CN1901529A - Quick frequency hopping and expanding communication method based on orthogonal frequency division duplexing - Google Patents
Quick frequency hopping and expanding communication method based on orthogonal frequency division duplexing Download PDFInfo
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- CN1901529A CN1901529A CNA2006100888437A CN200610088843A CN1901529A CN 1901529 A CN1901529 A CN 1901529A CN A2006100888437 A CNA2006100888437 A CN A2006100888437A CN 200610088843 A CN200610088843 A CN 200610088843A CN 1901529 A CN1901529 A CN 1901529A
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Abstract
This invention relates to a quick hop-expansion communication method based on OFDM, in which, an transmission end generates frequency expansion sequence, sub-carrier distribution signals and FH sequences according to user request, carries out direct sequence frequency expansion or code process then to modulate symbols then distributes the modulated signals to the sub-carriers of communication signals of users according to the sub-carrier distribution signals to be added with circulation prefix for D/A conversion then modulates the received analog signal to the carrier frequency generated according to the FH sequence, the receiving end receives signals then carries out de-FH, A/D conversion and removing the circulation prefix and de-modulates the modulation signals on the sub-carrier of the user communication signals to be output in series to get the user data after the symbol is de-modulated, de-coding or de-FH.
Description
Technical field
The present invention relates to a kind of quick frequency hopping spread spectrum (FHSS) communication method, belong to communication technical field based on OFDM.
Background technology
In order to improve message transmission rate, adopted the transmission means of OFDM (hereinafter to be referred as OFDM); In order to improve user capacity and to reduce inter-user interference, adopted " jumping spread spectrum " scheme of direct sequence spread spectrum and frequency hopping combination; In order to resist the time selective fading that high-speed mobile is brought effectively, adopted OFDM symbol and subcarrier two-stage hopping scheme, this scheme can also be resisted obstructive interference effectively.
The transmission means of OFDM has significantly improved the transmission rate of data with data parallel transmission on the experimental process carrier wave of serial.Because the message transmission rate on the single sub-carrier greatly reduces, and the OFDM character added Cyclic Prefix as protection at interval, makes the OFDM transmission to disturb and frequency selective fading anti-multipath effectively.On the other hand, because the subcarrier of OFDM propagation data effectively under the situation of carrier wave strict orthogonal only, the non-orthogonal meeting of the frequency spectrum of each subcarrier that frequency deviation causes causes serious system interference.This has proposed very high requirement to system synchronous, and particularly in mobile communication, ofdm signal is subjected to the influence of Doppler frequency shift and multipath and Doppler's diffusion takes place, and it is rather thorny that the realization of system synchronization also becomes.
The single carrier transmission mode that present most of mobile communication system adopt can reduce the system interference that Doppler frequency shift brings effectively, but, therefore just there is not the transfer rate of OFDM height under the situation of same frequency resources taking because the availability of frequency spectrum is less than the OFDM height.In addition, adopting the mobile communication standard of OFDM is representative (802.20 are just formulating the stage at draft) with IEEE802.16e and IEEE802.20.The distributing sub-carrier distribution manner that IEEE802.16 has adopted adjustable OFDM (scalable OFDM) technology and has been equivalent to frequency hopping is applicable to mobile environment effectively.802.20 the Flash-OFDM technology in the motion is the cycle with the OFDM character length, the subcarrier dynamic hop has resisted Doppler frequency shift and system interference effectively.As seen, introducing frequency hopping in ofdm system is the effective ways that countermeasure system disturbs.Owing to all just adopt the subcarrier frequency hopping in the said method, there are problems such as the limited and corresponding OFDMA system user of frequency hopping frequency number number is limited, therefore need carry out comprehensive Design and optimization in conjunction with common frequency-hopping system and spread spectrum system.The present invention proposes a kind of quick frequency hopping spread spectrum (FHSS) communication system based on OFDM (OFDM).The user data of this system at first passes through direct sequence spread spectrum or coding, is multiplexed into an OFDM character then, and the corresponding relation of data and each subcarrier is every through a symbol period saltus step once in the multiplex process.Simultaneously, several symbol periods of every process, saltus step also takes place in the carrier frequency of user OFDM character.The countermeasure system dynamically mobile middle interference that produces of height at a high speed effectively of this system, the transmission rate and the user capacity of increase system.
