U.S. patent application number 12/437497 was filed with the patent office on 2009-11-12 for low-power idle mode for network transceiver.
This patent application is currently assigned to AQUANTIA CORPORATION. Invention is credited to OZDAL BARKAN, HOSSEIN SEDARAT, WILLIAM WOODRUFF.
Application Number | 20090282277 12/437497 |
Document ID | / |
Family ID | 41267855 |
Filed Date | 2009-11-12 |
United States Patent
Application |
20090282277 |
Kind Code |
A1 |
SEDARAT; HOSSEIN ; et
al. |
November 12, 2009 |
LOW-POWER IDLE MODE FOR NETWORK TRANSCEIVER
Abstract
Low-power idle mode for network transceivers. In one aspect, a
method for reducing power consumption of a transceiver connected to
a communication network includes entering a low-power idle mode,
and in this mode, repeatedly turning off a transmitter of the
transceiver and turning on the transmitter according to a pattern,
where the pattern has been customized based on characteristics of
the receiver. Turning off the transmitter conserves power consumed
by the transceiver.
Inventors: |
SEDARAT; HOSSEIN; (SAN JOSE,
CA) ; BARKAN; OZDAL; (MOUNTAIN VIEW, CA) ;
WOODRUFF; WILLIAM; (PLEASANTON, CA) |
Correspondence
Address: |
SAWYER LAW GROUP PC
2465 E. Bayshore Road, Suite No. 406
PALO ALTO
CA
94303
US
|
Assignee: |
AQUANTIA CORPORATION
MILPITAS
CA
|
Family ID: |
41267855 |
Appl. No.: |
12/437497 |
Filed: |
May 7, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61051293 |
May 7, 2008 |
|
|
|
Current U.S.
Class: |
713/320 ;
370/201 |
Current CPC
Class: |
Y02D 50/20 20180101;
G06F 1/3209 20130101; G06F 1/3228 20130101; G06F 1/325 20130101;
Y02D 30/50 20200801 |
Class at
Publication: |
713/320 ;
370/201 |
International
Class: |
G06F 1/32 20060101
G06F001/32; H04J 3/10 20060101 H04J003/10 |
Claims
1. A method for reducing power consumption of a transceiver
connected to a communication network, the method comprising:
entering a low-power idle mode of the transceiver; and in the
low-power idle mode, repeatedly turning off a transmitter of the
transceiver and turning on the transmitter according to a pattern,
wherein while the transmitter is turned on, a control signal is
transmitted from the transmitter to the network for reception by a
receiver, and while the transmitter is turned off, no control
signal is transmitted to the network from the transmitter to
conserve power consumed by the transceiver, and wherein the pattern
has been customized based on characteristics of the receiver.
2. The method of claim 1 wherein the pattern has been customized
based on a duration and a frequency that the receiver requires for
the transmitted control signal to be received by the receiver in
order to maintain the receiver in a ready state for a later fully
active mode.
3. The method of claim 2 wherein the maintaining the receiver in a
ready state includes updating at least one filter of the
receiver.
4. The method of claim 3 wherein the at least one filter includes a
Far End Crosstalk (FEXT) canceller.
5. The method of claim 2 wherein the maintaining the receiver in a
ready state includes maintaining a timing lock of the receiver
relative to the transmitter.
6. The method of claim 1 wherein the turning off of the transmitter
provides a quiet interval and the turning on of the transmitter
provides a refresh interval, and wherein the pattern includes
providing at least one quiet interval and a plurality of refresh
intervals, at least two of the refresh intervals having different
durations.
7. The method of claim 1 wherein the pattern is provided as a
super-frame including a plurality of frames implementing the
pattern, wherein the frames in the super-frame include one or more
quiet frames in which no control signal is transmitted and one or
more update frames in which the control signal is transmitted to
the receiver.
8. The method of claim 7 wherein the super-frame provides a pattern
of the frames that includes a first amount of the update frames,
which are followed by a plurality of the quiet frames, and which
are followed by a second amount of the update frames, wherein the
first amount is different than the second amount.
9. The method of claim 7 wherein the super-frame includes one or
more idle frames, wherein the transmitter determines whether to
transmit the control signal or not during an idle frame based on at
least one characteristic of a near-end receiver of the
transceiver.
10. The method of claim 9 wherein the transmitter determines
whether to transmit the control signal or not during an idle frame
based on whether near-end filters of a near-end receiver of the
transceiver require updating to maintain a ready state for a later
fully active mode, wherein the near-end receiver is turned off and
turned on in conjunction with the transmitter.
11. The method of claim 1 further comprising transmitting a wakeup
signal while the transmitter is turned on, the wakeup signal
indicating to the receiver that the transceiver is exiting the
low-power idle mode.
12. The method of claim 1 wherein the pattern is customized based
on a negotiation of parameters performed by the transmitter and the
receiver before the low-power idle mode is entered.
13. The method of claim 1 wherein the transmitter and the receiver
communicate according to an Ethernet 10GBase-T standard.
14. The method of claim 1 further comprising deactivating a
preceding block of the transmitter such that the preceding of the
transmitted control signal is not performed in the low-power idle
mode.
15. The method of claim 14 wherein a modulation block in the
transmitter uses PAM-2 modulation during the low-power idle mode,
and wherein the precoding block includes a Tomlinson-Harashima
Precoding (THP) block.
16. The method of claim 1 wherein the transmitter is one of a
plurality of transmitters included in the transceiver, and further
comprising selecting the plurality of transmitters to be turned on
all the time during the low-power idle mode to reduce noise created
from a non-stationary crosstalk provided from the turning off of
the transmitter.
17. A method for reducing power consumption of a transceiver
connected to a communication network, the method comprising:
entering a low-power idle mode of the transceiver; and in the
low-power idle mode, repeatedly turning off a transmitter of the
transceiver and turning on the transmitter according to a pattern,
wherein while the transmitter is turned on, a control signal is
transmitted from the transmitter to the network for reception by a
receiver, and while the transmitter is turned off, no control
signal is transmitted to the network from the transmitter to
conserve power consumed by the transceiver, wherein the pattern is
provided as a super-frame including a plurality of frames
implementing the pattern, the frames in the super-frame including
one or more quiet frames in which no control signal is transmitted,
one or more update frames in which the control signal is
transmitted to the receiver, and one or more idle frames, wherein
the transmitter determines whether to transmit the control signal
or not during an idle frame based on at least one characteristic of
the transceiver.
18. The method of claim 17 wherein the transmitter decides whether
to transmit the control signal or not during an idle frame based on
whether near-end filters of a near-end receiver require updating to
maintain a ready state for a later fully active mode.
19. The method of claim 18 wherein the near-end filters of the
transceiver include at least one echo canceller and at least one
Near-End Crosstalk (NEXT) canceller.
20. A method for reducing power consumption of a transceiver
connected to a communication network, the method comprising:
entering a low-power idle mode of the transceiver; and in the
low-power idle mode, repeatedly turning off a plurality of
transmitters of the transceiver and turning on the plurality of
transmitters according to a pattern, wherein the turning off and
the turning on of the plurality of transmitters is staggered such
that each of the transmitters is turned on and only one of the
transmitters is turned on at any time, wherein while the one
transmitter is turned on, a control signal is transmitted from the
one transmitter to the network for reception by a receiver, and
while a particular transmitter is turned off, no control signal is
transmitted to the network from the particular transmitter to
conserve power consumed by the particular transceiver.
21. The method of claim 20 wherein the pattern is implemented by a
plurality of frames, wherein the frames include one or more quiet
frames in which no control signal is transmitted and one or more
update frames in which the control signal is transmitted for the
receiver, wherein the update frames are staggered such that only
one of the transmitters is active at any time.
22. The method of claim 20 wherein simplex communication is used
between the transceiver and a different transceiver connected to
the network.
23. The method of claim 22 wherein the transmitter is one of a
plurality of transmitters included in the transceiver, and wherein
each transmitter transmits a control signal on a different channel
at a different time, such that simplex communication is used on
each channel.
