WO2023164156A1 - Chargement de bits pour robustesse - Google Patents

Chargement de bits pour robustesse Download PDF

Info

Publication number
WO2023164156A1
WO2023164156A1 PCT/US2023/013855 US2023013855W WO2023164156A1 WO 2023164156 A1 WO2023164156 A1 WO 2023164156A1 US 2023013855 W US2023013855 W US 2023013855W WO 2023164156 A1 WO2023164156 A1 WO 2023164156A1
Authority
WO
WIPO (PCT)
Prior art keywords
bit loading
cable modem
qam modulation
qam
profiles
Prior art date
Application number
PCT/US2023/013855
Other languages
English (en)
Inventor
William T. Hanks
Original Assignee
Arris Enterprises Llc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Arris Enterprises Llc filed Critical Arris Enterprises Llc
Publication of WO2023164156A1 publication Critical patent/WO2023164156A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/2854—Wide area networks, e.g. public data networks
    • H04L12/2856—Access arrangements, e.g. Internet access
    • H04L12/2869—Operational details of access network equipments
    • H04L12/287—Remote access server, e.g. BRAS
    • H04L12/2876—Handling of subscriber policies
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/2854—Wide area networks, e.g. public data networks
    • H04L12/2856—Access arrangements, e.g. Internet access
    • H04L12/2869—Operational details of access network equipments
    • H04L12/2898—Subscriber equipments
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/38—Demodulator circuits; Receiver circuits

