Provided is a system and method for terrestrial digital broadcasting service using a single frequency network without additional equipment. The system and method synchronizes input signals into transmitting stations by inserting a transmission synchronization signal into a header of TS periodically, and solves the problematic ambiguity of the trellis encoder by including a trellis encoder switching unit separately and initializing a memory of the trellis encoder. The terrestrial digital broadcasting system includes: a broadcasting station for multiplexing video, voice and additional signals into transport stream (TS) and transmitting the TS to the transmitting stations and a transmitting stations for receiving the TS and broadcast the TS to receiving stations through a single frequency network.
|
0. 13. A trellis encoder initialization method, comprising:
creating a first feedback loop in a precoder by switching a content of a memory of the precoder to an input of the precoder where the feedback loop is created to initialize memory of the precoder after receiving values stored in the memory of the precoder from a first switching unit; and
creating a second feedback loop in a trellis coded modulation (TCM) encoder by switching the content of the memory of the TCM encoder to an input of the TCM encoder where the second feedback loop is created to initialize memory of the TCM encoder after receiving values stored in the memory of the TCM encoder from a second switching unit; and
wherein when memory of the precoder is initialized by the first feedback loop, the TCM encoder generates two initialization symbols in a predetermined data field period.
0. 9. A trellis encoder, comprising:
a precoder which includes one memory; a trellis coded modulation (TCM) encoder which includes two memories;
where the trellis encoder is configured to generate initialization symbols of a predetermined length in a predetermined data field period M and synchronize a transport stream outputted to receiving stations, where M is a natural number, wherein the trellis encoder includes:
a first switching unit for initializing output values of the trellis coded modulation (TCM) encoder and the memory of the TCM encoder performing switching to values stored in the memory of the TCM encoder instead of input signals to the TCM encoder every M period, wherein the TCM encoder includes a first feedback loop to initialize the memory of the TCM encoder after receiving the values stored in the memory of the TCM encoder from the first switching unit;
a second switching unit for initializing output values of the precoder and the memory of the precoder by performing switching to values stored in the memory of the precoder instead of input signals to the precoder every M period, wherein the precoder includes a second feedback loop to initialize the memory of the precoder after receiving the values stored in the memory of the precoder from the second switching unit; and
wherein when the memory of the precoder is initialized by the second feedback loop, the trellis encoder generates two initialization symbols in the predetermined data field period M.
0. 17. A digital broadcasting system including a switchable trellis encoder, the encoder comprising:
a precoder which includes one memory;
a trellis coded modulation (TCM) encoder which includes two memories; where the trellis encoder is configured to generate initialization symbols of a predetermined length in a predetermined data field period M and synchronize a
transport stream outputted to receiving stations, and M is a natural number, wherein the trellis encoder includes:
a first switching unit for initializing output values of the trellis coded modulation (TCM) encoder and the memory of the TCM encoder performing switching to values stored in the memory of the TCM encoder instead of input signals to the TCM encoder every M period, wherein the TCM encoder includes a first feedback loop to initialize the memory of the TCM encoder after receiving the values stored in the memory of the TCM encoder from the first switching unit;
a second switching unit for initializing output values of the precoder and the memory of the precoder by performing switching to values stored in the memory of the precoder instead of input signals to the precoder every M period, wherein the precoder includes a second feedback loop to initialize the memory of the precoder after receiving the values stored in the memory of the precoder from the second switching unit; and
wherein when the memory of the precoder is initialized by the second feedback loop, the trellis encoder generates two initialization symbols in the predetermined data field period M.
