TW200417209A - 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

200417209 V. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to the processing of carrier frequency offset in an orthogonal frequency division multiplexing system, especially using pilot subchannels in the frequency domain. Signal to estimate and compensate the carrier frequency offset, in order to improve the frequency offset and phase compensation device and method of the system. [Previous Technology] 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 · 1 1 a / g wireless local area network (WLAN), etc. Figure 1 is a block diagram of a typical 0fdM communication system 100. The OF DM system 100 is arranged at the transmitting end (TX) to place the data to be transmitted through the signal mapping device 1101 into N subchannels in the frequency domain (N is a power of 2), and Make the signals between each sub-channel have orthogonality (〇rth 〇g ο na 1 ity) to avoid "inter-carrier interference" (I Cl). Next, an inverse fast Fourier transform (I FFT) device 102 is used to convert the signal into a time domain signal, and the guard interval (GI) is added to the parallel-to-serial converter (parallel-ΐο- serial converter (P / S) 104, digital-to-analog converter (DAC) 105, and carrier modulation, which are transmitted via the channel; I 0 6. Receiver (rx) then 200417209 V. Description of the invention (2) Carrier demodulation and analog-to-digital converter (ADC) 107 sampling, the GI is removed, and the serial To the parallel converter (se: rial — t〇-paral lel converter (S / P) 110), and then send it to the fast Fourier transform (FFT) device ill to convert back to the frequency domain signal, and perform the channel in each sub-channel. Compensation (chan ire 1 compensation), and finally the signal demapping (signal demapping) device 1 1 3 demodulate the original transmission data. In this way, through j \ f sub-channels for parallel transmission, high-speed transmission can be achieved.

We refer to the output value of a set of N-point IFFTs as Symbols. And because the channel impulse response (CIR) is usually not ideal, it will cause a symbol to pass through channel 106 and affect the reception of subsequent symbols at the receiving end, resulting in "inter-symbol interference" (inter- symbol interference (ISI). In order to avoid the problem of ISI ’, an extra guard interval is generally added between the 0FDM symbols. There are two types of practice in the protection interval: (1) Zero-Padding (ZP),

And (2) Cyclic Prefix (CP). ZP is to join a continuous 0-hour GI, this method has better energy efficiency. CP is to copy a symbol after the segment signal is placed in the rain of that symbol. When this method can reduce the ICI between the sub-channels caused by the channel impulse response, this part of the signal processing is to increase the protection in Figure 1. The circuit of the interval 103 and the circuit of removing the protection interval 109 are completed. When demodulating the 0FDM signal, the received time domain signal needs to be converted into a frequency domain signal through F F T first, and demodulated in each subchannel. If

Page 7 200417209 V. Description of the invention (3)

The presence of a synchronization error in the time-domain signal input into the FFT will cause additional I C I and phase rotation in the output frequency-domain signal, causing its orthogonality to be destroyed and affecting system performance. Therefore, compared with other communication systems, the OFDM system requires higher accuracy of synchronization. For OF DM transmission systems, the synchronization error includes the following four items: (1) carrier frequency offset, (2) carrier phase error, and (3) sampling frequenCy (Ffff) and (4) sampling phase error. Among them, the impact of carrier phase error and sampling phase error on the 0FDM signal at the receiving end is mainly due to the fixed phase rotation in the output of each sub-channel in the frequency domain. Therefore, channel estimation and channel compensation mechanisms can be used. To eliminate. However, in addition to the carrier frequency offset and the sampling frequency offset, in addition to causing an additional / 1 C I ′, the output of each sub-channel will generate a cumulative phase rotation, resulting in a gradual degradation of system performance. At this point, the focus of the present invention is to propose some carrier frequency offset (hereinafter referred to as carrier frequency offset) and phase compensation methods applicable to the system, which use the signal of the pilot channel in the frequency domain to Carrier

= Track and compensate for various synchronization errors to improve the operating efficiency of the 0FDM system. [Summary of the invention] The application of the sub-i ΐming is mainly applied to the 0fm system, which is located at the transmitting end, Guan Beiyi, is coded as 0FDM symbols, and is divided into multiple sub-channels in the frequency domain. (Process And use a wave to perform modulation, in which the sub-channels

