Method and control circuit for the selection of a service channel in a mobile radio station.

The invention relates to a method for selecting one _OOrganization channel through a mobile radio station according to the preamble of claim 1.

Known radio transmission systems have fixed radio stations which, in spatial arrangement, form a cellular system with overlapping radio zones. The radius of such radio zones is between 2 and 30 kilometers, depending on the height of the antenna masts of fixed radio stations and the transmission power. Each radio zone is supplied by a fixed radio station. This can relay calls via so-called radio switching equipment from and to the public telephone network. Several neighboring radio zones can be combined into a so-called call area. The locations of all mobile radio stations are continuously recorded on the fixed page and stored in a so-called address book. If a mobile radio station changes the call area, there is a change in the address book.

Depending on the volume of traffic, the fixed radio stations of each radio zone of the radio transmission system are assigned a number of speech channels and at least one organizational channel. Different frequencies, spreading codes or time channels can also be used for different organizational channels in spatially adjacent radio zones. To distinguish between the organizational channel and the speaking channel, these are identified by a special message. In the event of failure or failure of a_Oorganization channel, each speech channel can take over the task of the organization channel by changing the code.

The search of the mobile radio station for an organization channel can take a long time if the radio transmission system has a multiplicity of transmission channels (organization channels and speech channels).

From European patent application EP-A2-0 111 972, a method for selecting an organization channel by a mobile radio station is known to avoid long search times with any arrangement of organization channels in the frequency band of the transmission channels. According to the known method, references to organization channels of adjacent stationary radio stations, references to an alternative channel assigned to the stationary radio station and references of the organization channel to itself are sent by the stationary radio station at variable time intervals. If several stationary channels are assigned to the fixed radio station, then references are also sent from the fixed radio station, whereby all sent references can contain, in addition to the channel number, additional information such as a country code and / or a partial quantity marking and / or a call zone marking.

Furthermore, from DE-OS 32 00 965 a neighboring radio cell organization channel reference system is known, in which, if the organization channels have free transmission capacities, references to organization channels from neighboring radio cells are sent. The content of the references is the organization channel frequency used, the mobile radio station carrying out level comparison measurements on the specified organization channel frequency at intervals.

An exchange of references between the fixed radio stations is necessary for keeping a network image. If, for example, five fixed radio stations are adjacent to the fixed radio station, each of these neighboring fixed radio stations must be informed in the event of an organizational channel failing and switching to a replacement channel assigned to the fixed radio station.

In a service-integrated radio transmission system, as a rule only a few services have to be available everywhere. The total bandwidth available in the integrated radio transmission system is divided in terms of time and area (geographic frequency repetition) according to the current demand. The fixed radio stations are only provided with devices for various services for which there is a need of the participants in the respective radio zones. The costs for an in-service radio transmission system essentially consist of the functions that are required at least for access to the in-service radio transmission system and the facilities required for handling the various services in accordance with the various subscriber devices. Such different subscriber devices can be, for example:<ul id="ul0001" list-style="none"><li>- a simple paging receiver with alphanumeric display;</li><li>- A "pocket phone" with a receive and a transmit frequency for use in a restricted geographic area and with reduced quality of service;</li><li>- A "dispatch device" (in the "dispatch service" a common radio transmission channel is used in the direction from the fixed radio station to the vehicles of a vehicle fleet, while in the rear direction each vehicle can occupy its own radio transmission channel) with a reception and few transmission frequencies for half-duplex operation;</li><li>- A "portable" with multiple receive and transmit frequencies for duplex operation and nationwide coverage, which can also be used in the vehicle;</li><li>- a mobile data terminal with a half-duplex transmission in a packet process with a low data rate;</li><li>- a "mobile office" (eg for construction sites, banks etc.) with transparent duplex transmission of 64 kbit / s, which is only operated in a stationary manner, etc.</li></ul>

If different types of subscriber devices and different services are operated in the radio transmission system and different organizational channels are also provided for the different services, then the references for all different organizational channels must be exchanged between the fixed radio stations. For example, if four different services are provided in the radio transmission system - for example a voice service, a data service with a low bit rate, a data service with a high bit rate, etc. - 20 references between the adjacent fixed radio stations are necessary in the example mentioned above.

