Source: http://www.google.com/patents/US7860175?ie=ISO-8859-1&dq=6526440
Timestamp: 2015-01-31 06:06:40
Document Index: 500944001

Matched Legal Cases: ['Application No. 2001', 'Application No. 2007', 'Application No. 2000', 'Application No. 2001', 'Application No. 2007', 'Application No. 2007']

Patent US7860175 - Method for seamlessly changing power modes in an ADSL system - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA DMT system and method with the capability to adapt the system bit rate on-line in a seamless manner. The DMT system provides a robust and fast protocol for completing this seamless rate adaptation. The DMT system also provides a framing and encoding method with reduced overhead compared to conventional...http://www.google.com/patents/US7860175?utm_source=gb-gplus-sharePatent US7860175 - Method for seamlessly changing power modes in an ADSL systemAdvanced Patent SearchPublication numberUS7860175 B2Publication typeGrantApplication numberUS 11/771,261Publication dateDec 28, 2010Filing dateJun 29, 2007Priority dateMar 12, 1999Fee statusPaidAlso published asUS8340200, US8718163, US20060188035, US20060274840, US20070019755, US20070133704, US20080037666, US20110064124, US20130094546Publication number11771261, 771261, US 7860175 B2, US 7860175B2, US-B2-7860175, US7860175 B2, US7860175B2InventorsMarcos C. TzannesOriginal AssigneeTzannes Marcos CExport CitationBiBTeX, EndNote, RefManPatent Citations (95), Non-Patent Citations (76), Referenced by (8), Classifications (28), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetMethod for seamlessly changing power modes in an ADSL systemUS 7860175 B2Abstract A DMT system and method with the capability to adapt the system bit rate on-line in a seamless manner. The DMT system provides a robust and fast protocol for completing this seamless rate adaptation. The DMT system also provides a framing and encoding method with reduced overhead compared to conventional DMT systems. The DMT system and method provide seamless rate adaptation with the provision of different power levels. This framing and encoding method enables a system with seamless rate adaptation capability. The system and method of the invention can be implemented in hardware, or alternatively in a combination of hardware and software.
1. A method of changing subchannel transmission parameters in a multicarrier transmitter configured to transmit data-carrying DMT symbols and non-data-carrying DMT symbols, with a non-data-carrying DMT symbol being transmitted after every N data-carrying DMT symbols, the method comprising:
signaling by the transmitter, a change in subchannel transmission parameters with a change in phase of one of the non-data-carrying DMT symbols, wherein the data-carrying DMT symbols are decoupled from a plurality of codewords and a plurality of ADSL frames.
2. The method of claim 1, wherein the change in the phase is 180 degrees.
3. The method of claim 1, wherein the change in subchannel transmission parameters comprises using updated subchannel transmission parameters after a predetermined number of DMT symbols following transmission of the one of the non-data-carrying DMT symbols.
4. The method of claim 1, wherein the one of the non-data-carrying DMT symbols is a sync symbol constructed by modulating all DMT carriers with a predefined sequence of bits.
5. The method of claim 1, wherein the one of the non-data-carrying DMT symbols is an inverted sync symbol.
6. The method of claim 1, wherein the subchannel transmission parameters includes an allocation of bits to a subchannel.
7. A method of changing subchannel reception parameters in a multicarrier receiver configured to receive data-carrying DMT symbols and non-data-carrying DMT symbols, with a non-data-carrying DMT symbol being received after every N data-carrying DMT symbols, the method comprising:
changing by the receiver, subchannel reception parameters based on a change in phase of one of the non-data carrying DMT symbols, wherein the data-carrying DMT symbols are decoupled from a plurality of codewords and a plurality of ADSL frames.
8. The method of claim 7, wherein the change in the phase is 180 degrees.
9. The method of claim 7, wherein the change in subchannel reception parameters comprises using updated subchannel reception parameters after a predetermined number of DMT symbols following reception of the one of the non-data-carrying DMT symbols.
10. The method of claim 7, wherein the one of the non-data-carrying DMT symbols is a sync symbol constructed by modulating all DMT carriers with a predefined sequence of bits.
