WO2002033995A2

WO2002033995A2 - Cellular network reconfiguration

Info

Publication number: WO2002033995A2
Application number: PCT/SE2001/002263
Authority: WO
Inventors: Bengt Persson
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2000-10-19
Filing date: 2001-10-16
Publication date: 2002-04-25
Also published as: WO2002033995A3; AU9614901A

Abstract

A radio communications network is coupled to an external network and includes a first network service node coupled to a first radio network controller. A first radio base station is coupled to the first radio network controller. Mobile radio terminals communicate over a radio interface with the first base station. A connection between the mobile radio terminal and the external network is set up by way of the first network service node, the first radio network controller, and the first base station. A determination is made if the configuration of the radio communications network is to be changed. In the transport reconfiguration in accordance with the present invention, a second radio network controller is established, and the active connection between the external network and the mobile terminal is transferred from the first radio network controller to the second radio network controller without disruption. The first base associated is now associated with and under the control of the second radio network controller. In a preferred, example embodiment of the present invention, the second radio network controller is associated with the first radio network controller, and more particularly, the second radio network controller is a logical radio network controller that uses processing resources also used by the first radio network controller. For example, a second, logical radio network controller may be established on the same or different physical node or platform that supports the first radio network controller.

Description

CELLULAR NETWORK RECONFIGURATION

FIELD OF THE INVENTION

The present invention relates to cellular radio networks More particularly, the present invention relates to reconfiguring cellular networks in response to permanent or temporary growth, equipment malfunctions, engineering changes, etc.

BACKGROUND AND SUMMARY OF THE INVENTION

A typical cellular mobile radio telephone system includes at least one radio network controller, at least one radio base station, and multiple radio terminals. Base stations and mobile tei mtnals communicate over a radio interface. The radio network conti oiler manages radio-related details for a call connection between a mobile terminal and a core network service node, such as a mobile switching center (MSC), that mterfaces the radio network with external networks like the Pubkc Switched Telephone Network (PSTN). In order to obtain ladio coverage of a geographical area, a number of base stations is usually required The geographical area is divided into cells, and each cell may either be serviced by a base station or may share a base station with a number of other cells.

The rapid development of cellular telephony has made the administration and reconfiguration of cellular networks a significant issue. Problems arise when, for example, growing numbers of mobile subscribers require existing cells to be split into several smaller cells or new cells to be added New base stations oi new core network service nodes, e g , mobile switching centers, may also need to be added oi may become temporal lly inoperative tequtung traffic through that base station or core network node to be temporarily reassigned

Although wπeline telephone networks typically have some type of administrative system, cellulai netwoiks have many parameteis and requirements which are not encountered in wiieltne networks and which are not satisfied by existing administrative systems. For example, wireline systems where subscnbers have a fixed location, the location of the mobile subscribers changes and must be tracked continuously in order to direct calls properly In addition, each cell has certain associated parameters or characteristics which must be properly monitored and maintained to ensure proper operation of the cellular network. One administration method for reconfiguring a cellular communications network is described in commonly- ssigned U.S. Patent No. 5,434,798, the disclosure of which is incorporated herein by reference.

A problem with traditional approaches to reconfiguring a cellular communications network is that ongoing active call communications must be disrupted in order for a reconfiguration, e.g., a capacity upgrade, to occur. In addition to the disruption of active communications, no new calls may be accepted until the reconfiguration is complete. A reconfiguration often takes significant amounts of time and may affect many existing nodes in the netwoik. Still further, if the reconfiguration is not successful on the first attempt, an additional "lollback" process may be needed to undo certain changes made in one or more nodes. Because of these factors, even the addition of a single node, e.g., a new MSC, to a cellular network is a major effort, creating significant disturbances, and posing significant risks and costs to cellular operators.

It is an object of the present invention to overcome the problems and minimize the efforts and risks associated with reconfiguring a celltilar radio communications netwoik

It is an object of the present invention to provide a method for reconfiguring a cellular network so that ongoing radio communications are not disrupted.

It is a further object of the present invention to ptovide a method for reconfiguring a cellular network that is quick, efficient, and cost effective.

