CN101981842A - Receiver - Google Patents
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- CN101981842A CN101981842A CN2009801107501A CN200980110750A CN101981842A CN 101981842 A CN101981842 A CN 101981842A CN 2009801107501 A CN2009801107501 A CN 2009801107501A CN 200980110750 A CN200980110750 A CN 200980110750A CN 101981842 A CN101981842 A CN 101981842A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/3488—Multiresolution systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0044—Control loops for carrier regulation
- H04L2027/0063—Elements of loops
- H04L2027/0067—Phase error detectors
Abstract
A receiver (10) is provided with a circuit (16) for discriminating multilevel modulation system, a circuit (17) for selecting phase correction system, a phase correction circuit (14), and a judgment circuit (15). The circuit (16) discriminates a multilevel modulation system used for a modulation signal on the basis of the modulation signal received from a transmitter. The circuit (17) selects a phase correction system to be used for the phase correction of the symbol of the modulation signal from a plurality of prepared phase correction systems on the basis of the multilevel degree of the multilevel modulation system discriminated by the circuit (16). The circuit (14) corrects the phase of the symbol using the phase correction system selected by the circuit (17). The circuit (15) judges the bit string of the symbol phase-corrected by the circuit (14) on the basis of the multilevel modulation system discriminated by the circuit (16).
Description
Technical field
The present invention relates to receiver, especially for the receiver of the communication system of having utilized adaptive modulation system.
Background technology
In the past, existed the communication system of having utilized adaptive modulation system.This communication system has the different a plurality of many-valued modulation system of many-valued degree (bit rate), for example switches the many-valued modulation system that will use according to self residing environment (circuit quality).In this case, can access best efficiency of transmission according to circuit quality.Here, as many-valued modulation system, for example BPSK (Binary Phase Shift Keying is arranged according to bit rate order from low to high, two-phase PSK), QPSK (Quadrature Phase Shift Keying, Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation, quadrature amplitude modulation) and mode (for example, with reference to the publication communique 2007-150906 of Japan, IEEE 802.11a-1999) such as 64QAM.
But the transmitter and the receiver that constitute communication system possess reference signal source separately.Reference signal source utilizes crystal emitter.The frequency of oscillation of each reference signal source of transmitter and receiver (back is called " reference frequency ") comprises error because of the precision of crystal emitter.Its result, carry out modulation treatment the emission pusher side reference frequency and carry out having produced between the reference frequency of receiver side of demodulation process the error of a few millionths.The error of this reference frequency becomes the reason of the phase place rotation of the data that receive in the receiver.The error rate (Bit Error Rate: back be called " BER ") of the generation of this phase place rotation after to demodulation brought very big influence.Therefore, receiver is proofreaied and correct in the phase place rotation of separating the data that timing butt joint receives.Particularly, using OFDM (Orthogonal Frequency Division Multiplexing, OFDM) under the situation of many-valued modulation of the multi-carrier modulation of modulation etc., the influence of the phase place rotation that causes because of the frequency error of separating timing becomes greatly.This is that the interval of phasing is elongated because the holding time of 1 symbol becomes big.
In the past, phasing mode as the phase place rotation correction that carries out symbol, have use pilot sub-carrier the phasing mode (for example, with reference to the publication communique 2008-22339 of Japan) and used the phasing mode (for example, with reference to the publication communique 2006-352746 of Japan) of frequency pilot sign.
In having used the phasing mode of pilot sub-carrier, cause existing in the transmission characteristic of signal under the situation of bigger frequency selectivity in influence because of multipath fading, it is big that correction error becomes.
Therefore, in the stronger transmission environment of frequency selectivity, the phasing mode of having used frequency pilot sign is effective.
On the other hand, used the phasing mode of frequency pilot sign, different with the phasing mode of having used pilot sub-carrier, not correction successively by each OFDM symbol.Therefore, the big more interval that then frequency pilot sign is embedded modulation signal of the many-valued degree of many-valued modulation system must be narrow and small more.So, if in adaptive modulation system, carry out satisfying the phasing of all many-valued modulation systems, then particularly in the lower many-valued modulation system of many-valued degree efficiency of transmission can descend.
In addition, for the phasing that has used frequency pilot sign, owing to before obtaining frequency pilot sign, can't carry out phasing, so it is long to carry out the interval of phasing.Therefore, under the situation of the many-valued modulation system of the many-valued degree of height, the error of phase place rotation may surpass allowed band in the demodulation process process.
Like this, in the phasing mode, exist being fit to and being not suitable for for many-valued modulation system.But receiver in the past uses identical phasing mode to the modulation signal that receives from transmitter.Therefore, receiver in the past can't carry out best phasing according to the many-valued modulation system of using in the transmitter.
Summary of the invention
The present invention finishes in view of the foregoing.The objective of the invention is to, a kind of receiver that can carry out best phasing according to the many-valued modulation system of using in the transmitter is provided.
The receiver that the present invention relates to is used to adaptive modulation communication system with transmitter, and this transmitter sends the modulation signal that use generates according to the selected many-valued modulation system of circuit quality from a plurality of many-valued modulation systems.Above-mentioned modulation signal has the symbol string of expression to the data of above-mentioned receiver transmission.Determined the corresponding relation of above-mentioned symbol and bit string by selected many-valued modulation system in the above-mentioned transmitter.The receiver that the present invention relates to possesses many-valued modulation system judegment part, phasing mode selection portion, phasing portion and detection unit.Above-mentioned many-valued modulation system judegment part constitutes, and differentiates the above-mentioned many-valued modulation system that is used for above-mentioned modulation signal according to the above-mentioned modulation signal that receives from above-mentioned transmitter.Above-mentioned phasing mode selection portion constitutes, and the many-valued degree of the above-mentioned many-valued modulation system that determines according to above-mentioned many-valued modulation system judegment part selects to be used for the phasing mode of phasing of the symbol of above-mentioned modulation signal from pre-prepd a plurality of phasing modes.Above-mentioned phasing portion constitutes the phase place of using the selected above-mentioned phasing mode of above-mentioned phasing mode selection portion to proofread and correct above-mentioned symbol.Above-mentioned detection unit constitutes, and the above-mentioned many-valued modulation system that determines according to above-mentioned modulation system judegment part is judged the corresponding bit string of above-mentioned symbol that has been corrected with in above-mentioned phasing portion phase place.
