Patent Document

REFERENCE TO EARLIER-FILED APPLICATIONS  
       [0001]     This application is a continuation-in-part of U.S. Utility application Ser. No. 10/788,505 titled “Network Interface Device and Broadband Local Area Network Using Coaxial Cable,” filed Feb. 13, 2004, which is a continuation of U.S. Utility application Ser. No. 09/910,412 titled “Network Interface Device and Broadband Local Area Network Using Coaxial Cable,” filed Jul. 21, 2001, which claims the benefit of U.S. Provisional Application Ser. No. 60/288,967 titled “Network Interface and Broadband Local Area Network Using Coaxial Cable,” filed May 4, 2001, all of which applications are incorporated herein, in their entirety, by this reference. This application is also a continuation-in-part of U.S. Utility application Ser. No. 10/322,834 titled “Broadband Network for Coaxial Cable Using Multi-carrier Modulation,” filed Dec. 18, 2002, which is a continuation of U.S. Utility application Ser. No. 10/230,687 titled “Broadband Network for Coaxial Cable Using Multi-carrier Modulation,” filed Aug. 29, 2002, now abandoned, which claims the benefit of the following U.S. Provisional Applications: (a) Ser. No. 60/316,820 titled “Broadband Local Area Network Using Coaxial Cable,” filed Aug. 30, 2001; (b) Ser. No. 60/363,420 titled “Method of Bit and Energy Loading to Reduce Interference Effects in Devices Sharing a Communication Medium,” filed Mar. 12, 2002; and (c) Ser. No. 60/385,361 titled “Power Loading to Reduce Interference Effects in Devices Sharing a Communication Medium,” filed Jun. 3, 2002, all of which applications are incorporated herein, in their entirety, by this reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of Invention  
         [0003]     The invention relates to broadband communication networks, and in particular to broadband communication networks utilizing coaxial cable.  
         [0004]     2. Related Art  
         [0005]     The worldwide utilization of external television (“TV”) antennas for receiving broadcast TV, and of cable television and satellite TV is growing at a rapid pace. These TV signals from an external TV antenna, cable TV and satellite TV (such as from direct broadcast satellite “DBS” system) are usually received externally to a building (such as a home or an office) at a point-of-entry (“POE”). There may be multiple TV receivers and/or video monitors within the building and these multiple TV receivers may be in signal communication with the POE via a broadband cable network that may include a plurality of broadband cables and broadband cable splitters. Generally, these broadband cable splitters distribute downstream signals from the POE to various terminals (also known as “nodes”) in the building. The nodes may be connected to various types of customer premise equipment (“CPE”) such as cable converter boxes, televisions, video monitors, cable modems, cable phones and video game consoles.  
         [0006]     Typically, these broadband cables and broadband cable splitters are implemented utilizing coaxial cables and coaxial cable splitters, respectively. Additionally, in the case of cable TV or satellite TV, the multiple TV receivers may be in signal communication with the broadband cable network via a plurality of cable converter boxes, also known as set-top boxes (“STBs”), that are connected between the multiple TV receivers and the broadband cable network via a plurality of network nodes.  
         [0007]     Typically, a STB connects to a coaxial cable from a network node (such as the wall outlet terminal) to receive cable TV and/or satellite TV signals. Usually, the STB receives the cable TV and/or satellite TV signals from the network node and converts them into tuned TV signals that may be received by the TV receiver and/or video signals that may be received by a video monitor.  
         [0008]     In  FIG. 1 , an example known broadband cable network  100  (also known as a “cable system” and/or “cable wiring”) is shown within a building  102  (also known as customer premises or “CP”) such as a typical home or office. The broadband cable system  100  may be in signal communication with an optional cable service provider  104 , optional broadcast TV station  106 , and/or optional DBS satellite  108 , via signal path  110 , signal path  112  and external antenna  114 , and signal path  116  and DBS antenna  118 , respectively. The broadband cable system  100  also may be in signal communication with optional CPEs  120 ,  122  and  124 , via signal paths  126 ,  128  and  130 , respectively.  
