CN1223122C - Method of soft switching in WCDMA network - Google Patents

Abstract

The present invention provides a soft switch method in a wideband code division multiple access network, which is suitable for the conditions that DRNC uses an ATM transmission technique, and SRNC and Node B both use an IP transmission techniques. The method of the present invention can overcome the problems that excessive nodes on a path of a service flow influences the utilization rate of bandwidth of an IP network when user equipment is mutually communicated with a network, and service is interrupted because of service delay in the prior art. The soft switch method of the present invention comprises the following steps that IP SRNC transmits a wireless link establishment request to ATM DRNC; the ATM DRNC transmits a wireless link establishment request to IP Node B which transmits a wireless link establishment response to the IP DRNC; the ATM DRNC transmits a wireless link establishment response to the IP SRNC; the IP SRNC and the IP Node B establish direct transmission load bearing; the IP SRNC transmits update messages of an active set to user equipment which transmits the update messages of the active set to the IP SRNC.

Description

Soft Handoff Method in Wideband Code Division Multiple Access Network

technical field

The present invention relates to a soft handoff method in a communication system, in particular to a WCDMA (Wideband Code Division Multiple Access, wideband code division multiple access) wireless access network, based on different versions of DRNC (Drift Radio network Controller, drift wireless network controller), Soft handover between SRNC (Serving Radionetwork Controller, Serving Radio Network Controller) and Node B (wireless base station of WCDMA network).

Background technique

Currently, 3GPP (The 3rd Generation Partnership Project) has two types of versions: R99 version and ROO version, and the ROO version also includes R4 and R5 versions. In the R99 version and the ROO version, the transmission technology on the radio access network side of the R4 version is based on ATM, while the transmission technology on the radio access network side of the R5 version is based on IP. Due to some advantages of IP transmission technology, it is expected that more and more ATM transmission technologies will be replaced in the future. Therefore, a new problem arises, that is, how the ATM node and the IP node communicate with each other.

At the same time, since soft handovers between RNCs (Radio Network Controllers, radio network controllers) occur frequently in the 3G network, each RNC reserves more resources for soft handover services. There are many times of soft handover, which may easily lead to the decline of communication quality, especially in the edge areas covered by RNCs, frequent movement of user equipment often leads to frequent handovers between two RNCs. Compared with intra-RNC soft handover, inter-RNC soft handover needs to be jointly processed by SRNC, Node B, and DRNC, resulting in huge overhead. Therefore, there is an urgent need for a solution that can perform soft handover between RNCs in an environment where different transmission technologies, ie, IP and ATM transmission technologies are mixed.

The following introduces the related content and method of soft handover between RNCs based on different transmission technologies in the prior art. Let me first introduce several important concepts about adjacent cells in soft handover:

The active set refers to the set of cells currently being used by the user equipment, and the execution result of the soft handover is reflected in the increase or decrease of the cells in the active set.

Observation set, the user equipment is observing the cells that are not in the active set according to the adjacent cell information given by UTRAN (Universal Mobile telecommunications System, universal mobile communication system), the user equipment measures the cells in the observation set, when the measurement results meet certain conditions , these cells may be added to the active set, so it is sometimes called the candidate set.

Detected set, the UE has detected the cells, but neither belong to the active set nor the observed set, UTRAN can ask the UE to report the measurement results of the detected set; since they do not belong to the neighbor cell list, they are sometimes called for an unlisted set.

In the prior art, the soft handover process between RNCs can be divided into the following steps:

1) The user equipment measures neighboring cells of the same frequency according to the measurement control information given by the SRNC, and reports the measurement results to the SRNC after processing;

2) The SRNC performs handover judgment on the reported measurement results, and decides whether to perform soft handover;

3) If a new wireless link needs to be added after the handover decision, the SRNC sends an RNSAP (Radio Network Subsystem Application Part, Radio Network Subsystem Application Part) message to the DRNC through the signaling gateway, thereby notifying the Node B to prepare resources;

4) After establishing a signaling connection between DRNC and Node B, SRNC first establishes a data bearer with DRNC, and then establishes a data bearer with Node B. Then notify the user equipment to add and/or delete wireless links through an active set update message;

5) After the user equipment successfully updates the active set, add a wireless link under the new Node B. If a cell needs to be deleted, the Node B is notified to release corresponding resources.