Summary of the invention
The objective of the invention is to propose a kind of quick frequency hopping spread spectrum (FHSS) communication method, so that big capacity, high data transmission rate, dynamically high and have a communication system of strong anti-interference ability at a high speed to be provided based on OFDM.For high data rate is provided, adopted the transmission means of OFDM (OFDM); In order to improve user capacity and to reduce inter-user interference, adopted " jumping spread spectrum " scheme of direct sequence spread spectrum and frequency hopping combination; In order to resist the time selective fading that high-speed mobile is brought effectively, adopted OFDM symbol and subcarrier two-stage hopping scheme, this scheme can also be resisted obstructive interference effectively.
The quick frequency hopping spread spectrum (FHSS) communication method based on OFDM that the present invention proposes may further comprise the steps:
(1) transmitting terminal produces frequency expansion sequence, subcarrier allocation signal and frequency hop sequences according to customer requirements;
(2) user data is carried out direct sequence spread spectrum or encoding process;
(3) data after the above-mentioned processing are carried out symbol-modulated, to produce modulation signal;
(4), above-mentioned modulation signal is assigned on each way carrier wave of user communications signals, and exports after adding Cyclic Prefix according to above-mentioned subcarrier allocation signal;
(5) output signal of above-mentioned steps (4) is carried out digital to analog conversion, obtain analog signal;
(6), produce carrier frequency by the frequency synthesizer of transmitting terminal, and above-mentioned analog signal is modulated on this carrier frequency according to above-mentioned frequency hop sequences;
(7) receiving terminal receives above-mentioned signal, and after carrying out frequency-selecting by the output signal of receiving terminal frequency synthesizer, carries out dehop according to the frequency hop sequences of above-mentioned transmitting terminal;
(8) signal behind the above-mentioned dehop obtains digital signal through the conversion of analog to digital after the i.e. A/D conversion;
(9) above-mentioned digital signal is removed Cyclic Prefix;
(10), serial output is come out in the demodulation from each way carrier wave of user communications signals of above-mentioned modulation signal according to the subcarrier allocation signal identical with transmitting terminal;
(11) signal to above-mentioned serial output carries out symbol demodulation;
(12) signal behind the above-mentioned symbol demodulation is decoded or separate spread spectrum operation and obtain user data.
In the said method, modulation signal is assigned to the method on each way carrier wave of signal of communication, may further comprise the steps:
(1) according to the subcarrier allocation signal of transmitting terminal, from the transmitting terminal sub-carrier signal, select the sub-carrier signal of corresponding frequencies, the modulation signal of importing is carried out exporting after " serial/parallel " conversion;
(2) parallel data of above-mentioned output and each way carrier wave are multiplied each other respectively and sue for peace back output.
In the said method, the method with modulation signal demodulation from each way carrier wave of user communications signals is come out may further comprise the steps:
(1) each way carrier signal and corresponding subcarrier are multiplied each other, obtain the data symbol that transmits on each subcarrier;
(2), from the sub-carrier signal of receiving terminal, select the sub-carrier signal of corresponding frequencies according to the subcarrier allocation signal identical with transmitting terminal;
(3) the input data symbol on selected each way carrier wave is carried out serial output after " parallel/serial " conversion.
The quick frequency hopping spread spectrum (FHSS) communication method that the present invention proposes based on OFDM, user data at first passes through direct sequence spread spectrum or coding, be multiplexed into an OFDM character then, the corresponding relation of data and each subcarrier is every through a symbol period saltus step once in the multiplex process.Simultaneously, several symbol periods of every process, saltus step also takes place in the carrier frequency of user OFDM character.The present invention can provide big capacity, high data transmission rate, dynamically high and have a communication system of strong anti-interference ability at a high speed.
Description of drawings
Fig. 1 is the FB(flow block) that sends signal in the inventive method.
Fig. 2 is the FB(flow block) of received signal in the inventive method.
