Determining bitloading profiles based on sNR measurements

Patent metadata

Field	Value
Publication number	US-9647786-B2
Application number	US-201314142246-A
Country	US
Kind code	B2
Filing date	Dec 27, 2013
Priority date	Dec 27, 2013
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

With the introduction of orthogonal frequency division multiplexing (OFDM) technology in to communication channels in a cable network, cable modems that receive data downstream over subcarriers of the OFDM channel are grouped in to modulation tiers based on at least one metric. A profile is generated for each OFDM channel based on the measurements across cable modems and subcarriers related to the OFDM channel, including the metric values used to group the cable modems in to the modulation tiers. Included in an OFDM profile may be a scheme for allocating marginal cable modems in to the plurality of modulation tiers. The methods and systems for generating modulation and coding scheme profiles enable more efficient modulation by network elements.

First claim

We claim:

1. A method for identifying a plurality of modulation tiers for grouping network elements communicating over an orthogonal frequency division multiplexed (OFDM) channel having a plurality of subcarriers, the method comprising:
defining a metric associated with a measurable characteristic of the network elements;
collecting measurements associated with the measurable characteristic for a plurality of the network elements communicating over the OFDM channel, each measurement corresponding to at least one of the plurality of network elements and a respective one of the plurality of subcarriers, wherein the measurements collected for the plurality of network elements communicating over the OFDM channel includes:
receiving digitally modulated signals returned from the plurality of network elements; and
calculating the measurements for each of the plurality of network elements based on downstream or upstream parameters by headend equipment that characterizes the digitally modulated signals returned from the plurality of network elements, wherein characterizing the digitally modulated signals returned from a network element to calculate the measurements comprises:
measuring an initial total power loading which is equal to total power of radio frequency (RF) energy present within a bandwidth of interest on an OFDM channel;
instructing a cable modem to transmit a first test signal on the OFDM channel at initial total power loading;
monitoring the first test signal at a headend of the OFDM channel; and
measuring at the headend at least one of modulation error ratio (MER0), signal-to-noise ratio (SNR0), packet error rate (PER0), or bit error rate (BER0);

for each of the plurality of network elements, translating the measurements collected for the respective network element in to at least one network element metric value;
dividing the OFDM channel into a plurality of modulation tiers each based on a range of the network element metric values determined from the measurements collected for the plurality of network elements, wherein each modulation tier is associated with a modulation level;
for each of the plurality of network elements, comparing the respective at least one network element metric value to the range of metric values associated with each of the plurality of modulation tiers; and
distributing each of the plurality of network elements to a modulation tier in the plurality of modulation tiers based on the comparison of the at least one network element metric value to the range of metric values associated with each of the plurality of modulation tiers.

2. The method of claim 1 , further comprising generating the profile of the OFDM channel based on an identification of the plurality of modulation tiers and the metric values associated with each of the plurality of modulation tiers.

3. The method of claim 1 , wherein the metric associated with a measurable characteristic of the network elements is a characteristic of at least one of a cable modem, a cable modem termination system (CMTS), or the OFDM channel.

4. The method of claim 1 , wherein the measurable characteristic of the network elements is at least one of a modulation error rate, a signal-to-noise ratio, a packet error rate, a bit error rate, or a number of cable modems.

5. The method of claim 1 , wherein the metric associated with the measurable characteristic of the network elements defined for each of the plurality of tiers includes at least one of:
a target of the measurable characteristic for a respective tier,
a threshold of the measurable characteristic for each respective tier,
an average of the measurable characteristic for a respective tier,
a minimum of the measurable characteristic for a lowest tier,
a maximum of the measurable characteristic for a highest tier,
a statistical distribution of the measurable characteristic among the tiers,
a percentage amount of the measurable characteristic for a respective tier, or
an equal distribution of the measurable characteristic for each tier.

6. The method of claim 1 , wherein the metric values associated with the metric defined for each of the plurality of modulation tiers includes at least one of a range of values, values calculated from the measurements for the plurality of network elements, user-defined values, cable operator-defined values, statistical approach values, a total number of cable modems divided by the number of tiers, or a percentage of the total number of cable modems.

7. The method of claim 1 , wherein distributing each of the plurality of network elements to a modulation tier based on the comparison of measurement collected for the plurality of network elements to the metric values associated with the plurality of modulation tiers is a distribution based on at least one a cable mode (CM) count per tier, a target CM measurement per tier, a target modulation measurement per tier, a statistical measurement per tier, or defined for each tier based on a standard deviation curve.

8. The method of claim 1 , wherein each of the plurality of modulation tiers has a threshold value of the measurable characteristic defined for each of the plurality of subcarriers.

9. The method of claim 8 , wherein the profile further includes a predetermined scheme for allocating marginal network elements to a tier in the plurality of modulation tiers.

10. The method of claim 1 , wherein a marginal network element is a network element in the plurality of network elements that is associated with two or more of the plurality of tiers.

11. The method of claim 10 , wherein the marginal network element is associated with two or more of the plurality of tiers due to having at least one first metric value for a first subcarrier that corresponds to one of the plurality of modulation tiers and at least one second metric value for another subcarrier that corresponds to another one or more of the plurality of modulation tiers.

12. The method of claim 10 , wherein the allocation of a marginal network element to a tier in the plurality of modulation tiers is based on a predetermined scheme.

13. The method of claim 12 , wherein the predetermined scheme comprises a scheme for allocating the marginal network element to a tier based on at least one of:
a closest fit, wherein the marginal network element is allocated to a tier with the smallest difference between the network element metric value for each OFDM subcarrier and a metric value associated with each of the plurality of modulation tiers for each OFDM subcarrier;
a primary tier, wherein the tiers are each defined by upper metric boundary values and lower metric boundary values, and the marginal network element is allocated to the tier in which the majority of the network element metric values for the plurality of subcarriers map;
the lowest tier in which the marginal network element has a metric value; or
the highest tier in which the marginal network element has a metric value.

14. The method of claim 1 , wherein the network element is at least one of a cable modem, set top box, television equipped with set top box, data over cable service interface specification (DOCSIS) terminal device, or a media terminal adapter (MTA).

15. The method of claim 1 , wherein profile defined for the plurality of modulation tiers in the OFDM channel are defined with initial values and are dynamically adjustable.

16. The method of claim 15 , wherein the profile is adjusted by adjusting each of the plurality of modulation tiers based on at least one of: improved signal-to-noise ratio (SNR) performance of at least one of the subcarriers, calcu

Assignees

• Arris Entpr Inc

Inventors

• Hanks William T
• Howe Jeffrey J
• Al-Banna Ayham

Classifications

• H04L5/006

  Quality of the received signal, e.g. BER, SNR, water filling · CPC title

• H04J11/0023 Primary

  Interference mitigation or co-ordination (direct sequence spread spectrum [DSSS] systems H04B1/7097; frequency hopping H04B1/713; allocation criteria for ingress interference avoidance H04L5/0062; frequency allocation criteria for requirements on out-of-channel emissions H04L5/0066; arrangements for removing intersymbol interference or baseband equalisers H04L25/03006; peak power aspects in multicarrier modulation H04L27/2614; power management H04W52/00; traffic scheduling H04W72/54, H04W72/541) · CPC title

• H04L43/10

  Active monitoring, e.g. heartbeat, ping or trace-route · CPC title

• H04L27/0012

  arrangements for identifying the type of modulation · CPC title

• H04L5/0046

  Determination of the number of bits transmitted on different sub-channels · CPC title