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

p0001The invention relates to a method for selecting a control channel by a mobile radio station according to the preamble of claim 1.

p0002Known radio transmission systems have fixed radio stations constituting a cellular system with overlapping radio zones in spatial arrangement. The radius of such radio zones is a function of the height of the antenna mast of fixed radio stations and the transmission power of 2-30 kilometers. Each radio zone is supplied by a fixed radio station. This can give talks on so-called mobile switching equipment to and from the public switched telephone network further. A plurality of adjacent radio zones can be combined to form a so-called paging area. On the fixed side, the whereabouts of all mobile radio stations are continuously recorded and stored in a so-called address book. Substituted a mobile radio station the calling area, so a change is made in the address book.

p0003The stationary radio stations each radio zone of the radio transmission system are depending on traffic, a number of voice channels and each associated with at least one control channel. In spatially adjacent radio zones and different frequencies, spreading codes or time slots can be used for various control channels. To distinguish them from control channel and voice channel they are characterized by a special message. In case of failure or malfunction of a control channel of each voice channel can take over the task of the control channel by changing the code.

p0004The search for the mobile station by a control channel can be slow when the radio transmission system having a plurality of communication channels (control channels and voice channels).

p0005From European Patent Application EP-A2-0 111 972 a method for selecting a control channel by a mobile radio station is known to avoid large scan times of any arrangement of control channels in the frequency band of the transmission channels. According to the known method references are sent on control channels of neighboring fixed radio stations, references to one of the stationary radio station associated protection channel and references of the control channel to itself from the stationary radio station to variable time intervals. Are the base radio station associated with several control channels, so are also sent from the stationary radio station references to it, with all references transmitted next to the channel number, additional information such as a country code and / or a subset of marking and / or may include a Rufzonenmarkierung.

p0006To carry out this process in a stationary radio station (BS) the fixed radio station includes a selection circuit which is connected to a switching device. Further, the fixed radio station includes a number of memories in which references to organization channels which are assigned to the stationary, and references to at least one of the stationary radio station also associated protection channel, as well as references to these control channels associated channel numbers are stored. The switching device is controlled by the selection circuit, and outputs information signals or references, which are supplied to a cylinder disposed in the stationary radio station transmitter.

p0007In the mobile station, a receiver is arranged, which receives the broadcasted by the transmitter wanted signals or references and supplies an evaluation circuit. Means connected to the evaluation circuit controls selection which is arranged in the mobile radio station switching means. The switching device is connected to a storage group in which Save the references to the base radio station associated control channels and the base radio station associated spare channels can be saved.

p0008Furthermore, from DE-OS 32 00 965 a neighboring cell site control channel reference system, in which when the control channels have free transmission capacity, references to control channels transmitted from neighboring radio cells. Contents of the references is used the control channel frequency, wherein the mobile station on the specified organization channel frequency at time intervals carries out level comparison measurements.

p0009Between the stationary radio stations, replacement of the references for the management of a grid image is necessary. Are the stationary radio station, for example, adjacent five fixed radio stations, so each of these neighboring fixed radio stations to inform in case of failure of a control channel and switch associated to one of the stationary radio station spare channel.

p0010In an integrated services radio transmission system only a few services must be available anywhere in the rule. Here, the space available in the integrated services radio transmission system overall bandwidth with respect to time and area (geographic frequency reuse) shall be allocated according to the actual requirements. The stationary radio stations are only provided with such facilities for various services, for which there is of the participants in the respective radio zones, a need. The cost of an integrated services radio transmission system are essentially composed of the functions that are required at least for access to integrated services radio transmission system and of the need for the provision of various services, complying with different subscriber equipment. Such different subscriber devices can be, for example:<ul><li>a simple pagers with alphanumeric display;</li><li>a "pocket-telephone" with a reception and a transmission frequency for use in a limited geographical area and a reduced quality of service;</li><li>a "dispatch unit" (the "dispatch service" is in the direction from the stationary radio station to the vehicles of a vehicle fleet used in each case a common radio transmission channel while in the return direction of each vehicle may occupy a separate radio transmission channel) having a receiver and a few transmission frequencies for half-duplex operation;</li><li>a "portable" with multiple receiving and transmitting frequencies for duplex operation and national supply, which can also be used in the vehicle;</li><li>a mobile data terminal with a half-duplex transmission in the packet method with a low data rate;</li><li>a "mobile office" (eg, construction, banking, etc.) with transparent duplex transmission of 64 kbit / s, which is operated stationary etc ..</li></ul>

