Mobile radio communication system

The invention relates to a mobile communication radio system according to the preamble of claim 1. In particular, it relates to an economical S teuerkanalauswahlsys^f em.

To supply a large number of mobile telephone subscribers many radio channels are needed. For example, should be planned for a mobile land-telephone system, the use of 1000 channels. For the most economical use of these radio channels, it is desired that each of the mobile units be provided with the function of being able to selectively use all the radio channels. In practice, however, it has been found that this is not technically possible and this desire from an economic point of view, serious disadvantages, so that a division of the mobile subscriber into a ^vnumber of groups and the use of different channels for the respective groups has been proposed. Further, in a mobile communication radio system equipped with a large number of radio channels, a radio channel is fixedly designated as a control channel, the remaining radio channels being used as speech channels, and the mobile devices in the control channel always being in a waiting state. Each of the mobile devices transmits control signals in the form of high-speed digital signals via the call and voice channel assignment control channel, etc., and communicates with a mobile radio station over a free voice channel, which in turn is allocated by the radio station. Where the mobile units are divided into a plurality of groups, the control channel changes with the groups. As mobile subscribers change their locations across the areas of large and small cities, it proves necessary to have a radio station in an area

bo with a small number of mobile telephone subscribers with respect to the control channel with a device equipment to the same extent to provide as a radio station in large cities, so that a recording of messages from the control channels of the respective groups is possible. For example, four groups of mobile telephone subscribers require four control channels; in an area with a small number of mobile subscribers

Consequently, low traffic density equipment is required for four control channels even when the number of voice channels used is about 2 to 10

The object of the invention is to provide a mobile communication radio system which simultaneously covers an area with a large number of mobile telephone subscribers and an area with a small number of mobile telephone subscribers and which simplifies the equipment of a mobile radio station in an area of ​​a small number mobile telephone subscriber admits

The object isj is achieved by the invention defined in claim 1 Advantageous embodiments of the invention can be found in the dependent claims.

In the solution according to the invention, the mobile telephone subscribers are divided into η groups, (n represents a positive, integer number greater than or equal to 2), in the area with a large number of mobile telephone subscribers for the subscriber groups own control channels are used and in the area with a small number of mobile subscribers of one of the above control channels is shared with at least two groups of mobile subscribers. Thus, a mobile radio station located in an area having a large number of mobile telephone subscribers requires transceivers for all the control channels associated with the mobile subscriber groups; however, in a mobile radio station where only a small number of mobile telephone subscribers are located, it is sufficient to provide a transmitter and a receiver only for the above common control channel.

In a mobile communications radio system, the service area is usually divided into a plurality of zones, with different voice and control channels being used in adjacent zones. As a result, a plurality of control channels are required throughout the service area, with the mobile telephone subscriber, after changing from one zone to another, scanning the aforesaid plurality of control channels and automatically entering the control channel of the new zone.

The plurality of groups are individually assigned a plurality of control channels, wherein a mobile telephone subscriber in each group occupies a control channel associated with the group in accordance with the zone in which the telephone subscriber resides. Thus, in an area having a small number of mobile telephone subscribers, a plurality of control channels are associated with at least two mobile subscriber groups, the mobile subscriber groups being automatically and in accordance with the zone classified in one of the common control channels.

In a certain ci-. For mobile telephone subscribers, the control channel used in the area with a large number of mobile telephone subscribers and the control channel used in the area with a small number of mobile telephone subscribers will be one and the same, but in other groups mobile telephone subscribers will differ said control channels from each other. In the latter group of mobile telephone subscribers, if the mobile telephone subscriber is not trapped after scanning the control channels associated with the area having a large number of mobile subscribers, it will automatically switch to the area with the small number of mobile subscribers common control channels are scanned with the aim of occupying one of them. When the control channel is intermittently interrupted for any reason during the subscriber's journey into the area with a large number of subscribers, the mobile subscriber joins and is placed in one of the common control channels, thereby making the calling operation impossible because the radio station is the telephone subscriber calls via the group's own control channel To avoid this, the radio station sends out a code, which indicates that the mobile telephone subscriber can intercept the common control channel and be classified therein if he has received this code and the telephone subscriber is not incorporated into the common channel if he has not received the code.