Definitions

  • the subject matter of this application generally relates to the creation and assignment of bit loading profiles to cable modems in a DOCSIS transmission architecture.
  • Orthogonal Frequency Division Multiplexing (OFDM) technology was introduced as a cable data transmission modulation technique during the creation of the CableLabs DOCSIS 3.1 specification.
  • OFDM technology was defined for use directly in the downstream direction and was adapted for multiple access (Orthogonal Frequency Division with Multiple Access - OFDMA) for use in the upstream direction.
  • OFDM technology In each direction, the relatively wide channel is subdivided into many small subcarriers.
  • each of these subcarriers may use its own Quadrature Amplitude Modulation (QAM) level, which equates to a different bit capacity per subcarrier QAM symbol.
  • QAM Quadrature Amplitude Modulation
  • minislot In the upstream direction, groups of subcarriers are combined and, when time multiplexed, create the atomic unit of upstream bandwidth assignment known as a “minislot.” In the upstream direction, all subcarriers of a minislot are assigned the same QAM level and thus all subcarriers of a minislot have the same bit capacity per QAM symbol.
  • each cable modem would be assigned its own vector of per-subcarrier QAM modulation levels, i.e. a. bit loading vector, that is uniquely optimized for that cable modem.
  • bit loading vector the DOCSIS 3.1 specification defines a compromise where groups of cable modems having similar RF characteristics can be assigned the same bit loading vector, if that vector is constructed such that that all cable modems assigned that vector could use it.
  • bit loading profiles could be reduced to a cost-manageable set of “bit loading profiles” that could each be assigned to multiple cable modems at once
  • the current generation of DOCSIS allows head ends that communicate with cable modems to utilize up to sixteen bit loading profiles per channel in the downstream direction and up to seven bit loading profiles per channel in the upstream direction.
  • the current generation of DOCSIS permits each cable modem to be assigned up to five profiles per channel in the downstream direction and up to two profiles per channel in the upstream direction.
  • FIG. 1 illustrates an Orthogonal Frequency Division Multiplexing technique.
  • FIG. 2 illustrates a Quadrature Amplitude Modulation technique
  • FIG. 3 shows a DOCSIS network transmission architecture for delivering content to a plurality of cable modems, organized into groups so as to reduce transmission errors, and where the cable modems each use one or more bit loading profiles.
  • FIG. 4 shows and exemplary noise-centric system for assigning bit loading profiles to cable modems based on measured capacity rather than measured noise.
  • OFDM is based on the well-known technique of Frequency Division Multiplexing (FDM).
  • FDM Frequency Division Multiplexing
  • different streams of information are mapped onto separate parallel frequency channels.
  • Each FDM channel is separated from the others by a frequency guard band to reduce interference between adjacent channels.
  • Orthogonal Frequency Division Multiplexing extends the FDM technique by using multiple subcarriers within each channel. Rather than transmit a high-rate stream of data with a single subcarrier, OFDM makes use of a large number of closely spaced orthogonal subcarriers that are transmitted in parallel. Each subcarrier is modulated with a conventional digital modulation scheme (e.g. QPSK, 16QAM, etc.) at low symbol rate. However, the combination of many subcarriers enables data rates similar to conventional single-carrier modulation schemes within equivalent bandwidths.
  • a conventional digital modulation scheme e.g. QPSK, 16QAM, etc.
  • adjacent orthogonal tones or subcarriers 1 and 2 may be each independently modulated with complex data. Though only two subcarn ers are illustrated in FIG. 1, those of ordinary skill in the art will appreciate that a ty pical OFDM transmission will include a large number of orthogonal subcarriers. As just note noted, subcarriers 1 and 2 (as well as all other subcarriers) are orthogonal to each other. Specifically, as can be seen in FIG. 1, subcarrier 1 has spectral energy comprising a sine function having a center frequency 3 with sidebands having peaks and nulls at regular intervals.
  • all frequency subcarriers 1, 2 etc. are combined in respective symbol intervals 4 by performing an Inverse Fast Fourier Transform (IFFT) on the individual subcarriers in the frequency domain.
  • Guard bands 5 may preferably be inserted between each of the symbol intervals 4 to prevent inter-symbol interference caused by multi-path delay spread in the radio channel. In this manner, multiple symbols contained in the respective subcarriers can be concatenated to create a final OFDM burst signal.
  • FFT Fast Fourier Transform
  • each subcarrier in an OFDM transmission may be independently modulated with complex data among a plurality of predefined amplitudes and phases.
  • FIG. 2 illustrates a Quadrature Amplitude Modulation (QAM) technique where a subcarrier may be modulated among a selective one of sixteen different phase/amplitude combinations (16QAM).
  • QAM Quadrature Amplitude Modulation
  • subcarrier 1 of FIG. 1 may in a first symbol interval transmit the symbol 0000 by having an amplitude of 25% and a phase of 45° and may in a second symbol interval transmit the symbol 1011 by having an amplitude of 75% and a phase of 135°.
  • the subcarrier 2 may transmit a selected one of a plurality of different symbols.
  • FIG. 2 illustrates a 16QAM modulation technique, but modem DOCSIS transmission architectures allow for modulations of up to 4096QAM.
  • each of the subcarriers 1, 2, etc. shown in FIG. 1 may operate with its own independent QAM modulation, i.e. subcarrier 1 may transmit a 256QAM symbol while subcarrier 2 may transmit a 2048QAM symbol.
  • a bit loading profile is a vector that specifies, for each subcarrier, the modulation order (16QAM, 256QAM, etc) used by the subcarrier during a symbol interval.
  • the current DOCSIS 3.1 specification allows each cable modem to be assigned up to five different bit loading profiles that it is allowed to use in the downstream direction, and up to two different bit loading profiles that it is allowed to use in the upstream direction.
  • the particular bit loading profile used for a given symbol interval is communicated between the cable modem and a head end, so that transmitted information can be properly decoded.
  • FIG. 3 illustrates a system that uses bit loading profiles to communicate data in a DOCSIS architecture.
  • a system 10 may include a Cable Modem Termination Service (CMTS) 12 typically found within a head end of a video content and/or data service provider.
  • the CMTS 12 communicates with a plurality of cable modems 16 at its customers' premises via a network through one or more nodes 14.
  • the network may be a hybrid fiber-coaxial network where the majority of the transmission distance comprises optical fiber, except for trunk lines to Optical Network Units (not shown) at the customers' premises and cabling from the ONUs to the cable modems 16, which are coaxial.
  • More recent architectures e.g. Fiber-to-the Premises (FTTP) however, have replaced the entire line from the ONUs to the upstream node with optical fiber.
  • FTTP Fiber-to-the Premises