5. A terrestrial digital broadcasting method using a single frequency network, comprising the steps of:
a) inserting a field synchronization header to transport stream (TS) transmitted to a plurality of transmitting stations in a predetermined data field period N in a broadcasting station, wherein N is a natural number;
b) detecting the field synchronization header and synchronizing starting points of the TS inputted to each transmitting station in the plurality of transmitting stations;
c) synchronizing the TS outputted to receiving stations by generating initialization symbols of a predetermined length every predetermined data field period M with respect to the inputted signal, and M is a natural number,
wherein the initialization symbols are generated by performing switching to input values stored in a memory of a trellis coded modulation (TCM) encoder, the TCM encoder including a first feedback loop to initialize a memory of the TCM encoder after receiving the input values stored in the memory of the TCM encoder from the performed switching, and input values stored in a memory of a precoder instead of the inputted signal, the precoder including a second feedback loop to initialize a memory of the precoder after receiving the input values stored in the memory of the precoder from the performed switching, and
when the memory of the precoder is initialized by the second feedback loop, two initialization symbols are generated in every predetermined data field period M; and
d) broadcasting the synchronized TS to the receiving stations.
1. A terrestrial digital broadcasting system, comprising:
a broadcasting station for multiplexing video, voice and additional signals into transport stream (TS) and transmitting the TS to transmitting stations; and
a plurality of transmitting stations for receiving the TS and broadcasting the TS to receiving stations through a single frequency network,
wherein the broadcasting station includes:
a transmission synchronization means for inserting a field synchronization header to the TS in a predetermined data field period N, wherein N is a natural number, and
wherein the plurality of transmitting stations include:
a transmission synchronization detecting means for synchronizing the TS transmitted from the broadcasting station based on the field synchronization header; and
a trellis encoding means for generating initialization symbols of a predetermined length in a predetermined data field period M and synchronizing the TS outputted to the receiving stations, and M is a natural number,
wherein the trellis encoding means includes:
a first switching unit for initializing output values of a trellis coded modulation (TCM) encoder and a memory of the TCM encoder performing switching to values stored in the memory of the TCM encoder instead of input signals to the TCM encoder every M period, wherein the TCM encoder includes a first feedback loop to initialize the memory of the TCM encoder after receiving the values stored in the memory of the TCM encoder from the first switching unit;
a second switching unit for initializing output values of a precoder and a memory of the precoder by performing switching to values stored in the memory of the precoder instead of input signals to the precoder every M period, wherein the precoder includes a second feedback loop to initialize the memory of the precoder after receiving the values stored in the memory of the precoder from the second switching unit; and
wherein when the memory of the precoder is initialized by the second feedback loop, the trellis encoding means generates two initialization symbols in the predetermined data field period M.
2. The system as recited in
3. The system as recited in
4. The system as recited in
6. The method as recited in
7. The method as recited in
8. The method as recited in
0. 10. The trellis encoder as recited in claim 9, wherein contents of the memories start to be initialized to zero as the first switching unit switches the content of the memory of the precoder and the second switching unit switches content of one of the memories of the TCM encoder.
0. 11. The trellis encoder as recited in claim 10, wherein an operation to switch to values stored in the memory of the TCM and an operation to switch to values stored in the memory of the precoder are performed at the same time.
0. 12. The trellis encoder as recited in claim 11, wherein the operation to switch to values stored in the memory of the TCM and the operation to switch to values stored in the memory of the precoder are performed with a temporal regularity.
0. 14. The method as recited in claim 13, wherein the content of each memory starts to be initialized as the first and the second feedback loops are created.
0. 15. The method as recited in claim 14, wherein the two switching units are operated at the same time.
0. 16. The method as recited in claim 15, wherein the two switching units are operated with a temporal regularity.
0. 18. The digital broadcasting system as recited in claim 17, wherein contents of the memories start to be initialized to zero as the first switching unit switches the content of the memory of the precoder and the second switching unit switches content of one of the memories of the TCM encoder.
0. 19. The digital broadcasting system as recited in claim 18, wherein an operation to switch to values stored in the memory of the TCM and an operation to switch to values stored in the memory of the precoder are performed at the same time.
0. 20. The digital broadcasting system as recited in claim 19, wherein the operation to switch to values stored in the memory of the TCM and the operation to switch to values stored in the memory of the precoder are performed with a temporal regularity.
|
The present invention relates to a system and method for providing terrestrial digital broadcasting service using a single frequency network; and, more particularly, to a system and method where a plurality of transmitting stations provide a terrestrial digital broadcasting service through a single frequency network.
