[0001] The present invention generally relates to communications systems and, more particularly, to a television (TV) system.

[0002] One of the most difficult problems for receivers is in the initial signal acquisition of the received signal. In many cases, the received signal contains some "training" or "synchronization" data (herein after "training data") that is known ahead of time by the receiver for help in acquiring the received signal. This training data is used by the receiver to perform initial channel acquisition as well as channel equalization on the received signal. However, this training data is limited since it must be sent periodically in the transmitted signal and takes up valuable bandwidth. In this regard, the training signal period may be too short, especially in the presence of difficult multi-path conditions, to allow for adequate channel equalization and channel acquisition. As such, embedding training data into the broadcast signal for receiver synchronization is a tradeoff between bandwidth utilization and the size/quality of the training data.

[0003] For example, in an ATSC (Advanced Television Systems Committee) Digital Television (DTV) signal, the field sync sequence can be used as the training sequence for converging an equalizer of a DTV receiver, where the equalizer compensates for channel distortion. This field sync training signal is transmitted every 313 ATSC data segments, i.e., every ATSC data field (every 24.2 milliseconds). However, in the presence of multi-path conditions, the training signal period may be too short for the equalizer of the receiver to converge to a correct solution.

SUMMARY OF THE INVENTION

[0004] A method and system for signal acquisition for use in a receiver is provided. In accordance with the principles of the invention, the training data is sent to the receiver via an alternate connection, such as an internet connection.

[0005] In an illustrative embodiment of the invention, a receiver (1) requests data from a server, located on a first network, the data associated with a first broadcast signal; (2) receives the data from the server; (3) receives the first broadcast signal on a first broadcast channel, the first broadcast signal comprising a delayed version of the data; and (4) performs signal acquisition on the received first broadcast signal using the received data from the server. Advantageously, use of data from the server provides much more training data to be sent to the receiver without having to increase, or even use, bandwidth in the first broadcast signal for conveying training data.

[0006] In another illustrative embodiment of the invention, an apparatus comprises a network interface for receiving data from a server; a broadcast receiver for receiving a broadcast signal from a broadcast channel, the broadcast signal comprising a delayed version of the received data; wherein the broadcast receiver performs signal acquisition on the received broadcast signal using the received data.

[0007] In accordance with the principles of the invention, signal acquisition as used herein includes channel acquisition and/or channel equalization. For example, a demodulator of a receiver uses received training data from a server for performing at least one of carrier acquisition or timing acquisition for performing channel acquisition; and/or an equalizer of the receiver uses the received training data for performing channel equalization.

[0008] In view of the above, and as will be apparent from reading the detailed description, other embodiments and features are also possible and fall within the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 shows an illustrative embodiment in accordance with the principles of the invention;

[0010] FIG. 2 shows an illustrative portion of a DVB-T2 frame in accordance with the principles of the invention;

[0011 ] FIG. 3 shows an illustrative flow chart for use in a receiver in accordance with the principles of the invention;

[0012] FIG. 4 shows another illustrative embodiment in accordance with the principles of the invention;

[0013] FIG. 5 shows an illustrative table for use in a receiver in accordance with the principles of the invention;

[0014] FIG. 6 shows another illustrative flow chart for use in a receiver in accordance with the principles of the invention;

[0015] FIG. 7 shows an illustrative device in accordance with the principles of the invention; and [0016] FIG. 8 shows another illustrative embodiment of a receiver in accordance with the principles of the invention.

DETAILED DESCRIPTION

[0017] Other than the inventive concept, the elements shown in the figures are well known and will not be described in detail. For example, other than the inventive concept, a set-top box or digital television (DTV) and the components thereof, such as a front-end, Hilbert filter, carrier tracking loop, video processor, remote control, etc., are well known and not described in detail herein. In addition, other than the inventive concept, familiarity with networking and current and proposed recommendations for TV standards is assumed and not described herein. Such as, e.g., the Internet Protocol (IP), the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), IEEE 802.1, IEEE 802.1Q and IEEE 802. lp, the Dynamic Host Configuration Protocol (DHCP) (e.g., see Request for Comment (RFC) 2132, Network Working Group, "DHCP Options and BOOTP Vendor Extensions", March 1997), NTSC (National Television Systems Committee), PAL (Phase Alternation Lines), SECAM (SEquential Couleur Avec Memoire), ATSC (Advanced Television Systems Committee), Chinese Digital Television System (GB) 20600-2006, Digital Video Broadcasting (DVB-T2) and DVB-H. It should also be noted that the inventive concept may be implemented using conventional programming techniques, which, as such, will not be described herein. Finally, like-numbers on the figures represent similar elements.

