JP7464071B2 - Receiving device, receiving method, transmitting device and transmitting method - Google Patents

Description

The present disclosure relates to a receiving apparatus, a receiving method, a transmitting apparatus and a transmitting method for transmitting and receiving payload data using Orthogonal Frequency Division Multiplexing (OFDM) symbols .

This application claims priority under the Paris Convention from UK Patent Application No. 1611071.0, the entire contents of which are incorporated herein by reference.

There are many examples of wireless communication systems that use Orthogonal Frequency Division Multiplexing (OFDM) to communicate data. For example, television systems configured to operate according to the Digital Video Broadcasting (DVB) standard use OFDM for terrestrial and cable transmission. OFDM can be generally described as providing K narrowband subcarriers (where K is an integer) that are modulated in parallel. Each subcarrier communicates modulated data symbols, such as quadrature amplitude modulation (QAM) symbols or quadrature phase shift keying (QPSK) symbols. The subcarriers are modulated in the frequency domain and converted to the time domain for transmission. Because data symbols are communicated in parallel on the subcarriers, the same modulation symbol can be communicated on each subcarrier for a long period of time. The subcarriers are modulated in parallel at the same time, so that the modulated carriers collectively constitute an OFDM symbol. Thus, an OFDM symbol includes multiple subcarriers, each of which is modulated simultaneously and has a different modulation symbol. During transmission, the OFDM symbol is preceded by a guard interval, into which the cyclic prefix of the OFDM symbol is inserted. The guard interval, if present, is intended to be of such duration that it absorbs any echoes of the transmitted signal that may result from multipath.

In a publication entitled "ATSC Standard: A/321, System Discovery and Signaling" ^[1] , it is proposed to include a preamble in a transmitted television signal carrying broadcast digital television programming for the television system known as the Advanced Television Systems Committee (ATSC) 3.0. The preamble includes a so-called "bootstrap" signal. The bootstrap signal is intended to provide a receiving device with a portion of the transmitted signal that is more likely to be detectable and thus can serve as an initial detection signal. This is because broadcasters are expected to offer multiple services within the broadcast signal rather than simply broadcasting television.

However, the current standard for broadcast networks, ISDB-T, which employs OFDM, where services are time division multiplexed (TDM) onto a single channel, has the problem that the capacity of mobile services is limited once the tuners are configured. As demand for portable television increases, these problems become more pronounced.

In the next standard, ISDB-T3, it is proposed to design a frame structure that can be configured for either frequency division multiplexing (FDM) or TDM. Such a frame structure is proposed in this specification and defined with respect to the embodiments of the present technology.

Further aspects and embodiments of the present disclosure are provided in the accompanying claims, including a transmitting device and a transmitting method.

According to various embodiments of the present disclosure, a transmitting device for transmitting payload data using orthogonal frequency division multiplexed OFDM symbols includes a frame builder configured to receive the payload data transmitted from a plurality of different channels and frame the payload data received from each of the channels for a plurality of time frames into a plurality of transmission payload data frames; a modulation unit configured to generate a frame synchronization OFDM symbol, one or more first signaling OFDM symbols, and one or more second signaling OFDM symbols for each of the plurality of payload data frames and modulate the one or more payload OFDM symbols with the payload data received from each of the channels; and a transmitting unit configured to transmit the plurality of payload data frames as a plurality of transmission frames, each of the plurality of transmission frames including one or more payload OFDM symbols, and a frame synchronization OFDM symbol followed by the one or more first signaling OFDM symbols followed by the one or more second signaling OFDM symbols for the one or more payload OFDM symbols. and a first OFDM symbol, the frame synchronization OFDM symbol and the one or more first signaling OFDM symbols being transmitted in a bandwidth equal to a radio frequency transmission bandwidth, the one or more second signaling OFDM symbols and the one or more payload OFDM symbols being transmitted in the radio frequency transmission bandwidth, the one or more second signaling OFDM symbols and the one or more payload OFDM symbols each being frequency divided to provide a plurality of frequency segments, the plurality of frequency segments each being a different frequency segment. A transmitting device is provided in which payload data is transmitted from a channel in which the one or more second signaling OFDM symbols in each of the frequency segments transmit one instance of a plurality of instances of physical layer signaling for detecting and recovering the payload data transmitted by the plurality of frequency segments from the one or more payload OFDM symbols for each channel, and the one or more first signaling OFDM symbols transmit first signaling data for detecting the second signaling OFDM symbols.

This disclosure relates to co-pending patent applications PCT/GB2014/050869, GB1305805.2, PCT/GB2014/050868, GB1305797.1, GB1305799.7, US14/226937, PCT/GB2014/050870, GB1305795.5 ... Supported by PCT/GB2014/050954, GB1312048.0, TW103121570, PCT/GB2014/051679, EP13170706.9, PCT/EP2014/061467, GB1403392.2, GB1405037.1, TW103121568, PCT/GB2014/051922, and GB1420117.2.

Various further aspects and features of the present disclosure are defined in the accompanying claims, including a method for transmitting payload data.

FIG. 1 is a schematic diagram showing the configuration of a broadcast transmission network. FIG. 2 is a schematic block diagram illustrating an exemplary transmission chain for transmitting broadcast data over the transmission network of FIG. FIG. 3 is a schematic diagram showing an OFDM symbol in the time domain including a guard interval. FIG. 4 is a schematic block diagram illustrating an exemplary receiving device for receiving data broadcast by the broadcast transmission network of FIG. 1 using OFDM. FIG. 5 is a schematic diagram illustrating a transmission frame for simultaneously transmitting payload data including multiple services in multiple segments separated in the frequency domain according to an embodiment of the present technology. FIG. 6 is a schematic block diagram of a portion of the transmitter shown in FIG. 2 for transmitting a frame synchronization OFDM symbol according to an embodiment of the present technology. FIG. 7 is a schematic diagram illustrating a pseudo-noise sequence generation circuit used to generate a frame synchronization OFDM symbol according to an embodiment of the present technology. FIG. 8 is a schematic diagram illustrating a frame synchronization OFDM symbol in the frequency domain according to one embodiment of the present technology. FIG. 9 is a flow chart illustrating an exemplary operation of a transmitter device in generating one or more frame synchronization OFDM symbols by cyclically shifting a time domain symbol sequence in accordance with one embodiment of the present technology. FIG. 10 is a schematic diagram illustrating a time domain structure of a frame synchronization OFDM symbol according to an embodiment of the present technology. FIG. 11 is a schematic diagram illustrating a second time domain of a first signaling OFDM symbol according to an embodiment of the present technology. FIG. 12 is a schematic block diagram of an exemplary receiver for detecting and recovering signaling from one or more frame synchronization OFDM symbols. FIG. 13 is a schematic block diagram of a receiving apparatus for detecting a frame synchronization OFDM symbol including identifying a trigger time for performing a forward Fourier transform on an OFDM symbol according to an embodiment of the present technology. FIG. 14 is a schematic block diagram of a correlator configured to detect a frame synchronization OFDM symbol according to an embodiment of the present technology. FIG. 15 is a flowchart showing detection in a receiving device of a sequence used and a frequency offset when generating a frame synchronization OFDM symbol and a first signaling OFDM symbol according to an embodiment of the present technology. FIG. 16 is a schematic block diagram of a portion of a receiver device, such as the example shown in FIG. 4, configured to detect relative cyclic shifts of signature sequences in accordance with an embodiment of the present technology. FIG. 17 is a schematic block diagram of a portion of a receiver device, such as the example shown in FIG. 4, configured to detect relative cyclic shifts of signature sequences in accordance with an embodiment of the present technology. FIG. 18 is a graph of block error rate versus symbol-to-noise ratio illustrating the performance difference between a method using conjugate multiplication as shown in FIGS. 16 and 17 and a frequency domain decoding algorithm using division in accordance with one embodiment of the present technology. FIG. 19 is a diagram illustrating segmented OFDM reception according to one embodiment of the present technology. FIG. 20 is a schematic block diagram of a portion of a narrowband receiver configured to detect relative cyclic shifts of signature sequences in accordance with one embodiment of the present technology.