24. The method of claim 23 wherein the transceiver includes a
plurality of receivers corresponding to the plurality of
transmitters, and wherein while one of the transmitters is
transmitting a control signal on one of the channels, one of the
receivers is receiving a different control signal on a different
one of the channels.
25. The method of claim 24 wherein the plurality of transmitters
are four transmitters, the plurality of receivers are four
receivers, and each of four channels is connected to a different
pair of the transmitters and receivers, and wherein the simplex
communication is ordered among the channels such that a first
channel is used as a transmitting channel while a third channel,
non-adjacent to the master channel, is used as a corresponding
receiving channel.
26. A method for reducing power consumption of a transceiver
connected to a communication network, the method comprising:
entering a low-power idle mode of the transceiver; and in the
low-power idle mode, repeatedly turning off a transmitter of the
transceiver and turning on the transmitter according to a pattern,
wherein while the transmitter is turned on, a control signal is
transmitted from the transmitter to the network for reception by a
receiver, and while the transmitter is turned off, no control
signal is transmitted to the network from the transmitter to
conserve power consumed by the transceiver, and wherein the pattern
is provided as at least one super-frame including a plurality of
frames implementing the pattern, the frames in the super-frame
including one or more quiet frames in which no control signal is
transmitted and one or more update frames in which the control
signal is transmitted for the receiver, and wherein a wakeup signal
is transmitted in one of the update frames to indicate that the
transmitter is to exit low-power idle mode.
27. The method of claim 26 wherein the receiver listens during
predefined frames of the one or more update frames for the wakeup
signal.
28. The method of claim 27 wherein the pattern and the predefined
frames are customized based on a negotiation of parameters
performed by the transmitter and the receiver before the low-power
idle mode is entered.
29. A transceiver including a mode for reducing power consumption,
the transceiver connected to a communication network, the
transceiver comprising: a transmitter operative to transmit data on
the communication network; and a near-end receiver operative to
receive data from the communication network, wherein the
transceiver includes a low-power idle mode in which the transmitter
is repeatedly turned off and turned on according to a pattern,
wherein while the transmitter is turned on, a control signal is
transmitted from the transmitter to the network for reception by a
far-end receiver, and while the transmitter is turned off, no
control signal is transmitted to the network from the transmitter
to conserve power consumed by the transceiver, wherein the pattern
is customized based on characteristics of the far-end receiver.
30. The transceiver of claim 29 wherein the pattern is customized
based on a duration and a frequency that the far-end receiver
requires for the transmitted control signal to be received by the
receiver in order to maintain the receiver in a ready state, the
maintaining the receiver in a ready state including updating at
least one filter of the receiver and maintaining a timing lock of
the receiver relative to the transmitter.
31. The transceiver of claim 29 wherein the turning off of the
transmitter provides a quiet interval and the turning on of the
transmitter provides a refresh interval, and wherein the pattern
includes providing at least one quiet interval and a plurality of
refresh intervals, at least two of the refresh intervals having
different durations.
32. The transceiver of claim 29 wherein the pattern is customized
based on a negotiation of parameters performed by the transmitter
and the receiver before the low-power idle mode is entered.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/051,293, filed May 7, 2008, and entitled,
"Extended Low-Power Idle (xLPI) for 10GBase-T Energy-Efficient
Ethernet," which is incorporated herein by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to electronic
communications, and more particularly to low-power operation of
transceivers used for transmission and reception of data in
networks.
BACKGROUND OF THE INVENTION
[0003] Network communication standards are widely used in computer
networks to communicate information between computers and other
electronic devices. One widely-used standard is Ethernet, including
several different standards for different network bandwidths. One
Ethernet standard is 10GBASE-T, allowing 10 gigabit/second
connections over unshielded or shielded twisted pair cables, over
distances up to 100 meters. There is a desire to have more
energy-efficient Ethernet standards for all flavors of Ethernet
including 10GBASE-T.
[0004] To reduce the power consumption of 10GBASE-T transceivers,
proposals have been suggested for a low-power idle (LPI) mode that
consumes less power. The LPI mode turns off most of the component
blocks of a transceiver during periods of inactivity, and
periodically turns on transceiver blocks for a short period to
maintain particular components of transceivers on the network and
to determine whether LPI mode should be exited and transceiver
power turned on for active operation.
[0005] For example, FIG. 1 shows a graph 2 illustrating a proposed
power scheme for a low-power idle mode in 10GBase-T. The
transceiver blocks consume full power in the nominal mode of 10G
operation during active operation. When the transceiver becomes
inactive due to having no data to transmit at time T1, the power
for the transceiver is turned off to a minimal level and the
transceiver enters low-power idle mode. However, the power is
periodically turned back on during low-power idle mode for two
purposes: 1) to maintain the proper states of near-end and far-end
receivers in the transceiver and connected transceivers, such as
updating filters and maintaining timing lock, so that the
transceivers can return to active operation more quickly, and 2) to
be able to detect reception of a transition bit sent by a far-end
transceiver, the transition bit requesting the local transceiver to
transition back to the nominal full-power mode of 10G operation.
Thus, after a predetermined number of time intervals (i.e.,
frames), power is brought back on at time T2 and kept on for a
predetermined number of frames, and is then returned to its minimal
level at time T3 for a number of frames. The interval of minimal
power level can be considered a quiet interval N during which power
is off, followed by a refresh interval M during which power is
temporarily brought back on (the interval N+M being the refresh
period). This sequence of quiet and refresh intervals is repeated
until a transition bit is detected during a refresh interval, such
as at time T4, at which point the power is maintained at the
fully-on level and the transceiver is transitioned back to full
power mode.
[0006] The average power consumed during the low-power idle mode is
much lower than in the nominal full power mode of 10G operation.
For example, the power savings is approximately proportional to the
duty cycle, which is N/(N+M). To provide a fast transition back to
the nominal full power mode, the desired transition time is small.
The transition time from LPI mode back to the nominal full power
mode is approximately equal to the refresh period, N+M.
[0007] Despite the advantages of the existing low-power idle mode,
there are some tradeoffs which decrease its effectiveness. For
example, the receivers in the powered-down local and far-end
transceivers require filter adaptation to train and maintain filter
states (e.g., for filters such as Near End Crosstalk (NEXT)
cancellers, Far End Crosstalk (FEXT) cancellers, equalizers and
echo cancellers), as well as timing updates to maintain a timing
lock with the Master transceiver. This adaptation and timing is
strongly coupled with the transition time and power savings,
because long and frequent adaptation intervals are desirable to
allow accurate filter adaptation and timing lock, yet short and
infrequent adaptation intervals are desirable to reduce power
consumption. Furthermore, short quiet intervals are desirable to
allow a short transition time, yet long quiet intervals are
desirable to reduce power consumption. These factors create
conflicts in design goals. However, existing inflexible low-power
idle mode implementations do not allow flexibility in accommodating
different receiver requirements, such as different durations and
frequencies required for filter adaptation and timing lock.
Furthermore, existing low-power idle mode implementations may
create non-stationary noise (e.g. crosstalk from too-close cables)
due to the frequent switching on and off of power during the
low-power mode, which degrades the performance of adjacent ports of
a transceiver. In addition, existing low-power idle mode
implementations do not specify additional techniques which can
provide additional power savings for a transceiver in low-power
idle mode.
[0008] Accordingly, what is needed are systems and methods that
provide low-power idle modes that permit greater flexibility in
receiver architecture within desired restrictions of power savings
and transition time, provide greater efficiency in the use of
refresh periods, provide reduced noise, and/or provide additional
power savings.
SUMMARY OF THE INVENTION
[0009] A low-power idle mode for a transceiver in a communication
network is disclosed. In one aspect, a method for reducing power
consumption of a transceiver connected to a communication network
includes entering a low-power idle mode of the transceiver, and, in
the low-power idle mode, repeatedly turning off a transmitter of
the transceiver and turning on the transmitter according to a
pattern, where the pattern has been customized based on
characteristics of a receiver. While the transmitter is turned on,
a control signal is transmitted from the transmitter to the network
for reception by the receiver, and while the transmitter is turned
off, no control signal is transmitted to the network from the
transmitter, to conserve power consumed by the transceiver.
