EP0511103B1 - Information transmitting system between ground and mobil stations, especially in ground-train communications - Google Patents

Abstract

The invention relates to an information transmission system between the ground and mobile units. The installation consists, for example, of a section of railway line V1, equipped with beacons between its rails. The various beacons are linked to nodes, such as Ni, Nj, Nk, which are themselves linked with a Nodal Transmission Centre CNT, on the one hand, and to fixed installations such as IF on the other hand, controlling a point motor for example. The system is applicable especially to the field of information transmission between the ground and railway rolling stock, locomotives, carriages or wagons, train sets or trains. <IMAGE>

Description

The present invention relates to a system for transmitting information between the ground and mobiles. It relates, more particularly, but not limited to, the transmission of information between the ground and railway mobiles, traction units, cars or wagons, trainsets or trains.

Various means are already known in the prior art which make it possible to ensure such communications. These various means can be classified according to different criteria. One of the criteria for classifying these resources is the scope of the area they cover.

Some of these means have a point coverage, that is to say limited to a few tens of centimeters, or even a few meters and can therefore only be used when the mobile passes in well-defined locations. Among these means, some are unidirectional, such as traditional light signaling or its repetition in the cabin by metal contact or inductive loop. More recent techniques, such as microwave or optics (infrared), allow the establishment of bidirectional links between a mobile and a "beacon" offering a high speed.

Document EP-A-252,199 describes an installation for the punctual transmission of data between the track and a vehicle traveling on it.

Other means of communication have more coverage. They are essentially radio means. The transceiver with which the mobile maintains exchanges (which in some cases are only one-way) is located either in space (telecommunications satellites) or on the ground. In the latter case, it is exceptionally a station with a large coverage and most often, because of the frequency band used, a set of fixed stations with a range limited to a few kilometers and therefore organized network. The information rate of these radio links is generally limited by the relative narrowness of the available frequency band. Even more than the overall speed, the speed by mobile is limited by the number of mobiles in the coverage area between which to share the available speed.

A third type of means of communication has coverage which is neither punctual nor extended to a relatively large area in its two dimensions. These are means whose coverage is somewhat linear, so as to cover a section of railway or road. The means used can be a radiating cable, a lossy waveguide, or even, in the case of the railway, the rails, but the transmission is then unidirectional.

Document FR-A-2 626 834 describes a transmission system between the ground and a vehicle, where antennas are carried by this vehicle. Two of these antennas are sections of transmission line arranged parallel to the path of the car, having a longer coverage in the longitudinal direction than in the transverse.

The disadvantages of punctual transmissions have long been their unidirectional nature. Recent progress has made it possible to ensure bidirectional transmissions at high speed and at low cost. They have the disadvantages of the narrowness of the area covered. First of all, the impossibility of establishing a relationship with a mobile stopped outside of a covered area. This is particularly annoying if it is a question of sending to a stopped train the authorization to resume its journey, because the stop precision makes it difficult for a mechanic to stop in the coverage area of a beacon, even if it is indicated. Secondly, the difficulty of sending a mobile in the process of stopping the authorization to resume its speed, so as to streamline traffic and save energy, unless the number of punctual beacons is multiplied. Thirdly, the speed generally available for transmission with a mobile is proportional not only to the speed of the link when it is established but also to the proportion of the time when it is established, that is to say at relationship between the length of the area covered by a point connection and the spacing between successive covered areas. Fourth, even if the average speed is sufficient, its discontinuous nature over time makes it necessary for a service like the telephone, asking a priori continuity, temporary storage, therefore a high apparent response time.

The drawbacks of extended coverage transmissions are essentially twofold. Firstly, the obligation to share between all the mobiles served by the same link an overall speed limited by the narrowness of the available frequency bands means that the speed available by mobile is generally very limited. Secondly, the presence of obstacles to propagation (foliage, trenches, tunnels) or obstacles causing multiple paths (hills, building) leads to accept that certain areas are poorly covered or not at all covered, to ensure their coverage, to implement expensive means of repetition. A third drawback affects certain particularly fast mobiles using radio transmission with a high modulation rate and certain modulation methods; this is the Doppler effect which can prohibit digital links with too fast mobiles.

The drawbacks of linear coverage transmissions are, as regards rail transmissions, their unidirectional nature and their very low bit rate, as regards radiating cables their cost and their still limited frequency range (it is difficult today hui to go up very much beyond 1 GHz) being able to prohibit to transpose on this particular antenna which is the cable a transmission in the open air (repetition in tunnel of connections with satellites, for example), and as regards slotted waveguides, their cost.

The present invention aims to allow transmissions between the ground and mobiles with a high information rate with each mobile, continuous coverage and at moderate cost.

The object of the invention is a ground-mobile transmission system, using on the ground side microwave transmission beacons of the type of those which are usually used to ensure punctual transmissions, characterized in that the coverage by the vehicle is extended in the direction of movement thereof, by equipping it with an antenna or other radiating device whose coverage in the direction of movement is much greater than that of 'a beacon in such a way that it reaches or exceeds the distance separating successive beacons. In this way, a continuous connection is allowed during the movement of the vehicle.

The transmission system according to the invention ensures in the best conditions the sharing of the available transmission resources and the routing of information between a Nodal Transmission Center and the punctual beacons successively covered by the antenna of a vehicle.

In summary, the invention relates to a system in which the roles which, in the state of the art of linear coverage transmissions, are respectively assigned to the ground and to the mobiles are reversed. It is the ground which carries, at more or less regular intervals, fairly simple beacons (linked together by a transmission network) and it is the mobile which carries a complex transceiver, connected to a large antenna , such as a radiating cable or a slotted waveguide placed for example over the entire length of a train, and which, through this antenna, is in permanent contact with at least one point beacon of an assembly. Because a beacon is only in contact with at most one mobile at a time, the speed guaranteed to a mobile is not at the expense of that assured to another mobile, provided that the terrestrial network connecting the beacons does not introduce any limitation.

The invention will be better understood on reading a preferred embodiment process and certain variants of this process, which is only indicated to illustrate the invention and which in no way restricts its scope, the latter which can be carried out according to any other equivalent process which will appear appropriate to those skilled in the art.

• la figure 1 représente schématiquement une section de ligne ferroviaire équipée de balises et d'un réseau de transmission les reliant à un centre nodal de transmissions, parcourue par une rame équipée d'un lecteur relié à une antenne répartie selon l'invention ;
• la figure 2 donne le détail d'un guide d'ondes à fentes équipant une rame et servant d'antenne répartie selon l'invention ;
• la figure 3 donne le détail d'un mode de fixation du guide d'ondes à fentes sous la caisse de la motrice et/ou des éléments de la rame ;
• les figures 4a, 4b et 4c donnent le détail de trois modes possibles de couplage entre guides d'ondes se trouvant sur des véhicules adjacents dans la rame ;
• la figure 5 donne un agencement de l'antenne-guide d'ondes en deux ensembles couvrant chacun une moitié de la rame et permettant d'assurer harmonieusement la transition entre une balise et la suivante, dans le cas d'une transmission continue;
• la figure 6 décrit l'architecture d'un réseau reliant entre eux et à un centre nodal de transmissions les noeuds auxquels sont raccordées les balises et éventuellement d'autres équipements répartis, tels que des contrôleurs d'aiguilles ;
• la figure 7 représente la structure d'un noeud.

The above characteristics, as well as other secondary characteristics and advantages, will appear in more detail in the description below of an embodiment, made with reference to the plates in the appendix, in which:

• FIG. 1 schematically represents a section of railway line equipped with beacons and a transmission network connecting them to a nodal transmission center, traversed by a train fitted with a reader connected to a distributed antenna according to the invention;
• Figure 2 shows the detail of a slotted waveguide fitted to a train and serving as a distributed antenna according to the invention;
• Figure 3 shows the detail of a method of fixing the slotted waveguide under the body of the powerplant and / or elements of the train;
• FIGS. 4a, 4b and 4c give details of three possible modes of coupling between waveguides located on adjacent vehicles in the train;
• FIG. 5 gives an arrangement of the waveguide antenna in two sets each covering one half of the train and making it possible to harmoniously ensure the transition between one beacon and the next, in the case of continuous transmission;
• FIG. 6 describes the architecture of a network connecting the nodes to which the beacons are connected and to a nodal transmission center possibly other distributed equipment, such as needle controllers;
• Figure 7 shows the structure of a node.

The mobile, which in the case taken for example is a train, is equipped with a "reader" as provided, essentially for hands-free tolling applications or for container identification, by the companies CGA-HBS (system Hamlet), Philips (Premid system), Marconi (Telepass system) or Amtech. This "reader" is coupled to an antenna placed under the mobile.