An embodiment of the present disclosure will now be described by way of example with reference to the accompanying drawings. In each drawing, similar parts are designated by corresponding reference numerals.

Embodiments of the present disclosure may be configured to form a transmission network for transmitting signals representing video and audio data, e.g., to form a broadcast network for transmitting television signals to a television receiving device. In some examples, the device for receiving the audio/video of the television signal may be a mobile device that receives the television signal while moving. In other examples, the audio/video data may be received by a conventional television receiving device, which may be fixed and connected to one or more fixed antennas.

The television receiving device may or may not include an integrated display for the television image, and may be a recorder device including multiple tuners and demodulators. The antenna may be built into the television receiving device. A connected antenna or a built-in antenna may be used to facilitate reception of different signals as well as television signals. Thus, embodiments of the present disclosure are configured to facilitate reception of audio/video data representing television programs by different types of devices in different environments.

It will be appreciated that receiving television signals using a mobile device while on the move can be more difficult because over-the-air reception conditions are significantly different from those of a conventional television receiving device that receives input from a fixed antenna.

An example of a television broadcasting system is shown in FIG. 1. A broadcast television base station 1 shown in FIG. 1 is connected to a broadcast transmission device 2. The broadcast transmission device 2 transmits signals received from the broadcast television base station 1 within the coverage area of the broadcast network. The television broadcasting network shown in FIG. 1 can operate as a so-called multi-frequency network. In a multi-frequency network, each broadcast television base station 1 transmits signals at a frequency different from the frequencies of other adjacent broadcast television base stations 1. The television broadcasting network shown in FIG. 1 can also operate as a so-called single-frequency network. In a single-frequency network, each broadcast television base station 1 transmits a radio signal simultaneously transmitting audio/video data so that the television receiving device 4 and the mobile device 6 within the coverage area of the broadcast network can receive the signal. In the example shown in FIG. 1, the signal transmitted from the broadcast television base station 1 is transmitted using orthogonal frequency division multiplexing (OFDM), so that even if signals are transmitted from different broadcast television base stations 1, each broadcast transmission device 2 can be configured to transmit the same signal that can be combined by the television receiving device. If the spacing between the broadcast television base stations 1 is such that the propagation time between signals transmitted by different broadcast television base stations 1 is less than or not substantially greater than the guard interval preceding the transmission of each OFDM symbol, the receiving device 4 and the mobile device 6 can receive the OFDM symbols and further recover data from the OFDM symbols by combining the signals transmitted from the different broadcast television base stations 1. Examples of broadcast network standards that employ OFDM in this way include DVB-T, DVB-T2, and ISDB-T.

2 is an exemplary block diagram of a transmission device forming part of a broadcast television base station 1 for transmitting data from an audio/video source. In FIG. 2, different audio/video channels 20, 22, and 24 generate different audio/video data representing television programs or content. The audio/video data is coded and modulated before being fed to a frame builder 26. The frame builder 26 is configured to form data to be transmitted in payload data frames or transmission time frames corresponding to a time division unit. For each payload data frame, physical layer signaling data is provided by a physical layer data block 28 and added to each payload data frame for transmission. That is, for each of the audio/video channels 20, 22, and 24, audio/video data is formed in a number of payload data frames for each of a number of time frames corresponding to a number of transmission frames generated in the transmission signal by the transmission device shown in FIG. 2. The frames may include a time division or frequency division interval with a preamble in which the physical layer signaling is transmitted, and one or more data transmission intervals in which the audio/video data generated by the audio/video channels 20, 22, and 24 is transmitted. The data may be interleaved and formed into symbols before being provided to the OFDM modulation unit 30. The output of the OFDM modulation unit 30 is passed to a guard insertion unit 32 which inserts guard intervals, and the resulting signal is provided to a transmission unit 40. The signal is transmitted from the transmission unit 40 by an antenna 42. Signaling and synchronization information generated by a signaling and synchronization generation unit 34 may be provided to the guard insertion unit 32. Signaling information to be transmitted together with the frame synchronization signal and the first signaling symbol is generated in a signaling information unit 36 and provided to a synchronization signal generation unit 38. The synchronization signal generation unit 38 generates the frame synchronization signal and the first signaling symbol. As described below, the signaling information may be expressed as a relative cyclic shift of the frame synchronization OFDM symbol in the time domain, as a signature sequence that modulates the first signaling OFDM symbol relative to the signature sequence of the frame synchronization OFDM symbol.

As in the conventional configuration, OFDM is configured to generate symbols in the frequency domain. In the frequency domain, data symbols to be transmitted are mapped onto subcarriers. The subcarriers are transformed to the time domain using an inverse Fourier transform. The inverse Fourier transform may form part of the OFDM modulation unit 30. In this way, data to be transmitted is formed in the frequency domain and transmitted in the time domain. As shown in FIG. 3, each time domain symbol is generated by a useful part of duration Tu seconds and a guard interval of duration Tg seconds. The guard interval is generated by copying a part of the useful part of the symbol having duration Tg in the time domain. However, the copied part may be generated from the end of the symbol. The receiver can be configured to detect the beginning of the useful part of the OFDM symbol by correlating the useful part of the time domain symbol with the guard interval. Starting from this beginning, samples of the time domain symbol can be transformed into the frequency domain by a fast Fourier transform. From the frequency domain, the transmitted data can be restored. Such a receiver is shown in FIG. 4.

In FIG. 4, the receiving antenna 50 is configured to detect the RF signal that has passed through the tuner 52 and been converted to a digital signal by the analog/digital converter 54. The guard interval is then removed by the guard interval remover 56. After detecting the optimal position for performing a fast Fourier transform (FFT) and converting the time domain samples to the frequency domain, the FFT unit 58 converts the time domain samples to form frequency domain samples. The samples are provided to the channel estimation and correction unit 60. The channel estimation and correction unit 60 estimates the transmission channel used for equalization, for example, using pilot subcarriers embedded in the OFDM symbol. After excluding the pilot subcarriers, all subcarriers containing data are provided to the demapper unit 62. The demapper unit 62 extracts data bits from the subcarriers of the OFDM symbol. These data bits are then provided to the deinterleaver 64, which deinterleaves the subcarrier symbols. The data bits are then provided to the bit deinterleaver 66. The bit deinterleaver 66 performs deinterleaving so that the error correction decoder can correct errors according to the error correction operation, for example, using redundant data included in the forward error correction coding process.

Framing Structure Figure 5 shows a schematic diagram of a framing structure of a frame according to an embodiment of the present technology that can be transmitted and received in the system described with reference to Figures 1 to 4. Figure 5 shows a proposed general structure of a transmission signal for transmitting data from different channels. For example, this structure can be used to transmit different television channels within an ISDB-T3 frame. As shown in Figure 5, the transmission frame includes:
A Frame Synchronisation OFDM symbol 501 that the receiver uses to detect the beginning of a frame and estimate the carrier frequency offset.
A first preamble including one or more (m) special OFDM symbols, sometimes referred to as first signaling OFDM symbols 502 (P1), which convey initial signaling information regarding the structure of the second preamble.
A second preamble comprising one or more OFDM symbols, sometimes referred to as second signaling OFDM symbols 504 and 505 (P2), carrying physical layer (Layer 1) parameters that describe how to carry the payload by the post-preamble waveform for all segments of the frame. Suitable parameters are described, for example, in the draft DVB and ATSC 3.0 physical layer standards at the filing date. In embodiments, the signaling data carried by each of the one or more second signaling OFDM symbols in the frame is identical. In one example, this may be structured in a loop carrying data for each segment. That is, the different frequency segments 507.1, 507.2, and 507.3 of the second signaling OFDM symbols 504 and 505 (P2) are instances of band information that defines the structure of the payload OFDM symbols 506 for the frequency segments 507.1, 507.2, and 507.3, respectively.
A post-preamble section including a number of payload OFDM symbols 506, which carry the payload and include services formed from audio/video data generated by different channels and divided into physical layer pipes (PLPs). The number of payload OFDM symbols 506 may be signaled by a second signaling OFDM symbol 504 and 505. The term physical layer pipe (PLP) is used to identify a channel of audio/video data that can be recovered from the transmitted frame.
Each channel provided by the frequency segments 507.1, 507.2 and 507.3 of the payload OFDM symbols is terminated by a frame close symbol (FCS) 508 before the next frequency synchronization OFDM symbol 511 and the first (P1) signaling OFDM symbol 512.

