DE3140402C1 - Information transmission system (telecommunications system) which consists of networks and uses a channel group by means of frequency jumps - Google Patents

Description

The present invention relates to a network Message transmission system, which by frequency hops used a channel group.

Such networks, the z. B. are known from US 41 93 030, are made of several Two-way radios are formed, which are connected to each other stand. Each network uses the channels on its own of the overall system according to a pseudo-random frequency hopping rule. The frequency hopping rule of a network must remain unknown to other networks; the rules of different Networks must be orthogonal, i. H. that to a certain Time a channel is no longer assigned to one network may be.

Such a system finds important applications on the Area of military radio links where it is imperative is required over secure connections with low vulnerability for interference from the enemy. The Process a channel for the shortest possible period of time Using from a large number of channels is called one safe measure to combat interference from the enemy considered.

The problem with this type of system is as follows: It its considered a device of a particular network that is based on Reception is switched to the broadcast of a nearby device to receive, of course, part of this particular network is. If a frequency jump occurs, use the certain one Network a new channel. It is not out of the question that this new channel by a remote device, which  belongs to another network, shortly before the occurrence of the mentioned Frequency hopping was used as the transmission channel, so that the runtime sent by the devices removed from it Wave needs to go to the device switched to reception to arrive, interference between the remote broadcast and the shipment of the nearby device.

The object of the present invention is a system of Specify the type mentioned, in which such disorders be avoided.

This object is achieved in that the Channel group is divided into different subgroups and that a different one of these sub-groups is used with each jump becomes.

Exemplary embodiments of the invention are described below of the drawings explained.

Fig. 1 of the invention schematically shows the arrangement of various geographic to a system according belonging radios.

Fig. 2 is a diagram showing the use of the frequency channels.

Figure 3 shows schematically the time distribution of the power used to transmit the information on a particular channel.

Fig. 4 shows the efficiency curves of a system in which the invention is not applied.

Fig. 5 shows a possible use of the available channels according to the invention.

Fig. 6 shows the efficiency curves of a system according to the invention.

FIG. 7 shows a circuit diagram of an embodiment of a radio device belonging to the system according to the invention for the use of the channels shown in FIG. 5.

Fig. 8 shows a first example of the use of the channels grouped into subgroups.

FIG. 9 shows a circuit diagram for a radio for using the channels shown in FIG. 8.

Fig. 10 shows a second example of the use of channels grouped into subgroups.

FIG. 11 shows a circuit diagram for a radio for using the channels shown in FIG. 10.

In Fig. 1 the geographical distribution of some devices belonging to a system according to the invention is shown very schematically. Such a system consists of networks R 0 , R 1 , R 2 , R 3 . . ., which are device groups. To 1 part in Fig. The units P 1, (R 0), P 2 (R 0), P 3 (R 0) and P 4 (R 0), as can be recognized by the bracketed term, the network R 0 . The devices P 1 ( R 2 ), P 2 ( R 2 ), P 1 ( R 3 ) are also shown. Each network uses one channel for a time Δ t ; then, after this time, a frequency hopping occurs on, and a different channel during a time period Δ t in use. Thus, with reference to FIG. 2, at time t 1 and for a duration of Δ t, the devices of the network R 0 can only be connected to one another via the channel CH 7 , the devices of the network R 4 via the channel CH 6 and the devices the network R 1 via the channel CH 5 ; Thereafter, at times t 2 and for a duration Δ t, the devices of the network R 0 can only be connected to one another via the channel CH 5 . The channels CH 7 and CH 6 are only used for the networks R 2 and R 5 during this time period Δ t . It should be noted that, within the intended application of this time, Δ t must be as short as possible so that as little information as possible can be used by the enemy so that he cannot determine the lawfulness of the channel change.