The invention will be explained in more detail by an embodiment with reference to ten figures. It shows

F i g. 1 is a block diagram schematically showing the structure of a mobile radio station and the structure of a mobile unit;

F i g. Fig. 2 shows the relationship between a radio range and a control channel in the event that the mobile units are not subdivided into groups;

3 shows the relationships between the transmitting and the receiving frequency band of the mobile device units and their grouping;

4 shows the relationships between the radio range and the control channel of a known system;

Fig. 5 shows the relationships between the radio area and the control channel in a mobile communication radio system according to the invention;

F i g. 6 shows in a block diagram the structure of a program control;

F i g. Fig. 7 is a flowchart showing the control operation for setting the control channel of each of the movable units of one of the two groups of movable units;

F i g. Fig. 8 is a flow chart showing the control procedure for the setting of the movable unit control control channel of the other group;

F i g. Fig. 9 shows an example of a control code as transmitted from the mobile radio station via the control channel;

F i g. 10 shows an example of a storage unit in which the relationship between a mobile radio station voice channel and a common mobile device group is stored.

FIG. 1 shows a transmitter / receiver 12 for a control channel contained in a mobile radio station, which is connected to an antenna 14 via a multiplexer 13. In addition, a plurality of transceivers 15 are connected to the antenna 14 via the multiplexer 13. The transceivers 12 and 15 are interconnected to a control unit 16 of the radio station. The controller 16 is connected to a circuit 18 via a mobile central office 17 for establishing connections to telephone terminals of conventional type. In some cases

the control unit 16 and the mobile central office 17 are arranged in their own radio stations, or the control unit 16 is divided into functional units, wherein only a part is in the mobile radio station. The participant is a mobile device unit 21 with antenna 22, which is fed via a multiplexer by a transmitter 25, or outputs signals to a receiver 24. The receiver 24 and the transmitter 25 are interconnected to a controller 26, a mobile device unit which communicates on the one hand with a mobile telephone 27 and on the other hand with a synthesizer 28 serving as a channel selection local oscillator. For the purpose of tuning the receiver 24 and the transmitter 25 to the control channel, the local oscillator 28 in the mobile unit 21 is always subjected to the control of the control unit 26. In this state, the mobile device unit 21 is in the waiting state via the control channel.

To generate a call, the user of the mobile device unit 21 picks up the handset of the telephone 27, thereby controlling the transmitter 25 with a call generation signal from the controller 26, which in turn modulates a carrier of the control channel and transmits the modulated carrier from the antenna 22. In the mobile radio station 11, the transmitted signal is received by the transmitter / receiver 12 via the antenna 14 and then supplied to the controller 16; In the control unit 16, the call generation signal of the mobile unit 21 is demodulated and a free radio conversation channel is selected. Together with a mobile device unit 21 characterizing code wrd sent from the transmitter / receiver 12 via the control channel a selected voice channel characterizing code. At the same time a Schleifenprüfon is sent by one of the transmitter / receiver 15 via the associated radio communication channel. The channel assignment code is decoded in the mobile unit 21 in the controller 26, used to drive the local oscillator 28 and so the receiver 24 and the transmitter 25 tuned to the assigned speech channel. If the receiver 24 receives the loop check sound from the mobile radio station 11, it is decided that the vote or Assignment of the speech channel is correct; from the transmitter 25, a loop check tone is further transmitted through the assigned speech channel. As soon as the loop check tone is received by the transceiver 15 of the mobile radio station 11, the controller 16 recognizes that the mobile unit 21 has been switched from the control channel to the associated speech channel and connects the transmitter / receiver 15 via the controller 16 to one between the controllers 16 and the central office 17 arranged message transmission circuit forth. From the central office 17 a signal triggering the transmission of dialing signals is delivered via the speech channel. After this signal has been received in the mobile unit 21, the number of the remote party is dialed to send dialing signals via the controller 26 of the mobile station 11. The central office 17 analyzes the dialing signals, feeds them to a subscriber of the usual type and thus establishes the connection ,

