Mobile Data: migration to MPLS

Today, many mobile operators are faced with the challenge of upgrading their infrastructure to support the future development of mobile data businesses. At the same time, they are working hard to reduce costs based on their own business objectives. To achieve this, far-sighted operators are trying to find out which aspects of their network design are lacking and find out why they cannot promote their current and future business development.
For many GPRS operators, one of the shortcomings is that the Base Station Controller (BSC) site return service gateway supports the transmission of GPRS data services on the node SGSN. As more and more GPRS services are activated and operators are accelerating to upgrade to the EDGE, the cost of controlling this part of the network becomes more and more important. EDGE will also increase bandwidth requirements, and its user data rate is as high as 384 kbps. This article will focus on this design issue, discuss the short-term and long-term advantages of migrating to MPLS-based design, and take into account the requirements of 3G in the future.
Today's GPRS Transmission Design
In the 3GPP standard design of GPRS, the Gb interface between the group control unit (PCU) and SGSN uses frame relay technology, as shown in ):

In practice, this Gb interface is usually implemented using multiple physical E1 FR interfaces on BSC/PCU and SGSN.
Most networks have multiple BSC/PCU sites, which converge to a small number of central sites. GPRS Support nodes are located in the central site. In these networks, the inter-board switching service connections use PDH and SDH transmission capacity, requiring a large amount of E1 channels. Although this method is widely known and proven, it is still lacking. The key issue is the lack of statistical multiplexing of data traffic, and the high operation cost resulting from the large number of E1 circuits provided by traditional transmission devices. In addition, each expansion or addition of new sites may require the ordering of additional circuits, which will increase operational overhead and require a longer planning cycle.
Investment in frame relay or ATM Switches
Another method that carriers can consider is to use a traditional Frame Relay/ATM network to centralize Gb traffic. Although this method can meet the needs of statistics multiplexing, it has many disadvantages: lack of flexibility in inter-board switching service connections, limited to traditional PDH/sdh wan interfaces such as: No Ethernet interfaces ); if the FR circuit communicates with the ATM in the uplink of the BSC site, the fixed ATM Cell overhead will lead to low efficiency. If the FR circuit does not have the inherent IP/MPLS function, the investment protection will be reduced, which means that, among these nodes, other IP traffic used by mobile operators must use independent infrastructure such as OSS or billed traffic, as R & D of traditional FR/ATM switches is gradually reduced, the service life of these platforms is also limited.
Optimized IP migration using MPLS 
One more effective solution is to deploy a modern MPLS solution to transmit the 2nd-layer FR circuit, as shown in ):

It has been proved that MPLS can not only handle IP services such as routing and layer-3 VPN, but also layer-3 transmission, and can be used for a variety of services including frame relay, ATM, and Ethernet. MPLS layer-4 transmission utilizes an efficient layer-3 frame Encapsulation within the MPLS of the edge (PE) node of the supplier. Shows the encapsulation method based on MPLS Frame Relay:

The MPLS solution utilizes the modern routing platform to handle a variety of layer 2nd and layer 3rd businesses without degrading performance or requiring additional hardware investment. MPLS solutions have many advantages:
Cost reduction-by integrating services at Layer 2nd and layer 3rd, you can reduce the extra investment of TDM/FR/ATM switches and IP routers to save costs. The uplink of the BSC site can use any type of interface that supports MPLS, including: Traditional WAN Interface ATM cells and PoS packet variables for STM-1 and STM-4) and Ethernet interface. For example, a bare optical fiber can connect to a site up to 80 kilometers from GE, while providing flexibility and increasing bandwidth.
Save operation costs-by running multi-service infrastructure, You can streamline the operation mode and reduce the dependence of daily operations on other departments, thus greatly reducing the transmission capacity consumed in this respect.
In the multi-vendor implementation environment, MPLS may have been deployed as the core data network technology, and other operators have a good understanding of and verified this. As 3GPP has completed the design standardization with IP as the center, the MPLS solution based on the modern routing platform conforms to the development direction of 3G technology. In this way, investment protection can be realized and long-term development can be adapted.
3G Investment Protection 
As mentioned above, many network protocols in the 3G Evolution plan proposed by 3GPP adopt IP technology. For example, in the first phase 3G defined by 3GPP 99, between the 3G wireless network controller (RNC) and SGSN, the Iu ps interface for Data Service uses IP over ATM AAL5:
It is clear that the network platform supporting gprs fr transmission between BSC/PCU and SGSN can also use MPLS network technology to transmit 3G Iu ps traffic, this is beneficial to operation and cost saving.
Summary
Mobile operators can integrate internal layer 2nd traffic through MPLS solutions to reduce long-term costs and better adapt to future requirements. This method also reflects the core development trends of many large wired and wireless operators who want to control investment in core ATM switches, it also integrates multi-service MPLS backbone networks that can simultaneously process ATM and IP services. The layer-3 MPLS service has gone far beyond the "Demo" stage. It is mature and has been verified and has been successfully deployed in a large operating network.