TRANSMISSION APPARATUS AND METHOD FOR TRANSMISSION OF DATA IN A MULTI-CARRIER BROADCAST SYSTEM
20170244465 · 2017-08-24
Assignee
Inventors
- Lothar Stadelmeier (Stuttgart, DE)
- Nabil LOGHIN (Stuttgart, DE)
- Joerg Robert (Vreden, DE)
- Samuel Asangbeng Atungsiri (Basingstoke, GB)
Cpc classification
H04B7/0689
ELECTRICITY
H04L5/005
ELECTRICITY
H04L1/0048
ELECTRICITY
H04L5/0048
ELECTRICITY
International classification
Abstract
A transmission apparatus and method, respectively, mapping payload data of mapping input data streams onto a mapping output data stream having a channel bandwidth for transmission in a multi-carrier broadcast system. To enable selection of robustness for transmission of data, the apparatus includes a frame forming mechanism mapping data blocks of at least two mapping input data streams onto frames of the mapping output data stream covering the channel bandwidth, each frame including a payload portion, the payload portion including plural data symbols and being segmented into data segments each covering a bandwidth portion of the channel bandwidth. The frame forming mechanism is configured to map the data blocks of the at least two mapping input data streams onto data symbols of the payload portion and includes a MIMO mode selector selecting a MIMO mode of the data blocks per data segment and/or per mapping input data stream.
Claims
1. (canceled)
2. A transmission apparatus comprising: circuitry configured to map multiple input data streams representing physical data pipes (PLPs) onto a transmission frame, the transmission frame having a channel bandwidth and including OFDM symbols following each other in a time direction and being arranged into groups of OFDM symbols, each group of OFDM symbols being assigned a MIMO mode, the MIMO modes being selected from a SISO scheme, a MISO scheme and a MIMO scheme, wherein a first group of OFDM symbols in the frame is assigned a different MIMO mode from a second group of OFDM symbols in the frame; and output circuitry configured to convey output data streams including one or more frames including the transmission frame to transmission circuitry.
3. The transmission apparatus according to claim 2, wherein a group of OFDM symbols is segmented into slices, and the circuitry is configured to map a single PLP to a slice.
4. The transmission apparatus according to claim 2, wherein the circuitry is configured to assign a different MIMO mode from one group of OFDM symbols to a next group of OFDM symbols in the time direction.
5. The transmission apparatus according to claim 4, wherein one group of OFDM symbols of the groups of OFDM symbols is segmented into slices.
6. The transmission apparatus according to claim 2, wherein each of the groups of OFDM symbols is a payload data portion.
7. The transmission apparatus according to claim 6, wherein a payload data portion includes a payload portion signaling block including detailed signaling information.
8. The transmission apparatus according to claim 7, wherein the detailed signaling information includes the MIMO mode.
9. The transmission apparatus according to claim 6, wherein the circuitry is configured to map a preamble to the frame, the preamble including high level signaling.
10. The transmission apparatus according to claim 2, further comprising pilot insertion circuitry configured to insert pilots according to different pilot patterns for the MIMO mode assigned to a group of OFDM symbols.
11. A method of transmitting data comprising: mapping, by circuitry, multiple input data streams representing physical data pipes (PLPs) onto a transmission frame, the transmission frame having a channel bandwidth and including OFDM symbols following each other in a time direction and being arranged into groups of OFDM symbols, each group of OFDM symbols being assigned a MIMO mode, the MIMO modes being selected from a SISO scheme, a MISO scheme and a MIMO scheme, wherein a first group of OFDM symbols in the frame is assigned a different MIMO mode from a second group of OFDM symbols in the frame; and conveying an output data stream comprising one or more frames including the transmission frame to transmission circuitry.
12. A receiver apparatus comprising: receiver circuitry configured to receive input data streams having a transmission frame structure and representing physical data pipes (PLPs); demapping circuitry configured to demap the input data streams from a transmission frame, the transmission frame having a channel bandwidth and including OFDM symbols following each other in a time direction and being arranged into groups of OFDM symbols, each group of OFDM symbols having associated thereto an indication of a MIMO mode, the MIMO modes being selected from a SISO scheme, a MISO scheme and a MIMO scheme, wherein a first group of OFDM symbols in the frame has associated thereto a different MIMO mode from a second group of OFDM symbols in the frame; and output circuitry configured to convey output data streams demapped from one or more frames including the transmission frame to post processing circuitry.
13. The receiver apparatus according to claim 12, wherein a group of OFDM symbols is segmented into slices, and the circuitry is configured to demap a single PLP from a slice.
14. The receiver apparatus according to claim 12, wherein the circuitry is configured to derive a different MIMO mode from one group of OFDM symbols to a next group of OFDM symbols in the time direction.
15. The receiver apparatus according to claim 14, wherein one group of OFDM symbols of the groups of OFDM symbols is segmented into slices.
16. The receiver apparatus according to claim 12, wherein each of the groups of OFDM symbols is a payload data portion.
17. The receiver apparatus according to claim 16, wherein a payload data portion includes a payload portion signaling block including detailed signaling information.
18. The receiver apparatus according to claim 17, wherein the detailed signaling information includes the MIMO mode.
19. The receiver apparatus according to claim 16, wherein the demapping circuitry is configured to demap a preamble to the frame,the preamble including high level signaling.
20. The receiver apparatus according to claim 12, further comprising pilot detection circuitry configured to detect pilots, the pilots having different pilot patterns for the MIMO mode associated with a group of OFDM symbols.
21. A method of receiving data comprising: receiving, by circuitry, input data streams having a transmission frame structure and representing physical data pipes (PLPs); demapping the input data streams from the transmission frame, the transmission frame having a channel bandwidth and including OFDM symbols following each other in a time direction and being arranged into groups of OFDM symbols, each group of OFDM symbols having associated thereto an indication of a MIMO mode, the MIMO modes being selected from a SISO scheme, a MISO scheme and a MIMO scheme, wherein a first group of OFDM symbols in the frame has associated thereto a different MIMO mode from a second group of OFDM symbols in the frame; and conveying output data streams demapped from one or more frames including the transmission frame to post processing circuitry.
Description
BRIEF DESCRIPTION OF DRAWINGS
[0068] These and other aspects of the present invention will be apparent from and explained in more detail below with reference to the embodiments described hereinafter. In the following drawings
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DESCRIPTION OF PREFERRED EMBODIMENTS
[0107]
[0108] For frame forming and mapping the data blocks of received mapping input data streams onto frames two different frame forming units 14 and 16 are provided. A first frame forming unit 14 maps the data blocks of a first group of mapping input data streams, e.g. of mapping input data streams S1, S2 and S3, onto first frames F1 having a first frame structure also covering the total channel bandwidth. In addition, the signalling data Si are incorporated into said first frames F1 for signalling the required data to receivers of a first type that are adapted for receiving and processing said first frames F1.