It will be noted that a “reader” is used, in the context of the present invention, for a component operating in the half-cycle, fulfilling the following functions:

To transmit in the train-to-ground direction, it modulates a carrier, generally in amplitude. To read the content of the message awaiting reading in the beacon equipping the rail line and intended for the train, it illuminates the beacon with an unmodulated microwave wave. The beacon reflects part of it, by modulating the reflected wave in amplitude (shorting of the antenna modulated by the content of a memory such as a shift register), in frequency or sometimes in phase, or by any other process.

The bit rates of such readers are typically around 500 kbit / s and can reach 1 Mbit / s but the bi-directional bit rate is only half as long as the response of the beacon, which requires unmodulated illumination , cannot be done at the same time as sending a message to the tag. Certain systems have a more limited bit rate but essentially in order to decrease the energy consumed by the beacon, which is a consideration of less importance with the transmission system of the invention, in which a remote supply of the beacons through the system terrestrial transmission will be as often as possible.

If we refer to Figure 1, we see that there is shown two channels V ₁ and V ₂ , each comprising two rails such as r ₁ and r ₂ . Tags, such as b, comprising an antenna are placed in the tracks between two sleepers t or on a sleeper. The reader L, carried by the mobile, is coupled to the waveguide placed under the mobile. Initially, we will assume that the mobile is a locomotive with a length of 12m, towing a freight train. We will assume that the antenna of the mobile is a GO slot waveguide located under the body of the mobile, in the longitudinal axis, and that its coverage is 15m (i.e. 1.5m more, on both sides other than the length of the guide). That is to say that it will be assumed that, when the mobile is moving, the connection with a point marker b above which it passes is possible over 15m of its course.

Assuming that the precision of the train stop by the mechanic is +/- 5m, we see that the antenna with 15m of cover allows him to stop his train above the antenna so as to be sure of be able to receive authorization to resume walking. Assuming that an ordinary "point" antenna, placed under the locomotive body allows data exchange only over a distance of 1.5m on either side of the location of the beacon, we see that the 'antenna with 15m of coverage allows the exchange of a volume of data 5 times greater. Assuming that the distance between two successive beacons is l = 200m and that the average speed in the coverage area is 256kbit / s, we see that the average speed accessible to a running train at constant speed is 19.2kbit / s , whatever this speed. Assuming that a telephone conversation requires a speed of 16kbit / s, we see that it is possible for the mechanic to talk to a ground controller, by accepting a delay in the transmission of speech equal to time required to traverse the uncovered area between two beacons. For a traffic speed of 100km / h, this delay is 6.6 seconds.

. Nous supposerons que l'antenne est réalisée sous la forme d'un guide d'ondes à fentes courant sous l'ensemble de la longueur du train et couvrant de ce fait une distance légèrement supérieure à 220m, donc à l'espacement entre deux balises, toujours supposé égal à 200m. Dans ces conditions, le train est en permanence au-dessus d'une balise au moins, et parfois de deux. On verra plus loin comment sont évitées les interférences potentielles entre deux balises couvertes simultanément. En conservant les valeurs numériques précédentes, on voit que le train est non seulement couvert en permanence, mais qu'il dispose en permanence d'un débit de 256kbit/s. Ce débit permet d'écouler de l'ordre de 15 communications téléphoniques, sans délai de transmission notable, et/ou un important volume de données, servant à l'exploitation ferroviaire ou permettant d'offrir des services feroviaires aux voyageurs (horaires, réservations) voire de leur offrir des services de bureautique mobile (connexion à des bases de données, transmission de télécopies, etc.). On peut aussi remarquer que, lorsque la rame est constituée de deux éléments, de 220m chacun, chacun de ces éléments peut bénéficier de la capacité de transmission indiquée, sans qu'il doive partager avec l'autre élément ou avec d'autres trains autre chose que l'utilisation du réseau terrestre qui relie les balises au Centre Nodal de Transmissions.Suppose now that the mobile is no longer a locomotive towing a freight train but a self-propelled train. We will take the example of a TGV-Atlantique, whose length is $\text{l ′ = l + ε = 220m}$

. We will assume that the antenna is made in the form of a slotted waveguide running under the entire length of the train and thereby covering a distance slightly greater than 220m, therefore at the spacing between two beacons , always assumed to be 200m. Under these conditions, the train is permanently above at least one beacon, and sometimes two. We will see below how potential interference between two tags covered simultaneously is avoided. Keeping the previous numerical values, we see that the train is not only permanently covered, but that it has a permanent bit rate of 256kbit / s. This speed allows for the flow of around 15 telephone calls, without significant transmission delay, and / or a large volume of data, used for rail operations or enabling rail services to be offered to travelers (timetables, reservations ) or even offer them mobile office services (connection to databases, fax transmission, etc.). We can also note that, when the train consists of two elements, of 220m each, each of these elements can benefit from the indicated transmission capacity, without having to share with the other element or with other trains other thing that the use of the terrestrial network which connects the beacons to the Nodal Center of Transmissions.

The various beacons are connected to nodes, such as Ni, Nj, Nk, themselves spaced 200m apart. These nodes are, in their turn, in connection with a Central Nodal of Transmissions, such as CNT on the one hand, and can on the other hand be connected to a fixed railway installation such as IF, controlling for example a needle motor .

If we now refer to FIG. 2, we see an embodiment of the antenna of the mobile. The production of this antenna is based on the use of a GO slot waveguide such as that used in the IAGO system of ground-train links developed by the company GEC-ALSTHOM, described in particular in the patent. French 2,608,119 dated 12.12.86 (but, in this system, the waveguide is placed in the track and the train has a point antenna connected to a traditional microwave transceiver). For a frequency of 2.45 GHz the waveguide is in the form of a rectangular extruded aluminum tube, the dimensions of which are of the order of 10.5 cm x 5.5 cm, pierced with slots f perpendicular to the track, spaced on the order of 4.5cm.

Referring to FIG. 3, we can see the detail of a method of fixing the slotted waveguide under the body of the powerplant and of the elements of the train, which ensures both the fixing and the protection of the waveguide. For this purpose, the waveguide 1 is protected from ballast projections by a steel strip 2 pierced with slots 3 so as not to mask the slots 4 of the aluminum tube and which ensures the fixing of the tube under the body 5 by means of bolts 6, for example, screwed into the body 5. The edges of the slits of the strip are bevelled, as shown in FIG. 3. At the cited frequency of 2.45 GHz, l weakening presented by the guide, with its slots, is around 18dB / km, or 4dB over the length of the train, and 2dB only if the reader is placed in the middle of the train and feeds two half-guides of a length of 110m each.

The guide placed under the body of the powerplant or a trailer is rigid. However, the undeformable train is articulated around ball joints usually located just below the intercirculations allowing travelers to pass from one trailer to another. Several solutions can be used to connect the waveguides of neighboring trailers.

Three of the possible connection solutions have been summarized in FIGS. 4a, 4b and 4c.

The first of these solutions, shown in FIG. 4a, consists in using a flexible waveguide in the connection area as is encountered in certain radar installations. This connection is consists of a flexible part, possibly consisting of two flexible parts s ₁ and s ₂ separable, connected respectively to the wave guides GO ₁ and GO ₂ .

The second of these solutions, represented in FIG. 4b, consists in connecting the two adjacent waveguides GO ₁ and GO ₂ by means of a coaxial cable Cx possibly separable into two parts, the ends of which join the interior. waveguides and ensure continuity through the dipoles d ₁ and d ₂ . The transition from a waveguide transmission to a coaxial transmission or vice versa loses only about 0.1dB. The weakening of the coaxial itself is of the order of 1dB / m, so that the crossing of 11 separations between trailers (extreme case where the reader is placed in one of the drive units) still takes only a little more 'about ten dB. In order to protect the coaxial against ballast projections, it is advantageously placed in a sheath such that the hoses ensuring, on conventional trains, the pneumatic connections; its protection can be reinforced by a sheet metal plate.

The third solution, shown in FIG. 4c, can be used on an articulated train like the TGV, in which the relative movements of neighboring trailers limit the travel of a guide relative to its neighbor. This solution consists in positioning them as opposite each other as possible, so that one captures almost all of the radiation that escapes from the other. For this purpose, each of the opposite ends of the waveguides GO ₁ and GO ₂ is extended by an aluminum element having the shape of a truncated pyramid, the small base of which corresponds to the section of the waveguides and whose large base is homothetic of it. Given the small clearance between the two ends of the waveguides, the loss of radiation is effectively reduced.

The referenced patent indicates how it is possible to use a slotted waveguide to safely measure speed. This measure is based on injecting a frequency such that between two successive slits the wave moves about half a wavelength. In this case, an antenna located a short distance from the guide detects nodes and bellies of amplitude whose count allows it to know the space traveled (and whose quotient of this count by time allows it to know the speed ). This possibility can be exploited by the reader. If, in addition to the frequency close to 2.45 GHz used for the transmission, it injects a frequency close to 2.7 GHz, the signal which is returned to it is modulated with the pitch of the slits.

