Communication system.

The invention relates to a communication system having at least one central device and having a plurality of independent subscriber stations, wherein a subscriber station expects to be issued by the central device access authorization by sending an access request.

From DE-OS 31 33 347.8 is a method of accessing transmission channels of a communication system having at least one central device, with at least a duplex transmission channel and a plurality of independent subscriber stations, in which access each subscriber station for a multiple access method to the duplex transmission channel can known.

The messaging system described in this document is a system for transmitting messages via radio links with stationary radio stations and mobile subscriber stations. Here each stationary radio station (central device) is assigned a set of duplex transmission channels. One (the organization channel) for transmitting control information for the operation and the other (the voice channels) are used for voice transmission.

The following is the first channel of the organization channel, on which the subscriber stations transmit their control information to the central facility, as a forward channel, the second channel on which the central device transmits its control information to the subscriber stations via called backchannel. Return channel of the organization channel is divided into time slots, the time slots of the Hinkanals for better utilization may be subdivided into a number of Rufschlitzen. To initiate the construction of a conversation with a subscriber of a telephone network or any other subscriber station, which originates from a subscriber station, the subscriber station selects randomly from one of these paging slots. In order to increase the usability of Hinkanales, they do not, however, send their full identification, whose signal length would take several paging slots, but an all subscriber stations the same signaling abbreviation.

This signaling Abbreviation informs the central device that a request for setting up a call is made by a subscriber station. within a time slot of the central facility are multiple signaling Abbreviation been received, so one of these subscriber stations is selected by the central device, said subscriber station by the number of Rufschlitzes in which she had sent, can be clearly determined. Then, the central unit sends to identify a call to the subscriber station. In this call, the number of Rufschlitzes is included in this subscriber station had sent her signaling abbreviation. This is the danger of destruction access and thus one time share, for the forward channel of the organization channel is only slightly used, reduced by shortening the duration of the individual access requests.

Each subscriber station, which had sent a signaling abbreviation in a paging slot and is not prompted by the expiration of a predetermined period of time to show their full identification must repeat their access request by retransmission of their signaling short character.

The return channel of the described in the aforementioned signature duplex transmission channel is formed by two different frequencies. However, duplex transmission channels can also be formed by time slots, wherein each channel is assigned a time slot and several time slots are combined into a time frame. The time frame can be organized both in a single frequency position or at several other frequented locations.

Object of the present invention is to improve a communication system of the aforementioned type so that access times are reduced and the capacity of the organization channel can be increased.

This object is achieved on the basis of the above-mentioned communication system, characterized in that the subscriber station access their desired repeated whenever it detects that another subscriber station that has sent its access request later, receives an access authorization.

The dependent claim 2 shows a configuration of the communication system, wherein the subscriber stations are classified in different priority classes.

The sub-claims 3 and 4 indicate an embodiment of the messaging system in which, by the way of the access authorizations a load control within the central device is made possible.

More vorteihafte embodiments of the invention are the subject matter of the further subclaims.

Embodiments describe the invention. Reference to the drawings shown in the Figures further details will be described and explained.

Shown in schematic representation:<ul><li>FIG. 1 a period of organization channel.</li><li>Fig. 2 is a block diagram of a mobile station.</li><li>Fig. 3 is a further block diagram of a mobile station.</li><li>Fig. 4 is a further block diagram of a mobile station.</li></ul>

A preferred embodiment of a communication system having at least one central device and having a plurality of independent subscriber stations, wherein a subscriber station by transmitting an access request expects to be issued by the central device access permission is a radiotelephone system with spatially variable subscriber stations. The application of the invention is not limited to such a radio telephone system, but is, for example, at Satelittenkommunikationssystemen or in networked computers on a "Local Area Network" applicable.

In the described radio telephone system move in the radio reception area of ​​a central device which is hereinafter referred to as a base station, a plurality of mutually independent subscriber stations, hereinafter referred to as mobile stations. The Funkemp reception range of the base station, for example, the radio cell of a cellular car phone network, such as the planned pan-D network. Radio communication between the mobile stations and the base station takes place on a limited number of duplex transmission channels. One of these duplex transmission channels is formed as a control channel.

