WO1995020274A1

WO1995020274A1 - One-way mobile telephone network cell expander device, and related network

Info

Publication number: WO1995020274A1
Application number: PCT/FR1995/000069
Authority: WO
Inventors: Luc Provost
Original assignee: Cofira Etudes Et Gestion
Priority date: 1994-01-24
Filing date: 1995-01-23
Publication date: 1995-07-27
Also published as: AU1580595A; FR2715522B1; FR2715522A1

Abstract

A one-way mobile telephone network cell expander device, and the related network, are disclosed. Each expander device includes a two-channel retransmitter circuit (0) for a mobile station/base station channel in a first frequency band and a base station/mobile station channel in a second frequency band. A first directional transceiver antenna (1) is linked to the retransmitter circuit (0) to provide reception in the first frequency band and transmission in the second frequency band for the mobile station/base station channel, and a second directional transceiver antenna (2) is linked to the retransmitter circuit (0) to provide reception in the second frequency band and transmission in the first frequency band for the base station/mobile station channel. The antennas (1 and 2) are electromagnetically separate, and the axis of the radiation pattern of the first and second antennas lies in two substantially parallel vertical planes. Said device is useful for providing GSM-type mobile telephone networks.

Description

UNIDIRECTIONAL EXTENSION DEVICE OF MOBILE RADIOTELEPHONY CELL, AND CORRESPONDING NETWORK

The invention relates to a unidirectional expander device for a mobile radiotelephony cell, and to the network thus obtained thanks to the use of several of these expander devices.

In order to allow telecommunication by mobile radiotelephony, in a determined coverage area, current mobile radiotelephony systems provide for the establishment of base stations, which make it possible to provide coverage of an area by subdivision into elementary cells to which a group of frequencies is allocated in a transmission band and in a reception band. In order to avoid interference phenomena from an elementary cell to a neighboring adjacent cell, it is imperative to organize frequency distribution plans, in order to generate a maximum distance between two cells provided with the same bands of frequencies.

For such cellular systems of mobile radiotelephony, the surface coverage of the zones requires a very high frequency space consumption. For these systems, a large majority of telecommunications traffic is actually carried out in urban areas and on the highways connecting them. In sparsely populated rural areas, such surface coverage is no longer essential, and it therefore appears advantageous to ensure, in such areas, no longer surface but substantially linear coverage of the main roads, which are the seat of the majority of traffic. However, the radio frequency coverage of a mobile radiotelephone cell, such as the GSM radiotelephone network, is very limited. On the one hand, the criteria for standardization of the GSM radiotelephony network currently set a limit beyond which the signal transmitted by a mobile is no longer received by its base station at a distance of 35 km. On the other hand, the usual mobiles have a limited transmission power for reasons of energy supply while the relief of the ground, even the vegetation, impose significant propagation attenuations. Thus, in the best case, one cannot hope to cover a distance greater than 25 km from a single base station, in the presence of a favorable environment free from any masking and any unevenness. In the most unfavorable cases, the radiofrequency coverage distance of an elementary cell can then be reduced to a few kilometers in uneven terrain.

In order to ensure radio frequency coverage of a road axis, it is therefore necessary to set up a very large number of successive base stations, which, in addition to the very significant cost of implementation for the network operator, poses a very delicate problem of planning the allocation of frequencies as mentioned previously, with the aim of reducing or eliminating interference phenomena.

The object of the present invention is to extend the radio frequency coverage of a mobile radiotelephony cell, of the GSM type, up to the limit value authorized by the corresponding normative provisions, by the use of a single base station. and one and the same group of frequencies. Another object of the present invention is the implementation of a unidirectional expander device of a mobile radiotelephone allowing a large economy of infrastructures while ensuring a substantially linear radiofrequency coverage along roads, motorways or roads. 'railway axes.

Another object of the present invention is also the implementation of a unidirec¬ tional expander device of a mobile radiotelephone cell making it possible to ensure radiofrequency coverage along road, motorway or rail axes, over long distances. distances from the latter, without however misuse of the authorized frequency spectrum for mobile radiotelephony.

