CN102710574A - Broadband wireless transmission method and system, transmitter and method, receiver and method - Google Patents
Broadband wireless transmission method and system, transmitter and method, receiver and method Download PDFInfo
- Publication number
- CN102710574A CN102710574A CN2012101712339A CN201210171233A CN102710574A CN 102710574 A CN102710574 A CN 102710574A CN 2012101712339 A CN2012101712339 A CN 2012101712339A CN 201210171233 A CN201210171233 A CN 201210171233A CN 102710574 A CN102710574 A CN 102710574A
- Authority
- CN
- China
- Prior art keywords
- module
- frequency
- serial
- mrow
- signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims abstract description 36
- 230000005540 biological transmission Effects 0.000 title claims abstract description 34
- 238000006243 chemical reaction Methods 0.000 claims abstract description 86
- 125000004122 cyclic group Chemical group 0.000 claims abstract description 31
- 238000013507 mapping Methods 0.000 claims abstract description 26
- 230000003321 amplification Effects 0.000 claims description 16
- 238000003780 insertion Methods 0.000 claims description 16
- 230000037431 insertion Effects 0.000 claims description 16
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 16
- 238000012545 processing Methods 0.000 claims description 14
- 230000001360 synchronised effect Effects 0.000 claims description 11
- 230000001427 coherent effect Effects 0.000 claims description 8
- 230000033001 locomotion Effects 0.000 abstract description 6
- 239000000969 carrier Substances 0.000 description 11
- 238000004891 communication Methods 0.000 description 11
- 238000005516 engineering process Methods 0.000 description 8
- 238000004088 simulation Methods 0.000 description 5
- 241000209094 Oryza Species 0.000 description 4
- 235000007164 Oryza sativa Nutrition 0.000 description 4
- 238000005562 fading Methods 0.000 description 4
- 235000009566 rice Nutrition 0.000 description 4
- 238000001514 detection method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Images
Landscapes
- Mobile Radio Communication Systems (AREA)
Abstract
The invention discloses a broadband wireless transmission method and a broadband wireless transmission system, a transmitter and a method, as well as a receiver and a method under high-speed movement environment. High-speed baseband signals serially input by a transmitting end are converted to be low-speed parallel baseband signals by series-to-parallel conversion, then MFDM (Multi-Frequency Difference Modulation) mapping is conducted, time-domain baseband signals are converted to be frequency-domain baseband signals which are converted to be time domain signals by IFFT (Inverse Fast Fourier Transform), a CP (Cyclic Prefix) is inserted and the parallel-to-series conversion is conducted, then the signals are sent to a radio frequency module and then are sent to an antenna to be transmitted, a receiving end converts the signals received by the antenna into digital baseband signals through the radio frequency module, the position synchronization is realized by a synchronization module, then the signals are subjected to series-to-parallel conversion, the CP is removed, the signals are sent to an FFT (Fast Fourier Transform) module and are converted to be frequency-domain baseband signals, then the MFDM mapping is removed, and time-domain baseband information is recovered. The Doppler frequency deviation caused by intersymbol interference and high-speed movement due to multipath propagation can be overcome, and the hardware structure of the receiver is simplified greatly due to the avoidance of channel estimation.
Description
Technical Field
The present invention relates to the field of broadband wireless communication, and in particular, to a method and a system for broadband wireless transmission in a high-speed mobile environment, a transmitter and a method, and a receiver and a method.
Background
With the economic development and the technological progress, people frequently travel by public transport means such as long-distance buses, subways, trains and the like, the running speed of the transport means is faster and faster, the highest speed of the buses on expressways can reach 120km/h, the running speed of the subways generally reaches 80km/h, the speed of high-speed trains can reach more than 250km/h, and the speed of maglev trains can reach 600 km/h. In the high-speed running of the traffic vehicle, how to provide better and faster services such as internet surfing, mail receiving and sending and the like for passengers in transit and how to transmit information and driving states in the vehicle to the ground in real time to ensure driving safety all put forward higher requirements on a broadband wireless transmission technology.
The broadband wireless transmission under the high-speed moving condition mainly solves the problem of double high, namely high-speed moving and high-speed data transmission. At present, the technology of applying various companies at home and abroad to a vehicle-ground broadband wireless communication system mainly comprises the following steps: the physical layers of WiFi, WiMAX and LTE all adopt Orthogonal Frequency Division Multiplexing (OFDM) transmission technology. The traffic vehicle runs in a complicated and changeable geographic environment at a high speed, the propagation environment of radio communication radio waves is very complicated, the propagation of the radio waves is the superposition result of various reflection and direct radiation, the multipath effect is obvious, and the received signals can generate serious Doppler frequency shift and expansion due to the high-speed motion of the vehicle. The OFDM technology can effectively combat intersymbol interference caused by multipath propagation by means of cyclic prefix, and the main effects of high-speed mobility are as follows:
1. inter-subcarrier Interference problem (ICI: Inter-Carrier Interference)
The OFDM technology has a fatal disadvantage that the whole OFDM system is extremely strict in orthogonality between subcarriers, any small carrier frequency offset destroys the orthogonality between the subcarriers to cause ICI, and phase noise also causes rotation and diffusion of symbol constellation points to form ICI. This is not the case with single carrier systems, and the phase noise and carrier frequency offset merely reduce the received SNR and do not cause interference with each other. When the vehicle moves at a high speed, Doppler shift and Doppler spread are obvious, so that orthogonality among subcarriers of the OFDM system is damaged, and the performance of the OFDM system is sharply reduced due to interference among the subcarriers.
In WiFi, WiMAX and LTE, ICI influence is reduced by means of subcarrier spacing, generally, frequency offset can be ignored when the subcarrier spacing is less than 2%, certain influence is caused between 2% and 4%, and the influence is large when the frequency offset exceeds 4%.
