Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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NETWORK 4UALITY OF SERVICE LOCALIZER
This patent document is a Continuation in Part of United States
Patent Application Serial No. 09/571,068, filed May 15, 2000, of
Smith et al., for SLICED BANDWIDTH DISTORTION PREDICTION,
now U.S. Patent No , and also a Continuation in Part of
United States Patent Application Serial No. 09/470,890, filed
December 22, 1999, of Smith et al., for METHOD AND APPARATUS
FOR AUTOMATED CORRELATION OF DIGITAL MODULATION
1o IMPAIRMENT, now U.S. Patent No
FIELD OF THE INVENTION
The present invention relates to quality of service estimation
is within a communication network, and more specifically to quality of
service estimations of communication mediums of a relatively time-
invariant communications system. Even more specifically, the present
invention relates to localizing quality of service estimations to specific
communication mediums or physical communication paths within a
2o relatively time-invariant communication network.
BACKC;ROUND OF THE INVENTION
In a communication system, signals comprising data are
typically transmitted from a transmitter to a receiver via a
25 communication medium or communication channel contained within
a communication link. The transmitter modulates and transmits
these signals at a specified modulation type (e.g. QPSK, 16-QAM, and
64-QAM) and at a specified data or signaling rate (e.g. 160k bits per
second) within the communication medium. Typically, the
3o communication medium (also referred to simply as a "medium") has a
particular range of frequencies or bandwidth, such as from 5 MHZ to
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42 MHZ, that the signals travel at over the communication link.
Additionally, the medium also refers to the physical path which the
signal travels over from a transmitter to a receiver.
As these data-bearing signals propagate over the medium
of the communication link, the signals experience distortion such that
the signals being received at a corresponding receiver are altered from
their transmitted form depending on noise levels, non-linearities, time
delays and reflections that are all frequency and medium dependent
upon the signals within the medium, for example. Specifically, the
to amplitude and phase of the signals are distorted, which is referred to
in the composite as medium dependent channel distortion (also
referred to as "channel distortion"). If the channel distortion of the
signal over a particular medium provides an acceptable signal to noise
ratio, for example, the receiver demodulates the signal and extracts
the data from the signal. Disadvantageously, if the channel distortion
is too great or the signal to noise ratio is unacceptable, the receiver
will demodulate the signals and potentially misinterpret the
information or data carried therein.
Knowledge of the channel distortion of a particular
2o communication medium (i.e., medium dependent channel distortion)
provides an estimation of the quality of service of the particular
communication medium. The quality of service for the particular
communication medium limits the signaling that can be transmitted
and received over the communication medium. For example, the
2s quality of service for a particular medium effects what levels or grades
of service, i.e. the modulation level and signaling rate, for signaling
that can be supported by the medium. Thus, in order to determine
what levels of service are possible over a particular medium, a quality
of service is determined for the particular medium based upon
30 channel distortion estimates.
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In a communication network, it would be desirable to
estimate the channel distortion for communication mediums between
any number of nodes within the communication network in order to
estimate the quality of service fox various components of the network
s and to provide an indication of the health of the network. A
communication network includes many communication mediums
between many different nodes within the communication network.
For example, a network hub communicates with many communication
devices, i.e., subscriber devices, within the network, such that a
to communication medium is defined between each of the subscriber
devices and the network hub. Each of these communication mediums
may have a different level of medium-dependent channel distortion
specific to that particular medium and resulting in potentially
different quality of service estimations for one or more of the
1s communication mediums. Thus, each of the communication
mediums within the communication network may actually support
different levels or grades of service, i.e. have a different quality of
service estimation.
Additionally, many of these different communication
2o mediums may share portions of the same physical communication
path (also referred to as the communication link) between the
respective subscriber device and the network hub. For example, in
communication networks spanning a large geographical area, e.g. a
hybrid fiber/ coax (HFC) system, the physical communication path
2s from one node, e.g. a subscriber device, in the network to another
node, e.g. the network hub, may include physical portions that are
shared by many communication mediums. Thus, simply estimating a
quality of service for a particular communication medium within the
communication network does not provide any information about
3o which physical portion of the physical communication path utilized by
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the communication medium is, for example, limiting the quality of
service supportable by the communication medium.
Dynamically allocated communication networks, in which
a subscriber device is dynamically connected to a network routing
device, i.e. a public switched telephone network (PSTN) switch hub,
Iocal area network (LAN), or wide area network (WAN), only allow the
ability of the network to estimate a quality of service for the particular
connection between the network routing device and the subscriber
device during the current physical connection. This estimation of the
quality of service is based upon the ability of the subscriber device to
connect itself to the terminating device, i.e., the network routing
device. Since the currently allocated physical connection path is for
the current communication only, a subsequent physical connection
from the network routing device to the same subscriber device may
involve an entirely different physical connection path depending on
the allocation of network resources, the availability of network
resources, etc. Thus, any quality of service estimation for the
communication medium involving the currently allocated physical
path will only be valid for the duration of the connection, since the
2o allocated physical path will likely be different in subsequent
allocations by the network routing device. Thus, the prediction of
what the next quality of service for the medium to that same
subscriber will be ambiguous due to the dynamic switching element in
the network that allocates the physical connection. Therefore, such
quality of service estimations would not provide an indication of the
health of the network over time, which may be used to indicate weak
points within the network or to indicate a degradation of service over a
localized section or path of network within the composite overall
network.
3o In a relatively time-invariant (i.e. the transmitter and the
receiver are relatively fixed in location with respect to one another)
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communications network that is non-dynamically allocated (i.e. the
physical transmission paths are known and relatively static over time),
such as a hybrid fiber/ coax (HFC) system, estimation of medium
dependent channel distortion for any one particular communication
s medium within the network is expensive and requires potentially
obtrusive, dedicated equipment to be physically connected to both the
transmitter and the receiver of the communications medium. For
example, the network provider may connect different equipment, e.g.
transmitters and receivers, each capable of transmitting and receiving
1o signaling of differing levels of quality of service in order to determine
if
the medium will support such signaling. Alternatively, the network
provider may physically connect an adaptive bandwidth and signaling
rate scan receiver in the communication path that can switch between
higher and lower modulation levels and signaling rates, such as the
15 HP89441 VSA (Vector Signal Analyzer made by Hewlett Packard),
along with an appropriate transmitter that can transmit signaling with
the different modulation levels and signaling rates. Alternatively, a
network analyzer, which is a two-port system, may be coupled to the
transmit and receive end of the communications path to analyze the
2o medium there between. Each of these devices requires physical
connection at both ends of the medium, i.e. the transmitting end and
the receiving end, and requires that any existing services be
interrupted during the testing process. Thus, the use of such
physically connected devices, especially in networks encompassing a
25 large geographic area, at all nodes within a given network is
prohibitively time consuming, expensive and results in the
interruption of services (when present) to subscribers of the network.