[0010] In another aspect, in a method for reducing power
consumption of a transceiver, a turning off and turning on of
plurality of transmitters in the transceiver is staggered such that
only one of the transmitters is turned on at any time. In another
aspect, in a method for reducing power consumption of a
transceiver, a super-frame is provided including one or more idle
frames, where the transmitter determines whether to transmit a
control signal or not during an idle frame based on at least one
characteristic of the transceiver. In another aspect, in a method
for reducing power consumption of a transceiver, a wakeup signal is
transmitted in one or more update frames to indicate that the
transmitter is to exit low-power idle mode. Other aspects can
provide other methods, systems and computer readable media for
reducing power consumption of a transceiver.
[0011] The inventions disclosed herein provide low-power idle modes
that can allow greater flexibility in receiver architecture within
desired restrictions of power savings and transition time, greater
efficiency in refresh periods, reduced noise, and/or additional
power savings.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 is a graph illustrating an existing technique for
providing a low-power idle mode for a transceiver;
[0013] FIG. 2 is a block diagram illustrating a communication
system suitable for use with the present invention;
[0014] FIG. 3 is a block diagram illustrating a first embodiment of
the present invention for a portion of a transmitter that can be
used in a communication network for implementing a low-power idle
mode of the present invention;
[0015] FIG. 4 is a diagrammatic illustration of an example protocol
signal stream for the low-power idle mode of the present
invention;
[0016] FIG. 5 is a flow diagram illustrating one embodiment of a
method of the present invention for providing low-power idle mode
for a transmitter;
[0017] FIG. 6 is a flow diagram illustrating one embodiment of a
method of the present invention for providing low-power idle mode
for a receiver;
[0018] FIG. 7 is a diagrammatic illustration of another embodiment
of the low-power idle mode of the present invention, in which one
channel at a time is used to transmit signals;
[0019] FIG. 8 is a table illustrating another embodiment of the
low-power idle mode of the present invention for achieving
additional power savings and simplifying the communication system;
and
[0020] FIG. 9 is a diagrammatic illustration of another embodiment
of the low-power idle mode of the present invention for achieving
reduced crosstalk.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0021] The present invention relates generally to electronic
communications, and more particularly to low-power operation of
transceivers used for transmission and reception of data in
networks. The following description is presented to enable one of
ordinary skill in the art to make and use the invention and is
provided in the context of a patent application and its
requirements. Various modifications to the preferred embodiment and
the generic principles and features described herein will be
readily apparent to those skilled in the art. Thus, the present
invention is not intended to be limited to the embodiment shown but
is to be accorded the widest scope consistent with the principles
and features described herein.
[0022] FIG. 2 is a block diagram illustrating a communication
system 10 suitable for use with the present invention. System 10
includes a first transceiver 12 and a second transceiver 14 which
can communicate with each other. Transceiver 12 includes
"transceiver components" including one or more transmitters 16 and
one or more receivers 18. Similarly, transceiver 14 includes
transceiver components including one or more transmitters 20 and
one or more receivers 22. The transmitters 16 (and 20) shown in
FIG. 1 can be considered individual "transmitters," as typically
referenced herein, or can be considered individual transmitter
channels which a transmitter block within the transceiver can
independently transmit signals on. Similarly, receivers 18 (and 22)
can be considered individual "receivers," as typically referenced
herein, or can alternately be considered individual receiver
channels which a receiver block within the transceiver can
independently receive signals on. The transmitters 16 and 20 and
receivers 18 and 22 are connected to one or more components (not
shown) of a computer system, device, processor, or other
"controller" associated with each respective transceiver which want
to communicate data over the communication network. For example,
transmitters 16 receive data and control signals from the
controller connected to transceiver 12 in order to send the data
over the network to other transceivers and controllers, while
receivers 18 receive data from other transceivers and controllers
via the network in order to provide the data to the controller
connected to first transceiver 12.
[0023] The transceiver 12 can communicate with the transceiver 14
over one or more communication channels of a communication link 24.
For example, for the 10GBase-T Ethernet standard, four
communication channels are provided on link 24, each channel
including a twisted pair cable. Thus, in that standard, there are
four transmitters 16 and four corresponding receivers 18 provided
in each of the transceivers 12 and 14, each transmitter associated
with one of the local near-end receivers in the same transceiver,
and each such transmitter/receiver pair dedicated to one channel
used for duplex communication. A transmitter/receiver pair in one
transceiver 12 communicates across a channel of link 24 to a
far-end transmitter/receiver pair in transceiver 14. A transmitter
16 and a receiver 22 that are connected to the same channel/link,
or two transceivers connected by the communication link 24, are
considered "link partners."
[0024] An interface 26 can be provided in transceiver 12 and an
interface 28 can be provided in transceiver 14 to allow data
transmissions between the transceivers to be routed to the
appropriate transceiver blocks. For example, interfaces 26 and 28
can include transformers to provide an open circuit inductance, and
circuitry used for directing signals or data (alternatively, some
or all circuitry can be included in other components, such as
transmitters 16 and receivers 18).
[0025] In one example from the point of view of transceiver 12,
data transmissions from a local transmitter 16 are provided to the
interface 26, which outputs the data on a corresponding channel of
the communication link 24. The data is received by the link
partner, the transceiver 14. The interface 28 of transceiver 14
provides the received data to its receiver 22 connected to that
same channel. Furthermore, due to noise effects such as near-end
crosstalk and echo, the data transmitted by transmitters 16 is also
received by the near-end receivers 18 in the same transceiver.
Filters can be used to filter out this noise so that the receivers
18 receive only data from other transceivers 14.
[0026] The low-power idle mode of the present invention provides a
refresh period, i.e., a duration in which one or more quiet
intervals and refresh intervals are alternated. During a quiet
interval, power consumption of link partner transmitter and
receiver is reduced to a low level, while during a refresh
interval, a transceiver component is turned on for a short time to
transmit control signals, train or maintain an optimal state, or
listen for a transition signal from a link-partner transceiver that
causes the transceiver component to return to the nominal, fully
active mode in which more power is consumed.
[0027] In some embodiments, the transceivers 12 and 14 are
asymmetric, such that data transmitted by a local transmitter has
no dependence or relation with data being received by the
corresponding local receiver. Furthermore, the transmitter and
receiver on either side of a link can be asymmetric so that both
need not be in low power idle mode. In addition, a local
transmitter and a corresponding local receiver for a channel can be
in or out of low-power idle mode independently of each other. In
some embodiments, all local transmitters (transmitter channels) in
one transceiver are all in low power mode, or all in nominal, fully
active mode, at the same time. Similarly, all local receivers (all
receiver channels) can be either in LPI mode or in active mode at
the same time. Each transceiver component can operate in a
low-power idle mode of the present invention in response to
determining that it will not be transmitting or receiving data.
[0028] Several conflicts and tradeoffs in the use of low-power idle
mode exist. Factors include transition time from low-power idle
mode to fully active mode, where a short quiet time and a short
adaptation time are desired to allow a short transition time.
Another factor is maintenance of the receiver in a "ready state,"
which is an optimal state that allows the receiver to resume full
power operation in the minimal time without having to retrain
filters or resynchronize timing. The maintenance of a receiver
therefore includes adaptation of filters to an optimal state and
maintaining a timing lock, where a long refresh time is desired to
allow more accurate filter adaptation and a frequent refresh time
is desired to maintain timing lock. Another factor is power
consumption, where a longer quiet interval and a shorter refresh
interval allow lower power consumption. For example, if the desired
power savings during low-power idle is 90% of full power
consumption, and the desired transition time is on the order of 10
us, then the refresh interval should be short, such as on the order
of 1 us. The present invention allows greater flexibility in
structuring quiet and refresh intervals of low-power idle mode to
accommodate these and other factors in transceiver operation, as
described in greater detail below.