200417209 Known data at the end of the introduction channel is compensated for the known information of the communication channel. Therefore, this issue is caused by the 0FDM system. The offset frequency of the channel is estimated to be two before and after the channel frequency. 4. Description of the invention (4) Contains at least one lead system for transmitting and detecting and estimating, using a pilot channel bit error, and demodulation with a plus sign. The compensated device, the carrier frequency offset includes: a guide to estimate the difference in the leader channel of the leader to estimate the carrier 'according to the frequency bit rotation; and a 0 FD Μ signal at the end of the bit accumulator. 0FDM of the present invention After the system is compensated, the residual uses a compensated leader difference to estimate the specific signal estimated by the residual device and a phase rotation and at least one data. The channel is used to transmit the fixed signal, which is estimated to avoid One of the objectives of the carrier frequency is to control the receiving end, the receiving OF DM signal meter device, and the response of the receiving rate; the one-frequency 0FDM symbol frequency phase accumulator (position the estimated carrier (phase phase rotation, in the sub-channel). The sub-channel is guided for system-related data. The present invention is to facilitate carrier frequency offset and related phase offset to influence the receiving end of the system, which is to provide a frequency offset compensation for the cumulative phase rotation of the receiving end and the transmitting end. Signal, the bias estimation device, calculates the cumulative phase rotator by using the phase response accumulator wave frequency offset of the estimated response value. The purpose of the domain compensation receiver is to propose a phase compensation device that can compensate the remaining phase error of the 0FDM signal at the receiving end through the frequency offset compensation device, which includes:-phase difference estimation split, 0FDM signal, the frequency offset The compensating device compensates the channel phase difference between the transmission of the channel signal. The buffer, f blocks the phase difference and estimates the residual phase error 'for use in compensating the next symbol device' to receive the symbol. Signals of each sub-channel, (5) 200417209 V. After the description of the invention and the use of the next character to send the OFDM system compensation for this phase, leave a guide for the symbol channel signal element, and use the original transmission bit rotator to The difference between the residual channel signals sent to compensate is to compensate for the positioning error. After channel compensation, the channel difference is received by the receiver to estimate the difference. It is the two frequency deviations before and after receiving the end position rotation; and 0FDM Channel to estimate each sub-bit rotator stored in the punch, plus the receiving end of the other, the remaining phase of the 0 FD Μ signal; a sub-channel signal of the pilot The phase between the pilot signals is used to compensate the phase of the 0FDM signal at the receiving end from the receiving end of the system which is known by the buffer estimation device. The phase difference in the pilot channel is used to estimate the carrier to compensate for the 0FDM signal at the receiving end. After the compensation device compensates, the signal of the phase difference channel between the signal * is transmitted in the pilot channel. Another object of the present invention is to compensate the phase error; the signal can also be channel compensated first to propose a phase receiving 0FDM signal. It includes: a frequency offset compensation device compensating device, which compensates from the channel of the line; the residual phase error of the data of the symbol is estimated after the channel compensation, and a residual phase error is proposed between the compensation and the transmitting end, which includes: a 0FDM symbol Furthermore, the signal residual phase error compensation device that accumulates the compensation of each sub-pass of a phase-compensation device is passed through a frequency offset compensation buffer, and the compensated buffer is connected to a signal and error of phase difference estimation; the sub-channel signal is used to compensate the module The carrier frequency offset frequency offset compensation frequency response phase rotation can be set, receiving the channel signal, and transmitting, A frequency offset compensation method is proposed based on the compensation 4 series. After the reading, the device can be used to ensure that all the sub-receivers are installed with the symbol and the transmission number and phase number. 0 > The device caused by opDM > estimates the value to supplement the frequency. And use the original each sub)) can be

Page 10 200417209 V. Description of the invention (6) The receiving end of the system compensates for the cumulative phase rotation of the receiving end OFDM ^ 1 caused by the carrier frequency offset between the receiving end and the transmitting end, which includes the following steps: (a) the receiving guide The signal of the primer channel is used to estimate the frequency response of the pilot channel; (b) The carrier frequency offset is estimated using the phase difference between the frequency response estimates of the two 0FDM symbols in the pilot channel; Calculate the cumulative phase rotation based on the estimated carrier frequency offset; and (d) compensate the 0 FD M signal at the receiving end based on the calculated cumulative phase rotation. Another object of the present invention is to propose a phase compensation method, which can compensate the residual phase error of the OFFDM signal at the receiving end of the system after being compensated by the frequency offset compensation device at the receiving end of the system, which includes the following steps: (a) using In the 0FDM signal of a symbol, the phase difference between the pilot channel signal compensated by the frequency offset compensation device and the channel compensation and the original transmission signal of the transmitting end is used to estimate the residual phase error; (b) the estimated residual The phase error is stored in a buffer; and (c) each sub-channel signal of the next symbol is compensated by the residual phase error stored in the buffer; wherein, a step (cO) can also be added before step (c): Each sub-channel signal of the next symbol performs channel compensation. Another object of the present invention is to propose a phase compensation method, which can compensate the residual phase error of the OFFDM signal at the receiving end of the system after being compensated by the frequency offset compensation device, which includes the following steps: (a) A buffer retains all the sub-channel signals of the 0FDM signal of a symbol after being compensated by the frequency offset compensation device; (b) takes the symbol's leading sub-channel signal from the buffer for channel compensation; (c) The phase difference between the signal after the channel compensation and the signal originally transmitted by the transmitter is used in the guide channel.

Page 11 200417209 V. Description of the invention (7) Estimated residual phase error; and (d) The data subchannel signal of the symbol taken from the buffer is taught to compensate with the estimated residual phase error. In order to allow your reviewers to further understand and agree with the present invention, the embodiments of the present invention are described in detail below with reference to the drawings. [Embodiment] Figure 2 is a block diagram of a carrier modulation and demodulation system with a carrier frequency offset. In Figure 2, 'Because the frequency of the local oscillator 21 and 22 will drift, the carrier frequency Λ of the transmitting end is not the same as the carrier frequency A of the receiving end. At this time, the fundamental frequency signal of the receiving end will be biased by the frequency. Shifting causes phase rotation, which causes signal demodulation errors and system performance. In the following analysis, the carrier frequency offset is expressed as Δ Δ / =-fc. In addition, it is assumed that the OFDM system uses N subchannels in the frequency domain, which includes at least one pilot subchannel, and the rest are data subchannels. The effect of carrier frequency offset on OFDM signal can be divided into two aspects: time domain and frequency domain. In the time domain, assuming that the time domain signal of the 0FDM symbol has N + NGI sampling points, where N is the number of FFT points and NGI is the number of GI points, the first sampling point between two consecutive 0FDM symbols There will be a phase difference of seven NGI) & fT, where T is the sampling interval. As the number of transmitted symbols increases, this phase difference causes a problem of cumulative phase rotation. In the frequency domain, assuming that the frequency response of the k-th sub-channel is & fixed, and the signal of the k-th sub-channel of the n-th 0FDM symbol at the transmitting end is', then the number of OF DM symbols at the receiving end is fixed. k sub-channel signals are

Page 12 200417209 V. Description of Invention (8). (㈣ 以 顺 + 叫 [(圮 声 Φ (Λ — △ /)] = ej [2 ^ (N + NGI) AJT + Le] mfJ ^ .φ (_Λ /) M-1 + β ^ ^ β. 〇 (^ Δ /) 2 = 〇Χϊ # λ) V -------- ν ---------- ^ 1C! Formula (1-1) where Α 无 = not the initial phase The difference '① (/) is a discrete-time Fourier transform (DTFT) corresponding to a rectangular window function where N points are all 1. That is, in formula (1-1), ① (-△ /) is the distortion factor of each sub-channel, where the amplitude distortion (amplitude δΐη (^ Δ / Τ) distortion) is ^^ / 0 and the phase distortion (phase distortion) is -1) Δ / Γ. Since in the 0FDM system, the guide channel is known to the transmitting and receiving end.

