DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Priority
Receipt is acknowledged of certified copies of papers required by 37 CFR 1.55.
Drawings
The drawings are objected to because some of the texts shown in some of the drawings are either too small or blurry. Corrected drawing sheets in compliance with 37 CFR 1.121(d) are required in reply to the Office action to avoid abandonment of the application. Any amended replacement drawing sheet should include all of the figures appearing on the immediate prior version of the sheet, even if only one figure is being amended. The figure or figure number of an amended drawing should not be labeled as “amended.” If a drawing figure is to be canceled, the appropriate figure must be removed from the replacement sheet, and where necessary, the remaining figures must be renumbered and appropriate changes made to the brief description of the several views of the drawings for consistency. Additional replacement sheets may be necessary to show the renumbering of the remaining figures. Each drawing sheet submitted after the filing date of an application must be labeled in the top margin as either “Replacement Sheet” or “New Sheet” pursuant to 37 CFR 1.121(d). If the changes are not accepted by the examiner, the applicant will be notified and informed of any required corrective action in the next Office action. The objection to the drawings will not be held in abeyance.
Specification
The lengthy specification has not been checked to the extent necessary to determine the presence of all possible minor errors. Applicant’s cooperation is requested in correcting any errors of which applicant may become aware in the specification.
Claim Objections
Claims 1-23 are objected to because of the following informalities:
1. (Proposed Amendment) A method of operating a receiver in a communication system in which at least one orthogonal frequency division multiplexing (OFDM) symbol is transmitted, each OFDM symbol including a cyclic prefix and a symbol body, the method comprising:
performing a Fast Fourier Transform (FFT) on intervals from each of a first start position, a second start position, and a third start position included in a received signal to a length of the symbol body, to generate a first FFT signal, a second FFT signal, and a third FFT signal for a specific OFDM symbol; and
estimating a frequency offset for the specific OFDM symbol based on the first to third FFT signals.
5. (Proposed Amendment) The method of claim 4, wherein the estimating the frequency offset based on the first to third IFFT signals comprises estimating the frequency offset using a cyclic prefix region of the specific OFDM symbol and a region in the symbol body corresponding to the cyclic prefix region as a cyclic prefix corresponding region in at least some of the first to third IFFT signals.
13. (Proposed Amendment) The method of claim 12, further comprising performing an FFT on the first IFFT signal compensated for the timing offset to acquire a resource block of a subchannel.
17. (Proposed Amendment) A receiving apparatus in a communication system in which at least one orthogonal frequency division multiplexing (OFDM) symbol is transmitted, each OFDM symbol including a cyclic prefix and a symbol body, the receiving apparatus comprising:
a Fast Fourier Transform (FFT) block configured to perform an FFT on intervals from each of a first start position, a second start position, and a third start position included in a received signal to a length of the symbol body, to generate a first FFT signal, a second FFT signal, and a third FFT signal for a specific OFDM symbol; and
a frequency offset estimation block configured to estimate a frequency offset for the specific OFDM symbol based on the first to third FFT signals.
19. (Proposed Amendment) The receiving apparatus of claim 17, wherein the frequency offset estimation block comprises:
an Inverse Fast Fourier Transform (IFFT) block configured to perform an IFFT only on resource blocks belonging to a specific subchannel of each of the first to third FFT signals to generate first to third IFFT signals; and
a frequency offset calculation block configured to estimate the frequency offset based on the first to third IFFT signals.
20. (Proposed Amendment) The receiving apparatus of claim 19, wherein the frequency offset calculation block is configured to estimate the frequency offset using a cyclic prefix region of the specific OFDM symbol and a region in the symbol body corresponding to the cyclic prefix region as a cyclic prefix corresponding region in at least some of the first to third IFFT signals.
Claims 2-4, 6-12, and 14-16 depend either directly or indirectly from claim 1, therefore they are also objected.
Claims 18, 19, and 21-23 depend either directly or indirectly from claim 17, therefore they are also objected.
Appropriate correction is required.