11. The method of claim 7, wherein the one of the non-data-carrying DMT symbols is an inverted sync symbol.
12. The method of claim 7, wherein the subchannel reception parameters includes an allocation of bits to a subchannel.
13. A multicarrier transmitter configured to transmit data-carrying DMT symbols and non-data-carrying DMT symbols, with a non-data-carrying DMT symbol being transmitted after every N data-carrying DMT symbols, the transmitter comprising:
means for determining or detecting that subchannel transmission parameters are to be changed; and
means for changing the subchannel transmission parameters by signaling a change in the subchannel transmission parameters with a change in phase of one of the non-data carrying DMT symbols, wherein the data-carrying DMT symbols are decoupled from a plurality of codewords and a plurality of ADSL frames.
14. The transmitter of claim 13, wherein the change in the phase is 180 degrees.
15. The transmitter of claim 14, wherein the change in subchannel transmission parameters comprises a utilization of updated subchannel transmission parameters after a predetermined number of DMT symbols following transmission of the one of the non-data carrying DMT symbols.
16. The transmitter of claim 13, wherein the one of the non-data-carrying DMT symbols is a sync symbol constructed by a modulation of all DMT carriers with a predefined sequence of bits.
17. The transmitter of claim 13, wherein the one of the non-data-carrying DMT symbols is an inverted sync symbol.
18. The transmitter of claim 13, wherein the subchannel transmission parameters includes an allocation of bits to a subchannel.
19. A multicarrier receiver configured to receive data-carrying DMT symbols and non-data-carrying DMT symbol, with a non-data-carrying DMT symbol being received after every N data-carrying DMT symbols, the receiver comprising:
means for determining or detecting that subchannel reception parameters are to be changed; and
means for changing the subchannel reception parameters based on a change in phase of one of the non-data-carrying DMT symbols, wherein the data-carrying DMT symbols are decoupled from a plurality of codewords and a plurality of ADSL frames.
20. The receiver of claim 19, wherein the change in the phase is 180 degrees.
21. The receiver of claim 19, wherein the change in subchannel reception parameters comprises a utilization of updated subchannel reception parameters after a predetermined number of DMT symbols following reception of the one of the non-data-carrying DMT symbols.
22. The receiver of claim 19, wherein the one of the non-data-carrying DMT symbols is a sync symbol constructed by a modulation of all DMT carriers with a predefined sequence of bits.
23. The receiver of claim 19, wherein the one of the non-data-carrying DMT symbols is an inverted sync symbol.
24. The receiver of claim 19, wherein the subchannel reception parameters includes an allocation of bits to a subchannel.
information stored in the storage media, that if executed by a processor coupled to a multicarrier transmitter, causes the processor to cause the multicarrier transmitter to signal a change in subchannel transmission parameters with a change in phase of one non-data-carrying DMT symbol of a plurality of non-data-carrying DMT symbols, wherein a plurality of data-carrying DMT symbols are decoupled from a plurality of codewords and a plurality of ADSL frames.
26. The article of manufacture of claim 25, wherein the change in phase is 180 degrees.
27. The article of manufacture of claim 25, wherein the information causes the processor to change the transmission parameters after a predetermined number of DMT symbols following a transmission of the one non-data-carrying DMT symbol.
28. The article of manufacture of claim 25, wherein the one non-data-carrying DMT symbol is a sync symbol constructed by modulating all DMT carriers with a predefined sequence of bits.
29. The article of manufacture of claim 25, wherein the one non-data-carrying DMT symbol is an inverted sync symbol.
30. The article of manufacture of claim 25, wherein at least one of the transmission parameters includes an allocation of bits to subchannels.
31. An article of manufacture, comprising
information stored in the computer-readable storage media that, if executed by a processor coupled to a multicarrier receiver, causes the processor to cause the multicarrier receiver to change reception parameters based on a change in phase of one non-data-carrying DMT symbol of a plurality of non-data-carrying DMT symbols, wherein a plurality of data-carrying DMT symbols are decoupled from a plurality of codewords and a plurality of ADSL frames.
32. The article of manufacture of claim 31, wherein the change in phase is 180 degrees.
33. The article of manufacture of claim 31, wherein the information causes the processor to change the reception parameters after a predetermined number of DMT symbols following a reception of the one non-data-carrying DMT symbol.
34. The article of manufacture of claim 31, wherein the one non-data-carrying DMT symbol is a sync symbol constructed by modulating all DMT carriers with a predefined sequence of bits.
35. The article of manufacture of claim 31, wherein the one non-data-carrying DMT symbol is an inverted sync symbol.
36. The article of manufacture of claim 31, wherein at least one of the reception parameters includes an allocation of bits to subchannels.