The unidirectional expander device of mobile radiotelephony cell, cell comprising a base station provided with a transceiver in a first and a second band of transmit frequencies of reception respectively, object of the present invention, is remarkable in that it comprises a dual-channel mobile / base station retransmitter circuit in a first frequency band, base / mobile station in the second frequency band. A first directional transmit-receive antenna interconnected by the retransmitter makes it possible to ensure reception in the first frequency band and transmission in the second frequency band, for the base station / mobile respectively mobile / station channel. basic. A second directional transmit-receive antenna interconnected to the re-transmit circuit makes it possible to ensure reception in the second frequency band and transmission in the first frequency band, for the base station / mobile respectively mobile / base station channel. . The first and second antenna are electromagnetically decoupled, the axis of the radiation pattern of the first and second antenna being contained in two substantially parallel vertical planes. The unidirectional mobile cell expander device, object of the present invention, finds application in the network equipment of mobile radiotelephone of road, motorway or rail axes in particular. It will be better understood on reading the description and on observing the drawings below in which: - Figure 1 represents a functional diagram of the unidirectional expander device of mobile radiotelephony cell object of the present invention, - Figure 2 represents specific radiation patterns of antennas used for implementation an expander device as shown in FIG. 1,

FIG. 3 represents a preferred arrangement of the various constituent elements of the mobile radiotelephone cell expander device which is the subject of the present invention,

FIG. 4 represents an illustrative diagram of a double-channel re-emitter used for the implementation of a unidirectional expander device of a mobile radiotelephony cell according to FIG. 1, FIG. 5a represents a layout diagram, from a base station of a mobile radiotelephony cell, a plurality of similar unidirec¬ tional expander devices to constitute a mobile radiotelephony network located along a road, motorway or rail axis,

FIG. 5b represents the structure of the signal frames transmitted by a base station and by a mobile provided with mobile radiotelephony equipment,

- Figures 5cl and 5c2 represent a theoretical explanatory diagram of the interference phenomenon between two successive extensor devices or between a base station and an expander device of the present invention.

A more detailed description of a unidirectional mobile radiotelephone cell expander device according to the object of the present invention will now be given in connection with FIG. 1 and the following figures.

In general, it is recalled that a mobile radiotelephony cell includes a base station, the base station being denoted SB, this base station being provided with a transceiver means in a first and a second band of respectively transmission and reception frequencies. The first and second frequency bands are denoted Δfl respectively Δf2. In a conventional manner, it is recalled that the transmission channel in the base station SB / mobile direction is designated by downlink and that the 95/00069

mobile transmission channel / base station SB is designated by uplink. Conventionally, the downlink allows the transmission of signals from the base station SB to the mobile in the second frequency band Δf2 while the uplink allows the transmission of signals from the mobile to the base station SB in the first band of frequencies Δfl.

According to a first advantageous characteristic of the unidirectional expander device of a mobile radiotelephony cell which is the subject of the present invention, it comprises a two-way re-emitting circuit, noted 0 in FIG. 1, this re-emitting circuit 0 allowing mobile communication / base station SB in the first frequency band Δfl respectively the base station / mobile communication in the second frequency band Δf2.

A first directional antenna, denoted 1, for transmission-reception is interconnected to the re-emitting circuit 0 to ensure reception in the first frequency band and transmission in the aforementioned second frequency band for the mobile uplink / base station SB respectively the downlink base station / mobile. A second directional transmit-receive antenna, denoted 2, is interconnected to the re-emitter circuit 0 to ensure reception in the second frequency band Δf2 and transmission in the first frequency band Δfl for the downlink base station / mobile respectively mobile uplink / SB base station.

According to a particular characteristic of the unidirectional mobile cell expander device of the present invention, the first and the second antenna are electromagnetically decoupled, the electromagnetic decoupling being represented by a dashed line, referenced E, in FIG. 1. In in addition, it is indicated that the axis of the radiation diagram of the first respectively of the second antenna is contained in two substantially parallel vertical planes, as will be described later in the description.

In general, it is indicated that the first and second antenna used are very high gain antennas, as directional as possible and whose radiation pattern has secondary lobes, denoted LS, very weakened so as to limit the risk air coupling between the aforementioned first and second antenna.

In FIGS. 2a, 2b and 2c, diagrams of typical radiation of the first and / or of the second antenna are shown, the main lobe being noted LP, and the secondary lobes LS. As shown in Figure 2a in particular, the first 1 and the second antenna 2 have in the vertical plane, a radiation pattern having an opening angle less than or equal to 10 °.

In addition, as shown in Figure 2b, the first antenna 1 has in a horizontal plane, orthogonal to the vertical plane and containing the axis of the radiation pattern of this antenna, an opening angle between 45 ° and 70 °, as shown in the above figure. As regards the second antenna 2, as shown in FIG. 2c, this presents in a horizontal plane a radiation diagram with an opening angle less than 10 ".

