# Patent

## Title
Dual layer signal processing in a layered modulation digital signal system

## Abstract

Systems and methods for receiving layered modulation for digital signals are presented. An exemplary apparatus comprises a tuner for receiving a layered signal and producing a layered in-phase signal and a layered quadrature signal therefrom, an analog-to-digital converter for digitizing the layered in-phase signal and the layered quadrature signal and a processor for decoding the layered in-phase signal and the layered quadrature signal to produce one or more discrete layer signals.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of Utility application Ser. No. 10/068,047, by Ernest C. Chen, Tiffany F. Furuya, Philip R. Hilmes, and Joseph Santoru, entitled “DUAL LAYER SIGNAL PROCESSING IN A LAYERED MODULATION SIGNAL SYSTEM,” filed Feb. 5, 2002, now U.S. Pat. No. 7,173,981 which is a continuation-in-part application and claiming the benefit under 35 U.S.C. Section 120 of the following co-pending and commonly-assigned U.S. utility patent application, which is incorporated by reference herein:
Utility application Ser. No. 09/844,401, filed Apr. 27, 2001, now U.S. Pat. No. 7,209,524 by Ernest C. Chen, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”.
This application is related to the following co-pending and commonly-assigned U.S. patent applications, which is incorporated by reference herein:
Application Ser. No. 10/068,039, filed Feb. 5, 2002, by Ernest C. Chen et al., entitled “PREPROCESSING SIGNAL LAYERS IN A LAYERED MODULATION DIGITAL SIGNAL SYSTEM TO USE LEGACY RECEIVERS”.
This application is related to the following applications:
Application Ser. No. 11/653,517, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Jan. 16, 2007, by Ernest C. Chen, which is a continuation of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/165,710, entitled “SATELLITE TWTA ON-LINE NON-LINEARITY MEASUREMENT,” filed on Jun. 7, 2002, by Ernest C. Chen, which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIG ITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/236,414, entitled “SIGNAL, INTERFERENCE AND NOISE POWER MEASUREMENT,” filed on Sep. 6, 2002, by Ernest C. Chen and Chinh Tran, which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/693,135, entitled “LAYERED MODULATION FOR ATSC APPLICATIONS,” filed on Oct. 24, 2003, by Ernest C. Chan, which claims benefit to Provisional Patent Application 60/421,327, filed Oct. 25, 2002 and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/913,927, entitled “CARRIER TO NOISE RATIO ESTIMATIONS FROM A RECEIVED SIGNAL,” filed on Aug. 5, 2004, by Ernest C. Chen, which is a continuation in part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 11/619,173, entitled “PREPROCESSING SIGNAL LAYERS IN LAYERED MODULATION DIGITAL SIGNAL SYSTEM TO USE LEGACY RECEIVERS,” filed Jan. 2, 2007, which is a continuation of application Ser. No. 10/068,039, entitled “PREPROCESSING SIGNAL LAYERS IN LAYERED MODULATION DIGITAL SIGNAL SYSTEM TO USE LEGACY RECEIVERS,”filed on Feb. 5, 2002, by Ernest C. Chen, Tiffany S. Funiya, Philip R. Hilmes, and Joseph Santoru now issued as U.S. Pat. No. 7,245,671, which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/693,421, entitled “FAST ACQUISITION OF TIMING AND CARRIER FREQUENCY FROM RECEiVED SIGNAL,” filed on Oct. 24, 2003, by Ernest C. Chen, now issued as U.S. Pat. No. 7,151,807, which claims priority to Provisional Patent Application Ser. No. 60/421,292, filed Oct. 25, 2002, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/692,491, entitled “ONLINE OUTPUT MULTIPLEXER FILTER MEASUREMENT,” filed on Oct. 24,2003, by Ernest C. Chen, which claims priority to Provisional Patent Application 60/421,290, filed Oct. 25, 2002, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/691,032, entitled “UNBLIND EQUALIZER ARCHITECTURE FOR DIGITAL COMMUNICATION SYSTEMS;” filed on Oct. 22, 2003, by Weizheng W. Wang, Tung-Sheng Lin, Ernest C. Chen, and William C. Lindsey, which claims priority to Provisional Patent Application Ser. No. 60/421,329, filed Oct. 25, 2002, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/962,346, entitled “COHERENT AVERAGING FOR MEASURING TRAVELING WAVE TUBE AMPLIFIER NONLINEARITY,” filed on Oct. 8, 2004, by Ernest C. Chen, which claims priority to Provisional Patent Application Ser. No. 60/510,368, filed Oct. 10, 2003, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 11/655,001, entitled “AN OPTIMIZATION TECHNIQUE FOR LAYERED MODULATION,” filed on Jan. 18, 2007, by Weizheng W Wang, Guancai Zhou, Tung-Sheng Lin, Ernest-C. Chen, Joseph Santoru, and William Lindsey, which claims priority to Provisional Patent Application 60/421,293, filed Oct. 25, 2002, and which is a continuation of application Ser. No. 10/693,140, entitled “OPTIMIZATION TECHNIQUE FOR LAYERED MODULATION,” filed on Oct. 24, 2003, by Weizheng W. Wang, Guancai Zhou, Tung-Sheng Lin, Ernest C. Chen, Joseph Santoru, and William Lindsey, now issued as U.S. Pat. No. 7,184,489, which is a continuation-in-part of application Ser. No. 09/844,401, entitled “AYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 11/656,662, entitled “EQUALIZERS FOR LAYERED MODULATION AND OTHER SIGNALS,” filed on Jan. 22, 2007, by Ernest C. Chon, Tung-Sheng Lin, Weizheng W. Wang. and William C. Lindsey, which claims priority to Provisional Patent Application 60/421,241, filed Oct. 25, 2002, and which i5 a continuation of application Ser. No. 10/691,133, entitled “EQUALIZERS FOR LAYERED MODULATED AND OTHER SIGNALS,” filed on Oct. 22,2003, by Ernest C. Chen, Tung-Sheng Un, Weizheng W. Wang, and William C. Lindsey, now issued as U.S. Pat. No. 7,184,473, which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/961,579, entitled “EQUALIZATION FOR TWTA NONLINEARITY MEASUREMENT” filed on Oct. 8, 2004, by Ernest