WO1999049675A2

WO1999049675A2 - Method and system for testing the availability of channels in a telecommunication system

Info

Publication number: WO1999049675A2
Application number: PCT/FI1999/000245
Authority: WO
Inventors: Petri Saarela
Original assignee: Nokia Networks Oy
Priority date: 1998-03-25
Filing date: 1999-03-24
Publication date: 1999-09-30
Also published as: FI107428B; FI980671A0; AU3037699A; FI980671A; WO1999049675A3; AR017476A1

Abstract

Method and system for testing the availability of channels in a telecommunication system, said telecommunication system comprising a local exchange (LE), an access node (AN) connected to a local exchange, a wireless communication system (WLL) connected to the access node, a terminal (MS) communicating via the wireless communication system with the access node (AN), the terminal (MS) having a limited mobility area (3) within predetermined cell areas of the wireless communication system so that a call can be set up from within all the cell areas comprised in the mobility area, in which method calls are transmitted via the most suitable cell area, i.e. link cell (1), and a cell (2) adjoining the link cell within the mobility area has been defined as an adjacent cell to the link cell and/or included in its BCCH allocation list, in which case said cell area (2) has been defined as a stand-by cell or the link cell (1). According to the invention, the availability of the terminal (MS) is tested during the call via the stand-by cells and/or adjacent cells comprised in the mobility area. The measurement results are reported in the access node (AN).

Description

METHOD AND SYSTEM FOR TESTING THE AVAILABILITY OF CHANNELS IN A TELECOMMUNICATION SYSTEM

The present invention relates to a method as defined m the preamble of claim 1 and to a system as defined in the preamble of claim 8 for testing the availability of channels m a telecommunication system. LL system ( LL, Wireless Local Loop) refers to a system in which the subscriber is connected to a telephone network via a wireless communication system. A subscriber interface is achieved by using a special communication terminal. In principle, the terminal functions like a mobile telephone known in itself, but it can be assigned a limited mobility area within which it can function. The wireless communication system can be implemented using mobile communication technology, e.g. GSM technology (GSM, Global System for Mobile Communications) .

As the communication terminal used by a WLL subscriber is typically a fixed terminal, its ability to function is heavily dependent on the presence of base station coverage. If the base station m the normal coverage area of the terminal is disabled m consequence of a fault or an operating action and the coverage of the adjacent cell is not sufficient to allow connection setup, the result is an interruption in the use of the terminal. Normally, when a call is made from a terminal, it is not possible to select the cell through which the call is to be transmitted. The ter- mmal selects the one of the cells that provides the best communication. Thus, measurement results during a call can only be obtained for the cell on which the terminal has been locked.

The ob ect of the present invention is to eliminate the drawbacks described above. A specific object of the present invention is to disclose a new type of method for improving the reliability of a WLL system via testing of a stand-by system.

As for the features characteristic of the invention, reference is made to the claims. The telecommunication system of the invention comprises a local exchange connected to an access node. The access node communicates with a terminal via a wireless communication system. The mobility area of the terminal is limited in accordance with the WLL system, comprising a number of predetermined cell areas. Of the cell areas within the mobility area, the one that provides the best communication is selected as the link cell for the terminal. A list of cells adjacent to the link cell contains the BCCH frequencies (BCCH, Broadcast Control Channel) of those of the adjoining cells which have been defined as adjacent cells to the cell area in question. A BCCH allocation list contains those BCCH frequencies of adjoining cell areas which the terminal is to measure. A cell area included in the list of adjacent cells and/or in the BCCH allocation list for the link cell can be defined as a stand-by cell for the link cell .

According to the invention, availability of the terminal is tested during a call via stand-by cells and/or adjacent cells defined in the mobility area .

In a preferred embodiment of the invention, a test call is made e.g. to a suitable test number, whereupon the access node tests the communication per- formance via each cell area defined as a stand-by cell. The access node performs a hand-over via each cell area defined as a stand-by cell.

In a preferred embodiment of the invention, a test call is made e.g. to a suitable test number, whereupon the access node tests the communication performance via each cell area defined as a stand-by cell . The access node performs a channel hand-over via each cell area defined as a stand-by cell. This is done to ensure that the mobility area is functional.

In a preferred embodiment of the invention, subscriber monitoring is activated in the access node, producing as a result a report of measurement results concerning the link cell used and its stand-by cells, obtained during the call.

In a preferred embodiment of the invention, subscriber monitoring is activated in the access node, producing as a result a report of measurement results concerning the link cell used and its adjacent cells, obtained during the call.

