RU2719541C9 - Single-channel radio communication method - Google Patents

Abstract

FIELD: radio engineering and communication.

SUBSTANCE: invention relates to automatic radio communication and is intended for data transmission between mobile and fixed subscribers. Result is obtained by generating packets of 2^N bits, encoding with a binary code so that the number of digits in the code word n=log₂N matches the order of phase manipulation 2, 4, 6, 16, accurate synchronization of time scales on the transmitting and receiving sides, and corresponding operations at receiving side.

EFFECT: technical result of invention consists in increase of information transfer speed.

1 cl

Description

The invention relates to automatic radio communication and is intended for data transmission between mobile and fixed subscribers.

A known method of HF radio communication using HFDL (High Frequency Data Link) technology, built on the basis of the ARINC 635 specification [1], optimizes, in terms of communication reliability, spectral and economic efficiency, an Air-to-Ground packet communication system in which a large number of aircraft ( up to 2500) is served by a small number of frequency channels (up to 48-60) and ground stations (up to 16) in the time and frequency division multiple access mode. The method of data exchange in the HFDL system is described in detail in [1]. HFDL defines both channel composition procedures with automatic selection of the operating frequency, and all other procedures for automatic communication at all levels (physical, channel and subnetwork) with multi-parameter adaptation of the radio link in frequency, transmission rate, types of modulation and coding, as well as spatial diversity of terrestrial stations guaranteeing reliability (residual error probability) not worse than 10 ^-6 . The HFDL system uses the same set of frequencies for channeling and communication. The high spectral efficiency of the system is achieved through the use of a combined frequency division multiple access (FDMA) and time division (TDMA) channel multiple access protocol. The frequency division protocol is provided by assigning different frequency channels (between two and six) to different HF terrestrial stations (HF LS). The TDMA protocol is provided by the fact that the usage time of each frequency channel is divided into 32 second frames, and each frame is divided into 13 access time slots with a duration of 2.461538 s, equal to the transmission time of one data packet of 2.343888 s plus 117.65 ms per uncertainty in the propagation delay time and desynchronism in the radio link. At all HF frequencies, ground stations periodically (in the first slot of each frame) emit marker signals, the quality of which is evaluated by aircraft when choosing a communication frequency. The aircraft selects for communication any channel whose marker signal quality is acceptable or best, registers on that channel at the ground station, and communicates there until the channel quality meets the required level. Several aircraft can choose one communication channel and register on it. Each HF channel of the HFDL system is used by all aircraft registered on it in a time division multiple access mode. The HF ground station provides control over the TDMA protocol by signaling assignment markers for aircraft-reserved slots, random access slots, and slots for transmission from the ground. The HF ground station predicts the system characteristics (packet transmission delay) on each of its frequency channels and sets the channel busy flag in the marker when a critical number of aircraft have registered on the channel in order to stop new correspondents from accessing it and guarantee the specified system characteristics (packet transmission delay no more than admissible). Depending on the quality of the channel and the amount of data transmitted in the message, the optimal type of multiposition phase shift keying and coding is selected. At the same time, the message duration and the 1800 baud rate provided by a single-tone modem do not change.

To ensure a given level of communication reliability in the area of responsibility of each HF ground station from the general list of HF frequencies (48-60 channels with one sideband) allocated for the HFDL system, at the control point of the HF data exchange system, it is assigned for each HF ground station for each temporary interval of a day with a duration of (1-2) hours, a set of (2-6) active frequencies, optimal in terms of radio wave propagation and electromagnetic compatibility, bring the assigned set of frequencies together with the time interval for its activation to each RF ground station through the ground communication subsystem, realizing, thus, the frequency division multiple access protocol divides the usage time of each frequency channel into time frames of 32 s, and each frame is divided into 13 time slots of 2.461538 s to implement the time division multiple access (TDMA) protocol.

At the end of each frame, at each HF ground station, for each slot of the next frame, assignment is made to use that slot for transmission from the ground, or for transmission from a specific aircraft upon its prior request for an access slot, or for transmissions from any aircraft in random access mode.

From each HF ground station on all active frequencies in the first slot of each frame, marker signals are emitted that contain the assignment of the use of each slot of the current frame, as well as receipts for messages received from the HF BS in the previous two frames.

