TWI252657B - Carrier frequency offset and phase compensation device of OFDM system and method thereof - Google Patents

Abstract

The invention provides carrier frequency offset and phase compensation device of OFDM system and method thereof to compensate the phase rotation of receiver's OFDM signal resulting from the carrier offset between receiver and transmitter of system. The frequency offset compensation device and method utilize the phase difference of frequency response estimation value of two consecutive OFDM symbols in pilot subchannel of system to estimate carrier offset and father calculate the accumulated phase rotation to compensate the OFDM signal of receiver. The phase compensation device and method receive the signal of each subchannel signal of OFDM signal compensated by the frequency offset compensation device and method and further utilize the signal through further channel compensation of the pilot subchannel along with the phase difference between transmitted signal of transmitter to estimate phase error for compensating signal of each subchannel.

Description

1252657 V. INSTRUCTION DESCRIPTION (1) Technical Field of the Invention The present invention relates to processing of carrier frequency offset in an orthogonal frequency division multiplexing system, and more particularly to using a pilot subchannel of a frequency domain. Signal, frequency offset and phase compensation device and method for estimating and compensating carrier frequency offset to improve OFDM system performance. [Prior Art] With the advent of the broadband era, new broadband communication technologies are becoming increasingly important. In recent years, orthogonal frequency division multiplexing (OFDM) technology has been widely used in high-speed transmission system standards, such as Asymmetric Digital Subscriber Line (ADSL), IEEE 802.11a /g. Wireless local area network (WLAN), etc. Figure 1 is a block diagram of a typical OF DM communication system 100. The OF DM system 100 is connected to the signal (signal 1 mappi ng) device 1 〇1 in the N subchannels of the frequency domain (N is a power of 2) at the transmitting end (Tx). ), and the signals between the sub-channels have orthogonality to avoid "inter-carrier interference" (ICI), and then use an inverse fast Fourier transform (IFFT) device. 1 0 2 is converted into a time domain signal, and after the guard interval (GI), it is parallelized to a parallel-to-serial converter (P/S) 104, a bit-to-analog converter (digital-to-analog converter, DAC) 105, and carrier modulation, transmitted via channel 106. Receiving end

1252657 V. Description of the invention (2) After carrier demodulation and analog-to-digital converter (ADC) 10 7 sampling, the GI is removed 'and serialized to the parallel converter (serial -to-parallel converter, S/P) 110, and then sent to the fast Fourier transform (FFT) device 111 to convert back to the frequency domain signal, and perform channel compensation in each subchannel respectively. The signal demapping device 1 1 3 demodulates the original transmission data. In this way, high-speed transmission can be achieved by parallel transmission through n sub-channels. We call the output value of a set of N-point IFFTs a symbol (Symb〇l). Since the channel impulse response (CIR) is usually not ideal, it will cause a symbol to affect the reception of subsequent symbols at the receiving end after passing through channel 1 〇6, resulting in "inter-symbol interference" (inter- Symb〇l interference, isi). To avoid the problem of is I, an extra guard interval is usually added between OFDM symbols. There are two types of guard intervals: (Z Zero - Padding, ZP) and (2) Cyclic Pref ix (CP). ZP is the join - a series of 0 as GI, this method It has better energy efficiency. CP is the GI that is placed in the symbol after the symbol is copied. This method can reduce the ICI of each sub-pass caused by the channel impulse response. The 5-hole number processing of the part is completed by adding the circuit 103 of the protection zone and the circuit 1〇9 of the protection zone in Fig. 1. 曰 When demodulating the OF DM signal, the received time domain signal is first received. , the mother FFT converts back to the frequency domain signal, and demodulates separately in each subchannel.

1252657 V. Description of the invention (3) When the time domain signal of the input FFT has a synchronization error, it will cause additional ICI and phase rotation in the output frequency domain signal, causing its orthogonality to be destroyed, affecting the system. efficacy. Therefore, OFDM systems require more precision for synchronization than other communication systems. For the OF DM transmission system, the synchronization error includes the following four items: (1) carrier frequency offset, (2) carrier phase error, and (3) sampling frequency offset (sampling frequency) Offset) and (4) sampling phase error. Among them, the influence of the carrier phase error and the sampling phase error on the 〇FDM signal at the receiving end mainly results in a fixed phase rotation in the output of each subchannel in the frequency domain, so channel estimation and channel compensation can be used. Mechanism to eliminate. However, the addition of the carrier frequency offset and the sampling frequency offset in addition to causing additional I C I ' will result in cumulative phase rotation of each sub-channel output, resulting in progressive degradation of system performance. In view of this, the focus of the present invention is to propose some carrier frequency offset (hereinafter referred to as carrier frequency offset) and phase compensation method suitable for the system, which utilizes the signal of the pilot subchannel in the frequency domain. The carrier is tracing and compensating for the t-type synchronization error to enhance the operator of the 0FDM system. SUMMARY OF THE INVENTION The second invention is mainly applied to an OFDM system, which is sent at the transmitting end, and is coded into a FDM symbol, which is placed in a sub-channel transmission and transmission process of a plurality of frequency domains and utilizes a The carrier is modulated, and the subchannels