37. A multicarrier transceiver comprising: a transmitter configured to change transmission parameters and to transmit data-carrying DMT symbols and non-data carrying DMT symbols,
wherein the transmitter is further configured to transmit a non-data-carrying DMT symbol after every N data-carrying DMT symbols,
wherein a change in subchannel transmission parameters is signaled, by the transmitter, with a change in phase of one of the non-data-carrying DMT symbols, and
wherein the data-carrying DMT symbols are decoupled from a plurality of codewords and a plurality of ADSL frames.
38. The transceiver of claim 37, wherein the change in phase is 180 degrees.
39. The transceiver of claim 37, wherein the change in subchannel transmission parameters comprises using updated subchannel transmission parameters after a predetermined number of DMT symbols following a transmission of the one of the non-data-carrying DMT symbols.
40. The transceiver of claim 37, wherein the one of the non-data-carrying DMT symbols is a sync symbol constructed by a modulation of all DMT carriers with a predefined sequence of bits.
41. The transceiver of claim 37, wherein the one of the non-data-carrying DMT symbols is an inverted sync symbol.
42. The transceiver of claim 37, wherein the subchannel transmission parameters includes an allocation of bits to subchannels.
43. A multicarrier transceiver comprising: a receiver configured to change subchannel reception parameters and to receive data-carrying DMT symbols and non-data-carrying DMT symbols,
wherein the receiver is further configured to receive a non-data-carrying DMT symbol after every N data-carrying DMT symbols, and
wherein a change in subchannel reception parameters is determined by the receiver based on a change in phase of one of the non-data-carrying DMT symbols,
44. The transceiver of claim 43, wherein the change in phase is 180 degrees.
45. The transceiver of claim 43, wherein the change in subchannel reception parameters comprises a utilization of updated subchannel reception parameters after a predetermined number of DMT symbols following a reception of the one of the non-data-carrying DMT symbols.
46. The transceiver of claim 43, wherein the one of the non-data-carrying DMT symbols is a sync symbol constructed by a modulation of all DMT carriers with a predefined sequence of bits.
47. The transceiver of claim 43, wherein the one of the non-data-carrying DMT symbols is an inverted sync symbol.
48. The transceiver of claim 43, wherein the subchannel reception parameters includes an allocation of bits to subchannels.
49. The method of claim 1, wherein the subchannel transmission parameters includes a power level of a subchannel.
50. The method of claim 7, wherein the subchannel reception parameters includes a power level of a subchannel.
51. The transmitter of claim 13, wherein the subchannel transmission parameters includes a power level of a subchannel.
52. The receiver of claim 19, wherein the subchannel reception parameters includes a power level of a subchannel.
53. The transceiver of claim 37, wherein the subchannel transmission parameters includes a power level of a subchannel.
54. The transceiver of claim 43, wherein the subchannel reception parameters includes a power level of a subchannel.
55. The article of manufacture of claim 25, wherein the transmitter is configured to transmit the plurality of data-carrying DMT symbols and the plurality of non-data-carrying DMT symbols, and wherein the information causes the processor to cause the transmitter to transmit a non-data carrying DMT symbol after every N data-carrying DMT symbols.
56. The article of manufacture of claim 31, wherein the multicarrier receiver is configured to receive the plurality of data-carrying DMT symbols and the plurality of non-data-carrying DMT symbols.
RELATED APPLICATIONS This application is a continuation of U.S. application Ser. No. 11/675,369 filed Feb. 15, 2007, which is a continuation of U.S. application Ser. No. 11/534,843 filed Sep. 25, 2006, which is a continuation of U.S. application Ser. No. 11/409,336 filed on Apr. 24, 2006, which is a continuation of U.S. application Ser. No. 11/246,162 filed on Oct. 11, 2005, which is a continuation of U.S. application Ser. No. 11/144,645 filed Jun. 6, 2005, which is a continuation application of U.S. Ser. No. 10/962,589 filed Oct. 13, 2004, which his a continuation of U.S. application Ser. No. 10/653,271 filed Sep. 3, 2003, which is a continuation of Ser. No. 10/351,402 filed Jan. 27, 2000, which is a continuation of U.S. application Ser. No. 09/522,870 filed Mar. 10, 2003 and is now patented as U.S. Pat. No. 6,567,473, which claims the benefit of and priority to: U.S. provisional application Ser. No. 60/124,222, filed Mar. 12, 1999, entitled �Seamless Rate Adaptive (SRA) ADSL System�, U.S. provisional application Ser. No. 60/161,115, filed Oct. 22, 1999, entitled �Multicarrier System with Stored Application Profiles�, and U.S. provisional application Ser. No. 60/177,081, filed Jan. 19, 2000, entitled �Seamless Rate Adaptive (SRA) Multicarrier Modulation System and Protocols,� which copending provisional applications are incorporated herein by reference in their entirety.
