1. A flow control system in a square-grid expanded switch having an array of output buffer modules having a plurality of rows and columns, wherein one output part is associated with a plurality of output buffers each belonging to different rows and same column, the system comprising:
a backpressure controller provided in each of the output buffer modules, for generating a backpressure control signal when an amount of data stored in an output buffer included in a corresponding output buffer module exceeds a predetermined threshold, to avoid an overflow of the output buffer; and
a common backpressure generator provided in each of the output buffer modules, for generating a common backpressure control signal when a backpressure control signal is generated by at least one of backpressure controllers provided in output buffer modules belonging to a corresponding column and outputs the common backpressure control signal to a plurality of input buffers storing data to be forwarded to an output port associated with the output buffer.
2. A flow control system in a square-grid expanded switch comprising:
MN input ports, where M and N are integers;
MN output ports,
MN input modules corresponding to respective ones of the MN input ports, each of the input modules including MN input buffers corresponding to respective ones of the MN output ports;
an MM array of output buffer modules, wherein M rows of the array are associated with respective ones of M input port groups obtained by dividing the MN input ports by N,
M columns of the array are associated with respective ones of M output port groups obtained by dividing the MN output ports by N, and
each of the output buffer modules includes N output buffers, wherein each of the MN output ports is associated with a corresponding output buffer included in each of M output buffer modules on a corresponding column, wherein each of the N output buffers is associated with N corresponding input buffers included in respective ones of N input modules of a corresponding input port group,
the system comprising:
a backpressure controller provided in each of the output buffer modules, wherein the backpressure controller generates a backpressure control signal when an amount of data stored in each output buffer included in a corresponding output buffer module exceeds a predetermined threshold, to avoid an overflow of the output buffer; and
a common backpressure generator provided in each of the output buffer modules, wherein the common backpressure generator generates a common backpressure control signal when a backpressure control signal is generated by at least one of backpressure controllers provided in output buffer modules belonging to a corresponding column and outputs the common backpressure control signal to MN input buffers associated with the output buffer and (M1) corresponding output buffers included in respective ones of (M1) output buffer modules belonging to the corresponding column.
3. The flow control system according to claim 2, wherein the common backpressure generator comprises:
an array of OR gates connected to the backpressure controller, wherein each of the OR gates combines the backpressure control signal generated by the backpressure controller and another backpressure control signal generated by another backpressure controller belonging in the corresponding column to produce the common backpressure control signal and outputs it to the N input buffers associated with the output buffer and a corresponding OR gate of another array of OR gates connected to another backpressure controller belonging in the corresponding column.
4. The flow control system according to claim 2, wherein the common backpressure generator comprises;
an array of maximum value detectors connected to the backpressure controller, wherein each of the maximum value detectors detects a maximum backpressure control signal among backpressure control signals generated by the backpressure controller and other backpressure controllers belonging in the corresponding column to output the maximum backpressure control signal as the common backpressure control signal to the N input buffers associated with the output buffer and a corresponding maximum value detector of another array of maximum value detectors connected to another backpressure controller belonging in the corresponding column.
5. A flow control method for use in a square-grid expanded switch having an array of output buffer modules having a plurality of rows and columns, wherein one output port is associated with a plurality of output buffers each belonging to different rows and same column, the method comprising the steps of:
determining whether an amount of data stored in an output buffer included in a corresponding output buffer module exceeds a predetermined threshold;
when an amount of data stored in the output buffer exceeds the predetermined threshold, generating a backpressure control signal to avoid an overflow of the output buffer;
generating a common backpressure control signal when a backpressure control signal is generated in at least one of output buffer modules belonging to a corresponding column; and
supplying the common backpressure control signal to a plurality of input buffers storing data to be forwarded to an output port associated with the output buffer.
6. In a square-grid expanded switch comprising:
MN input ports, where M and N are integers;
MN output ports;
MN input modules corresponding to respective ones of the MN input ports, each of the input modules including MN input buffers corresponding to respective ones of the MN output ports;
an MM array of output buffer modules, wherein M rows of the array are associated with respective ones of M input port groups obtained by dividing the MN input ports by N,
M columns of the array are associated with respective ones of M output port groups obtained by dividing the MN output ports by N, and
each of the output buffer modules includes N output buffers, wherein each of the MN output ports is associated with a corresponding output buffer included in each of M output buffer modules on a corresponding column, wherein each of the N output buffers is associated with N corresponding input buffers included in respective ones of N input modules of a corresponding input port group, a flow control method comprising the steps of:
a) generating a backpressure control signal when an amount of data stored in each output buffer included in a corresponding output buffer module exceeds a predetermined threshold, to avoid an overflow of the output buffer; and
b) generating a common backpressure control signal when a backpressure control signal is generated in at least one output buffer modules belonging to a corresponding column; and
c) outputting the common backpressure control signal to MN input buffers associated with the output buffer and (M1) corresponding output buffers included in respective ones of (M1) output buffer modules belonging to the corresponding column.
7. The flow control method according to claim 6, wherein the step (c) comprises the step of:
combining the backpressure control signal and another backpressure control signal generated by another output buffer module belonging in the corresponding column to produce the common backpressure control signal.
8. The flow control method according to claim 6, wherein the step (c) comprises the step of:
detecting a maximum backpressure control signal among backpressure control signals generated by at least one output buffer modules belonging in the corresponding column to produce the common backpressure control signal.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for computing dummy signals to reduce interference in a communications system comprising:
specifying a frequency range within the communications system to hold the dummy signals;
setting a clipping function;
incorporating a least squares solution for the dummy signals into the clipping function; and
iterating the clipping function with the incorporated least squares solution until a terminating condition is reached, wherein interference in the communications system is reduced.