Page 13 200417209 V. Description of the invention (9) Signal, we can use the following formula to obtain the estimated value of the frequency response of the guide channel: Η n, kej [2m (N + NGI) ^ A9] 7 /, · Φ ( -δ /) + γηΛ • n, k Equation (1-2) where k is the pilot index of the pilot channel, and mn, k is the known signal, which is the remaining ICI term and noise item. From the above analysis, it can be known that the carrier frequency offset can be estimated by using the phase difference between the frequency response values of the two OFFDM symbols before and after. If the OF DM system uses K pilot channels, when estimating the carrier frequency offset, the phase difference between the frequency response estimates of the two OF DM symbols before and after each pilot channel can be calculated and added. After summing up, find the average value, which is 2π (Ν + Νσι) Α / ηΤ Κ it = pilot index Formula (1-3) where «is the carrier frequency bias estimated by the nth symbol When the carrier frequency deviation is not large, the influence of the ICI term * in the formula (: 1-2) can be ignored, and the amplitude distortion and phase distortion can be eliminated by channel compensation.

Page 14 200417209 V. Description of Invention (10) It is only necessary to compensate the cumulative phase rotation in the frequency domain. The invention of a frequency offset compensation device for compensating in the frequency domain is not mentioned. The frequency offset compensation device 30a can compensate the carrier frequency offset 7 between the receiving end and the transmitting end of the system in the 3F domain of the 0FDM system and rotate in the cumulative phase of the frequency OFDM signal. Frequency offset compensation device ^ human · end primer channel estimation device 31, receives the FD_ system guide ^ 5 · two leading numbers to estimate the frequency response of the guide sub channel (such as the formula of alum and frequency offset estimation device 32 Connect to the guide channel estimation = use the phase difference between the two 0FDM symbols in the guide channel to estimate the carrier frequency offset; a phase accumulator value estimation device 32, based on the frequency offset The frequency deviation cumulative phase rotation estimated by the estimation device 32; and a phase rotator 34a coupled to the phase 'totalizer 33 to compensate the 0FDM signal at the receiving end according to the cumulative phase calculated by the phase accumulator 33 (that is, ( [Bu 丨) In the frequency domain, when the carrier frequency deviation is large, since the influence of the ICI term Γ # is eliminated, the better method is to return to the time domain to compensate for the cumulative phase rotation term force. Therefore, the present invention proposes- The structure of the frequency offset compensation device for compensating in the time domain is shown in Figure B. The frequency offset compensation device 30b can compensate the carrier between the receiving end and the transmitting end of the 0fdm system. The frequency offset is the cumulative phase rotation of the 0FDM signal at the receiving end. Frequency offset compensation The device 30b contains the same components as the frequency offset compensation device 30, except for the phase rotator. Among the 30 types of frequency offset compensation devices, the phase rotator 34a is coupled to the output of the FFT device 111. Compensation in the frequency domain; while in the frequency offset

Page 15 200417209 V. Description of the invention (11) In the compensation device 3 0 b, the phase rotator 3 4 b is coupled to the input of the F F T device 1 11, that is, the compensation is performed in the time domain. Utilizing the aforementioned frequency offset compensation device 30a or 30b, the present invention proposes a frequency offset compensation method, which includes the steps shown in Figure 4: 41 'introductor channel estimation device 31 receives the signal of the pilot channel to estimate The frequency response of the pilot sub-channel; 42 The frequency offset estimation device 32 estimates the carrier frequency offset by using the phase difference between the frequency response estimates of the two preceding and subsequent 0fdm symbols in the pilot sub-channel;

4 3 The phase accumulator 3 3 calculates the accumulated phase rotation based on the carrier frequency offset estimated in step 4 2; and # 44 phase rotator 34a or 34b compensates the 0FDM signal at the receiving end according to the accumulated phase rotation calculated in step 43. 'If the 0FDM system includes a plurality of guide channels, in step ", the frequency response of each guide channel is estimated separately, and in step 42, the two front and rear 0FDM channels are included in each guide channel. The phase differences of the estimated frequency response values of the symbols are added up, and then the average value is calculated to estimate the carrier (1-3)).

If a frequency offset compensation device 30a is used, step 44 is to compensate the frequency domain signal of the 0FDM signal at the receiving end; if a frequency offset compensation device is used, + step 4 4 is to compensate the time domain signal of the 0F DM signal at the receiving end. ^ Each sub-channel of 30a / 30b compensation needs to be set (that is, the OF DM signal of the receiving terminal passes the receiving end after frequency offset compensation |, there will still be residual phase error. If OF DM system, coherent demodulation (coherent demodulation)

200417209 V. Description of the invention (12) The amplitude and phase of the channel signal must be consistent with the sub-channel signal originally transmitted by the transmitting end), then a mechanism is needed to compensate for this residual phase error. Assume that after compensation by the frequency offset compensation device 30a / 3 Ob, the signal of the k-th subchannel of the nth OFDM symbol at the receiving end is represented by formula (2-1), where is the residual phase error, and the remaining ICI terms and noise The term again assumes that k is the index value of the guide sub-channel, and it can be inferred from equation (2-1) that the result of the channel signal at the receiver end after channel compensation is ~

