CN101572683A - Method, devices and system for orthogonal frequency division multiplexing - Google Patents
Method, devices and system for orthogonal frequency division multiplexing Download PDFInfo
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- CN101572683A CN101572683A CNA2008100670455A CN200810067045A CN101572683A CN 101572683 A CN101572683 A CN 101572683A CN A2008100670455 A CNA2008100670455 A CN A2008100670455A CN 200810067045 A CN200810067045 A CN 200810067045A CN 101572683 A CN101572683 A CN 101572683A
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Abstract
The embodiment of the invention discloses a method for orthogonal frequency division multiplexing. The method comprises the following steps: available bandwidth of a transmitter is divided into a plurality of sub-frequency bands, and the bandwidths of the sub-frequency bands are adapted to a plurality of demodulating bandwidths of receivers; the sub-frequency bands are partially overlapped or no protective frequency band is arranged between the adjacent sub-frequency bands; each sub-frequency band comprises a group of sub-carriers, and the sub-carriers of different frequency bands are mutually orthogonal; the bandwidth of at least one of the sub-frequency bands is equal to the bandwidth of the receiver with the minimum demodulating bandwidth; and the data of each sub-frequency band is processed. The embodiment of the invention also provides the transmitter, the receiver and a system for orthogonal frequency division multiplexing. The use of the method, the devices and the system provided can effectively utilize the bandwidth resources.
Description
Technical field
The embodiment of the invention relates to communication technical field, particularly the technology of OFDM.
Background technology
OFDM (Orthogonal Frequency Division Multiplex, OFDM) adopt multi-transceiver technology, the basic thought of multi-transceiver technology is that a bandwidth carrier is divided into a plurality of subcarriers, and transmits data simultaneously on a plurality of subcarriers that mark off.
Long Term Evolution (Long Term Evolution LTE) adopts the OFDM technology, according to the LTE agreement, and access terminal (Access Terminal, AT) the demodulation bandwidth of support 20MHz of LTE.But according to the demand of LTE+ as can be known, AT in the future need support higher demodulation bandwidth, to obtain higher transmission rate.The AT that has multiple demodulation bandwidth with regard to existence as the AT that maximum demodulation bandwidth among the LTE is 20MHz, also has the new A T of the bigger demodulation bandwidth of support like this, such as the demodulation bandwidth of supporting 40MHz, and the AT that base station support simultaneously has multiple demodulation bandwidth.
In order to support the AT of multiple demodulation bandwidth, the method of prior art as shown in Figure 1, base station side adopts the multicarrier form to send, the data of sub-band 1 and sub-band 2 are mapped to respectively on the available subcarrier of sub-band 1 and sub-band 2, and the OFDM modulation of ordering by N1 point and N2 respectively, be the carrier modulation of f1, f2 through centre frequency respectively again, promptly carry out frequency up-conversion operation, go out by antenna transmission then.The signal of two sub-frequency bands is not overlapping on frequency domain, and leaves the certain protection frequency band.At receiver, the AT that the demodulation bandwidth is little can select one of them frequency band as service band; Signal on two carrier waves of the big AT of demodulation bandwidth demodulation simultaneously for example, is modulated at the data on the sub-band 1, can be received by AT1, and the bandwidth that the demodulation bandwidth of AT1 and sub-band 1 are corresponding is identical, and AT1 separates the FFT that timing employing N1 is ordered.
There are the following problems at least in the prior art: leave the certain protection frequency band between the transmitter adjacent sub-bands, yet the protection frequency band can not carry data, has wasted band resource.
Summary of the invention
The technical problem that the embodiment of the invention will solve provides a kind of method, Apparatus and system of OFDM, solving in the prior art because of system supports accessing terminal of multiple demodulation bandwidth, and the problem of the band resource that causes waste.
In view of this, the embodiment of the invention provides a kind of method of OFDM modulation, and this method comprises: the available bandwidth of transmitter is divided into a plurality of sub-bands, and the multiple demodulation bandwidth of the bandwidth of described sub-band and receiver is suitable; Overlap between the described sub-band or adjacent described sub-band between do not protect frequency band; Each described sub-band comprises one group of subcarrier, and is mutually orthogonal between the sub-carriers of different frequency bands; The bandwidth of at least one described sub-band is smaller or equal to the bandwidth of the receiver with minimum demodulating bandwidth; Data to each sub-band are handled.
The embodiment of the invention provides a kind of method of OFDM demodulation, and this method comprises: obtain the centre frequency of sub-band that can demodulation, and the centre frequency of demodulation carrier wave is transferred on the described centre frequency; Use described demodulation carrier wave to carry out demodulation to the received signal, obtain time-domain signal; Described time-domain signal is carried out filtering, obtain time-domain signal, the bandwidth of described time-domain signal is smaller or equal to the sampling bandwidth of receiver ofdm demodulator; Described filtered time-domain signal is sampled and the OFDM demodulation, and the sample strip of described sampling is wider than the bandwidth of time-domain signal of the available subcarrier correspondence of receiver ofdm system; To separating mapping through the signal after the described OFDM demodulation.
The embodiment of the invention provides a kind of transmitter, this transmitter comprises: bandwidth dividing unit, be used for the bandwidth of described transmitter is divided into a plurality of sub-bands, the multiple demodulation bandwidth of the bandwidth of described sub-band and receiver is suitable, overlap between described sub-band, or do not protect frequency band between the adjacent sub-bands, each sub-band comprises one group of available subcarrier, and mutually orthogonal between the sub-carriers of different frequency bands, and have the bandwidth of the bandwidth of a sub-frequency bands at least smaller or equal to receiver with minimum demodulating bandwidth; Data processing unit is used for the data of each sub-band are handled, and sends.