[0109] A second group of mapping input data streams, e.g. the mapping input data streams S1, S4 and S5, are provided to the second frame forming unit 16 which maps them onto second frames F2 having a second frame structure covering the total channel bandwidth. The second frame structure is generally different from the first frame structure, and the second frames F2 are generally provided for reception and processing by different types of receivers. Also the second frame forming unit 16 uses signalling data Si for incorporation into the second frames F2 for use by the receivers, wherein the signalling data incorporated into the first frames F1 are generally different from the signalling data incorporated into the second frames F2, which shall, however, not exclude that the same structure of the signalling data and the signalling concept is used in both types of frames. Those frames F1, F2, in particular both sequences of first frames F1 and second frames F2 generated by the first frame forming unit 14 and the second frame forming unit 16, are then further processed by a stream forming unit 18 which alternately arranges one or more first frames F 1 and one or more second frames F2, thus forming the mapping output data stream Q. Said mapping output data stream is then outputted by a data output 20 for further processing and/or transmission.
[0110]
[0111] The transmitter 30 comprises a first pre-processing unit 32 and a second pre-processing unit 34. The first pre-processing unit 32 receives transmitter input data streams I1, I2, . . . , Im and pre-processes them to obtain the mapping input data streams S1, S2, . . . , Sm. The transmitter input data streams I1, I2, . . . , Im may, for instance, be one or more (e.g. MPEG-2) transport stream(s) and/or one or more generic stream(s), and the data may be carried therein in individual Physical Layer Pipes PLPs.
[0112] The first pre-processing unit 32 is, in this exemplary embodiment, adapted in accordance with the DVB-T2 standard and comprises elements for input processing and Bit Interleaved Coding & Modulation (BICM). Such means may include means for CRC encoding, header insertion, padding insertion, scrambling, FEC encoding (LDPC/BCH) bit interleaving, bit to cell demultiplexing, cell to constellation mapping, constellation rotation and cyclic Q-delaying, cell interleaving and time interleaving, just to name a few elements that are generally provided as explained in detail in the DVB-T2 standard. Those elements are commonly known and described in detail in the DVB-T2 standard so that no further explanations are provided here.
[0113] The second pre-processing unit 34 is, in this exemplary embodiment, adapted for pre-processing the received transmitter input data streams I1, I2, . . . , Ip, which may be different from, partly equal or completely equal to the transmitter input data streams I1, I2, . . . , Im (which depends mainly on the kinds of services provided to the different types of receivers). In an embodiment, said pre-processing may be performed in the same or in a similar way as described in the DVB-T2 standard (or, alternatively, in the DVB-C2 standard), possibly with additional adaptions according to the needs of the desired application. Hence, said pre-processing unit 34 comprises, in this exemplary embodiment, means for input processing and Bit Interleaved Coding & Modulation (BICM). Said means may particularly comprise means for input stream synchronization, null packet detection, CRC-encoding, header insertion, scrambling, FEC (BCH/LDPC) encoding, bit interleaving, bit to cell demultiplexing, cell to constellation mapping and frame header insertion. Again, these means are generally known and described in detail in the DVB-T2 standard and the DVB-C2 standard so that no further explanations are provided here.
[0114] It shall be noted that any time reference is made to any standard herein, the various explanations provided in the cited standard, particularly in the DVB-T2 standard and the DVB-C2 standard, to which reference has been made above and will be made below, are herein incorporated by reference herewith.
[0115] The output of the first and second pre-processing units 32, 34 are then provided as mapping input data streams S1, S2, . . . , Sm and S1, S2, . . . , Sp to the mapping apparatus 10, which is generally adapted as explained above with respect to
[0116] Next, frame forming in the first frame forming unit 14 shall be explained. If applied in transmitter 30 as depicted in
[0117] Block diagrams of various embodiments of the second frame forming unit 16 are schematically depicted in
[0118] The data slices, more precisely the bursts of the data slices, are then subjected to data slice processing including frequency interleaving and a pilot insertion, so that the complete OFDM symbol for the corresponding data slice is generated. Preferably, a pairwise frequency interleaving is performed and all pilots are added, i.e. the scattered and continual pilots for channel estimation and synchronization. Preferably, the bandwidth of the data slices is a multiple of 24, which ensures a constant number of payload OFDM subcarriers (generally per four (temporally) consecutive segments). Generally, only after some (e.g. four) data symbols the pilot pattern is repeated, but not after each data symbol. This allows channel estimation in frequency and time direction with reduced overhead.
[0119] The output from the data slice processing, the preamble, edge pilots and scrambling sequences, are then further processed. In particular, the different data slices and the preamble are assembled to the complete framing structure to be used for the second frames F2. Furthermore, the edge pilot next to the highest OFDM subcarrier is added. Additionally, scrambling of the data is preferably performed. Finally, one or more OFDM modulators 164a, 164b may be provided for OFDM modulation in each processing path.
[0120] The MIMO mode selection unit 1614 provides the ability to select for each mapping input data stream S1, S2, . . . , Sp individually the MIMO mode to be used for the data blocks of the respective mapping input data stream S1, S2, . . . , Sp. Hence, it can be determined for each mapping input data stream S1, S2, . . . , Sp by which antenna configuration the data blocks of the mapping input data stream S1, S2, . . . , Sp shall be transmitted. For instance, it may be determined that for the data blocks of the first mapping input data stream S1 the SISO scheme is selected, that for the data blocks of the second mapping input data stream S2 the MISO scheme is selected, and that for the data blocks of the third mapping input data stream S3 a MIMO scheme with spatial multiplexing is selected. For this purpose, more than one mapping unit 163a, 163b is provided, which allows splitting the signal outputted from a PLP processing unit 161 onto various paths for individual processing, which various paths are then provided to different transmission antennas. For instance, two transmission antennas (and, hence, two mapping units 163a, 163b and two OFDM modulators 164a, 164b) may be provided, e.g. to allow the data to be split between the two transmission antennas on the same frequency in such a way that the two transmission antennas will not much interfere with each other. In particular, e.g. in MISO scheme the preprocessing of the signals is such that the receiver can separate the signals, and in MIMO scheme both the receiver and the transmitter may have multiple antennas for reception and transmission, respectively, which numbers can be equal or different. This enables that even interfering signals can be reconstructed. More details as well as further examples will be explained below.
[0121] In another embodiment of the second frame forming unit 16b illustrated in
[0122] Further, according to this embodiment, a time and frequency intcrleaver 1615 (e.g. implemented as separate units for time interleaving and frequency interleaving) is provided in each PLP processing unit 161, and the MIMO selection unit 1614 is further adapted for selecting the pilot pattern individually for each mapping input data stream S1, S2, ..., Sp. In this way, preferably the pilot density in time and/or frequency direction can be selected, in particular depending on the number of transmission antennas, to select the robustness of the data transmission with respect to reliable channel estimation at the receiver.
[0123] In still another embodiment of the second frame forming unit 16c illustrated in
[0124] Further, in this embodiment, for each mapping input data stream S1, S2, . . . , Sp a separate pilot pattern selection unit 1616 is provided for selecting the pilot pattern individually for each mapping input data stream S1, S2, . . . , Sp.
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[0126] The output from the data slice processing units 168, the preamble, edge pilots and scrambling sequences, are then provided to one or more framing units 169, which assembles the different data slices and the preamble to the complete framing structure to be used for the second frames F2. Furthermore, it adds the edge pilot next to the highest OFDM subcarrier. Additionally, it performs the scrambling of the data. Finally, one or more OFDM modulators 164a, 164b are provided for OFDM modulation.