Yn, ke gas X'qi < dn, k formula (2-2) where i / t is estimated using the system's previous preamble, and the frequency response of the k-th subchannel A is the remaining ICI Term and miscellaneous

Page 17 200417209 V. Description of Invention (13) Information item. From the above analysis, it can be known that the residual phase error can be estimated by using the phase difference between the channel compensation result of the guide channel and the specific ideal value of the original guide channel. If the 0FDM system uses K guide channels, when estimating the residual phase error, the phase difference between the channel compensation result of each guide channel and the specific ideal value of the original guide channel can be calculated and added together. Find the average, that is,

K

A: = pilot index

When the phase noise of the local oscillators 21 and 22 is not large, and the residual phase error of two consecutive OF DM symbols does not change much, the guide channel of the previous OF DM symbol may be used The phase error estimation value obtained by the signal is compensated for the sub-channel signal of the next 0FDM symbol. Therefore, the invention provides a framework of a delay type phase compensation device, as shown in FIG. 5A. Here, "delayed" refers to the estimation using the previous symbol and the latter symbol. The phase compensation device 50a can be compensated at the receiving end of the 0FDM system. The 0FDM signal at the receiving end is compensated by the frequency offset compensation devices 30a / 3b, and the remaining phase error is compensated, which includes: a phase difference estimation device 5 丨In the 0FDM signal, the frequency offset compensation device 3 (^ / 3〇1) and the symbol element are used.

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200417209

112 compensated pilot channel signal (that is, in (2_2)), and use the phase difference between the pilot channel signal and the system's original transmission signal to estimate the residual phase error; a buffer 52. The residual phase error estimated by the phase difference estimation device 51 is stored for compensating the next symbol, and a phase rotator 53 is received by each sub-channel signal of the next symbol and buffered. The stored residual phase error is compensated. The structure of FIG. 5A can also be slightly modified. As shown in FIG. 5β, the components included in the phase compensation device 50b are exactly the same as those of the frequency offset compensation device 50a. In operation, the structure of FIG. After the channel signal of the next symbol element is compensated by the channel repair device 112, it is then sent to the phase rotator $ 3. Using the aforementioned phase compensation device 50a, the present invention proposes a type of phase compensation method, which includes the steps shown in FIG. 61: 61 phase difference estimation device 51 1 utilizes a symbol of 0FDM signal via the frequency compensation device 50a / 5 Ob And the channel compensation device ι12 compensated the phase difference between the leader signal and the original transmission signal of the system transmitter, to calculate the residual phase error; 6 2 Store the residual phase error estimated in step 6 1 in the buffer 5 2 And 6 3 compensate the next phase of each sub-channel signal with the residual phase error stored in the buffer 5 2. 'If the OF DM system includes a plurality of pilot channels, then in step 6 丨, the phase difference of each pilot channel signal of the symbol is different, and the average value is added to the summation, and then averaged. Value to estimate the residual phase error (as shown in Equation =). 3

200417209

If the phase compensation device 50b is used, the compensation methods in steps 61-63, and step r63, before performing phase compensation, * use the channel compensation device 1 1 2 to compensate each sub-channel signal of the next symbol.

When the local oscillators 21 and 22 have large phase noise, the residual phase error of the 0FDM symbol will also change greatly. At this time, the earthquake uses the signal of the sub-channel guided by a 0FDM symbol. The obtained phase error estimates are compensated for the same sub-channel signal of the 0FDM symbol. Therefore, a 〆 buffer is needed to retain the signals of all sub-channels of a complete 0 FDM symbol ^, first using the guided sub-channel estimation The residual phase error is then compensated for the data subchannel. Accordingly, the present invention provides a framework of a buffered phase compensation device, as shown in FIG. 7A. Here, "buffering" means to reserve a symbol for the subsequent phase estimation and compensation of the same symbol. The phase compensation device 7〇a can be used at the receiving end of the 0FDM system to compensate the residual phase error of the 0FDM signal at the receiving end after being compensated by the frequency offset compensation device 3 a / 3 0 b, which includes a buffer 5 | 7 1 'receive and reserve a symbol of 0 FD Μ signals, all sub-channel tfl numbers after frequency offset compensation device 3 0 a / 3 0 b compensation; a guide sub-channel compensation device 72, from buffer 71 Receive the pilot channel signal of the symbol for

Channel compensation (the result is one of equation (2-2)); a phase difference estimation device 7 3 is coupled to the guide sub-channel compensation device 7 2 and uses the signal and system after the channel compensation in the guide sub-channel 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 sub-channel signal of the symbol from the buffer 71 and uses the residual phase estimated by the phase difference estimation device 73. Errors are compensated.

Page 20 200417209 L. Description of the invention (16) The wooden structure of the figure 7A can also be slightly modified as shown in figure 7B. The phase compensation 7 0 b contains the same elements as the frequency offset compensation device 7 08. However, in Figure # 7, the structure of a data sub-channel compensation device 75 is first converted by a data sub-channel compensation device 75, and then sent to a phase rotation using the aforementioned phase compensation device 70a. The present invention proposes A buffered 2 phase compensation method includes the steps shown in Figure 8:

Buffer 71 is reserved—for all OFDM signals of the symbol, all the sub-channel signals are compensated by the frequency offset compensation device 30a / 30b; the sub-channel compensation is set 7 2 and the guide of the symbol is taken from the buffer 7 1 Introduce the channel signal for channel compensation; 83 Phase difference estimation device 73 uses the phase difference between the channel number in the pilot channel and the signal originally transmitted by the system transmitter to estimate the residual phase error; and 84 phase rotation The decoder 74 takes out the data sub-channel signal of the symbol from the buffer 71 and compensates it with the residual phase error estimated in step 83. If the 0FDM system includes a plurality of guide channels, in step 83, the system

: Don't calculate the phase difference of the signal of each pilot channel of this symbol, and then calculate the average value to estimate the residual phase error (as shown in formula (2-3)). If the phase compensation device 70b is used, the compensation method is the same as that in steps 81-84. Before performing phase compensation, the data sub-channel compensation & set 7 5 is used to compensate the data sub-channel signal of the symbol. In the present invention, the two aforementioned frequency offset compensation devices may also be used.