At each HF onboard station, based on the results of assessing the quality of marker signal reception, the best communication frequency is selected (HF radio channel "Air-to-Ground").

Each HF airborne station registers on the HF channel it has chosen at the HF ground station corresponding to this channel, exchanges packet data in TDMA mode via the HF air-to-ground radio channel between the HF ground station and the HF airborne station that is registered on it, until while the quality of the RF air-to-ground radio channel exceeds the acceptable level. If the quality of the HF radio channel deteriorates below the acceptable level, a new HF radio channel is selected for the onboard station and it is registered on the new selected HF radio channel. Packet data is exchanged through the ground communication network between HF ground stations and the control point of the HF communication system, as well as users of the communication system - air traffic control towers (ATC) and airlines (AL).

In the process of exchanging packet data, a packet message for an air traffic controller or UAL containing the address of the recipient - the ATC or UAL control center, as well as the sender's address (address of the aircraft according to the ICAO version), is formed in the onboard communication control unit (onboard router), transmitted to the HF onboard station, where it is packaged in a package intended for transmission over the HF radio channel, then transmitted over the radio channel to the HF ground station where the HF aircraft station is registered, where it is packaged in a package intended for transmission over the terrestrial communication subsystem, and transmitted through the interface to the ground communication subsystem, from where it is transmitted through the interface to the ATC or AL control center.

A packet message for the CCP containing the address of the recipient - the CCP, as well as the address of the sender (address of the board according to the ICAO version), is formed in the HF onboard station, where it is packaged in a packet intended for transmission over the HF radio channel, transmitted over the radio channel to the HF ground station , on which the HF airborne station is registered, where it is packaged in a packet intended for transmission over the terrestrial communication subsystem, transmitted through the interface to the terrestrial communication subsystem, from where it is transmitted through the interface to the control center.

In the opposite direction, a packet message from an ATC or AL control center containing the recipient's address - (ICAO aircraft address), as well as the sender's address - an ATC or AL control center, is formed at the ATC or AL control center, transmitted through the interface) to the ground communication subsystem , from where the packet is broadcast through the interface to the HF ground station on which the HF onboard station is registered - the destination, where it is packaged into a packet intended for transmission over the HF radio channel, and then transmitted over the radio to the HF onboard station - destination.

A packet message from the CCP for the aircraft, containing the recipient's address - (the address of the aircraft according to the ICAO version), as well as the sender's address - CC, is formed in the CCP, transmitted through the interface to the terrestrial communication subsystem, from where it is broadcast through the interface to the HF ground station, to which the onboard station is registered - the addressee, where it is packaged into a packet intended for transmission over the HF radio channel, and transmitted over the radio channel to the HF BS - addressee.

The disadvantages of analog are as follows:

- information transfer rate does not exceed 1800 baud;

- Increasing the speed of information transfer will require a significant change in the algorithms of work and software and hardware.