p0011If the radio transmission system, different types of subscriber devices and operated various services and are also different control channels provided for the various services, the references must be exchanged for different control channels between the fixed radio stations. Four different services are provided for example in the radio transmission system - for example, a voice service, a data service with low bit rate, a data service with a high bit rate, etc. - as in the example previously mentioned 20 references between the adjacent stationary radio stations necessary.

p0012The invention is based is to specify in an integrated services radio transmission system, a method for selecting a control channel by the mobile stations, in which the number of references to be checked is small the task.

p0013This object is achieved by a method having the features of claim 1.

p0014In the present process is the communication channel to provide information on the design of control channels a simplex communication channel, which is transmitted similar to a broadcast channel from the base radio station. The communication channel informs the mobile stations on the configuration (arrangement) of the control channels in the integrated services radio transmission system. In the system level thus the communication channel is placed over the control channels, the mobile radio station for access to the network only has to scan the small number of different lying in the overall frequency band of the integrated services radio transmission system communication channels.

p0015The inventive process can also occur in a digital radio transmission system for use in the back and forth direction of the radio transmission channels each have a different modulation method is applied. In the direction from the stationary radio station to the associated mobile radio stations (forward direction) of each transmission channel is spread by spread spectrum modulation. The spread radio transmission channels thus formed are overlaid in the stationary radio station to each other and the wideband composite signal thus obtained is transmitted in a common frequency band. In the direction from the mobile stations to the fixed radio station (reverse direction) the message transmission takes place in mutually separated, narrow-band radio transmission channels.

p0016Each base radio station has a channel set for example, 32 transmission channels. The individual transmission channels of a channel set can be separated for example by verschiedeneSpreizcodewörter (CDMA) and / or different time slots (TDMA). For example, the different time channels in a time-division multiplex frame are combined with four time slots, then each time-division multiplex frame thus formed is spread with suitably selected code words, which make it possible to transmit a plurality of time division multiplex frames at the same time and with the same carrier frequency. For example, if per channel set eight different code words used, the channel set contains eight TDMA frame with four time slots, ie together 32 transmission channels per channel set.

p0017In such a digital radio transmission system, comprising for example, 20 different carrier frequencies only a search for that carrier frequency with the highest amplitude is in the mobile radio station after switching required, whereby the radio cell is determined and the received message stream is scan according to the references. This is a simple way allows the mobile stations of the network access and it is only to check a small number of references.

p0018Preferred embodiments of the invention are characterized in the further dependent claims.

p0019The control device for implementing the process both in the stationary radio station and in the mobile stations requires little additional circuitry, as each existing facilities can already be used with.

p0020The invention is described in more detail below with reference to an embodiment shown in the drawings and explained. It shows:<dl id="dl0001"><dt>Fig. 1</dt><dd>the block diagram of the control device in the fixed radio station and the mobile radio station and</dd><dt>FIG. 2</dt><dd>the logical structure and allocation of the various references in the novel process.</dd></dl>

p0021In the radio transmission system fixed radio stations BS arranged for a cellular system spatially. Each stationary radio station BS are associated with a number of transmission channels, one of these transmission channels (control channel) is used for signaling for controlling the system functions. This includes for example the transmission of election information in the development of discussions on the various subscriber units or mobile stations MS.