The embodiment of the invention provides a kind of receiver, and this receiver comprises: the frequency acquiring unit is used to obtain the centre frequency of sub-band that can demodulation, and the centre frequency of demodulation carrier wave is transferred on the described centre frequency; Signal acquiring unit is used to receive time-domain signal; The carrier wave demodulation unit is used to use described demodulation carrier wave that the time-domain signal that described signal acquiring unit receives is carried out carrier wave demodulation; Filter unit is used for the signal of described carrier wave demodulation unit output is carried out filtering, obtains time-domain signal, and the bandwidth of described time-domain signal is smaller or equal to the sampling bandwidth of described receiver ofdm demodulator; The sampling demodulating unit, the time-domain signal that is used for the output of described filter unit is sampled and the OFDM demodulation, and the sample strip of described sampling is wider than the bandwidth of time-domain signal of the available subcarrier correspondence of receiver ofdm system; Separate map unit, be used for the data of described sampling demodulating unit output are separated mapping, obtain the data of described receiver.
The embodiment of the invention provides a kind of system, this system comprises: transmitter, comprise: bandwidth dividing unit, be used for the bandwidth of described transmitter is divided into a plurality of sub-bands, the multiple demodulation bandwidth of the bandwidth of described sub-band and receiver is suitable, overlap between described sub-band, or do not protect frequency band between the adjacent sub-bands, each sub-band comprises one group of available subcarrier, and mutually orthogonal between the sub-carriers of different frequency bands, and have the bandwidth of the bandwidth of a sub-frequency bands at least smaller or equal to receiver with minimum demodulating bandwidth; Data processing unit is used for the data of each sub-band are handled, and sends.Receiver comprises: the frequency acquiring unit is used to obtain the centre frequency of sub-band that can demodulation, and the centre frequency of demodulation carrier wave is transferred on the described centre frequency; Signal acquiring unit is used to receive time-domain signal; The carrier wave demodulation unit is used to use described demodulation carrier wave that the time-domain signal that described signal acquiring unit receives is carried out carrier wave demodulation; Filter unit is used for the signal of described carrier wave demodulation unit output is carried out filtering, obtains time-domain signal, and the bandwidth of described time-domain signal is smaller or equal to the sampling bandwidth of described receiver ofdm demodulator; The sampling demodulating unit, the time-domain signal that is used for the output of described filter unit is sampled and the OFDM demodulation, and the sample strip of described sampling is wider than the bandwidth of time-domain signal of the available subcarrier correspondence of receiver ofdm system; Separate map unit, be used for the data of described sampling demodulating unit output are separated mapping, obtain the data of described receiver.
The methods, devices and systems of the OFDM that the embodiment of the invention provides, be divided into a plurality of the available bandwidth of transmitter and sub-band receiver demodulation bandwidth adaptation, when the assurance system can support the receiver of multiple demodulation bandwidth, saved the band resource of transmitter.Simultaneously, the sample strip of receiver is wider than the bandwidth of the time-domain signal of available subcarrier correspondence in the receiver ofdm system, has guaranteed that receiver can obtain the data of oneself from the signal that receives.
Description of drawings
Fig. 1 carries out the method flow schematic diagram of OFDM for transmitter in the prior art;
A kind of transmitter that Fig. 2 provides for the embodiment of the invention carries out the schematic flow sheet of OFDM modulation;
The another kind of transmitter that Fig. 3 provides for the embodiment of the invention carries out the schematic flow sheet of OFDM modulation;
The schematic flow sheet that a kind of receiver that Fig. 4 provides for the embodiment of the invention connects carries out the OFDM demodulation;
The schematic diagram of a kind of transmitter bandwidth division methods that Fig. 5 provides for the embodiment of the invention;
The schematic diagram of the another kind of transmitter bandwidth division methods that Fig. 6 provides for the embodiment of the invention;
The schematic diagram of the another kind of transmitter bandwidth division methods that Fig. 7 provides for the embodiment of the invention;
The schematic diagram of the another kind of transmitter bandwidth division methods that Fig. 8 provides for the embodiment of the invention
The structural representation of a kind of transmitter installation that Fig. 9 provides for the embodiment of the invention;
The structural representation of the another kind of transmitter installation that Figure 10 provides for the embodiment of the invention;
The structural representation of the another kind of transmitter installation that Figure 11 provides for the embodiment of the invention;
The structural representation of a kind of receiver apparatus that Figure 12 provides for the embodiment of the invention;
A kind of system configuration schematic diagram that Figure 13 provides for the embodiment of the invention;
Embodiment
In order to solve the not high problem of transmitter bandwidth resource utilization in the prior art, the embodiment of the invention provides a kind of method, transmitter, receiver and system of OFDM.Below in conjunction with accompanying drawing the embodiment of the invention is elaborated.
The embodiment of the invention provides a kind of transmitter to carry out the method that OFDM is modulated, and is illustrated in figure 2 as the schematic flow sheet of this method, comprising:
S201, the available bandwidth of transmitter is divided into a plurality of sub-bands; make that the multiple demodulation bandwidth of the bandwidth of sub-band and receiver is suitable; sub-band is overlapped; or not protection between the adjacent sub-bands; each sub-band comprises one group of available subcarrier; and mutually orthogonal between the sub-carriers of different frequency bands, and, require to have at least the bandwidth of the bandwidth of a sub-frequency bands smaller or equal to AT with minimum demodulating bandwidth in order to support the AT of multiple demodulation bandwidth.