In general digital broadcasting service systems, transmitting stations are positioned based on the natural configurations, natural features and broadcasting coverage, and broadcasting data are transmitted in a frequency band allocated to each transmitting station, which is called a plural frequency network mode.
The conventional broadcasting service system requires a great deal of frequency resources, because the same broadcast data is broadcasted on a plurality of frequencies. Since the same frequency cannot be used in the regions of short distance due to the generation of interference, the conventional technology is very inefficient in the aspect of using frequencies. Therefore, it is desirable to use single frequency network.
However, if digital television (TV) broadcasting is operated using a conventional digital TV transmission system, many problems occur. First, since the distances and channel environments between the broadcasting station 100 and the respective transmitting stations are different, a first transmitting station receives the TS which is different from that received by a second transmitting station at the same time.
In other words, since the first transmitting station 130 and the second transmitting station 170 are not synchronized temporally, the starting point of channel modulation is different in each of the transmitting stations 130 and 170. As a result, the output signals are not the same. Therefore, when the signals are broadcasted on a single frequency network, the output signals cannot be discriminated. That is, if the signals transmitted from a plurality of transmitting stations are not the same, the signals become noise to each other in the same frequency band. These noise signals are not discriminated in a receiving station.
Secondly, because the initial states of the memories of a TCM encoder 137 and a precoder 138 in a transmitting station are not the same, even if the same signal is inputted into different transmitting stations, different signals are outputted from the transmitting stations. This phenomenon is called ambiguity of a trellis encoder.
To solve the problems, a method of “Transmitter Synchronization for Terrestrial Broadcasting” is suggested as an Advanced Television Systems Committee (ATSC) standard by Merrill Weiss Group. The ATSC is established to deliberate advanced television (ATV), which is a next-generation terrestrial television technology.
According to the “Transmitter Synchronization for Terrestrial Broadcasting,” the broadcasting station matches the periods of signals inputted to transmitting stations by transmitting a cadence signal (CS) periodically, and solves the problematic ambiguity of the trellis encoder by transmitting a trellis code state packet (TCSP) signal separately. The TCSP signal is a signal carrying information on the memory of the trellis encoder.
However, the method causes another problems that the broadcasting station requires complicated additional equipment, such as a data randomizer, an RS encoder, a data interleaver, a trellis encoder, a CS adder and a TCSP adder to transmit a TCSP signal, and that the portion of a control signal in a TS is increased and, thus, STL load is weighed down.
It is, therefore, an object of the present invention to provide a system and method for providing digital television broadcasting service using a single frequency network in which input signals into transmitting stations are synchronized.
In accordance with an aspect of the present invention, there is provided a terrestrial digital broadcasting system, including: a broadcasting station for multiplexing video, voice and additional signals into transport stream (TS) and transmitting the TS to the transmitting stations; and a transmitting stations for receiving the TS and broadcasting the TS to receiving stations through a single frequency network, wherein the broadcasting station includes: a transmission synchronization unit for inserting a field synchronization header to the TS in a predetermined data field period N, and wherein the transmitting stations include: a transmission synchronization detecting unit for synchronizing the TS transmitted from the broadcasting station based on the field synchronization header; and a trellis encoding unit for generating initialization symbols of a predetermined length in a predetermined data field period M and synchronizing the TS outputted to the receiving stations.
In accordance with another aspect of the present invention, there is provided a terrestrial digital broadcasting method using a single frequency network, including the steps of: a) inserting a field synchronization header to transport stream (TS) transmitted to a plurality of transmitting stations in a predetermined data field period N in a broadcasting station; b) detecting the field synchronization header and synchronizing starting points of the TS inputted to each transmitting station in the transmitting stations; c) synchronizing the TS outputted to receiving stations by generating initialization symbols of a predetermined length every predetermined data field period M with respect to the inputted signal; and d) broadcasting the synchronized TS to the receiving stations.
The above and other objects and features of the present invention will become apparent from the following description of the preferred embodiments given in conjunction with the accompanying drawings, in which:
Other objects and aspects of the invention will become apparent from the following description of the embodiments with reference to the accompanying drawings, which is set forth hereinafter.