Known analogue according to the method of application [2]. This method of radio communication consists in the fact that marker signals are emitted from each HF ground station in the first slot of each TDMA frame of the channel access protocol on all frequencies, which are periodically assigned and activated in the control center of the HF communication system of the HF range. To implement the FDMA protocol for accessing communication channels, according to which different HF ground stations have different sets of active operating frequencies, each HF airborne station is registered at the corresponding HF ground station at the best HF communication frequency selected by the HF airborne station based on the results of its assessment of the quality of reception of marker signals . Then, between the HF ground station and the HF aircraft station registered on it, packet data is exchanged until the quality of the Air-to-Ground channel of the HF band allows. If the quality of the Air-Ground channel of the HF band deteriorates below the permissible level, a new channel is selected at the HF onboard station and registered on this channel at the new or old HF ground station, but at a new operating frequency. Through the terrestrial communication subsystem, packet data is exchanged between each HF ground station and air traffic control and airline control centers, as well as the control point of the HF communication system. At each RF ground station, the best frequency for receiving messages from each other RF ground station is selected based on the results of assessing the quality of marker signal reception using additional RF ground-to-ground receivers and ground-to-ground demodulators of a single-tone multi-position phase shift keying signal. The audibility table is formed based on the results of the selection of the best reception frequencies, in which they indicate the sign of their availability (inaccessibility) for the terrestrial communication subsystem, the identifiers of the ground stations and the corresponding numbers of the best reception frequencies with the codes of the recommended maximum allowable data transfer rates. On each frequency channel, one channel access frame slot is allocated for transmitting messages in the Ground-to-Ground direction. The audibility table is transmitted simultaneously by N RF transmitters in slots that are allocated for ground-to-ground reporting. Then receive tables of audibility from other RF ground stations at pre-selected best reception frequencies using additional RF receivers and demodulators "Earth-to-Earth" single-tone multi-position phase-shift keying signal. Based on the received audibility tables, an Earth-to-Earth network connectivity table is formed, in which the identifiers of ground stations are indicated with signs of their availability (inaccessibility) for the terrestrial communication subsystem and the numbers of the best reception and transmission frequencies corresponding to them with codes of recommended maximum allowable data transfer rates. The Earth-to-Earth network connectivity table is used to select communication frequencies (receive and transmit) with other HF NS. A data packet received at an inaccessible HF ground station from an HF on-board station registered on it is transmitted simultaneously with the audibility table via the HF radio channel in the "Ground-to-Ground" slot to another available HF NS, from which it is broadcast to the ATC control center or UAL or to the control point of the HF communication system through the terrestrial communication subsystem. A data packet from an ATC or ATC control tower or from a CCP destined for an HF aircraft station that is registered to an inaccessible HF ground station is transmitted through the ground communication subsystem to an accessible HF NS, from which it is then broadcast over the HF ground-to-ground radio channel range to an inaccessible HF ground station, and from which it is then transmitted via the HF air-to-ground radio channel to the HF airborne station. The data packet from the CCP, addressed to the inaccessible HF ground station, is transmitted through the terrestrial subsystem to the accessible HF ground station, from where it is broadcast over the HF ground-to-ground radio channel to the inaccessible HF ground station.

The disadvantages of analog are as follows:

- it is impossible to increase the speed of information transfer without a significant change in the algorithms of operation and software and hardware;

- due to the need to organize multi-channel work, the implementation of this method requires dozens of ground stations, data exchange networks between them and appropriate computing resources.

There is a known method of data transmission in conditions of multipath propagation of radio signals [3], which includes, on the transmitting side of the data transmission channel, the operations of generating message packets with guard intervals before packets, modulating bit packets, generating bit packets, generating spreading signals in the form of an orthogonal derivative of the Walsh and Barker signal system , expanding the spectra of bits of packets by the direct sequence method, increasing the duration of bits of packets in time within packets, compacting bits of packets in time within packets of amplifying the power of radio signals and emitting them by a transmitting antenna. On the receiving side of the channel, the operations of receiving, amplifying and demodulating radio signals of inverse time conversion of signal durations, multi-channel code separation of beam signals by shape, formation of copies of expanding signals, separation of message signals in a multi-channel solver by the likelihood ratio criterion, time delay of message signals in accordance with the original sequence of messages in packets on the transmitting side.

The disadvantages of analog should include:

- the inability to increase the speed of information transfer;

- to implement the method, a transmitter power amplifier with a linear amplitude characteristic (class A mode) is required, which has a low efficiency;

- processes of synchronization of transmitting and receiving digital signal processing equipment have not been implemented.

The closest to the claimed method in terms of technical essence is the radio communication method given in [4, Fig. 1.2, sheet 33], which is taken as a prototype. The method consists of sequentially performed operations with the input information, namely: formatting the input information (conversion to a form convenient for the source encoder), encryption, channel coding, multiplexing, pulse modulation (modulation at a low frequency), bandpass modulation (formation of a radio signal at radio frequency), spread spectrum, multiple access, amplification of the radio signal in the transmitter and with the help of an antenna radiation into the communication channel. At the receiving side, the transmitted radio signals in the receiver are distinguished among others, provide multiple access and despreading, demodulate and sample, detect radio signals, decompress, channel decode, decrypt, source decode and convert information to the original format.

