Data transmission method via a member device of a group call

p0001The invention provides a method for transmitting data by a device member of a caller group. The field of the invention is that of mobile telephony. Specifically the field of the invention is that group calls, the most accurate field itself being suitable for use by administrative services font type and / or emergency aid, the list is not exhaustive .

p0002An object of the invention is to enable a transmission in real time non-voice data during a group call. In the invention means real time in less than a second, and anyway faster than the transmission of a short message (SMS).

p0003In the state of the art call groups are known. A caller group consists of a set. A terminal is, for example, a mobile phone connected to a mobile network via a base station. In a call group each terminal can hold two roles: speaker or earphone. At a given moment in a group there is only one speaker. The speaker outputs voice data which are broadcast to be received by all party headphones.

p0004In a call group there may be at least one distributor device with extended capabilities compared to a standard terminal or just being a user terminal having a special status among the users of the Appeal Panel.

p0005For a given cell phone network, all terminals headphones belonging to the same ring group uses the same radio resource, ie the same communication channel to receive voice data sent by the speaker.

p0006Some applications, especially in the field of law enforcement and emergency relief, require fill transmit non-voice data at any time and in a very short time. At any moment in particular stands including while the user is currently making or answering a call using a caller groups to which it is registered.

p0007Another requirement in this area is to identify the person or device that is the speaker. To do this it is necessary that the speaker transmits an ID.

p0008In the prior art, the only possible solution to issue such non-voice message is to send an SMS. However emit an SMS takes at least several seconds. The use of SMS is not possible.

p0009This object is for terminals with the role of speaker by multiplexing voice data with non-voice data to be transmitted. The principle of the invention is to use for the transmission of voice data a first codec into believing the network a second codec is used, the flow rate of the first codec being lower than the second codec rate. This has the effect of freeing up space in the frames sent by the second codec. This freed up is used to transmit non-voice data. In the invention the non-voice data transmitted comprise a frame identifier for reconstituting the non-voice data transmitted. It is indeed likely that we should more frames to transmit non-voice data.

p0010A codec is an electronic device, or a program that converts an audio or analog or digital video signal into a digitally encoded signal at the time of issue, and can perform the reverse operation at the reception. The term codec is an encoder contraction - decoder.

p0011In the same groups call this problem is solved for the terminals having the headphone role in making a substitution of temporary group to the terminal which non-voice data to be transmitted. In this new group the terminal performs a resource request to transmit data, and once the resource obtained the terminal transmits the data. At the end of the show, the terminal returns to his original caller group. The start of transmission of data is done in about 500 ms 300ms in the most favorable case, if the second group is permanently established and the free resource in time of application.

p0012The invention thus relates to a method for transmitting data by a device member of a caller group, said device having the role of speaker in said group call, the device emitting therefore at least voice information characterized in that :<ul><li>Voice information is obtained by applying a first codec on a sound message,</li><li>sound information is supplemented by data to be transmitted to form a data frame,</li><li>the data frame is transmitted as the result of the encoding of a sound message by a second codec, the flow of the second codec is greater than the first codec rate.</li></ul>

p0013Advantageously, the invention is also characterized in that the data to be transmitted includes a frame identifier.

p0014Advantageously, the invention is also characterized in that the data frame comprises a header including at least a flag specifying to the infrastructure responsible for routing the frame that the said frame should be routed without processing of its contents.

p0015Advantageously, the invention is also characterized in that the first codec is an AMR codec 4,75Kbit / s, the second codec is an AMR codec 6,7Kbit / s AMR codec providing classes of bits, the bits d a given class of the first codec are transmitted as bits of the same class of the second codec.

p0016Advantageously, the invention is also characterized in that the bits of a frame identifier are transmitted as bits of maximum importance in the second codec.

p0017Advantageously, the invention is also characterized in that each frame comprising N bits available for the transmission of data, a word of M bits, where M is greater than N, is transmitted via as many frames required to be transmitted.

p0018Advantageously, the invention is also characterized in that the data to be transmitted are bits of an identifier of the device.

p0019Advantageously, the invention is also characterized in that the device identifier is coded on 192 bits.

p0020Advantageously, the invention is also characterized in that the data to be transmitted are bits of a status code, said code being selected via a menu of a man machine interface of the device.

