SAE-Based Multi-Access Network Solution

Challenges and Opportunities for Operators

The introduction of 3G and LTE technologies has driven the rapid growth of mobile broadband, and as a result, there is an increasing need for convergence of telecommunications, Internet, and multimedia. An increasing number of subscribers are using mobile phones to access Internet services such as Web Browser, Instant Messaging, Skype, YouTube, and online games. In response, many operators have deployed or are deploying HSPA/LTE networks worldwide. With large scale legacy Circuit-Switched (CS) and Packet-Switched (PS) devices, they must take into account the smooth evolution to LTE/SAE while protecting existing investments.

System Architecture Evolution (SAE) proposed by 3GPP aims to make full use of existing architecture to ensure smooth evolution in the PS domain. LTE has been widely accepted by operators as the technology of choice for their future mobile networks, and in the era of mobile Internet, there will be a more complicated ecological environment and longer value chain. Every operator desires a share of the market. It is therefore important for operators to lead in integrated mobile broadband access. However, they will face some challenges. With the introduction of HSPA and LTE technologies, higher bandwidth will be required for existing mobile networks evolving towards broadband. Ensuring mobile and service continuity for coexistence of different access modes (fixed and mobile), coexistence of different access bandwidths (2G, 3G and 4G), and coexistence of different wireless standards (CDMA, WCDMA, TD-SCDMA, and WiFi/WiMAX) also poses a challenge.

To tackle these challenges, operators must have a packet core network with a unified platform in order to save on investment and maintenance costs. This allows multi-access users to share network resources, provides unified policy and service experience, and ensures mobile and service continuity among multiple access modes.

3GPP SAE Architecture

To simplify network structure, the control plane must be separated from the user plane, and all-IP access realized. 3GPP has defined a multi-access network architecture that supports LTE access, legacy 2G and 3G access, non-3GPP access, and ensures interoperability among different access modes, as shown in Figure 1.

The 3GPP multi-access network architecture contains basic network elements such as Mobility Management Entity (MME), System Architecture Evolution Gateway (SAE-GW), and Home Subscriber Server (HSS). These are used for LTE access and interworking with Non-3GPP networks.

For interworking with 2G/3G networks, GPRS Tunneling Protocol (GTP) based mobility is adopted, and Serving GPRS Support Node (S4 SGSN) is used to support legacy access for UTRAN and GERAN. For interworking between LTE and legacy networks, S4 SGSN is used for signaling between EPC nodes, and for mobility between 2G/3G and E-UTRAN 3GPP access networks. For interworking with non-3GPP access networks, Mobile IP (MIP) based mobility is adopted, and Packet Data Network Gateway (PGW) acts as the anchor point for intra non-3GPP network mobility (as well as mobility between 3GPP and non-3GPP networks).

ZTE’s SAE-Based Multi-Access Network Solution

As a leading supplier of core network infrastructure, ZTE has been committed to developing multi-access integrated packet core network products. Based on 3GPP SAE architecture, ZTE has put forward “ZEPS”―an innovative mobile broadband integrated access solution (see Figure 2). By classifying functions of network elements into various access modes, operators can build a simplified, converged, access-agnostic network that supports multiple access modes and smooth evolution to LTE/LTE+ with low TCO. ZEPS has the following features:

Unified network elements: It provides a Universal Subscriber Profile Platform (ZXUN USPP) for unified user data management; a Resource and Charging Control Platform (ZXUN RCP) for unified service control and charging; NetNuman for unified network management; ZXUN uMAC as unified mobility management node; ZXUN xGW as unified packet network gateway; and SDR for unified radio network access.

Integrated and access-agnostic network: It supports multiple access modes including mobile and fixed broadband access.

Flatter architecture: It provides integrated user plane with single user plane node, optimized handoff, and reduced signaling in network element integration.

Separation of control and bearer: The network control method does not need altering when the bearing technique changes, thereby improving network extensibility.

Low TCO: Hardware sharing saves CAPEX and simplified network architecture reduces OPEX.

By effectively combining six unified network elements, ZEPS provides an intelligent, access-agnostic, low-TCO, and high-bandwidth network. ZXUN uMAC and ZXUN xGW separate control-plane and user-plane as defined in 3GPP SAE, and minimize media transmission delay. They also support multi-network access, reduce additional inter-NE signaling, and ensure smooth evolution to LTE and LTE+. ZXUN RCP works with ZXUN xGW to provide flexible, optimized operation and management of packet services. SDR-based Uni-RAN provides a cost-effective means of sustainable evolution while protecting existing investments.

Conclusion

ZTE’s SAE-based multi-access network solution is designed for an LTE/LTE+ application scenario. With separation of control plane and user plane, as well as multi-access, all-IP capabilities, the solution supports smooth evolution to LTE/EPC while maintaining compatibility with legacy networks. This helps multi-network operators save on TCO, overcome difficulties in multi-network operation, and take initiatives in mobile packet service development.