When the train is in a position such that it covers two beacons at the same time, one on its front and the other on its rear, there is no radio interference in the train-to-ground direction (again that the information being received by two distinct beacons, it is more economical that only one sends it to the nodal center of communications). On the other hand, if the reader illuminates two beacons with the same unmodulated frequency and these beacons modulate the reflected wave, it is very possible that the two waves received by the mobile will interfere and make it difficult to receive the signal correctly. information (although it is possible, if the reader is at one end of the train, that there is capture of the weakest wave, having traveled twice the length of the train, by that, less weakened, which only traveled a few meters on the train).

Several methods can be used, which make it possible to overcome these disturbances.

An embodiment is the object of Figure 5.

A first method would consist in using two readers L ₁ and L ₂ , which transmit on slightly different wavelengths, so that the signals at various frequencies can coexist without their reception being disturbed. These readers would be on board in 3, corresponding to the middle part of the train.

Another would be that the reader is located in the middle of the train at 3 and can transmit as desired through one or the other of the two guides G ₁ and G ₂ each traversing half of the train. The emission of a short message and the measurement of the quality of the response of one and the other allow the reader to choose one of the two tags (and, by letting him know that it is chosen, to get her to have the messages intended for this train addressed by the nodal transmission center).

The preferred method, however, is yet another method. It consists of continuously transmitting on two frequencies close to 2.7 GHz but distinct, so as to obtain at least one of them, because half of the guide in which it is sent covers a beacon, a continuous measurement of speed. It is sometimes the first beacon, sometimes the second, with an overlap during which two beacons are covered and can both provide speed in safety. The observation of the response of a new beacon (and an associated quality measure) makes it possible to decide when to use one or the other of the two waveguides to run the transmissions.

We realize that the intensive but sporadic nature of the beacon speed, the distribution of beacons along a line, at intervals which allow a high speed bandwidth transmission from one to the other Basically, the fact that two successive trains on a given track are generally spaced a distance which is often more than 2 kilometers, or in other words that only one train is on a certain section of line, the desire to avoid a break in a transmission line resulting in the impossibility of communicating with the trains being on a certain section of line, the relatively high number of beacons which makes one wish that the communication nodes to which they are attached have a simple structure, the fact that these nodes can also be advantageously connected to fixed installations such as controllers needles or announcement systems at level crossings, are all characteristics specific to transmissions which must link the beacons to the nodal transmission center. For these reasons, the ground-train communications systems according to the invention are advantageously supplemented by an adapted and specific system for managing terrestrial communications which is in a way the guarantor of performance and its economy.

We will return in more detail to what has been said above, from an embodiment, presented with reference to FIGS. 6 and 7.

A short range microwave transmission can therefore be the "ground-train jump" link in a communications network between a transmission center and all the trains traveling on a line. In order for this network to be globally interesting, the terrestrial network for connecting the microwave beacons must offer a level of performance compatible with that of the beacons, high availability and moderate cost. It must also be capable of handling other transmissions of interest to fixed points located on the track or in its vicinity: fixed stations of the ground-train radio, motors and needle controllers, passage management systems level, possibly telephone access points, etc.

An outline of a possible solution will be described below, based on a loop connection of close but rudimentary nodes, with dynamic management of a capacity which, thanks to this, may remain generally weak.

• 1 - l'aspect système,
• 2 - la résistance aux défaillances, ou processus de reconfiguration,
• 3 - la gestion des transmissions,
• 4 - le format de la trame,
• 5 - l'architecture du noeud.

We will successively address:

• 1 - the system aspect,
• 2 - resistance to failures, or reconfiguration process,
• 3 - transmission management,
• 4 - the format of the frame,
• 5 - the architecture of the node.

1 - Regarding the system aspect , we will first make some assumptions about the tags and their implementation:

We will assume that the speed of the desirable link between a beacon and what we will call the Nodal Transmission Center (CNT) is of the order of 250kbit / s, full-duplex. This figure assumes a ground-to-train transmission with a speed greater than 500 kbit / s, because this transmission must be done on a half-day basis. The speed must be more than double the speed of the link with the CNT because account must be taken of the exchange of service data between train and beacon, turnaround times, dead times linked to the determination by the train of the beacon to be used when it is above two beacons simultaneously (although the use of two readers or a second frequency used for example for a speed measurement in safety makes it possible to ensure this determination in masked time ). The available bandwidths easily allow this speed. The consideration which sometimes limits it, namely the economy of a battery which is supposed to last several years, should probably not play a role if the beacons are remotely powered by the connection network.

We will assume that the spacing of two consecutive beacons on the same track is 200m. Of course, it does not have to be as short on all the lines, but 200m is the maximum spacing allowing to ensure the continuity of the coverage to a TGV train of 200m and therefore to offer services which to have a commercial quality requires this continuity, like the telephone.

• un très grand nombre de balises à desservir, réparties linéairement et à très faible distance les unes des autres,
• une très faible proportion de ces balises à être à un moment donné en contact avec un train (pour un espacement moyen entre TGV de 20km, proportion de 2% s'il s'agit de rames doubles, 1% si elles sont simples ; pour des locomotives espacées de 3 km et ayant une couverture de 15m, proportion de 0,5%),
• une grande vitesse de déformation du "pattern" du trafic (pour un TGV circulant à 360km/h, le contact avec une balise ne dure que 2 s ; pour une locomotive roulant à 110km/h et dont le guide d'ondes assure une couverture de 15m, ce contact ne dure que 0,5s),
• pour les balises en contact avec un train, un débit instantané qui peut être très élevé, mais qui n'est sans doute pas le même pour toutes,
• un grand souci de disponibilité, dans la mesure où le réseau doit être un outil du contrôle-commande des circulations.

With these values, we realize that the necessary connection network must meet completely unusual characteristics:

• a very large number of beacons to be served, distributed linearly and at a very short distance from each other,
• a very small proportion of these tags to be in contact with a train at any given time (for a average distance between TGVs of 20km, proportion of 2% in the case of double trainsets, 1% in the case of single trains; for locomotives spaced 3 km apart and with a coverage of 15m, proportion of 0.5%),
• a high speed of deformation of the traffic pattern (for a TGV traveling at 360km / h, contact with a beacon lasts only 2 s; for a locomotive traveling at 110km / h and whose waveguide provides coverage 15m, this contact only lasts 0.5s),
• for beacons in contact with a train, an instantaneous speed which can be very high, but which is undoubtedly not the same for all,
• a great concern for availability, insofar as the network must be a tool for traffic control.

• un noeud tous les 200m,
• une liaison MICTN1, à 2,048Mbit/s,
• une liaison en double anneau entre deux Centres Nodaux de Transmission,
• un adressage direct des trains, conduisant à une structure de noeuds simple.

Taking these characteristics into account leads to imagine a network whose characteristics are as follows:

• a node every 200m,
• a MICTN1 link, at 2.048Mbit / s,
• a double ring link between two Nodal Transmission Centers,
• direct addressing of trains, leading to a simple node structure.

a) knots spaced 200 m apart

• 100m pour une ligne à double voie, à condition de les disposer et de les relier en quinconce,
• 200m pour une ligne quelconque, sachant que, s'il y a plus d'une voie, un noeud devra raccorder plusieurs balises,
• plus de 200m (par exemple 400, si l'on dispose un noeud à mi-distance de deux groupes de balises, soit à 100m de chaque, ou 600, si on dispose un noeud à côté d'un groupe de balises et lui confie le raccordement des deux groupes situés à 200m).

If the beacons of the same channel are spaced by 200m (it is understood that it will also be necessary to consider the case where the spacing is greater), we can consider several spacing for the nodes:

• 100m for a double track line, provided they are staggered and connected,
• 200m for any line, knowing that, if there is more than one channel, a node will have to connect several beacons,
• more than 200m (for example 400, if you have a node halfway between two groups of tags, either 100m from each, or 600, if you have a node next to a group of beacons and entrusts him with the connection of the two groups located 200m).

It seems that 100 m should not be retained, because a solution must be general.

It seems that 400m or more should not be retained, since the cabling risks becoming complex, poor availability for an entire group of beacons and that a high-speed transceiver with 400m range, more than 4 transceivers at lower speed and range 100m, may cost more than two transceivers at higher speed and range 200m plus additional node logic.