In a preferred embodiment of the invention, the mobility area is verified by moving the terminal within the limits of the mobility area during the testing, thus avoiding unexpected disturbances that may result e.g. from topographic variations in the area.

In a preferred embodiment of the invention, the wireless communication system used is based on a digital mobile communication system, preferably the GSM system.

The system of the invention comprises means for testing the availability of the terminal during a call via stand-by cells and/or adjacent cells comprised in the mobility area.

In a preferred embodiment, the system comprises means for making a test call to allow the access node to test the communication performance via a cell area defined as a stand-by cell.

In a preferred embodiment, the system comprises means for making a test call to allow the access node to test the communication performance via a cell area defined as an adjacent cell. In a preferred embodiment, the system comprises means for activating subscriber monitoring in the access node, producing a report of measurement re- suits concerning the link cell used and its stand-by cells, obtained during the call.

In a preferred embodiment, the system comprises means for activating subscriber monitoring in the access node, producing a report of measurement results concerning the link cell used and its adjacent cells, obtained during the call.

In a preferred embodiment, the system comprises means for verifying the mobility area when the terminal is moved within the limits of the mobility area during the testing.

The invention provides the advantage that the method can be used to test whether the terminal, mobility area and stand-by cells are functional during installation or subsequently after possible changes in wireless communication conditions.

In the following, the invention will be described by the aid of a few examples of its embodiments by referring to the attached drawing, wherein Fig. 1 presents a diagram representing an example of a system in which the method of the invention is used,

Fig. 2 presents an example of the method of the invention, and Fig. 3 presents a diagram representing a detail of a system according to an embodiment of the invention.

Fig. 1 shows a wireless local loop WLL, in which subscriber terminals MS are connected over a wireless link via a base station BS to an access node AN and from the access node to a wired network local exchange LE via a V5 interface consistent with the ETS 300 347-1 standard.

Open interfaces (V5.1 and V5.2) between an access node and a telephone exchange are defined in the ETSI (European Telecommunications and Standards Institute) standards of the ETS 300 324 and ETS 300 347 series. V5 interfaces enable subscribers belonging to a physically separate access network, which may be a wired or a wireless network, to be connected using a standard telephone exchange interface . In Fig. 2, a mobile station 1 is depicted within its link cell 1. The base station in the link cell 1 is BS1. Base station BS2 is surrounded by cell area 2. Cells 1 and 2 together form a mobility area 3. The mobility area may also consist of a larger number of cells.

Cell area 2 is defined as a stand-by cell for the link cell 1. A cell area defined as a stand-by cell must be comprised in a list of adjacent cells and/or a BCCH allocation list for the link cell. Ac- cording to the invention, availability of the terminal MS is tested during a call via stand-by cells and/or adjacent cells. The system comprises testing means 4, which are e.g. software processes in the access node AN. Included in the list of adjacent cells are also cells not comprised in the mobility area but adjoining to it. The access node AN ignores any information relating to these cells.

The testing is carried out in conjunction with installation or during use by making a test call to a certain test number from the mobile station MS. This activates means 5 and 7, such as e.g. suitable software process, in the access node AN. During this test call, the access node AN performs a handover at certain intervals, first to a first stand-by cell, from which the call is further handed over to the next stand-by cell until all cells defined as stand-by cells have been tested. In this way, the communication performance via each cell area defined as a stand-by cell is established. This call to a certain test number activates monitoring means 7 in the access node AN, producing a report of measurement results obtained during the call for two directions, from the base station BS to the terminal MS and vice versa.

When a call is made to a second test number, a handover sequence as above is obtained but this time relating to the mobility area defined for the terminal MS, activating means 5 and 6, such as e.g. suitable software processes, in the access node AN. The access node AN performs a handover with each cell comprised m the adjacent cell definitions for the link cell 1 within the mobility area 3 while the terminal MS remains stationary. By testing the terminal MS via all the cells within the mobility area, the operation of the terminal MS m the entire mobility area can be verified, using means 9. In this case, the actual link cell is changed and handovers are again performed in a corresponding manner. To ensure successful handovers m all directions, adjoining cell areas within the mobility area must be included in each other's adjacent cell definitions. A call to this second test number also activates subscriber monitoring means 8 in the access node, producing reports as above. In an embodiment of the invention, the terminal is moved within the mobility area during the testing, thus making it possible to test the effects of local disturbances, e.g. topographic variations, on signal levels in the mobility area.

