A radio system and a data transmission in a radio system

Radio system and method for transmitting data in a radio system

The invention relates to a radio system and method 5 for transmitting data in a radio system comprising mobile radio stations and a plurality of fixed radio stations spaced apart in the radio system area, each having a paging radio channel for signaling between the fixed radio station and the mobile radio stations. through.

Radiotelephone systems in accordance with Recommendations MPT1343 and 1327 published by the English Department of Trade and Industry (DTI) define the transmission of SDM (Short Data Message) and EDM (Extended Data Message) data messages transmitted on a paging channel in the course of other control signaling. SDM data transmission can be used to transfer either short alphanumeric text messages or application-specific data over a network in both directions between two subscriber devices or other devices such as computers, etc. Certain groups of characters and the corresponding maximum number of characters can be included in one SDM message. An EDM message consists of a maximum of four interconnected SDM25 messages. However, since the data transmission takes place in the presence of normal control signaling on the paging channel, this data transmission has the disadvantage that even in relatively simple applications it blocks the paging channel so that the control signaling is disturbed and even the telephone traffic in the system is endangered. Therefore, the data transmission capacity obtained in this way remains very low. For more efficient data transmission for radio systems according to MPT1343 and 1327, a separate free - form data transmission using external modems35 and. For each modem call, a normal traffic channel is reserved, so that the control signaling does not interfere with the data transmission during the modem call. However, the use of external modems and the reservation of the entire traffic channel is an expensive and unnecessarily complicated solution for the customer for intermittent and relatively low-capacity data transmission, for which, however, normal SDM / EDM data transmission is not sufficient.

It is an object of the present invention to substantially increase the transmission capacity of SDM / EDM type data transmission in a radio system and to avoid the additional cost caused by external modems.

This is achieved by a radio system of the type described in the introduction, which according to the invention is characterized in that the radio system comprises at least one paging radio channel to which mobile radio stations are commanded for data transmission but with transmitted control signaling preventing mobile radio stations from selecting a radio channel.

The basic idea of ​​the present invention is that a mobile radio station is always routed for SDM / EDM data transmission to a specific paging channel (or data channel). From the point of view of the radio system, this data channel-specific data channel is similar to the actual paging channel, but the system25 transmitted in its signaling, which defines the radio system used for mobile stations, is chosen so that no mobile radio station can select this radio channel as a paging channel. Such a data channel may have several mobile stations simultaneously performing data transmission in the same way as a normal paging channel. However, the data channel lacks all the normal control signaling that is not required for SDM / EDM data transmission, so there is no need to restrict data transmission due to control signaling. Of course, such a data channel reserved for data transmission is also caused to become blocked if there is sufficient data transmission, but even then the voice traffic of the radio network, which is generally considered the most important in radiotelephone networks, is not endangered. In addition, several channels can be reserved for data traffic depending on the capacity need.

The invention provides a new data transmission method between a normal SDM / EDM transmission and a conventional modem call. The system differs purely from the radio system according to MPT1343 / 1327 in that in connection with SDM / EDM data calls, the network manager must be able to command mobile radio stations always on a specific dedicated data channel. Thus, it requires only changes to the network management and also minor changes to the radiotelephone software.

The invention also relates to a method for transmitting data in a radio system comprising mobile radio stations and a plurality of fixed radio stations spaced apart in the area covered by the radio system, each having a radio channel acting as a paging channel for signaling between the fixed radio station and the mobile radio stations. wherein in the method, the mobile radio station requests permission to transmit user data by sending a paging request message to the fixed radio station, the fixed radio station issues a user data transmission permission by sending an acknowledgment message on the paging channel, the mobile radio25 station transmits a user data message in response to receiving the acknowledgment message. The method is characterized in that after receiving a request to send user data from a mobile radio station on a paging channel, the fixed radio station sends a command to the mobile radio station to switch to a data channel reserved for data transmission only to a paging radio channel.

The invention further relates to a method for transmitting data in a radio system comprising mobile radio stations and a plurality of fixed radio stations 4 located in the area covered by the radio system, each having a radio channel acting as a paging channel for signaling between the fixed radio station and the mobile radio stations. in which the fixed radio station sends a paging message for packet data transmission to the mobile station on the paging channel, and the mobile radio station sends an acknowledgment message to the fixed radio station as an acknowledgment on the paging channel. The method is characterized in that after receiving an acknowledgment message from the mobile radio station on the paging channel, the fixed radio station sends a command to the mobile radio station to switch for data transmission only to the radio channel operating on the paging channel reserved for data transmission.

The invention will now be described in more detail by means of embodiments with reference to the accompanying drawings, in which Figure 1 illustrates a radio system in which the invention can be applied and Figure 2 illustrates a connection between a mobile switching center and a base station, and Figures 3 and 4 are signaling diagrams of some data transmission methods.

