Patent Application
20120257520
1. Field of the Invention
The present invention relates generally to network communication and, more particularly, to an apparatus for power management in a network communication system.
2. Description of the Prior Art
As the demand for high speed communication between personal computers grows, new-generation Ethernet protocol and devices have been developed for achieving higher data rate. For the new-generation Ethernet devices that operate at a high data rate, especially portable devices such as laptops, power consumption has been a major concern. Specifically, during a low traffic status wherein no downstream data packet from local medium access control (MAC) transmitter needs to be transmitted, idle patterns, i.e., physical layer (PHY) idle patterns used for synchronization of remote peer devices with local devices and for equalization of channel effects, are still transmitted from local PHY transmitter to the remote peer PHY receiver through a physical channel medium. For transmitting the aforementioned PHY idle patterns, the local PHY transmitter and remote peer PHY receiver need to continue operating and thus consume redundant power. Accordingly, a low power idle (LPI) protocol specified in IEEE 802.3 az. has been proposed so as to address the power consumption issue mentioned above.
With all the advantages in power management, however, the LPI protocol may only be applicable to new-generation Ethernet devices, for example, the MAC devices 11 and 17 and the PHY devices 10 and 16. In order to be compliant with the LPI protocol, MAC devices and PHY devices of older generations, i.e., legacy MAC devices and legacy PHY devices are required to be modified. However, the MAC devices are usually integrated into a system-on-a-chip (SOC). Modifying the MAC devices within the SOC so as to support LPI protocol will cause a great cost since the whole SOC may need to be re-designed and re-spun. On the contrary, the PHY devices are sometimes implemented as stand-alone chips apart from the SOC that contains the MAC devices. If an auto-LPI PHY device, i.e., a PHY device that is capable of initiating and proceeding the LPI protocol when coupling to the legacy MAC device may be provided, such power management can be achieved at low cost by merely replacing existing chip that contains legacy PHY device with an alternative one containing an auto LPI PHY device.
It may therefore be desirable to have an apparatus that is capable of modifying a legacy PHY device to be an auto-LPI PHY device.
Examples of the present invention may provide an apparatus for power management in a network communication system including a legacy first network device. The apparatus comprises a second network device, which serves as a client device to the first network device, to operate in one of a first state, a second state and a third state, wherein the second network device is allowed to receive a first traffic from the first network device in the first state, disabled in the second state and recovered in order to receive a second traffic from the first network device in the third state, a detector to detect if the second traffic is to be transmitted from the first network device and generate a first signal as a request for the transmission of the second traffic, an identifier to identify if a low traffic status occurs in the first traffic and generate a second signal indicating the low traffic status, and a controller to switch the second network device among the first, second and third states, wherein the controller is configured to switch the second network device from the first state to the second state and disable the second network device in response to the second signal, and switch the second network device from the second state to the third state and hold the first network device from transmitting the second transmission traffic in response to the first signal.
Some examples of the present invention may also provide an apparatus for power management in a network communication system including a legacy first network device. The apparatus comprises a second network device to serve as a client device to the first network device, a detector to generate a first signal if an idle status occurs in a first traffic from the first network device, and generate a second signal if a second traffic posterior to the first traffic is to be transmitted from the first network device, an identifier in response to the first signal to generate a third signal if the idle status exceeds a predetermined period of time, and a controller to disable the second network device in response to the third signal and hold the first network device from transmitting the second traffic in response to the second signal.
Additional features and advantages of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The features and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
Reference will now be made in detail to the present examples of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
The apparatus 20, coupled to the first network device 21, may include a second network device 22, a detector 23, an identifier 24 and a controller 25. The second network device 22, for example, an LPI physical layer (PHY) transceiver 22, may receive downstream data packets from the first network device 21, and may be coupled with remote peer devices, that is, the remote LPI PHY transceiver 26 and in turn the remote LPI MAC device 27. The second network device 22 may receive from the first network device 21 at least one media independent interface (MII) data signal and at least one MII controlling signal associated with the at least one MII data signal.
The detector 23 may be configured to monitor the at least one MII data signal or the at least one MII controlling signal, generate a first signal, for example, an idle indicator for the identifier 24 and generate a second signal, for example, a transmission request indicator for the controller 25.
