FR2749460A1 - METHOD AND APPARATUS FOR TRANSMISSION OF VERIFICATION DATA - Google Patents

Abstract

A communications device (101) transmits information packets through a communications link (108). A controller (106) coupled to the transmitter and to a receiver (110) calculates first verification data based on a predetermined criterion. The controller (106) receives second verification data from the other communication device and compares the first and second verification data. The information is retransmitted if the first and second verification data is not equal. The receiving communication device includes a controller (118). The controller (118) calculates the second verification data and commands a transmitter (116) to transmit the second verification data to the first communication device.

Description

Headline

  METHOD AND APPARATUS FOR TRANSMITTING DATA FROM

VERIFICATION

  The present invention relates to error detection techniques and more particularly the transmission of information intended to verify the

  exact reception of the information transmitted.

  We want to transmit ever greater amounts of information through communication systems such as computer networks, telephone systems and wireless interfaces. Service providers want faster transmission speeds so that they can satisfy more users. High speed makes it possible to adapt more subscriber terminals to existing equipment and reduce the costs associated with supporting additional subscribers. Subscribers want faster transmission speeds so that large amounts of data associated with images and software can be downloaded

without substantial delay.

  Another important consideration regarding these systems is the degree of trust, ensuring that the information transmitted has been faithfully received on a receiving device. Certain types of data, such as software, require a higher degree of confidence than other types of data such as digitized voice signals. In general, verification data, such as checksum or cyclic redundancy check (CRC) data is transmitted with the information. Verification data is calculated based on a predetermined criterion, such as

a mathematical relationship.

  In particular, the prior techniques segment the information strings into information packets, each packet further containing verification data. The information packet containing the verification data is transmitted by the communication link. The receiving device receives the information packet, decodes it and extracts the corresponding information and verification data. The reception device then performs a calculation of the verification data according to the predetermined criterion from the information received. The receiving device compares the calculated verification data with the received verification data. If they do not match, an error is detected and the receiving device sends a negative acknowledgment (KNACK) to the transmission side. If they match, the receiving device sends a positive acknowledgment (ACK) to the transmitting device. The transmitting device uses the ACK / KNACK state to determine whether to retransmit each packet or send a new packet. Following an ACK signal, a new packet is transmitted or the communication ends if the last packet has been transmitted. At the receiving device, the received packets are reassembled into the complete data block and other error detection rules

can be applied.

  Several potential errors may occur in this system. They result from one or more of the following causes: the information was altered during the transmission, the verification data was altered during the transmission and the ACK / KNACK signal changed state (for example a KNACK signal became a ACK signal). If data or verification bits are not detected, the information received and / or processed will be considered as correct data, which will cause an error. If a KNACK is converted to ACK,

  an incorrect data packet will not be forwarded.

  One technique for reducing the chances of accepting erroneous data is to use a large number of bits for the verification data. The number of bits used for verification data is directly related to the degree of confidence in the accuracy of the information received. The more bits the verification data contains, the smaller the number of information values received having the predetermined relationship for receiving the verification data. The fewer the values that produce verification data, the greater the chance of detecting errors in the information received. However, increasing the ratio between the verification data bits and the information bits can reduce the speed of information transmission. It is therefore desirable to propose a method of communicating information which makes it possible to have a transmission speed which is more independent of the ratio between the verification data bits and the information bits. According to a first aspect of the present invention, a method is proposed for verifying in a first communication device that the information transmitted by the first communication device has been received by a second communication device, comprising the steps of calculating a first verification data in the first communication device according to a predetermined criterion, characterized by the transmission of information in the direct direction without the first verification data; receiving a second verification data transmitted in the opposite direction from the second communication device; comparing the first and second verification data; and retransmission of information if the first and

  second verification data is not equal.

  According to a second aspect of the present invention, a method is proposed for verifying the information transmitted by a first communication device, communicating with a second communication device via a communication link, comprising the steps of transmitting information in the direct direction from the first communication device to the second communication device without verification data; for calculating a first verification data item in the first communication device according to a predetermined criterion, characterized by the reception of information at the second communication device, calculating a second verification data item in the second device communication from the information received; the transmission of the second verification data to the first communication device; receiving the second verification data by the first communication device; comparing the first and second verification data in the first communication device; and detecting an error in the first communication device if the first and second verification data does not

not match.

