What Is a Network Controller Card?

RNC (Radio Network Controller, Radio Network Controller) is the main network element in the third generation (3G) wireless network. It is a part of the access network and is responsible for mobility management, call processing, link management and handover mechanism.
RnC Synonym wireless network controller generally refers to RnC

Chinese name: Wireless network controller
Foreign name: Radio Network Controller
Types of: Key network element

Make up: Components of an access network
Function: Provide mobility management
Task: Manage radio access carriers used to transmit data

RnC Introduction

The Universal Terrestrial Radio Access Network (UTRAN) in the third generation mobile communication network (3G) is composed of a base station controller (Radio Network Controller, RNC) and a base station (Node B), so RNC is UTRAN Exchange and control elements. RNC is also called a radio network controller. As a key network element of the 3G network, RNC, it is mainly used to manage and control multiple base stations below it. The entire function of RNC is divided into two parts: radio resource management function and control function. The radio resource management is mainly used to maintain the stability of wireless propagation and the quality of service of the wireless connection; the control function includes all functions related to the establishment, maintenance and release of radio bearers.

RnC advanced tasks

The RNC and the RNC are interconnected through a standard Iur interface, and the RNC and the core network are interconnected through an Iu interface. The RNC mainly completes functions such as connection establishment and disconnection, handover, macro-diversity integration, and radio resource management control.

Advanced tasks of the Radio Network Controller (RNC) include

1) Manage radio access carriers used to transmit user data;

2) Manage and optimize wireless network resources;

3) Mobility control;

4) Wireless link maintenance. The radio network controller (RNC) has functions such as framing distribution and selection, encryption, decryption, error checking, monitoring, and status inquiry.

RnC function overview

The RNC is divided into multiple subsystems such as service, signaling, asset management, transmission, operation and maintenance according to functions, as shown in the figure:

Functional division

The BSP & DRIVER subsystem provides isolated hardware services for other subsystems, including functions such as CPU boot, OS startup, and interface chip device driving.

The supporting platform subsystem provides the isolation of the underlying RTOS platform and the distribution of multiprocessor systems for other subsystems

Running platform, complete process scheduling, timer management, memory management, inter-process / inter-board communication, equipment

Management and other functions.

The bearer subsystem mainly includes the transport layer bearer of user data, and the physical and link shared by signaling and data

Layer bearing. The transport layer bearer of user data directly corresponds to the underlying IP support of the internal data transfer of the user plane,

Including the IPOA microcode processed by the network processor on the PS Iu interface protocol processing board, and the ATM on the interface board

<-> Microcode for IP conversion, UDP / IP code on DSP, etc .; physical and link shared by signaling and data

The layer bearer corresponds to the processing of the related ATM IMA, the processing of AAL2 and AAL5 SAR on the interface board.

The system management subsystem performs functions such as power-on control, master-slave switchover control, and real-time state detection of the entire system.

The resource and data management subsystem provides data services to other subsystems. In addition, based on RNC's distributed architecture,

On the basis of traditional database functions, a series of auxiliary functions such as data synchronization between processors need to be added.

The operation and maintenance subsystem implements system configuration, performance management, fault, and safety management.

The transmission network subsystem provides transmission support for the wireless part, excluding parts below ATM CPCS and user bearer

section.

The high-level signaling subsystem is mainly responsible for covering the 3GPP 25 series, including Uu interface, Iu interface, Iub interface,

Layer 3 control plane protocol processing including Iur interface, including radio resource management, mobility management, signaling

Connection management, etc.

The service processing subsystem is mainly responsible for realizing the mutual data between the wireless interface and the Iu interface according to the requirements of the service QoS.

Forwarding, scheduling, etc. ^[1]

RnC bridge function

The Radio Network Controller (RNC) also provides a bridging function for connecting to IP packet switched networks. The Radio Network Controller (RNC) supports not only traditional ATM AAL2 (voice) and AAL5 (data) functions, but also IP over ATM (IPoATM) and packet over data (POS) functions on SONET. The high growth rate of wireless users places higher requirements on IP technology, which means that future platforms must be able to support both IPv4 and IPv6. Note that the actual network transmission will depend on the situation of the carrier. In R99, there is usually a SONET ring between RNC and Node B, and its function is equivalent to a metropolitan area network (MAN). Through the add / drop multiplexer (ADM), data streams can be extracted from or added to the SONET ring. This topology allows multiple RNCs to access multiple Node Bs to form a network with excellent flexibility.

RnC product architecture

The hardware of the RNC system is modularly designed according to functions, and a unified standard interface is used between subsystems to facilitate future system expansion, new functions, and equipment maintenance.