The identifier 24 may be configured to generate a third signal, for example, a low traffic indicator for the controller 25. Furthermore, the controller 25 may be configured to generate a fourth signal, for example, an LPI_tx signal for the second network device 22 and generate a fifth signal, for example, a pause signal for the first network device 21.
In one example according to the present invention, the second network device 22 may operate in one of a first, a second and a third states. Specifically, the second network device 22 may operate in an “ACTIVE” state, a “SLEEP” state and a “WAKE” state. When operating in the “ACTIVE” state, the second network device 22 may receive downstream data packets, i.e., a current burst of packets (or termed as “first traffic”), from the first network device 21. The current burst of packets may be transmitted in the form of the at least one MII data signal. Meanwhile, the detector 23 may monitor the at least one MII data signal or the at least one MII controlling signal and detect if there's an idle status associated with the current burst of packets.
Once an idle status is detected, the detector 23 may issue an idle indicator to the identifier 24 so as to instruct the identifier 24 to identify if there is a low traffic status associated with a downstream data flow that carries the downstream data packets. Furthermore, once a low traffic status associated with the downstream data flow is identified, the identifier 24 may issue a low traffic indicator to the controller 25 so as to instruct the controller 25 to assert the LPI_tx signal to a voltage level of logic high given the positive logic. In another example, the controller 25 may alternatively de-assert the LPI_tx signal to a voltage level of logic low given the negative logic. By asserting the LPI_tx signal, the controller 25 may instruct the second network device 22 to operate in the “SLEEP” state. When operating in the “SLEEP” state, the second network device 22 may enter the LPI mode, wherein the power consumption of the second network device 22 may be reduced.
Moreover, when the second network device 22 operates in the “SLEEP” state, the detector 23 may monitor the at least one MII controlling signal and thereby detect a request from the first network device 21 for transmitting the further incoming data packets, i.e., a next burst of packets (or, termed as “second traffic”). Once the request for transmitting the next burst of packets is detected, the detector 23 may issue a transmission request indicator to the controller 25 so as to instruct the controller 25 to de-assert the LPI_tx signal. By de-asserting the LPI_tx signal, the controller 25 may switch the second network device 22 to operate in the “WAKE” state. Moreover, when operating in the “WAKE” state, a recovery process may be performed for the second network device 22 so that the second network device 22 may be recovered from the LPI mode and ready to receive the next burst of packets from the first network device 21. In one example, the recovery process may include synchronizing the remote peer devices, i.e., the PHY transceiver 26 and the MAC device 27 at a remote site so that the remote peer devices may become ready for receiving the next burst of packets. Simultaneously, the controller 25 may be further instructed to assert a pause signal. By asserting the pause signal, the controller 25 may instruct the first network device 21 to hold from transmitting the next burst of packets for a time period until the second network device 22 is ready for receiving the next burst of packets.
If the second network device 22 is recovered for receiving the next burst of packets, the controller 25 may be instructed to de-assert the pause signal so as to allow the first network device 21 to transmit the next burst of packets. Meanwhile, the controller 25 may switch the second network device 22 back to operate in the “ACTIVE” state where the second network device 22 may receive a subsequent burst of packets from the first network device 21. The detailed operation of the power management scenario for the apparatus 20 will be described in the following paragraph by reference to
Furthermore, when the transmission of the last data unit “DN” of the current burst of packets is completed, “TX_EN” may be de-asserted to a logic-low voltage level, which denotes that the transmission of the current burst of packets is finished and no further downstream data packets in the current burst of packets are to be transmitted through “TXD.”
The detector 23 may monitor the voltage level of “TX_EN” and detects if there is an idle status associated with the current burst of packets. When a de-assertion of “TX_EN” is detected by the detector 23, an idle status associated with the data units “D0”, “D1”, . . . and “DN” of the current packets may be thereby determined. The detector 23 may assert the idle indicator to logic high in response to the detection of an idle status. The idle indicator may retain in the logic high status through the whole idle period.
In one example, the payload of the downstream data packets may have been encoded as encoded bit patterns and transmitted through “TXD”. If no further downstream data packets are to be transmitted, idle patterns instead of the encoded bit patterns of the payload may be transmitted through “TXD”. Consequently, an idle status associated with the current burst of packets may be detected by monitoring the bit patterns transmitted through “TXD”. In that case, in one example, the detector 23 may include a comparator to compare bit patterns transmitted through “TXD” with idle patterns pre-stored in the detector 23. When the transmission of the last data unit “DN” is completed, idle patterns transmitted through “TXD” may be monitored by the detector 23 and compared with those pre-stored in the detector 23. As a result, an idle status may be detected.
