分类： LINUX
2008-02-25 14:47:15
Third Generation (3G) is a generic name for technologies that support high-quality voice, high-speed data and video in wireless cellular networks. In Europe, W-CDMA/3G services are called the Universal Mobile Telephony System (UMTS). An overview of the UMTS wireless network UTRAN (Terrestrial Radio Access Network) is shown below.
The UMTS Terrestrial Radio Access Network (UTRAN) includes the Radio Network Controller (RNC), the 3G Base stations (Node Bs) and the air interface (Tower) to the mobile equipment (ME).
A brief description of the different network elements and interfaces in a UMTS network is provided in the following table:
| 3G Network Functions | |
|---|---|
| MSC | The Mobile Switching Center (MSC) switch, including the Visitor Location Register (VLR), is a switch that serves the Mobile Equipment (ME) in its current location for Circuit Switched (CS) services. |
| GMSC | The Gateway MSC (GMSC) switch serves the UMTS network at the point where it is connected to the external CS network. |
| MGW | The MSC and GMSC handle control functionality, but user data goes through the Media Gateway (MGW), which performs the actual switching for user data and network inter-working processing. |
| SGSN | The Serving GPRS Support Node (SGSN) covers functions similar to the MSC for packet data, including VLR type functionality |
| GGSN | The Gateway GPRS Support Node (GGSN) connects the Packet-Switched (PS) core network to other networks such as the Internet. |
| Node B | A 3G Base station (Node B) handles radio channels, including the multiplexing/demultiplexing of user voice and data information. |
| RNC | The Radio Network Controller (RNC) is responsible for controlling and managing the multiple base stations (Node Bs) including the utilization of radio network services. |
| 3G Network Interfaces | |
|---|---|
| Uu | The Uu is the interface between the UMTS Terrestrial Radio Access Network (UTRAN) and the ME, including phones, laptops and PDAs. |
| Iub | The lub is the interface between the NodeBs and the RNCs. Typically, multiple T1/E1 links from each Node B are aggregated to one or several ATM STM-1 (OC-3) links or one STM-4 link. |
| Iur | The lur is the interface between the RNCs for soft handover. Usually implemented on one or several ATM STM-1 (OC-3) links or one STM-4 (OC-12) link. |
| Iucs | The lucs is the core network interface between the RNCs and circuit-switched voice network. It is usually implemented on an STM-4 (OC-12) link or an Ethernet link. |
| Iups | The lups is the core network interface between the RNCs and packet-switched data network. It is usually implemented on an STM-4 (OC-12) link or an Ethernet link. |
The Radio Network Controller (RNC) is responsible for controlling and managing the multiple base stations (Node Bs). The RNC also performs user data processing to manage soft handoff and the utilization of radio network services. This processing requires significant packet handling and manipulation, as well as complex higher-level protocols. The density of the selector function is a major factor determining the capacity of an RNC.
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| Design Challenges |
The rising cost of the infrastructure needed to provide sufficient capacity for advanced mobile Internet services is a key challenge facing cellular operators and other mobile telecommunications service providers. Wireless equipment manufacturers must be able to add more flexibility and processing power to line cards without inflating system cost or exceeding the power budget.
Specific design challenges for RNC include:
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| Solution |
Technology standards for 3G will change, and new access technologies will be introduced. A scalable processing platform that can evolve with technology is needed so equipment vendors can maintain a distinct competitive advantage.
Freescale's host processors containing PowerPC® cores and PowerQUICC™ III family of integrated communications processors must handle more user plane processing functions. These processors are good choices because they are scaleable, cost-effective and provide exceptional MIPS per watt ration. In addition, providing a high level of support for applications protocols, development systems and cross-supplier engagements is essential.
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| Key Benefits |
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| Diagrams |
High-level RNC functions can be partitioned, as illustrated below.
Network Interface Cards (NICs) handle various network interfaces (such as T1 / E1s and OC-3), terminating network protocols (such as ATM) and Inter-working with the backplane.
Radio (RNL) Cards perform high-performance processing of intensive Radio Interface tasks, including Radio Link Control, MAC processing and encryption (Kasumi). These cards are the most MIPs-intensive components of an RNC data plane. Therefore, high-performance PowerQUICC processors with integrated security and several high-speed interconnect options are an ideal solution.
Finally, control and application cards handle host RNC signalling stacks for Radio Resource Control, OAM and management databases. Therefore high performance PowerPC processors with several high-speed interconnect options are an ideal solution.
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