Design of single user tracking in WRNC system This paper introduces a mechanism to enable the RNC (Radio Network Control) within the radio network controller to easily and accurately collect the statistical information of each link in the single-user data processing, so that the single-user information can be quickly counted and checked to improve the problem Analysis efficiency. With the rapid development of 3G networks, WCDMA systems are being commercialized on a large scale. In the past, some commonly used positioning methods, such as breakpoint debugging and LogView, have become increasingly difficult to meet the needs of the field. Compared with the simple laboratory environment, the field positioning problem will be more difficult. At present, for the instability of HSDPA / HSUPA service rate and the failure of PS service (Packet Stream data service), the common troubleshooting methods are very limited, and the positioning is very difficult. . In addition to the special circumstances of many users in the field and large interference data, the traditional positioning method simply cannot obtain the relevant statistical information and traffic tracking information of a single user, which brings many difficulties to the location and resolution of the problem.
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1 The occurrence and phenomenon of rate problems
There are three main reasons for the internal rate problem of RNC: (1) improper processing of data packets by the user plane and abnormal packet loss; (2) the connection parameters passed to the user plane by the control plane are incorrect, and the user plane and the bearer cannot be connected; (3 ) The user plane itself is not properly handled when handling various connection relationships.
In practical applications, the rate phenomena in several different situations are as follows: (1) the upstream and downstream rates are unstable when the HSDPA / HSUPA service is running; (2) the rate decoupling occurs during the HSDPA / HSUPA service; (3) HSDPA / HSUPA The PS service cannot reach the contracted expected rate; (4) The rate is normal.
2 Traditional positioning methods and defects
At present, the traditional rate positioning method is divided into three types: SHELL command positioning, DSP printing positioning and signaling tracking positioning.
But for field positioning, these traditional positioning methods are difficult to achieve. First of all, the SHELL command positioning, the number of field interface boards is large, and carries different services. It is extremely troublesome to enter the SHELL commands in turn between the interface boards. At the same time, the SHELL command can only track all business traffic information, and cannot target specific users. Lack of pertinence. Secondly, the external field has strict requirements for printing. Generally, it is not allowed to open internal printing. The official commercial bureau has relatively few resources. Opening a lot of internal printing will affect the operation of the entire system. Finally, the signaling tracking only records the basic information of the control plane, and cannot really help the user plane inspection.
Therefore, for such problems, a good positioning method is needed to lock the problem to the specific interface or FP level. Single-user tracking is designed for this defect, and its advantages are: (1) Data reporting is recorded through background signaling tracking, which is conducive to observation; (2) Data tracking uses FP as the unit to directly locate the business channel and locate accurately ; (3) No additional overhead is added to normal equipment operation, and no extra manual operation is required, which is convenient to use.
3 Design and implementation of single user tracking
3.1 Overall overview of WCDMA system
The WCDMA system is mainly composed of three core parts, which are divided into a core network (CN), a radio network controller (RNC) and a base station (NodeB). RNC connects CN and NodeB and plays an important role in WCDMA. The IUR port is used to connect RNC and RNC. RNC is divided into three parts: CRNC (control RNC), SRNC (service RNC) and DRNC (drift RNC) [5].
3.2 Data flow tracked by a single user
The path of the data flow in the RNC is divided into two, one is to directly enter the SRNC through the IUB port, and reach the CN through the IU port; the other is to reach the DRNC through the IUB port, then from the DRNC to the SRNC through the IUR port, and finally reach the CN [6] . If you can count the data packets of each FP at each node and compare the data traffic of each node, you can quickly locate the data loss interface and FP.
3.3 Overall design of single user tracking
The protocol architecture of each interface of UTRAN is designed according to a common protocol model, as shown in Figure 1. The design principle is that the floors and planes are logically independent of each other. From a horizontal perspective, the protocol structure mainly includes two layers: the wireless network layer and the transmission network layer. All UTRAN related issues are only related to the wireless network layer, and the transport network layer is only the standardized transmission technology adopted by UTRAN, and has nothing to do with the specific functions of UTRAN. Viewed from the vertical plane, the protocol structure includes control plane, user plane, transmission network control plane and transmission network user plane [1]. 
This design is divided into the following modules according to the protocol architecture of UTRAN: message processing module, control plane, user plane, bearer management module and signaling tracking module.
The entire single-user tracking design idea is shown in Figure 2, where the solid line represents the control flow and the dotted line represents the data flow. 
For control information, the task of tracking the media plane is distributed to the message processing module (Daemon), and Daemon notifies the control plane CP (Control Plane) and the user plane UP (User Plane). The control plane notifies the bearer management module BM (Bear Management, BM) to establish and delete related bearer tracking when the bearer link is established and deleted. Extract relevant information from the message and send a message to inform the interface board. After receiving the message, the interface board sets the filtering conditions and performs filtering statistics on the processed messages.
For the data service flow, after collecting the tracking information, the interface board and the user plane directly report the tracking information to Daemon. Daemon will check the content of the message and report it to the background.
3.4 Implementation process of single user tracking
In order to successfully realize the traffic reporting of each interface FP under the framework of the existing system, the following two processes are designed: task start and data reporting and verification.
3.4.1 Start of single user tracking on the media
The start-up process for single-user tracking is:
(1) The background sends an EV_UE_MEDIA_START_REQ request message to the signaling tracking module (ToolKit). The message carries the IMSI number and tracking flag to be tracked to ToolKit.