We therefore retain the hypothesis of a node every 200m. Each node must manage 1 beacon (on single track), 2 (on double track) or even more on certain lines or in the station area. It must also manage the connection of neighboring fixed equipment (fixed stations of the ground-train radio, needle controllers if they are managed by IPOCAMPE, level crossings, etc.).

b) MIC TN1 link at 2.048Mbit / s

An important choice concerns the support, namely optical fiber or copper. Optical fiber has the advantage of total insensitivity to disturbances and that of high capacity. It has the disadvantage that there are at present only on a relatively low line mileage, although increasing, while copper is widespread. It also has the drawback that its performance in terms of transmission presupposes in practice powerful nodes and which therefore risk being costly.

If we aim to use a banal copper support, the quarter with a diameter of 0.4mm, we are condemned in practice at the lowest level of the MIC links, the TN1 link offering a bit rate of 2.048Mbit / s.

It should be noted, however, that the PTT standard with a pitch of 1,800m between MIC repeaters on 0.4mm copper quadrant undoubtedly offers an economical solution for lines where one would not wish to offer a continuous transmission.

We can think that the cost of an HDB3 repeater (two integrated circuits and a tuned coil) constitutes a maximum limit to what will be the cost of a transmission at the same speed over a length limited to 200m.

2.048Mbit / s would allow, subject to efficient capacity management, the connection of approximately 7 TGV trainsets which would simultaneously use all of the 250kbit / s capacity that was assumed to be authorized for each (or less, if some of these trains are multiple elements). For an average spacing of 20km, a MIC link would allow normal management of around 70km. We will see later that it seems interesting to space double the CNTs (around 150km), a failure resulting in the fact that one of them only has to manage a part of its previous load , but its neighbor takes care of the tags it can no longer reach. Under these conditions, a link cut would at worst result in a halving of the capacity that can be allocated to a train.

The above discussion shows that a TN1 link, provided that it is managed dynamically, allows the management of a few tens of km. It is a priori an acceptable value. Above all, the limitations are easy to push back, if the individual speeds increase, if the spacing of the trains is reduced or if one wishes to manage longer line sections: it suffices to connect directly by a conventional MIC link of the sub- sections of the line section to manage. It will therefore be assumed that the transmission takes place at a rate of 2.018Mbit / s.

C) ring connection (Figure 6)

Such a low overall speed cannot be shared effectively between nodes that can each "call" such a high speed only if all of the information is accessible in each node. Hence the choice of a ring structure, in which each node retransmits all of the information to its neighbor that he received, possibly modified from what he himself extracted or added to it.

One way or the other, the ring must be closed so that the CNT manages both transmission and reception. The simplest is that the return path is the same as that of the outward journey, that is to say that the topology is that of a loop borrowing only one line to go and return .

From the strict point of view of logical processing, it is not necessary for the information to pass back to the return in each of the nodes crossed on the outward journey. It is however interesting from the point of view of the transmission and that of the reconfiguration.

From the point of view of the transmissions, one could certainly envisage a return with "boots of seven leagues", with for example a step of repetition of 1800m and thus jumping 8 knots each time. However, this leads to a well asymmetrical solution. In addition, the only points where reconfiguration would be possible are those where both directions of transmission are available. This would imply that a failure could make a relatively large part of a line "blind". This does not seem acceptable.

It will therefore be assumed that each node n _j is connected, in the two directions of transmission, to each of its two neighbors n _i and n _k . However, the information will only be processed in one direction; the other will be limited to ensuring the function of repetition and reconfiguration.

If it seems a priori expensive to secure each beacon and even each node, because the consequences of such a local failure are a priori not very significant, it is not the same with protection against link cuts. However, such cuts will not fail to occur.

It seems insufficiently effective to seek security by another route using the same route, because the rescue service can be vulnerable to the same event as that which affects the normal route. he seems almost impossible and in any case ruinous to ensure each node by a link taking another route than the line, a PTT link for example ....

The good solution seems to rescue a link by the one which prolongs it, in other words, to attack a line by the two ends, each one being connected to a Nodal Center of Transmissions. This does not mean that, in normal operation, each one must intervene in the connection of a given node but only that it must be possible, in the event of break of the connection, to connect to a CNT all the nodes being on the same side as him of the cut.

d) direct addressing of trains

• le Centre Nodal de Transmissions (CNT), responsable de la gestion d'une ligne et des raccordements à d'autres réseaux ou serveurs,
• le "noeud", étape sur la liaison terrestre, responsable local de la transmission, de la reconfiguration et de l'extraction ou insertion d'informations dans la boucle,
• la "balise", en entendant sous ce vocable le contrôleur qui la gère,
• le "train", destinataire final des échanges (on suppose qu'il assure les fonctions de passerelle avec les vrais destinataires finaux que sont les systèmes embarqués ou le téléphone).

The logical structure of the network leads to distinguish several levels:

• the Nodal Transmission Center (CNT), responsible for managing a line and connections to other networks or servers,
• the "node", a step on the terrestrial link, responsible for local transmission, reconfiguration and extraction or insertion of information in the loop,
• the "beacon", by hearing under this term the controller who manages it,
• the "train", the final recipient of the exchanges (we assume that it performs the gateway functions with the real final recipients, that is the on-board systems or the telephone).

Given the speed of the reconfigurations of traffic requested when a train passes from a beacon to its neighbor, and given the desire to limit the overhead, it seems interesting to seek a solution in which, to "speak" to a train, the CNT does not explicitly address the connection node of the moment, or even the beacon, but directly to the train, regardless of where it is located. In this way, the change of beacon of a train only concerns the train itself, the beacon that it leaves and that under which it is registered. The "hand-over" does not not concern the CNT. This reduces its workload and above all speeds up the process and facilitates the non-interruption of a continuous flow of data.

This supposes that the train, through its dialogue with the beacon, is capable of having in the node the information making it possible to intercept the information intended for it and to know when and where to inject data supplied by the train.

Similarly, addressing the train by the CNT must be as efficient as possible in order to limit the overhead. In view of the low number of trains at any given time under the jurisdiction of a CNT, this suggests that dynamic numbers be assigned to them.

2 - Regarding the management of failures , the system will be reconfigured as explained below.

It has been indicated that the most suitable connection structure appears to be that of a folded-over ring in which each node was crossed twice, a first time giving the opportunity for logical processing and a second time for the title a simple transmission repeater.

It was also indicated that the protection against a break in the connection led to consider connecting all of the nodes between two places quite distant from a line (we will assume l ₂ = 200km) to two CNTs located at both ends, and to seek security making it possible to vary the limit of the areas of competence of each.

We will now examine how to translate these principles, referring to Figures 6 and 7.

As in the description below, the structure of a knot represented in FIG. 7 will often be used, the meanings of the various bodies designated by letters have been gathered below. EG: left entrance GB: Loop manager ED: Right entry E: Entrance SG: Left exit S: Exit SD: Right exit EI: Extractor / Injector BD: Data bus BA: Address bus BT: Time base FGD: Fifo of dynamic management P _d : Dynamic door P _s : Static door K ₁ : Comparator K ₂ : Comparator NA: Abbreviated number RS: Selection register R ₁ , R ' ₁ : Registers R ₂ , R ' ₂ : Registers F ₁ E: Input FiFo F ₂ E: Input FiFo F ₁ S: Output FiFo F ₂ S: Output FiFo A: Attention; DI: Data In; DO: Data Out ST: Frame synchronization; CO: Clock Out FSV: FiFo empty output.

• 1.EG vers L vers SD et ED vers SG: cas d'un noeud intermédiaire gauche n_j.
• 2.EG vers L vers SG (ED et SD n'étant reliés à rien) : cas du dernier noeud à gauche n_m.
• 3.ED vers L vers SD (EG et SG n'étant reliés à rien) : cas du dernier noeud à droite (n+1)_m'.
• 4.ED vers L vers SG et EG vers SD : cas d'un noeud intermédiaire à droite (n+1)j'.

All the nodes are identical. each has 2 inputs EG and ED, two outputs SD and SG and a logic L. It can operate in 4 modes, by calling L the logic part:

• 1.EG to L to SD and ED to SG: case of a left intermediate node n _j .
• 2.EG to L to SG (ED and SD not being connected to anything): case of the last node on the left n _m .
• 3.ED to L to SD (EG and SG not being connected to anything): case of the last node on the right (n + 1) _{m '} .
• 4.ED towards L towards SG and EG towards SD: case of an intermediate node on the right (n + 1) j '.

Without anticipating too much about the technical solution chosen, we will assume that it uses the transmission of fixed frames of 8kbits (therefore corresponding to a frequency of 250 frames per second). We will also assume that each frame has a synchronization pattern and can include an area carrying an order (we will see more far that this zone can be the first two bytes of the ACS Static Capacity Affection zone).

A loss of synchronization on more than n frames (n = 16?) Puts a node in a reconfiguration mode. In this mode, it switches to pure transparency (that is to say that its logic L does not inject any bit). In this transparency mode, it switches between modes 1 and 4, remaining for approximately a duration of two frames in each, until it has "hooked" the frame synchronization.