[0029] FIG. 3 is a block diagram illustrating a first embodiment of
the present invention for a portion 50 of a transmitter that can be
used in a communication network for implementing a low-power idle
mode of the present invention. Transmitter portion 50 transmits
signals to one or more link partner receivers that are connected to
the transmitter via the communication network. Portion 50 is a
simplified representation, and other well-known portions of the
transmitter are not shown in FIG. 3, such as a digital to analog
converter (DAC), clock generator, line driver, etc. Transmitter
portion 50 of FIG. 3 is specific to an Ethernet 10GBase-T
embodiment, but different, equivalent components can be used in
other embodiments for different communication standards or
implementations. Transmitter portion 50 can be implemented in
hardware (e.g. one or more processors, memory, logic circuitry,
etc.), in software, or in a combination of hardware and
software.
[0030] In low-power idle mode, the transmitter has no actual data
from a controller to transmit, and so a low-power idle mode control
signal stream is created, e.g., by a transmitter component of the
transceiver. In some embodiments, the control signal stream can be
encoded using spread spectrum modulation. In the example embodiment
shown, the control signal stream is created by a linear feedback
shift register (LFSR) 54 which produces a pseudo-random sequence of
bits. In some embodiments, a training LFSR 54 can be used. The
output of the LFSR 54 is provided to an adder 56, which adds the
bit stream to a control bit d provided on an input 58 to the adder.
For example, the adder 56 can perform single-bit addition with the
received bits to output a single bit output stream. In one example
hardware embodiment, the adder 56 can be implemented with an XOR
gate or operation. In the described embodiment, the control bit d
controls whether or not the transmitter stays in a low power idle
mode for each frame, e.g. for each particular bit value received by
the adder 56 if there is one bit per frame. Thus, according to the
example protocol of the present invention described below, the
transmitter sets the control bit d to 1 if the current frame to be
transmitted is desired to be a Wakeup frame, i.e. whether the
transceiver now needs to go into full power operation, and is 0
otherwise. The values of the control bit d for different types of
frames are described in greater detail below with respect to FIG.
4, and can be implemented using different values as appropriate for
different embodiments.
[0031] The output of the adder 56 is provided to a pulse amplitude
modulation (PAM) block 60. The PAM modulator 60 translates the bits
of the bit stream to signal levels for transmission during the
low-power idle mode. In some embodiments of the present invention,
as shown in FIG. 3, PAM-2 modulation is used during low-power idle
mode. For example, PAM-2 modulation translates the bits to either
of two signal levels, e.g., +1 V and -1 V. PAM-2 modulation
provides power savings advantages and is described in greater
detail below. In other embodiments, any suitable modulation can be
used, including the modulation used for a particular standard, such
as DSQ128 (PAM-16) for Ethernet 10GBase-T communication. The PAM
block 60 provides the modulated data to a mixer 62, which
multiplies the data with a control signal q provided on an input 64
to the mixer. The signal q controls whether or not the transmitter
is in a "quiet mode," i.e. the current frame is a Quiet frame,
during which the transmitter does not transmit any data and
conserves power. In the described example, if the signal q is 0,
then the output of the mixer is zero, which causes the transmitter
to not transmit any data. If the signal q is 1, then it is a
non-quiet frame (e.g., an Update or Wakeup frame). The signal q
thus changes based on how the quiet periods and refresh periods
have been defined for the current communication; the transmitter
determines the value of q based on what type of frame should be the
current frame. The values of the signal q for different types of
frames are described in greater detail below with respect to FIG.
4, and can be implemented using different values as appropriate for
different embodiments.
[0032] Optionally, the signal output of the mixer 62 can be
provided to a precoder 66 which can cancel interference known to
the transmitter. For example, the 10GBase-T standard specifies that
Tomlinson-Harashima Precoding (THP) can be used in transmission. If
the precoder 66 is used, the signal q can also be provided to the
precoder 64 to control the quiet intervals of the low power idle
mode. The output of the precoder 66 is provided to a power back-off
(PBO) block 68 which can be used to reduce output power to achieve
a desired performance of the transmitter in transmitting the data
(reduce interference or nonlinearity, etc.). The same power
back-off level used in the normal, fully active mode (such as is
standardized in 10GBase-T) can also be used during the low-power
idle mode (e.g. during refresh intervals). The power backoff block
68 outputs the resulting signal on a corresponding channel to a
link partner (and the signal is also typically received by the
near-end receiver in the same transceiver). In some embodiments,
the block 68 provides the signal to the interface 26 or 28 of the
transceiver (not shown), which sends the signal to appropriate
transceiver(s).
[0033] FIG. 4 is a diagrammatic illustration of an example pattern
for a protocol signal stream 100 for the low-power idle mode of the
present invention. Each frame of the stream 100 represents a unit
of time. For example, in the 10GBase-T standard, a frame can be a
Low Density Parity Check (LDPC) frame, which is 320 ns. Other frame
types or durations can be used in other embodiments. In the
described embodiment, each frame provides 1 bit of information,
which indicates one of two things to a receiving transceiver: 1)
stay in low-power idle mode, or 2) transition from low-power idle
mode to full operation in fully active mode (e.g., Full 10 G
operation). Other embodiments can provide a different number of
bits per frame or other suitable signalling; however, using 1 bit
per frame in low-power mode and/or using 1 bit to signal a Wakeup
frame can provide additional power savings.
[0034] The protocol of the present invention provides a number of
types of frames that may be used to implement a low-power idle mode
of operation for a transmitter of a transceiver. Different bit
values or signals can be used in other embodiments to indicate the
frames. The types of frames can include:
[0035] Down frame: A predefined number of Down frames are
transmitted by a transmitter to indicate to a second, link partner
receiver the desire of the transmitter to go into low-power idle
mode. The link partner receiver examines the received value(s) of
Down frames in order to recognize whether the transmitter is going
into low-power idle mode. Multiple Down frames can be sent to
ensure correct decoding of the Down frames. The Down frames may
include any amount of information as needed for a particular
embodiment.
[0036] Super-frame: A predefined sequence of frames which is sent
periodically from the transmitter while the transmitter is in
low-power idle mode. The super-frame can include a number of types
of individual frames, including Quiet frames, Update frames, Idle
frames, and Wakeup frames, and can be customized in format based on
the characteristics of far-end and/or near-end receivers or other
components of the transceivers or network. The construct of a
super-frame can be similar or different for each of multiple
transmission channels of the communication link (such as the four
channels used for 10GBase-T). For some embodiments (such as the
simplex communication described below), the number of frames in a
super-frame can be made identical for all the channels.
[0037] Quiet frame: No transmission of signals is performed from
the transmitter during a Quiet frame, i.e. the transmitter is
"turned off" (powered down to a minimal allowed power level) to
conserve power expenditure. (The receiver may or may not also be
turned off during a quiet period, as described below). To provide a
Quiet frame in the example embodiment of FIG. 3, the control bit d
is 0, and the control signal q is 0.
[0038] Update (or Refresh) frame: The transmitter is turned on or
kept on so that this type of frame is transmitted to be received by
the link partner receiver to allow the link partner receiver to be
maintained in a ready state, e.g., update its receiver filters and
maintain a timing lock with the transmitter. Far-end filters, such
as equalizers and FEXT cancellers, need to be adapted based on
periodically received signals from a link partner transceiver,
where the adaptation compensates for drift in the filters due to
temperature changes in the receiver or other changes over time.
These filters may, for example, compare received signals to known
expected signals, and the filters are adapted accordingly. A timing
lock must also be maintained between two link partners to allow a
short transition time between low-power idle mode and fully active
mode of a transceiver component (the receiver needs the timing
lock, and also the far-end transmitter in some embodiments), and
Update frames allow a link partner to continue to synchronize and
lock timing relative to the other link partner. Furthermore, a
local; near-end receiver also receives Update frames from the
corresponding local transmitter in the same transceiver and can use
these Update frames to update/adapt NEXT and Echo cancellers at the
near-end receiver. To provide an Update frame in the example
embodiment of FIG. 3, the control bit d is 0, and the control
signal q is 1, such that the control signal transmitted is 0.
