The NP (Number Portability) service refers to the user changing the carrier but the subscriber number remains unchanged. China is currently conducting field trials of mobile number portability services in some cities. In order to provide a better service experience for users after the number portability, the field trial phase requires that the services currently used by the mobile network to communicate with each other can be used normally after the number portability, including voice services, point-to-point short message services, and point-to-point multimedia. Message business, etc.
After the number portability is implemented, the user's ISDN number cannot indicate the network where the user is located. Therefore, in a local network that provides number portability, when the operator network receives a phone call, a short message, or a multimedia message, it needs to query the number portability database ( NPDB) to determine the current contracted network of the called user, and to select the routing according to the routing number returned by the database.
From the perspective of the number portability service routing technology, there are two technical issues that need to be considered:
· Which operator is responsible for querying the number portability database. After the number portability is implemented, a session process may pass through up to three carrier networks, including the originating carrier network where the calling user is located, the receiving carrier network where the called user is located, and possibly the network owned by the called number. The inter-network routing scheme, which operator is responsible for querying the database, is the first issue we need to consider.
How to query the number portability database. When the operator queries the number portability database in the network, what technical solution is needed is the second problem that we need to consider.
This paper will analyze the advantages and disadvantages of different technical solutions from the above two levels, combined with the actual situation of China's telecommunication network, and introduce the technical solutions determined by the field test in China.
1 China's number ported inter-network routing solution1.1 Comparison of different routing schemes
International number portability usually has two inter-network routing schemes, one is the originating operator network query database, and the other is the network query database owned by the called number. The routing diagrams are shown in Figure 1 and Figure 2, respectively.
Figure 1 originating network query database
Figure 2 The called number has network query dataåŽ
As shown in Figure 1, the originating network query refers to the network of the carrier where the calling user directly queries the number portability database. After obtaining the information of the current operator of the called user, the session is directly connected to the current subscription network of the called user. , that is, the receiving carrier network. The receiving carrier network may belong to the same network as the originating carrier network, or may belong to the same network as the called number owning network, and may also be a third-party carrier network.
As can be seen from Figure 2, the called party has a network query, which means that the carrier's carrier network connects the session to the called number to own the network according to the original route. The called number owning network is responsible for querying the number portability database. After obtaining the information of the current operator of the called user, the session is directly connected to the current subscription network of the called user, that is, the receiving carrier network. The receiving carrier network may belong to the same network as the originating carrier network, or may belong to the same network as the called number owning network, and may also be a third-party carrier network. If the called user is a user that is brought to the originating carrier network, the receiving carrier network and the originating carrier network are the same carrier network, and a route bypass is generated.
Many of the international organizations have made theoretical comparisons on the advantages and disadvantages of these two routing schemes.
The biggest advantage of the originating network query relative to the called number having the network query is that routing detours are avoided and network resources are wasted. However, this scheme also has certain shortcomings. Since all called numbers (including the local network and other network numbers) must be queried to determine the subscription network, if the proportion of users is high, this method can reduce signaling. The number of transfer times and connection time is higher. On the contrary, if the proportion of users is low, this method will cause a large number of invalid queries of the originating network to the NPDB, and thus the efficiency is low.
The called number has a network query scheme that is applicable to the case where the originating network does not have the ability to initiate an inquiry to the NPDB, including the originating network being a fixed network (assuming that only mobile number portability is carried out), or a network outside the carrying area. This method can reduce the number of times the database is queried if the ratio of carrying users is small. However, when the user brings the network to the originating network, the scheme will generate a routing bypass; and when the called user carries the third-party network, the number-owned network also participates in the call forwarding process, wasting network resources.
In the field trial of mobile number portability in China, during the selection of the inter-network routing scheme, the network routing of various services in China's existing network, the number portability management policy during the field trial, and the network architecture of China's current network are analyzed. Factors, weighed the cost of each operator's transformation and the advantages and disadvantages of various programs, and finally determined the routing plan for various types of business during the field test. The following will be analyzed by business category.
1.2 Voice service between mobile users
For the voice service between mobile users, the field trial phase determines the way in which the originating carrier network is used to query the database.
In China, when determining the inter-network routing scheme for voice services, each operator initially held different opinions. Each family analyzed the network situation of the operator, the size of the user, and the situation of the inter-network call. The inter-network routing scheme most suitable for the operator was proposed.
At present, the scale of each operator in China is quite different. For networks with smaller users, they are more inclined to have the network number query scheme for the called number. This is mainly because if the originating query is used, all the inter-network traffic also needs to access the database, and for the operators with smaller users, the inter-network traffic accounts for a large proportion of all traffic, so the new database query The amount will be relatively large, and the amount of network transformation is relatively large. In particular, for a local network that implements one-way number portability, only operators that are not allowed to carry out are allowed to have a network query scheme using the called number, and may even not need to construct an NPDB, and the network transformation amount is relatively small. However, this solution increases the burden of carrying the operator, wastes the line relay resources, and increases the dialing delay of the call-carrying number.