Page 21 200417209 V. Description of the invention (17) 30 a / 3 Ob and four phase compensation devices 50a / 50 b / 70a / 7 Ob, depending on the actual needs of the 0FDM system, choose one of them and combine them into a compensation module. To completely deal with the problem of phase rotation of the OF DM signal at the receiving end caused by the carrier frequency offset. Figure 9 is an example of such a compensation module. The frequency offset compensation device 3 Ob and the phase compensation device 70a can be used in OF DM systems with a large carrier frequency offset and phase noise. Looking further at FIG. 9, the guide channel estimation device 3 1 in the frequency offset compensation device 30 b performs the operation of formula (1-2), and the guide channel compensation device 72 in the phase compensation device 70 0a performs Operation of Formula (2-2)

/ V is calculated. If you divide equation (2-1) by Xn k and // i n, k n, k e + Ω n, k Equation (2-4) Ω

A is the remaining I C I, where k is the index value, term and noise term of the pilot sub-channel. From the above analysis, it can be known that the residual phase error can be estimated as follows (assuming that the OFDM system uses K pilot channels)

Page 22 200417209 V. Description of the invention (18) ΑΘ. Η A: = pilot index In the formula (2-5)-(2-4), the corpse # is the guide channel, which is estimated by the channel and the channel. The result after compensation; in view of FIG. 9, it can be regarded as y # obtained after processing by the guide = channel estimation device 31 and the guide channel compensation device 72. Here, we can slightly modify the structure of the phase compensation device in Figure 9, as shown in Figure 2 =. The block 1000 in FIG. 10 can be regarded as a phase compensation device, which is a part of the structure to compensate for the residual phase rotation. In block 1 0 0, after the signal has been processed by the guide channel estimation device 3 丨 and the guide channel compensation crack 72, the last result is the A p operation, which is 1: and the phase difference estimation device im executes ( 2 ~ 3)) is simple. In addition, the phase difference estimation device 73 (the signal of the execution f sub-channel 'is not like the integrated / material buffer 1001, which is only used to store data, so it can save space. In other words, the punch π needs to store all sub-channel signals The frequency deviation and phase mismatch of the device wave: The structure of Figure 10 can be used not only for the design and cost of the localized oscillating body, but also for the 0FDM system. The use of #### 制 制 本 发明 的 # 围. The implementation of the present invention will be described in detail in the examples of the present invention, but not limited to making changes and adjustments. The spirit and norms of ^ will not be equal to that of Yiyuan. In summary, the present invention has been implemented in 200417209 V. Description of the invention (19) The nature of the invention has already met the requirements of the invention patent stipulated in the Patent Law. Examining committee members are willing to review and grant patents for prayer. 200417209 Brief description of the diagram ^ Second, a typical qFdm communication system diagram-is a block diagram of the right fanyu, solid-M /, with carrier frequency Figure 2A is a block diagram of the system for performing compensation and demodulation in the frequency domain according to the present invention. The structure B of the head offset compensation device was originally prepared to be compensated in the time domain. @ The offset compensation device's structure is too double-mouthed. Figure ^ " ΓcurrencyΊ 贝 Ί Figure 4 is the current date ^^^ Figure 5A of the frequency offset compensation method is a flow chart of Xiao Qin on the current day. Figure 5B is another diagram of the present invention—an architecture diagram of the delay U. FIG. 6 is an architecture diagram of the delayed phase compensation of the present invention. Figure 7 is an operation flowchart of the buffered phase compensation method of the present invention < Figure 7B is a block diagram of the invention's flat arrangement. Figure 8 is a phase compensation device of the present invention. Knowing the buffered phase and the old wooden structure. Figure 9 is a flow chart of the inventor's action. Figure 10 is a schematic diagram of the example of Figure 9; Explanation of figure numbers of the diagram: 10 signal corresponding device 103-Add protection zone to analog conversion; 1 ϋ 7-Analog to Syrian master digital converter 110—Serial to parallel conversion piano 112_ Channel compensation device 1 0 0- 0 FD Μ communication system 102- IFFT device 1 0 4-parallel to serial converter 1 0 6-channel 1 0 9-shift The guard interval 111- FFT circuit device 113-- signal corresponding means Solution

200417209 Brief description of the diagram 2 1-Local oscillator 3 0a-Frequency offset compensation device 31-Leader channel estimation device 3 3-Phase accumulator 3 4 b-Phase rotator, 4 1 ~ 4 4- Frequency offset compensation 5 0a-phase compensation device 5 1-phase difference estimation device 5 3-phase rotators 61 to 63-delayed phase of the present invention 7 0a-phase compensation device 7 1-buffer 7 3-phase difference estimation device 7 5 -Data sub-channel compensation device 8 1 ~ 8 4-Buffered phase of the present invention 1 0 0 0-Phase compensation device 1 0 0 2-Phase difference estimation device 2 2-Local oscillator 30b-Frequency offset compensation device 3 2- Frequency offset estimation device 34a-Operation flow of phase rotator method 5 0 b-Phase compensation device 5 2-Operation flow of buffer compensation method 70b-Phase compensation device 72-Guide channel compensation device 7 4-Phase rotator compensation Method action flow 1 0 0 1-data buffer

Page 26

Claims (1)