FIELD OF THE INVENTION This invention relates generally to communication systems and methods using multicarrier modulation. More particularly, the invention relates to communication multicarrier systems and methods using rate adaptive multicarrier modulation.
BACKGROUND OF THE INVENTION Multicarrier modulation (or Discrete Multitone Modulation (DMT)) is a transmission method that is being widely used for communication over difficult media. Multicarrier modulation divides the transmission frequency band into multiple subchannels (carriers), with each carrier individually modulating a bit or a collection of bits. A transmitter modulates an input data stream containing information bits with one or more carriers and transmits the modulated information. A receiver demodulates all the carriers in order to recover the transmitted information bits as an output data stream.
Bits per Subchannel
Total bits Per DMT symbol
The next layer in the ADSL system is the Frame/FEC layer 120, which provides functionality associated with preparing a stream of bits for modulation, as shown in FIG. 1. This layer contains the Interleaving (INT) block 122, the Forward Error Correction (FEC) block 124, the scrambler (SCR) block 126, the Cyclic Redundancy Check (CRC) block 128 and the ADSL Framer block 130. Interleaving and FEC coding provide impulse noise immunity and a coding gain. The FEC 124 in the standard ADSL system is a Reed-Solomon (R-S) code. The scrambler 126 is used to randomize the data bits. The CRC 128 is used to provide error detection at the receiver. The ADSL Framer 130 frames the received bits from the ATM framer 142. The ADSL, framer 130 also inserts and extracts overhead bits from module 132 for modem to modem overhead communication channels (known as EOC and AOC channels in the ADSL standards).
N FEC =S�N FRAME +R; where R is the number of R-S checkbytes in a codeword and (2) S is the same positive integer in Equation (1).
In particular, because of condition #1 every DMT symbol has a fixed number of overhead framing bytes. This is a problem when the data rate is low and the overhead framing bytes consume a large percentage of the possible throughput resulting in a lower payload. For example, if the date rate supported by the line is 6.144 Mbps, this will result in a DMT symbol with about 192 bytes per symbol (192*8*4000=6144000 bps). In this case, one overhead framing byte would consume 1/1 92 or about 0.5% of the available throughout. But if the date rate is 128 kbps or 4 bytes per symbol the overhead framing byte will consume � or 25% of the available throughput. Clearly this is undesirable.
SUMMARY OF THE INVENTION According to the principles of the invention, ADSL DMT systems and methods are provided that change transmission bit rates in a seamless manner during operation. The ADSL DMT systems and methods operate according to protocols that allow the seamless change of transmission bit rates during operation to be initiated by either the transmitter or the receiver. The ADSL DMT systems and methods provide for seamless changes of transmission bit rates during operation that change transmission bit rates between power levels that range from full power to low power.
DETAILED DESCRIPTION The principles of the invention may be employed using transceivers that include a transmitter, such as that described in FIG. 1 above, and a receiver. In general terms, an ADSL system includes both a transmitter and a receiver for each communication in a particular direction. In the discussion that follows, an ADSL DMT transmitter accepts digital input and transmits analog output over a transmission line, which can be a twisted wire pair, for example. The transmission can also occur over a medium that includes other kinds of wires, fiber optic cable, and/or wireless connections. In order to utilize the transmitted signal, a second transceiver at the remote end of the transmission line includes a receiver that converts the received analog signal into a digital data stream for use by devices such as computers or digital televisions, for example. For bidirectional communication using a pair of transceivers, each transceiver includes a transmitter that sends information to the receiver of the other member of the pair, and a receiver that accepts information transmitted by the transmitter of the other member of the pair.