In embodiments, the frame frequency synchronization OFDM symbol 501 is immediately followed by one or more first signaling OFDM symbols 502. In embodiments, the last symbol of the one or more first signaling OFDM symbols 502 in the frame is immediately followed by one or more second signaling OFDM symbols 504 and 505. In embodiments, the last symbol of the one or more second signaling OFDM symbols 504 and 505 in the frame is immediately followed by a payload OFDM symbol 506.

As described above, the transmission frame is further divided into M frequency segments 505.1, 507.2, and 507.3, which also divide each OFDM symbol of the frame. The number of segments M per frame is configurable and is signaled by the first signaling OFDM symbol.

The frame synchronization OFDM symbol and the first signaling OFDM symbol are wideband in nature, since they are configured to span the entire channel bandwidth. However, they can be detected and decoded by both a wideband receiver whose bandwidth spans the entire channel and a narrowband receiver whose bandwidth is equal to the bandwidth of one of the M segments. The second signaling OFDM symbol and the payload OFDM symbol are both modulated separately for each segment, and then concatenated in the frequency domain in segment order, prior to transformation to the time domain by IDFT. Therefore, in the case of frequency segmentation, the second signaling OFDM symbol and the payload OFDM symbol must each be decoded for each segment.

In various embodiments, the radio frequency transmission bandwidth 514 of the transmission signal shown in FIG. 5 represents a bandwidth for a frame of about 6 Mhz or about 8 Mhz. However, it will be understood that these are merely examples and that other radio frequency transmission bandwidths may be used such that embodiments of the present disclosure are not limited to these bandwidths.

The following paragraphs describe how the first signaling OFDM symbol can be constructed, how the first signaling OFDM symbol can carry signaling information, how the information carried by the first signaling OFDM symbol is decoded in the receiving device, as well as how the frame synchronization OFDM symbol can be constructed in the transmitting device and how the frame synchronization OFDM symbol can be detected in the receiving device.

Synchronization signal Figure 6 is a schematic block diagram of a part of the transmitting device shown in Figure 2 arranged to transmit a frame synchronization signal. In Figure 6, a signature sequence generator 600 is arranged to generate a signature sequence which is mapped by a subcarrier mapping and zero padding unit 602 to the subcarriers of the OFDM symbols constituting the frame synchronization OFDM symbol. The frequency domain signal is then transformed to the time domain by an inverse Fourier transform unit 604. The signaling information to be transmitted in the frame synchronization signal is provided by a first input 605 to a cyclic shifter 606. The cyclic shifter 606 also receives by a second input 607 a time domain OFDM symbol representing the frame synchronization OFDM symbol. In embodiments of the present technology, the operation of the cyclic shifter 606 in combination with its inputs may correspond to the signaling and synchronization generator 34 shown in Figure 2. As will be explained below, the signaling information is represented as a signature sequence that modulates the first signaling OFDM symbol relative to the signature sequence of the frame synchronization OFDM symbol as a relative cyclic shift of the frame synchronization OFDM symbol in the time domain. The first signaling OFDM symbol is then provided to a guard interval insertion unit 608 that adds a guard interval to the frame synchronization OFDM symbol in such a way that the OFDM symbols that make up the frame synchronization OFDM symbol are transmitted by a transmission unit 609.

The frame sync OFDM symbol has a similar structure to the first ATSC 3.0 bootstrap symbol described in A/321 ^[2] . The frame sync OFDM symbol is a 2048p FFT size OFDM symbol. The value of p can be one of {0.25, 0.5, 1, 2, 4}, which allows the frame sync OFDM symbol to be a {512, 1K, 2K, 4K, 8K} FFT size OFDM symbol, respectively.

As shown in FIG. 6, the signature sequence generator 600 includes a pseudorandom sequence generator 610 used to generate the signature sequence and a Zadoff-Chu (ZC) sequence generator 612. These two sequences are multiplied by a multiplier 614, and the multiplied sequence is mapped to subcarriers of the OFDM symbol by a subcarrier mapping and zero padding unit 602. As shown in FIG. 6, a seed value for the pseudorandom sequence generator 610 is provided at a first input 620, and a second input 622 provides an indication of the root of the Zadoff-Chu sequence generator 612. The ZC sequence is generated using the following Equation 1:

（ｑは、ＺＣ系列のルートとして定義されている。）

(q is defined as the root of the ZC sequence.)

As described with reference to FIG. 6, the frame-synchronized OFDM symbol is constructed in the frequency domain by mapping the coefficients of a Zadoff-Chou (ZC) sequence multiplied by positive and negative coefficients generated by a pseudo-noise (PN) sequence generator shown in FIG. 7 to its subcarriers. Thus, the multiplied sequence according to the embodiments is described as a (ZC*PN) sequence.

Fig. 7 is a schematic diagram of a pseudo-noise generation circuit 610 forming part of the signature sequence generation unit 600 shown in Fig. 6 for use in generating a frame synchronization OFDM symbol according to an embodiment of the present technology. The PN sequence is generated by the generation circuit shown in Fig. 7 using the following (polynomial) Equation 2. At the beginning of each frame, a selected 16-bit seed g is used to initialize each element 701, 702, 704, and 706 (r _I ). This seed has the form shown in Equation 3.

（ただし、各ビット７１１、７１２、７１４、７１６、７１８、及び７１９（ｇ_ｉ）は、０又は１のいずれかのバイナリ値を有する。１６ビットシードｇを形成するために、これらを複数の加算要素７２１、７２２、７２４、及び７２６により組み合わせる。）

(where each bit 711, 712, 714, 716, 718, and 719 (g _i ) has a binary value of either 0 or 1, which are combined by multiple addition elements 721, 722, 724, and 726 to form the 16-bit seed g.)

The mapping of (ZC*PN) sequences to symmetrically form signature sequences on OFDM symbols is shown in Figure 8.

As shown in FIG. 8, in the frequency domain, the frame synchronization signal can be considered to include two equal parts 810 of a symmetric Zadoff-Chu (ZC) sequence. Each symbol in the Zadoff-Chu sequence is configured to modulate an active carrier 812. Correspondingly, the PN sequence is configured to modulate a subcarrier as shown by line 814. The other subcarriers of the frame synchronization signal are unused and are therefore set to zero, e.g., as shown at the ends of the frame synchronization signal 820 and 822.

The length of the (ZC*PN) sequence _Na is a configurable parameter called the number of useful subcarriers per frame sync OFDM symbol. This means that the (ZC*PN) coefficients are mapped only to the central _Na subcarriers of the frame sync OFDM symbol, and the other subcarriers (at the low and high band edges of the symbol) are set to zero. The (ZC*PN) sequence has mirror symmetry in its construction, with the central coefficient set to zero.

As shown in Figure 8, the ZC sequence and the PN sequence are mapped to the OFDM subcarriers in a mirror symmetric manner with respect to the central DC subcarrier of the OFDM symbol. The subcarrier value of the nth symbol of frame sync (0 <= n < N _B ) can be calculated as shown in Equations 4 and 5 below, where N _H = (N _ZC - 1)/2, N _B is the number of symbols, and p(k) is an element of the PN sequence. The ZC sequence is determined by its root q. The root q may be the same for each symbol, but the PN sequence increases with each symbol.

The last symbol reverses the phase of the subcarrier values for that particular symbol (i.e. rotates 180 degrees). This provides a clear indication of the end of the frame sync and preamble signal. This is provided if there is another symbol, in which case the receiving device provides a clear indication of the last OFDM symbol. That is, any number of synchronization and signaling OFDM symbols can be used. Thus, the receiving device can detect the phase reversal and therefore the end of the frame sync signal.

In one example, signaling data can be transmitted in the first signaling symbol by performing a data-determined cyclic shift of the frame-synchronous OFDM symbol in the time domain. This is done by the cyclic shift block shown in Figure 6. The process for transmitting the signaling bits is summarized in Figure 9.

