U.S. patent application number 14/867489 was filed with the patent office on 2016-01-21 for packet detector.
The applicant listed for this patent is AWARE, INC.. Invention is credited to Joon Bae KIM, Stuart SANDBERG, Marcos C. TZANNES.
Application Number | 20160020934 14/867489 |
Document ID | / |
Family ID | 42813307 |
Filed Date | 2016-01-21 |
United States Patent
Application |
20160020934 |
Kind Code |
A1 |
TZANNES; Marcos C. ; et
al. |
January 21, 2016 |
PACKET DETECTOR
Abstract
There are several exemplary ways to more efficiently communicate
an out-of-domain seed to a receiver--in a first technique, the seed
can be indicated in the header portion or data portion of a packet.
For example, the header portion of the packet could contain one or
more bit fields that indicate the value of the LFSR seed used for
the preamble portion of the packet. The receiver would learn the
out-of-domain seed after receiving a first out-of-domain packet and
decoding the header portion of that packet. After learning the
out-of-domain seed, the receiver could send a packet indicating the
value of the out-of-domain seed to the local master. The local
master could then transmit the value of the out-of-domain seed in
the header portion or data portion of a local MAP frame.
Inventors: |
TZANNES; Marcos C.; (Alamo,
CA) ; KIM; Joon Bae; (Lexington, MA) ;
SANDBERG; Stuart; (Action, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AWARE, INC. |
Bedford |
MA |
US |
|
|
Family ID: |
42813307 |
Appl. No.: |
14/867489 |
Filed: |
September 28, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14614138 |
Feb 4, 2015 |
9154355 |
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14867489 |
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14259316 |
Apr 23, 2014 |
8953657 |
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14614138 |
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13376400 |
Mar 27, 2012 |
8718118 |
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PCT/US2010/042850 |
Jul 22, 2010 |
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14259316 |
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61227673 |
Jul 22, 2009 |
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Current U.S.
Class: |
370/471 |
Current CPC
Class: |
H04L 25/03866 20130101;
H04L 27/2602 20130101; H04L 27/3472 20130101; H04L 27/2613
20130101; H04L 27/2614 20130101; H04L 69/22 20130101; H04L 27/2647
20130101; H04L 5/0044 20130101; H04L 7/042 20130101 |
International
Class: |
H04L 27/26 20060101
H04L027/26; H04L 27/34 20060101 H04L027/34; H04L 29/06 20060101
H04L029/06 |
Claims
1. A method of OFDM communication comprising: transmitting, by a
transmitter, a packet including a header portion and preamble
portion, wherein: the preamble portion includes a plurality of OFDM
symbols modulated using a constellation scrambler, the
constellation scrambler includes an LFSR generator that is
initialized with a seed, and the header portion of the packet
contains one or more bit fields that contain information that can
be used to determine a value of the seed used to generate the
preamble portion of the packet.
2.-26. (canceled)
Description
RELATED APPLICATION DATA
[0001] This application is a Continuation of U.S. patent
application Ser. No. 14/259,316, filed Apr. 23, 2014, now U.S. Pat.
No. 8,953,657, which is a Continuation of U.S. patent application
Ser. No. 13/376,400, filed Mar. 27, 2012, now U.S. Pat. No.
8,718,118, which is a National Stage Application under 35 U.S.C 371
of PCT Application No. PCT/US2010/042850, having an international
filing date of Jul. 22, 2010, which designated the United States,
which PCT application claims the benefit of and priority under 35
U.S.C. .sctn.119(e) to U.S. Patent Application No. 61/227,673,
filed Jul. 22, 2009, entitled "Method, System, Means,
Computer-Readable Media and Protocol for Improved Packet Detector,"
each of which are incorporated herein by reference in their
entirety.
FIELD OF THE INVENTION
[0002] An exemplary aspect of this invention relates to
communications systems. More specifically, exemplary methods,
systems, means, protocols and computer-readable storage media, are
directed toward an improved packet detector.
BACKGROUND
[0003] Conventional multi-user communication systems use
frame-based (or packet-based) transmission to communicate between
two or more users over a shared channel based on OFDM. Examples of
such systems include IEEE 802.11x (Wireless LAN), IEEE 802.16
(WiMAX) and ITU G.9960 (G.hn). These systems use OFDM transmission
(also referred to sometimes as Discrete MultiTone (DMT)) which
divides the transmission frequency band into multiple sub-carriers
(also referred to as tones or sub-channels), with each sub-carrier
individually modulating a bit or a collection of bits.
[0004] Conventional methods of packet detection use a predefined
preamble as specified, for example, in the standards above. The
G.hn standard uses predefined OFDM symbols modulated with an all
ones bit as specified in Section 7.1.4.5.2.1.1 of G.hn and rotated
with the Constellation Scrambler in Section 7.1.4.3.3 of G.hn. For
convenience, the text contained in Sections 7.1.4.5.2.1.1 and
7.1.4.3.3 of G.hn is contained in Appendix A. A method for
supporting multiple reference sequences to modulate the preamble is
ITU Contribution 09BM-038 (contained in Appendix B). 09 MB-038
proposes to allow different reference sequences to modulate the
preamble subcarriers. The different sequences may be defined by a
properly chosen set of seeds that initialize the already specified
LFSR generator. This LFSR (Linear Feedback Shift Register)
generator provides the pseudo-random di-bit sequence that modulates
the non-masked preamble sub-carriers. Allowing the use of different
reference sequences among different networks can serve as another
mechanism for mitigating disturbances from neighboring networks in
PLC environments.
SUMMARY
[0005] However, our analysis shows that methods that use a
threshold-based cross-correlation approach to detect packets (as
proposed in 09BM-038) can result in at least (up to) 3 dB of
performance loss.
[0006] Therefore, a first exemplary aspect is at least directed
toward methods, systems, means, protocols and computer-readable
storage media and associated program(s) for an improved packet
detector.
[0007] The analysis further shows that the performance loss of
conventional methods can be overcome by using receiver algorithms
that use knowledge of the seed of the constellation scrambler LFSR
used by the out-of-domain (e.g., neighboring network) transmitter.
In an exemplary embodiment, the receiver compares detection results
using a local (or domain) LFSR seed and an out-of-domain LFSR seed.