[0018] As noted earlier, one of the most difficult problems for receivers is in the signal acquisition of the received signal. While the presence of training data in the received broadcast signal may help the receiver to acquire the received broadcast signal, in some situations, such as difficult multi-path conditions, the amount of received training data is either not enough to acquire the received broadcast signal or causes the receiver to take a long time to acquire the received broadcast signal. Since the presence of training data in the received broadcast signal already takes up bandwidth that could be better used for other purposes, simply increasing the amount of training data in the broadcast signal and further reducing the available bandwidth may not be a viable option to improve signal acquisition performance by the receiver. Therefore, and in accordance with the principles of the invention, training data is sent to the receiver via an alternate connection, such as an internet connection. [0019] An illustrative embodiment of the invention is shown in FIG. 1. In this illustrative embodiment, the receiver communicates with a server over the internet to access a portion of the broadcast signal before it is transmitted. The accessed data is just normal transmitted data. The key is that the receiver would now know the correct data before receiving it. With this approach, much more training data could be sent to the receiver without increasing the use of bandwidth in the transmitted signal. The illustrative embodiment of FIG. 1 comprises, in general, a transmitting portion, receiving portion and an internet (or network) portion. The transmitting portion is associated with a broadcaster (e.g., broadcaster 1) and comprises data delay 1 10, modulator 1 15 and antenna 1 16. The receiving portion is associated with, e.g., a digital television (DTV), and comprises antenna 140 and receiver 145. Finally, the internet portion comprises internet server 105, internet 130 and network interface 150. Only those portions relevant to the inventive concept are shown and described below. It should be also be noted that the elements shown in FIG. 1 do not have to be physically co-located. For example, network interface 150 may be physically separate from receiver 145.

[0020] For the transmitting portion, data 109 (e.g., a program being broadcast by broadcaster 1) is applied to data delay 110, which delays the data before application to modulator 115. In the context of this example, data 109 represents a DTV signal such as a DVB-T2 or ATSC transport stream comprising a plurality of packets conveying program and system information along with elementary streams, e.g., video and audio, representing one, or more, programs, as known in the art. Illustratively, a DVB-T2 compatible signal is assumed for data 109. This is illustrated in FIG. 2. As shown in FIG. 2, a DVB-T2 compatible signal is comprised of a sequence of super frames, each super frame comprising, at most, 256 T2 frames (numbered from 0 to 255). Each T2 frame is, at most, 250 milli- seconds long. Each T2 frame carries physical layer pipes (PLPs) and LI signaling (e.g., see ETSI EN 302 755 and ETSI TS 102 831). The PLPs carry the services, e.g., programs for viewing by a user. Returning to FIG. 1, it is assumed that modulator 1 15 performs any additional coding and modulates the delayed data 11 1 to provide a broadcast signal 1 16 for broadcast via antenna 120. For the receiving portion, e.g., a digital television (DTV), the broadcast signal is received via antenna 140 to provide a received signal 144 to receiver 145. The later performs signal acquisition on the received signal in accordance with the principles of the invention using data provided from the internet portion. After acquiring the received signal, receiver 145 provides data 146, which represents, e.g., the program transmitted by broadcaster 1 for viewing by a user on a display (not shown). Turning now to the internet portion, this comprises internet server 105, internet 130 and network interface 150. The internet 130, represented in FIG. 1 by the cloud symbol, is representative of any network, or collection of networks, for providing a packet-based transport system such as what has become known today as the internet. This network, or collection of networks, may be wired and/or wireless. Internet server 105 is a server as known in the art and is associated with broadcaster 1 and is coupled to the internet via path 106, which may be wired and/or wireless and include other servers/routers. Illustratively, the internet address associated with internet server 105 is also associated with broadcaster 1. Internet server 105 stores a portion of the bit stream (data 109) that is being broadcast (in delayed form) via antenna 120. The stored portion of the bit stream from data 109 is referred to hereafter as the "internet training data". This internet training data is a portion of the data about to be communicated, i.e., while the internet training data may include video information, it may also include header information, error-correction information, etc. As shown in FIG. 2, internet training data 195 comprises two DVB-T2 frames. However, any portion, or any number, of DVB-T2 frames can be used. Indeed, the amount of data included in the internet training data on internet server 105 can be fairly large, e.g., many thousands of bits such as 100K bits in size. Illustratively, the internet server would provide continuous access to all of the data about to be transmitted. Although the receiver could continuously poll the internet server for training data, it is assumed herein that the receiver only uses the training data for signal acquisition. After the signal is acquired, then the receiver has a baseline and only needs to track changes in the signal which is much easier and can be done with only the small amount of training data that is sent in the broadcast signal itself. The receiver could also try to monitor the quality of the received signal (e.g., bit error rate), and if it seemed to be getting bad, request some training data to reset its operating state. The internet training data on internet server 105 would be available for some time period before the respective portion of the bit stream is actually broadcast (e.g., 1 second). As such, in this example, data delay 110 provides a 1 second delay. Receiver 145 queries internet server 105 via network interface 150 to retrieve the internet training data, via internet 130, before this stored portion is actually broadcast. Network interface 150 is coupled to the internet via path 149, which may be wired and/or wireless and include other servers/routers. Receiver 145 then uses this retrieved data as a training signal for performing signal acquisition of the received broadcast signal from broadcaster 1 and for periodic high accuracy parameter updating.