         [0009]     In  FIG. 2 , another example known broadband cable system is shown within a building (not shown) such as a typically home. The cable system  200  may be in signal communication with a cable provider (not shown), satellite TV dish (not shown), and/or external antenna (not shown) via a signal path  202  such as a main coaxial cable from the building to a cable connection switch (not shown) outside of the building. The cable system  200  may include a POE  204  and main splitter  206 , a sub-splitter  208 , and STBs A  210 , B  212  and C  214 .  
         [0010]     Within the cable system  200 , the POE  204  may be in signal communication with main splitter  206  via signal path  216 . The POE  204  may be the connection point from the cable provider which is located external to the building of the cable system  200 . The POE  202  may be implemented as a coaxial cable connector, transformer and/or filter.  
         [0011]     The main splitter  206  may be in signal communication with sub-splitter  208  and STB A  210  via signal paths  218  and  220 , respectively. The sub-splitter  208  may be in signal communication with STB B  212  and STB C  214  via signal paths  222  and  224 , respectively. The main splitter  206  and sub-splitter  208  may be implemented as coaxial cable splitters. The STB A  210 , B  212  and C  214  may be implemented by numerous well known STB coaxial units such as cable television set-top boxes and/or satellite television set-top boxes. Typically, the signal paths  202 ,  216 ,  218 ,  220 ,  222  and  224  may be implemented utilizing coaxial cables.  
         [0012]     In an example operation, the cable system  200  would receive CATV, cable and/or satellite radio frequency (“RF”) TV signals  226  via signal path  202  at the POE  204 . The POE  204  may pass, transform and/or filter the received RF signals to a second RF signal  228  that may be passed to the main splitter  206  via signal path  216 . The main splitter  206  may then split the second RF signal  228  into split RF signals  230  and  232 . The split RF signal  230  is then passed to the sub-splitter  208  and the split RF signal  232  is passed to the STB A  210  via signal paths  218  and  220 , respectively. Once the split RF signal  232  is received by the STB A  210 , the STB A  210  may convert the received split RF signal  232  into a baseband signal  238  that may be passed to a video monitor (not shown) in signal communication with the STB A  210 .  
         [0013]     Once the split RF signal  230  is received by the sub-splitter  208 , the sub-splitter  208  splits the received split RF signal  230  into sub-split RF signals  234  and  236  that are passed to STB B  212  and STB C  214  via signal paths  222  and  224 , respectively. Once the sub-split RF signals  234  and  236  are received by the STB B  212  and STB C  214 , respectively, the STB B  212  and STB C  214  may convert the received sub-split RF signals  234  and  236  into baseband signals  240  and  242 , respectively, that may be passed to video monitors (not shown) in signal communication with STB B  212  and STB C  214 .  
         [0014]     As the utilization of the numbers and types of CPEs in buildings increase (such as the number of televisions, video monitors, cable modems, cable phones, video game consoles, etc., increase in a typical home or office environment), there is a growing need for different CPEs to communicate between themselves in a network type of environment within the building. As an example, users in a home may desire to play network video games between different rooms in home environment utilizing the coaxial cable network installed throughout the home. Additionally, in another example, users in a home may want to share other types of digital data (such video and/or computer information) between different rooms in a home.  
         [0015]     Unfortunately, most broadband cable networks (such as the examples shown in both  FIG. 1  and  FIG. 2 ) presently utilized within most existing buildings are not configured to allow for easy networking between CPEs because most broadband cable networks utilize broadband cable splitters that are designed to split an incoming signal from the POE into numerous split signals that are passed to the different nodes in different rooms.  
         [0016]     As an example, in a typical home the signal splitters are commonly coaxial cable splitters that have an input port and multiple output ports. Generally, the input port is known as a common port and the output ports are known as tap ports. These types of splitters are generally passive devices and may be constructed using lumped element circuits with discrete transformers, inductors, capacitors, and resistors and/or using strip-line or microstrip circuits. These types of splitters are generally bi-directional because they may also function as signal combiners, which sum the power from the multiple tap ports into a single output at the common port.  
         [0017]     However, presently many CPEs utilized in modern cable and DBS systems have the ability to transmit as well as receive. If a CPE is capable of transmitting an upstream signal, the transmitted upstream signal from that CPE typically flows through the signal splitters back to the POE and to the cable and/or DBS provider. In this reverse flow direction, the signal splitters function as signal combiners for upstream signals from the CPEs to the POE. Usually, most of the energy from the upstream signals is passed from the CPEs to the POE because the splitters typically have a high level of isolation between the different connected terminals resulting in significant isolation between the various CPEs.  