p0022In the radio transmission system, different types of subscriber sets and different services can be operated. Each stationary radio station BS are at least one control channel CCH, and a message transmission channel COCH assigned to which is a simplex message transmission channel which is operated similar to a broadcast channel. On the message transmission channel COCH references NC to be sent to message transmission channels COCH of neighboring fixed radio stations BS. Furthermore, at least one reference CC assigned to one of the stationary radio station BS channel CCH is transmitted on the communication channel COCH. Content of the references NC and CC are at least the message transmission channels COCH or the channels CCH allocated addresses (ie, frequency, time, code). Furthermore, the base radio station BS sends to variable time intervals on the communication channel MR COCH references to this itself, wherein said reference MR denotes the message transmission channel COCH as such. Finally, the base radio station BS transmits to variable intervals on the message transmission channel COCH a reference SC to an associated substitute channel COCH-SC, wherein content of the link SC also is the address of the spare channel COCH-SC. In the references NC, SC, MR and CC may be a coded message for a country code and / or a subset of marking and / or Rufzonenmarkierung and / or service mark and / or charging information and / or system operator identification are sent.

p0023In a radio communication system with variable assignment of the channels back and forth direction by the base radio station BS of the transmitted in message transmission channel COCH reference relates CC only the execution (downlink) of the control channel CCH and the thus determined control channel CCH is a reference to a control channel CCH (ie uplink direction from the mobile station MS to the base station BS) sent in the reverse direction.

p0024In Fig. 1 is a block diagram of the control device is illustrated in stationary radio station BS and mobile station MS. The base radio station BS has a selecting circuit AS, which is connected to a switch unit SE and which controls the switching operation of the switching means SE. For the selection circuit AS which is arranged in the stationary radio station BS control device (microprocessor) can be used with. With the switching device SE various memories are connected and controlled by the selecting circuit AS of the memory content of the memory is different in each case read out and supplied via the switching device a SE arranged in the stationary radio station BS transmitter S. In a memory SPMR the reference MR of message transmission channel COCH stored on itself. The reference to a SC the message transmission channel COCH associated substitute channel COCH-SC is stored in a memory SPSC. In a memory SPNC the references NC stored on message transmission channels COCH of neighboring fixed radio stations BS and the references to the CC of the stationary radio station BS associated channels CCH are stored in a memory SPCC. In a memory SPREF references REF are on channels CCH of the return direction (uplink) saved These references REF execution (downlink) are sent into the associated channels CCH.

p0025At variable intervals references CC, NC, SC and MR are transmitted from the base radio station BS and received in a cylinder disposed in the mobile radio station MS receiver E. After decoding and demodulation references CC, NC, MR and SC a related receiver E selection circuit AWS are fed, which in turn is connected to a switching device SMS and controls. With the switching means SMS a memory SNC to store the references NC to message transmission channels COCH adjacent stationary radio stations BS, a memory SMR for storing the reference MR of the message transmission channel COCH on itself and a storage SSC for storing the reference SC to a the communication channel COCH are associated substitute channel COCH-SC connected. In a memory of SREF transmitted in the control channel CCH of execution reference REF is stored on the associated control channel CCH of the return direction.

p0026When switching the mobile station MS or in non-compliance of the contents of the reference MR of message transmission channel COCH on itself, the mobile radio station MS starts a search for references MR, selects the transmitted in the message transmission channel COCH references CC an appropriate channel CCH and turns on these around. The thus obtained current network picture is stored in memories SNC, SMR and SSC.