  According to a third aspect of the present invention, a system is proposed which comprises a first communication device communicating with a second communication device via a communication link, the first communication device comprising a transmitter for transmitting the information. by a communication link, a receiver for receiving the information at the second communication device and a controller coupled to the transmitter for calculating the first verification data in the first communication device from the information, according to a predetermined criterion, the second communication device comprising a receiver for receiving information coming from the communication link; a transmitter for transmitting the information via the communication link and a controller, characterized in that the controller of the first communication device is designed to receive the second verification data at the level of the first communication device and to compare the first and second data verification and retransmit the information if the first and second verification data are not equal; and the controller of the second communication device is designed to calculate the second verification data and to command the transmitter to transmit the second verification data to the first communication device. According to a fourth aspect of the present invention, a communication device is provided for transmitting information packets to another communication device, comprising a transmitter for transmitting the information to the other communication device via a communication link; a receiver for receiving information from the communication link; and a controller coupled to the transmitter and the receiver for calculating the first verification data in the first communication device from the information according to a predetermined criterion, characterized in that the controller is designed to receive the second data from verification at the first communication device and compare the first and second verification data and retransmit the information if the first and

  second verification data is not equal.

  According to a fifth aspect of the present invention, a communication device is provided for receiving information packets from a communication device and helping the sending communication device to verify that the correct information is received, comprising a receiver for receiving information from a communication link; a transmitter for transmitting information via the communication link and a controller, characterized in that the controller is designed to calculate the verification data and to instruct the transmitter to transmit the data

  verification at the first communication device.

  According to a sixth aspect of the present invention, a method is proposed for operating a receiving communication device and helping a sending communication device to verify that the data transmitted in a direct direction by the sending communication device has been faithfully received in the device. of receiving communication, the method comprising the steps of receiving information from the sending communication device, characterized by calculating verification data from information received by the receiving communication device according to a predetermined criterion; and transmission of the verification data in the opposite direction to the device for

sender communication.

  The invention will now be described, by way of an example, with reference to the accompanying drawings, among 2k of which: FIG. 1 is a functional diagram illustrating a communication system in which the invention can be advantageously used; Figure 2 is a block diagram illustrating a radiotelephone system in which the invention can be employed; Figure 3 is a flow diagram illustrating the operation of a source in the systems of Figures 1 and 2; Figure 4 is a flow diagram illustrating the operation of a destination terminal in the systems of Figures 1 and 2; and FIGS. 5 to 8 illustrate the operation of a system according to FIGS. 1 to 4. A method of operating a transmitting communication device comprises the calculation of a first verification data item in the transmitting communication device from the information transmitted according to a predetermined criterion. The sending communication device receives second verification data. The first and second data

are compared.

  A method of operating a receiving communication device includes receiving information from a communication link, calculating the second verification data from the information received and transmitting the second verification data to the communication device

transmitter.

  A transmitter communication device operates using the transmission method and a receiver communication device operates using the method of the receiver means. A method of operating the system and a system are also described. A communication system 100 (FIG. 1) comprises a first communication device, a transmitting communication device, 101 and a second communication device, a receiving communication device, 103. The first communication device 101 comprises

  a transmitter 104 coupled to a source terminal 102.

  The transmitter 104 operates under the control of a transmission controller 106 to transmit information originating from a source terminal 102 to a communication link 108. The information received from the communication link 108 is detected by a receiver 110, which operates under the control of an emission controller

106.

  The second communication device 103 comprises a receiver 114 and a transmitter 116 associated with a destination terminal 120. A reception controller 118 communicates with the transmitter 116 and the receiver 114 and controls their operation. The destination terminal receives information from the source terminal 102 via the communication link and can for example be a user interface comprising keys, a display, a memory, a

  combination of these or equivalent.