C. Chen, which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODUlATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/532,632, entitled “LOWER COMPLEXITY LAYERED MODULATION SIGNAL PROCESSOR,” flied on Apr. 25, 2005, by Ernest C. Chen, Weizheng W. Wang, Tung-Sheng Lin, Guangcai Zhou, and Joseph Santoru, which is a National Stage Application of PCT US03/32264, filed Oct. 10, 2003, which claims priority to Provisional Patent Application 60/421,331, entitled “LOWER COMPLEXITY LAYERED MODULATION SIGNAL PROCESSOR,” filed Oct. 25, 2002, by Ernest C. Chen, Weizheng W. Wang, Tung-Sheng Lin, Guangcai Zhou, and Joseph Santoru, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/532,631, entitled “FEEDER LINK CONFIGURATIONS TO SUPPORT LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 25, 2005, by Paul R. Anderson, Joseph Santoru and Ernest C. Chen, which is a National Phase Application of PCT US03/33255, filed Oct. 20, 2003, which claims priority to Provisional Parent Application 60/421,328, entitled “FEEDER LINK CONFIGURATIONS TO SUPPORT LAYERED MODULATION FOR DIGITAL SIGNALS,” filed Oct. 25, 2002, by Paul K. Anderson, Joseph Santoru and Ernest C. Chen, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FQR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/532,619, entitled “MAXIMIZING POWER AND SPECTRAL EFFICIENCIES FOR LAYERED AND CONVENTIONAL MODULATIONS,” filed on Apr. 25, 2005, by Ernest C. Chen, which is a National Phase Application of PCT Application US03/32800, filed Oct. 16, 2003, which claims priority to Provisional Patent Application 60/421,288, entitled “MAXIMIZING POWER AND SPECTRAL EFFICIENCIES FOR LAYERED AND CONVENTIONAL MODULATION,” filed Oct. 25,2002, by Ernest C. Chen and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS;” filed on Apr. 27,2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524,
Application Ser. No. 10/532,524, entitled “AMPLITUDE AND PHASE MATCHING FOR LAYERED MOD ULATION RECEPTION,” filed on Apr. 25, 2005, by Ernest C. Chen, jeng-Hong Chen, Kenneth Shurn, and Joungheon Oh, which is a National Phase Application of PCT Application US03/31199, filed Oct. 3, 2003, which claims priority to Provisional Patent Application 60/421,332, entitled “AMPLITUDE AND PHASE MATCHING FOR LAYERED MODULATION RECEPTION,” filed Oct. 25, 2002, by Ernest C. Chen, Jeng-Hong Chen, Kenneth Shum, and Joungheon Oh, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524, and also claims priority to;
Application Ser. No. 10/532,582, entitled “METHOD AND APPARATUS FOR TAILORING CARRIER POWER REQUIREMENTS ACCORDING TO AVAILABILiTY IN LAYERED MODULATION SYSTEMS,” filed on Apr. 25, 2005, by Ernest C. Chen, Paul K. Anderson and Joseph Santoru, now issued as U.S. Pat. No. 7,173,977, which is a National Stage Application of PCT Application US03/32751, filed Oct. 15, 2003, which claims priority to Provisional Patent Application 60/421,333, entitled “METHOD AND APPARATUS FOR TAILORING CARRIER POWER REQUIREMENTS ACCORDING TO AVAILABILITY IN LAYERED MODULATION SYSTEMS,” filed Oct. 25, 2002, by Ernest C. Chen, Paul R. Anderson and Joseph Santoru, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/532,509, entitled “ESTIMATING THE OPERATING POINT ON A NONLINEAR TRAVELING WAVE TUBE AMPLIFIER,” filed on Apr. 25, 2005, by Ernest C. Chen and Shamik Maitra, now issued as U.S. Pat. No. 7,230,480, which is a National Stage Application of PCT Application US03/33130 filed Oct. 17, 2003, and which claims priority to Provisional Patent Application 60/421,289, entitled “ESTIMATING THE OPERATING POINT ON A NONLINEAR TRAVELING WAVE TUBE AMPLIFIER,” filed Oct. 25, 2002, by Ernest C. Chen and Shamik Maitra, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/519,322, entitled “IMPROVING HIERARCHICAL 8PSK PERFORMANCE,” filed on Dec. 23, 2004 by Ernest C. Chen and Joseph Santoru, which is a National Stage Application of PCT US03/020862 filed Jul. 1, 2003, which claims priority to Provisional Patent Application 60/392,861, filed Jul. 1, 2002 and Provisional Patent Application 60/392,860, filed Jul. 1, 2002, and which is also related to application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
Application Ser. No. 10/519,375, entitled “METHOD AND APPARATUS FOR LAYERED MODULATION,” filed on Jul. 3, 2003, by Ernest C. Chen and Joseph Santoru, which is a National Stage Application of PCT US03/20847, filed Jul. 3, 2003, which claims priority to Provisional Patent Application 60/393,437 filed Jul. 3, 2002, and which is related to application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS,” filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524; and
Application Ser. No. 10/692,539, entitled “ON-LINE PHASE NOISE MEASUREMENT FOR LAYERED MODULATION”, filed Oct. 24, 2003, by Ernest C. Chen, which claims priority from Provisional Patent Application 60/421,291, filed Oct. 25, 2002, entitled “ON-LINE PHASE NOISE MEASUREMENT FOR LAYERED MODULATION”.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to systems for receiving digital signals, and in particular, to systems for receiving layered modulation in digital signals.
2. Description of the Related Art
As various digital signal communication systems and services evolve, there is a burgeoning demand for increased data throughput and added services. However, it is more difficult to implement improvements in old systems and new services when it is necessary to replace existing legacy hardware, such as transmitters and receivers. New systems and services are advantaged when their appearance does not render legacy hardware obsolete. In the realm of wireless communications, this principle is further highlighted by the limited availability of electromagnetic spectrum. Thus, it is not possible (or at least not practical) to merely transmit enhanced or additional data at a new frequency.