In FIG. 9, in step S900, a frequency domain sequence is formed in the frequency domain by the sequence generation unit 600. In step S902, an inverse Fourier transform is performed by the IFFT unit 604 to convert the frequency domain signal to the time domain. Thus, in step S904, the sequence is formed in the time domain. As shown in step S906, signaling bits are formed, which are then interpreted as relative cyclic shift values in step S908. In step S910, the relative shift values are converted to absolute shift values. As shown by the arrow S912, the time domain sequence formed in step S904 is then shifted according to the absolute cyclic shift determined in step S910. Finally, in step S914, the time domain sequence to be transmitted is generated.

In one example of a time domain structure , each frame synchronization OFDM symbol is formed by the transmitting device from three parts, designated A, B, and C. As mentioned above, the OFDM symbol is usually formed with a guard interval, which is generated by copying a section of the OFDM symbol in the time domain, as a preamble to the OFDM symbol to account for multipath reception at the receiving device. Each frame synchronization OFDM symbol is formed in one of two ways. The frame synchronization OFDM symbol and the first signaling symbol formed in the time domain by different methods are shown in Figures 10 and 11. As shown in Figures 10 and 11, the data carrying part of the symbol, which is the original configuration of the OFDM symbol before the guard interval is added, is represented as section A (1001, 1101). Section A (1001, 1101) is therefore derived as a 2048p-point IFFT of the frequency domain structure with or without the above-mentioned cyclic shift to represent the signaling bits carried by the frame synchronization OFDM symbol. where interval A (1001, 1101) is the useful part of the symbol consisting of 2048p samples formed by IFFT. Intervals B (1002, 1102) and C (1004, 1104) consist of samples taken from the end of interval A (1001, 1101) with a frequency shift of ±f _Δ equal to the subcarrier spacing introduced by the transmitter to the samples of interval B (1002, 1102) and are correspondingly removed at the receiver. Each frame synchronization OFDM symbol and the first signaling symbol consist consistently of 3072p samples. where section A (1001, 1101) consists of 2048p samples, section C (1004, 1104) consists of 520p samples and samples 1006, 1008, 1106 and 1108 from section A (1001, 1101), and section B (1002, 1102) consists of the last 504p sample and samples 1006 and 1106 from section C (1004, 1104) to which a frequency shift of ± _fΔ has been applied.

The Frame Synchronization OFDM symbol provides for synchronous detection of the particular (ZC*PN) sequence it transmits, employing a C-A-B structure as shown in Figure 10, with a frequency shift of + _fΔ applied to interval B (1002). The (ZC*PN) can be selected to signal the major and minor standards in use, an alert status that can be used to provide an emergency alert condition, transmitter identity, transmitter location, etc.

One or more first signaling symbols carry signaling information and adopt a B-C-A structure as shown in FIG. 11 including a phase-inverted final symbol providing the end of the preamble signal as described above, and apply a frequency shift of −f _Δ to interval B (1102).

The Frame Sync OFDM symbol shall be used for initial time synchronization and may signal other aspects of the system via the selection of ZC root and/or PN seed parameters. This symbol does not signal any additional information. Also, the cyclic shift of this symbol shall always be 0.

A differentially encoded absolute cyclic shift M _n (0≦M _n <N _FFT ) is applied to the nth first signaling OFDM symbol and is calculated by summing the absolute cyclic shift for symbol n-1 and the relative cyclic shift for symbol n modulo the length of the time-domain sequence.

Then, an absolute cyclic shift is applied to obtain a shifted time domain sequence from the output of the IFFT operation.

Frame Synchronization at the Receiver: The wideband receiver needs to detect the presence of the Frame Sync OFDM symbol as a marker of the start of a frame. The receiver will be pre-configured with the correct values for p, _Na , and Δf. The Frame Sync OFDM symbol can be detected in the time domain, but further processing must be done in the frequency domain, e.g. to find any carrier frequency offset and/or to see which (ZC*PN) sequence is used. However, detecting the Frame Sync OFDM symbol is equivalent to detecting the start of a frame.

12 is a schematic block diagram showing the application of the receiving device shown in FIG. 4 when operating to detect the presence of a frame synchronization OFDM symbol. As shown in FIG. 4, the signal detected by the antenna 50 is fed to the RF tuner 52 and then to the A/D converter 54. The received digital sampled signal is then fed to the forward Fourier transform processing unit 58 and also to a first input of the switch 1201. The switch 1201 is controlled by the control unit 1202 to switch the received digital sampled signal between the frame synchronization detection unit 1204 and the second of the two frame synchronization processing units 1206 and 1210. The frame synchronization detection unit 1204 generates a trigger signal that is fed to the FFT processing unit 58 via the channel 1208 to identify the most useful part of the received signal that is transformed from the time domain to the frequency domain for the purpose of verifying the frame synchronization signal and recovering the signaling data. The output of the FFT processing unit 58 provides the received signal transformed into the frequency domain to the first frame synchronization processing unit 1210. The first frame synchronization processor 1210 is configured to generate a first estimate of the channel transfer function (CTF) H(z) at the output channel 1212.

An exemplary detector of the frame synchronization OFDM symbol of the preamble signal is shown in FIG. 13. As mentioned above, only the first frame synchronization OFDM symbol has a C-A-B structure transmitted for initial synchronization. FIG. 13 is an exemplary block diagram of a detector of the frame synchronization OFDM symbol. As shown in FIG. 13, the received discrete time signal r(n) is provided to a delay unit 1301 and a C-A-B structure detector 1302. The C-A-B structure detector 1302 generates an estimate of the fine frequency offset (FFO) by a first output 1304. The fine frequency offset is a frequency shift smaller than the OFDM symbol subcarrier spacing that may occur during the transmission of the frame synchronization OFDM symbol. Also, the output from the second channel 1306 is an indication of a timing trigger indicating the period of the received OFDM symbol, which is transformed by the FFT processor 58 to capture as much energy as possible of the received OFDM frame synchronization OFDM symbol. However, before transforming the received frame synchronization OFDM symbol to the frequency domain, the total frequency offset is removed in the multiplier 1308. The multiplier 1308 receives the delayed received signal from the delay 1301 at a first input and the inverse of the total frequency offset formed by the adder 1310 and the tone generator 1312 at a second input. The total frequency offset is formed by the adder 1310 from one or both of the fine frequency offset (FFO) estimated by the C-A-B structure detector 1302 and provided to the first input and the integer frequency offset (IFO) estimated by the frame synchronization signal processor 1310. The total frequency offset is input to the tone generator 1312, which generates a sinusoidal tone at a frequency equal to the total frequency offset. The frame synchronization signal processor 1210 generates the IFO by correlating the frequency domain subcarriers with a regenerated signature sequence generated by a combination of the ZC sequence modulated by the PN sequence. The position of the peak in the correlation output is then used to estimate the IFO, which is the frequency domain displacement of a number of subcarriers relative to a reference frequency within the dominant frequency band of the frame synchronization signal. In this way, the total frequency offset is estimated and removed by the multiplier 1308 and tone generator 1312 from the FFO estimated by the structure detector 1302 and the IFO estimated by the frame synchronization signal processor 1210.

As mentioned above, the C-A-B structure detector 1302 shown in FIG. 13 for detecting the frame synchronization OFDM symbol is used to generate the FFO and indicate the useful portion of the input signal burst for the forward Fourier transform (FFT).

Figure 14 is a schematic block diagram of a correlator configured to detect a frame synchronization OFDM symbol according to an embodiment of the present technology. This detection indicates the start of part A of the frame synchronization OFDM symbol on which an FFT can be performed. The remaining part of the process includes the detection of the (ZC*PN) sequence used in the frame synchronization OFDM symbol, followed by the decoding of the signaling parameters transmitted by the next first signaling OFDM symbol. Each of the next first signaling OFDM symbols uses the same known segments of the ZC and PN sequences as the frame synchronization OFDM symbol. Therefore, we start by listing which ZC (sequence root) and PN (sequence seed) sequences were used.