[0039] Idle frame: This frame can be chosen by the first
transceiver to be either a Quiet frame (transmitting no signal), or
an Update frame. The transmitter (or connected controller) can
determine whether to use an Idle frame as a Quiet frame or an
Update frame (the link partner receiver has no control over the use
of an Idle frame and thus cannot assume it is either a Quiet frame
or an Update frame). The transmitter can decide whether to transmit
a control signal or not during an Idle frame based on the known
characteristics of its corresponding near-end receiver of the
transceiver. For example, a particular Idle frame can be useful to
use as an Update frame to allow updates to the near-end receiver,
such as adaptation and updates of Echo and NEXT cancellers at the
local receiver that use the signals sent from the local transmitter
to determine how to cancel echo and crosstalk caused by that
transmitter. Such filters may be more complex than far-end filters
such as FEXT cancellers, and thus may require additional Idle
frames (beyond the number of actual Update frames) to complete
filter updates. Based on the parameters of the super-frame, the
transmitter knows whether additional Update frames will be needed
for the near-end receiver, and sets particular Idle frames to
Update frames as appropriate. Idle frames can also be used as
Update frames to obtain additional time to update far-end
receivers, in some embodiments. If the Idle frame is used as an
Update frame, the transmitter is turned on or kept on and the Idle
frame is transmitted like an Update frame.
[0040] For other Idle frames, the transmitter may know that the
local receiver needs no additional Update frames during these Idle
frames (e.g. the near-end receivers may need no further filter
update time), and these Idle frames are set as Quiet frames to
conserve power, in which the transmitter is turned off or kept off.
In some embodiments, the transmitter can determine on the fly
whether an Idle frame is to be used as Update frame or a Quiet
frame. For example, logic in the local receiver may determine that
an echo canceller requires more Update frames, so the receiver
sends this information to the transmitter which then sets more
appropriate Idle frames to Update frames; or if the logic
identifies that the echo canceller is already at an optimal state,
it can inform the transmitter that additional Update frames are not
needed and that a particular Idle frame can be a Quiet frame. To
provide an Idle frame in the example embodiment of FIG. 3, the
control bit d is 0, and the control signal q is 0 or 1 (0 if Quiet,
1 if Update).
[0041] Wakeup frame: A Wakeup frame includes a Wakeup signal that
is transmitted to indicate to the link partner receiver that the
transmitter is going to return to fully active mode from low-power
idle mode and that the link partner receiver needs to be ready for
this transmission. In one aspect of the present invention, the
Wakeup frame is transmitted by the transmitter using the same
transmitting components of the transmitter as the Update/Idle
frames. Thus, this aspect of the present invention allows the same
signalling mechanism and method to be used both for transmitting
refresh periods as well as wakeup signals. In this embodiment, a
Wakeup frame is transmitted in place of a particular Update frame
or Idle frame. The link partner expects and decodes the Wakeup
frame at predefined frame periods within a super-frame. In the
described embodiment, a Wakeup frame may only replace an Update
frame or an Idle frame and may not replace a Quiet frame. Other
embodiments can use Wakeup frames in other ways. To provide a
Wakeup frame in the example embodiment of FIG. 3, the control bit d
is 1, and the control signal q is 1, such that the signal
transmitted is 1. In other embodiments, any suitable Wakeup signal
can be used in a Wakeup frame.
[0042] Up frame: After the Wakeup frame, a predefined number of Up
buffer frames are transmitted before the first transceiver enters
fully active operation, to indicate to the link partner receiver
that the transmitter is entering fully active mode. In some
embodiments, the Up frames can hold the same values as the Wakeup
frame (e.g. a value of 1 in the example embodiment of FIG. 3).
Multiple Up frames can be sent to ensure correct decoding of the Up
frames.
[0043] In FIG. 4, the types of frames described above are shown in
an example pattern providing a sequence of frames to be transmitted
by the transmitter to a link partner receiver. The transmitter is
initially transmitting data in a fully active mode, such as in Full
10GBase-T operation, with active mode frames 102 to a link partner
receiver over a channel of the communication link. At this time,
the link partner receiver is receiving the data while in its own
fully active mode. It is also assumed that particular parameters of
the protocol, such as predefined amounts and sequences of
particular types of frames in a super-frame, have already been
negotiated or determined as is appropriate for the
transceivers.
[0044] At some point, the transmitter determines that it will go
into the low-power idle mode. The transmitter transmits a
predetermined number of Down frames 104 to indicate to the
link-partner receiver that the transmitter is going into low-power
idle mode. In low-power idle mode, the transmitter transmits the
predetermined super-frame, which allows the transmitter to be
powered down for Quiet frames and requires it to be powered up and
transmitting control signals for Update frames. In this particular
example, the super-frame includes the following pattern of
individual frames: 5 Quiet frames 106, 2 Idle frames 108, 6 Update
frames 110, 3 Idle frames 112, 2 Update frames 114, 3 Idle frames
116, 2 Update frames 118, 4 Idle frames 120, and 9 Quiet frames
122. This pattern of frames causes a pattern of turning off and
turning on the transmitter according to the type of frame being
transmitted.
[0045] During the Quiet frames 106 the transmitter transmits
nothing and is turned off (powered down to a minimal allowed power
level), which allows power conservation at the transceiver. The
Idle frames 108 can be used as Quiet frames or Update frames,
allowing customization for different types of local receivers; if
these frames are used as Update frames, the transmitter is turned
on for each such frame. The transmitter is turned on (or kept on)
to transmit the 6 Update frames 110 to allow the receiver to
maintain its receiver in a ready state, e.g., adapt/update its
filters and maintain the timing lock with the transmitter, and to
allow the near-end receiver to update. For example, FEXT, NEXT, and
echo cancellers can be adapted during the Update frames based on
the signal received from the transmitter(s), to determine how to
cancel echo and crosstalk caused by signal transmissions on the
link 24. The 3 Idle frames 112 allow some flexibility for the
transmitter to send more Update frames if needed after the 6 Update
frames 110 to allow further receiver updates; otherwise, these
frames are Quiet frames in which the transmitter is turned off. The
2 Update frames 114 are provided by the transmitter to allow the
link partner receiver to maintain its timing lock with the
transmitter. The 3 Idle frames 116 following the Update frames 114
allow flexibility for the transmitter to send more Update frames if
needed; otherwise, they are Quiet frames. The following 2 Update
frames 118 are sent by the transmitter to again allow the link
partner receiver to maintain the timing lock, followed by the 4
Idle frames 120 which allow further flexibility to send more Update
frames, if needed. Finally, the 9 Quiet frames 122 allow power
conservation by the first transceiver.
[0046] The super-frame thus indicates the quiet and refresh
intervals of the transmitter during the low-power idle mode. For
example, the super-frame of FIG. 4 shows particular Quiet frames,
during which the transmitter is in a quiet interval and turned off,
and is not transmitting any signals. During the Update and Idle
frames, the transmitter is turned on (or kept on from the previous
frame being Update/idle) and is in a refresh interval during which
the transmitter transmits frames to the link partner receiver and
the near-end receiver for receiver state maintenance. When the
transmitter is in refresh intervals, transmitting Update and Idle
frames, it is consuming power.
[0047] The super-frame is repeated twice more in the example of
FIG. 4. In the third super-frame, the transmitter has determined
that it should return to the fully active mode and leave the
low-power idle mode. Thus, it sends a Wakeup frame 124 to notify
the link partner receiver that it is leaving low-power idle mode.
This Wakeup frame can be positioned at any of one or more
predefined frame locations within a refresh interval of the
super-frame so that the link partner receiver can examine those
predefined locations to detect the Wakeup frame. The link partner
receiver is in a low-power idle mode of its own, and will only be
powered on and listening for Wakeup frames during refresh
intervals. After the Wakeup frame 124, three Up frames are
transmitted to ensure the link partner receiver knows of the
transition. After the Up frames, the transmitter transmits data in
the active mode with active mode frames 128.
