IE912140A1

IE912140A1 - Adaptive tunnel supply

Info

Publication number: IE912140A1
Application number: IE214091A
Authority: IE
Original assignee: Kapsch Ag
Priority date: 1990-07-03
Filing date: 1991-06-21
Publication date: 1992-01-15
Also published as: NO178418C; FI913176A; ES2028769T1; AT394797B; FI913176A0; NO912335L; ATA141490A; NO178418B; GR920300013T1; NO912335D0; EP0465457A2; MC2271A1; EP0465457A3

Abstract

Device for self-adjusting coverage of a tunnel (1), an underpass or the like with a down-link frequency channel and an allocated up-link frequency channel in a mobile radio system with a plurality of down- link frequency channels which can be radiated from a base station (2) and a plurality of respectively allocated up-link frequency channels which can be radiated from a mobile station (3), where a free-space scanner receiver (6, 10), which scans the down-link frequency channels radiated from the base station into the free space and locks them onto an initially free down-link frequency channel, a tunnel transmitter (7, 11) connected downstream which is frequency-synchronous with the free-space scanner receiver (6, 10) and which radiates this down-link frequency channel into the tunnel, a tunnel scanner receiver (8, 12) which scans the up-link frequency channels radiated from the mobile station into the tunnel and locks them onto an active up-link frequency channel, and a free-space transmitter (9, 13) connected downstream which is frequency-synchronous with the tunnel scanner receiver (8, 12) are provided, where said free-space transmitter radiates this up-link frequency channel into the free space, and where the tunnel scanner receiver in the locked-on state adjusts the free- space scanner receiver to the allocated down-link frequency channel.

Description

Adaptive tunnel supply The invention relates to a device for the selfadjusting supply of a tunnel, underpass or the like, with a downlink frequency channel and an associated uplink frequency channel in a mobile radio system with a plurality of downlink frequency channels which can be transmitted from a base station and a plurality of respectively associated uplink frequency channels which can be transmitted from a mobile station.

The fundamentals, modes of operation and definitions of the mobile radio systems mentioned, generally of cellular design, are given, for example, in Total Access Communications System, Mobile Station - Land Station, Compatibility Specification, Issue 3, October 1984, British Telecom Research Laboratories, or the corresponding US Specification US EIA CIS-3, EIA Engineering Department.

At present, the connection between the mobile station and base station is interrupted when travelling through a tunnel, underpass or the like.

In principle, it is also possible to arrange a base station with a radio cell in the tunnel. However, this has decisive disadvantages. On the one hand, the field strength gradient in the tunnel is extremely high, so that the time which is available to the system, during the journey through the tunnel, for a handover from one base station to the next is too short. In systems which do not permit any handover during an existing connection, the rapid field strength decline leads to loss of the connection. On the other hand, routing the necessary modulation or exchange lines to a base station arranged in the tunnel is costly and complicated.

Therefore, the invention aims to provide a device of the type mentioned at the beginning, which makes an operationally reliable connection available in a tunnel, in a economical and simple manner.

This object is achieved according to the invention by providing a free-space scanner-receiver which scans the downlink frequency channels transmitted from - 2 the base station into free-space and locks on to an initially free downlink frequency channel, a tunnel transmitter, which is connected downstream of the freespace scanner-receiver in a frequency-synchronous manner, and transmits this downlink frequency channel into the tunnel, a tunnel scanner-receiver which scans the downlink frequency channels transmitted by the mobile station into the tunnel and locks on to an active uplink frequency channel, and a free-space transmitter, which is connected downstream of the tunnel scanner-receiver in a frequency-synchronous manner and transmits this uplink frequency channel into free-space, and by the tunnel scanner- receiver adjusting, in the steady state condition, the free-space scanner-receiver to the associated downlink frequency channel.

As a result, only those frequency channels which are required for a connection are fed into the tunnel. If all the frequency channels present in the free-field were fed into the tunnel in a broadband manner, this would lead to insurmountable intermodulation problems and overloading problems. The system according to the invention now adjusts itself automatically to the frequency channels necessary for a connection to a mobile station located in the tunnel and feeds only these frequency channels into the tunnel or transmits them out of the tunnel into free-space. The system according to the invention thus extends the transmitting and receiving area of the base station adaptively into the tunnel.

In systems with a combined call and traffic channel per connection channel, the tunnel can be supplied with a connection by means of a single device of this kind. In systems with a call channel and a separate traffic channel per connection channel, two devices according to the invention are necessary. Furthermore, a plurality of devices according to the invention can of course be arranged in a tunnel in order to be able to establish connections simultaneously with a plurality of mobile stations located in the tunnel.

