KR20210138841A - Method and apparatus for communication for operating data transmission of unmanned aircraft system - Google Patents

Abstract

Provided are a communication method for transmission of data for a mission of an uncrewed aerial vehicle and a device thereof. The communication method comprises the steps of setting a channel in a set frequency band for mission communication assigned to the uncrewed aerial vehicle, configuring a radio frame for the set channel, and transmitting and receiving data for the mission through the channel set based on the radio frame. The radio frame includes two or more subframes of which use is selectively determined. Each subframe includes two preamble durations and a plurality of slot durations, and each slot includes a single carrier-frequency domain equalization (SC-FDE) data block and an SC-FDE pilot block. The device operates in an adjacent band of the uncrewed aerial vehicle control communication and can communicate without interfering with the uncrewed aerial vehicle control communication.

Description

Communication method and apparatus for transmission of data for mission of an unmanned aerial vehicle

The present invention relates to unmanned aerial vehicle communication, and more particularly, to a communication method and apparatus for transmitting mission data of an unmanned aerial vehicle.

The data link of the UAV system may be divided into a control communication link and a mission communication link. A mission data link is a mission-related data link that is generally wider than a control communication link. On the other hand, the control communication link is a link for transmitting data related to UAV flight control, status monitoring, and system management. Disaster security drones are being considered to improve public safety as a disaster security prevention and response plan using unmanned aerial vehicles. LTE mobile communication technology is currently being considered as the main communication link for LTE mobile communication technology has the advantage of enabling greater coverage and quality of service (QoS) management compared to existing unlicensed band low-power communication technologies such as WiFi, which is widely used in existing UAVs. However, LTE mobile communication technology also has a problem in that communication is interrupted outside the coverage of existing mobile communication networks such as mountains and sea.

Considering that unmanned aerial vehicles should be able to be operated anytime and anywhere in Korea in a disaster and security situation, an auxiliary communication link is essential for stable control and mission performance of unmanned aerial vehicles even in areas where LTE mobile communication, the main communication link, is not available. For this purpose, unlicensed band communication technology such as WiFi, which is widely used in existing UAVs, can be considered, but it is difficult to limit coverage and ensure a stable communication link due to small power limitation and interference. Accordingly, in Korea, for the stable operation of UAVs and expansion of UAV operations, the C-band frequency, which is a licensed frequency band for UAV control and missions, has been distributed.

The C band frequency for control communication distributed in Korea is 5030-5091 MHz band, and it is a control communication frequency for stable entry of UAVs into national airspace internationally in ITU-R WRC-12, and a harmonious frequency newly distributed internationally am. On the other hand, the 5091-5150 MHz band was allocated for domestic use for the C band frequency for mission communication.

It is possible to secure a more stable communication link than communication in the C band, which is a licensed frequency band, than in the low power unlicensed band. Considering the domestic UAV frequency policy, the communication link in this licensed frequency band is considered as a secondary communication link of the LTE main communication link of the disaster security UAV.

Unlike the C-band control communication technology, the C-band frequency for mission communication is a band that is currently distributed as a communication frequency for UAV missions only in Korea, and has not been standardized until now. Therefore, in the case of mission communication, it is required to derive a new transmission waveform technology capable of reducing the size and weight suitable for small unmanned aerial vehicles.

An object of the present invention is to provide a communication method and apparatus for transmitting data for a mission of an unmanned aerial vehicle.

Another object of the present invention is to provide a communication method and apparatus capable of communicating without interference with communication for controlling an unmanned aerial vehicle while operating in an adjacent band of communication for controlling an unmanned aerial vehicle.

According to an embodiment of the present invention, there is provided a communication method in which an unmanned aerial vehicle transmits and receives data for a mission. The communication method may include: setting a channel in a set frequency band for mission communication allocated to the UAV; constructing a radio frame for the set channel; and transmitting and receiving data for the mission through the set channel based on the radio frame, wherein the radio frame includes two or more subframes whose use is selectively determined, each subframe is 2 It includes a preamble period and a plurality of slot periods, and each slot includes a single carrier-frequency domain equalization (SC-FDE) data block and an SC-FDE pilot block.

In one implementation, the radio frame includes: a frame consisting of only continuous downlink; a frame composed of only a non-continuous downlink in consideration of interference with control communication allocated to the UAV; a frame composed of a bidirectional uplink and downlink having asymmetry; a frame composed of a bidirectional uplink and downlink having symmetry; It may be at least one of frames including guard sections of different lengths between uplink and downlink according to the operating radius.

In one implementation, in the radio frame, the SC-FDE pilot block may be disposed after every 5 SC-FDE data blocks in consideration of the speed of the UAV and multipath delay spread.

In one implementation, the SC-FDE pilot block or SC-FDE data block included in the slot may include N _cp cyclic prefix (CP) samples and N _{block,samples} block samples.

In one implementation, the number of symbols included in the slot, the number of pilot symbols included in the SC-FDE pilot block, and the number of data symbols included in the SC-FDE data block are determined based on a subframe configuration. can be decided.

In one implementation, the two preamble sections include a first preamble block and a second preamble block, and the sequence of the first preamble block is generated through a first set-th root Zadoff-Chu sequence having a fractional length, and the first The sequence of 2 preamble blocks and the sequence of the SC-FDE pilot block may be generated through a second set-th root Zadoff-Chu sequence having an even length.