p0021Advantageously, the invention is characterized in that the status code comprises 16 bits.

p0022The invention will be better understood from reading the following description and examining the accompanying figures. They are presented for illustrative purposes and in no way limit the invention. The figures show:<ul><li>Figure 1 is a summary illustration of a ring group.</li><li>2 shows a generic step illustration of the method according to the invention.</li><li>FIG 3 illustrates steps of the method according to the invention for multiplexing voice data and non-voice.</li></ul>

p0023Figure 1 shows a network 101 that supports telecommunications group calls. Such a network is for example a GSM network. The network 101 includes a number of base stations, such as base stations 102 to 105. These base stations are connected terminals, here mobile phones. 1 shows a terminal 106 connected to the base station 102, terminals 107 and 108 connected to the base station 103, a terminal 109 connected to the base station 104, and a splitter 110 connected to the station 105 basic or directly to the network 101.

p0024In the example described the network 101 is a GSM network, but in practice the invention applies to all upper-generation networks or equal to 2, and more generally to any network that supports group calls.

p0025The devices 106 to 110 are all in communication in the same first call group identified by a group calling Gid1 identifier. The characteristic of a caller group is that for a given base station, all terminal device and headphones of the same call group share the same radio resource.

p0026A splitter is a device having a special role in the call group. A dispatcher is being used by a user to coordinate the actions of members of the Appeal Panel, a splitter is connected to a centralized room like a road or a PC, for example the police.

p0027Consider the 106 phone and its user. In practice when an action is attributed to a device, it is performed by a microprocessor of the device controlled by instruction codes of a program memory of the device. For the sake of clarity microprocessors and memories are not shown for the devices involved in this description.

p0028The phone 106 is active in a first call group managed by the network 101.

p00292 shows a step 201 test data existing transmitting carried at regular intervals by a terminal according to the invention. Step 201 can also be caused by a hardware interrupt sent to the microprocessor 106 phone after a user action.

p0030In one example it is assumed that the telephone 106, according to the invention comprises a data memory to be transmitted in which the phone 106 processor records non-voice data to be transmitted. The data memory is filled at regular intervals whether the data should be issued at regular intervals, it is filled due to some of the telephone user 106. Such action is for example the validation of an option to a menu of a man machine interface of the phone 106. selecting this option has the effect of writing the data to be transmitted in the data memory.

p0031If the data memory is empty, that is to say, if there is no data to transmit, then passes from step 201 to step 202 corresponding to the normal activities of the phone 106. Otherwise we proceeds from step 201 to a step 203 for determining the role of the 106 phone call in the group.

p0032The phone 106 is either in speaker, earphone evening. He is speaker if the user has requested, via a button PTT, and got the word in the call group to which it belongs. Get the word means in a caller group, get the resources for transmitting voice data which is then received by all other members of the group call. If a phone call group is not speaker, then it's earpiece.

p0033If the phone 106 is speaker then it proceeds from step 203 to a step 204 of multiplexing the data to be transmitted with voice data. Or the phone 106 proceeds to step 206 to talkgroup change.

p0034In some applications, it is required that the phone is the speaker identifies himself and thus transmit its identifier. In this case at regular intervals phone 106 writes in its data memory ID. Conventionally such an identifier is encoded by 24 bytes, that is to say 192 bits.

p0035In another application, compatible with the previous, the user of the telephone 106 must promptly issue a status message. In this case the user selects the status message to be issued in a menu, which has the effect of causing writing in the identifier data of phone memory and 106 status code message. An identifier is typically encoded by 24 bytes, and a status message by 2 bytes, or a total of 208 bits.

p00362 illustrates step 204. Figure 2 shows a message 201 of voice. Such a message is in fact a bit in an orderly sequence corresponding to 20ms of sound picked up by a telephone microphone 106. The message 201 is processed by a first codec. This treatment is accomplished either by a dedicated circuit or by the microprocessor of the telephone 106 controlled by specific instruction codes and corresponding to the first codec. The result of processing the message by the codec 201 202 203 coded message.