Figure 1 shows a radiotelephone system in which the geographical area covered by the system is divided into smaller radio areas, i.e. radio cells C1, C2 and C3, so that adjacent cells are contiguous or preferably overlap in their edge areas. Each cell C1, C2 and C3 has at least one fixed multichannel transceiver apparatus BS1, BS2 and BS3, which is referred to herein as a base station. All base stations BS1, BS2 and BS3 are connected by fixed connections, such as cables, to the mobile switching center MX, which thus controls several base stations BS. Each voice is assigned certain frequency channels for voice or data connections, so that at least the cells close to each other have different frequencies at the same time, at which their tu95093 base stations BS are in radio communication with the subscriber stations or radiotelephones MS in the cells.

Figure 2 illustrates one embodiment of the connection between the mobile switching center MX and the base station BS. The mobile switching center includes several base station interface units BSIU (Base Station Interface Unit), each of which acts as a link between the call control computer CCC (Channel Control Computer) and the base station radio channel unit ChU (Channel Unit). Each base station has a plurality of radio channel units ChUs, each comprising a radio transceiver. The channel unit ChU can operate on one predetermined radio channel (frequency) or the mobile switching center MX can dynamically allocate channels on a call-by-call basis by forcing the channel unit ChU to operate on the desired radio channel of the system.

The interface unit BSIU has four main functions: to control access to the associated radio channel, to convert and forward messages between the radio units, i.e. the channel units ChU and the call control computer CCC, to connect the exchange's voice paths to the radio channel and to control and monitor the base station operation. One BSIU controls one channel, which may be either a traffic channel or a paging channel (control channel) used by the system for control signaling, such as call set-up signaling. The signaling used on the paging channel is preferably in accordance with MPT 1327. Typical signaling includes connection calls and acknowledgments sent between the base station and the radiotelephone, as well as commands sent by the base station to switch to a particular traffic channel for a call.

MPT1343, paragraph 14, defines the transmission of short data messages on the control channel between the radiotelephones MS and the mobile switching center MX via the base station BS. This defined data transmission allows HEAD messages containing free-form data to be sent on the control channel in both directions, i.e. from the MS to the MX and

From MX to MS. The term HEAD message, in this context, means both the HEAD address codeword and the associated data codewords. The procedures defined in paragraph 14 of MPT1343 support a solution in which one segment of free-form data is transmitted. A segment is an amount of free-form data that can be included in a single HEAD message, as defined in Section 3.1 of MPT1332. However, it is possible to link segments to up to four segments.

The data transmission according to the specification MPT1343 takes place on the paging channel as follows when the MS transmits via MX to another MS. The calling radio unit MS requests the transmission of a short data message (SDM) by sending a random paging message RQC (Random Access) to the base station BS on the paging channel.

Request) addressed to another radio unit, a fixed network device, or a data service. The base station BS forwards the message to the mobile switching center MX. The mobile switching center checks the reachability of the called (assigned) radio unit using the general reachability check message AHY before sending a short data message request AHYC (defined in clauses 5.5.3.2.1 and 5.5.3.2.8 of MPT1343) to the calling radio unit MS via the same paging channel BS. On the same paging channel, the calling radio unit MS sends a HEAD message to the base station BS and thereby to the mobile switching center, which includes up to four data code words. The mobile switching center MX then forwards this data by sending the same HEAD message to the recalled radio unit MS, which must respond with an acknowledgment.

In accordance with the procedures specified in MPT1343, paragraph 14. The MX sends an acknowledgment to the calling radio unit to indicate that the called radio unit has received a HEAD message. If a group is called instead of a radio unit, the radio units in that group do not acknowledge the HEAD message, in which case the MX sends an acknowledgment to the calling radio unit stating whether the MX has received the HEAD message and forwarded it to that group.

If the calling MS transmits data to a subscriber of the fixed network, the signaling for the naturally called MS described above is omitted, and the MX forwards the data to the subscriber of the fixed network.

If the MX transmits the data itself or forwards it from the fixed network subscriber, the signaling for the naturally calling MS described above is omitted.

In the present invention, interference with signaling related to call set-up and maintenance, and thereby interference with telephone traffic as a result of SDM / EDM data transmission, is prevented by reserving a separate paging channel for data transmission that does not transmit control signaling other than necessary to provide data transmission. This signaling includes the so-called ALOHA message authorizing the radiotelephones MS listening to the paging channel to send the above-mentioned RQC message to the base station BS. The signaling messages sent by the system include a system-identifying SYS code, which allows radiotelephones to know that the radio channel belongs to their own system. The SYS code to be used on the paging channel reserved for data transmission according to the invention is selected so that no radiotelephone MS can select this radio channel as the paging channel which it would start monitoring and on which it would perform signaling other than SDM / EDM data transmission. The use of the SYS code and the selection of the paging channel is described in Chapter 9 of MPT1332.

In the following, the invention is illustrated using, as an example, SDM / EDM data transmission from an MS via a radio system to another MS.