As shown in Fig. 14, the received discrete-time signal r(n) is fed to a delay 1402 and a multiplier 1408, where it is frequency shifted corresponding to the frequency adjustment ^ej2πfT of the tone generator 1401. The output of the multiplier 1408 is fed to two further delays 1404 and 1406, which serve to delay the received signal by a number of samples equal to the number of A, A_B and B portions of the frame synchronization OFDM symbol. The output of each delay is passed to further multipliers 1410, 1412 and 1414, where it is multiplied by the complex conjugate of the received discrete-time signal r(n) and fed to moving average filters 1416, 1418 and 1420, where it is correlated with the received signal according to the delays A, A+B and B. The output of the moving average filter 1416 is delayed by a delay element 1422, and the outputs of the moving average filters 1418 and 1420 are upscaled by scaling elements 1424 and 1426, respectively. The outputs of the two scaling elements 1424 and 1426 are summed in a summer 1428. The output of the summer is then multiplied by the output of the delay element 1422 by a multiplier 1430 to generate a peak combined sample. The peak combined sample is generated by correlating each section C, A, and B of the received signal with a respective copy to identify the peak at which the FFT trigger point is found at output 1432. The phase of the peak accordingly determines the FFO provided at output 1434.

The used (ZC*PN) sequence is mapped to the subcarriers of the frame synchronous OFDM symbol. For ATSC 3.0, the used sequence is formed by the multiplication of
Multiply the ZC sequence by the root q=137,
The PN sequence is multiplied by one of the generator seeds in Table 2 below.

Other PN sequence seeds and other possible generator polynomials can be defined and used. Thus, for ATSC 3.0, there are eight possible (ZC*PN) sequences that the transmitter can use. In embodiments of the present technology, all eight sequences are pre-generated and stored at the receiver. When attempting to detect which of the eight sequences was used, the receiver can correlate each stored sequence in turn with the FFT result of the A part of the frame sync OFDM symbol. The sequence that gives the maximum peak correlation is the (ZC*PN) sequence used at the transmitter. The frequency offset is the relative bin position of that peak correlation from _-Fmax to _Fmax , where _Fmax is the maximum target integer frequency offset in FFT bins.

A flow chart of this procedure is shown in Figure 15. _R1 (k) is the FFT of the frame sync OFDM symbol and _Ci (k) is the i-th (ZC*PN) sequence. Once the integer frequency offset and the (ZC*PN) sequence are detected, the receiver can proceed to decode the first signaling OFDM symbol after correcting for the frequency offset.

The flowchart shown in FIG. 15 may be summarized as follows.
Start: At the beginning of processing, the received symbols are in the frequency domain, as shown in Figure 15. In embodiments, the symbol spectrum is derived from an FFT of the spectral power components above 2048p, and may be oversampled.
S1501: At the start of the loop, the variable index of the reference signature sequence is initialized to i=1.
S1502: This performs a circular correlation between the received frequency domain OFDM symbol and the i-th signature sequence.
S1504 and S1506: If the reference signature sequence i is the same as that used in the transmitting device, a significant peak is detected in the cross-correlation output within the IFO. If no significant peak is detected, the process proceeds to step S1508, where the variable index i of the reference signature sequence is incremented and cross-correlation is attempted on the next reference signature sequence. Candidate reference signature sequences may be pre-stored in the receiving device with an index based on the combination of the Zadoff-Chu root and PN generator seed used to generate the particular sequence.
S1510: If no significant peak in the cross-correlation is found, the current value i becomes the index of the desired reference signature sequence. If the spectrum is oversampled, the relative position of the peak in the cross-correlation output is used to determine the integer frequency offset (IFO) and fine frequency offset (FFO).
At stop, the process ends.

Detection signaling of the first signaling data is transmitted by each first signaling OFDM symbol. A parameter of the signaling is encoded as a relative cyclic shift by the A part of the first signaling OFDM symbol. And the relative cyclic shift is differentially encoded from symbol to symbol. In one example, the decoding process can detect the cyclic shift in a given symbol, which can then be differentially decoded with the cyclic shift of the previous symbol. In one example, the differential cyclic shift is determined as part of the decoding process itself. This is advantageous in that it avoids a rather computationally intensive explicit channel estimation and correction.

Let R _n (k), H _n (k), P _n (k), and Z _n (k) be the received spectral sequence, the channel transfer function, the used PN sequence, and the used ZC sequence for the nth symbol, respectively, where k is the subcarrier index. Let M _n-1 be the absolute cyclic shift at symbol n-1, while m is the incremental cyclic shift for symbol n-1 that encodes the signaling parameters carried by symbol n. Then, for the first signaling OFDM symbols n-1 and n, the following Equation 16 holds for a given frame:

That is, if we use the same ZC sequence for the frame synchronization OFDM symbol and all first preamble symbols of a given frame, and designate the noise of symbol n as N _n (k), then we can write Equation 17 below.

Let us assume that n-1=0, M _n-1 =0, i.e. there is no cyclic shift in the frame sync OFDM symbol of the frame. The decoding algorithm involves dividing R _n (k) by R _n-1 (k) to find the phase gradient of the residual signal, which represents the cyclic shift of m samples between the two symbols. Thus, it can be calculated as in Equation 18 below:

If the duration of each frame synchronization OFDM symbol or first preamble symbol is short, it is reasonable to assume that for a given center frequency _f0 and relative receiver speed v=c/ _f0 , where c is the speed of light, the channel remains substantially constant between two consecutive symbols, i.e., Equation 19 below holds:

As an example, for f ₀ =690 MHz, which is at the top end of the UHF band used for television, v needs to exceed approximately 1564 km/h for the channel to change significantly from symbol to symbol.

In the above formula, the noise multiplicatively increases, making the analysis difficult and degrading the performance. Nevertheless, since the relative cyclic shift that we wish to decode is in the phase gradient, the amplitudes of the component results in the above formula are not particularly important. Therefore, the division by R _n-1 (k) can be changed to a multiplication by its conjugate, which avoids cumbersome calculations and adds all the noise to the main phase signal. As far as the phase gradient is concerned, the result of the division is equal to the result of the multiplication by the conjugate.

The second and third terms on the right hand side are modulation noise, while the last term is simply white noise since P _n and P _n-1 are positive and negative series. Since all noises increase by addition, the combining exponent of these terms depends on the SNR of the received signal. Therefore, at a reasonable level of SNR, it is expected that the argument or phase trajectory of the result will be dominated by the first term on the right hand side. In this way, by detecting the phase gradient of the result, the relative cyclic shift m between the two symbols can be detected. The cyclic shift can also be detected by performing an IFFT on the result and taking the sample position of the peak amplitude, since the following Equation 22 holds:

This algorithm is shown in Fig. 16. According to the receiving device shown in Fig. 16, the down-converted signal is received by the RF tuner 52, and after passing through the guard interval removal unit 56, all prefixes and postfixes are removed from the received signal. The received signal is fed to two branches. In the first branch, the received signal is delayed by a number of samples equal to the useful part of an OFDM symbol by a delay unit 1601, so that the previous received spectral sequence R _n-1 is transformed by a first FFT unit 1604. The received signal is also fed through a second branch, so that each received symbol is also transformed by a second FFT unit 1602. Here, the conjugate 1606 of the output of the first FFT unit 1604 is multiplied by the output of the second FFT unit 1602 in a multiplier unit 1608. The result of the multiplication unit 1608 is then divided by a division unit 1610 into multiple PN sequences used for the current and previous symbols 1620 and provided to an IFFT unit 1612. The signal that has passed through the IFFT unit 1612 and has been IFFT-transformed is provided to a peak detection unit 1614 and subtracted by a subtraction unit 1618 from the 2048p spectral output components.

Further processing of the peak positions at the output of the peak detector, i.e., subtraction from 2048p, can be avoided if R _n-1 (k) is divided by R _n (k). In this case, using conjugation instead of division, the related equation becomes Equation 23 below.

This technique is shown in Figure 17.

Figure 17 is substantially identical to Figure 16, so only the differences will be described. In contrast to Figure 16, the receiver shown in Figure 17 forms the conjugate of the currently received spectral sequence R _n . The spectral sequence R _n is conjugated by a conjugator 1606 and multiplied by a multiplier 1608 with the output of the previously received FFT transformed spectral sequence R _n-1 . The result of the multiplier 1608 is then divided by a divider 1610 with the multiple PN sequences used for the current and previous symbols 1720. No subtraction from 2048p is required here. The final output is therefore received from a peak detector 1614.

