CN112583444A - Spread spectrum device for cyclic frequency shift orthogonal frequency division multiplexing access - Google Patents

Spread spectrum device for cyclic frequency shift orthogonal frequency division multiplexing access Download PDF

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CN112583444A
CN112583444A CN201910922909.5A CN201910922909A CN112583444A CN 112583444 A CN112583444 A CN 112583444A CN 201910922909 A CN201910922909 A CN 201910922909A CN 112583444 A CN112583444 A CN 112583444A
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domain symbols
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江政宪
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Hangzhou Lianxintong Semiconductor Co ltd
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贵州濎通芯物联技术有限公司
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
    • H04L27/2692—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with preamble design, i.e. with negotiation of the synchronisation sequence with transmitter or sequence linked to the algorithm used at the receiver
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2697—Multicarrier modulation systems in combination with other modulation techniques

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Abstract

The invention provides a frequency spreading device of cyclic frequency shift orthogonal frequency division multiplexing access, comprising: at least one communication device for transmitting signals according to a frequency band, the frequency band having Q sub-bands, each sub-band having M sub-carriers, the Q sub-bands having respective independent cyclic frequency shift values, and the communication device being configured to utilize the cyclic frequency shift values to perform a conversion between a sequence of bits and Q frequency domain symbols; wherein, Q frequency domain symbols are generated according to Q data of Q stations, and the Q stations have corresponding Q sub-bands; q stations have the corresponding string of bits and are allocated to Q subbands; and the cyclic frequency shift values are cycles of a frequency sequence, and different cyclic frequency shift values correspond to different bit values. When the device is used for uplink transmission, the power peak-to-average ratio is very low, the cost of a front-end amplifier can be reduced, and meanwhile, the device can also greatly reduce the signal collision probability caused by transmission of a plurality of workstations.

Description

Spread spectrum device for cyclic frequency shift orthogonal frequency division multiplexing access
Technical Field
The present invention relates to a Frequency spreading device, and more particularly, to a Cyclic-Frequency Shift (CFS) Orthogonal Frequency Division Multiplexing Access (OFDMA) Frequency spreading device.
Background
Cyclic-Frequency Shift Orthogonal Frequency Division multiplexing (CFS-OFDM) is a Spread Spectrum technique in which information is transmitted by Cyclic Frequency Shift values of a wideband OFDM signal. Its advantages are low S/N ratio, high transmission power, and long distance communication. By the Cyclic Preamble (CP), the channel of the multipath has better performance than the conventional Spread Spectrum techniques such as Direct Sequence Spread Spectrum (DSSS), Frequency Hopping Spread Spectrum (FHSS), and wideband Chirp Spread Spectrum (CSS). By properly selecting the frequency domain signal, the signal in the time domain has extremely low power peak-to-average ratio, so the linearity requirement of the RF gain amplifier at the transmitting end is very low, and the cost of the amplifier can be greatly reduced.
Disclosure of Invention
The purpose of the CFS-OFDMA spread spectrum device of the invention is to enable a base station (Access Point, hereinafter referred to as AP) to simultaneously use a plurality of sub-bands and a plurality of workstations (hereinafter referred to as station), and the AP and the plurality of stations simultaneously communicate through CFS-OFDM, thereby achieving the effect of improving the overall transmission rate. When uplink transmission is carried out, each workstation only needs to transmit the CFS-OFDM signal of the workstation, so that the power peak-to-average ratio of the signal is extremely low, and the cost of a front-end gain amplifier is greatly reduced
The invention provides a CFS-OFDMA device, comprising: at least one communication device for transmitting signals according to a frequency band, the frequency band having Q sub-bands, each sub-band having M sub-carriers, the Q sub-bands having respective independent cyclic frequency shift values, and the communication device being configured to utilize the cyclic frequency shift values to perform a conversion between a sequence of bits and Q frequency domain symbols; wherein, Q frequency domain symbols are generated according to Q data of Q stations, and the Q stations have corresponding Q sub-bands; q stations have the corresponding string of bits and are allocated to Q subbands; and the cyclic frequency shift values are cycles of a frequency sequence, and different cyclic frequency shift values correspond to different bit values.