It may be desirable to change the modem data rate after training due to a change in the channel characteristics or because the application running over ADSL has changed. Examples of changing channel characteristics include changes in the noise on the line, changes in the crosstalk from other services in the bundle or on the same line, changes in the levels and presence of Radio Frequency Interference ingress, changes in the line impedance due to temperature changes, changes in the state of equipment on the line (e.g. a phone going from on-hook to off hook, or vice versa), and the like. Examples of changes in applications include power down modes for a PC, a user changing from Internet browsing to two-way video conferencing, a user changing from internet browsing to voice over DSL with or without internet browsing, and the like. It is often desirable or required to change the data rate of the modem. It is highly desirable that this data rate change occurs in a �seamless� manner, i.e., without data bit errors or an interruption in service. However DMT ADSL modems specified in the prior art standards are not capable of performing seamless data rate adaptation.
Condition #4 described previously, does not allow the size of the BAT to change without modifying the R-S coding, interleaving and framing parameters. If the BAT, and NBAT, could be modified during operation, i.e., if more or fewer bits were allocated to carriers in a DMT symbol, the data rate could be changed. Condition #4 requires that when the number of bits NBAT in the BAT changes the size of the R-S codeword (and therefore interleaving parameters) must also be modified. Modifying the interleaving and coding parameters on-line requires re-initializing the interleaver. Re-initialization of the interleaver always results in a �flushing� of the interleave memory. This flushing of memory will result in data errors and the transition will not be seamless.
PRIOR ART EXAMPLE #1 The line capacity is 192 bytes per DMT symbol (6.144 Mbps). The codeword size is 192, which includes 16 checkbytes and 1 overhead framing byte, (assuming ANSI T1.413 framing mode #3). The total framing overhead (i.e., checkbytes+overhead framing bytes) per DMT symbol is 16+1=17, and therefore the framing overhead is 17/192=8.8% of the available throughput. In this case the framing overhead is reasonable.
PRIOR ART EXAMPLE #2 The line capacity is 4 bytes (128 kbps). The codeword is constructed from 16 DMT symbols and is 16*4=64 bytes. There are 16 R-S checkbytes (1 checkbyte per DMT symbol) and there is 1 overhead framing byte (assuming ANSI T1.413 framing mode #3). The total framing overhead (checkbytes+overhead framing bytes) per DMT symbol is 1+1=2 bytes, and therefore the framing overhead is 2/4=50% of the available throughput. This is highly inefficient.
EXAMPLE #1 This is exactly the same as the standard compliant training example (Prior Art Example #1) given above. Codeword sizes, DMT symbol sizes and overhead are the same. Therefore the framing overhead is 17/192=8.8% of the available throughput as well.
EXAMPLE #2 The line capacity is 4 bytes (128 kbps). The codeword is constructed independently of the DMT symbol and therefore could be set to 192 bytes, (as an example). This is also the size of the ADSL frame. We use 16 R-S bytes and 1 overhead framing byte per codeword or ADSL frame. There are 192/4=48 DMT symbols in 1 codeword. The total overhead (checkbytes+overhead framing bytes) per 48 DMT symbols is 1+16=17 bytes or 17/48=0.35 bytes per 1 DMT symbol. The framing overhead is 0.35/4=8.8% of the available throughput.
4. The receiver sends the new BAT and the new data rate to the transmitter using the AOC or EOC channel. This corresponds to �NSRA Request� by the receiver.
5. The transmitter receives the �NSRA Request�.
6. The transmitter uses an inverted synchronization (sync) symbol as a flag to signal the receiver that the new BAT is going to be used. The new BAT is used for transmission on the first frame, or a finite number of frames, following the inverted sync symbol. The inverted sync symbol operates as a rate adaptation �SRA Go� message sent by the transmitter.
7. The receiver detects the inverted sync symbol (�SRA Go�) and the new BAT is used for reception on the first frame, or a finite number of frames, following the inverted sync symbol.
4. The transmitter sends to the receiver the new desired data rate using the EOC or AOC channel. This is an �NSRA Request� message.
5. The receiver receives the NSRA request message. If the channel can support the new data rate then the receiver proceeds to step 6. If the channel can not support the new data rate then the receiver sends an �SRA Deny� message back to the transmitter using the EOC or AOC channel.
6. The receiver sends the new BAT to the transmitter using the AOC or EOC channel based on the new data rate. This corresponds to an �NSRA Grant� request by the receiver.