Based on these detection results a packet is declared as "detected"
or "not detected." For example, a first cross-correlation can be
performed using a received signal with a first predefined signal
generated using a first LFSR seed (e.g., for in-domain packets). A
second cross-correlation can be performed using the received signal
with a second predefined signal generated using a second LFSR seed
(e.g., for out-of-domain packets). A comparison can be made between
the first and second cross-correlation to determine if the packet
is an in-domain (local) packet or from the other network. This
method can be extended to any number of networks. For example, if
there are n networks, there n cross-correlations could be
determined. A comparison could be made between the n
cross-correlations to determine if the packet is an in-domain
(local) packet or from one of the n other networks.
[0008] There are several exemplary ways to communicate the
out-of-domain seed to the receiver.
[0009] In accordance with a first an exemplary embodiment, the seed
can be indicated in the header portion or data portion of a packet.
For example, the header portion of the packet could contain one or
more bit fields that contain information that can be used to
determine the value of the LFSR seed used for the preamble portion
of the packet. The receiver would learn the out-of-domain seed
after receiving a first out-of-domain packet and decoding the
header portion of that packet. After learning the out-of-domain
seed, the receiver could send a packet indicating the value of the
out-of-domain seed to the local master. The local master could then
transmit the value of the out-of-domain seed in the header portion
or data portion of a local MAP frame (as described in the exemplary
embodiment below) to other transceivers in the local domain.
[0010] Alternatively, or in addition, the seed can be indicated in
the header portion or data portion of an out-of-domain MAP frame.
The receiver would learn the out-of-domain seed after receiving an
out-of-domain MAP frame. For example, the header portion and/or
data portion of the out-of-domain MAP frame could contain one or
more bit fields that contain information that can be used to
determine the value of the LFSR seed used for the preamble portion
of the packets sent in the neighboring (out-of-domain) network. The
receiver would learn the out-of-domain seed after receiving a
out-of-domain MAP frame and decoding the header portion and/or data
portion of the MAP frame.
[0011] Alternatively, or in addition, one or more out-of-domain
seeds can be indicated in the header portion or data portion of the
local MAP frame. For example, the header portion of the MAP frame
could contain one or more bit fields that contain information that
can be used to determine the value of the one or more out-of-domain
LFSR seeds used for the preamble portion of packets from one or
more other (neighbor) domains.
[0012] Alternatively, or in addition, a receiver may receive a
plurality of out-of-domain packet(s) in order to determine the LFSR
seed used for the preamble portion of the packets. For example, the
receiver may process the out-of-domain packet(s) using a plurality
of seeds to determine the seed that is being used by the other
domain. This may be done, for example, during a diagnostic mode in
which other transmitters in the local network are silent. After
learning the out-of-domain seed, the receiver could send a packet
indicating the value of the out-of-domain seed to the local master.
The local master could then transmit the value of the out-of-domain
seed in the header portion or data portion of a local MAP frame (as
described in the embodiment above).
[0013] Exemplary Receiver Detection Technique
[0014] The preamble transmitted in a given network contains several
consecutive repetitions of the same subblock. The subblock is
LFSR-modulated based on that particular network's seed.
[0015] Let x.sub.m.sup.n, m=0, . . . , M-1, denote the sequence of
transmitted samples for network n's subblock.
[0016] For the first step in the detection process, the receiver
continuously determines the autocorrelation between consecutive
received subblocks of the reception, until observing several
consecutive high correlations. The correlation for the kth subblock
is determined as
a k = m = 0 M - 1 r m k - 1 r m k ##EQU00001##
where: r.sub.m.sup.k is the mth sample of the kth received
subblock. Upon observing large |a.sub.k| for several consecutive k,
the receiver can declare a preliminary detection.
[0017] Due to the periodic nature of the preamble, a preliminary
detection can occur for a preamble transmitted from the local
network, or a neighbor network. The second step in the detection
process is to determine if the initial detection is of a preamble
in the local network. Toward this determination, for a given k with
large |a.sub.k|, the receiver determines the cross-correlation
functions:
.rho. i k , n = m = 0 M - 1 x m + i n r m k ##EQU00002##
where m+i is modulo M.
[0018] If the received preamble is from network n, a sequence
.rho..sub.i.sup.k,n, i=0, . . . , M-1 is an estimate for the
channel impulse, and will tend to have much of its energy
concentrated in a small number of samples i. However, if the
received preamble is not from network n, the sequences
.rho..sub.i.sup.k,n will have less concentration in their
energy.
[0019] The cross-correlation function results .rho..sub.i.sup.k,n
are compared and/or processed and used to determine whether the
packet was from the local network or a neighbor network. For
example, from .rho..sub.i.sup.k,n, the receiver calculates
v.sup.k,n, the ratio of the energy in the j largest magnitudes in
.rho..sub.i.sup.k,n, i=0, . . . , M-1, divided by the total energy.
The network n for which the mean of v.sup.k,n over k, is maximum is
determined to be the network from which the preamble has been
transmitted. If this network n is the local network, processing for
demodulating the remainder of the packet is initiated; otherwise
the detection process begins again.
[0020] Exemplary aspects of the invention are directed toward a
method of OFDM communication including:
[0021] transmitting, by a transmitter, a packet comprising a header
portion and preamble portion,
[0022] wherein the preamble portion comprises a plurality of OFDM
symbols modulated using a constellation scrambler,
[0023] wherein the constellation scrambler comprises an LFSR
generator that is initialized with a seed, and
[0024] wherein the header portion of the packet contains one or
more bit fields that contain information that can be used to
determine the value of the seed used for the preamble portion of
the packet.
[0025] Exemplary aspects of the invention are also directed toward
a method of OFDM communication including:
[0026] receiving, by a receiver, a packet comprising a header
portion and preamble portion,
[0027] wherein the preamble portion comprises a plurality of OFDM
symbols modulated using a constellation scrambler,
[0028] wherein the constellation scrambler comprises an LFSR
generator that is initialized with a seed, and
[0029] wherein the header portion of the packet contains one or
more bit fields that contain information that can be used to
determine the value of the seed used for the preamble portion of
the packet.
[0030] Exemplary aspects of the invention are also directed toward
means for OFDM communication including:
[0031] means for transmitting, by a transmitter, a packet
comprising a header portion and preamble portion,
[0032] wherein the preamble portion comprises a plurality of OFDM
symbols modulated using a constellation scrambler,
[0033] wherein the constellation scrambler comprises an LFSR
generator that is initialized with a seed, and
[0034] wherein the header portion of the packet contains one or
more bit fields that contain information that can be used to
determine the value of the seed used for the preamble portion of
the packet.