The conventional method of increasing spectral capacity is to move to a higher-order modulation, such as from quadrature phase shift keying (QPSK) to eight phase shift keying (8PSK) or sixteen quadrature amplitude modulation (16QAM). Unfortunately, QPSK receivers cannot demodulate 8PSK or 16QAM signals. As a result, legacy customers with QPSK receivers must upgrade their receivers in order to continue to receive any signals transmitted with an 8PSK or 16QAM modulation.
Layered modulation enables systems and methods of transmitting signals to accommodate enhanced and increased data throughput without requiring additional frequency bands. Systems using layered modulation can provide enhanced and increased throughput signals for new receivers while remaining compatible with legacy receivers. Newer layered modulation techniques (such as detailed in U.S. patent application Ser. No. 09/844,401, filed Apr. 27, 2001, and entitled “LAYERED MODULATION FOR DIGITAL SIGNALS) also provide the unique advantage of allowing transmission signals to be upgraded from a source separate from the legacy transmitter. In other words, the layered signals can be asynchronous and/or non-coherent.
Related receiver systems for layered signals have also been described, such as those found in U.S. Pat. No. 4,039,961, which is incorporated by reference herein. However, such receiver systems are based on analog circuits, synchronized by a voltage control oscillator. In addition, such receiver systems are limited because they are designed to only receive coherent layered signals, i.e. signals that are synchronously produced.
Furthermore, because additional signal processing usually introduces unwanted noise, it is also important to minimize the amount of processing performed on a received signal. A single processor which accommodates high speed decoding of the multiple layers introduces a minimum of additional noise. A processor that can demodulate and decode a layered signal into distinct signal layers, enables separate downstream transports (e.g. MPEG decoders) to directly receive less noisy signals.
There is a need for systems and methods for receiving and processing the layered modulation signals. There is also a need for systems and methods for decoding layered signals digitally. There is further a need for a single integrated processor for decoding distinct signals of a layered signal. The present invention meets these needs.
SUMMARY OF THE INVENTION
The present invention provides a flexible and expandable apparatus that can be implemented with high speed logic circuit capable of performing demodulator functions and processing of received layered modulation signals in real-time. The invention utilizes high speed digitization of the incoming signal to prepare it for further high speed digital processing. The digital processing demodulates and decodes the distinct layers of layered signal. The invention enables a receive system architecture wherein the incoming layered signal is processed by a single decoder to produce distinct layer signals for further decoding, thereby minimizing signal noise and cost. The processor can be included in a single integrated receiver/decoder (IRD) further comprising a separate transport for each decoded signal layer.
An exemplary apparatus comprises a tuner for receiving a layered signal and producing a layered in-phase signal and a layered quadrature signal therefrom, an analog-to-digital converter for digitizing the layered in-phase signal and the layered quadrature signal and a processor for decoding the layered in-phase signal and the layered quadrature signal to produce one or more discrete layer signals.
In one embodiment, the invention comprises one or more transports, such as for MPEG decoders, each receiving and decoding one of the one or more discrete layer signals to be displayed.
The high speed digital processor performs many functions in decoding the signal layers. The processor demodulates and decodes the upper layer from the layered in-phase signal and the layered quadrature signal to produce the upper layer signal for a video transport. The processor also produces an ideal upper layer signal including an ideal in-phase upper layer signal and an ideal quadrature upper layer signal from the decoded upper layer signal and subtracts these from the layered in-phase signal and the layered quadrature signal, respectively, to produce the lower layer in-phase signal and the lower layer quadrature signal of the lower signal layer. The layered in-phase signal and the layered quadrature signal can be delayed to synchronize the subtraction. Delaying the layered in-phase signal and the layered quadrature signal can be done by correlating the demodulated upper layer signal to the ideal upper layer signal to determine the proper delay.
After the lower layer signal is produced by the subtraction, the processor further demodulates and decodes the lower layer in-phase signal and the lower layer quadrature signal to produce the lower layer signal for a video transport. In doing so, the processor can match filter the lower layer in-phase signal and the lower layer quadrature signal.
In other embodiments, generating the ideal upper layer signals can comprise advanced signal processing. For example, processor can apply a signal map to the ideal in-phase upper layer signal and the ideal quadrature upper layer signal, the signal map accounting for transmission distortions of the layered signal. The signal processing can also comprise pulse shaping the ideal in-phase upper layer signal and the ideal quadrature upper layer signal. Signal processing can also comprise amplitude and phase matching the ideal in-phase upper layer signal and the ideal quadrature upper layer signal with the layered in-phase signal and the layered quadrature signal, respectively.