In one implementation, the first set number indicates a cell ID, the sequence of the first preamble block is a root sequence associated with the cell ID, and the sequence of the second preamble block and the sequence of the SC-FDE pilot block include a set number It may be a route sequence generated by applying a group hopping pattern that is differently applied according to a cell ID, a slot number, and a pilot block number through a group having a root sequence of .

In one implementation, the data transmission and reception is performed based on an SC-FDE scheme, the SC-FDE scheme has a root raised cosine (RRC) filter, and a roll-off index used for the RRC filter is 0.3 of can have a value.

In one implementation, a second M sequence of a gold sequence is used for scrambling of the SC-FDE data block, and the second M sequence is 2 ¹⁵ +n _s 2 ⁸ +N _{Cell_ID in association with a cell ID.} can be initialized to

According to another embodiment of the present invention, a communication device for transmitting and receiving data for a mission is provided. The communication device may include a network interface device; and a processor configured to transmit and receive data for the mission through the network interface device, wherein the processor sets a channel in a set frequency band for communication for a mission assigned to the UAV; setting a radio frame for the set channel; and transmitting and receiving data for the mission through the set channel based on the radio frame, wherein the radio frame includes two or more subframes whose use is selectively determined, each subframe includes two preamble durations and a plurality of slot durations, and each slot includes a single carrier-frequency domain equalization (SC-FDE) data block and an SC-FDE pilot block.

In one implementation, the radio frame includes a frame consisting of only continuous downlink; a frame composed of only a non-continuous downlink in consideration of interference with control communication allocated to the UAV; a frame composed of a bidirectional uplink and downlink having asymmetry; a frame composed of a bidirectional uplink and downlink having symmetry; It may be at least one of frames including guard sections of different lengths between uplink and downlink according to the operating radius.

In one implementation, in the radio frame, the SC-FDE pilot block may be disposed after every 5 SC-FDE data blocks in consideration of the speed of the UAV and multipath delay spread.

In one implementation, the number of symbols included in the slot, the number of pilot symbols included in the SC-FDE pilot block, and the number of data symbols included in the SC-FDE data block are determined based on a subframe configuration. can be decided.

In one implementation, the two preamble sections include a first preamble block and a second preamble block, and the sequence of the first preamble block is generated through a first set-th root Zadoff-Chu sequence having a fractional length, and the first The sequence of 2 preamble blocks and the sequence of the SC-FDE pilot block may be generated through a second set-th root Zadoff-Chu sequence having an even length.

In one implementation, the first set number indicates a cell ID, the sequence of the first preamble block is a root sequence associated with the cell ID, and the sequence of the second preamble block and the sequence of the SC-FDE pilot block include a set number It may be a route sequence generated by applying a group hopping pattern that is differently applied according to a cell ID, a slot number, and a pilot block number through a group having a root sequence of .

Unlike the C-band control communication technology, the mission communication band is currently distributed as the communication frequency for the UAV mission only in Korea, and standardization has not been carried out so far. However, according to an embodiment of the present invention, mission communication from the UAV to the wireless station can be smoothly performed in a non-line-of-sight (NLOS) environment while operating in an adjacent band of communication for controlling the UAV. In addition, it is possible to provide a communication method and apparatus capable of being mounted on a small and light UAV while operating without interference with communication for controlling the UAV.

1 is a diagram showing the structure of a radio frame according to an embodiment of the present invention.
2 is a diagram illustrating the structure of a subframe of a radio frame according to an embodiment of the present invention.
3 is a diagram illustrating the structure of a slot of a subframe according to an embodiment of the present invention.
4 is a diagram showing the structure of a block of a slot according to an embodiment of the present invention.
5 is an exemplary diagram illustrating signal transmission for each configuration according to an embodiment of the present invention.
6 is a flowchart of a communication method according to an embodiment of the present invention.
7 is a diagram showing the structure of a communication device according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, when a part "includes" a certain component, this indicates that other components may be further included, rather than excluding other components, unless otherwise stated.

In the present specification, expressions described in the singular may be construed in the singular or plural unless an explicit expression such as “a” or “single” is used.

In addition, terms including ordinal numbers such as first, second, etc. used in an embodiment of the present invention may be used to describe the constituent elements, but the constituent elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component.

In addition, in an embodiment of the present invention, an unmanned aerial system (UAS) may be an aircraft capable of autonomously flying and manipulating through control using a wireless link without a pilot on board. For example, the unmanned aerial vehicle may be a small unmanned aerial vehicle flying at a low altitude, such as a drone. Also, as an example, the unmanned aerial vehicle may be a medium or large-sized unmanned aerial vehicle having a certain weight or more. In this case, the mid-to-large UAV may be a UAV flying at a medium or high altitude. However, in the present invention, the unmanned aerial vehicle is not limited to those described above.

Hereinafter, a communication method and apparatus for transmitting mission data of an unmanned aerial vehicle according to an embodiment of the present invention will be described.

In an embodiment of the present invention, when considering a small and lightweight UAV mission scenario, a new waveform technology for communication for an UAV mission satisfies the following requirements.