[0035] Exemplary aspects of the invention are also directed toward
means for OFDM communication including:
[0036] receiving, by a receiver, a packet comprising a header
portion and preamble portion,
[0037] wherein the preamble portion comprises a plurality of OFDM
symbols modulated using a constellation scrambler,
[0038] wherein the constellation scrambler comprises an LFSR
generator that is initialized with a seed, and
[0039] wherein the header portion of the packet contains one or
more bit fields that contain information that can be used to
determine the value of the seed used for the preamble portion of
the packet.
[0040] Exemplary aspects of the invention are also directed toward
an OFDM communication system including:
[0041] a transmitter capable of transmitting a packet comprising a
header portion and preamble portion,
[0042] wherein the preamble portion comprises a plurality of OFDM
symbols modulated using a constellation scrambler,
[0043] wherein the constellation scrambler comprises an LFSR
generator that is initialized with a seed, and
[0044] wherein the header portion of the packet contains one or
more bit fields that contain information that can be used to
determine the value of the seed used for the preamble portion of
the packet.
[0045] Exemplary aspects of the invention are also directed toward
an OFDM communication system including:
[0046] a receiver capable of receiving a packet comprising a header
portion and preamble portion,
[0047] wherein the preamble portion comprises a plurality of OFDM
symbols modulated using a constellation scrambler,
[0048] wherein the constellation scrambler comprises an LFSR
generator that is initialized with a seed, and
[0049] wherein the header portion of the packet contains one or
more bit fields that contain information that can be used to
determine the value of the seed used for the preamble portion of
the packet.
[0050] Exemplary aspects of the invention are also directed toward
a non-transitory computer-readable media having stored thereon
instructions that, if executed by a processor, perform OFDM
communication including:
[0051] instructions that generate a packet for transmission, the
packet comprising a header portion and preamble portion,
[0052] wherein the preamble portion comprises a plurality of OFDM
symbols modulated using a constellation scrambler,
[0053] wherein the constellation scrambler comprises an LFSR
generator that is initialized with a seed, and
[0054] wherein the header portion of the packet contains one or
more bit fields that contain information that can be used to
determine the value of the seed used for the preamble portion of
the packet.
[0055] Exemplary aspects of the invention are also directed toward
a non-transitory computer-readable media having stored thereon
instructions that, if executed by a processor, perform OFDM
communication including:
[0056] instructions that process a packet after reception, the
packet comprising a header portion and preamble portion,
[0057] wherein the preamble portion comprises a plurality of OFDM
symbols modulated using a constellation scrambler,
[0058] wherein the constellation scrambler comprises an LFSR
generator that is initialized with a seed, and
[0059] wherein the header portion of the packet contains one or
more bit fields that contain information that can be used to
determine the value of the seed used for the preamble portion of
the packet.
[0060] Exemplary aspects of the invention are also directed toward
a method of OFDM communication including detecting a packet by
performing at least two cross-correlation functions using at least
two different LFSR seeds and comparing the results of the at least
two cross-correlation functions.
[0061] Any of the above aspects and further aspects may be located
in a network management system or network operation device that is
located inside or outside the network and/or the transceiver(s). In
particular, aspects that are related to seed(s) in a packet may be
done in such a device. The network operation or management device
that is located inside or outside the network may be managed and/or
operated by a user, consumer, service provider or power utility
provider or a governmental entity.
[0062] These and other features and advantages of this invention
are described in, or are apparent from, the following detailed
description of the exemplary embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0063] The exemplary embodiments of the invention will be described
in detail, with reference to the following figures, wherein:
[0064] FIG. 1 illustrates an exemplary communications
environment;
[0065] FIG. 2 is a flowchart outlining an exemplary method for
improved packet detection;
[0066] FIG. 3 is a flowchart outlining another exemplary method for
improved packet detection;
[0067] FIG. 4 is a flowchart outlining another exemplary method for
improved packet detection;
[0068] FIG. 5 is a flowchart outlining another exemplary method for
improved packet detection;
[0069] FIG. 6 is a flowchart outlining an exemplary method for
transmitting a packet;
[0070] FIG. 7 is a flowchart outlining an exemplary method of
receiving a packet;
[0071] FIG. 8 is a flowchart outlining an exemplary method for a
system to transmit and receive a packet;
[0072] FIG. 9 is a flowchart outlining an exemplary method for
generating and transmitting a packet;
[0073] FIG. 10 is a flowchart outlining an exemplary method for
receiving a packet;
[0074] FIG. 11 is a flowchart outlining another exemplary method
for receiving a packet;
[0075] FIG. 12 in Appendix A illustrates a G.9960 Constellation
Scrambler; and
[0076] FIG. 13 in Appendix B illustrates loss due to "false"
detection of a neighbouring network preamble.
DETAILED DESCRIPTION
[0077] The exemplary embodiments of this invention will be
described in relation to communications systems, as well as
protocols, techniques and methods for improved packet detection,
such as a DSL or multimode multicarrier communications environment,
a home network or an access network, or in general any
communications network operating using any communications
protocol(s). Examples of such home or access networks include home
powerline networks, access powerline networks, home coaxial cable
network, access coaxial cable network, wireless home networks,
wireless corporate networks, home telephone networks and access
telephone networks. However, it should be appreciated that in
general, the systems, methods, and techniques of this invention
will work equally well for other types of communications
environments, networks, and/or protocols.
[0078] The exemplary systems and methods of this invention will
also be described in relation to wired or wireless modems and/or a
software and/or a hardware testing module, a telecommunications
test device, or the like, such as a DSL modem, an ADSL modem, and
xDSL modem, a VDSL modem, a line card, a G.hn transceiver, a MOCA
transceiver, a Homeplug.RTM. transceiver, a power line modem, a
wired or wireless modem, test equipment, a multicarrier
transceiver, a wireless wide/local area network system, a satellite
communications system, a network-based communications systems, such
as an IP, Ethernet or ATM system, a modem equipped with diagnostic
capabilities, or the like, or a separate programmed general purpose
computer having a communications device that is capable of
operating in conjunction with any one or more of the following
communications protocols: MOCA, G.hn, Homeplug, IEEE 802.11, IEEE
802.3 or the like. However, to avoid unnecessarily obscuring the
present invention, the following description omits well-known
structures, operations and devices that may be shown in block
diagram form or are otherwise summarized or known.
