The Research On Load Adjust And Optimization Of No.7 Signalling Network Link In JILIN Province

1.ExordiumWith the continuous development of communication technology and the evolution of the network structure, it is imperative to integrate the traditional PSTN network, Intelligent Network and NGN network. CNC Jilin Branch, as the largest fixed-network operator in Jilin Province, hold about 1.89 million telephones user and 4.97 million PHS users. The total users are about 6.86 million. At the same time, Jilin Network Communications Corporation should guarantee some important Communications which relate to the national economy and people's livelihood, such as medical and health care, finance and insurance, fire and police. In order to ensure operating the Telecommunication Networks normally, Perfect signalling mode is necessary, in addition to switching equipment and transmission systems. No. 7 Signalling Network, as the Supporting Network of Telecommunications Networks, differs from other Service Networks. The Signalling Network guarantees the users'service through reliable support to Communications Network rather than providing user-oriented service directly. Therefore the main development direction of Signalling Network is to enhance Network reliability and quality of operation.2.Introduction of No.7 signallingThe general target of No.7 signalling system is to provide an international standard general signalling system, its generality decides that the whole system will need contain many functions of different applications and its structure should be prone to flexible expansion for application function in the future.No.7 Signalling System propose only four functional level requirements in the yellow book's proposal in 1980. But with the development of ISDN and Intelligent Network, it needs to transfer the message which relate and unrelate to connection between circuits. So they added the SCCP to increase the MTP's functions in the premise of not changing MTP in the Redbook in 1984. No.7 Signalling System transfer signalling message in the form of unequal length. A message is transferred transparently between the end-users as a whole. In order to transmit reliably, some necessary control fields are also attached to each message, which form the actual signalling unit sent in the data link.China built No.7 Signalling Network high signalling transfer point HSTP throughout the country in 1993. China's No.7 signalling network adopts three-level structure, the first level known as the High Signalling Transfer Point (HSTP) is the senior level of Signalling Network known .The second is the Low Signalling Transfer Point (LSTP) ,the third is the Signalling Points (SP) which is composed of various exchanging bureaus and special services centres (Service Control Point). HSTP is responsible for transferring signalling message of the second-level LSTP and the third-level SP which follow the High signalling transfer point. LSTP is responsible for transferring signalling message of the third-level SP which follows the Low Signalling Transfer Point. In China No.7 signal Network uses the mode of A, B plane connection between HSTPs. All HSTPs in A or B plane connect as a mesh and HSTPs in A connect with HSTPs in B in pairs. Two-level signalling network, LSTP and SP, are adopted by Chinese local telephone network. The two-level Signalling Network mainly uses zoning fixed connection mode. It is also permitted to connect freely in some districts.Jilin Province built No.7 Signalling Network throughout the province in 1996. There are a pair of HSTPs (A and B) set in ChangChun .They connected with each other and accessed to A and B planes of countrywide HSTP Network respectively. And set eight pairs LSTPs in all. LiaoYuan and SiPing shared a pair of LSTPs installed in SiPing city. One pair of LSTPs was set respectively in other prefuture level cities. The provincial LSTPs were divided into A and B points which transit routing and share load between each other. One pair of LSTPs cross-connected with A or B of the HSTP in ChangChun. A and B point of ChangChun's HSTP and each LSTP composed star network respectively. Different LSTPs Communicate with each other through HSTP in Changchun.3.Research on routing Principle of No.7 signalling networkSignalling Link selection coding (SLS) is used to share load of the signalling link and signalling routing. Message finds the route depending on the address carried by itself when detouring in the Signalling Network. Under normal conditions, there are more than one signalling link which can get to the destination (DPC + SSF by definition). Selection of signalling routing function must choose the above-mentioned signalling link, which corresponds to a SLS counterpart. Message which is used to route has two sources: coming from the user of MTP and the Level 2 of MTP (the signalling link). Messages which come from MTP user and signalling link contain DPC, SSF, and SLS. Destination that the message will get to is pointed by DPC. SSF denote the Network layer where DPC is. SLS is code which is used to choose signalling link in load sharing mode.No.7 signalling message is the MSU message. Signalling load sharing divides into two parts: one is going to the same DPC (Signalling destination) between different sets of link; the other exists in different link of the same link set. According to the difference between SLS and MSU, different link sets or signalling links are chosen to achieve sharing goals. SLS is a domain of MSU, so SLS has been identified once MSU is identified. The link that the signalling unit chooses to occupy changes along with the SLS's changes, which achieve load sharing of link. In addition to the purpose of load sharing, the role of SLS is to ensure ordinal control. Through setting different sets of link selective mask and different link selective mask and carrying out specific operations with SLS of message received, load sharing for MTP signalling is achieved. When a link is not available, other links'principle of sharing load make it same that the load both of STP1 and ST2 undertake. HUAWEI uses masking mode and ALCATEL BELL uses the allocation shifted mode of dynamic cycle, which achieve routing of message.4.The optimized adjustment scheme on load of Signalling NetworkSLS carried by message corresponds to a SLS of corresponding link through a certain algorithm, which determine which link the No.7 signalling message chooses, So it form the link's load owning to choosing the link. Network load is derived from local calls business, inter-network calls business, toll call business and intelligent business call in JiLin province. We can determine adjustment scheme on the link's load by analyzing message flow of No.7 signalling in the various types of traffic call. The formation of a load on the network is not decided by routing rules at some point, but set the routing rules after overall consideration according to the position of every node in all nodes in the Network and form a reasonable organic network model, only by so doing can the problem of uneven load be resolved. We can find out the regularity of uneven load after a period of statistical analysis. After adjusting the mode of STP single node, we find out the change regularity of load and adjust times without number. The result is that the optimized routing model of STP point load'even distribution is find. According to the location of each node in the optimized routing model, the routing mode is set and load distribution is achieved unevenly.5.The summaryI researched a method of network optimization through a large number of practices again and again in the practical work and established the model of network optimization routing. Then the method was applied in the actual work. There was an obvious effect through adjustment and transformation for No.7 Signalling Network by the end of 2007 in Jilin Province. Before adjustments, the total load of link, from LSTP1 and LSTP2 to SAU in ChangChun, was very uneven (LSTP1 load is doubled of LSTP2); the load of single link from LSTP to SAU was up to 0.65 Erl, at the same time the minimum load was only 0.13Erl in the link of a same direction. After adjusting by the method discussed in the thesis, the total load of link, from LSTP1 and LSTP2 to SAU, is same and there is hardly difference for load between links at the same position. Achieve the goal to optimize and adjust Network Completely.In No.7 network structure and forming reason of link load, other provinces are similar to Jilin Province. So result of this thesis research: "optimized routing network model" is also suitable for other provinces to adjust and optimize the No.7 Signalling Network. After the two provinces being adjusted by optimized routing Network model, two provinces'HSTPs can adjust their No.7 signalling routing data between them according to optimized routing model in this thesis. They make routing model between them and obtain the optimized routing network model of the whole network. Finally, we achieve the goal that the load of national No.7 signalling link is adjusted evenly and Network is optimized.