Furthermore, such equipment does not account for the fact that the
tested physical communication path is likely shared with multiple
3o communication mediums.
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The present invention advantageously addresses the
above and other needs.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other aspects, features and advantages of
the present invention will be more apparent from the following more
particular description thereof, presented in conjunction with the
following drawings wherein:
FIG. 1 is a block diagram illustrating a relatively time-
1o invariant communication network in which a quality of service is
localized to a particular subscriber or physical communication path of
the communication network in accordance with one embodiment of
the present invention;
FIG. 2 is a block diagram of a system for localizing a
quality of service of a relatively time-invariant communications
network, such as shown in FIG. l, including a distortion estimator for
estimating a medium dependent channel distortion and corresponding
quality of service estimation between differing nodes in the network
and also including a quality of service localizer for localizing a
2o particular quality of service estimation to a likely physical
communication path within the network, in accordance with another
embodiment of the present invention;
FIG. 3 is a diagram of a cable modem communication
network including multiple hubs in which a quality of service is
localized, by the system of FIG. 2, for example, to a particular
subscriber or physical communication path within the network in
accordance with yet another embodiment of the present invention;
FIG. 4 is a diagram of the cable modem communication
network of the FIG. 3 illustrating a single hub having multiple serving
3o groups and also illustrating various defined mediums over shared and
non-shared physical communication paths;
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FIG. 5 is a table which illustrates the various
communications mediums relating to a pool of subscribers within
serving groups within hubs for the cable modem communications
network 300 of FTGS. 3 and 4;
s FIG. 6 is a table mapping the individual subscribers
within serving groups of a single hub and also illustrating which
mediums provide information on the health of the communication
network of FIG. 3 and 4 by a given subscriber when comparatively
analyzed; and
1o FIG. 7 is a flowchart of the method of localizing a quality
of service to a particular subscriber or physical communication path
of a relatively time-invariant communications network, for example,
the networks of FIGS. 1. through 4, in accordance with an embodiment
of the present invention.
Is Corresponding reference characters indicate
corresponding components throughout the several views of the
drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
2o The following description of the presently contemplated
best mode of practicing the invention is not to be taken in a limiting
sense, but is made merely for the purpose of describing the general
principles of the invention. The scope of the invention should be
determined with reference to the claims.
2s The present invention advantageously addresses the
needs above as well as other needs by providing a method and system
for localizing the quality of service of a relatively time-invariant, non-
dynamically switched communication network such that the quality of
service of the network may be analyzed in a physical piece-wise
3o fashion over time without interrupting existing services.
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In one embodiment, the invention can be characterized as
a method of quality of service localization within a relatively time-
invariant communications network comprising the steps of: receiving
quality of service estimations for a plurality of communications
s mediums, wherein each of the plurality of communications mediums
is defined between a respective one of a plurality of transmitters
located within the communications network to a common receiving
point of the communications network, wherein each communications
medium is conveyed over at least one shared physical
1o communications path and at least one non-shared physical
communications path; and comparing the quality of service
estimations in order to localize a respective quality of service
estimation to a likely physical communication path within the
communications network.
15 In another embodiment, the invention can be
characterized as a system for quality of service localization comprising
a relatively time-invariant communications network that includes a
common receiving point; a plurality of transmitters for transmitting
signaling to the common receiving point; and a plurality of
2o communications mediums coupling respective ones of the plurality of
transmitters to the common receiving point, wherein each of the
plurality of communications mediums is conveyed over at least one
shared physical communications path and at least one non-shared
physical communications path to the common receiving point. Also
2s included in the system is a quality of service localizes coupled to the
common receiving point, wherein the quality of service localizes
localizes, based upon the analysis of quality of service estimations
received from the common receiving point, a particular quality of
service estimation to a likely physical communication path within the
3o communications network.
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Referring first to FIG. l, a block diagram is shown
illustrating a relatively time-invariant communication network in
which a quality of service is localized to a particular subscriber or
physical communication path of the network in accordance with one
embodiment of the present invention. The network 100 comprises an
Internet 102, headend 104, media converter 106, and subscribers
108, 110, 112 and 114. While subscribers 108, 110, 112, and 114
are illustrated, it is understood that the network 100 may include any
number of subscribers. Internet 102 may be any information
to network, for example, a global information network. Internet 102 is
coupled to the headend 104. The headend 104 communicates with
the Internet 102 and with subscribers 108, 110, 112 and 114. The
headend 104 is coupled to the media converter 106 via physical
communication path 116 (also referred to as communication link
116). The media converter 106 is coupled to subscribers 108, 110
112 and 114 via physical communication paths 118, 120, 122, 124,
126 and 128 (also referred to as communication links 118, 120, 122,
124, 126 and 128). Communication between the headend 104 and
the subscribers 108, 110, 112 and 114 is effected by the media
2o converter 106.
In a hybrid fiber j coax (HFC) cable system, physical
communication path 116 comprises a fiber optic cable that supports
communications between the headend 104 and the media converter
106, and physical communication paths 118, 120, 122, 124, 126 and
2s 128 each comprise coaxial cable that each support communications
between the media converter 106 and subscribers 108, 110, 112 and
114.
The media converter 106 converts the media over which
the communication occurs. For example, in a HFC system, the media
3o converter 106 passes signals between the fiber optic cable, I.e.
physical communication path 116, and the coaxial cable, I.e. physical
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communication path 118. However, the media converter 106 may be
unnecessary if a continuous medium is used between the headend
104 and the subscribers 108, 110, 112 and 114. Any suitable
medium or media may be used as the respective physical
5 communication paths between the headend 104 and the subscribers
108, 110, 112 and 114. For example, besides fiber optic cable and
coaxial cable other media such as twisted pair cable, wixeless, or
satellite communications links may be used.