The disadvantages of the prototype include:

- the inability to increase the speed of information transfer;

- the presence of operations (multiplication, multiple access, spectrum expansion and narrowing), which are not required for the implementation of the single-channel radio communication method;

- processes of synchronization of transmitting and receiving digital signal processing equipment have not been implemented.

The technical problem to be solved by the claimed invention is to increase the speed of information transfer.

The specified technical result is achieved by the fact that in the known method of single-channel radio communication, in which the input information from the source is divided into frames on the transmitting side and markers are formed at the beginning of each frame, and markers are allocated on the receiving side, which includes sequentially performed input information formatting operations on the transmitting side from the source, namely, conversion to a form convenient for the operation of the source encoder, encryption, channel coding, as well as sequentially performed operations of generating a radio signal, amplifying it in the transmitter and emitting it into the communication channel using an antenna, and on the receiving side including sequentially performed operations separation of transmitted radio signals in the receiver, phase demodulation and sampling, as well as sequentially performed operations of channel decoding, decoding, decoding the source and converting information to the original format, while on the transmitting and receiving sides, time scales als are synchronized with one-second marks from the output of the receiver of global navigation satellite systems, on the transmitting side, after the channel coding operation, the message frame is written into the register and packets of 2N bits are sequentially formed from it in time, encoded with a binary code so that the number of bits in the code word n=log2N coincided with the order of phase manipulation 2, 4, 6, 16, arrange the code words in ascending order of the time of appearance of the code word, form a transmitted packet, at the beginning of which a marker is set, orthogonal to the bits of the transmitted packet and coinciding in time with a one-second mark from the output of the global navigation receiver satellite systems or located at a known delay from it, are manipulated in phase with a given order, transmitted to form a radio signal and converted into a radio signal at a given radio frequency, and on the receiving side, after phase demodulation and sampling operations, a strobe is formed in the time interval, where o a marker is expected, a marker is allocated that synchronizes the time scale of the receiving side, with the help of which, after sampling the received signals, synchronous recording is started in the pulse register of the received packet, from the output of which n-bit code words are sequentially removed in time, which, using channel decoding and decoding translate into N-bit messages, set them sequentially in time in the order of the packets and restore the signal parameters of the message frame for the next source decoding operation.

The essence of the method is as follows. The input information from the source, which can be both in analog and discrete form, is formatted - converted to a form convenient for the source encoder, for example, digitized using analog-to-digital conversion by sampling in time and amplitude quantization . Then, after redundancy reduction in the source encoder, the messages are encrypted to provide cryptographic protection, channel noise-immune coding is performed. Next, the messages are divided into frames, and each bit of the message frame is written into a register of 2 ^N bits, and packets of 2 ^N bits are formed from it sequentially in time, which are encoded in binary code so that the number of bits in the code word n=log ₂ N coincides with the order of phase manipulation 2, 4, 6, 16, arrange the code words in ascending order of the time of appearance of the code word and form a transmitted packet from them. If the amount of input information exceeds 2 ^N bits, then it is divided into several frames. The rest of the bits after splitting are padded with zeros up to a value of 2 ^N .

At the beginning of each packet, a marker is set that is orthogonal to the bits of the transmitted packet and coincides in time with a one-second mark from the output of the receiver of global navigation satellite systems or is located from it at a known, for example, pseudo-random delay. The formation of code words is carried out with guard intervals before the bits that make them up. The shape of the marker representation must be orthogonal to the transmitted codewords. The width of the spectrum of the output bit (signal) of the low-frequency modulator is matched with the bandwidth of the radio communication channel to implement the optimal information transfer rate.

Then the generated packet with the marker is manipulated in phase with a given order of 2, 4, 8, 16, transmitted to form a radio signal, converted into a radio signal at a given radio frequency, amplified in the transmitter and emitted into the communication channel using an antenna. The phase keying order is chosen based on a compromise between the information transfer rate and the level of the signal power ratio and the mixture of noise and interference, the lower this level, the smaller the keying order should be.