Furthermore, when an idle status is detected, the detector 23 may issue the idle indicator to the identifier 24, instructing the identifier 24 to identify whether there is a low traffic status associated with the downstream data flow that carries the burst of packets. Identification of the low traffic status will be discussed in the following paragraphs by reference to
Referring back to
In the “SLEEP” state, the second network device 22 may enter the LPI mode and may then be disabled so that power consumption may be therefore reduced. In one example, the second network device 22 may be formed by digital integrated circuits including sequential logic elements. In that case, power consumption may be largely due to the toggling of clocks for the function of the sequential logic elements. Accordingly, the gated clocks, i.e., the conditionally running clocks to which most sequential logic elements may refer when functioning to receive the downstream data packets in the “ACTIVE” state, may be stopped from toggling so that the power consumption may be minimized. In another example, most of the elements within the analog front end (AFE) of the second network device 22 may be further disabled from operation so that power consumption may be further reduced.
Moreover, when the second network device 22 operates in the “SLEEP” state, the detector 23 may detect whether there is a request for the transmission of a next burst of packets. In one example, when the next burst of packets is to be transmitted from the first network device 21, “TX_EN” may be asserted again. The assertion of “TX_EN” may then be detected by the detector 23, which may subsequently assert a transmission request indicator and issue the transmission request indicator to the controller 25.
In response to the asserted transmission request indicator, the controller 25 may de-assert the LPI_tx signal, instructing the second network device 22 to leave from the LPI mode (i.e., SLEEP state) so as to receive the next burst of packets. However, before the second network device 22 is fully ready to receive the next burst of packets, a recovering process is needed to be performed to the second network device 22. Accordingly, immediately after de-asserting the LPI_tx signal, the controller 25 may instruct the second network device 22 to switch from the “SLEEP” state to a “WAKE” state wherein the recovering process may be performed.
Specifically, in the “WAKE” state, the recovering process may further include waking up the link partners, i.e., the remote peer LPI PHY receiver 26 using the physical layer LPI protocol. After a predefined period, the remote peer LPI PHY receiver 26 may be wakened up to be synchronized with the local transmitter, i.e., the second network device 22, and the second network device 22 may be fully ready to receive the next burst of packets from the first network device 21. To ensure the completion of the processing process, the duration of the “WAKE” state is required to be greater than a threshold, for example, a second threshold T2th. In one example, the second threshold T2th may be set as the aforementioned predefined period that allows the second network device 22 to be fully ready to receive the next burst of packets. (Therefore, the second threshold T2th may be a designer's choice and may depend on how the second network device 22 is implemented and how long a period the synchronization process between the second network device 22 and the remote link partner is needed). Next, when the duration of the “WAKE” state exceeds the second threshold T2th, the controller 25 may switch the second network device 22 to the “ACTIVE” state wherein the second network device 22 may start to receive the next burst of packets from the first network device 21.
Considering the behavior of the first network device 21 during the “WAKE” state, since the second network device is not ready to receive the next burst of packets from the first network device 21, the controller 25 may assert and issue the pause signal to the first network device 21 that may hold or stop the first network device from transmitting the next burst of packers. Specifically, the beginning of the next packet may be a sequence of preambles including a few data units D0N to D032 (a data unit, for example, the first data unit D0N is formed as a 4-bit nibble). The sequence preambles, i.e., the data units D0N to D032 were early designed for synchronization purpose and were not expected to be completely received by the remote peer LPI PHY receiver 26. Therefore, it is acceptable to drop a certain amount of such preambles. Accordingly, in one example, the first (D0N) or the following few data units D1N, D2N, etc. may be simply dropped before the first network device 21 is stopped from transmitting the next burst of packets (not shown in
In operation, the first timer 241 may be enabled by the idle indicator received at the input port “en”. Once the first timer 241 is enabled and starts to count the time, the first configurable value indicating the counted time registered in the register may be accumulated and compared with a first time-out threshold during the whole idle period. In one example, the first time-out threshold may be configured as the first threshold T1th. If the first configurable value reaches the first time-out threshold, that is, the time from an idle status being detected exceeds the first threshold T1th, the first timer 241 may issue a first time-out indicator through the output port “time out”. The first time-out indicator may then serve as a low traffic indicator.
