NL1013659C2 - System for providing radio coverage in an enclosed environment for radio transmission purposes. - Google Patents

Description

The invention relates to a system for providing radio coverage in an enclosed environment for radio transmission purposes for VHF radio traffic, comprising a number of transceiver base stations arranged within said enclosed environment. at a number of locations and 10 that are able to transmit simultaneously.

Such a system is known from the American O.S. No. 5,432,838.

This involves the use of a number of base stations to achieve a more complete radio coverage in an underground mine or similar environment, for example under water.

Simultaneous broadcasting is used for emergency messages.

However, this system does not provide a solution for providing complete radio coverage in, for example, large building complexes such as, for example, office complexes, hospitals, prisons, tunnels and the like for VHF radio traffic.

However, there is a need for a system for mobile radio communication in said complex large buildings, tunnels, etc. whereby the users communicate directly with each other via walkie-talkies wherever they may be within the boundaries of the system, without the necessity is to perform additional operations such as, for example, entering mobile or group numbers.

The invention now provides such a system, which is to that end characterized in that all transceiver base stations are star-connected via a fixed internal 4-wire house telephone via a concentrator unit and in that the transmitters of the transceiver base stations transmit it to one or more receivers signal from an identified transmitting radio received simultaneously from the transceiver base stations

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2 rebroadcast the same frequency at all locations through the concentrator unit.

In this way, a relatively simple and inexpensive system for mobile radio communication in complex 5 large buildings, tunnels, etc. with minimum HF power is provided, whereby each user has direct connection to all users and the central control within the limits of the building without any additional actions. service area of the system.

In particular, radio coverage can be obtained in a relatively large or specific working area without the use of multiple channels, while still satisfying the government requirements with regard to maximum antenna height and transmission power. It should be noted that it is known per se to use 15 radios as a means of communication in which no time is lost due to call origination, a conversation can be monitored by all users of the radio network and intervention if necessary (no congestion in emergencies). However, communication between radios is limited by its maximum range and deteriorates when used in buildings.

In such cases, duplex traffic is then sometimes chosen, whereby at a central point a base station receives the signal from the transmitting radio and retransmits it to the other radios of the network.

However, if the building in which the walkie-talkies are used is very large and coverage is also required in basements and / or underground parking spaces, etc. duplex traffic no longer appears to be sufficient.

30 One could think of an increase in the transmitting power of the radios, but this does not appear to be the right solution and is moreover not allowed by all kinds of government regulations and regulations in this area.

The invention will now be further elucidated with reference to the drawing and the description below.

Fig. 1 schematically shows, by way of example, an advantageous embodiment of the invention.

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Fig. 2 schematically shows the operation of the system according to FIG. 1.

Referring now to Fig. 1, a large building complex 1,2,3,4 with an underground tunnel or basement 5 is schematically shown. Consider, for example, sports complexes, football stadiums, office buildings, etc.

In each building, transceivers SO have been placed at deliberately chosen set-up points in order to obtain sufficient spread of the HF field strength.

10 The transceivers SO are suitable for full duplex traffic. Furthermore, measures known to those skilled in the art have been taken to prevent possible problems caused by the simultaneous transmission.

Each transceiver ZO is connected via a fixed internal 4-wire house line Hl to a (usually) centrally located Concentrator Unit 6. In this way, a separate transmitter and receiver line is provided.

The concentrator unit is the body where all 4-wire line connections from the base stations come in, the 20 connections to a fixed control station are present and the connection to a monitor receiver is located, which blocks the transmission command in case of reception of a co-user.

The concentrator unit includes the following: 25 - direct current control of both transmitter control and reception signaling; - level compensation of receiver and transmitter audio; - line monitoring of transmission and reception line; - phase monitoring of transmission and reception line; 30 - HF power monitoring of each transmitter; - standard configuration with 6 base stations with expansion options up to 11 + 17 + 23 etc., * - emergency power monitoring base stations.

Advantageously, the length of the house line connection between base station and concentrator unit is less than 3 km.

The transmitters operate advantageously in the 170 MHz band and / or in the 80 MHz band. The transmission power of the 1 G v 4 base stations is low, for example 500 mW ERP (Effective Radiated Power).

A central control 7 is connected to the Concentrator Unit 6 via an internal house line Hlb. The Pn 5 radios are standard PMR and are suitable for semi-duplex traffic. An appropriate antenna Cd, such as, for example, a so-called Crossed Dipole antenna, is advantageously connected to each transceiver ZO which is placed within the environment closed for radio transmission purposes, i.e. in the building, basement or tunnel, etc.

Such an antenna with a certain direction pattern, which is known to those skilled in the art and will therefore not be described in further detail, has the property that the vertically polarized field used for this application is mainly radiated downwards and upwards. As a result, the field strength at 800 meters is less than 1 dBuV, while there is still sufficient field strength in the building complex.