We will take the case of a complete initialization and an intact link. The CNT2 will not issue anything at first. The CNT1 will continuously transmit a frame comprising only the synchronization pattern and 1s in the rest of the frame. The nodes having regained synchronization will remain in mode 1 where they have hung, and this step by step starting with the node closest to CNT1. If the non-attached nodes switch between mode 1 and mode 4 approximately every two frames, we see that they will hang on the CNT1 at a rate of a little more than one per frame (on average, two in 1 , 5 weft: at the moment when a node clings, its immediate neighbor has a chance on two to be in a phase where it also clings, the neighbor of the neighbor therefore has a chance on four, etc., it i.e. about two knots on average hook simultaneously; the first knot that didn't hang did not do so because it was facing the wrong way; it has a one in two chance to hang on from the next frame and one chance in two to wait again for the next one, but, when it hangs, there will be another on average to hang on at the same time as it). If n ₁ is the number of nodes that we want to manage from CNT ₁ , we see that at the end of n ₁ frames, we are almost sure that the last node to manage, which we will call m, has hooked up (if we wait longer, all the nodes between CNT ₁ and CNT ₂ will eventually hang in mode 1 on CNT ₁ and CNT ₂ will receive the information sent by CNT ₁ ; we could also decide to wait for this moment). With a frequency of 250 frames / s and a node spacing of 200m, 100 km of line will "hang" in 1.5s.

The nodes having hooked up the synchronization receive a 1 throughout the part of the frame which is not the synchronization pattern. They therefore receive it in particular in the first two bytes of the ACS Static Capacity Allocation zone which normally designate a node, by a 12-bit number, and a gate of this node, by a 4-bit number. The code they receive in this area, 65535, normally designates gate 15 of node 4095 (which must not exist). It will be interpreted as giving the order to stay in the reset mode.

CNT ₁ will then send to node m, named by name, an order to switch to mode 2 (a Static Capacity Assignment defined by its node number and, for example, door number 15). The CNT ₁ will then receive, by the loop finally closed, the series of information that it sent. The reset of the first loop is complete. The CNT ₂ can then do the same, by sending the initialization pattern on which, step by step, all the remaining nodes will catch on. There is indeed no competition to fear from CNT ₁ since node m is looped in mode 2. When all the remaining nodes are hooked up, CNT ₂ can give the most distant m ′ the order to pass through mode 3 (a Static Capacity Assignment defined by its node number and, for example, door number 14). The initialization of the second mouth is complete.

In normal mode, that is to say outside the case of a link break or the failure of a node, the CNTs can agree to move the border of their respective action zones. Whoever restricts his area of action must do so first, by sending the new last node the loopback code. We will assume that it is CNT ₁ . The abandoned nodes then pass, at the end of a timer, in the synchronization search mode if n ₂ is the number of nodes to be made. go under the authority of CNT ₂ , it must go into synchronization mode for a duration of around n ₂ frames (the other nodes have not lost their synchronization). It can then send the loopback order to the new last node.

It can be seen that, during this reshuffling process, some nodes could neither receive nor transmit, while others continued to receive but could not transmit. It is therefore a process that is best avoided. If it has to be applied, it is better to do it node by node, so as to reduce the duration of the disturbance (ten ms).

In the event of a link being broken, or a node failing, the process to be implemented is close to the process which has just been indicated. The CNT, no longer receiving any feedback, goes into resynchronization mode, then tries, step by step, to loop back on the increasingly nearer nodes, until the loop is established. He then knows which node ensured the closure. He informs the other CNT, which is trying to extend its jurisdiction to the neighbor of this node.

3. With regard to the management of transmissions , the following description assumes that the interface between a beacon and the node to which it is connected is, as indicated below, thanks to an input FIFO F ₁ E, a FIFO output F ₁ S, one control wire at input ("Attention") A and two control wires at output Synchro Frame and empty FIFO) ST and FSV. It therefore in principle comprises 19 wires, which can be reduced to 12 if the data wires are multiplexed.

a) Case of a train benefiting from an abbreviated number and covered by a beacon

Or a tag covered for some time already by a train. The node has known (for some time) the abbreviated train number, which it has assigned to the door through which the beacon is connected.

At the start of each frame (every 4 ms), the node writes to the output FIFO F ₁ S the number of the new frame and outputs a signal on the Synchro Trame ST wire. When it receives this signal, the beacon knows that the bytes intended for the train in the frame i-1 are in the output FIFO F ₁ S, terminated by the additional byte giving the number of the new frame. The number of data bytes received by a node during a frame is always equal to the number of bytes transmitted by the node in this same frame. It is therefore known to the tag, which must have noted this number during the previous frame. The tag can "get ahead" in reading the data bytes, by testing the emptiness of the FIFO.

The beacon is able to transmit to the train, when it interrogates it, the bytes of data received. It must also indicate to the train the number of the new frame, which helps it to keep the synchronization, which need only be approximate.

It is the responsibility of the beacon to have supplied the input FIFO F ₁ E with (at least) the number of bytes to be transmitted in the new frame i in time, and it is therefore the responsibility of the train of having provided them to him in time. The beacon receives the indication of the number of bytes to be transmitted (and the corresponding data bytes) from the train. This number will most often be the same from one frame to another, but nothing prevents it from varying, according to a known law of the train. Transmitting them in time means that they must have been stored in the input FIFO F ₁ E before the node has the opportunity to transmit them. As the beacon does not know this moment, it must assume that the transmission begins from byte 64 of the frame, but nothing prevents it from getting ahead. When the input FIFO F ₁ E is empty while it is requested to supply bytes of data, the transmission is done as a replacement by copying the bits received from upstream (this behavior is used in hand-over) .

b) case of a train covering a new beacon while it is still in contact with the previous one

If a train approaches a new beacon i, it starts a dialogue with it (but up to a certain moment not with the CNT through this beacon). Once there. satisfactory connection quality, the train indicates its abbreviated number to the beacon. He also tells him from which frame n he wishes to carry out the hand-over, that is to say use the new tag i for his exchanges with the CNT rather than the current tag j. It indicates it in the i tag but does not care to indicate it in the j tag.

During the interval corresponding to frame i-1, the tag enters the abbreviated number into the input FIFO F ₁ E. Then it sends a signal on the Attention wire A. This causes the abbreviated number to be read. by the node, its copying in the selection register associated with the door as well as in the output FIFO F ₁ S. The beacon thus has the opportunity to verify that the abbreviated number has been correctly received and, if not, to pass it on again.

The train transmits to the beacon i the data to be sent in the frame n. The tag enters them into the input FIFO F ₁ E which connects it to its node. During the transmission of this frame n, it is again from the tag j that the train must read the data which was intended for it in the frame n-1.

As the train has not sent to the tag j any data to be transmitted in frame n, the input FIFO F ₁ E of the latter cannot provide data when the selection mechanism gives it the opportunity. The vacuity of the input FIFO F ₁ E not only causes the non-transmission and its replacement by the transparent retransmission of the bytes received from the upstream node but also the deselection of the gate, that is to say the resetting to 0 the selection register associated with the door to which the beacon j is connected. The node j has again become available for a next train.

Note that any underrun has the same effects as ending the use of a tag. We must therefore avoid blocking which would result from the fact that the input FIFO F ₁ E may contain the end of the data to be transmitted, which would prevent reinitialization by the train which caused the underrun or initialization by the next train. This is why the underrun must cause, at the start of the next frame, the purging of any FIFO content.

c) Case of a train covering a new beacon when it was no longer covered but has an abbreviated number

When a quality contact is established with the beacon, the train transmits its abbreviated number and the indication of the frame from which it wishes to transmit (in principle, the following). The node, knowing the abbreviated number but not having received in the frame an indication of capacity allocated to the train, transmits at the end of the frame a request for allocation of capacity. A certain number of frames will pass before the CNT has received this request, has processed it and decided on an assignment and can indicate it in a frame at the start. Until this time, the node will reissue the allocation request in each frame. When it receives an assignment, it will know that the corresponding bytes in the frame received are to be transmitted to the beacon, the number of the frame will be for the train the implicit indication of the number of bytes transmitted and therefore to be renewed. The link will have remained inactive only in practice, the physical time of the loop's journey plus a frame duration (or two?).

It is likely that the data transmitted by the CNT through the last two frames sent to the previous beacon could not have been received by the train (unless the train has deliberately decided to stop transmitting when 'it was still well covered by this tag). It is the responsibility of the procedure used between the CNT and the train (or higher level processes) to ensure the necessary recovery.

d) Case of a train covering a new beacon when it does not yet have an abbreviated number

A train which does not yet have a short code (because it arrives in the area covered by the CNT without announcement by the CNT that it has left or because it comes out of a period of inactivity) uses as abbreviated number a null value. This is detected by the node when the selection register is loaded and causes it to send to the CNT a message requesting the allocation of a static multiplexing capacity with the train, defined not by the abbreviated number that it has not yet but by the number of the node and the door to which the tag is connected.

