iCore Radio Network Controller - Seminar Report

INTRODUTION

iCore Radio Network Controller

The iCore Radio Network Controller (RNC) leverages the foundation technologies of the Tecore portfolio: completely standards-based; all-IP; scalable—with pico, micro and macro versions to fit a range of network sizes.

Tecore has adopted 3GPP for 3G and 4G infrastructure due to the robustness of end-to-end transport via IP, introduction of the IP Multimedia Subsystem (IMS) core network, and support for multiple access technologies, all of which have been principal features of Tecore's current architecture. The RNC controls the NodeBs, performs radio resource management, handles security functions, congestion control, and admission control, and delivers voice traffic to the media gateway and data traffic to the Serving GPRS Support Node (SGSN). Tecore’s RNC is compliant with 3GPP releases 5, 6 and 7, for an IP-centric solution interoperable with any standards-compliant NodeBs.

The RNC is also available as an integrated module on the iCore platform. iCore is a scalable, all-IP core network platform capable of supporting 2G GSM and CDMA and 3G networks simultaneously. Together with the iCore UMTS Mobile Switching Center (UMSC) and Home Subscriber Server (HSS), the RNC enhances support for 3G services and further streamlines the smallest multi-technology network-in-a-box in the industry. Rural and emerging mobile network operators can optimize total cost of ownership by avoiding the expense of separate RNCs, and supporting multivendor radio access networks from one core network. These operators can utilize any 3GPP standards-compliant NodeBs with Tecore’s iCore for their RNC and core network elements. Given the continuing dominance of voice traffic compared to data, iCore’s capability to switch voice traffic in a centralized manner represents a significant network cost saving for the operator.

Rural and emerging mobile network operators have waited for the national carriers to prove out 3G services and the industry is now moving swiftly to catch up. These operators need a lower threshold of investment, ability to scale the network with the subscriber base, and built-in path to 4G. Tecore provides the optimal solution by enabling UMTS on a multi-technology core that can bridge protocols and generations.

Commercial Carriers

The RNC can be deployed on a standalone basis, on a carrier-grade platform, as part of a macro 3G network. It can also be integrated into a complete, multi-technology iCore network from Tecore, allowing operators to reap revenues from 2G services while fulfilling demand for next-generation devices and applications.

Rural and Remote Systems

The challenge facing many operators today is how to provide service to rural and remote areas in an economic fashion while maintaining the same services as their main network. For these scenarios, Tecore offers the Rural Village System (RVS). The RVS turns remote build-outs that are traditional loss leaders to revenue potential. The RVS is a flexible network solution for distributed deployments in multiple wireless technologies and includes the iCore network elements and any combination of RAN elements (2G GSM or CDMA, and 3G UMTS) to meet the operator’s needs. Targeted at scenarios for hundreds to several thousand subscribers, the RVS provides a compliant solution that extends the network to previously unreachable (technically or economically) locations.

Government / Military Systems

The RNC is ideal for tactical and first responder systems where the latest communication technologies, streamlined operation and mission-critical security features are essential. A complete, multi-technology voice and data-capable mobile network contained in a single ruggedized case can be operational in one hour.With scalability based on standalone or integrated operations, this system

is ideal for environments ranging from embassies to the battlefield.

UMTS 3G Mobile Wireless Network Architecture

Universal Mobile Telecommunications System (UMTS), standardized by the 3GPP, is the 3G mobile communication technology successor to GSM and GPRS. UMTS combines the W-CDMA, TD-CDMA, or TD-SCDMA air interfaces, GSM's Mobile Application Part (MAP) core, and the GSM family of speech codecs.

W-CDMA is the most popular cellular mobile telephone variant of UMTS in use. UMTS, using W-CDMA, supports up to 14.0 Mbit/s data transfer rates in theory with High Speed Downlink Packet Access (HSDPA), although the performance in deployed networks could be much lower for both uplink and downlink connections.

A major difference of UMTS compared to GSM is the air interface forming Generic Radio Access Network (GeRAN). It can be connected to various backbone networks like the Internet, ISDN, GSM or to a UMTS network. GeRAN includes the three lowest layers of OSI model. The network layer (OSI 3) protocols form the Radio Resource Management protocol (RRM). They manage the bearer channels between the mobile terminals and the fixed network including the handovers.

The UMTS standard is an extension of existing networks based on the GSM and GPRS technologies. In UMTS release 1, a new radio access network UMTS terrestrial radio access network (UTRAN) is introduced. UTRAN, the UMTS radio access network (RAN), is connected via the Iu to the GSM Phase 2+ core network (CN). The Iu is the UTRAN interface between the radio network controller (RNC) and CN; the UTRAN interface between RNC and the packet-switched domain of the CN (Iu–PS) is used for PS data and the UTRAN interface between RNC and the circuit-switched domain of the CN (Iu–CS) is used for CS data.

UTRAN is subdivided into individual radio network systems (RNSs), where each RNS is controlled by an RNC. The RNC is connected to a set of Node B elements, each of which can serve one or several cells. Two new network elements, namely RNC and Node B, are introduced in UTRAN.