It will now be explained in detail what happens at the times when the channels are changed, for what. B. the channel CH 7 is viewed at time t 2 . This time t 2 is selected in the device P 2 and is known with an accuracy of δ t , which is determined by the synchronization errors of the clock generators of the devices. At this moment t 2 , the devices of the network R 2 use the channel CH 7 , and the devices of the network R 0 switch to the channel CH 5 . However, since the device P 1 ( R 0 ) is a distance "d" away, its transmission would still be received if the device P 2 ( R 2 ) during a time t _pg , which is equal to the transit time of the wave from the device P 1 ( R 0 ) to device P 2 ( R 2 ), no measures are taken. This scope for the use of one and the same channel by two networks is partially avoided by the pre-switching time T _S that is present in the transmitting device with each channel change (see FIG. 3). If the time it takes for the transmitter to go from its highest transmission power P _MAX to an interruption of the transmission and the time it takes for the transmitter to come back to power is denoted by T _M , the following relationship is obtained :

T _M + T _S < t _pg + 2 δ t (1)

With a maximum range d = 375 km, with t _pg = 1.25 ms, a value is obtained that is greater than the value T _M + T _S = 0.75 ms possible through technology. It is therefore necessary to increase T _S to satisfy inequality (1). An efficiency p can be defined, which represents the percentage of the time that can be used for message transmission. If the period of time during which a message is effectively transmitted is designated T _P , one obtains for ρ :

From this it can be seen that this efficiency becomes worse and worse as the running time increases: in order to compensate for the disadvantageous influence of this time, the accuracy δ t of the clock generators can also be improved, which increases the cost of the material.

FIG. 4 shows the drop in the efficiency ρ as a function of errors δ t for the various values of T _P , where T _M + t _pg = 1.5 ms.

To avoid this sharp drop, the channel group is divided into N different sub-groups and a different one of these sub-groups is used for each jump.

In Fig. 5 a channel group ECH with the channels CH 0 through CH is shown 63rd For example, this group is divided into N = 2 different sub-groups SECHA and SECHB . The subgroup SECHA includes the channels with an even code CH 0 , CH 2 ,. . . CH 62 , and the subgroup SECHB those with an odd number CH 1 , CH 3 ,. . . CH 63 . To simplify the explanation, the use of these channels by a single network, the network R 0 , is examined. Between the times tt 1 and tt 2, the channel CH 58 belonging to the subgroup SECHA is used; thereafter, channel CH 27 of subgroup SECHB is used between times tt 2 and tt 3 , and channel CH 40 of subgroup SECHB is used between times tt 3 and tt 4 .

It can now improve the efficiency be determined.

In case N , inequality (1) is replaced by:

T _M + T _S + (N -1) · (T _P + 2 T _M + T _S ) | t _pg + 2 δ t (3)

For ρ one can write:

If one eliminates T _P , the combination of equations (3) and (4) yields:

Various efficiency curves are shown in FIG. 6. Various values for T _P are given on the ordinate on the right; equation (4) indicates the relationship between ρ and T _P. The curves are drawn for t _pg = 1.25 ms, T _M = 0.25 ms, T _S = 0.5 ms.

One can clearly see that one cannot obtain large ρ and δ t if T _P and N are small. A comparison with FIG. 4 shows the gain at ρ for a given δ t .

Fig. 7 shows schematically a belonging to the system according to the invention device. This device comprises a transceiver 1 , which enables message transmission on the various channels CH 0 to CH 63 ; the channel is selected by the frequency of a frequency generator 2 , which is controlled by a recoder 3 ; this transcoder 3 , which is provided with input connections F 0 , F 1 , F 2 , F 3 , F 4 , F 5 , makes it possible to establish a relationship between the 64 channels and the binary elements f 0 , f 1 , which are connected to its input connections and f 2 , f 3 , f 4 , f 5 to produce existing binary code; this relationship is shown in Table 1 below:

Table 1

The connections F 1 , F 2 , F 3 , F 4 , F 5 are connected to the outputs FS 1 , FS 2 , FS 3 , FS 4 and FS 5 of an arrangement 10 , which for the connections B 0 , B 1 , B 2 , B 3 , B 4 lying different identification codes provide different numerical codes; such a device is described in detail in patent application P 31 28 016.1.