Claim Rejections - 35 USC § 102
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
The following is a quotation of the appropriate paragraphs of 35 U.S.C. 102 that form the basis for the rejections under this section made in this Office action:
A person shall be entitled to a patent unless –
(a)(1) the claimed invention was patented, described in a printed publication, or in public use, on sale, or otherwise available to the public before the effective filing date of the claimed invention.
(a)(2) the claimed invention was described in a patent issued under section 151, or in an application for patent published or deemed published under section 122(b), in which the patent or application, as the case may be, names another inventor and was effectively filed before the effective filing date of the claimed invention.
Claims 1-23 are rejected under 35 U.S.C. 102(a)(2) as being anticipated by McCormick et al. (US 12,003,350 B1), hereinafter “McCormick”.
McCormick illustrates a modem 1900 in FIG. 19 with various components such as a modem transmitter 1902 which can correspond to the transmitter 502 shown in FIG. 6A. The modem 1900 can include a networking interface 1906 for communication between a first high speed serial interface 1908 and a second high speed serial interface 1910, as well as an Ethernet interface 1912. The modem transmitter 1902 can provided data to a beamforming interface 1914 and a high seed serial interface 1916 for transmission of electromagnetic signals to another node in the network. A modem receiver 1904 can be similar to the receiver 512 shown in FIG. 6B which can receive signals received via the high seed serial interface 1916 and the beamforming interface 1914. Signals can then be provided to the networking interface 1906. The modem 1900 can include an embedded processor 1918, which for example, can be an ARM processor developed by Advanced RISC Machines. Any processor can be utilized. The processor 1918 can run software for managing the configuration of the waveforms. The software can include one or more programmed firmware, such as MAC firmware which can include instructions to configure the chip for its particular task, implement the functions of any component, or mode as described herein. Instructions for operating the modem can be stored in a computer-readable storage medium or device and can be used to perform operations disclosed herein for configuration of the modem, establishing parameters and processing received signals and generating and transmitting signals.
McCormick also teaches that the modem can further include a fast-Fourier transformer (FFT) that utilizes the estimation of the carrier frequency offset to trigger a proper symbol FFT timing and a decoder that utilizes the estimation of the carrier frequency offset to apply frequency correction. The single waveform can include an orthogonal frequency division multiplexing (OFDM) signal including a radio frame having one or more bursts. A burst of the one or more bursts can include a first portion including burst detection data, a second portion including channel characteristic estimation data, a third portion including payload data, and fourth portion including first pilot data and a fifth portion including second pilot data. The first portion in a time domain can be included in the burst prior to the second, third, fourth, and fifth portions in the time domain. In one aspect, the first portion can include a pseudo-random noise sequence inserted in the time domain. See column 3, lines 6-22.
Regarding claim 17, as shown in at least FIG. 19, McCormick illustrates a receiving apparatus (modem receiver 1904 ) in a communication system in which at least one OFDM symbol is transmitted, each OFDM symbol including a cyclic prefix and a symbol body, the receiving apparatus comprising: an FFT block configured to perform a Fast Fourier Transform (FFT) on intervals from each of a first start position, a second start position, and a third start position included in a received signal to a length of the symbol body, to generate a first FFT signal, a second FFT signal, and a third FFT signal for a specific OFDM symbol; and a frequency offset estimation block configured to estimate a frequency offset for the specific OFDM symbol based on the first to third FFT signals (Col. 3, lines 6-22).
The Applicant notes that the modem, which includes an FFT processor and a frequency offset decoder, is functionally encompassed by the receiving apparatus recited in claim 17. The claim broadly outlines how standard-compliant OFDM receivers extract burst data in environments affected by signal shifts, such as Doppler shifts or local oscillator mismatches.
Here is how the system inherently satisfies claim 17:
Cyclic Prefix (CP) & Symbol Body: Orthogonal Frequency Division Multiplexing (OFDM) inherently operates using a symbol body (containing the data) preceded by a Cyclic Prefix, which is required to prevent Inter-Symbol Interference (ISI).
Three Start Positions: To reliably figure out where an OFDM symbol starts, a receiver typically evaluates multiple hypotheses by sliding a window in the time domain. By performing an FFT on different intervals, the receiver generates multiple FFT signals corresponding to different timing alignments (e.g., Early, On-Time, and Late).