At this time, if SRNC and Node B have different transmission methods, among which DRNC is an IP transmission method, as shown in Figure 1, the user plane conversion needs to be performed through the interworking IWU (Interworking Unit, Interworking Unit) and DRNC on the transmission path, and the process comparison complex. Therefore there are following disadvantages:

1. There are too many nodes on the path of the service flow during intercommunication, which affects the bandwidth utilization of the IP network;

2. Increased service delay may lead to service interruption and bring adverse effects to operators.

Contents of the invention

The purpose of the present invention is to propose a new soft handover method for the problems referred to above, which is applicable to the situation that DRNC adopts ATM transmission technology, and both SRNC and Node B adopt IP transmission technology.

In addition, this method can overcome the problems of low bandwidth utilization caused by too many nodes on the transmission path in the prior art, and possible service interruption due to service delay.

The soft handover method in the broadband code division multiple access network provided by the present invention comprises the following steps: Step 1: IPSRNC (serving radio network controller) sends wireless link establishment request to ATM DRNC by IWU; Step 2: ATM DRNC to IP SRNC The resource information contained in the said request message is judged. When available, ATM DRNC sends a wireless link establishment request to IP NodeB through NBAP (Node B Application Part, Node B application part), including the following parameters: IP service wireless network The IP address of the controller, the UDP port number of the IP service wireless network controller; Step 3: IP Node B assigns the resources required by the ATM DRNC in the above wireless link establishment request, and sends a wireless link establishment response to the IP DRNC after completion ; Step 4: ATM DRNC sends wireless link to IP SRNC to set up a response, including following parameters: IP address and UDP port number of IP wireless base station; Step 5: IP SRNC and IP Node B do not establish direct transmission bearer through ATM network; Step 6 and Step 7: IP Node B and IP SRNC establish synchronization for the wireless link established in the above steps; Step 8: IP SRNC sends an active set update message to user equipment; Step 9: User equipment sends activity to IP SRNC A message that the set update is complete.

In the present invention, the wireless link establishment request message in step 1 includes the following resource information: cell ID, transmission format set of each DCH, set of transmission format sets, frequency, uplink scrambling code, IP address of SRNC , The local UDP port number assigned by the SRNC.

In the present invention, the wireless link establishment response message in step 3 includes the following parameters: IP address and UDP port number of IPNode B.

According to the soft switching method of the present invention, since the nodes on the path of the intercommunication service flow are reduced, the broadband utilization rate of the IP network is guaranteed. At the same time, due to the shortened path, service delay is reduced, thereby avoiding factors that may cause service interruption.

Figure overview

Fig. 1 is the soft handover path schematic diagram under IP SRNC and IP Node B condition in the prior art;

Fig. 2 is the soft handoff path schematic diagram under IP SRNC and IP Node B condition among the present invention;

Fig. 3 is the flow chart of soft handover under the condition of IP SRNC and IP Node B among the present invention.

specific embodiment

Fig. 2 shows the direct transmission bearer path under the condition of ATM DRNC, IP SRNC and IP Node B proposed in the present invention.

According to the transmission path shown in Figure 2, it can be seen that after the present invention realizes direct transmission, the transmission path is greatly optimized, and the number of intermediate nodes is reduced by more than half, plus the processing delay of low-speed link processing and IWU , the optimization of the delay should also be considerable.

The process of the direct transmission method proposed by the present invention will be described in detail below.

Step 1: The IP SRNC sends a wireless link establishment request to the ATM DRNC through the IWU. The message includes, for example: cell ID, transmission format set of each DCH, set of transmission format sets, frequency, uplink scrambling code, IP of SRNC Address, local UDP port number assigned by SRNC and other parameters.

Thus a new radio link is added between user equipment and ATM DRNC. If this is the first wireless link established between the two, then this wireless link establishment request establishes a new Iur signaling connection, and all future RNSAP signaling related to the user equipment will use this Iur signaling connection.

Step 2: ATM DRNC judges the resource information contained in the request message of IP SRNC to determine whether it is available. If available, ATM DRNC sends a wireless link establishment request to IP Node B through NBAP (Node B Application Part, Node B application part). The request includes such parameters as: cell ID, transmission format set of each DCH, transmission format set set, frequency, uplink scrambling code, SRNC IP address, local UDP port number assigned by SRNC, etc.

In the present embodiment, since ATM DRNC knows that IP Node B is an IP node, so when sending a message, it carries IP address and UDP port number of IP SRNC.