16 and 17, according to the embodiments of the present technology, a configuration is provided for estimating first signaling data by detecting a cyclic shift of a signature sequence transmitted by a frequency-synchronized OFDM symbol and one first signaling OFDM symbol. As shown in the example of FIG. 16, the FFT units 1602 and 1604 are configured to continuously transform the time length of the effective portion of each of the frequency-synchronized OFDM symbol and one or more first signaling OFDM symbols into the frequency domain. It will be understood that in another example, a single FFT unit can be used instead of the two FFT units 1602 and 1604 to operate sequentially. The multiplier 1608 is configured to receive each frequency domain sample of the current first signaling OFDM symbol and multiply each sample with the conjugate generated by the conjugate unit 1606 of the corresponding sample of one of the frame synchronization OFDM symbols or one of the one or more first signaling OFDM symbols immediately preceding the current first signaling OFDM symbol to generate an intermediate sample for each subcarrier sample. The IFFT unit 1612 is configured to convert the intermediate samples obtained from the current first OFDM symbol into the time domain. The cyclic shift detector formed from the peak detector 1614 is configured to estimate the first signaling data transmitted by each of the one or more first signaling OFDM symbols by detecting the cyclic shift of the signature sequence present in each of the one or more first signaling OFDM symbols from the peaks of the intermediate samples converted into the time domain.

Thus, according to embodiments of the present technology, a receiver device can be configured to detect the first signaling data by detecting the relative cyclic shift between the frequency-synchronized OFDM symbol and the first signaling OFDM symbol. This results in only additive noise being present in the detection process. Thus, conjugate multiplication as shown in Figures 16 and 17 provides an advantage since the signaling data can be accurately estimated by detecting the cyclic shift of the signature sequence with a lower signal-to-noise ratio.

Figure 18 is a graph of block error rate versus symbol-to-noise ratio showing the performance difference between a method using conjugate multiplication as shown in Figures 16 and 17 and a frequency domain decoding algorithm using division according to one embodiment of the present technology.

The plot is for an additive white Gaussian noise (AWGN) channel and it can be clearly seen that a conjugate multiplication algorithm as employed in embodiments of the present technology is vastly superior in terms of SNR compared to one that uses actual division. In the presence of multipath, this comparison becomes even more pronounced.

In narrowband reception, the receiving device only tunes to the relevant segment. This is shown in the representation of the signal transmitted by the transmitting device structure according to one embodiment of the present technology in FIG. 19. FIG. 19 shows a plot of signal power versus frequency for frequency-divided OFDM symbols used to transmit second signaling and payload data by the exemplary receiving device shown in FIG. 20 for γ=7. The receiving device shown in FIG. 20 corresponds to the example shown in FIG. 16, so only the differences between FIG. 16 and FIG. 19 will be described. It will be understood that the exemplary narrowband receiving device can also be implemented by making corresponding changes to the example shown in FIG. 17.

In the narrowband receiver example shown in Figure 20, the received signal can be sampled at a lower rate because the radio frequency detector/tuner 52 and receiver only receives signals within the narrowband frequency Seg3 of Figure 19. Thus, the input sampling rate of the receiver can be reduced by a factor of γ. Similarly, the following adjustments are made for the exemplary receiver shown in Figure 20 relative to the examples shown in Figures 16 and 17:
The delay 1601 at the input reduces to N _u /γ.
Accordingly, the size of the FFT units 1602 and 1604 is reduced by N _u /γ.

Since the signal is sampled at a lower rate than the full band radio frequency transmission bandwidth signal, the length of each CAB region of the time domain symbol is reduced by /γ. Correspondingly, the lengths of all delay and moving average filters in Figure 14 will also be reduced by a factor γ. The scaling unit 1622 is also configured to divide (or multiply) a section of the PN sequence by _Pn *Pn _-1 using samples from the received narrowband signal generated as an intermediate result at the output of the multiplier unit 1608.

When detecting the relative cyclic shift, all relevant subcarriers as described above are processed using either the scheme shown in Figure 16 or Figure 17. Before performing the final IFFT, a segment of relevant subcarriers obtained by dividing by _Pn *Pn _-1 from the scaling unit 1622 (or multiplying by - since both are positive and negative) is fed to the IFFT unit 1612, with each subcarrier in the correct position and all other subcarriers set to zero. That is, the upsampling unit 2001 is configured to add zero samples to the frequency domain samples provided at the output of the division unit 1610. The IFFT size applied by the IFFT unit 1612 is then applied as if a fullband receiver was used. This output then provides a phase gradient in a manner corresponding to the cases of Figures 16 and 17. The peak height of the output of the IFFT unit 1612 is affected by the absolute number of subcarriers in the processing segment. This means that if the FFT size of the first signaling OFDM symbol is small, the peaks will be much smaller and therefore block errors will be more likely to occur compared to the case of a larger FFT size.

Thus, according to embodiments of the present technology, the radio frequency demodulation circuit of the receiving device is configured to detect and recover radio signals within a bandwidth corresponding to one of the frequency segments of the one or more second signaling OFDM symbols and the one or more payload OFDM symbols. The inverse Fourier transform is configured to transform intermediate samples generated by multiplying the frequency domain samples of the current first signaling OFDM symbol by the conjugate of the previous frequency synchronization OFDM symbol (where each sample corresponds to a complex sample of each detected subcarrier of the segment of the OFDM symbol). The intermediate samples are transformed into the time domain and are indicative of the results of the current symbol of the one or more first OFDM symbols, but are upsampled according to a bandwidth corresponding to the radio frequency transmission bandwidth. This allows the cyclic shift detection unit to detect the cyclic shift of the signature sequence from the time domain intermediate samples generated for the intermediate samples whose bandwidth has been increased to the radio frequency transmission bandwidth.

Thus, according to one example, the upscaling unit 2001 is configured to receive intermediate samples in the frequency domain and add zero samples to the intermediate samples, which correspond to the frequency domain equivalent of the radio frequency transmission bandwidth.

As can be seen from the above description, embodiments of the present technology can provide a configuration that allows both time division multiplexing and frequency division multiplexing of services within the same radio frequency channel. This is achieved according to embodiments of the present technology by adopting the proposed frame structure shown in Figure 5. This can increase the capacity of mobile services.