[0127] The embodiments illustrated in
[0128] According to embodiments of the present invention the selection of the MIMO mode and/or the pilot pattern and the mapping of the data blocks onto data symbols of the frame is performed such that the MIMO mode and/or the pilot pattern changes from data symbol to data symbol, from a group of data symbols to a next group of data symbols (in time direction), from frame to frame, from a group of frames to a next group of frames, from data segment to data segment and/or from a group of data segments to a next group of data segments.
[0129] The frame structure of the second frames F2 as generated by such embodiments of the second frame forming unit 16 is schematically depicted in
[0130] These figures show the frame structure of the second frame F2 as defined in the DVB-C2 standard. This frame structure uses the concept of absolute OFDM, according to which all frequencies are aligned to the absolute frequency 0 MHz, which is identical to the OFDM subcarrier index k=0. The OFDM subcarrier frequencies of the following OFDM subcarriers are given by f =(1/T.sub.u). k, where T.sub.u is the duration of the useful OFDM symbol part. Hence, the start and stop frequencies of the signal can also be given in OFDM subcarrier indices instead of a middle frequency of the signal. The start and the stop frequency are given by K.sub.min and K.sub.max, respectively. It shall be noted, however, that the used of absolute OFDM is not essential for the present invention.
[0131] It is important to note that the concept of absolute OFDM can be used, but must not necessarily be used. For instance, in an embodiment, both the first and second frames F1, F2 are aligned to a frequency raster and use the concept of absolute OFDM, whereas in another embodiment both the first and second frames F1, F2 are not aligned to a frequency raster and do not use the concept of absolute OFDM. The second frames F2, however, make use of the concept of segmented OFDM as illustrated in
[0132] The frame F2 has a preamble portion 40 and a payload portion 50. The signalling data are mapped on the preamble portion 40, which comprises (in time direction) one or more preamble symbols 41 (e.g. L.sub.p preamble symbols 41 as shown in
[0133] The payload portion 50 is segmented into data segments 51 (also called data slices, e.g. 5 data slices as shown in
[0134] As can also be seen from
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[0136] Adopting the superframe structure as defined in the DVB-T2 standard the first frames F1 represent the T2-frames, and the second frames F2 are placed into the parts reserved for the FEF frames. For instance, in a practical embodiment the F1 frames (formed in accordance with the DVB-T2 standard) are provided for reception by stationary receivers (e.g. in accordance with the DVB-T2 standard), and the second frames F2 (e.g. formed in accordance with a DVB-C2 standard or according to any new rules) are provided for reception by mobile receivers (e.g. according to the upcoming DVB-NGH standard).
[0137] Next, embodiments for mapping the data blocks of a mapping input data stream onto the second frame F2 shall be explained. In a first embodiment, which is generally in consistence with the frame structure defined in the DVB-C2 standard, the data blocks of a particular mapping input data stream are mapped onto a single data segment or two or more (neighbouring or not neighbouring) data segments. For instance, referring to
[0138] According to another embodiment as schematically depicted in
[0139] In a single data segment data blocks belonging to various mapping input data streams can thus be transmitted according to this embodiment of the present invention. These data blocks may be pre-processed in the same manner, but also in different manner (e.g. with different MODCODs) to provide different levels of robustness to the different mapping input data streams. For instance, as proposed according to an embodiment of the present invention, different MIMO modes and/or different pilot patterns may be applied to the data blocks of the individual mapping input data streams. Further, in an alternative or in addition, different MIMO modes and/or different pilot patterns may be applied to the data blocks mapped onto the individual data segments.
[0140] While it is generally possible, that at a particular time also more than one data symbol (i.e. from different data segments) carry a data block of the same mapping input data stream, the embodiment shown in
[0141] The mapping structure of the data blocks of a particular mapping input data stream can be kept regular, as shown in
[0142] Further, time gaps are preferably introduced between data blocks of a mapping input data stream, during which no data symbol of any data segment carries a data block of said particular mapping input data stream. For instance, as shown in
[0143] The bandwidth of the data segments 51 may be kept equal and predetermined, as shown in
[0144] According to still another embodiment of the mapping, the mapping of data blocks of a particular mapping input data stream may be kept constant within a particular frame F2, but may be changed from frame F2 to the next frame F2, i.e. a frequency hopping may be provided from frame to frame (or from a first group of frames to the next group of frames), but not within frames.
[0145] According to still another embodiment a data block can be split up in frequency direction for use by data symbols from different mapping input data streams. This is illustrated in
[0146] Next, various embodiments for signalling the required signalling information about the mapping of the data blocks onto the data segments and the data symbols of the second frames shall be explained. In a first embodiment only the preamble signalling blocks comprise all the signalling information required for a transmitter to receive and demap all the intended data blocks. This embodiment would, however, require that the preamble signalling blocks are quite large (in frequency and/or time), since the preamble has typically a high pilot density for robust channel estimation and synchronization leading to the result that less signalling capacity is available in the preamble. Hence, putting a lot of signalling information into the preamble signalling blocks would further increase their size, which is generally not preferred.
[0147] In another embodiment, illustrated in
[0148] As shown in
[0149] According to another embodiment multiple pointers are included in the pointer block 44, which point to several payload portion signalling blocks, e.g. to the payload portion signalling blocks 53a-53c. After deinterleaving and decoding said payload portion signalling blocks 53a-53c sufficient low level signalling information and location information (e.g. pointers) for finding the next set of payload portion signalling blocks 53d-53f as well as the next group of data blocks. Thus, according to such an embodiment, a set of pointers is transmitted during several bursts (i.e. payload portion signalling blocks) and provides information on the next bursts (i.e. payload portion signalling blocks) of the following set as well as the next data blocks.
[0150] Another embodiment for signalling shall be explained with reference to
[0151] Still further, according to this embodiment, at least one of said payload portion signalling blocks 53a-53c (or the whole set together, in particular after deinterleaving and decoding) provides information, in particular a pointer, by which the receiver finds at least the first data block 52a (or the group of next data blocks) of the desired data stream. Said data block 52a does not only contain the actual payload data, but also contains in-band signalling information comprising low level, more detail signalling information about the mapping of the data blocks of said particular mapping input data stream onto the data segments of the frames. This in-band signalling information thus enables the receiver to find the next data block 52b of the same data stream. Hence, from this moment on the receiver is no longer obliged to receive and decode the signalling information comprised in the preamble and/or in the payload portion signalling blocks, but the in-band signalling information contained in the data blocks 52a, 52b, . . . is sufficient for finding all data blocks of the desired data stream and maybe also of other “related” data streams (for enabling faster zapping to related services).
[0152] According to a modification of said embodiment, not each single data block contains sufficient information for finding the next data block, but several data blocks 52a, 52b are treated as a unit. Only after deinterleaving and decoding all of them, the in-band signalling information is available including information about the next “unit” (i.e. group of data blocks).
[0153] Hence, generally the receiver is not obligated to receive the preamble or the payload portion signalling blocks, which may again be considered as a separate signalling data stream mapped onto the payload portion of the frame. However, if the position of the data blocks is not known at the time the current mapping input data stream was encoded, it can also point to the position of the next payload portion signalling block. It shall be noted that the payload portion signalling blocks do generally not only comprise signalling information for a single mapping input data stream, but for all mapping input data streams.