In the case of the call to the mobile unit 21 by the radio 11, the unit 21 is transmitted via the control channel a call signal which receives the control unit 21 and then via the control channel under the control or control of the control unit 26, a call-response signal to the radio station 11 sends. Once the radio station 11 receives this answer signal, a free radio talk channel is assigned by the same operations described above and the mobile unit 21 is tuned to the associated channel.

After reception of the loop check signal by the radio station 11, a speech circuit according to the manner described above is connected through and subsequently a telephone subscriber answer tone is transmitted by the control unit 16 via the speech channel. If the mobile telephone subscriber sends an answer sound signal in response to the warning signal, this is detected in the radio station 11 and the information about the subscriber's answer is forwarded to the central office 17 via a signal line of the speech circuit, thus establishing the speech connection. The control operations described in connection with the control units 16 and 26 can be realized by a program control which uses a certain type of electronic computer. For example, devices and methods can be used, as indicated in US-PS 36 63 762.

In the event that the mobile device unit moves within a wide range, this large service area is divided into a plurality of zones Z1 to Z24, for example into four adjacent group forming zones, as shown in FIG. 2 is shown. In order to cover the large area, control channels Pa 1, Pa 2, Pa 3 and Pa 4 are assigned to the four zones of each group. For example, a mobile device unit arranged in the zone is always in its waiting state in the control channel Pa 1, the signal / noise ratio, ie the signal-to-noise ratio of the control channel, being constantly monitored. When the mobile unit has moved its location to the zone Zu, the signal / noise ratio of the control channel Pa 1 is degraded. If the signal / noise ratio falls below a reference value, the control channels are exchanged in order to select a control channel with a good signal / noise ratio; in the present example, this is the control channel Pa 2, the receiver 24 and the transmitter 25 being tuned to the selected control channel and remaining in their waiting state. Funküonsabläufe this type can be carried out automatically in accordance with a control program, which is stored in a control memory of a microcomputer, wherein the microcomputer is included for example in the control unit 26.

As shown in FIG. 3, the transmitting frequency band AFt and the receiving frequency band AFr of the mobile telephone subscriber are separated from each other by frequency sections. In the mobile unit 21, both frequency bands are separated by means of one multi-frequency band.

As the number of mobile users increases and the number of channels used increases, the frequency bands AFt and AFr become wide. Assuming that the carrier frequencies used are the same as all the others, the normalized bandwidth increases and thus causes The design of transmitting and Empfangstrennfilter great difficulty and leads to a cumbersome and expensive filter.

In view of this difficulty, it has been proposed to divide the transmission frequency band AFt into two upper and lower bands AFta and AFtb and the reception frequency band AFr into two upper and lower bands AFra and AFrb as shown in FIG. In this case, the mobile telephone subscribers of a group A use the tapes AFta and AFra and the telephone subscribers of a group B the tapes AFtb and ZlFrZ. This measure reduces the normalized bandwidth of transmit and receive separation filters and facilitates the sizing of the filter so that it can be made cheap and small. 3 shows in addition to the division of the transmission frequency band A Ft and the reception frequency band AFr in two frequency bands the simultaneous use of Frequeiubändern A Fic and AFrc, which are assigned to the groups A and B to ensure an economic frequency utilization. However, such common frequency bands AFtc and AFrc need not always be provided.