         [0018]     The isolation creates a difficult environment to network between the different CPEs because the isolation results in difficulty for transmitting two-way communication data between the different CPEs. Unfortunately, CPEs are becoming increasingly complex and a growing number of users desire to connect these multiple CPEs into different types of networks.  
         [0019]     Therefore, there is a need for a system and method to connect a variety of CPEs into a local network, such as local-area network (“LAN”), within a building such as a home or office. Additionally, there is a need for a system and method to connect a variety of CPEs into a local network, such as a LAN, within a building such as a home or office while allowing the utilization of an existing coaxial cable network within the building.  
       SUMMARY  
       [0020]     A broadband cable network (“BCN”) for determining a common bit-loading modulation scheme for communicating between a plurality of nodes in the BCN is disclosed. The BCN may include a transmitting node within the plurality of nodes where the transmitting node is capable of sending a probe signal to the plurality of nodes, and at least one receiving node within the plurality of nodes in signal communication with the transmitting node. The at least one receiving node is capable of transmitting a first response signal in response to receiving the probe signal. The first response signal includes a first bit-loading modulation scheme determined by the at least one receiving node. The transmitting node is further capable of determining the common bit-loading modulation scheme from the first response signal.  
         [0021]     The BCN may further include a sub-plurality of receiving nodes within the plurality of nodes wherein the sub-plurality of receiving nodes are capable of transmitting a sub-plurality of response signals in response to receiving the probe signal. The sub-plurality of response signals may include other bit-loading modulation schemes and each bit-loading modulation scheme may be determined by a receiving node within the sub-plurality of receiving nodes. The transmitting node may be capable of determining the common bit-loading modulation scheme from the first response signal and the sub-plurality of response signals.  
         [0022]     As an example of operation, the BCN is capable of transmitting a probe signal from the transmitting node to the plurality of receiving nodes and receiving a plurality of response signals from the corresponding receiving nodes of the plurality of receiving nodes, wherein each of the response signals includes a bit-loading modulation scheme determined by the corresponding receiving node. The BCN is further capable of determining the common bit-loading modulation scheme from the received plurality of response signals.  
         [0023]     Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The invention can be better understood with reference to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views.  
         [0025]      FIG. 1  shows a block diagram of an example implementation of a known broadband cable system within a building.  
         [0026]      FIG. 2  shows a block diagram of another example implementation of a known broadband cable system within the building shown in  FIG. 1 .  
         [0027]      FIG. 3  shows a block diagram of an example implementation of a broadband cable network (“BCN”) within a building.  
         [0028]      FIG. 4  shows a functional diagram showing the communication between the different nodes shown in the BCN of  FIG. 3  in a unicast mode.  
         [0029]      FIG. 5  shows another functional diagram showing the communication between the different nodes shown in the BCN of  FIG. 3  in a broadcast mode.  
         [0030]      FIG. 6  shows a block diagram of an example implementation of the BCN shown in  FIG. 3  when node A is communicating to node B.  
         [0031]      FIG. 7  shows a block diagram of another example implementation of the BCN shown in  FIG. 3  when node A is communicating to node C.  
         [0032]      FIG. 8  shows a block diagram of an example implementation of the BCN shown in  FIG. 3  when node C is communicating to node B.  
         [0033]      FIG. 9  shows a plot of the transfer function versus frequency for the channel path between node A and node B and the channel path between node A and node C shown in both  FIGS. 6 and 7 .  
         [0034]      FIG. 10A  shows a plot of the bit-loading constellation versus carrier number for the channel path between node A and node B shown in  FIG. 9 .  
         [0035]      FIG. 10B  shows a plot of the bit-loading constellation versus carrier number for the channel path between node A and node C shown in  FIG. 9 .  
         [0036]      FIG. 10C  shows a plot of the bit-loading constellation versus carrier number for the resulting broadcast channel path between node A and node B and node A and node C based on the constellations shown in  FIGS. 10A and 10B .  