[0154] Hence, according to this embodiment the signalling information specific to a particular mapping input data stream is provided in-band in the data blocks of said mapping input data streams, e.g. attached at the beginning or at the end of the data blocks. It is also possible to interleave said signalling information together with the FEC-encoded data blocks by a common interleaver, or the signalling information may be combined with the uncoded payload data (either completely at the beginning or end or sub-divided into several portions), and then a common FEC-encoding followed by interleaving is performed, preferably by use of a common interleaver, i.e. over multiple FEC-coded blocks. This provides the advantage of longer time diversity and, after the separation into various data segments, also more frequency diversity.
[0155] According to the present invention, further information is preferably included in the signalling information, in particular in the payload portion signalling blocks, which informs the receiver about the selected MIMO mode per mapping input data stream and/or per data segment and, if required, about the selected pilot pattern per mapping input data stream and/or per data segment.
[0156] A simple block diagram illustrating the steps for retrieving of the signalling information in the receiver, if the signalling information is mapped onto the frame F2 as illustrated in
[0157] It shall be noted that the same principles and the same embodiments for signalling information can be used if the pointer unit 44 is included in the other preamble 45 (i.e. the postamble) of a frame.
[0158] The preferred embodiment of a receiver only needs to obtain the signalling information stored in a preamble portion, then accesses a payload portion signalling block a single time, and from then on uses only the in-band signalling information. The in-band signalling information preferably includes a pointer to the next data block of the data stream and to the next payload portion signalling block (which is useful if a payload portion signalling block is provided in every frame of the same type, but is otherwise not needed since then enough preamble symbols are in between from which the signalling information can also be provided in some embodiments). Only, if the receiver wants to switch to another service, a payload portion signalling block has to be accessed again a single time to obtain the required signalling information related to the new service.
[0159] An example of the signalling information that can be included in the payload portion signalling blocks is illustrated in the following table, where the entries are either self-explaining, or as defined in the T2 standard, or as described below: [0160] FRAME_NUMBER: This 8-bit field indicates the frame number of the last burst of the time interleaving frame. [0161] NUM_PLP: This 8-bit field signals the number of PLPs present in the current DVB-NGH signal. [0162] The following fields appear for every signalled PLP: [0163] PLP_ID: 8-bit identifier of the PLP. [0164] PLP_IDENTIFICATION: This 16-bit field uniquely identifies a PLP within a network. [0165] PLP_QAM_MODE: This 4-bit field signals the QAM mode of the PLP (including rotated constellations). [0166] PLP_FEC_MODE: This 4-bit field signals the FEC mode of the PLP (including FEC code length). [0167] PLP_MIMO_MODE: This 2-bit field signals the MIMO mode of the PLP according to the following table:
TABLE-US-00001 TABLE 1 PLP_MIMO_MODE field PLP_MIMO_MODE 00 01 10 11 mode SISO MISO MIMO reserved [0168] PLP_PILOT_PATTERN: This 3-bit field identifies the pilot pattern in which the PLP is transmitted. [0169] PLP_TYPE: This 8-bit field indicates the PLP type. [0170] PLP_PAYLOAD_TYPE: This 8-bit field signals the payload type, e.g. TS, GSE. [0171] NUM_ASSOCIATED_PLP: This 3-bit field indicates the number of PLPs that are associated with this PLP. [0172] The following two fields appear for each associated PLP: [0173] ASSOICATED_PLP_ID: This 8-bit field indicated the PLP ID of the associated PLP. [0174] ASSOCIATION_TYPE: This 2-bit field signals the association type, e.g. local service or incremental redundancy. [0175] INTERLEAVING_TYPE: This 2-bit field indicates the time interleaver type. [0176] NUM_SIGNALLED_TI_FRAMES: This 2-bit field indicates the number of signalled time interleaving frames for the given PLP minus 1, so NUM_SIGNALLED_TI_FRAMES=0 corresponds to one TI frame. [0177] The following fields appear for each signalled time interleaving frame: [0178] TI_NUM_BURSTS: This 3-bit field signals the number of bursts for the given time interleaving frame. [0179] TI_FRAME_NUMBER: This 8-bit field indicates the frame number in which the time interleaving frame starts. If the number is smaller than the frame number of the current frame, the TI_FRAME_NUMBER refers to the following super frame. [0180] INTRASYMBOL_POINTER: This 11-bit field points to the start of the time interleaving frame within an OFDM symbol. [0181] The following fields appear for each time interleaving burst: [0182] DATA_SLICE_ID: This 4-bit field indicates the Data Slice number containing the burst. [0183] PILOT_PATTERN: This 3-bit field indicates the pilot pattern used in the given data slice. In case of a postamble, this signalling gets valid for the next frame. [0184] OFDM_SYMBOL_NUMBER: This 8-bit field indicates the OFDM symbol number of the next given burst. If the number is lower than the number of the previous burst, this burst is transmitted within the next frame. [0185] The following field only appears if there are associated PLPs: [0186] ASSOCIATED_PLP_IDX: This 3-bit field indicates the index of the associated PLP in the NUM_ASSOICATED_PLP loop. A value of 0 means that no PLP is currently associated. [0187] TIME_INTERLEAVER_SIZE: This 8-bit field indicates the length of the time interleaving frame in multiples of LDPC codewords. [0188] NUM_HANDOVER_PLP: This 8-bit field indicates the number of PLPs that will be signalled in the handover signalling [0189] The following fields appear for every signalled handover PLP. [0190] PLP_IDENTIFICATION: This 16-bit field uniquely identifies the PLP within a network. [0191] NUM_ALTERNATIVE_CELLS: This 8-bit field indicates the number of alternative cells within the given network that also carry the PLP. [0192] The following fields appear for every alternative cell: [0193] START_FREQUENCY: This 24-bit field indicates the start frequency of the alternative cell. [0194] CELL_ID: This 16-bit field indicates the cell ID of the alternative cell. [0195] CRC32: This 32-bit cyclic redundancy check ensured correctness of the data.
TABLE-US-00002 FIELD SIZE FRAME_NUMBER 8 bit NUM_PLP 8 bit for i = 1 ... NUM_PLP { PLP_ID 8 bit PLP_IDENTIFICATION 16 bit PLP_QAM_MODE 3 bit PLP_FEC_MODE 4 bit PLP_MIMO_MODE 2 bit PLP_PILOT_PATTERN 3 bit PLP_TYPE 8 bit PLP_PAYLOAD_TYPE 8 bit NUM_ASSOCIATED_PLPs 3 bit For NUM_ASSOCIATED_PLPs { ASSOCIATED_PLP_ID 8 bit ASSOCIATION_TYPE 2 bit } INTERLEAVING_TYPE 2 bit NUM_SIGNALLED_TI_FRAMES 2 bit for i = 1 ... TI_NUM_BURSTS 3 bit TI_FRAME_NUMBER 8 bit INTRASYMBOL_POINTER 11 bit for i = 1 ... NUM_BURSTS { DATA_SLICE_ID 4 bit OFDM_SYMBOL_NUMBER 8 bit PILOT_PATTERN 3 bit if (NUM_ASSOCIATED_PLP > 0) { ASSOCIATED_PLP_IDX 3 bit } } TIME_INTERLEAVER_SIZE 8 bit } } NUM_HANDOVER_PLPs 8 bit for i = 1 ... NUM_HANDOVER_PLPs { PLP_IDENTIFICATION 16 bit NUM_ALTERNATIVE_CELLS 8 bit for j = 1 ... NUM_ALTERNATIVE_CELLS { START_FREQUENCY 24 bit CELL_ID 16 bit } } CRC32 32 bit
[0196] A further embodiment for signalling information is illustrated with reference to
[0197] Additionally, some offset signalling information 57a, 57b indicating changes of the mapping of the data blocks 55a-55f, 56a-56f between said particular group of second frames 50a and said subsequent group of second frames 50b can be included into in-band signalling information or into one or more payload portion signalling blocks mapped onto data symbols of said particular second frame. Hence, at the end of a group of (one or more) second frames said offset signalling information 57a can be mapped as in-band signalling information into one or more data blocks 55c, 56c. Alternatively, said offset signalling information 57b can be mapped into one or more payload portion signalling blocks 53c. Said offset signalling information 57a, 57b indicates how the signalling information changes from this group of second frames 50a to the next group of second frames 50b (or any other subsequent frame) so that in the next (or subsequent) group(s) of second frames 50b all the signalling information must not necessarily be mapped into payload portion signalling blocks or must at least not be obtained by the receiver. In other words, mainly some offset information is mapped into the frames, particularly to save time (in the receiver).