A further development of the invention for mobile - 3 radio systems with a fixed downlink frequency channel and a fixed uplink frequency channel which are in each case jointly associated with all the downlink and uplink frequency channels is characterised by providing an adjustable frequency free-space receiver which receives the fixed downlink frequency channel transmitted by the base station into free-space, a tunnel transmitter, which is connected downstream of the free-space receiver in a frequency-synchronous manner and transmits this downlink frequency channel into the tunnel, an adjustable frequency tunnel receiver, which receives the fixed uplink frequency channel transmitted by the mobile station into the tunnel, and a free-space transmitter which is connected downstream of the tunnel receiver in a frequency15 synchronous manner and transmits this uplink frequency channel into free-space. By virtue of this measure, no further adaptive tunnel supply is required for the channel, for example a common call channel in systems with separate call and traffic channels, which is common for all the connection channels, but rather only a simplified design with permanently set receivers. The constructional outlay can thus be reduced for such systems.

In both embodiments, it can be provided according to the invention that the outputs of the free-space receivers, free-space scanner-receivers, tunnel receivers and tunnel scanner-receivers are fed via demodulators to a processing logic system which sets the transmitting and receiving frequencies as a function of the control traffic on the channels, and tracks, seizes and releases said transmitting and receiving frequencies by changing the control traffic.

Processing logic systems of this kind, for example microprocessors, are easily programmable for these tasks, by which means the circuit outlay can be reduced.

In this respect, it is also advantageous if the free-space scanner-receivers or tunnel scanner-receivers are formed by adjustable frequency receivers driven by - 4 the processing logic system, the processing logic system being programmed to tune the receiving frequencies.

The processing logic system can also be used for monitoring whether there are active connection channels to a base station associated with the tunnel location or whether the channels are so-called entrained channels. In this case, the teaching of the invention provides for the processing logic system to reduce the transmitting power of the free-space transmitters for an active connection channel which is not contained in a stored channel table. As a result, a reduction in field strength is produced which causes the system to handover to the correct, associated base station.

With all the embodiments of the invention it is favourable if a signal regenerator is connected between a free-space receiver, free-space scanner-receiver, tunnel receiver or tunnel scanner-receiver and the freespace transmitter or tunnel transmitter respectively connected downstream of it. In this way, the operating reliability of the connection produced is substantially increased.

In this arrangement, it is possible in a simple manner for a free-space receiver, free-space scannerreceiver, tunnel receiver or tunnel scanner-receiver to be an FM receiver and the signal regenerator to be formed by the limiting amplifier and the channel bandpass filter of this FM receiver, as a result of which conventional receiver modules can be used.

The frequency synchronisation of the transmitters with the upstream receivers is advantageously achieved in that the frequency mixers of a free-space receiver, freespace scanner-receiver, tunnel receiver or tunnel scanner-receiver with the corresponding frequency mixers of the free-space transmitter or tunnel transmitter respectively connected downstream are connected in each case to a common oscillator. This constitutes a simple and reliable way of achieving frequency synchronisation.

However, the frequency mixer of a free-space transmitter or tunnel transmitter can likewise be - 5 connected to a controllable oscillator which is driven by a frequency measuring stage, the input of which is connected to the output of the free-space receiver, freespace scanner-receiver, tunnel receiver or tunnel scanner-receiver respectively connected upstream. As a result, any possible frequency drift of the received signal can be compensated. The frequency measuring stage determines the deviation of the received frequency from a preset nominal frequency and adjusts the mixing oscil10 lator of the transmitter such that the desired nominal frequency is obtained again after mixing.

The invention also provides a device for supplying a tunnel located between two adjacent base stations with in each case one connection channel to a base station, the distinguishing feature of said device being that the free-space transmitters, free-space receivers and free-space scanner-receivers of a first device for the self-adjusting supply of a tunnel with a downlink frequency channel and an associated uplink frequency channel are arranged on the one side of the tunnel and the free-space transmitters, free-space receivers and free-space scanner-receivers of a second device for the self-adjusting supply of a tunnel with a downlink frequency channel and an associated uplink frequency channel are arranged on the other side of the tunnel and that the transmitting and receiving areas of the tunnel transmitters, tunnel receivers or tunnel scanner-receivers are extended 10 to 100 m, preferably 20 to 50 m, in each case starting from the tunnel mouth lying opposite the associated base station, into free-space.

