WO1995023474A2

WO1995023474A2 - Method for signalling a poor radio connecion

Info

Publication number: WO1995023474A2
Application number: PCT/FI1995/000068
Authority: WO
Inventors: Jussi Sarpola; Vesa HEIKKILÄ; Ari-Pekka Taskila; Hannu Asujamaa; Heimo PENTIKÄINEN; Olli Liinamaa; Pekka Rusi; Seppo Vehmer
Original assignee: Nokia Telecommunications Oy
Priority date: 1994-02-18
Filing date: 1995-02-14
Publication date: 1995-08-31
Also published as: FI940783A0; WO1995023474A3; AU1708295A; FI940783A

Abstract

The present invention relates to a method for signalling a poor radio connection to the user of a subscriber station (1) of a radio system which implements a wireless local loop, said subscriber station comprising a terminal equipment (3) and a user interface (2), the terminal equipment (3) comprising receiving means for receiving signals transmitted on the calling channel of the radio system. In order to signal a disturbed radio connection in a manner that is simple and easy to understand if the terminal equipment (3) does not hear the calling channel of the radio system when the user interface (2) switches to an off-hook state, the generation and application of a predetermined voice-frequency signal to the subscriber station (1) user is started via the user interface (2). The invention also relates to a subscriber station by which the method of the invention can be utilized.

Description

Method for signalling a poor radio connection

The present invention relates to a method for signalling a poor radio connection to the user of a subscriber station of a radio system which implements a wireless local loop, said subscriber station comprising a terminal equipment and a user interface, the terminal equipment comprising receiving means for receiving signals transmitted on the calling channel of the radio system. The invention further relates to a subscriber station of a radio system which implements a wireless local loop, said subscriber station comprising a terminal equipment and a user interface, the terminal equipment comprising receiving means for receiving signals transmitted on the calling channel of the radio system.

The present invention relates to a WLL system (Wireless Local Loo ), i.e. to a radio system which implements a wireless local loop and in which subscriber stations are connected by a radio link via base stations to the public switched telephone network (PSTN) . It is possible to connect any type of conventional telephone set to a WLL system via a special terminal equipment, the radio path being thus invisible as regards the user.

In this context, a subscriber station refers to the equipment that a user has at his disposal for transmitting and receiving telecommunication signals. In the case of the WLL system, a subscriber station includes a WLL terminal equipment, which consists of a radio section and a teleadapter (to which a user interface such as a telephone is connected), and a user interface connected to the terminal equipment, i.e. a telephone, telefax, computer/modem combination or similar. In the present application, an off-hook state is used to refer to a state which is created when for instance a phone user lifts the receiver to make a call. The subscriber station of the WLL system is arranged to continuously listen to the calling channel of the radio system in order to detect calls possibly directed to the subscriber station. In disturbance situations, when the subscriber station does not hear the calling channel of the radio system, the subscriber station must be able to signal the created disturbance situation to the station user. Since any telephone set adapted to be used in the public telephone network can be used as a user interface in the WLL system, the signalling of a disturbance situation must be such that it requires no special characteristics of the user interface.

The object of the invention is to provide a method by means of which a subscriber station can signal a disturbance in the radio connection in a manner that is simple and easy to understand as regards the user. These objects are achieved with the method of the invention, characterized in that if the terminal equipment does not hear the calling channel of the radio system when the user interface enters an off-hook state, the generation and application of a predetermined voice- frequency signal to the subscriber station user is started via the user interface.

The invention is based on the idea that when a disturbance caused in the radio connection is signalled to a subscriber station user by sound signals when the subscriber station user tries to use the subscriber station, no special characteristics are required of the user interface in order to signal the alarm.

In a preferred embodiment of the method of the invention, the "busy" tone used in the public switched telephone network is used as the sound signal. The most significant advantage of this preferred embodiment of the invention is that the telephone user recognizes the sound signal immediately and understands that it is not possible to use the phone at that particular moment. Correspondingly, if for instance a telefax comprising means for identifying a sound signal applied thereto is used as a user interface, this apparatus recognizes the "busy" tone generally used in the telephone network and operates as it is programmed to do in that situation.

The invention also relates to a subscriber station for implementing the method of the invention. The subscriber station of the invention is characterized in that the terminal equipment comprises a signal generator responsive to the receiving means and the user interface for generating and applying a predetermined voice-frequency signal to the user interface if the receiving means does not hear the calling channel when the user interface enters an off-hook state. The preferred embodiments of the method and system of the invention are disclosed in the appended dependent claims 2 - 3 and 5 - 6.

In the following, the invention will be described by means of its first preferred embodiment with reference to the accompanying figure, which shows a block diagram of a part of the WLL system in which the method of the invention is applicable. The figure shows a subscriber station 1, which comprises a telephone 2 and a terminal equipment 3. The telephone 2 shown in the figure is a conventional telephone that can be connected to the public telephone network. Instead of the telephone 2, it is possible to use quite as well some other user interface such as a telefax or computer/modem combination in the system shown in the figure. In the figure, the telephone 2 and the terminal equipment 3 are connected by a two-wire line 4, via which signals can be transmitted between the terminal equipment and the telephone. The terminal equipment 3 comprises signal processing means for fitting a speech path onto the radio channel. Signal processing means of this type are for instance a radio section, which comprises an antenna 8, a radio transmitter and a radio receiver, and a teleadapter, which adapts the radio section for the conventional telephone 2.

The subscriber station 1 communicates with a base station 5 (three base stations BS are shown in the figure) with radio-frequency signals via the antenna 8, calls being transmitted via this base station to a subscriber network element 6 and further to the PSTN (Public Switched Telephone Network), i.e. to a fixed telephone network 7.

The base stations 5 correspond to the parts of the NMT-450i (Nordisk Mobil Telefon) cellular radio system. As regards signalling, the subscriber station 1 thus operates like a conventional subscriber station of the NMT-450i system.

The receiver belonging to the radio parts of the terminal equipment 3 is arranged to continuously listen to the calling channel of the base station 5 in order to detect calls directed to the subscriber station 1. When the user of the subscriber station 1 lifts the receiver of the telephone 2, the terminal equipment 3 observes that the user interface enters an off-hook state. The terminal equipment 3 thus immediately verifies whether its receiver hears the calling channel of the radio system. If the calling channel is not audible for some reason, the signal generator located in the terminal equipment starts to generate and apply a voice-frequency signal to the user interface, i.e. to the telephone 2. This voice-frequency signal is preferably the same as the "busy" sound signal used in the public switched telephone network, i.e. a discontinuous 425 +/- 25 Hz -frequency signal, in which the length of the tone sequences and the silent sequences between them is 300 ms.

It will be apparent that the above-mentioned description and the figure relating to it are only intended to illustrate a preferred embodiment of the method and system of the invention without restricting the invention to it. The preferred embodiments of the method and system of the invention may thus vary within the scope of the appended claims.

Claims

1. A method for signalling a poor radio connection to the user of a subscriber station (1) of a radio system which implements a wireless local loop, said subscriber station comprising a terminal equipment (3) and a user interface (2), the terminal equipment (3) comprising receiving means for receiving signals transmitted on the calling channel of the radio system, c h a r a c t e r i z e d in that if the terminal equipment (3) does not hear the calling channel of the radio system when the user interface (2) enters an off- hook state, the generation and application of a predetermined voice-frequency signal to the subscriber station (1) user is started via the user interface (2).

2. A method according to claim 1, c h a r ¬ a c t e r i z e d in that the user interface (2) consists of a telephone set.

3. A method according to claim 1 or 2, c h a r a c t e r i z e d in that the voice-frequency signal is a "busy" tone.

4. A subscriber station (1) of a radio system which implements a wireless local loop, said subscriber station comprising a terminal equipment (3) and a user interface (2), the terminal equipment (3) comprising receiving means for receiving signals transmitted on the calling channel of the radio system, c h a r a c ¬ t e r i z e d in that the terminal equipment (3) comprises a signal generator responsive to the receiving means and the user interface (2) for generating and applying a predetermined voice-frequency signal to the user interface (2) if the receiving means does not hear the calling channel when the user interface (2) enters an off-hook state.

5. A subscriber station according to claim 4, c h a r a c t e r i z e d in that the user interface (2) is a telephone set.

6. A subscriber station according to claim 4 or 5, c h a r a c t e r i z e d in that said predetermined voice-frequency signal is a "busy" tone.