[0198] Another embodiment of a mapping apparatus 60 according to the present invention is schematically depicted in
[0199] In other words, the data blocks are mapped onto said frame F such that they are spread in time and frequency over various data symbols and various data segments of the frame F2 as shown in
[0200] The transmitter 70 shown in
[0201] It shall be noted that the frame forming unit 64 shown in
[0202]
[0203] In the first embodiment of the transmitter 70a shown in
[0204] The second mapping input data stream S2, e.g. a news service, is provided to a second MIMO mode selection unit 1614b, which selects that MISO processing shall be applied to the data blocks of this second mapping input data stream S2. Accordingly, the data stream S2 is split off into (at least) two output streams S21, S22, which may be coded differently (e.g. by an Alamouti encoder; not shown) and which are provided to different mapping units 163a, 163b. Therein, the data blocks of said output streams S21, S22 are mapped onto the different mapping output data streams Qa, Qb, which are provided to the different transmission antennas 76a, 76b for broadcasting. For receiving these data blocks the receiver generally only requires a single reception antenna and a single reception path to process the received mapping output data streams Qa, Qb until they are combined to obtain the information contained in the received service (i.e. in the data stream S2). Thus, this news service can be detected by any receiver (independent of the number of deployed receive antennas) and the transmission is reliable, because of the MISO scheme.
[0205] The advantages of MISO vs. MIMO are the high robustness and simple detection (1 reception antenna is sufficient).. The robustness of MISO can be further increased if MIMO is used with the same data rate as with a single transmission antenna. On the other hand, the performance of spatial multiplexing MIMO drops rapidly if the spatial distribution coefficients (channel coefficients) are correlated. This is, for instance, the case if the antennas are located close to each other, as is e.g. the case in a small handheld device having two antennas. In contrast, a MISO method has in worst case (completely correlated channel coefficients) the same performance as a SISO method.
[0206] The third mapping input data stream S3, e.g. a music service, is provided to a third MIMO mode selection unit 1614c, which selects that SISO processing shall be applied to the data blocks of this second mapping input data stream S3. Accordingly, the data stream S3 is processed into a single output stream S31, which is provided to at least one of said mapping units 163a, 163b. Generally, mapping of the data blocks of said output stream S31 onto one mapping output data stream Qa or Qb and transmission over one transmission channel is sufficient. Preferably, however, the identical data blocks are mapped onto both mapping output data streams Qa, Qb and are thus also broadcast by all different transmission antennas 76a, 76b as is typically done in single frequency networks. Again, for receiving these data blocks the receiver generally only requires a single reception antenna and a single reception path to process the received mapping output data streams Qa, Qb until they are combined to obtain the information contained in the received service (i.e. in the data stream S3). Compared to MIMO and MISO the described SISO method has the advantages of simple detection, in particular with respect to channel estimation, and less energy consumption.
[0207] While in the embodiment of the transmitter 70a the selection of the MIMO mode is available per mapping input data stream, in the embodiment of the transmitter 70b shown in
[0208] Further embodiments of the transmitter include pilot pattern selection means in addition or instead of MIMO mode selection means. For instance, the MIMO mode selection means shown in
[0209] For allowing channel estimation scattered pilots are added to the data slices. The addition of these scattered pilots is already done within individual data slices, as it is possible to have different pilot densities within different data slices of the same signal.
[0210] The equalisation of SISO signals requires the estimation of a single channel transfer function, only. However, as the neighbouring data slices may use MIMO or MISO signals, the edge pilots and the preamble pilots carry MIMO or MISO pilots. Though, edge pilots and preamble pilots are not part of the data slice pilots. Different pilot densities can be supported. The pilot patterns PP0 and PP1 are intended for large Single Frequency Networks, while the pilot schemes PP2 and PP3 have reduced overhead. Furthermore, PP0 and PP2 are optimized for high speed reception, as they have an increased pilot density in the time direction. In another embodiment the edge pilot density is selected with the highest possible density of a complete data segment, a complete frame or the complete data transmission.
[0211] Within a data slice a given cell is a scattered pilot if
k.sub.DSmod(D.sub.x.Math.D.sub.y)=D.sub.x(l mod D.sub.y) k=1, . . . , N.sub.DS−1,
where k.sub.DS is the subcarrier number within the data slice, and I is the symbol number within the frame, respectively. Further, Dx indicates the difference in carrier index between adjacent scattered-pilot-bearing carriers and Dy indicates the difference in symbol number between successive scattered pilots on a given carrier. The values for D.sub.x and D.sub.y are given in the following table:
TABLE-US-00003 Pilot Pattern D.sub.X D.sub.Y PP0 4 2 PP1 4 4 PP2 8 2 PP3 8 4
[0212]
[0213] The modulation sequence of the pilots is
Re{c′.sub.m,l,k.sub.
where A.sub.SP is the boosting level of the scattered pilots as defined in the following table.
TABLE-US-00004 Pilot Pattern A.sub.SP PP0 4/3 PP1 4/3 PP2 4/3 PP3 7/4
Furthermore, no scrambling is applied at this point as the complete scrambling is performed in the framing section.
[0214] The transmission of MIMO or MISO services requires additional pilots, as two different channel transfer functions have to be estimated by the receiver. However, in contrast to DVB-T2, the possibility to support also large Single Frequency Networks shall be provided. Hence, an additional pilot pattern is overlaid to the SISO pilots, i.e. the inverted pilots. Hence, a cell is a non-inverted pilot if
k.sub.DS mod(D.sub.x.Math.Dhd y)=D.sub.x(l mod D.sub.y) k=1, . . . , N.sub.DS−1,
and an inverted pilot if
k.sub.DS mod(D.sub.x.Math.D.sub.y)=D.sub.x[(l+D.sub.y/2)modD.sub.y] k=1, . . . , N.sub.DS−1,
where the values D.sub.x and D.sub.y are again defined in the above table. The modulation sequence for the transmitters of MIMO OR MISO group 0 is:
Re{c.sup.0′.sub.m,l,k.sub.