1252657 V. INSTRUCTIONS (4) Include at least one guide for transmitting detection and estimation, using pilot channel bit error, and adding demodulation. The compensation device may have a carrier frequency offset including: a known characteristic of the pilot source channel receiving end is compensated, and the frequency and at least one data of the channel channel estimated by the OFDM system are generated. The specific signal 'channel is used to transmit the fixed signal' estimate to avoid the carrier frequency to estimate the carrier frequency offset in the pilot sub-channel, and the difference between the two is to estimate the carrier frequency offset; a) 'the estimated rotation according to the frequency offset; The OF DM signal of the accumulation end calculated by a phase rotation accumulator. The receiving end of the OF DM system of the present invention, the receiving end OFDM signal meter device, the receiving rate response; the frequency phase accumulator of the one-frequency OFDM symbol (the estimated carrier (phase phase rotation, in the sub-channel) The subchannel is guided to perform system related data. The present invention is to improve the carrier frequency offset and the related phase offset. The receiving end of the system is to provide a frequency offset compensation cumulative phase rotation of the receiving end and the transmitting end, and its pilot The signal of the channel, the bias estimation device, the phase accumulator of the phase response accumulator using the phase response estimation value, and the phase compensation device according to the phase time domain or the frequency domain compensation receiving one. At the receiving end, the residual phase error of the OFDM signal received by the receiving end is compensated by the frequency offset compensation device, which includes: a phase difference estimating device, which compensates and channels the frequency offset compensation device by using a symbol OFDM signal Compensating for the phase error of the phase difference between the channel signal and the transmitting end originally transmitting the signal; a buffer storing the phase difference estimated residual phase error to Compensation at a symbol; and a phase rotator receiving the next symbol of each sub-channel signal, the pilot sub-difference compensation, means to estimate the estimated residual

Page 9 1252657 V. Description of the invention (5) Each sub-segment of the next symbol stored in the buffer is fed into the phase rotator and the receiving end of the other OFDM system of the present invention, after compensation, the residual phase remains. The OFDM signal of a symbol and the channel element are guided, and the original transmission is rotated, and the receiving end of the phase system compensates the local number of the transmission channel by using the phase of the receiving phase; a pilot sub-channel signal Using the phaser between the pilots to transmit signals, from the other receiving end of the buffer difference estimating device, compensating for the difference in the phase sub-channel of the OFDM signal to estimate the offset of the OF DM signal device at the carrier end. The phase difference signal between the numbers in the lead channel. The residual phase channel signal is compensated. Compensation for receiving bit error, medium, frequency channel compensation, to perform the channel, the position difference is used to estimate the receiver to receive the estimated residual, and the receiving end and the bit rotation, before and after the two frequency offsets; An OFDM signal is estimated by the channel complement to estimate the residual error plus an advanced compensation channel; wherein, after compensation, the phase compensation terminal OF DM signal is included in the frequency: a buffer offset compensation device compensation device Buffer channel compensation; the residual phase of the residual phase of the one-phase channel compensator is misinterpreted: a complement error between the transmitter and the receiver: the OFDM symbol is used to calculate the residual phase compensation of the residual phase compensation after the sub-compensation The frequency difference phase device of the carrier-frequency offset of the compensation module, the channel signal, and the difference, can be set to I, and can be used in the offset compensation device to ensure that all the sub-carriers are received and the carrier is estimated. And the transmitter side '' and one phase signal, and compensate. A compensating device capable of OFDM frequency offset, responding to the estimated value rotation, to compensate for receiving the frequency, and using the transmitting end to compensate for another purpose of each sub-invention, proposes a frequency offset compensation method, which can

Page 10 1252657 V. Description of the invention (6) The receiving end of the system compensates for the cumulative phase rotation of the 0 FD number at the receiving end caused by the carrier frequency offset between the receiving end and the transmitting end, which includes the following steps: (a) receiving guidance The signal of the subchannel is used to estimate the frequency response of the pilot subchannel; (b) the carrier frequency offset is estimated by using the phase difference of the frequency response estimates of the two OFDM symbols in the pilot subchannel; (c) Estimating the carrier frequency offset, calculating the cumulative phase rotation; and (d) compensating the OFDM signal at the receiving end according to the calculated cumulative phase rotation. Another object of the present invention is to provide a phase compensation method, which can compensate the residual phase error after the OFDM signal of the receiving end is compensated by the frequency offset compensation device at the receiving end of the system, and includes the following steps: (a) utilizing In the OFDM signal of a symbol, the phase difference between the pilot subchannel signal after the channel offset compensation and the channel compensation is transmitted by the frequency offset compensation device to estimate the residual phase error; (b) the estimated residual The phase error is stored in a buffer; and (c) the residual phase error stored in the buffer compensates for each subchannel signal of the next symbol; wherein step (c) may also be preceded by a step (c0): Channel compensation is performed for each subchannel signal of the next symbol. Another object of the present invention is to provide a phase compensation method for compensating the residual phase error of the OFDM signal received by the frequency offset compensation device at the receiving end of the system, which includes the following steps: (a) All subchannel signals compensated by the frequency offset compensation device in the OFDM signal of one symbol by one buffer; (b) the pilot subchannel signal of the symbol is taken out from the buffer for channel compensation; Using the pilot subchannel, the phase difference between the signal compensated by the channel and the original transmitted signal of the transmitting end

Page 11 1252657 V. Description of the invention (7) Estimating the residual phase error; and (d) taking the data subchannel signal of the symbol from the buffer and compensating for the estimated residual phase error. In order to enable the reviewing committee to have a better understanding and recognition of the present invention, the embodiments of the present invention will be described in detail with reference to the drawings. [Embodiment] FIG. 2 is a block diagram of a carrier modulation and demodulation system having a carrier frequency offset. In Figure 2, due to the drift of the local oscillators 21 and 22, the carrier frequency 发射 at the transmitting end is not the same as the carrier frequency 接收 at the receiving end. At this time, the fundamental frequency signal at the receiving end will be due to the frequency. The offset causes phase rotation, which causes signal demodulation to generate errors and system performance to deteriorate. In the following analysis, the carrier frequency offset table is not ^f = L-fc. In addition, it is assumed that the OF DM system uses N sub-channels in the frequency domain, including at least one pilot sub-channel, and the rest are data sub-channels. The influence of carrier frequency offset on OFDM signals can be divided into time domain and frequency domain. In terms of time domain, it is assumed that the time domain signal of the OFDM symbol has N + NGI sampling points, where N is the number of points of the FFT, and NGI is the number of points of the GI, then the first sampling point of two consecutive OFDM symbols There will be a phase difference of ΐπ, Ν + NGI) & fT, where T is the sampling interval. As the transmitted symbols increase, this phase difference causes a problem of cumulative phase rotation. In the frequency domain, assuming that the frequency response of the kth subchannel is & fixed, and the kth subchannel signal of the nth OFDM symbol at the transmitting end is, the kth of the nth OFDM symbol at the receiving end The subchannel signal is