7. The transmitter receives the �NSRA Grant�.
8. The transmitter uses an inverted sync symbol as a flag to signal the receiver that the new BAT is going to be used. The new table is used for transmission on the first frame, or a finite number of frames, following the inverted sync symbol. The inverted sync signal operates as a rate adaptation �SRA Go� message sent by the transmitter.
9. The receiver detects the inverted sync symbol (�SRA Go�) and the new table is used for reception on the first frame, or a finite number of frames, following the inverted sync symbol.
This protocol of the invention is more robust than conventional rate adaptation techniques because it does not use the EOC or AOC channel to send the �SRA Go� message for synchronizing the transition to the new data rate. In conventional rate adaptation techniques, messages sent over the EOC and AOC channel can easily become corrupted by noise on the line. These overhead channels are multiplexed into the data stream at the framer and therefore are transmitted with quadrature amplitude modulation over a finite number of DMT subchannels. Impulse noise or other noise that occurs on the line can easily cause bit errors in the AOC channel message; the message can be lost. If the �SRA Go� message is corrupted and not received by the receiver, then the receiver does not know if the SRA request was granted or not. The transmitter, on the other hand, assumes the �SRA Go� message was received and switches to the new data rate and transmission parameters. The receiver, which did not receive the grant message, does not know when to switch to the new rate. The modems are unsynchronized and data errors occur.
The protocol of the invention is robust because, unlike conventional rate adaptation techniques, the �SRA Go� message is not sent via an EOC or AOC message that can easily be corrupted. Instead the grant of the rate adaptation request is communicated via an inverted sync symbol. The sync symbol is defined in the ANSI and ITU standards as fixed non-data carrying DMT symbol that is transmitted every 69 symbols. The sync symbol is constructed by modulating all the DMT carriers with a predefined PN sequence using basic QPSK (2 bit QAM) modulation. This signal, which is used throughout the modern initialization process, has special autocorrelation properties that make possible the detection of the sync symbol and the inverted sync symbol even in highly noisy environments. An inverted sync symbol is a sync symbol in which the phase information in the QAM signal is shifted by 180 degrees. Other phase shifts (other than 180 degrees) of the sync symbol can be used as well for the SRA Go message. Using the sync symbol for the �SRA Go� message makes the rate adaptation protocol very robust even in the noisiest environments.
The Fast SRA (FSRA) protocol seamlessly changes the data rate on the line faster than the NSRA protocol. This is important for certain applications that are activated and de-activated instantaneously over time or when sudden channel changes occur. In the FSRA protocol, �stored BATs� are used to speed up the SRA handshake and enable quick changes in data rate. Unlike profiles used in G.992.2, the stored BAT does not contain the R-S coding and interleaving parameters since these parameters are not effected when a rate change occurs using constant percentage overhead framing.
3. The receiver sends a message to the transmitter specifying which stored BAT is to be used for transmission based on the new channel and/or application condition. This corresponds to an �FSRA Request� by the receiver.
4. The transmitter receives the �FSRA Request�.
5. The transmitter uses an inverted sync symbol as a flag to signal the receiver that the requested stored BAT will be used for transmission. The stored BAT is used for transmission on the first frame, or a finite number of frames, following the inverted sync symbol. The inverted sync signal corresponds to a rate adaptation �SRA Go� message sent by the transmitter.
6. The receiver detects the inverted sync symbol (�SRA Go�) and the new BAT is used for reception on the first frame, or a finite number of frames, following the inverted sync symbol.
3. The transmitter sends a message to the receiver specifying which stored BAT is to be used for transmission, based on the new channel and/or application condition. This corresponds to an �FSRA Request� by the transmitter.
4. The receiver receives the �FSRA Request�.
5. The receiver sends back to the transmitter the �FSRA Grant� message to grant the �FSRA request�.
6. The transmitter receives the �FSRA Grant�.
7. The transmitter uses an inverted sync symbol as a flag to signal the receiver that the requested stored BAT will be used for transmission. The specified stored BAT is used for transmission on the first frame, or a finite number of frames, following the inverted sync symbol. The inverted sync signal corresponds to a rate adaptation �SRA Go� message sent by the transmitter.
8. The receiver detects the inverted sync symbol (�SRA Go�) and the new BAT is used for reception on the first frame, or a finite number of frames, following the inverted sync symbol.