[0215] The modulation sequence for the non-inverted pilots of MIMO or MISO group 1 is:
Re{c.sup.1′.sub.m,l,k.sub.
while the modulation sequence for the inverted pilots of MIMO or MISO group 1 is:
Re{c.sup.1′.sub.m,l,k.sub.
[0216] The values for A.sub.SP are again given in the above table. Furthermore,
[0217] The edge pilots are generally selected such that they are fitting with the pilot patterns of one or more neighbouring data segments. For instance, a multiple of the pilot patterns of the two neighbouring data segments, between which the (common) edge pilots are provided, can be selected. If there is only a single neighbouring data segment (if the edge pilots are provided at the beginning or end (in frequency direction) of a frame), the pilot pattern is fitted to the pilot pattern of the single neighbouring data segment. In other words, the single edge pilots, that are common to the one or more neighbouring data segments, must be compatible and fit with the pilot patterns of these one or more neighbouring data segments.
[0218]
[0219] An embodiment of a (stationary) receiver 100 is schematically depicted in
[0220] An embodiment of the demapping apparatus 104 is schematically depicted in
[0221] The received demapping input data stream Q′ is then provided to a stream demapping unit 112, in which the first frames F1 are demapped from the demapping input data stream Q′. These first frames F1 are then provided to a frame demapping unit 114, in which they are further demapped for obtaining a desired mapping output data stream Sx′, which is then outputted by the data output 116 for post-processing by the post-processing unit 106.
[0222] The stream demapping and frame demapping performed in this embodiment of the demapping apparatus 104 is commonly known and, for instance, be performed in accordance with the DVB-T2 standard, if the demappping apparatus 104 is part of a stationary receiver 100 in accordance with the DVB-T2 standard, as is the case in this embodiment. Hence, no further details need to be explained here, as all these details are generally known in the art. The F1 frames may, for instance, be the T2 frames of a superframe structure shown in
[0223] An embodiment of a receiver 120 in accordance with the present invention is schematically depicted in
[0224] In an example at two reception antennas 121a, 121b and two receiving units 122a, 122b (the reception antennas may also be part of the receiving units 122) the receiver input data stream Qa′, Qb′ are received. These are provided to a demapping apparatus 124, which includes MIMO mode detection units 123a, 123b, which detect the MIMO mode applied to the data blocks of the mapping input data streams and/or the data segments in the transmitter, e.g. by evaluating the respective signalling information indicating said MIMO mode and/or by evaluating the received signals (e.g. by detection of the respective pilot pattern). Depending thereon, a corresponding processing is performed. For instance, if to the service that shall be received by the receiver, a MIMO mode is applied, the corresponding MIMO decoding (e.g. an Alamouti decoding) is applied that corresponds to the encoding performed in the encoder.
[0225] Further, in an embodiment it is possible, in particular for a MIMO receiver, to switch off one or more reception paths (e.g. by a control unit 125 via a feedback from the MIMO mode detection units 123a, 123b to the respective reception antenna 121a, 121b and/or the respective receiving unit 122a, 122b), e.g. if SISO or MISO scheme is applied to the desired service, since then over all transmission paths substantially identical data are transmitted. In this way power can be saved. Still further, in an embodiment the data received over the different reception paths may be combined to improve the quality of the received data.
[0226] In other broadcast systems, e.g. according to DVB-T2, the complete frame is either transmitted in SISO scheme or in MISO scheme. In the latter case the receiver must always equalize spatially. If also MIMO scheme is available so that per frame MIMO scheme is selected or not, the receiver must always have multiple reception antennas and apply spatial equalization. According to the present invention, however, different classes of receivers can be used in the same broadcast system and by use of the same broadcast signals. In particular, receivers that can receive MIMO signals, but also receivers that can at least receive MIMO or SISO signals can be used according to the present invention. Thus, the present invention enables also the use of a receiver having only a single reception antenna, which may receive and decode MISO and SISO signals, but ignores MIMO signals.
[0227] The output of the MIMO mode detection units 123a, 123b is pro vided to demapping units 124a, 124b, which may also be a combined demapping unit in an embodiment (e.g. if spatial equalization has to be performed). Therein, the desired data stream is demapped (and, if necessary, decoded in separate or a combined decoding unit(s) 127 provided in one or both of said demapping units 124a, 124b, or generally in the demapping apparatus 124), which is thereafter subjected to post-processing in the post-processing unit 126, to obtain the desired receiver output data stream ly'. The post-processing in the post-processing 126 may generally be similar or identical to the post-processing performed in the post-processing unit 106 of the receiver 100, however is adapted such that it interrelates with the pre-processing performed in the pre-processing unit 34 of the transmitter 30. Hence, if the pre-processing in the pre-processing unit 34 of the transmitter 30 is, for instance, performed in accordance with the DVB-T2 or DVB-C2 standard, the post-processing in the post-processing unit 126 is adapted accordingly in accordance with the respective standard.
[0228] Similarly, in another embodiment of the transmitter, in addition to or instead of the MIMO mode detection units 123a, 123b respective pilot pattern detection units may be provided for detection of the pilot patterns. Based on the detected pilot pattern, the receiver may decide to perform channel estimation either in time and/or frequency direction (interpolation) and decide what kind of further processing of the received data is required.
[0229] It shall be noted that multiple services multiplexing is also possible according to the present invention, according to which different PLPs are transmitted over the different transmit antennas in case of MIMO. For example, two different PLPs might be mapped onto the different transmission paths of a MIMO encoded data symbols, while the receiver might e.g. process one PLP instantaneously, and store another PLP for later use or combine both PLPs (as in case of scalable video coding).
[0230] An embodiment of one path of the demapping apparatus 124 is schematically depicted in
[0231] At the data input 130 the demapping input data stream Q′ is received, which is provided for stream demapping in a stream demapping unit 132. Here, the frames F2 are demapped from the demapping input data stream Q′. These frames F2 may, for instance, be incorporated into the superframe structure as provided according to the DVB-T2 standard as FEF frames as shown in
[0232] In particular, said frame demapping unit 134 is adapted for demapping said second frames F2 comprising a preamble portion 40 and a payload portion 50 into said demapping output data stream Sy′. Said frame demapping unit 134 is particularly adapted for demapping the signalling data Si from the preamble portion 40 and for demapping the data blocks of the demapping output data stream Sy′ from the payload portion 50 by use of said signalling information Si. The derived demapping output data stream Sy′ is then provided to a data output 136 for output to the post-processing unit 126.
[0233] Since the frame structure of the second frames F2 uses, as explained above, a segmented concept, according to which the payload portion is segmented into data segments, a narrow-band receiver 120 can be used, which, in some embodiments, must not be able to be tuned to and receive the complete channel bandwidth of the complete frame F2, but must only be able to be tuned to and receive a bandwidth portion of said total channel bandwidth. This is possible, despite the frame structures of both the first and second frames F1, F2 use the total channel bandwidth, which, however, can slightly vary for the two types of frames (e.g. 7.61 MHz for a first type, and 7.62 MHz for the second type of frames), i.e. the channel bandwidth of both types is in the same order.