The invention is based on the object of specifying in a service-integrated radio transmission system a method for selecting an organizational channel by the mobile radio stations, in which the number of references to be checked is small.

This object is achieved by a method having the features of patent claim 1.

In the method according to the invention, the message transmission channel is for information about the design of _Oorganization channels a simplex message transmission channel, which is transmitted comparable to a broadcast channel from the fixed radio station. The message transmission channel informs the mobile radio stations of the configuration (arrangement) of the organization channels in the integrated radio transmission system. The message transmission channel is thus arranged on the system level above the organization channels, the mobile radio station only having to search for the small number of different message transmission channels lying in the overall frequency band of the integrated service transmission system for network access.

The method according to the invention can also be used in a digital radio transmission system in which a different modulation method is used in the forward and backward direction of the radio transmission channels. In the direction from the fixed radio station to the mobile radio stations assigned to it (outward direction), each transmission channel is spread by spread modulation. The spread radio transmission channels formed in this way are superimposed on one another in the fixed radio station and the broadband sum signal thus obtained is transmitted in a common frequency band. In the direction from the mobile radio stations to the fixed radio station (reverse direction), the message transmission takes place in separate, narrow-band radio transmission channels.

Each fixed radio station has a channel set, for example of 32 transmission channels. The individual transmission channels of a channel set can be separated from one another, for example, by different spreading code words (CDMA) and / or different time channels (TDMA). For example, the different time channels are combined in a time-division multiplex frame with four time channels each, then each time-division multiplex frame thus formed is spread with appropriately selected code words, which allow several time-division multiplex frames to be transmitted simultaneously and with the same carrier frequency. For example, if eight different code words are used per channel set, the channel set contains eight different time-division multiplex frames, each with four_Z.channels, in total 32 transmission channels per channel set.

In such a digital radio transmission system with, for example, 20 different carrier frequencies, only a search for that carrier frequency with the highest amplitude is required in the mobile radio station after switching on, as a result of which the radio cell is determined and the received message stream is to be searched for the references. This will make it easy_AIn this way, the mobile radio stations have access to the network and only a small number of references need to be checked.

Preferred embodiments of the invention are characterized in the further subclaims.

The control device for carrying out the method both in the fixed radio station and in the mobile radio stations requires only a small amount of additional circuitry, since existing devices can also be used.

The invention is described and explained in more detail below with reference to an embodiment shown in the drawing. It shows:<ul id="ul0002" list-style="none"><li>Fig. 1 shows the block diagram of the control device in the fixed radio station and the mobile radio station and</li><li>Fig. 2 shows the logical structure and assignment of the various references in the method according to the invention.</li></ul>

Fixed radio stations are in the radio transmission system _BS spatially arranged according to a cell system. A number of transmission channels are assigned to each fixed radio station BS, one of these transmission channels (organization channel) being used for signaling to control the system functions. This includes, for example, the transmission of election information when building_Ge-talks to the various subscriber devices or mobile radio stations MS.

Different types of subscriber devices and different services can be operated in the radio transmission system. Each stationary radio station BS is assigned at least one organization channel CCH and a message transmission channel COCH, which is a simplex message transmission channel that is operated in a manner comparable to a radio channel. On the message transmission channel COCH, references NC to message transmission channels COCH of adjacent fixed radio stations B_S sent. Furthermore, at least one reference CC to an organization channel CCH assigned to the fixed radio station BS is sent on the message transmission channel COCH. The contents of the references NC and CC are at least the addresses assigned to the message transmission channels COCH or the organization channels CCH (ie frequency, time, code). Furthermore, the fixed radio station BS transmits references MR to the message transmission channel COCH itself at variable time intervals, the reference MR identifying the message transmission channel COCH as such. Finally, the stationary radio station BS transmits a reference SC to a spare channel COCH-SC assigned to it at variable time intervals on the message transmission channel COCH, the content of the link SC also being the address of the spare channel COCH-SC. In the references NC, SC, MR and CC, a coded message for a country code and / or a partial quantity marking and / or a call zone marking and / or service marking and / or charge information and / or system operator identification can be sent.