In this way one can concentrate the HF energy of the transmitters there where necessary.

The operation of the system of fig. 1 will now be further elucidated with reference to fig. 2.

With reference to Fig. 2, a walkie-talkie Pn, which is for instance located in the underground tunnel 5, makes an oral call to two walkie-talkies Pn, which are for instance located in building 1 and building 4.

In addition to the speech, the call also contains an underband tone frequency which is decoded and filtered out in the respective transceivers SO to prevent the system from receiving unwanted signals.

In the example of Fig. 2, the call is only received in transceivers 2, 3 and 5 (solid lines in bold).

Via the receiver lines of the 4-wire house line connection Hl 35 the speech, combined with a "decoder ok" signal, goes to the Concentrator Unit 6.

In the Concentrator Unit 6, the speech signals of the respective transceivers 2, 3 and 5 are combined to 101355 9 * 5 at a constant level. One or more "decoder ok" signals in the Concentrator Unit 6 result in a start for all transmitters ZO simultaneously.

Together with the combined speech level of the receivers 5, a transmitter start signal is placed on the transmitter lines of the 4-wire house line connection H1. As a result, all transmitters are turned on and the speech received on receivers 2, 3 and 5 is retransmitted.

The radio Pn in building 1 now receives the call via the 10 transceivers ZO placed in buildings 1 and 2, while the radio Pn in building 4 receives the call via the transceivers ZO placed in the buildings 2, 3 and 4 (broken lines in bold).

Speaking back, for example, to the walkie-talkie Pt in building 4 is identical, which will not be described in further detail here.

In order to avoid possible problems with phase rotation of lines which make speech unintelligible, a phase monitoring circuit can advantageously be incorporated in the Concentrator Unit 6, as already stated above. Such a circuit is known to those skilled in the art and will therefore not be used here. be described in more detail.

Advantageously, the phase monitoring of the 4-wire internal house lines H1, the transmitter start and the decoder ok signals are carried out using a DC circuit. The system according to the invention is future-proof, i.e. with extensions or conversions of the buildings, tunnels, basements, etc. in which the system is used, 30 base stations are very easy to move or to add.

The system according to the invention advantageously has 9 channels in the 170 MHz band.

Furthermore, in practice the system according to the invention appears to work even up to a distance of approximately 300-600 m outside the building complexes.

Various modifications of the system of the invention will be apparent to those skilled in the art after the above 101CSC? 6 description and drawings and therefore need not be further explained.

Such modifications are understood to fall within the scope and scope of the invention.

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Claims (10)

System for providing radio coverage in a radio transmission-enclosed environment for VHF 5 radio traffic, comprising a plurality of transceiver base stations located within a plurality of locations within said enclosed environment and capable of transmitting simultaneously, characterized in that that all transceiver base stations are connected to each other in a star-shaped manner via fixed internal 4-wire house telephone lines via a concentrator unit and that the transmitters of the transceiver stations receive the signal of an identified transmitting radio station simultaneously on one or more receivers of the transceiver base stations rebroadcast on the same frequency at all locations through the concentrator unit. System according to claim 1, characterized in that the transceiver base stations have a low transmit power. 20 System according to claim 2, characterized in that the transmission power is approximately 500 mW ERP (Effective Radiated Power). System according to any one of claims 1-3, characterized in that the transceiver base stations are connected to antennas placed within said enclosed environment. System according to claim 4, characterized in that the antennas are "Crossed Dipole" antennas which radiate mainly upwards and downwards. 6. System as claimed in any of the claims 1-5, characterized in that the house line connection between transceiver base station and concentrator unit has a length of less than 3 km. 1 01 3659-- System according to any one of claims 1-6, characterized in that the transmitters operate in the 170 MHz band. 8. System as claimed in any of the claims 1-6, characterized in that the transmitters operate in the 80 MHz band. System according to any one of claims 1-8, characterized in that the concentrator unit is connected to a fixed bedside station. 10. System as claimed in any of the claims 1-9, characterized in that the concentrator unit is connected to a monitor receiver, which blocks a transmission command in case of reception of a co-user. 11. System according to any one of claims 1-10, characterized in that the speech level compensation of the reception path is determined by the decoded reception signal in the concentrator unit. 12. A system according to any one of claims 1-11, characterized in that the phase monitoring of the 4-wire internal house telephone lines, the transmitter start and decoder ok signals are performed by a DC circuit. 13. System according to any one of claims 1-12, characterized in that said enclosed environment consists of a large building complex. 14. System according to any one of claims 1-13, characterized in that said enclosed environment consists of a tunnel. 101 SS; 5 -