The terrestrial digital broadcasting system using a single frequency network, which is an American style, is illustrated in
The broadcasting station 400 inputs a video signal 402 which is compressed by using a Motion Picture Experts Group 2 (MPEG-2), a voice signal 404 compressed by using a dolby AC-3, and a control signal 406 for controlling a transmitting station to a multiplexer 408 to generate TS, which is a digital data stream.
Meanwhile, a transmission synchronization unit 420 of the broadcasting station 400 inputs a predetermined transmission synchronization signal, which will be described later, to a particular header of the TS, periodically. According to an Advanced Television Systems Committee A.53 (ATSC A.53) standard, a value of 4716 is inserted as a header information to a header of TS. Here, the 4716 value is a hexadecimal number.
However, in the present invention, a transmission synchronization unit 420 inputs a value of B816, which is obtained by inversing the value of 4716 on a bit by bit basis, as a field synchronization header every N data fields periodically. The data field period, N, is a natural number that can be adjusted according to communication environment flexibly. That is, if the communication environment is in good condition, N can be a large number. Otherwise, if it is in poor condition, a field synchronization signal should be transmitted frequently by making the N value small. It is obvious to those skilled in the art that the N value can be changed variously according to the communication environment of the terrestrial digital broadcasting system. Therefore, the present invention should be understood not limited to a particular N value.
Into the other segment headers 620, the value of 4716 is stored as header information just as the prior art. The number of the other segment headers is defined as X, X being a natural number larger than 1. Since N is 1 in the present embodiment, X becomes 311.
The field synchronization header synchronizes the input signals into the transmitting stations. In this embodiment, since the first transmitting station 430 and the second transmitting station 470 have different distances from the broadcasting station 400 and they are in different communication environments, different signals are inputted into the first and second transmitting stations 430 and 470 at the same time. In order to transmit the same output signals, the starting points of data for processing should be the same. The starting points of data for processing can be synchronized at the transmitting stations, as the transmission synchronization unit 420 inserts the field synchronization header. TS with a field synchronization signal inserted thereto is transmitted to the transmitting stations through a studio to transmitter (STL) 410.
Meanwhile, the first transmitting station 430 receives the TS and transmits it to a transmission synchronization detector 431. If the value of B816, which is a field synchronization header, and X data segment headers, 4716, are detected, the transmission synchronization detector 431 recognizes that valid TS are being received. Then, channel encoding and subsequent signal processing are carried out from a data segment having a field synchronization header B816.
Since the same operation is performed in the second transmitting station 470, synchronization is maintained even though there is more or less temporal difference from the signal inputted to the first transmitting station 430 and the starting point of data for processing can be synchronized.
The channel encoding process of the present invention is performed in a channel encoder 432, the structure of which is shown in
The TCM encoder 810 and the precoder 820 process input signals X1 and X2 in the conventional way and generate symbols. Here, each of the memory 830-832 is initialized at every M data fields, M being a natural number. The initialization is performed switching the input signals X1 and X2 in a switching unit 850.
That is, when the switching is performed as shown in the wave lines of the drawing, the signals of each of the memory 830-832 are used for performing exclusive OR instead of the input signals X1 and X2. This way, each of the memory 830-832 can be initialized to a ‘0’state, which is a null state. If each of the memory 830-832 of the trellis encoder 436 is initialized in each transmitting station, the subsequent data fields are generated in the same symbols.
The number M of data fields is a natural number that can be adjusted flexibly according to the communication channel environment between the transmitting station and each receiving stations. If the transmission channel environment is in good condition, M can be a large number. Otherwise, if it is in poor condition, M can be a small number. It is obvious to those skilled in the art that the value of M can be changed variously according to the communication environment of the terrestrial digital broadcasting system. Therefore, the present invention should be understood not limited to a particular M value.
