Preprocess of signal layer in layered modulation digital signal system for use in conventional type receiver

【0001】

[Technical field to which the invention belongs]

Cross-reference of related applications This partial continuation application is entitled "Layered Modulation for Digital Signals" under Section 120 of the US Patent Act, and is filed in XXXXX with US Patent Application No. XXXXX and "Layered Modulation Signals". Claims the priority of US Patent Application No. XXXXX, filed in XXXXX, entitled "Dual Layer Signal Processing in Systems". Both applications are incorporated herein by reference.

【0002】

The present invention generally relates to a system that receives a digital signal, and more particularly to a system that receives layered modulation as a digital signal.

【0003】

[Conventional technology]

With the development of various digital signal communication systems and services, the demand for increased data throughput and additional services is rapidly increasing. However, if it is necessary to replace existing conventional hardware such as transmitters and receivers, it is more difficult to improve old systems and realize new services. New systems and services have advantages when existing traditional hardware is available. In the field of wireless communications, this principle is further emphasized by the limited availability of electromagnetic spectra. Therefore, it is not possible (or at least impractical) to simply transmit extended or additional data at a new frequency.

【0004】

Traditional methods of increasing spectral capacitance move to higher order modulations, such as from 4-phase phase modulation (QPSK) to 8-phase phase modulation (8PSK) or 16 quadrature amplitude modulation (16QAM). That is. Unfortunately, QPSK receivers cannot demodulate 8PSK or 16QAM signals. As a result, traditional customers with QPSK receivers must upgrade their receivers in order to continue to receive any signal transmitted by 8PSK or 16QAM modulation.

【0005】

Layered modulation allows signal transmission systems and methods to accommodate improved and increased data throughput without requiring additional frequency bands. Systems that utilize layered modulation can provide improved and increased throughput signals for new receivers while maintaining compatibility with traditional receivers. Newer layered modulation techniques (as detailed in US Patent Application No. XXXXX, entitled "Layered Modulation for Digital Signals", filed in XXXXX) are also separate from conventional transmitters. It offers the unique advantage of being able to upgrade the transmitted signal from the source. In other words, the layered signal can be asynchronous and / or non-coherent.

【0006】

Related receiver systems for layered signals, such as the receiver system found in US Pat. No. 4,039,961, are also described and are incorporated herein by reference. However, such receiver systems are based on analog circuits and are synchronized by a voltage controlled oscillator. Moreover, such receiver systems have limitations. This is because they are designed only to receive coherent layered signals, that is, synchronously generated signals.

【0007】

Correspondence with conventional receivers is also important when extending existing systems by adopting layered modulation. Proper design of layered modulated signals can allow conventional receivers to receive traditional layers of signal, but conventional receivers do not have access to new signal layers. Moreover, it may not always be possible (or preferable) to accommodate conventional receivers when designing new layered modulated signals. In such cases, conventional receivers will not be compatible with the new layered modulated signals.

【0008】

[Problems to be Solved by the Invention]

There is a need for systems and methods that receive and process layered modulated signals. There is also a need for systems and methods that allow conventional receivers to receive all layers of layered signals. In addition, there is a need for systems and methods that enable conventional receivers to operate even if the layered modulated signal is not compatible with conventional receivers. The present invention satisfies these needs.

【0009】

[Means for solving problems]

The present invention provides a flexible and expandable device. This device can be realized by high-speed logic circuit technology that can perform demodulation functions and process received layered modulated signals in real time. The present invention takes advantage of the high speed digitization of incoming signals and prepares them for faster digital processing. The present invention allows for a receiving system structure in which the incoming signal is split and directed separately to a separate integrated receiver / decoder (IRD). This system facilitates compatibility with traditional IRDs. One conventional IRD may be used to receive the upper modulation layer as it would receive a conventional non-layered signal. In this IRD, the lower modulation layer is ignored as noise. Another conventional IRD receives the preprocessed signal and extracts the undermodulated signal and converts it into a signal compatible with the conventional IRD.

【0010】

An exemplary device is a tuner that receives a layered signal and produces a layered in-phase signal and a layered orthogonal phase signal from it, and an analog-digital converter that digitizes the layered in-phase signal and the layered orthogonal phase signal. A processor that decodes a layered in-phase signal and a layered orthogonal-phase signal to generate a single-layer in-phase signal and a single-layer orthogonal-phase signal, and a single-layer in-phase signal and a single-layer orthogonal-phase signal. A digital-analog encoder that converts a single-layer in-phase analog signal to a single-layer orthogonal-phase analog signal, and a single-layer in-phase analog signal and a single-layer orthogonal-phase analog signal to be modulated into a single-layer signal. It includes a modulator to generate.