  • each cable modem 16 would be assigned a bit loading profile specifically tailored to the performance characteristics of that cable modem. For example, higher nodulation orders can be assigned to subcarriers experiencing higher a SNR characteristic over a channel used by a cable modem, and lower modulation orders may be best for subcarriers with a low SNR characteristic. In this manner, the bandwidth efficiency of transmissions to and from a cable modem are high when if the cable modem’s ideal bit loading vector closely follows the bit loading profile in use by the cable modem.
  • CMTS Cable Modem Termination Service
  • FIG. 3 shows an example where cable modems 16 are segmented into groups 18, 20, and 22 where the cable modems 1 in each group are assigned a common bit loading profile by the CMTS 12. This virtually guarantees that not all cable modems will use a bit loading profile that closely follows its optimum bit loading vector.
  • the CMTS 12 preferably divides cable modems 16 into groups that each have similar performance characteristics.
  • the CMTS 12 may periodically include in the downstream transmission known pilot tones that together span the entire OFDM downstream bandwidth.
  • Each cable modem 16 then uses these pilots to measure its error for received downstream transmissions at each subcarrier frequency, where the error at a particular modulation frequency is measured based on the vector in the I-Q plane (shown in FIG. 2) between the ideal constellation point at that modulation order and the actual constellation point received by the receiver.
  • error measurements may comprise any of several available forms, including the actual error vector, the Euclidian distance between these two points, or the Modulation Error Ratio (MER) calculated from the error vector.
  • the error measurement may be expressed as a maximum QAM value that a cable modem may reliably use at a given subcarrier, given the measured error.
  • the DOCSIS 3.1 PHY specification contains tables that map modulations orders to the minimum carrier-to-noise ratios (approximated by MER) required to carry them, as shown in the following exemplary table in the downstream direction:
  • CNR Carrier Boise Ration is defined as the total signal power in an occupied bandwidth divided by the total noise in that occupied bandwidth, and ideally is the equivalent of equalized MER.
  • the process is generally reversed; the CMTS 12 commands each cable modem to send known pilot tones to the CMTS together spanning the entire OFDM upstream bandwidth in a single upstream probing signal for each particular cable modem 16.
  • the CMTS 12 uses these received probing signals to estimate the upstream modulation error vectors for each of the cable modems.
  • the CMTS 12 uses these vectors to organize the cable modems into “N” groups of cable modems, where “N” is at most the number of profiles available to the collection of cable modems.
  • N is at most the number of profiles available to the collection of cable modems.
  • cable modems could be arranged in up to sixteen groups for receiving signals in the downstream direction and up to seven groups for receiving signals in the upstream direction.
  • a set of available bit loading profiles may be generated for the head end to assign to the population of cable modems serviced by the head end in each of the upstream and downstream directions, and subsequently the cable modems in each group may be assigned profiles from this set
  • some methods may select an initial or starting set of bit loading profiles, each representing a different tier or quality of service, where the bit loading profiles are subsequently adjusted based upon the groupings of cable modems as appropriate where, say a small change in a profile can bring several cable modems into that tier or to guarantee a tier of service to a specific cable modem.
  • the nearest five bit loading profiles, ordered by vector distance should be assigned to the cable modem in the downstream direction and the nearest two bit loading profiles, ordered by vector distance should be assigned to the cable modem in the upstream direction.
  • RF Quadrature Amplitude Modulation techniques trade noise immunity for channel capacity for channels within the same amount of bandwidth.
  • the assignment of higher orders of channel modulation can increase the information capacity of a channel occupying a region of RF spectrum but this will also reduce the amount of tolerated interference on the channel.
  • Current RF networking devices may assign modulation levels (a.k.a. bitloading) to entire channels or perhaps to spectral regions of channels to maximize channel capacity in the presence of noise.
  • modulation levels a.k.a. bitloading
  • a budget is created for the maximum amount of interference that is expected be present in each region on the channel.
  • the network device will then assign a modulation order which is appropriate for this expected noise level.
  • a calculated channel capacity can then be assumed for customer traffic. The device will attempt to assign traffic up to a significant fraction of this calculated channel capacity.
  • This approach is capacity-centric, rather than robust-centric (noise immunity). If an unforeseen event causes interference in excess of the interference budget, the unexpected interference may cause communications to fail, even when the current level of modulation provides excess capacity for the demanded traffic. To guard against this failure, some existing systems poll subscriber devices for metrics of modulation error ratios (MER). These metrics are collected periodically and the bitloading of certain channels may be adjusted to fit the MER measurements. This method also attempts to maximize the channel throughput and therefore offers a minimum of channel RF robustness at each interval. This method can adjust to noise conditions only at a rate set by the metrics collection polling interval, however.
  • MER modulation error ratios
  • this invention seeks to maximize noise robustness for the current traffic demand.
  • the idea is to find the lowest modulation scheme (with the most noise-immunity) that will support the current traffic demand.
  • a “cushion” of extra bandwidth may be configured that could be added to each of multiple thresholds, described as follows.
  • a series of increasing thresholds of traffic demand could be configured to allow the system to automatically adjust (thus increasing the modulation order) to an increasing traffic demand. In this case, the system would adjust the modulation of the channels to allow the capacity of the next higher threshold, plus the cushion for all but the highest threshold.
  • a series of decreasing thresholds (not necessarily exactly matching the series of increasing thresholds) could be configured to allow the noise robustness to increase by decreasing the overall capacity to meet the new (lower) traffic demand, plus the cushion.
  • FIG. 4 shows such an implementation where traffic demand over a communication network fluctuates over time between a plurality of different traffic demand levels.
  • a number of thresholds are set, each associated with a particular level of traffic demand.
  • the thresholds are preferably set to include a small cushion of bandwidth to accommodate bursts.
  • this invention When implemented, this invention would provide a good trade-off between noise immunity and traffic demand. Note that, if desired, the uppermost increasing threshold could be configured to provide the same noise budget noise immunity and capacity of the methods currently used while providing noise immunity benefits at lower traffic levels. This invention provides noise immunity benefit over the PMA solution in all cases except when the system is running at maximum capacity Tn addition, this invention can adjust to traffic demand much faster than the expected PMA solution metrics polling interval.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)