In general, it is indicated that relative to the first and the second antenna, each of these antennas has a front-rear decoupling greater than or equal to 30 dB.

By way of nonlimiting example, it is indicated that the first antenna whose function consists in allowing radiation towards or from mobiles can be constituted by a Kathrein type antenna, carrying the reference K 73 226, this antenna having an opening angle of radiation in the horizontal plane of the order of 60 ° and an opening angle of the radiation pattern in the vertical plane of the order of 8 °. With regard to the second antenna 2, it is indicated that this can be constituted by a paraboli¬ type antenna of the Andrew KP 10 820 A type or of the KP 13 820 B type. It is indicated that with regard to this type of 'antenna, the gain thereof is between 25 and 28 dB. As shown in addition in FIG. 3, it is indicated that the first and the second antenna 1, 2 can be mounted on a metal support, denoted SM, forming a pylon, each antenna being connected to the dual-channel retransmitter circuit. 0 by coaxial cable connections for example.

In order to ensure the electromagnetic decoupling between the first and the second antenna 1, 2, these are mounted on the pylon or metal support Sm so that the origin of the emission-reception point is distant in a substantially parallel direction in the vertical plane by a distance, denoted dO, greater than or equal to 10.λ, where λ denotes the maximum wavelength of the transmission signal of the first and second frequency bands Δfl, Δf2.

Finally, it is indicated that the above-mentioned antennas may include a radiating element constituted by a half-wave dipole for example, the parabolic structure of the antenna being however reserved for the second antenna.

A more detailed description of the double-channel re-emitting circuit 0 will now be given in conjunction with FIG. 4.

As will be observed in the above-mentioned figure, the re-emitting circuit 0 advantageously comprises a first channel, denoted I, comprising in cascade a bandpass filter 11 allowing the transmission of the first frequency band Δfl and an HF amplifier, denoted 12. It is indicated that the HF amplifier 12 is a gain amplifier adjustable very linear, class A type for example.

The double-channel retransmitter circuit 0 also includes a second channel, denoted II, comprising in cascade a bandpass filter 21 allowing the transmission of the second frequency band Δf2 and an HF amplifier, denoted 22, analogous to the HF amplifier 12 .

The first and second channels 1, 2 are interconnected in parallel by means of a first and a second duplexer 10, 20. The first duplexer 10 receives and transmits a signal in the first frequency band Δfl for the channel mobile uplink / base station, this signal being successively filtered by the band filter 11 then amplified by the HF amplifier 12 and delivered to the second duplexer 20. The second duplexer 20 receives and transmits a signal in the second frequency band Δf2 for the downlink base station / mobile, this signal being delivered to the band filter 21 then to the HF amplifier 22 and finally to the first duplexer 10. The first duplexer 10 thus ensures respectively the reception of a signal transmitted by the mobile to the base station in the first frequency band Δfl and the transmission to this same mobile of a signal from the base station in the second frequency band Δf2. The second duplexer 20 ensures the reception of a signal on the mobile base station downlink in the second frequency band Δf2 and the transmission on the mobile uplink / base station channel in the first frequency band Δfl.

Preferably, it is indicated that the above frequency bands Δfl and Δf2 can have values equal to 25 MHz, the first frequency band Δfl possibly being between 890 and 915 MHz and the second frequency band Δf2 possibly being between 935 and 960 MHz.

Of course, it will be understood that the transmission of the signals by the downlink between base station SB and mobile respectively on the uplink between mobile and base station can be carried out by means of a or more unidirectional extender devices of mobile radiotelephony cell object of the present invention, each mobile radiotelephony cell, thanks to the implementation of the aforementioned extender devices, then being configured in a real network as will be described below in the description in conjunction with Figures 5a, 5b, 5cl and 5c2.

In FIG. 5a, a base station, denoted SB, is shown in a succession of unidirectional extender devices for mobile radiotelephony cells, denoted El to En, these devices being installed on metal supports as previously described in the description. tion.

In general, it is indicated that the first expander device El is distant from the base station SB by a distance dl, the successive expander devices E2 to En-1 being distant from a distance d2 to dn-1 so as to cover a total distance of coverage, denoted Dn, in the direction of a road axis in a determined direction, to another successive base station SB + 1.

The mobile radiotelephony telecommunication network thus formed comprises, for a base station SB and between two successive base stations forming a mesh, a plurality of substantially identical adjacent unidirectional extender devices as described above in the description.