         [0037]      FIG. 11  shows a flowchart illustrating the method performed by the BCN shown in  FIG. 3 .  
     
    
     DETAILED DESCRIPTION  
       [0038]     In the following description of the preferred embodiment, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration a specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.  
         [0039]     In  FIG. 3 , a block diagram of an example implementation of a broadband cable network (“BCN”)  300  utilizing common bit-loading within a customer premises (“CP”)  302  is shown. The CP  302  may be a building such as a home or office having a plurality of customer premises equipment (“CPE”)  304 ,  306  and  308  in signal communication with the BCN  300  via a plurality of corresponding CPE signal paths  310 ,  312  and  314 . The BCN  300  may be in signal communication optionally with an external antenna (not shown), cable provider (not shown) and/or direct broadcast satellite (“DBS”) provider (not shown) via external BCN path  316 .  
         [0040]     The BCN  300  may include a point-of-entry (“POE”)  320 , a splitter network  322  and a plurality of nodes such as node A  324 , node B  326  and node C  328 . The splitter network  322  may be in signal communication with the POE  320 , via signal path  330 , and the plurality of nodes  324 ,  326  and  328  via signal paths  332 ,  334  and  336 , respectively. The nodes  324 ,  326  and  328  may be in signal communication with the CPEs  304 ,  306  and  308  via signal paths  310 ,  312  and  314 , respectively.  
         [0041]     In an example operation, the BCN  300  receives input radio frequency (“RF”) signals from optionally the external antenna (not shown), cable provider (not shown) and/or direct broadcast satellite (“DBS”) provider (not shown) at the POE  320  via external BCN path  316 . The BCN  300  then passes the input RF signals from POE  320  to the splitter network  322 , via signal path  330 , and the splitter network  322  splits the input RF signal into split RF signals that are passed to the nodes  324 ,  326  and  328  via signal paths  332 ,  334  and  336 , respectively. It is appreciated by those skilled in the art that the BCN  300  may be implemented as a coaxial cable network utilizing coaxial cables and components.  
         [0042]     In  FIG. 4 , a functional diagram  400  showing the communication between various nodes  402 ,  404  and  406  corresponding to the nodes in the BCN  300 ,  FIG. 3 , is shown. The nodes  402 ,  404  and  406  may be interconnected between node pairs utilizing corresponding inter-node channels between the node pairs. It is appreciated by those skilled in the art that even if the nodes are individually connected with one another via a signal inter-node channel between the node pairs, each inter-node channel between node pairs may be asymmetric. Therefore, inter-node channels between node A  402 , node B  404  and node C  406  may be asymmetric and therefore utilize different bit-loading modulation schemes depending on the direction of the signals between the nodes. As a result, the typically asymmetric inter-node channels between node A  402 , node B  404  and node C  406  may be described by the corresponding direction-dependent node channels AB, BA, AC, CA, BC and CB.  
         [0043]     As an example, node A  402  is in signal communication with node B  404  via signal paths  408  and  410 . Signal path  408  corresponds to the AB channel and signal path  410  corresponds to the BA channel. Additionally, node A  402  is also in signal communication with node C  406  via signal paths  412  and  414 . Signal path  412  corresponds to the AC channel and signal path  414  corresponds to the CA channel. Similarly, node B  404  is also in signal communication with node C  406  via signal paths  416  and  418 . Signal path  416  corresponds to the BC channel and signal path  418  corresponds to the CB channel.  
         [0044]     In this example, the AB channel corresponds to the channel utilized by node A  402  transmitting to node B  404  along signal path  408 . The BA channel corresponds to the reverse channel utilized by node B  404  transmitting to node A  402  along signal path  410 . Similarly, the AC channel corresponds to the channel utilized by node A  402  transmitting to node C  406  along signal path  412 . The CA channel corresponds to the reverse channel utilized by node C  406  transmitting to node A  402  along signal path  414 . Moreover, the BC channel corresponds to the channel utilized by node B  404  transmitting to node C  406  along signal path  416 . The CB channel corresponds to the reverse channel utilized by node C  406  transmitting to node B  404  along signal path  418 .  