The RNC enables autonomous radio resource management (RRM) by UTRAN. It performs the same functions as the GSM BSC, providing central control for the RNS elements (RNC and Node Bs).

Node B is the physical unit for radio transmission/reception with cells. Node B connects with the UE via the W–CDMA Uu radio interface and with the RNC via the Iub asynchronous transfer mode (ATM)–based interface. Node B is the ATM termination point.

3G

(3rd Generation) Typically refers to the current generation of data transmission capabilities over a cellular network for Internet access and real-time video. The major 3G technologies are EV-DO for CDMA networks, such as used by Verizon and Sprint, and HSDPA for GSM networks for carriers such as AT&T and T-Mobile. For example, the iPhone 3G, Apple's second generation iPhone, uses HSDPA. 

The universal mobile telecommunication system (UMTS) is a 3G wireless system that delivers high-bandwidth data and voice services to mobile users. UMTS evolved from global systems for mobile communications (GSM). UMTS has an air interface based on W-CDMA and an Internet protocol core network based on general-packet radio service (GPRS). Figure 1 shows the infrastructure of a UMTS wireless network.

The Radio Network Controller (or RNC) is a governing element in the UMTS radio access network (UTRAN) and is responsible for control 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.

Functionality

The main functions of the RNC are management of radio channels (on the Uu-, or air-, interface) and the terrestrial channels (towards the MGW and SGSN). Radio Resource Management functionality includes the following:

• Outer Loop Power Control
• Load control
• Admission Control
• Packet scheduling
• Handover control
• Macrodiversity combining (see also macrodiversity)
• Security functions
• Mobility Management

Additionally, RNC may also perform further resource optimization by deploying vendor-specific algorithms such as:

• Dynamic Radio Bearer Control
• Adaptive Multi Rate Control
• Iub Overbooking (trunking efficiency)
• RNC is also a place to access all services which provided by CN (core network).

Interfaces

RNC Interfaces

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 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 interface which uses WCDMA technology. Starting R5, IP bearers can be used over FE instead. Physically, these interfaces can be carried over SDH over optical fiber, E1 (sometimes referred to as PDH) - over 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 and loop configurations.

Protocols

Iub, Iu and Iur protocols all carry both user data and signalling (that is, control plane).

• Signalling protocol responsible for the control of the Node B by the RNC is called NBAP (Node-B Application Part). NBAP is subdivided into Common and Dedicated NBAP (C-NBAP and D-NBAP), where Common NBAP controls overall Node B functionality and Dedicated NBAP controls separate cells or sectors of the Node B. NBAP is carried over Iub. In order for NBAP to handle common and dedicated procedures, it is divided into: NodeB Control Port (NCP) which handles common NBAP procedures and Communication Control Port (CCP) which handles dedicated NBAP procedures.

• Control plane protocol for the transport layer is called ALCAP (Access Link Control Application Protocol). Basic functionality of ALCAP is multiplexing of different users onto one AAL2 transmission path using channel IDs (CIDs). ALCAP is carried over Iub and Iu-CS interfaces.

• Signalling protocol responsible for communication between RNC and the core network is called RANAP (Radio Access Network Application Part), and is carried over Iu interface.

• Signalling protocol responsible for communications between RNCs is called RNSAP (Radio Network Subsystem Application Part) and is carried on the Iur interface.

RNC Roles

In a relationship to a UE (in a soft handover situation) an RNC can play two different roles. These are:

• D-RNC: Drift RNC
• S-RNC: Serving RNC

However, as far as the NodeB is concerned, the RNC may play a third role:

• C-RNC: Controlling RNC

It is important to know that one RNC can assume more than one role at any time.

·         The Radio Network Controller (or RNC) is a governing element in the Universal Mobile Telecommunications System UMTS radio access network (UTRAN), which is responsible for control the Node Bs that are connected to it. Node B is a term used in UMTS to denote the BTS (base transceiver station). Usually the latest cell phones or mobile phones support 3G network allow access to TV, Internet and other on demand services like Navigation and scheduling systems. This is being developed to support the ever increasing need to mobile phones network users. This also an active area of research which may lead to digital convergence.

·         

The functionality of the controller includes controlling and managing the radio transceivers in the Node B equipment, as well as management tasks like soft handoff. The main functions of the RNC are management of radio channels and the terrestrial channels. Radio Resource Management functionality includes Outer Loop Power Control, Load control, Admission Control, Packet scheduling, Handover control, Macrodiversity combining, Security functions and Mobility Management.

·         The RNC performs tasks in a 3G wireless network analogous to those of the Base Station Controller (BSC) in a 2G or 2.5G network. It interfaces with GPRS Service Nodes (SGSNs) and Gateways (GGSNs) to mediate with the network service providers. The connection from the RNC to a Node B is called the User Plane Interface Layer and it uses T1/E1 transport to the RNC.

·         Due to the large number of Node B transceivers, a T1/E1 aggregator is used to deliver the Node B data over channelized OC-3 optical transport to the RNC. The OC-3 pipe can be a direct connection to the RNC or through traditional SONET/SDH transmission networks. A typical RNC can be built on a PICMG or Advanced TCA chassis. It contains several different kinds of cards specialized for performing the functions and interacting with the various interfaces of the RNC.