FIG. 1 shows a time detail the dialogue on the organization channel. The control channel is divided into time slots. Line a in Fig. 1 shows the forward channel of the control channel on which to send the mobile stations and line b in Fig. 1 shows the return channel on which the base station transmits. All mobile stations that want to carry out a call origination, are first in the so-called ringing phase, in which they send an access request on the forward channel.

Since several access requests simultaneously sent these access requests would overlap and could thus at most to enforce an access request per time slot, each time slot is divided into eight call slots. By means of the base station transmitted synchronization signals each paging slot is numbered sequentially. Based on these Rufschlitznummer each paging slot is clearly distinguishable both for the base station, as for all mobile stations. As the number of Rufschlitznummern time is too large, the numbering of the next Rufschlitzes is started again with the number zero in the exemplary embodiment, after reaching a determinable maximum value.

The access request of a mobile station comprises a signaling Abbreviation, whose signal length requires only a paging slot for transmission. In which call each mobile station transmits slot, is determined by a arranged in the mobile station random. In this way, there is a high probability that at several access requests some access requests reach the base stations without conflict. In line a of FIG. 1 sends the paging slot no. 42, a mobile station A, the paging slot no. 46, a mobile station D and the paging slot no. 47, a mobile station E. In the paging slot no. 44 have two mobile stations B and C at the same time sent an access request , Go both access requests with approximately the same field strength at the base station, so an access conflict in the time slot no. 44 produced marked with X. Access conflicts are ignored by the base station.

Fig. 2 shows a block diagram of a built-up from a reception part 1 and a transmitting section 2, and an evaluation device 3 mobile station. By arranged in the evaluation device 3 sequencer 31 the transmission of the access request is triggered. A arranged in the receiving part 1 and not shown synchronization device delivers at the output RSN of the receiving part 1 the current assigned by the base station Rufschlitznummer. With the transmission of the access request this current Rufschlitznummer is stored in a register 32nd In this way, each mobile station noted the Rufschlitznummer in which it has sent its access request. Thus, the register 32 of the mobile station A contains the Rufschlitznummer 42, the registers of the mobile stations B and C, the Rufschlitznummern 44 and so on.

After the transmission of the access request, the mobile stations are added by the sequence controller 31 the ringing phase of the waiting phase. In the waiting phase they expect from the base station sent to them access authorization, with the them a speech channel is allocated, where they can continue the call setup.

The data received from the base station conflict-free access requests, in line a of Figure 1 marked with * are processed in the order they arrive. Since the received signaling Abbreviation contains no information about the subscriber station which has sent the signaling Designation, at the time of reception of a signaling token's assigned each of the Baisstation Rufschlitznummer serves as a distinguishing tool between the calling mobile stations. Each access request is managed in the base station in a file with this Rufschlitznummer.

Since this stored Rufschlitznummer simultaneously to form the ranking, in which get assigned to their access permissions, the mobile stations, serving, these managed by the base station Rufschlitznummern be referred to as the authorization numbers.

The base station is now an access authorization sent in the order in which the conflict-free access requests sequentially example to the mobile stations A, D and E. For this purpose, any access authorization includes each access request authorization assigned number. In time slot, which 48 begins with the paging slot no., The base station therefore sends an access permission For example, including the authorization number 42 and the channel number XX a free speech channel.

The Rufschlitznummer contained in the credential is all located in the waiting phase mobile stations A, B, C, D and E evaluated and forwarded to a further output BN of the receiving part. 1 This output BN is connected to a first input of a comparator 33rd A second input of the comparator 33 is connected to the output of register 32nd The comparator 33 has two outputs, which are connected to the sequence control 31st If the two applied to its output speed values ​​match, it outputs a signal to its first output. Exceeds the numerical value on its first input the numeric value, which is applied to its second input, it emits a signal at its second output.