The FSRA protocol can be completed very quickly. It requires only the exchange of two messages (FSRA grant and FSRA Request) and an inverted sync symbol. FSRA is faster than NSRA because the BAT is stored and need not be exchanged. As in the NSRA protocol, the FSRA protocol is also very robust in noisy environments since it uses inverted sync symbols for the �SRA Go�.
Full power mode is used during normal operations of the transceiver. Low power transmission modes are often used in transceivers in order to conserve power in cases when data does not need to be transmitted over the line. Many modems have low power modes or �sleep� modes that enable a transceiver to operate at a significantly lower power level when the transmission requirements are reduced. Many modems also have protocols that enable them to enter and exit these low power modes very quickly so that the user is not negatively effected by the modem's transition into the low power mode state. The SRA protocols provided of the invention are used to enter and exit from low power modes in a very fast and seamless manner.
Low Data Rate LPM This is low power mode with a very low data rate (e.g. 32 kbps). Only a few of the subchannels are active. The data connection is maintained. The pilot tone may also be transmitted in order to maintain loop timing.
Zero Data Rate LPM This is a low power mode with an effectively 0 kbps data rate, i.e., no subchannels are modulating data. A data connection is not maintained. The pilot tone may also be transmitted in this case in order to maintain loop timing.
In a second embodiment, the transmitter can transition directly to step 7 of the transmitter initiated FSRA protocol described above, and send the inverted sync symbol to indicate transition into the low power mode. The receiver detects the inverted sync and transitions to the low power mode. In this case, since an FSRA request has not been sent by the transmitter, the receiver recognizes that an inverted sync symbol received without a FSRA request transmitted indicates that the transmitter is switching to low power mode. The low power mode BAT is (predefined by the system) or is identified and stored previously so that both the transmitter and the receiver use the BAT. In an alternative second embodiment, in step 7 the transmitter sends a different signal that is predefined by the transmitter and the receiver to be the signal used for transition into low power mode without an �FSRA request.� For example, the transmitter may send a sync symbol with 45 degree phase rotation, rather than the inverted (180 degree) sync symbol. A sync symbol with a 45 degree phase rotation indicates that the transmitter is transitioning into low power mode using the stored BAT associated with the low power mode on the first frame, or a finite number of frames, following the sync symbol with a 45 degree rotation.
The transmitter-initiated entry into low power mode as defined in the second embodiment has the advantage that it does not require the reverse channel to make the transition. The reverse channel is defined as the communications channel in the opposite direction, i.e., here, the communications channel used to send the FSRA messages from the receiver to the transmitter. This is advantageous because the reverse channel may already be in low power mode with no data connection. If there is no data ready to be sent the transmitter can simply transition to low power mode. This is an important power savings technique since the transmitter consumes a large portion of the power, as it is required to send the signal down the line. Transmitter-initiated transition into low power modes is also useful in �soft modem� (PC host based) implementations. In a soft modem implementation, the host processor is performing the modem transceiver functions and many other PC applications at the same time. If the host processor must perform another task that does not allow it to run the ADSL transmitter, the processor can quickly transition the transmitter to the low power mode by sending the inverted sync symbol, or the sync symbol with 45 degree rotation. After this the host processor resources can be consumed by the other task. The ADSL transmitter sends no signal (0 kbps) onto the line.
According to the SRA protocols, there are two embodiments the receiver can use to exit the low power mode-. In the first embodiment, receiver-initiated exit from low power mode can be accomplished using the receiver initiated NSRA or FSRA protocol if the low power mode still has at least a slow data connection in the reverse direction (Low data rate LPM). This is necessary because the receiver must be capable of sending the SRA request back to the transmitter along with the BAT to be used. If the transmitter has not turned off the sync symbol in low power mode the NSRA or FSRA protocols would be used as described above. If the transmitter sync symbol is turned off while in low power mode, the �SRA Go� is sent by the transmitter by turning the sync symbol back on. The receiver detects the presence of the sync symbol (with or without inversion) as a flag to synchronize the change in data rate.
In a second embodiment, there is no data connection in the reverse direction (Zero Data Rate LPM). The receiver initiates an exit by first completing a �transmitter-initiated exit from low power mode� (described below) in the reverse direction. This enables the data connection in the reverse direction. The receiver uses the receiver initiated NSPA or FSRA protocol to exit from low power mode in it's own direction. As described above, if the transmitter sync symbol is turned off while in low power mode, the �SRA Go� is sent by the transmitter by turning the sync symbol back on. The receiver detects the presence of the sync symbol (with or without inversion) as a flag to synchronize the change in data rate.