◆ Maximum transfer rate: 7 Mbps or higher

◆ Maximum communication radius: 30 km

◆ Maximum number of UAVs supported: 4

◆ Operation required in low-altitude UAV operation environment

▶ Consider multipath fading

Required to operate in a low-altitude UAV operation environment

▶ Consider multipath fading

◆Mutual compatibility with C-band communication link for control

▶ Interference with adjacent control frequencies

◆ Supports various transmission rates

◆ Small, lightweight and low-power design required

▶ Low Peak To Amplitude Power Ratio (PAPR) and low complexity receiver design

◆ One-way communication link

An embodiment of the present invention provides a transmission waveform technology having the following main characteristics in consideration of the requirements as described above.

◆ Frame structure

▶ 10ms frame structure identical to LTE frame structure for LTE-based upper layer application

▶ 50ms super frame structure based on GPS (Global Positioning System) that is the same as the frame structure of C-band communication standard technology for control

◆ Waveform

▶ From the SWaP (Size, Weight and Power) point of view of the small UAV, a single transmission wave method is selected in consideration of the amplifier non-linearity characteristics (excellent PAPR characteristics compared to existing multi-carrier systems such as WiFi)

▶ SC-FDE (Single Carrier - Frequency Domain Equalization) method applied for low-complexity operation even in a multi-fading channel environment

◆ Pilot deployment

▶ Pilot deployment considering the speed of the UAV over 150km/h

▶ Pilot arrangement considering 1~2us delay spread

◆ Preamble

▶ Application of Zadoff-Zu sequence with excellent PAPR characteristics

◆ Modulation method

▶ QPSK, 16QAM (or 8PSK)

◆ Encoding method

▶ Punctured Turbo Coding

◆ MCS (Modulation and Coding Scheme) mode

▶ Supports various encoding modes (minimum 0.4 Mbps, maximum 7 Mbps or more)

◆ Spectral Efficiency

▶ Applying transmission filtering to improve the transmission spectrum characteristics

A communication method according to an embodiment of the present invention having the characteristics as described above will be described in more detail.

The multiple access scheme for a Physical Uplink Payload Channel (hereinafter PUPCH) for an uplink mission is based on a Single Carrier-Frequency Domain Equalization (SC-FDE) scheme with a cyclic prefix (CP). . As a duplexing method, time division duplex (hereinafter referred to as TDD) is applied.

1 is a diagram showing the structure of a radio frame according to an embodiment of the present invention.

In an embodiment of the present invention, unless otherwise specified, the sizes of various fields in the time domain are expressed in time units of Ts=1/(15000x2048) seconds.

_{A radio frame according to an embodiment of the present invention has a length of T f} =50 ms, and a plurality of subframes (eg, subframes 1 to 5) having a length of _{T sf} =10 ms, as shown in FIG. 1 , a radio frame according to an embodiment of the present invention. is composed of Whether to use each subframe is determined by an indication of a higher layer. When a subframe is not used, the subframe is not transmitted. A radio frame number corresponding to every integer multiple of 20 starts at an integer multiple of 1 second in Coordinated Universal Time (UTC) time.

2 is a diagram illustrating the structure of a subframe of a radio frame according to an embodiment of the present invention.

Each subframe _{has a length of T sfi} =10ms (i=1 to 5), respectively, and is composed of a continuous data segment portion. As shown in FIG. 2 , the data segment is composed of two preamble sections and N _sf,slot slot sections, and has the same structure and length regardless of the subframe number. In an embodiment of the present invention, since the SC-FDE scheme is used as the transmission waveform, two preamble sections include a first preamble SC-FDE symbol and a second preamble SC-FDE symbol.

A subframe includes N _sf,slot slots, and a supported configuration is shown in Table 1 below. Table 1 shows the number of slots transmitted in a subframe according to various subframe configuration options. The configuration of the subframe may be determined by a higher layer according to the operating environment.

subframe
Configuration

the number of slots in the subframe,

0 11

3 is a diagram illustrating the structure of a slot of a subframe according to an embodiment of the present invention.

A slot has a length of Tslot=N _slot,blocks ×(N _cp,samples +N _{data_block,samples} )+N _{slot,pilot_block} × N _cp,samples +N _{pilot_block,samples} ), N _{slot,SC-FDE_blocks} SC- Includes FDE blocks. The SC-FDE blocks are _{composed of N slot, data_blocks} SC-FDE data blocks and N _{slot, pilot_block} SC-FDE pilot blocks. Supported configurations are shown in Table 2 below.

subframe
Configuration Number of SC-FDE blocks in a slot
N _{slot, SC-FDE_blocks} Number of pilot SC-FDE blocks in a slot
N _{slots, pilot_blocks} Number of data SC-FDE blocks in a slot
N _{slots, data_blocks} 0 24 4 20

In the slot, the SC-FDE pilot block is inserted after every 5 SC-FDE data blocks, as shown in FIG. 3 . The positions of the SC-FDE pilot blocks according to the configuration are shown in Table 3 below.

Configuration Spacing between SC-FDE pilot blocks First SC-FDE pilot block position in slot Second SC-FDE pilot block location in slot 3rd SC-FDE pilot block position in slot 4th SC-FDE pilot block position in slot 0 6 5 11 17 23

4 is a diagram showing the structure of a block of a slot according to an embodiment of the present invention.