In this way, compare all the mobile stations A, B, C, D and E is present in the waiting phase the received with the access authorization authorization number with their respective stored in the register 32 Rufschlitznummer. But the mobile station A determines a match of these two numbers. The signal at the first output of the comparator 33, the sequencer 31 is instructed to leave the waiting phase and further continue the call setup with the base station on the assigned access level in the speech channel XX.

All mobile stations receive the access permissions, which contain an authorization number which is lower than the stored Rufschlitznummer, remain in the waiting phase. These are the mobile stations B, C, D and E. During the waiting period, they do not send a re-access request made. In this way, the control channel is not used by the mobile stations located in the waiting phase, also not if it causes will have to wait through a large number of access requests of other mobile stations, long time. This has the advantage that the load of the control channel can be kept as low as possible, especially in the times with many access requests and thus less access collisions can be expected from calling mobile stations.

The next assigned in the managed by the base station received access requests authorization number has the numerical value of 46. The next access authorization, which is sent from the base station in the time slot, which begins with the paging slot no. 56, therefore, includes the authorization number 46 and the channel number XY one free speech channel. The mobile station D know then, that it may continue its discussion on the structure of speech channel XY specified in the credential.

By comparing the authorization number 46 with their own stored Rufschlitznummer 44 determine the mobile stations B and C, they have been ignored. This is the indicator for them that their access request from the base station could not be received. Only now leave both mobile stations B and C through the output of the second output of the comparator 33 their waiting period and by the sequencer 31 is reset in the ringing phase. In one of the following call slots they send back from an access request. Due to the arranged in the sequence control random send the mobile stations B and C most likely but then in various Rufschlitzen, for example in the Rufschlitzen no. 67 and no. 70, and thus avoid, at least among themselves, an access conflict.

In this way it is prevented that mobile stations, de ren access requests, the base station could not reach, it may find itself again and send an access request. Advantageously, however, send only those mobile stations, regardless of how long they have to wait for permission to access, then access it again desire if their access request has not actually reached the base station. Furthermore, the permission to access the control located in the waiting phase mobile stations must not contain any additional information, so that the assignment of the return channel is not thereby increased. The burden of Hinkanales and the number of access collisions is reduced, however.

With the described arrangement, a so-called load control of the radio telephone network is possible. Meeting at the mobile station a lot of access requests from mobile stations a so causes the base station that the transmission of the access permissions will be delayed, without any need to fear that the present in the waiting phase mobile stations stop up by renewed access requests to the forward channel.

In a further, not shown embodiment of the embodiment of a timer circuit is arranged in each mobile station. This timer circuit is started with the transmission of an access request. Receives the mobile station due to its access request a specific permission for them to access, then the timer circuit reset. Runs the predefined by means of the timer circuit time within the waiting phase, so the mobile station will again by the timer circuit is reset in the ringing phase. In this way it is ensured that mobile stations whose access request has been lost and it can not be ascertained, because in the meantime, no permissions are assigned, re-send an access request after a predetermined waiting period. The predetermined duration of this timer circuit is dependent on the intended load on the organization channel. It is in the embodiment in the order of ten seconds.

In a further embodiment of the invention, the base station transmits at greater intervals from an access level with the instantaneous Rufschlitznummer. Since this access authorization is preceded no access request, it is called a pseudo access. In this way it is ensured that only a small number or no access requests are also times in which received, mobile stations whose access request has not been received, obtained with this pseudo access authorization with an authorization number, which enables them to recognize the loss of their access request and then submit a new access request. The sending of such a pseudo access authorization provides the advantage that the circuit scale can be omitted for the disposed in each mobile station timer circuit and the detection of a Rufverlustes is possible only with the already described circuit arrangement for detecting an access authorization.

The order of access of the mobile stations of the cellular telephone system described is based on an absolute numbering of the call slots on transmitted from the base station, for example, in synchronization signals Rufschlitznummern. As absolute numbering but can also be used for example, the system time of the radiotelephone system.

In the circuit arrangement described below, a relative numbering is used instead of an absolute numbering. For relative numbering an access request is the time interval between the access request and received permission to access or to equivalent size, for example, the number of intervening time slots used.

