Abstract:
A method for improving the data rate of data for M/H receivers and for improving the quality of channel estimation in an ATSC-M/H transport data stream marks the transport data packets determined for the transmission of data for M/H receivers in N (e.g., 38) consecutively transmitted transport data packets in an ATSC-M/H-slot of the uncoded ATSC-M/H transport data stream originally determined for the transmission of data for stationary receivers. Coded data for M/H receivers are inserted in the marked transport data packets and introduce training sequences in segments of data fields of the coded ATSC-M/H transport data stream containing marked transport data packets.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application Ser. Nos. 61/162,275 filed Mar. 21, 2009, and 61/265,572 filed Dec. 1, 2009, which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field 
     The invention generally relates to communication systems, and more particularly to improving the data rate of mobile data and the quality of channel estimation in an ATSC-M/H (Advanced Television Systems Committee—Mobile/Handheld) transport data stream. 
     2. Related Art 
     ATSC transport data stream content and function is described in U.S. patent application Ser. No. 11/276,473, entitled “APPARATUS, SYSTEMS AND METHODS FOR PROVIDING ENHANCEMENTS TO ATSC NETWORKS USING SYNCHRONOUS VESTIGIAL SIDEBAND (VSB) FRAME SLICING”, filed Mar. 1, 2006 and U.S. Pat. No. 7,532,677, entitled “APPARATUS, SYSTEMS AND METHODS FOR PRODUCING COHERENT SYMBOLS IN A SINGLE FREQUENCY NETWORK”, which issued on Sep. 27, 2007, both of which are hereby incorporated by reference in their entirety. In an ATSC-M/H transport data stream, transport data packets containing data for stationary (or “fixed” or “main stream”) receivers and transport data packets containing data for M/H receivers are transmitted. As shown in  FIG. 3 , the data structure of an ATSC-M/H transport data stream is organized in ATSC-M/H data frames each containing 5 ATSC-M/H sub-frames. Each ATSC-M/H sub-frame is subdivided into 16 ATSC-M/H slots, where each slot contains 156 transport data packets. An ATSC-M/H slot (i.e., 156 transport data packets) can be filled with data for stationary receivers. Alternatively, an ATSC-M/H slot may contain 118 transport data packets with data for M/H receivers and 38 transport data packets of data for stationary receivers. The 118 transport data packets containing data for M/H receivers are referred to as an M/H group and a collection of M/H groups is referred to as an M/H parade which can carry one or two M/H ensembles. Each M/H ensemble represents a logical pipe for IP based datagrams of one television (TV) program or service. 
     The M/H ensembles carried by the M/H parades include a specific number of ATSC-M/H slots in an ATSC sub-frame. Also, a potential mobile TV carrier holding a FCC License outside the broadcast band (e.g., channels 2-51) may wish to use ATSC M/H. This mobile TV carrier is not restricted by the FCC in the use of bandwidth in the ATSC-M/H transport data stream and is not required to transmit a specific minimum rate of TV data for stationary receivers as are normal ATSC broadcasters (e.g., channel 2-51). Nevertheless, a TV carrier intending to transmit only data for M/H receivers is limited by the requirements of the current ATSC-M/H standard which defines the data structure of the ATSC-M/H transport data stream. If each ATSC-M/H slot of the M/H ensemble containing only data for stationary receivers is substituted by an ATSC-M/H slot containing a combination of 118 transport data packets for M/H receivers and 38 transport data packets for stationary receivers, only 75% of the total bandwidth can be used for transmitting data for M/H receivers. 
     As shown in  FIG. 1 , an ATSC-M/H slot of a coded ATSC-M/H transport data structure is organized in regions A, B, C and D, where each region contains one or more segments. Only region A provides training sequences (i.e., known symbol sequences to aid the M/H receiver&#39;s equalizer in channel estimation and to track fading channels known to exist in the mobile environment). The regions B, C and D are positioned symmetrically around region A do not provide training sequences. As a result, the transmission quality of an ATSC-M/H transmission is reduced in regions B, C, and D. Thus, in a time varying transmission channel the channel estimation, the signal equalization and the subsequent decoding is downgraded in time periods corresponding to the occurrence of segments in regions B, C and D in the ATSC-M/H transmission data stream. 