As a result, on the one hand the connection channels to both base stations are fed into the tunnel and on the other hand the transmitting and receiving areas of the tunnel supplies are extended into free-space so that when an active mobile station drives out of the tunnel, the connection to the base station on the other side of the tunnel is still briefly maintained in order to give the system sufficient time to carry out a handover to the base station on the exit side of the tunnel. - 6 The invention is now explained in greater detail with reference to the exemplary embodiments illustrated in the drawings, in which: Fig. 1 shows the device according to the invention for 5 supplying a tunnel in the area of a single base station with two variable downlink or uplink frequency channels and a fixed downlink or uplink frequency channel; Fig. 2 shows a device according to the invention for 10 supplying a tunnel located between two adjacent base stations with a variable downlink or uplink frequency channel and a fixed downlink or uplink frequency channel; Fig. 3 shows a tunnel supply according to the invention 15 which is controlled by processing logic; Fig. 4 shows a receiver or scanner-receiver according to the invention with a frequency-synchronous transmitter connected downstream; and Fig. 5 shows a receiver or scanner-receiver according to 20 the invention with a transmitter with automatic frequency correction connected downstream.

Fig. 1 shows a tunnel 1, a base station 2 and a mobile station 3 which is moving in the tunnel in the illustrated example. The free-space 4 in the area of the tunnel mouths is located in the transmitting or receiving area of base station 2.

An aerial cable 5, for example a coaxial cable with randomly distributed shielding slits of a known type, which is already frequently laid in tunnels for the purpose of radio receiving, is routed through the tunnel 1.

The aerial cable 5 serves as a common transmitting and receiving aerial for the tunnel transmitters 7, 11, 15, tunnel scanner-receivers 8, 12 and tunnel receivers 16 described later in detail. Their aerial inputs and outputs can be connected to the aerial cable at any desired point so that not only is the arrangement shown in Fig. 1 possible but also, for example, all the tunnel transmitters, receivers and scanner-receivers - 7 can be connected to one end of the aerial cable and can thus be arranged in the area of a tunnel mouth. Likewise, individual or separate aerials can be used instead of one aerial cable.

For the simplest application of a mobile radio system, in which a single downlink frequency channel serving as a combined downlink, call and traffic channel and a single uplink frequency channel serving as a combined uplink, call and traffic channel are provided per connection channel, only one free-space scannerreceiver 6, one tunnel transmitter 7, one tunnel scannerreceiver 8 and one free-space transmitter 9 are required.

The free-space scanner-receiver 6 receives a corresponding downlink frequency channel from the base station 2 and feeds this channel into the tunnel 1 via the tunnel transmitter 7 connected downstream. The tunnel scanner-receiver 8 receives the corresponding associated uplink frequency channel from the mobile station 3 and transmits this channel into free-space 4.

The free-space scanner-receiver 6 is adjusted to lock on to the first free downlink channel to be found. The tunnel transmitter 7 connected downstream is frequency-synchronised and transmits this same downlink frequency channel into the tunnel. This frequency syn25 chronisation means that the transmitter transmits on a radio frequency which is the same as the receiving frequency of the receiver connected upstream of it, or is uniquely associated with it.

The tunnel scanner-receiver 8 is adjusted to lock on to the first active uplink frequency channel to be found. The free-space transmitter 9 connected downstream is frequency-synchronised and transmits this same uplink frequency channel into free-space.

The detection of a free or active frequency channel in the scanner-receivers 6, 8 can occur, for example, by means of measurements of the receiving field strength.

For the application where a downlink frequency channel serving as a downlink call channel, a further - 8 downlink frequency channel serving as a downlink traffic channel, an uplink frequency channel serving as an uplink call channel and a further uplink frequency channel serving as an uplink traffic channel are provided for each connection channel, a further set of free-space scanner-receiver 10, tunnel transmitter 11, tunnel scanner-receiver 12 and free-space transmitter 13 are required. One transmitter and receiver set 6-9 serves to supply the tunnel with the call channel and the other transmitter and receiver set 10 - 13 to supply the tunnel with the traffic channel.

In this case, the scanner-receivers 6, 8, 10, 12 can be connected to one another via lines 18 in order to be able to control one another in such a way that they do not lock on to the same frequency channels.

The transmitter and receiver sets 6-9 and/or 10 to 13 can be duplicated as desired in order to supply a tunnel with a plurality of connection channels. In this case also, the scanner-receivers should be connected to one another via lines 18 and should control one another in order to prevent locking on to the same frequency channels.