Page 12 1252657 V. Description of invention (8) e^N+N^+^.[(Hk ·ΧΜί,)® Φ(/Λ -Δ/)] ei[2ym(N+NGI)A^ -^Αθ ] e /[2 ^¢1^+^)4/7+Ai9] e —v —

ICI (1-1) where hM 2 & - b is the initial phase difference, and 〇 (/) is a discrete time Fourier transform corresponding to a rectangular window function with an N point of 1 (discrete- Time Fourier transform, DTFT), that is, «=〇1(7) fragrant black (1 - 1), Φ (-Δ is the distortion factor of each subchannel, where amplitude distortion (ampntude sin(^4 /T) distortion) is skl (phase) to phase distortion (phase dis tort i on ) is <NV)^fT. Since in the OF DM system, the pilot subchannel is known to transmit the receiving end.

Page 13 1252657 V. Invention Description (9) Signal, we can use the following formula to obtain the frequency response estimation value of the pilot subchannel: Λ ej[2m(N+NGI)^A9] njc (1-2) Where k is the pilot index of the pilot subchannel X n, where k is a known signal, and the remaining ICI items and noise items. From the above analysis, it can be known that the carrier frequency offset can be estimated by using the phase difference of the frequency response estimates of the two OFDM symbols before and after. If the OFDM system uses K pilot subchannels, when estimating the carrier frequency offset, the phase difference between the frequency response estimates of the two OFDM symbols in each of the pilot subchannels can be separately calculated, and then added. , get the average value, that is, KA: = pilot index

2π{Ν + NGI) AfJ Equation (1 -3) where « is the carrier frequency offset estimated by the nth symbol. When the carrier frequency offset is not large, the influence of the I C I term in the equation (;1 -2) can be ignored, and the amplitude distortion and phase distortion can be eliminated by channel compensation.

Page 14 1252657 V. Description of the invention (10) Therefore, it is only necessary to compensate for the cumulative phase rotation in the frequency domain. Therefore, the present invention emits a frequency offset compensation apparatus for compensating in the frequency domain, as shown in FIG. 2, the frequency offset compensation apparatus 30a can be at the receiving end of the OFDM system, and between the receiving end and the transmitting end of the ^ domain compensation system. The carrier frequency offset causes reception: the cumulative phase rotation of the OFDM signal. The frequency offset compensating device 3A includes: - the pilot channel estimating device 31 receives the pilot subchannel number of the 〇FDM system to estimate the frequency response of the pilot subchannel (as shown by the equation (丨-2)), The frequency offset estimating device 32 is coupled to the pilot subchannel estimating device 3 to estimate the carrier frequency offset by estimating the phase difference of the frequency response of the two 〇FDM symbols in the leading subchannel; a phase accumulator 3, coupled to the 苜, the counting device 3 2, according to the carrier frequency offset estimated by the frequency offset estimating device 32, the cumulative phase rotation; and a phase rotator 34a coupled to the phase 'ticger 33, According to the cumulative phase rotation calculated by the phase accumulator 33, the OFDM signal at the receiving end is compensated (i.e., γ in the divisor), the evening domain, and when the carrier frequency offset is large, it is difficult due to the influence of the ICI term. In the f elimination, it is preferable to return to the time domain compensation cumulative phase rotation. Therefore, the present invention proposes a frequency offset compensation device that is compensated in the time domain = structure, as shown in Fig. 3B. The device 3〇b can be connected to the time domain compensation system at the 1st end of the 〇FDM system. The carrier frequency offset between the receiving end and the transmitting end is the cumulative phase rotation of the receiving end OFDM signal. The frequency offset compensation f is set to 3卟Z and the components included are almost the same as the frequency offset compensating device 30a except for the phase chirp portion. The frequency offset compensation device 3, the phase rotator 34a is the output of the phase 'FT device 1 1 1 , that is, compensated in the frequency domain;

Page 15 1252657 V. INSTRUCTION DESCRIPTION (Π) In the compensation device 3 0 b, the phase rotator 3 4 b is coupled to the input of the F F Τ device 1 1 1 , that is, compensated in the time domain. With the foregoing frequency offset compensating device 30a or 30b, the present invention proposes a frequency offset compensating method, which comprises the steps of FIG. 4: 41 $Introduction channel estimating device 31 receives the signal of the guiding subchannel to estimate the guiding subchannel Frequency response; 42 frequency offset estimating means 32 estimates the clipping frequency offset by using the phase difference of the frequency response estimates of the two 〇FDM symbols in the leading subchannel; 4 3 phase accumulator 3 3 according to step 4 2 estimated carrier frequency offset, calculating cumulative phase rotation; and 4 4 phase rotator 3 4 a or 3 4 b accumulating phase rotation according to step 43 to compensate the OFDM signal of the receiving end. μ ' If the OFDM system includes a plurality of pilot subchannels, then in step 41, the frequency response of each pilot subchannel is estimated, and in step 42, the front and rear of each pilot channel are The phase differences of the frequency response estimates of the two OFDM symbols are summed, and the average value is used to estimate the carrier frequency offset (as shown by equations (1 to 3)). If the frequency offset compensation device 3 0 a is used, step 44 compensates the frequency domain number of the receiving end 〇 FD Μ矾. If the frequency offset compensation device 3 〇 ^ is used, step 44 compensates the receiving terminal OF DM signal. Time domain signal. The 0 F D signal at the receiving end will still have a residual phase error after being compensated by the frequency offset compensation set 3 〇 3 〇 b. If each subchannel of the FDM system needs to perform coherent demodulation (ie, receive terminal pass)