     What is needed is a method for increasing the total possible data rate available for M/H mobile services and improving the quality of channel estimation in an ATSC-M/H by introducing additional training sequences in transport data stream. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention meets the above-identified needs by using a portion or all of the 38 transport data packets of an ATSC-M/H slot originally designated to be used for transmitting data for stationary receivers for transmitting data for M/H receivers. This new mobile region is referred to herein as region E and is shown in  FIG. 2  as the region corresponding to ATSC data for mobile receivers. The rate of transmitted data for M/H receivers in the ATSC-M/H transport data stream can be increased by using a portion of the 38 packets in region E for mobile, increasing in steps from the current 75% transmission rate for mobile up to 100% mobile. The transport data packets, whose contents are changed from data for stationary receivers to data for M/H receivers, are marked to indicate that the respective content in a stationary receiver should be ignored and that the respective content in a M/H receiver should be received and decoded. 
     In addition, training sequences containing marked transport data packets are introduced in segments of data fields in the coded transport data stream, particularly the coded ATSC-M/H transport data stream. The marked transport data packets can be positioned in segments of regions B, C, D and E of the coded transport data stream, which are originally not arranged with the training sequences. As a result, the training sequences are distributed throughout the coded transport data stream for better channel estimation and signal equalization. In addition, mobile data in each corresponding time period of the transmission also is correctly decoded. 
     The data for M/H receivers are inserted symmetrically starting in the center of the, e.g., 38 consecutively transmitted transport data packets region E originally determined for data for stationary receivers in an ATSC-M/H slot and expand outward. The data are separated by at least one or more transport data packet for stationary service on the edges of Region E as shown in  FIG. 3  when the data rate for mobile is less than 100% and will consume the whole 38 packets with mobile when 100% of the data rate for mobile only is desired. The stationary packets are placed on the edges of the 38 packet region as shown in  FIG. 3  to ensure the buffer model of the ATSC transport data stream is maintained for stationary receivers. 
     In a first example embodiment, training sequences are introduced into parts of the segments containing only the, e.g., 38 consecutively transmitted transport data packets originally designated for data for stationary receivers. Thus, only the, e.g., 38 consecutively transmitted transport data packets in an ATSC-M/H slot contain new training sequences are decoded in a comparable manner as the transport data packets transmitted in a region A ( FIG. 1 ) which also carry training sequences. 
     In a second example embodiment, training sequences are introduced throughout regions B, C, D and E. Thus, the transport data packets throughout the ATSC-M/H slot (i.e., the transport data packets in, e.g., 118+38 packets) are decoded in a comparable manner as the transport data packets transmitted in region A ( FIG. 1 ) of the coded ATSC-M/H transport data stream which carry native training sequences. 
     In one example aspect of the invention, the marking of transport data packets, whose contents are changed from data for stationary receivers to data for M/H receivers, is performed by using a value of the packet identifier (PID) in the header of the transport data packet, which is not occupied by the ATSC-M/H standard. 
     In another example aspect of the invention, the marking of transport data packets, whose contents are changed from data for stationary receivers to data for M/H receivers, is performed by using a transport data packet without any payload data, whose data point to the first and the last marked transport data packet. 
     In yet another example aspect of the invention, the marking of transport data packets, whose contents are changed from data for stationary receivers to data for M/H receivers, is performed by using values in a multiprotocol encapsulation (MPE) header of a protocol data unit (PDU) containing several MPEG2 transport data packets, which normally indicate the first and the last MPEG2 transport data packet of the PDU and which can be used for indicating the first and the last marked transport data packet. 
     In yet another example aspect of the invention, the marking of transport data packets, whose contents are changed from data for stationary receivers to data for M/H receivers, is performed by using the adaptation field in the MPEG2 transport data, which is not reserved for standardized content and which can be used for indicating the first and the last marked transport data packet. 
     The data for M/H receivers in that transport data packets, which are originally determined for stationary receivers, can be coded with the identical code in case of the transport data packets in an M/H group, e.g., with Reed-Solomon code in combination with a trellis-based serial-concatenated convolution code, or with a combination of a low-density-parity-check code and a Bose-Chaudhuri-Hocquenghen code. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the following drawings. 