Of course, the advantages of the originating network query are also obvious. It is recognized that the originating network query can reduce the routing bypass, does not involve the number owning the network, does not waste the line relay resources, does not increase the dialing delay of the call carrying number because of the number portability, and can better guarantee the quality of service to the user. Therefore, most countries in the world have adopted this type of routing.
Finally, we have comprehensively considered the entire communication industry in China, and determined the technical solution of using the originating network query. This kind of program is very beneficial for China to carry out number portability business in the country in the future.
1.3 Voice service between fixed users and mobile users
For voice services between fixed users and mobile users, the field trial phase determines the way in which the called number has a network query database.
We have already analyzed the advantages and disadvantages of the two routing schemes. However, since the on-site number of mobile users is only carried in the field trial phase in China, in order not to affect the fixed network, we have determined the way in which the called mobile number has a network query.
Considering that after the reorganization of telecommunications, all operators in China are full-service operators. In the future, when fixed and mobile integrated gateways are built by operators, they can also be gradually transformed into the way of originating network queries, that is, the originating fixed network will be in session. After connecting to the mobile network of the operator, after the database is queried by the mobile network, the connection can be continued to reduce the negative effects caused by the route bypass.
1.4 Point-to-point short message service
For the point-to-point short message service, the field trial phase determines the way in which the called number has a network query database.
At present, the point-to-point short message service in China is not exactly the same as the Lunan method of the telephone service. Therefore, when selecting a technical solution, it is necessary to comprehensively consider the actual situation of the short message service. The plan should be considered based on the following status:
· At present, the short message service of each operator in China is set in the province as the short message center. Therefore, the NPDB queried by the short message center should contain at least the NP data of all users in the province.
· The SMSC does not communicate with each other, that is, the originating user belongs to the short message center and can send the short message to all users in the country. The SMSCs are interconnected by the SMSCs in each province. The short message is sent to the short message center of the called party by the calling user, and then the short message is sent to all the users of the local network.
· The inter-network SMS is based on the originating network, that is, the network is directly connected to the location of the calling user.
In the above background, we have carried out a detailed analysis of the network transformation of the two routing schemes of the short message service.
(1) Using the originating network query
Since the originating network query is required, the originating short message center (SMSC) needs to query the NPDB of the called number in all the short messages between the intranets. The network transformation requirements are as follows:
· The SMSC of the whole network should be modified. For the other network number, the HER process should also be triggered, and the network cannot be sent directly.
· For the remote network number of the other network, the originating SMSC needs to add the GT data of all the local and other network user numbers in the signaling network of the G network in order to be able to query the remote HLR or access the NPDB in the remote network; in the C network signaling network It is necessary to add GT data for all users of this website and other users in the province. Or build an NPDB for all SMSC queries in the country. The NPDB needs to store NP user data of all local networks in the country; however, if the proportion of users carrying the transfer is relatively high, the capacity requirement for the NPDB will be relatively large.
• For SMSC, Internet Gateway (IWGW), and Signaling Transfer Point (STP): The called number with the Routing Number (RN) prefix can be identified.
(2) Using the called number to have a network query
It only needs to modify the SMSC, IWGW, STP and other equipments, and it is required to identify the called number with the RN prefix. The called number owns the network SMSC and needs to trigger the access to the HLR for the other network number. Others still maintain the existing SMSC. Access to the HLR process does not require additional modifications.
It can be seen that for the short message service, the network transformation request of the originating network query mode is very complicated. Even if the number portability is carried out only on several local networks, the whole network device needs to be modified; and the number owning network query is used for the existing network device. The transformation is rare and worth recommending. However, the resulting routing problem is also unavoidable, and the complexity of the settlement caused by routing bypass needs to be considered by the regulatory department.
It can also be seen that if the number portability is carried out in the country in the future, the actual voice service transformation has also completed the configuration of the STP office data of the entire network, that is, the GT translation data of all the segments of the network is added in the whole network. Therefore, the originating query can be ignored compared to the called number with the amount of modification added by the network query. At that time, we should consider changing the routing scheme of the short message service to the method of originating network query, which can solve the routing detour and the settlement problems brought by it.
1.5 point-to-point multimedia messaging service
The point-to-point multimedia message service between mobile users, the field trial phase determines the way to use the originating carrier network to query the database.
On this issue, the operators in China have consistently chosen the way of sending inquiries from the beginning. This is determined by the service routing of the multimedia message.
For the multimedia message service, the calling side needs to access the ENUM DNS to query the home multimedia message center of the called user, and the ENUM DNS is centralized in the country. Therefore, if you use the originating network query, you only need to modify or create the ENUM DNS of the whole network to make it have NPDB related functions. In the field test phase, the NPDB only needs to store the NP information of all NP numbers in the test site.
2 Technical solution for querying database in China's carrier networkAt present, there are many technical methods for querying the number portability database in the carrier network. The internationally popular solutions are divided into two modes: signaling and intelligent network:
The intelligent network method mainly accesses the NPDB through the switching node to complete the translation of the number. At present, most mobile MSCs have the capability of SSP. Therefore, the key point of the intelligent network implementation is that the switch analyzes the number dialed by the user and then goes to the database to query the routing number.