1252657 V. INSTRUCTIONS (12) The amplitude and phase of the signal must be identical to the subchannel signal originally transmitted by the transmitter. A mechanism is needed to compensate for this residual phase error. It is assumed that after the compensation by the frequency offset compensation device 30a/30b, the kth subchannel signal of the first OFDM symbol at the receiving end is the equation (2 - 1), and the remaining ICI terms and the residual phase error signal of the Δ mn are residual. The term again assumes that k is the index value of the pilot subchannel, and it can be inferred from equation (2-1) that the result of the pilot subchannel signal at the receiving end is kn,k after being compensated by the channel.

Hk where (2-2) where /Δ is estimated using the system preamble (prearnb 1 e) and the frequency response of the kth subchannel is the remaining 1C I term and miscellaneous

Page 17 !252657

From the above analysis, it can be seen that the residual phase error can be determined by the phase difference between the channel compensation result and the specific ideal value of the original guide subchannel. If the OFDM system uses K pilot subchannels, when estimating the residual phase estimation error, the phase difference between the channel compensation result of each pilot subchannel and the specific ideal value of the original primer channel can be separately calculated, and then added, I $ has the average value, that is,

Equation (2-3) When the phase noise of the local oscillators 21 and 22 is small, and the residual phase error of two consecutive OF DM symbols does not change much,

The phase error estimate derived from the pilot subchannel signal of the previous OFDM symbol is used to compensate for the subchannel signal of the latter OFDM symbol. Therefore, the present invention proposes an architecture of a delay phase compensating apparatus, as shown in Fig. 5; Division: = 22: refers to the use of the previous symbol to obtain the latter symbol. The phase compensation Jun 詈 R π compensates the receiving end OFDM signal via the buccal offset a at the receiving end of the 0FDM system, the phase error of the replenishment, which includes the compensated device 30a/3〇b compensation, and the residual OF DM signal, The frequency offset compensation phase difference estimating device 5 1 'receives a symbol 1 member device 30a/30b and a channel compensation device

苐18页1252657 V. INSTRUCTIONS (14) 1 1 2 The compensated pilot subchannel signal (ie, in equation (2-2)), and between the pilot subchannel signal and the system transmitting end originally transmitting the signal a phase difference to estimate the residual phase error; a buffer 5 2 storing the residual phase error estimated by the phase difference estimating means 51 for compensating for the next symbol; and a phase rotator 53 for receiving the Each subchannel signal of a symbol is compensated by the residual phase error stored in the buffer 52. The structure of FIG. 5A can also be slightly modified as shown in FIG. 5B, wherein the phase compensation device 50b includes the same components as the frequency offset compensation device 50a, but in operation, the architecture of FIG. The sub-channel signal of the symbol is compensated by the channel compensating device 1 12 and then sent to the phase rotator 53. With the foregoing phase compensating device 5 〇a, the present invention provides a delay phase compensating method, which comprises the steps of FIG. 6: 6 1 phase difference estimating device 51 uses a symbol OFDM signal, and the frequency offset compensating device 50a/5 Ob and the channel compensation device 112 compensates the phase difference between the pilot subchannel signal and the original transmission signal of the system transmitter to estimate the residual phase error; 62 stores the residual phase error estimated in step 61 in the buffer The buffers 5 2; and 63 compensate the respective sub-channel signals of the next symbol with the residual phase error stored in the buffer 52. If the OF DM system includes a plurality of guide subchannels, in step 61, the phase difference of each pilot subchannel signal of the symbol is separately calculated and given

Page 19 1252657 V. Description of the invention (15) If the phase compensating device 50b is used, the compensation method is the same as step 6b, but in step 63, before the phase compensation, the channel compensating device 1 1 2 is used to compensate Each subchannel signal of a symbol. When the local oscillators 2 1 and 2 2 have large phase noise, the residual phase error of two consecutive OFDM symbols will also change greatly. In this case, the pilot subchannel by an OF DM symbol should be used. The phase error estimate obtained by the signal compensates for the data subchannel signal of the same OFDM symbol, so a buffer is needed to preserve the signals of all subchannels of a complete OF DM symbol, first using the pilot subchannel estimation. The residual phase error is compensated for the data subchannel. Accordingly, the present invention proposes an architecture of a buffered phase compensation device, as shown in Figure VII. Here, "buffered" means that one symbol is reserved for subsequent phase estimation and compensation for the same symbol. The phase compensating device 70a can compensate the residual phase error after the OFDM signal of the OFDM system is compensated by the frequency offset compensation device 3 0a/3 Ob at the receiving end of the OFDM system, and includes: a buffer 71, receiving and retaining a character In the OFDM signal of the element, all the sub-channel signals compensated by the frequency offset compensation device 3 0a/3 Ob; a pilot sub-channel compensation device 7 2 receives the pilot sub-channel signal of the symbol from the buffer 7 1 , To proceed

Channel compensation (the result is the I ntk phase difference estimation device 73 in equation (2-2), coupled to the pilot subchannel compensation device 72, using the signal and system after channel compensation in the pilot subchannel The transmitting end originally transmits the phase difference between the signals to estimate the residual phase error; and a phase rotator 74 receives the data subchannel signal of the symbol from the buffer 71 and uses the residual phase estimated by the phase difference estimating means 73. The error is compensated.