The SC-FDE data/pilot block, which is divided into an SC-FDE pilot block and an SC-FDE data block according to the shape, _{has a length of T Block} = (N _cp,samples +N _{block,samples} )T _s , as shown in FIG. Similarly, it _{consists of N cp} CP samples (T _s length unit samples) and N _{block,samples} block samples, and M _{block,symbols} modulation symbols are transmitted. The SC-FDE pilot block and the SC-FDE data block have the same structure.

Thus, T _Block =T _{Data_Block} =T _{Pilot_Block} , N _{block,samples} =N _{Data_block,samples} =N _{Pilot_block,samples} , and M _{block,symbols} =M _{Data_block,symbols} =M _{Pilot_block,symbols} . Where T _{Data_} Block denotes an SC-FDE data block length, TPilot _{_Block} the SC-FDE represents the pilot block length, N _{Data_block, samples} are SC-FDE data block represents the number of samples, N _{Pilot_block, samples} are SC-FDE pilot represents the number of block samples, M _{Data_block,symbols} represents the number of SC-FDE data block modulation symbols, and M _{Pilot_block,symbols} represents the number of SC-FDE pilot block modulation symbols. According to the configuration, the SC-FDE data/pilot block configuration is shown in Table 4 below.

Configuration Number of modulation symbols in SC-FDE data/pilot block M _{block,symbols} Number of modulated samples in SC-FDE data/pilot block N _{block,samples} Number of modulation symbols in CP samples in SC-FDE data/pilot block
M _cp,symbols Number of modulated samples of CP samples in SC-FDE data/pilot block
N _{cp, samples} 0 256 1024 32 128

The SC-FDE pilot block has a _length of T pilot_Block = (N _cp,samples +N _{pilot_block,samples} )T _s and consists of N _cp,samples CP samples and N _{pilot_block,samples} pilot samples, and M _{Pilot_block,symbols} Conveys a pilot symbol sequence.

An SC-FDE data block has a _length of T data_Block =(N _cp,samples +N _{data_block,samples} )T _s and consists of N _cp,samples CP samples and N _{ata_block,samples} data samples, and M _{data_block,symbols} Carries a sequence of data symbols.

The first (or first) SC-FDE preamble block has a _length of T 1st_preamble_block = (N _CP,samples +N _{1st_preamble_block,samples} )T _s , N _CP,samples CP samples and N _{1st_preamble_block,samples} preamble block samples It consists of M _{1st_preamble_block,symbols,} and delivers a symbol sequence. The first SC-FDE preamble block configuration is shown in Table 5.

Configuration Number of modulation symbols in the first SC-FDE preamble block M _{1st_preamble_block,symbols} Number of samples of the first SC-FDE preamble block N _{1st_preamble_block,symbols} Number of modulation symbols of CP samples in the first SC-FDE preamble block
M _cp,symbols Number of modulation samples of CP samples in the first SC-FDE preamble block
N _{cp, samples} 0 256 1024 128 512

The second (or second) SC-FDE preamble block has a _length of T 2nd_preamble_block = (N _CP,samples +N _{2nd_preamble_block,samples} )T _s , N _CP,samples CP samples and N _{2nd_preamble_block,samples} preamble block samples It consists of M _{2nd_preamble_block,symbols,} and delivers a sequence of symbols. According to the configuration, the second SC-FDE preamble block configuration is shown in Table 6.

Configuration Number of modulation symbols in the second SC-FDE preamble block M _{2nd_preamble_block,symbols} Second SC-FDE preamble block sample number N _{2nd_preamble_block,symbols} Number of modulation symbols of CP samples in the second SC-FDE preamble block
M _cp,symbols Number of modulation samples of CP samples in the second SC-FDE preamble block
N _{cp, samples} 0 256 1024 128 512

The first preamble block sequence is _{generated as follows through the q 1st} root Zadoff-Chu sequence of a prime number having a length of _{M 1st_preamble_block,symbols.} Here, q ₁ may have an arbitrary fixed value, for example, may be an integer greater than or equal to 0.

Here, N _{cell_ID} represents a cell ID.

The second SC-FDE preamble block and pilot block sequence are _{generated through the q 2, i-} th root Zadoff-Chu sequence of an even length having a length of _{M 2nd_preamble_block,symbols} =M _{pilot_block,symbols defined as follows.} .

Here, q _2,i may have various values, for example, may have a fixed value such as _{q 2,i =127.}

The generated q _2,i- th root Zadoff-Chu sequence is _{divided into groups of u={u 0} , u ₁ , ..., u ₂₉ }, and the i-th group has a value of _{u i} =q _{2,i .} From the generated Zadoff-Chu sequence group u, the second preamble and pilot block sequence group x are defined as follows according to the following group hopping pattern.

where f _gs ( n _s ) and f _ss are defined as

Here, c is obtained from a Gold sequence generator having a length of 31 initialized by _{c init as follows.}

Here, the second preamble block sequence has _{a value of n s} =0, and the j (0≤j≤3)-th pilot block sequence of the i-th (0≤i≤33) slot has a value of n _s =4xi+j+1 have

According to an embodiment of the present invention, the second preamble sequence and the pilot sequence are among the 30 root sequences by applying a group hopping pattern that is differently applied according to a cell ID, a slot number, and a pilot block number through a group having 30 root sequences. It can be based on one being created.