         FIG. 1  shows a data structure of a time interval in a coded ATSC-M/H transport data stream, 
         FIG. 2  shows a data structure of a time interval in an ATSC-M/H transport data stream, 
         FIG. 3  shows a time diagram of an uncoded ATSC-M/H transport data stream, and 
         FIG. 4  depicts a flowchart of an exemplary process for improving the data rate of M/H data and the quality of channel estimation in an ATSC-M/H transport data stream. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 2 and 4 , initially in step S 10 , a predetermined number of consecutively transmitted transport data packets out of, e.g., 38 transport data packets in an ATSC-M/H slot originally designated for data for stationary receivers are marked for data for M/H receivers. Thus, more than 118 transport data packets of the respective ATSC-M/H slot are filled with data for M/H receivers in this example. The marked and consecutively transmitted transport data packets of the respective ATSC-M/H slot are positioned symmetrical to the center of the, e.g., 38 transport data packets originally designated for data for stationary receivers, referred to herein as region E. 
     Between the marked transport data packets and the, e.g., 118 transport data packets originally designated for data for M/H receivers, in the respective and in the subsequent ATSC-M/H slots enough transport data packets with data for stationary receivers are positioned to fulfill the requirements concerning underflow of the buffer for data for stationary receivers in the buffer model according to ISO/IEC 13818-1. The number of transport data packets with data for stationary receivers between the, e.g., 118 transport data packets originally determined for data for M/H receivers and the marked transport data packets depends on the data rate of the ATSC-M/H transport data stream at the output of the ATSC-M/H multiplexer and buffer size in the MPEG2 buffer model. Furthermore, the transport data packets filled with data for stationary receivers between the transport data packets filled with M/H receivers data can be used for transmitting a TV program with relatively little content or a forecast channel. 
     In a first example embodiment, the marking of the transport data packets is achieved by a specific value of the packet identifier (PID) in the header of the respective marked transport data packet, where the specific value of the packet identifier for marking the respective transport data packet is not yet reserved for other applications in the ATSC-M/H or MPEG2 standard. 
     In a second example embodiment, one transport data packet of the, e.g., 38 transport data packets originally determined for data for stationary receivers, which does not include any payload data, is used for marking the transport data packets. Instead of containing payload data, this transport data packet contains a pointer to the first and to the last marked transport data packet designated for data for M/H receivers in the respective ATSC-M/H-slot. 
     In a third example embodiment, the transport data packets provided for data for M/H receivers from the, e.g., 38 transport data packets originally determined for data for stationary receivers and representing each a MPEG2 transport data packet are assembled into a protocol data unit (PDU) and transported by a multi-protocol encapsulation method (MPE) in the transport layer. Furthermore, each PDU contains a multi-protocol encapsulation header with a pointer pointing to the first MPEG2 transport data packet and a pointer pointing to the last MPEG2 transport data packet of the PDU. Thus, in the transport layer, it is possible to use these two pointers in the multi-protocol encapsulation header of a PDU containing the marked transport data packets used for marking. 
     In a fourth example embodiment, the adaptation field in an MPEG2 transport data packet is used for marking a transport data packet originally determined for data for stationary receivers as a transport data packet for data for M/H receivers. If the adaptation field flag in the header of an MPEG2 transport data packet is set, the adaptation field is valid and can be used for transmitting any data. Thus, by setting the adaptation field flag in the header of the MPEG2 transport data packet the adaptation field of MPEG2 transport data packet can be used for inserting mark data marking the transport data packet as a container for M/H receiver data. 
     In step S 20 , the supplementary data for M/H receivers are inserted in the marked transport data packets of the respective ATSC-M/H slot as shown in the last line in  FIG. 3 . 
     In the post-processor of an ATSC-M/H transmitter, the data for M/H receivers inserted in the marked transport data packets are coded using the identical code as for coding the data for M/H receivers in the 118 consecutively transmitted transport data packets of each M/H group, such as Reed-Solomon-block-code in combination with a Series-Concatenated-Convolutional-Code (SCCC) or with a Parallel-Concatenated-Convolutional-Code (PCCC). For improved error correction, the data for M/H receivers inserted in the marked transport data packets can be coded in a more robust and reliable code, for example by using a low-density-parity-check-code (LDPC-code) combined with a Bose-Chaudhuri-Hocquenghen-code (BCH-code). 