Fig. 3 is the FB(flow block) that the present invention sends the modulation of signal process sub-carriers.
Fig. 4 is the FB(flow block) of received signal process sub-carriers of the present invention demodulation.
Fig. 5 is a system bandwidth schematic diagram of the present invention.
Fig. 6 is that the single OFDM character of the present invention subcarrier is divided schematic diagram.
Fig. 7 is a transmission schematic diagram of the present invention.
Embodiment
The quick frequency hopping spread spectrum (FHSS) communication method that the present invention proposes based on OFDM, wherein signal process of transmitting block diagram as shown in Figure 1, at first transmitting terminal produces frequency expansion sequence, subcarrier allocation signal and frequency hop sequences according to customer requirements; User data is carried out direct sequence spread spectrum or encoding process; Data after handling are carried out symbol-modulated, to produce modulation signal; According to the subcarrier allocation signal, above-mentioned modulation signal is assigned on each way carrier wave of user communications signals, and adds Cyclic Prefix; This signal of communication is carried out digital to analog conversion, obtain analog signal; According to frequency hop sequences, produce carrier frequency by the frequency synthesizer of transmitting terminal, and above-mentioned analog signal is modulated on this carrier frequency.Wherein signal receiving course block diagram as shown in Figure 2, receiving terminal receives above-mentioned signal, and after carrying out frequency-selecting by the output signal of receiving terminal frequency synthesizer, carries out dehop according to the frequency hop sequences of above-mentioned transmitting terminal; Signal behind the dehop obtains digital signal through the conversion of analog to digital after the i.e. A/D conversion; This digital signal is removed Cyclic Prefix; According to the subcarrier allocation signal identical, the demodulation from each way carrier wave of user communications signals of above-mentioned modulation signal is come out serial output with transmitting terminal; Signal to serial output carries out symbol demodulation; Signal behind the symbol demodulation decoded or separate spread spectrum operation obtain user data.
In the said method, modulation signal is assigned to the method on each way carrier wave of signal of communication, its FB(flow block) as shown in Figure 3, subcarrier allocation signal according to transmitting terminal, from the transmitting terminal sub-carrier signal, select the sub-carrier signal of corresponding frequencies, the modulation signal of importing is carried out exporting after " serial/parallel " conversion; The parallel data of above-mentioned output and each way carrier wave are multiplied each other respectively and sue for peace back output.
In the said method, with the method that modulation signal demodulation from each way carrier wave of user communications signals is come out, its FB(flow block) multiplies each other each way carrier signal and corresponding subcarrier as shown in Figure 4, obtains the data symbol that transmits on each subcarrier; According to the subcarrier allocation signal identical, from the sub-carrier signal of receiving terminal, select the sub-carrier signal of corresponding frequencies with transmitting terminal; Input data symbol on selected each way carrier wave is carried out serial output after " parallel/serial " conversion.
In order to explain particular content of the present invention and function, at first sketch ofdm system.Ofdm system sends user data through walking abreast behind the serial to parallel conversion on the plurality of sub carrier wave of a frequency band (being labeled as W), the parallel data cell that sends is the OFDM character, and subcarrier bandwidth is Δ F, and the OFDM character data is partly long to be T
d, the Cyclic Prefix of adding is long to be T
a, the character total length is designated as T.At receiving terminal, the demodulation of OFDM character becomes the user data of reception behind parallel serial conversion.General when comprising a plurality of user in the system, can adopt the mode that adds spreading code or orthogonal frequency division multiplexing multiple access (OFDMA) to carry out multiple access and insert.
The present invention is based on a kind of quick jumping spread spectrum system of OFDM.The total frequency band of system is U=NW, and N is an integer.Because the shared bandwidth of each OFDM character is W, be cycle saltus step in the N sub-frequency bands with some OFDM character lengths so allow to send data.Simultaneously, in each OFDM character cycle, saltus step also takes place in the subcarrier of OFDM character carrying data.For the frequency of transmission data, such structural support fast frequency changes, so the present invention is a kind of two-stage quick frequency hopping system.In order further to reduce interference and to support a plurality of users, user data carried out spread spectrum or coding before entering OFDM two-stage hopping structure.The sequence association design of frequency expansion sequence and OFDM two-stage frequency hopping makes the interference of entire system drop to minimum.