In general, it is indicated that a base station SB and a unidirectional expander device adjacent to this base station SB as well as two adjacent unidirectional expander devices, such as the expander devices El, E2 to En-2, En -1, form two successive transmit-receive stations with respect to a mobile provided with a mobile radiotelephony device.

According to a first particularly advantageous aspect of the telecommunications network by mobile radio object of the present invention, it is indicated that for two

SITEPLACE (RULE $ 2 successive unidirectional extender devices, the uplink / downlink link gains, these gains being adjustable in particular at the level of the dual-channel retransmitter circuit 0 previously described, are taken as close as possible to the propagation attenuation between two unidirectional expander devices successive aforementioned.

In addition, according to a particularly advantageous characteristic of the network thus constituted, it is indicated that the configuration and the arrangement of the antennas on the metal supports SM is such that the assumption of propagation in free space between two successive unidirectional extender devices respectively between SB base station and adjacent expander are verified. For this purpose, we indicate that the equivalent antenna heights satisfy the simplified Fresnel criterion according to the relation: h ≥ N λ dn 4

A particular configuration of a network obtained within the framework of the implementation of the unidirectional extender device of mobile radiotelephony cell of GSM type along a motorway axis will now be given in the description with the usual assumption according to which the power The base station SB's emission is 20 watts and that of mobiles is 8 watts, such an assumption corresponding to the most probable case in open country.

As regards the choice of antennas, these can be constituted as previously mentioned in the description, very high gain antennas as directional as possible having very weakened side lobes, so as to limit the risk of coupling by the air route which can, in general, be used. It is also indicated that it is possible to couple two elementary antennas to constitute a single antenna, the first and / or the second antenna, in order improve the gain and directivity of the entire system.

In general, and taking into account the hypotheses formulated above, the sensitivity of the receivers and the transmitting power of the mobiles limit the coverage of a GSM-type mobile radiotelephony cell at a maximum distance Dm of less than 25, 6 km.

For an 8 watt power transmitter, coverage is thus limited to 25.6 km and it is therefore practically necessary to set up a base station every 51 km along a road axis to obtain total coverage.

Taking into account the preceding hypotheses, the insertion of a first extension device at a distance of about 25.6 km does not pose any particular problem insofar as, by setting the maximum value the gain of the dual-channel retransmitter, higher power is obtained in the direction of the downlink for any distance less than the aforementioned limit value 25.6 km separating this first extender from the base station.

However, the balance of the downlink requires that the distance between the aforementioned expander circuit and any mobile is less than a specific value of 14.2 km. In the case where we now introduce a second expander device in cascade with the first, a particularly advantageous measure as mentioned previously in the description, consists, in terms of coverage, in imposing that the gains of the uplink and of the downlink are at least equal to the propagation attenuation between two retransmitters.

In order for the distance separating two successive extensor devices to be the greatest possible, the active and passive gains, the antenna gains, must be as high as possible. Taking into account the antennas used, the maximum distance d2 to dn-1 separating two devices aforementioned extensors cannot be greater than dn-1 = 8.9 km. Under these conditions, in accordance with a particularly advantageous aspect of the network of extender devices, object of the present invention, a chain of a determined number N of expander device between two base stations SB can be used, which makes it possible to increase the coverage initially limited to 25.6 km.

Taking into account the preceding elements, it is indicated that the separation of two successive extensor devices of approximately dn-1 = 9 km does not in any way increase the propagation losses.

Given the hypothesis of propagation in free space between two extensor devices, the equivalent antenna heights satisfy the aforementioned criterion, which implies:

- for dn-1 = 8.9 km the equivalent height of the antenna is h = 30 m,

- for dn-1 ≈ 25.6 km, the equivalent antenna height is h = 50 m. Taking into account the specifications of the GSM mobile radio protocol limiting radio frequency coverage to approximately 35 km, in particular due to the time of synchronization of the mobiles on the base station and the guard time of each burst allowing the transmission of radiotelephone communications, these parameters limiting the access time between a given mobile and the base station at the start of communication, the advantage of the expander circuits is then limited to maximum coverage by installing a single expander circuit in accordance with the object of the present invention .

In fact, if we take into account the delay due to the delay in propagation in the expander circuit of all the signals transmitted on the uplink and the downlink, this delay being worth at most 3 μs, this corresponding to a distance of 900 meters for a wave propagating at the speed of light. The cover maximum is then reduced to 34.1 km.

