GB2237478A

GB2237478A - Radio telephony system

Info

Publication number: GB2237478A
Application number: GB8923808A
Authority: GB
Inventors: Richard J Barnett; Robert W Rowe
Original assignee: British Aerospace PLC
Current assignee: BAE Systems PLC
Priority date: 1989-10-23
Filing date: 1989-10-23
Publication date: 1991-05-01
Also published as: GB8923808D0

Abstract

A radio telephony system includes a central switching station 1 linked to one or more radio base stations 2. One or more remote translator stations 4 is linked to the or each base station 2 so that the or each station 2 has its own associated directly linked remote translator station or stations 4. <IMAGE>

Description

RADIO TELEPHONY SYSTEM This invention relates to a radio telephony system.

A known type of radio telephony system is the cellular radio telephony system which allows mobile users to communicate with each other on the system via a series of low power radio base stations. Each station covers one of a group of adjoining 'cells' which together form an overall coverage area, and groups of stations are coupled to a central switching station, for example by land line.

Whilst this form of system can provide effective links between users in the same cell and over large areas. it is expensive, requiring high transmission powers, and does not allow mobile telephone use within buildings.

This is due to the use in the known cellular system of frequencies of 900 MHz or less for good propagation conditions over the large cell areas coupled with high transmit power mobile user stations. As conventional cellular systems are designed to provide services mainly to vehicle based terminal equipment which can operate at high transmit powers they can cover large areas provided in-building coverage, with its attendant high penetration losses, is excluded.

The use of large cells allows a widely separated distribution of radio base stations supporting these cells. The -large area supported by each base station and the number of subscribers located within this area justify the capital required to provide a base station.

However, the Personnel Communication Networks (PCN) proposed for operation in the United Kingdom will be allocated bandwidth in the 1.7 to 1.9 GHz region. At this frequency the propagation characteristics are worse than those of existing systems. This combined. with the need to provide in-building service requires that the cell sizes used by the PCN systems are much smaller than the conventional cellular systems operating at 900 MHz. With the use of small cells, the coverage of large areas requires a much larger number of cells. Using conventional cellular hardware this would require a radio base station per cell and would require a very heavy capital investment.

There is thus a need for a radio telephony system which reduces the costs associated with the provision of a Personal Communications Network by a reduction in the hardware per cell, and consequently a reduction in the cost per cell.

According to one aspect of the present invention there is provided a radio telephony system for providing telephone facilities, including a central switching station, one or more radio base stations linked to the central switching station, and one or more remote translator stations linked to the or each radio base station so that the or each radio base station has its own associated directly linked remote translator station or stations.

Preferably the or each remote translator station includes means for the reception and transmission of signals at a first frequency from or to a user, means for modulation and demodulation of signals at said first frequency to a second frequency and means for reception and transmission of signals at the second frequency from or to the associated radio base station.

Conveniently the system is constructed to operate at a first frequency of 1.8 GHz and at a second frequency of 38 GHz.

Advantageously the system includes a plurality of cordless, digital, two way, mobile user terminals linkable to the or each remote translator station.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a block diagram of a conventional standard cellular network configuration not according to the present invention, Figure 2 is a block diagram of a radio telephony system according to a first embodiment of the present invention showing the network configuration, and Figure 3 is a diagrammatic representation of a remote translator station for use in the radio telephony system of Figure 2.

A radio telephony system according to a first embodiment of the present invention, as shown in Figure 2 of the accompanying drawings, includes a central switching station 1, one or more radio base stations 2 linked to the central switching station in any convenient manner such as by pulse coded modulated terrestrial links 3 and one or more remote translator stations (RTS) 4, linked to the or each radio base station 2, so that the or each radio base station 2 has its own associated directly linked remote translator station or stations 4. In the illustrated embodiment of Figure 2, two radio base stations 2 are shown, one of which is provided with six remote translator stations 4 and the other of which is provided with three remote translator stations 4.

For comparison purposes, Figure 1 shows a conventional standard cellular network configuration in which a plurality of radio base stations 2 are coupled or linked by pulse coded modulated terrestrial links to a single central switching station 1.

In the embodiment of the invention shown in Figures 2 and 3, the or each remote translator station 4 also includes means 6 for modulation and demodulation of signals at said first frequency to a second frequency and means 7 for reception and transmission of signals at the second frequency from or to the associated radio base station 2. Preferably the remote translator station is constructed to operate at a first frequency of 1.8 GHz and at a second frequency of 38 GHz. The radio telephony system of the invention also includes a plurality of cordless, digital, two way mobile user terminals (not shown) linkable to the or each remote translator station 4.

The RTS 4 provide the minimum set of functions that are required to support a cell. The majority of processing required by the system is performed at the radio base station 2 with the RTS 4 being linked to the base stations 2 by the use of 38 GHz links 8. The functions performed by the RTS 4 are as follows: Reception and transmission of 1.8 GHz signals from or to the users in the cell.

Modulation and demodulation of received 1.8 GHz signals.

The minimum of signal processing.

Modulation and demodulation of signals to 38 GHz for the line of sight link 8 back to the next level up in the hierarchy, i.e. the central switching station 1.

By distributing the architecture of the cellular system to a lower level, through the use of the RTS 4, the equipment required per cell in the system is reduced.

Current radio base stations 2 occupy, at the absolute minimum, a rack of equipment installed in a relatively large container on the ground. By contrast, the RTS 4 is extremely small, simple, inexpensive and easily installed typically on existing structures such as a lamp post 9, as shown in Figure 3.

Claims

1. A radio telephony system for providing telephone facilities, including a central switching station, one or more radio base stations linked to the central switching station, and one or more remote translator stations linked to the or each radio base station so that the or each radio base station has its own associated directly linked remote translator station or stations.

2. A system according to Claim 1, wherein the or each remote translator station includes means for the reception and transmission of signals at a first frequency from or to a user, means for modulation and demodulation of signals at said first frequency to a second frequency and means for reception and transmission of signals at the second frequency from or to the associated radio base station.

3. A system according to Claim 2, wherein the or each remote translator station is constructed to operate at a first frequency of 1.8 GHz and at a second frequency of 38 GHz.

4. A radio telephony system according to any one of Claims 1 to 3, including a plurality of cordless, digital, two way, mobile user terminals linkable to the or each remote translator station.

5. A radio telephony system for providing telephone facilities, substantially as hereinbefore described and as illustrated in the accompanying drawings.