According to this invention, select the phasing mode based on the many-valued degree of the above-mentioned many-valued modulation system of using in the above-mentioned transmitter.Therefore, can correspondingly with the above-mentioned many-valued modulation system used in the above-mentioned transmitter carry out best phasing.
Preferably, above-mentioned transmitter has primary modulation mode and secondary modulation mode.Above-mentioned primary modulation mode is the many-valued modulation system that according to the rules benchmark is selected from the different a plurality of many-valued modulation system of many-valued degree, generates the primary modulation symbol of the above-mentioned symbol of expression.Above-mentioned secondary modulation mode is a multi-carrier modulation.Above-mentioned secondary modulation mode generates the secondary modulation symbol according to a plurality of subcarrier stacks that above-mentioned primary modulation symbol will constitute complex amplitude.Above-mentioned secondary modulation mode constitutes the above-mentioned modulation signal that is made of a plurality of above-mentioned secondary modulation symbols.Above-mentioned modulation signal has frequency pilot sign every the stipulated time.Above-mentioned frequency pilot sign is known secondary modulation symbol for above-mentioned receiver.Above-mentioned known secondary modulation symbol is made of the subcarrier with known complex amplitude.Above-mentioned secondary modulation symbol comprises pilot sub-carrier.Above-mentioned pilot sub-carrier is known subcarrier for above-mentioned receiver.Above-mentioned known subcarrier has known complex amplitude.Above-mentioned phasing mode selection portion constitutes, if the above-mentioned many-valued degree of the above-mentioned many-valued modulation system that above-mentioned many-valued modulation system judegment part determines is less than setting, then select to use above-mentioned frequency pilot sign to proofread and correct the 1st phasing mode of the phase place of above-mentioned symbol, if above-mentioned many-valued degree is more than setting then select to use above-mentioned pilot sub-carrier to proofread and correct the 2nd phasing mode of the phase place of above-mentioned symbol.
In this case, when the many-valued degree of the above-mentioned many-valued modulation system of in above-mentioned transmitter, using during, even the phasing of above-mentioned frequency pilot sign that carried out the phasing effect is also bigger in the stronger transmission environment of frequency selectivity use less than setting.On the other hand, when the many-valued degree of the above-mentioned many-valued modulation system of in above-mentioned transmitter, using when setting is above, realize easily high-transmission efficient use the phasing of above-mentioned pilot sub-carrier.So, can correspondingly with the above-mentioned many-valued modulation system used in the above-mentioned transmitter carry out best phasing.
More preferably, above-mentioned phasing mode selection portion constitutes, if the above-mentioned many-valued degree of the above-mentioned many-valued modulation system that above-mentioned many-valued modulation system judegment part determines is less than setting, then only select above-mentioned the 1st phasing mode, if above-mentioned many-valued degree is more than setting then select above-mentioned the 1st phasing mode and above-mentioned the 2nd phasing mode.
In this case, always used above-mentioned the 1st phasing of above-mentioned frequency pilot sign.Therefore, the control of above-mentioned phasing portion becomes simple.And, in above-mentioned the 1st phasing mode, by each above-mentioned subcarrier execution of phase correction.So,, also always can realize the effect of phasing preferably even under the stronger communication environments of frequency selectivity.
Further preferred, above-mentioned phasing portion constitutes, when in above-mentioned phasing mode selection portion, having selected under the situation of above-mentioned the 1st phasing mode and above-mentioned the 2nd phasing mode, according to above-mentioned the 1st phasing mode the phase place of above-mentioned symbol is proofreaied and correct again after according to above-mentioned the 2nd phasing mode the phase place of above-mentioned symbol being proofreaied and correct.
In this case, can use pilot sub-carrier to carry out phasing by each symbol.And, can remove the error that produces because of the phasing that has used pilot sub-carrier by the phasing that has used frequency pilot sign.So, can carry out best phasing to the bigger many-valued modulation system of many-valued degree.
Preferably, use the efficiency of transmission under the situation that the selected above-mentioned phasing mode of above-mentioned phasing mode selection portion proofreaies and correct the phase place of above-mentioned symbol to set the afore mentioned rules value according to above-mentioned phasing portion.
In this case, can correspondingly with the many-valued modulation system used in the above-mentioned transmitter carry out best phasing, and can improve efficiency of transmission.
Description of drawings
Fig. 1 is the skeleton diagram of the receiver of execution mode 1.
Fig. 2 is the skeleton diagram that possesses the communication system of the same receiver.
Fig. 3 is the key diagram of 16QAM planisphere.
Fig. 4 is the key diagram of the configuration of subcarrier and pilot sub-carrier.
Fig. 5 is the key diagram of the structure of ofdm signal.
Fig. 6 is the key diagram of the embedded structure of frequency pilot sign.
Fig. 7 is the skeleton diagram of the receiver of execution mode 2.
Embodiment
(execution mode 1)
The receiver 10 of present embodiment has constituted adaptive modulation communication system (back is called " communication system ") with transmitter 20 as shown in Figure 2.Communication system is carried out the packet communication based on the ofdm signal of being modulated (being the OFDM modulation in the present embodiment) by transmitter 20.In addition, be used for from transmitter 20 to the transmission channel 30 of receiver 10 transmission OFDM modulating waves can be wired also can be wireless.
Here, transmitter 20 has many-valued degree different a plurality of many-valued modulation system, for example 16QAM and 64QAM as the primary modulation mode.Transmitter 20 is selected many-valued modulation system (that is to say that transmitter 20 carries out Adaptive Modulation) with the benchmark of regulation during carrying out symbol when coupling a plurality of many-valued modulation system different from many-valued degree.For example, transmitter 20 selects the highest many-valued modulation system of many-valued degree so that the transmission speed of data is the fastest.In addition, transmitter 20 also can be according to the many-valued modulation system of Capacity Selection of the state (circuit quality) of transmission channel 30 and data so that transmission speed more than fixed value.
In addition, transmitter 20 possesses the reference signal source (not shown) with crystal emitter.Transmitter 20 uses the reference frequency of reference signal source emission to carry out inverse discrete Fourier transform (OFDM modulation) and frequency translation.In addition, in receiving device 10, also possesses reference signal source.