Wherein, the multiple demodulation bandwidth of the bandwidth of sub-band and receiver is suitable specifically to be meant: under the condition that the transmitter bandwidth allows, the bandwidth of transmitter is divided into the sub-band that equates with various demodulation bandwidth.
S202, together with the data multiplex on all sub-bands, and be mapped on the available subcarrier of ofdm system, guarantee that the data map of each sub-band is to the available subcarrier of each sub-band in the time of mapping, available subcarrier is exactly to be used for the subcarrier of modulating data, and the data of different sub-bands take different subcarriers on same OFDM symbol.
In the present embodiment, for convenience AT obtains the centre frequency of each sub-band, carries to be used for the pilot frequency sequence of frequency correction in the data of part or each sub-band.
In the present embodiment, comprise system parameters in the partial data frame of parton frequency band, this system parameters can send by broadcast channel, at this moment, system parameters comprises the bandwidth of parton frequency band, the centre frequency that can also comprise the parton frequency band, and/or the information such as biasing of parton frequency band and book mid-band frequency, system parameters can also send by unicast tunnel, this moment, this parameter was including but not limited to the centre frequency of parton frequency band, and/or the biasing of parton frequency band and book mid-band frequency.
S203, will be among the step S202 carry out the OFDM modulation, form OFDM time domain baseband signal through the data after the mapping, the OFDM modulation comprise the reverse fast fourier transform of N point and add Cyclic Prefix (CyclicPrefix, CP).
In the present embodiment, when selecting the value of N, make the frequency band of the time-domain signal correspondence after changing comprise all sub-bands.
S204, carry out carrier modulation through the data after the OFDM modulation, comprise operations such as up-conversion, and send above-mentioned.
In the present embodiment, the centre frequency of modulated carrier is by the position of the residing frequency spectrum of frequency band of carrying data and the division methods decision of frequency band, and generally the centre frequency of modulated carrier is the centre frequency of the shared whole frequency band of whole sub-bands.
The embodiment of the invention is divided into a plurality of sub-bands at transmitter with available bandwidth; make that the multiple demodulation bandwidth of the bandwidth of sub-band and receiver is suitable; sub-band can be overlapped, or does not protect frequency band between the adjacent sub-bands, has saved the band resource of transmitter.Simultaneously, transmitter is gone out the data transmission after multiplexing by a shared carrier wave with the data OFDM of each sub-band together, has saved devices such as OFDM modulator and carrier modulator, has reduced system and has realized cost.
The embodiment of the invention provides another kind of transmitter to carry out the method that OFDM is modulated, and is illustrated in figure 3 as the schematic flow sheet of this method, comprising:
S301 is consistent with step S201, does not repeat them here.
S302, with the data map of each sub-band to the available subcarrier of each sub-band.
In the present embodiment, for convenience AT obtains the centre frequency of each sub-band, can also carry to be used for the pilot frequency sequence of frequency correction in the data of part or each sub-band.
In the present embodiment, comprise system parameters in the partial data frame of parton frequency band, the explanation of the send mode of this system parameters and the content synchronization that comprises rapid 202 does not repeat them here.
S303, the data on each sub-band are carried out OFDM modulation respectively, comprise and carry out reverse fast fourier transform respectively, convert time-domain signal to, each time-domain signal is added the Cyclic Prefix of equal length respectively, and the subcarrier spacing of each sub-band equates corresponding to each sub-band;
S304, will carry out carrier modulation respectively, and be modulated to respectively on the modulated carrier of each sub-band correspondence, and send through the data after the OFDM modulation.
In the present embodiment, the subcarrier spacing of modulated carrier equates with the subcarrier spacing of other modulated carriers or is integral multiple arbitrarily, and the integral multiple of the subcarrier spacing that is spaced apart sub-band between the centre frequency of any two modulated carriers.
In the present embodiment, the transmission zero-time of the OFDM symbol of different carrier is identical, can prevent the intersymbol interference of OFDM of different carrier like this.For the subcarrier quadrature between the different sub-bands of further guaranteeing transmitter, all modulated carrier shared frequencies a reference sources.
The embodiment of the invention is divided into a plurality of sub-bands with the available bandwidth of transmitter; make that the multiple demodulation bandwidth of the bandwidth of sub-band and receiver is suitable; sub-band is overlapped, and does not perhaps protect frequency band between the adjacent sub-bands, has saved the band resource of transmitter.Simultaneously, the method for the embodiment of the invention does not need existing transmitter is made significantly modification, relatively is easy to realize in existing transmitter.
The method that a kind of receiver that the embodiment of the invention provides carries out the OFDM demodulation is illustrated in figure 4 as the schematic flow sheet of this method, comprising:
S401, obtain the centre frequency of sub-band that can demodulation, and the centre frequency of demodulation carrier wave is transferred on this centre frequency;
Particularly, receiver carries out Cell searching, obtains pilot frequency sequence, extracts the centre frequency of respective frequency sub-bands from the detection signal of pilot frequency sequence.Receiver can also obtain the system parameters that comprises in the broadcast channel on this sub-band, receiver is according to system parameters and the demodulation bandwidth of oneself, calculate the centre frequency of sub-band that can demodulation, and according to the centre frequency of preset parameter (including but not limited to: the demodulation bandwidth of this receiver, the load of each sub-band) chooser frequency band, and the centre frequency of demodulation carrier wave is transferred on this centre frequency.