[0079] For purposes of explanation, numerous details are set forth
in order to provide a thorough understanding of the present
invention. It should be appreciated however that the present
invention may be practiced in a variety of ways beyond the specific
details set forth herein. Furthermore, while the exemplary
embodiments illustrated herein show various components of this
system collocated, it is to be appreciated that the various
components of the system can be located at distant portions of a
distributed network, such as a communications network, node, within
a Domain Master, and/or the internet, or within a dedicated
secured, unsecured, and/or encrypted system and/or within a network
operation or management device that is located inside or outside
the network. As an example, a Domain Master can also be used to
refer to any device, system or module that manages and/or
configures any one or more aspects of the network or communications
environment.
[0080] Thus, it should be appreciated that the components of the
system can be combined into one or more devices, or split between
devices, such as a modem, a station, a Domain Master, a network
operation or management device, a node or collocated on a
particular node of a distributed network, such as a communications
network. As will be appreciated from the following description, and
for reasons of computational efficiency, the components of the
system can be arranged at any location within a distributed network
without affecting the operation thereof. For example, the various
components can be located in a Domain Master, a node, a domain
management device, such as a MIB, a network operation or management
device, or some combination thereof. Similarly, one or more of the
functional portions of the system could be distributed between a
modem and an associated computing device/system, and/or in a
dedicated test and/or measurement device.
[0081] Furthermore, it should be appreciated that the various links
5, including the communications channel(s) connecting the elements
can be wired or wireless links or any combination thereof, or any
other known or later developed element(s) capable of supplying
and/or communicating data to and from the connected elements. The
term module as used herein can refer to any known or later
developed hardware, software, firmware, or combination thereof,
that is capable of performing the functionality associated with
that element. The terms determine, calculate, and compute and
variations thereof, as used herein are used interchangeable and
include any type of methodology, process, technique, mathematical
operational or protocol. The terms transceiver and modem are also
used interchangeably herein. The terms transmitting modem and
transmitting transceiver as well as receiving modem and receiving
transceiver are also used interchangeably herein.
[0082] The term management interface is related to any type of
interface between a management entity and/or technician and a
transceiver, such as, a CO-MIB or CPE-MIB as described, for
example, in ITU standard G.997.1, which is incorporated herein by
reference in its entirety.
[0083] Moreover, while some of the exemplary embodiments described
herein are directed toward a transmitter portion of a transceiver
performing certain functions, this disclosure is intended to
include corresponding receiver-side functionality in both the same
transceiver and/or another transceiver, and vice versa.
[0084] FIG. 1 illustrates an exemplary communications environment
1. The communications environment 1, in addition to well known
componentry, includes a plurality of transceivers or endpoints or
nodes 100, that are connectable to and capable of exchanging
information with one or more other transceivers or endpoints or
nodes in one or more other networks, such as out-of-domain network
210, out-of-domain network 220, in-domain (local) network 230, and
a local (domain) master 240 via wired or wireless links 5 and
network(s) (not shown). The transceiver(s) 100, in addition to
well-known componentry, includes a constellation scrambler and LFSR
generator module 102, a local LFSR seed management module 110, an
out-of-domain LFSR seed management module 120, a cross-correlation
module 130, a seed communication module 140, transmitter module
150, receiver module 160, controller/processor 105 and memory 107.
The various transceivers or endpoints in the environment 1 are
capable of being connected to one or more other transceiver or
endpoints by links such as one or more of directly connectable to
one or more other transceivers (or networks) as well as indirectly
connectable 7 to one or more other transceivers (or networks)
through one or more transceivers as illustratively shown by the
non-limiting links illustrated in FIG. 1.
[0085] As discussed, there are several exemplary techniques for
communicating an out-of-domain seed to, for example, a receiver
portion that includes receiver module 160 of transceiver 100.
[0086] In accordance with the first exemplary embodiment, the seed
can be indicated in of the header portion and/or data portion of a
packet. For example, a transceiver having a seed communication
module can assemble a packet where the header portion of the packet
could contain one or more bit fields that contain information that
can be used to determine the value of the LFSR seed used for the
preamble portion of the packet. For example, the transceiver could
be a transceiver in the local network 5 or the transceiver could be
a transceiver in the neighboring network 220 (out-of-domain).
[0087] When the packet is received, the receiver portion of
transceiver 100 could learn the out-of-domain seed after decoding
the information contained in the header portion of the packet.
After learning the out-of-domain seed, which is managed and can be
stored by the out-of-domain LFSR seed management module 120, the
receiver portion of transceiver 100 could cooperate with the seed
communication module 140 such that the transceiver 100 could send a
packet indicating the value of the determined out-of-domain seed
to, for example, the local master 240. The local master 240 could
then transmit the value of out-of-domain seed in the header portion
and/or data portion of a local MAP frame as discussed in greater
detail hereinafter, to one or more other transceivers in the
in-domain (local) network 230.
[0088] In accordance with another exemplary embodiment, a seed can
be indicated in a header portion and/or data portion of an
out-of-domain MAP frame. For example, the header portion and/or
data portion of the out-of-domain MAP frame could contain one or
more bit fields that contain information that can be used to
determine the value of the LFSR seed used for the preamble portion
of the packets sent in the neighboring (out-of-domain) network. The
receiver would learn the out-of-domain seed after receiving an
out-of-domain MAP frame and decoding the header portion and/or data
portion of the MAP frame. After receiving the out-of-domain MAP
frame, the transceiver 100 could notify one or more of the local
master 240 and/or other endpoints and/or nodes and/or transceivers
within the in-domain network 230 of the out-of-domain seed.
[0089] In accordance with one exemplary embodiment, this is done by
utilizing a local MAP frame, where the transceiver assembles a
local MAP frame with bit field(s) that contain information that can
be used to determine the value of one or more out-of-domain LFSR
seeds that were used for a preamble portion of packets from one or
more other domains.
[0090] In accordance with another exemplary embodiment, one or more
out-of-domain seeds can be indicated in a header portion and/or
data portion of a local MAP frame. For example, upon receipt of a
local MAP frame by the transceiver 100, the header portion of the
MAP frame could contain one or more bit fields that contain
information that can be used to determine the value of one more
out-of-domain LFSR seeds used for the preamble portion of packets
from one or more other domains. These out-of-domain LFSR seeds can
be stored and/or managed by the out-of-domain LFSR seed management
module 120.