Like this, transmitter 20 sends the OFDM modulating wave that uses from a plurality of many-valued modulation systems (16QAM, 64QAM) the selected many-valued modulation system of benchmark in accordance with regulations and generate.
Here, in the many-valued modulation system of the high many-valued degree of 64QAM etc., the permissible error angle when using the bit string of the complex symbol decision symbol on the complex number plane is less.Therefore, need carry out phasing by each symbol.Below, be that example describes the permissible error angle among the QAM with 16QAM.
Fig. 3 has represented the symbol configuration (signaling point configuration) on bit string [0000]～[1111] corresponding complex number plane with 16QAM.Here Gray code is made as prerequisite.Blueline L1 among Fig. 3 presses the mid point of Q (Quadrature-Phase) direction of principal axis by the line segment between each symbolic point that connects bit string [1110] and bit string [1010].Blueline L2 presses the mid point of I (In-Phase) direction of principal axis by the line segment between each symbolic point that connects bit string [1010] and bit string [1011].The complex symbol that receiver 10 receives be present in comprise bit string [1010] by the situation among blueline L1, the L2 area surrounded A12 under, be estimated as this complex symbol and represent that the probability of bit string [1010] is higher.But in fact, the complex symbol that the phase place rotation (reference arrow Q1) that reason produces in the error of reference frequency can cause being present in transmitter 20 in the regional A12 may not be present in the regional A12 in receiver 10.In this case, in the judgement of bit string, produce mistake.
The if there is no error of reference frequency, the corresponding complex symbol of bit string [1010] that receives with receiver 10 then is that the center is Gaussian Profile with the symbolic point of expression bit string [1010].Therefore, not breaking away from original zone with symbolic point is permissible error angle θ 1 contradiction not that condition is set each symbolic point.For example, under the situation of 16QAM, permissible error angle θ 1[degree] be 16.88.
The permissible error angle θ 1 that has represented representative QAM in the table 1.Permissible error angle θ 1 becomes big along with many-valued degree and diminishes as can be seen from Table 1.
[table 1]
| Many-valued modulation system | 16QAM | 64QAM | 256QAM | 1024QAM |
| Permissible error angle θ 1 (degree) | 16.88 | 10.55 | 7.69 | 6.06 |
Then, the phase place rotation of each OFDM symbol of producing because of the error of reference frequency in the OFDM modulation is discussed.As the main cause of the phase error that produces owing to the rotation of the phase place of OFDM symbol, these two kinds of the errors (the 2nd error) when error (the 1st error) in the time of can considering the needed carrier frequency synchronization of demodulation process (frequency translation) of OFDM and sample frequency synchronous (fast Fourier transform).If the sample frequency of fast Fourier transform is made as fs, the size (FFT size) of fast Fourier transform is made as the N point, will protect the time at interval (Guard Interval) to be made as Tgi, then the holding time Ta of each OFDM symbol represents with following formula (1).
[numerical expression 1]
Phase error based on the 1st error and the 2nd error is an additivity.Therefore, if with carrier frequency be made as fc, will modulate and two processing of demodulation between the reference frequency error be made as e, the phase error angle θ 2[degree of each OFDM symbol then] represent with following formula (2).
[numerical expression 2]
For example, specification (the specification IEEE 802.11a of the WLAN that IEEE (U.S. electric institute of electronics) formulates) according to IEEE 802.11a-1999, if allowing the reference frequency error of each reference signal source is 20ppm, then can reach the reference frequency error e of 40ppm in two processing of modulation and demodulation.For the error of carrier frequency fc,, generally converge on the frequency error of fs/2 by utilizing the automatic frequency correction circuit of receiver.So top formula (2) can be deformed into following formula (3).
[numerical expression 3]
In addition; specification according to IEEE 802.11a-1999; the sample frequency fs of fast Fourier transform is that the holding time Ta of 20MHz, OFDM symbol is that the big or small N of 4 μ sec (wherein, protection interlude Tgi be 0.8 μ sec), fast Fourier transform is 64 points.
If the specification according to IEEE 802.11a-1999 is calculated top formula (3), then phase error angle θ 2 is 2.88.So, in 64QAM, just surpassed permissible error angle θ 1 with 4 symbols.In addition, according to the specification of IEEE 802.11a-1999, requiring 1 grouping maximum is 1000 bytes.Therefore, if additional redundant digit based on error correction, then the OFDM symbol that can send in 1 grouping is about 27 symbols.So, surpassing under the situation of permissible error angle θ 1 correctly 1 grouping of demodulation with 4 symbols.
Therefore, IEEE 802.11a-1999 regulation is as follows: be made as pilot sub-carrier PSC1～PSC4 that it doesn't matter with transfer of data with 4 in whole 52 subcarriers as shown in Figure 4,48 of being left are made as the subcarrier SC0～SC47 that is used for transfer of data.Therefore, can use pilot sub-carrier PSC1～PSC4 to carry out phasing by each OFDM symbol.
But, making under the situation that has bigger frequency selectivity in the transmission characteristic of signal in influence because of multipath fading, the S/N of frequency that embeds pilot sub-carrier is than might extremely worsening.In this case, used the correction error of the phasing mode of pilot sub-carrier to become big.Therefore, special when being the many-valued modulation system of high many-valued degree, enforcement phasing BER sometimes can worsen on the contrary.For example, near the pilot sub-carrier PSC1 in Fig. 4, owing to frequency characteristic 1000 worsens, so used the precision of the phasing of pilot sub-carrier PSC1 to reduce.
In the stronger transmission environment of frequency selectivity, it is effective using the phasing mode of frequency pilot sign.Frequency pilot sign is made of known symbol in receiving device 10 and transmitter 20.In addition, frequency pilot sign was embedded in the modulation signal (grouping) that is made of the OFDM symbol at interval with regular time.Therefore, can use frequency pilot sign to carry out phasing by each subcarrier.
But the phasing mode of having used frequency pilot sign is not the correction successively by each OFDM symbol.Therefore, the big more interval that then embeds frequency pilot sign in modulation signal of the many-valued degree of many-valued modulation system must be narrow and small more.For example, in 16QAM, it is enough embedding frequency pilot sign every 5 symbols in modulation signal.Relative therewith, in 64QAM, the interval that must embed frequency pilot sign in modulation signal is set for every 3 symbols.So, in adaptive modulation system, if constitute the phasing that can carry out satisfying whole many-valued modulation systems, then particularly efficiency of transmission reduction in the lower many-valued modulation system of many-valued degree.
