the interface to the GSM network, which will be discussed shortly.
Now that we...