(2) ToolKit adopts a response processing mechanism. After receiving the message, it immediately responds to the background, notifying that the message has been received. ToolKit maintains a state table (TraceUE) about various tracking tasks of UE. Judging from the IMSI number in the message, if the saved IMSI number cannot be queried in the ToolKit module, it indicates that the process is wrong and the process ends directly. If the IMSI number exists and is already in the tracking state, it means that the tracking is repeated and ends directly. If the IMSI number is in an untracked state, ToolKit will create a context about the UE and save it in the TraceUE information for future query and use.
(3) ToolKit needs to send a message EV_START_MEDIA_TRACE to the message processing module (Daemon). Daemon decides which modules need to send trace messages according to different messages.
(4) Daemon sends a message EV_START_MEDIA_TRACE to the media plane to the user plane. After receiving the tracking instruction message, the user plane records the tracking information, so that when the bearer interface is called to establish the connection table, it indicates that the data on the bearer link needs to be tracked, so that the data amount information can be directly reported from the user plane.
(5) Daemon sends an EV_START_MEDIA_TRACE message to each terrestrial interface (IUB / IUR / IU), triggering each terrestrial interface to send tracking instructions to its respective underlying link.
(6) After receiving the tracking message of the media single user, each terrestrial standard module searches for the transport layer information about the UE according to the IMSI number, starts the message sending mechanism, and then carries the bearer related to the UE to the bearer management The module sends an EV_START_LINK_TRACE message to trigger that the underlying bearer about this UE is marked as tracking. This message not only needs to carry all the information (BearId, bindingID, TransportAddress, etc.) when the bearer link is established, but also adds the flag bit tracked by the media plane. After receiving the message, the underlying bearer management module BM needs to traverse and check the bearer information, and mark the relevant fields of the bearer link that really needs to be tracked, which is convenient for later statistics.
3.4.2 Reporting time and verification of single user tracking on media
(1) Reporting time alignment
The reporting of data is the result of accumulation within a certain period of time. In order to ensure the accuracy of business data statistics, it is necessary to ensure the consistency of the system time on each board. To ensure this, the strategy of aligning the initial zero clearing time and the statistical reporting time is adopted.
Statistic initial clearing time alignment: When the bearer link is established, the interface board clears the statistical information corresponding to this link. The user plane processing board also uses a similar method to clear statistics on related bearers.
The time alignment of statistical reporting is implemented in two ways: (1) The granularity of reporting is agreed, for example, 15 s, 30 s, 60 s, etc. (2) Align by the absolute time on the board. For example, on the premise of time alignment, report at 15 s, 30 s, 45 s, and 60 s per minute. In order to align the reporting time, a new soft clock that records absolute time is maintained on the DSP. The soft clock reference is synchronized by HOST, which can periodically correct the clock on the DSP.
(2) Reporting channels
In order to check the information, two reporting methods are designed: (1) There are keep-alive messages between each interface module of the CP and the UP, and the keep-alive messages will trigger the UP to report all the users on different interfaces (IUB, IUR, IU) Statistics of the bearer link. After receiving the keep-alive message, UP finds that the user is being tracked by the media plane, and then calls the data reporting interface to report statistics. At this time, the user plane will query the bearer information that was tracked at startup. Through the internal mechanism, the tracking information is forwarded to Daemon until it is sent to the background. (2) When each CP interface module sends a keep-alive message to the UP and finds that the user is being tracked by the media, it sends a data report request message EV_START_LINKTRACERPT_REQ to the BM module. After receiving the message, the BM will notify the user according to the locally saved tracking user information. Interface board. The interface board reports the tracking information to Daemon until the background.
(3) Check of statistical information
When the user plane calls the bearer interface to send packets, it will filter based on the information of the bearer tracked in the interface. When receiving a message, the message is filtered according to the information in the bearer connection table.
For the interface board, the bearer management module needs to set filtering conditions on the statistical information. For different load types, the filter conditions are inconsistent. In the ATM mode, IUB, IUCS, and IUR need to filter the information of incoming and outgoing network elements based on the information of VPI, VCI, and CID, and IUPS needs to complete the filtering of incoming and outgoing calls based on the TEID of the opposite end and the local end. In IP mode, IUB, IUCS, and IUR complete the filtering of incoming and outgoing network elements based on the local IP address and UDP port number. IUPS requires the TEID of the local and peer to determine.
In order to check the statistical information with the user plane, for each bearer link, the control plane also needs to inform the bearer management module of the filtering direction, interface type, link attributes and global identification information of the user.
Daemon summarizes and checks the data reported by the two channels to prevent inconsistency of statistical information and improve the accuracy of information reporting.
4 Test results of single user tracking
This design has been tested and verified in the WRNC system. Figure 3 is the signaling analysis of the Iu port in the service report message. 
This includes some statistical cells tracked by a single user. Such as: IuupUlPsRecvNum, IuupUlPsSendNum, IuupDlPsRecvNum and Iuup DlPsSendNum, etc., respectively record the amount of data sent and received in the upstream and downstream PS domain. From the figure, it can be seen that the upstream sending and receiving data volume of IuUp is 21, which means that the data sending and receiving of this FP is normal, and there is no abnormal situation.
It can be seen from Figure 3 that the solution successfully collects and reports business data. The signaling trace in the background clearly records the type and data of each FP in each standard interface.
This solution realizes the reporting and statistics of user data of each interface within the RNC, and completely solves the complexity and inaccuracy of traditional rate problem positioning. The accurate positioning, easy observation and easy operation make the positioning method much better than the traditional positioning method.
In the application of the commercial bureau, single-user tracking can greatly shorten the positioning time of the rate problem and greatly reduce the interference of other users in the field. This design has played an important role in improving operator satisfaction and rapidly advancing the deployment of 3G in China.