[0021 ] An illustrative method for use in a receiver in accordance with the principles of the invention is shown in FIG. 3. In step 405, receiver 145 of FIG. 1 receives, e.g., from a user via a remote control (not shown), a request to change the channel to the channel associated with broadcaster 1. In step 410, receiver 145 requests, via network interface 150, associated internet training data from internet server 105. In step 415, receiver 145 receives the requested internet training data from internet server 105. In step 420, receiver 145 tunes to the requested channel to receive the broadcast signal, e.g., received signal 144. In step 425, receiver 145 performs signal acquisition on received signal 144 using the internet training data from internet server 150 to acquire the received signal and provide data 146 which represents at least the selected program for viewing by a user on a display (not shown).

[0022] As noted earlier, and in accordance with the principles of the invention, signal acquisition as used herein includes channel acquisition, e.g., by a demodulator of the receiver; and/or channel equalization, e.g., by an equalizer of the receiver. With respect to the equalizer, the equalizer uses the received training data for performing channel equalization. With respect to training, the process itself is well known and will not be described in detail herein. For example, when training data is included in the received broadcast signal (broadcast training data), the receiver uses the known training data sequence to generate an error signal for use in adapting tap coefficients of the equalizer. For example, the output of the equalizer, which represents the received broadcast training signal, with distortion, is compared to the known broadcast training signal to provide an error signal for further adapting the equalizer to reduce the channel distortion. In the case of internet training data, the same approach is used, i.e., the received portion of the broadcast data corresponding to the internet training data is compared to the internet training data for adapting the equalizer. Since there is now more training data, this will improve equalizer performance. Similarly, with respect to the demodulator, the demodulator uses received training data from a server for performing at least one of carrier acquisition or timing acquisition for performing channel acquisition. Like channel equalization, carrier acquisition and/or timing acquisition using training data is known in the art and is not described further herein. [0023] In terms of the receiver applying the internet training data to the correct portion of the received signal, this can be performed in any number of ways. For example in current systems, the training data that is included in the broadcast signal is aligned to the start of some "broadcast" frame (e.g., the PI symbol in the T2 frame in the DVB-T2 based system or the Sync signal in an ATSC-based system). On initial acquisition, the receiver does a correlation between the known training data and the received signal. When the correlation exceeds some threshold, the receiver knows it has found the corresponding training sequence in the received broadcast signal and therefore now knows where it is in the received signal since it knows the signal structure. In a practical system using training data over the internet, something similar is performed, i.e., the received internet training data is lined up with a received broadcast frame. However, it does not necessarily have to be performed this way. For example, a frame offset could be sent along with the training data. This way, the data in the received broadcast frame can be located that corresponds to the internet training data even if it is not aligned with a frame boundary.

[0024] Although FIG. 3 shows a flow chart in the context of a channel change at the DTV, the request for internet training data from the internet server can also be performed by the DTV at other times, e.g., at startup, or at intervals of time thereafter (periodically, or aperiodically). In this context, e.g., equalizer parameters can be occasionally updated to improve the accuracy of the equalizer.