For the application in a mobile radio system in which a specific, fixed downlink frequency channel and a specific fixed uplink frequency channel are jointly associated with all the downlink and uplink frequency channels, for example if the call channel is common to all the connection channels and only the traffic channels are different for each connection channel, an adjustable frequency free-space receiver 14 with a frequencysynchronous tunnel transmitter 15 connected downstream and an adjustable frequency tunnel receiver 16 with a frequency-synchronous free-space transmitter 17 connected downstream are provided. The adjustable free-space receiver 14 is set to the fixed downlink frequency channel, for example to the downlink call channel, and the adjustable tunnel receiver 16 is set to the associated uplink frequency channel, for example to the uplink call channel.

The arrangement according to the invention is capable of fulfilling all the requirements with respect to the operating states occurring. This is explained with reference to a mobile radio system having a call channel common to all connection channels and one traffic channel per connection channel: In the quiescient state, the free-space scannerreceiver 6 locks on to a free downlink traffic channel and feeds the latter into the tunnel via the tunnel transmitter 7. The tunnel scanner-receiver 8 constantly monitors whether an uplink traffic channel is being used in the tunnel.

The general downlink call channel is constantly fed in to the tunnel via the free-space receiver 14 and the tunnel transmitter 15 and transmitted out of the tunnel into free-space via the tunnel receiver 16 and the free-space transmitter 17.

The mobile stations 3, moving in the tunnel, lock on to the channels fed in.

A call to a mobile station in the tunnel is transmitted into the tunnel via the downlink call channel. The mobile station concerned answers the call on the uplink call channel, informs the base station that it has a free traffic channel available and uses it. The activa25 tion of an uplink traffic channel in the tunnel is detected by the tunnel scanner-receiver 8. The tunnel scanner-receiver 8 locks on to this channel and transmits it to the base station via the free-space transmitter 9. At the same time, via the line 19 the tunnel scanner30 receiver stops the scanning pass of the free-space scanner-receiver 6 and sets the latter forcibly onto the associated downlink traffic channel.

In the case of a call from a mobile station in the tunnel, the same basic process occurs except that the establishment of the connection begins on the uplink call channel and is answered on the downlink call channel.

When the connection is interrupted, the uplink frequency channel becomes free, which is detected by the tunnel scanner-receiver 8. The latter now continues its - 10 scanning pass for an active uplink traffic channel and at the same time cancels the blocking and forced setting of the free-space scanner-receiver sets via the line 19.

When an active mobile station drives into the 5 tunnel, the tunnel scanner-receiver 8 locates the active uplink traffic channel, locks on to it and forcibly sets the free-space scanner-receiver to the associated downlink traffic channel.

When an active mobile station drives out of the 10 tunnel, the tunnel scanner-receiver 8 continues its search for an active uplink traffic channel again and cancels the forced setting of the free-space scannerreceiver, which from now on searches for a free traffic channel again and locks on to it.

Fig. 2 shows a tunnel 1 which is located between two adjacent base stations 2 and 2', which are defined in the mobile radio station as adjacent cells. The freespace 4 in the area of one tunnel mouth is located in the transmitting and receiving area of base station 2 and the free-space 4' in that of base station 2'.

The illustrated device is used for supplying the tunnel 1 with in each case one connection channel to a base station 2, 2', a connection channel consisting of one downlink/uplink call channel, which is common to all the connection channels to a base station, and one downlink/uplink traffic channel per connection channel.

For this purpose, the free-space transmitters, receivers and scanner-receivers of transmitter and scanner-receiver sets 6-9 and of transmitter and receiver sets 14 - 17 according to Fig. 1 are arranged in the transmitting and receiving area 4. The free-space transmitters, receivers and scanner-receivers of sets 6' - 9' and 14' to 17' of the same kind are arranged in the transmitting and receiving area 4'.

Furthermore, the transmitting and receiving areas of the tunnel transmitters, receivers and scannerreceivers are each extended from the tunnel mouth lying opposite the associated base station into free-space by extending, for example, the aerial cable by 10 to 100 m, preferably 20 to 50 m, into free-space, as is shown by the dashed lines 20, 20'. This serves to maintain for a further specific period in the free-space area 4' a connection channel to the base station 2 from a mobile station 3 driving out of the tunnel, so that the mobile radio system has sufficient time automatically to carry out a handover and to establish a new connection channel to the base station 2'. The same holds for the opposite driving direction, when driving out into the free-space area 4, in order to maintain the connection to the base station 2' until the system has established a new connection to the base station 2.