A radio communications network is coupled to an external network and includes a first netwotk ser vice node coupled to a first radio network controller. A first base station is coupled to the first radio network controller Mobile i adio terminals communicate over a radio interface with the first base station A connection between a mobile radio terminal and the external network is set up by way of the first network service node, the first radio network controller, and the first base station A determination is made if the configuration of the radio communications network is to be changed Non- limiting, example reconfiguration activities include the addition of a second network service node, a second 1 adio network controller, a second base station, and cell adding, splitting, combining, and reassignment. In the transparent reconfiguration in accordance with the present mvention, a second radio network controller is established, and the active connection between external network and mobile terminal is transferred from the first radio network conti oiler to the second radio network controller without disruption. The first base station is now associated with and under control of the second radio network controller. In a prefeπed, example embodiment of the present invention, the second radio network controller is associated with the first radio network controller, and more particularly, the second radio network controller is a logical radio network controller that uses processing resources also used by the first radio network controller. For example, a second, logical radio network controller may be established on the same physical node that supports the first radio network controller.

Defining a new logical RNC may include, for example, providing that new RNC with a node identity, defining certain interface points, and allocating resources to the new RNC. Because the same node that controls the base station before and after the reconfiguration, in the preferred embodiment, the reconfiguration is quite simple and straightforward. By using the same resources, likely including both hardware and software, in that same physical node before and after the reconfiguration, signaling and traffic communications associated with active connections are readily maintained.

One typical appkcation of the present invention is when a second network service node is added to the radio communications network Using the newly-established second l dio network controller, the active connection is transfetred from the first netwoik service node to the second network service node in a manner that is transparent to the external network and to the mobile terminal involved in the connection Sometime aftei the establishment ol the second radio network controller, control of a second base station may be transferred from the first radio network controller to the second radio network controller. Any active connections being supported by the second base station also are not interrupted during the transfer of control to that second base station.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of the present invention may be more readily understood with reference to the following description taken in conjunction with the accompanying drawings.

Fig. 1 illustrates a radio communications network in accordance with one example embodiment of the present invention;

Fig. 2 illustrates example procedures that may be used to implement one example embodiment of the present invention;

Fig. 3 illustrates another example radio communications network to which the present invention may be advantageously employed;

Fig. 4 is a function block diagram illustrating in further detail a radio network controller and a base station; and

Fig. 5 is a flowchart diagram illustrating example procedures implementing another example embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular embodiments, procedures, techniques, etc. in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. For example, the present invention may be implemented in any cellular radio communications system. One specific, non- limiting application of the invention described below is in a UMTS/WCDMA radio communications system.

In some instances, detailed descriptions of well-known methods, interfaces, devices, and signaling techniques are omitted so as not to obscure the description of the present invention with unnecessary detail. Moreover, individual function blocks are shown in some of the figures. Those skilled in the art will appreciate that the functions may be implemented using individual hardware circuits, using software functioning in conjunction with a suitably programmed digital microprocessor or general purpose computer, using an application specific integrated circuit (ASIC), and/or using one or more digital signal processors (DSPs).

Fig. 1 illustrates, in block diagram form, a radio communications network 10 in which the present invention may be advantageously employed. First and second network service nodes 12 and 14, respectively, have been identified as old and new. The old core network service node 12 has been existing and operational in the radio communications network 10. In this reconfiguration example, the new core network service node 14 is to be added to the network 10. For purposes of example only, the core network service nodes in this example are assumed to be mobile switching centers (MSCs). However, other types of core network service nodes, such a packet-switched core node, may be employed. The MSCs 12 and 14 interface the radio network 10 with external networks, such as the PSDN/ISDN network, other radio networks, and data networks. The MSCs 12 and 14 are coupled to a radio access network 16 made up of one or more radio network controllers. In this example, one or more active connections is established by way of the old MSC 12, the old radio network controller 18, and the base stations 22 and 24. Initially, the old radio network controller 18 controls two base stations, BSl and BS2, corresponding to reference numerals 22 and 24, respectively. Each base station is responsible for one or more cell coverage areas that may include one or more mobile terminals 26. In this example, active call connections exists between the old MSC 12 and two mobile terminals 26 by way of the old radio network controller 18 and the first and second base stations 22 and 24. As illustrated in function block format in Fig. 2, the present invention may be employed when the configuration of the mobile radio communication system 10 is to be changed (block 30). Reconfiguration may be necessary in a number of situations, e.g., the addition (or deletion) of a core network service node, a radio network controller, or a base station, and cell adding, cell splitting, cell combining, and cell reassignment.