The identification codes are used to identify various networks belonging to the system. The various binary elements b 0 , b 1 , b 2 , b 3 , b 4 make it possible to designate 32 networks in the manner given in Table 2 below:

Table 2

The arrangement 10 is formed by an exchange arrangement BR 0 , the outputs of which form the connections FS 1 to FS 5 and which inputs have G 1 , G 2 , G 3 , G 4 and G 5 . This arrangement supplies a binary word at its outputs, which is the result of a permutation of any order of the binary elements applied to its inputs. To facilitate the explanation of the functioning of the system, it can be assumed that this arrangement BR 0 performs a zero-order permutation, that is to say that it behaves as if the inputs G 1 , G 2 , G 3 , G 4 and G 5 were directly associated with it the outputs FS 1 , FS 2 , FS 3 , FS 4 and FS 5 are connected. This arrangement 10 further comprises a group of modulo-2 adders A 1 , A 2 , A 3 , A 4 , A 5 , the outputs of which are connected to the inputs G 1 , G 2 , G 3 , G 4 , G 5 , wherein the first inputs of these adders A 1 , A 2 , A 3 , A 4 and A 5 are each connected to the connections B 4 , B 3 , B 2 , B 1 and B 0 . The second inputs of these adders receive pseudo-random sequences from binary elements which are generated by a generator GEN for pseudo-random sequences; the second input of adder A 1 receives a sequence labeled SQ 1 , the second input of adder A 2 receives a sequence SQ 2 , and so on. . .

The different sequences depend on a key that is selected from a very large number. The sequence SQ 1 depends on a key C 1 , the sequence SQ 2 on a key C 2 , the sequence SQ 3 on a key C 3 , the sequence SQ 4 on a key C 4 , SQ 5 on C 5 . However, to ensure that the codes at inputs G 1 , G 2 , G 3 , G 4 and G 5 are orthogonal, certain keys are common to several networks; the key C 2 is common to the networks whose binary element b 4 is the same. The key C 3 is common to the networks whose binary elements b 4 , b 3 are the same; this key is called C 3 ( b 4 , b 3 ); there are also the keys C 4 ( b 2 , b 3 , b 4 ) and C 5 ( b 1 , b 2 , b 3 , b 4 ). The various codes are supplied to the connections FS 1 to FS 5 of the arrangement 10 in the rhythm 1 / Δ t of a clock generator 20 . A circuit 25 which, for. B. consists of a simple flip-flop, provides a sequence of binary elements with alternating values 0, 1, 0, 1, 0,. . ., so that for each Δ t either one of the even channels ( CH 0 , CH 2 , ... CH 62 ) or one of the odd channels ( CH 1 , CH 3 ... CH 63 ) is selected. In a system according to the invention there can be very closely adjacent radio devices belonging to different networks. It is therefore necessary that these devices do not interfere with each other; for this it is necessary to make a radio frequency coupling of these devices. To achieve this decoupling, the frequencies of the channels used by the networks in question are separated from one another by a value which is at least equal to a certain value. This particular value is determined by the 64 channels being divided into 8 subgroups SG 0 , SG 1 ,. . . SG 7 can be divided. The subgroup SG 0 consists of the channels CH 0 , CH 1 ,. . . CH 7 , the subgroup SG 1 from the channels CH 8 . . . CH 15 , etc. Now only the four subgroups SG 1 , SG 3 , SG 5 and SG 7 (see FIG. 8) are used, so that between each of these subgroups there is an unused subgroup whose width corresponds to a certain value . An even or an odd channel in the subgroup used is now used alternately with each jump; the usable channels are shown in FIG. 8. Thus, the odd channels of subgroups SG 1 , SG 3 , SG 5 and SG 7 can be used between times tt 1 and tt 2 , while the even channels of these same subgroups can be used between times tt 2 and tt 3 . Then the odd channels can be used again between times tt 3 and tt 4 .