Fig. 3 shows an arrangement consisting of an adjustable frequency free-space receiver 21 with a frequency-synchronous tunnel transmitter 22 connected downstream and a tunnel scanner-receiver 23 with a frequency-synchronous free-space transmitter 24 connected downstream, the function of which arrangement corresponds to the transmitter and scanner-receiver set 6 to 9 according to Fig. 1.

The outputs of the receiver 21 and of the scanner-receiver 23 are fed via demodulators 25 and 26 to a processing logic system 27 which monitors and evaluates the control traffic on the channels and adjusts the transmitting and receiving frequencies of the transmitters and receivers as a function of the control traffic, and tracks, seizes and releases these channels using the control traffic.

The processing logic system 27 can be programmed, inter alia, to tune the receiving frequencies of the receivers 21 and 23 and functionally to form scannerreceivers with these receivers.

The processing logic system can contain stored channel tables which, for example, specify the assignment of the frequency channels to the base stations. If a connection channel is detected which comprises frequency channels which are not associated with the base stations, which indicates a connection channel which is entrained from another base station, the processing logic system 27 reduces the transmitting power of the free-space transmitters 24 in order to cause the base station to perform a handover.

Furthermore, the processing logic system 27 can 5 evaluate the channel transmitting quality, in that it is programmed to carry out random evaluations of the transmitted signals.

Fig. 4 and Fig. 5 show the frequency synchronisation, according to the invention, of the receivers or scanner-receivers, with the transmitters connected downstream of them. The illustrated design forms the basis of the transmitter/receiver series circuits 6/7, 8/9, 10/11, 12/13, 14/15, 16/17, 6'/7', 8'/9', 14'/15', 16'/17', 21/22 and 23/24. The free-space scanner-receiver 6 and the tunnel transmitter 7 are illustrated as representative of the others.

The receiver 6 is an FM receiver with two-stage frequency mixing of a known type and consists of a series circuit comprising a radio-frequency input amplifier 25, a first frequency mixer 26, an intermediate frequency bandpass filter 27, an intermediate frequency amplifier 28, a second frequency mixer 29, a limiting amplifier 30 and a channel bandpass filter 30. The limiting amplifier 30 and the channel bandpass filter 31 ensure signal regeneration. However, a special signal regenerator could likewise be connected downstream of the receiver 6.

The transmitter 7 is an FM transmitter with twostage frequency mixing of a known type and consists of a series circuit comprising a first frequency mixer 32, an intermediate frequency amplifier 33, an intermediate frequency bandpass filter 34, a second frequency mixer 35, a radio-frequency bandpass filter 36 and a radiofrequency output amplifier 37.

The frequency mixers 29 and 32 or 26 and 35, each carrying out reciprocal frequency mixing, are connected in each case to a common oscillator 38 or 39. As a result, the frequency synchronisation of the transmitter with the receiver connected upstream is ensured.

The oscillator 39 is adjustable and in the case of the scanner-receivers 6, 8, 10, 12, 6', 8' is driven by a control device (not illustrated) in a known manner, or by the processing logic system 27.

Fig. 5 shows a circuit for frequency correction of the first intermediate frequency of the transmitter 7 in that the first frequency mixer of the transmitter is not connected to the oscillator 38 associated with the corresponding receiver frequency mixer but rather to a separate, controllable oscillator 41. The latter is driven by a frequency mixing stage 40 which is terminated at the output of the limiting amplifier 30 of the receiver 6 and measures the deviation of the receiving frequency from a preset nominal frequency and drives the oscillator 32 in such a way that the desired reference intermediate frequency occurs after the frequency mixer

Claims

1. Patent claims 1· Device for the self-adjusting supply of a tunnel, underpass or the like, with a downlink frequency channel and an associated uplink frequency channel in a mobile 5 radio system with a plurality of downlink frequency channels which can be transmitted from a base station and a plurality of respectively associated uplink frequency channels which can be transmitted from a mobile station, characterised in that a free-space scanner-receiver (6, 10 10) which scans the downlink frequency channels transmitted from the base station into free-space and locks on to an initially free downlink frequency channel, a tunnel transmitter (7, 11), which is connected downstream of the free-space scanner-receiver (6, 10) in a frequency15 synchronous manner and transmits this downlink frequency channel into the tunnel, a tunnel scanner-receiver (8, 12), which scans the downlink frequency channels transmitted by the mobile station into the tunnel and locks on to an active uplink frequency channel, and a free-space 20 transmitter (9, 13), which is connected downstream of the tunnel scanner-receiver (8, 12) in a frequency-synchronous manner, are provided, which free-space transmitter transmits this uplink frequency channel into free-space, and in that, in the steady state condition, the tunnel scanner25 receiver adjusts the free-space scanner-receiver to the associated downlink frequency channel.