The signaling method is mainly in the existing signaling process, and simultaneously queries the database and obtains the next routing number. A functional entity of a Signaling Relay (SRF) can be added between two SPs (which can be MSC, HLR, SMSC, etc.). The SRF function that is cascaded between SPs can usually be implemented in STP or in a separate physical entity.
Considering that the access number portability database is an act within the carrier network, different operators adopt different schemes and may not affect the communication requirements between the networks. Therefore, in the field test phase, China stipulates that each operator can customize according to its own network. Choose a technical solution to access the database.
By evaluating the network architecture of the network and minimizing the transformation of existing network equipment and signaling networks, Chinese operators have basically adopted the construction of new HLR equipment, built NPDB in HLR equipment, and utilized MSC (for voice). Service), SMSC (for point-to-point short message service) accesses the signaling process of the HLR to achieve access to the number portability database. From the point of view of the process of accessing the database, we can understand the scheme chosen by the operator of our country as a special signaling scheme, that is, the function of the SRF is built in the HLR device. The multimedia message service has explicitly used the MMSC to access the EUNM DNS process to query the NPDB. It can also be understood as a special signaling scheme, but the business logic is relatively simple. This article will not focus on the analysis, but mainly implement voice for Chinese operators. Introduction and analysis of business and short message scenarios.
2.1 Telephone service
The scheme for accessing the NPDB of the carrier voice service in China is as follows: The SRF device with the NPDB function is built in the HLR, that is, the HLR (represented by 1) of the existing network is upgraded, and the NPDB of the user is built in the built-in network; HLR (indicated by 2), built-in network to bring the user's NPDB. The process of querying the HLR by the MSC triggers the query of the NPDB. If the called party is a number owned by the network, accessing the HLR (1) according to the route before the NP can determine whether the user carries it; if the called party is his network number, the MSC needs to directly access the HLR (2) to determine whether the user is carrying. The requirements for this type of network transformation are as follows:
• Upgrade the existing HLR(1) to have NPDB functionality.
· Each local network needs to create a new HLR (2) with NPDB function;
The LR signaling of the routing query class needs to be modified by the HLR (1) and the HLR (2). For the case of the called subscriber of the other network, it is required to be able to return the RN+called user number as the roaming number;
The related network element device needs to identify the routing code indicating the operator network, and for the inter-network call, the call can be connected to the network according to the indication of the routing code.
Among them, for the upgrade of HLR (1), there are also two implementations. One solution is that after the user of the local network carries out, the operator directly modifies the data of the HLR (1) of the existing network, and sets the roaming number of the carrying user to the RN+called user number. In another solution, the HLR (2) periodically updates the data in the original home HLR (1) to ensure that the HLR (1) can change the existing signaling process when the user is called. In this case, the correct route to the carrying user is implemented. Obviously, the former HLR (2) device has relatively simple functions and a short development cycle. However, each time a user carries out, the user data in the HLR (1) needs to be changed, so it is more suitable for a network with fewer HLR devices on the live network. The NPDB function of the latter scheme is actually implemented in HLR (2), the function is more complicated, and the development cycle is longer. HLR (1) only uses the original location update process, and does not need to modify the HLR (1) of the existing network, so it is more suitable for the network with more HLR devices on the live network. This is also an important reason why different operators in China have chosen different solutions.
2.2 Short message service
Similar to the telephony service, the short message service also uses the signaling process of the SMSC accessing the HLR in the short message service process to trigger the query of the NPDB to obtain the information of the current subscription network of the user, and then route the short message.
The implementation of the short message service should be considered on the basis of the transformation of the voice service to the network. Since it has been determined that the short message service adopts the inter-network route in which the called number has the network query database, the route from the originating network to the called number owning network is unchanged according to the original routing scheme.
When the called party owns the network's SMSC to access the HLR (1), according to the configuration that the voice service has been completed, for the carried user, the visited wireless mobile office (VMSC) address of the user in the HLR (1) will be directed to the HLR (2) After the SMSC obtains the VMSC address, the short message will be sent to the HLR (2), and the HLR (2) will add the RN before the called number and forward it to other operators through the Internet. It can be seen that in the short message service, in addition to the function of simulating the VMSC, the HLR (2) also simulates the function of the short message center and forwards the short message to the Internet. For the incoming user, the HLR (2) directly returns the user's real VMSC address and completes the routing of the short message.
3 ConclusionThe implementation of number portability, although there are a variety of technical solutions can be achieved, but from the process of determining the field test technology program in China and the process of testing, we also found that any solution is not perfect, with the operator network scale, network The architecture, existing service routing, user size, proportion of traffic within the network, the open range of number portability, and open policies all have a very close relationship. It is impossible for any kind of solution to meet the requirements of all operators at the same time. We can only stand at the perspective of the whole industry. Under the premise that the scope of the number portability business in China has not yet been determined, a trial phase of technology has been tentatively determined. Program. The solution we chose is not necessarily the best. Therefore, after the end of the field test, we also need to evaluate the cost of transformation, the complexity of the transformation, the user's response, etc., and then consider the technical solution for carrying the number in the future according to the actual situation.
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