[0091] In accordance with another exemplary embodiment, the
receiver portion of transceiver 100 may receive a plurality of
out-of-domain packet(s) in order to determine the LFSR seed used
for the preamble portion of the packets. For example, the receiver
portion of transceiver 100 may process the out-of-domain packet(s),
in cooperation with the cross-correlation module 130, using a
plurality of seeds, from one or more of the local LFSR seed
management module 110 and the out-of-domain LFSR seed management
120 to determine the seed that is being used by the other domain.
This may be done, for example, to a diagnostic mode where the other
transceivers in the local network are silent. After learning the
out-of-domain seed, the transceiver 100 (cooperating with
transmitter module 150) could send a packet indicating the value of
the out-of-domain seed to, for example, the local master 240. The
local master 240 could then, for example, transmit the value of the
out-of-domain seed in a header portion and/or data portion of a
local MAP frame to one or more other transceivers in the in-domain
network 230.
[0092] FIG. 2 is a flowchart outlining an exemplary technique for
improving packet detection according to an exemplary embodiment. In
particular control begins in step S200 and continues to step S210.
In step S210, a transceiver from an out-of-domain network
determines a packet for transmission. Next, in step S220, an LFSR
generator seed is indicated in one or more of the header portion or
data portion of a packet. For example, the header portion of the
packet could contain one or more bit fields that contain
information that can be used to determine the value of the LFSR
seed used for the preamble portion of the packet. Then, in step
S230, a receiver learns of the out-of-domain seed after receiving
and decoding one or more of the header portion and data portion of
the packet. Control then continues to step S240.
[0093] In step S240, and after decoding and determining a seed for
the out-of-domain packet, a determination is made whether a local
master should be notified. If a local master is to be notified,
control continues to step S242 with control otherwise jumping to
step S250.
[0094] In step S242, the recipient of the out-of-domain packet can
send a packet indicating the value of the out-of-domain seed to the
local master. For example, the header portion and/or data portion
of the MAP frame could contain one or more bit fields that contain
information that can be used to determine the value of the LFSR
seed used for the preamble portion of the packets sent in the
neighboring (out-of-domain) network. Next, in step S244, a
determination is made whether a notification should be made by a
local MAP frame. If the notification is to be made by a local MAP
frame, control continues to step S246 with control otherwise
jumping to step S250.
[0095] In step S246, a local MAP frame is assembled with bit
field(s) that indicate the value of one or more out-of-domain LFSR
seeds used for the preamble portion of packets from one or more
other domains. Control then continues to step S250.
[0096] In step S250, one or more cross-correlations can be
performed to determine, for example, whether the packet was from a
transceiver or endpoint that is from an out-of-domain network, or
from an in-domain network. Based on these cross-correlations,
packets from the in-domain network are declared as "detected" and
packets from outside of the in-domain are declared as "not
detected." "Detected" packets are decoded and sent to the upper
layer as necessary whereas "not detected" packets can be discarded
and not processed further. Control then continues to step S270
where the control sequence ends.
[0097] FIG. 3 is a flowchart outlining another exemplary technique
for improving packet detection according to an exemplary
embodiment. In particular control begins in step S300 and continues
to step S310. In step S310, a transceiver learns an out-of-domain
seed after receiving an out-of-domain MAP frame. Next, in step
S320, a determination is made whether a local master should be
notified. If a local master is to be notified, control continues to
step S322 with control otherwise jumping to step S330.
[0098] In step S322, the recipient of the MAP frame can send a
packet indicating the value of the out-of-domain seed to the local
master. Next, in step S324, a determination is made whether a
notification should be made by a local MAP frame. If the
notification is to be made by a local MAP frame, control continues
to step S326 with control otherwise jumping to step S330.
[0099] In step S326, a local MAP frame is assembled with bit
field(s) that contain information that can be used to determine the
value of one or more out-of-domain LFSR seeds used for the preamble
portion of packets from one or more other domains. Control then
continues to step S330.
[0100] In step S330, a cross-correlation can be performed to
determine, for example, whether the packet was from a transceiver
or endpoint that is from an out-of-domain network, or from an
in-domain network. Based on this cross-correlation, packets from
the in-domain network are declared as "detected" and packets from
outside of the in-domain are declared as "not detected." Control
then continues to step S350 where the control sequence ends.
[0101] FIG. 4 illustrates an exemplary technique for learning about
a seed form an out-of-domain transceiver according to an exemplary
embodiment. In particular, control begins in step S400 and
continues to step S410. In step S410, a receiver learns about an
out-of-domain seed after receiving a local MAP frame. Next, in step
S420, a cross-correlation is performed with, in step S430, packets
declared as detected for in-domain network packets and as not
detected for out-of-domain packets. Control then continues to step
S440 where the control sequence ends.
[0102] FIG. 5 is a flowchart outlining another exemplary technique
for improving packet detection according to an exemplary
embodiment. In particular control begins in step S500 and continues
to step S510. In step S210, a plurality of out-of-domain packets
are received. Next, in step S520, the plurality of received packets
are processed using a plurality of seeds and a comparison made to
determine the seed(s) being used by the other domain(s) that sent
the packet(s). Then, in step S530, a determination is made whether
a local master should be notified. If a local master is to be
notified, control continues to step S532 with control otherwise
jumping to step S540.
[0103] In step S532, the recipient of the out-of-domain packet(s)
can send a packet indicating the value of the determined
out-of-domain seed to the local master. Next, in step S534, a
determination is made whether a notification should be made by
using a local MAP frame. If the notification is to be made by a
local MAP frame, control continues to step S536 with control
otherwise jumping to step S5400.
[0104] In step S536, a local MAP frame is assembled with bit
field(s) that indicate the value of one or more out-of-domain LFSR
seeds used for the preamble portion of packets from one or more
other domains. Control then continues to step S540.
[0105] In step S540, a cross-correlation can be performed to
determine, for example, whether the packet was from a transceiver
or endpoint that is from an out-of-domain network, or from an
in-domain network. Based on this cross-correlation, packets from
the in-domain network are declared as "detected" and packets from
outside of the in-domain are declared as "not detected." Control
then continues to step S560 where the control sequence ends.