[0025] Another illustrative embodiment is shown in FIG. 4 and provides for the inclusion of a plurality of broadcasters as represented by broadcasters 200-1 (Bi), 200-2 (B ₂ ) and 200-3 (B ₃ ). In this example, broadcaster 200-1 transmits a signal 201-1 on channel 1 (CHi), broadcaster 200-2 transmits a signal 201-2 on channel 2 (CH ₂ ) and a broadcaster 200- 3 transmits a signal 201-3 on channel 3 (CH ₃ ). In accordance with the principles of the invention a DTV 210 can be tuned to each of these channels for receiving programming conveyed thereon and DTV 210 has an internet connection (wired and/or wireless) for coupling to path 215. DTV 210 performs the method illustrated by the flow chart shown in FIG. 3. For example, when a user (not shown) selects, via a remote control (not shown), to view programming from broadcaster 2 (i.e., channel change step 405 of FIG. 3), DTV 210 then requests internet training data from the associated server, in this example represented by B ₂ server 220-2 (step 410 of FIG. 3). As illustrated in FIG. 3, DTV 210 can access the associated servers of various broadcasters via path 215. The latter is representative of an internet connection and represents servers/routers of a data network and can be wired and/or wireless. As also shown in FIG. 4, broadcaster 1 has an associated Bi Server 220-1 and broadcaster 3 has an associated B ₃ server 220-3. As described with respect to FIG. 1, each server stores a portion of the signal being transmitted (in delayed form) by that broadcaster for use as internet training data. When DTV 210 receives the internet training data from server 220-2 (step 415 of FIG. 3), DTV 210 tunes to channel 2 of broadcaster 200-2 (step 420 of FIG. 3). As known in the art, the frequency assignments for the channels of each broadcaster are known a priori depending on the geographical location of DTV 210. After tuning to channel 2, DTV 210 performs signal acquisition on signal 201-2 using the received internet training data from B ₂ server 220-2. It should be noted that although FIG. 4 illustrates the use of separate servers for each broadcaster, the inventive concept is not so limited and, e.g., one server could be used for more than one broadcaster.

[0026] In the context of a plurality of broadcasters, it is assumed that DTV 210 stores a table of addresses as shown in FIG. 5. Table 400 provides a list of broadcasters that support the provisioning of internet training data. As can be observed from table 400, channel 1 of broadcaster Bi is associated with internet address www.broadcasterl.com, channel 2 of broadcaster B ₂ is associated with internet address www.broadcaster2.com and channel 3 of broadcaster B ₃ is associated with internet address www.broadcaster3.com. It is assumed that the IP (Internet Protocol) addresses shown in table 400 are appropriately translated by a DNS server (domain name server) (not shown) when these IP addresses are used by DTV 210. When DTV 210 receives a request to change channels, e.g., to channel 2 of broadcaster 2, DTV 210 illustratively also performs the flow chart shown in FIG. 6 after step 410 of FIG. 3. In step 450, DTV 210 checks table 400 of FIG. 5 to see if there is an entry for the selected channel. In this example, since channel 2 was selected, table 400 shows a corresponding entry for an internet address for an associated server. Since internet training data is available, DTV 210 continues with step 410 of FIG. 3. If internet training data is not available, DTV 210 only uses the training data in the received broadcast signal in step 455 after tuning to broadcaster 2. Various modifications to table 400 of FIG. 5 can be made in accordance with the principles of the invention. For example, instead of using the channel identifier, a broadcaster name could be used.

[0027] The IP address information of associated servers shown in table 400 of FIG. 5 can be initialized in a variety of ways. For example, since the DTV has an internet connection, the simplest way is to have a central server with this information that the DTV could access. The DTV would need to know its general location (e.g., IP address) and then the DTV could find all of the potential channels in its area along with their internet server addresses. This could be performed as a part of initialization of the DTV. The general location can be, e.g., provided as a factory setting in the DTV, or entered by the user into the DTV using a remote control based upon information from, e.g., user documentation for the DTV. Alternatively, the DTV may have access to smart applications (smart apps) via the internet connection, where, e.g., there is a smart app for each channel to initialize the IP address information for each channel. As another example, this information can be acquired from broadcasters individually by viewing a respective webpage of a broadcaster that indicates this feature is available and that lists the corresponding IP address, which is then entered by a user via the remote control of DTV 210 via a user interface screen (not shown). As yet another example, the information can be provided in the program and system information (PSIP) conveyed in the transport stream of the broadcast signal when DTV 210 first tunes to a channel of a broadcaster. There is a drawback to this approach, since the first time DTV 210 tunes to a channel, the broadcast training data may have to be used, subsequent tunings to the channel can then use the internet training data if available.

[0028] A high-level block diagram of an illustrative device in accordance with the principles of the invention is shown in FIG. 7. Device 500 (e.g., a television) includes a receiver 510 and a display 520. Illustratively, receiver 510 is a DVB-T2 compatible receiver. (However, the inventive concept is not so limited and receiver 510 could alternatively be described in the context of being ATSC compatible.) Receiver 510 receives a broadcast signal 144 (e.g., via an antenna not shown) for processing to recover therefrom, e.g., an HDTV (high definition TV) video signal for application to display 520 for viewing video content thereon. Device 500 is a processor-based system and includes one, or more, processors and associated memory as represented by processor 560 and memory 565 shown in the form of dashed boxes in FIG. 7. In this context, computer programs, or software, (e.g., representing the flow charts of FIGs. 3 and 6) are stored in memory 565 for execution by processor 560. As noted, processor 560 is representative of one, or more, stored-program control processors and these do not have to be dedicated to any one particular function of device 500, e.g., processor 560 may also control other functions of the device. Memory 565 is representative of any storage device, e.g., random-access memory (RAM), read-only memory (ROM), etc.; may be internal and/or external to the device; and is volatile and/or non-volatile as necessary.