Furthermore, in operation, a communication medium is
to defined between the headend 104 and subscriber 108 and includes
physical communication paths 116, 118 and 120. Similarly, the
communication medium defined between the headend 104 and
subscriber 110 includes physical communication paths 116, 118, 124
and 126; the communication medium defined between the headend
104 and subscriber 112 includes physical communication paths 116,
118 and 122; and the communication medium defined between the
headend 104 and subscriber 114 includes physical communication
paths 116, 118, 124 and 128. As such, physical communication
paths 120, 122, 126 and 128 represent non-shared physical
2o communication paths while physical communication paths 116, 118
and 124 represent shared physical communication paths. Fox
example, physical communication path 124 is "shared" by
communications between subscribers 110 and 114 and the headend
104 only, while physical communication path 126 is only used for
communications between subscriber 110 and the headend 104, i.e.
physical communication path 126 is a "non-shared" physical
communication path.
As data-bearing signals propagate over the various
communication mediums using the respective physical
3o communication paths, the respective communication mediums
introduce variable amounts of "medium dependent channel distortion"
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(also referred to as channel distortion). Thus, signals transmitted over
a respective communication mediums occupying a respective physical
communication path/ s are altered from their transmitted form as they
propagate to respective receivers of the network. The Ievel of channel
distortion depends on noise levels, non-linearities, time delays and
reflections that are all frequency and medium dependent upon the
signals within the communication medium, for example. Such
channel distortion contributors include amplifiers, lasers, poor signal
grounds and faulty subscriber units, for example.
.I~.nowledge of the channel distortion (i.e., medium
dependent channel distortion) of a particular communication medium
provides an estimation of the quality of service of the particular
communication medium. The quality of service for the particular
communication medium limits the signaling that can be transmitted
and received over the communication medium. For example, the
quality of service for a particular medium effects what levels or grades
of service, i.e. the modulation level and signaling rate, for signaling
that can be supported by the medium. Thus, in order to determine
what levels of service are possible over a particular medium, a quality
of service is determined for the particular medium based upon
channel distortion estimates.
In accordance with one embodiment of the invention, a
system and method are provided for localization of medium dependent
channel distortions of a relatively time-invariant communication
network Z 00. Localization refers to an ability to analyze a network at
a fine granularity to determine system limitations in a physical piece-
wise fashion within the communication network 100. As such,
estimates of the level of channel distortion are obtained for each of the
respective communication mediums that occupy one or more of the
3o physical communication paths 116, 118, 120, 122, 124, 126 and 128.
These channel distortion estimates are used to determine the
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estimations of quality of service supportable by the respective
communication mediums.
Furthermore, by comparing these quality of service
estimates with each other, a channel distortion may be localized to a
specific geographic physical communication path within the network.
For example, a channel distortion may be localized to a specific
subscriber, a specific non-shared physical communication path, or a
specific shared physical communication path within the network 100.
Such determinations may be made by the network management
to remotely without the need to physically install testing equipment or
physically inspect portions of the communication network 100.
Therefore, the qualii_y of service for a particular subscriber located at a
specific geographic location can be ascertained while providing
services to a subscriber pool or when initially setting up new services.
This allows the network provider the opportunity to localize network
degradation remotely, precisely, and automatically.
Advantageously, the network management, typically
located within the headend 104 employs non-obtrusive channel
distortion estimates using the techniques described in, but not limited
2o to, United States Patent Application Serial No. 09/571,068, filed May
15, 2000, of Smith et al., for SLICED BANDWIDTH DISTORTION
PREDICTION, Attorney Docket No. PD-05944AM, now U.S. Patent No
and United States Patent Application Serial No.
09/470,890, filed December 22, 1999, of Smith et al., for METHOD
2s AND APPARATUS FOR AUTOMATED CORRELATION OF DIGITAL
MODULATION IMPAIRMENT, Attorney Docket No. PD-05924AM,
now U. S. Patent No , both of which are incorporated herein
by reference. The channel distortion techniques described in these
references are briefly described with reference to FIG. 2.
3o In one embodiment, the network management (e.g. in the
headend 104) uses the channel distortion estimation methods to
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gather information from a pool of transmitters (e.g. subscribers 108,
110, 112 and 114), which is then used to analyze the network 100
along any piece-wise connection within the communication network
100.
s This embodiment represents a departure from the known
prior art in that it is possible to remotely localize the quality of service
of the relatively time-invariant communication network 100 in a
physical piece-wise fashion in order to remotely determine what
quality of service of signaling is supportable in specific geographic
1o portions of the communication network 100. Advantageously, this is
accomplished without having to physically inspect the physical piece-
wise connection or to connect test equipment up to each individual
physical connection.
Referring next to FIG. 2, a block diagram is shown of a
15 system for localizing a quality of service of a relatively time-invariant
communication network, such as shown in FIG. 1, including a
distortion estimator for estimating a given level of distortion between
differing nodes in the network and also including a quality of service
localizes for localizing a particular quality of service estimation to a
20 likely physical communication path within the network, in accordance
with another embodiment of the present invention. Shown is a
communication network 200 including transmitters 202, 204 and
206, communication mediums 208, 210 and 212, receiver 214 (also
referred to as a "common receiving point" 214), a distortion estimator
25 216, a memory 218, a quality of service localizes 220 (also referred to
as a QoS localizes 220), and a network management controller 222
(also referred to as a system controller/reporting subsystem 222).
Each transmitter 202, 204 and 206 is coupled to the
receiver 214 via a respective one of the communication mediums 208,
30 210 and 212. The receiver 214 is coupled to the distortion estimator
216, which is coupled to the memory 218. The memory 218 is
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coupled to the QoS localizer 220 which, in turn, is coupled to the
network management controller 222.
In operation, each transmitter 202, 204 and 206 and the
receiver 214 are separate points or nodes within the communication
network 200. For example, transmitter 202 is located at subscriber
108 of FIG. 1 and the receiver 214 is located at the headend 104 of
FIG. 1, while communication medium 208 represents the medium
utilizing over physical communication paths 120, 118 and 116 of FIG.
1. The communication network 200 is a relatively time-invariant
to network, i.e.~ the physical connection linking the respective
transmitters to the receiver is relatively time-invariant or relatively
fixed. As such, the physical communication path linking each
transmitter to the receiver 214 is known and unique, i.e. the network
is not dynamically switched such that communications from one node
to another occupy a different physical path every time they
communicate. Furthermore, the physical communication path may
comprise a variety of physical mediums, for example, the
communication mediums 208, 210 and 212 may utilize fiber links,
cable links, multi-point microwave links, or geo-synchronous satellite
links, for example.
Signaling is transmitted from each transmitter 202, 204
and 208 to the receiver 214 via the respective communication medium
208, 210 and 212. As described above, and depending on the transfer
function of the respective communication medium 208, 210 and 212,
zs the transmitted signal will be altered from its transmitted form. This
is known as medium-dependent channel distortion (also referred to
simply as channel distortion). This channel distortion is caused by
noise levels, non-linearities, time delays and reflections that are all
frequency and medium dependent upon the signals within the
3o medium, for example. For example, communication medium 208 may
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introduce a differing level of channel distortion than communication
medium 210.