S402, carry out carrier wave demodulation to the received signal, comprise operations such as down-conversion, obtain baseband signal or intermediate-freuqncy signal;
S403, the signal behind the carrier wave demodulation is carried out low pass or bandpass filtering, the pass band width of filter is enough little, with the bandwidth that the guarantees filtered time-domain signal sampling bandwidth smaller or equal to the receiver ofdm demodulator;
S404, filtered time-domain signal is sampled and the OFDM demodulation, recover the signal on the sub-band;
In the present embodiment, sample strip is wider than the bandwidth of the time-domain signal of available subcarrier correspondence in the receiver ofdm system;
S405, the signal on the sub-band that obtains among the S404 is separated mapping, obtain the data of this receiver.
The sample strip that receiver adopts in the embodiment of the invention is wider than the bandwidth of the time-domain signal of available subcarrier correspondence in the receiver ofdm system, guarantee from the signal that receives, to obtain the data of this receiver, reduced the signal interference problem that embodiment of the invention transmitter sub-band division method is brought.
For the vivider explanation embodiment of the invention transmitter and the communication process of receiver, the embodiment of the invention provides the method for following several transmitter sub-band division, carries out the example explanation.
Method one, be illustrated in figure 5 as the schematic diagram of this method: for the bandwidth of 40MHz, if the centre frequency of carrier wave is f0, adopt 4096 OFDM modulation, subcarrier be spaced apart 15kHz, whole sequential frequency band is divided into a plurality of sub-bands, and f0-600*15kHz-10MHz is a sub-frequency bands to f0-600*15kHz+10MHz, is made as sub-band 1; F0+599*15kHz-10MHz is a sub-frequency bands to f0+599*15kHz+10MHz, is made as sub-band 2; F0-20MHz is a sub-band 3 to f0+20MHz.The centre frequency of sub-band 1 is f0-600*15kHz, and the centre frequency of sub-band 2 is f0+599*15kHz, and the centre frequency of sub-band 3 is f0.The available subcarrier of sub-band 1 is 1200 subcarriers of the centre of sub-band 1; The available subcarrier of sub-band 2 is 1200 subcarriers of the centre of sub-band 2.The available subcarrier of sub-band 3 is 2534 subcarriers of the centre of sub-band 3.Among Fig. 5, the subcarrier of dash area is that AT1 and the AT2 of 20MHz is unavailable for the demodulation bandwidth, is that the new A T3 of 40MHz is then available for the demodulation bandwidth.If as the working band of AT1 and AT2, then the base station sends data only on effective subcarrier of this frequency band corresponding AT respectively for sub-band 1 and sub-band 2, and all effective subcarriers can be used for sending data to AT3 on the frequency band 3.
Method two is illustrated in figure 6 as the schematic diagram of this method, for the bandwidth of 40MHz, if the centre frequency of carrier wave is f0, adopt 4096 OFDM modulation, subcarrier be spaced apart 15kHz, whole sequential frequency band is divided into a plurality of sub-bands, and f0-20MHz is a sub-frequency bands to f0, is made as sub-band 1; F0 is a sub-frequency bands to f0+20MHz, is made as sub-band 2; F0-20MHz is a sub-band 3 to f0+20MHz.The centre frequency of sub-band 1 is f0-10MHz, and the centre frequency of sub-band 2 is f0+10MHz, and the centre frequency of sub-band 3 is f0.The available subcarrier of sub-band 1 is 1200 subcarriers of the centre of sub-band 1; The available subcarrier of sub-band 2 is 1200 subcarriers of the centre of sub-band 2.The available subcarrier of sub-band 3 is 2534 subcarriers of the centre of sub-band 3.Among Fig. 6, the subcarrier of dash area is that AT1 and the AT2 of 20MHz is unavailable for the demodulation bandwidth, is that the new A T3 of 40MHz is then available for the demodulation bandwidth.If as the working band of AT1 and AT2, then the base station sends data only on effective subcarrier of this frequency band corresponding AT respectively for sub-band 1 and sub-band 2, and all effective subcarriers can be used for sending data to AT3 on the frequency band 3.
Method three, be illustrated in figure 7 as the schematic diagram of this method, bandwidth for 40MHz, if the centre frequency of carrier wave is f0, adopt 4096 OFDM modulation, subcarrier be spaced apart 15kHz, whole sequential frequency band is divided into a plurality of sub-bands, f0-10MHz is a sub-frequency bands to f0+10MHz, is made as sub-band 1; F0-20MHz is a sub-band 2 to f0+20MHz.The centre frequency of sub-band 1 is f0, and the centre frequency of sub-band 2 is f0.The available subcarrier of sub-band 1 is 1200 subcarriers of the centre of sub-band 1; The available subcarrier of sub-band 3 is 2400 subcarriers of the centre of sub-band 3, and the protection frequency band of 2MHz has respectively been stayed on both sides.Among Fig. 7, the demodulation bandwidth of AT1 is 20MHz, and the subcarrier that the dotted line of AT1 correspondence is outer is that the AT of 20MHz is unavailable for the demodulation bandwidth, is that the new A T2 of 40MHz is then available for the demodulation bandwidth.If sub-band 1 is as the working band of AT1, then the base station sends data only on effective subcarrier of this frequency band corresponding AT, and all effective subcarriers can be used for sending data to AT2 on the frequency band 3.