Step 3: IP Node B assigns the resources required by ATM DRNC in the above wireless link establishment request, and sends a wireless link establishment response to IP DRNC after completion. In addition to including IP Node B's own IP address and UDP port number, the message also includes parameters such as signaling link termination.

Step 4: ATM DRNC sends a wireless link establishment response to IP SRNC. The message includes the IP address of the Node B, its UDP port number, and information about adjacent cells.

Step 5: After receiving the wireless link establishment response, the IP SRNC obtains the IP address and UDP port number of the IP Node B through the RNSAP message, and establishes a wireless link bearer with the IP Node B. Thus, a direct transmission bearer is established between the IP SRNC and the IPNode B.

Step 6 and Step 7: IP Node B and IP SRNC establish synchronization for the wireless link established in the above steps by exchanging appropriate dedicated channel protocol frames "Downlink Synchronization" and "Uplink Synchronization". The downlink transmission is then started by the IP Node B. It should be noted that if the above synchronization cannot be established, it means that the purpose cannot be achieved. In this case, the SRNC may choose to resend the bearer setup with the DRNC.

Since in this embodiment, the SRNC knows that the DRNC is an ATM node, it can choose not to include its own IP address and UDP port number in the wireless link establishment request, so as to adapt to the ATM mode.

In the above situation, the DRNC cannot adopt the direct transmission bearer establishment, and will establish the transmission bearers of the Iur interface and the Iub interface in sections through the currently used method. Since this is part of the prior art, in this specification

Step 8: After the IP SRNC establishes synchronization with the IP Node B, it sends an active set update message to the user equipment, that is, requests to add a wireless link to the user equipment.

Step 9: The user equipment sends a message that the update of the active set is completed to the SRNC.

It should be noted that if there are multiple IP Node Bs added to the active set of the user equipment under the ATM DRNC, the above process will be repeated.

When the IP SRNC decides to migrate, it sends a migration request message to the core network (CN). After the CN receives the message, it initiates the establishment of the wireless access bearer between the CN and the ATM DRNC, and at the same time, the IP DRNC initiates the transmission bearer with the IP NodeB. After the above two bearers are completed, the original radio bearers between the core network and IP SRNC, and between IP SRNC and IP Node B will be released. Thus ATM DRNC becomes ATM SRNC, and the migration process is completed.

The present invention optimizes the processing and signaling flow of the existing DRNC to realize the establishment of direct transmission bearer when the DRNC, SRNC and Node B are not in the same transmission mode.

Claims (3)

1. the soft handover method in the WCDMA network is characterized in that comprising following steps:

Step 1:IP service wireless network controller sends Radio Link by interworking unit to the ATM floating radio network controller and sets up request;

The resource information that comprises in the described request message of step 2:ATM floating radio network controller to the IP service wireless network controller is judged, but when the time spent, the ATM floating radio network controller sends Radio Link by wireless base station applications part to the IP wireless base station and sets up request, comprises following parameter: the IP address of IP service wireless network controller, the udp port of IP service wireless network controller number;

Step 3:IP wireless base station assigns the ATM floating radio network controller to set up resource needed in the request at above-mentioned Radio Link, sends Radio Link to the IP floating radio network controller after finishing and sets up response;

Step 4:ATM floating radio network controller sends Radio Link to the IP service wireless network controller and sets up response, comprises following parameter: the IP address of IP wireless base station and udp port number;

Direct transmission bearer is set up without atm network in step 5:IP service wireless network controller and IP wireless base station;

Step 6 and step 7:IP wireless base station and IP service wireless network controller are set up synchronously for the Radio Link of being set up in above-mentioned steps;

Step 8:IP service wireless network controller sends the message that active set upgrades to subscriber equipment;

Step 9: subscriber equipment sends active set to the IP service wireless network controller and upgrades the message of finishing.

2. the changing method in the WCDMA network as claimed in claim 1, it is characterized in that the described Radio Link in step 1 is set up and comprised following resource information in the request message: the local terminal udp port that the IP address of the transmission format set of sub-district ID, each designated lane, the set of TFS Transport Format Set, frequency, uplink scrambling code, service wireless network controller, service wireless network controller are distributed number.

3. the changing method in the WCDMA network as claimed in claim 1 is characterized in that, the described Radio Link in step 3 is set up and comprised following parameter in the response message: the IP address of IP wireless base station and udp port number.

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