[0106] FIG. 6 is a flowchart outlining an exemplary method for
transmitting a packet. In particular, control begins in step S600
and continues to step S610. In step S610, a transmitter transmits a
packet that includes a header portion and preamble portion. The
preamble portion includes a plurality of OFDM symbols modulated
using a constellation scrambler. The constellation scrambler
includes an LFSR generator that is initialized with a seed, where
the header portion of the packet contains one or more bit fields
that contain information that can be used to determine a value of a
seed used for initializing an LFSR generator that was used to
generate the preamble portion of the packet. Control then continues
to step S620 where the control sequence ends.
[0107] FIG. 7 is a flowchart outlining an exemplary method of
receiving a packet. In particular, control begins in step S700 and
continues to step S710. In step S710, a receiver receives a packet
that includes a header portion and preamble portion. The preamble
portion includes a plurality of OFDM symbols that were modulated
using a constellation scrambler. The constellation scrambler used
an LFSR generator that was initialized with a seed, where the
header portion of the packet contains one or more bit fields that
contain information that can be used to determine a value of the
seed that was used to generate the preamble portion of the packet.
Control then continues to step S720 where the control sequence
ends.
[0108] FIG. 8 is a flowchart outlining an exemplary method for a
system to transmit and receive a packet. In particular, control
begins in step S800 and continues to step S810. In step S810, a
transmitter transmits a packet including a header portion and
preamble portion. Next, in step S820, a receiver receives the
packet that includes the header portion and preamble portion, where
the preamble portion includes a plurality of OFDM symbols modulated
using a constellation scrambler, where the constellation scrambler
comprises an LFSR generator that is initialized with a seed, and
the header portion of the packet contains one or more bit fields
that contain information that can be used to determine a value of
the seed used to generate the preamble portion of the packet.
Control then continues to step S830 where the control sequence
ends.
[0109] FIG. 9 is a flowchart outlining an exemplary method for
generating and transmitting a packet. In particular, control begins
in step S900 and continues to step S910. In step S910, the preamble
portion of the packet is generated using an LFSR generator that is
initialized with a seed. Next, in step S920, a packet comprising a
header portion and the preamble portion is transmitted, where the
header portion of the packet contains one or more bit fields that
contain information that can be used to determine a value of the
seed used by the LFSR generator to generate the preamble portion of
the packet. Control then continues to step S930 where the control
sequence ends.
[0110] FIG. 10 is a flowchart outlining an exemplary method for
receiving a packet. In particular, control begins in step S1000 and
continues to step S1110. In step S1010, a receiver receives a
packet that includes a header portion and preamble portion. Next,
in step S1020, the packet is detected using the preamble portion,
where the preamble portion was generated using an LFSR generator
that was initialized with a seed, and wherein the header portion of
the packet contains one or more bit fields that contain information
that can be used to determine a value of the seed used to generate
the preamble portion of the packet. Control then continues to step
S1030 where the control sequence ends.
[0111] FIG. 11 is a flowchart outlining another exemplary method
for receiving a packet. In particular, control begins in step S1100
and continues to step S1110. In step S1110, a receiver receives a
packet that includes a header portion and preamble portion. Next,
in step S1120, one or bit fields in the header portion are decoded
to determine a value of a seed used for initializing an LFSR
generator that was used to generate the preamble portion of the
packet. Control then continues to step S1130 where the control
sequence ends.
[0112] As used herein the terms network and domain have the same
meaning and are used interchangeably. Also, the terms receiver,
receiving node and receiving transceiver have the same meaning and
are used interchangeably. Similarly, the terms transmitter,
transmitting node and transmitting transceiver have the same
meaning and are used interchangeably. The terms transceiver and
modem also have the same meaning and are used interchangeably.
While the term home network has been used in this description, the
description is not limited to home networks but in fact applies
also to any network, such as enterprise networks, business
networks, or any network with a plurality of connected nodes. The
terms transceiver, node and modem have the same meaning and are
used interchangeably in the description. The term frame and packet
have the same meaning and are used interchangeably in the
description. The term header and PHY-frame header have the same
meaning and are used interchangeably in the description.
[0113] The terms network and home network have the same meaning and
are used interchangeably in the description. While the term Home
network has been used in this description, the description is not
limited to home networks but in fact applies also to any network,
such as enterprise networks, business networks, or any network with
a plurality of connected nodes.
[0114] While the above-described methods and systems can be
described with respect to a port (or endpoint) in a network, they
can also be implemented in a dedicated module such as a test or
network optimization module. This dedicated module could be plugged
into the network and act as a Domain Master or with the cooperation
of the Domain Master could initiate the various measurement
techniques, gather the measurements from the port(s) in the
network, analyze the measurements and use the measured information
to detect and diagnose problems in the network and/or to optimize
or improve the performance of a network.
[0115] The above-described methods and systems and can be
implemented in a software module, a software and/or hardware
testing module, a telecommunications test device, a DSL modem, an
ADSL modem, an xDSL modem, a VDSL modem, a linecard, a G.hn
transceiver, a MOCA transceiver, a Homeplug transceiver, a
powerline modem, a wired or wireless modem, test equipment, a
multicarrier transceiver, a wired and/or wireless wide/local area
network system, a satellite communication system, network-based
communication systems, such as an IP, Ethernet or ATM system, a
modem equipped with diagnostic capabilities, or the like, or on a
separate programmed general purpose computer having a
communications device or in conjunction with any of the following
communications protocols: CDSL, ADSL2, ADSL2+, VDSL1, VDSL2, HDSL,
DSL Lite, IDSL, RADSL, SDSL, UDSL, MOCA, G.hn, Homeplug.RTM. or the
like.
[0116] Additionally, the systems, methods and protocols of this
invention can be implemented on a special purpose computer, a
programmed microprocessor or microcontroller and peripheral
integrated circuit element(s), an ASIC or other integrated circuit,
a digital signal processor, a flashable device, a hard-wired
electronic or logic circuit such as discrete element circuit, a
programmable logic device such as PLD, PLA, FPGA, PAL, a modem, a
transmitter/receiver, any comparable means, or the like. In
general, any device (or one or more equivalent means) capable of
implementing a state machine that is in turn capable of
implementing the methodology illustrated herein can be used to
implement the various communication/measurement methods, protocols
and techniques according to this invention.