Method four, the three kinds of methods in front all are to adopt 1 cover OFDM modulator, adopt 1 carrier wave to realize the multiplexing and OFDM modulation of a plurality of sub-bands.The embodiment of the invention adopts a plurality of carrier waves, a plurality of OFDM modulator to realize the multiplexing and OFDM modulation of a plurality of sub-bands respectively.When a plurality of operators are assigned to adjacent bandwidth, adopt this method can improve the utilance of frequency band, reduce the waste of protection frequency band.
As shown in Figure 8, division schematic diagram for the base station side subcarrier, at first to guarantee the subcarrier spacing of each sub-band, OFDM modulation parameters such as CP length are identical, and the integral multiple that is spaced apart subcarrier spacing between the centre frequency of two sub-frequency bands, in order to guarantee sub-band precision at interval, two carrier wave shared frequencies a reference sources are as crystal oscillator or PLL, atomic clock, gps signal etc.
Among Fig. 8, adopt two sub-frequency bands in the time of base station, be spaced apart 1200*15kHz between sub-band.Each sub-band is 20MHz, adopts 2048 OFDM modulator emission, and subcarrier spacing is 15kHz.The frequency band of two sub-frequency bands has overlapping each other, and lap is divided into two, and is used for sending the data of the AT of carrier wave 1 service near the part of sub-band 1 centre frequency, is used for sending the data of the AT of sub-band 2 services near the part of sub-band 2 centre frequencies.
For the little AT of demodulation bandwidth, only need the data on demodulation sub-band 1 or the sub-band 2, centre frequency is set to the centre frequency (f1 or f2) of two sub-frequency bands respectively; For the big AT of demodulation bandwidth, can be with the centre frequency f0 of whole frequency band centre frequency as the demodulation carrier frequency, the data on two sub-frequency bands of demodulation simultaneously.
For the sub-band division method of the above transmitter that provides, the demodulation bandwidth be the AT of LTE of 20MHz in order from the signal that the base station sends, to demodulate the data of oneself, need satisfy following 3 conditions:
1, the sample strip of the OFDM demodulation of AT is wider than the available bandwidth of AT, and available bandwidth refers to the shared bandwidth of available subcarrier in the ofdm system.
2, the pass band width of the low pass of AT or band pass filter (can be analog filter or digital filter) is smaller or equal to the sampling rate of ofdm demodulator.
3, AT separates timing, and the centre frequency of demodulation carrier wave (being the centre frequency of the transmitter sub-band corresponding with receiver) is the centre frequency of the sub-band at this AT place.
From the agreement of LTE as can be known, the sampling rate of AT is 30MHz, greater than effective bandwidth 20MHz, satisfies condition 1; For the AT that supports 20MHz, from agreement as can be known, respectively there is the protection frequency band of 1MHz on the bandwidth both sides of 20MHz, and then the bandwidth of the low pass of this AT or band pass filter satisfies condition 2 about 18MHz; By on 1.5MHz bandwidth middle on sub-band 1 or the sub-band 2, placing and the identical synchronizing channel of LTE agreement, can make this AT carry out Cell searching, and frequency calibration, can satisfy condition 3, for example, on sub-band 1, centre frequency with sub-band 1 is the synchronizing pilot that the center sends LTE, AT obtains this Frequency point, carries out Cell searching near this Frequency point, the line frequency of going forward side by side calibration.
The sub-band division method of the transmitter that the embodiment of the invention provides can be overlapped the sub-band that marks off, and does not perhaps protect frequency band between the adjacent sub-bands, has saved the band resource of transmitter, and supports AT with multiple demodulation bandwidth.
The embodiment of the invention is provided for first embodiment of the transmitter of OFDM, is illustrated in figure 9 as the structural representation of transmitter, and this transmitter comprises:
Bandwidth dividing unit 901, be used for the transmitter bandwidth is divided into a plurality of sub-bands; the multiple demodulation bandwidth of the bandwidth of sub-band and receiver is suitable; sub-band can be overlapped; perhaps do not protect frequency band between the adjacent sub-bands; each sub-band comprises one group of available subcarrier; and mutually orthogonal between the sub-carriers of different frequency bands, and have the bandwidth of the bandwidth of a sub-frequency bands at least smaller or equal to AT with minimum demodulating bandwidth.
Data processing unit 902, be used for the data of each sub-band are handled, and send.
The embodiment of the invention is divided into a plurality of sub-bands at transmitter with available bandwidth; make that the demodulation bandwidth of the bandwidth of sub-band and various receiver is suitable; do not protect frequency band between the adjacent sub-bands; sub-band can be overlapped; make full use of the bandwidth resources of transmitter, improve usage factor of system resource.
The embodiment of the invention is provided for second embodiment of the transmitter of OFDM, when specifically being the method deal with data as first embodiment that adopts the transmitter OFDM, the concrete structure schematic diagram of transmitter first embodiment as shown in figure 10:
The function of bandwidth dividing unit 1001 does not repeat them here with bandwidth dividing unit 901.
Data processing unit 902 specifically comprises: Multiplexing Unit 1002, data map unit 1003, OFDM modulating unit 1004, carrier modulation unit 1005 and transmitting element 1006.
Multiplexing Unit 1002 is used for carrying out the data of all sub-bands multiplexing.
For convenience AT obtains the centre frequency of each sub-band, and data map unit 1003 also is used for data on part or each sub-band and carries and be used for the pilot frequency sequence of frequency correction.
OFDM modulating unit 1004 is used for the data of data map unit 1003 outputs are carried out the OFDM modulation, forms the time domain baseband signal.
