CN115664510B

CN115664510B - Physical layer frame structure, communication method and communication device for low-orbit satellite communication

Info

Publication number: CN115664510B
Application number: CN202211687449.0A
Authority: CN
Inventors: 敬军; 周长军; 隋超; 杨辉; 曾德忠
Original assignee: Beijing Taiji Jiangtai Technology Development Co ltd
Current assignee: Beijing Taiji Jiangtai Technology Development Co ltd
Priority date: 2022-12-28
Filing date: 2022-12-28
Publication date: 2023-08-18
Anticipated expiration: 2042-12-28
Also published as: CN115664510A

Abstract

The application discloses a physical layer frame structure, a communication method and a communication device for low-orbit satellite communication, which belong to the field of satellite communication, wherein a physical layer frame comprises a synchronous word, a frame header and a plurality of information payloads, and pilot frequency is selectively inserted after the information payloads according to different application environments; the data length of the frame header is set to be 16 bits; the information payload is either viterbi coded or BCH coded. By the method, the signal can be continuously received in a long-distance and high-dynamic narrow-band transmission environment, and the signal can still normally work when the dynamic change of the low-orbit satellite is relatively large, and meanwhile, continuous 65536 bytes of continuous reception can be supported, so that the success rate of communication is greatly increased, and the signal transmission in a narrow-band burst mode is ensured.

Description

Physical layer frame structure, communication method and communication device for low-orbit satellite communication

Technical Field

The application belongs to the field of satellite communication, and particularly relates to a physical layer frame structure, a communication method and a communication device for low-orbit satellite communication.

Background

Satellite communications are divided by orbit and mainly comprise: geostationary orbit (GEO), medium Earth Orbit (MEO), low Earth Orbit (LEO), inclined geosynchronous orbit (IGSO), etc., wherein LEO orbit is less than 2000km, global seamless coverage throughout the day can be achieved by networking several tens to hundreds of satellites, and LEO orbits are adopted by satellites such as iridium satellites, globalities, star chains (starlinks), etc. In the low-orbit satellite communication scheme published abroad, the main frequency bands are mainly concentrated in Ka, ku and V frequency bands. In the field of emergency rescue, communication equipment at home and abroad is mainly used as emergency equipment, and the requirements of miniaturization and low power consumption cannot be met.

The most common communication system in the prior art is a LoRa system proposed by semtech company, and a plurality of techniques such as Hamming coding, gray coding, interleaving and the like are adopted in a LoRa physical layer, so that the receiving sensitivity of signals is greatly improved. The frame format of the LoRa system includes four parts, namely a Preamble (Preamble), a Header (Header), a Payload (Payload) and a Cyclic Redundancy Check (CRC). However, the Payload content takes up 8 bits, so that in a packet of LoRa data, the subsequent Payload content is 255 bytes at maximum, and the transmission data amount in a frame is 255 bytes at maximum, so that the data amount is too small; for a high dynamic scene, error codes are easy to generate because of no frequency offset tracking method; with simple hamming coding, the Eb/N0 of the signal cannot be reduced (the ratio of the energy required by the communication system to transmit one bit of information to the noise power spectral density is a system index for measuring the performance normalization of the whole communication system).

Therefore, a communication scheme for low-orbit satellites is needed to solve the above-mentioned problems.

Disclosure of Invention

In order to solve the defects of the prior art, the application provides a new physical layer frame structure for low-orbit satellite communication, which is applicable to a low-orbit satellite communication system and solves the communication requirements of high dynamics and low sensitivity; the pilot frequency band is inserted into the signal frame structure, so that the time offset and the frequency offset can be calibrated regularly. By the method, the signal can be continuously received in a long-distance and high-dynamic narrow-band transmission environment, and the signal can still normally work when the dynamic change of the low-orbit satellite is relatively large, and meanwhile, continuous 65536 bytes of continuous reception can be supported, so that the success rate of communication is greatly increased, and the signal transmission in a narrow-band burst mode is ensured.

The technical effects to be achieved by the application are realized by the following scheme:

according to a first aspect of the present application, there is provided a physical layer frame structure for low-orbit satellite communication, wherein a physical layer frame comprises a synchronization word, a frame header and a plurality of information payloads, and a pilot frequency is selectively inserted after the information payloads according to different application environments; the data length of the frame header is set to be 16 bits; the information payload is either viterbi coded or BCH coded.

Preferably, in low orbit satellite communications, one of the pilots is provided after each information payload.

Preferably, the sync word consists of a fixed 200 upchirp signals and 2 downchirp signals.

Preferably, the frame header consists of a data length, an inserted pilot interval, a playoad coding mode and BCH coding.

Preferably, the data length is set to 16 bits, the insertion pilot interval is set to 8 bits, and the playoad coding mode is set to 3 bits.

Preferably, the pilot consists of 1 upchirp signal and 1 downchirp signal.

According to a second aspect of the present application, there is provided a method of low-orbit satellite communication, wherein a physical layer frame structure for low-orbit satellite communication as described in any one of the above is used between a communication device and a low-orbit satellite.

According to a third aspect of the present application there is provided a low orbit satellite communications device comprising a signal generator for generating a signal conforming to the physical layer frame structure as described in any one of the preceding claims.

The application has the technical effects that the signal to noise ratio can still be normally received by using a linear frequency modulation mode under the condition of not increasing the bandwidth of the signal, and the transmission distance is greatly improved; in addition, the signal tracking is realized by inserting up/down pilot frequency, and the Doppler change rate can be resisted by 300Hz/s; enabling ground terminals to use lower transmit power for communication services with low-orbit satellites.