Below in conjunction with accompanying drawing detail of the present invention and execution mode are described in further detail.
Seeing also Fig. 1, is sender structural representation of the present invention.At first, user data is carried out direct sequence spread spectrum or encoding process, both optional one.If select to carry out encoding process, can carry out interleaving treatment thereafter.Certainly, if select spread spectrum and wish further to reduce error probability, can before spread spectrum, add chnnel coding.Then, the data of output enter the symbol-modulated operation, produce such as BPSK QPSK, symbols such as MQAM.The symbols streams of this serial enters subcarrier-modulated.Subcarrier-modulated optionally is assigned to the user data character of importing on each subcarrier according to the subcarrier allocation signal that the subcarrier allocation operation provides.The work that we finish the subcarrier allocator among the figure is called " interior frequency hopping ".Afterwards, the signal of output will add Cyclic Prefix, and carry out the conversion (D/A) of digital to analogy.Output signal then is modulated on the carrier frequency of frequency synthesis output.The generation of carrier frequency is by the decision of frequency hop sequences generating run, and we are referred to as " outer frequency hopping ".From the structure of sender as can be seen, spread spectrum, interior frequency hopping, outer frequency hopping all need the support of frequency expansion sequence or frequency hop sequences, from the angle of system, need three kinds of sequences of combined optimization to reach the optimum of overall system performance.This feature dots in the drawings.
Seeing also Fig. 2, is receiver structure schematic diagram of the present invention.At first carry out dehop after the output signal frequency-selecting of received signal and frequency synthesis operation, frequency hop sequences is identical with the outer frequency hop sequences of making a start.Output signal is removed Cyclic Prefix through conversion (A/D conversion) back of analog to digital, enters subcarrier demodulator.The subcarrier allocation signal that subcarrier demodulator provides according to subcarrier allocation operation, with user data from the subcarrier of correspondence by selecting after the parallel/serial conversion demodulation to get off and the symbol demodulation module is exported in serial.The symbol demodulation module is corresponding with the symbol-modulated module, symbols such as demodulation BPSK, QPSK, MQAM.The data based situation of making a start of output has two kinds of selections, and a kind of is to separate spread spectrum, and another is the back decoding that deinterleaves.If what transmitting terminal adopted is the mode that adds chnnel coding before the direct sequence spread spectrum, then separate the corresponding channel-decoding of the laggard row of spread spectrum.
Seeing also Fig. 3, is the schematic diagram of system of the present invention sub-carriers modulation.The signal of input has two, is respectively the user data symbol and the subcarrier allocation signal of serial.The subcarrier allocation signal is produced by the subcarrier allocation operation, in fact is exactly frequency hop sequences (interior frequency hop sequences).The user data character becomes parallel data after entering " selecting serial/parallel conversion " structure, and corresponding relation is by the subcarrier allocation signal deciding.If user's parallel data is less than sub-carrier number, then in the place's zero padding of residue subcarrier.Such as 128 subcarriers are arranged, only utilize wherein 112, need zero padding on then remaining 16 subcarriers.Parallel data is modulated on each way carrier wave, exports behind all signal plus.Subcarrier maker among the figure generates each way carrier wave.
Seeing also Fig. 4, is the schematic diagram of system of the present invention sub-carriers demodulation.The signal of input has two, is respectively OFDM character and subcarrier allocation signal after the prefix.The subcarrier allocation signal is by producing with the subcarrier allocation operation of making a start identical.The OFDM character of input at first restores parallel data symbol through behind each way carrier wave demodulation, and user data symbol obtains user data symbol after passing through " selecting parallel/serial conversion " again.Select the form of parallel/serial conversion identical, the actual dehop function of having finished interior frequency hopping of this step with transmitting terminal.At last, the user data symbol serial of generation output.
Enumerate a design example below, so that further specify the function of system.