p0027In FIG. 2, the logical structure of the references and their assignment to one another is shown. The various blocks of this structure have the meaning given below:<tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="left">short name</entry><entry namest="col2" nameend="col2" align="left">importance</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">COCH / BS</entry><entry namest="col2" nameend="col2" align="left">COCH an adjacent BS</entry></row><row><entry namest="col1" nameend="col1" align="left">CCH / HR; A; a, b, c</entry><entry namest="col2" nameend="col2" align="left">CCH execution; A service; Subset a, b, c</entry></row><row><entry namest="col1" nameend="col1" align="left">CCH / HR; B; a, b</entry><entry namest="col2" nameend="col2" align="left">CCH execution; Service B; Subset a, b</entry></row><row><entry namest="col1" nameend="col1" align="left">CCH / HR, A; d, e, f</entry><entry namest="col2" nameend="col2" align="left">CCH execution; A service; Subset d, e, f</entry></row><row><entry namest="col1" nameend="col1" align="left">CCH / RR; A; a, b, c</entry><entry namest="col2" nameend="col2" align="left">CCH return direction; A service; Subset a, b, c</entry></row><row><entry namest="col1" nameend="col1" align="left">CCH / RR; A; d, e</entry><entry namest="col2" nameend="col2" align="left">CCH return direction; A service; Subset d, e</entry></row><row><entry namest="col1" nameend="col1" align="left">CCH / RR; A; f</entry><entry namest="col2" nameend="col2" align="left">CCH return direction; A service; Subset f</entry></row><row><entry namest="col1" nameend="col1" align="left">CCH / RR; B; a, b</entry><entry namest="col2" nameend="col2" align="left">CCH return direction; Service B; Subset a, b</entry></row></tbody></tgroup></table></tables>

p0028In an integrated services radio transmission system different organizational channels for the various services provided (in FIG. 2 indicated by A and B) and the total amount of the operated in the wireless coverage area of ​​the base radio station BS mobile radio stations MS can be divided into subsets af. Only on this lower in the system hierarchy of channels CCH so references (CCH-marker, REF) transmitted to the base radio station BS associated channels CCH, while the references NC to the base radio station BS adjacent stationary radio stations BS higher in a system level are handled.

p0029In the table below shows that - at a variable by the base radio station BS assignment of channels in forward and reverse directions - will transmit the reference CC on the message transmission channel COCH in the forward direction, while the reference REF for this channel CCH assigned channel rear direction on the relevant channel CCH is transmitted. <tables id="tabl0002" num="0002"><table frame="all"><tgroup cols="4" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="39.37mm" /><colspec colnum="2" colname="col2" colwidth="39.37mm" /><colspec colnum="3" colname="col3" colwidth="39.37mm" /><colspec colnum="4" colname="col4" colwidth="39.37mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" /><entry namest="col2" nameend="col2" align="center">reference</entry><entry namest="col3" nameend="col3" align="center">is transferred in</entry><entry namest="col4" nameend="col4" align="left">Recalls</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="right">1</entry><entry namest="col2" nameend="col2" align="left">MR</entry><entry namest="col3" nameend="col3" align="right">COCH</entry><entry namest="col4" nameend="col4" align="left">COCH</entry></row><row><entry namest="col1" nameend="col1" align="right">2</entry><entry namest="col2" nameend="col2" align="left">SC</entry><entry namest="col3" nameend="col3" align="right">COCH</entry><entry namest="col4" nameend="col4" align="left">COCH-SC</entry></row><row><entry namest="col1" nameend="col1" align="right">3</entry><entry namest="col2" nameend="col2" align="left">NC</entry><entry namest="col3" nameend="col3" align="right">COCH</entry><entry namest="col4" nameend="col4" align="left">neighboring COCH</entry></row><row><entry namest="col1" nameend="col1" align="right">4</entry><entry namest="col2" nameend="col2" align="left">CC</entry><entry namest="col3" nameend="col3" align="right">COCH</entry><entry namest="col4" nameend="col4" align="left">CCH execution</entry></row><row><entry namest="col1" nameend="col1" align="right">5</entry><entry namest="col2" nameend="col2" align="left">CCH-marker</entry><entry namest="col3" nameend="col3" align="right">CCH</entry><entry namest="col4" nameend="col4" align="left">CCH execution</entry></row><row><entry namest="col1" nameend="col1" align="right">6</entry><entry namest="col2" nameend="col2" align="left">REF</entry><entry namest="col3" nameend="col3" align="right">CCH</entry><entry namest="col4" nameend="col4" align="left">CCH return direction</entry></row></tbody></tgroup></table></tables>

p0030On the channel CCH may also have a reference (CCH-marker) on the control channel CCH itself be transferred. This reference is used to check the Umschaltevorgangs by the mobile radio station MS from the message transmission channel COCH on the control channel CCH. This reference improves the safety of Umschaltevorganges and is for system operation is not absolutely necessary.