The following numbered paragraphs define further exemplary aspects and features of the present technology.
Paragraph 1
A transmitter for transmitting payload data using orthogonal frequency division multiplexed OFDM symbols, comprising:
a frame builder configured to receive the payload data transmitted from a plurality of different channels and to frame the payload data received from each of the channels for a plurality of time frames into a plurality of payload data frames for transmission;
a modulation unit configured to generate a frame synchronization OFDM symbol, one or more first signaling OFDM symbols, and one or more second signaling OFDM symbols for each of the plurality of payload data frames, and to modulate the one or more payload OFDM symbols with payload data received from each of the channels;
a transmitter configured to transmit the plurality of payload data frames as a plurality of transmission frames;
each of the plurality of transmission frames includes one or more payload OFDM symbols preceded by a frame synchronization OFDM symbol followed by the one or more first signaling OFDM symbols followed by the one or more second signaling OFDM symbols;
1. A transmitting device, wherein the frame synchronization OFDM symbol and the one or more first signaling OFDM symbols are transmitted in a bandwidth equal to a radio frequency transmission bandwidth, the one or more second signaling OFDM symbols and the one or more payload OFDM symbols are transmitted in the radio frequency transmission bandwidth, the one or more second signaling OFDM symbols and the one or more payload OFDM symbols are each frequency divided to provide a plurality of frequency segments, each of the plurality of frequency segments carrying payload data from a different channel, the one or more second signaling OFDM symbols in each of the frequency segments carrying one instance of a plurality of instances of physical layer signaling for channel-by-channel detection and recovery of the payload data transmitted by the plurality of frequency segments from the one or more payload OFDM symbols, and the one or more first signaling OFDM symbols carry first signaling data for detecting the second signaling OFDM symbol.
Paragraph 2
The transmitting device according to paragraph 1, further comprising:
a signature sequence combiner configured to modulate the frame synchronization OFDM symbol with a signature sequence and to modulate the one or more first signaling OFDM symbols and one or more first signaling OFDM symbols in the time domain cyclically shifted with respect to a preceding symbol;
A transmitting apparatus, wherein the cyclic shift of the one or more first signaling OFDM symbols in the time domain represents the first signaling data transmitted in the one or more first signaling OFDM symbols.
Paragraph 3
A transmitting device according to paragraph 1 or 2,
The first signaling data includes an indication of the number of the frequency segments.
Paragraph 4
A transmitting device according to any one of paragraphs 1, 2, or 3,
The first signaling data includes an indication of an emergency situation.
Paragraph 5
A transmitting device according to any one of paragraphs 1, 2, 3, or 4,
The first signaling data includes an indication of a Fourier transform size and a guard interval to be used for the one or more second signaling OFDM symbols and the one or more payload OFDM symbols.
Paragraph 6
A transmitting device according to any one of paragraphs 1 to 5,
the modulation unit associated with the transmitter is adapted to form the frame synchronization OFDM symbol according to a first time domain structure comprising a first portion C consisting of a plurality of samples of a useful portion of the frame synchronization OFDM symbol and a portion A comprising the useful portion of the frame synchronization OFDM symbol;
A portion B of said first portion is copied to form a postamble of said frame synchronization OFDM symbol.
Paragraph 7
A transmitting device according to any one of paragraphs 1 to 6,
the modulation unit associated with the transmitting device is adapted to form the one or more first signaling OFDM symbols by a first part B consisting of a plurality of samples of a useful part of the first signaling OFDM symbol, a part A comprising the useful part of the first signaling OFDM symbol, and a part C comprising the useful part of the first signaling OFDM symbol,
The portion A is copied to form a second portion of the first signaling OFDM symbol.
Paragraph 8
A transmitting device according to paragraph 1,
The signature sequence includes a combination of a Zadoff-chu sequence and a pseudorandom noise sequence.
Paragraph 9
1. A method for transmitting payload data using orthogonal frequency division multiplexed OFDM symbols, comprising:
receiving said payload data transmitted from a plurality of different channels;
framing payload data received from each of the channels for a plurality of time frames into a plurality of payload data frames for transmission;
generating a frame synchronization OFDM symbol, one or more first signaling OFDM symbols, and one or more second signaling OFDM symbols for each of the plurality of payload data frames;
modulating one or more payload OFDM symbols with payload data received from each of said channels;
transmitting said plurality of payload data frames as a plurality of transmit frames;
each of the plurality of transmission frames includes one or more payload OFDM symbols preceded by a frame synchronization OFDM symbol followed by the one or more first signaling OFDM symbols followed by the one or more second signaling OFDM symbols;
13. A method for transmitting a signaling OFDM symbol, comprising: transmitting the frame synchronization OFDM symbol and the one or more first signaling OFDM symbols in a bandwidth equal to a radio frequency transmission bandwidth; transmitting the one or more second signaling OFDM symbols and the one or more payload OFDM symbols in the radio frequency transmission bandwidth; each of the one or more second signaling OFDM symbols and the one or more payload OFDM symbols being frequency divided to provide a plurality of frequency segments, each of the plurality of frequency segments carrying payload data from a different channel; the one or more second signaling OFDM symbols in each of the frequency segments carrying one instance of a plurality of instances of physical layer signaling for channel-by-channel detection and recovery of the payload data transmitted by the plurality of frequency segments from the one or more payload OFDM symbols; and transmitting the one or more first signaling OFDM symbols first signaling data for detecting the second signaling OFDM symbol.
Paragraph 10
10. The transmission method according to paragraph 9, further comprising:
modulating said frame synchronous OFDM symbol with a signature sequence;
modulating the one or more first signaling OFDM symbols and one or more first signaling OFDM symbols in the time domain cyclically shifted with respect to a preceding symbol;
A cyclic shift of the one or more first signaling OFDM symbols in the time domain represents the first signaling data transmitted in the one or more first signaling OFDM symbols.
Paragraph 11
11. The transmission method according to paragraph 9 or 10, further comprising:
The first signaling data includes an indication of the number of the frequency segments.
Paragraph 12
12. The method of transmission according to any one of paragraphs 9, 10, or 11, further comprising:
The first signaling data includes an indication of an emergency situation.
Paragraph 13
13. A method of transmission according to any one of paragraphs 9, 10, 11 or 12, comprising:
The first signaling data includes an indication of a Fourier transform size and a guard interval to be used for the one or more second signaling OFDM symbols and the one or more payload OFDM symbols.
Paragraph 14
The transmission method according to any one of paragraphs 9 to 13, further comprising:
forming said frame synchronization OFDM symbol according to a first time domain structure comprising a first portion C of a plurality of samples of a useful portion of said frame synchronization OFDM symbol and a portion A comprising said useful portion of said frame synchronization OFDM symbol;
A portion B of said first portion is copied to form a postamble of said frame synchronization OFDM symbol.
Paragraph 15
The transmission method according to any one of paragraphs 9 to 14, further comprising:
forming said one or more first signaling OFDM symbols from a first portion B consisting of a plurality of samples of a useful portion of said first signaling OFDM symbol, a portion A including said useful portion of said first signaling OFDM symbol, and a portion C including the useful portion of said first signaling OFDM symbol;
said portion A being copied to form a second portion of said first signaling OFDM symbol.
Paragraph 16
10. A transmission method according to paragraph 9, comprising:
The signature sequence includes a combination of a Zadoff-chu sequence and a pseudorandom noise sequence.
Paragraph 17
1. A receiving apparatus for detecting and recovering payload data from a received signal, comprising:
1. A radio frequency demodulation circuit configured to detect and recover a received signal formed and transmitted by a transmitting device transmitting the payload as Orthogonal Frequency Division Multiplexing (OFDM) symbols from a plurality of different channels in one or more of a plurality of transmission frames, each of the plurality of transmission frames including a frame synchronization OFDM symbol followed by one or more first signaling OFDM symbols and one or more second OFDM symbols followed by one or more payload OFDM symbols, the one or more payload OFDM symbols carrying payload data for each of the plurality of different channels from one time frame of a plurality of time frames, the frame synchronization OFDM symbol and the one or more first signaling OFDM symbols being transmitted in a bandwidth equal to a radio frequency transmission bandwidth, and the one or more second OFDM symbols being transmitted in a bandwidth equal to a radio frequency transmission bandwidth. a radio frequency demodulation circuit for transmitting a plurality of second signaling OFDM symbols and the one or more payload OFDM symbols in the radio frequency transmission bandwidth, the one or more second signaling OFDM symbols and the one or more payload OFDM symbols being frequency divided to provide a plurality of frequency segments, each of the plurality of frequency segments providing one instance of a plurality of instances of physical layer signaling for channel-by-channel detection and recovery of payload data from different channels and the payload data transmitted by the plurality of frequency segments from a corresponding segment of the one or more payload OFDM symbols, the one or more first signaling OFDM symbols carrying first signaling data for detecting the second signaling OFDM symbols;
a detection circuit configured to detect, from the frequency synchronous OFDM symbol, a synchronization timing for converting a time length of a useful portion of the one or more first signaling OFDM symbols of the payload OFDM symbol into a frequency domain;
a forward Fourier transform circuit configured to transform the time lengths of the one or more first signaling OFDM symbols or the payload OFDM symbols from the time domain to the frequency domain in accordance with the determined synchronization timing;
a demodulation circuit configured to recover the first signaling data from the first signaling OFDM symbol, to detect and recover the physical layer signaling data from one of the frequency segments of the one or more second signaling OFDM symbols using the first signaling data, and to recover the payload data from one of the frequency segments of the one or more payload OFDM symbols for each time frame.
Various further aspects and features of the technology are defined in the appended claims, and the features of the dependent claims can be combined in various ways with the features of the independent claims other than the specific combinations recited for the dependent claims. Changes may be made to the above-described embodiments without departing from the scope of the technology. For example, the processing elements of the embodiments may be implemented in hardware, software, and digital or analog circuitry. Moreover, although certain features are described as being related to a particular embodiment, those skilled in the art will appreciate that various features of the above-described embodiments may be combined in accordance with the technology.
[1] ATSC Standard: A/321, System Discovery and Signaling (Doc. A/321:2016): March 23, 2016 [2] ATSC Candidate Standard: System Discovery and Signaling (Doc. A/321 Part 1), Advanced Television Systems Committee, July 15, 2015