Each of the memory 830-832 is initialized periodically by the switching operation in the switching unit 850. If the M values of all transmitting stations are the same, the trellis encoders 436 of the transmitting stations are initialized in the same period. Eventually, the signals inputted into the transmitting stations are the same, as described in
Meanwhile, an initial symbol is inserted in a predetermined period, i.e., a data field period M, instead of a data symbol in the switching unit 850. That is, instead of input signals X1 and X2, signals stored in each of the memory 830-832 are inputted to an input terminal to generate an initialization symbol. When each of the memory 830-832 is initialized, two initialization symbols are generated for one trellis encoder 436. Meanwhile, in the ATSC A.53, 12 trellis encoders are used during the channel encoding process. Thus, a total of 24 initialization symbols are generated and inserted in a period of M.
In the section of 24 initialization symbols, an error occurs. This error, however, can be corrected in an error correction unit of the receiving station. The longer the period, i.e., M, becomes, the smaller error occurs.
When the channel encoding is completed in the channel encoder, the broadcast data are transmitted to each broadcast coverage through a VBS modulator 440, a frequency up-converter 442, and a high-power amplifier 444. As each process is the same as that of the conventional technology, further description will be omitted.
As described above, the input signals into a plurality of transmitting stations are synchronized by inserting a field synchronization signal to TS which is inputted to the transmitting station in a predetermined period, the period being N data fields. The output signals of the transmitting stations are synchronized by initializing the memory of the trellis encoder of the transmitting station in a predetermined period, the period being M data fields.
Therefore, the input signals into the transmitting stations are all synchronized and the output signals therefrom are all synchronized. Therefore, all the transmitting stations can provide terrestrial digital broadcasting using the same single frequency. Since a frequency can be reused in nearby regions, the frequency utility efficiency can be increased and, also, diversity gain can be acquired by using a plurality of transmitting stations.
While the present invention has been described with respect to certain preferred embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.
Kim, Seung-Won, Ahn, Chieteuk, Park, Sung-Ik, Lee, Yong-Tae
Patent | Priority | Assignee | Title |
11224002, | Jul 16 2018 | Qualcomm Incorporated | Multi-cell notification zone single frequency network |
11496978, | Jun 07 2017 | Electronics and Telecommunications Research Institute | Gateway signaling method for frequency/timing offset, and device therefor |
11564190, | Jun 07 2017 | Electronics and Telecommunications Research Institute | Gateway signaling method for frequency/timing offset, and device therefor |
Patent | Priority | Assignee | Title |
5802107, | Sep 13 1996 | Zenith Electronics Corporation | Symbol rotator |
6744822, | Aug 14 2000 | Koninklijke Philips Electronics N V | FEC scheme for encoding two bit-streams |
7100182, | Jun 11 2001 | LG Electronics Inc. | Digital VSB transmission system |
7315579, | Feb 28 2001 | AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LIMITED | Trellis coded modulation tails |
7564905, | Dec 20 2002 | Electronics and Telecommunications Research Institute | System and method for providing terrestrial digital broadcasting service using single frequency network |
20020140867, |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Jul 21 2011 | Electronics and Telecommunications Research Institute | (assignment on the face of the patent) | / |
Date | Maintenance Fee Events |
Jan 06 2014 | ASPN: Payor Number Assigned. |
Mar 03 2017 | REM: Maintenance Fee Reminder Mailed. |
Jul 21 2017 | EXP: Patent Expired for Failure to Pay Maintenance Fees. |
Date | Maintenance Schedule |
Jul 02 2016 | 4 years fee payment window open |
Jan 02 2017 | 6 months grace period start (w surcharge) |
Jul 02 2017 | patent expiry (for year 4) |
Jul 02 2019 | 2 years to revive unintentionally abandoned end. (for year 4) |
Jul 02 2020 | 8 years fee payment window open |
Jan 02 2021 | 6 months grace period start (w surcharge) |
Jul 02 2021 | patent expiry (for year 8) |
Jul 02 2023 | 2 years to revive unintentionally abandoned end. (for year 8) |
Jul 02 2024 | 12 years fee payment window open |
Jan 02 2025 | 6 months grace period start (w surcharge) |
Jul 02 2025 | patent expiry (for year 12) |
Jul 02 2027 | 2 years to revive unintentionally abandoned end. (for year 12) |