The present invention relates generally to wirelessly sending and receiving information about programming provided by satellite signals, and more specifically, to wirelessly sending and receiving satellite programming information about programs carried by multiple satellite digital radio signals to multiple satellite digital radio receivers.
Trucks, boats, automobiles and other vehicles are commonly equipped with various signal communication devices such as radios for receiving broadcast radio frequency (RF) signals, processing the RF signals, and broadcasting audio information to passengers. Satellite digital audio radio (SDAR) services have become increasingly popular, offering digital radio service covering large geographic areas, such as North America. Other geographic areas, such as Europe, are also beginning to offer SDAR services. These services typically receive uplinked programming which, in turn, is provided to subscriber RF receivers via satellites or terrestrial receivers. Each subscriber to the service generally possesses a digital radio having an RF receiver and one or more antennas for receiving the digital broadcast.
In satellite digital audio radio services systems, the radio RF receivers are generally configured to tune to certain frequencies, receive digital data signals at those frequencies, and decode the digital data signals, which typically include many channels of digital audio. In addition to broadcasting the encoded digital quality audio signals, the satellite service may also transmit data that may be used for various other applications. The broadcast signals may include advertising, information about warranty issues, information about the broadcast audio programs, and news, sports, and entertainment programming. Thus, the digital broadcasts may be employed for any of a number of satellite audio radio, satellite television, satellite Internet, and various other consumer services.
The broadcast signals typically take the form of multiple data streams that are transmitted at different frequencies. Each of the multiple data streams that are transmitted at different frequencies are broken into frames for transmitting data.
In a typical system, data slots 36 are assigned to provide channels of information, such as, for example, audio channels. For example, slots 10 and 11 could be assigned to provide a music channel “A”. In this example, subscribers who wish to listen to music channel “A” would select channel “A” on their receiver. The receiver would tune to the RF frequency on which data stream 6 is transmitted, and would decode the data present in slots 10 and 11 of each data frame 30 that is received to provide audio to the subscribers. It should be appreciated that the receiver is able to identify the location of slots 10 and 11 of data stream 6 by knowing the location of the frame synchronization symbol 32, and position of slots 10 and 11 of data stream 6 relative to the frame synchronization symbol 32.
As noted above, the SDAR system is typically configured to provide multiple streams of data at various frequencies, each stream of which can contain multiple channels of information.
What is needed is a method for transmitting and receiving SDAR channel directory information for multiple SDAR data streams that minimizes the system bandwidth required while reducing the amount of time needed to receive complete directory information in system receivers.
In accordance with one aspect of the present invention, a system for sending and receiving satellite channel information is provided. The system includes a transmitter configured to transmit multiple RF satellite signals at different frequencies. The RF satellite signals include multiple data frames including frame synchronization symbols. The frame synchronization symbols occur at different times in the multiple RF satellite signals. Data slots in the data frames are positioned in the frames relative to the frame synchronization symbols. The system also includes satellite channel information located in a designated data slot in the data frames. The designated data slot is positioned within each data frames such that said designated slot in each of said multiple RF satellite signals occurs at different times in each of the multiple RF satellite signals. The system also includes a receiver configured to receive multiple RF satellite signals and monitor designated data slots to extract satellite channel information.
In accordance with another aspect of the present invention, a method for sending and receiving satellite channel information is provided. The method includes the step of providing at least first and second RF satellite signals at first and second RF frequencies, respectively. The method also includes the steps of providing multiple data frames in each of the at least first and second RF satellite signals, and providing frame synchronization symbols within the multiple data frames such that the frame synchronization symbols of the at least first RF satellite signal are offset in time from the frame synchronization symbols of the at least second RF satellite signal. The method further includes the step of providing data slots within the multiple data frames that are positioned within each data frame relative to the frame synchronization symbol of the data frame in which the multiple data frames are located. The method still further includes the step of providing satellite channel information in at least one designated data slot of each data frame, such that the slots containing satellite channel information in the at least first RF satellite signal are offset in time from the slots containing satellite channel information in the at least second RF satellite signal.
In accordance with yet another aspect of the present invention, a method for sending and receiving satellite channel program information is provided. The method includes the step of providing at least four RF satellite signals, each at its own RF frequency, to multiple RF receivers. The method also includes the step of providing multiple, periodically repeating, data frames in each of the satellite signals. The method further includes the steps of providing frame synchronization symbols in each of the data frames of the satellite signals, such that the frame synchronization symbols in each of the satellite signals occur at a different time than the frame synchronization symbols of the other satellite signals.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
In the present embodiment, terrestrial repeater 8 employs forward error correction codes and a modulation scheme that are the same as those employed in satellites 10. In an alternate embodiment, forward error correction codes and modulation schemes employed by terrestrial repeater 8 are different than those employed by satellites 10. Although not specifically shown in
As shown, the satellite transmitters 16 include processing circuitry 17 coupled to transmit circuitry 25. Processing circuitry 17 includes logic 19 coupled to memory 21, in which is stored a transmit algorithm 23. Processing circuitry 17 of transmitter 16 receives programming signals from an external source, executes the transmit algorithm 23 in logic 19 to format the programming signals for transmission, and provides the formatted signals to transmit circuitry 25 for transmission. Satellite transmitters 16 are configured to transmit the multiple data streams 40-43 of
Satellite receiver 24 includes receiver circuitry 35 coupled to receive processing circuitry 27. Receiver circuitry 35 receives signals transmitted from transmitters 16, and provides the signals to receive processing circuitry 27 for decoding. Receive processing circuitry 27 includes logic 29 and memory 31 in which receive algorithm 33 is located. Logic 29 executes algorithm 33 to decode the signals received from receive circuitry 35, and provide output to users of satellite receiver 24. Satellite receiver 24 is configured to monitor non-overlapping, designated channels in streams 40-43 that contain satellite channel information in the form of erasure codes, and to extract satellite channel information from the monitored, non-overlapping channels, as discussed below. In the present embodiment, the satellite receiver 24 is configured in this manner by programming the memory 31 located in the satellite receiver 24, such that logic 29 monitors designated non-overlapping channels in streams 40-43, extracts the channel information in the form of erasure codes, and decodes the erasure codes to provide channel information. In an alternate embodiment, satellite receiver 24 is configured to operate in this manner by configuring logic and/or discrete circuit elements in the satellite receiver 24.