200417209 VI. Application for Patent Scope 1 · This type is used for an upside-down, the system is a line modulation of a plurality of frequency domains, in which a specific signal end is transmitted to compensate the receiving end of the 0FDM signal containing: a guide estimate one frequency the value one Phase counting one phase 2 · As applying position rotation 3 · As applying position rotation 4. As applying some sub equipment to the transmitting end: J = M) The frequency offset compensation equipment in the system transmits d to 0fdm symbol, divided In the process of this ambiguity, the process of estimating the position of the rotator calculated by using the phase difference bit accumulator device of the pilot offset estimation device installed in the lead channel, and using the phase difference bit accumulator device of the pilot channel, please refer to the patent converter. The patent reference converter is to supplement the patent reference channel. It is estimated that these sub-channels contain at least :::: with 1 wave: the frequency offset compensation device is set, using the system's receiving end and the transmitting two receiving-number accumulation. The product phase bismuth caused by the carrier frequency offset between f and the 'the frequency offset compensation strikes the packet estimation device and receives the frequency response of the leader channel; the signal of the primer channel' is coupled to the center; Channel estimation device using the frequency of two OFDM symbols The carrier frequency offset is estimated by the response technique; the frequency offset estimation device calculates a cumulative phase rotation based on the carrier frequency offset estimated by the frequency offset; tapping to the phase accumulator to accumulate the product phase rotation to compensate the receiving end. FDM signal. ° The frequency offset compensation device described in item 1 above, wherein the compensation receiver is a frequency domain signal of an 0FDM signal. The frequency offset compensation device according to item 1, wherein the relative time-domain signal of the OF signal at the receiving end. The frequency offset compensation device described in the first item, wherein if there are a plurality of guide channels, the guide channel is estimated ^ Shi Bei Yi Xuan Nu This lacquer primer I! Eliminates jkS, ancient, beginning K nfe _ 200417209 6. The patent application range estimation device sums up the phase difference between the frequency response estimates of the two 0FDM symbols το in each channel of the piano, s, sound, and some-introduction channels. Then, calculate the average value to estimate the carrier frequency offset. 〃 5. —A phase compensation device used in an orthogonal frequency division multiplexing (0FDM) system. The system encodes data into 0FDM symbols at the transmitting end and divides them into multiple sub-channels in the frequency domain. Transmission, transmission process and the use of an incoming ΓΓί sub-channel contains at least-used to transmit a specific signal-the primer channel 'The system's receiving end includes a frequency offset compensation device to compensate for the difference between the receiving end and the transmitting end. Carrier # &, ▲ 丄 # & ^ & Carrier frequency deviation caused by the carrier ⑽ dm flood phase phase bismuth rotation, and a channel compensation device for channel compensation for this signal, today >士 于 # 取 ^ The salt phase compensation device is located at the receiving end of the system to compensate for the residual phase error after the receiver's 0FDM signal compensation. The w ^ device supplements the phase compensation device and includes: a phase difference estimation device, receiving _You-npnu ^ s ^ Fu Fanzhi 〇 In the FDM signal, the I and ° offset signals are compensated by the boating value compensation device and the channel, and the phase between the signals of the pilot channel = t pilot channel Difference to estimate residual phase error This transmission uses a buffer to store the phase difference and estimate the external difference for use; ^ β T / The residual phase estimated by the meter device is wrong to be used to compensate the next sign-phase rotator, which receives the next number ' And the second stored in the buffer: compensated by the residual phase error of some sub-channel signals. 6. The phase compensation device, such as the 5th in the scope of patent application, where the following Page 苐 Page 28 200417209 VI. Scope of patent application The signals of the sub-channels of a symbol are compensated by the channel compensation device before being sent to the phase rotator. 7. The phase compensation device according to item 5 of the scope of patent application, wherein if the sub-channels include a plurality of leading sub-channels, the phase difference estimation device separately calculates the frequency of the symbol via the frequency offset compensation device and the channel. The phase difference between each of the pilot channel signals compensated by the compensation device and the original transmission signal is summed, and then the average value is calculated to estimate the residual phase error. 8. —A phase compensation device used in an orthogonal frequency division multiplexing (0FDM) system. The system encodes data into 0FDM symbols at the transmitting end and divides them into multiple sub-channels in the frequency domain for transmission and transmission. In the process, a carrier is used for modulation. The sub-channels include at least one guide sub-channel for transmitting specific signals and at least one data sub-channel for transmitting data. The system includes a frequency offset compensation device. It is used to compensate the phase rotation of the 0FDM signal at the receiving end caused by the carrier frequency deviation between the receiving end and the transmitting end. The phase compensation device is located at the receiving end of the system to compensate the 0FDM signal at the receiving end after the frequency offset compensation device compensates. For the remaining phase error, the phase compensation device includes: a buffer that receives and retains a single symbol of the 0FDM signal, all of the sub-communication signals that are compensated by the frequency offset compensation device; a pilot channel compensation A device for receiving the pilot channel signal of the symbol from the buffer for channel compensation; a phase difference estimation device coupled to the pilot channel compensation device, using the Primer channel, the transmit signal after the channel compensation with the system Page 29 200417209 6. The phase difference between the originally transmitted signals at the end of the patent application range is used 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 estimation device The estimated residual phase error is compensated. 9. The phase compensation device as described in item 8 of the scope of patent application, wherein the data sub-channel signal of the symbol is firstly channel-compensated by a data sub-channel compensation device at the receiving end of the system, and then sent to the phase rotator. . 10. The phase compensation device as described in item 8 of the scope of patent application, wherein if the sub-channels include a plurality of leading sub-channels, the phase difference estimation device separately calculates each of the symbols after the channel compensation. The phase difference between these pilot channel signals and the original transmission signal is added up, and then the average value is calculated to estimate the residual phase error. 