Claims (17)

1. A receiver for detecting and recovering payload data from a received signal of orthogonal frequency division multiplexed OFDM symbols, comprising:
the received signal further comprises one or more first signaling OFDM symbols comprising a symbol that is differentially encoded by cyclically shifting a synchronization OFDM symbol;
the synchronous OFDM symbol having a useful portion and a copy of at least a portion of the useful portion generating at least a guard interval;
The receiving device includes:
Detecting a portion of the synchronous OFDM symbol;
- detecting at least one said first signaling OFDM symbol by using a detected portion of said synchronization OFDM symbol from samples of a differentially encoded portion of said synchronization OFDM symbol and/or from sample copies of said portion, said portion constituting said first signaling OFDM symbol;
a circuit configured to utilize the recovered first signaling data of the first signaling OFDM symbol to obtain second signaling data from at least one second signaling OFDM symbol per time domain structure;
the time domain structure having a plurality of frequency segments, in each of which at least one second signaling OFDM symbol is provided for detecting a payload OFDM symbol ;
the payload OFDM symbols are aligned to a post-preamble waveform in a frequency segment immediately following the at least one second signaling OFDM symbol;
the receiving device recovers payload data for a physical layer pipe from the payload OFDM symbols;
The physical layer pipe is arranged in the time domain structure for frequency division demultiplexing. 2. A receiving device according to claim 1, wherein the frequency segments are provided with at least one second signaling OFDM symbol carrying signaling data for recovering all payload data symbols of all frequency segments of a frame. 3. The receiving device according to claim 1,
A receiving device, wherein at least one physical layer pipe in the frame provides a mobile television service. 4. The receiving device according to claim 3,
A receiving device, wherein one or more physical layer pipes within said frame provide mobile television services, said physical layer pipes being frequency division multiplexed. 3. The receiving device according to claim 1,
The synchronous OFDM symbol is utilized by the receiver by upsampling samples of the detected portion of the synchronous OFDM symbol. 3. The receiving device according to claim 1,
The first signaling data is recovered by upsampling a detected portion of the at least one first signaling OFDM symbol. 7. The receiving device according to claim 6,
The detected portion of the at least one first signaling OFDM symbol is detected when the receiver is operating in a narrowband mode. 3. The receiving device according to claim 1,
The first signaling data is recovered by upsampling samples of a differentially encoded portion of the synchronized OFDM symbol and/or a copy of said portion. 3. The receiving device according to claim 1,
The first signaling data is recovered by upsampling samples of a useful portion of the at least one first signaling OFDM symbol. 3. The receiving device according to claim 1,
The detected synchronous OFDM symbol is
causing said circuitry to determine a start of a time domain frame and a carrier frequency offset;
The circuitry correlates a signature sequence with at least a portion of the synchronised OFDM symbol and derives third signalling data from the correlation, thereby providing the third signalling data to the receiver. 11. The receiving device according to claim 10,
The third signaling data includes an indication of at least one of an emergency alert status, a transmitting device identifier, and a transmitting device location. 3. The receiving device according to claim 1,
The recovered first signaling data provides an indication of a number of frequency segments in a frame. 3. The receiving device according to claim 1,
A fast Fourier transform size of the at least one first signaling OFDM symbol defines a number of bits transmitted by one first signaling OFDM symbol. 1. A method for detecting and recovering payload data from a received signal of orthogonal frequency division multiplexed OFDM symbols, comprising:
the received signal further comprises one or more first signaling OFDM symbols comprising a symbol that is differentially encoded by cyclically shifting a synchronization OFDM symbol;
the synchronous OFDM symbol having a useful portion and a copy of at least a portion of the useful portion generating at least a guard interval;
detecting a portion of the synchronous OFDM symbol;
- using a portion of the detected synchronization OFDM symbol from samples of a differentially encoded portion of the synchronization OFDM symbol constituting the first signaling OFDM symbol and/or from sample copies of said portion to detect at least one of the first signaling OFDM symbols;
utilizing the recovered first signaling data of the first signaling OFDM symbols to obtain second signaling data from at least one second signaling OFDM symbol per time domain structure;
Including,
the time domain structure having a plurality of frequency segments, in each of which at least one second signaling OFDM symbol is provided for detecting a payload OFDM symbol ;
the payload OFDM symbols are aligned to a post-preamble waveform in a frequency segment immediately following the at least one second signaling OFDM symbol;
The method includes recovering payload data for a physical layer pipe from the payload OFDM symbols;
The physical layer pipes are arranged in the time domain structure for frequency division demultiplexing. 1. A transmitter for transmitting payload data as orthogonal frequency division multiplexed OFDM symbols, comprising:
a synchronous OFDM symbol having a useful portion and a copy of at least a portion of said useful portion generating at least a guard interval;
at least one first signaling OFDM symbol having a symbol that is differentially encoded by cyclically shifting the synchronization OFDM symbol;
a circuit configured to adjust a transmission frame including:
the synchronization OFDM symbol is adjusted such that a part or all of the synchronization OFDM symbol is recovered so that a receiving device can detect at least one first OFDM signaling symbol from samples of a guard interval of the at least one first signaling OFDM symbol;
the transmission frame comprises, due to a time domain structure, a number of frequency segments, each of which is provided with at least one second signaling OFDM symbol;
the plurality of frequency segments having second signaling data immediately following the at least one second signaling OFDM symbol for detecting payload OFDM symbols in the frequency segment;
the payload OFDM symbol comprises payload data for a physical layer pipe;
the physical layer pipe is arranged in the time domain structure for frequency division demultiplexing for mobile services ;
The payload OFDM symbols comprise other frequency segments carrying time division multiplexed services.
Transmitting device. 1. A method of transmitting payload data as orthogonal frequency division multiplexed OFDM symbols, comprising:
adjusting a transmission frame including a synchronization OFDM symbol, at least one first signaling OFDM symbol, and a post-preamble waveform;
the synchronous OFDM symbol having a useful portion and a copy of at least a portion of the useful portion generating at least a guard interval;
the at least one first signaling OFDM symbol comprises a symbol that is cyclically shifted and differentially encoded from the synchronization OFDM symbol;
the synchronization OFDM symbol is adjusted such that a part or all of the synchronization OFDM symbol is recovered so that a receiving device can detect at least one first OFDM signaling symbol from samples of a guard interval of the at least one first signaling OFDM symbol;
the post-preamble waveform includes, for a time domain structure, a number of frequency segments each provided with at least one second signaling OFDM symbol;
the plurality of frequency segments having second signaling data immediately following the at least one second signaling OFDM symbol for detecting payload OFDM symbols in the frequency segment;
the payload OFDM symbol comprises payload data for a physical layer pipe;
the physical layer pipe is arranged in the time domain structure for frequency division demultiplexing for mobile services ;
The payload OFDM symbols comprise other frequency segments carrying time division multiplexed services.
Transmission method. 1. A receiver for detecting and recovering payload data from a received signal of orthogonal frequency division multiplexed OFDM symbols, comprising:
a circuit configured to detect a phase-inverted synchronization OFDM symbol following the synchronization OFDM symbol and the at least one first signaling OFDM symbol;
the phase-inverted synchronization OFDM symbol defines an end of the first signaling OFDM symbol;
The OFDM symbol comprises a plurality of frequency segments;
In the payload OFDM symbol, frequency division multiplexed physical layer pipes represent multiple television channels;
at least one television channel in the frequency segment is a channel for mobile reception and the frequency segment is arranged in a frequency-division manner;
the physical layer pipe is recoverable from a received signal by a second signaling OFDM symbol;
the second signaling OFDM symbol carries second signaling data for each frequency segment in the radio frequency band of the frame, providing the same signaling data for all frequency segments of the frame;
The payload OFDM symbol is aligned to a post-preamble waveform in a frequency segment immediately following the second signaling OFDM symbol.
Receiving device.