1252657

The structure of Figure 7A can also be slightly repaired. The components included in the 7 0 b are invited to phase//, the phase compensation operation of τ, the structure of Figure 7Β; ^ compensation device... identical, but the data of the symbol The sub-channel signal H is rotated by the data sub-channel compensation device 75. After the channel compensation is performed, the phase is rotated and the phase compensation dream is used. ^ ^ 斗,士娜, 严严七,+好,置七 0 a, there is no explicit slow-motion phase compensation method, the package Λ Λ 藏 0 0 B Figure 8 steps: 81 to buffer 7 1 to retain a 斡 ^ / 疋 疋 OFDM signal, the frequency is lower than the 30a/30b compensation of the female shoulder Partial compensation for the province...7, = a, Λ all sub-channel signals; in the set 7 2, the symmetry channel signal is taken out from the buffer 7 1 to perform channel compensation; the 导 兀 guide j j difference estimation device 73 utilizes The residual phase error between the pilot =, Λ γ, s signal and the original transmission signal of the system transmitter; and the estimation of the 1 82 83 84 phase rotator 74 to retrieve the symbol number of the symbol from the buffer 71, And the residual phase error estimated in step 83 is used. If the 0FDM system includes a plurality of guide subchannels, then step: In order to calculate the phase difference of each pilot subchannel signal of the symbol, after summing up, the average value is used to estimate the residual phase error (as shown in the figure). Qiao (2~3 If the phase compensation device 7 0 b is used, the compensation method is the same as the step only in step 8 4, before the phase compensation is performed, the data sub-channel signal of the symbol is compensated by the data sub- 8 4 , the device 7 5 In the present invention, the above two types of frequency offset compensation may also be placed.

1252657 V. Invention Description (17) 3 0 a/30b and four phase compensation devices 50a/50b/70 a/70b, depending on the actual needs of the OFDM system, each of them is combined into a compensation module for complete processing The carrier frequency offset causes the phase rotation of the OF DM signal at the receiving end. Figure 9 is an example of such a compensation module. The frequency offset compensation device 3 0 b and the phase compensation device 7 0 a can be used for the OF DM system in which the carrier frequency offset and phase noise of the local oscillator are large. Further, referring to FIG. 9, the pilot subchannel estimating device 31 in the frequency offset compensating device 30b performs the operation of Equation (1-2), and the pilot subchannel compensating device 72 in the phase compensating device 70a performs as The operation of equation (2-2) is calculated. If Z# of equation (2 -1) is divided by X n,k and slice *

Pn,k = e + Ω Equation (2 -4) Ω

For the rest of the ICI, where k is the index value, term and noise term of the pilot subchannel. From the above analysis, the residual phase error can be estimated by the following equation (assuming that the OFDM system uses K guide subchannels)

Page 22 1252657 V. Invention Description (18) Allow = pilot index Equation (2-5) In Equation (2-4), /V is the result of the pilot subchannel, after channel estimation and channel compensation; As seen in Fig. 9, it can be regarded as the result of processing by the pilot sub-channel estimating means 31 and the guiding sub-channel compensating means 72. Therefore, we can slightly modify the architecture of the phase compensation device in Figure 9, as shown in Figure 10. Block 10 of Figure 10 can be viewed as a phase compensation device that is part of the architecture that compensates for residual phase rotation. In block 100, the signal is processed by the pilot subchannel estimating means 31 and the pilot subchannel compensating means 72, and the result is the corpse. The operation performed by the phase difference estimating means 1 0 0 2 is Equation (2-5), which is simpler than the phase difference estimating means 73 (Execution Equation (2 - 3)). In addition, the data buffer 1 0 0 1 is only used to store the signal of the resource subchannel, unlike the buffer 7 1 which needs to store all the subchannel signals, thus saving space. In other words, the architecture of Figure 10 can be used not only for OFDM systems where the carrier frequency offset and phase noise of the local oscillator are large, but also further simplify the hardware design and cost. The above description of the present invention is intended to be illustrative of the preferred embodiments of the invention. It will be apparent to those skilled in the art that such modifications and adaptations may be made without departing from the spirit and scope of the invention. In summary, the present invention is implemented

Page 23 1252657

Page 24 1252657 Schematic description of the diagram Figure 1 is a block diagram of a typical OFD Μ communication system. Figure 2 is a block diagram of a carrier modulation and demodulation system with carrier frequency offset. Figure 3 is a block diagram of a frequency offset compensation apparatus for compensating in the frequency domain. FIG. 3B is a schematic diagram of a frequency offset compensation apparatus for compensating in the time domain according to the present invention. FIG. 4 is an operation flowchart of the frequency offset compensation method of the present invention.

Figure 5A is an architectural diagram of a delay phase compensation device of the present invention. Figure 5B is a block diagram of another delay phase compensation device of the present invention. Figure 6 is a flow chart showing the operation of the delay phase compensation method of the present invention. Figure 7A is a block diagram of a buffered phase compensation device of the present invention. Figure 7B is a block diagram of another buffered phase compensation device of the present invention. Figure 8 is a flow chart showing the operation of the buffered phase compensation method of the present invention. Figure 9 is an architectural diagram of an example of a compensation module combined in accordance with the present invention. Figure 10 is a block diagram of the resulting architecture after a slight change in Figure 9. Description of the figure: 1 0 0 - 0 FD Μ Communication System 102 - IFFT device 1 0 4 - Parallel to 亊 column converter 106 - Channel 1 0 9 - Circuit for removing guard interval 1 1 1 - FF Τ Device 1 1 3 - Signal solution corresponding device 1 0 1 - Signal corresponding device 1 0 3 - Circuit for increasing guard interval 1 0 5 - Digital to analog converter 1 0 7 - Analog to digital converter 1 1 0 - Serial to Parallel converter 1 12-channel compensation device 1252657 Brief description of the description 2 2 - Local oscillator 30b - Frequency offset compensation device 3 2 - Frequency offset estimation device 3 4 a - Operation flow of the phase rotator method 5 0b - Phase compensation device 5 2 - Buffer 2 1 - Local oscillator 3 0a - Frequency offset compensation device 31 - Guide subchannel estimation device 3 3 - Phase accumulator 3 4b - Phase rotator 4 1 to 4 4 - Frequency offset compensation of the present invention 5 0a-phase compensating device 5 1 - phase difference estimating device 5 3 - phase rotator 6 1 to 6 3 - operation flow 70b of the delayed phase compensating method of the present invention - phase compensating device 72 - guiding subchannel compensating device 7 4 - Phase rotator 7 0a - Phase compensation device 7 1 - Buffer 7 3 - Phase difference estimation device 75 - Data sub Channel compensation apparatus 1001-- data buffer 8 1~8 4 - buffered phase compensation operation flow of the method of the present invention 1000-- phase compensation means 1002-- phase difference estimating means