According to the principle of system modular design, the RNC hardware system is divided into the following six subsystems, namely: switching subsystem, access subsystem, business processing subsystem, network synchronization subsystem, central control subsystem, and alarm subsystem. The product architecture is shown in the figure:

RNC Product Architecture

The functions of each subsystem of the RNC product are described below:

· Access subsystem: It provides Iu, Iub and other interface access functions, and consists of access boards.

· Switch subsystem: Provides equipment internal control and business data exchange. It consists of a primary exchange board and a secondary exchange board.

· Service processing subsystem: It completes Iu, Iub, Uu and other interface service plane protocol processing functions. It consists of GTP-U processing board and wireless network service processing board.

Central control subsystem: completes the functions of transmission network, wireless network signaling, system control, operation and maintenance, etc., and consists of a signal processing board and a global processing board.

Network synchronization subsystem: completes system clock generation and distribution functions, and consists of a network synchronization board, a switch board clock drive module, a service board, and an access board clock synchronization module.

· Alarm subsystem: completes system environment monitoring and alarm functions, including global board, alarm box, etc.

The connection interfaces of the various subsystems inside the RNC device are as follows:

· IF1, IF2, IF3 are Ethernet interfaces. Service data and control signaling use independent physical interfaces without affecting each other. Among them, the GE interface is used to transmit service data; the FE interface is used to transmit equipment control data.

· IF4 is the control interface for system-to-network synchronization, using FE interface.

IF5 is a clock interface. The clocks of the boards in the access subsystem are distributed through the switching subsystem.

· IF6 is the audible and visual alarm interface of the device, which uses the FE interface.

· IF7 is the chassis management interface of the device, which transmits the information of each circuit board and the chassis management module, which conforms to the IPMI interface specification.

RnC interface description

The Iub connects the Node B transceiver and the Radio Network Controller (RNC). This can usually be achieved through a T-1 / E-1 link, which is usually concentrated in the T-1 / E-1 aggregator and provides traffic to the RNC through the OC-3 link.

Iur RNC-to-RNC connection for call handover, usually through an OC-3 link.

The core network interface between the lu-cs RNC and the circuit switched voice network. It is usually implemented as an OC-12 rate link.

The core network interface between the lu-ps RNC and the packet-switched data network. It is usually implemented as an OC-12 rate link ^[2] .

RnC traffic model

Evaluation of internal performance indicators by using the traffic model derived from UMTS Report 6 (see UMTS Report 6 at http://www.umts-forum.org/servlet/dycon/ztumts/umts/Live/en/umts / Resources_Reports_06_index). This model designed a traffic load designed to represent a typical UMTS network in 2005. It mixes voice and data streams, which requires 384 Kpbs of bandwidth per user. Using this traffic model, a Radio Network Layer (RNL) card using the IXP2800 network processor can handle 72,000 users, resulting in a mixed load of circuit-switched and packet-switched traffic of 3,540 Erlang. Using a low-demand traffic model containing only circuit-switched voice calls, the card can handle 180,000 users. A radio network layer (RNL) card based on this design can be combined with line cards and other ATCA components to create a very powerful compact radio network controller (RNC) data panel system. The system in Figure 5 shows a standard 19-inch ATCA bracket with a 14-card slot. One bracket can handle 500,000 users' traffic and support 555 Mbps packet-switched data throughput. Multiple racks can be interconnected in a single telecommunications rack to support higher density. The system in Figure 5 includes a total of 12 cards, including spare cards, which provide carrier-grade reliability and stability. All line cards and wireless network layer (RNL) cards use Intel IXP2XXX network processors to provide high performance, wire-speed transmission, switching, and protocol processing. Line cards have the ability to support all WAN interfaces, from T-1 / E-1 to synchronous optical network (SONET) and Gigabit Ethernet speeds. In this example system, the line cards are deployed in a 2 + 1 configuration: two active line cards and a spare line card. The radio access network (RAN) side has eight active OC-3 interfaces and eight additional OC-3 interfaces for failover. There are also two active OC-12 core network interfaces and two standby interfaces. Line cards comply with the Synchronous Optical Network (SONET) Automatic Protection Switching (APS) standard for failover. These cards can be interconnected using an ATCA 3.1 compliant Ethernet switching fabric. It contains two Ethernet switching cards to support various connection options between the cards. A feasible alternative design is to use an Ethernet switch as a mezzanine card for two wireless network layer (RNL) cards. This design has the distinct advantage that it frees up two node slots for revenue-generating cards.

Provides significant performance and cost savings

Compared to alternatives, combining ATCA and IXP2XXX network processors can provide significant performance and cost savings. Current radio network controller (RNC) designs often require multiple racks of equipment to support user densities of 100,000 to 200,000. The example design can support 500,000 users from one rack in a telecommunications rack, a significant savings in power costs and central office space.