BRIEF DESCRIPTION OF THE DRAWINGS
Referring now to the drawings in which like reference numbers represent corresponding parts throughout:
FIGS. 1A-1C illustrate the relationship of signal layers in a layered modulation transmission;
FIGS. 2A-2C illustrate a signal constellation of a second transmission layer over a first transmission layer non-coherently;
FIG. 3 is a block diagram for a typical transmission system for a receiver of the invention;
FIG. 4 is a block diagram of a receiving architecture of the invention;
FIG. 5 is a block diagram of a layered modulation decoder of the invention; and
FIG. 6 describes a method of a layered modulation decoding according to the invention.



DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In the following description, reference is made to the accompanying drawings which form a part hereof, and which show, by way of illustration, several embodiments of the present invention. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.
1. Overview
The present invention provides for the reception of non-coherent layered modulation signals using legacy and multi-layer receivers. The signal layers can be independently modulated and coded. The layered signal is passed through a high speed digitizer to prepare it for digital processing. Processing the digitized layered signal yields the distinct layer signals which can then be presented to separate transports for conversion to a video signal.
2. Layered Signals
FIGS. 1A-1C illustrate the basic relationship of signal layers in a layered modulation transmission. FIG. 1A illustrates a upper layer signal constellation 100 of a transmission signal showing the signal points or symbols 102. FIG. 1B illustrates the lower layer signal constellation of symbols 104 over the upper layer signal constellation 100 where the layers are coherent. FIG. 1C illustrates a lower signal layer 106 of a second transmission layer over the upper layer constellation where the layers may be non-coherent. The lower layer 106 rotates about the upper layer constellation 102 due to the relative modulating frequencies of the two layers in a non-coherent transmission. Both the upper and lower layers rotate about the origin due to the upper layer modulation frequency as described by path 108.
FIGS. 2A-2C illustrate a signal constellation of a lower transmission layer over the upper transmission layer after upper layer demodulation. FIG. 2A shows the constellation 200 before the upper carrier recovery loop (CRL) and FIG. 2B shows the constellation 204 after CRL. In this case, the signal points of the lower layer are rings 202. FIG. 2C depicts a phase distribution of the received signal with respect to nodes 102. As mentioned above, relative modulating frequencies cause the lower layer constellation to rotate around the nodes of the upper layer constellation. After the lower layer CRL this rotation is eliminated. The radius of the lower layer constellation is determined by its power level. The thickness of the rings 202 is determined by the carrier to noise ratio (CNR) of the lower layer.
FIG. 3 is a block diagram for a typical system 300 of transmitting and receiving layered signals, with at least one of the signals being a legacy signal and the others including a non-legacy signal. Separate transmitters 316A, 316B, as may be located on any suitable platform, such as satellites 306A, 306B, are used to non-coherently transmit different layers of a signal of the present invention. They may also exist on the same platform. Uplink signals are typically transmitted to each satellite 306A, 306B from one or more transmit stations 304 via an antenna 302. The layered signals 308A, 308B (downlink signals) are received at receiver antennas 312, 320, such as satellite dishes, each with a low noise block (LNB) 310, 318 where they are then coupled to integrated receiver/decoders (IRDs) 314, 322.
One IRD 322 is legacy device which only discerns the upper layer (legacy signal) of the layered signals 308A, 308B. It demodulates and decodes the upper layer and ignores the lower layer (non-legacy signal) as noise. The other IRD 314 is capable of demodulating and decoding both layers of the layered signals 308A, 308B, with an integrated layered modulation decoder which will be detailed hereafter. It should be noted that antennas 312, 320 can each comprise more than one directional receiving dish to receive layered signals 308A, 308B from separate satellites as will be detailed in the receiver system described hereafter.
Because the signal layers may be transmitted non-coherently, separate transmission layers may be added at any time using different satellites 306A, 306B or other suitable platforms, such as ground based or high altitude platforms. Thus, any composite signal, including new additional signal layers will be backwards compatible with legacy receivers which will disregard the new signal layers. To ensure that the signals are distinguishable, the combined signal and noise level for the lower layer must be at or below the allowed noise floor for the upper layer. Alternate receiver systems employing the invention described here can be constructed to decode signals having more than two signal layers.
3. Reciever System
FIG. 4 is a block diagram of a receiving architecture for testing the invention method. Emulated layered signals 400A, 400B are received by receiving dishes 402A, 402B (which can alternately be combined in a single dish with a single LNB). The signals 400A, 400B can each be transmitted by distinct transmitters from separate satellites, but they exist in interfering frequency bands, e.g. 12.5 GHz. The received layered signals 400A, 400B are then directed through respective low noise blocks (LNBs) 404A, 404B and attenuators 406A, 406B. The LNBs 404A, 404B convert each of the received layered signals 400A, 400B to an intermediate frequency range, e.g. 950-1450 MHz. The layered signals are combined at the summation block 408, with their relative power levels adjusted by the attenuators 406A, 406B.
It should be noted that the details regarding the reception of the layered signal up to the summation block 408 are not critical to the operation of the invention and shown only as one example. Many designs are possible. For example, as previously mentioned, the same receiver dish can be used for both layered signals 400A, 400B. Two acceptably interfering layered signals provided at the same input is all that is required for the invention to function.
The combined layered signals 400A, 400B are input to a layered modulation decoder 410 of the invention. The decoder processes the layered signals 400A, 400B to separate the layered signals 400A, 400B into two distinct signals, one for each layer. The distinct signals are each input to separate transports 412A, 412B (e.g. MPEG decoders) for further processing to produce separate video signals. The video signals are then communicated to displays 414A, 414B. Of course, alternate architectures can employ a single display 414 switched between the transports 412A, 412B. Similarly, a single transport 412 can be employed, switched between the two signal layer outputs of the layered modulation decoder 410. The layered modulation decoder 410 and video transports 412A, 412B can all be combined as part of a stand alone IRD 314 for receiving and decoding both layered signals.