[0234] The size of the bandwidth portion of the receiver 120 depends on the bandwidth portion covered by data blocks of the desired demapping output data stream Sy′. If, for instance, all the data blocks of the desired demapping output data stream Sy′ are stored in a single data segment only, it is sufficient if the receiver can be tuned to and receive the bandwidth covered by said data segment. lf, as provided in another embodiment, the data blocks of the desired demapping output data stream Sy′ (in frequency direction) cover two or more (neighbouring or not neighbouring) data segments at a particular moment in time, the receiver must be able to be tuned to and receive a larger bandwidth portion. Further, the invention also enables the use of receivers that are able to receive the complete channel bandwidth and not only a portion thereof, as is the case in preferred receivers of the present invention.
[0235] The information about the bandwidth portion, in particular its size and its frequencies, are generally signalled from the transmitter to the receiver within the signalling information. This signalling information also contains information about the locations of the data blocks of the various data streams, to enable the receiver to change its tuning accordingly. As explained above, particularly with reference to
[0236]
[0237] The layout of such a receiver 140 is schematically shown in
[0238] For reception of the receiver input data stream Q′, a single antenna and a single tuner is generally sufficient in the receiver. Receivers (e.g. mobile receivers) may, however, also be provided with two or more antennas and/or two or more tuner, which can particularly be used to advantage if the data blocks of the data stream that shall be received are spread (in time and/or frequency) over more than one data segment and/or data symbol. For instance, in case of spreading in time, a first antenna (and/or tuner) can be controlled to receive a first data block mapped onto a first data segment and the second antenna (and/or tuner) can be controlled to “look ahead” in time (e.g. be tuned to another frequency) for reception of the next data block mapped onto another data segment at the appropriate time. In another embodiment, in particular in case of spreading in frequency, both antennas (and/or tuners) can be controlled to receive the data blocks mapped onto the two data segments at the same time. In this way, tuning time in the receiver can be saved and more sleeping times for the receivers can possibly be provided. Further, in an embodiment, a receiver having two reception antennas can use the second reception antenna to “look ahead” and receive a second service (that is e.g. stored in the receiver) while the first reception antenna receives a first service, for whose reception the second reception antenna is not needed, i.e., for SISO or MISO scheme.
[0239] Preferably, at least two reception antennas are provided in a mobile receiver to make use of the various MIMO modes explained above. However, MIMO and MISO can also be used with transmitters and receivers having more than two antennas, and also Alamouti coding is just one example of a coding scheme used in MISO. Other space/time as well as space/frequency coding schemes can be used as well.
[0240] As explained above, it is one target of state of upcoming mobile broadcast standards such as NGH to provide mixed MIMO (or MISO) and SISO operation. This allows a higher level of flexibility, e.g. different services can be received with different robustness, decoding complexity or even receiver types (handheld, in-car, single or double reception antenna).
[0241] MIMO or MISO transmission schemes (both schemes are sometimes commonly denoted by the term MIXO) can be beneficial, because they exploit the spatial dimension (more robustness / higher data rates). However, SISO is still the more proven technique and requires only one transmission antenna. Introduction of MIXO for future broadcasting could be achieved by two approaches:
[0242] A) Introducing MIXO transmission could be done in a “hard cut” manner: change the complete network from SISO to MIMO and transmit from thereon with several (e.g., two) transmission antennas exclusively. It is to be noted that a typical MIXO scheme for broadcasting applies dual-polarized MIXO, i.e., one antenna element transmits with a vertically polarized component, the other element uses horizontally polarized radio waves
[0243] B) For graceful introduction of MIXO schemes, it is possible to use SISO for some time, then change to MIXO, back to SISO and so on. In DVB-T2, the standard even allows to subsequently transmit a T2 Frame in SISO operation, while the next T2 Frame could use MISO.
[0244] Changing from MIXO to SISO transmission induces that during SISO transmission the second transmission antenna is switched off. This is however hardly possible, if the transmit towers radiate large transmission powers (as is typically done in terrestrial broadcasting).
[0245] Thus, having pure MIXO and SISO in subsequent (and rather short) time intervals is impossible, if the transmit antennas require a constant transmit power.
[0246] As explained above in segmented OFDM it is possible to use certain data segments (data slices) for SISO transmission, while others are used for MIXO providing in particular the advantage of reduced pilot overhead for channel estimation. Receivers for MIXO generally estimate twice the number of channels as two transmit antennas are used.
[0247] The general separation in frequency direction is depicted in
[0248] Assuming in an example that a first transmission antenna transmits data during SISO operation (e.g., the vertically polarized antenna), for MIXO further transmission antennas are used. In this example, only one further transmission antenna (i.e. a second antenna), which e.g. might be the horizontally polarized transmission antenna, is provided. Thus, in this example, all subcarriers of the segmented OFDM use the vertical component, while the subcarriers used in the MIXO segments further use the horizontal subcarriers (at the corresponding frequencies), as can be seen in
[0249] While the vertically polarized OFDM signal can be generated by a normal OFDM modulation, the horizontal signal can be generated with two approaches.
[0250] In a first approach all subcarriers are set to zero, where no horizontal component is to be transmitted (i.e. in the SISO segments). Then, OFDM coding is performed using the complete bandwidth (of all data segments, including the SISO segments with the inserted zeros in frequency domain), i.e. single OFDM symbols are formed for the horizontally polarized subcarriers.
[0251] In a second approach a narrowband OFDM coding is performed for each MIXO data segment in the equivalent complex baseband and the individual signals are mixed to the center frequencies of each corresponding data segment. In the example, two OFDM signals are generated, one with ⅕ and another one with ⅖ of the complete bandwidth. The first one OFDM signal is shifted to the second data segment, the other OFDM signal is shifted to the last two data segments. However, frequency and time synchronization generally need to be rather accurate.
[0252] Both approaches generally yield the same result, which can be interpreted as using zero-padding for SISO subcarriers, i.e. those subcarriers which are not transmitted over a particular transmission antenna.
[0253] A further possible solution would be that the horizontal subcarriers in the SISO data segments are not filled with zeros, but rather are replaced by the same symbols as used in the SISO part, which are transmitted over the vertical antenna. However, typically, there is a rather large cross-polar discrimination (XPD, about 10 dB), which means that the horizontally SISO segments are received by a pure SISO receiver with smaller power (up to 3 dB loss, if two antennas are used in the MIMO or MISO scheme).
[0254] As typically both transmission antennas should radiate the same power, the subcarriers of the MIXO data segments are preferably be boosted by an appropriate scaling factor (indicated by larger arrays in
[0255] However, there could be practical problems, as the receiver would typically detect the power imbalances between the different transmitted signals. For most MIXO schemes, this impedes decoding. Thus, power imbalances between the transmitter components should preferably be avoided in some cases. The following approach enables this.
[0256] For the following example the overall transmission power (which would be used for SISO-only transmission and which would be transmitted over all N_seg segments) is denoted as P_SISO, the number of MIXO data segments is denoted by N_MIXO and the number of transmission antennas used for MIXO is denoted by N_ant. Then all subcarriers of both transmission antennas are downscaled (compared to the SISO-only case) by a factor such that the overall radiated power is still P_SISO.
[0257] More precisely, the downscaling of the power for all subcarriers is, for instance, computed by the factor D=P_SISO/(N_seg−N_MIXO+N_ant* N_MIXO). The downscaling of the magnitudes of all subcarriers is done appropriately with √D.
[0258]
[0259] The second antenna (horizontal) in this example could in addition be used to furter reduce the peak-to-average power ratio (PAPR—typical problem for OFDM). Moreover, in an embodiment some non-zero symbols are inserted, e.g. tone reservation carriers at the positions of the pilots. Newly inserted pilots however still need to be orthogonal to the original SISO pilots, i.e. all related channel estimation functionalities need to be maintained. Preferably, the boosting factor explained above should then be reduced accordingly. Thus, these newly inserted pilots do not disturb the original pilots, if the receiver treats them as MIXO pilots, thereby eliminating the new pilots. This could be exploited to further reduce the PARP by selecting the pilots appropriately. For instance, in a brute force approach all permutations are tried and the one is selected, which minimizes the PAPR.
[0260] As mentioned above, the further transmission antennas use differently polarized subcarriers than the first antenna. For instance, in an embodiment of a transmission apparatus 30′ as depicted in
[0261] Next, a further embodiment of a transmission apparatus for use in various broadcast systems is described.
[0262] Generally, SISO transmissions use only one transmission antenna, while MIXO transmissions take advantage of several transmission antennas (wherein two transmission antennas is the most likely case in the upcoming DVB-NGH systems).
[0263] If MIMO and SISO services are mixed in time, e.g. partitioned by the help of frames, it occurs that one transmission antenna operates constantly, while the second (and further) transmission antenna only transmits during the MIXO transmission periods as schematically shown in
[0264] In order to achieve the same overall transmission power level on the channel the SISO power level of the single transmission antenna generally should be 3 dB higher compared to the power level on each of the two MIXO transmission antennas, i.e. during MIXO operation the same power has to be radiated as in SISO operation, thus splitting the power onto two transmission antennas (3 dB loss).
[0265] Having different power levels on different transmission antennas is generally no problem for transmission systems with limited transmission power levels (WLAN, WIMAX, LTE, . . . ). These systems can easily switch between different MIMO and SISO schemes. This is different for large scale transmission systems, e.g. nationwide terrestrial broadcast systems such as DVB-T2 or the upcoming NGH standard systems. The transmission apparatus of these broadcast networks typically covers very large areas, therefore the transmission power level needs to very high. It is quite difficult to switch on and off frequently blocks of a high power level signal chain, which would be needed on the second transmission path of the NGH MIMO scheme (during SISO transmission periods).
[0266] It is therefore proposed to allocate the power level in a way that it is kept constant over the different transmission periods (i.e. SISO and MIXO frames). This means that the SISO transmission power (being so far fed to a single transmit antenna) is split up to the two (or more) transmission paths. Logically the two transmission paths build therefore a kind of SFN (Single Frequency Network).
[0267]
[0268] For fixed reception conditions (i.e. where the polarization of the reception is aligned to the transmission polarization) the received signal strength might be decreased by 3 dB. On the other hand, portable and mobile receivers gain from the increased polarization diversity, as different reception angles can always deploy the overlaid (or combined) reception field strengths of both transmission polarizations. Mobile receivers will in average have therefore better reception conditions. This is even more true if reception diversity with different receiver paths (e.g. orthogonal reception antennas) is applied.
[0269] In summary, the present invention enables the use of narrow-band receivers having a low power consumption even if the frame structure used by the transmitter of the multi-carrier broadcast system has a much broader channel bandwidth. Further, various embodiments are provided, which enable further savings in power consumption of receivers, which is particularly important for mobile receivers. Still further, an increased or at least selectable robustness for selected services due to the use of time and/or frequency diversity in the mapping of data blocks of the services onto frames having a segmented frame structure can be achieved.
[0270] A data segment of the payload portion can be used only for a single data stream or can be split up in time and/or frequency direction for use by data blocks of two or more data streams. The respective use of the data segment, i.e. the mapping of the data blocks of the various data streams on the data segments of the frames, can be static (i.e. continuously fixed) for the whole transmission of a data stream, can be quasi-static (i.e. fixed for a group of frames or only a single frame, i.e. can be changed from frame to frame) or can be continuously changed (i.e. also with frames). In the latter embodiments more signalling is required compared to the first (static) embodiment.
[0271] Further, according to the present invention various levels of robustness and various data rates can be selected by the transmitter and can be received by the receiver through the ability to select the MIMO mode and/or the pilot pattern per PLP and/or per data slice. For instance, a low resolution data stream can be transmitted using SISO or MISO and a corresponding high resolution data stream can be transmitted in MIMO.
[0272] The invention also enables the application of scalable video coding, according to which the same data are transmitted as a high resolution data stream (with lower robustness) and as a low resolution data stream (with higher robustness). If the receiver is, e.g. due to bad reception conditions, not able to receive the high resolution data stream it can switch to the corresponding (“associated”) low resolution data stream.
[0273] The invention has been illustrated and described in detail in the drawings and foregoing description, but such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims
[0274] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
[0275] A computer program may be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.
[0276] Any reference signs in the claims should not be construed as limiting the scope.
[0277] In an embodiment of the receiver said MIMO mode detection means is adapted for detecting one of a SISO scheme, MISO scheme or MIMO scheme.
[0278] In an embodiment of the receiver said MIMO mode detection means is adapted for detecting the MIMO mode from frame to frame or from a group of frames to a next group of frames.
[0279] In an embodiment of the receiver said MIMO mode detection means is adapted for detecting the MIMO mode from data symbol to data symbol or from a group of data symbols to a next group of data symbols.
[0280] In an embodiment of the receiver said pilot pattern detection means is adapted for detecting edge pilots between neighboring data segments, said edge pilots fitting with the pilot patterns of both neighboring data segments.
[0281] In an embodiment of the receiver said pilot pattern detection means is adapted for detecting the pilot pattern from frame to frame or from a group of frames to a next group of frames.
[0282] In an embodiment of the receiver said pilot pattern detection means is adapted for detecting the pilot pattern from data symbol to data symbol or from a group of data symbols to a next group of data symbols.
[0283] In an embodiment of the receiver said MIMO mode detection means and/or said pilot pattern detection means is adapted for demapping signalling information from said frame, said signalling information including MIMO mode information indicating the selected MIMO mode of the data blocks per data segment and/or per mapping input data stream and/or pilot pattern information indicating the selected pilot pattern per data segment and/or per mapping input data stream.
[0284] In an embodiment of the receiver said frame demapping means is adapted for demapping said signalling information from one or more preamble signalling blocks mapped onto preamble symbols of a preamble portion of said frames, from one or more payload portion signalling blocks mapped onto data symbols of said payload portion or in-band from one or more data blocks mapped onto data symbols of said payload portion.
[0285] In an embodiment of the receiver it comprises one or more demapping units per reception path of a receiver, into which said apparatus is included, wherein said one or more demapping units are adapted for individually demapping the data blocks from the provided demapping input data stream.
[0286] In an embodiment of the receiver at least one demapping unit comprises decoding means for decoding the data blocks provided to said at least one demapping unit.
[0287] In an embodiment of the receiver said frame demapping means is adapted for demapping the data blocks of a demapping output data stream from various data symbols and various data segments of said frame, over which said data blocks are spread in time and frequency.
[0288] In an embodiment of the receiver said receiving unit comprises at least two receiving sub-units for receiving different demapping input data streams, and said receiver apparatus further comprises a control unit for switching off at least one receiving sub-units or for combining the reception signal received by said receiving sub-unit, it the MTMO mode detection unit has detected that the demapping input data stream currently received uses SISO scheme or MISO scheme.