A data symbol sequence is generated through the following process.

First, for each codeword q, a bit block b ^(q) (0), ..., b ^(q) (M ^(q) bit-1) transmitted in codeword q in one slot (where M ^(q) bit represents the number of bits transmitted in codeword q) must be scrambled with a cell-specific scrambling sequence before modulation. The scrambled bit block b ^'(q) (0), ..., b ^'(q) (M ^(q) bit-1) is defined as follows.

Here, the scrambling sequence c ^(q) (i) is defined at the bottom. The scrambling sequence generator defined below is initialized with c _init = n _RNTI ·215+n _s ·28+N _{Cell_ID} at the beginning of each slot. Here, n _RNTI is a value corresponding to a Radio Network Temporary Identifier (RNTI) related to PDPCH transmission transmitted from a higher layer, and n _s represents a slot number.

One codeword is transmitted in each slot.

For each codeword q, the scrambled bit block b ^'(q) (0), ..., b ^'(q) (M ^(q) block,bit-1) is modulated. In this case, a PSK-based modulation such as Quadrature Phase Shift Keying (QPSK) or 8PSK (Phase-shift Keying) or a QAM-based modulation scheme such as 16QAM (Quadrature Amplitude Modulation) or 64QAM may be used. Here, in consideration of the onboard radio station SWaP (Size, Weight and Power), etc., in order to use a low-spec high-power amplifier, it is possible to select modulation methods QPSK and 8PSK with good linearity, and 16QAM, 64QAM, etc. Higher-order modulation can be applied. Here, QPSK, 8PSK, and 16QAM modulation are applied according to higher layer signaling in consideration of the SWaP of the onboard wireless station and the required data rate for HD (High Definition) level image transmission.

A plurality of symbol blocks d ^(q) (0), ..., d ^(q) (M ^(q) _{data_block,symbols} -1) generated according to modulation are mapped to SC-FDE data blocks in each slot. For each codeword q, the mapped SC-FDE data block sequence a ^data _m,l is defined as follows.

where m=(n mod M _{data_block,symbols} ), l=n/M _{data_block,symbols} .

A pseudo-noise sequence for scrambling is defined by a Gold sequence having a length of 31. An output sequence c(n) having a length of MPN for n=0, 1, ..., M _{PN -1 is defined as follows.}

Here, N _c =1600, and the first m sequence x ₁ is _{initialized to x 1} (n) = 0 for _{x 1} (0) = 1, n = 1, 2, ..., 30. The second m sequence x ₂ is initialized by c _init with a value depending on the application in which the gold sequence is used (Σ ³⁰ _i = 0 x ₂ (i)x2 ^{i ).} For example, when a gold sequence is used for scrambling, the second m sequence is initialized with _{c init} =n _RNTI ·2 ¹⁵ +n _s ·2 ⁸ +N _{Cell_ID .}

For the first SC-FDE preamble block of each subframe, -M _filt N _{symbol, oversamples} T _s /2≤t<(N _cp,samples +N _{1st_preamble_block,samples} )T _s +M _filt N _{symbol,oversamples} T _s In the /2 range, the time-continuous signal s _{1st_preamble} (t) for the first SC-FDE preamble block is defined as in Equation 9 below. N _{symbol, oversamples} means the number of samples per modulation symbol and has a value of 4. M _filt represents the length of the transmit filter pulse p(t) for the modulation symbol.

Here, the x _q1 sequence means the first SC-FDE preamble block sequence, and the modulation symbol period T is defined as _{T=N symbol, oversamples} xT _s. And, the transmission filter pulse p(t) for the modulation symbol is defined as a root-raised-cosine (RRC) filter as follows.

Here, β is a roll-off factor and has a value of 0.3.

Next, for the second SC-FDE preamble and pilot block of each subframe, -M _filt N _{symbol, oversamples} T _s /2≤t <(N _cp,samples +N _{2nd_preamble/pilot_block,samples} )T _s +M _filt In the range of N _{symbol, oversamples} T _{s /2, a time-continuous signal s 2nd_preamble/pilot} (t) for the second SC-FDE preamble or pilot block is defined as in Equation 11 below. N _{symbol, oversamples} means the number of samples per modulation symbol and has a value of 4. M _filt represents the length of the transmit filter pulse p(t) for the modulation symbol.

Here, the x _q2 sequence represents the second SC-FDE preamble and pilot block sequence generated according to the method of generating the second SC-FDE preamble and pilot block sequence.

Next, for the l-th SC-FDE data block of each subframe, -M _filt N _{symbol, oversamples} T _s /2≤t<(N _cp,samples +N _{data_block,samples} )T _s +M _filt N _{symbol,oversamples} In the _{range T s /2, the time-sequential signal s data,l} (t) for the l-th SC-FDE data block is defined as in Equation 12 below. N _{symbol, oversamples} means the number of samples per modulation symbol and has a value of 4. M _filt represents the length of the transmit filter pulse p(t) for the modulation symbol.

Here, a _m,l sequence represents the m-th modulation symbol sequence of the l-th SC-FDE data block in the slot as follows.

The symbol rate R _mod has 7,680,000sps (symbols per second), and when the roll-off index 0.3 of the RRC symbol transmission filter is considered, the transmission bandwidth has 9,984,000 Hz.