Where mobile device units are grouped in this way, the individual groups are assigned different control channels. For example, the complete service area, as shown in FIG. 4, covered by zone amounts, wherein the control channels Pat to Pa 4 of the movable device group A of each zone and the control channels Pb 1 to Pb 4 of a movable group B are assigned to each zone. The in F i g. 4 Reference numerals Zm denote an area in which the number of mobile subscribers is large, as in a metropolitan city (the area Zm is hereinafter referred to as the metropolis), and Zs denotes an area in which the number of mobile subscribers is small. as is true in a small town (the area Zs is referred to as the small town). Although traffic density is low in the small town of Zs, however, since the mobile units of the two groups A and B enter and leave the area of ​​small town Zs, it is necessary to have a transmitter / receiver for two control channels in the radio station of each zone, ie Provide control channels Pa for the group A and Pb for the group B. This leads to the disadvantage that the equipment of the radio station in terms of traffic density is very extensive.

According to an embodiment of the invention, in the small town Zs, the control channels Pa 1 to Pa 4 are assigned together not only to the group A but also to the group B. In accordance therewith, in the radio station of each zone of the small town Zs, as shown in FIG. 5, only the transmitter / receiver for the control channel Pa is provided. For example, if a mobile unit from the group B from the zone Z_n to Z_H in the city Zm has changed the location, as indicated by an arrow 31 in FIG. 5, deterioration of the signal-to-noise ratio experienced by the control channel Pb 1 in the zone Z \\ is recognized by the mobile unit, and the control channels Pb 2 to Pb 4 are sequentially indexed by the unit Aim to find a channel with good signal / noise ratio. In this case, the mobile unit recognizes a good signal / noise ratio in the channel Pb 4 and assumes its waiting state in the control channel Pb 4. In the case of a mobile unit from the group A, the switching of the control channel of Pa 1 to Pa 4 takes place in the same way.

On the other hand, in case of a change of location of a mobile unit of the group A from the zone Z | 2 of the city Zm to the zone Z₃In the small town, as indicated by an arrow 32, the same process takes place, with the control channel being switched from Pa 2 to Pa i. In the case of a group B mobile unit whose signal / noise ratio in the control channel Pb 2 in the zone Zn is deteriorated, a control channel having a good signal / noise ratio first within the group B under the control channels Pb 1 to Pb 4 is searched but can not be found, the control channels assigned to group A Pal to Pa4 are searched for a channel with good signal / noise ratio. As a result of this operation, the mobile unit recognizes that the control channel Pa has a good signal-to-noise ratio and enters a waiting state in that channel.

For example, in the zone Zn of the city Zm, if the signal-to-noise ratio of the control channel Pb 2 is deteriorated due to radio field propagation or other causes, there is a possibility that the group B moving unit in the zone Z1 may be the one above described search operation for selecting a control channel to occupy the control channel Pa 2 of the group A and that it is thereby made impossible make a call of the mobile unit B from the radio station of the zone Zn. In order to avoid this, a code is inserted in the small town Zs, which indicates that the mobile units of the group B in the control channels Pa 1 to Pa 2 can also be used, in case of unavailability of this code, the mobile units of group B be prevented from the use of the control channels Pa 1 to Pa 4, even if the signal / noise ratio of the control channels Pb ί to Pb 4 has poor values.

As described above, the process of selecting the control channel can be performed by a program controller using an electronic calculator. F i g. FIG. 6 shows a central processing unit 33, a read / write memory 34 and a read memory 35, which are interconnected via a common data bus 36. The data bus 36 is also connected to an input / output circuit 37 which is connected to the one shown in FIG. 1 An input / output circuit 38 is connected to the transmitter 25 (F i g. 1) and a latch circuit 39 in turn connected to the local oscillator 28. The input / output circuit 37 outputs a signal indicative of the signal / noise ratio of the control channel, further comprising a code indicating that control channels other than those for a particular group of mobile device units can be interrogated, and finally various other signals. Various control programs are stored in the read memory 35. In the read / write memory 34, data necessary for the processing are temporarily stored and are read out again or used for rewriting in the read / write memory 34. When a code indicates that latch circuit 39 is latching a channel, top local oscillator 28 (Figure 1) is driven by the code and receiver 24 and transmitter 25 are tuned to the assigned channel, respectively. It is appropriate that the

Control channels Pa: l to Pa 4 and Pb 1 to Pb 4 within the common frequency bands AFlc and AFrc (Fig. 3) to arrange.