The link thus established is between an addressing and capacity allocation process in the CNT and an initialization process in the train. This exchange allows the train to indicate its complete machine number and its capacity requirements. In return, insofar as it has free abbreviated numbers, the CNT indicates to the train the abbreviated number it must use and the assigned rate (how many times 32 bytes per frame, or in each of the 16 frames of a multiframe if this capacity is not constant). Once this initial dialogue is complete, the CNT breaks the static link. The beacon, after having noted this break by the fact that it no longer receives a byte in the output FIFO F ₁ S, initializes the dynamic exchange by placing in the input FIFO F ₁ E, the abbreviated number of the train and sending the Attention signal to A.

The deactivation of an abbreviated number is automatic, upon expiry of a delay without transmission (of 5 minutes for example). To avoid an interpretation error, the CNT still waits a certain time before reassigning the same abbreviated number to another train.

When a dynamic capacity transmission is established, the train may have to ask the CNT to modify the speed (for example due to the appearance of new needs or their disappearance). He must do it through the data flow it sends to the CNT, which it is assumed that a certain subset is intended for link management. The CNT can modify the flow by itself, either because of a change in requirements or to distribute the shortage.

e) Connection of objects with static capacity

• le débit peut être rendu régulier par l'utilisation de FIFOs; comme il est relativement lent, les données peuvent être échangées sur une liaison série; deux fils suffisent, un par sens.
• la capacité étant fixe ne nécessite pas de fil de contrôle autre qu'une horloge, fournie par le noeud, et donnant le rythme bit,
• la capacité "fixe" peut cependant être modifiée par le CNT; l'intérêt est, par exemple, de tester à faible cadence le contrôleur d'une aiguille dont ne s'approche aucun train et d'augmenter la cadence lorsqu'un train s'approche (contrôle "impératif"); le noeud peut parfaitement être télécommandé et faire varier le rythme de l'horloge bit qu'il fournit à l'unité raccordée.

The connection of objects benefiting from a static capacity (fixed ground-train radio station or needle controller, for example) is quite similar to that of trains, with a few differences:

• the flow can be made regular by the use of FIFOs; as it is relatively slow, data can be exchanged on a serial link; two sons are enough, one per direction.
• the capacity being fixed does not require a control wire other than a clock, supplied by the node, and giving the bit rhythm,
• the "fixed" capacity can however be modified by the CNT; the interest is, for example, to test at low cadence the controller of a needle which no train approaches and to increase the cadence when a train approaches ("imperative"control); the node can perfectly be remote-controlled and vary the rhythm of the bit clock that it provides to the connected unit.

We can even consider a variation of the locally controlled static flow. One application would be telephone access points made available to equipment agents (in principle, not mechanics, because stopping a locomotive above a beacon offers a permanent and high speed ). The agent should plug in equipment including the handset, call keypad and appropriate conversion equipment (digital to analog, with filtering, and vice versa). A variant would be that the plugged-in equipment is itself the basis of a cordless telephone allowing remote access in an area of a hundred meters. The transmission problem posed is to provide a link only from the moment the equipment is plugged in, and if necessary to provide a different speed during the call and call establishment phase and during the conversation phase. A call button should be installed, the effect of which is the sending by the node of a debit request with the door to which the terminal is connected.

• octets 0-2 : NTS Numérotation de Trame et Synchronisation
• octets 3-31 : ACD Affectation de Capacité Dynamique
• octets 32-36 : ACS Affectation de Capacité Statique
• octets 37-n : DMS Données Multiplexées Statiquement
• octets n-991 : DMD Données Multiplexées Dynamiquement
• octets 992-1023 : RCD Requêtes de Capacité Dynamique

4. With regard to the format of the frame , a format is proposed below, presented for the sole purpose of showing the feasibility of the system and its degree of complexity. We choose a frame length of 1024 bytes. This choice results from a compromise between the desire to associate a sufficient number of data bytes (here up to 955) with the overhead (here 69 bytes) and that of ensuring the efficiency of the dynamic management of capacity thanks to a high frame frequency (here 250 frames / s for a bit rate of 2,048 Mbit / s).

• bytes 0-2: NTS Frame Numbering and Synchronization
• bytes 3-31: ACD Dynamic Capacity Allocation
• bytes 32-36: ACS Static Capacity Allocation
• bytes 37-n: DMS Statically Multiplexed Data
• bytes n-991: DMD Dynamically Multiplexed Data
• bytes 992-1023: RCD Dynamic Capacity Requests

NTS Frame Numbering and Synchronization (bytes 0-2)

Bytes 0 and 1 contain a synchronization pattern. Byte 2 contains a frame number. Only the last four bits are used to define the frame in the multiframe, but all 8 bits are used to distribute a clock with a period of about one second. The frame number is used on the one hand to ensure a sub-multiplexing making it possible to offer low bit rates at some doors and on the other hand to coordinate hand-overs.

ACD Dynamic Capacity Allocation (bytes 3-31)

Each of bytes 3 to 30 (byte 31 always contains 0) assigns to a certain train a transmission capacity of 32 bytes in the DMD area of Dynamically Multiplexed Data of the frame. The train concerned is designated by an abbreviated number, 1 byte, which has been previously assigned to it by the Nodal Transmission Center (CNT). The same train can be assigned a multiple capacity of 32 bytes in the frame, which does not have to correspond to contiguous zones of DMD. It can also have a number of zones which varies from one frame to another but in a manner agreed in advance according to the number of the frame in the multiframe. For a frame rate of 250, each capacity increment of 32 bytes corresponds to a bit rate increment of 64,000 bit / s. The lowest bit rate that can be dynamically assigned is 32 bytes every 16 frames, or 4 kbit / s. The highest is 28 x 32 bytes per frame, or 1,792 Mbit / s. Address 0 is never assigned to a train and its use in ACD therefore does not affect a memory area (but it may be the subject of a static assignment). There is no provision for general dissemination on all trains. The reason is the difficulty not of sending the information to the nodes but of delivering it to the trains by superimposing it on the information normally delivered. One could however envisage the diffusion of an alert using an additional wire of the interface. A more complex message must in principle be sent individually to each train by the CNT.

ACS Static Capacity Allocation (bytes 32-36)

• la première, de 12 bits, désigne un noeud. Les noeuds ont un numéro fixé en EPROM. Deux numéros identiques ne doivent pas se trouver dans une zone de ligne gérée, en normal ou en secours, par un même CNT; le numéro 4095 est réservé au mode de reconfiguration,
• la deuxième zone, de 4 bits, désigne une porte du noeud; les portes 14 et 15 sont réservées au mode de reconfiguration,
• la troisième zone, de 24 bits, désigne les octets affectés. Les 14 premiers bits désignent une adresse d'octet dans la trame (10 bits) et un numéro de trame dans une multi-trame (4 bits). Les 9 bits suivants constituent un masque disant desquels des 9 derniers bits de la zone précédente ne pas tenir compte : les 5 premiers sont relatifs aux 5 derniers bits de la zone d'adresse et les 4 derniers au numéro de trame. Ainsi, un masque nul représente une capacité de 1 octet par multitrame soit, pour une fréquence de trame de 250, un débit de 125 bit/s; un masque de 111 (en binaire) représente une capacité d'un octet dans une trame sur deux, soit un débit de 1 kbit/s; un masque de 111111 représente une capacité de 4 octets dans chaque trame, soit un débit de 8 kbit/s. Une valeur de 0 dans la zone d'adresse supprime une allocation précédente.

This zone allows the modification of the capacities assigned to semi-static multiplexing (DMS zone). Only one capacity can be modified per frame. The ACS zone consists of 3 sub-zones:

• the first, of 12 bits, designates a node. The nodes have a number fixed in EPROM. Two identical numbers must not be in a line area managed, in normal or in emergency, by the same CNT; the number 4095 is reserved for the reconfiguration mode,
• the second zone, of 4 bits, designates a gate of the node; doors 14 and 15 are reserved for the reconfiguration mode,
• the third area, 24 bits, indicates the bytes affected. The first 14 bits designate a byte address in the frame (10 bits) and a frame number in a multi-frame (4 bits). The next 9 bits constitute a mask saying which of the last 9 bits of the previous zone do not take into account: the first 5 relate to the last 5 bits of the address zone and the last 4 to the frame number. Thus, a null mask represents a capacity of 1 byte per multiframe, that is, for a frame frequency of 250, a bit rate of 125 bit / s; a mask of 111 (in binary) represents a capacity of one byte in every second frame, ie a bit rate of 1 kbit / s; a mask of 111111 represents a capacity of 4 bytes in each frame, or a bit rate of 8 kbit / s. A value of 0 in the address field removes a previous allocation.