Seeing also Fig. 5, is native system bandwidth schematic diagram.System bandwidth is U, is divided into the N sub-frequency bands, and the width of each frequency band is W, and the carrier frequency of each sub-band is f
0, f
1..., f
N-1Because the frequency band of single OFDM character is W, so system allows the saltus step on this N frequency of OFDM character.In addition, Fig. 6 is the subcarrier dividing condition of single OFDM character, and the bandwidth of OFDM character is W among the figure, and the bandwidth of subcarrier is Δ F, and the number of subcarrier is W/ Δ F.It is unit generation saltus step with the character cycle that system allows the subcarrier of user data correspondence.
Seeing also Fig. 7, is transmission schematic diagram of the present invention, and abscissa is the time, and ordinate is a frequency.The sub-band of system is with period T
HFor unit generation saltus step, in each period T
HIn, all OFDM characters transmit in fixing sub-band.But the subcarrier of user data correspondence then is unit generation saltus step with the character cycle in the OFDM character.
Provide concrete parameter below.System adopts the 10MHz bandwidth, is divided into 8 sub-frequency bands, each sub-band bandwidth 1.25MHz.The sub-band jumping figure is that per second 1000 is jumped, and then the cycle of every jumping is 1ms, 8 of the defeated OFDM characters of every jump set, and each OFDM character cycle is 125us, sub-carrier number is 128 and all utilizes that the about 10kHz. modulation system of each subcarrier bandwidth adopts QPSK.Spread spectrum adopts 32 Walsh sequence to carry out direct sequence spread spectrum.Then system user capacity is 32 * 8=256, message transmission rate 64kbps.
Claims (3)
1, a kind of quick frequency hopping spread spectrum (FHSS) communication method based on OFDM is characterized in that this method may further comprise the steps:
(1) transmitting terminal produces frequency expansion sequence, subcarrier allocation signal and frequency hop sequences according to customer requirements;
(2) user data is carried out direct sequence spread spectrum or encoding process;
(3) data after the above-mentioned processing are carried out symbol-modulated, to produce modulation signal;
(4), above-mentioned modulation signal is assigned on each way carrier wave of user communications signals, and exports after adding Cyclic Prefix according to above-mentioned subcarrier allocation signal;
(5) output signal of above-mentioned steps (4) is carried out digital to analog conversion, obtain analog signal;
(6), produce carrier frequency by the frequency synthesizer of transmitting terminal, and above-mentioned analog signal is modulated on this carrier frequency according to above-mentioned frequency hop sequences;
(7) receiving terminal receives above-mentioned signal, and after carrying out frequency-selecting by the output signal of receiving terminal frequency synthesizer, carries out dehop according to the frequency hop sequences of above-mentioned transmitting terminal;
(8) signal behind the above-mentioned dehop obtains digital signal through after the conversion of analog to digital;
(9) above-mentioned digital signal is removed Cyclic Prefix;
(10), serial output is come out in the demodulation from each way carrier wave of user communications signals of above-mentioned modulation signal according to the subcarrier allocation signal identical with transmitting terminal;
(11) signal to above-mentioned serial output carries out symbol demodulation;
(12) signal behind the above-mentioned symbol demodulation is decoded or separate spread spectrum operation and obtain user data.
2, the method for claim 1 is characterized in that the method on each the way carrier wave that modulation signal is assigned to signal of communication described in the step (4), may further comprise the steps:
(1) according to the subcarrier allocation signal of transmitting terminal, from the transmitting terminal sub-carrier signal, select the sub-carrier signal of corresponding frequencies, the modulation signal of importing is carried out exporting after " serial/parallel " conversion;
(2) parallel data of above-mentioned output and each way carrier wave are multiplied each other respectively and sue for peace back output.
3, the method for claim 1 is characterized in that the method that modulation signal demodulation from each way carrier wave of user communications signals is come out described in the step (10), may further comprise the steps:
(1) each way carrier signal and corresponding subcarrier are multiplied each other, obtain the data symbol that transmits on each subcarrier;
(2), from the sub-carrier signal of receiving terminal, select the sub-carrier signal of corresponding frequencies according to the subcarrier allocation signal identical with transmitting terminal;
(3) the input data symbol on selected each way carrier wave is carried out serial output after " parallel/serial " conversion.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101547020B (en) * | 2009-04-15 | 2012-05-23 | 北京航空航天大学 | Method for realizing data links of unmanned aerial vehicle for multilevel orthogonal coding spectrum spread |
| CN102638436A (en) * | 2012-04-28 | 2012-08-15 | 南京大学 | Method and system for realizing high-security fast frequency-hopping transmission |
| CN101635578B (en) * | 2009-08-18 | 2013-01-02 | 中国科学院微电子研究所 | Two-stage capture method and two-stage capture device for frequency hopping spread spectrum (FHSS) communication system |
| CN104780133A (en) * | 2014-12-26 | 2015-07-15 | 北京航天科工世纪卫星科技有限公司 | Frequency hopping anti-interception method in orthogonal frequency division multiplexing (OFDM) system |
| CN112152664A (en) * | 2020-09-25 | 2020-12-29 | 中国电子科技集团公司第五十四研究所 | Anti-multipath anti-interference signal sending method based on time division multiple access |
| CN112152663A (en) * | 2020-09-25 | 2020-12-29 | 中国电子科技集团公司第五十四研究所 | Anti-multipath anti-interference signal receiving method based on time division multiple access |
| CN112737997A (en) * | 2020-12-25 | 2021-04-30 | 上海微波技术研究所（中国电子科技集团公司第五十研究所） | Navigation communication integrated signal waveform construction method and system based on FH-OFDM |
| CN113131966A (en) * | 2021-04-15 | 2021-07-16 | 上海金卓科技有限公司 | Data sending and receiving method and device for wireless communication |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101547020B (en) * | 2009-04-15 | 2012-05-23 | 北京航空航天大学 | Method for realizing data links of unmanned aerial vehicle for multilevel orthogonal coding spectrum spread |
| CN101635578B (en) * | 2009-08-18 | 2013-01-02 | 中国科学院微电子研究所 | Two-stage capture method and two-stage capture device for frequency hopping spread spectrum (FHSS) communication system |
| CN102638436A (en) * | 2012-04-28 | 2012-08-15 | 南京大学 | Method and system for realizing high-security fast frequency-hopping transmission |
| CN102638436B (en) * | 2012-04-28 | 2014-07-30 | 南京大学 | Method and system for realizing high-security fast frequency-hopping transmission |
| CN104780133A (en) * | 2014-12-26 | 2015-07-15 | 北京航天科工世纪卫星科技有限公司 | Frequency hopping anti-interception method in orthogonal frequency division multiplexing (OFDM) system |
| CN104780133B (en) * | 2014-12-26 | 2018-03-16 | 北京航天科工世纪卫星科技有限公司 | A kind of frequency hopping anti-intercepting and capturing method in ofdm system |
| CN112152664A (en) * | 2020-09-25 | 2020-12-29 | 中国电子科技集团公司第五十四研究所 | Anti-multipath anti-interference signal sending method based on time division multiple access |
| CN112152663A (en) * | 2020-09-25 | 2020-12-29 | 中国电子科技集团公司第五十四研究所 | Anti-multipath anti-interference signal receiving method based on time division multiple access |
| CN112152664B (en) * | 2020-09-25 | 2021-07-27 | 中国电子科技集团公司第五十四研究所 | Anti-multipath anti-interference signal sending method based on time division multiple access |
| CN112152663B (en) * | 2020-09-25 | 2021-08-31 | 中国电子科技集团公司第五十四研究所 | Anti-multipath anti-interference signal receiving method based on time division multiple access |
| CN112737997A (en) * | 2020-12-25 | 2021-04-30 | 上海微波技术研究所（中国电子科技集团公司第五十研究所） | Navigation communication integrated signal waveform construction method and system based on FH-OFDM |
| CN112737997B (en) * | 2020-12-25 | 2022-09-13 | 上海微波技术研究所（中国电子科技集团公司第五十研究所） | Navigation communication integrated signal waveform construction method and system based on FH-OFDM |
| CN113131966A (en) * | 2021-04-15 | 2021-07-16 | 上海金卓科技有限公司 | Data sending and receiving method and device for wireless communication |
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