Often, especially in communication networks 200 covering
a large geographic region, such as a hybrid fiber/coax (HFC) network,
5 these channel distortions can widely vary. The level of channel
distortion effects the quality of service of signaling that is supportable
by the communication medium, i.e. what modulation and signaling
rates are supported.
In addition to the physical communication path being
to known and unique for each transmitter within the communication
network 200, the receiver 2I4 receives the identity of a respective
transmitter 202, 204 and 206 within the communications from the
respective transmitter 202, 204 and 206. This information is gathered
by the receiver 214 since the receiver 214 is time synchronized with
15 each transmitter 202, 204 and 206 at each subscriber; thus, the
receiver 214 knows the originating transmitter for each signal
received. Furthermore, each received signal itself will typically contain
header information, e.g. in a preamble, that contains transmitter
identif cation which identifies the originating transmitter to the
2o receiver. For example, the IP (Internet Protocol), TID (Transmission
Identification), SID (System Identification) or MAC (Media Access
Controller) addresses are known for each transmitter 202, 204 and
206 ands are inherent in the signaling protocol that allow the receiver
to reconstruct the signal. With the knowledge of each transmitter's
2s software identification, the geographic location within the
communication network 200 can be correlated to this software
identification tag.
It is noted that although one receiver 214 is illustrated,
receiver 214 may be embodied as multiple receivers. However, each of
3o the multiple receivers are located within a common geographic point
or node within the communication network 200. For example, each of
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the multiple receivers is located within the headend I04 of FIG. 1.
Thus, the receiver 2I4 geographically represents a "common receiving
point".
Once the signaling is received at the receiver 214, a
distortion estimator 216 determines an estimate of the channel
distortion present in the respective communication medium 208, 210
and 212 using the received signaling from each respective transmitter
202, 204 and 206. From the channel distortion estimate, a quality of
service estimation is determined. This quality of service estimation
to indicates what quality of service signaling, i.e. what specific
modulation level and signaling rate, is supportable by the particular
communication mediums 208, 210 and 212. These estimations are
stored in memory 218.
The distortion estimator 216 is illustrated as optional
is because the quality of service estimation may be roughly estimated
through trial and error or by simply determining a quality of service
estimation for each communication medium 208, 2I0 and 212 based
upon bit error rate or packet error rate of signaling received at the
receiver 2I4. These quality of service estimations need not be
2o analytically precise, and may be as simple as determining whether of
not any service has been established for a particular node or medium
(e.g. mediums 208, 210 and 212). As such, any comparative metric
may be use to gather information about the quality of service across
the geographic network and the collected data (e.g. the quality of
25 service estimations) may then be used to determine network topology
relative, and thus, localize network and medium performance.
Preferably, the level of channel distortion is estimated
using a specific technique by the distortion estimator 216. Examples
of two exemplary non-obtrusive and remote channel distortion
3o estimation techniques employed by the distortion estimator 216
include the techniques described in United States Patent Application
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Serial No. 09/571,068, filed May 15, 2000, of Smith et al., for SLICED
BANDWIDTH DISTORTION PREDICTION, Attorney Docket No. PD-
05944AM, now U.S. Patent No , and United States Patent
Application Serial No. 09/470,890, filed December 22, 1999, of Smith
et al., for METHOD AND APPARATUS FOR AUTOMATED
CORRELATION OF DIGITAL MODULATION IMPAIRMENT, Attorney
Docket No. PD-05924AM, now U.S. Patent No , which have
been previously incorporated herein by reference. The two exemplary
techniques are preferable since neither requires the obtrusive testing
to equipment or other dedicated equipment be connected to the
communication mediums to the be tested or analyzed.
The following is a brief summary of an embodiment of the
channel distortion estimation method as described in United States
Patent Application Serial No. 09/571,068, filed May 15, 2000, of
Smith et al., for SLICED BANDWIDTH DISTORTION PREDICTION,
Attorney Docket No. PD-05944AM, now U.S. Patent No
First, a plurality of short duration test signals are transmitted over a
communication medium to be analyzed from the transmitter, e.g.
transmitter 202, to the receiver 214 of the communication medium
208. Each of the plurality of test signals occupies a different
narrowband slice or a different position in frequency of the
communication medium 208 having a given frequency bandwidth.
For example, each test signal has a test bandwidth which is about
20% of the given bandwidth of the communication medium 208.
These test signals may be transmitted simultaneously with an existing
service by either multiplexing the test signals with the existing service
or by moving the existing service to a different position in frequency
within the given bandwidth. Thus, the plurality of test signals non-
obtrusively are transmitted over the communication medium 208 to
3o the receiver 214.
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At the receiver 214, as is normally done, the test signals
(as well as the normal signaling) are processed with an equalizer to
obtain equalizer coefficients. Since the receiver 214 receives data
indicating the identity of the specific transmitter 202, the receiver 214
s knows which transmitter 202, 204 and 206 within a network
transmitted each of the test signals (e.g. transmitter 202). A phase
distortion estimator (embodied within the distortion estimator 216)
then analyzes the equalizer coefficients for each of the test signals in
order to determine a time when a dominant channel distortion occurs
to for each of the test signals. The phase distortion estimator then
determines a differential group delay between the time of the
dominant channel distortion for each of the received test signals from
a particular transmitter 202. Advantageously, this differential group
delay approximates the phase distortion of the specific communication
1s medium 208. Similarly, the phase distortion is determined for each of
the respective transmitters using communications mediums, e.g.
transmitters 202, 204 and 206 using communication mediums 208,
210 and 212, respectively.
At the same time the phase distortion is determined, the
2o amplitude distortion for the particular communication medium 208 is
also determined, for example, by an amplitude distortion estimator
(embodied within the distortion estimator 216). As such, the received
test signals (the same test signals as described above) are processed
with an autocorrelator or a fast Fourier transform (FFT) within the
2s receiver 214, which are well known in the art, in order to determine
the power of each of the received test signals from each transmitter.
Each of the power estimations for each of the test signals received
from respective transmitters using respective communication
mediums are analyzed to determine an amplitude ripple across the
3o entire given bandwidth of each communication medium 208, 210 and
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212. This amplitude ripple approximates the amplitude distortion of
the particular communication medium 208, 210 and 212.
Now, having estimated both the phase distortion and the
amplitude distortion of a particular communication medium, the
s transfer function is known for the particular communication medium.