FIG. 9 shows an embodiment detail of a radio device belonging to a system according to the invention, which enables the use of the channels according to FIG. 8. The code for identifying the networks here comprises four binary elements b 0 ', b 1 ', b 2 ', b 3 ', which are applied to the connections B 0 ', B 1 ', B 2 'and B 3 '. These connections are connected to the first inputs of the four modulo-2 adders A 5 , A 4 , A 2 and A 1 , the second inputs of which receive the sequences SQ 5 , SQ 4 , SQ 2 and SQ 1 from a generator GEN . The subgroups are defined by the binary elements present at the inputs F 5 , F 4 , F 3 of the converter; since the binary element f 3 is always "1", you can see that you are only dealing with the subgroups whose key figure contains an odd number. The exchange arrangement BR 0 consists of two parts BR 0 ' and BR 0'' . The part BR 0 'causes any permutation between the binary elements present at its connections G 5 and G 4 and outputs them to the inputs F 5 and F 4 again, the connections G 5 and G 4 with the outputs of the adders A. 5 and A 4 are connected. The part BR 0 '' causes any permutation between the binary elements applied to its connections G 3 and G 1 and outputs them again at connections F 2 and F 1 , the connections G 2 and G 1 with the outputs of the adders A 2 and A 1 are connected. The connection F 0 is connected to the output of the circuit 25 , which alternately supplies logic "1" and "0".

It is possible to divide the channel group differently. Still starting from subgroups, as shown schematically in FIG . B. a first subgroup can be used, which includes all channels (ie simultaneously the even and the odd channels) of the subgroups, whose numerical identification number is odd: That is, the subgroups SG 1 , SG 3 , SG 5 and SG 7 , and second Subgroup all channels of those subgroups whose numerical code is even; with each jump you will of course change from one subgroup to the other. Fig. 11 shows the way in which subgroups can be obtained. The number of the subgroups is determined by the binary elements applied to the connections F 5 , F 4 , F 3 ; In order to pass from the subgroups with an even identification number to the subgroups with an odd identification number, the connection F 3 is connected to the circuit 25 . The connections F 5 and F 4 are connected to a part BR 0 'of the exchange arrangement, the connections F 2 , F 1 , F 0 of the converter are connected to the outputs of the second part BR 0 ''of the exchange arrangement; the parts BR 0 ′ BR 0 ′ ′ work independently of one another, but in the same rhythm. The inputs of part BR 0 'are connected to the outputs of modulo-2 adders A 5 and A 4 , and those of part BR 0 ''are connected to the outputs of adders A 2 , A 1 and A 0 . The inputs of these adders A 5 , A 4 , A 3 , A 2 , A 1 , A 0 receive the applied to the connections B 0 ', B 1 ', B 2 ', B 3 ', B 4 ', B 5 ' binary identification code. The second inputs of these adders receive the binary elements of the sequences SQ 5 , SQ 4 , SQ 2 , SQ 1 and SQ 0 supplied by the generator GEN . It can be seen that in this last-described manner, that shown in FIGS. 11 and 10 is, the available channel group is used in the best possible way if you want to provide high-frequency decoupling.

Claims (2)

1. Networks existing communication system that uses a channel group through frequency hops, characterized in that the channel group is divided into different sub-groups and that a different one of these sub-groups is used with each jump. 2. Message transmission system according to claim 1, in which each network identified by an identification code comprises a plurality of radio devices, each of which contains a frequency generator which serves to determine the channel used, characterized in that each radio device ( P 1 , P 2 ,...) To control its frequency generator ( 2 ), a transcoder ( 3 ) which converts a numerical code located at its inputs ( F 0 , F 1 ,...) into information determining the channel used, an arrangement ( 10 ) for delivering sequences numerical codes depending on the identification codes, the outputs ( FS 1 , FS 2 ,...) of which are connected to the inputs ( F 1 , F 2 ,...) of the transcoder ( 3 ) and contain a circuit ( 25 ), which provides alternating numerical data and whose output is connected to one of the inputs ( F 0 , F 3 ) of the transcoder ( 3 ).