Research And Practice Of SIGTRAN Protocol Stack Based Network Architecture For GSM Core Network

As the new standards and techniques of next generation telecommunication such as 3G and 4G come forth,many new requirements have been raised for enhancement of the telecommunication network and service such as more efficient broadband,faster expansion,more flexible to new service,easier for new service development and so on.This means it's urgent for GSM mobile network to transform from legacy TDM network to the IP style one.To make this transform happen,SIGTRAN protocol family presents themselves as a technique for smooth evolution.SIGTRAN protocol stack is a group of protocols based on the IP network,in the meanwhile,acting as adaptors beneath the upper layer user protocols.As signaling protocols serving for GSM core network, SCTP and M3UA are selected to work over IP protocol and take the role as MTP3 protocol to support and adapt to SCCP layer.With the rich experience of TCP and UDP implementation in real world,SCTP is a connection oriented and IP based protocol specially designed for telecommunication network.It has some key characteristics, which overcome the shortage of TCP & UDP in areas like security, performance and congestion control.SCTP protocol has mechanisms like multi-homed association,Cookie echo,multi-stream with independent sequenced data packet inside each stream,etc.These characters make SCTP work well for telecommunication over IP.M3UA is one of the many protocols above SCTP layer.It is adapted in GSM core network to take the same role like MTP3 supporting SCCP layer.With M3UA protocol,the modification and different work style of lower layers keep transparent to SCCP and up layers.Protocols over M3UA such as TCAP and MAP can work over IP just like what they did in legacy network.After the description of concepts above and basing on these concepts,several network models are created to depict the possibilities, which may exist in reality such as a pure SIGTRAN network or a combination of SIGTRAN and legacy networks.Taking ALCATEL's next generation HLR product as an example,a network infrastructure design for lab environment to simulate all kinds of network models is produced.With this network design,new SIGTRAN HLR can be fully and functionally tested to insure the quality of development.In the meanwhile,cost saving is considered.The result data of the simulation network will prove the design is correct.Then,still taking ALCATEL next generation HLR as an example,a suggestion will be made for the smooth evolution of GSM core network from legacy PCM network to a full IP network without impacting existing GSM services.At last part of this paper,a small piece of discussion will be made for the QoS and security consideration for implementing services over an IP network.The basic purpose of this paper is the research and construction of SIGTRAN protocol stack based network architecture for the GSM core network.