【0011】

It is preferred that the layered signal be designed to be compatible with the conventional receiver so that at least one signal layer can be decoded directly from the layered signal by the conventional receiver. The device produces a single layer signal that can also be decoded by a conventional receiver.

【0012】

To facilitate high speed signal processing, the processor may include logic circuits. Decoding by the processor may start by matching filtering the layered in-phase signal and the layered quadrature phase signal.

【0013】

In one embodiment, the processor demodulates a layered in-phase signal and a layered quadrature phase signal and decodes the upper layer signal from these signals. The processor also generates an ideal noise-free upper layer signal from the decoded upper layer signal, including an ideal in-phase upper layer signal and an ideal orthogonal phase upper layer signal, and layered in-phase signal and layered orthogonal phase. The ideal in-phase upper layer signal and the ideal right-angled phase upper layer signal are subtracted from the signals to generate a single lower layer in-phase signal and a single lower layer right-angled phase signal. In yet another embodiment, the layered in-phase signal and the layered quadrature signal are delayed to synchronize the subtraction.

【0014】

In another embodiment, generating the ideal upper layer involves signal processing the ideal in-phase upper layer signal and the ideal quadrature upper layer signal. Signal processing an ideal upper layer signal involves a variety of elements, including pulsing an ideal in-phase upper layer signal and an ideal quadrature upper layer signal. Signal mapping to address transmission distortions in the transmission of layered analog signals can also be applied to ideal in-phase upper layer signals and ideal quadrature upper layer signals. The ideal upper layer signal is processed by amplitude and phase matching with the layered signal, which can also improve the signal subtraction result.

【0015】

BEST MODE FOR CARRYING OUT THE INVENTION

Refer to the drawings in which the same reference numbers represent the corresponding parts throughout.

【0016】

In the following description, reference is made to the accompanying drawings which form part of this description and show some embodiments of the invention by illustration. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.

【0017】

1. Introduction The present invention provides the reception of a non-coherent conventional layered modulated signal using a conventional receiver. The signal layers may be independently modulated and encoded. Signal layers that are incompatible with conventional receivers are preprocessed in a layered modulation decoder and converted to a compatible format. Thus, all layers of a layered modulated signal split the incoming signal, direct it to a different conventional receiver, preprocess it as needed to extract the required layer, and extract it in a compatible format. Receive by presenting. At least one layer of the signal is preferably compatible with conventional receivers without preprocessing.

【0018】

2. Layered signals Figures 1 to 3 and 4 to 6 show the format of the QPSK signal in the two-layer example. FIGS. 1 to 3 show the basic relationship between signal layers in layered modulation transmission. FIG. 1 shows the arrangement 100 of the upper layer signal of the transmitted signal indicating the signal point, i.e. symbol 102. FIG. 2 shows the placement of the lower layer signal of symbol 104 with respect to the placement 100 of the upper layer signal, and these layers are coherent. FIG. 3 shows the lower signal layer 106 of the lower transmit layer with respect to the arrangement of the upper layer, and these layers may be non-coherent. Due to the relative modulation frequencies of the two layers in non-coherent transmission, the lower layer 106 rotates around the arrangement 102 of the upper layer. As described by path 108, the upper layer modulation frequency causes both the upper and lower layers to rotate around the origin.

【0019】

4 to 6 show the signal arrangement of the lower transmission layer with respect to the upper transmission layer after demodulation of the upper layer. FIG. 4 shows the placement 200 before the upper carrier recovery loop (CRL), and FIG. 5 shows the placement 204 after the CRL. In this case, the signal point on the lower layer is ring 202. FIG. 6 shows the phase distribution of the received signal with respect to the node 102. As mentioned above, due to the relative modulation frequency, the lower layer arrangement rotates around the node of the upper layer arrangement. This rotation is no longer needed after the lower layer CRL. The radius of the lower layer placement is determined by its power level. The thickness of the ring 202 is determined by the carrier-to-noise ratio (CNR) of the lower layer.

【0020】

FIG. 7 is a block diagram of a general system 300 that transmits and receives layered signals. Separate transmitters 316A, 316B may be located on any suitable platform such as satellites 306A, 306B, which are used to non-coherently transmit different layers of the signals of the present invention. It should be noted that these transmitters may be located on the same platform. Uplink signals are generally transmitted from one or more transmitting stations 304 to each satellite 306A, 306B via antenna 302. The layered signals 308A and 308B (downlink signals) are received by receiving antennas 312 and 320 (these may be one antenna instead), such as a satellite dish, and each of these antennas has low noise. It has blocks (LNB) 310,318 (which may also be one LNB). In addition, these antennas are coupled to a conventional integrated receiver / decoder (IRD) 322. One of the layered signals 308A may be distinguished and processed directly by the conventional IRD322. It should be noted that one satellite dish with one LNB may be used to receive both the upper and lower layers.

【0021】

According to the present invention, one conventional IRD314 obtains received layered signals 308A, 308B preprocessed by the layered modulation decoder 324. The layered modulation decoder 324 separates one of the layered signals 308B and converts it into a format compatible with conventional IRD314,322. Note that the antennas 312 and 320 each have more than one directional receiving dish and can receive layered signals 308A, 308B from different satellites, as detailed in the receiver system described below. Should.

【0022】

In addition, the signal layer may be transmitted non-coherently, so it is always possible to add a separate transmission layer using different satellites 306A, 306B, or other suitable platforms such as ground-based or high altitude platforms. Can be done. Therefore, any composite signal, including the newly added signal layer, is backwards compatible with conventional receivers that ignore the new signal layer. The combined signal and noise level of the lower layer must be equal to or lower than the noise floor allowed for the upper layer to ensure that the signal is identified. An alternative receiver system that employs the present invention described herein may be configured to decode a signal with more than two signal layers.

【0023】

3. Receiver system FIG. 8 is a block diagram of a receiver structure showing the method of the present invention. The emulated layered signals 400A, 400B are received by the receiving dishes 402A, 402B (alternatively, they may be combined in one dish with one LNB). The signals 400A and 400B may be transmitted from one or different satellites by different transmitters, but they are present in an interference frequency band such as 12.5 GHz. The received layered signals 400A, 400B are induced via the low noise blocks (LNB) 404A, 404B and the attenuators 406A, 406B, respectively. The LNB404A and 404B convert each of the received layered signals 400A and 400B into an intermediate frequency range such as 950MHz to 1450MHz. The layered signal is combined in addition block 408 with relative power levels adjusted by the attenuators 406A, 406B.

【0024】

It should be noted that the details regarding the reception of layered signals up to additive block 408 are not critical to the operation of the present invention and are shown as an example only. Various designs are possible. For example, as described above, the same receiving dish may be used for both the layered signals 400A, 400B. Only the result of obtaining two acceptable interfering layered signals at the same input is sought.

【0025】

The synthesized layered signals 400A and 400B can be distributed by the distributor 410 and the layered signals can be directed to the conventional IRD412A and 412B, respectively. One conventional IRD412A demodulates and decodes the upper layer signals of signals 400A, 400B, and ignores the others as noise. The decoded upper layer signal is distributed to the display device 414A. On the other hand, the conventional IRD412B is such that the lower layer signals of the signals 400A and 400B are converted into signals compatible with the conventional IRD412B (and the upper layer signals of the signals 400A and 400B are efficiently filtered out. To obtain the layered signals 400A and 400B preprocessed by the layered modulation decoder 416. The converted lower layer signal is then demodulated and decoded by the conventional IRD412B, and the result is distributed to the display device 414B. Of course, the alternative structure may employ a single display device that can be switched between signals from separate IRD412A, 412B.

【0026】

4. Layered Modulation Decoder Figure 9 is a block diagram of the layered modulation decoder 416 of the present invention. The layered modulation decoder 416 preprocesses the incoming layered signal, extracts the lower layer signal, and converts it into a signal that can be decoded by a conventional receiver, as described above.

【0027】

After the distributor 410, the incoming layered signal is top-tuned by the tuner 500 and converted into a baseband common mode (I) signal and a quadrature phase (Q) signal. The individual signals may be filtered by a lowpass filter 502 for digitization. The signal is then digitized by an analog-to-digital converter (ADC) 504 with a high sampling rate and sufficient resolution. Dual channel ADC504 or separate ADCs may be used for separate in-phase and quadrature signals. The digitized signal is then transmitted to processor 506.

【0028】

The processor 506 that extracts the lower layer signal may be configured as a logic circuit. The incoming digitized in-phase and quadrature signals are first split into two paths. These are the upper layer signal and the composite layered signal. On the signal path for the upper layer, the in-phase signal and the quadrature phase signal are first sent via the frequency capture loop 508. The signal may then be filtered by a finite impulse response (FIR) matched filter 510. The demodulator 512 uses a carrier wave and a timing recovery loop to demodulate the signal to produce the demodulated layered in-phase signal and quadrature phase signal. The demodulated signal is then decoded by the decoder 514, which appropriately incorporates Viterbi decoding, deinterleaved, and Reed-Solomon (RS) decoding capabilities to accurately determine the upper layer symbol. The decoded upper layer symbol is then added to the encoder 516 to generate an ideal upper layer signal (ie, an upper layer signal transmitted without noise and / or interference of the lower layer signal). The encoded signal is regenerated as a component of the in-phase signal and the quadrature phase signal. Various signal processing techniques may be utilized for these signals to produce the ideal upper layer.

【0029】

The ideal upper layer signal may be filtered by FIR matched filter 518. Transmission characteristics (such as amplifier non-linearity) may be addressed by the signal map 520, which includes an amplitude modulation vs. amplitude modulation (AM / AM) map and / or an amplitude modulation vs. phase modulation (AM / PM). There is a map etc. These signal maps 520 may be updated to accommodate changes in satellite transmission characteristics. These signal maps 520 are applied to the encoded signal (522) and simulate the downlink transmission of the upper layer signal. Similarly, an additional FIR matched filter 526 may be applied after the transmission characteristics have been addressed (522). In addition, the upper layer amplitude and phase matching function 528 is driven by a demodulated layered signal and an ideal restored upper layer signal and is also used to generate matching coefficients. This matching factor is applied to the restored upper layer signal (524), and the restored upper layer signal is appropriately sized compared to the layered signal so that it is maximally erased when the signal is finally subtracted. And ensure that the phase is rotated.

【0030】

Finally, the ideal restored in-phase signal and quadrature phase signal for the upper signal are subtracted from the layered in-phase signal and layered quadrature phase signal produced by the demodulator in the subtractor 538. The timing and phase compensation function 532 is applied to the second layered path entering processor 506 using the information from the demodulator 512. A fixed delay 534 may be added to the second layered signal path to determine the appropriate delay and align the layered signal with the ideal signal to generate a matching factor of 528. The delayed layered signal is distributed and in one path the FIR matched filter 530 may be applied to the signal before generating the matching factor 528. The second delayed layered signal path is delayed again (536) and properly aligned with the ideal upper layer signal for subtraction 538. The result of the subtraction is the lower layer in-phase signal and quadrature phase signal.

【0031】

The lower layer in-phase signal and quadrature phase signal are output from the subtractor 538 and first converted to an analog signal by the digital-to-analog converter (DAC) 540. Since the DAC is the reverse of what was originally digitized, the same sampling rate and resolution can be used. Following this, the analog morphological signal is filtered by a lowpass filter 542 and sent to a modulator 544 (eg, a QPSK modulator) in a format that can be decoded by a conventional receiver, lower as the output of processor 416. Layer signals can be generated.

【0032】

FIG. 10 shows a method of layered modulation decoding according to the present invention. At block 600, a layered signal is received, which produces a layered in-phase signal and a layered quadrature signal. The layered in-phase signal and layered quadrature signal are then digitized at block 602. At block 604, the layered in-phase signal and the layered quadrature signal are decoded to produce a single-layer in-phase signal and a single-layer quadrature signal. Then, in block 606, the single layer in-phase signal and the single-layer quadrature phase signal are converted into a single-layer in-phase analog signal and a single-layer quadrature analog signal. Finally, at block 608, the single layer in-phase analog signal and the single layer quadrature analog signal are modulated to produce a single layer signal.

【0033】

Conclusion The above description, including preferred embodiments of the present invention, is presented for purposes of illustration and explanation. It is not intended to be exhausted in the exact form disclosed, nor is it intended to limit the invention to this exact form. Various modifications and changes are possible with respect to the above teachings. The scope of the invention is not limited by this detailed description, but rather is intended to be limited by the claims attached herein. The detailed description, examples, and data described above provide a complete description of the manufacture and use of the present invention. The present invention is present in the claims made below, as many embodiments of the invention are made without departing from the scope of the invention.

[Simple explanation of drawings]

FIG. 1 shows the relationship between signal layers in layered modulation transmission.

FIG. 2 shows the relationship between signal layers in layered modulation transmission.

FIG. 3 shows the relationship between signal layers in layered modulation transmission.

FIG. 4 shows the arrangement of signals in a non-coherent second transmit layer with respect to a first transmit layer.

FIG. 5 shows the arrangement of signals in a non-coherent second transmit layer with respect to a first transmit layer.

FIG. 6 shows the arrangement of signals in a non-coherent second transmit layer with respect to a first transmit layer.

FIG. 7 is a block diagram relating to a general transmission system for the receiver of the present invention.

FIG. 8 is a block diagram of the receiving structure of the present invention.

FIG. 9 is a block diagram of the layered modulation decoder of the present invention.

FIG. 10 is a layered modulation / decoding method according to the present invention.