However, according to a particularly advantageous aspect of the mobile radiotelephone network object of the present invention, it is possible to increase the radio frequency coverage distance up to substantially 120 km by allocating for each mobile, as shown in FIG. 5b, two time intervals on them. eight time slots in the TDMA frame instead of one. This distance corresponds to the initial 35 km plus the distance corresponding to a half-time interval of the frame, ie 577 μs, as shown in the lower part of FIG. 5b. In the upper part of FIG. 5b, we find the classic case in which the delay between the base station SB and the mobile MS is limited to a value τO. The duration of xO being coded on 64 bits and for a bit rate of 271 kb / s, τO is limited to 118 μs, which corresponds to approximately 35 km.

Otherwise, in accordance with the representation in the lower part of FIG. 5b, the association of two time intervals with the same mobile MS makes it possible to obtain a maximum delay of T / 2 + xO which corresponds to a distance of 121.9 km.

In such a case, by allocating to each mobile MS two time intervals, it is therefore possible to associate up to nine expander devices in accordance with the object of the present invention, each separated by a distance of 8.9 km . The assembly of a base station and the aforementioned devices is therefore capable of constituting the mesh of a general network in order to ensure coverage of a road, motorway or rail-focused.

In general, it is indicated that a base station and a unidirectional expander device adjacent to this base station as well as two adjacent unidirectional expander devices form two successive transmit-receive stations with respect to a mobile MS considered.

According to a particularly advantageous aspect of the network object of the present invention, each unidirectional expander device is distant from a base station respectively from a unidirectional expander device adjacent to a distance, designated by dl respectively dn-1 in FIG. 5a, greater than or equal to a distance critical to suppress one-channel interference from two successive transmit-receive stations vis-à-vis the mobile.

Indeed, as shown in FIGS. 5cl and 5c2, there are areas of the road or motorway journey provided with a network in accordance with the object of the present invention, where a mobile moving on this road or motorway axis receives signals at the same frequency from two successive transmit-receive stations base stations respectively expander device as previously mentioned.

In the case of Figure 5cl in which the mobile vis-à-vis the downward path is located downstream of two successive expander circuits, E _n _ _k _ ₁ and E _n . _k or SB + 1, this mobile receives signals at the same frequency from the two expander devices or from the base station and the first expander device.

The respective journey times are written, for the signals received by the mobile: Relation (1) c Relation (2) t2 = dn-k + τ + V + h ² - dn-k + d + xcce where:

Relation (3) t2 - tl = x with x <3 μs, transmission delay of each dual channel re-emitter.

In the case of Figure 5c2, on the contrary, the mobile is found along the downstream path upstream of an extension device, the mobile MS being interposed between the two extender devices E _n . _k . ₁ , ^J nk for example, the preceding relations are written: Relation (4) tl = d

Relation (5) t2 = dn-k x + V ((ddnn - k-dr + tr dn-k + X + dn-k-d

from where :

Relation (6) t2 - tl = 2 (O-to) + x.

The condition t2-tl <16 μs implies: Relation (7) d> d _n . _k - 1.95 km.

However, the standardization provisions of the GSM-system require the receiver to equalize delays up to 16 μs, all successive signals whose delays do not exceed 16 μs being therefore considered as one and the same signal.

Given this condition, the risks of interference appear for a distance d on either side of the downstream expander device along the downward path d> d _n . _k - 1.95 km.

In the context of two cochannel signals, the GSM standard according to the 0505 ETSI recommendation, requires a separation of cochannel signals greater than or equal to 9dB. This value leads to two values d 'and d "of the distance d between which the aforementioned separation ratio imposed by the GSM standard is not respected.

However, it can be ensured that the system works if, in the interval defined by the values d 'and d ", the delays are less than 16 μs.

Theoretical studies have shown that for a minimum value h according to the Fresnel criterion previously mentioned corresponding to the distance d _n . _k , we see that for d _n . _k <10.2 km, the condition is fulfilled.

However, between the base station and the first expander, there is an interference zone for which the delays are greater than 16 μs.

Theoretical calculations show that, under the conditions indicated above, the length of this zone is given by Δ ≈ 1 km approximately.

For a distance dl = 25.6 km previously indicated, there is therefore an interference zone of 1 km long between 22.6 km and 23.6 km approximately from the base station and in which the signal ratio at the cocanal interference can go down to values of 2dB.

Consequently, the distance dl = 25.6 km previously mentioned is too great and it is advantageous to reduce this distance dl to 10.2 km to avoid problems due to interference, which makes it possible to carry out the implementation of several successive expanders to achieve maximum coverage. It is then indicated that the successive distances d2, dn-1 to dn separating two successive extensor devices can then be chosen equal to 8.9 km as already mentioned in the description.