Knowing the transfer function of a particular communication medium,
conventional signal processing simulators, such as "System View by
Elanix" developed by Elanix, Inc. of Westlake Village, CA or "SPW"
developed by Cadence Design Systems, Inc. of San Jose, CA, or
to mathematically based theoretical limits that can be worked out with
pencil and paper are used to quantitatively determine the quality of
service supportable by each communication medium 208, 210 and
212. In other words, it can be determined if the particular
communications medium will support a given signaling rate and a
is given modulation level. This may be done by the distortion estimator
216 or alternatively, done by the network management controller 222.
The following is a brief summary of an embodiment of the
channel distortion estimation method as described in United States
Patent Application Serial No. 09/470,890, filed December 22, 1999, of
2o Smith et al., for METHOD AND APPARATUS FOR AUTOMATED
CORRELATION OF DIGITAL MODULATION IMPAIRMENT, Attorney
Docket No. PD-05924AM, now U.S. Patent No Digitally
modulated signaling is received at the receiver 214 from a respective
transmitter 202 via a communication medium 208. The receiver 214
2s extracts soft decision data from the digitally modulated signal. The
soft decision data is digital data represented, fox example, in two's
complement form with on a 8-bit I value and one 8-bit Q value
representing the location on the I/Q plane of a symbol represented by
the soft decision data. The soft decision data is input to an
3o impairment correlator (embodied within the distortion estimator 216).
The impairment correlator stores the locations in signal space for the
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soft decision data over time for each particular communication
medium and applies an impairment mask to the soft decision data.
This embodiment includes a variety of stored impairment
masks that each correspond to a different type of channel distortion
s that may be introduced by the particular communication medium
208. For example, depending on the type of channel distortion
introduced by the communication medium, the location of the soft
decision data (also referred to as symbols) within signal space will be
different or predictably offset from its ideal location. This technique
to uses predetermined impairment masks that indicate where the soft
decision data should be generally located within signal space given a
specified channel distortion. Additionally, different impairment masks
may be applied for symbol level distortions and constellation level
distortions. For example, different impairment masks are stored
15 specific to the following types of channel distortion: a phase noise
impairment mask; a continuous wave (CW) noise impairment mask; a
signal reflection impairment mask; an I/Q imbalance impairment
mask; a compression impairment mask; an amplitude
modulation(AM)-to-phase modulation(PM) impairment mask; a
2o composite phase noise and CW noise impairment mask; and any other
composite impairment mask for correlating multiple types of
impairment.
As such, different types of impairment masks are applied
to the soft decision data, as described above. For each impairment
2s mask, the impairment correlator determines a subset of the soft
decision data that fall within the particular impairment mask. This is
done by determining the number of occurrences of soft decision data
that fall within the impairment mask. Then a correlation weight is
calculated for each impairment mask. In one, embodiment, this
3o correlation weight may be calculated as the ratio of the number of
occurrences of the soft decision data that fall within the impairment
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mask to the total number of occurrences of soft decision data. A
correlation weight is determined for each impairment mask.
Then, all of the correlation weights are compared to
determine a likelihood, typically in the form of a percentage, that a
s channel distortion of a particular communication medium is due to a
particular distortion type and also an indication of the severity of the
channel distortion (e.g. when compared to a desired signal to noise
ratio). Thus, this process yields a likelihood of the source of a specific
channel distortion and an estimated level of channel distortion.
1o From this information, one skilled in the art could then
determine what quality of service is supportable for each particular
communication medium. For example, using the above mentioned,
conventional signal processing simulators, such as "System View by
Elanix" developed by Elanix, Inc. of Westlake Village, CA or "SPW"
Zs developed by Cadence Design Systems, Inc. of San Jose, CA, may be
used to quantitatively determine what quality of service is supportable
by the particular communication medium 208, 210 and 212; thus,
providing a quality of service estimation for each communication
medium 208, 210 and 212. This may be done by the distortion
2o estimator 216 or alternatively, done by the network management
controller 222.
It is noted that in either case, the distortion estimator 216
outputs a quality of service estimation, which indicates what quality of
service for signaling is supported by a particular communication
2s medium, e.g. communication mediums 208, 210 and 212.
Furthermore, advantageously, in either case, estimations
of the quality of service supportable by each particular communication
medium 208, 210 and 212 is obtained without having to connect test
equipment or to physically inspect the physical path of each
3o communication medium. Such estimations may be determined locally
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at the receiver 214 or remotely at a network management controller
222 coupled to the receiver 214.
Next, the quality of service estimations specific to each
communication medium 208, 210 and 212 are stored in memory 218.
The QoS localizer 220 uses the quality of service estimations stored in
memory 218 to make quantitative determinations as to the health of
the communication network 200. For example, this stored
information is used to determine what physical portions or physical
communication paths of the communication network 200 are able to
1o support signaling at what specific quality of service levels. In order to
accurately localize the quality of service of the communication
network 200, the QoS localizer 220 must take into account the
physical communication paths that are "shared" between respective
communication mediums. For example, certain physical
communication paths, or physical portions of the communication
network, are shared by other communication mediums, while some
physical communication paths are unique to only one communication
medium, i.e. the physical communication path is non-shared. Thus,
in this embodiment, the QoS localizer 220 knows which physical
2o communication paths are shared and non-shared. A more complete
description of the comparative process performed by the QoS localizer
220 is described with reference to FIGS. 3-6 below.
Furthermore, the quality of service estimations may be
monitored over time to determine if there is a degradation of the
quality of service available to certain subscribers. And
advantageously, by comparatively analyzing the respective quality of
service estimations for different communication mediums 208, 210
and 212, the specific physical communication path that is most likely
limiting the quality of service may be identified. All of this is
3o advantageously performed without having to connect test equipment
to each transmitter and receiver in the communication network 200
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(which would be prohibitively expensive and interrupt existing
services) or without actually having to physically inspect the various
physical communication paths to determine why a particular
subscriber has a reduced quality of service capability.
The QoS localizes 220 forwards data to the network
management controller 222, which stores the data for use by network
providers. The information provided is used to track the quality of
service for every physical piece-wise connection in the communication
network 200 over time. Thus, when a degradation in the quality of
to service supportable in a particular communication medium is
detected, the specific physical communication path may be inspected
to determine and correct the source of the degraded quality of service.