The setting operation for the control unit of the mobile unit of group A takes place, for example, in accordance with the flow chart shown in FIG. After switching on the power supply with the program step S \ is set to the next step 52 / of the control channel Paiauf »1«. In the next step 53, the check is made to see if the last selectable control channel has already been included in the process or not; this is detected by the decision as to whether or not the value 5 has been reached, since in the present example the channel Pa 4 is the last channel. If / has not accepted the value 5, receiver and transmitter are tuned to the control channel Pai, ie to Pa 1, with the program step 5s. In the program step 6, it is determined whether the signal / noise ratio at this time is good or not good. If there is a deteriorated signal / noise ratio, then in step 7, a "1" is added to /, so that in this example / = 2 and the program jumps back to program step S3, again to check whether / = 5 or not. If this is not the case, the receiver and transmitter are tuned to the control channel Pa 2 (i = 2) and their signal / noise ratio is checked in a similar manner. In the following, similar operations are repeated. If the signal / noise ratio is not good at the time of setting the receiver and the transmitter in the last channel Pa 4, the sequential scanning of the control channels Pa 1 through Pa 4 is repeated until the program step 5t, a good signal / noise Ratio is obtained after / = 5 detected in the program step 53, / = 1 set in the next program step St and the program step S5 is completed. This means that the search state of the control channel is maintained. If in program step S₆ a good signal / noise ratio is detected, the process continues in the program to step S₈; In this case, it is checked whether the telephone receiver is removed or not. When the handset is detached, this causes the jump to a mobile device call generation program. If the handset is not picked up, it is checked in step S) whether a call signal has been received or not; when the call signal is detected, the operation proceeds to a call sequence program. If no call signal is detected, a check is made with program step Sio as to whether the signal / noise ratio has deteriorated. If there is no degradation of the signal / blur ratio, this results in a return of the program to the program step Ss and a subsequent repetition of the operations. This means that the state in which the steps Ss through Sio are repeated represents the wait state. When a deterioration of the signal-to-noise ratio is detected, the program returns to step Si to resume the seek of the control channel.

It will now be described with reference to FIG. 8 describes the tuning operation of the control channel in the mobile equipment unit of group B. With the program steps Si to Sio, the same program processes as those in the setting of the control channel in the mobile unit unit of the group A, but in this case the program steps in connection with the control channels Pb 1 to Pb 4 are achieved. If in the program step Sj / = 5, ie when all of the control channels Pb 1 to Pb 4 assigned to the group B have been sequentially switched, the program proceeds to the program step Su where / = 1 is set in the control channel Pai shared. With the subsequent program step S12, it is checked whether the sampling of the control channel Pai is completed or not. In the present example, it is checked whether / the control channel Pai has assumed the value 5 or not. If this is not true, transmitter and receiver are set or tuned with the program step Sn on the control channel Pa 1.