It will be noted that the following variant would have been content with 16 bits to indicate the bytes affected, but it is less flexible to handle. The first 14 bits designate, with perhaps unnecessary precision as we will see, a byte address in the frame (10 bits), followed by a frame number in the multiframe (4 bits). All the 0's that end the zone indicate how many of the least significant bits among the first 14 ignore. For example, the value (expressed in binary) 1100110011010111 affects the address byte 1100110011 in frame 0101, ie a bit rate of 125 bit / s. The value 1100110011011100 affects the same address in 1 frame out of 4, i.e. a speed of 1 kbit / s. The value 1100110010000000 assigns the 8 address bytes 1100110000 to 1100110111 in each frame, i.e. a speed of 16 kbit / s.

In the frames that the CNT does not use to modify the static assignments, the 40 bits sent by it are at 0. The nullity of the first 16 bits can be taken advantage of by a node to request a static assignment to one of its dynamic doors, as indicated for the mechanism for assigning an abbreviated number to a train that does not already have one, or even to one of its static doors, as the possibility was mentioned for the connection of telephones . This node, noting the nullity of the first 16 bits, writes its own number and that of the door concerned in the last 16. Of course, it is possible that several nodes act in the same way during the same frame. The mechanism indicated shows that it is the last crossing "which wins". As a node will send the same request, frame after frame, until it has obtained an abbreviated number for the door in question, this collision has no other drawback than delaying the assignment.

DMS Statically Multiplexed Data (bytes 37-n)

The Statically Multiplexed Data DMS area is managed according to static or more exactly weakly dynamic multiplexing, the allocation mechanism of which is indicated by the ACS Static Capacity Allocation area. Through the multi-frame game, individual bit rates can range between 125 bit / s and 64 kbit / s.

DMD Dynamically Multiplexed Data (n-991 bytes)

Set of 32 byte areas dynamically assigned to transmission with trains according to the indications provided by the ACD Dynamic Capacity Allocation area. The boundary n of separation between the DMS area of Statically Multiplexed Data and the DMD area of Dynamically Multiplexed Data is managed by the CNT and is not known to the nodes (and need not be). The DMS and DMD zones can even be nested.

RCD Dynamic Capacity Requests (bytes 992-1023)

Each bit in this area corresponds to a train, defined by its abbreviated number. The CNT initially sets the entire area to 0. Each node crossed can set certain bits to 1, but not to 0 (i.e. each node transmits downstream the logical fusion of what it received from upstream and what it added). It puts at 1 the position corresponding to a train of which one of its doors includes the abbreviated number in its selection register if, for this train, it was not unable to provide the bytes requested through the ACD area. In other words, it puts a 1 for a train which has provided all of the requested bytes or for which no transmission capacity has yet been allocated. For a train for which one of its doors contains the abbreviated number, it does not put a 1 if there has been underrun and in particular if no byte has been supplied. This last case can be that of a train which has ceased to be covered (and it is by this mechanism that the CNT is informed) or that of a train covered continuously but which has just carried out a hand -over. In the latter case, the CNT will not even be notified: it will still receive a 1, but this 1 will have been added by the node to which the new tag is connected.

5. With regard to the architecture of a node , this can be summarized in a synthetic way as indicated below (Figure 7).

1. External interfaces Static interface

• 1 fil Data In, DI
• 1 fil Attention (dans le cas de bornes d'accès téléphonique) A

Entrance :

• 1 wire Data In, DI
• 1 wire Caution (in the case of telephone access terminals) A

• 1 fil Data Out, DO
• 1 fil Clock Out, CO

Exit :

• 1 wire Data Out, DO
• 1 wire Clock Out, CO

Note that the bit rate is subject to change. For example, if the door corresponds to a needle controller, a control center can request, when approaching a train, a speed of 4 kbit / s and be satisfied, at other times, with a speed of 125 bit / s.

Dynamic interface

• 8 fils Data In, DI
• 1 fil Attention, A

Entrance :

• 8 wire Data In, DI
• 1 wire Attention, A

• 8 fils Data Out, DO
• 1 fil Synchro Trame, ST
• 1 fil FIFO Sortie vide, FSV

Exit :

• 8 wire Data Out, DO
• 1 wire Synchro Trame, ST
• 1 wire FIFO Empty output, FSV

Note that the 8 wires of Data In and 8 wires of Data Out can be replaced by 8 wires of Data, bidirectional, and a direction selection wire, managed by the connected device. A parallel interface seems preferable to a serial interface, both because the short distances between beacon and node allow it (a few meters) and that it seems interesting to reduce the flow, this one being able to be high, the environment electrically polluted and the mode of transmission should be kept simple.

2. Internal architecture

• a) reconfiguration,
• b) extraction-injection,
• c) base de temps,
• d) gestion des capacités,

et gérant un bus d'adresses BA et un bus de données BD (ce dernier étant un bus série) et, raccordées à ces bus :

• des portes à gestion dynamique Pd,
• des portes à gestion statique Ps.

The architecture of the node can be broken down into a certain number of common organs, ensuring the following functions:

• a) reconfiguration,
• b) extraction-injection,
• c) time base,
• d) capacity management,

and managing an address bus BA and a data bus BD (the latter being a serial bus) and, connected to these buses:

• doors with dynamic management Pd,
• doors with static management Ps.

a) Reconfiguration

As indicated above in the comment relating to the management of failures, the node has 2 inputs EG and ED and two outputs SD and SG and it can operate in 4 modes depending on the position it occupies in the loop considered.

The reconfiguration unit ensuring the functions described above comprises only the electronic relays ensuring the contacts corresponding to the four modes. It is the BT time base which must search for synchronization, send the code ordering the switchover in modes 1 and 4 alternately (with a period for two half-waves corresponding to the duration of approximately 4 frames) as long as it does 'did not find the sync, inhibit any transmission other than a repetition as long as it recognizes the OFFFF code (hexadecimal) in the ACS zone, and recognize a possible order to switch to mode 2 or 3.

A possible technological problem to report is that during the resynchronization, it will happen that two neighboring beacons both seek simultaneously to "drive" the link between them.

b) Extraction-Injection

The overall performance of the loop is partly linked to the crossing time of each node. It seems impossible to go below a bit time but it is desirable not to go above it, in particular not to add a time-byte.

Despite the passage from an HDB3 mode to a pure binary mode and vice versa, it must be possible to repeat with a delay of 1 bit time (necessary in particular to generate the appropriate parity rapes). The bit intended to possibly replace a received bit must be available at the same time as this bit. In practice, this means that on the one hand, an 8-bit register is constantly filling up from the bits received from upstream and sometimes copied onto a bus, and an 8-bit register that can be emptied in series on the downstream link, which is loaded at the latest when you need the first of its bits. An injection flip-flop must select the upstream serial input or the downstream serial output of the write register. These registers can be distributed and duplicated in the doors if it is decided to use a serial bus for data transfer. All of these functions are gathered in FIG. 7 under the reference E / I.

It is undoubtedly advisable to indicate the reaction times to wait. If the distance from CNT1 to CNT2 is 200 km and if the propagation speed in the cable is 200,000 km / s, if there is a node every 200 m, therefore in the case of extreme reconfiguration 1000 nodes crossed each twice, if the crossing time is 1 bit-time, then the total duration of the loop's journey is 3 ms, ie a little less than a frame period. If the CNT has infinite processing power, that is to say if it is capable of taking into account in a frame that it transmits capacity requests that it received in the previous one, it runs between when a train requests transmission capacity and when it obtains 4 frame periods. To take into account the processing times, it is more reasonable to count on 5 frame periods, ie 20 ms. This duration corresponds to a journey of 2 m for a TGV traveling at 360 km / h, and 1 m for a locomotive traveling at 180 km / h. It therefore does not excessively affect the transmission capacity of a train without continuous coverage. We see that the challenge of having a crossing time of 1 bit time rather than byte time is around 4 ms. It would therefore still be acceptable to "take your time". Let’s add that, in the case of a locomotive with only one byte per multi-frame, the request is sent from the first frame, but the capacity waiting time can be extended by 15 frames, or 60 ms, or another 3 m for a locomotive traveling at 180 km / h. We can see the advantage of equipping the microwave reader with an antenna with an elongated cover, loss cable or slotted waveguide.