Reconfiguration may also encompass certain cell parameter changes due to engineering or administrative changes. In this non-limiting example, the reconfiguration is the addition of a new MSC 14.

A new RNC 20 is established in the radio access 16 network to take over control of base station 24 as well as any active connections currently being supported by the station 24 (block 32). That transfer of responsibility for second base station 24 and any associated active connections is performed without disruption to those connections in a manner that is "transparent" to the mobile terminal 26 and the old MSC handling that connection. One example way of effecting a transparent reconfiguration is to establish a logical RNC that uses the same resources as the old RNC 18. An identifier is assigned to the new RNC 20, and that identifier is associated with the new MSC 14. Alternatively, a Server-Gateway RNC architecture may be employed. Each RNC has its own Server node that controls the radio network. Hardware resources for the Gateway nodes that manipulate the user-plane information flow are shared. When the responsibility for a connection is transferred from an old RNC to a new RNC, state information and perhaps other information on resources used in Gateway nodes are transferred between the old and new RNCs.

In addition to reconfiguring the second base station 24 to the new RNC 20, additional base stations may be assigned to the new RNC 20 (block 34). For example, a location area of coverage assigned to the old MSC, and thereby the old radio network controller, may include multiple base stations. By transferring that location area to the new MSC and the new radio network controller 20, the radio network controller 20 becomes responsible for those base stations in that location area. In addition, a new location area may be defined and associated with the new radio network controller 20. Because the same RNC hardware resources, and possibly even some of the same software resources, are used to create the new logical RNC 20, active connections are readily maintained. State information for the user flow does not need to be transferred. In addition, reconfiguration can be handled quite quickly, without disruption, and in a resource effective manner. Further advantages include simplified operation achieved through the de-coupling of changes to the different node types, security added through simple rollback, and the absence of traffic disturbances.

Anothei advantageous application of the present invention is now described in the non-limiting, example context of a universal mobile telecommunications system (UMTS) 100 shown in Fig. 3. A representative, circuit-switched, external core network, shown as a cloud 120 may be for example the public switched telephone network (PSTN) and/or the integrated services digital network (ISDN). Another circuit-switched, external core network may correspond to another Public Land Mobile radio Network (PLMN) 130. A representative, packet-switched, external core network shown as cloud 140 may be for example an IP network such as the Internet. The core networks are coupled to corresponding network service nodes 160. The PSTN/ISDN network 120 and other PLMN network 130 are connected to a circuit-switched core node (CSCN), such as a Mobile Switching Center (MSC), that provides circuit-switched services. The UMTS 100 may co-exist with an existing cellular network, here the Global System for Mobile Communications (GSM), wheie the MSC 180 is connected to a base station subsystem (BSS) 220 which in turn is connected to a radio base station 230. The packet-switched network 140 is connected to a packet-switched core node (PSCN), e.g., a General Packet Radio Service (GPRS) node 200 tailored to provide packet-switched type services in the context of GSM, which is sometimes referred to as the Serving GPRS Service Node (SGSN). Each of the core network service nodes 180 and 200 also connects to a UMTS terrestt tal radio access network (UTRAN) 240 over a radio access network interface. The UTRAN 240 includes one or more radio network controllers (RNCs) 260 coupled to each other and to a plurality of base stations (BSs) 280. Preferably, radio access over the radio interface in the UMTS 100 is based upon wideband, Code Division Multiple Access ( CDMA) with individual radio channels allocated using CDMA channelization or spreading codes Of course, other access methods may be employed like the well known TDMA access used in GSM WCDMA provides wide bandwidth for multimedia services and other high transmission rate demands as well as robust features like diversity handoff and RAKE receivers to ensure high quality communication service in a frequently changing environment. Each mobile station is assigned its own scrambling code in order for a base station 280 to identify transmissions from that particular mobile station. The mobile station also uses its own scrambling code to identify transmissions from the base station either on a general broadcast or common channel or transmissions specifically intended for that mobile station. That scrambling code distinguishes the scrambled signal from all of the other transmissions and noise present in the same area.