  The communication system 100 can be a radiotelephone system, a cable system, a land line telephone system, a local area network (LAN), a large network (WAN), a combination of these systems or any other transmission network. In these systems, the source terminal 102 can be a means of storing data such as a random access memory (RAM), a read only memory (ROM), an electrically erasable reprogrammable memory (EEPROM), a hard disk drive, a

  floppy disk, a mechanism for storing data on CD-

  ROM, a database storage means or any other suitable memory means or else the source terminal 102 can be connected to a data source such as a computer, a user input device such as keys, a application device that generates data or equivalent. The first communication device 101 can be any suitable communication device such as a modulator / demodulator (modem), a telephone, a cellular radiotelephone, a wireless radiotelephone, a digital transceiver, a high frequency modem (HF) or equivalent and the source terminal 102 can be

  integrated into this device or external.

  Communication link 108 can be a wireless link, a cable, a pair of twisted wires, a cable

fiber optic or equivalent.

  The second communication device 103 can be any communication device, compatible with the communication device 101. Thus, the second communication device 103 can be a modem, a radiotelephone, a digital transceiver, a base, a computer, a telephone or equivalent. The destination terminal 120 is any device which allows the user to easily access or manipulate the information received from the source terminal 102. Thus, the destination terminal 120 can be a user interface, such as a numeric keypad (not shown) and a display (not shown) in a box common to the transmitter 116, to the reception controller 118 and to the receiver 114 or else the destination terminal 120 can be a memory which stores the information downloaded from a source terminal 102 or the destination terminal 120 can be a device such as a personal computer, a laptop or a calculator format laptop, coupled to the receiver 114 to receive the data transmitted by the source terminal 102. In many systems, the source terminal 102 and the destination terminal 120 will be connected to a transmitter and to a receiver, which facilitates bidirectional communications. A radiotelephone system is described in FIG. 2. It comprises a device, for example a radiotelephone, 201 connected to a device, for example a base, 203 via a wireless link 205. The device 203 is in turn connected to a telephone communication system 207. The telephone communication system 207 is in turn connected to a central device 209 which can be a communications central, a direct service provider, a computer system, a server, a data terminal or equivalent. The central device 209 comprises a receiver 216 and a transmitter 214 associated with a central terminal 120; a controller 218 communicates with the transmitter 214 and the receiver 216, and controls the operation thereof. In this system, the terminal 202 is the user interface, comprising keys and a display, and a memory, which is generally found in mobile radiotelephones. The device 201 can accept messaging, E-Mail (electronic mailbox), or can receive software programs from a central device 209. The device 201 and the central device 209 can thus exchange a

  relatively large amount of data.

  The speed at which data is transmitted between the device 201 and the central device 209 determines the speed at which the terminal 202 operates as perceived by the user. The speed at which they communicate also determines the number of remote terminals that can be accepted by the central device 209 and therefore has an influence on the capacity of the whole system. It is therefore desirable to provide the highest possible throughput for the link between the device 201 and the central device 209, since any increase in the transmission speed results in an increase in the capacity and an improvement in the performances, such as the

perceives the user.

  To determine with certainty that the data is reliably transferred between the central terminal 220 and the remote terminal 202, verification data, in the form of checksum or CRC, is used. The information is formatted into packets comprising control bits and information, which are transmitted in the forward direction. Each

  packet can for example include a sequence number.

  Verification data is derived from the information and transmitted in reverse. Verification data is derived from any suitable conventional mathematical relationship, such as relationships well known in the art. In general, the larger the size of the verification data, the smaller the number of combinations of information bits that can produce the verification data. Consequently, for data requiring a high degree of confidence, such as downloaded software, a large number of verification bits, for example 64 bits, is required. For other types of data, such as digitized voice signals, a significantly lower number of bits, for example 16 bits, can be used for verification data. This verification data is transmitted from the device receiving the information to the device transmitting the information in the opposite direction, opposite to the direct direction. The operation of the reception controller 118, represented in FIG. 3, will now be described with reference to FIG. 1. At the start, it is noted that the data to be transmitted from the source terminal 102 to the destination terminal 120 will be divided into a plurality of

  segments or packets. In the following description, we

  assume that the information is divided into three equal length packets. However, the number and size of packages can vary without departing from the spirit of the invention. With reference to FIG. 3, the transmission controller 106 controls the entry of the first packet coming from the source terminal 102 in the transmitter 104 for transmission via the communication link 108, as indicated in box 301. The controller d transmission 106 will also calculate and store the first data of

  verification, CS1, as indicated in box 304.