In addition, for the phasing that has used frequency pilot sign, owing to before obtaining frequency pilot sign, can't carry out phasing, so it is long to carry out the interval of phasing.Therefore, under the situation of the many-valued modulation system of the many-valued degree of height, in the demodulation process process, also might surpass permissible error angle θ 1.
So, transmitter 20 so that receiver 10 can optionally use frequency pilot sign phasing and used the mode of the phasing of pilot sub-carrier to generate modulation signal.
For example, modulation signal (grouping) is made of short preamble SP, long preamble LP and data portion D as shown in Figure 5.
In order to set up timing synchronization, (X1～X10) constitutes short preamble SP every basic cycle T1 (=0.8 μ sec) transmitter 20 and known synchronization pattern (specific pattern) X of receiver 10 to be repeated 10 times.That is to say, constitute short preamble SP by the repeating signal of basic cycle T1.
For channel estimating, transmitter 20 and all known synchronization pattern Y repetition 2 times (Y1, Y2) of receiver 10 are constituted long preamble LP every basic cycle T2 (=3.2 μ sec).
Data portion D is the zone that is used to transmit the data of the information of preserving data bit and modulation system etc.
In modulation signal, according to the short preamble SP of the arranged in order of short preamble SP, long preamble LP, data portion D, long preamble LP and data portion D.
In addition, the protection of the later half part in each zone being duplicated and obtaining GI1, GI2 have at interval been added in each regional front of long preamble LP and data portion D.Can reduce the influence of multipath by protection interval GI1, GI2.
Automatic frequency correction circuit 11 uses short preamble SP and long preamble LP to proofread and correct the phase place rotation of each ofdm signal after baseband signal having been carried out analog/digital conversion (AD conversion).
Bigger frequency error between the reference frequency of the short preamble SP detection of automatic frequency correction circuit 11 initial uses transmitter 20 and the reference frequency of receiver 10.For example carry out the detection of frequency error by multiplying each other with conjugate complex number of modulation signal that has postponed basic cycle T1 and the modulation signal behind the basic cycle T1.
Then, automatic frequency correction circuit 11 uses long preamble LP to detect frequency error.According to having used the detection of the frequency error of long preamble LP with the same order of the detection of the frequency error that has used short preamble SP.If use long preamble LP, then can detect 1/{2T2} (=fs/{264}) this smaller frequency error.
Automatic frequency correction circuit 11 will use the antiphase of short preamble SP and the detected frequency error of long preamble LP and the modulation signal that receives to multiply each other.Thus, automatic frequency correction circuit 11 carries out phasing (frequency correction).
Protection is removed circuit 12 at interval and is removed by transmitter 20 additional protection interval GI1 and GI2 in modulation signal.
Fast Fourier transform circuit 13 usefulness are carried out discrete Fourier transform based on the sample frequency of reference frequency to ofdm signal.Thus, fast Fourier transform circuit 13 is used for the multicarrier demodulation that partial wave becomes a plurality of sub-carrier signals.Extract the component of the complex symbol of each subcarrier thus.
Phase-correcting circuit 14 is proofreaied and correct the phase place rotation based on the primary modulation symbol of frequency error.Phase-correcting circuit 14 possesses the portion of inferring 141, equalization portion 142 and phase error and removes portion 143.
Inferring portion 141 uses frequency pilot signs to infer the impulse response of frequency field of the transmission channel 30 of each subcarrier.The transmission characteristic of each subcarrier is represented in impulse response.About following the modulation signal of preamble, infer portion 141, the given data (synchronization pattern X or the long preamble LP synchronization pattern Y of short preamble SP) of preamble is considered as frequency pilot sign, infers the phase place rotation and the amplitude error (impulse response of each subcarrier) of this given data.About the modulation signal of back, per stipulated time has frequency pilot sign, infers phase place rotation and amplitude error according to this given data.For the phase place rotation and the amplitude error of inferring out, can be made as use next frequency pilot sign proofread and correct before effectively, also can be used for the correcting value to the correcting value of next frequency pilot sign and current pilot symbol carried out suitable weighted and the value that obtains is made as the corrected value based on next frequency pilot sign.In addition, for frequency pilot sign, also can be with the complex amplitude of whole subcarriers as given data, but also can only in the subcarrier of the bigger frequency field of frequency selectivity, embed given data.In this case, the transmission characteristic that derives the subcarrier that does not embed given data according to the transmission characteristic of the subcarrier that has embedded given data gets final product.
The contrary characteristic that the impulse response of each subcarrier of inferring out in the portion 141 will be inferred by equalization portion 142 multiplies each other with the then complex symbol of each subcarrier of preamble.Thus, the distortion that frequency domain is proofreaied and correct by each subcarrier by equalization portion 142, and proofread and correct based on the phase place of frequency error and rotate.In addition, to the bigger transmission channel of amplitude change, not only amplitude error is also proofreaied and correct in the phase calibration rotation.
Like this, infer the 1st phasing mode that portion 141 and equalization portion 142 use the phase place of frequency pilot sign correction symbol.Used the phasing of frequency pilot sign, owing to carry out phasing by each subcarrier, so even in the stronger transmission environment of frequency selectivity, the good phase calibration result is arranged also.
In addition, in the present embodiment, as shown in Figure 4,4 in whole 52 subcarriers is and the irrelevant pilot sub-carrier PSC1～PSC4 of transfer of data that remaining 48 is the subcarrier SC0～SC47 that is used for transfer of data.Symbol on pilot sub-carrier PSC1～PSC4 is given data (known symbol).
Phase error is removed portion 143 and is used 4 pilot sub-carrier PSC1～PSC4 to carry out the phasing of each OFDM symbol.Phase error is removed portion 143 and is detected frequency error in each pilot sub-carrier according to the known symbol of pilot sub-carrier PSC1～PSC4.Phase error is removed portion 143 and is used detected frequency error computing identical OFDM symbol to be carried out the phase error of each complex symbol that discrete Fourier transform obtains.And phase error is removed portion 143 antiphase and each complex symbol of the phase error that calculates is multiplied each other.Thus, phase error is removed the phase place rotation of portion's 143 corrections based on the symbol of frequency error.