c) Time Base

• elle reconstitue le rythme bit à partir de la réception amont et, en l'absence de réception, synthétise un rythme approximativement égal,
• elle crée le rythme de trame,
• elle recherche le motif de synchronisation (en attendant sa fin en temps normal dans le deuxième ou le troisième octet de ce qu'elle s'attend à être la nouvelle trame); si le motif n'est pas trouvé dans plus de n trames consécutives, elle passe dans le mode de resynchronisation où elle le cherche partout,
• elle lit le numéro de trame à la suite du motif de synchronisation,
• elle multiplexe sur un bus parallèle d'adresses BA, le numéro de trame et de bit (17 fils) et le numéro abrégé de train (8 bits) fourni par le FIFO de gestion dynamique FGD, un 18ème fil assurant le multiplexage entre les deux informations (ou encore, dans un premier temps le numéro de bit (13 bits) et dans un deuxième temps le numéro de trame (4 bits) et le numéro abrégé de train (8 bits), ce qui limite à 14 le nombre de fils du bus,
• elle reconnaît les ordres concernant une porte série, dans les octets 32-33 et envoie à la porte appropriée un signal de sélection à la fin de l'octet 36 pour que celle-ci enregistre les informations présentées sur le bus série de données BD,
• elle présente une information de validation aux portes parallèles pendant les octets 992-1023, de façon que celles-ci, si elles ont reconnu le numéro abrégé de leur train dans les 8 bits de poids faible du bus d'adresses BA, ajoutent un 1 sur le bus série d'écriture si elles n'ont pas connu d'underrun lorsqu'il leur a été demandé de fournir des octets de données,
• elle envoie une impulsion d'écriture au FIFO de gestion dynamique FGD pendant les octets 0 à 31, et lui présente un octet 0 sur le bus de données pendant les octets 0, 1, 2, et 31; elle envoie à ce FIFO une impulsion de lecture tous les 32 octets et lui donne la maîtrise de 8 fils du bus d'adresse BA dans une phase sur deux de la présentation d'adresses sur ce bus.

The BT time base has multiple functions:

• it reconstructs the bit rate from the upstream reception and, in the absence of reception, synthesizes an approximately equal rate,
• it creates the frame rhythm,
• it searches for the synchronization pattern (until it normally ends in the second or third byte of what it expects to be the new frame); if the pattern is not found in more than n consecutive frames, it goes into resynchronization mode where it searches for it everywhere,
• it reads the frame number following the synchronization pattern,
• it multiplexes on a parallel bus of BA addresses, the frame and bit number (17 wires) and the abbreviated train number (8 bits) provided by the dynamic management FIFO FGD, an 18th wire ensuring the multiplexing between the two information (or, firstly the bit number (13 bits) and secondly the frame number (4 bits) and the abbreviated train number (8 bits), which limits the number of wires to 14 from the bus,
• it recognizes the commands relating to a serial port, in bytes 32-33 and sends a selection signal to the appropriate gate at the end of byte 36 so that it stores the information presented on the serial data bus BD,
• it presents validation information to the parallel doors during bytes 992-1023, so that these, if they have recognized the abbreviated number of their train in the 8 least significant bits of the address bus BA, add a 1 on the serial write bus if they did not know an underrun when they were asked to provide bytes of data,
• it sends a write pulse to the dynamic management FIFO FGD during bytes 0 to 31, and presents it with a byte 0 on the data bus during bytes 0, 1, 2, and 31; it sends an impulse to this FIFO reads every 32 bytes and gives it control over 8 wires of the BA address bus in every other phase of the address presentation on this bus.

d) Capacity Management and Doors

Dynamic capacity management involves writing and reading the FGD dynamic management FIFO. This FIFO is filled, starting from bytes 0 to 31 of the frame (bytes 0-2 and 31 corresponding to a padding). Each non-zero byte represents the abbreviated number of a train authorized to use the group of 32 bytes corresponding to its rank in the FIFO to receive and transmit data. Consequently, each byte of the FIFO is presented, for 32 consecutive byte times, on the address bus BA (where it is multiplexed with the bit time and the frame number) and it is the dynamically managed gates which compare in C ₁ and NA the abbreviated train number presented to the one entered in their assignment register. If there is a match, at each byte time, they read a byte in the input FIFO F ₁ E and write one in the output FIFO F ₁ S. Caution: the reading of a byte must take place before the inject on the line; writing a byte can only take place after it has been received. As the crossing time of a node is only 1 bit time, all writes must take place (almost) one byte time before the readings of the same address. One solution is that the gate Pd copies all the byte times the fact that it has read, and does not write until it has read a byte earlier. It is undoubtedly desirable that the transfer of the data is done in series on a wire bit by bit rather than in parallel byte by byte.

The management of the static capacities and of the rhythms managed by RS is done by the comparison in C ₂ of the byte time (and frame number) presented on the address bus BA and of what the door has stored as control information, namely the same kind of information, plus a mask explaining which bits to ignore in the comparison. This ordering information was presented in series, and stored in parallel in a 24-bit register. Data transfers could also be done in series. The gate Ps also includes a selector making it possible to choose which of the wires of the address bus BA to be used to give the rhythm to the external serial link, regular rhythm even if the data arrive in packets.

The foregoing description of the architecture of a node uses only wired logic elements. It is obviously not excluded to carry out certain functions thanks to a microcontroller and the appropriate software.

Claims (13)

1. A short-range transmission system between ground beacons (b) and mobile stations, said mobile stations being equipped with an antenna or another radiating device (GO), characterized in that said antenna or said radiating device (GO) has a coverage in the direction of movement of the mobile station which is very much greater than that of one beacon, such that this coverage attains or exceeds the distance between successive beacons.
2. A short-range transmission system between ground beacons (b) and mobile stations according to Claim 1, in which the antenna borne by the mobile station is a radiating cable.
3. A short-range transmission system between ground beacons (b) and mobile stations according to Claim 1, in which the antenna borne by the mobile station is a slotted waveguide (GO).
4. A short-range transmission system between ground beacons (b) and mobile stations according to Claim 3, in which the mobile station is formed by a set of several vehicles each bearing a waveguide (GO) acting as an antenna and the waveguides of two adjacent vehicles are connected by a flexible waveguide (s₁, s₂).
5. A short-range transmission system between ground beacons (b) and mobile stations according to Claim 3, in which the mobile station is formed by a set of several vehicles each bearing a waveguide (GO) acting as an antenna and the waveguides of two adjacent vehicles are connected by a coaxial cable (Cx) to which they are adapted.
6. A short-range transmission system between ground beacons (b) and mobile stations according to Claim 3, in which the mobile station is formed by a set of several vehicles each bearing a waveguide (GO) acting as an antenna and the waveguides (GO) of two adjacent vehicles, when the vehicles are in alignment, are aligned with each other and at a short distance from one another so as to permit coupling by radiation (b₁, b₂).
7. A short-range transmission system between ground beacons (b) and mobile stations according to Claim 1, in which the antenna is formed by two slotted waveguides (GO) such that the zone of coverage of one has at least one part which in the longitudinal direction does not belong to the zone of coverage of the other.
8. A short-range transmission system between ground beacons (b) and mobile stations according to Claim 3 or Claim 7, in which the wavelength of the radiated signal or of one of the radiated signals is close to a sub-multiple of the pitch of the slots.
9. A short-range transmission system between ground beacons (b) and mobile stations according to Claim 1, in which a ring connection connects to each other and to a Nodal Transmission Centre (CNT) the nodes (Ni, Nj) to which beacons (b) are connected which succeed one another on the route or the railway line, or at least some of these nodes.
10. A short-range transmission system between ground beacons (b) and mobile stations according to Claim 9, in which a plurality of nodes is distributed between two Nodal Transmission Centres (CNT₁, CNT₂), all comprising means for configuring two rings in topological continuity, each managed by one of the Nodal Transmission Centres and comprising means for determining this distribution.
11. A short-range transmission system between ground beacons (b) and mobile stations according to Claim 10, in which these means consist:

    - a. in that each node (Nj) having lastingly lost synchronisation searches for a certain message structure alternatively on the input from one (Ni) and the other (Nk) of its neighbours,

    - b. in that, while a node (Nj) is effecting the search on one side it retransmits from the other side what it receives,

    - c. in that a Nodal Transmission Centre (CNT₁) emits said message for a sufficient time to permit the nodes to lock on to it gradually,

    - d. in that this Nodal Transmission Centre (CNT₁) addresses a relooping command by name to one node (Nm) which it intends to make the last node of the ring.
12. A short-range transmission system between ground beacons (b) and mobile stations according to Claim 9, in which the information is structured in frames, part of this information describes to what recipient part of the frame is assigned and, if applicable, another part of the frame is assigned permanently or semi-permanently.
13. A short-range transmission system between ground beacons (b) and mobile stations according to Claim 1, in which the recipients are trains and means exist at the trains, the beacons and the nodes so that, by means of the beacons with which they are in contact, the trains indicate to the nodes which manage these beacons the addressing information permitting the node to extract from the frame the information intended for the train and to inject into the frame the information coming from the train.

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