2. Channel estimation problem
The sub-carrier of OFDM adopts PSK modulation or QAM modulation mode, the receiving end adopts coherent detection mode, and the coherent detection requires accurate channel information. Due to the high-speed movement of vehicles and the change of geographic environment, channel parameters of a wireless transmission channel change rapidly along with time, accurate channel estimation is difficult to carry out, the error of the existing channel estimation algorithm increases along with the increase of the movement speed of the vehicles, and the error is also the main reason for limiting OFDM communication between vehicles and the ground.
In the conventional channel estimation technology based on pilot frequency adopted in WiFi, WiMAX and LTE, under the condition of high-speed movement, the transmission channel changes rapidly, the accuracy of channel estimation is reduced, and the communication performance is reduced sharply.
Due to the reasons, the performances of the WiFi, WiMAX and LTE all decline with the increase of the moving speed, the WiFi supports the moving speed of 80Km/h at the highest, the transmission rate is reduced to about 10Mbps, the WiMAX has the transmission rate of about 8Mbps at the moving speed of 120Km/h, and the LTE can provide the access service of about 100kbps for the high-speed moving user at 350 Km/h.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a broadband wireless transmission method and system, a transmitter and method, a receiver and a method under a high-speed mobile environment, which can overcome intersymbol interference caused by multipath propagation and Doppler frequency offset caused by high-speed mobile, and greatly simplify a receiving hardware structure because channel estimation is not needed.
The principle of the invention is as follows: high-speed baseband signals input in series at a transmitting end are converted into low-speed parallel baseband signals through serial-to-parallel conversion, then multi-frequency differential modulation (MFDM) mapping is carried out, time domain baseband signals are converted into frequency domain baseband signals, the frequency domain baseband signals are converted back to a time domain through Inverse Fast Fourier Transform (IFFT), and the time domain baseband signals are transmitted to an antenna to be transmitted after Cyclic Prefix (CP) insertion and parallel-to-serial conversion; the receiving end converts the antenna receiving signal into a digital baseband signal through a radio frequency module, realizes bit frame synchronization through a synchronization module, then carries out serial-parallel conversion and removes a Cyclic Prefix (CP), and sends the digital baseband signal to a Fast Fourier Transform (FFT) module to be converted into a frequency domain baseband signal, and then carries out demapping through multi-frequency differential modulation (MFDM) to restore time domain baseband information.
The invention discloses a broadband wireless transmission method, which comprises the following steps:
the method comprises the following steps: converting a digital baseband signal to be transmitted of a user, which is input in series, into a parallel digital baseband signal with a lower rate according to the modulation order of an OFDM subcarrier;
step two: performing MFDM modulation mapping on the baseband signals after serial-parallel conversion, and converting time domain baseband signals into baseband signals of which the frequency domain is formed by combining subcarrier frequencies;
step three: the frequency domain signal of one OFDM symbol is converted into a time domain signal of the OFDM symbol through IFFT;
step four: inserting CP in front of OFDM symbol and making parallel-serial conversion;
step five: modulating the OFDM baseband signal to a radio frequency band, and transmitting the signal to an antenna after power amplification;
step six: OFDM radio frequency signals received by an antenna are converted into digital baseband signals after being amplified and frequency mixing;
step seven: the received baseband signals are subjected to synchronous processing to realize bit frame synchronization;
step eight: after the baseband signals are processed synchronously, serial-parallel conversion is carried out and CP is removed;
step nine: performing FFT on the baseband signal without the CP, and converting the baseband signal of the time domain into a baseband signal of the frequency domain;
step ten: and demodulating the information carried by the OFDM subcarrier frequency by using a noncoherent demodulation mode according to the MFDM modulation mapping table.
The invention relates to a broadband wireless transmitting method, which comprises the following steps:
the method comprises the following steps: converting a digital baseband signal to be transmitted of a user, which is input in series, into a parallel digital baseband signal with a lower rate according to the modulation order of an OFDM subcarrier;
step two: performing MFDM modulation mapping on the baseband signals after serial-parallel conversion, and converting time domain baseband signals into baseband signals of which the frequency domain is formed by combining subcarrier frequencies;
step three: the frequency domain signal of one OFDM symbol is converted into a time domain signal of the OFDM symbol through IFFT;
step four: inserting CP in front of OFDM symbol and making parallel-serial conversion;
step five: modulating the OFDM baseband signal to a radio frequency band, and sending the modulated OFDM baseband signal to an antenna for transmitting after power amplification.
The invention relates to a broadband wireless receiving method, which comprises the following steps:
the method comprises the following steps: OFDM radio frequency signals received by an antenna are converted into digital baseband signals after being amplified and frequency mixing;
step two: the received baseband signals are subjected to synchronous processing to realize bit frame synchronization;
step three: after the baseband signals are processed synchronously, serial-parallel conversion is carried out and CP is removed;
step four: performing FFT (fast Fourier transform) on the baseband signal without the CP, and converting the baseband signal of the time domain into a baseband signal of the frequency domain;
step five: and demodulating the information carried by the OFDM subcarrier frequency by using a noncoherent demodulation mode according to the MFDM modulation mapping table.