Like this, phase error is removed the 2nd phasing mode that portion 143 is used to use the phase place of pilot sub-carrier correction symbol.
Modulation system judging circuit 16 is differentiated the many-valued modulation system that is used for modulation signal according to the modulation signal that receives from transmitter 20.In the present embodiment, the information of the modulation system that is comprised the data portion D according to the modulation signal that receives from transmitter 20, (identical OFDM symbol carried out obtain after the discrete Fourier transform each complex symbol) many-valued modulation system of differentiating each OFDM symbol is 16QAM or 64QAM.
Correcting mode is selected the many-valued degree of circuit 17 according to the many-valued modulation system that determines in the modulation system judging circuit 16, selects to be used to proofread and correct the phasing mode of phase place of the symbol of modulation signal from pre-prepd a plurality of phasing modes.In the present embodiment, it is to select the 1st phasing mode under the situation of 16QAM in the differentiation result of modulation system judging circuit 16 that correcting mode is selected circuit 17, selects the 2nd phasing mode differentiating under the situation that the result is 64QAM.
Selected above-mentioned phasing mode is proofreaied and correct the phase place of symbol in the phase-correcting circuit 14 use correcting modes selection circuit 17.
The phase error angle θ 2 of each OFDM symbol is 2.88 ° as described above.Table 2, the value of expression θ 1/ θ 2 in each many-valued modulation system of QPSK, 16QAM and 64QAM.In addition, table 2 has represented in order to be no more than permissible error angle θ 1 in the demodulation process process frequency pilot sign to be embedded the minimum mark space M (positive integer of the maximum of θ 1/ θ below 2) of modulation signal.Table 2 has also been represented frequency pilot sign to be embedded efficiency of transmission P1=M/ (M+1) under the situation of modulation signal with minimum mark space M.
[table 2]
| Many-valued modulation system | QPSK | 16QAM | 64QAM |
| θ1/θ2 | 15.63 | 5.86 | 3.66 |
| |
15 | 5 | 3 |
| P1＝M/M+1 | 0.94 | 0.83 | 0.75 |
As shown in Figure 6, in each many-valued modulation system, frequency pilot sign PS is embedded in the modulation signal every M symbol.Thus, prevented that phase error surpasses permissible error angle θ 1 in the demodulation process process.In addition, efficiency of transmission also becomes the highest.
In the 1st phasing mode of using frequency pilot sign, proofread and correct longer than the situation of using pilot sub-carrier at interval.This is because be every M symbol the opportunity that the equalization parameter of equalization portion 142 is updated.So, in the many-valued modulation system of the many-valued degree of height, be under the situation of 64QAM (minimum mark space M=3), if the interval of frequency pilot sign 5 just have that in demodulation process process phase error surpasses permissible error angle θ 1 may.
On the other hand, the 2nd phasing mode of use pilot sub-carrier PSC1～PSC4 is the correction successively by each OFDM symbol.Therefore, can carry out best phasing by each OFDM symbol (at identical OFDM symbol is carried out each complex symbol that discrete Fourier transform obtains).So, even the many-valued modulation system of high many-valued degree can prevent that also phase error is above the situation generation of permissible error angle θ 1 in the demodulation process process.
In the 1st phasing mode, need the interval of the big more frequency pilot sign that then in modulation signal, embeds of many-valued degree short more.Therefore, efficiency of transmission becomes lower easily.As shown in table 2 such, efficiency of transmission P1=0.83 in 16QAM, efficiency of transmission P1=0.75 in 64QAM.On the other hand, in the 2nd phasing mode, be used for pilot sub-carrier PSC1～PSC4 with 4 in whole 52 subcarriers.Therefore, having used the efficiency of transmission P2 under the situation of pilot sub-carrier is 0.92 (=48/52).So the 2nd phasing mode realizes high-transmission efficient easily than the 1st phasing mode.
Such as previously discussed, according to the receiver 10 of present embodiment, select the phasing mode based on the many-valued degree of the many-valued modulation system of using in the transmitter 20.Therefore, can correspondingly with the many-valued modulation system used in the transmitter 20 carry out best phasing.
Particularly, under the situation of many-valued degree less than setting (with the corresponding many-valued degree of 64QAM) of the many-valued modulation system of in transmitter 20, using, even the phasing of frequency pilot sign that carried out the phasing effect is also bigger in the stronger transmission environment of frequency selectivity use.On the other hand, the many-valued degree of the many-valued modulation system of in transmitter 20, using under the situation more than the setting (with the corresponding many-valued degree of 64QAM), realize easily high-transmission efficient use the phasing of pilot sub-carrier.So, can correspondingly with the many-valued modulation system used in the transmitter 20 carry out best phasing.
Yet the phasing mode selects circuit 17 also can constitute as following.Promptly, if the many-valued degree of the many-valued modulation system that determines in the many-valued modulation system judging circuit 16 is less than setting (with the corresponding many-valued degree of 64QAM) then the phasing mode selects 17 in circuit to select the 1st phasing mode, if many-valued degree is more than setting (with the corresponding many-valued degree of 64QAM) then the phasing mode selects circuit 17 to select the 1st phasing mode and the 2nd phasing modes.
In this case, always used the phasing of frequency pilot sign.Therefore, the control of phase-correcting circuit 14 becomes simple.And, in the 1st phasing mode, press each subcarrier execution of phase correction.So,, also can make the effect of phasing become big even under the stronger transmission environment of frequency selectivity.
Yet, infer the impulse response that portion 141 uses the known symbol of preamble and infer transmission channel 30 with the frequency pilot sign of fixed intervals embedding in modulation signal.For frequency pilot sign, all subcarriers have been embedded given data.Therefore, if use frequency pilot sign, then can carry out high-precision phasing to all subcarriers.But, before obtaining frequency pilot sign, can't carry out the inferring of impulse response of transmission channel 30.That is to say, in the phasing that uses frequency pilot sign, proofread and correct elongated at interval.Therefore, under the situation of the many-valued modulation system of the many-valued degree of height, in the demodulation process process, may surpass subcarrier complex amplitude, be the permissible error angle θ 1 of primary modulation symbol.