1 1. A compensation module used in an orthogonal frequency division multiplexing (0FDM) system. The system encodes data into 0FDM symbols at the transmitting end and divides them into multiple sub-channels in the frequency domain for transmission and transmission. In the process, a carrier is used for modulation. The sub-channels include at least one guide sub-channel for transmitting specific signals and at least one data sub-channel for transmitting data. The compensation module is located in the system. The receiving end compensates for the phase rotation of the 0FDM signal at the receiving end caused by the carrier frequency offset between the receiving end and the transmitting end. The compensation module includes: a frequency offset compensation device, which uses two 0FDM symbols in the front and rear of the guide channel The phase difference of the frequency response of the element is used to estimate the carrier frequency offset, and then the cumulative phase rotation is calculated to compensate for the 0 FD Μ at the receiving end. Page 30, 200417209, when receiving the phase channel information between the sub-channel channel compensation, the 11th compensation receiving end range, the 11th receiving receiving range number 11 guidance, the frequency response will be obtained. Of it. A guide channel estimation device around the eleventh item is received to estimate the frequency of the guide channel. A frequency offset estimation device is coupled to the guide channel, and the difference between the front and back digits is used to estimate the carrier. The carrier frequency offset compensation estimated by the estimation device is installed with a time domain compensation module using the number and the frequency domain compensation module number of the remaining compensation module number. Then, the phase of these frequency guide values is determined by the The difference after the channel signal is used to estimate the number. Each of the sub-channels described in the 0 FD MU message and the 0 FD MU message should estimate the inducer response; the 0FDM symbol frequency offset of the introducer channel, the estimation device, calculates the signal of the accumulated six, patent application range; And a phase compensation device with a 0FDM signal, and then compensate these by the transmission signal 1 2. If the patent application compensation device is compensated 1 3. If the patent application compensation device is compensated 1 4. If the patent application sub channel contains Estimate the carrier frequency offset of two 0FDM symbols and find the average value of 15 Phase error, where the frequency offset signal. , Where the frequency offset signal. Wherein, if the offset compensation devices are in the channel, the back and forth differences are added up, the compensation module, wherein the signal of the frequency offset channel, the estimation device, and the frequency response of the element are rotated according to the phase of the frequency offset product; Page 31 200417209 6. Scope of patent application and a phase rotator, which is coupled to the phase accumulator, and compensates the 0FDM signal at the receiving end with the accumulated phase rotation calculated by the phase accumulator. 16. The compensation module according to item 11 of the scope of patent application, wherein if the sub-channels include a plurality of guiding sub-channels, the phase compensation device estimates the residual phase error by using the symbol. After the channel compensation for each of the pilot sub-channel signals, the phase difference between the signal and the original transmission signal is added up, and then the average value is obtained. 17. The compensation module according to item 11 of the scope of patent application, wherein the receiving end of the system includes a channel compensation device for channel compensation of the signals of the sub-channels, and the phase compensation device includes: a The phase difference estimation device receives a 0 FD Μ signal of one symbol, and the pilot sub-channel signal after being compensated by the frequency offset compensation device and the channel compensation device, and uses the pilot sub-channel signal and the system transmitter's original Transmitting the phase difference between the signals to estimate the residual phase error; a buffer storing the residual phase error estimated by the phase difference estimating device for compensating the next symbol; and a phase rotator receiving the next symbol These sub-channel signals are compensated by the residual phase error stored in the buffer. 18. The compensation module according to item 17 of the scope of patent application, wherein the sub-channel signals of the next symbol are compensated by the channel compensation device before being sent to the phase rotator for compensation. Page 32 200417209 VI. Patent application scope 19. The compensation module according to item 11 of the patent application scope, wherein the phase compensation device includes a buffer, the offset compensation device, a guide channel, a guide channel, and a signal channel. The phase difference is estimated to be mounted on the original end of the guide; and the rotator is to be compensated. The patent channel includes a signal phase compensation device, a data buffer, a frequency offset compensation, a pilot channel passing the pilot 0 FD Μ signal, and a signal passing through the frequency channel; the receiver receives the symbol. Sub-channel compensation device; Sub-channel compensation device, the difference between the signal after compensation and the system to estimate the residual phase, the residual phase error compensation module of the sub-channel estimates of the symbols, and one of the symbols at the end of the symbol The sub-channel goes into the phase rotator. Compensation module, in which the system is configured to receive the frequency response of the pilot channel, the reserved 0FDM signal of a symbol, the signal passing through the sub-channel; in the 0FDM signal of the symbol, the subsequent pilot channel signal Use the phase error signal of the transmission error to add 2 0. Such as the applied data compensation device 2 1 · If you apply for a receiving terminal channel to receive and retain the compensation device number after compensation, you can set up, engage in the channel, and send the signal 'from the buffer The 19th signal of the phase difference estimation channel is firstly guided by the channel compensation channel of the 11th channel, and the estimation includes:, receiving and installing the compensation compensation device channel estimation of all the symbols, and filling from the slow channel to the Guide the complement of the system described by the phase-pulse receiver device of the channel tween, and then send the said complement to estimate the data after installing the guide, and receive the device for processing Page 33 200417209 6. Apply for a patent range number for channel compensation; a phase difference estimation device that compensates for the difference between the guide channels of the guide; and a younger and one-phase supplier. This phase error is compensated. The lead channel compensation device receives the communication number to estimate the residual phase error data buffer to receive the residuals estimated by the phase difference estimation device of the symbol. 