2. The method of claim 1, wherein the clipping function is c\u03b1x(x), wherein x represents the dummy signals, and wherein the clipping function constrains x to \xb1\u03b1x.
3. The method of claim 2, wherein the clipping function specifies a maximum value for the dummy signals.
4. The method of claim 2, wherein the clipping function specifies a maximum and a minimum value for the dummy signals.
5. The method of claim 1, wherein the incorporating comprises adding a zero to the clipping function, and wherein the clipping function can then be expressed as: xi+1=c\u03b1x(xi+m(AH Axi\u2212AHb)), where xi and xi+1 represent iterations of the dummy signals, c\u03b1x(x) is the clipping function, m is a scalar constant, A is a expressible as:
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AH is a Hermetian transpose of A, b is expressible as
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ak(fl) is the magnitude of the k-th sidelobe of frequency range l, a0 is the magnitude of the 0-th sidelobe of frequency range l, sn is a signal on frequency range n, and s0 is the 0-th signal on frequency range n.
6. The method of claim 1, wherein the terminating condition is a specified number of iterations.
7. The method of claim 1, wherein the terminating condition is that the signal in a band to be notched is sufficiently small.
8. A method for reducing interference comprising:
determining a first frequency range of interference;
specifying a second frequency range to hold dummy signals;
computing the dummy signals, wherein the computing comprises
setting a clipping function;
incorporating a least squares solution for the dummy signals into the clipping function;
iterating the clipping function with the incorporated least squares solution until a terminating condition is reached;
the method further comprising
inserting the dummy signals and data into a transmission unit; and
transmitting the transmission unit.
9. The method of claim 8, wherein the determining comprises:
receiving interference information; and
parsing the interference information to determine the first frequency range of interference.
10. The method of claim 9, wherein the interference information is provided in the form of a list.
11. The method of claim 8, wherein the second frequency range encompasses the first frequency range and a predetermined amount of bandwidth.
12. The method of claim 11, wherein the predetermined amount of bandwidth is used to carry the dummy signals.
13. The method of claim 12, wherein a portion of the predetermined amount of bandwidth is located at a start and a stop end of the second frequency range, and wherein the dummy signals are placed at both the start and the stop end.
14. The method of claim 8, wherein the second frequency range spans a portion of the transmission unit, and the method further comprising after the inserting, placing data into portions of the transmission unit outside of the second frequency range.
15. The method of claim 8, wherein the transmitting occurs over a wired communications channel.
16. The method of claim 15, wherein the wired communications channel is a digital subscriber line (DSL).
17. The method of claim 8, wherein the transmitting occurs over a wireless communications channel.
18. The method of claim 8, wherein the determining and specifying are performed once, and wherein the computing, inserting, and transmitting are performed for each transmission unit.
19. The method of claim 18, wherein the dummy signals are stored in a memory after the computing, and wherein the dummy signals are read from the memory prior to the inserting.
20. A transmitter comprising:
a data unit coupled to a data source, the data unit containing circuitry to insert data and dummy signals into subchannels as a part of a transmission unit;
a compute unit coupled to the data unit, the compute unit to compute the dummy signals, wherein a least squares optimization is used to iteratively compute the dummy signals, and wherein a constraint is directly imposed on a power of the dummy signals during each iteration using a clipping function;
a digital-to-analog converter (DAC) coupled to the data unit, the DAC to convert the transmission unit into an analog transmission unit; and
a data port coupled to the DAC, the data port to inject the analog transmission unit onto a communications channel.
21. The transmitter of claim 20, wherein a portion of the computations performed by the compute unit can be performed during a training period and saved to a memory for later use.
22. The transmitter of claim 21, wherein there are a plurality of transmission units, and wherein the compute unit computes the dummy signals for each transmission unit.
23. The transmitter of claim 20, wherein the transmitter is used in a digital subscriber line communications system, and the transmitter further comprising an inverse Fourier transform unit coupled to the data unit, the inverse Fourier transform unit to convert the transmission unit into a time domain representation.
24. The transmitter of claim 20, wherein the communications channel is an asymmetric digital subscriber line.
25. The transmitter of claim 20, wherein the transmitter transmits wirelessly, and wherein the data port is an antenna.
26. An electronic device comprising:
a data port for transmitting and receiving data;
a receiver coupled to the data port, the receiver containing circuitry to convert data received from the data port into digital data; and
a transmitter coupled to the data port, the transmitter comprising
a data unit coupled to a data source, the data unit containing circuitry to insert data and dummy signals into subchannels as a part of a transmission unit;
a compute unit coupled to the data unit, the compute unit to compute the dummy signals, wherein a least squares optimization is used to iteratively compute the dummy signals, and wherein a constraint is directly imposed on a power of the dummy signals during each iteration using a clipping function; and
a digital-to-analog converter (DAC) coupled to the data unit, the DAC to convert the transmission unit into an analog transmission unit and to provide the analog transmission unit to the data port to be transmitted.
27. The electronic device of claim 26, wherein the data port is coupled to a communications channel, and wherein the communications channel is a digital subscriber line (DSL).
28. The electronic device of claim 27, wherein the communications channel is an asymmetric digital subscriber line (ADSL).
29. The electronic device of claim 26, wherein the data port is coupled to a communications channel, and wherein the communications channel is a wireless link.