[0117] Furthermore, the disclosed methods may be readily
implemented in software stored on a non-transitory
computer-readable storage media using object or object-oriented
software development environments that provide portable source code
that can be used on a variety of computer or workstation platforms.
Alternatively, the disclosed system may be implemented partially or
fully in hardware using standard logic circuits or VLSI design.
Whether software or hardware is used to implement the systems in
accordance with this invention is dependent on the speed and/or
efficiency requirements of the system, the particular function, and
the particular software or hardware systems or microprocessor or
microcomputer systems being utilized. The communication systems,
methods and protocols illustrated herein can be readily implemented
in hardware and/or software using any known or later developed
systems or structures, devices and/or software by those of ordinary
skill in the applicable art from the functional description
provided herein and with a general basic knowledge of the computer
and telecommunications arts.
[0118] Moreover, the disclosed methods may be readily implemented
in software that can be stored on a computer-readable storage
medium, executed on programmed general-purpose computer with the
cooperation of a controller and memory, a special purpose computer,
a microprocessor, or the like. The systems and methods of this
invention can be implemented as a program embedded on personal
computer such as an applet, JAVA.RTM. or CGI script, as a resource
residing on a server or computer workstation, as a routine embedded
in a dedicated communication system or system component, or the
like. The system can also be implemented by physically
incorporating the system and/or method into a software and/or
hardware system, such as the hardware and software systems of a
test/modem device.
[0119] While the invention is described in terms of exemplary
embodiments, it should be appreciated that individual aspects of
the invention could be separately claimed and one or more of the
features of the various embodiments can be combined.
[0120] While the exemplary embodiments illustrated herein discuss
the various components collocated, it is to be appreciated that the
various components of the system can be located a distant portions
of a distributed network, such as a telecommunications network
and/or the Internet or within a dedicated communications network.
Thus, it should be appreciated that the components of the system
can be combined into one or more devices or collocated on a
particular node of a distributed network, such as a
telecommunications network. As will be appreciated from the
following description, and for reasons of computational efficiency,
the components of the communications network can be arranged at any
location within the distributed network without affecting the
operation of the system.
[0121] It is therefore apparent that there has been provided, in
accordance with the present invention, systems and methods for
combining data and probe frames. While this invention has been
described in conjunction with a number of embodiments, it is
evident that many alternatives, modifications and variations would
be or are apparent to those of ordinary skill in the applicable
arts. Accordingly, it is intended to embrace all such alternatives,
modifications, equivalents and variations that are within the
spirit and scope of this invention.
Appendix A
Text from G.9960 (G.hn)
7.1.4.5.2.1.1 Modulation of the Preamble Symbol
[0122] For the non-masked sub-carriers of the preamble, a bit
sequence of all 1's shall be mapped using the 1-bit constellation
as specified in .sctn.7.1.4.3.1.2. Other bit sequences are for
further study. The LFSR generator shall be initialized at the
beginning of each one of the used preamble sections to a seed that
is preamble section and medium dependent as defined in .sctn.7.2.
The output of the mapper shall be subsequently rotated using the
two bits that are the LSBs of the LFSR, s1, and s2, as defined in
Table 7-26 (constellation scrambler) resulting in constellation
point Z. The LFSR shall be advanced by 2 bits for each preamble's
sub-carrier (either masked or not).
7.1.4.3.3 Constellation Scrambler
[0123] The phase of constellation points generated by the
Constellation Mapper shall be shifted in accordance with the
pseudo-random sequence generated by a Linear Feedback Shift
Register (LFSR) generator, as shown in FIG. 12.
FIG. 12/G.9960--Constellation Scrambler
[0124] The LFSR generator shall implement the polynomial
g(x)=x.sup.13+x.sup.12+x.sup.11+x.sup.8+1 and shall be advanced by
2 bits for each sub-carrier. The two LSB's of the register shall be
taken to determine the phase shift as shown in Table 7-26. The
shift of the LFSR for subcarrier index k will be 2k.
TABLE-US-00001 TABLE 7-26 G.9960 - Constellation phase shift versus
LSFR output LFSR OUTPUT S2 S1 PHASE SHIFT (rad) 0 0 0 0 1 .pi./2 1
0 .pi. 1 1 3.pi./2
Appendx B
Proposed Method for G.Hn Standard
ITU--Telecommunication Standardization Sector Temporary Document
09BM-038
Study Group 15 Original: English
Baltimore, Md.--22-26 Jun. 2009
Question: 4/15
SOURCE.sup.1: CopperGate Communications
[0125] TITLE: G.hn: Supporting multiple reference sequences to
modulate the preamble
ABSTRACT
[0126] This paper proposes to allow different reference sequences
to modulate the preamble subcarriers. The different sequences may
be defined by a properly chosen set of seeds that initialize the
already specified LFSR generator. This LFSR generator provides the
pseudo-random di-bit sequence that modulates the non-masked
preamble sub-carriers. Allowing the use of different reference
sequences among different networks can serve as another mechanism
for mitigating disturbances from neighbouring networks in PLC
environments.
1. INTRODUCTION
[0127] The current G.hn draft specifies the Constellation Scrambler
as the LFSR generator that pseudo-randomly modulates the non-masked
preamble subcarriers. It is further specified that this LFSR
generator shall be initialized at the beginning of each one of the
used preamble sections to a seed that is preamble section and
medium dependent. We suggest to amend this definition and allow the
use of a seed drawn from a TBD set of seeds. This extension will
give rise to mechanisms that mitigate the problem of neighbouring
G.hn networks.
2. MULTIPLE SEED AND NEIGHBOURING NETWORKS
[0128] Performance degradation due to cross-talk from neighbouring
networks is a key concern in PLC. As the penetration rate for PLC
technology increases, the chance for having multiple apartments
with PLC installations in the same building also increases.
Considering interference from neighbouring networks, we would like
to distinguish between two basic scenarios: high cross-talk and low
cross-talk scenario.
[0129] High Cross-Talk Scenario
[0130] Under this scenario, collision between transmissions from
two networks would end up with an erroneous reception. In this
case, the only feasible solution is to avoid collisions. Current
approaches for mitigating the neighbouring networks interferences
were relating to this scenario. An effort was made to coordinate
the networks and the goal was to share the overall network capacity
among the various networks (apartments). For the symmetric case
where the various networks experience similar physical conditions,
the outcome would be a rate degradation by the factor of "N", where
N is the number of active networks.