  The transmitter 104 then resets the counter to zero and transmits the first packet via the link of

  communication 108, as indicated in box 306.

  The transmission controller 106 determines whether a second verification data item, CS2, is received from the communication link 108, as indicated in box 308. If a second verification data item CS2 is not received, the transmission controller 106 determines whether the counter has reached a threshold in decision box 309. If it has reached the threshold, the subroutine ends. This indicates that the data cannot be transmitted reliably. If the threshold is not reached, the data packet is retransmitted and the counter is incremented,

as indicated in box 312.

  When the second verification data CS2 is received from the communication link 108, the transmission controller 106 compares the second verification data CS2 received from the communication link 108 with the first verification data CS1 determined internally in the controller d transmission 106, as indicated in decision box 310. If CS1 is not equal to CS2, the emission manager 106 again determines whether the threshold has been reached, as indicated in box 309; otherwise, the packet is retransmitted, as indicated in box 312. The transmission controller 106 will continue to command the transmitter 104 to retransmit the packet, until CS1 is equal to CS2 or until the counter threshold is reached. The counter threshold can for example allow up to 5 attempts to

transmission for each packet.

  When CS1 is equal to CS2, as determined in box 310, the emission controller 106 determines if there is other information to be transmitted, as indicated in decision box 314. If there are other information to be transmitted, the next packet is loaded into the transmitter 104 to be transmitted via the communication link, as indicated in box 316. The transmission controller 106 then calculates the verification data item CS1 for the packet following and repeat the process described above to transmit this new packet. The packets continue to be transmitted and, if necessary, retransmitted until it is determined at the level of decision box 314 that all the information packets have been transmitted or else until the threshold of the counter be reached as a result of several

  attempts to transmit one of the packets.

  When all the information has been transmitted, as determined in box 314, the transmission manager 106 transmits an acknowledgment message, as indicated in box 318. The transmission manager 106 will continue to command the transmitter 104 to transmit the acknowledgment message until an acknowledgment message is received as determined in box 320. The reception controller 118, associated with the destination terminal 120, performs the described operation with reference to FIG. 4. On reception of the information, the reception controller 118 resets a timer, as indicated in box 410. The reception controller 118 then determines whether the time allocated by the timer has elapsed, as indicated in decision box 412. If the time has elapsed, the subroutine ends because communication with the transmitting communication device is assumed to have been interrupted. If the time has not expired, the reception manager 118 determines whether the information is an acknowledgment message as indicated in decision box 400. If the message is an acknowledgment message, a message acknowledgment of receipt, ACK-ACK, is transmitted, as indicated in box 414. If it is not an acknowledgment message, the stage manager 118 determines whether the packet is an information packet, as indicated in decision box 401. If the reception controller 118 does not detect an information packet, it goes to box 412 and determines whether the time allocated has elapsed. If the reception controller 118 determines that an information packet is received, as indicated in decision box 401, it identifies the segment packet number, as indicated in box 402. The received packet is then temporarily kept for subsequent storage at the location

  suitable, associated with the package, as indicated in box 404.

  It will be admitted that the packets can be identified in terms of the total number of packets constituting the information block, such as for example the packet one in three,

two out of three and three out of three.

  The reception controller 118 calculates the second verification data item CS2 from the information received as a function of the predetermined mathematical relationship used by the transmission manager 106 to calculate CS1, as indicated in box 406. CS2 calculated by the reception manager 118 is then communicated to the receiver 110 via the communication link 108, as indicated in box 408. Each time a packet is received, which has a sequence number identical to that of a packet already received previously , the packet is a retransmission and the previously received packet is deleted. Whenever a new packet number differs from a previously received packet number, the immediately preceding packet is stored in its appropriate location. Thus, when a packet is retransmitted, the reception controller 118 overwrites the previously received packet. Each time a packet is received for the first time, the receiving controller 118 assumes that the previous packet was a

  valid transmission and this packet is stored.