4. Layered Modulation Decoder
FIG. 5 is a block diagram of a layered modulation decoder 410 of the invention. The layered modulation decoder 410 decodes both layers of an incoming layered signal to yield a separate signal for each layer, as previously discussed.
The incoming layered signal is first tuned to convert it to a baseband in-phase (I) and quadrature (Q) signal by tuner 500. The separate signals can then be filtered by a low pass filter 502 in preparation for digitizing. The signals are then digitized at a high sampling rate and sufficient resolution by an analog-to-digital converter (ADC) 504. A dual channel ADC 504 or separate ADCs can be used for the separate in-phase and quadrature signals. The digitized signals are then communicated to a processor 506.
The processor 506 for extracting a lower layer signal can be implemented as a logic circuit. The entering digitized in-phase and quadrature signals can be first split into two paths. On the signal path for the upper layer, the in-phase and quadrature signals can first be passed through a frequency acquisition loop 508. They can then be filtered through a finite impulse response (FIR) matched filter 510. A demodulator 512 demodulates the signals, with carrier and timing recovery loops, and produces demodulated layered in-phase and quadrature signals. The demodulated signals are then decoded by decoder 514 which can incorporate Viterbi decoding, deinterleaving and Reed-Solomon (RS) decoding functions as appropriate to accurately determine the upper layer symbols. The decoded upper layer symbol signal can then be output from the processor 506, where it can be communicated to a transport 412A and subsequently converted to video.
Back in the processor 506, the decoded upper layer symbol signal is also applied to an encoder 516 in order to produce an ideal upper layer signal (i.e. an upper layer signal transmitted without the noise and interference of the lower layer signal). The encoded signal is again produced as in-phase and quadrature signal components. A variety of signal processing techniques can be applied to these signals to produce the ideal upper layer.
The ideal upper layer signal can be filtered through an FIR matched filter 518. Characteristics of the transmission (e.g. amplifier nonlinearities, etc.) can be accounted for by signal maps 520, such as an amplitude modulation to amplitude modulation (AM/AM) map and/or an amplitude modulation to phase modulation map (AM/PM). The signal maps 520 are applied 522 to the encoded signals to simulate downlink transmission of an upper layer signal. These signal maps 520 can be updated to account for changes in the transmission characteristics of the satellite. Similarly, a pulse shaping function 526 (one example being an FIR matched filter) can also be applied after accounting for the transmission characteristics (by applying 522 the signal maps). In addition, an upper layer amplitude and phase matching function 528, driven by the demodulated layered signal and the ideal reconstructed upper layer signals, can be used to generate matching coefficients. The matching coefficients are applied 524 to the reconstructed upper layer signal to ensure that it is appropriately scaled in magnitude and rotated in phase as compared to the layered signal, for maximum cancellation in the final signal subtraction.
Ultimately, the ideal reconstructed in-phase and quadrature signals for the upper layer are subtracted from the layered in-phase and quadrature signals that are produced by the demodulator at a subtractor 538. A timing and phase compensation function 532 is applied to the second layered path entering the processor 506, using information from the demodulator 512. A fixed delay 534 can be applied to the second layered signal path to determine the appropriate delay to align the layered and ideal signals to generate matching coefficients 528. The delayed layered signal is split and, in one path, an FIR matched filter 530 can be applied to it before generating matching coefficients 528. The second delayed layered signal path is delayed 536 again to align it appropriately with the ideal upper layer signal for subtraction 538. The results of the subtraction are the in-phase and quadrature signals of the lower layer.
The in-phase and quadrature signals of the lower layer are then translated into the proper signal format for a transport 412B to convert to video. The lower layer signal undergoes frequency acquisition 540 and a digital filter 542 (e.g. an FIR matched filter) can operate on the signals. The signals can then be demodulated at demodulator 544, to have the lower carrier removed in this case. Finally the demodulated in-phase and quadrature signals can be appropriately decoded by decoder 546 to produce a signal compatible with the video transport 412.
FIG. 6 describes a method of a layered modulation decoding according to the invention. At block 600, a layered signal is received and a layered in-phase signal and a layered quadrature signal are produced therefrom. At block 602, the layered in-phase signal and the layered quadrature signal are digitized. Finally, at block 604, the digitized layered in-phase signal and the layered quadrature signal are decoded to produce one or more discrete layer signals. An upper layer signal is demodulated and decoded from the layered in-phase signal and the layered quadrature signal to produce an upper one of the one or more discrete layer signals. An ideal upper layer signal including an ideal in-phase upper layer signal and an ideal quadrature upper layer signal are produced from the decoded upper layer signal and subtracted from the layered in-phase signal and the layered quadrature signal, respectively, to produce a lower layer in-phase signal and a lower layer quadrature signal of a lower one of the one or more discrete layer signals. The layered in-phase signal and the layered quadrature signal are delayed to synchronize the subtraction. Delaying the signals comprises correlating the layered in-phase signal and the layered quadrature signal are delayed by to the ideal in-phase upper layer signal and the ideal quadrature upper layer signal.
5. Conclusion
The foregoing description including the preferred embodiment of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto. The above specification, examples and data provide a complete description of the manufacture and use of the invention. Since many embodiments of the invention can be made without departing from the scope of the invention, the invention resides in the claims hereinafter appended.