[0029] Another illustrative embodiment of a receiver 300 in accordance with the principles of the invention is shown in FIG. 8. Only that portion of receiver 300 relevant to the inventive concept is shown. Receiver 300 includes radio frequency (RF) front end 305, analog-to-digital (A/D) converter 310, demodulator 315, equalizer 320, processor 350, network interface 355 and memory 360. Other than the inventive concept, the functions of the various elements shown in FIG. 8 are well known and will only be described very briefly herein. Processor 350 is representative of one or more microprocessors and/or digital signal processors (DSPs) and may include memory for executing programs and storing data. In this regard, memory 360 is representative of memory in receiver 300 and includes, e.g., any memory of processor 350. An illustrative bidirectional data and control bus 301 couples various ones of the elements of receiver 300 together as shown. Bus 301 is merely representative, e.g., individual signals (in a parallel and/or serial form) may be used, etc., for conveying data and control signaling between the elements of receiver 300.

[0030] RF front end 305 down-converts and filters the signal 304 received via an antenna (not shown) to provide a near base-band signal to A/D converter 310, which samples the down converted signal to convert the signal to the digital domain and provide a sequence of samples 31 1 to demodulator 315. The latter comprises automatic gain control (AGC), symbol timing recovery (STR), carrier tracking loop (CTL), and other functional blocks as known in the art for demodulating signal 31 1 to provide demodulated signal 316, which represents a sequence of signal points in a constellation space, to equalizer 320. The equalizer 320 processes demodulated signal 316 to correct for distortion, e.g., inter-symbol interference (ISI), etc., and provides equalized signal 321. This signal is further processed by receiver 300 as known in the art (as represented by ellipses 391) to eventually recover the program on the selected channel for viewing by a user on a display (not shown).

[0031 ] In accordance with the principles of the invention, processor 350 controls demodulator 315 and/or equalizer 320 to utilize internet training data for performing signal acquisition (channel acquisition and/or channel equalization). For example, processor 350 controls the training mode of equalizer 320 via control signal 353. In this context, processor 350 performs the flow charts of FIGs. 3 and 6 to determine if training data from the internet is available via network interface 355. If internet training data is available then equalizer 320 is trained using the internet training data. Use of the broadcast training data in the received broadcast signal is optional. If internet training data is not available, then only the training data in the received broadcast signal is used to train equalizer 320.

[0032] As described above, and in accordance with the principles of the invention, a receiver receives training data from an alternate connection, such as an internet connection, for use in performing signal acquisition of a broadcast signal received from a broadcast channel. Advantageously, use of training data from the alternate connection provides much more training data to be sent to the receiver without having to increase, or even use, bandwidth in the first broadcast signal for training data. In fact, it may be possible to reduce, if not eliminate, the training data included in the broadcast signal to free up additional bandwidth for other services.

[0033] It should be noted that illustratively only a portion of the program being broadcasted is used as training data. The internet primarily provides a broadband one-to-one connection. As such, it may not be practical to distribute the entire program as training data via the internet since the internet is not at this time conducive to a one-to-many distribution as is a broadcast network.

[0034] In view of the above, the foregoing merely illustrates the principles of the invention and it will thus be appreciated that those skilled in the art will be able to devise numerous alternative arrangements which, although not explicitly described herein, embody the principles of the invention and are within its spirit and scope. For example, although a possible size of the training data was indicated as 100K bits, other sizes for the training data are possible and can be less, or more, than 100K bits. Indeed, in accordance with the principles of the invention, as much training data as required by the receiver may be provided. In addition, although illustrated in the context of a DTV, the inventive concept is also applicable to a mobile television receiver where the internet connection is provided via a cellular phone service. Also, although illustrated in the context of separate functional elements, these functional elements may be embodied in one, or more, integrated circuits (ICs). Similarly, although shown as separate elements, e.g., network interface 150, any or all of the elements may be implemented in a stored-program-controlled processor, e.g., a digital signal processor, which executes associated software, e.g., corresponding to one, or more, of steps. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention.