DE112018000446T5 - SYSTEM AND METHOD FOR PICTURE AND DEMAPPING OF DIGITIZED SIGNALS FOR OPTICAL TRANSMISSION - Google Patents

Abstract

An optical network includes a transmitter section configured to transmit a digitized symbol stream over a digital optical link, a mapping unit located within the transmitter section and configured to transmit the transmitted digitized symbol stream with a mapping code prior to transmission over the digital optical And a demapping unit located within the receiver section and configured to map the reconstructed coded symbol stream into an uncoded digitized signal, which is adapted to encode a link, a receiver section adapted to recover the encoded symbol stream from the digital optical link digitized symbol stream at the transmitter section prior to encoding by the imaging unit.

Description

Cross-reference to related applications

This application is a continuation-in-part of December 19, 2017 submitted US Patent Application Ser. No. 15 / 847.417 that the advantage and the priority of the provisional US Patent Application Ser. No. 62 / 435.961 filed on 19 December 2016. This application also claims the benefit and priority of provisional US Patent Application Ser. No. 62 / 448.044 , filed January 19, 2017. The disclosures of all of these earlier applications are incorporated herein by reference in their entirety.

background

The field of the disclosure generally relates to fiber optic communication networks, and more particularly to digitalization techniques in hybrid coaxial fiber optic networks.

State of the art

Typical hybrid fiber coaxial (HFC) architectures use only a few long fiber strands from a hub to a node, but often many short fiber strands are used to cover the shorter distances, typically from older HFC nodes to end users. Traditional Multiple Service Operators (MSOs) offer a variety of services, including analog / digital TV, video on demand (VoD), telephony and high-speed Internet, over HFC networks that use both fiber and coaxial cable.

1 is a schematic representation of a conventional HFC network 100 , which is suitable for providing video, voice and data services to subscribers The HFC network 100 includes a master headboard 102 , a hub 104 , a fiberglass knot 106 and end user / participant 108 , An optical fiber 110 transmits analog optical signals and connects the link between master headend 102 , Hub 104 and fiber optic knots 106 , A variety of coaxial cables 112 transmit high frequency (RF) modulated analog electrical signals and connect the fiber optic node 106 with the respective end consumers 108 ,

In operation, the fiber optic node converts 106 the optical analog signals from the fiber 110 into the RF modulated electrical signals, then over the coaxial cables 112 to the end users / participants 108 be directed. In some cases, the HFC network implements 100 a fiber-deep architecture or fiber low architecture. The HFC network 100 can also have electrical amplifiers 114 use each along the coaxial cable 112 are arranged to send the analog RF signals to the respective end users 108 to reinforce. In the HFC network 100 Both the optical and the electrical signals are from the hub 104 up to the subscriber's home of the end user 108 in analog form. Typically, a cable modem termination system (CMTS) is either at the head end 102 or at the hub 104 and provides complementary functionality to cable modems (CMs) (not shown), each to the end user 108 are arranged.

More recently, the Data Over Cable Service Interface Specification (DOCSIS) has been established as a standard international interface that enables high bandwidth data transmission with the Internet Protocol (IP) into an existing HFC network, such as the HFC network 100 to involve. The latest DOCSIS standard, DOCSIS 3.1, provides (1) the ability to extend the transmitted spectrum in both upstream and downstream directions beyond the bandwidth available so far, and (2) to use the spectrum itself more efficiently. However, a DOCSIS 3.1 HFC network (ie supporting Orthogonal Frequency Division Multiplexing (OFDM)) requires significantly higher system performance for both the upstream and downstream signals compared to its prior DOCSIS HFC network counterpart, especially with respect to the carrier Noise Ratio (CNR) or Modulation Error Ratio (MER).

The DOCSIS 3.1 physical layer specification defines the downstream minimum required CNR performance of low density parity check (LDPC) OFDM signals in the additive white Gaussian noise (AWGN) channel, as shown in Table 1 below. For example, a typical OFDM Quadrature Amplitude Modulation (QAM) of 1024 (1K QAM) requires a signal performance of 34dB CNR or about 41-41.5 decibels (dB) CNR for the 4K QAM modulation format option in the direction of downstream. A similar situation also occurs in the upstream transmission path according to DOCSIS 3.1, as also shown in Table 2 below.

In such analog HFC systems, the quality of the recovered RF signal channel (eg, for end-user CMs 108 ) according to the carrier-to-composite noise (CCN) or CCN ratio. The CCN of an HFC fiber link provides the combination of noise components (eg, shot noise, thermal noise, laser noise (ie, hub / head-end laser transmission, etc.), intermodulation noise (eg, second, third, and higher-order components) and noise Crosstalk (eg, non-linear fiber interactions such as four-wave mixing, cross-phase modulation, Raman crosstalk, etc.). Continuous envelope and high peak-to-average power ratio (PAPR) are particularly important in terms of OFDM signals. That is, OFDM signals are very sensitive to nonlinear intermodulation, especially to composite triple beat (CTB). Second order non-linear products are out-of-band and are typically filtered. However, most third-order nonlinear products are in-band and cause problems with overlaps with existing carriers. Table 1: CM minimum CNR power in the AWGN channel Constellation (QAM) CNR (dB) up to 1 GHz CNR (dB) up to 1.0-1.218 GHz 4096 41 41.5 2048 37.0 37.5 1024 34.0 34.0 512 30.5 30.5 256 27.0 27.0 128 24.0 24.0 64 21.0 21.0 16 15.0 15.0 Table 2: CMTS minimum CNR performance in the AWGN channel Constellation (QAM) CNR (dB) 4096 43.0 2048 39.0 1024 35.5 512 32.5 256 29.0 128 26.0 64 23.0 32 20.0 16 17.0 8th 14.0 QPSK 11.0

Accordingly, the link loss and the analog linear distortions significantly limit the achievable link budget of the conventional HFC network. Even more pronounced is the impact on the achievable link budget for high-order modulation formats aiming for a high data rate. Conventional analogue optics technology can not keep up with the increasing demand for data on legacy HFC networks. However, the replacement of such old HFC networks would be very expensive and therefore impractical.

Disclosure of the invention

Short Summary

In one embodiment, an analog signal processor includes a sampling unit configured to (i) filter a received analog time domain signal in the frequency domain into a low frequency end of a corresponding frequency spectrum, (ii) sample the filtered analog signal at a frequency that is substantially higher as the low-frequency end, and (iii) to distribute quantization noise over an extended Nyquist zone of the corresponding frequency spectrum. The processor further includes a noise shaping unit configured to shape the distributed quantization noise from the low frequency end of the corresponding frequency spectrum such that the filtered analog signal and the shaped quantization noise are substantially separated in the frequency domain, and a quantization unit configured to: Apply a delta sigma modulation to the filtered analog signal using at least one quantization bit and output a digitized bitstream substantially following the amplitude of the received analog time domain signal.

In one embodiment, a hybrid fiber optic coaxial (HFC) network is provided. The network includes an optical hub configured to transmit a digitized bit stream over a digital optical link, a fiber node configured to receive the digitized bit stream through the digital optical link, and convert the received digitized bit stream into a delta link. sigma demodulated analog signal, and at least one end user configured to receive the delta-sigma demodulated analog signal from the fiber node.

In one embodiment, an optical network includes a transmitter section configured to transmit a digitized symbol stream over a digital optical link, a mapping unit disposed within the transmitter section and configured to mapped the transmitted digitized icon stream Encoding code prior to transmission over the digital optical link, a receiver section adapted to recover the encoded symbol stream from the digital optical link, and a demapping unit located within the receiver section and adapted to recovered coded symbol stream into an uncoded digitized signal corresponding to the digitized symbol stream at the transmitter section prior to encoding by the mapping unit.

In one embodiment, a symbol mapping method is provided for a digitized signal. The digitized signal includes a series of transmitted symbols having a Gaussian distribution of symbol amplitude values. The method includes a step of mapping the first symbol to a second symbol of the series of transmitted symbols for at least one input event of a first symbol of the series of transmitted symbols. The first symbol has a first symbol amplitude value and the second symbol has a second symbol amplitude value that is greater than the first symbol amplitude value. The method further includes a step of mapping the second symbol to the first symbol in at least one occurrence of the second symbol.

list of figures

• 1 ist eine schematische Darstellung bzw. Veranschaulichung eines konventionellen HFC-Netzes.
• 2A-2B sind grafische Veranschaulichungen, die die jeweiligen Funktionsprinzipien eines konventionellen Abtastverfahrens 200 im Vergleich zu einem exemplarischen Modulationsprozess darstellen.
• 3 ist eine grafische Veranschaulichung, die ein Funktionsprinzip eines Demodulationsprozesses für das in 2B dargestellte modulierte digitalisierte Ausgangssignal gemäß einer Ausführungsform darstellt.
• 4A-B sind schematische Veranschaulichungen eines exemplarischen HFC-Netzwerks unter Verwendung des in 2B dargestellten Delta-Sigma-Modulationsprozesses und des in 3 dargestellten Delta-Sigma-Demodulationsprozesses.
• 5A-B sind schematische Veranschaulichungen eines exemplarischen digitalisierten verteilten Netzwerks unter Verwendung des in 2B dargestellten Delta-Sigma-Modulationsprozesses und des in 3 dargestellten Delta-Sigma-Demodulationsprozesses.
• 6A-B sind schematische Veranschaulichungen eines exemplarischen Hochfrequenz über Glas Netzwerks unter Verwendung des in 2B dargestellten Delta-Sigma-Modulationsprozesses und des in 3 dargestellten Delta-Sigma-Demodulationsprozesses.
• 7 ist ein schematisches Blockdiagramm eines exemplarischen Signalmappingprozesses auf Systemebene gemäß einer Ausführungsform.
• 8 ist eine grafische Veranschaulichung, die ein nicht zugeordnetes elektrisches Augendiagramm eines digitalisierten Signals nach der Delta-Sigma-Digitalisierung gemäß einer Ausführungsform darstellt.
• 9 ist eine grafische Veranschaulichung, die ein elektrisches Augendiagramm eines digitalisierten Signals nach der Delta-Sigma-Digitalisierung unter Implementierung eines Flip-Mapping-Prozess darstellt.
• 10 ist eine grafische Veranschaulichung einer Flip-Mapping-Tabelle, die mit dem digitalisierten Signal des in 9 dargestellten elektrischen Augendiagramms implementiert werden kann.
• 11A-B sind grafische Veranschaulichungen, die ein Vergleichsergebnis eines übertragenen Signals mit und ohne Implementierung der in den 9 und 10 dargestellten Flip-Mapping-Prozesse darstellen.
• 12A-B sind grafische Veranschaulichungen, die ein vergleichendes Ergebnis eines elektrischen Augendiagramms eines pseudozufälligen Binärsequenz-PAM4-Signals mit dem eines Signals, das einen einheitlichen Mapping-Prozess gemäß einer Ausführungsform implementiert, darstellen.
• 13A-B sind grafische Veranschaulichungen alternativer Symbolzuordnungstabellen, die mit dem digitalisierten Signal des in 12B dargestellten elektrischen Augendiagramms implementiert werden können.
• 14A-B sind grafische Veranschaulichungen, die ein vergleichendes Ergebnis eines Signals, das den in 13A dargestellten einheitlichen Mapping-Prozess implementiert, mit einem Signal, das den in 13B dargestellten alternativen einheitlichen Mapping-Prozess implementiert, darstellen.
• 15 ist eine grafische Veranschaulichung einer Symboltabelle, die das Symbolmapping der verschiedenen hierin beschriebenen Prozesse vergleicht.

These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent the same parts throughout the drawings:

• 1 is a schematic representation or illustration of a conventional HFC network.
• 2A-2B are graphical illustrations illustrating the respective functional principles of a conventional scanning method 200 compared to an exemplary modulation process.
• 3 is a graphical illustration illustrating a principle of operation of a demodulation process for the in 2 B represents modulated digitized output signal according to an embodiment.
• 4A-B FIG. 10 are schematic illustrations of an exemplary HFC network using the in 2 B illustrated delta-sigma modulation process and the in 3 illustrated delta-sigma demodulation process.
• 5A-B FIG. 4 are schematic illustrations of an exemplary digitized distributed network using the in 2 B illustrated delta-sigma modulation process and the in 3 illustrated delta-sigma demodulation process.
• 6A-B FIG. 4 are schematic illustrations of an exemplary high frequency over glass network using the in 2 B illustrated delta-sigma modulation process and the in 3 illustrated delta-sigma demodulation process.
• 7 FIG. 12 is a schematic block diagram of an exemplary system-level signal mapping process, according to one embodiment.
• 8th FIG. 4 is a graphical illustration depicting an unassigned electrical eye diagram of a digitized signal after delta-sigma digitization according to one embodiment. FIG.
• 9 FIG. 4 is a graphical illustration illustrating an electrical eye diagram of a digitized signal after delta-sigma digitization implementing a flip-mapping process. FIG.
• 10 Figure 4 is a graphical illustration of a flip-mapping table associated with the digitized signal of the in 9 illustrated electrical eye diagram can be implemented.
• 11A-B are graphical illustrations showing a comparison result of a transmitted signal with and without the implementation of the 9 and 10 represent illustrated flip-mapping processes.
• 12A-B FIG. 10 is graphical illustrations illustrating a comparative result of an electrical eye diagram of a pseudorandom binary sequence PAM4 signal with that of a signal implementing a uniform mapping process according to one embodiment. FIG.
• 13A-B are graphical illustrations of alternative symbol mapping tables associated with the digitized signal of the in 12B illustrated electrical eye diagram can be implemented.
• 14A-B are graphical illustrations that are a comparative result of a signal that the in 13A implemented a unified mapping process, with a signal representing the in 13B illustrated alternative uniform mapping process implemented.
• 15 Figure 4 is a graphical illustration of a symbol table comparing the symbol mapping of the various processes described herein.

Unless otherwise indicated, the drawings contained herein are intended to illustrate the features of the embodiments of this disclosure. These features are believed to be applicable to a variety of systems, including one or more embodiments of this disclosure. Therefore, the drawings are not intended to encompass all conventional features known to those skilled in the art as necessary to practice the embodiments disclosed herein.

Detailed description

In the following specification or description and claims, reference is made to a number of terms which are defined with the following meanings.

The singular forms "a", "an", "the", "the" and "the" include plural references unless the context clearly dictates otherwise.

"Optional" or "optional" means that the event or circumstance described below may or may not occur, and that the description includes instances in which the event occurs and instances in which it does not occur

Approximate language as used throughout the specification and claims may be used to adapt to any quantitative indication that could reasonably vary without resulting in a change in the basic function to which it refers. Accordingly, a value that is changed by one or more terms such as "about,""about," and "substantially" should not be limited to the precise value specified. In at least some cases, the approximate language may correspond to the accuracy of an instrument for measuring the value. Here and throughout the specification and claims range limitations may be combined and / or be replaced; these areas are labeled and include all subdomains contained therein unless the context or language indicates otherwise.

According to the embodiments described herein, a digital optical network implements a digital optical connection over a digitized distributed network or using a digitized analog signal over the conventional HFC network. The digital optical network according to the present systems and methods is less affected by link losses and also realizes a higher tolerance to nonlinear noise from the laser (eg the head end / hub) or the fiber itself if the optical power is above the sensitivity of the receiver (eg an end user). The present digital optical network is therefore advantageously able to realize transmissions over longer distances, to support wavelengths per fiber and to effectively eliminate the contribution of the optical noise to the CNR. In addition, the CMTS and the respective CMs may operate at higher modulation formats according to the advantageous techniques described herein.

In the embodiments, the optical digital transmission is performed using delta-sigma modulation and demodulation. Important steps in the optical digital transmission process are analog-to-digital (A / D) and digital-to-analog (D / A) conversion. The sub-processes A / D conversion (ADC) and D / A conversion (DAC) comprise two important factors: (1) sampling rate; and (2) bit resolution. The minimum sampling rate is generally determined according to the Nyquist sampling theorem, while bit resolution is important to quantization noise determination. In some of the embodiments described below, a DOCSIS digitizing scheme using delta-sigma modulation and demodulation is applied to variations of a conventional HFC network and implements one or more of (i) oversampling, (ii) decimation filtering, and ( iii) Quantization noise shaping to achieve ultra-high resolution and anti-aliasing filtering. The present embodiments are therefore particularly advantageous for audio applications, precise temperature measurements and scales.

The present systems and methods are further capable of implementing low pass filtering which does not require the processing latency experienced in conventional HFC networks. In addition, the present optical digital transmission systems and networks achieve even lower latencies than those experienced with traditional ADC / DAC approaches. Low latencies are a particularly critical factor in virtual reality and immersive applications that will need to support networks of the future. By utilizing frequency selective digitization, the present embodiments are even more capable of the amount of data needed to represent the analog spectrum, such as the analog cable signal of the HFC network 100 . 1 , above, advantageous to reduce.

2A-2B are graphical illustrations illustrating the respective functional principles of a conventional scanning method 200 compared to an exemplary modulation process 202 represent according to one embodiment. The process 200 Figure 4 illustrates the operation of a conventional Nyquist Shannon sample ADC for an analog signal 204 (illustrated the time domain or the time domain). In the embodiment of the process 200 bandwidth limits the analog signal 204 in the appropriate frequency range (eg using a low-pass filter 206 , at frequency fB). In the in 2A The example shown is the quantization noise 208 is not correlated with the frequency of the input signal and evenly distributed over the Nyquist bandwidth fS / 2. The process 200 performs Nyquist sampling 210 of the analog signal 204 (ie, at the Nyquist frequency) and quantizes each sample through multiple quantization bits to the multi-bit quantization signal 212 to create.

Because the quantization noise of a Nyquist ADC is approximately Gaussian and uniformly distributed across the Nyquist zone, a very large number of quantization bits are required to match the signal-to-noise ratio (SNR) (eg, CNR or MER) of the resulting digitized signals 212 sure. Such a large number of required quantization bits imposes very high demands on the effective number of bits (ENOB), but also leads to low spectral efficiency and a data rate bottleneck. That is, in the prior art, a narrow-band analog signal after digitization may consume an enormous transmission bandwidth due to the large number of quantization bits per sample.

These disadvantages of conventional scanning techniques will be in accordance with the exemplary modulation process 202 solved. As in 2 B shown, a processor uses 214 of an A / D converter (not in 2 B shown) in the exemplary modulation process 202 a delta-sigma modulation to use an oversampling ADC having one or two quantization bits on an input signal 216 used to get an output signal 218 to create. In some embodiments, the output signal is 218 binary (eg one-bit Quantization). In other embodiments, the output is 218 a PAM4 output signal (eg two-bit quantization).

In particular, the modulation process implements 202 an oversampling subprocess 220 , a noise-shaping sub-process 222 and a quantization sub-process 224 , In the oversampling subprocess 220 the modulation process feels 202 the analog input signal 216 (eg a DOCSIS RF signal) at a high frequency and spreads the quantization noise over an extended Nyquist zone 226 , The modulation process 202 then implements the noise shaping subprocess 222 to push the quantization noise out of the signal band. In the in 2 B The illustrated example places a low-pass delta-sigma modulator 228 the analog signal 216 in the low frequency end of the spectrum, and a noise transfer function 230 acts as a high pass filter to push the quantization noise to the high frequency end out of the signal band, so that the analog signal 216 is separated from the noise in the frequency domain. The delta-sigma modulation technique of the modulation process 202 gives the binary (eg on / off key (OOK)) signal 218 (1) or the non-binary signal 218 (2) (eg, PAM4 (Four-Amplitude Pulse Amplitude Modulation)) depending on the one- or two-bit quantization and has a baud rate equal to the oversampling ADC of the sub-process 220 is. Accordingly, the resulting output binary or non-binary signal follows 218 generally the amplitude of the analog input signal 216 in an average sense.

According to the advantageous technique of the modulation process 202 The output generated by the present delta-sigma modulation methods provides a high bit rate bitstream (eg, output 218 ), which has an amplitude which is generally equal to the amplitude of the analog input signal (eg input signal 216 ) follows a weighted moving average. In the exemplary embodiment, an averaging process implements the low-pass filtering and is thus able to smooth the high-frequency oscillation of the digitized bit stream. The use of low pass filtering also allows easier and more reliable fetching, ie modulation, of the original analog signal from the digitized bit stream, as discussed below 3 described.

3 is a graphical illustration that is a working principle of a demodulation process 300 for the modulated digitized output signal 218 . 2 B , above, represents. More specifically, a processor implements 302 in the demodulation process 300 a delta sigma demodulation to an analog signal 304 from the digitized bitstream 218 . 2 B , using a low-pass filter 306 recover. This advantageous technique is much simpler compared to the conventional Nyquist DAC, which reads the quantization bits of each sample and converts the read quantization bits to an appropriate output level. A frequency domain diagram 308 illustrates the advantages of the present delta-sigma method in the frequency domain over the more sophisticated conventional Nyquist demodulation techniques. That is, the low-pass filter 306 Effectively eliminates out-of-band noise and filters out the recovered analog signal 304 at the low frequency end. In this example, the recovered analog signal has 304 , as in 3 shown, due to the noise shaping an uneven noise floor 310 ,

4A-B FIG. 10 are schematic illustrations of an exemplary digitized HFC network. FIG 400 using the modulation method 202 . 2 B , and the demodulation process 300 . 3 , The digitized HFC network 400 is similar in its overall structure to the HFC network 100 , except that the digitized HFC network 400 is adapted to implement delta-sigma modulation and demodulation in place of the conventional A / D and D / A conversion techniques. In particular, the HFC network includes 400 a headboard 402 , a hub 404 , a fiber node 406 , End user / participant 408 and at least one glass fiber 410 that the link between headboard 402 , Hub 404 and fiber nodes 406 combines. The glass fiber 410 is also adapted to transmit digitized bitstreams of the downstream and / or upstream optical signals. A variety of coaxial cables 412 connect the fiber node 406 with the respective end user 408 and transmit the analog electrical signals therebetween. The digitized HFC network 400 optionally implements the amplifiers 414 along the coaxial cable 412 ,

In some embodiments, both the digitized upstream and downstream optical signals are over the same optical fiber 410 transfer. In such cases, the hub includes 404 an optical multiplexer / demultiplexer 416 for respectively combining / splitting the downstream and upstream optical signals, and the fiber node 406 also includes an optical multiplexer / demultiplexer 418 , Multiplexer / demultiplexer 416 . 418 may be passive devices such as diplexers or active configuration devices. In other embodiments, the upstream and downstream transmit downstream signals along separate fibers, and multiplexing is optional (eg, when multiple optical signals are transmitted in the same direction).

4B illustrates an exemplary architecture 420 for implementing the delta-sigma modulation and demodulation processes of the digitized HFC network 400 , In operation of the architecture 420 is a downstream analog signal (eg analog signal 216 . 2 B) from a CMTS 422 of the head 402 / hub 404 by a downstream delta-sigma modulator 424 (eg using the modulation method 202 . 2 B) converted to digitize the analog signal into a digital signal. In the exemplary embodiment, the downstream analog signal is an analog DOCSIS RF signal from a broadcast service of the CMTS 422 or may represent an edge QAM technology or a Converged Cable Access Platform (CCAP). A bitstream (eg output 218 . 2 B) passing through the downstream modulator 424 is generated drives a downstream digital optical transmitter 426 to the downstream digitized bitstream over the fiber 410 to be transmitted by a digital optical downstream receiver 428 of the fiber node 406 Will be received.

At the fiber node 406 converts a storm downstream delta sigma demodulator 430 (eg through the demodulation process 300 . 3 ) the downstream electric digital bitstream from the storm downstream demodulator 430 again into analog form, this demodulated downstream analog signal being transmitted over an existing HFC cable infrastructure, such as via coaxial cable 412 , Amplifier 414 and optional taps 432 , can be transferred.

In the further operation of the digitized HFC network 400 For example, upstream transmissions are performed similarly to the downstream transmissions, but in reverse order. That is, the fiberglass node 406 receives an analog RF signal from one or more end users 408 , An upstream delta-sigma modulator 434 converts the upstream analog signal into a digital upstream bitstream comprising a digital upstream optical transmitter 436 of the fiber node 406 drives the upstream digitized bitstream across the fiber 410 to be transmitted by an optical upstream digital receiver 438 the hub 404 Will be received. An upstream delta-sigma demodulator 440 converts the upstream electrical digital bit stream into an analog form, which is then sent from the CMTS 422 can be received.

As described above, for upstream transmissions, a different optical wavelength than for downstream transmissions may be used. Alternatively, the downstream and upstream digitized bitstreams may be separately transmitted over separate 410DS and 410US optical fibers, respectively. In the alternative embodiments, an electrical diplexer 442 and / or optical multiplexers / demultiplexers (eg elements 416 . 418 . 4A) used when node aggregation and / or nodal division is desired. The present embodiments are therefore particularly advantageous for fiber-constrained network environments encountered by many today's cable operators, in which more limited conventional node aggregation and splitting techniques are often implemented to maximize fiber utilization.

By making the delta-sigma modulation and demodulation processes complementary (or equal) in both the upstream and downstream directions, the present techniques can be used to advantage in existing legacy HFC networks without significant hardware modifications to the present invention CMTS in the headend / hub or existing infrastructure between fiber nodes and end users (ie, electrical amplifiers, taps, etc.) are required. In the in the 4A-4B In the exemplary embodiment illustrated, the optical connection between the hub and the fiber optic node is expanded to a digital optical connection. Through this digital optical connection is the digitized HFC network 400 Therefore, it is advantageously able to use several different optical transport technologies, such as direct optical detection or coherent optical detection, depending on oversampling rate and SNR requirements for the different transmission conditions (eg legacy fiber, distance, etc.) and the resulting link capacity. Through these advantageous techniques, the present systems and methods are capable of achieving significantly longer transmission distances through the use of high-performance, delta-sigma-modulation-based digital transmission.

Currently, transport in the cable environment is asymmetrical. Accordingly, the requirements for HFC systems that implement the present delta-sigma modulation techniques may also be applied asymmetrically. However, according to the delta-sigma modulation techniques described herein, only the transmitter side experiences increased complexity of the oversampling sub-processes. In contrast to Such complexity is not required on the receiver side. That is, the implementation costs on the receiver side are minimal. However, the asymmetry of conventional HFC networks can also significantly reduce implementation costs on the sender side. For example, some DOCSIS 3.1 implementations use a high-split scenario, such as 1.2 GHz downstream / 200 MHz upstream. Accordingly, the cost of upstream transmission is further reduced compared to the cost of downstream transmission because the upstream bandwidth accounts for a fraction of the downstream bandwidth. Since many end-users do not fully utilize the available upstream transport, the customer's need for sampling could be even lower in practice, and hence the resulting cost for the customer's sender implementation.

In addition, the digital optical connection of the upgraded node reached according to the in the 4A-B A significantly improved reliability in comparison with conventional techniques intended to support higher DOCSIS power levels. That is, the delta-sigma modulation / demodulation techniques of the present embodiments will have higher reliability than conventional remote CMTS, remote PHY and A / DD / A digitization approaches. The delta-sigma modulation and demodulation processes described herein are therefore particularly suitable for supporting heterogeneous service environments that include wireless backhaul and business connections according to end-user requirements, while at the same time greatly simplifying operational complexity for all end-users.

5A-B Figures 10 are schematic illustrations of an exemplary digitized distributed network 500 using the modulation process 202 . 2 B , and the demodulation process 300 . 3 , As in 5A represented is the distributed network 500 structurally similar to the digitized HFC network 400 and includes a headboard 502 , a hub 504 , a fiber node 506 , End user / participant 508 , at least one glass fiber 510 , a variety of coaxial cables 512 and optional amplifiers 514 , The distributed network 500 however, it is different from the digitized HFC network 400 in operation, as related to 5B explained in more detail.

5B illustrates an exemplary distributed architecture 516 to implement the delta-sigma modulation and demodulation processes of the distributed network 500 , The operation of the distributed architecture 516 differs from the operation of the architecture 420 . 4 , in that the distributed architecture 516 distribute the PHY layer into the HFC network. That is, the distributed architecture 516 distributes the PHY layer to the fiber node 506 (or the PHY shelf), causing the PHY, for example, from a CMTS 518 (ie, the CCAP core), thereby making it possible to eliminate the need for an analog laser (not shown) at the headend 502 / hub 504 to eliminate. In this embodiment, the CMTS 518 thus functionally converted to a digital fiber-optic Ethernet connection (eg, a network aggregation layer for an optical Ethernet or a passive optical network (PON)), and the fiber 510 Functionally serves as optical Ethernet digital fiber.

At the fiber node 506 receives a digital optical transceiver or transceiver 520 the digital signals from the CMTS 518 on a downstream distributed MAC / PHY layer 522 for conversion by a downstream delta-sigma demodulator 524 in an analog signal. Similarly, an upstream delta-sigma modulator converts analog signals from end users 508 into digitized signals for an upstream distributed MAC / PHY layer 528 um, to her the digital optical transceiver 520 for upstream transport over the fiber 510 provide. Similar to the architecture 420 . 4 , can the distributed architecture 516 also a diplexer 530 and at least one tap 532 include. This example uses the distributed architecture 516 Advantageously, the downstream delta sigma demodulator 524 as a D / A converter and the upstream delta sigma modulator 526 as an A / D converter. Therefore, the delta-sigma modulation and demodulation techniques of the 5A-B each in both upstream and downstream directions are fully implemented.

According to this embodiment, a low-cost demodulation method is provided. The implementation achieves ultra-high resolution for RF signal conversion and is capable of using either direct or coherent recognition technologies using the optical connection between headend / hub and fiber node. By the economic simplification of the distributed architecture 516 needs the distributed network 500 only one delta-sigma modulator / demodulator pair at the fiber node 506 for the HF digital conversion.

6A-B FIG. 10 are schematic illustrations of an exemplary radio frequency over-the-glass (RFoG) network. FIG 600 using the modulation process 202 . 2 B , and the demodulation 300 . 3 , As in 6A is the RFoG network 600 the digitized HFC network 400 structurally similar and includes a headboard 602 , a hub 604 , a fiber node 606 , End user / participant 608 , at least one glass fiber 610 , a variety of coaxial cables 612 and optional amplifiers 614 , However, the RFoG network 600 is different from the digitized HFC network 400 in that the RFoG analog optic transmits RF over fiber instead of the coaxial cable to a termination unit (eg, an optical network unit (ONU) or an optical network terminal (ONT), not individually shown) in the respective customer premises of the end users 608 is used.

6B illustrates an exemplary RFoG architecture 616 to implement the delta-sigma modulation and demodulation processes of the RFoG network 600 , The RFoG architecture 616 is similar to architecture 420 . 4 , and includes a CMTS 618 , a downstream delta-sigma modulator 620 , a digital downstream optical transmitter 622 , a hub diplexer 624 (or multiplexer / demultiplexer), a fiber node diplexer 626 (or multiplexer / demultiplexer), a digital optical downstream receiver 628 , a downstream delta-sigma demodulator 630 , an upstream delta-sigma modulator 632 , a digital optical upstream transmitter 634 , a digital optical upstream receiver 636 the hub 604 and an upstream delta-sigma demodulator 638 , In the embodiment, the RFoG architecture is included 616 furthermore at least one optical splitter 640 that goes along the fiberglass 610 is arranged. The downstream delta sigma demodulator 630 and the upstream delta-sigma modulator 632 communicate with a customer premises facility (CPE) 642 at least one end user 608 ,

According to the in the 6A-B shown advantageous embodiments, a significant improvement in the transmission power of the digital connection of the RFoG network 600 through the introduction of delta-sigma modulation and demodulation processes at both the headend / hub and customer premises / end users, effectively replacing the optical link with digital transmissions. The architecture and operation of the RFoG network 600 are particularly beneficial for customer users with existing home coaxial cabling and / or CPEs; the implementation of the RFoG network 600 does not require any hardware changes to such existing infrastructure. In addition, the digital fiber optic deep architecture of the RFoG network enables 600 a further increase to the end users 608 delivered data rate. When using the splitter 640 Also, the splitting ratio can be further increased due to the higher power budget margin achievable by such digital links.

In accordance with the advantageous systems and methods described above, efficient digitization techniques over conventional HFCs in RFoG networks can be used to significantly extend the transport capacity of existing fiber strands without the need for significant hardware modifications or costs. The systems and methods described herein utilize existing fiber infrastructures to increase the capacity of such existing infrastructures, but without increasing receiver-side complexity. The present embodiments also take advantage of the existing network transmission asymmetry to further reduce transmitter-side complexity. The present systems and methods thus significantly extend the life of existing fiber infrastructures and also make existing optical wavelengths more efficient. Through the techniques described herein, a fiber optic communication network will achieve increased scalability so that the network can grow flexibly with the increasing demand of the cable customers.

Embodiments of analog digitization systems and methods are described in detail above. However, the systems and methods of this disclosure are not limited to the specific embodiments described herein, but the components and / or steps of their implementation may be used independently and separately from other components and / or steps described herein. Moreover, the embodiments may be implemented and utilized in conjunction with other access networks using fiber and coaxial transmission.

Mapping and de-mapping of digitized signals for optical transmission

The digitization of analog signals can significantly improve the achievable SNR / CNR and capacity over digital optical links. As described above, the delta-sigma ADC is an improvement over the conventional Nyquist ADC in that it has a high oversampling rate and a small number of quantization bits (1-2 bits). As described above, the conventional Nyquist ADC operates at the Nyquist sampling rate and uses many quantization bits to suppress the quantization noise while the delta-sigma ADCs use only 1 or 2 quantization bits and the oversampling technique for expanding the Nyquist Leave the zone. The delta-sigma ADC also uses Noise shaping techniques to move the quantization noise out of the signal band and to improve the in-band SNR so that the effective quantization bit number is increased.

The embodiments herein and below are described herein with particular reference to DOCSIS signals (and DOCSIS 3.1), but the present embodiments also offer significant advantages over other multicarrier signals such as Wi-Fi, WiMAX, UWB, LTE and 5G radio signals. The digitizing processes of the present embodiments are still further applicable to analog signals for front and / or backhaul applications.

The following embodiments provide systems and methods for transmitter-side symbol mapping buz. Mapping of digitized signals after delta-sigma digitization (DSD) and receiver-side symbol mapping of retrieved signals. The remapping processes map the retrieved signals to the originally digitized signal sequences. The innovative techniques described herein increase system performance while reducing the cost of lower node and higher bandwidth for customer applications while leveraging existing optical components and fiber infrastructure.

In an exemplary embodiment for OOK signals generated by 1-bit DSD, a symbol mapping process encrypts the bit stream to avoid successive 0's or 1's so that the digitized signal not only has the same set of 0 bits and 1 bits, but also 0's and 1s equally spaced in time sequence to facilitate optical transmission and clock recovery at the digital receiver. For PAM4 signals generated by 2-bit DSD, on the other hand, a symbol mapping process alters the distribution of ± 1 and ± 3 symbols, so that the digitized symbols are evenly distributed to ± 1en and ± 3en for the optical communication link, as in FIG Described below.

The use of analog signals is widespread in HFC networks in the cable television industry. The use of analog signals, however, is questioned by the appearance of DOCSIS 3.1. In analog systems, e.g. DOCSIS 3.0 and earlier HFC networks, the quality of the received RF signals is determined by the composite carrier-to-noise ratio (CCNR), which is limited by a combination of noise and nonlinear impairments by electrical and optical domains.

By transforming signal waveforms from single-carrier to multi-carrier OFDM, DOCSIS 3.1 supports higher-order modulation formats for improved spectral efficiency, increased data capacity, and more flexible assignment of spectral resources. However, OFDM signals are characterized by continuous envelopes and a high peak-to-average power ratio (PAPR) which makes the OFDM signals susceptible to transmission impairments and nonlinear distortions. For example, third order distortions such as composite triple beat (CTB), Create in-band interference components that overlap with the existing OFDM subcarriers and are difficult to filter. In addition, to meet the demanding CNR requirements for high-order modulation formats (e.g., 1024QAM and higher) of DOCSIS 3.1, conventional analog fiber technologies have reached their limits. The achievable connectivity budget of the conventional system is significantly limited by the nonlinear distortion of the analog signals.

According to the innovative embodiments described herein, the transmission performance of DOCSIS 3.1 signals in HFC networks is significantly enhanced by utilizing digital connections to leverage existing digital fiber communication technologies in HFC networks, such as coherent data center interconnect (DCI) or direct intensity modulation (FIG. IM-DD) PONs. Digital connections are more robust to power loss and nonlinear impairments, and the received optical power is kept above the receiver sensitivity. These innovative techniques provide increased fiber distance, increased head end / stroke coverage, and improved transmission interference tolerance. With digital error-free transport, the transmission disturbances of digital connections can be essentially isolated from the quality of the received RF signals. That is, the CNR degradation contributed by optical / electrical noise and distortion can be eliminated. In addition, by utilizing wavelength division multiplexing (WDM) technology, the digital optical systems of the present embodiments can support multiple wavelengths per fiber, thus enabling future capacity expansion.

The embodiments described herein are different from conventional Nyquist digitization, which involves symmetrical complexity of AD / DA operations at the transceiver side having; The delta-sigma digitizing (DSD) techniques of the present embodiments provide asymmetric complexity for AD and DA operations.

7 FIG. 10 is a schematic block diagram of an exemplary signal mapping process. FIG 700 at the system level. In an exemplary embodiment, the process is 700 with respect to a coherent optical network system 702 implements a transmitter section 704 and a receiver section 706 includes, via an optical transmission link 708 (eg for direct or coherent detection) communicate with each other in functional communication. In the exemplary embodiment, the transmitter section 704 the head end and / or the optical hub and includes a complex high-speed ADC (not in 7 ) configured to perform the above described oversampling, noise shaping and quantization processes (1-bit or 2-bit) to convert the analog input signals to digital outputs (OOK and PAM4, respectively).

Also in an exemplary embodiment, the receiver section includes 706 a fiber node and filter (also not in 7 shown) configured to perform the DAC processes described above. As described above, the process is different 700 from the conventional Nyquist ADC, which eliminates quantization noise through the use of many quantization bits. In contrast, the process can 700 implement a delta-sigma ADC to shift the quantization noise outside the band. Accordingly, on the side of the receiver section 706 a low pass filter (LPF) or band pass filter (BPF) can be used to filter out the desired signal. At the same time or approximately simultaneously, the digitized signal can be converted back to its analog waveform by eliminating the out-of-band quantization noise. According to this advantageous configuration, channel frequency demultiplexing and D / A conversion can both be implemented by a single device.

This asymmetry of the AD / DA operations of delta-sigma digitization can be further advantageously implemented in point-to-multipoint architectures such as PONs, mobile front-end networks, and HFC networks. In an exemplary embodiment, the complex ADC of the process 700 centralized at the head end / hub and shared by multiple fiber nodes. In contrast, the simplified LPF / BPF in each fiber node of the optical connection 708 distributed to act as both a DAC and a channel demultiplexer. In accordance with this advantageous system architecture, the cost and complexity of fiber optic node design can be significantly reduced, while at the same time improving system reliability.

In an exemplary embodiment, the process is 700 implemented with respect to a DOCSIS 3.1 transmission. DOCSIS 3.1 uses OFDM signals that have a continuous envelope and Gaussian distributed amplitudes, ie there are more samples of small amplitude than larger amplitude samples. In the exemplary embodiment, after the 1-bit delta-sigma digitization, the DOCSIS 3.1 signals are digitized into OOK signals. Although, in this example, the number of 0-bits and 1-bits is the same, due to the continuous envelope of the input OFDM signals, there will also be many consecutive 0's or 1's. To improve the transmission performance and the clock recovery of the receiver section 706 to facilitate, the process implements 700 also a symbol mapping to encrypt the bit sequence and thereby avoid successive 0s or 1s. Thereafter, symbol matching may be performed, and the digitized signal generated therefrom not only has an equal number of 0-bits and 1-bits, but also has 0s and 1s evenly distributed in the transmitted time sequence.

Similarly, after 2-bit delta-sigma digitization, the 4-symbol DOCSIS 3.1 signals, ie, ± 1 and ± 3, can be digitized into PAM4 signals due to the Gaussian distribution of the analog input signal (eg, signal 216 . 2 ), the set of these four symbols also has a Gaussian distribution, ie there are more ± 1s than ± 3s. As described below, the process handles 700 this distribution problem by adjusting the symbol distribution of the digitized signals to more evenly balance the amount of each transmitted symbol. In accordance with these advantageous techniques, the present embodiments utilize the capacity of the digital fiber link (eg, link 708 ) and maintain the zero modification of commercial DSP algorithms in coherent / IM-DD digital receivers. As described above, these techniques are not based on DOCSIS 3.1 and can also be applied to other transmitted signals such as Wi-Fi, WiMAX, UWB, LTE and 5G radio signals with the support of multi-carrier modulation formats.

As described below, process implements 700 in addition to the system flow 710 ("(1)," dashed lines) mapping and demapping flow techniques ("(2)") using only the delta-sigma digitizing techniques described above. In the exemplary embodiment, the transmitter implements 704 for an analog input signal 712 a delta-sigma digitizing subprocess 714 to ADC on the analog input signal 712 perform. When delta-sigma digitization is implemented without mapping, the process goes 700 from the delta-sigma digitization sub-process 714 to a digital signal modulation sub-process 716 via (eg E / O conversion). According to the exemplary embodiment, the process includes 700 but also a digital signal shaping sub-process 718 after the delta-sigma digitization in the sub-process 714 but before the digital signal modulation in the subprocess 716 performed to a distribution mapping of the digitized signal on the transmitter side, ie the transmitter section 704 to provide.

In further operation, after the modulation in the sub-process 716 the modulated signal over the optical transmission link 708 transfer. On the receiver side, ie the receiver section 706 , the process implements 700 then a digital signal recovery subprocess 720 (eg O / E conversion and processing). In the event that the distribution mapping is not from the subprocess 718 has been implemented, the process becomes 700 from the recovery subprocess 722 respectively. 720 to a delta sigma demodulation subprocess 722 from which the recovered analog signals 724 to be obtained. According to the exemplary embodiment, the process includes 700 but further a digital signal demolding process 726 after the digital signal recovery in the subprocess 720 but before the delta sigma demodulation in the subprocess 722 to perform a distribution demapping of the digitized signal on the receiver side, ie the transmitter section 706 to provide before the analogue conversion.

In the exemplary embodiment, the process adds 700 on the transmitter side (ie transmitter section 704 ) after the delta-sigma digitization of the input analog signal 712 in the subprocess 714 a symbol mapping subprocess (ie subprocess 718 ) one. Similarly, the process uses 700 a symbol demapping subprocess (ie subprocess 726 ) on the receiver side (ie receiver section 706 ) to map / demap the signal back to the original signal sequences and then place the demapped signal into a DAC (ie delta sigma demodulation subprocess 722 ) for digital-to-analog conversion. In the exemplary embodiment, a mapping code is used 728 from the digital signal shaping subprocess 718 to the digital signal de-molding process 726 transmitted to the over the optical transmission link 708 to modify transmitted signal distribution. In some embodiments, the mapping code becomes 728 via the optical transmission connection 708 transfer. In other embodiments, the mapping code becomes 728 transmitted via alternative communication channels.

According to the exemplary configuration of the process 700 eliminates the need for existing commercial digital signal recovery algorithms after the delta-sigma digitization or after the transmission of the signals over the optical transmission link 708 because the signal mapping / demapping subprocesses 718 / 726 according to their own mapping code 728 be performed. In some embodiments, the multiple subprocesses of the process become 700 one or more hardware units (eg, ADC, DAC, modulator, demodulator, mapper, demapper) configured to perform one or more of the respective functions. In other embodiments, the plurality of sub-processes are software programmed by at least one processor of the sender section 704 and / or the receiver section 706 implemented. In at least one embodiment, the sub-processes are performed by a combination of hardware units and software programming. In an exemplary embodiment, the DAC includes an LPF and / or a BPF.

8th is a graphical illustration showing an unmapped electrical eye diagram 800 of a digitized signal after delta-sigma digitization (eg sub-process 714 . 7 ). In an exemplary embodiment, the eye diagram represents 800 a PAM4 signal after the delta-sigma digitization. In this example, the occurrence of +1 and -1 symbols each having a probability of p _1, whereas the occurrence of +3 and -3 icons each have a probability of p ₃ and the total probability of occurrence of all four symbols is 100%.

This total probability can be represented according to the following equation: $$2{\text{<figure-callout id="1" label="p" filenames="DE112018000446T5\_0007.png,DE112018000446T5\_0008.png" state="{{state}}">p</figure-callout>}}_1+2{\text{<figure-callout id="3" label="p" filenames="DE112018000446T5\_0014.png,DE112018000446T5\_0017.png" state="{{state}}">p</figure-callout>}}_3=100\text{\%}$$

As described above, OFDM signals follow the Gaussian distribution, and ultimately result in more small amplitude samples than large amplitude samples. Therefore, there are many more ± 1 symbols (small amplitude) in the digitized PAM4 signal than ± 3 symbols (large amplitude), ie p ₁ >> p ₃ . Accordingly, as in the eye diagram 800 you can see areas 802 with greater intensity, the ± 1 symbol levels, while ranges 804 due to the unequal distribution, they represent the ± 3 symbol levels with less intensity.

9 is a graphical representation that is an electrical eye diagram 900 of a digitized signal after delta-sigma digitization that implements a flip-mapping process. In this example, the electrical eye diagram represents 900 the PAM4 signal of the eye diagram 800 after delta-sigma digitization and after implementation of a flip-mapping sub-process (discussed below with respect to FIG 10 described).

In the exemplary embodiment, the flip mapping subprocess of the eye diagram maps 900 the ± 1 symbols to the ± 3 symbols too, but with unchanged sign, and vice versa. That is, the flip-mapping of the symbols is as follows: +3 → +1; +1 → +3; -1 → -3; -3 → -1. Accordingly, since p ₁ >> p ₃ , there are significantly more ± 3 symbols after flip-mapping than ± 1 symbols. Accordingly, as in the eye diagram 900 you can see the areas 902 with greater intensity represents the ± 3 symbol levels, while the ranges 904 with less intensity represent the ± 1 symbol levels, in contrast to the eye diagram 800 ,

This inverse can be represented according to the following equation: $${\text{y}}_{\text{n}}=\text{sgn}\left({\text{x}}_{\text{n}}\right)\left(4-\left|{\text{x}}_{\text{n}}\right|\right)$$

Where x _{n is} the symbol value of the digitized sequence of n symbols and y _{n is} the symbol value of the digitized sequence after applying the flip mapping subprocess.

10 is a graphical representation of a flip-mapping table 1000 Using the digitized electrical eye diagram signal 900 . 9 , can be implemented. The flip mapping table 1000 Graphically illustrates the compliance of the flips of the above with respect to 9 described flip-mapping sub-process. In an exemplary embodiment, the flip-mapping table 1000 in corresponding databases from the transmitter (ie transmitter section 704 . 7 ) and the receiver (ie receiver section 706 . 7 ) and interposed as a code (ie mapping code 728 . 7 ) are communicated.

11A-B are graphs showing a comparative result of a transmitted signal with and without the implementation of the 9 and 10 represent illustrated flip-mapping processes. In particular, presents 11A a transmitted signal 1100 on which a delta-sigma digitizing sub-process has been implemented, but no mapping sub-process, and 11B provides a mapped signal 1102 that is the transmitted signal 1100 after applying a flip-mapping sub-process to it. In this example, the signals become 1100 . 1102 as 16QAM 16GBaud signals over a 40km transmission at 128Gb / s. Accordingly, after implementation of the flip-mapping sub-process, the signal magnitude smoothes significantly around the center frequency, as compared to a mapped signal comparison 1102 with the transmitted (unmapped) signal 1100 is apparent.

12A-B FIG. 10 is graphs illustrating a comparative result of a pseudo-random binary sequence (PRBS) PAM4 signal with a result of a signal on which a unitary mapping sub-process (subprocess A, described below) has been implemented. In particular, presents 12A an electrical eye diagram 1200 a PRBS based PAM4 signal, and 12B makes an electrical eye diagram 1202 a signal that implements a uniform mapping subprocess A.

In an exemplary embodiment, the uniform mapping subprocess A uses an encryption code. S _{n represents} a periodic pseudorandom bitstream of 0 and 1 values with equal probabilities (ie 50% are 0s and 50% are 1s). For an input symbol x _n , the value is flipped if the value S _n = 1, but remains unchanged if S _n = 0. Thus, the uniform mapping subprocess A can be used together with the one described above with respect to FIG 9 and 10 , above, flip-mapping process described. Accordingly, as from a comparison of Eye diagrams 1200 and 1202 can be seen after the implementation of the uniform mapping sub-process A, the respective ± 1 and ± 3 symbols evenly distributed. That is, the eye diagram 1202 The mapped signal is almost identical to the eye diagram 1200 the PRBS based PAM4 signal.

13A-B are graphical representations of alternative symbol mapping tables 1300 and 1302 Using the digitized electrical eye diagram signal 1202 . 12B , can be implemented.

The symbol mapping table 1300 corresponds to the uniform mapping subprocess A, which has been described above with respect to FIG 12A-B has been described. In the exemplary embodiment, using encryption code S _n , 50% of the +3 symbols are mapped to a +1 symbol (eg, S _n = 1) while the other half of the +3 symbols remain unchanged (eg, S _n = 0). The arrangement of the symbols +1, -1 and -3 is similarly determined as by the following equation for the symbol mapping table 1300 (Mapping subprocess A): $${\text{y}}_{\text{n}}=\{\begin{array}{c}{\text{x}}_{\text{n}}\left({\text{S}}_{\text{n}}=0\right)\\ \text{sgn}\left({\text{x}}_{\text{n}}\right)\left(4-\left|{\text{x}}_{\text{n}}\right|\right)\left({\text{S}}_{\text{n}}=1\right)\end{array}$$

The symbol mapping table 1302 is similar to the symbol mapping table 1300 but uses an additional value for the encryption key S _n . That is, according to symbol mapping table 1302 (for the uniform mapping thread "B"), the scrambling code S _{n represents} a periodic pseudo-random bit stream of -1, 0 and 1 values with probabilities of 25%, 50% and 25% respectively (ie (ie 25% of the events are -1, 50% of the events are 0 and 25% of the events are 1) In this alternative embodiment, for an input symbol x _n, the value is flipped with an unchanged sign if S _n = 1, and the Value is flipped with its sign also vice versa if S _n = -1 If S _n = 0, both the value and the sign of x _n remain unchanged.

The resulting values y _n can be represented according to the following equation: $${\text{y}}_{\text{n}}=\{\begin{array}{c}{\text{x}}_{\text{n}}\left({\text{S}}_{\text{n}}=0\right)\\ \text{sgn}\left({\text{x}}_{\text{n}}\right)\left(4-\left|{\text{x}}_{\text{n}}\right|\right)\left({\text{S}}_{\text{n}}=1\right)\\ -\text{sgn}\left({\text{x}}_{\text{n}}\right)\left(4-\left|{\text{x}}_{\text{n}}\right|\right)\left({\text{S}}_{\text{n}}=-1\right)\end{array}$$

Concretely, looking at the +3 symbol, 25% of the +3 symbols are assigned to a +1 symbol, another 25% of the +3 symbols to a -1 symbol, and the remaining 50% to the +3 symbol Symbols remain unchanged (ie mapped to a + 3 symbol). The arrangement of the symbols +1, -1 and -3 is similarly determined according to the same calculations.

Similar to the implementation of the above in terms of the 12A-B The uniform mapping subprocess A described above, the implementation of the uniform mapping subprocess B also distributes the symbols ± 1 and ± 3 equally after the mapping and thus generates an eye diagram (not shown) which is also almost identical to the eye diagram 1200 of the PRBS based PAM4 signal. That is, an eye diagram created according to the uniform mapping subprocess B is identical to the eye diagram created after the uniform mapping subprocess A. 1202 (and thus also with the 1-diagram or eye diagram 1200 the PRBS based PAM4 signal). Accordingly, the two uniform mapping subprocesses A and B can be successfully implemented to modify the symbol distribution and to map the respective input signal with statistical accuracy to a PRBS signal.

14A-B are graphical representations that represent a comparative result of a signal representing the in 13A implemented unified mapping process, with a signal that the in 13B implemented alternative uniform mapping process implemented. In particular, presents 13A a transmitted signal 1300 on which the uniform mapping subprocess A has been implemented, and 13B represents a transmitted signal 1302 on which the uniform mapping subprocess B has been implemented. In this example, the signal becomes 1300 as a 16QAM 16GBaud signal over a 40km transmission at 128Gb / s and the signal 1302 as a 16QAM 32GBaud signal over a 40km transmission at 256Gb / s. Accordingly, as from a comparison of the signals 1300 and 1302 As can be seen, the various uniform mapping sub-processes are successfully implemented for similar input signals, but with different symbol rates and data rates.

15 is a graphical representation of a symbol table 1500 comparing the symbol mapping techniques of the subprocesses described above. In this example, the respective probabilities in each mapping pass (ie, "match A" for the unitary mapping subprocess A and "match B" for the unitary mapping subprocess B) are for the respective scrambling code S _n labeled ("Scrambler A" and "Scrambler B"). As from the symbol table 1500 As can be seen, the respective probabilities of symbol occurrence vary depending on whether only one delta-sigma digitizing sub-process is implemented on the analog signal, or a flip-mapping sub-process and a two-valued or three-valued uniform mapping / scrambling sub-process as well are implemented. As described with respect to the embodiments described above, the mapping and demapping techniques of the present systems and methods significantly improve the quality and performance of a digitized signal transmitted over an optical link.

Although specific features of various embodiments of the disclosure may not be shown in some drawings and in others, this is for convenience only. In accordance with the principles of the disclosure, a particular feature illustrated in a drawing may be referenced and / or claimed in combination with features of the other drawings. For example, the following list of exemplary claims represents only a portion of the possible combinations of elements that are possible from the systems and methods described herein.

a (i). An optical network comprising: a transmitter section configured to transmit a digitized symbol stream over a digital optical link; a mapping unit disposed within the transmitter section and configured to encode the transmitted digitized symbol stream with a mapping code prior to transmission over the digital optical link; a receiver section configured to recover the coded symbol stream from the digital optical link; and a demapping unit disposed within the receiver section and configured to map the recovered coded symbol stream into an uncoded digitized signal corresponding to the digitized symbol stream at the transmitter section prior to being coded by the mapping unit.

bi). The system of claim a (i), wherein the transmitter section comprises an analog-to-digital converter configured to digitize an analog input signal.

c (i). The system of claim b (i), wherein the analog-to-digital converter is configured to perform delta-sigma digitization on the analog input signal.

d (i). The system of claim c (i), wherein the analog-to-digital converter is arranged within the transmitter section such that the delta-sigma digitization of the analog input signal is implemented by the mapping unit prior to encoding the transmitted digitized stream.

egg). The system of claim c (i), wherein the receiver section comprises a digital-to-analog converter configured to convert the uncoded digitized signal to a recovered analog signal.

f (i). The system of claim e (i), wherein the digital-to-analog converter is configured to perform delta-sigma demodulation on the uncoded digitized signal.

g (i). The system of claim f (i), wherein the digital-to-analog converter is located within the receiver section such that the delta-sigma demodulation of the uncoded digitized signal is implemented after the mapping of the recovered encoded stream by the demapping unit.

Hi). The system of claim a (i), wherein the system is configured to transmit a signal in accordance with one or more of the following wireless signal specifications: DOCSIS 3.1, Wi-Fi, WiMAX, UWB, LTE, and 5G.

i (i). The system of claim a (i), wherein the digitized symbol stream is digitized according to at least one of an OOK and a PAM4 signal format.

a (ii). A symbol mapping method for a digitized signal, the digitized signal including a series of transmitted symbols having a Gaussian distribution of symbol amplitude values, the method comprising the steps of: mapping the first symbol for at least one input event of a first symbol of the series of transmitted symbols a second symbol of the series of transmitted symbols, the first symbol having a first symbol amplitude value and the second symbol having a second symbol amplitude value greater than the first symbol amplitude value; and mapping the second symbol to the first symbol in at least one occurrence of the second symbol.

b (ii). The method of claim a (ii), wherein the sign of the first and second symbols remains unchanged after being assigned to the other of the first and second symbols.

c (ii). The method of claim a (ii), further comprising the step of applying a scrambling code to each input event of the first and second symbols.

d (ii). The method of claim c (ii), wherein the scrambling code comprises a periodic pseudo-random bit stream of 0 and 1 values having substantially equal entry probabilities.

e (ii). The method of claim d (ii), wherein upon each occurrence of the first input symbol, the first symbol is mapped to the second symbol if the encryption key has a value of 1 and the first symbol remains unchanged if the encryption key has a value of 0 has.

f (ii). The method of claim c (ii), wherein the scrambling code comprises a periodic pseudo-random bitstream of -1, 0, and 1 values, wherein the -1 and 1 values each have a 25% probability of occurrence, and wherein the 0 value has a 50% probability of occurrence. having.

g (ii). The method of claim f (ii), wherein for each occurrence of the first input symbol, the first symbol is mapped to the second symbol if the encryption key has a value of -1 or 1, and the first symbol remains unchanged if the encryption key has a value of 0 has.

h (ii). The method of claim g (ii), wherein upon each mapping of the first symbol to the second symbol, the symbol amplitude value of the mapped first symbol is equal to the symbol amplitude value of the second symbol, the sign of the mapped first symbol remains unchanged if the encryption key has a value of 1 and the sign of the mapped first symbol is reversed if the encryption key has a value of -1.

i (ii). The method of claim a (ii), wherein the first symbol has a value of ± 1 and the second symbol has a value of ± 3.

j (ii). The method of claim a (ii), wherein the series of transmitted symbols represents a PAM4 signal.

k (ii). The method of claim a (ii), wherein the digitized signal is a DOCSIS 3.1 signal.

Some embodiments involve the use of one or more electronic or computing devices. Such devices typically include a processor or controller, such as a general purpose central processing unit (CPU), a graphics processing unit (GPU), a microcontroller, a reduced instruction set computer (RISC), an application specific integrated circuit (ASIC), a programmable logic controller Logic circuit (PLC), a FPGA (Field Programmable Gate Array), a DSP device and / or other circuit or other processor capable of performing the functions described herein. The processes described herein may be encoded as executable instructions contained in a computer-readable medium, including but not limited to a storage device and / or storage device. Such instructions, when executed by a processor, cause the processor to perform at least a portion of the methods described herein. The above examples are exemplary only and are therefore not intended to limit in any way the definition and / or meaning of the term "processor".

This written description uses examples to disclose the embodiments, including the best mode, and also to enable any person skilled in the art to practice the embodiments, including making and using devices or systems, and performing included methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal implementation of the claims, or if they include equivalent structural elements with insubstantial differences from the literal implementation of the claims.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

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• US 62448044 [0001]

Claims (20)

Optical network comprising: a transmitter section configured to transmit a digitized stream of symbols over a digital optical link; a mapping unit disposed within the transmitter section and configured to encode the transmitted digitized symbol stream with a mapping code prior to transmission over the digital optical link; a receiver section configured to recover the coded symbol stream from the digital optical link; and a demapping unit located within the receiver section and configured to map the recovered coded symbol stream into an uncoded digitized signal corresponding to the digitized symbol stream at the transmitter section prior to being coded by the mapping unit. System after Claim 1 wherein the transmitter section comprises an analog-to-digital converter configured to digitize an analog input signal. System after Claim 2 wherein the analog-to-digital converter is adapted to perform delta-sigma digitization on the analog input signal. System after Claim 3 wherein the analog-to-digital converter is arranged within the transmitter section such that the delta-sigma digitization of the analog input signal is performed prior to the encoding of the transmitted digitized current by the mapping unit. System after Claim 3 wherein the receiver section comprises a digital-to-analog converter configured to convert the uncoded digitized signal into a recovered analog signal. System after Claim 5 wherein the digital-to-analog converter is adapted to perform delta-sigma demodulation on the uncoded digitized signal. System after Claim 6 wherein the digital-to-analog converter is disposed within the receiver section such that the delta-sigma demodulation of the uncoded digitized signal is implemented after the mapping of the recovered coded stream by the demapping unit. System after Claim 1 The system is adapted to transmit a signal in accordance with one or more of the wireless or wireless signal specifications DOCSIS 3.1, Wi-Fi, WiMAX, UWB, LTE and 5G. System after Claim 1 wherein the digitized symbol stream is digitized according to at least one of an OOK and a PAM4 signal format. A symbol mapping method for a digitized signal, the digitized signal including a series of transmitted symbols having a Gaussian distribution of symbol amplitude values, the method comprising the steps of: Mapping the first symbol, for at least one input occurrence of a first symbol of the series of transmitted symbols, to a second symbol of the series of transmitted symbols, wherein the first symbol is a first symbol amplitude value and the second symbol is a second symbol Symbol amplitude value greater than the first symbol amplitude value; and Mapping the second symbol to the first symbol in at least one occurrence of the second symbol. Method according to Claim 10 wherein the sign of the first and second symbols remains unchanged after mapping to the other of the first and second symbols. Method according to Claim 10 further comprising the step of applying a scrambling code to each input event of the first and second symbols. Method according to Claim 12 wherein the scrambling code comprises a periodic pseudo-random bit stream of 0 and 1 values having substantially equal occurrence probabilities. Method according to Claim 13 wherein for each occurrence of the first input symbol, the first symbol is mapped to the second symbol when the encryption key has a value of 1 and the first symbol remains unchanged when the encryption key has a value of 0. Method according to Claim 12 wherein the scrambling code comprises a periodic pseudo-random bitstream of -1, 0 and 1 values, the -1 and 1 values each having a 25% probability of occurrence and the 0 value having a 50% probability of occurrence Method according to Claim 15 wherein for each occurrence of the first input symbol, the first symbol is mapped to the second symbol if the encryption key has a value of -1 or 1, and the first symbol remains unchanged if the encryption key has a value of 0. Method according to Claim 16 wherein, each time the first symbol is mapped to the second symbol, the symbol amplitude value of the mapped first symbol is equal to the symbol amplitude value of the second symbol, the sign of the associated first symbol will remain unchanged if the encryption code is one Value of 1, and the sign of the mapped first symbol is reversed if the encryption key has a value of -1. Method according to Claim 10 , where the first symbol has a value of ± 1 and the second symbol has a value of ± 3. Method according to Claim 10 , where the series of transmitted symbols represents a PAM4 signal. Method according to Claim 10 , where the digitized signal is a DOCSIS 3.1 signal.

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