The invention relates to a broadband wireless transmission system, which comprises a transmitting end and a receiving end, wherein the transmitting end is connected with the receiving end;
the transmitting end comprises a coding module, a transmitting serial-parallel conversion module, an MFDM modulation module, an IFFT module, a CP insertion module, a parallel-serial conversion module and a transmitting radio frequency module; wherein,
the coding module: encoding a signal to be transmitted by a user;
a transmitting serial-parallel conversion module: converting the serial digital baseband signals output by the coding module into parallel digital baseband signals with lower speed according to the modulation order of the OFDM subcarrier;
MFDM modulation module: the base band signal converted by the transmitting serial-parallel conversion module is subjected to MFDM modulation mapping, and a time domain base band signal is converted into a base band signal of which the frequency domain is formed by combining subcarrier frequencies;
an IFFT module: converting the frequency domain signal of one OFDM symbol output by the MFDM modulation module into a time domain signal of the OFDM symbol;
and a CP insertion module: inserting CP in front of OFDM symbol output by IFFT module;
a parallel-serial conversion module: performing parallel-serial conversion on the signal output by the CP insertion module;
a transmitting radio frequency module: modulating the OFDM baseband signal output by the parallel-serial conversion module to a radio frequency band, and transmitting the modulated OFDM baseband signal to an antenna for transmission after power amplification;
the receiving end comprises a receiving radio frequency module, a synchronization module, a receiving serial-parallel conversion module, a CP removing module, an FFT module, an MFDM demodulation module and a decoding module; wherein,
a receiving radio frequency module: the OFDM radio frequency signal received by an antenna is converted into a digital baseband signal after amplification and frequency mixing;
a synchronization module: carrying out synchronous processing on the baseband signals received by the receiving radio frequency module to realize bit frame synchronization;
a receive serial-to-parallel conversion module: performing serial-parallel conversion on the baseband signal output by the synchronization module;
and a CP removing module: removing CP from the baseband signal output by the receiving serial-parallel conversion module;
an FFT module: performing FFT on the baseband signal without the CP, and converting the baseband signal of the time domain into a baseband signal of the frequency domain;
MFDM demodulation module: demodulating information carried by OFDM subcarrier frequency by using a noncoherent demodulation mode according to the MFDM modulation mapping table;
a decoding module: and restoring the demodulation information output by the MFDM demodulation module into a signal transmitted by a user.
The invention relates to a broadband wireless transmitter, which is characterized in that: the system mainly comprises a coding module, a transmitting serial-parallel conversion module, an MFDM modulation module, an IFFT module, a CP insertion module, a parallel-serial conversion module and a transmitting radio frequency module; wherein,
the coding module: encoding a signal to be transmitted by a user;
a transmitting serial-parallel conversion module: converting the serial digital baseband signals output by the coding module into parallel digital baseband signals with lower speed according to the modulation order of the OFDM subcarrier;
MFDM modulation module: the base band signal converted by the transmitting serial-parallel conversion module is subjected to MFDM modulation mapping, and a time domain base band signal is converted into a base band signal of which the frequency domain is formed by combining subcarrier frequencies;
an IFFT module: converting the frequency domain signal of one OFDM symbol output by the MFDM modulation module into a time domain signal of the OFDM symbol;
and a CP insertion module: inserting CP in front of OFDM symbol output by IFFT module;
a parallel-serial conversion module: performing parallel-serial conversion on the signal output by the CP insertion module;
a transmitting radio frequency module: and modulating the OFDM baseband signal output by the parallel-serial conversion module to a radio frequency band, and transmitting the modulated OFDM baseband signal to an antenna for transmission after power amplification.
The invention relates to a broadband wireless receiver, which is characterized in that: the device mainly comprises a receiving radio frequency module, a synchronization module, a receiving serial-parallel conversion module, a CP removing module, an FFT module, an MFDM demodulation module and a decoding module; wherein,
a receiving radio frequency module: the OFDM radio frequency signal received by an antenna is converted into a digital baseband signal after amplification and frequency mixing;
a synchronization module: carrying out synchronous processing on the baseband signals received by the receiving radio frequency module to realize bit frame synchronization;
a receive serial-to-parallel conversion module: performing serial-parallel conversion on the baseband signal output by the synchronization module;
and a CP removing module: removing CP from the baseband signal output by the receiving serial-parallel conversion module;
an FFT module: performing FFT on the baseband signal without the CP, and converting the baseband signal of the time domain into a baseband signal of the frequency domain;
MFDM demodulation module: demodulating information carried by OFDM subcarrier frequency by using a noncoherent demodulation mode according to the MFDM modulation mapping table;
a decoding module: and restoring the demodulation information output by the MFDM demodulation module into a signal transmitted by a user.
Compared with the prior art, the invention has the following characteristics:
(1) the OFDM technique using the inserted Cyclic Prefix (CP) overcomes the intersymbol interference caused by multipath propagation. According to the time delay statistical characteristic of the transmission environment, the length of the cyclic prefix of the OFDM symbol is reasonably selected to be larger than the maximum time delay expansion of the channel, so that the multipath component of one OFDM symbol can not cause interference to the next symbol.
(2) Channel estimation is not required with non-coherent detection methods. The modulation mode of the subcarrier in the OFDM is PSK or QAM, coherent demodulation is needed during receiving, and accurate channel information is needed to recover the amplitude and the phase. The OFDM-MFDM adopts a subcarrier MFDM modulation technology, the frequency difference of subcarriers is used for carrying information, a receiving end can adopt a noncoherent demodulation mode without channel information and carrier phase information, namely, channel estimation is not required in a high-speed mobile environment, and compared with the OFDM, the complexity of the hardware of a receiver can be greatly simplified.
(3) And the Doppler frequency offset is overcome by adopting subcarrier differential modulation. Because the non-coherent demodulation MFDM modulation technology is adopted, the information is transmitted by utilizing the subcarrier frequency difference, and the influence of Doppler frequency offset on a wireless transmission system can be ignored.
Drawings
Fig. 1 is a block diagram of a broadband wireless transmission system (including a transmitting end and a receiving end).
FIG. 2 is a schematic structure diagram of OFDM-5 FDM.
FIG. 3 is a plot of the received bit error rate for OFDM-5FDM in the Gaussian channel.
FIG. 4 shows the received bit error rate for OFDM-5FDM in the Rice time varying channel.
FIG. 5 is a plot of the OFDM-5FDM received bit error rate for a multipath time varying channel.
Detailed Description
A broadband wireless transmission method in a high-speed mobile environment, as shown in fig. 1, includes the following steps:
at the transmitting end.
(1) Serial-to-parallel conversion of baseband signals
The information to be transmitted by the user is converted into a digital baseband signal to be input in serial after being coded, and the digital baseband signal is converted into a parallel digital baseband signal with lower speed to be output according to the modulation order of OFDM.
The serial-to-parallel conversion is the same as that in the conventional OFDM, and actually relates to the modulation order of the subcarrier, that is, the information bit carried by the subcarrier. If the conventional OFDM subcarriers are modulated by 64QAM, each subcarrier carries 6-bit information, and each 6-bit group of serial information needs to be grouped during serial-parallel conversion, each subcarrier of the MFDM modulation mode of the invention carries M-1bit information, and each M-1bit group of serial information needs to be grouped during serial-parallel conversion.
(2) MFDM modulation mapping
The MFDM modulates baseband information by frequency difference of a plurality of subcarriers, groups N used subcarriers of the OFDM into one group of M adjacent subcarriers, where N is an integer multiple of M, and may allocate each subcarrier group to different users to implement OFDMA, or allocate all subcarrier groups to one user to implement high-speed data transmission. For the sub-carriers in the packet, "1" indicates that the sub-carrier is actually used in transmission (i.e., the transmission power corresponding to the frequency is non-zero), "0" indicates that the sub-carrier is not used in transmission (i.e., the transmission power corresponding to the frequency is zero), "11" or "00" (i.e., no change) for two adjacent sub-carriers indicates that data "0" is transmitted, and "10" or "01" (i.e., change) for two adjacent sub-carriers indicates that data "1" is transmitted. Thus, an OFDM symbol can be modulated with (M-1) bit information by using the difference between adjacent frequencies of a group of M sub-carriersInformation, band utilization of
The band utilization increases with M, but a baseband modulation table with M too large becomes complex. From another perspective, the frequency combinations of each group of actually used subcarriers are common
In whichThe case of (i.e. zero transmit power for all frequencies in the packet) indicates that the packet is not used and can be allocated to a user so that it cannot be used to convey user data, so the choice of subcarrier depending on the actual use in the packet can only indicate 2MPossible in-1, and thus only (M-1) bits can be transferred. MFDM modulation is from 2M-1 is selected from 2M-1 frequency combination forms a baseband modulation table, mapping the serial-to-parallel converted baseband signal to a frequency combination of subcarriers, i.e. a time-domain basisThe band signal is converted into a baseband signal whose frequency domain is composed of a combination of subcarrier frequencies.
(2) IFFT operation
The frequency domain baseband signal modulated by the MFDM sends the frequency domain signal of one OFDM symbol to an IFFT module for operation and is converted into a time domain signal of the OFDM symbol.
(3) Inserting CP and parallel-to-serial conversion
In practical communication systems, the channel receives signals that are the sum of signals from different transmission paths, thus creating multipath effects, causing inter-symbol interference (ISI) and ICI, which severely affect the information transmission rate. The CP signal is filled in front of the OFDM symbol, and as long as the multipath propagation delay is less than the CP time length, ISI (inter-symbol interference) cannot be generated in the demodulation process.
(4) Radio frequency conversion
Modulating the OFDM baseband signal to a radio frequency band, and sending the modulated OFDM baseband signal to an antenna for transmitting after power amplification.
At the receiving end.
(5) Radio frequency conversion
OFDM radio frequency signals received by the antenna are converted into digital baseband signals after being processed by low-noise small-signal amplification, frequency mixing and the like.
(6) Receive synchronization
The received baseband signals are processed by a synchronous processing module to realize carrier synchronization, the oscillation frequency of a receiver needs to be in the same frequency and phase with the transmitted carrier, sample value synchronization is realized, the sampling frequencies of a receiving end and a transmitting end are consistent, OFDM symbol synchronization is realized, and the IFFT and FFT start-stop moments are consistent.
(7) Serial-to-parallel conversion and CP removal
After synchronous processing, the baseband signals are subjected to serial-parallel conversion, CP is removed, and the baseband signals are sent to an FFT module for time domain to frequency domain conversion.
(8) FFT operation
The baseband signals after synchronization and CP removal processing are sent to an FFT module for Fourier transformation, and the baseband signals of the time domain are converted into baseband signals of the frequency domain.
(9) MFDM demodulation
And demodulating the information carried by the OFDM subcarrier frequency by using a noncoherent demodulation mode according to the MFDM modulation mapping table without channel estimation, and then restoring the information into user information by decoding.
The broadband wireless transmission system designed according to the method in the high-speed mobile environment, as shown in fig. 1, includes a transmitting end and a receiving end. Wherein:
the transmitting end, namely the broadband wireless transmitter, mainly comprises a coding module, a transmitting serial-parallel conversion module, an MFDM modulation module, an IFFT module, a CP insertion module, a parallel-serial conversion module and a transmitting radio frequency module.
The coding module: encoding a signal to be transmitted by a user;
a transmitting serial-parallel conversion module: converting the serial digital baseband signals output by the coding module into parallel digital baseband signals with lower speed according to the modulation order of the OFDM subcarrier;
MFDM modulation module: the base band signal converted by the transmitting serial-parallel conversion module is subjected to MFDM modulation mapping, and a time domain base band signal is converted into a base band signal of which the frequency domain is formed by combining subcarrier frequencies;
an IFFT module: converting the frequency domain signal of one OFDM symbol output by the MFDM modulation module into a time domain signal of the OFDM symbol;
and a CP insertion module: inserting CP in front of OFDM symbol output by IFFT module;
a parallel-serial conversion module: performing parallel-serial conversion on the signal output by the CP insertion module;
a transmitting radio frequency module: modulating the OFDM baseband signal output by the parallel-serial conversion module to a radio frequency band, and transmitting the modulated OFDM baseband signal to an antenna for transmission after power amplification;
the receiving end, namely the broadband wireless receiver, mainly comprises a receiving radio frequency module, a synchronization module, a receiving serial-parallel conversion module, a CP removing module, an FFT module, an MFDM demodulation module and a decoding module.
A receiving radio frequency module: the OFDM radio frequency signal received by an antenna is converted into a digital baseband signal after amplification and frequency mixing;
a synchronization module: carrying out synchronous processing on the baseband signals received by the receiving radio frequency module to realize bit frame synchronization;
a receive serial-to-parallel conversion module: performing serial-parallel conversion on the baseband signal output by the synchronization module;
and a CP removing module: removing CP from the baseband signal output by the receiving serial-parallel conversion module;
an FFT module: performing FFT on the baseband signal without the CP, and converting the baseband signal of the time domain into a baseband signal of the frequency domain;
MFDM demodulation module: demodulating information carried by OFDM subcarrier frequency by using a noncoherent demodulation mode according to the MFDM modulation mapping table;
a decoding module: and restoring the demodulation information output by the MFDM demodulation module into a signal transmitted by a user.
The present invention is further illustrated by the following specific examples. For the OFDM-MFDM modulation system, 256 OFDM subcarriers are taken, wherein 160 subcarriers are used for transmitting information, and an OFDM-5FDM structure is shown in FIG. 2. For 160 used subcarriers of OFDM, the subcarriers are grouped into 5 groups, which can be divided into 32 groups, and the frequency combination of each group of 5 subcarriers is common:
it can be seen that each group of subcarriers can transmit 4-bit information at most, i.e. 16 combinations are selected from 31 frequency combinations, and the 5FDM modulation table is shown in table 1. Wherein f is1f2f3f4f5For a set of 5 sub-carrier frequencies, "1" indicates that the frequency exists, "0" indicates that the frequency does not exist, two adjacent sub-carriers are "11" or "00" to indicate that data "0" is transmitted, and two adjacent sub-carriers are "10" or "01" to indicate that data "1" is transmitted.
Table 15FDM modulation mapping table
| Baseband (bit) | f1f2f3f4f5 |
| 0000 | 11111 |
| 0001 | 11110 |
| 0010 | 11100 |
| 0011 | 11101 |
| 0100 | 11000 |
| 0101 | 11001 |
| 0110 | 11011 |
| 0111 | 11010 |
| 1000 | 01111 |
| 1001 | 01110 |
| 1010 | 01100 |
| 1011 | 01101 |
| 1100 | 01000 |
| 1101 | 01001 |
| 1110 | 01011 |
| 1111 | 01010 |
Let S denote the value range of the MFDM modulation map, which is identical to the second column of Table 1, SiA mapping symbol representing the ith carrier group, which takes a certain row of the second column of table 1, obviously with SiBelongs to S, and then let PiDenotes SiSet of indices corresponding to medium non-zero subcarriers, e.g. when SiP at 01001i=2, 5, then SiThe corresponding time domain expression is:
wherein{ωi,kIs the angular frequency of the non-zero sub-carriers, TsFor one OFDM symbol period, one OFDM-MFDM symbol can be represented as:
wherein N is the number of sub-carriers used by OFDM, M is the number of sub-carriers in each group, and N is an integral multiple of M. The OFDM-MFDM symbol is added with a cyclic prefix, then is subjected to serial-parallel conversion and radio frequency conversion, and is transmitted out through an antenna. In a high-speed mobile environment at both ends or one end of a transceiver, a radio electromagnetic wave signal generally experiences time-varying multipath fading, and a typical time-varying multipath fading channel is as follows:
wherein L is the number of multipath paths, AlIs the time-varying complex fading coefficient, omega, of the l-th pathlDoppler shift, Δ τ, for the l-th pathlIs the delay of the ith path relative to the reference path. After the receiving end signal is subjected to radio frequency conversion and cyclic prefix removal, the signal expression of the receiving end signal is as follows:
where w (t) is white gaussian noise, the received signal corresponding to the i-th carrier group is:
wherein, wi(t) is white gaussian noise with band limitation, and the band is limited in the frequency range of the ith carrier group. After Fourier transform, the above formula is:
then for the ith OFDM-MFDM subcarrier group, the energy of each subcarrier is:
where Δ ω is the subcarrier spacing, let | ωl|<Δ ω/2, then:
the length of time of CP is selected to be greater than Δ τlmaxThereby eliminating ISI. In addition, the frequency interval of the sub-carriers is smaller than the coherence bandwidth Bc, Bc ≈ 1/delta taulmaxIf the fading of adjacent subcarriers is approximately equal, the MFDM demodulation can be performed by using the energy difference between adjacent subcarriers, that is, there are:
in the formula EthFor the decision threshold, half of the energy of the non-zero sub-carriers in the sub-carrier group may be selected, and the 2 nd sub-carrier in table 1 is a non-zero sub-carrier.
Selecting a carrier frequency fc=5.8GHz, subcarrier Nf=256, useful subcarriers Nfused=160, subcarrier spacing Δ f =312.5kHz, cyclic prefix Tg=0.8 μ s, OFDM symbol period TsThe simulation result of the OFDM-5FMD bit error rate in Gaussian noise channel is shown in FIG. 3, and the simulation result is Eb/N0About 13dB, the error rate can reach 10-3。
Under a two-path Rice channel, the moving speed of a vehicle at a communication receiving end is selected to be 0km/h, 120km/h, 360km/h and 600km/h respectively, the maximum delay value of the Rice channel is 0.75us, and the Doppler frequency offset of the two paths is set to be omega1＝-ω2The simulation result of the bit error rate of the OFDM-5FMD is shown in FIG. 4, and four curves of 0km/h, 120km/h, 360km/h and 600km/h are shown in Eb/N0Smaller, fully overlapping, with Eb/N0The larger the size, the smaller the difference between the four curves.
Under a four-path Rayleigh channel, namely no direct path exists, the moving speeds of vehicles at the communication receiving end are respectively selected to be 0km/h, 120km/h, 360km/h and 600km/h, and the delay is set to be [ 00.050.10.2 ]]The bit error rate simulation result of us, OFDM-5FMD is shown in figure 5, four curves of 0km/h, 120km/h, 360km/h and 600km/h are consistent with the change rule of figure 4, Eb/N0Smaller, fully overlapping, with Eb/N0The larger the size, the smaller the difference between the four curves.
From the analysis and simulation results, the OFDM-MFDM method provided by the invention has a simple structure, adopts a non-coherent demodulation method at a receiving end, and does not need to carry out channel estimation. Under typical vehicle-ground communication channels, namely a Rice channel and a Rayleigh channel, the method provided by the invention is insensitive to the moving speed of a communication end, namely has good robustness to Doppler frequency offset, and is suitable for realizing broadband wireless communication under a high-speed moving environment.
Claims (6)
1. The broadband wireless transmission method is characterized by comprising the following steps:
the method comprises the following steps: converting a digital baseband signal to be transmitted of a user, which is input in series, into a parallel digital baseband signal with a lower rate according to the modulation order of an orthogonal frequency division multiplexing subcarrier;
step two: carrying out multi-frequency differential modulation mapping on the baseband signals after serial-parallel conversion, and converting time domain baseband signals into baseband signals of which the frequency domain is formed by combining subcarrier frequencies;
step three: converting a frequency domain signal of an orthogonal frequency division multiplexing symbol into a time domain signal of the orthogonal frequency division multiplexing symbol through inverse fast Fourier transform;
step four: inserting a cyclic prefix before an orthogonal frequency division multiplexing symbol and performing parallel-serial conversion;
step five: modulating an orthogonal frequency division multiplexing baseband signal to a radio frequency band, and transmitting the modulated signal to an antenna for transmission after power amplification;
step six: the orthogonal frequency division multiplexing radio frequency signal received by the antenna is converted into a digital baseband signal after amplification and frequency mixing;
step seven: the received baseband signals are subjected to synchronous processing to realize bit frame synchronization;
step eight: after the baseband signals are processed synchronously, serial-parallel conversion is carried out and the cyclic prefix is removed;
step nine: performing fast Fourier transform on the baseband signal without the cyclic prefix, and converting the baseband signal of the time domain into a baseband signal of the frequency domain;
step ten: and demodulating the information carried by the orthogonal frequency division multiplexing subcarrier frequency by using a non-coherent demodulation mode according to the multi-frequency differential modulation mapping table.
2. The broadband wireless transmitting method is characterized by comprising the following steps:
the method comprises the following steps: converting a digital baseband signal to be transmitted of a user, which is input in series, into a parallel digital baseband signal with a lower rate according to the modulation order of an orthogonal frequency division multiplexing subcarrier;
step two: carrying out multi-frequency differential modulation mapping on the baseband signals after serial-parallel conversion, and converting time domain baseband signals into baseband signals of which the frequency domain is formed by combining subcarrier frequencies;
step three: converting a frequency domain signal of an orthogonal frequency division multiplexing symbol into a time domain signal of the orthogonal frequency division multiplexing symbol through inverse fast Fourier transform;
step four: inserting a cyclic prefix before an orthogonal frequency division multiplexing symbol and performing parallel-serial conversion;
step five: modulating the orthogonal frequency division multiplexing baseband signal to a radio frequency band, and sending the modulated signal to an antenna for transmitting after power amplification.
3. The broadband wireless receiving method is characterized by comprising the following steps:
the method comprises the following steps: the orthogonal frequency division multiplexing radio frequency signal received by the antenna is converted into a digital baseband signal after amplification and frequency mixing;
step two: the received baseband signals are subjected to synchronous processing to realize bit frame synchronization;
step three: after the baseband signals are processed synchronously, serial-parallel conversion is carried out and the cyclic prefix is removed;
step four: after the cyclic prefix is removed, the baseband signal is subjected to fast Fourier transform, and the time-domain baseband signal is converted into a frequency-domain baseband signal;
step five: and demodulating the information carried by the orthogonal frequency division multiplexing subcarrier frequency by using a non-coherent demodulation mode according to the multi-frequency differential modulation mapping table.
4. Broadband wireless transmission system, including transmitting terminal and receiving terminal, its characterized in that:
the transmitting end comprises a coding module, a transmitting serial-parallel conversion module, a multi-frequency differential modulation module, an inverse fast Fourier transform module, a cyclic prefix insertion module, a parallel-serial conversion module and a transmitting radio frequency module; wherein,
the coding module: encoding a signal to be transmitted by a user;
a transmitting serial-parallel conversion module: converting the serial digital baseband signals output by the coding module into parallel digital baseband signals with lower speed according to the modulation order of the orthogonal frequency division multiplexing subcarrier;
a multi-frequency differential modulation module: carrying out multi-frequency differential modulation mapping on the baseband signals converted by the transmitting serial-parallel conversion module, and converting time domain baseband signals into baseband signals of which the frequency domain is formed by combining subcarrier frequencies;
an inverse fast Fourier transform module: converting a frequency domain signal of an orthogonal frequency division multiplexing symbol output by the multi-frequency differential modulation module into a time domain signal of the orthogonal frequency division multiplexing symbol;
a cyclic prefix insertion module: inserting a cyclic prefix before the orthogonal frequency division multiplexing symbol output by the inverse fast Fourier transform module;
a parallel-serial conversion module: performing parallel-serial conversion on the signal output by the cyclic prefix insertion module;
a transmitting radio frequency module: modulating the orthogonal frequency division multiplexing baseband signal output by the parallel-serial conversion module to a radio frequency band, and transmitting the modulated signal to an antenna after power amplification;
the receiving end comprises a receiving radio frequency module, a synchronization module, a receiving serial-parallel conversion module, a cyclic prefix removing module, a fast Fourier transform module, a multi-frequency differential demodulation module and a decoding module; wherein,
a receiving radio frequency module: the method comprises the steps that an orthogonal frequency division multiplexing radio frequency signal received by an antenna is amplified and subjected to frequency mixing processing and then converted into a digital baseband signal;
a synchronization module: carrying out synchronous processing on the baseband signals received by the receiving radio frequency module to realize bit frame synchronization;
a receive serial-to-parallel conversion module: performing serial-parallel conversion on the baseband signal output by the synchronization module;
a cyclic prefix removal module: removing the cyclic prefix from the baseband signal output by the receiving serial-parallel conversion module;
a fast Fourier transform module: performing fast Fourier transform on the baseband signal without the cyclic prefix, and converting the baseband signal of the time domain into a baseband signal of the frequency domain;
a multi-frequency differential demodulation module: demodulating information carried by orthogonal frequency division multiplexing subcarrier frequency by using an incoherent demodulation mode according to a multi-frequency differential modulation mapping table;
a decoding module: and restoring the demodulation information output by the multi-frequency differential demodulation module into a signal transmitted by a user.