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In the present embodiment of the invention, slots 1 and 2 of each of data frames 50, 60, 70, and 80, referred to for convenience as slot groups 53, 63, 73, and 83, are configured by the transmitter in the system to include satellite channel information for data streams 40-43 of the system. Receivers in the system are configured to know that slots 1 and 2 of each of streams 40-43 contain satellite channel information. Receivers in the system are also configured to know the amount of time between frame synchronization symbols of the various streams, and therefore, the location of slots 1 and 2 in each of streams 40-43. Receivers in the system are configured to gather satellite channel information from slot groups 53, 63, 73, and 83 by changing frequencies during periods in which the receivers are not monitoring a given slot for other programming information. This allows the receivers to gather satellite channel information from slot groups 53, 63, 73, and 83 without negatively impacting the reception of desired programming information. Due to the offset nature of the frame synchronization symbols 52, 62, 72, and 82 of streams 40-43 and the offset of the slots 1-104 in each of streams 40-43, receivers in the system are configured to receive satellite channel information at least three times during each frame period 96.
For example, if a user of a receiver is monitoring program information that is being transmitted in slot group 54 of stream 40 (i.e., slots 26 and 27 of data frame 50 of stream 40), and wishes to obtain satellite channel information about programs being broadcast on other slots of stream 40, or other slots of streams 41, 42 and 43, the receiver is configured to switch, when it is not monitoring slot group 54, to other streams to receive and decode satellite channel information transmitted in slots 1 and 2 of those streams (i.e. slot groups 63, 73 and 83), as well as slot group 53 of stream 40. More specifically, after the receiver has received the data in slot group 54 in a given data frame 50, the receiver may switch to other frequencies (i.e., streams) to monitor various channels without impacting the programming being received in slot group 54. In the present example, the receiver, after receiving slot group 54 in a given data frame 50, switches to stream 42 to receive satellite channel information provided in slot group 73 of stream 42, switches to stream 43 to receive satellite channel information in slot group 83 being broadcast in stream 43, and switches back to stream 40 to receive satellite channel information being broadcast in slot group 53 of stream 40. The receiver then utilizes the information gathered from the slot groups 73, 83 and 53 containing the satellite channel information to decode the programming guide and provide satellite programming information to the user. It should be appreciated that the receiver is configured to switch to other frequencies and gather the satellite channel information, after which time it can switch back to the frequency and channel that it had previously been monitoring in time to receive the next data packet provided in that slot group (in this case, slot group 54). It should also be noted that the information in slot 63 of stream 41 has been lost due to the fact that the receiver is receiving slot 54 of stream 40 during that time.
The satellite channel information provided by the satellite transmitter in the slot groups 53, 63, 73, and 83 is provided using an erasure code. More specifically, in the present embodiment, the information is provided in the form of a digital fountain code that is programmed into each of the slot groups 53, 63, 73, and 83. The nature of erasure codes, and more specifically, digital fountain codes, is that a receiver can reconstruct a message sent using erasure codes in multiple packets, regardless of the order in which the multiple packets are received. Based on this, the receiver of the present embodiment can be configured to reconstruct the transmitted satellite channel information through streams 40, 41, 42 and 43 sent in slot groups 53, 63, 73, and 83, provided that it receives a sufficient number of packets, regardless of the order in which these packets were received. In the present embodiment, the transmitter is configured to divide the satellite programming information into erasure codes, and program those erasure codes into slot groups 53, 63, 73, and 83, such that a receiver receiving three or more slot groups, regardless of order, can reconstruct the transmitted satellite channel information. Therefore, in the previous example, even though slot 63 was lost, information received in slot groups 53, 73, and 83 is sufficient to reconstruct the transmitted satellite channel information.
As discussed above, by offsetting the frame synchronization symbols, and therefore the frames, of the separate streams 40-43, as generally illustrated in
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The above description is considered that of the preferred embodiments only. Modifications of the invention will occur to those skilled in the art, and to those who make or use the invention. Therefore, it is understood that the embodiments shown in the drawings and described above are merely for illustrative purposes, and not intended to limit the scope of the invention, which is defined by the following claims, as interpreted according to the principles of patent law, including the doctrine of equivalents.
Number | Name | Date | Kind |
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6442385 | Marko | Aug 2002 | B1 |
6798791 | Riazi et al. | Sep 2004 | B1 |
20070133420 | Guven et al. | Jun 2007 | A1 |
Number | Date | Country | |
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20080019297 A1 | Jan 2008 | US |