WO1997024009A1

WO1997024009A1 - Simulation of distance between base station and mobile terminal

Info

Publication number: WO1997024009A1
Application number: PCT/SE1996/001444
Authority: WO
Inventors: Anders Perjons
Original assignee: Telia Ab
Priority date: 1995-12-22
Filing date: 1996-11-11
Publication date: 1997-07-03
Also published as: SE9504627L; SE9504627D0

Abstract

The invention relates to a device and a procedure at a cellular radio communication system for simulation of that a mobile telephone is at a big distance from a base station. This simulation can be effected by that one delays a transmitted RF-signal between the mobile telephone and the base station. The delay is effected in such a way that the RF-signal is mixed down to an MF-signal, at which the MF-signal is delayed by means of a delay device. After the delay of the MF-signal, one again mixes it up to an RF-signal.

Description

TITLE OF THE INVENTION: SIMULATION OF DISTANCE BETWEEN

BASE STATION AND MOBILE TERMINAL

TECHNICAL FIELD

The present invention relates to a device and a procedure at a cellular radio communication system for simulation of that a mobile terminal is at a big distance from a base station.

PRIOR ART

New functions are continuously coming within the mobile telephony which operators willingly want to verify as a part of the quality work. A number of new functions which are coming in GSM need equipment which can simulate delay of the radio interface which corresponds to a wave propagation from some kilometres to 150 kilometres. Such equipments do not exist commercially on the market today, and to make delays directly on radio signals is very difficult.

To make measurements on extended cells (cells with a radius of more than 35 kilometres) is required that the mobile terminal is at a big distance from the base station, which includes both practical and technical problems. The aim with the present invention consequently is to effect a device and a procedure which makes possible simulation of that the mobile terminal is at a big distance from the base station. This in order to make measurements on extended cells in laboratory environment.

SUMMARY OF THE INVENTION

The above mentioned aim is effected by means of a device and a procedure which is defined by the characterizing part of the patent claim 1 respective 10. Further characteristics of the present invention are presented in the dependent patent claims.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

The invention relates to a test equipment which shall be used to simulate that a mobile terminal, preferably an ordinary mobile telephone, is at a big distance from a base station.

This simulation is necessary to make it possible to perform measurements on extended cells in a laboratory environment. One more application of the invention is to make measurements of changes of distance between a base station and a mobile terminal in a laboratory environment.

So far the above described measurements have been performed by that the measurement operator with mobile telephone has went far away, for instance 50 kilometres, from the base station, at which measurements on the base station and the mobile telephone has been performed. This method is both expensive and very unpractical.

By means of the present invention these measurements can be performed in a research laboratory. New technology regarding extended cells can consequently be directly tested and verified in a research laboratory. This results in that new technology more rapidly can be put on the market, and that measurements on extended cells become cheaper to perform. The test equipment according to the following invention functions in such a way that it mixes down a radio frequency signal (RF-signal) to an intermediate frequency signal (MF-signal) on 70/71 MHz by means of a mixer. The MF-signal is then delayed for just any time interval by means of a delay device depending on which distance between the base station and the mobile telephone one wants to simulate.

After that the MF-signal is mixed up to the normally utilized RF-signal. For the sake of symmetry, the delay is performed both on uplink and downlink.

The delay device can consist of a number of carefully selected filters with amplifiers for different delay values which are cascade connected by means of utilization of switches, which makes possible different delays such as for instance 0-150 μs in steps of 1 μs.

The delay device also can be arranged in a way that the MF-signal is first A/D-converted with the intention to after that be delayed for just any time interval in a shift register, whereupon the delayed MF-signal is D/A-converted. One more embodiment of the delay device is to cascade connect a number of acoustic surface wave filters (SAW- filters) which then will effect wanted delays. Surface wave filters have a comparatively long time delay which can be utilized. A ground for delay can be arranged with a BAW, Bulk Acoustic Wave delay line, for instance 150 μs. One way to realize the present invention is to utilize a modified commercial GSM-repeater which breaks up the MF- signal on 70/71 MHz, which signal is then delayed by means of one of the above mentioned delay devices. The delay device shall of course be electronically controllable for the different delays that shall be used.

The above described is only to be regarded as advantageous embodiments of the invention, and the extent of protection of the invention is only defined by what is indicated in the following patent claims.

Claims

PATENT CLAIMS

1. Device at a cellular radio communication system for simulation of that a mobile terminal is at a big distance from a base station, c h a r a c t e r i z e d in that it effects delay of a transmitted RF-signal between said mobile terminal and said base station.

2. Device according to patent claim 1, c h a r a c t e r i z e d in that it frequency transposes the RF-signal to an MF-signal, at which the MF-signal is delayed by means of a delay device, after which the device again frequency transposes the delayed MF-signal to a delayed RF-signal.

3. Device according to patent claim 2, c h a r a c t e r i z e d in a mixer which effects the frequency transposition.

4. Device according to any of the patent claims 2 or 3, c h a r a c t e r i z e d in that the delay device consists of a number of filters with amplifiers for different delay values which are cascade connected by means of utilization of switches, which makes possible different delays such as for instance 0-150 microseconds in steps of 1 microsecond.

5. Device according to the patent claims 2 or 3, c h a r a c t e r i z e d in that the delay device consists of cascade connected acoustic surface wave filters and/or BAW, Bulk Acoustic delay line.

6. Device according to any of the patent claims 2 or 3, c h a r a c t e r i z e d in that the delay device consists of an A/D-converter, shift registers with different lenghts, and a D/A-converter.

7. Device according to any of the patent claims 2-6, c h a r a c t e r i z e d in that said MF-signal is located to the intermediary frequency 71 MHz, alternatively 70 MHz.

8. Device according to any of the patent claims 2-7, c h a r a c t e r i z e d in that it effects delay on both uplink and downlink.

9. Device according to any of the patent claims 2-8, c h a r a c t e r i z e d in that a modified repeater is utilized as mixer.

10. Procedure at a cellular radio communication system for simulation of that a mobile terminal is at a big distance from a base station, c h a r a c t e r i z e d in that a transmitted RF-signal between said mobile terminal and said base station is delayed.

11. Procedure according to patent claim 10, c h a r a c t e r i z e d in that the RF-signal is mixed down to an MF-signal, which MF-signal is delayed by means of a delay device, at which the delayed MF-signal is again mixed up to a delayed RF-signal.

12. Procedure according to patent claim 11, c h a r a c t e r i z e d in that the delay of the MF- signal is effected on both uplink and downlink.

13. Procedure according to the patent claims 11 or 12, c h a r a c t e r i z e d in that said delay is effected by a number of filters with amplifiers for different delay values, which filters are cascade connected by means of utilization of switches, which makes possible different delays such as for instance 0-100 microseconds in steps of 1 microsecond.

14. Procedure according to any of the patent claims 11 or 12, c h a r a c t e r i z e d in that the delay is effected by means of cascade connected acoustic surface wave filters and/or acoustic delay line.

15. Procedure according to any of the patent claims 11 or 12, c h a r a c t e r i z e d in that said delay is effected by that the MF-signal is A/D-converted and then delayed in a shift register with just any length, after which the signal is D/A-converted to a delayed MF-signal.

16. Procedure according to any of the patent claims 11-

15, c h a r a c t e r i z e d in that a modified repeater is utilized to break up the MF-signal on 71 MHz, after which delay equipment is connected.

17. Procedure according to any of the patent claims 10-

16, c h a r a c t e r i z e d in that it is utilized to perform measurements on cells with extended cell radius in a laboratory environment.