5. A broadband wireless transmitter, characterized by: the device mainly comprises a coding module, a transmitting serial-parallel conversion module, a multi-frequency differential modulation module, an inverse fast Fourier transform module, a cyclic prefix insertion module, a parallel-serial conversion module and a transmitting radio frequency module; wherein,
the coding module: encoding a signal to be transmitted by a user;
a transmitting serial-parallel conversion module: converting the serial digital baseband signals output by the coding module into parallel digital baseband signals with lower speed according to the modulation order of the orthogonal frequency division multiplexing subcarrier;
a multi-frequency differential modulation module: carrying out multi-frequency differential modulation mapping on the baseband signals converted by the transmitting serial-parallel conversion module, and converting time domain baseband signals into baseband signals of which the frequency domain is formed by combining subcarrier frequencies;
an inverse fast Fourier transform module: converting a frequency domain signal of an orthogonal frequency division multiplexing symbol output by the multi-frequency differential modulation module into a time domain signal of the orthogonal frequency division multiplexing symbol;
a cyclic prefix insertion module: inserting a cyclic prefix before the orthogonal frequency division multiplexing symbol output by the inverse fast Fourier transform module;
a parallel-serial conversion module: performing parallel-serial conversion on the signal output by the cyclic prefix insertion module;
a transmitting radio frequency module: and modulating the orthogonal frequency division multiplexing baseband signal output by the parallel-serial conversion module to a radio frequency band, and sending the modulated signal to an antenna for transmitting after power amplification.
6. A broadband wireless receiver, characterized by: the device mainly comprises a receiving radio frequency module, a synchronization module, a receiving serial-parallel conversion module, a cyclic prefix removing module, a fast Fourier transform module, a multi-frequency differential demodulation module and a decoding module; wherein,
a receiving radio frequency module: the method comprises the steps that an orthogonal frequency division multiplexing radio frequency signal received by an antenna is amplified and subjected to frequency mixing processing and then converted into a digital baseband signal;
a synchronization module: carrying out synchronous processing on the baseband signals received by the receiving radio frequency module to realize bit frame synchronization;
a receive serial-to-parallel conversion module: performing serial-parallel conversion on the baseband signal output by the synchronization module;
a cyclic prefix removal module: removing the cyclic prefix from the baseband signal output by the receiving serial-parallel conversion module;
a fast Fourier transform module: performing fast Fourier transform on the baseband signal without the cyclic prefix, and converting the baseband signal of the time domain into a baseband signal of the frequency domain;
a multi-frequency differential demodulation module: demodulating information carried by orthogonal frequency division multiplexing subcarrier frequency by using an incoherent demodulation mode according to a multi-frequency differential modulation mapping table;
a decoding module: and restoring the demodulation information output by the multi-frequency differential demodulation module into a signal transmitted by a user.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210171233.9A CN102710574B (en) | 2012-05-29 | 2012-05-29 | Broadband wireless transmission method and system, transmitter and method, receiver and method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210171233.9A CN102710574B (en) | 2012-05-29 | 2012-05-29 | Broadband wireless transmission method and system, transmitter and method, receiver and method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN102710574A true CN102710574A (en) | 2012-10-03 |
| CN102710574B CN102710574B (en) | 2014-12-10 |
Family
ID=46903137
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201210171233.9A Expired - Fee Related CN102710574B (en) | 2012-05-29 | 2012-05-29 | Broadband wireless transmission method and system, transmitter and method, receiver and method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN102710574B (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103051579A (en) * | 2012-12-10 | 2013-04-17 | 桂林电子科技大学 | Vehicle-mounted wireless transmission system, vehicle-mounted wireless transmission method, transmitter, transmitting method, receiver and receiving method |
| CN103249225A (en) * | 2013-04-10 | 2013-08-14 | 安徽海聚信息科技有限责任公司 | WiFi (Wireless Fidelity) technology-based LED control system |
| CN107211023A (en) * | 2015-02-02 | 2017-09-26 | 英特尔Ip公司 | Device, system and the method being wirelessly transferred are transmitted according to physical layer scheme |
| CN107925533A (en) * | 2015-09-24 | 2018-04-17 | 英特尔公司 | V2X performance enhancements in high velocity environment |
| CN109302191A (en) * | 2017-12-12 | 2019-02-01 | 上海创远仪器技术股份有限公司 | A kind of multiport 5G communication signal emitting platform and method |
| CN110166399A (en) * | 2019-06-17 | 2019-08-23 | 桂林电子科技大学 | A method of the multicarrier system based on fractional order C transformation is anti-fading |
| CN110602005A (en) * | 2019-06-26 | 2019-12-20 | 哈尔滨工业大学 | Method for realizing signal time-frequency domain energy averaging by two time-domain component equipower weighting transformation |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1588836A (en) * | 2004-07-15 | 2005-03-02 | 上海交通大学 | Star dividing difference time spaced modulation and demodulation method for quick fading channel |
| US20050270969A1 (en) * | 2004-04-24 | 2005-12-08 | Jin-Kyu Han | Apparatus and method for providing a broadcasting service in a mobile communication system |