Data in the form of one transport block is transmitted to the encoding unit for each slot and encoded through the following steps.

First, a cyclic redundancy check (CRC) is inserted into a transport block. A transport block is divided into code blocks, and a CRC is inserted into each of the divided code blocks.

Next, turbo encoding is performed on the code block. Rate matching is performed on turbo-coded code blocks.

After the rate matching process, a code block concatenation process is performed. The rate-matched code blocks are concatenated to form a sequence of coded data bits.

Meanwhile, channel coding is performed on the control information to form a sequence of coded control bits, and then, the sequence of coded data bits and the sequence of coded control bits are multiplexed to output a multiplexed sequence of bits.

Bits encoded through the steps described above are additionally applied with a channel interleaver in the following process.

Define the input vector sequences to the channel interleaver as g ₀ , g ₁ , g ₂ , g ₃ , ..., g _{H'-1 .} Here, H' represents the total number of modulation symbols in a slot. The output bit sequence from the channel interleaver is derived as follows.

(1) The number of rows in the matrix, C _mux has a value of _{C mux} =N _{slot,data_blocks.} The rows of the matrix are numbered 0, 1, ..., C _{mux -1 from the left row.} N _{slot,data_blocks} represents the number of SC-FDE data blocks in the slot.

(2) The number of columns in the matrix, R _mux, has a value of R _mux =(H'·Q _m )/C _mux , and R' _mux is defined as R' _mux =R _mux /Q _{m .} The columns of the rectangular matrix are numbered 0, 1, ..., R _mux -1 from the top.

(3) The input vector sequence g _k (k=0, 1, ..., H'-1) is written _{in a (C mux} xR _mux ) matrix as a set unit of _{Q m columns.} At this time, starting with the vector y _o from the 0 to the (Q _m -1) column of the 0 matrix, the already entered matrix items are skipped.

The related pseudocodes are as follows.

(4) The output of the block interleaver is a bit sequence read for each column _{of the (C mux} xR _{mux ) matrix.} Vector sequences after channel interleaving are defined as h ₀ , h ₁ , h ₂ , h ₃ , ..., h _H'-1 .

The modulation order and transport block size (hereinafter referred to as TBS) are determined as shown in Table 7 according to the modulation and coding method. _{The index I MCS} for the modulation and coding scheme is given by a higher layer.

configuration 0 configuration 1 MCS
index
I _MCS modulation order
Q _m Transport block size for configuration 0
A MCS
index
I _MCS tampering
degree
Q _m Transport block size for configuration `1
A 0 2 1032 0 2 1032 One 2 2088 One 2 2088 2 2 3752 2 2 3752 3 3 5160 3 4 5160 4 3 6456 4 4 6456 5 3 10296 5 4 10296

Power control controls the transmission power of a physical channel (PDPCH) for a downlink mission in an aircraft radio station (ARS). The power control method is selectively applied.

In the case of not transmitting a PDPCH channel simultaneously with a physical downlink control channel (PDCCH) for downlink control in subframe i in ARS, ARS transmission power for PDPCH transmission is defined as follows.

When a PDPCH channel is transmitted simultaneously with a physical channel for downlink control (PDCCH) in subframe i in ARS, ARS transmission power for PDPCH transmission is defined as follows.

는 PDCCH 채널 송신 전력을 나타내며, P_{O_PDPCH}은 상위 계층에서 주어지는 서빙 지상 무선국(GRS, Ground Radio Station)에서 수신되는 목표 PDPCH 수신 전력에 대한 파라미터를 나타내고, PL은 ARS에서 계산되는 서빙 GRS에 대한 dB 스케일 하향링크 경로 손실 추정값을 나타낸다. 경로 손실값 PL은 PL=PUCCH_RSTP-PUCCH_RSRP로 계산되며, 여기서 PUCCH_RSTP는 상위계층에서 제공되는 PUCCH 참조 신호 송신 전력 값을 나타내고, PUCCH_RSRP는 상위계층에서 제공되는 PUCCH 참조 신호 수신 전력 값을 나타낸다.Here, P _CMAX , a linear value, represents the ARS transmit power given by the upper layer,

represents the PDCCH channel transmission power, P _{O_PDPCH} represents a parameter for the target PDPCH reception power received from the serving ground radio station (GRS) given in the upper layer, and PL is the dB scale for the serving GRS calculated in the ARS Indicates the downlink path loss estimate. The path loss value PL is calculated as PL=PUCCH_RSTP-PUCCH_RSRP, where PUCCH_RSTP represents a PUCCH reference signal transmission power value provided from an upper layer, and PUCCH_RSRP represents a PUCCH reference signal reception power value provided from an upper layer.

5 is an exemplary diagram illustrating signal transmission for each configuration according to an embodiment of the present invention.

In FIG. 5 , Configuration 1 is configured only in downlink and shows a configuration in which signals are continuously transmitted. In contrast, configuration 2 (Configuration 2) shows a configuration that consists of only downlink, but does not transmit a signal in slots of some subframes. This is a configuration to avoid interference with the C-band control communication that is available adjacent to the data link for the C-band mission. In the case of C-band control communication, the 50ms-long frame structure is a signal transmission in the first subframe of 23ms length, followed by a guard period of 1.3ms in length, and then signal transmission in a subframe of 23ms in length, and the last includes a guard interval of 2.7 ms. Configuration 2 can avoid interference with the control communication by not transmitting the mission data signal during the guard period of the control communication.