On the receiving side, the transmitted radio signals in the receiver are distinguished from other radio signals, phase demodulation and sampling are carried out [4]. The threshold level for quantization of the received signals is determined by the maximum level of mutual noise and interference at the receiver output. Then a strobe is formed in the time interval where the marker is expected to appear, for example, using a timing circuit with leading and lagging gating [4, Fig. 10.13 sheet 648]. The efficiency of marker extraction is determined, for example, by the autocorrelation function of the signal selected during the formation of the marker, for example, a Barker code with a low level of its side lobes [4, 5]. When extracting a marker from the received signals, for example, correlation processing is carried out by multiplying them by a copy of the transmitted marker, formed, for example, in accordance with the Barker code [4-6]. The marker synchronizes the time scale of the receiving side, with the help of which, after sampling and quantization of the received signals, synchronous recording is started in the pulse register of the received packet, from the output of which n-bit code words are sequentially removed in time. These code words are converted into N-bit messages using channel decoding and decryption, they are set sequentially in time in the order of packets, and the parameters of the message frame signals are restored for further source decoding and information conversion to the original format. To improve the quality of input information recovery, the rate of writing to the packet bit register on the transmitting side must be identical to the rate of reading it from the register on the receiving side.

A feature of the proposed method is that it is not the input information that is transmitted in the radio communication channel, but its “display” on the phase plane, which occupies a smaller number of bits. be 8 times more than if the information was transmitted bit by bit, with N=64, n=8 and using phase shift keying 4PSK - 16 times more, etc. These data are given without taking into account the time intervals allotted for the marker and guard intervals. The upper limit of the information transfer rate is limited by the value of the root-mean-square error in determining the time of an accurate one-second mark from the output of the receiver of global navigation satellite systems and the accuracy of the reference frequency generator of the time scalers on the transmitting and receiving sides.

Literature:

1. ARINC 635-3. specification. HF Data Link Protocols. 12/2000.

2. RF patent No. 2286030.

3. RF patent No. 2663240.

4. Sklyar Bernard. Digital communication. Theoretical foundations and practical application. Ed. 2nd, corrected: Per. from English. - M.: Williams Publishing House, 2003. 1104 p. (Fig. 1.2, sheet 33 - prototype).

5. M.V. Ratynsky. Fundamentals of cellular communications / Ed. D.B. Zimina - M.: Radio and communication, 1998. 248 p.

6. H.F. Harmut. Transfer of information by orthogonal functions. Per. from English. N.G. Dyadyunova and A.I. Senina, M., "Communication", 1975. 272 p.

Claims (1)

A method of single-channel radio communication, in which the input information from the source is divided into frames on the transmitting side and markers are formed at the beginning of each frame, and markers are allocated on the receiving side, which includes sequentially performed formatting operations on the transmitting side of the input information from the source, namely, transformation to the form, convenient for the operation of the source coder, encryption, channel coding, as well as sequentially performed operations of generating a radio signal, amplifying it in the transmitter and emitting it into the communication channel using an antenna, and on the receiving side including sequentially performed operations of extracting the transmitted radio signals in the receiver, phase demodulation and sampling, as well as sequentially performed operations of channel decoding, decoding, decoding the source and converting information to the original format, while on the transmitting and receiving sides the time scales are synchronized with one-second marks from the output of the global receiver navigation satellite systems, characterized in that on the transmitting side, after the channel coding operation, the message frame is written to the register and packets of 2 ^N bits are sequentially formed from it in time, encoded with a binary code so that the number of bits in the code word n=log ₂ N coincided with the order of phase manipulation 2, 4, 6, 16, arrange the code words in ascending order of the time of appearance of the code word, form a transmitted packet, at the beginning of which a marker is set, orthogonal to the bits of the transmitted packet and coinciding in time with a one-second mark from the output of the global navigation receiver satellite systems or located from it at a known delay, are manipulated in phase with a given order, transmitted to form a radio signal and converted into a radio signal at a given radio frequency, and on the receiving side, after phase demodulation and sampling operations, a strobe is formed in the time interval where the appearance of marker, highlight mark ep, which synchronizes the time scale of the receiving side, with the help of which, after sampling the received signals, synchronous recording is started in the pulse register of the received packet, from the output of which n-bit code words are sequentially removed in time, which, using channel decoding and decryption, are converted into N-bit messages, set them sequentially in time in the order of the packets, and restore the signal parameters of the message frame for the next source decoding operation.