On the other hand, phase error is removed the impulse response that portion's 143 use pilot sub-carriers are inferred transmission channel 30.Therefore, can upgrade the impulse response of transmission channel 30 by each OFDM symbol.But, be that impulse response according to pilot sub-carrier utilizes extrapolation and interpolation to calculate about the presumed value of the impulse response of the subcarrier (that is to say the subcarrier that is used for transfer of data) beyond the pilot sub-carrier.Therefore, the presumed value of impulse response that is used for the subcarrier of transfer of data contains error.
So, upgrade impulse response if only use phase error to remove portion 143, then owing in equalization portion 142, using the contrary characteristic that calculates according to the impulse response after upgrading to carry out equalization, so all can accumulate at each renewal time error of impulse response.Therefore, if through certain time then the accumulation of error can surpass allowance (permissible error angle θ 1), the disappearance of the effect of phasing.Particularly because its permissible error angle of many-valued modulation system θ 1 that many-valued degree is bigger is more little, so the possibility that the effect of phasing disappears is higher.
So, the many-valued degree of the many-valued modulation system that determines in many-valued modulation system judging circuit 16 (has selected to select in the circuit 17 situation of the 1st phasing mode and the 2nd phasing mode in the phasing mode) under the situation more than the setting (with the corresponding many-valued degree of 64QAM), preferably, phase-correcting circuit 14 constitutes as following.That is, phase-correcting circuit 14 is proofreaied and correct the phase place of symbol according to the 1st phasing mode after according to the 2nd phasing mode the phase place of symbol being proofreaied and correct again.
By doing like this, can use pilot sub-carrier to carry out phasing by each OFDM symbol.And, the error that produces owing to the phasing that has carried out the use pilot sub-carrier can be removed by the phasing that has used frequency pilot sign, so, can carry out best phasing to the bigger many-valued modulation system of many-valued degree.
Yet, in above-mentioned example, select the setting of circuit 17 to be made as corresponding many-valued degree the phasing mode with 64QAM.But, also can use the phasing modes to select the efficiency of transmission under the situation that circuit 17 selected phasing modes proofread and correct the phase place of symbol to set setting according to phase-correcting circuit 14.
For example, consider that transmitter 20 has QPSK, 16QAM and the 64QAM situation as many-valued modulation system.
In this case, to differentiate the many-valued modulation system that is used for modulation signal be any of QPSK, 16QAM and 64QAM to the information of the modulation system that comprises the data portion D of many-valued modulation system judging circuit 16 according to the modulation signal that receives from transmitter 20.
Here, under the situation of the 1st phasing mode, each efficiency of transmission P1 of QPSK, 16QAM and 64QAM was 0.97,0.83 and 0.75 (with reference to table 2).
On the other hand, under the situation of the 2nd phasing mode, efficiency of transmission P2 is 0.92.
In this case, the phasing mode selects circuit 17 at the efficiency of transmission P1 many-valued modulation system higher than efficiency of transmission P2 (=0.92), selects to use the phasing of frequency pilot sign.That is, to select circuit 17 be to select the 1st phasing mode under the situation of 0.97 QPSK at efficiency of transmission P1 to the phasing mode.On the other hand, at the efficiency of transmission P1 many-valued modulation system lower, select to use the phasing of pilot sub-carrier than efficiency of transmission P2.That is, to select circuit 17 be to select the 2nd phasing mode under the situation of 0.83 16QAM at efficiency of transmission P1 to the phasing mode.Equally, to select circuit 17 be to select the 2nd phasing mode under the situation of 0.75 64QAM at efficiency of transmission P1 to the phasing mode.
That is to say that the phasing mode selects the many-valued degree of the many-valued modulation system (QPSK or 16QAM or 64QAM) that circuit 17 uses to be lower than the phasing that uses pilot sub-carrier under the situation based on the setting of efficiency of transmission P2 in transmitter 20.On the other hand, the phasing mode many-valued degree of selecting the many-valued modulation system that circuit 17 uses in transmitter 20 uses the phasing of frequency pilot sign under based on the situation more than the setting of efficiency of transmission P2.
For this situation, can correspondingly with the many-valued modulation system of use in the transmitter 20 carry out best phasing, and can improve efficiency of transmission.
(execution mode 2)
The receiver 40 of present embodiment is used for carrier wave communication system.
The data that 20 pairs in the transmitter that is used for carrier wave communication system mails to receiver 40 are carried out error correction coding.In addition, transmitter 20 is according to generating complex symbol (symbol coupling) by the corresponding relation of the symbol of many-valued modulation system decision and the bit string data after according to error correction coding.Transmitter 20 is after the DA conversion of complex symbol being carried out suitable waveform formation processing, by baseband signal and carrier multiplication are carried out frequency translation, after in the frequency band of necessity, carrying out displacement, the signal stipulated amplifies and generates modulating wave, and this baseband signal is to use the symbol string that obtained by the filter filtering of removing the aliasing signal that produces in the DA conversion to generate.Transmitter 20 sends the modulating wave that generates to transmission channel 20.
Here, transmitter 20 has many-valued degree different a plurality of many-valued modulation system, for example QPSK and 16QAM.Transmitter 20 is selected the fastest many-valued modulation system of transmission speed (that is to say that transmitter 20 carries out Adaptive Modulation) according to the state of transmission channel 30 from the different a plurality of many-valued modulation system of many-valued degree when carrying out the symbol coupling.
In addition, and transmitter 20 possesses the reference signal source (not shown) with crystal emitter.Transmitter 20 uses the reference frequency of reference signal source emission to carry out said frequencies conversion etc.In addition, in receiver 40, also possesses reference signal source.
The receiver 40 of present embodiment possesses A/D converter 41, FIR filter 42, downward sample circuit 43, phase-correcting circuit 44, decision circuit 45, many-valued modulation system judging circuit (many-valued modulation system judegment part) 46 and phasing mode and selects circuit (phasing mode selection portion) 47 as shown in Figure 7.The analog signal processing circuit that has omitted in the drawings that signal in the simulation part amplifies, disturbing wave is removed filter etc.