## Claims

1. A method of transmitting a coded signal having an upper layer signal and a lower layer signal, comprising the steps of:
combining the upper layer signal and the lower layer signal;
encoding the combined upper layer signal and lower layer signal;
assigning first symbols to the upper layer signal portion of the encoded combined upper layer signal and the lower layer signal;
assigning second symbols to the lower layer signal portion of the encoded combined upper layer signal and the lower layer signal;
delaying the first symbols;
mapping and modulating the delayed first symbols;
mapping and modulating the second symbols;
transmitting the delayed mapped and modulated first symbols; and
transmitting the mapped and modulated second symbols.

2. The method of claim 1, wherein the step of encoding the combined upper layer signal and lower layer signal further comprises the step of inserting timing data into the encoded combined upper layer signal and lower layer signal, the timing data including predetermined lower layer signal data.

3. The method of claim 2, wherein the timing data includes blocks of initialization data.

4. The method of claim 2, wherein the timing data is inserted periodically.

5. The method of claim 1, wherein the step of encoding the combined upper layer signal and lower layer signal further comprises the step of inserting timing data into at least a portion of the upper layer signal and into the lower layer signal.

6. The method of claim 5, wherein the timing data includes blocks of initialization data.

7. The method of claim 5, wherein the timing data is inserted periodically.

8. The method of claim 1, wherein the upper layer signal is delayed by an amount of time necessary for a receiver of the transmitted coded signal to remodulate and re-encode a demodulated upper layer signal.

9. An apparatus for transmitting a coded signal having an upper layer signal and a lower layer signal, comprising:
means for combining the upper layer signal and the lower layer signal;
means for encoding the combined upper layer signal and lower layer signal;
means for assigning first symbols to the upper layer signal portion of the encoded combined upper layer signal and the lower layer signal;
means for assigning second symbols to the lower layer signal portion of the encoded combined upper layer signal and the lower layer signal;
means for delaying the first symbols;
means for mapping and modulating the delayed first symbols;
means for mapping and modulating the second symbols;
transmitting the delayed mapped and modulated first symbols; and
means for transmitting the mapped and modulated second symbols.

10. The apparatus of claim 9, wherein the means for encoding the combined upper layer signal and lower layer signal further comprises means for inserting timing data into the encoded combined upper layer signal and lower layer signal, the timing data including predetermined lower layer signal data.

11. The apparatus of claim 10, wherein the timing data includes blocks of initialization data.

12. The apparatus of claim 10, wherein the timing data is inserted periodically.

13. The apparatus of claim 9, wherein the means for encoding the combined upper layer signal and lower layer signal further comprises means for inserting timing data into at least a portion of the upper layer signal and into the lower layer signal.