     The data for M/H receivers inserted in the marked transport data packets can only be decoded by ATSC-M/H receivers capable of recognizing the marked transport data packets containing supplementary data for M/H receivers. 
     In step S 30 , training sequences are inserted in the segments of regions B, C, D, and/or E which are near the border of the ATSC-M/H slots in the coded ATSC-M/H transport data stream. 
     In a fifth embodiment of the invention, the training sequences are only inserted in parts of the segments in Region E, which corresponds to the, e.g., 38 transport data packets originally determined for data for stationary receivers, as can be seen in the lines indicating training sequences and positioned only in the trapezoid areas of the coded ATSC-M/H transport data stream in the above part of the diagram in  FIG. 2 . 
     In a sixth embodiment of the invention, the training sequences are inserted throughout the segments belonging to regions B, C and D (see the below part of the diagram in  FIG. 2 ). Thus, the training sequences are inserted in ranges of the coded ATSC-M/H transport data stream belonging to the 38 transport data packets originally determined for data for stationary receivers of the respective ATSC-M/H slot and to the transport data packets of the respective preceding ATSC-M/H slot and/or of the respective subsequent ATSC-M/H slot. 
     In one sub-embodiment of the invention, the training sequences can be inserted at both borders of the respective ATSC-M/H slot in the segments of regions B, C and D. In another sub-embodiment of the invention the training sequences can only be inserted at one border of the respective ATSC-M/H slot in the segments of regions typed B, C and D, i.e. at the border to the respective preceding ATSC-M/H slot or at the border to the respective subsequent ATSC-M/H slot. 
     The training sequences are inserted in the ATSC-M/H transport data stream by using a post processor to perform post processing between the interleaving and the 8-VSB-Trellis-encoding according to the ATSC-M/H standard. The training sequences are preceded by, e.g., 12 bytes for configuring the 8-VSB-trellis-encoder to a specific known starting state in which the 8-VSB-trellis-encoder begins encoding of the known training sequences in a code being specific for training sequences and that are known in advance to the M/H receiver. 
     The training sequences can only be decoded from ATSC-M/H receivers qualified for recognizing the training sequences positioned in the segments of regions B, C, D and or E. 
     The scope of the invention is not limited by the features of the embodiments described above. Other and especially future digital TV transmission standards combining the transmission of data for stationary and M/H receivers, which are not described herein, are inside the scope and the spirit of the present invention. 
     Software embodiments of the present invention may be provided as a computer program product, or software, that may include an article of manufacture on a machine accessible or machine- or computer-readable medium having instructions. The instructions on the machine accessible or machine- or computer-readable medium may be used to program a computer system or other electronic device. The machine- or computer-readable medium may include, but is not limited to floppy diskettes, optical disks, CD-ROMs and magneto-optical disks or other types of media/machine/computer-readable medium suitable for storing or transmitting electronic instructions. 
     The techniques described herein are not limited to any particular software configuration. They may find applicability in any computing or processing environment. The terms “machine accessible medium”, “machine-readable medium” and “computer-readable medium” used herein shall include any medium that is capable of storing, recording or transmitting a sequence of instructions for execution by the machine and that cause the machine to perform any one of the methods described herein. Furthermore, it is common in the art to speak of software, in one form or another (e.g., program, procedure, process, application, module, unit, logic and so on) as taking an action or causing a result. Such expressions are merely a shorthand way of stating that the execution of the software by a processing system causes the processor to perform an action to produce a result. 
     While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant art(s) that various changes in form and detail can be made therein without departing from the spirit and scope of the present invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. 
     In addition, it should be understood that the figures illustrated in the attachments, which highlight the functionality and advantages of the present invention, are presented for example purposes only. The architecture of the present invention is sufficiently flexible and configurable, such that it may be utilized (and navigated) in ways other than that shown in the accompanying figures. 
     Further, the purpose of the foregoing Abstract is to enable the U.S. Patent and Trademark Office and the public generally, and especially the scientists, engineers and practitioners in the art who are familiar with patent and legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The Abstract is not intended to be limiting as to the scope of the present invention in any way. It is also to be understood that the steps and processes recited in the claims need not be performed in the order presented.