Different types of control channels are shown bridging the radio interface. For example, in the forward or downlink direction, there are several types of broadcast channels including a general broadcast channel (BCH), a paging channel (PCH), and a forward access channel (FACri) for providing various types of control messages to mobile stations In the reverse oi uplink direction, a random access channel (RACH) is employed by mobile stations whenever access is desired to perform location registration, call origination, page response, and other types of access operations.

Simplified function block diagrams of the radio network controller 260 and base station 280 are shown in Fig. 4. The radio network controller 260 includes a memory 300 coupled to data processing circuitry 302 that performs numerous radio and data processing operations required to perform its control function and conduct communications between the RNC and other entities such as the core network service nodes, other RNCs, and base stations Data processing circuitry 302 may include any one or a combination of suitably programmed or configured general purpose computer, microprocessor, microcontroller, dedicated logic circuitry, DSP, ASIC, etc , as described above The base station 280 includes a data processing and control unit 304 which, in addition to performing processing operations relating to communications with the RNC 260, performs a number of measurement and control operations associated with base station radio equipment including transceivers 306 connected to one or more antennas 308.

Again, for this non-limiting example, the reconfiguration is in the form of the addition of a new MSC to the radio network. However, other types of reconfigurations are envisioned, e g., adding a new logical RNC. In the UMTS system, the interface between the core network nodes, e.g., the MSC, and the UTRAN, is called the lu interface. An access point is estabkshed and maintained byway of the lu interface for each connection with a mobile terminal. The access point is assigned certain transmission identifiers for signaling and user traffic information. Because certain nodes, such as RNC nodes, are defmed as logical units performing certain functions, two RNCs may be implemented on different physical nodes or on the same physical node. The present invention takes advantage of the logical rather than physical definition of an RNC. In one preferred embodiment, a single physical RNC node supports plural logical RNCs. In another embodiment, the logical RNCs may be implemented using physically separate RNC nodes using a Server-Gateway RNC implementation described earker. But for this example embodiment, described below in conjunction with Fig. 5, one physical RNC node supports two (or more) logical RNCs using common hardware and software resources.

Referring to the flowchart diagram in Fig. 5, initially a call connection is established between an external network, e.g , the PSTN 120, and a mobile terminal 300 via an old MSC, an old RNC, and base station X (block 400). Each existing MSC may be assigned a particular location area that usually includes multiple cells and/or base stations. The new MSC is established to take over control of some of the base stations currently controlled by the old MSC including base station X (block 404). The location area of the old MSC may be divided into two location areas, or alternatively, a new location area may be established with associated base stations or cells (block 402) This may be accomplished by a human operator who couples a laptop computer or other programming device to the old MSC and the old RNC to configure the new location area When a new MSC is established, it is assigned a new signaling ID by the human operatoi so that new signaling links can be established with the existing core network nodes. A new, logical RNC is defined on an existing RNC node/platform (block 406) The human operator uses a laptop or other device coupled to the existing RNC platform and assigns a new identifier for the new logical RNC as well as the identity of its controlling MSC, i.e., the new MSC. In addition to the RNC and MSC identities and the location area(s) and/or cell(s) associated with the new RNC, interface access points and signaling end point identifiers for the lu interface are defined to allow the new RNC and the new MSC to interact and provide a user plane for new mobile connections. Additional implementation-specific information, such as configuration of hardware and software resources, and assignment of resources may also need to be set up. One or more base stations transferred byway of the newly- assigned or created location areas are associated with the new RNC and the new MSC (block 408).

Information is broadcast from the newly- assigned base stations over a broadcast channel to identify the new RNC identity as well as the new location area identity associated with the new RNC (block 410). After the broadcast, new traffic connections may be estabkshed using the new RNC. Idle mobile terminals located m the new location area announce themselves as being present in the new location area (block 412).