Abstract

L'invention concerne également des systèmes et des procédés de sélection dynamique d'un ordre de modulation QAM dans un profil de chargement de bits d'au moins un modem câble. Les systèmes et les procédés préférés sélectionnent un ordre de modulation à l'aide d'une mesure de capacité dans un système de transmission au modem câble.
PCT/US2023/013855 2022-02-24 2023-02-24 Chargement de bits pour robustesse WO2023164156A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US202263313493P 2022-02-24 2022-02-24
US63/313,493 2022-02-24

Publications (1)

Publication Number Publication Date
WO2023164156A1 true WO2023164156A1 (fr) 2023-08-31

Family

ID=85778690

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2023/013855 WO2023164156A1 (fr) 2022-02-24 2023-02-24 Chargement de bits pour robustesse

Country Status (1)

Country Link
WO (1) WO2023164156A1 (fr)

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9647786B2 (en) 2013-12-27 2017-05-09 Arris Enterprises, Inc. Determining bitloading profiles based on sNR measurements

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9647786B2 (en) 2013-12-27 2017-05-09 Arris Enterprises, Inc. Determining bitloading profiles based on sNR measurements

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
"Integrated broadband cable telecommunication networks (CABLE); Fourth Generation Transmission Systems for Interactive Cable Television Services - IP Cable Modems; Part 2: Physical Layer; DOCSISÂ 3.1", vol. CABLE WG1, no. V1.1.1, 15 February 2017 (2017-02-15), pages 1 - 217, XP014287564, Retrieved from the Internet <URL:http://www.etsi.org/deliver/etsi_ts/103300_103399/10331102/01.01.01_60/ts_10331102v010101p.pdf> [retrieved on 20170215] *
ABEDIN SUMAYIA ET AL: "A Novel Approach for Profile Optimization in DOCSIS 3.1 Networks Exploiting Traffic Information", IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT, IEEE, USA, vol. 16, no. 2, 1 June 2019 (2019-06-01), pages 578 - 590, XP011728855, DOI: 10.1109/TNSM.2019.2901879 *

Similar Documents

Publication Publication Date Title
US7369579B2 (en) Method and system for timing controlled signal transmission in a point to multipoint power line communications system
US9647786B2 (en) Determining bitloading profiles based on sNR measurements
US9647801B2 (en) Method for selecting modulation tiers for transmissions over an orthogonal frequency division multiplexed (OFDM) channel
US10020974B2 (en) Upstream pilot structures in point-to-multipoint orthogonal frequency-division multiplexing (OFDM) communication systems
US5557612A (en) Method and apparatus for establishing communication in a multi-tone data transmission system
EP0755601B1 (fr) Amelioration d&#39;un appareil a frequences vocales discretes compatibles avec les lignes d&#39;abonnees numeriques asymetriques
US20020131455A1 (en) Method and apparatus for coordinating multi-point to point communications in a multi-tone data transmission system
US20020122437A1 (en) Method and apparatus for coordinating multi-point to point communications in a multi-tone data transmission system
WO2007127250A2 (fr) Ofdma basé sur une radiocommunication cognitive
US10469303B2 (en) Systems and methods for determining the number of channel estimation symbols based on the channel coherence bandwidth
WO2014176255A1 (fr) Attribution de ressources d&#39;accès multiple à division de fréquence orthogonale(ofdma) dans des réseaux à spécifications d&#39;interfaces de services par câble de données (docsis)
US20230239410A1 (en) Ofdm and ofdma profile assignments for cable modems
KR20040009956A (ko) 홈 네트웍에서 스테이션 인식 및 링크 설정 방법
US12003392B2 (en) Data aggregation for communications network optimization
WO2023164156A1 (fr) Chargement de bits pour robustesse
US20230396460A1 (en) Bitrate optimized clustering for ofdm/ofdma profile generation
US20230412326A1 (en) Systems and methods for ofdma power equalization
US20230124322A1 (en) Systems and methods for measuring mobile interference in ofdm data
CN115086128A (zh) 用于自动排除受损副载波的系统和方法
Pathania et al. BER Performance of OFDM Technique using RS Coding for Wireless Communication Systems
AU8364301A (en) Method and apparatus for coordinating multi-point to point communications in a multi-tone data transmission system
AU8364201A (en) Method and apparatus for coordinating multi-point to point communications in a multi-tone data transmission system

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 23713993

Country of ref document: EP

Kind code of ref document: A1