Page 26

Claims (1)

1252657 VI. Application for Patent Range 1. A method for a quadrature split, a complex line transfer transmitter, the receiver includes: a guide estimate, a frequency, a value, a phase, a phase, and a phase. The system is based on a sub-pass change in the frequency domain, wherein the specific signals are used to compensate the phase of the system-side OF DM signal. For the calculation of the rotation of the accumulating device, please use the patent transponder to request the patent channel package to estimate the estimated pass-through device, the channel difference to estimate the device, and the Moma estimation device to engage the cumulative phase range. The first compensation range includes the frequency offset compensation transmitter in each frequency multiplex (OFDM) system, and encodes the data into OFDM symbols, which are placed in the channel transmission, and are transmitted by using a carrier into the subchannel. At least one pilot subchannel, wherein the frequency offset compensation device is located at a cumulative phase rotation caused by a carrier frequency offset between the receiving end and the transmitting end of the system, the frequency offset compensating device package device, Receiving the signal of the guiding subchannel, responding to the frequency of the channel; coupling to the guiding subchannel estimating device, using the frequency response of the two OFDM symbols before and after the carrier frequency offset, and connecting to the frequency offset estimation The device estimates the carrier frequency offset according to the frequency offset, accumulates the phase rotation, and connects to the phase accumulator, and the phase accumulator bit rotates to compensate the 0 FD Μ signal of the receiving end. The frequency offset compensation apparatus of claim 1, wherein the frequency domain signal of the OFDM signal of the receiving end. The frequency offset compensation apparatus of claim 1, wherein the phase-end signal of the OFDM signal of the receiving end. The frequency offset compensation device of claim 1, wherein if the subchannel is guided, the pilot subchannel estimates a frequency response of the pilot subchannels, and the frequency Page 27 1252657 VI. The patented range bias estimation device sums the phase differences of the frequency response estimates of the two OFDM symbols in each of the guide subchannels, and then estimates the average value. Carrier frequency offset. 5. A phase compensating apparatus for use in an orthogonal frequency division multiplexing (OFDM) system, the system is configured to encode data into OFDM symbols at a transmitting end, and distribute the sub-channels in a plurality of frequency domains for transmission. In the process, a carrier is used for modulation, wherein the subchannels include at least one pilot subchannel for transmitting a specific signal, and the receiving end of the system includes a frequency offset compensation device for compensating between the receiving end and the transmitting end. The carrier frequency offset causes phase rotation of the OFDM signal at the receiving end, and a channel compensation device is used for channel compensation of the signals of the subchannels. The phase compensation device is located at the receiving end of the system to compensate the receiving end OF DM After the signal is compensated by the frequency offset compensation device, the phase compensation device includes: a phase difference estimating device that receives a symbolic OFDM signal and is compensated by the frequency offset compensation device and the channel compensation device. Directing the subchannel signal and estimating the residual phase error by using the phase difference between the pilot subchannel signal and the original transmitted signal of the system transmitter; And storing a residual phase error estimated by the phase difference estimating device for compensating for a next symbol; and a phase rotator for receiving the subchannel signals of the next symbol and storing the residual by the buffer The phase error is compensated. 6. The phase compensation device according to claim 5, wherein the lower portion is 1252657 VI. Application for Patent Range The sub-channel signals of a symbol are first compensated by the channel compensation device and then sent to the phase rotator. 7. The phase compensation device of claim 5, wherein if the sub-channels comprise a plurality of guide sub-channels, the phase difference estimating device respectively calculates the frequency offset compensation device and the channel of the symbol The phase difference between each of the pilot subchannel signals compensated by the compensation device and the original transmitted signal is summed, and then the average value is used to estimate the residual phase error. 8. A phase compensation apparatus for use in an orthogonal frequency division multiplexing (OFDM) system, wherein the system encodes data into OF DM symbols at a transmitting end and distributes them in sub-channels of a plurality of frequency domains. During transmission, a carrier is used for modulation, wherein the sub-channels include at least one pilot subchannel for transmitting a specific signal, and at least one data subchannel for transmitting data, the system includes a frequency offset compensation device. For compensating for the phase rotation of the OFDM signal at the receiving end caused by the carrier frequency offset between the receiving end and the transmitting end, the phase compensating device is located at the receiving end of the system to compensate the compensation of the receiving end OFDM signal by the frequency offset compensating device. The residual phase error, the phase compensation device comprises: a buffer, receiving and retaining one of the symbolic OFDM signals, all of the subchannel signals compensated by the frequency offset compensation device; and a pilot subchannel compensation The device receives the pilot subchannel signal of the symbol from the buffer for channel compensation; and a phase difference estimating device coupled to the guiding subchannel compensation device, In the pilot subchannel, the signal compensated by the channel is transmitted by the system Page 29 1252657 6. The patent application scope originally transmits the phase difference between the signals to estimate the residual phase error; and a phase rotator receives the data subchannel signal of the symbol from the buffer, and uses the phase difference estimating device The estimated residual phase error is compensated. 9. The phase compensation device of claim 8, wherein the data subchannel signal of the symbol is first channel compensated by a data subchannel compensation device at the receiving end of the system, and then sent to the phase rotator. The phase compensation device of claim 8, wherein if the subchannels comprise a plurality of guide subchannels, the phase difference estimating device respectively calculates each of the symbols after the channel compensation The phase difference between the pilot subchannel signals and the original transmitted signals is summed and then averaged to estimate the residual phase error. 