  The receive manager 118 will continue to receive and store packets until an acknowledgment message, ACK, detected in decision box 400 is received. In response to the acknowledgment, the receipt manager 118 saves the last received packet and commands the transmitter 116 to return an acknowledgment of receipt (ACK-ACK) message to the transmitter communication device 101, as indicated in

box 414.

  This protocol for transmitting data via a communication link, such as a high frequency wireless link, results in an increase in the efficiency of data transfer, a significant improvement in data throughput and a reduction delays. In addition, it has the additional advantage of providing a slight improvement in the residual bit error rate. By increasing the efficiency of subscriber service networks, it is possible to increase the overall capacity of the operator's system and therefore support more users using the present invention.

  The operation of the communication system 100 will now be described with reference to FIG. 5. The communication device 101 comprises a buffer 500 placed in the transmission controller 106, which stores the three data packets to be transmitted by the transmitter 104 The transmission controller 106 processes the information of the first packet to generate the information packet 502 and a first verification data item 504. The first verification data item 504 is stored in the

emission manager 106.

  The information packet 502 is transmitted by the communication link 108. The information 506 is received by the receiver 114. The information 506 may be identical to the information packet 502 or they may have been modified during the transmission by the link 108. The reception controller 118 processes the information to generate the verification data 1'CS 508. This verification data 508 is communicated to the receiver 110 via the communication link and the transmission controller 106 receives the verification data 1 "CS 510. The verification data 1" CS 510 can be modified by the verification data 1'CS 508 transmitted by the transmitter 116. The emission controller 106 compares the verification data 1 "CS 510 with the verification data 1CS 504 to determine if they are equal. If the verification data are different, the emission controller 106 will subtract will send the information packet 502. The transmission controller 106 will continue to retransmit the information packet 502 until it determines that the second verification data item 1 "CS and the first verification data item 1CS are identical or until the maximum number

  failed transmission attempts is reached.

  Each time the information packet 502 is retransmitted, the reception controller 118 replaces the previous information 506 with the information 506

newly received.

  FIG. 6 illustrates the transmission of a second information packet 600. To transmit the second packet, the first 2CS verification data item 604 of the second packet is calculated by the transmission controller 106. The second information packet 602 is generated by the transmission controller 106 and transmitted via the communication link by the transmitter 104. The receiver 114 receives the information packet 614, possibly altered by the transmission by the communication link 108. The controller 118 receives the received information packet 614 and stores the first packet in the buffer 501. A second verification data item 2'CS 608, associated with the second received information packet 614, is calculated in the reception controller 118 and transmitted to the receiver 110 by the transmitter 116. The transmission controller 106 compares the 2 "CS verification data received 610 with the 2CS 604 verification data. transmission equalizer 106 will continue to retransmit the second information packet 602 until the verification data 2 "CS 610 and the verification data 2CS 604 match for the second packet or until the maximum number of attempts transmission is reached. The transmission manager 106 will then determine whether there is any information to be transmitted since the

  third packet has not yet been transmitted.

  The third packet is transmitted as shown in FIG. 7. The transmission controller 106 generates a verification data item 3CS for the third packet. The latter is generated and communicated to the receiver 114 in the manner described above for the second packet. The reception controller 118 processes the received information packet 706 so as to generate a second 3'CS verification data item 708 for the third packet and the second packet is saved in the buffer 501. The verification data item is communicated to the receiver 114 The received verification data 3 "CS is compared to the verification data 3CS for the third packet. This process is repeated during the retransmission of the third packet, until it is determined that the checksums 3CS and 3 "CS are equal or until the maximum number of transmission attempts is reached. When it turns out that the sums are equal, the transmission controller 106 determines that all the packets have been transmitted and received by the reception controller 118. The transmission controller 106 will then transmit an acknowledgment signal ACK 800 at the destination terminal 120, as shown in FIG. 8. The reception manager 118 will acknowledge receipt of the acknowledgment of receipt, store the third packet in buffer 501 and transmit an acknowledgment of receipt of the acknowledgment of receipt, namely the signal ACK-ACK 804, to the receiver 110. The transmission controller 106 continues to transmit the signal ACK 800 to the receiving communication device 103 until the transmitting communication device 101 receives the signal ACK-ACK 806 or until the maximum number of attempts to

transmission is reached.