[0048] A super-frame of the present invention allows a greater
amount of flexibility compared to previous low-power idle
implementations. For example, in prior proposed protocols, no
flexible super-frame is used; rather, a rigid format must be used,
consisting of a fixed amount of Update (refresh) frames, followed
by a fixed amount of Quiet frames, and repeating this sequence (as
shown in FIG. 1). Thus, in the prior proposal, a large, fixed
amount of refresh frames were always transmitted to ensure that the
filters could be updated, followed by a fixed amount of quiet
frames to conserve power, and this sequence was repeated. This
inflexible approach of using only longer and frequent refresh
intervals in the prior proposals did not allow optimal use of
refresh and quiet intervals for power conservation. This is because
receiver filter adaptation and timing lock typically require
different refresh durations and frequencies. For example, filter
updates may require longer but less frequent refresh intervals,
while maintaining a timing lock may require more frequent but
shorter refresh intervals. These characteristics were not exploited
in the prior proposals, and filter adaptation and timing locks were
forced to always be performed within worst-case refresh intervals,
thus expending more power than was necessary.
[0049] In contrast, the super-frame of the present invention allows
the pattern of quiet intervals (Quiet frames) and refresh intervals
(Update frames) to be customized as desired. The types of frames
described above can be arranged in any desired sequence and number,
e.g., to achieve a more efficient use of power and retain a small
desired transition time, based on the different characteristics of
receivers, such as filter adaptation and timing locks. The Update
and Quiet frames need not be transmitted in a fixed repeating
pattern, but can be arranged to accommodate the different
requirements of different receivers. The pattern can be arranged
based on a duration and a frequency of refresh intervals that
optimizes (or increases efficiency of) the maintenance of one or
more particular receivers in a ready state. Thus, the set of 6
Update frames in the super-frame example of FIG. 4 can provide a
longer refresh interval to allow the filters to be adapted/updated
(and timing lock maintained), but the longer interval occurs less
frequently as allowed by this particular filter adaptation. In
addition, the two later sets of the shorter refresh intervals of 2
Update frames in the example super-frame are more frequent to allow
the timing to be synchronized, but are also short as allowed by the
timing synchronization. This super-frame avoids always sending the
larger amount of Update frames, which consumes more power.
Furthermore, the Update and Quiet frames within a super-frame can
be arranged in any desired pattern of sequence and number in
different embodiments to accommodate a particular requirements of a
link partner receiver (and/or a near-end receiver), such as a
shorter filter adaptation or longer timing lock.
[0050] The use of the Idle frames of the present invention also
allows design flexibility and efficient power conservation. Sending
Update frames or Quiet frames in place of Idle frames, based on
particular receiver characteristics, accommodates a large range of
near-end receiver characteristics.
[0051] Thus, the present invention decouples the receiver's updates
from the transition scheme, by imposing fewer restrictions on the
receiver architecture. This provides better scalability, where the
receiver updates are more independent of and minimally impact the
power savings or the transition time, allowing more freedom for a
designer as to how much power savings and transition time is
provided in a communication system.
[0052] The receivers 18 and 22 of the transceivers 12 and 14 can be
implemented in many different ways. Typically, a receiver (or a
component before the receiver in the transmission stream) will have
filters including echo cancellers, NEXT cancellers, and FEXT
cancellers which cancel or reduce noise and allow the intended
transmitted data to be determined from the received data stream. In
the communication system of the present invention, each receiver
can maintain synchronization with remote transmitters at the bit
level, frame level, and super-frame level. If an embodiment is
using a staggering, single-active channel technique (as described
below with respect to FIGS. 7-8), then the receiver can also
maintains synchronization at the transmit channel level.
[0053] A receiver is typically turned on so it can receive data in
fully active mode. When it receives and recognized Down frames from
the link partner transmitter, the receiver goes into its low-power
idle mode. In low-power mode, the receiver is turned off during
quiet intervals, and turned on periodically during refresh
intervals to receive Update frames. Update frames are used by the
receiver to update its filters and maintain a timing lock with the
link partner transmitter. Idle frames are normally quiet but can
optionally be used as Update frames, as determined by the
transmitter; thus, the receiver cannot assume that any Idle frame
is quiet or refresh.
[0054] The receiver resumes fully active mode when it detects a
Wakeup frame indicating that the transmitter is returning to active
operation and transmitting data. The Wakeup frame instructs the
receiver to exit low-power idle mode and enter fully active mode so
that it can receive transmitted data from the link partner. The
receiver listens for a Wakeup frame within the super-frame from the
link partner transmitter. A Wakeup frames is transmitted within a
refresh interval and can be transmitted within specific,
predetermined frames within a super-frame, which replace Update
frames and/or Idle frames in a super-frame. The receiver decodes
every frame that has been predefined to potentially be a Wakeup
frame within a super-frame, to extract the information and
determine if it is a Wakeup frame based on the extracted
information. For example, one embodiments can define three
particular Update frames to potentially hold a Wakeup signal, while
other embodiments may define less or more (or all) Update or Idle
frames as potential Wakeup frames. In the example embodiment shown
in FIG. 3, a frame will hold a bit of 1 if it is a Wakeup frame and
hold a bit of 0 if it is not a Wakeup frame.
[0055] FIG. 5 is a flow diagram illustrating one embodiment of a
method 150 of the present invention for providing low-power idle
mode for a transmitter. For explanatory purposes, the method
describes a transmitter and a link partner receiver connected over
a communication network. Method 150 (and 170, described below) can
be implemented by one or more processors provided in a transceiver
or connected to a transceiver (such as in a connected computer
system or electronic device), and can be implemented using
hardware, software, or both hardware and software. The methods can
be implemented using a computer program product accessible from a
computer readable medium providing program instructions or code for
use by or implemented by a computer system or processor. A computer
readable medium can be any apparatus that can contain, store,
communicate, propagate, or transport the program for use by or in
connection with the processor or computer system. The medium can be
an electronic, magnetic, optical, electromagnetic, infrared, or
semiconductor system (or apparatus or device) or a propagation
medium. Examples of a computer-readable storage medium include a
semiconductor or solid state memory, magnetic tape, a removable
computer diskette, a random access memory (RAM), a read-only memory
(ROM), a rigid magnetic disk and an optical disk (CD-ROM, DVD,
etc.).
[0056] The method begins at 152, and in step 154, applicable
transceivers on the network determine parameters for their
low-power idle modes. Such parameters can include the frames which
can be Wakeup frames, the number of Up or Down frames, the layout
of the different types of frames in a super-frame in low-power idle
mode, the use of THP or not in low-power idle mode, etc. In some
embodiments, the parameters are predetermined before the
transceivers are connected and cannot be changed. In other
embodiments, the transceivers can auto-negotiate the parameters
when they are connected via the network, and/or at other later
times. For example, two transceivers can communicate their
characteristics to each other and can decide on a number of Down
frames, a number of Up frames, and/or a particular super-frame
structure (including the pattern of Update, Idle, and Quiet frames,
and which frames are Wakeup frames) that accommodates the
particular filters of the transceivers and also efficiently allows
a large number of quiet frames. In some embodiments, other
low-power idle mode parameters can also be negotiated, such as the
use of PAM-2 and/or THP or not in the low-power idle mode, whether
THP is used in a per-frame basis, etc. (described in greater detail
below). In some negotiation embodiments, some of these parameters
can be predefined and fixed. In flexible, customizable super-frame
embodiments as discussed above, the super-frame structure can be
negotiated so that the advantages of flexibility can be fully
realized.
[0057] After the determination of the parameters, the transmitter
is assumed to be running in the fully active mode in this example
method. In step 156, the transmitter determines to go into the
low-power idle mode. This determination can be based on any of a
variety of different causes or events. For example, a controller
(such as a computer system, device, processor, etc. connected to
the transmitter) may determine that it will not need to transmit
data for a long period of time (e.g. over a threshold period of
time). In step 158, the transmitter transmits super-frames
including multiple frames from its transmitter during its low-power
idle mode, the super-frames constructed according to the parameters
determined in step 154. These super-frames can include Update and
Quiet frames, and Idle frames in some embodiments, as described
above with reference to FIG. 4. During the Quiet frames, no control
signals are is actually transmitted, allowing conservation of
power.