A/D translation circuit 41 uses the reference frequency of reference signal source (not shown) emission of transmitter 40 to generate carrier wave.A/D translation circuit 41 carries out down-conversion generation baseband signal by above-mentioned carrier wave and the modulation signal that receives via transmission channel 30 are multiplied each other to modulation signal.41 pairs of baseband signals of A/D translation circuit are carried out analog/digital conversion and are exported to FIR filter 42.
43 pairs of baseband signals of accepting via FIR filter 42 of sample circuit are carried out to down-sampling downwards.Sample circuit 43 is to the baseband signal of phase-correcting circuit 44 outputs behind down-sampling downwards.
Phase-correcting circuit 44 possesses phase error and removes portion 441, modulator 442 and phase estimating portion 443.Phase-correcting circuit 44 optionally uses the phasing mode of having utilized modulation again and has used phasing mode these two kinds of phasing modes of frequency pilot sign to proofread and correct phase place rotation based on frequency error.
Remove portion 441, modulator 442 and phase estimating portion 443 by phase error and used the phasing mode of modulation again.Under the situation of having used again the phasing mode of modulation, phase error is removed portion 441 with the keep intact constant decision circuit 45 that is sent to of the output of downward sample circuit 43.The IQ signal that the bit string that modulator 442 is judged decision circuit 45 is transformed on the complex plane utilizes plural number to carry out the modulation again of symbolism.The modulation signal again of 443 pairs of modulators of phase estimating portion 442 output and downwards output long-pending of sample circuit 43 carry out computing.Thus, phase estimating portion 443 calculates phase error.The antiphase (phase coefficient) that phase error is removed the phase error that portion 441 calculates phase estimating portion 443 multiplies each other with each complex symbol.Thus, phase error is removed the phase place rotation of portion's 441 corrections based on frequency error.That is to say that phase-correcting circuit 44 has used the phasing of modulation again.Used again the phasing of modulation to be performed on a regular basis.
Remove the phasing mode that portion 441 has used frequency pilot sign by phase error.Here, though the frequency pilot sign in the present embodiment is the known symbol with known phase, be not the frequency pilot sign after the such multi-carrier modulation of execution mode 1.But, used the phasing mode of this known symbol identical with execution mode 1, therefore omit its explanation.
The many-valued modulation system that many-valued modulation system judging circuit 46 is differentiated each grouping according to the information of the modulation system that comprises the modulation signal that receives from transmitter 20 is QPSK or 16QAM.
The phasing mode selects circuit 47 to be chosen in the phasing mode that will carry out in the phase-correcting circuit 44 according to the many-valued degree of the many-valued modulation system that determines in the many-valued modulation system judging circuit 46.
Here, under the situation of 16QAM, because the intersymbol distance on the complex plane is shorter, so the permissible error angle θ 1 of each symbolic point compares less with QPSK.Therefore, be under the situation of 16QAM for many-valued modulation system, if use and the same phasing mode of above-mentioned QPSK, then may comprise more mistake in the bit string after the demodulation, the complex symbol after the modulation may not be correct again.
So it is under the situation of QPSK in the differentiation result of many-valued modulation system judging circuit 46 that the phasing mode is selected circuit 47, selected to use the phasing mode of modulation again.It is under the situation of 16QAM in the differentiation result of many-valued modulation system judging circuit 46 that the phasing mode is selected circuit 47, selects to have used the phasing mode of frequency pilot sign.
Decision circuit 45 is according to the corresponding bit string of symbol that many-valued modulation system is judged with phase place is corrected in phase-correcting circuit 44 that determines in the many-valued modulation system judging circuit 46.In more detail, decision circuit 45 is transformed into soft decision value with phase place in the phase-correcting circuit 44 by each complex symbol of revisal by separating mapping according to the many-valued modulation system that determines in the many-valued modulation system judging circuit 46.Thus, the not shown data processing circuit output of decision circuit 45 in receiver 40 or outside the receiver 40 is from the bit string of the data of transmitter 20 receptions.
As described above, the receiver 40 of present embodiment, under the situation of many-valued degree less than setting (with the corresponding many-valued degree of 16QAM) of the many-valued modulation system of in transmitter 20, using (QPSK or 16QAM), used the phasing of modulation again.In addition, receiver 40, when the many-valued degree of the many-valued modulation system of in transmitter 20, using under the situation more than the setting (with the corresponding many-valued degree of 16QAM), used the phasing of frequency pilot sign.
Like this, according to receiver 40, select the phasing mode based on the many-valued degree of the many-valued modulation system of using in the transmitter 20.Therefore, can correspondingly with the many-valued modulation system used in the transmitter 20 carry out best phasing.
Claims (5)
1. a receiver is characterized in that,
Be used from adaptive modulation communication system with transmitter one, and this transmitter sends the modulation signal that uses from a plurality of many-valued modulation systems the selected many-valued modulation system of benchmark according to the rules and generate,
Above-mentioned modulation signal has the symbol string of the data that send to above-mentioned receiver of indicating;
Determined the corresponding relation of above-mentioned symbol and bit string by selected many-valued modulation system in the above-mentioned transmitter;
Above-mentioned receiver possesses many-valued modulation system judegment part, phasing mode selection portion, phasing portion and detection unit;
Above-mentioned many-valued modulation system judegment part constitutes, and differentiates the above-mentioned many-valued modulation system that is used for above-mentioned modulation signal according to the above-mentioned modulation signal that receives from above-mentioned transmitter;
Above-mentioned phasing mode selection portion constitutes, the many-valued degree of the above-mentioned many-valued modulation system that determines according to above-mentioned many-valued modulation system judegment part selects to be used for the phasing mode of phasing of the symbol of above-mentioned modulation signal from pre-prepd a plurality of phasing modes;
Above-mentioned phasing portion constitutes the phase place of using the selected above-mentioned phasing mode of above-mentioned phasing mode selection portion to proofread and correct above-mentioned symbol;
Above-mentioned detection unit constitutes, and the above-mentioned many-valued modulation system that determines according to above-mentioned modulation system judegment part is judged the corresponding bit string of above-mentioned symbol that has been corrected with in above-mentioned phasing portion phase place.