The OFDM modulating unit comprises signal conversion unit 10041, is used for the data of data map unit 1003 outputs are carried out the reverse fast fourier transform of N point, and wherein, the value of N will make the frequency band of the time-domain signal correspondence after changing comprise all sub-bands.
Carrier modulation unit 1005 is used for the time domain baseband signal of OFDM modulating unit 1004 outputs is modulated to modulated carrier.
Transmitting element 1006 is used for the data of carrier modulation unit 1005 outputs are sent.
The embodiment of the invention is divided into a plurality of sub-bands at transmitter with available bandwidth; make that the demodulation bandwidth of the bandwidth of sub-band and various receiver is suitable; do not protect frequency band between the adjacent sub-bands; perhaps sub-band is overlapped; simultaneously, transmitter is gone out the data transmission after multiplexing by a shared carrier wave with the data OFDM of each sub-band together; save devices such as OFDM modulator and carrier modulator, reduced system cost.
The embodiment of the invention is provided for the 3rd embodiment of the transmitter of OFDM, when specifically being the method deal with data as second embodiment that adopts the transmitter OFDM, the concrete structure schematic diagram of transmitter first embodiment as shown in figure 11, the embodiment of the invention describes with the data instance of launching two sub-frequency bands, and this transmitter comprises:
The function of bandwidth dividing unit 1101 does not repeat them here with bandwidth dividing unit 901.
Data processing unit 902 specifically comprises: data map unit 1102, OFDM modulating unit 1103, carrier modulation unit 1104 and transmitting element 1105.
Wherein, data map unit 1102, be used for the data map of each sub-band available subcarrier to each sub-band, for example, there are the data of two sub-frequency bands to need to send in the embodiment of the invention, transmitter just comprises two data map unit 1102, respectively the data of two sub-frequency bands is shone upon.
For convenience AT obtains the centre frequency of each sub-band, and data map unit 1102 also is used for carrying in the data of part or each sub-band and is used for the pilot frequency sequence of frequency correction.
OFDM modulating unit 1103 is used for the data of described data map unit 1102 outputs are carried out the OFDM modulation respectively.
OFDM modulating unit 1103 comprises signal conversion unit 11031, be used for the data of data map unit 1102 outputs are carried out reverse fast fourier transform respectively, obtain the time-domain signal of respective frequency sub-bands, Cyclic Prefix adding device 11032, be used for the time-domain signal of signal conversion unit 11031 output is added Cyclic Prefix respectively, the length of the Cyclic Prefix that each time-domain signal is added is all identical.
Wherein, have the data of two sub-frequency bands to need to send in the invention process, the base station just comprises two OFDM modulating units 1103, respectively the OFDM data of this two sub-frequency bands is modulated.
Carrier modulation unit 1104, be used for the data corresponding to each subcarrier of OFDM modulating unit 1103 outputs are carried out carrier modulation respectively, to send as the data that two sub-frequency bands are arranged in the embodiment of the invention, carrier modulation unit 1104 comprises carrier modulation unit 11041, its centre carrier frequency is f1, with carrier modulation unit 11042, its centre carrier frequency is f2, modulates the data corresponding to two sub-frequency bands respectively.
Wherein, the subcarrier spacing of modulated carrier equates with the subcarrier spacing of other modulated carriers or is integral multiple arbitrarily, and the integral multiple of the subcarrier spacing that is spaced apart sub-band between the centre frequency of any two modulated carriers.
In order to ensure the precision of the subcarrier spacing of transmitter, the transmitter that the embodiment of the invention provides also should comprise frequency reference source 1105, for two carrier modulation unit in the carrier modulation unit 1104 provide frequency reference.
Transmitter unit 904 is specially transmitting element 1106, is used for the data of carrier modulation unit 1105 outputs are sent.
The embodiment of the invention is divided into a plurality of sub-bands at transmitter with available bandwidth; make that the demodulation bandwidth of the bandwidth of sub-band and various receiver is suitable; do not protect frequency band between the adjacent sub-bands; or sub-band is overlapped; and adopt a plurality of carrier waves, a plurality of OFDM modulator to realize the multiplexing and OFDM modulation of a plurality of sub-bands respectively; when a plurality of operators are assigned to continuous bandwidth, adopt this transmitter can improve the utilance of frequency band, reduce the waste of protection frequency band.
The embodiment of the invention also provides a kind of receiver that is used for OFDM, is the structural representation of receiver as shown in figure 12, and this receiver comprises:
Frequency acquiring unit 1201 is used to obtain the centre frequency of sub-band that can demodulation, and the centre frequency of demodulation carrier wave is transferred on this centre frequency;
Particularly, frequency acquiring unit 1201 also comprises pilot frequency sequence acquiring unit 12011, is used to carry out Cell searching, obtains pilot frequency sequence, extracts the centre frequency of respective frequency sub-bands from the detection signal of pilot frequency sequence; Also comprise system parameters acquiring unit 12012, be used for obtaining system parameters from the sub-band of above-mentioned pilot frequency sequence correspondence, also comprise centre frequency computing unit 12013, according to this system parameters and the demodulation bandwidth of oneself, calculate the centre frequency of sub-band that can demodulation, also comprise centre frequency selected cell 12014, be used for (including but not limited to: the demodulation bandwidth of this AT according to preset parameter, the load of each sub-band), the centre frequency of chooser frequency band from the centre frequency that centre frequency computing unit 12013 calculates, for example, can select the centre frequency of the sub-band of optimal demodulation effect, also can be to select at random, and this centre frequency that will select be as the centre frequency of demodulation carrier wave.