Drawings

In order to more clearly illustrate the embodiments of the application or the prior art solutions, the drawings which are used in the description of the embodiments or the prior art will be briefly described below, it being obvious that the drawings in the description below are only some of the embodiments described in the present application, and that other drawings can be obtained according to these drawings without inventive faculty for a person skilled in the art.

Fig. 1 is a schematic diagram of a physical layer frame structure for low-orbit satellite communication according to an embodiment of the application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be clearly and completely described below with reference to specific embodiments and corresponding drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

As shown in fig. 1, in the physical layer frame structure of the low-orbit satellite communication in an embodiment of the present application, the physical layer frame includes a synchronization word, a frame header, and a plurality of information payloads (playload), and pilot (pilot) is selectively inserted after the information payloads according to the application environment; the data length of the frame header is set to be 16 bits; the information payload is either viterbi coded or BCH coded.

Compared with the traditional LoRa system applied to short byte burst communication, the data length is set to 16 bits at the frame head position in the embodiment, so that 65535 byte data can be transmitted; the pilot field is added in the frame structure, so that the method can be used for tracking frequency offset in a high dynamic environment, and effective Doppler compensation during long-time transmission is ensured; compared with the LoRa system using Hamming code, the embodiment increases the coding mode of the playoad data, does not use Hamming code, adopts Viterbi code or BCH code with better performance, and improves Eb/N0 of the signal. Eb/N0 refers to the ratio of the energy required by the communication system to transmit one bit of information to the noise power spectral density, where Eb: energy in bits, in Joules (Joules); n0: the power spectral density of noise in Watts per hertz (Watts per Hz);

in this embodiment, viterbi coding is preferred, and Eb/N0 is improved without increasing the signal bandwidth, which is advantageous for improving the communication sensitivity and increasing the transmission distance.

In an embodiment of the application, pilot can be selected not to be inserted under the ground low dynamic environment, so that continuous signal receiving can be realized, bandwidth can be saved, pilot data can be inserted at intervals according to the need during low orbit satellite communication, and the communication stability is greatly improved.

The sync word in one embodiment of the application consists of a fixed 200 up chirp signal and 2 down chirp signals. 200 upchirp are used for capturing of the early signal and frequency offset calculation and tracking, wherein 200 upchirp can reduce the false detection probability of the signal on one hand and can estimate the Doppler change rate at the same time. The 2 downchirp signals are used in conjunction with 200 upcharps to calculate frequency offset and timing offset.

In one embodiment of the application, the frame header consists of a data length, an inserted pilot interval, a playoad coding mode and a BCH coding. Wherein the data length is set to 16 bits, 65535 bytes of data can be transmitted; the interval of the inserted pilot frequency is set to be 8 bits, which means that the pilot frequency can be freely inserted in 0 to 255 symbol, and for the application scene with large frequency change rate, a small interval can be configured, so that the frequency of frequency tracking is increased, and the frequency deviation caused by high dynamic can be calibrated through each frequency tracking; the playoad coding mode is set to be 3 bits, 8 coding modes can be available, and different coding modes can be selected according to different signal sensitivities.

In one embodiment of the application, the pilot consists of 1 upchirp signal and 1 downchirp signal.

The application has the technical effects that the signal to noise ratio can still be normally received by using a linear frequency modulation mode under the condition of not increasing the bandwidth of the signal, and the transmission distance is greatly improved; in addition, a mode of inserting up/down pilot frequency is adopted to realize signal tracking; enabling ground terminals to use lower transmit power for communication services with low-orbit satellites.

It should be noted that the foregoing detailed description is exemplary and is intended to provide further explanation of the application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present application. As used herein, the singular is intended to include the plural unless the context clearly indicates otherwise. Furthermore, it will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, steps, operations, devices, components, and/or groups thereof.

It should be noted that the terms "first," "second," and the like in the description and the claims of the present application and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or otherwise described herein.

Furthermore, the terms "comprise" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those elements but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Spatially relative terms, such as "above … …," "above … …," "upper surface at … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial location relative to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "over" other devices or structures would then be oriented "below" or "beneath" the other devices or structures. Thus, the exemplary term "above … …" may include both orientations of "above … …" and "below … …". The device may also be positioned in other different ways, such as rotated 90 degrees or at other orientations, and the spatially relative descriptors used herein interpreted accordingly.

In the above detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, like numerals typically identify like components unless context indicates otherwise. The illustrated embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein.

The above is only a preferred embodiment of the present application, and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A low-orbit satellite communication method is characterized in that a physical layer frame used between communication equipment and a low-orbit satellite comprises a synchronous word, a frame header and a plurality of information payloads, and pilot frequency is selectively inserted after the information payloads according to different application environments; the data length of the frame header is set to be 16 bits; the information payload adopts Viterbi coding or BCH coding; in low orbit satellite communication, one pilot is arranged after each information payload; the synchronization word is composed of 200 fixed upchirp signals and 2 downchirp signals, wherein the 200 upchirp signals are used for capturing a pre-signal and calculating and tracking frequency offset, and the 2 downchirp signals are matched with the 200 upchirp signals to calculate frequency offset and timing deviation.

2. The method of claim 1 wherein the header consists of a data length, an inserted pilot interval, a playload coding scheme, and BCH coding.

3. The method of claim 2, wherein the data length is set to 16 bits, the pilot interval is set to 8 bits, and the playoad coding mode is set to 3 bits.

4. The method of claim 1, wherein the pilot consists of 1 up chirp signal and 1 down chirp signal.

5. A low-orbit satellite communication device, comprising a signal generator for generating a signal conforming to the physical layer frame in the low-orbit satellite communication method according to any one of claims 1 to 4.