| CN1753397A (en) * | 2004-09-20 | 2006-03-29 | 北京三星通信技术研究有限公司 | The transmission method of training symbol and method for synchronous |
| CN101753504A (en) * | 2008-12-16 | 2010-06-23 | 华为技术有限公司 | Differential modulation and demodulation method, transmitter and receiver |
-
2012
- 2012-05-29 CN CN201210171233.9A patent/CN102710574B/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20050270969A1 (en) * | 2004-04-24 | 2005-12-08 | Jin-Kyu Han | Apparatus and method for providing a broadcasting service in a mobile communication system |
| CN1588836A (en) * | 2004-07-15 | 2005-03-02 | 上海交通大学 | Star dividing difference time spaced modulation and demodulation method for quick fading channel |
| CN1753397A (en) * | 2004-09-20 | 2006-03-29 | 北京三星通信技术研究有限公司 | The transmission method of training symbol and method for synchronous |
| CN101753504A (en) * | 2008-12-16 | 2010-06-23 | 华为技术有限公司 | Differential modulation and demodulation method, transmitter and receiver |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103051579A (en) * | 2012-12-10 | 2013-04-17 | 桂林电子科技大学 | Vehicle-mounted wireless transmission system, vehicle-mounted wireless transmission method, transmitter, transmitting method, receiver and receiving method |
| CN103249225A (en) * | 2013-04-10 | 2013-08-14 | 安徽海聚信息科技有限责任公司 | WiFi (Wireless Fidelity) technology-based LED control system |
| CN107211023B (en) * | 2015-02-02 | 2021-04-02 | 英特尔Ip公司 | Apparatus, system, and method for transmitting wireless transmission according to physical layer scheme |
| CN107211023A (en) * | 2015-02-02 | 2017-09-26 | 英特尔Ip公司 | Device, system and the method being wirelessly transferred are transmitted according to physical layer scheme |
| US11012179B2 (en) | 2015-02-02 | 2021-05-18 | Intel IP Corporation | Apparatus, system and method of communicating a wireless transmission according to a physical layer scheme |
| CN107925533B (en) * | 2015-09-24 | 2022-06-17 | 苹果公司 | V2X performance enhancement in high speed environments |
| CN107925533A (en) * | 2015-09-24 | 2018-04-17 | 英特尔公司 | V2X performance enhancements in high velocity environment |
| US11418286B2 (en) | 2015-09-24 | 2022-08-16 | Apple Inc. | V2X performance enhancements in high speed environments |
| CN115297453A (en) * | 2015-09-24 | 2022-11-04 | 苹果公司 | V2X performance enhancement in high speed environments |
| CN115297453B (en) * | 2015-09-24 | 2023-09-12 | 苹果公司 | V2X performance enhancement method and device in high-speed environment |
| CN109302191A (en) * | 2017-12-12 | 2019-02-01 | 上海创远仪器技术股份有限公司 | A kind of multiport 5G communication signal emitting platform and method |
| CN110166399A (en) * | 2019-06-17 | 2019-08-23 | 桂林电子科技大学 | A method of the multicarrier system based on fractional order C transformation is anti-fading |
| CN110602005A (en) * | 2019-06-26 | 2019-12-20 | 哈尔滨工业大学 | Method for realizing signal time-frequency domain energy averaging by two time-domain component equipower weighting transformation |
Also Published As
| Publication number | Publication date |
|---|---|
| CN102710574B (en) | 2014-12-10 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN102710574A (en) | Broadband wireless transmission method and system, transmitter and method, receiver and method | |
| CN101778069B (en) | OFDM signal channel estimation combination ICI self elimination method | |
| CN101753512A (en) | Shortwave high speed data transmission method based on single carrier frequency-domain equalization | |
| CN101986631A (en) | Time- and frequency-domain unified single carrier modulation signal transmission method | |
| CN101119350B (en) | OFDM system, fast synchronization method and sending terminal equipment | |
| CN103973619A (en) | Signal transmission method for single-carrier modulation with time-frequency domain combination | |
| CN109347526B (en) | IM-OFDM signal processing method for Internet of vehicles | |
| CN101394385B (en) | Method for promoting OFDM system based on time domain processing combined channel estimation | |
| CN104735014A (en) | Timing synchronization method based on preamble difference correlation | |
| CN104253772A (en) | Channel estimation method for orthogonal frequency division multiplexing system | |
| CN101547170A (en) | Method for estimating time-varying channel parameter suitable for multi-carrier transmission of OFDM | |
| Mahmud et al. | Performance evaluation of OFDM hybrid number and index modulation for 6G Mobile system | |
| CN102780656A (en) | Method and device for eliminating multi-symbol subcarrier jamming and performing channel estimation jointly | |
| CN104253782A (en) | Residual carrier deviation and sampling deviation estimation method and compensation method | |
| CN101958866B (en) | Pilot frequency insertion method and module | |
| CN103001918B (en) | The transmission method of nonorthogonal polynomials expansion data | |
| CN1593046A (en) | Partial response signaling for orthogonal frequency division multiplexing | |
| CN104243390A (en) | Sliding window-based estimation compensation method for CO-OFDM optical phase noise | |
| CN202652251U (en) | Broadband wireless transmission system, transmitter and receiver | |
| CN103001916A (en) | Time domain reshaping method of orthogonal frequency division multiplexing (OFDM) communication system | |
| CN102801682B (en) | Signal detection method of OFDM (Orthogonal Frequency Division Multiplexing) system | |
| CN1750429A (en) | Doppler shift estimating method for orthogonal frequency division multiplex mobile communication system | |
| CN103051579A (en) | Vehicle-mounted wireless transmission system, vehicle-mounted wireless transmission method, transmitter, transmitting method, receiver and receiving method | |
| CN202979012U (en) | Vehicle-mounted wireless transmission system, vehicle-mounted wireless emitter and vehicle-mounted wireless receiver | |
| CN101115047B (en) | OFDM receiving and dispatching system for high speed mobile environment |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20141210 Termination date: 20210529 |