         [0045]     In example of operation, in order for node A  402  to transmit the same message to both node B  404  and node C  406  using the AB channel along signal path  408  and AC channel along signal path  412 , node A  402  will need to transmit (i.e., “unicast”) the same message twice, once to node B  404  and a second time to node C  406  because channel AB and channel AC may utilize different bit-loading modulation schemes.  
         [0046]     In  FIG. 5 , another functional diagram  500  showing the communication between various nodes  502 ,  504  and  506  corresponding to the nodes in the BCN  300 ,  FIG. 3 , is shown. In  FIG. 5 , node A  502  may transmit a message in a broadcast mode (also known as a “multicast” mode) simultaneously to node B  504  and node C  506  using an A-BC channel via signal path  508 . The message transmission utilizing the A-BC channel, along signal path  508 , is the equivalent of simultaneously transmitting a broadcast message from node A  502  to node B  504  via an AB channel along signal path  510  and to node C  506  via an AC channel along signal path  512  in a fashion that is similar to transmission described in  FIG. 4 . However, in order to insure that both node B  504  and node C  506  receive the transmissions broadcast signal from node A  502 , node A  502  utilizes a bit-loading modulation scheme that is known as a common bit-loaded modulation scheme. The common bit-loaded modulation scheme transmitted via the A-BC channel, along signal path  508 , is a combination of the bit-loading modulation scheme transmitted via the AB channel, along signal path  510 , and the AC channel, along signal path  512 .  
         [0047]     It is appreciated by those skilled in the art that the different channels typically utilize different bit-loading modulation schemes because the channels are physically and electrically different in the cable network. Physically the channels typically vary in length between nodes and electrically vary because of the paths through and reflections from the various cables, switches, terminals, connections and other electrical components in the cable network. Bit-loading is the process of optimizing the bit distribution to each of the channels to increase throughput. A bit-loading scheme is described in U.S. Utility application Ser. No. 10/322,834 titled “Broadband Network for Coaxial Cable Using Multi-carrier Modulation,” filed Dec. 18, 2002, which is incorporated herein, in its entirety, by reference.  
         [0048]     The BCN may operate with waveforms that utilize bit-loaded orthogonal frequency division multiplexing (OFDM). Therefore, the BCN may transmit multiple carrier signals (i.e, signals with different carrier frequencies) with different QAM constellations on each carrier. As an example, over a bandwidth of about 50 MHz, the BCN may have 256 different carriers which in the best circumstances would utilize up to 256 QAM modulation carriers. If instead the channel is poor, the BCN may utilize BPSK on all the carriers instead of QAM. If the channel is good in some places and poor in others, the BCN may utilize high QAM in some parts and lower types modulation in others.  
         [0049]     As an example, in  FIG. 6 , a block diagram of an example implementation of the BCN  600  is shown. The BCN  600  may be in signal communication with a cable provider (not shown), satellite TV dish (not shown), and/or external antenna (not shown) via a signal path  602  such as a main coaxial cable from the customer premises to a cable connection switch (not shown) outside of the customer premises.  
         [0050]     The BCN  600  may include a POE  604  and main splitter  606 , a sub-splitter  608 , nodes A  610 , B  612  and C  614 , and STBs A  616 , B  618  and C  620 . Within the BCN  600 , the POE  604  may be in signal communication with main splitter  606  via signal path  622 . The POE  604  may be the connection point from the cable provider which is located external to the customer premises of the BCN  600 . The POE  604  may be implemented as a coaxial cable connector, transformer and/or filter.  
         [0051]     The main splitter  606  may be in signal communication with sub-splitter  608  and node C  614  via signal paths  624  and  626 , respectively. The sub-splitter  608  may be in signal communication with node A  610  and node B  612  via signal paths  628  and  630 , respectively. The main splitter  606  and sub-splitter  608  may be implemented as coaxial cable splitters. Node A  610  may be in signal communication with STB A  616  via signal path  632 . Similarly, node B  612  may be in signal communication with STB B  618  via signal path  634 . Moreover, node C  614  may be in signal communication with STB C  620  via signal path  636 . STBs A  616 , B  618  and C  620  may be implemented by numerous well known STB coaxial units such as cable television set-top boxes and/or satellite television set-top boxes. Typically, the signal paths  602 ,  622 ,  624 ,  626 ,  628 ,  630 ,  632 ,  634  and  636  may be implemented utilizing coaxial cables.  