  A comparison between the previous system and the current system will now be described. The possible errors that may occur when using the prior art system are: 1) the information and verification data will not be altered; 2) the information will be altered, but not the verification data; 3) the information will not be altered, but the verification data will be altered; 4) information and verification data will be altered; and) ACK / KNACK will be altered. Of the above possibilities, only the first situation is desirable. The second possibility may go unnoticed, since multiple errors in the data may cancel each other out, the error detection mechanism may not detect errors in the data. The third situation will always be detected. However, unnecessary data retransmission will occur, which will reduce efficiency. The fourth situation may go undetected because of incorrect verification data

  may coincide with the wrong data.

  The probability of an incorrect decision, which leads to the acceptance of a message with incorrect data, is given by the following equation: PUEM = (1-p) (q) (1-r) + (1-p ) (1-q) (1-s) (1) op is the probability of an error-free data transmission; q is the probability of a CRC error-free transmission; r is the probability of data failures that do not cancel each other out; and s is the probability that the random CRC does not match the information currently

  received [1- (1 / space number of CRC)].

  Adding verification data to packet data messages for transmission over a radio interface, when used with direct error correction (FEC) and acknowledgment protocol (ARQ), allows forwarding the data securely (i.e. having low residual bit error rates and / or low message error rates). However, the verification data uses useful capacity, which could otherwise be used to increase the throughput of data transmissions. The problem is particularly serious when the amount of data transmitted is relatively large for system information rates, as is the case for transferring software or data files via a wireless radio interface or transmission of image data over a network

public computing.

  For example, in existing cellular radiotelephone systems, when a service is provided to a subscriber terminal, the latter negotiates with a base a speed and a degree of confidence. Throughput can be reduced if a higher degree of confidence is required. In addition, a delay in the rate at which data becomes available at the destination terminal may

  be communicated according to the level of confidence required.

  Thus, there can be an exchange between the degree of confidence and the flow. When the number of verification bits is increased, the total number of bits necessary to transmit a particular information packet is also increased, which slows down the information rate for a given bit rate of the channel. A decrease in throughput is also due to an increase in the number of frames of information data that are discarded due to the errors detected. Whenever information is rejected due to errors

  detected, it must be retransmitted.

  For some existing systems, the efficiency losses when transmitting verification data with the information are as follows. It can be noted that in general, the existing packet data transfer protocols, wireless, are only efficient at 80-94% due to the overload which consists in transferring the verification data with the

  information, from the transmitter side to the receiver side.

  The Trans European Trunked Radio voice plus data system (TETRA V + D) has a 32-bit CRC which protects a variable length field in the upper layer TL-SDU, which can have a size of 32 bytes, 64 bytes, 128 bytes , 256 bytes, 512 bytes, 1024 bytes, 2048 bytes or 4096 bytes. This gives an overload of between 0.1% and 12.5% depending on the size of the TL-SDU. The lower layer maximum slot signaling uses a 16-bit CRC protecting 268 bits of information, including the segment header. This adds an additional 5.9% surcharge. The total efficiency is: (100 - 12.5%) x (100 - 5.9%) = 82% (short packages in the most unfavorable case) 0.999 x (100 - 5.9%) = 94% ( long packets in the most favorable case) The Personal Access Communications System (PACS) having a burst level CRC of 16 bits protecting 80 bits of information, produces an overload%. The 16-bit packet level checksum protecting up to 18464 bits has an overload of about 0.09%. Total efficiency is:% * 99.91% = about 80% (in the most favorable case) The DECT (Digital European Cordless Telephone) system has logical link control (LLC) protection for network layer messages , thanks to which 464 bits are protected by a 16-bit checksum, which gives an overload of 3.4%. For average access time control (MAC) protection of a 256-bit LLC packet, a 16-bit CRC is used.

  which results in an additional surcharge of 6.25%.