1 1. A compensation module for an orthogonal frequency division multiplexing (OFDM) system, which is configured to encode data into OFDM symbols at a transmitting end, and distribute them in sub-channels of a plurality of frequency domains for transmission. The process is modulated by a carrier, wherein the subchannels include at least one pilot subchannel for transmitting a specific signal, and at least one data subchannel for transmitting data, and the compensation module is located in the system. The receiving end compensates the phase rotation of the receiving end OFDM signal caused by the carrier frequency offset between the receiving end and the transmitting end, and the compensation module comprises: a frequency offset compensating device, wherein the front and rear OF DM are used in the guiding subchannel The phase difference of the frequency response of the symbol is used to estimate the carrier frequency offset, and then the cumulative phase rotation is calculated to compensate the OFDM at the receiving end. 1252657 6. Applying for a patent range signal; and a phase compensation device, receiving the subchannel signals of the OFDMA^ number compensated by the frequency offset compensation device, and using the signal after the channel compensation in the guide subchannel And the phase difference between the transmitting signal of the transmitting end of the system is used to estimate the residual phase error to compensate the signals of the sub-channels. The compensation module of claim 11, wherein the frequency offset compensation device compensates for a frequency domain signal of the OFDM signal at the receiving end. The compensation module of claim 11, wherein the frequency offset compensation device compensates for a time domain signal of the OFDM signal at the receiving end. The compensation module of claim 11, wherein if the sub-channels comprise a plurality of guide sub-channels, the frequency offset compensation device estimates each of the carrier frequency offsets In some of the pilot subchannels, the phase differences of the frequency response estimates of the two OFDM symbols are summed and averaged. The compensation module of claim 11, wherein the frequency offset compensation device comprises: a pilot subchannel estimating device receives the signal of the guiding subchannel to estimate a frequency response of the guiding subchannel; a frequency offset estimating device coupled to the guiding subchannel estimating device, using the guiding In the channel, the frequency difference of the frequency response of the two OFDM symbols is used to estimate the carrier frequency offset; a phase accumulator is coupled to the frequency offset estimating device, and the carrier frequency offset estimated by the frequency offset estimating device is used. , calculating the cumulative phase rotation; Page 31 1252657 VI. Patent application scope and a phase rotator coupled to the phase accumulator, the accumulated phase rotation calculated by the phase accumulator compensates the OFDM signal of the receiving end. The compensation module of claim 11, wherein if the sub-channels comprise a plurality of guide sub-channels, the phase compensation device estimates the residual phase error After the channel compensation, each of the pilot subchannel signals is summed with the phase difference between the original transmission signals, and then averaged. The compensating module of claim 11, wherein the receiving end of the system comprises a channel compensating device for channel compensation of the signals of the subchannels, the phase compensating device comprising: a phase difference estimating device receives the symbol of the OFDM signal, and compensates the pilot subchannel signal compensated by the channel compensation device by the frequency offset compensation device, and transmits the pilot subchannel signal and the transmitting end of the system a phase difference between the signals to estimate a residual phase difference; a buffer storing the residual phase error estimated by the phase difference estimating means for compensating for the next symbol; and a phase rotator for receiving the next one The subchannel signals of the symbols are compensated by the residual phase error stored in the buffer. 18. The compensation module of claim 17, wherein the sub-channel signals of the next symbol are first compensated by the channel compensation device, and then sent to the phase rotator for compensation. Page 32 1252657 VI. Patent application scope 19. If applying for special compensation device, a buffer offset compensation, a pilot sub-injection, a phase difference estimation, and a derivative error; a phase-spinning signal, supplemented with 2 0. Special data sub-compensation device 2 1. If the phase compensation range of the application-specific receiving end sub-channel is included, the receiving device supplements the channel-compensating signal meter device to pass the original transmission and the converter, and pays for it. The channel range of the profit channel includes a guide signal, and the device is a data buffer, and the frequency offset compensation comprises a guide subchannel supplementing the compensation module according to the guide item, wherein the compensation module And retaining, in the OFDM signal of a symbol, all of the sub-channel signals after the frequency compensation; receiving, by the buffer, the derivative of the symbol for channel compensation; and coupling to the guiding a subchannel compensating device, in a profit path, a phase difference between a signal compensated by the channel and a signal sent by the system to estimate a residual phase, and a residual phase error estimated by the subchannel difference estimating means for receiving the symbol from the buffer The compensation module of item 19, wherein the symbol number is first compensated by a data subchannel of the receiving end of the system, and then sent to the phase rotator. The compensation module according to Item 1, wherein the system introduction channel estimation device is configured to receive the guidance to estimate a frequency response of the guidance subchannel, and the method includes: receiving and retaining a symbol of the OF DM signal The signal of the data subchannel after the compensation is compensated; the receiving device receives the OFDM signal of the symbol, and the pilot subchannel signal processed by the channel estimating device Page 33 1252657 6. Applying the patent range number for channel compensation; a phase difference estimating device receiving the channel sub-channel compensated pilot channel signal from the pilot sub-channel compensation device to estimate the residual phase error; The first phase rotator receives the data subchannel signal of the symbol from the data buffer and compensates for the residual phase error estimated by the phase difference estimating means. The compensation module of claim 2, wherein the frequency offset compensation device comprises: a frequency offset estimation device coupled to the guide subchannel estimation device, wherein the guide subchannel is used Estimating the carrier frequency offset by the phase difference of the frequency response estimation values of the two OFDM symbols before and after; a phase accumulator coupled to the frequency offset estimating device and calculating according to the carrier frequency offset estimated by the frequency offset estimating device And accumulating phase rotation; and a second phase rotator coupled to the phase accumulator, and accumulating the phase rotation signal calculated by the phase accumulator to compensate the time domain signal of the receiving end of the terminal. 