Signal acquiring unit 1202 is used for received signal;
Carrier wave demodulation unit 1202, the demodulation carrier wave that is used for using frequency acquiring unit 1201 to aim at, the time-domain signal that signal acquiring unit 1202 is received carries out carrier wave demodulation, promptly carries out operations such as down-conversion, obtains baseband signal or intermediate-freuqncy signal;
Filter unit 1203, be used for the signal behind the carrier wave demodulation is carried out filtering, this is filtered into low-pass filtering or bandpass filtering, obtains time-domain signal, the pass band width of filter unit 1203 is enough little, and the bandwidth of time-domain signal that makes output is smaller or equal to the sampling bandwidth of receiver ofdm demodulator;
Sampling demodulating unit 1204 is used for filtered time-domain signal is sampled and the OFDM demodulation, recovers the signal on the sub-band, and wherein, sample strip is wider than the bandwidth of time-domain signal of the available subcarrier correspondence of receiver ofdm system;
The receiver that provides in the invention process is when sampling, sample strip is wider than the bandwidth of the time-domain signal of available subcarrier correspondence in the receiver ofdm system, thereby can from the signal that receives, obtain the data of this receiver, reduce the signal interference problem that transmitter sub-band division method is brought.
The embodiment of the invention provides a kind of system of OFDM, and this system comprises transmitter and receiver, wherein,
Description among the concrete operations of transmitter such as the above-mentioned embodiment is not described in detail at this; Description among the concrete operations of receiver such as the above-mentioned embodiment is not described in detail at this.
The embodiment of the invention is divided into a plurality of sub-bands at transmitter with available bandwidth; make that the multiple demodulation bandwidth of the bandwidth of sub-band and receiver is suitable; do not protect frequency band between the adjacent sub-bands; perhaps overlap between sub-band; and guarantee the bandwidth of the bandwidth of at least one sub-band smaller or equal to the AT of minimum demodulating bandwidth; simultaneously; the sample strip of receiver is wider than the bandwidth of the time-domain signal of available subcarrier correspondence in the receiver ofdm system; guarantee that receiver can demodulate the data of oneself from the data that receive, reduced the signal interference problem that transmitter sub-band division method is brought.
The above; it only is the embodiment of the embodiment of the invention; but the protection range of the embodiment of the invention is not limited thereto; anyly be familiar with those skilled in the art in the technical scope that the embodiment of the invention discloses; the variation that can expect easily or replacement all should be encompassed within the protection range of the embodiment of the invention.Therefore, the protection range of the embodiment of the invention should be as the criterion with the protection range of claim.
Claims (23)
1, a kind of method of modulating in OFDM is characterized in that, this method comprises:
The available bandwidth of transmitter is divided into a plurality of sub-bands, and the multiple demodulation bandwidth of the bandwidth of described sub-band and receiver is suitable;
Overlap between the described sub-band, or do not protect frequency band between adjacent described sub-band;
Each described sub-band comprises one group of subcarrier, and is mutually orthogonal between the sub-carriers of different frequency bands;
The bandwidth of at least one described sub-band is smaller or equal to the bandwidth of the receiver with minimum demodulating bandwidth;
Data to each sub-band are handled.
2, method according to claim 1 is characterized in that, described data to each sub-band are handled specifically and comprised:
The data of described each sub-band are carried out multiplexing, and with the data map after multiplexing to the available subcarrier of ofdm system, make the data of each sub-band on an OFDM symbol, take different subcarriers.
3, method as claimed in claim 2 is characterized in that, described data to each sub-band are handled further and comprised:
The data transaction that is mapped on the available subcarrier of described ofdm system is become time-domain signal;
The frequency band of described time-domain signal correspondence comprises the frequency band of all sub-bands.
4, the method for claim 1 is characterized in that, described data to each sub-band are handled specifically and comprised: with the data map of described each sub-band to the available subcarrier of described each sub-band.
5, method as claimed in claim 4 is characterized in that, described data to each sub-band are handled also and comprised:
The data that are mapped to described each sub-band are converted to and the corresponding time-domain signal of described each sub-band;
Described time-domain signal is added the Cyclic Prefix of equal length respectively.
6, method as claimed in claim 5 is characterized in that, described data to each sub-band are handled further and comprised:
The time-domain signal that has added Cyclic Prefix is modulated on the modulated carrier of described each sub-band correspondence;
The subcarrier spacing of any described modulated carrier equates with the subcarrier spacing of other any described modulated carriers, or is the integral multiple of the subcarrier spacing of other any described modulated carriers;
Interval between the centre frequency of any two described modulated carriers equals the integral multiple of described subcarrier spacing.
7, claim as claimed in claim 6 is characterized in that, the modulated carrier shared frequencies a reference source of described each sub-band correspondence.
8, as any described method of claim of claim 1-7, it is characterized in that described method also comprises: on each sub-band or in the data on the parton frequency band, carry pilot frequency sequence.
9, as any described method of claim of claim 1-7, it is characterized in that described method also comprises: the partial data on the parton frequency band in described each sub-band comprises system parameters;
Described system parameters comprises at least one parameter in the biasing of centre frequency, parton frequency band and book mid-band frequency of bandwidth, parton frequency band of parton frequency band.