p0037In one example, the codec 202 is the AMR codec (Adaptive Multi Rate for multiple adaptive flow rate) having a flow 4.75kbit / s. Coded message 203 is a message of 95 bits including himself two messages: a message containing 42 bits VA called class A, and a message called VB 53 bits of class B. Class A bits are considered more important than the class B bits are protected by an error correcting code in the header of an AMR frame. In practice this error correcting code is a CRC (checksum) of 8 bits.

p0038The message 203 is then processed by a processing algorithm 204 according to the invention. The algorithm produces a 204 T frame according to a second codec, codec being second in an example the AMR codec having a flow 6.7kbit / s. In all cases the flow rate of the second codec is higher than the first codec rate.

p0039The frame produced T has a header H and a body C. The body C is divided into two messages A and B. A message has 58 bits called Class A and 76 Class B called bits In the invention the message a comprises the message bits VA, a frame identifier IDT and a message data D1. The message B has the VB message and a data D2 message.

p0040In an embodiment of the invention the IDT identifier is encoded on 7 bits D1 message while having 9 bits. D2 message includes 23 bits.

p0041The identifier IDT is, for example, increasing a cyclic counter to each transmitted frame. Cyclic means here that goes back to zero when it reaches the maximum value allowed by its dynamics. Alternatively the value of the identifier IDT is a function of the nature of the data transmitted via the D1 and D2 messages.

p0042In our example D1 and D2 messages for transmitting up to 32 bits in an AMR frame. These bits are read from the memory 210 to 106. If the telephone data memory 210 has more than 32 bits, for example N = 192, then the N bits are divided into 32 bit packets that are transmitted in successive frames identified via IDT ID.

p0043The header H includes a CRC used to protect the message A, idC a field identifying the codec used for body data C, and a flag F indicating the infrastructure elements carrying the frame T which must not perform treatment on the body content C. in the described implementation of the invention the idC field identifies the AMR codec 6.7kbit / s.

p0044Frame T once produced is processed and issued, in a step 205 following step 204, as a normal voice frame in a caller group. Upon receipt of the frame T earphones devices perform the conventional data verification operations in a caller group, then recompose the message 203 for voice data to be broadcast acoustically. The headphones also recover devices D1 and D2 messages to reconstruct the non-voice data transmitted by the device speaker. The invention is based on the principle that the devices of the call group know the structure modified according to the invention of voice frames exchanged in the call group.

p0045In the invention the structure described for the T frame is retained even if the speaker device has no non-voice data to be transmitted. In this case D1 and D2 messages are empty. In this case, for example, using a predetermined frame identifier value corresponding to a frame having no non-voice data in D1 and D2 messages. It therefore becomes unnecessary to process the contents of messages D1 and D2 to the reception of voice frames.

p0046In step 206 the telephone earpiece 106 is in the first talkgroup. However the user wishes to issue non-voice data. In step 206, the terminal 106 then changes talkgroup. In the signaling data from the network terminal 101 read an identifier of a second call group. The user wishing to transmit non-voice data, these having been written in the data memory, then the terminal activates the second call group

p0047The second call group has at least a privileged destination device non-voice data sent by the phone 106. In our example this is the privileged recipient splitter 110.

p0048In this second call group phone 106 requests the transmission resources enabling it to issue its non-voice data. For example, it applies to become speaker. These resources obtained, the phone emits 106 Non-voice data in a step 207, then reinstates the first call group in a step 208 following step 207.

p0049The step 207 corresponds to steps 204 and 205. Step 207 is distinguished by the fact that the VA and VB messages are empty. In other words the telephone 106 transmits frames according to the first and second codec, the second codec having a rate greater than the first codec, a frame according to the second codec having more bits a frame according to the first codec, the frames issued by the listener device being issued according to the second codec but using the surplus bits relative to the first codec capability.

p0050Alternatively, as there is no voice data to be transmitted, the phone 106 uses all of the bits of the messages A and B for transmitting the non-voice data. This will convey a message in packages of 134 bits instead of 32 bits packages. In this variant there is no multiplexing between voice data and non-voice data.

p0051In the second group, only one device, eg the dispatcher reacts to the transmission of data by phone 106. Other devices eventually enrolled in this second group are not notified of the activity of the phone 106 in the second group or if they are, they do not take into account.

p0052This description is meant by non-voice data digital information transmitted over voice data usually transmitted in a call group. In practice, these non-voice data may correspond to sounds.