Next, configuration 3 (Configuration 3) is a configuration that does not transmit a communication signal for a mission during the uplink transmission period for control of the C band. This is a configuration so that the transmission signal for mission does not interfere with the reception signal for control in the onboard radio station.

Next, Configuration 4 to Configuration 7 show configurations in the case of supporting a communication link for a two-way mission rather than a unidirectional link. The uplink/downlink change of the bidirectional link is made within a 10ms subframe, and shows a configuration that operates the same for each subframe.

Configuration 4 is a configuration showing an asymmetric DL configuration. The start starts with a downlink, and the downlink transmission section is configured to be long because the amount of mission data traffic performed by the UAV is larger than the amount of data traffic transmitted from the wireless station to the UAV in the normal mission data link. The structure reflects this, and a guard interval exists between the downlink and the uplink. The length of the guard interval may consist of one or more slots according to the cell operating radius. The preamble and slot structures for downlink transmission apply the same preamble and slot structures as described above, and the preamble and slot structures used in the uplink and downlink are applied as they are to increase the ease of implementation.

Configuration 5 is a frame configuration in consideration of uplink and downlink symmetric traffic. For example, in the case of performing a voice microphone broadcasting mission through an unmanned aerial vehicle, the amount of voice traffic transmitted from the terrestrial radio station to the on-board radio station and the amount of voice traffic transmitted from the on-board radio station to the terrestrial radio station may be similar. Configuration 5 is different from configuration 4 only in the length of the slot section used for uplink and downlink, and the preamble and slot structure are applied the same.

Configuration 6 shows the configuration for uplink and downlink with relatively small asymmetry compared to configuration 4, and configuration 7 protects more than configuration 4 due to the increase in the communication radius between the terrestrial radio station and the mounted radio station. It shows the configuration when a section is needed. In addition, the same method can be applied in the case of other uplink asymmetric traffic, such as when uplink traffic is more than downlink, and when guard sections of different sizes are required according to the operating radius.

Based on these configurations, the radio frame according to an embodiment of the present invention has a frame composed of only continuous downlink, a frame composed only of non-contiguous downlink in consideration of interference with control communication allocated to the UAV, and asymmetry. It may be composed of one of a frame composed of a bidirectional uplink and downlink, a frame composed of a bidirectional uplink with symmetry, a frame including guard sections of different lengths between uplinks and downlinks according to an operating radius, and the like.

6 is a flowchart of a communication method according to an embodiment of the present invention.

The UAV may set a channel for data transmission/reception (S100). Next, the UAV may configure a frame for the set channel (S110). Here, as described above based on FIGS. 1 to 5, the setting channel is a channel within the set frequency band for mission communication allocated to the UAV, and may be an adjacent channel of the channel for control communication of the UAV. Data transmission and reception in such a channel may be performed based on the SC-FDE scheme. Also, as an implementation example, a frame includes a plurality of subframes, and whether to use the frame may be selectively determined by a higher layer of each subframe. In addition, the subframe may consist of two preamble periods and N _sf,slot slot periods. In addition, as an implementation example, each slot is _{composed of N slot, data_blocks} SC-FDE data blocks and N _{slot, pilot_block} SC-FDE pilot blocks, and the SC-FDE pilot block includes a set number of, for example, 5 SC- It may be inserted after the FDE data block, and a block of each slot may consist of N _cp CP samples and N _{block,samples} block samples. In addition, as an embodiment, a preamble sequence having excellent PAPR and good auto correlation and cross correlation properties to reduce inter-cell interference may be used. For example, in the subframe, the sequence of the first preamble block constituting the two preamble sections is generated through the q1 th root Zadoff-Chu sequence of decimal length, and the second preamble block is the q2 th root Zadoff-Chu of the even length. generated by sequence.

Thereafter, the unmanned aerial vehicle may perform data transmission/reception through a set channel, and performs data transmission/reception in the SC-FDE method (S120).

7 is a diagram showing the structure of a communication device according to an embodiment of the present invention.

7 , the communication device 100 according to an embodiment of the present invention includes a processor 110 , a memory 120 , an input interface device 130 , an output interface device 140 , and a network interface device. 150 and a storage device 160 , which may communicate over a bus 170 .

The processor 110 may be configured to implement the methods described with reference to FIGS. 1 to 6 above.

The processor 110 may be a central processing unit (CPU) or a semiconductor device that executes instructions stored in the memory 120 or the storage device 160 .

The memory 120 is connected to the processor 110 and stores various information related to the operation of the processor 110 . The memory 120 may store instructions to be executed by the processor 110 or may temporarily store instructions by loading the instructions from the storage device 160 . The processor 110 may execute instructions stored in or loaded from the memory 120 . The memory may include a ROM 121 and a RAM 122 .

In an embodiment of the present invention, the memory 120/storage device 160 may be located inside or outside the processor 110 , and may be connected to the processor 110 through various known means.

The input interface device 130 may be configured to receive input data and transmit it to the processor 110 . The output interface device 140 may be configured to output the processing result of the processor 110 .

The network interface device 150 may be configured to receive data input through a network and transmit it to the processor 110 , or to transmit a processing result of the processor 110 to another device through the network.