Frequency Offset Estimation Block: The receiving system uses the differences between these multiple FFT signals (specifically the phase rotations across the frequency domain) to calculate the Carrier Frequency Offset (CFO). This is exactly what the quoted claim refers to as a “frequency offset estimation block”.
Further, because the described modem burst starts with a time-domain pseudo-random noise (PN) sequence (or preamble), the receiver can use it to determine approximate burst timing. Once this initial synchronization is established, the system uses the multi-point FFT and frequency offset block to fine-tune the exact symbol timing and apply the frequency correction to the decoder. In telecommunications, any modem that adjusts its FFT decoding window based on the measured frequency and timing offsets inherently mirrors the architectural logic laid out in this type of receiver as recited in claim 17.
Regarding method claim 1, the steps recited therein correspond to the elements of apparatus claim 17 for the same reasons discussed above.
Regarding claims 2 and 18, the modem described above reflects modern configurable Orthogonal Frequency Division Multiplexing (OFDM) architectures (such as in satellite or 5G systems), which are uniquely built to combat Carrier Frequency Offset (CFO) and recover timing efficiently. The three positions recited in the claims inherently form a multi-hypothesis sliding-window correlator or search space for OFDM symbol detection.
The Three Start Positions
The First Start Position: This is the base estimation point calculated by correlating a known time-domain training sequence (e.g., the pseudo-noise burst detection data) with the received signal. It identifies the rough location of the OFDM symbol.
The Second Start Position: This position leads the first position by a predetermined time length. It is the beginning of the search window used to combat Inter-Symbol Interference (ISI).
The Third Start Position: This position lags behind the first start position by the predetermined time length, marking the end of the symbol search window.
Therefore, by using this 3-position search method, the modem extracts highly accurate boundaries, allowing the decoder to use CFO estimation to completely correct phase and frequency errors before processing the payload data.
Regarding claim 3, McCormick describes an Orthogonal Frequency Division Multiplexing (OFDM) modem system designed to process signal bursts with pilot, payload, and training sequences. Inherently, wherein the predetermined time length is a length of the cyclic prefix is simple a structural limitation in OFDM synchronization methods.
Regarding claims 4 and 19, the modem described in claim 17 can inherently utilize Fast-Fourier Transform (FFT) and decoding combined with Carrier Frequency Offset (CFO) estimation to accurately align timing and correct frequency shifts. The system calculates the frequency offset using a specific logic:
IFFT Per Resource Block: An Inverse Fast Fourier Transform (IFFT) is performed only on specific subchannels of the received FFT signals.
Frequency Offset Calculation: The resulting IFFT signals are evaluated to estimate the exact frequency offset.
Since the IFFT mechanism is a natural extension of the burst structure, the burst contains known reference segments (like burst detection data, pilot data, and pseudo-random noise sequences), the receiver already has a clean template. By passing these known, localized subchannels through an IFFT, the receiver can instantly compare the received time-domain sequence with the local template to estimate the CFO accurately and efficiently.
Regarding claims 5 and 20, they are standard and inherently valid in digital communications. They describe a foundational, robust method for synchronizing and demodulating Orthogonal Frequency Division Multiplexing (OFDM) signals, typically using the Minn or Schmidl & Cox algorithms for burst mode.
In an OFDM transmitter, a copy of the end of the symbol data block is appended to the beginning to form the Cyclic Prefix (CP). Because this CP is an exact, delayed replica of the end of the symbol body, they carry identical information, just separated in time.
At the receiver:
The CP region and the corresponding region in the symbol body are separated by exactly N samples (where N is the size of the symbol FFT).
By correlating these two specific regions, the receiver naturally highlights the phase shift between them.
This phase shift directly equates to the Carrier Frequency Offset (CFO).
Further, because the frame is structured with dedicated burst detection data (like a preamble) preceding payload and pilot data, the modem can instantly estimate the CFO at the very beginning of the packet. This allows it to compute frequency and timing synchronization before attempting to decode the payload.