2 If the patent application range compensation device includes: A frequency offset estimation device uses the Phase-phase accumulator of the estimated value of the guide, the time estimated by the estimation device and a second accumulation time 2 3 ·-a method for placing in the complex carrier channel, The channel is lightly connected to the guide sub-channel estimation device, and the carrier frequency offset is estimated by the frequency response f of the two 0FDM symbols before and after. 4 The frequency offset estimation device calculates the cumulative phase rotation phase rotator based on the carrier frequency offset of the frequency. Calculated domain signal. In a quadrature, the system is modulated in a number of frequency domains, and is transmitted to the phase accumulator for transmission, and the phase ’and product phase are used to rotate to compensate the receiving end ’s 0FDM signal. The frequency offset in a 77-frequency multiplexed (OFDM) system is supplemented by the transmitting end to encode the data into 0FDM symbols, and the sub-channels are transmitted and used during transmission. These sub-channels include at least one leader sTL number, , The frequency offset compensation method is used to Page 34 200417209 6. The receiving end of the patent-applied system compensates for the carrier phase offset between the receiving end and the transmitting end that causes the cumulative phase rotation of the 0FDM signal at the receiving end. The frequency offset method includes the following steps: (1) Receiving the guide The signal of the primer channel is used to estimate the frequency response of the pilot channel. (B) The carrier frequency is estimated by using the phase difference between the frequency response estimates of the two OFDM symbols in the pilot channel. (C) Calculate the cumulative phase rotation based on the carrier frequency offset estimated in step (b); and ", (d) Compensate the 0 FD Μ signal at the receiving end according to the cumulative phase rotation calculated in step (c). In step a): and step 2 4 • The frequency offset compensation method described in item 23 of the patent application scope is mixed (d) is to compensate the frequency domain signal of the OF DM signal at the receiving end. 2 5 · If the scope of patent application The frequency offset compensation method described in item 23 is miscellaneous. (D) is the time domain signal for compensating the receiver ’s FDM signal. C 2 6 · The frequency offset compensation method described in item 23 of the patent application scope. The subchannel contains a complex number. Guide channels, the steps are = Estimate the frequency response of each of these guide channels. In jb), the phase difference between the two 0FDM and I frequency response estimates in each of these guide channels is added up, and then calculated. Its flat value is used to estimate the carrier frequency offset. + The phase compensation wheat # in the positive-frequency division multiplexing (0FDM) system is used to encode data into 0FDM symbols at the transmitting end, which is divided into multiple frequency domains. Sub-channel transmission, using a V during transmission Page 35 200417209 VI. Patent application carrier modulation, where the sub-channels include at least one guide sub-channel for transmitting specific signals, and the receiving end of the system includes a frequency offset compensation device to compensate the receiving end and the The phase rotation of the 0FDM signal at the receiving end caused by the carrier frequency offset between the transmitting ends, and a channel compensation device for channel compensation of the signals of these channels. The phase compensation method is used at the receiving end of the system. To compensate the 0FDM signal at the receiving end by the frequency offset compensation device. After the compensation, the residual phase error, the phase compensation method includes the following steps: (a) using a symbol of the 0FDM signal, the frequency offset compensation device and The phase difference between the signal of the pilot channel after compensation by the channel compensation device and the signal originally transmitted by the transmitting end of the system to estimate the residual phase error; (b) storing the residual phase error estimated in step (a) in a buffer And (c) compensating the sub-channel signals of the next symbol with the residual phase error stored in the buffer. If you want to use it, please use it before you apply. Please apply 0) ♦ N) y apply for C ο as usual; c 2 method f symbol / 1 fixed supplement ^ position M: subhead d} reimbursement ο \ C supplement € / TIC Set the W item @ a 7 steps to repay the steps in the same way some of the yuan ’s message, if the legal party in the law of the compensation MΠΤ > The description of the complement phase 2 Fanli special request for the compensation in the compensation MΠΤ > a) In step C, this step is followed by the set, and it is said that the compensation of the partial offset of the compensator will guide the complex number of the warp to include the symbol. Page 36 2041172 09. Patent application scope The phase difference between each of these guide bows and signal after the device compensation is added up, and the% scream signal is added to the residual phase error from the original transmission meter. Μ 'and then calculate the average value to estimate-a method used in an orthogonal frequency division multiplexing (0F method, the system is at the transmitting end of the phase compensation in the data system in a plurality of frequency domain sub-channel transmission " The code is 0FDM symbols, and the carrier is modulated by subcarriers. Among these sub-processes, a pilot signal channel is used and a packet is used to transmit at least a special channel. The system includes-frequency damage. : The carrier frequency offset between the data carrier and the transmitting end for transmitting data: 2 f set, used to compensate for the 30% of the receiving end OFDM signal caused by the receiver ’s pain, Φ0 #)) C ) »Aγ ^ ^ -rtq U Μ afL ^ 旎 turn, the phase compensation method is used at the receiving end of the system, the receiving end 0FDM signal is compensated by the frequency offset compensation device, the residual phase error, the phase compensation The method includes the following steps: / The buffer retains all the sub-channel signals of the symbol FD Μ signal after being compensated by the frequency offset compensation device; #The buffer takes out the guide sub-channel of the symbol Signal for ^ channel compensation; in the guide channel, the signal after channel compensation and the judgment should be used _ ▼ 〇 -... Simultaneously, the transmitting station originally estimates the residual phase difference between the transmitted signals ¥ m d) ψ is% The buffer takes out the symbol ... ^ Miscellaneous (c) The estimated residual phase error is compensated. Phase error; and the supplementary name of the data sub-channel signal of the element ^ residual phase error > the phase compensation method described in item 30 of the patent scope, wherein in step 2, the channel of the data sub-channel signal of the broken element is firstly channeled 31 200417209 VI. After applying for patent scope compensation, only the residual phase error estimated in step (c) is used for compensation. 32. The phase compensation method as described in item 30 of the scope of patent application, wherein if the sub-channels include a plurality of guiding sub-channels, in step (c), the channel compensation of the Weiyuan is calculated separately. The phase difference between each of these pilot channel signals and the original transmission signal is summed, and then the average value is calculated to estimate the residual phase error. Page 38