In conclusion, it is indicated that the successive association of nine retransmitters or expander devices in accordance with the object of the present invention mounted on pylons of 30 meters and for which the separation distance between the base station and the first device extensor is 10.2 km, each successive extensor device being separated by 8.9 km, makes it possible to cover approximately 100 km, Dn = 91.6 km of a highway with a single base station. In addition, the preceding concept can easily be extended taking into account the fact that a base station can transmit and receive in both directions of a road or rail axis with an appropriate air system, which makes it possible to obtain a radio frequency coverage from a single radio station base covering around 200 km.

Taking into account studies carried out with regard to the study of the case where a mobile close to an expander device saturates the amplifier and the intermodulation following the cascading of repeaters, it is indicated that it may be appropriate to implement the control of the transmission power of the mobiles at the base station level. This control is a parameter available to the network operator. Finally, it is indicated that the use of two time intervals of the TDMA frame by mobile makes it possible to obtain greater coverage, as described above, the number of possible simultaneous communications being however divided by two correlatively. Finally, it is indicated that the network as described previously in the description can be supplemented by means of radiating cables for the passage of road, motorway or railway tunnels, for example, and that, under these conditions, the mobile radiotelephony network object of the present invention has a great flexibility of implementation and use.

Claims

CLAIMS 1. Unidirectional expander device of a mobile radiotelephony cell, cell comprising a base station provided with a transceiver means in a first and a second band of transmit frequencies respectively of reception, characterized in that said device expander includes:

a dual channel mobile / base station re-transmitting means in the first frequency band, base / mobile station in the second frequency band;

- A first directional transmit-receive antenna interconnected to said re-emitting means to ensure reception in the first frequency band and transmission in the second frequency band, for the mobile channel / base station respectively base station / mobile;

a second directional transmit-receive antenna interconnected to said re-emitting means to ensure reception in the second frequency band and transmission in the first frequency band, for the mobile channel / base station respectively base station / mobile, said first and second antennas being electromagnetically decoupled, the axis of the radiation pattern of the first and second antenna being contained in two substantially parallel vertical planes.

2. Device according to claim 1, characterized in that the first and the second antenna have in the vertical plane a radiation diagram having an opening angle less than or equal to 10 °.

3. Device according to claim 2, characterized in that said first antenna has in a horizontal plane orthogonal to the vertical plane and containing the axis of the radiation diagram of this antenna an opening angle of between 45 ° and 70 ° and in that said second antenna has in a horizontal plane a radiation diagram with an opening angle of less than 10 °.

4. Device according to one of claims above, characterized in that to ensure the electromagnetic separation between the first and the second antenna, the axis of the radiation pattern of said antennas at the origin of the emission-reception point is distant, in a direction substantially parallel to said vertical plane, with a distance d> 10.λ where λ denotes the maximum wavelength of the emission signal of the first and second frequency bands.

5. Device according to one of claims 1 to 4, characterized in that said double-channel re-emitting means comprises:

- a first channel comprising in cascade a band pass filter allowing the transmission of the first frequency band, an HF amplifier, - a second channel comprising in cascade a band pass filter allowing the transmission of the second frequency band, an HF amplifier,

- a first and a second duplexer, the first and the second channel being interconnected in parallel through the first and the second duplexer, said first and second duplexer respectively receiving a signal in the first frequency band for the channel mobile / base station, respectively transmitting and receiving a signal in the second frequency band for the base station / mobile channel on an input-output port.

6. Telecommunication network by mobile radiotelephone, comprising a plurality of base stations each provided with a transceiver means in a first and a second transmission-reception frequency band, characterized in that said network comprises between two stations successive base stations, forming a mesh, a plurality of substantially identical adjacent unidirectional expander devices, according to one of the claims 1 to 4, a base station and a unidirectional expander device adjacent to this base station respectively two devices unidirectional expanders adjacent forming two successive transmit-receive stations with respect to a mobile, each unidirectional expander being distant from a base station respectively from an adjacent unidirectional expander by a distance greater than or equal to a critical distance making it possible to suppress the cochannel interference of two successive transmit-receive stations with respect to the mobile.

7. Network according to claim 6, characterized in that each mesh of the network allows an intercommunication between mobile and transmitting station on a single pair of first respectively second frequency band.

8. Use of a network according to one of claims 6 or 7 along a traffic lane.