The state machine 251 may receive the low traffic indicator, the transmission request indicator and a “WAKE” state time-out indicator from the identifier 24, the detector 23 and the second timer 252, respectively, and output the LPI signal and the pause signal based on the received low traffic indicator, transmission request indicator and “WAKE” state time-out indicator. Furthermore, the state machine 251 may schedule the transition of the operating states, i.e., the “ACTIVE” state, the “SLEEP” state and the “WAKE” state of the second network device 22. The second timer 252 may be configured to count the time that the second network device 22 stays in the “WAKE” state and output a “WAKE” state time-out indicator to the state machine 251 accordingly.
In one example, the state machine 251 may be a finite-state machine (FSM) having a first, a second and a third states corresponding to the “ACTIVE”, the “SLEEP” and the “WAKE” states of the second network device 22, respectively. Furthermore, the first, the second and the third states of the state machine 251 may be transited in the manner of “first to second”, “second to third” and “third to first”. The aforesaid transitions may be triggered by the low traffic indicator, the transmission request indicator and the “WAKE” state time-out indicator. The transitions will be discussed in detailed in the paragraph below by reference to
Under the third state, in response to a “WAKE” state time-out indicator, the state transition of the state machine 251 may be again triggered and the state machine 251 may then switch from the third state back to the first state. Once returning to the first state, the state machine 251 may immediately de-assert the pause signal. In response to the de-asserted pause signal, the second network device 22 may be switched back from the “WAKE” state to the “ACTIVE” state.
Referring back to
Next, at step 502, during the period that the current burst of packets are under transmission, a detector 23 illustrated in
Next, at step 503, it is determined whether the idle status associated with the current burst of packets is detected. If confirmative, at step 504, an identifier 24 illustrated in
Next, at step 505, it is determined whether the low traffic status associated with the downstream data flow is identified. If yes, at step 506, the second network device 22 may be switched to operate in a second state, for example, a “SLEEP” state illustrated in
Next, at step 507, when operating in the second state, i.e., the “SLEEP” state, the second network device 22 may enter an LPI mode. As described previously, in the LPI mode, the second network device 22 may be disabled. By disabling the second network device 22, power consumption thereof may be reduced.
Next, at step 508, when the second network device 22 operates in the “SLEEP” state, the detector 23 may keep monitoring “TX_EN” so as to detect if there is a request for transmitting a next burst of packets (or, termed as “second traffic”) from the first network device 21. If the next burst of packets is to be transmitted from the first network device 21, “TX_EN” may be asserted to a voltage level of logic high, the request for transmitting the next burst of packets may be thereby detected.
Next, at step 509, it is determined whether the request for transmitting the next burst of packets is detected. If yes, at step 510, the second network device 22 may be switched to operate in a third state, for example, a “WAKE” state illustrated in
Next, at step 511, when the second network device 22 operates in the “WAKE” state, the first network device 21 may be held from transmitting the next burst of packets because the second network device 22 is not ready for receiving the next burst of packets. That is, at steps 506 to 508, the second network device 22 is operating in the LPI mode and disabled from operation. As a result, at step 511, the second network is not recovered for receiving the next burst of packets.
Accordingly, at step 512, a recovering process may be performed for the second network device 22 so that the second network device 22 may be recovered from disablement and ready for receiving the next burst of packets.
Next, at step 513, it is determined whether the second network device 22 is recovered for receiving the next burst of packets. If confirmative, at step 514, the second network device 22 may be switched back to operate in the “ACTIVE” state. Subsequently, at step 515, the second network device 22 may perform the reception of the next burst of packets from the first network device 21. Referring back to step 513, if the second network device 22 is not ready for receiving the next burst of packets, at step 511, the second network device 22 may keep operating in the “WAKE” state.
It will be appreciated by those skilled in the art that changes could be made to the examples described above without departing from the broad inventive concept thereof It is understood, therefore, that this invention is not limited to the particular examples disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.
Further, in describing representative examples of the present invention, the specification may have presented the method and/or process of the present invention as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the specification should not be construed as limitations on the claims. In addition, the claims directed to the method and/or process of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the present invention.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.