The communication device 100 according to an embodiment of the present invention having such a structure may be an unmanned aerial vehicle.

The embodiment of the present invention is not implemented only through the apparatus and/or method described above, but a program for realizing a function corresponding to the configuration of the embodiment of the present invention, a recording medium in which the program is recorded, etc. Also, such an implementation can be easily implemented by those skilled in the art to which the present invention pertains from the description of the above-described embodiments.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improved forms of the present invention are also provided by those skilled in the art using the basic concept of the present invention as defined in the following claims. is within the scope of the right.

Claims (15)

A communication method for transmitting and receiving data for a mission by an unmanned aerial vehicle, comprising:
setting a channel in a set frequency band for mission communication assigned to the UAV;
constructing a radio frame for the set channel; and
Transmitting and receiving the mission data through the set channel based on the radio frame
includes,
The radio frame includes two or more subframes whose use is selectively determined, each subframe includes two preamble durations and a plurality of slot durations, and each slot includes a single carrier-frequency domain (SC-FDE). Equalization) data block and an SC-FDE pilot block. According to claim 1,
The radio frame
a frame composed of only continuous downlink;
a frame composed of only a non-continuous downlink in consideration of interference with control communication allocated to the UAV;
a frame composed of a bidirectional uplink and downlink having asymmetry;
a frame composed of a bidirectional uplink and downlink having symmetry;
Frame including guard sections of different lengths between uplink and downlink according to operating radius
At least one of, a communication method. According to claim 1,
In the radio frame, the SC-FDE pilot block is disposed after every 5 SC-FDE data blocks in consideration of the speed of the UAV and multipath delay spread. According to claim 1,
The SC-FDE pilot block or SC-FDE data block included in the slot includes N _cp cyclic prefix (CP) samples and N _{block,samples} block samples. According to claim 1,
The number of symbols included in the slot, the number of pilot symbols included in the SC-FDE pilot block, and the number of data symbols included in the SC-FDE data block are determined based on a subframe configuration. Way. According to claim 1,
The two preamble sections include a first preamble block and a second preamble block, and the sequence of the first preamble block is generated through a first set-th root Zadoff-Chu sequence having a fractional length, and of the second preamble block A sequence and a sequence of the SC-FDE pilot block are generated through a second set-th root Zadoff-Chu sequence of an even length. 7. The method of claim 6,
The first setting number indicates a cell ID, and the sequence of the first preamble block is a root sequence associated with the cell ID,
The sequence of the second preamble block and the sequence of the SC-FDE pilot block is a route generated by applying a group hopping pattern that is applied differently according to a cell ID, a slot number, and a pilot block number through a group having a set number of route sequences. A method of communication, which is a sequence. According to claim 1,
The data transmission and reception is performed based on the SC-FDE scheme, the SC-FDE scheme has a root raised cosine (RRC) filter, and the roll-off index used in the RRC filter has a value of 0.3, communication method. According to claim 1,
A second M sequence of a gold sequence is used for scrambling of the SC-FDE data block, and the second M sequence is initialized ^{to 2 15} +n _s 2 ⁸ +N _{Cell_ID in association with a cell ID,} communication method. A communication device for transmitting and receiving data for a mission, comprising:
network interface device; and
a processor configured to transmit and receive data for the mission through the network interface device
including,
The processor may perform an operation of setting a channel in a set frequency band for mission communication assigned to the unmanned aerial vehicle;
setting a radio frame for the set channel; and
Transmitting and receiving data for the mission through the set channel based on the radio frame
is configured to perform
The radio frame includes two or more subframes whose use is selectively determined, each subframe includes two preamble durations and a plurality of slot durations, and each slot includes a single carrier-frequency domain (SC-FDE). Equalization) data block and an SC-FDE pilot block. 11. The method of claim 10,
The radio frame
a frame composed of only continuous downlink;
a frame composed of only a non-continuous downlink in consideration of interference with control communication allocated to the UAV;
a frame composed of a bidirectional uplink and downlink having asymmetry;
a frame composed of a bidirectional uplink and downlink having symmetry;
Frame including guard sections of different lengths between uplink and downlink according to operating radius
At least one of, a communication device. 11. The method of claim 10,
In the radio frame, the SC-FDE pilot block is disposed after every 5 SC-FDE data blocks in consideration of the speed and multipath delay spread of the UAV. 11. The method of claim 10,
The number of symbols included in the slot, the number of pilot symbols included in the SC-FDE pilot block, and the number of data symbols included in the SC-FDE data block are determined based on a subframe configuration. Device. 11. The method of claim 10,
The two preamble sections include a first preamble block and a second preamble block, and the sequence of the first preamble block is generated through a first set-th root Zadoff-Chu sequence having a fractional length, and of the second preamble block A sequence and a sequence of the SC-FDE pilot block are generated through a second set-th root Zadoff-Chu sequence of an even length. 15. The method of claim 14,
The first setting number indicates a cell ID, and the sequence of the first preamble block is a root sequence associated with the cell ID,
The sequence of the second preamble block and the sequence of the SC-FDE pilot block is a route generated by applying a group hopping pattern that is applied differently according to a cell ID, a slot number, and a pilot block number through a group having a set number of route sequences. A sequence, a communication device.

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