2 3 . A frequency offset compensation method used in an orthogonal frequency division multiplexing (OFDM) system, which encodes data into OFDM symbols at a transmitting end and is divided into subchannels of a plurality of frequency domains. Transmitting and transmitting, and using a carrier for modulating, wherein the sub-channels include at least one guiding sub-channel for transmitting a specific signal, and the frequency offset compensation method is used for 1252657 VI. Patent application scope 1~"~·· The receiving end of the system compensates the carrier frequency offset between the receiving end and the transmitting end to cause the cumulative phase rotation of the FDM signal at the receiving end. The frequency offset compensation method includes the following steps: The party (a) receives the signal of the guiding subchannel to estimate the guiding; the frequency response of the sy 逍 逍 ;; (b) using the pilot subchannel, the frequency response estimation of the two OFDM symbols before and after Measuring the phase difference of the carrier to estimate the carrier frequency offset; (c) calculating the cumulative phase rotation based on the carrier frequency offset estimated in step (b); (d) Compensate the 〇 F D Μ signal at the receiving end according to the cumulative phase rotation calculated in step (c). 2 4 · The frequency offset compensation method described in claim 23, wherein the step (d) is to compensate the frequency domain signal of the receiving end (10) signal. 25. The frequency offset compensation method according to claim 23, wherein the step (d) is to compensate the time domain signal of the OFDM signal at the receiving end. 2 6 The frequency offset compensation method according to claim 23, wherein if the subchannels comprise a plurality of guide subchannels, in step (a), each of the guides is estimated separately The frequency response of the channel, and in step (b), the phase difference of the frequency response estimates of the two 〇fDM symbols in each of the guide subchannels is summed, and then the average value is obtained. Estimate the carrier frequency offset. ~ ', 2 is.: Seed use;: Phase compensation method in Orthogonal Frequency Division Multiplex (〇FDM) system, which is used to encode data into 〇FM symbols at the transmitting end, and is divided into multiple frequency bands. Sub-channel transmission of the domain, using an is sink mm\ during transmission Page 35 1252657 6. Patent application range carrier modulation, wherein the sub-channels include at least one pilot subchannel for transmitting a specific signal, and the receiving end of the system includes a frequency offset compensation device for compensating the receiving end and The carrier frequency offset between the transmitting end causes phase rotation of the OFDM signal at the receiving end, and a channel compensating device is used for channel compensation of the signals of the sub-channels. The phase compensation method is used at the receiving end of the system. Compensating the residual phase error after the OFDM signal of the receiving end is compensated by the frequency offset compensating device, the phase compensating method comprises the following steps: (a) using a symbol OFDM signal, the frequency offset compensating device and the channel compensation Comparing the phase difference between the pilot subchannel signal compensated by the device and the original transmitted signal of the system transmitter to estimate the residual phase error; (b) storing the residual phase error estimated in step (a) in a buffer; (c) Compensating for the subchannel signals of the next symbol with the residual phase error stored in the buffer. 2 8. The phase compensation method according to claim 27, wherein the step (c) further comprises a step (cO): (c 0) using the channel compensation device to compensate the sub-symbols of the sub-symbols Channel signal. The phase compensation method according to claim 27, wherein if the sub-channels comprise a plurality of guide sub-channels, in step (a), the frequency offset of the symbol is separately calculated. Compensation device and channel compensation Page 36 1252657 VI. Scope of Patent Application The phase difference between each of these pilot subchannel signals after compensation by the device and the original transmitted signal is summed up and then averaged to estimate the residual phase error. 30. A phase compensation method for an Orthogonal Frequency Division Multiplexing (OFDM) system, which encodes data into OFDM symbols at a transmitting end, and distributes them in sub-channels of a plurality of frequency domains, and transmits The process is modulated by a carrier, wherein the sub-channels include at least one pilot subchannel for transmitting a specific signal, and at least one data subchannel for transmitting data, the system includes a frequency offset compensation device. The phase compensation method is used to compensate the phase shift of the receiving terminal OF DM signal caused by the carrier frequency offset between the receiving end and the transmitting end. The phase compensation method is used to compensate the receiving end OFDM signal by the frequency offset compensating device at the receiving end of the system. After the residual phase error, the phase compensation method comprises the following steps: (a) retaining all of the subchannel signals compensated by the frequency offset compensation device in a OFDM signal with a buffer; Extracting the pilot subchannel signal of the symbol from the buffer for channel compensation; (c) using the pilot subchannel, the signal compensated by the channel and the transmitting signal of the system transmitting the signal The phase difference is used to estimate the residual phase error; and (d) the data subchannel signal of the symbol is taken from the buffer and compensated by the residual phase error estimated in step (c). 3 1. The phase compensation method described in claim 30, wherein in step (d), the data subchannel signal of the symbol is first channeled. Page 37 1252657 VI. Scope of application for patents After compensation, the residual phase error estimated in step (C) is compensated. 3 2. The phase compensation method according to claim 30, wherein if the sub-channels comprise a plurality of guide sub-channels, in step (c), the channel compensation of the symbol is respectively calculated. The phase difference between each of the pilot subchannel signals and the original transmitted signal is summed and then averaged to estimate the residual phase error.