  The total efficiency is: 96.7% x 93.75% = 90.7% Thus, with these existing systems, there can be an exchange between the flow and the degree of confidence

  ensuring that the data has been received accurately.

  Other known systems are also not effective at%. An improved system incorporating the present invention transmits the verification data in reverse. This has an advantage, namely that ACK / KNACK messages are no longer necessary, except for the sending side which sends a message

  ACK / KNACK final at the end of the data transmission.

  Furthermore, and more importantly, it allows more data to be transmitted during each slit / frame / burst. This increases the throughput efficiency for each transmission, from 80-94% if using the conventional method used in existing systems, to 100% if using this new method. Transmission of verification data in reverse is particularly advantageous when the flow in one direction is significantly higher than the flow

in the opposite direction.

  With the new method, there are four possibilities for transmitting information packets: 1) the information will not be altered and the verification data will match; 2) the information will not be altered and the verification data will not match; 3) the information will be altered and the verification data will not match; or 4) the information will be altered and the data of

verification will match.

  The first and third possibilities are correct. The second will cause unnecessary retransmission. The fourth will produce an error because erroneous data will be accepted. The probability of an incorrect decision, which would lead to the acceptance of a message with incorrect data, is given by the equation: PUEM = (1-p) (q) (1-r) + (1-p) (r) (1-q) (1-s) (2) The PUEM given by equation 2 is even safer than that given by equation 1, because it includes the component (r) in the second member of the sum. (r) is the probability that several errors in the information do not cancel each other, so that the second verification data will correspond to the information; this probability can be expected to be very slightly less than 1. The invention essentially benefits from the fact that the verification data are compared with the original data in the transmission controller 106 and not with the data received in the

reception manager 118.

  The comparison of the effectiveness between the old and the new protocol approach depends on the assumption that the probability of seeing an error fit into the verification data is the same for both approaches. This must be achieved by careful design of the FEC and by embedding algorithms in cellular systems. This may be easier to achieve when verification data is transmitted downlink in cellular systems, since this transmission is, in general, continuous and there is a greater chance of being able to finely nest the data from

  verification in the other information transmitted.

  Because the comparison of the verification data is performed on the transmitter side, the ACK / KNACK messages have been almost completely eliminated by this invention. The capacity of the communication system 100 is directly linked to the increase in throughput. Capacity is the number of subscriber units that the cellular system can manage, the number of terminals that a server can manage or the number of subscribers that a service provider

  live computer services can support.

  The faster the data can be transmitted, the shorter the time required to transmit the data for a particular user. Many hardware systems are designed to increase the capacity of communication systems. The present invention allows an increase in capacity without significant modifications to the hardware. Thus, the gain in terms of speed is a significant gain in a communication system where the service provider must increase the

  communication system capacity.

  In addition, the present invention increases the degree of confidence without reducing the direct throughput, since no additional bits are added in the forward direction. The confidence level can be increased by adding bits to the verification data communicated in reverse. This can cause more retransmissions

  before the verification data matches.

  It will be appreciated that the method of the present invention can be used for transmissions in both

  directions of a two-way communication system.

  For messaging between the devices 201 and 203, the direct direction goes from the device 201 to the device 203. In this case, the manager 103 of the device 201 is the emission manager and the manager 118 of the device

  203 is the reception manager.

  Conversely, the direct direction goes from device 203 to device 201 when the data is transmitted to device 201. In this case, the emission controller is the controller 118 in the device 203 and the controller

  reception is the controller 106 in the device 201.