With the program step Sh, it is decided whether the signal / noise ratio is good at this time or not, and if the signal / noise ratio is degraded, the value / = / + 1 is set at the program step Sis and then the program step S | 2 It is checked whether / has accepted the value 5 or not. Transmitter and receiver are then tuned to the next control channel Pa 2 at program step Si3. In this way, the control channels Pa 1 to Pa 4 are searched. If the signal / noise ratio is recognized as good with the program step Sh, the program jumps to step Si₆which checks whether or not a code has been received, the code / indicating that the mobile equipment units of the group B can use the common control channels Pa 4. If the code / is detected, the program leads to program step Ss, with which the wait state is given, as described above in connection with F i g. 7 has been described. If the code / is not recognized, the program step S17 adds "1" to / and the program returns to program step S12, continuing the search in the control channels Pa 1 to Pa 4. If 5 has assumed the value in the program step S12 /, and none of the control channels Pa 1 to Pa 4 has a good signal / noise ratio, or even if one of the channels has a good signal / noise ratio and the code / not is detected, it is decided that the moving equipment unit of the group B moves in the city Zm and the program returns to program step S? back to resume the selection of the control channels PbX to Pb 4. F i g. 9 shows a format example of a control signal transmitted by the radio station via the control channel. The control signal is composed of the codes G> to C₂, which indicate a call generation signal, a paging signal, etc., further from the codes Ao to Am soft identify the number of the mobile unit and the assigned channel number, etc., and finally from a code / indicating that the mobile units of the Group ßdie control channels Pa 1 to Pa 4 can also use. To control the mobile units of each group are a method of transmitting and receiving all information via a control channel associated with the respective zone and a method of assigning a plurality of control channels to the respective zone and their individual use according to their function intended. An example of the method last described uses a Steuerkana! for call generation for the control of

Call origination from the mobile unit and a call termination control channel for call end control to the mobile unit. In this case, it is up to the caller control channel that the mobile unit is in the waiting state. This control channel is as described above in connection with FIG. 5 is predetermined, and a code designating the control channel for call generation is transmitted from the radio station via the call termination control channel. In the case of a call generation from the mobile device unit, this is achieved via the assigned channel for the call generation. It is also possible to insert the above-mentioned code in the control signal after the code of the control channel for the call generation has been routed via the above-mentioned call termination control channel. In the above description, the mobile units are divided into two groups; however, the invention is equally applicable to the case of dividing the mobile unit units into three or more groups. Furthermore, the respective groups of mobile device units are described in connection with the use of various speech channel bands; However, the invention is equally applicable to the case in which the speech channels used by the respective groups are arranged in the same frequency band and the respective groups are controlled by their own control channels. Furthermore, a control channel is assigned to a radio zone; it should be noted, however, that a control channel may also be allocated to a plurality of adjacent radio zones. In other words, the present invention is also applicable to the case where, in some cases, the speech channel differs from the zones, but only one control channel is shared with the plurality of zones and therefore the control channel zone is larger than the talk zone.

As is apparent from the above, since the mobile telephone subscribers are divided into a plurality of groups, the mobile unit units of a mobile control system of a communication radio system according to the present invention can be dimensioned and constructed without difficulty and at a low cost and in a small size. Further, the likelihood that the control channel is busy is reduced in the interest of fast connection establishment. In addition, in a low traffic density area, a control channel is commonly used for a plurality of mobile subscriber groups; this means that only a minimum number of control channels required by the traffic component is required so that the equipment of the radio station with control channel devices can be of small size. Further, in a high traffic density area in such a case, it is avoided that the mobile device units of each group in the other channel channels than in the group are put in the waiting state.

According to the above, in the case of allocating speech channels which differ with the group of mobile units, and in the case where a free telephone channel is allocated differently in the radio station, there is the possibility of allocating a non-adjustable speech channel in the mobile unit. In order to prevent such a possibility, codes 43 (Figure 10) identify the groups of mobile device units to which the speech channels are respectively assigned. Each of the codes 43 is stored in a memory 41 of the control unit 16 of the radio station, with a code 42 as the address of each

Speech channel CH.

The control code sent from the mobile unit to the mobile station via the control channel includes a group code identifying the membership of the mobile units. If the mobile radio station has selected a free speech channel of the zone due to a call generation signal or a call answer signal, as described above, the memory 41 will go over the selected speech channel

and then comparing the group code thus read out and the group code transmitted from the mobile unit. If the two group codes coincide with each other, a code characterizing the selected speech channel is inserted in the control code and transmitted by the mobile radio station via the control channel. By storing the group heard to v / elcher the speech channel, and by comparing the group of the selected speech channel with the group of

mobile unit, therefore, the possibility of assigning a non-adjustable or deployable voice channel can be avoided to a mobile device unit.

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