In a radio transmission system with changeable assignment of the channels in the forward and backward direction by the fixed radio station BS, the reference CC transmitted in the message transmission channel COCH relates only to the execution (downlink) of the organization channel CCH and in the organization channel CCH determined in this way becomes a reference to an organization channel CCH sent in the reverse direction (uplink ie in the direction from the mobile radio station MS to the fixed radio station BS).

In Fig. 1 is the block diagram of the control device in the fixed radio station BS and mobile radio station M._S shown. The stationary radio station BS has a selection circuit AS, which is connected to a switching device SE and which controls the switching process of the switching device SE. A control device (microprocessor) arranged in the fixed radio station BS can also be used for the selection circuit AS. Various memories are connected to the switching device SE and controlled by the selection circuit AS, the memory content of the various memories is read out and fed via the switching device SE to a transmitter S arranged in the fixed radio station BS. The reference MR of the message transmission channel COCH to itself is stored in a memory SPMR. The reference SC to a spare channel COCH-SC assigned to the message transmission channel COCH is stored in a memory SPSC. The references NC to message transmission channels COCH of adjacent fixed radio stations BS and the references CC to the organizational channels assigned to the fixed radio station BS are stored in a memory SPNC_CCH are stored in a memory SPCC. References REF to organizational channels CCH of the reverse direction (uplink) are stored in a memory SPREF. These references REF are sent in the associated organizational channels CCH of the execution (downlink).

At variable time intervals, references CC, NC, SC and MR are sent by the fixed radio station BS and received in a receiver E arranged in the mobile radio station MS. After decoding and demodulation, the references CC, NC, MR and SC are fed to a selection circuit AMS connected to the receiver E, which in turn is connected to and controls a switching device SMS. The switching device SMS includes a memory SNC for storing the references NC to message transmission channels COCH of adjacent fixed radio stations BS, a memory SMR for storing the reference MR of the message transmission channel COCH to itself and a memory SSC for storing the reference SC to one assigned to the message transmission channel COCH Spare channel COCH-SC connected. The reference REF transmitted in the organization channel CCH of the execution to the associated organization channel CCH of the execution is stored in a memory SREF.

When switching on the mobile radio station MS or if the content of the reference MR of the message transfer does not match^GU.N^Gscanals COCH on itself, the mobile radio station MS starts a search for references MR, selects a suitable organization channel CCH from the references CC transmitted in the message transmission channel COCH and switches to this. The current network image obtained in this way is stored in the memories SNC, SMR and SSC.

2 shows the logical structure of the references and their assignment to one another. The different blocks of this structure have the following meaning:<tables id="tabl0001" num="0001"><img file="EP0240073A2_D0001.tif" /></tables>

In a service-integrated radio transmission system, different organizational channels (indicated by A and B in FIG. 2) are provided for the different services and the total amount of mobile radio stations MS located in the radio coverage area of ​​the fixed radio station BS can be divided into subsets a to f. It is only at this lower level in the system hierarchy of the organization channels CCH that references (CCH markers, REF) are sent to the organization channels CCH assigned to the stationary radio station BS, while the references NC to the stationary radio stations BS adjacent to the stationary radio station BS in a higher one System level.

The table below shows that - in the case of an assignment of channels in the forward and backward direction that can be changed by the fixed radio station BS - the reference CC is transmitted in the forward direction on the message transmission channel COCH, while the reference RE_F for the channel assigned to this organizational channel CCH is transmitted in the reverse direction on the relevant organizational channel CCH.<tables id="tabl0002" num="0002"><img file="EP0240073A2_D0002.tif" /></tables>

On the organization channel CCH, a reference (CCH markers) can also be transferred to the organization channel CCH itself. This reference is used to check the switching process by the mobile radio station MS from the message transmission channel COCH to the organization channel CCH. This reference increases the safety of the switching process and is not absolutely necessary for system operation.