[0058] In step 160, the process checks whether the transmitter
should return to the fully active mode. T his change of mode can be
triggered by any of a number of different causes or events. For
example, the connected controller may determine that it needs to
transmit new data to the link partner receiver, and to transmit
such data, the transmitter needs to be in fully active mode. If the
transmitter will not return to fully active mode, then the process
returns to step 158. Otherwise, a return to fully active mode is
initiated at step 162, in which the transmitter transmits a Wakeup
frame and Up frames to the link partner receiver to indicate its
return to active mode. In step 164, the transmitter has returned to
fully active mode and can transmit data, and the process is
complete at 166. The process can initiate step 156 if the
transmitter again determines that it can go into low-power idle
mode to conserve power.
[0059] FIG. 6 is a flow diagram illustrating one embodiment of a
method 170 of the present invention for providing low-power idle
mode for a receiver. The method begins at 172, and in step 174,
applicable transceivers on the network determine parameters for
their low-power idle modes. Such parameters can include the frames
which can be Wakeup frames, the number of Up or Down frames, the
layout of the different types of frames in a super-frame in
low-power idle mode, etc. As in the method of FIG. 5, the
parameters may be predetermined before the transceivers are
connected and cannot be changed, or the transceivers can
auto-negotiate some or all of the parameters when they are
connected via the network and/or at other later times.
[0060] After the determination of the parameters, the receiver is
assumed to be running in the fully active mode in this example
method. In step 176, the receiver determines to go into the
low-power idle mode. This occurs when the receiver receives Down
frames from the far-end transmitter, indicating that the
transmitter is going into low-power idle mode. In step 178, the
receiver operates in low-power idle mode according to the
parameters determined in step 174. This includes powering up during
a refresh interval to receive an Update frame from the link partner
transmitter (or to receive an Update frame from any near-end
transmitter if that near-end transmitter is in low-power idle
mode). The receiver uses the Update frames to update filters (such
as Echo, NEXT, and FEXT cancellers) and to maintain a timing lock
with the link partner transmitter. If the current frame is a Quiet
frame in a quiet interval, no signal has been transmitted, the
receiver can turn off at step 178 and conserve power.
[0061] In step 180 (e.g. for each received frame), the process
checks whether the receiver should return to the fully active mode,
which is determined by whether the receiver has detected a Wakeup
frame from the link partner transmitter. This indicates that the
link partner transmitter is going to transmit data to the receiver
and so the receiver should be in fully active mode to receive the
data. If no Wakeup frame is received, the process returns to step
178 to receive the next frame. If a Wakeup frame has been detected,
then in step 182 the receiver confirms the reception of the
predetermined Up frames, and in step 184 the receiver returns to
fully active mode to begin receiving data from the link partner
transmitter. The process is then complete at 186. The process can
initiate step 176 if the receiver again determines that it can go
into low-power idle mode to conserve power.
[0062] FIG. 7 is a diagrammatic illustration of another embodiment
200 of the low-power idle mode of the present invention, in which
one channel at a time is used to transmit control signals. As shown
in FIG. 1, multiple channels may be available to transmit data by a
transceiver, where each channel has its own pair of transmitter and
receiver at each end of the link. For example, the 10GBase-T
standard provides four channels which can be used. The embodiment
of FIG. 7 allows a collective use of the multiple channels for
transmission to conserve additional power, by activating only one
channel at a time for transmission and keeping the other transmit
channels quiet for power conservation, and then sequencing this
channel use for each of the other transmission channels at
different times. This transmission using only one active channel at
a time is performed when all local transmitters are in low-power
idle mode. In the example of FIG. 7, low-power mode super-frames
are used as described above for the embodiment of FIG. 4. Other
embodiments can used other types or arrangements of refresh and
quiet intervals.
[0063] The embodiment of FIG. 7 provides a refresh period in the
four different channels at different, sequential times based on the
refresh interval during low-power idle mode. For example, as shown
in FIG. 7, when four transmit channels are available, the first
channel A can be used to transmit a refresh interval including a
super-frame of Update and Idle frames (after two Down frames). At
the same time, channels B, C, and D are kept quiet and are not
providing Update or Idle frames, and so their transmitters are
conserving power. After the refresh interval on channel A, at frame
202 Quiet frames have begun on channel A. In addition, the refresh
interval, including Update and Idle frames, begins on channel B at
this time. Similarly, the Update and Idle frames of channel B have
finished by frame 204, and Quiet frames are provided on channel B
and a refresh interval starts on channel C. Likewise, at frame 206
Quiet frames are provided on channel C, and the refresh interval
starts on channel D. After the last Update/Idle frame of the
refresh interval on channel D, Quiet frames start on channel D
starting with frame 208, and the next refresh interval starts on
channel A.
[0064] This technique for activating only one transmitter and
transmit channel at a time (and thus turning off the transmitters
in the transceiver for the other channels) can significantly
increase power savings for the transceiver. For example, about 75%
additional power savings can be obtained. This is due to the fact
that the transmitter for only one channel uses power at a time and
thus only one of the multiple transmitters is using power at a
time, instead of four transmitters and receivers (or other plural
amount). This allows more Quiet frames to be used on each channel,
saving power overall. A long quiet interval is provided on each
channel, which normally would not be possible due to the timing
recovery/lock requiring more frequent refresh intervals. However, a
refresh period on any one of the channels allows the timing lock to
be maintained for all channels (timing recovery is shared among all
channels), and since the refresh periods are staggered, the refresh
periods occur frequently enough to maintain timing lock.
[0065] FIG. 8 is a table 250 illustrating another embodiment of the
low-power idle mode of the present invention for achieving
additional power savings and simplifying the communication system.
In this embodiment, simplex communication (signal transmission in
one direction on a channel at a time) is used to obtain additional
power savings, instead of the standard duplex communication used in
standards such as 10GBase-T.
[0066] The simplex communication is used when both link partner
transceivers of a communication link are in low-power idle mode and
are synchronized in their use of channels. Both link partners can
go into low-power idle mode at approximately the same time, or one
link partner can go into low-power idle mode first, followed by the
other link partner and then channel order is synchronized between
them. Only one of the transmit channels is used at a time and only
one of the receive channels is used at a time in this simplex
communication embodiment (which is not possible in fully active
mode in which all channels are used). Thus, the simplex
communication is preferably used in conjunction with the method of
using staggered refresh intervals as shown in the embodiment of
FIG. 7, which uses one active transmit channel at a time.
[0067] The simplex communication of this embodiment provides a
further ordering of Master and Slave channels (Master and Slave
being designations of the two linked transceivers). This further
ordering guarantees simplex communication and that no overlap
(duplex) communication occurs. In this example, it is assumed that
the staggering of the transmissions on the channels is performed so
that "adjacent" channels A, B, C, and D are active in that order
for each direction, as in FIG. 7. Table 250 includes a channel
ordering for a particular transceiver being a Master that transmits
signals over a channel, and the link-partner transceiver being a
Slave that transmits signals over a different and non-adjacent
channel at the same time. Thus, there is only one transmit channel
and only one receive channel (a different one) active at the same
time. (FIG. 7 shows the transmit channels only). From the
perspective of one transceiver, Channel A is used to transmit a
super-frame from a first transmitter as Master, while channel C is
used to receive a super-frame at the third receiver from the Slave.
Next, channel B is used to transmit a super-frame from the second
transmitter as Master, while channel D is used to receive a
super-frame at the fourth receiver from the Slave. Then channel C
is used for the Master and channel A for the Slave, channel D for
Master and channel B for Slave, and so on. Thus, the simplex
communication is ordered among the channels such that when one of
the channels is used as a master transmit channel, a non-adjacent
channel to the master channel is used as a slave transmit channel.
The far-end transceiver is coordinated with the near-end
transceiver so that channels are staggered synchronously.
[0068] This use of sequential Master and Slave having an unused
channel between them guarantees simplex operation for the channels,
since it prevents overlaps in use from Master and Slave (e.g., if
adjacent channels were used sequentially, such as Master on A and
Slave on B, there would be a chance that an adjacent channel might
have an overlap of use for Master at the same time as Slave (duplex
operation), e.g. on Channel B when the Master was moved to B and
the Slave moved to C). The simplex communication embodiment also
assumes that the same length of super-frame is used by all the link
partners, in order to guarantee the simplex operation of these
embodiments.