2. Device according to Claim 1 for mobile radio systems having a fixed downlink frequency channel and a fixed uplink frequency channel which are in each case 30 jointly associated with all the downlink and uplink frequency channels, characterised in that an adjustable frequency free-space receiver (14), which receives the fixed downlink frequency channel transmitted by the base station into free-space, a tunnel transmitter (15), which 35 is connected downstream of the free-space receiver (14) in a frequency-synchronous manner and transmits this downlink frequency channel into the tunnel, an adjustable frequency tunnel receiver (16), which receives the fixed uplink frequency channel transmitted by the mobile - 15 station into the tunnel, and a free-space transmitter (17) which is connected downstream of the tunnel receiver (16) in a frequency-synchronous manner are provided, which free-space transmitter transmits this uplink 5 frequency channel into free-space.

3. Device according to Claim 1 or 2, characterised in that the outputs of the free-space receivers, freespace scanner-receivers, tunnel receivers and tunnel scanner-receivers are fed via demodulators (25, 26) to a 10 processing logic system (27) which adjusts the transmitting and receiving frequencies as a function of the control traffic on the channels, and tracks, seizes and releases the said frequencies by changing the control traffic. 15

4. Device according to Claim 3, characterised in that the free-space scanner-receivers or tunnel scannerreceivers are formed by adjustable frequency receivers (21, 23) driven by the processing logic system (27), the processing logic system (27) being programmed to tune the 20 receiving frequencies.

5. Device according to Claim 3 or 4, characterised in that the processing logic system (27) reduces the transmitting power of the free-space transmitters (9, 13, 17) for an active connection channel which is not con25 tained in a stored channel table.

6. Device according to one of Claims 1 to 5, characterised in that a signal regenerator is connected between a free-space receiver, free-space scanner-receiver, tunnel receiver or tunnel scanner-receiver and the free30 space transmitter or tunnel transmitter respectively connected downstream of it.

7. Device according to Claim 6, characterised in that a free-space receiver, free-space scanner-receiver, tunnel receiver or tunnel scanner-receiver is an FM 35 receiver and the signal regenerator is formed by the limiting amplifier (30) and the channel bandpass filter (31) of this FM receiver.

8. Device according to one of Claims 1 to 7, characterised in that the frequency mixers (29, 26) of a - 16 free-space receiver, free-space scanner-receiver, tunnel receiver or tunnel scanner-receiver with the corresponding frequency mixers (32, 35) of the free-space transmitter or tunnel transmitter respectively connected down5 stream are connected in each case to a common (38 or 39) oscillator.

9. Device according to one of Claims 1 to 7, characterised in that the frequency mixer (32) of a free-space transmitter or tunnel transmitter is connected to a con10 trollable oscillator (41) which is driven by a frequency measuring stage (40), the input of which is connected to the output of the free-space receiver, free-space scanner-receiver, tunnel receiver or tunnel scannerreceiver respectively connected upstream. 15 10. Device for supplying a tunnel located between two adjacent base stations with in each case one connection channel to a base station, according to one of Claims 1 to 9, characterised in that the free-space transmitters (9, 17), free-space receivers (14) and free-space 20 scanner-receivers (6) of a first device for the selfadjusting supply of a tunnel with a downlink frequency channel and an associated uplink frequency channel are arranged on one side of the tunnel and the free-space transmitters (9', 17'), free-space receivers (14') and 25 free-space scanner-receivers (6') of a second device for the self-adjusting supply of a tunnel with a downlink frequency channel and an associated uplink frequency channel are arranged on the other side of the tunnel, and in that the transmitting and receiving areas of the 30 tunnel transmitters (7, 15, 7', 15'), tunnel receivers (6, 6') or tunnel scanner-receivers (8, 8') are extended

10. To 100 m, preferably 20 to 50 m, in each case starting from the tunnel mouth lying opposite the associated base station (2, 2'), into free-space.

11. A device according to Claim 1 for the self-adjusting supply of a tunnel, underpass or the like, substantially as hereinbefore described with particular reference to and as illustrated in the accompanying Drawings.