In the mobile station shown in FIG. 3, a clock circuit included in the synchronization part of the receiving part 1 generated at the beginning of a Rufschlitzes an output pulse which is supplied via the output RST of the receiving part 1, a counter 34. The clock generator circuit is synchronized with the base station. Such a timer circuit is usually already present in each mobile station in order to ensure the time-synchronous transmission, such as the access request. A reset input R of the counter 34 is connected to the sequence controller 31, which corresponds in function and construction of the sequence controller shown in Fig. 2. By the reset input of the counter 34 signal applied to the sequence control of the count output of the counter 34 remains at zero until the sequence control 31 has sent an access request. Now increases at each clock pulse at the counting of the count of the counter 34 by one each. The counter output of the counter 34 is connected to the first input of a comparator 33rd By means of the evaluation contained in the receiving section 1 is supplied to the authorization number contained in the respective received access authorization to the second input of the comparator 33 via the output BN of the receiving part. 1 The comparator 33 generates two output signals. At its first output, an output signal is generated when the count of the counter 34 and the authorization number match. an output signal is generated from its second output when the count of the counter 34 is greater than the received authorization number. These two signals are fed to the sequencer 31 and cause the already described state changes as ringing phase, waiting phase, etc .. When sending an access request, the counter 34 starts counting the elapsed Rufzeitschlitze. When sending an access level, the base station indicated in the access authorization, the number of paging slots that lies between the reception of this access level triggering access request and the transmission of the access authorization. For this purpose is stored in the exemplary embodiment in the base station simultaneously with the storage of the access request override the current Rufschlitznummer. In the transmission of the access authorization the number of past paging slots is determined from the difference of the current now Rufschlitznummer and the stored Rufschlitznummer.

The relative numbering has the advantage that the complexity in the mobile station can be reduced, since from the received synchronization signals, only a Rufschlitztaktsignal must be dissipated, which is already required for synchronization of the paging slots in relation to the absolute numbering. This need the synchronization signals do not contain the Rufschlitznummer. This leads to a reduction of the synchronization signals to be transmitted as well as to a reduction of the total system complexity.

Because of signal processing times, the transmission of the access permission to some timeslots can move. The resulting necessary correction to the number of paging slots, which lies between the calculation of the number of desired paging slots and the transmission of the access authorization must be taken into account. This is most easily in that in calculating the number of paging slots in the base station, a corresponding correction value is added.

With the stated radiotelephone system all mobile stations are of equal rank. The access permissions are therefore issued in the order in which the access requests.

In a further embodiment of the invention, the mobile stations are divided into different priority classes. A mobile station having a higher priority must be given their access rights from a mobile station with a lower priority. However, it is also possible that the priority of a mobile station access request may be different to access desired. For example, each mobile station, regardless of which priority class it belongs, take the highest priority for an emergency call.

Fig. 4 shows a block diagram of a mobile station, wherein such priority classes can be considered. The embodiment shown in Fig. 4 proceeds from the embodiment shown in Fig. 2 and is also provided with switching means, which are needed to take account of the priority classes.

For this purpose, each mobile station stores in addition to storing the Rufschlitznummer in the register 32, the priority of their access request in a second register 35. The output of register 35 is connected to the input of a second comparator 36th The Zugriffswün cal be processed by the mobile station in order of priority and within a priority class according to their order of arrival. To this end, the priority of that your access is indicated simultaneously in the access authorization. The priority class included in the access authorization is determined by the evaluation unit contained in the receiving portion 1 and is supplied via an output PK a second input of the second comparator 36th A loss of one's own access request is determined by the mobile station in that it receives a reply from the base station whose Rufschlitznummer is larger than its stored Rufschlitznummer yet received priority class is lower than or equal to the stored priority class. In this case, the mobile station from its waiting phase returns to the calling phase. For this purpose, the outputs of the comparator 33 and the second comparator 36 respectively by means of an AND gate 37, 38 are linked.