[0069] Simplex communication as described above can allow a simpler
receiver to be used in the transceivers that will reduce power
consumption of the components. For example, no Echo or FEXT
cancellers are needed, and only total 1 NEXT canceller and 1 feed
forward equalizer (FFE) may be needed at one time. In a 10GBase-T
embodiment, each channel requires one Feed Forward Equalizer (FFE),
one Echo canceller, three NEXT cancellers (three transmitters to
one receiver), and three FEXT cancellers. Thus, the non-use of the
Echo and FEXT cancellers, and most of the NEXT cancellers and FFEs,
greatly simplifies the receiver components of the transceivers. The
unused cancellers and equalizers can be turned off during this
low-power idle mode embodiments, which reduces power
consumption.
[0070] FIG. 9 is a diagrammatic illustration of another embodiment
300 of the low-power idle mode of the present invention for
achieving reduced crosstalk. This embodiment can be used on its own
for a transceiver, or with one or more of the other embodiments
described herein as appropriate. For example, the operating mode of
FIG. 9 can be used selectively in a communication system when
needed, e.g., when noise from non-stationary crosstalk is expected
to increase above a predetermined threshold amount such that it
becomes a limiting factor for link performance.
[0071] In the embodiment of FIG. 9, the transmitters on all four
channels 302, 304, 306, and 308 are kept on all the time. One way
to implement this constant active status is to define the
super-frame as having all Update frames and no Quiet or Idle
frames, as shown in FIG. 9.
[0072] When not using the embodiment of FIG. 9, low-power idle mode
may create a non-stationary (time-varying) noise environment due to
the constant alternating between quiet and refresh periods in which
control signals are not transmitted and then transmitted (as in the
embodiments described above). This alternating transmission creates
crosstalk on the channels which fluctuates over time, and thus is
non-stationary. For example, a non-stationary noise environment can
cause 0.5 dB of signal-to-noise ratio (SNR) loss from the
non-stationary characteristic.
[0073] The constant transmission of FIG. 9 for this embodiment of
the present invention prevents the fluctuation in crosstalk and
other noise occurring in other low-power idle modes. The
elimination of the alternating quiet and refresh intervals provides
a stationary alien crosstalk environment for neighboring ports on a
transceiver, thus reducing or eliminating the non-stationary
crosstalk typically observed in previous low-power idle modes. The
stationary crosstalk environment provides constant crosstalk which
can be better adapted to and reduced by the receiver than the
non-stationary crosstalk.
[0074] Keeping all transmitters on all the time will consume more
power than if the transmitters are turned off during quiet periods.
However, the receivers need not be kept on all the time like the
transmitters. For example, a receiver can be turned on periodically
according to a refresh period to update itself with received frames
and to look for Wakeup frames, as in the embodiments described
above, and thus conserve power. Furthermore, additional desired
power savings can be achieved in other ways to compensate for the
increased power consumption, such as with one or more of the
techniques described below.
[0075] Other techniques can be used in embodiments of the present
invention to reduce power consumption and/or simplify the
components. These techniques can be used in their own embodiments,
or can be combined with any of the above embodiments or with each
other, as appropriate. Several of the embodiments allow a receiver
to be simplified, resulting in more performance margin allowing
reduction of power consumption of the receiver.
[0076] In some embodiments, PAM2 modulation can be used during low
power idle mode to simplify the receiver significantly. PAM2
distinguishes only two distinct signal levels, which is much less
than the 16 distinct signal levels used by DSQ128, the standard
modulation used in 10GBase-T. PAM2 thus allows more margin to
simplify the receiver components. For example, the feed forward
equalizer (FFE) can be shorter/simpler, no crosstalk cancellers may
need to be used, and a simpler/lower power analog front end (AFE)
can be used. When using PAM2, the transmitter is not as noisy as in
normal operation as when using DSQ128. The AFE (including
components such as, for example, a digital to analog converter
(DAC) and line driver for the transmitter path, and a low pass
filter, gain stage, and analog to digital converter (ADC) for the
receiver path) consumes a relatively large amount of power, since
noise is desired to be reduced; however, reasonable performance can
often still be achieved if the noise floor is raised with a
simplified AFE.
[0077] In some embodiments, THP precoding can be deactivated or
turned off during low-power idle mode (e.g., during low-power idle
mode or only during refresh intervals of the low-power idle mode).
In some embodiments, the use of THP during low-power idle mode can
be negotiated between transceivers when they connect to the
network. The deactivation of THP allows the implementation of the
Echo and NEXT cancellers to be simplified, thus reducing power
consumption. For example, without the THP precoding, the input to
the Echo and NEXT cancellers is known to be a few discrete values
provided from the PAM-2 modulation, which can simplify the Echo and
NEXT cancellers. A disadvantage is that non-linearity in the analog
components of the transceiver may not be detected, and filter
adaptation may behave differently under non-THP operation. During
fully active mode, THP and thus more complex Echo/NEXT cancellers
are used. In one example, two blocks or versions of each Echo and
NEXT canceller can be provided in a receiver: simple and complex
versions. When THP is active, then the more complex cancellers
implemented for a large number of levels can be used, with the
simpler versions turned off. During low-power idle mode, when THP
is turned off, the simpler version of the cancellers can be used,
which consumes less power, and the more complex versions are turned
off.
[0078] In some embodiments, the THP precoding can be turned off for
all frames transmitted during low-power idle mode. In other
embodiments, THP preceding is turned off only for some of these
frames, e.g. at a per-frame basis. For example, the transmitter can
perform or not perform THP precoding for each frame transmitted
during low-power idle mode, based on predefined parameters that
indicate this information for each frame. In some embodiments, the
transceiver can auto-negotiate with other transceivers as to which
frames during low-power idle mode are to have THP preceding, and
which frames are not.
[0079] The combination of PAM2 modulation and elimination of THP
preceding in low-power idle mode can provide even greater power
savings, because the PAM2 modulation only provides two values (+1
and -1) to the Echo and NEXT cancellers, thus simplifying them to a
greater degree and allowing more power conservation.
[0080] Some embodiments of the present inventions use 1 bit per
frame in the low-power idle mode, as described above. This allows a
reduction of power, since many less bits per frame need be sent
than in fully active mode which may use multiple bits per frame,
such as the nominal full power mode of 10 G operation that uses
DSQ128 modulation with 256 bits per LDPC frame.
[0081] Some embodiments can remove the need for a parity check such
as Low Density Parity Check (LDPC) during low-power idle mode
(especially when using PAM-2 instead of a more complex modulation,
since PAM-2 would not use LDPC). LDPC encoding and decoding is used
in the 10GBase-T standard, but the decoding can be turned off in
the receiver in low-power idle mode to simplify the receiver,
encoding can also be turned off in the transmitter, which provides
more margin to reduce power consumption.
[0082] The embodiments of the present invention provide significant
advantages in an extended low-power idle mode for transceivers on a
communication network. Greater power savings can be achieved with
more efficient use of quiet and refresh intervals. Furthermore,
various receiver architectures and implementations are
accommodated, allowing power savings to be more efficiently tuned
to the particular characteristics of different types of receivers,
and allowing more independence of filter adaptation from power
consumption and transition time, permitting design freedom to
determine a desired power savings and transition time. In addition,
the embodiments of the invention allow asymmetry between link
partners. For example, link partners can go into low-power mode
independently, and can choose different sets of parameters for
low-power idle mode. Further embodiments allow additional power
savings through the use of one or more of techniques such as
providing one active channel at a time, providing staggered,
simplex communication, and using processing that allows simplified
components, such as PAM2, no THP, and no LDPC. In some embodiments,
a stationary crosstalk environment can be maintained, thus reducing
or eliminating non-stationary crosstalk that may be present in
low-power idle modes.
[0083] Although the present invention has been described in
accordance with the embodiments shown, one of ordinary skill in the
art will readily recognize that there could be variations to the
embodiments and those variations would be within the spirit and
scope of the present invention. For example, other network
standards can be used with the embodiments shown where similar
requirements are applicable. Accordingly, many modifications may be
made by one of ordinary skill in the art without departing from the
spirit and scope of the appended claims.
* * * * *