According to the SRA protocols, there are two embodiments the transmitter can use to exit from low power mode. In the first embodiment, the transmitter uses the entire transmitter initiated FSRA or NSRA process and requests the transition. This requires that there is a data connection in both directions (Low data rate LPM) so the protocol messages can be exchanged. As in the receiver-initiated exit from low power mode, if the transmitter has not turned off the sync symbol in low power mode the NSRA or FSRA protocols would be used as described above. If the transmitter had turned the sync symbol off while in low power mode, then the �SRA Go� is sent by the transmitter by turning the sync symbol back on. The receiver detects the presence of the sync symbol (with or without inversion) as a flag to synchronize the change in data rate.
In the second embodiment, the transmitter can exit the low power mode by transitioning directly to step 7 of the transmitter initiated FSRA protocol. The transmitter sends the inverted sync symbol to indicate transition out of the low power mode. This requires that a sync symbol be sent during the low power mode. This protocol does not require a low data rate LPM. The receiver detects the inverted sync and exits the low power mode. The receiver is designed to recognize that an inverted sync symbol received without a FSRA request indicates the transmitter is exiting from low power mode. The full power mode BAT is identified and stored previously in the connection so that both the transmitter and the receiver have the BAT. For example, the BAT to be used upon exiting a low power mode can be defined by the system to default to the BAT of the last full power connection. Alternatively, the transmitter can send a different signal that is predefined by the transmitter and the receiver to be the signal used for transition out of low power mode without an �FSRA request�. For example, the transmitter can send a sync symbol with 45 degree phase rotation, rather than the inverted (180 degree) sync symbol. When the receiver detects the sync symbol with a 45 degree phase rotation, the receiver recognizes that the transmitter is transitioning out of low power mode using the stored BAT associated with the full power mode on the first frame, or a finite number of frames, following the sync symbol with a 45 degree rotation. If the transmitter had turned the sync symbol off while in low power mode, then the �SRA Go� is sent by the transmitter by turning the sync symbol back on. The receiver detects the presence of the sync symbol (with or without a phase shift) as a flag to synchronize the change in data rate.
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B.V., LlcMethod for synchronizing seamless rate adaptationUS8045603Aug 18, 2010Oct 25, 2011Daphimo Co. B.V., LlcMethod and a multi-carrier transceiver supporting dynamic switching between active application setsUS8340162 *Oct 18, 2011Dec 25, 2012Daphimo Co. B.V., LlcMethod for synchronizing seamless rate adaptationUS8340200 *Nov 18, 2010Dec 25, 2012Daphimo Co. B.V., LlcMethod for seamlessly changing power modes in an ADSL systemUS8351491Sep 10, 2010Jan 8, 2013Daphimo Co. B.V., LlcMethod and multi-carrier transceiver with stored application profiles for supporting multiple applicationsUS8718163 *Dec 3, 2012May 6, 2014Intellectual Ventures Ii LlcMethod for seamlessly changing power modes in an ADSL systemUS20120093172 *Oct 18, 2011Apr 19, 2012Daphimo Co.B.V., LlcMethod for synchronizing seamless rate adaptationUS20130094546 *Dec 3, 2012Apr 18, 2013Marcos C. TzannesMethod for seamlessly changing power modes in an adsl system* Cited by examinerClassifications U.S. Classification375/260, 375/222International ClassificationH04L27/28Cooperative ClassificationH04L27/02, H04W52/267, H04L1/0002, H04L1/0025, H04L27/2647, H04L27/2626, H04L1/0071, H04L1/0006, H04L27/2602, H04L1/0046, H04L1/0016, H04L1/0009, H04B1/38, H04L1/0057, H04L5/1438European ClassificationH04L1/00A9A, H04W52/26R, H04L1/00A1, H04L1/00A3, H04L27/26M1P, H04L27/26M3, H04L1/00A5, H04L5/14R, H04L1/00B7V, H04L27/26M5Legal EventsDateCodeEventDescriptionMay 28, 2014FPAYFee paymentYear of fee payment: 4Jan 25, 2013ASAssignmentOwner name: INTELLECTUAL VENTURES II LLC, DELAWAREFree format text: MERGER;ASSIGNOR:DAPHIMO CO. 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