         [0052]     As an example of operation, if node A  610  transmits a message to node B  612 , the message will propagate through two transmission paths from node A  610  to node B  612 . The first transmission path  640  travels from node A  610  through signal path  628 , sub-splitter  608  and signal path  630  to node B  612 . The second transmission path includes transmission sub-paths  642  and  644 . The first sub-path  642  travels from node A  610  through signal path  628 , sub-splitter  608 , signal path  624 , main splitter  606  and signal path  622  to POE  604 . The second sub-path  644  travels from POE  604 , through signal path  622 , main splitter  606 , signal path  624 , sub-splitter  608  and signal path  630 .  
         [0053]     The first transmission path  640  is typically very lossy and experiences a high amount of attenuation because of the isolation between the outputs of sub-splitter  608 . The second transmission path, however, does not experience the attenuation of the first transmission path  640 . The second transmission path results from the transmission of message signal  646  from node A  610  to the POE  604  along the first sub-path  642  which results in a reflected message signal  648  from the POE  604 . The reflected message signal  648  results from impedance mismatches between the POE  604  and the rest of the BCN  600 .  
         [0054]     As another example, in  FIG. 7 , another block diagram of an example implementation of the BCN  700  is shown. Similar to  FIG. 6 , in  FIG. 7 , the BCN  700  may be in signal communication with a cable provider (not shown), satellite TV dish (not shown), and/or external antenna (not shown) via a signal path  702  such as a main coaxial cable from the customer premises to a cable connection switch (not shown) outside of the customer premises.  
         [0055]     The BCN  700  may include a POE  704  and main splitter  706 , a sub-splitter  708 , nodes A  710 , B  712  and C  714 , and STBs A  716 , B  718  and C  720 . Within the BCN  700 , the POE  704  may be in signal communication with main splitter  706  via signal path  722 . The POE  704  may be the connection point from the cable provider which is located external to the customer premises of the BCN  700 . The POE  704  may be implemented as a coaxial cable connector, transformer and/or filter.  
         [0056]     The main splitter  706  may be in signal communication with sub-splitter  708  and node C  714  via signal paths  724  and  726 , respectively. The sub-splitter  708  may be in signal communication with node A  710  and node B  712  via signal paths  728  and  730 , respectively. The main splitter  706  and sub-splitter  708  may be implemented as coaxial cable splitters. Node A  710  may be in signal communication with STB A  716  via signal path  732 . Similarly, node B  712  may be in signal communication with STB B  718  via signal path  734 . Moreover, node C  714  may be in signal communication with STB C  720  via signal path  736 . STBs A  716 , B  718  and C  720  may be implemented by numerous well known STB coaxial units such as cable television set-top boxes and/or satellite television set-top boxes. Typically, the signal paths  702 ,  722 ,  724 ,  726 ,  728 ,  730 ,  732 ,  734  and  736  may be implemented utilizing coaxial cables.  
         [0057]     As an example of operation, if node A  710  transmits a message to node C  714 , the message will propagate through two transmission paths from node A  710  to node C  714 . The first transmission path  740  travels from node A  710  through signal path  728 , sub-splitter  708 , signal path  724 , main splitter  706  and signal path  726  to node C  714 . The second transmission path includes transmission sub-paths  742  and  744 . The first sub-path  742  travels from node A  710  through signal path  728 , sub-splitter  708 , signal path  724 , main splitter  706  and signal path  722  to POE  704 . The second sub-path  744  travels from POE  704 , through signal path  722 , main splitter  706 , and signal path  726  to node C  714 .  
         [0058]     The first transmission path  740  is typically very lossy and experiences a high amount of attenuation because of the isolation between the outputs of sub-splitter  708  and main splitter  706 . The second transmission path, however, does not experience the attenuation of the first transmission path  740 . The second transmission path results from the transmission of message signal  746  from node A  710  to the POE  704  along the first sub-path  742  which results in a reflected message signal  748  from the POE  704 . The reflected message signal  748  results from mismatches between the POE  704  and therest of the BCN  700 .  