In one embodiment, wherein the at least one communication device comprises a receiving device and a transmitting device, when the Q station performs uplink transmission, the transmitting device transmits a synchronization packet to the Q station by broadcast to confirm the transmission start time of each Q station; after the Q station receives the synchronous packet, the Q station transmits the corresponding time domain packet in the Q sub-bands corresponding to the Q data through a CFS-OFDM signal at the same time after a fixed time according to the reference point of the transmission time axis of the synchronous packet.
In one embodiment, the Q frequency domain symbols may be arranged according to the order of the M subcarriers; alternatively, the Q frequency domain symbols may be staggered according to the order of the M subcarriers.
Drawings
FIG. 1 is a diagram illustrating one bit value for different combinations of cyclic frequencies.
Fig. 2 is a block diagram of a CFS-OFDMA spreading apparatus according to an embodiment of the present invention.
Fig. 3 is a block diagram of a transmitting device of a CFS-OFDMA spreading apparatus according to an embodiment of the present invention.
Fig. 4 is a schematic diagram illustrating a subband splitting method of a CFS-OFDMA spreading apparatus according to an embodiment of the present invention.
Fig. 5 is a schematic diagram illustrating a subband splitting method of a CFS-OFDMA spreading apparatus according to an embodiment of the present invention.
Fig. 6 is a block diagram of a receiving device of a CFS-OFDMA spreading device according to an embodiment of the present invention.
Fig. 7 is a diagram illustrating synchronization packets for uplink transmission of a CFS-OFDMA spreading device according to an embodiment of the present invention.
Reference numerals:
100 CFS-OFDMA spreading device
110 communication device
200 conveying device
210_1 to 210_ Q Gray code encoding units
220_1 to 220_ Q modulation unit
230 OFDM transmission unit
231 packet component unit
232 window unit
233 cycle preamble unit
234N point inverse Fourier transform unit
240 transmission circuit Tx
300 receiving device
310_1 ~ 310_ Q Gray decoding unit
320 demodulation module
321_ 1-321 _ Q peak value judging unit
322_1 ~ 322_ Q circular convolution unit
330 OFDM receiving unit
331 packet detecting unit
332 loop preamble removal unit
333N point Fourier transform unit
340 receive circuit Rx
Detailed Description
An embodiment of the present invention provides a CFS-OFDM technology, which is a new Spread Spectrum technology (Spread Spectrum), can provide extremely stable Wired (Wired) and Wireless (Wireless) transmission, and is widely applied to all communication systems. When there are multiple stations in the wireless network, we can divide the whole bandwidth into several sub-bands, each sub-band is used for different stations. The AP can simultaneously transmit with a plurality of stations by CFS-OFDM. This multiple access scheme is called CFS-OFDMA. In addition to the stable transmission effect of the original CFS-OFDM, the CFS-OFDMA can simultaneously communicate with a plurality of stations at one time, thereby improving the overall transmission efficiency of the network and greatly reducing the signal collision probability caused by mass transmission among the stations. During uplink transmission (uplink), each station only needs to transmit the CFS-OFDM signal of its own sub-band, so that the power Peak to average power ratio (Peak to average power ratio) is very low, the linear requirement for the front-end amplifier is greatly reduced, and the cost can be reduced. By combining the advantages, the CFS-OFDMA method is very suitable for a large-scale network system with thousands of stations, such as the wireless Internet of things.
In one embodiment, the sequentially arranged cyclic frequency ordering may be regarded as a first combination pattern, and the frequencies are shifted to the left or right in a cyclic manner as other combination patterns, each combination pattern corresponding to a cyclic frequency shift value. As described in more detail below. FIG. 1 is a diagram illustrating one bit value for different combinations of cyclic frequencies. As shown in FIG. 1, in the present embodiment, the sequentially arranged frequencies are sorted by S11S12S13S14As a first combination aspect, the cyclic frequency shift value m is specified to be 0 and to be the first subband. After shifting the frequencies to the left by one unit in a cyclic manner, a frequency sequence S is formed12S13S14S11As a second combination, the cyclic frequency shift value m is 1 and is the first subband, and so on. In this embodiment, different cyclic frequency combinations correspond to different cyclic frequency shift values, and different cyclic frequency shift values correspond to different bit values, and the bit values may be binary codes or gray codes.
TABLE 1
Cyclic frequency shift value m b2b1 g2g1 Subcarrier content
0 00 00 S11S12S13S14
1 01 01 S12S13S14S11
2 11 10 S13S14S11S12
3 10 11 S14S11S12S13
For example, when N is 4, information of k 2 bits may be transferred by a cyclic frequency shift value. As shown in Table 1 above (taking the first sub-band as an example), m is a cyclic frequency shift value to transmit two bits of information, and the binary value is b2b1Gray coded as g2g1The original subcarrier content is S11S12S13S14When the cyclic frequency shift is 1, the subcarrier sequence is changed to S12S13S14S11When the cyclic frequency shift is 2, the subcarrier sequence is changed to S13S14S11S12And so on. The example of Table 1 is a left-going cyclic shift, but the cyclic shift of the present invention is not limited to a left-going or right-going cyclic shift.
Referring to table 1 and equation S (mod (k + m, N)), in one embodiment, the CFS-OFDM transmission signal can satisfy the following equation (1):
Figure BDA0002218079390000041
wherein, N is the number of all frequency domain subcarriers, s (k) is a frequency domain symbol, k represents the kth subcarrier, s (N) is a time domain symbol, N is the nth time point, m represents the cyclic frequency shift value, the subcarrier is taken as a unit, mod (., N) is module N, i.e. the remainder is taken for N, and N can be realized by the power of two.
Since the possible value of the cyclic frequency shift m is 0-N-1, at most K-log can be transmitted by symbol (symbol) of a CFS-OFDM2(N) bits of information.
Theoretically, s (k) can be any aperiodic signal as the CFS-OFDM signal, but s (k) can be selected appropriately to obtain better transmission quality. The appropriate selection includes selecting a Peak to average power ratio (PAPR) having an optimal auto-correlation (auto-correlation) characteristic and a lowest power in a time domain. For example, when s (k) is selected as shown in the following formula (4), the two advantages are obtained:
Figure BDA0002218079390000051
in the present embodiment, the PAPR of the real part or the imaginary part in the time domain is about 3dB, and auto-correlation (auto-correlation) is much greater than 0 only when k is 0, and is 0 in the case of k is 0, so that it is a very good choice as CFS-OFDM. The embodiment can reduce the linearity requirement of the RF gain amplifier at the transmitting end, and can greatly reduce the cost of the amplifier.
The CFS-OFDMA spread spectrum device according to an embodiment of the present invention is a CFS-OFDM-based communication technology, which divides a frequency band into a plurality of sub-bands, and increases the transmission rate of the CFS-OFDM by several times by simultaneously operating a plurality of stations using a plurality of CFS-OFDM channels.
Fig. 2 is a block diagram of a CFS-OFDMA spreading apparatus according to an embodiment of the present invention. As shown in fig. 2, according to an embodiment of the present invention, the spread spectrum device 100 of CFS-OFDMA includes at least one communication device 110, and the communication device 110 performs signal transmission according to a frequency band; please note that the frequency band has Q sub-bands, each sub-band has M sub-carriers, the Q sub-bands have independent cyclic frequency shift values, the Q sub-bands correspond to the Q frequency domain symbols, and the communication device 110 uses the cyclic frequency shift values to perform the conversion between the string of bits and the Q frequency domain symbols; wherein, Q frequency domain symbols are generated according to Q data of Q station, the Q station has corresponding Q sub-bands; q station has the corresponding string of bits and distributes to the Q sub-bands; and the cyclic frequency shift values are cycles of a frequency sequence, and different cyclic frequency shift values correspond to different bit values.
Assuming that the whole frequency band has M sub-carriers, the whole frequency band can be divided into Q sub-bands according to Q station stations, each sub-band is allocated to one station for use, and then the AP transmits with CFS-OFDM and Q station stations simultaneously, so that the overall network transmission rate is increased by several times. For example, assuming that M is 1024, CFS-OFDM can transmit log per symbol2(1024) 10 bits. If cut into 8 sub-bands, each with 128 sub-carriers, the CFS-OFDM of each sub-band may transmit log2(128) With 7 bits, in CFS-OFDMA, eight stations transmit simultaneously, and each symbol can transmit 8 × 7-56 bits, i.e. the transmission rate can reach 5.6 times of the original transmission rate. Since the AP communicates with multiple stations simultaneously using CFS-OFDM, this method is called CFS-OFDMA.
In one embodiment, the at least one communication device 110 includes a transmitting device 200, and in one embodiment, may further include a receiving device 300. The transmitter 200 is used to convert a string of bits into a plurality of frequency domain symbols and convert the frequency domain symbols into a transmission signal St. The receiving apparatus 300 is configured to receive a transmission signal St, convert the transmission signal St into a plurality of frequency domain symbols, and convert the frequency domain symbols into a string of bits.
Fig. 3 is a block diagram of a transmitting device of a CFS-OFDMA spreading apparatus according to an embodiment of the present invention. As shown in fig. 3, a transmitter 200 of a CFS-OFDMA spreader 100 at a downlink (downlink) transmitter of the CFS-OFDMA spreader includes: the Q modulation units 220_1 to 220_ Q simultaneously convert M sub-carriers in the Q sub-bands into the Q frequency domain symbols, and the Q frequency domain symbols are functions of a plurality of cyclic frequency shift values.
Referring to fig. 3 again, the transmitter 200 of the CFS-OFDMA spreading apparatus 100 may further include: q Gray code encoding units 210_1 to 210_ Q, an OFDM transmission unit 230 and a transmission circuit Tx 240. In this embodiment, the Data to be provided to the Q stations are Data _1 to Data _ Q, and after being gray-coded by Q gray code coding units 210_1 to 210_ Q, the gray code coding units 210_1 to 210_ Q simultaneously convert the bit format of the string from Q binary codes to Q gray codes according to the Q sub-Data, so as to minimize a bit error rate when the symbol demodulation error occurs. The OFDM transmitting unit 230 converts the Q frequency domain symbols into a time domain symbol, and forms a time domain packet with the time domain symbol. The transmission circuit Tx 240 converts the time domain packet into a transmission signal St, and transmits the signal through a network line or a wireless signal.
In one embodiment, the OFDM transmission unit 230 includes an N-point inverse fourier transform (ifft) unit 234, a Cyclic Preamble (CP) unit 233, a window unit 232, and a packet composition unit 231. An N-point Inverse Fourier Transform (N-IFFT) unit 234 is coupled to the Q modulation units 220_ 1-220 _ Q, respectively, and the N-point Inverse Fourier Transform unit 234 transforms the N frequency domain symbols into N time domain symbols according to the N frequency domain symbols, in other words, the N-point Inverse Fourier Transform unit 234 is used to Transform the Q frequency domain symbol combinations into time domain symbols. The cyclic preamble unit 233 copies a part of the symbols at the end of the N-point time domain symbol packet to the front end of the N-point time domain symbols. The window unit 232 is coupled to the cyclic preamble unit 233 for reducing interference of the time-domain packet in the adjacent frequency band. The packet composition unit 231 combines the preamble, header, payload and generates the time-domain packet using the N-point time-domain symbols. In one embodiment, the transmitting device 200 can minimize the bit error rate by using gray code, the decimal digital value after gray code conversion is the value of cyclic frequency shift, and the signal is converted into the time domain by inverse fourier transform according to the formula (1) according to the cyclic frequency shift value. Next, a Cyclic Prefix (CP) is added to boost immunity to the multipath. Finally, a window range is added to reduce interference to adjacent frequency bands.
Please note that, the subband splitting method of the spreading apparatus 100 of CFS-OFDMA is not limited as long as the subbands are subsets of the whole spectrum band. However, it is generally easier to cut the sub-bands into sub-bands of the same size, i.e. each sub-band has the same number of sub-carriers N-M/Q.
There are two practical ways of slicing, the first is called a region-type sub-band, as shown in fig. 4, there are three sub-bands, each sub-band has four sub-carriers, which are represented by different patterns, and as can be seen from fig. 4, the sub-carriers of each sub-band are continuous; wherein the sub-carrier S11S12S13S14For a given cyclic frequency shift value m of 0 and for the first subband, the subcarrier S21S22S23S24For a given cyclic frequency shift value m of 0 and for the second sub-band, the sub-carrier S31S32S33S34In order to specify the third subband with the cyclic frequency shift value m equal to 0, only three subbands are shown in fig. 4, but the present invention should not be limited thereto.
The second type is referred to as distributed sub-bands, where the sub-carriers of each sub-band are evenly staggered, as shown in fig. 5. The distributed sub-bands have the advantage of better channel dispersion, and the disadvantage of easier interference between sub-bands.
In other words, the Q frequency domain symbols can be arranged according to the order of the M subcarriers; alternatively, the Q frequency domain symbols may be staggered according to the order of the M subcarriers.
The transmitting end of the spread spectrum device of CFS-OFDMA distributes the Data _1 to Data _ Q to Q gray code encoding units 210_1 to 210_ Q, then Q modulation units 220_1 to 220_ Q perform cyclic frequency shift (cyclic frequency shift) on their respective sub-bands according to the information, and finally the entire frequency domain signal is integrated and converted into time domain symbols by the N-point inverse fourier transform unit 234, added with cyclic preamble, and transmitted out through the transmitting circuit Tx 240 after passing through the window.
Fig. 6 is a block diagram of a receiving device of a CFS-OFDMA spreading device according to an embodiment of the present invention. As shown in fig. 6, in a CFS-OFDMA spreader uplink (downlink) receiving end, a receiving apparatus 300 of a CFS-OFDMA spreader 100 may include: a receiving circuit Rx 340, an OFDM receiving unit 330, Q demodulation modules 320_1 to 320_ Q and Q Gray decoding units 310_1 to 310_ Q. The receiving circuit Rx 340 receives a transmission signal St through a network cable or a wireless signal, and then converts the transmission signal St into a time-domain packet. The Rx circuit Rx 340 may comprise an Analog Front End (AFE), which may comprise, for example, an Analog filter (Analog filter), a signal gain device, and an Analog-to-digital converter (adc) for processing the transmission signal St.
The OFDM receiving unit 330 receives the time domain packet and converts the time domain packet into the frequency domain symbols. In one embodiment, the OFDM receiving unit 330 includes: a Packet detection (Packet detection) unit 331, a cyclic preamble removal unit 332, and an N-point Fast Fourier Transform (N-FFT) unit 333. The Packet detection (Packet detection) unit 331 is used to monitor the time domain signal, estimate whether there is a time domain Packet according to the frame preamble, and adjust the gain. The cyclic-preamble removal unit 332 removes the cyclic preamble in the time-domain packet to restore the plurality of N-point time-domain symbols. The N-point fourier transform unit 333 transforms a plurality of N-point time domain symbols into a plurality of frequency domain symbols, in other words, the N-point fourier transform unit 333 allocates the Q frequency domain symbols to the M sub-carriers in the Q sub-bands and restores the time domain symbols to the Q frequency domain symbols.
After the signal is detected by the packet detection unit 331, the cyclic preamble is removed, and the cyclic preamble is converted to the frequency domain by the N-point fourier transform unit 333, and each sub-band is demodulated by CFS-OFDM, so as to solve the original data transmitted by the Q station.
Q demodulation modules 320_ 1-320 _ Q for simultaneously demodulating the Q frequency domain symbols corresponding to the M sub-carriers and converting the Q frequency domain symbols into corresponding different bit values according to the corresponding cyclic frequency shift value.
The Q demodulation modules 320_ 1-320 _ Q are used to demodulate the Q frequency domain symbols into a corresponding string of bits simultaneously. Please note that, the Q Gray code decoding units 310_ 1-310 _ Q are used to convert the format of the string of bits from Q Gray codes to Q binary codes when the format of the string of bits is Gray codes.
In the present embodiment, the demodulation modules 320_1 to 320_ Q respectively include cyclic convolution units 322_1 to 322_ Q and peak determination units 321_1 to 321_ Q. The cyclic convolution units 322_ 1-322 _ Q are used for respectively carrying out cyclic convolution on the Q frequency domain symbols; the peak determining units 321_1 to 321_ Q are respectively coupled to the cyclic convolution units 322_1 to 322_ Q, determine a plurality of peaks of the cyclic convolution result as the cyclic frequency shift values of the Q frequency domain symbols, and convert the cyclic frequency shift values into the string of bits.
The OFDM receiving unit 330 of the CFS-OFDMA spread spectrum device performs cyclic preamble removal after the signal is detected by the packet detecting unit 331, converts the signal to the frequency domain through the N-point fourier transform unit 333, and performs CFS-OFDM demodulation, including cyclic convolution, peak determination, and gray decoding, on each sub-band, to decode the original data.
Please refer to fig. 7, please note that, in the uplink transmission of the spreading apparatus of CFS-OFDMA, since multiple stations must transmit CFS-OFDM signals in their respective sub-bands at the same time, synchronization is needed to ensure that the time error of each station starting transmission is within the tolerable range. The synchronization usually is performed by the AP transmitting a synchronization packet (synchronization packet) in a broadcast (broadcast or multicast) manner, and each station receives the synchronization packet and then uses the synchronization packet as a reference point of a transmission time axis; after a fixed time, the Q stations transmit the corresponding time domain packets of the Q data in the corresponding Q sub-bands through a CFS-OFDM signal; in other words, for the AP, the AP only detects the time-domain packets transmitted by the Q stations and combined in the air.
In one embodiment, the synchronization packet includes which frequency band should be used by each station to ensure that each station uses a different frequency band to transmit the corresponding time domain packet; the method of sending the synchronization packet is not limited to the method, and the sending device of the CFS-OFDMA spreading device may send the synchronization packet to the Q station, which should not be construed as a limitation to the invention.
The device and the method of the invention have the following characteristics: the CFS-OFDMA spread spectrum device is a multiplex communication technology based on CFS-OFDM, the frequency band is divided into a plurality of sub-frequency bands, the AP and a plurality of stations simultaneously utilize the CFS-OFDM for transmission, and the transmission rate of the CFS-OFDM is increased by multiple times; the cost of a front-end amplifier can be reduced due to the extremely low peak-to-average power ratio of the signal during uplink transmission; when the CFS-OFDMA frequency spreading device carries out uplink transmission, each station only transmits the CFS-OFDM signal of the station, the power peak-to-average ratio is very low, and the cost of a front-end amplifier can be reduced; the spread spectrum device of CFS-OFDMA allows multiple stations to transmit simultaneously, thus greatly reducing the probability of signal collision caused by multiple station transmission.
The present invention has been described in terms of the above embodiments, but the scope of the present invention is not limited thereto, and various modifications and changes can be made by those skilled in the art without departing from the gist of the present invention within the scope of the claims of the present invention.

Claims (10)

1. A cyclic frequency shift ofdm access spreading apparatus, comprising:
at least one communication device for transmitting signals according to a frequency band, the frequency band having Q sub-bands, each sub-band having M sub-carriers, the Q sub-bands having respective independent cyclic frequency shift values, and the communication device being configured to utilize a plurality of the cyclic frequency shift values to perform a conversion between a series of bits and Q frequency domain symbols;
wherein the Q frequency domain symbols are generated according to Q data of Q stations having corresponding Q sub-bands; the Q stations have the corresponding string of bits and are allocated to the Q subbands; and the cyclic frequency shift values are cycles of a frequency sequence, and different cyclic frequency shift values correspond to different bit values.
2. The apparatus according to claim 1, wherein said at least one communication device comprises a receiving device and a transmitting device, and when said Q station performs uplink transmission, said transmitting device transmits a synchronization packet to said Q station by broadcast to confirm the time when each of said Q stations starts to transmit; after the Q station receives the synchronous packet, the Q station transmits the corresponding time domain packet in the Q sub-bands corresponding to the Q data at the same time through a cyclic frequency shift orthogonal frequency division multiplexing spread spectrum signal according to the synchronous packet as a reference point of a transmission time axis.
3. The spread spectrum device of claim 2, wherein the transmitting means comprises:
q modulation units, which simultaneously convert the M sub-carriers in the Q sub-bands into the Q frequency domain symbols, wherein the Q frequency domain symbols are a function of a plurality of the cyclic frequency shift values; and
a spread spectrum transmission unit of orthogonal frequency division multiplexing converts the Q frequency domain symbols into a time domain symbol, and forms a time domain packet by the time domain symbol.
4. The spreading device of claim 3, wherein the Q frequency domain symbols are arranged according to the order of the M subcarriers; alternatively, the Q frequency domain symbols may be staggered according to the order of the M subcarriers.
5. The spreading device of claim 3, wherein the time domain symbols satisfy the following equation:
Figure FDA0002218079380000011
wherein, N is the number of each frequency domain subcarrier of the spread spectrum transmission unit of orthogonal frequency division multiplexing, s (k) is the frequency domain symbol, k represents the kth subcarrier, s (N) is the time domain signal, N is the nth time point, m represents the cyclic frequency shift value, the subcarrier is taken as the unit, mod (., N) is the remainder to N, and N can be the power of two; and
the Q frequency domain symbols S (k) all satisfy the following formula:
Figure FDA0002218079380000021
6. the spread spectrum device of claim 5, wherein the OFDM spread spectrum transmitter unit comprises:
an N-point inverse Fourier transform unit for transforming the Q frequency domain symbol combinations into the time domain symbol;
a cyclic preamble unit for copying a part of the symbols at the end of the time domain symbols to the front end of the time domain symbols to generate the time domain symbols;
a window unit coupled to the cyclic pilot unit for reducing interference of the time domain symbol on adjacent frequency bands; and
a packet forming unit for generating the time domain packet by using the time domain symbol.
7. The apparatus according to claim 3, wherein said transmitting means further comprises:
and Q Gray code encoding units for converting the format of the string of bits from Q binary codes to Q Gray codes.
8. The spread spectrum device of claim 2, wherein the receiving means comprises:
an orthogonal frequency division multiplexing spread spectrum receiving unit for converting the time domain packet into the frequency domain symbols;
q demodulation modules, which are used to demodulate the Q frequency domain symbols corresponding to the M sub-carriers at the same time, and convert them into different corresponding bit values according to the corresponding cyclic frequency shift value.
9. The apparatus according to claim 8, wherein the Q demodulation modules respectively comprise:
a cyclic convolution unit for performing cyclic convolution on the Q frequency domain symbols respectively; and
and a peak value judging unit, coupled to the cyclic convolution unit, for judging a plurality of peak values of the cyclic convolution result as the cyclic frequency shift values of the Q frequency domain symbols corresponding to the cyclic convolution result, and converting the cyclic frequency shift values into the string of bits.
10. The spread spectrum apparatus according to claim 8,
the spread spectrum receiving unit of the orthogonal frequency division multiplexing comprises:
a packet detection unit for estimating whether the time domain packet exists;
a cyclic preamble removing unit for removing the cyclic preamble in the time domain packet to restore to a plurality of time domain symbols; and
an N-point Fourier transform unit for distributing the Q frequency domain symbols to the M sub-carriers in the Q sub-bands and restoring the time domain symbols to the Q frequency domain symbols,
moreover, the receiving device further comprises:
and the Q gray code decoding units are used for converting the format of the string of bits from Q gray codes to Q binary codes.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108206801A (en) * 2016-12-16 2018-06-26 万高芯科技股份有限公司 Frequency spreading device for cyclic frequency shift orthogonal frequency division multiplexing
TW201840141A (en) * 2017-04-26 2018-11-01 萬高芯科技股份有限公司 Multi-section cyclic-frequency shift orthogonal frequency division multiplex spread spectrum device
TW201902164A (en) * 2017-05-19 2019-01-01 濎通科技股份有限公司 Cyclic-frequency shift orthogonal frequency division multiple access spread spectrum device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108206801A (en) * 2016-12-16 2018-06-26 万高芯科技股份有限公司 Frequency spreading device for cyclic frequency shift orthogonal frequency division multiplexing
TW201840141A (en) * 2017-04-26 2018-11-01 萬高芯科技股份有限公司 Multi-section cyclic-frequency shift orthogonal frequency division multiplex spread spectrum device
TW201902164A (en) * 2017-05-19 2019-01-01 濎通科技股份有限公司 Cyclic-frequency shift orthogonal frequency division multiple access spread spectrum device

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