It is noted that the system of FIG. 2 may be implemented
to include a program storage device readable by a machine, tangibly
1s embodying a program of instructions executable by the machine to
perform the method steps performed by the distortion estimator 216,
the QoS localizes 220 (e.g. the steps listed with reference to the
flowchart of FIG. 7 below), and/ or the network management controller
222. To allow the machine to execute the program of instructions, the
2o machine may include a processor, such as a microprocessor (e.g. a
digital signal processor) or other logic circuitry capable of executing
the program of instructions. The distortion estimator 216, QoS
localizes 220 and the network management controller 222 may be
implemented using either hardware, software, or a combination
25 thereof, for example using a general purpose microprocessor, a
microcontroller, and/or application specific logic circuits, and
software and/or firmware cooperatively related to them. Furthermore,
the distortion estimator 216, QoS localizes 220, and the network
management controller 222 may be embodied as separate components
30 located apart from one another or may comprise a single integrated
unit at one physical location. For example, these components may be
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located within the receiver 214, e.g. the receiver of the headend 104 of
FIG. 1, or may be coupled to the receiver 214. However, typically,
these components are all embodied in the headend of the hybrid
fiber/coax system.
s Referring next to FIG. 3, a diagram is shown of a cable
modem communication network including multiple hubs in which a
quality of service is localized, by the system of FIG. 2, for example, to
a particular subscriber or physical portion, e.g. physical
communication path of the network in accordance with yet another
embodiment of the present invention. Shown is a communication
network 300 including a cable modem termination system 302 (CMTS)
(also referred to as residing within the headend 104 of FIG. 1), hub 1
304 having serving groups 306 and 308, hub n 310 having serving
groups 312 and 314, bidirectional amplifiers 316, subscriber network
15 taps 318, subscriber devices 320, fiber links 322 (which represent
physical communication paths), and cable links 324 (which also
represent physical communication paths).
The cable modem communication network 300 is an
example of a relatively time-invariant communications network having
2o a generally known geographic/network topology. For example, in this
embodiment, the CMTS 302 represents a common node of the
communication network 300 (e.g. the CMTS 302 is contained within
the headend of FIG. 1) and communicates with the individual
subscriber devices 320 located in relatively fixed geographic positions
2s over a given geographic region. In the multi-hub configuration
illustrated, multiple hubs, e.g. hub 1 304 through hub n 310, are
coupled to the CMTS 302 via respective fiber links 322. Each hub
then is coupled to each of the respective subscriber devices 320 via
cable links 324. The subscriber devices 320 serviced by each hub are
3o grouped according to service groups, e.g. service groups 306 and 308
under hub 1 304. Each hub, e.g. hub 1 304, is similar to the media
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converter of FIG. 1. converting communications to and from fiber links
322 and cable links 324.
Within a service group, e.g. service group 306, the cable
link 324 couples to a bidirectional amplifier 316 to amplify the signals
5 in either the upstream direction (i.e. the direction from the respective
subscriber devices 320 to the CMTS 302) and in the downstream
direction (i.e. the direction from the CMTS 302 to each subscriber
device 320). At various geographic points on the cable link 324, a
respective subscriber network tap 313 is coupled to the cable to allow
1o respective subscriber devices 320 to be coupled to the hub. The
specific connections will be discussed in more detail with reference to
FIGS. 4-6.
As can be seen, the cable modem communication network
300 can support multiple hubs, each having multiple serving groups
15 servicing multiple subscriber devices. In operation, each subscriber
device 320 is typically a cable modem unit located at a subscriber's
residence or place of business. The subscriber device 320 contains
both a transmitter for transmitting signaling to the CMTS 302 and
also contains a receiver for receiving signaling from the CMTS 302. As
2o is known in the art, such cable modem communication networks 300
may be used by network providers to provide television, Internet and
telephony services, for example, to subscribers via their subscriber
devices 320.
It is noted that the cable modem communication network
2s 300 may include a variety of different architectures and still benefit
from the techniques of several embodiments of the invention, as long
as the communication network includes a transmitter .pool that has a
defined, and relatively time-invariant, physical connection. As such,
the physical path for each subscriber devices 320 in the
3o communication network 300 is known and unique for each subscriber
device 320 in the service axea.
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Referring next to FIG. 4, a diagram is shown of the cable
modem communication network of the FIG. 3 illustrating a single hub
having multiple serving groups. Shown is hub n 310 having a fiber
link 322 (which represents a physical communication path) to the
s CMTS 302, serving group 1 312 through serving group X 314 coupled
to the hub 310 via cable links. Also illustrated are the bidirectional
amplifiers 316, subscriber network taps 318, and subscriber devices
320. Furthermore, the cable links of FIG. 4 are illustrated as "shared"
physical communication paths 401, 402, 404, 406, 408, 418, 420,
422, 424 and 426 and also as "non-shared" physical communication
paths 410, 412, 414, 416, 428, 430, 432 and 434.
Additionally, the respective communication mediums
utilizing respective physical communication paths are labelled in the
form Mrrx~~, where "M" is the communication medium. Also, the
1s specific subscriber devices 320, i.e. transmitters of FIG. 2, are labelled
in the form of SNxYZ where "S" is the subscriber device. In both cases,
"N" is the hub identifier; "X" is the serving group within a given hub
identifier; "Y" is the transmitter identifier (which can be IP, MAC, TID,
SID or any other address correlated to the physical connection in the
2o network); "Y"' is the network medium identifier; and "Z" is the
transmitter's vendor identifier.
"Y"' indicates whether the particular communication
medium is a "backbone" communication medium (when Y'=0), i.e. a
communication medium utilizing a "shared" physical communication
2s path, or a medium utilizing a "non-shared" physical communication
path (when Y'~0) that is only utilized by one subscriber device 320.
When Y'=0, "Y" indicates how deep into the communication network
300 the Yth transmitter resides. For example, if Y=4 and Y'=0 in the
Mrrx~~ field (e.g. Mrrx~>), this indicates that the communication
3o medium is the communication networks backbone connection,
medium Mrrx4o, and that it will be shared by all transmitters with Y>4
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and that this transmitter will share Mrrx~<4>o network backbone
connections. In other words, the transmitter (i.e. SNx4Z) at the fourth
subscriber device 320 will utilize medium MNX44 (i.e. a non-shared
physical communication path from transmitter Srrx4z to the subscriber
network tap 318 connection to the backbone), medium Mrrx4o (i.e. a
shared physical communication path which is also shared with the
5~, 6~,... nth transmitters), Mrrxoo (i.e. a shared physical
communication path 406 for the 3rd, 4~, 5~, 6~,...nth transmitters),
Mrrxzo (i.e. a shared physical communication path 404 for the 2nd, 3rd,
l0 4~, 5~, 6~,.:.nth transmitters), and Mrrxio (i.e. shared physical
communication paths 401, 401 and 322 for the 1St, 2nd, 3rd, 4~n, 5~,
6~,...nth transmitters).
