are responsive to said selector for switchably coupling said at least a second power supply to the power supply input of the corresponding at least one of the plurality of amplifiers coupled to the at least one selected input signal line and further switchably coupling power supply inputs of remain- 5 ing unselected ones of the plurality of amplifiers to said first power supply.
In an another embodiment of the invention a method for amplifying of input signals on corresponding ones of a plurality of input signal lines is disclosed. The method 1° comprises the acts of:
detecting which among the input signal lines includes input signal amplitudes above a selected threshold;
choosing among the input signal lines with input signal amplitudes above the selected threshold, at least a selected one of the input signal lines for further amplification;
amplifying the at least a selected one of the input signal lines at up to at least a second power level greater than a first power level, and amplifying remaining unselected ones of 2o the input signal lines at up to the first power level.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features and advantages of the present invention will become more apparent to those skilled in the 25 art from the following detailed description in conjunction with the appended drawings in which:
FIG. 1 shows a communication system with a pair of multi-mode multi-channel modem line cards coupled to one
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another by a binder of subscriber lines between a public switched telephone network (PSTN) central office (CO) and a remote site.
FIG. 2 is a detailed hardware block diagram of one of the modem line cards shown in FIG. 1. 35
FIGS. 3-4 are detailed hardware block diagrams of alternate embodiments of the portion of the transmit path shown in the AFE of FIG. 2.
FIG. 5 is a graph showing the statistical distribution of voltages for a typical ADSL signal. 40
FIG. 6 is a graph which shows the statistical probability for the various voltage levels shown in FIG. 5.
FIG. 7 is a process flow diagram of the processes associated with statistical multiplexing of line driver power in a ^ multi-channel environment in accordance with an embodiment of the invention.
DETAILED DESCRIPTION OF THE
EMBODIMENTS
50
An apparatus and method for reducing power required for a multi-channel X-DSL line driver is disclosed. Statistical multiplexing of limited power supply is utilized to satisfy peak power demands for a plurality of X-DSL line drivers using either a switched power supply or switched amplifi- 55 cation across the line drivers. A method for scaling the power resources is disclosed as well as a method for dealing with contention between channels for limited power supplies. The invention may be used with multi-channel X-DSL line drivers interfacing with any of a number of multi- go channel supply architectures. The apparatus may be applied with equal advantage to communication protocols other than X-DSL. The apparatus may be applied with equal advantage in wired and wireless media.
FIG. 1 shows a communication system with a pair of 65 multi-mode multi-channel modem line cards coupled to one another by a binder of subscriber lines between a public
4
switched telephone network (PSTN) central office (CO) and a remote site. The system includes a CO 100 and a remote line card 156 positioned at a remote terminal 150. The CO and remote line card are coupled to one another via a subscriber line binder 170 which includes individual subscriber lines 172,174, 176.
Each of the subscriber line connections terminates on the CO end, in the frame room 102 of the CO. From this room connections are made for each subscriber line via splitters and hybrids to both a DSLAM 104 and to the voice band racks 106. The splitter shunts voice band communications to dedicated line cards, e.g. line card 112 or to a voice band modem pool (not shown). The splitter shunts higher frequency X-DSL communications on the subscriber line to a selected line card, e.g. line card 116, within DSLAM 104. The line cards of the current invention are universal, meaning they can handle any current or evolving standard of X-DSL and may be upgraded on the fly to handle new standards.
Voice band call set up is controlled by a Telco switch matrix 114 such as SS7. This makes point-to-point connections to other subscribers for voice band communications across the public switched telephone network 132. The X-DSL communications may be processed by a universal line card such as line card 116. That line card includes a plurality of AFE's 118-120 each capable of supporting a plurality of subscriber lines. The AFEs are coupled via a packet based bus 122 to the DSP 124. For downstream communications from the CO to the remote site, the DSP modulates the data for each communication channel, the AFE transforms the digital symbol packets assembled by the DSP and converts them to an analog signal which is output on the subscriber line associated with the respective channel. For upstream communications from the remote site to the CO the AFE each received channel is converted to a digitized data sample which is sent to the DSP for demodulation. The DSP is capable of multi-protocol support for all subscriber lines to which the AFE's are coupled. Communications between AFE's and DSP(s) may be packet based, in which embodiment of the invention a distributed architecture such as will be set forth in the following FIG. 2 may be implemented. The line card 116 is coupled to a back-plane bus 128 which may be capable of off-loading and transporting low latency X-DSL traffic between other DSPs for load balancing. The back-plane bus of the DSLAM also couples each line card to the Internet 130 via server 108. Each of the DSLAM line cards operates under the control of a DSLAM controller 110 which handles global provisioning, e.g. allocation of subscriber lines to AFE and DSP resources. The various components on the line card form a plurality of logical moderns each handling upstream and downstream communications across corresponding subscriber lines. In an alternate embodiment of the invention discrete modems would each couple to an associated one of the subscriber lines rather than the logical modem shown. When an X-DSL communication is established on a subscriber line, a specific channel identifier is allocated to that communication. That identifier is used in the above mentioned packet based embodiment to track each packet as it moves in an upstream or downstream direction between the AFE and DSP.
At the remote site a similar line card architecture is shown for line card 156 which forms a plurality of logical modems connected to corresponding ones of subscriber lines 172, 174,176. That line card includes AFEs 158, a packet bus 160 and a DSP. In an alternate embodiment of the invention the termination at the remote site 150 would be a set of discrete modems each coupled to an associated one of the subscriber