Because the same RNC hardware and other resources including, e.g., state mformation, connections through internal and external switches, data buffers, etc., are employed in the new logical RNC, each transferred connection remains physically and logically the same in the new RNC as it was in the old RNC Only the control of the base station through winch the connection passes is transferred to the new RNC. The new RNC initiates connection, e.g , disconnect. In this way, there is no interruption or disruption to the active call connections. Once the new RNC is established, subsequent reallocattons of base stations between the two RNCs configured on the same node may be performed transparently, if desired (block 414). When an active connection is completed at call termination, the idle mobile terminal announces its presence to the new MSC and new RNC as in block 412

While the pi esent invention has been described with respect to particular example embodiments, those skilled in the art will recognize that the present invention is not limited to those specific embodiments described and illustrated herein. Different formats, embodiments, adaptations besides those shown and described, as well as many modifications, vaπations and equivalent arrangements may also be used to implement the invention. While systematic bits and parity bits are given as examples of important and less important bits, other groups and types of bits may be identified as important and less important. Accordingly, it is intended that the invention be limited only by the scope of the claims appended hereto

Claims

WHAT IS CLAIMED IS:

1. In a radio communications network (10) coupled to an external network and including a first network service node (12) coupled to a first radio network controller (18), a first base station (22) coupled to the first radio network controller, where mobile radio terminals (26) communicate over a radio mterface with the first base station, a method including setting up a connection between a mobile radio terminal and the external network by way of the first network service node, the first radio network controller, and the first base station, the method characterized by determining that the configuration of the radio communications network is to be changed; establishing a second radio network controller (20); and transferring the connection from the first radio netwoik controllei to the second radio network controller, wherein the transfer is made without interruption.

2. The method in claim 1, further comprising providing a second network service node for the radio communications network, and transferring control of the connection from the first network service node to the second network service node.

3. The method in claim 1, further comprising: associating the first base station with the second radio network controller.

4. The method in claim 3, further comprising- sometime after establishing the second radio network controller and associating the first base station with the second radio network controller, transferrmg control of a second base station from the first radio network controller to the second radio network controller, wherein an active connection being supported by the second base station is not interrupted dunng the transfer of control to the second base station.

5. The method in claim 1, wherein the second radio network controller is associated with the first radio network controller.

6. The method in claim 5, wherein the second radio network controller is a logical radio network controller that uses resources also used by the first radio network controller.

7. The method in claim 1, wherein the configuration change is one of the following: adding, splitting, or rearranging of base station cells.

8. The method in claim 1, wherein the connection transfer is transparent to the mobile radio terminal and the external network.

9. The method in claim 1, further comprising: assigning the second radio network controller an identifier, and associating one or more cells associated with the base station with the second radio network controller.

10. The method in claim 1, further comprising: establishing a second new network service node, and transferring control of one or more base stations (22, 24) from the first network service node to the second network service node, wherein the transfer is performed without disrupting the connection, and wherein the transferred connection is supported in the radio network by the second network service node coupled to the second radio network controller which is coupled to the one or more base stations.

11. The method in claim 10, wherein the one or more base stations broadcast an identifier associated with the second radio network controller.

12. The method in claim 10, wherein the second radio network controller is associated with the first radio network controller.

13. The method in claim 12, wherein the second radio network controller is a logical radio network controller that uses resources also used by the first radio network controller.

14. The method in claim 10, further comprising: establishing a new coverage area associated with the second radio network controller that includes the one or more base stations.

15. The method in claim 14, further comprising: transferring control of another base station from the first network service node to the second network service node without disrupting active connections supported by the other base station.

16. A radio network (10) comprising a first radio base station (22) communicating with a mobile radio terminal (26) over a radio interface, and a first radio network controller (18) coupled to the first radio base station for supporting a communication between the mobile radio terminal and an external network, characterized by: a second radio network controller (20), newly-established in the radio network, assuming control of the communication in the radio network from the first radio network controller without disrupting the communication.

17. The radio network in claim 16, further comprising: a first radio network control node (12) coupled to the first radio network controller and initially interfacing with the external network to support the communication; a second, newly-created control node (14) interfacing with the external network to support the communication after the second radio network controller assumes control of the communication from the first radio network controller.

18. The radio network in claim 17, wherein the first and second radio network controllers are mobile switching nodes.

19. The radio network in claim 17, wherein the first and second radio network controllers are packet switching nodes.

20. The radio network in claim 16, wherein a second base station (24) associated with the first radio network control node is transferred to the second radio network controller without disruption of active communications with mobile terminals.

21. The radio network in claim 16, wherein the second radio network controller is a logical radio network controller that uses resources also used by the first radio network controller.

22. The radio network in claim 16, wherein the second radio network controller is a logical radio network controller configured on the same physical node as the first radio network controller.

23. The radio network controller in claim 16, wherein the second radio network controller is a logical network controller configured on a physical node different than the first radio network controller.