The calling radiotelephone MS transmits SDM / EDM data transmission if it wishes to transmit an RQC message in the normal way on a normal paging channel (not mentioned data transmission channel) in which it requests a data transmission permit. Once the radio system has verified that the destination of the data transmission (e.g. another radiotelephone) is found, the system commands both parties to the data transmission by means of a normal handover message (goto-channel message) to said radio channel operating in the manner of the paging channel in which the data transmission is performed. Several radiotelephones can be assigned to the same data channel at the same time, the exact number of which depends on the amount of data transmission. The call control CCC of the mobile switching center MX preferably controls the number of telephones on one such data channel so that the effective transmission rate of the data channel per individual radiotelephone does not fall unreasonably down, e.g. below a certain threshold.

Figure 3 is a signaling diagram illustrating the application of the present invention to multi-segment SDM / EDM data transmission between two radiotelephones MS in accordance with clause 14 of MPT1343. In step 1, the calling radiotelephone MS requests an SDM transmission by sending an RQC message on the normal paging channel. The value of the SLOTS field of the RQC message is 11, which indicates that three time slots are required from the channel for a HEAD message containing the first segment of a multi-segment transmission (MST).

In step 2, after receiving the RQC message, the fixed network (MXs and BSs) sends an AHY message to the called radiotelephone MS on the normal paging channel, by which it checks the reachability of the called radio unit MS. The MS called in step 3 sends an ACK message to the network on the normal paging channel as an acknowledgment to the AHY message.

The network then commands the radio units MS for the data session to the radio channel corresponding to the paging channel reserved for data transmission by sending them a handover command GO-TO-CHANNEL on the normal paging channel, which contains the number of said channel. When the radio units MS have switched to a data transmission channel, the network transmits to the calling radio unit MS on this channel some

An AHYC message in which the DESC field is set to state 100. The first bit of the DESC field indicates that multi-segment transmission is supported. The second and third bits of the field indicate that the first data segment is being requested. The SLOTS field is set to state 11, which indicates that the network has reserved three time slots from the radio channel for the HEAD message containing the first data segment to be transmitted.

In step 5, the calling MS sends a HEAD message containing the first data segment on the data transmission channel. The GFI field of the HEAD message indicates the data format. The field NEG = 10 indicates that there are two more segments to be transmitted. The field CSEG = 1 indicates that three time slots from the data transmission channel are required for a HEAD message containing the next segment.

In step 6, the network sends an AHYC message to the calling MS, in which the field DESC is set to state 101 to request a HEAD message containing another data segment to be transmitted. The SLOTS field is set to state 11 to indicate that three time slots have been allocated for the HEAD message. In step 7, the calling MS sends a HEAD message containing the second data segment to be transmitted. Field NSEG = 01, indicating that one or more data segments are being transmitted. The field CSEG = 0 indicates that two time slots are required for the HEAD message containing the next segment.

In step 8, the network sends an AHYC message to the calling MS, where the field DESC = 110 requests a HEAD message containing the third data segment to be sent. The SLOTS field is set to state 10, which indicates that two time slots have been allocated to the HEAD message. In step 9, the calling MS sends a HEAD message containing the third segment. The NSG field is not transmitted or has a status of 00, indicating that all segments have been transmitted.

The network then sends, in step 10, to the called MS a HEAD message containing the first of said data segments on the same or another paging channel reserved for data transmission in the system. The MS called in step 11 sends an ACKB message acknowledging that the HEAD message has been successfully received.

In step 12, the network sends a HEAD message to the called MS on the data channel containing one of said data segments and the called MS acknowledges the successful reception by sending an ACK message on the data channel at step 13. The network then sends the HEAD message containing the last data segment on the data channel to the called MS (step 14). ), which acknowledges receipt by sending an ACK message (item 16).

The network then sends an ACK message to the calling MS indicating that the data transfer has been completed successfully (step 17).

After the data transmission is completed, the network sends a command to the MS in a GO-TO_CHANNEL message to switch back to the original paging channel. It is also possible that after the end of the data transmission, the MS is allowed to stay for a limited time for the radio channel operating as a paging channel to wait for a new data transmission, if the network knows that one is coming.

Figure 4 is a signaling diagram illustrating the application of the present invention to multi-segment SDM / EDM data transmission from a network to a radiotelephone MS in accordance with clause 14 of MPT1343. In step 21, the fixed network (MXs and BSs) sends an AHY message to the radiotelephone MS on the normal paging channel, by which it checks the reachability of the called radio unit MS. The MS called in step 22 sends an ACK message to the network on the normal paging channel as an acknowledgment for the AHY message.

The network then commands the radio unit MS to the radio channel corresponding to the paging channel reserved for data transmission by sending it a handover command GO-TO-CHANNEL on the normal paging channel 11, which contains the number of said channel.

Thereafter, at steps 23-28, data is transmitted from the network to the radiotelephone MS by similar signaling as at steps 10-16 in Fig. 3. After the data transmission is completed, the network sends a command to the MS in a GO-TO-CHANNEL message to switch back to the original paging channel.

The figures and the related description are intended to illustrate the present invention only. In particular, the radio system and method of the invention may vary within the scope of the appended claims.