Fig. 3 presents a diagram representing a detail of a system according to an embodiment of the invention. Fig. 3 shows a network management system NMS connected to an access node AN. In this example, stand-by cells are defined by means 10 via the network management system NMS. In conjunction with the definition of a stand-by cell, a limit value for the minimum acceptable signal level is also defined. The limit value is transmitted to means 14 analysing stand-by cell availability. If necessary, the analysis means transmit a message to alarm means 13. The network man- agement system NMS comprises means for receiving an alarm from the access node AN.

The access node AN is provided with means 12 for sending a cell list to the terminal MS. The termi- nal MS is provided with means 16 for receiving a cell list, means 17 for measuring the signal level and means 18 for sending measurement data to the access node AN. The access node AN comprises means 15 for receiving measurement data from the terminal MS. The invention is not restricted to the examples of its embodiments described above, but many variations are possible within the scope of the inventive idea defined by the claims.

Claims

1. Method for testing the availability of channels in a telecommunication system comprising a local exchange (LE) , an access node (AN) connected to a local exchange, a wireless communication system (WLL) connected to the access node, a communication terminal (MS) communicating via the wireless communication system with the access node (AN) , the terminal (MS) having a limited mobility area (3) within predetermined cell areas of the wireless communication system so that a call can be set up from within all the cell areas comprised in the mobility area, in which method calls are transmitted via the most suitable cell area, i.e. link cell (1), and a cell (2) adjoining the link cell within the mobility area has been defined as an adjacent cell to the link cell and/or included in its BCCH allocation list, in which case said cell area (2) has been defined as a stand-by cell for the link cell (1) , characteri sed in that the availability of the terminal (MS) is tested during the call via the stand-by cells and/or adjacent cells comprised in the mobility area.

2. Method as defined in claim 1, characteri sed in that a test call is made, whereupon the access node (AN) tests the communication performance via a cell area defined as a stand-by cell.

3. Method as defined in claim 1, characterised in that a test call is made, whereupon the access node (AN) tests the communication perform- ance via a cell area defined as an adjacent cell.

4. Method as defined in any one of claims 1 - 3, characterised in that subscriber monitoring is activated in the access node (AN) , producing as a result a report of measurement results concerning the cell used and its stand-by cells, obtained during the call.

5. Method as defined in any one of claims 1 - 3, characterised in that subscriber monitoring is activated in the access node (AN) , producing as a result a report of measurement results concerning the cell used and its adjacent cells, obtained during the call.

6. Method as defined in any one of claims 1 -

5, characterised in that the mobility area (3) is verified by moving the terminal within the lim- its of the mobility area during the testing.

7. Method as defined in any one of claims 1 -

6, characteri sed in that the wireless communication system used is based on the GSM system.

8. System for eliminating interruptions in the use of a telecommunication system, said telecommunication system comprising a local exchange (LE) , an access node (AN) connected to a local exchange, a wireless communication system (WLL) connected to the access node, a terminal (MS) communicating with the ac- cess node (AN) via the wireless communication system, the terminal (MS) having a limited mobility area (3) within predetermined cell areas of the wireless communication system so that a call can be set up from within all the cell areas comprised in the mobility area, in which system calls are transmitted via the most suitable cell area, i.e. link cell (1), and a cell (2) adjoining the link cell within the mobility area has been defined as an adjacent cell to the link cell and/or included in its BCCH allocation list, in which case said cell area (2) has been defined as a stand-by cell for the link cell (1), characte ri sed in that the system comprises means (4) for testing the availability of the terminal (MS) during a call via stand-by cells (2) and/or adjacent cells (2) comprised in the mobility area.

9. System as defined in claim 8, characterised in that the system comprises means (5, MS) for making a test call, causing the access node (AN) to test the communication performance via a cell area defined as a stand-by cell (2) .

10. System as defined in claim 8, char - ac t eri s ed in that the system comprises means (6,

MS) for making a test call, causing the access node (AN) to test the communication performance via a cell area defined as an adjacent cell (2) .

11. System as defined in any one of claims 8 - 10, charact eri s ed in that the system comprises means (7) for activating subscriber monitoring in the access node (AN) , producing as a result a report of measurement results concerning the cell (1) used and its adjacent cells (2), obtained during the call.

12. System as defined in any one of claims 8

- 11, charact eri s ed in that the system comprises means (8) for activating subscriber monitoring in the access node (AN) , producing a report of meas- urement results concerning the cell used and the adjacent cells, obtained during the call.

13. Method as defined in any one of claims 8

- 12, characteri s ed in that the system comprises means (9) for verifying the mobility area when the terminal (MS) is moved within the limits of the mobility area (3) during the testing.