Relating these mediums Mrrx~~ to the communication
mediums 208, 210 and 212 of FIG. 2, if transmitter 202 is transmitter
is SNX3z, then communication medium 208 includes MNX33a Mrrx3o, Mrrx2o
and Mrrxio, and the receiver 214 is typically located at the CMTS 302.
Note also that medium MNxss utilizes non-shared physical
communication path 432; medium Mrrxso utilizes shared physical
communication path 424; medium Mrrxzo utilizes shared physical
2o communication path 422; and medium MNxio utilizes shared physical
communication paths 420, 418 and 322. Thus, it is important to
recognize that each communication medium of FIG. 2 (i.e.
communication mediums 208, 210 and 212) is defined as a composite
medium from a respective transmitter (e.g. SIVxYZ) to a common
25 receiving point (e.g. CMTS 302), and includes at least one shared
medium (e.g. Mrrx~~ where Y'=0) and one non-shared medium (e.g.
Mrrx~~ where Y'~0). Furthermore, each shared medium (e.g. Mrrx~
where Y'=0) includes one or more shared physical communication
paths (e.g. 322, 418, 420, 422, etc.) and each non-shared medium
30 (e.g. Mrrx~° where Y'~0) includes one or more non-shared physical
communication paths (e.g. 428 or 430).
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Briefly referring to FIG. 5, a table 500 is shown which
illustrates the various communications mediums relating to a pool of
subscribers within serving groups within hubs for the cable modem
communications network 300 of FIGS. 3 and 4. This table 500 uses
the above notation for the fields of the transmitters SIVXYZ and the
mediums Mrr~~.
Referring back to FIG. 4, the subscript "Z" (i.e. the
transmitter's vendor identifier) is used to denote the vendor who
manufactured or supplied the specific transmitter. For example, Z=0
1o corresponds~to transmitters made by vendor A, Z=1 corresponds to
transmitters made by vendor B, etc. As such, when analyzing the
network, differences in quality of service may be localized to a specific
transmitter/ subscriber device 320 made by a respective vendor; thus,
indicating that the particular vendor may be producing sub-standard
is equipment.
Having labeled the topology of the communication
network 300 and using one or more of the techniques described with
reference to FIG. 2 to determine a quality of service estimation for a
given communication medium between a particular transmitter (e.g.
2o SrrxYZ)and a common receiving point (e.g. CMTS 302), the network
provider is able to localize medium dependent channel distortions to a
likely physical communication path within the network 300. This is
accomplished by comparatively analyzing the quality of service
estimations for each communication medium (e.g. communication
2s mediums 208, 210 and 212). Constructing a network topology such
as illustrated in FIGS. 3 and 4, enables the network provider to
understand the specific mediums (Mrixx~°) making up each
communication medium (e.g. communication medium 208, 210 and
212) from the transmitter (e.g. SNxYZ) to the receiver (e.g. CMTS 302),
3o keeping in mind that there are shared mediums and non-shared
mediums utilizing shared physical communication paths (e.g. 322,
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418, 420, etc.) and non-shared physical communication paths (e.g.
428, 430, etc.). Thus, a particular quality of service limitation may be
localized to a particular physical communication path without having
to physically inspect or test each physical communication path in the
s communication network. Similarly, the network can be analyzed for
certain physical communication paths that for one reason or another
are able to support signaling with a higher quality of service than
others (e.g. there is less channel distortion in a particular physical
communication path due to microreflections from the subscriber
1o network tap~the particular subscriber device 320. The following
illustrate several examples of the possible analysis that could be
performed using the techniques of one or more embodiments of the
invention.
is EXAMPLE 1
Given three transmitters Srriiz, Srri2z and Srrisz (of FIG. 4)
having shared mediums MN130 (utilizing shared physical
communication path 406), MN120 (utilizing shared physical
communication path 404) and Mrriio (utilizing shared physical
2o communication paths 402, 401 and 322) and having non-shared
mediums Mrri i i (utilizing non-shared physical communication path
410), MN122 (utilizing non-shared physical communication path 412)
and Mrriss (utilizing non-shared physical communication path 414).
Using one of the channel distortion estimation and quality of service
25 estimation methods described with reference to FIG. 2 at the
distortion estimator 216, a quality of service estimation is obtained for
the composite communication mediums between from each
transmitter (i.e. SNllza SN12Z and SN13Z) to the common receiving point
(i.e. CMTS 302). Thus, a quality of service estimation is obtained for a
3o communication medium from Srri iz to the CMTS 302 (covering Mrri i i
and MNiio), a communication medium from Sr~l2z to the CMTS 302
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(covering Mrri22, Mrriao and Mrriio), and a communication medium from
the SN13Z to the CMTS 302 (covering Mrriss, Mrriso, Mrriao and Mrriio).
In the case that the QoS estimation for Srriiz is fine (i.e.
remains at or near a desired level over time), while the quality of
5 service estimations for Srri2z and SNisz have degraded (i.e. have
dropped below a desired level over time), it can be concluded that it is
likely that the shared medium Mrri2o is at fault, as it is the only shared
medium between the degraded service. Note that this indicates that
there is likely a problem with medium Mrri2o utilizing shared physical
1o communication path 404, not that there is a problem with medium
MN120. This is expressed as a likelihood since it is also possible that
both the transmitters Srrizz and Srrisz are faulty. Although at this
point, it is not determined with certainty which physical component of
the network is at fault, the likelihood of erroneous analysis decreases
15 as the number of transmitters and depth of the network increases.
Yet another possibility is that the both Mrriaa and Mrriss are at fault
and another transmitter further into the network would be allowed to
qualify medium Mrriao as being fine, i.e. able to support the desired
grade of service. Regardless, the network provider can localize the
2o degradation point closer to the real source of the problem, i.e. most
likely Mrriao utilizing shared physical communication path 404. Thus,
advantageously, by comparatively analyzing the quality of service
estimations for each transmitter, a limitation to the quality of service
within a network can be localized to a given piece-wise physical
25 connection within the network without physically inspecting or locally
testing each physical connection in the network.
It is noted that instead of representing these quality of
service estimations in terms of "fine" or "degraded", they can be
compared relative to respective numerical or quantitative
3o measurements, such that degradations may be ranked according to
severity.
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EXAMPLE 2
In the event that the quality of service estimations for all
three transmitters Srriiz, Srrizz and Srrisz were degraded individually,
s we can conclude that medium Mrnio utilizing shared physical
communication paths 402, 401 and 322 is the likely source of error,
since it is the only medium shared by all three transmitters Srriiz,
SNI2Z and SN13Z. Again, the likely source of error is localized to a given
physical portion of the communication network without local testing
or physical inspection of the entire network.
EXAMPLE 3
In the event that the quality of service estimations for
transmitters Srriiz and Srri3z are of acceptable quality while the quality
is of service estimation for transmitter SN122 1S degraded, it can be
concluded that medium MN122 1S likely at fault and that the health of
the network's backbone is not at risk. Thus, the network provider
would then send personnel to find and correct the fault Wlth MN122.
This fault could be in the non-shared physical communication path
412 utilized by the medium Mrri2a or the physical network backbone
connection (e.g. at subscriber network tap 318) or that the particular
transmitter Srn2z is faulty. Furthermore, depending on the value of
"Z", the vendor of the transmitter may be identified and compared to
the quality of service estimations obtained for other transmitters from
the same vendor. Thus, it may be determined whether or not it is
likely that the transmitter is at fault depending on the vendor
identifier. For example, a poor quality vendor has been allowed into
the network, such that the quality of service for signaling produced
from transmitters made by Vendor A decreases after a shorter
operating life than comparable transmitters made by other vendors.
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Although only three specific examples are described, there a
are many other scenarios within the communication network 300 in
which a quality of service may be localized to particular physical
communication path at a geographic location within the
communication network 300. The possible paths may be extended on
a hub basis to determine if a degradation is due to hub degradation or
the performance of the GMTS or the headend itself is at fault. For
example, with reference to FIG. 3, the quality of service estimations for
transmitters under hub 1 304 may be compared with the quality of
to service estimations for other hubs, e.g. hub n 310, in order to
estimate whether there is a problem with a specific hub of the
communication network 300.
Additionally, quality of service estimations can be
similarly compared to determine if a degradation in the quality of
service is due to an entire serving group that serves a respective hub.
For example, quality of service estimations for communication
mediums within a serving group are compared to quality of service
estimations for communication mediums of other serving groups
under the same hub to determine if there is a problem with an entire
2o serving group under a single hub. Briefly referring to FIG. 6, a
table 600 is shown mapping the individual subscribers within serving
groups of a single hub (i.e. hub 1 304) and also illustrating which
mediums (e.g. mediums MNXYY>) provide information on the network
health by a given subscriber when comparatively analyzed, as
2s described above. As shown an [x] indicates which mediums provide
information about the network health of a particular subscriber within
the communication network. For example, mediums Mlllo and M1111
provide information about the network health by transmitter Slllz,
while mediums Mlllo, M112o, Mllso, and Muss provide information
3o about the network health by transmitter Sllsz within the
communication network 300.
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Thus, advantageously, the network provider is able to
localize a source of network degradation to its likely source, e.g. a
physical communication path, within the network without the need to
send qualified personnel into the field. Instead of sending a
technician into the field to check each of the high level nodes and then
possibly have to search the next highest density node point, etc., for
the root cause of potentially one subscriber's degradation. Further
advantageously, the network provider is able to detect degradation in
the quality of service of a given piece-wise connection within relatively
to time-invariant communication network having unique and known
physical connections and correct them before they become
catastrophic to the customer/ subscriber. Furthermore, the network
provider is also able to determine the worst performing network
connections, with which to make the necessary judgment calls on the
best solution that fits a financial budget.
Referring next to FIG. 7, a flowchart is shown of a method
of localizing a quality of service to a particular subscriber or portion of
a relatively time-invariant communications network, for example, the
networks of FIGS. 1 through 4, in accordance with an embodiment of
2o the present invention.
Preliminary steps include estimating the channel
distortion of a plurality of communication mediums of a relatively
time-invariant communication network, such as described with
reference to FIGS. 1-4. These communications mediums (e.g.
2s communications mediums 203, 210 and 212 of FIG. 2 including the
various mediums Mrlxx~° of FIGS. 3 and 4) are defined between
respective transmitters (e.g. transmitters 202, 204 and 206 of FIG. 2
or transmitters SNxYZ of FIGS. 3 and 4) of a transmitter pool and a
common receiving point (e.g. receiver 214 of FIG. 2 or CMTS 302 of
3o FIGS. 3 and 4). The specific channel distortion estimations are
performed according to any of the techniques described with reference
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to FIG. 2, for example, by the distortion estimator 216 of FIG. 2.
These channel distortion estimations (i.e. medium dependent channel
distortion estimations) are used to determine a quality of service
estimation for signaling supported by each of the respective
communication mediums, e.g. signaling having what modulation level
and signaling rate is supported by the particular medium using
conventional techniques.
In accordance with one embodiment of the invention,
these quality of service estimations are obtained or received from
1o memory or directly, e.g. from the distortion estimator, for each of the
plurality of communication mediums (Step 702). Each of the plurality
of communication mediums are defined between a respective
transmitter of a pool of transmitters and the common receiving point
of the relatively time-invariant communication network. Each of the
~s communication mediums is conveyed over at least one shared
physical communication path and at least one non-shared physical
communication path. In one embodiment, the QoS localizer 220 (e.g.
located in the CMTS 302 of the headend 104) receives the quality of
service estimations for each transmitter in the network from a
2o distortion estimator 216 (e.g. located in the CMTS 302 of the headend
104) of FIG. 2.
These quality of service estimations are stored within a
memory (Step 704), e.g. memory 218 of FIG. 2, which may be located
within or coupled to the common receiving point, e.g. located in the
2s CMTS 302 of the communication network 300 of FIGS. 3 and 4. The
storing step may be performed before and after the receiving step (i.e.
Step 702).
Next, the quality of service estimations are comparatively
analyzed in order to localize a given quality of service to a specific
3o physical communication path, either shared or non-shared (Step 706).
Next, based on the comparing step, a particular quality of service
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estimation is localized to a likely physical communication path
associated with the particular quality of service estimation (Step 708).
These comparing and localizing steps are performed, in one
embodiment, to geographically localize a particular physical
5 communication path likely causing a degradation in service or likely
associated with a particular quality of service within the
communication network. For example, several examples are described
above illustrating the comparing and localizing steps.
While the invention herein disclosed has been described
1o by means of. specific embodiments and applications thereof, numerous
modifications and variations could be made thereto by those skilled in
the art without departing from the scope of the invention set forth in
the claims.