Claims (19)

  1. Method for verifying in a first communication device that the information transmitted by the first communication device has been received by a second communication device, comprising the steps of: calculating a first verification data item in the first communication device communication according to a predetermined criterion, characterized by the transmission (306) of information in the direct direction without the first verification data; receiving (308) a second verification data item transmitted in the opposite direction from the second communication device; comparing (310) the first and second verification data; and retransmitting (312) the information if the first and second verification data are not equal. 2. Method according to claim 1, in which packets (500) comprising information which is transmitted sequentially (316, 306) and first and second verification data which are calculated (304, 406) for each packet, each being retransmitted (312) until the first and second verification data for this packet are equal (310) or until the maximum number of retransmissions is reached (309).   3. A method of operating a receiving communication device so that it assists a sending communication device to verify that the data transmitted in the forward direction by the first and second verification data has been received accurately by the communication device. receiving communication, the method comprising the steps of: receiving information from the sending communication device, characterized by calculating (406) verification data from the information received by the receiving communication device according to a criterion predetermined; and transmitting (408) the verification data to the transmitting communication device in the reverse direction. The method of claim 3, wherein the information includes sequential information packets and wherein the receiving communication device stores (404) a first packet   after receiving a second packet (401).   5. The method of claim 3, wherein the information comprises sequential packets comprising information and wherein the receiving communication device deletes a first previously stored packet when a first packet retransmitted is received.   The method of claim 5, wherein the first retransmitted packet is stored (404) when second packet is received (401).   7. Method for verifying information transmitted by a first communication device communicating with a second communication device via a communication link, the method comprising the steps of: transmission of information in the direct direction of the first device communication to the second communication device, without verification data; calculating first verification data in the first communication device according to a predetermined criterion, characterized by the reception (401) of information at the second communication device; calculating (406) second verification data in the second communication device from the information received; transmitting (408) the second verification data to the first communication device; receiving (308) the second verification data by the first communication device; comparing (310) between the first and second verification data in the first communication device; and detecting an error in the first communication device if the first and second data of verification do not match.   8. The method of claim 7, further comprising the steps of retransmission (312) of information if the first and second verification data does not are not equal.   9. The method of claim 7, wherein the information comprises packets (500) comprising information which is transmitted sequentially (314, 316) and wherein a first verification data and a second verification data are calculated for each packet, each being retransmitted (312) until the first and second verification data for that packet are equal (310) or until the maximum number of retransmissions is reached (309).   10. The method of claim 9, wherein the second communication device stores (404) a   first packet after receipt of a second packet.   11. The method of claim 9, wherein the second communication device deletes a first previously stored packet when a first packet retransmitted is received.   The method of claim 11, wherein the first retransmitted packet is stored (404) when second package is received.   13. System comprising a first communication device communicating with a second communication device via a communication link, the first communication device comprising: a transmitter for transmitting information via a communication link , a receiver for receiving information at the second communication device and a controller coupled to the transmitter for calculating a first verification datum in the first communication device from the information according to a predetermined criterion, the second device A communication device comprising: a receiver for receiving information via the communication link, a transmitter for transmitting information via the communication link and a controller, characterized in that the controller of the first communication device is designed to receive ( 308) second verification data at the first communication device and compare (310) the first and second verification data and transmit (312) the information if the first and second verification data are not equal; and the controller of the second communication device being designed to calculate (406) the second verification data and to command the transmitter to transmit (408) the second verification data to the   first communication device.   The system of claim 13, wherein the second communication device includes a buffer (501) for storing received information packets and overwriting a packet when a retransmission of the same packet is received.   15. Communication device for transmitting information packets to another communication device, comprising; a transmitter for transmitting the information to another communication device via the communication link; a receiver for receiving information via the communication link; and a controller coupled to the transmitter and the receiver for calculating first verification data in the first communication device from the information according to a predetermined criterion, characterized in that the controller is designed to receive (308) a second verification data at the first communication device and compare (310) the first and second verification data and transmit (312) the information if the first and   second verification data is not equal.   16. A communication device for receiving information packets from a communication device and for helping the sending communication device to verify that correct information is received, comprising: a receiver for receiving information via of the communication link, a transmitter for transmitting the information via the communication link and a controller, characterized in that the controller is designed to calculate (406) the verification data and order the transmitter to transmit (408) the data   first communication device.   17. Method or device according to any one of   claims 1 to 16, wherein the   communication communicate through a high frequency link (205).   18. Method or device according to any one of   Claims 1 to 16, in which a device for   communication is coupled to a data source and the other device is a storage device or data processing.   19. Method or device according to any one of   claims 1 to 16, wherein one of the devices   of communication is a radiotelephone and the other a base.