The Radio Network Controller ( RNC ) is a governing element in the UMTS radio access network ( UTRAN ) and is responsible for controlling the Node Bs that are connected to it. The RNC carries out radio resource management , some of the mobility management functions and is the point where encryption is done before user data is sent to and from the mobile. The RNC connects to the Circuit Switched Core Network through Media Gateway ( MGW ) and to the SGSN (Serving GPRS Support Node) in the Packet Switched Core Network .
8-719: The logical connections between the network elements are known as interfaces. The interface between the RNC and the Circuit Switched Core Network (CS-CN) is called Iu-CS and between the RNC and the Packet Switched Core Network is called Iu-PS. Other interfaces include Iub (between the RNC and the Node B) and Iur (between RNCs in the same network). Iu interfaces carry user traffic (such as voice or data) as well as control information (see § Protocols ), and Iur interface
16-445: A cell phone is simultaneously connected to two or more cells (or cell sectors) during a call. If the sectors are from the same physical cell site (a sectorised site), it is referred to as softer handoff . This technique is a form of mobile-assisted handover, for IS-95 / CDMA2000 CDMA cell phones continuously make power measurements of a list of neighboring cell sites, and determine whether or not to request or end soft handover with
24-415: A copper wire or microwave radio . Several E1s can be bundled to form an IMA Group. Since the interfaces are logical , many interfaces can be multiplexed onto the same transmission line. The actual implementation depends on the network topology ; examples are chain, distant star, mesh and loop configurations. Iub, Iu and Iur protocols all carry both user data and signalling (that is, control plane). In
32-533: A relationship to a UE (in a soft handover situation) an RNC can play two different roles. These are: However, as far as the NodeB is concerned, the RNC may play a third role: It is important to know that one RNC can assume more than one role at any time. An RNC also controls the power of a NodeB. Soft handover Soft handover or soft handoff refers to a feature used by the CDMA and W-CDMA standards, where
40-573: Is mainly needed for soft handovers involving 2 RNCs though not required as the absence of Iur will cause these handovers to become hard handovers . Until 3gpp R4, all the interfaces in the UTRAN are implemented using ATM only, except the Uu (air) interface which uses WCDMA technology. Starting R5, IP bearers can be used over Ethernet instead. Physically, these interfaces can be carried over SDH over optical fiber, E1 (sometimes referred to as PDH ) - over
48-451: The cell sectors on the list. Due to the properties of the CDMA signaling scheme, it is possible for a CDMA phone to simultaneously receive signals from two or more radio base stations that are transmitting the same bit stream (using different transmission codes) on the different physical channels in the same frequency bandwidth. If the signal power from two or more radio base stations is nearly
56-478: The cell site sectors that are actively supporting a call in soft handover send the bit stream that they receive back to the Radio Network Controller (RNC), along with information about the quality of the received bits . The RNC examines the quality of all these bit streams and dynamically chooses the bit stream with the highest quality. Again, if the signal degrades rapidly, the chance is still good that
64-413: The same, the phone receiver can combine the received signals in such a way that the bit stream is decoded much more reliably than if only one base station were transmitting to the subscriber station. If any one of these signals fades significantly, there will be a relatively high probability of having adequate signal strength from one of the other radio base stations. On the uplink (phone-to-cell-site), all
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