[0131] Low Cross-Talk Scenario
[0132] The cross-talk level from neighbouring networks is in many
cases relatively low. As the SNR in PLC is anyway quite low, and
the bandwidth in G.hn is very wide, it is beneficial in many cases
to relate to the cross-talk from the neighbouring network as
another noise source. In this case, we will not try to coordinate
the various networks in the building to avoid collisions. Instead,
we would like to ignore the transmissions from alien networks. With
this approach, transmission from one network may step over
transmission from another network.
[0133] A clear prerequisite for the above approach is to reduce the
probability of false detection of key signals like: [0134] G.hn
preamble signal [0135] PRS, in use signals
[0136] We will now look into a simple example focusing around the
preamble detection. Let's assume that all the networks are using
the same preamble and that the cross-talk level from neighbouring
networks is low. In this case we would like to ignore as much as
possible the transmission from other networks. FIG. 13 depicts this
scenario. In this figure, network #1 is our network while network
#2 in the disturbing neighbouring network.
[0137] FIG. 13: Loss Due to "False" Detection of a Neighbouring
Network Preamble
[0138] Rough Evaluation of the Loss Due to a Wrong Preamble
Detection
[0139] Looking at FIG. 13 we can notice that false preamble
detection "blinds" the receiver for a time period comprising of the
following elements: [0140] Preamble length, minus the time period
for preamble detection. The detection time is relatively short so
this period can be roughly approximated to 1 OFDM symbol. [0141]
PHY-frame header--one symbol [0142] Processing of the PHY-frame
header, i.e., FFT, frequency domain processing, decoding and
parsing. This may last 1-2 symbols.
[0143] Summarizing the different elements we end up with a dead
period of 3-4 symbols where the receiver is "blind". The exact
numbers depend on the exact implementation details. The resulting
loss is about 3-4 symbols out of every transmission cycle (on
average). Let's assume for example an average packet length of 10
data symbols (approximately 0.7 msec including preamble, FC and
IFG). In this example, the loss would be in the range of 20-30%. A
more detailed analysis can be made, taking into account the full
transmission cycle including the ACK and PRS signals. The result is
still similar to the above results. It should be noted that this
example assumes a single neighbour!
3. WHAT HAS TO BE DONE IN G.HN
[0144] The current approach in G.hn is that all G.hn devices share
the same parameters--all preambles, PRS, and in-use signals are
identical. As a consequence, one network is likely to detect
transmissions from other networks, even if its cross-talk level is
low and should not cause a significant capacity loss.
[0145] To improve our immunity to cross-talk created by
neighbouring networks we suggest to build a mechanism where each
network will use different signals for its key sections: preamble,
PRS, and in use signals. The ground for implementing this mechanism
is already in place. The preamble signal is already defined based
on an LFSR, initiated with a TBD seed. The extra step we need to
take is to define that various networks may use different seeds.
Key elements in a complete solution: [0146] Dynamic seed selection.
Each domain master shall independently select a seed for its
network. [0147] Additional MAP fields for communicating the
networks' seed to the nodes. Specifically, we suggest to use the
Auxiliary Information Filed in the MAP in order to indicate the
index of the seed chosen. [0148] Seeds bank. Each domain master
shall pick its seed from the predefined seeds bank. The seed bank
shall be defined such that the selected seeds generate
pseudo-random sequences (and derived sequences) which are close to
being orthogonal. [0149] Default seed for all MAP messages. A
single predefined MAP seed will be common for all networks.
[0150] This contribution starts with the first two steps by
suggesting to accept dynamic seeds selection as a means for
mitigating cross-talk from neighbouring networks. We also suggest
the required additions to the MAP structure needed to support this
function. The specific seed values are left for further study.
4. PROPOSAL
<<<Start of Text>>>
7.1.4.5.2.1.1 Modulation of the Preamble Symbol
[0151] The non-masked preamble's sub-carriers shall be modulated
using a default reference BPSK sequence, of all 1's. Other
reference sequences are for further study. The reference sequence
shall be subsequently rotated as specified in .sctn.7.1.4.3.3
(Constellation scrambler). The LFSR generator shall be initialized
at the beginning of each one of the used preamble sections to a
seed as selected by the MAP message from a TBD seed set, that is
preamble section and medium dependent as defined in .sctn.7.2.
[0152] For non-masked preamble's sub-carrier i, Zi shall be
generated by rotating Pi using the two bits that are the LSBs of
the LFSR, s1, and s2, as defined in Table 7-26.
[0153] The LFSR shall be advanced by 2 bits for each preamble's
sub-carrier (either masked or not).
<<<End of Text>>>
<<<Start of Text>>>
TABLE-US-00002 [0154] TABLE 8-45 G.hn -Type of auxiliary
information Type Value Description Auxiliary 00.sub.16 A 1-octet
field indicating no valid data in information the auxiliary
information field indicator Domain name 01.sub.16 A 32-octet field
indicating domain name represented in ASCII characters PSM
02.sub.16 A variable-length field indicating future hibernation
scheduled hibernation periods for a node(s) schedule in low-power
mode and idle mode, as described in .sctn.8.8.3.1.3. Selected seed
03.sub.16 A single octet field indicating the index for preamble of
the seed selected to initialize the modulation LFSR for preamble
generation, as described in .sctn.7.1.4.5.2.1.1 Reserved
04.sub.16-FF.sub.16 Reserved by ITU-T
<<<End of Text>>>
5. REFERENCES
[0155] [1] G.hn 09GS-R12R3 "G.hn: Draft text for G.hn--version
3.3R2", Editor for G.hn, Geneva, Switzerland, 11-15 May 2009.
6. SUMMARY
[0156] It is proposed to agree on the following new items
TABLE-US-00003 5.0.1.2.2.48 Open Should the text for
.sctn.7.1.4.5.2.1.1 09BM-038 "Modulation of the preamble symbol"
shall be revised according to 09BM-038 (Section 4)? 6.6.29 Open
Should the text for 8.8.3.1 09BM-038 "Auxiliary information" shall
be revised according to 09BM-038 (Section 4)? 6.6.30 Open Shall
G.hn define a mechanism for 09BM-038 facilitating each domain
master to select its own seed for the preamble reference
signal?
* * * * *