2. receiver according to claim 1 is characterized in that,
Above-mentioned transmitter has primary modulation mode and secondary modulation mode;
Above-mentioned primary modulation mode is the many-valued modulation system that according to the rules benchmark is selected from the different a plurality of many-valued modulation system of many-valued degree, generates the primary modulation symbol of the above-mentioned symbol of expression;
Above-mentioned secondary modulation mode is a multi-carrier modulation, and a plurality of subcarrier stacks that will constitute complex amplitude according to above-mentioned primary modulation symbol generate the secondary modulation symbol, constitute the above-mentioned modulation signal that is made of a plurality of above-mentioned secondary modulation symbols;
Above-mentioned modulation signal has frequency pilot sign every the stipulated time;
Above-mentioned frequency pilot sign is known secondary modulation symbol for above-mentioned receiver;
Above-mentioned known secondary modulation symbol is made of the subcarrier with known complex amplitude;
Above-mentioned secondary modulation symbol comprises pilot sub-carrier;
Above-mentioned pilot sub-carrier is known subcarrier for above-mentioned receiver;
Above-mentioned known subcarrier has known complex amplitude;
Above-mentioned phasing mode selection portion constitutes, if the above-mentioned many-valued degree of the above-mentioned many-valued modulation system that above-mentioned many-valued modulation system judegment part determines is less than setting, then select to use above-mentioned frequency pilot sign to proofread and correct the 1st phasing mode of the phase place of above-mentioned symbol, if above-mentioned many-valued degree is more than setting then select to use above-mentioned pilot sub-carrier to proofread and correct the 2nd phasing mode of the phase place of above-mentioned symbol.
3. receiver according to claim 2 is characterized in that,
Above-mentioned phasing mode selection portion constitutes, if the above-mentioned many-valued degree of the above-mentioned many-valued modulation system that above-mentioned many-valued modulation system judegment part determines is less than setting, then only select above-mentioned the 1st phasing mode, if above-mentioned many-valued degree is more than setting then select above-mentioned the 1st phasing mode and above-mentioned the 2nd phasing mode.
4. receiver according to claim 3 is characterized in that,
Above-mentioned phasing portion constitutes, when in above-mentioned phasing mode selection portion, having selected under the situation of above-mentioned the 1st phasing mode and above-mentioned the 2nd phasing mode, according to above-mentioned the 1st phasing mode the phase place of above-mentioned symbol is proofreaied and correct again after according to above-mentioned the 2nd phasing mode the phase place of above-mentioned symbol being proofreaied and correct.
5. receiver according to claim 2 is characterized in that,
Use the efficiency of transmission under the situation that the selected above-mentioned phasing mode of above-mentioned phasing mode selection portion proofreaies and correct the phase place of above-mentioned symbol to set the afore mentioned rules value according to above-mentioned phasing portion.
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| JP2008-082122 | 2008-03-26 | ||
| JP2008082122A JP5215704B2 (en) | 2008-03-26 | 2008-03-26 | Adaptive demodulation method |
| PCT/JP2009/056110 WO2009119736A1 (en) | 2008-03-26 | 2009-03-26 | Receiver |
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| JP (1) | JP5215704B2 (en) |
| KR (1) | KR101209501B1 (en) |
| CN (1) | CN101981842B (en) |
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| WO2010070884A1 (en) * | 2008-12-15 | 2010-06-24 | パナソニック株式会社 | Receiver apparatus and receiving method |
| JP5669668B2 (en) * | 2011-05-18 | 2015-02-12 | 三菱電機株式会社 | Demodulator and communication device |
| IN2014DN08872A (en) | 2012-04-24 | 2015-05-22 | Nec Corp | |
| SG11202000079UA (en) * | 2017-07-06 | 2020-02-27 | Sony Corp | Communication device and communication method |
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| CN1674574A (en) * | 2004-03-23 | 2005-09-28 | 三洋电机株式会社 | Receiving method and apparatus |
| WO2007029406A1 (en) * | 2005-09-07 | 2007-03-15 | Nec Corporation | Adaptive radio/modulation apparatus, receiver apparatus, wireless communication system and wireless communication method |
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| JP2000269919A (en) * | 1999-03-16 | 2000-09-29 | Matsushita Electric Ind Co Ltd | Ofdm communication unit |
| JP3844951B2 (en) * | 2000-09-21 | 2006-11-15 | 三菱電機株式会社 | Receiver and adaptive equalization processing method |
| US6587697B2 (en) * | 2001-05-14 | 2003-07-01 | Interdigital Technology Corporation | Common control channel uplink power control for adaptive modulation and coding techniques |
| JP2004364321A (en) * | 2001-06-01 | 2004-12-24 | Sony Corp | Inverse spread apparatus, propagation line estimate apparatus, receiver and interference suppressing apparatus, inverse spread, propagation line estimate, reception and interference suppressing method, program for them, and recording medium with the program recorded thereon |
| DE60206356T2 (en) * | 2002-04-16 | 2006-05-11 | Sony International (Europe) Gmbh | Orthogonal frequency division multiplexing (OFDM) with channel prediction |
| TWI229981B (en) * | 2003-10-06 | 2005-03-21 | Chunghwa Telecom Co Ltd | Receiver of multi-carrier communication system |
| JP4359162B2 (en) * | 2004-02-24 | 2009-11-04 | 三洋電機株式会社 | Receiver |
| TWI268068B (en) * | 2004-11-10 | 2006-12-01 | Ind Tech Res Inst | Method and device for modulation recognition of digitally modulated signals with multi-level magnitudes |
| KR20080071484A (en) * | 2005-12-06 | 2008-08-04 | 로무 가부시키가이샤 | Frequency modulator and fm transmission circuit using the same |
| WO2008129811A1 (en) * | 2007-03-23 | 2008-10-30 | Panasonic Corporation | Radio transmission device and radio reception device |
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| CN1674574A (en) * | 2004-03-23 | 2005-09-28 | 三洋电机株式会社 | Receiving method and apparatus |
| WO2007029406A1 (en) * | 2005-09-07 | 2007-03-15 | Nec Corporation | Adaptive radio/modulation apparatus, receiver apparatus, wireless communication system and wireless communication method |
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| CN101981842B (en) | 2014-05-14 |
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| KR20100126568A (en) | 2010-12-01 |
| TWI385990B (en) | 2013-02-11 |
| WO2009119736A1 (en) | 2009-10-01 |
| TW201014291A (en) | 2010-04-01 |
| HK1154131A1 (en) | 2012-04-13 |
| JP5215704B2 (en) | 2013-06-19 |
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