Regarding claims 6, 7, and 21, they align with modern, high-performance Software-Defined Radios (SDR) and digital modems designed for Orthogonal Frequency Division Multiplexing (OFDM) bursts. As described in claim 17 above, the modem inherently applies to the claims used for Doppler shift compensation and receiver synchronization.
In OFDM, the transmitter takes a block of symbols and applies an Inverse Fast Fourier Transform (IFFT) to generate a time-domain waveform. The receiver then uses a Fast Fourier Transformer (FFT) to demodulate the signal. Because Carrier Frequency Offset (CFO) often caused by Doppler shifts to rotate the phase of the incoming signal linearly across time, it artificially distorts the timing estimates. By estimating CFO, the modem can adjust its “proper symbol FFT timing” to compensate for phase shifts caused by frequency mismatch.
An OFDM symbol is preceded by a Cyclic Prefix (CP), which is just a repetition of the tail end of the symbol attached to its beginning.
The Concept: Because the CP is a replica of a later segment in the symbol, the distance in samples between the CP and that later segment is mathematically known (the LCP length).
The Math: If a frequency offset Δf is present, the receiver's time-domain signal, r(t), will be shifted by ej2piΔft. If you multiply the CP region with the identical region later in the symbol (the CP corresponding region), the original data cancels out, leaving only a phase difference that is directly proportional to Δf.
Leading/Lagging Windows: The quoted text uses three positions: the estimated start position, a position leading by a predetermined time, and a position lagging behind. This provides a search window for the exact start of the symbol.
Cross-Correlation: By isolating the exact CP region and the CP corresponding region, the modem calculates a cross-correlation to find where they perfectly line up.
Estimation: The phase angle of this mathematical cross-correlation yields the exact Carrier Frequency Offset Δf.
Pseudo-random noise sequences (or known training symbols/Unique Words) in the burst's first portion allow the modem to detect where a burst begins and conduct the initial rough timing estimation.
Pilots (the fourth and fifth portions) exist to help track phase and frequency deviations over the course of the burst, updating the CFO calculations as the channel environment fluctuates.
Further, using cross-correlation between the CP and its corresponding region is a widely recognized standard in digital communications (famously known as the Schmidl & Cox or van de Beek algorithms), making this a highly robust approach for dealing with Doppler shifts and timing offsets in OFDM signals.
Regarding claims 8, 12, 22, and 23, they inherently apply to and forms standard, well-known digital signal processing (DSP) claims in wireless communications because the modem includes a Fast-Fourier Transform (FFT) block and a decoder that rely on carrier frequency offset (CFO) and timing offset (TO) estimations to ensure proper signal reception.
Further the Frequency Offset Compensation corrects the mismatch between the transmitter's and receiver's local oscillators, or compensates for the Doppler shift from moving objects. In an Orthogonal Frequency Division Multiplexing (OFDM) system, subcarriers rely on strict mathematical orthogonality. If there is a frequency offset, the orthogonality is destroyed, causing Inter-Carrier Interference (ICI) and a massive spike in bit error rate (BER). Frequency compensation unwraps the phase and brings the received signal's carrier frequencies to their expected locations.
Regarding claims 9-11, a modem that uses distinct burst structures and Carrier Frequency Offset (CFO) estimation for frequency correction and symbol timing fully supports and inherently anticipates operations like a reduced-size FFT and resource demapping. When an OFDM burst preamble (such as a pseudo-random noise sequence) is isolated in the time domain, it can be mathematically compensated for CFO and used to target specific subchannels without processing the entire broadband signal.
Regarding claim 13, as described in claim 17 above, a receiver modem processes burst-based OFDM frames using this pipeline to combat signal degradation. Claim 13 is a standard step for processing localized frequency bursts.
Standard Modem Receiver Pipeline
Step 1: Burst Detection: The modem uses the first portion of a burst, typically a pseudo-random noise (PN) sequence (a preamble) inserted in the time domain to detect when a burst starts.
Step 2: Offset Estimation: The modem's logic estimates the Timing Offset (TO) and Carrier Frequency Offset (CFO).
Step 3: CFO & TO Correction: The decoder applies frequency correction based on the CFO estimation, and the timing offset is compensated to correct the symbol boundary.