14. The apparatus of claim 13, wherein the timing data includes blocks of initialization data.

15. The apparatus of claim 13, wherein the timing data is inserted periodically.

16. The apparatus of claim 9, wherein the upper layer signal is delayed by an amount of time necessary for a receiver of the transmitted coded signal to remodulate and re-encode a demodulated upper layer signal.

17. An apparatus for transmitting a coded signal having an upper layer signal and a lower layer signal, comprising:
an encoder, for encoding a combined upper layer signal and lower layer signal;
a first symbol assigner, for assigning first symbols to the upper layer signal portion of the encoded combined upper layer signal and the lower layer signal;
a second symbol assigner, for assigning second symbols to the lower layer signal portion of the encoded combined upper layer signal and the lower layer signal;
a delay element, communicatively coupled to the first symbol assigner, for delaying the first symbols;
a first mapper and modulator, for mapping and modulating the delayed first symbols;
a second mapper and modulator, for mapping and modulating the second symbols;
a transmitter, communicatively coupled to the first mapper and modulator, for transmitting the delayed mapped and modulated first symbols; and
a second transmitter, communicatively coupled to the second mapper and modulator, for transmitting the mapped and modulated second symbols.

18. The apparatus of claim 17, wherein the encoder inserts timing data into the encoded combined upper layer signal and lower layer signal, the timing data including predetermined lower layer signal data.

19. The apparatus of claim 18, wherein the timing data includes blocks of initialization data.

20. The apparatus of claim 18, wherein the timing data is inserted periodically.

21. The apparatus of claim 17, wherein the encoder inserts timing data into at least a portion of the upper layer signal and into the lower layer signal.

22. The apparatus of claim 21, wherein the timing data includes blocks of initialization data.

23. The apparatus of claim 21, wherein the timing data is inserted periodically.

24. The apparatus of claim 17, wherein the upper layer signal is delayed by an amount of time necessary for a receiver of the transmitted coded signal to remodulate and re-encode a demodulated upper layer signal.

25. A method of decoding a coded input signal having an upper layer modulated signal and a lower layer modulated signal, comprising the steps of:
demodulating the input signal to produce an upper layer signal;
delaying the input signal;
demodulating the delayed input signal to produce a lower layer signal;
combining the upper layer signal and the lower layer signal; and
decoding the combined upper layer signal and the lower layer signal.

26. The method of claim 25, wherein:
the coded input signal includes initialization data having predetermined lower layer signal data; and
the combined upper layer signal and the lower layer signal are decoded according to the initialization data.

27. The method of claim 25, wherein:
at least a portion of the coded input signal includes a separately encoded upper layer signal and lower layer signal; and
the at least a portion of the coded input signal is decoded according to the initialization data.

28. The method of claim 25, wherein the step of demodulating the delayed input signal to produce a lower layer signal comprises the steps of:
re-encoding and remodulating the upper layer signal;
extracting the lower layer signal from the input signal by subtracting the re-encoded and remodulated upper layer signal from the input signal.

29. The method of claim 28, wherein the input signal is delayed by an amount of time necessary to re-encode and remodulate the upper layer signal.

30. The method of claim 25, further comprising the step of de-interleaving the decoded combined upper layer signal and the lower layer signal.

31. An apparatus for decoding a coded input signal having an upper layer modulated signal and a lower layer modulated signal, comprising:
means for demodulating the input signal to produce an upper layer signal;
means for delaying the input signal;
means for demodulating the delayed input signal to produce a lower layer signal;
means for combining the upper layer signal and the lower layer signal; and
means for decoding the combined upper layer signal and the lower layer signal.

32. The apparatus of claim 31, wherein:
the coded input signal includes inserted initialization data having predetermined lower layer signal data; and
the combined upper layer signal and the lower layer signal are decoded according to the initialization data.

33. The apparatus of claim 31, wherein:
at least a portion of the coded input signal includes a separately encoded upper layer signal and lower layer signal; and
the at least a portion of the coded input signal is decoded according to the initialization data.

34. The apparatus of claim 31, wherein the means for demodulating the delayed input signal to produce a lower layer signal comprises:
means for re-encoding and remodulating the upper layer signal;
means for extracting the lower layer signal from the input signal by subtracting the re-encoded and remodulated upper layer signal from the input signal.

35. The apparatus of claim 34, wherein the input signal is delayed by an amount of time necessary to re-encode and remodulate the upper layer signal.

36. The apparatus of claim 31, further comprising the step of de-interleaving the decoded combined upper layer signal and the lower layer signal.

37. An apparatus for decoding a coded input signal having an upper layer modulated signal and a lower layer modulated signal, comprising:
a demodulator for demodulating the input signal to produce an upper layer signal;
a delay element, communicatively coupled to the input signal for delaying the input signal;
a second demodulator for demodulating the delayed input signal to produce a lower layer signal, the second demodulator communicatively coupled to the delay element;
a combiner for combining the upper layer signal and the lower layer signal, the combiner communicatively coupled to the first demodulator and the second demodulator; and
a decoder, communicatively coupled to the combiner, the decoder for decoding the combined upper layer signal and the lower layer signal.