10, a kind of method of OFDM demodulation is characterized in that, comprising:
Obtain the centre frequency of sub-band that can demodulation, and the centre frequency of demodulation carrier wave is transferred on the described centre frequency;
Use described demodulation carrier wave to carry out demodulation to the received signal, obtain time-domain signal;
Described time-domain signal is carried out filtering, obtain time-domain signal, the bandwidth of described time-domain signal is smaller or equal to the sampling bandwidth of receiver ofdm demodulator;
Described filtered time-domain signal is sampled and the OFDM demodulation, and the sample strip of described sampling is wider than the bandwidth of time-domain signal of the available subcarrier correspondence of receiver ofdm system;
To separating mapping through the signal after the described OFDM demodulation.
11, method as claimed in claim 10 is characterized in that, the described centre frequency of obtaining sub-band that can demodulation is specially:
Obtain pilot frequency sequence, from described pilot frequency sequence, obtain the centre frequency of the sub-band of described pilot frequency sequence correspondence.
12, method as claimed in claim 11 is characterized in that, the described centre frequency of obtaining described sub-band further comprises:
Obtain the system parameters that described sub-band comprises;
Calculate the centre frequency of sub-band that can demodulation according to described system parameters, and from described centre frequency, select the centre frequency of described conciliation carrier wave according to preset parameter.
13, a kind of transmitter is characterized in that, the transmitter support has the receiver of multiple demodulation bandwidth, and described transmitter comprises:
Bandwidth dividing unit, be used for the bandwidth of described transmitter is divided into a plurality of sub-bands, the multiple demodulation bandwidth of the bandwidth of described sub-band and receiver is suitable, overlap between described sub-band, or do not protect frequency band between the adjacent sub-bands, each sub-band comprises one group of available subcarrier, and mutually orthogonal between the sub-carriers of different frequency bands, and has the bandwidth of the bandwidth of a sub-frequency bands smaller or equal to the receiver with minimum demodulating bandwidth at least;
Data processing unit is used for the data of each sub-band are handled, and sends.
14, transmitter as claimed in claim 13 is characterized in that, described data processing unit specifically comprises:
Multiplexing Unit is used for carrying out the data of described each sub-band multiplexing; With,
The first data map unit is used for making the data of different sub-bands take different subcarriers on same OFDM symbol the data map of the described Multiplexing Unit output available subcarrier to ofdm system.
15, transmitter as claimed in claim 14 is characterized in that, described data processing unit further comprises:
The OFDM modulating unit is used for the data of described first data map unit output are carried out the OFDM modulation; With,
Carrier modulation unit is used for the signal of described OFDM modulating unit output is modulated to modulated carrier;
Transmitting element is used to send the data that described carrier modulation unit is exported.
As claim 14 or 15 described transmitters, it is characterized in that 16, the described first data map unit also is used for carrying pilot frequency sequence on each sub-band or on the parton frequency band.
17, transmitter as claimed in claim 13 is characterized in that, described data processing unit specifically comprises the second data map unit, is used for the data map of each sub-frequency bands available subcarrier to each sub-frequency bands.
18, transmitter as claimed in claim 17 is characterized in that, described data processing unit further comprises:
Signal conversion unit is used for data with the output of the described second data map unit and is converted to time-domain signal corresponding to described each sub-band;
The Cyclic Prefix adding device is used for the Cyclic Prefix that adds equal length corresponding to the time-domain signal of each sub-band to described;
Carrier modulation unit is used for the data of described prefix adding device output are modulated with each modulated carrier respectively;
The frequency reference source unit is used to described each modulated carrier that frequency reference is provided; With,
Transmitting element is used to send the data that described carrier modulation unit is exported.
19, as any described transmitter of claim among the claim 17-18, it is characterized in that the described second data map unit also is used for carrying pilot frequency sequence on each sub-band or on the parton frequency band.
20, a kind of receiver is characterized in that, described receiver comprises:
The frequency acquiring unit is used to obtain the centre frequency of sub-band that can demodulation, and the centre frequency of demodulation carrier wave is transferred on the described centre frequency;
Signal acquiring unit is used to receive time-domain signal;
The carrier wave demodulation unit is used to use described demodulation carrier wave that the time-domain signal that described signal acquiring unit receives is carried out carrier wave demodulation;
Filter unit is used for the signal of described carrier wave demodulation unit output is carried out filtering, obtains time-domain signal, and the bandwidth of described time-domain signal is smaller or equal to the sampling bandwidth of described receiver ofdm demodulator;
The sampling demodulating unit, the time-domain signal that is used for the output of described filter unit is sampled and the OFDM demodulation, and the sample strip of described sampling is wider than the bandwidth of time-domain signal of the available subcarrier correspondence of receiver ofdm system;
Separate map unit, be used for the signal of described sampling demodulating unit output is separated mapping, obtain the data of described receiver.
21, receiver as claimed in claim 20 is characterized in that, described frequency acquiring unit specifically comprises the pilot frequency sequence acquiring unit, is used to obtain pilot frequency sequence, extracts the centre frequency of described sub-band from the detection information of described pilot frequency sequence.
22, receiver as claimed in claim 21 is characterized in that, described frequency acquiring unit also comprises:
The system parameters acquiring unit is used for obtaining the system parameters that described sub-band comprises;
The centre frequency computing unit is used for the system parameters obtained according to described system parameters acquiring unit, and the demodulation bandwidth of described receiver, calculates the centre frequency of the sub-band that described receiver can demodulation; With,
The centre frequency selected cell is used for the centre frequency that calculates from described centre frequency computing unit, selects the centre frequency of described demodulation carrier wave.
23, a kind of system, this system comprises:
As any described transmitter of claim among the claim 13-19; With,
As any described receiver of claim among the claim 20-22.
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