Step 4: Channel Estimation: The modem reads the second portion (channel characteristic estimation data) to adapt to signal fading and multi-path distortion.
Step 5: FFT Execution: The time-aligned, corrected signal is then pushed into the Fast-Fourier Transformer (FFT).
Step 6: Data Decoding: The FFT output generates the individual subcarriers within a resource block. The receiver then processes the payload, first pilot, and second pilot data for channel tracking and data recovery.
Regarding claims 14-16, as described in claim 15, the receiver provides an optimal blueprint for digital signal demodulation, it is a logical extension of this modem architecture as recited in the claims for the following reasons:
Separation of Data and Estimation Components: By structuring the burst so that burst detection data, channel estimation, and payload data are clearly separated, the receiver obtains the necessary baseline parameters before processing the heavy payload. This allows the modem to confidently map where symbols begin.
The Role of Demodulation Reference Signals (DMRS): A Demodulation Reference Signal (DMRS) is fundamentally known at both the transmitter and the receiver. It serves as a dedicated benchmark for synchronization and phase-tracking. Once burst boundary estimates and coarse frequency corrections are applied, the modem uses the DMRS within the subcarriers to refine timing offset estimates with exceptional precision.
Combining Time and Frequency Domain Processing:
In the Time Domain: Initial burst detection (the pseudo-random noise sequence) allows the system to find the coarse start of a symbol to establish proper Fast-Fourier Transform (FFT) windows.
In the Frequency Domain: The first three portions (burst detection, channel estimation, and payload) are converted into subcarriers via the FFT. Calculating timing offsets on these FFT signals ((Sn) allows the receiver to track phase rotations across adjacent subcarriers and detect minute timing misalignments.
Further, if the Carrier Frequency Offset (CFO) goes uncompensated, it ruins subcarrier orthogonality, leading to Inter-Carrier Interference (ICI). Utilizing the DMRS allows the modem to track residual CFO and apply ongoing frequency corrections. By fine-tuning the timing offset simultaneously using these DMRS-aided FFT signals, the modem ensures the decoder operates at the lowest possible Bit Error Rate (BER).
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure.
KAWAUCHI et al. relates to a receiving apparatus including: first to third position determination sections configured to determine the start position of an FFT interval which serves as a signal interval targeted for FFT by an FFT section; a selection section configured to select one of those start positions of the FFT interval which are determined by the first through the third position determination section; and the FFT section configured to perform FFT on the OFDM time domain signal by regarding the start position selected by the selection section as the start position of the FFT interval in order to generate the first OFDM frequency domain signal.
Srinivasan et al. relates to a communication system utilizing a cyclic prefix comprising a receiver configured to perform time tracking and determine an FFT window position based on a metric related to inter-symbol interference (ISI) and inter-carrier interference (ICI), determine an early energy for signal paths earlier than the current FFT window position, determine a late energy for signal paths later than the current FFT window position, determine the metric based on the early and late energies, compute an update amount for the FFT window position based on the metric, and update the FFT window position based on the update amount with a time tracking loop (TTL).
LEE illustrates configuration of an OFDM symbol in Figure 5 for carrying a reference signal and illustrates a receiver structure of a terminal receiving a reference signal. As shown in FIG. 14, the terminal receives first 512 samples 1408a using an MS reception beam #1 1410a after a duration 1412a which corresponds to channel delay spread of the OFDM symbol 1402. After reception beam transition 1412b, the second 512 samples 1408b are received using an MS reception beam #2 1410b. After reception beam transition 1412c, the third 512 samples 1408c are received using an MS reception beam #3 1410c. After reception beam transition 1412d, the fourth 512 samples 1408d are received using an MS reception beam #4 1410d. Each 512 samples 1408a, 1408b, 1408c, and 1408d are passed through a 512-point FFT.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to Young T. Tse whose telephone number is (571)272-3051. The examiner can normally be reached Mon-Fri 10:30am-7pm.
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If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Chieh M Fan can be reached at 571-272-3042. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300.
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/Young T. Tse/Primary Examiner, Art Unit 2632
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