38. The apparatus of claim 37, wherein:
the coded input signal includes inserted initialization data having predetermined lower layer signal data; and
the combined upper layer signal and the lower layer signal are decoded according to the initialization data.

39. The apparatus of claim 37, wherein:
at least a portion of the coded input signal includes a separately encoded upper layer signal and lower layer signal; and
the at least a portion of the coded input signal is decoded according to the initialization data.

40. The apparatus of claim 37, further comprising:
an encoder communicatively coupled to the decoder, the encoder for re-encoding the upper layer signal;
a modulator, communicatively coupled to the encoder, the modulator for remodulating the upper layer signal; and
a differencer module, communicatively coupled to the modulator and the second demodulator, for extracting the lower layer signal from the input signal by subtracting the re-encoded and remodulated upper layer signal from the input signal.

41. The apparatus of claim 40, wherein the input signal is delayed by an amount of time necessary to re-encode and remodulate the upper layer signal.

42. The apparatus of claim 37, further comprising a de-interleaver, communicatively coupled to the decoder, the de-interleaver for de-interleaving the decoded combined upper layer signal and the lower layer signal.

43. A method of decoding a coded input signal having an upper layer modulated signal and a lower layer modulated signal, comprising the steps of:
demodulating the input signal to produce an encoded upper layer signal;
demodulating the input signal to produce an encoded lower layer signal;
multiplexingly applying the encoded upper layer signal and the encoded lower layer signal to a signal encoder to produce the upper layer signal and the lower layer signal;
wherein the step of demodulating the input signal to produce an encoded lower layer signal comprises the steps of re-encoding and remodulating the upper layer signal, and extracting the lower layer signal from the input signal by subtracting the re-encoded and remodulated upper layer signal from the input signal.

44. The method of claim 43, further comprising the step of de-interleaving the upper layer signal and the lower layer signal.

45. A method of decoding a coded input signal having an upper layer signal and a lower layer signal, comprising the steps of:
demodulating the coded input signal to produce a coded upper layer signal;
demodulating the coded input signal to produce a coded lower layer signal; and
multiplexingly decoding the coded upper layer signal and the coded second layer signal;
wherein the step of demodulating the coded input signal to produce a coded lower layer signal comprises the steps of decoding the coded upper layer signal, re-encoding and remodulating the decoded upper layer signal, and extracting the lower layer signal from coded input signal by subtracting the re-encoded and remodulated upper layer signal from the input signal.

46. The method of claim 45, wherein the step of alternately decoding the coded upper layer signal and the coded second layer signal comprises the step of alternately applying the coded upper layer signal and the coded lower layer signal to a decoder.

47. An apparatus for decoding a coded input signal having an upper layer modulated signal and a lower layer modulated signal, comprising:
means for demodulating the input signal to produce an encoded upper layer signal;
means for demodulating the input signal to produce an encoded lower layer signal;
means for multiplexingly applying the encoded upper layer signal and the encoded lower layer signal to a signal decoder to produce the upper layer signal and the lower layer signal;
wherein the means for demodulating the input signal to produce an encoded lower layer signal comprises means for re-encoding and remodulating the upper layer signal, and means for extracting the lower layer signal from the input signal by subtracting the re-encoded and remodulated upper layer signal from the input signal.

48. The apparatus of claim 47, further comprising means for de-interleaving the upper layer signal and the lower layer signal.

49. An apparatus for decoding a coded input signal having an upper layer signal and a lower layer signal, comprising:
means for demodulating the coded input signal to produce a coded upper layer signal;
means for demodulating the coded input signal to produce a coded lower layer signal; and
means for multiplexingly decoding the coded upper layer signal and the coded second layer signal;
wherein the means for demodulating the coded input signal to produce a coded lower layer signal comprises means for decoding the coded upper layer signal, means for re-encoding and remodulating the decoded upper layer signal, and means for extracting the lower layer signal from coded input signal by subtracting the re-encoded and remodulated upper layer signal from the input signal.

50. The apparatus of claim 49, wherein the means for alternately decoding the coded upper layer signal and the coded second layer signal comprises means for alternately applying the coded upper layer signal and the coded lower layer signal to a decoder.

51. An apparatus for decoding a coded input signal having an upper layer modulated signal and a lower layer modulated signal, comprising:
a first demodulator for demodulating the input signal to produce an encoded upper layer signal;
a second demodulator for demodulating the input signal to produce an encoded lower layer signal;
a multiplexer, communicatively coupled to the first demodulator and the second demodulator, the multiplexer for multiplexingly applying the encoded upper layer signal and the encoded lower layer signal to a signal decoder;
an encoder, communicatively coupled to the decoder, for re-encoding the upper layer signal;
a modulator, communicatively coupled to the encoder, the modulator for remodulating the re-encoded upper layer signal; and
an extractor, communicatively coupled to the modulator and the second demodulator, the extractor for extracting the lower layer signal from the input signal by subtracting the re-encoded and remodulated upper layer signal from the input signal.

52. The apparatus of claim 51, further comprising a de-interleaver, communicatively coupled to the decoder.