         [0059]     As still another example, in  FIG. 8 , another block diagram of an example implementation of the BCN  800  is shown. Similar to  FIGS. 6 and 7 , in  FIG. 8 , the BCN  800  may be in signal communication with a cable provider (not shown), satellite TV dish (not shown), and/or external antenna (not shown) via a signal path  802  such as a main coaxial cable from the customer premises to a cable connection switch (not shown) outside of the customer premises.  
         [0060]     The BCN  800  may include a POE  804  and main splitter  806 , a sub-splitter  808 , nodes A  810 , B  812  and C  814 , and STBs A  816 , B  818  and C  820 . Within the BCN  800 , the POE  804  may be in signal communication with main splitter  806  via signal path  822 . The POE  804  may be the connection point from the cable provider which is located external to the customer premises of the BCN  800 . The POE  804  may be implemented as a coaxial cable connector, transformer and/or filter.  
         [0061]     The main splitter  806  may be in signal communication with sub-splitter  808  and node C  814  via signal paths  824  and  826 , respectively. The sub-splitter  808  may be in signal communication with node A  810  and node B  812  via signal paths  828  and  830 , respectively. The main splitter  806  and sub-splitter  808  may be implemented as coaxial cable splitters. Node A  810  may be in signal communication with STB A  816  via signal path  832 . Similarly, node B  812  may be in signal communication with STB B  818  via signal path  834 . Moreover, node C  814  may be in signal communication with STB C  820  via signal path  836 . STBs A  816 , B  818  and C  820  may be implemented by numerous well known STB coaxial units such as cable television set-top boxes and/or satellite television set-top boxes. Typically, the signal paths  802 ,  822 ,  824 ,  826 ,  828 ,  830 ,  832 ,  834  and  836  may be implemented utilizing coaxial cables.  
         [0062]     As an example of operation, if node C  814  transmits a message to node B  812 , the message will propagate through two transmission paths from node C  814  to node B  812 . The first transmission path  840  travels from node C  814  through signal path  826 , main splitter  806 , signal path  824 , sub-splitter  808  and signal path  830  to node B  812 . The second transmission path includes two transmission sub-paths  842  and  844 . The first sub-path  842  travels from node C  814  through signal path  826 , main splitter  806 , and signal path  822  to POE  804 . The second sub-path  844  travels from POE  804 , through signal path  822 , main splitter  806 , signal path  824 , sub-splitter  808  and signal path  830  to node B  812 .  
         [0063]     The first transmission path  840  is typically very lossy and experiences a high amount of attenuation because of the isolation between the outputs of sub-splitter  808  and main splitter  806 . The second transmission path, however, does not experience the attenuation of the first transmission path  840 . The second transmission path results from the transmission of message signal  846  from node C  814  to the POE  804  along the first sub-path  842  which results in a reflected message signal  848  from the POE  804 . The reflected message signal  848  results from mismatches between the POE  804  and rest of the BCN  800 .  
         [0064]     In  FIG. 9 , a plot  900  of the maximum bit-loading constellation  902  versus frequency  904  is shown for the channel path utilized by node A to transmit to node B and the channel path utilized by node A to transmit to node C. Line  906  represents the AB channel and line  908  represents the AC channel. The AB channel has a null  910  that represents the reflection distance from the POE to node B. The AC channel has nulls  912  and  914 . Null  912  represents the reflection distance from the POE to node C and null  914  represents a harmonic that is a multiple value of the value of null  912 . In general, the nulls are caused by the properties, e.g., amplitudes and time delays, that are unique to each transmission path in the network.  
         [0065]     Returning to  FIG. 5 , the BCN, in order to insure that both node B  504  and node C  506  are able to receive a broadcast signal transmitted from node A  502 , utilizes a bit-loading modulation scheme that is known as the common bit-loaded modulation scheme. The common bit-loaded modulation scheme transmitted via the A-BC channel, along signal path  508 , is a combination of the bit-loading modulation scheme transmitted via the AB channel, along signal path  510 , and the AC channel, along signal path  512 .  
         [0066]     Therefore, in  FIG. 10A , a plot  1000  of carrier frequency signals of various bit-loading constellations  1002  versus carrier number  1004  for the AB channel path between node A and node B is shown. Line  1006  represents the AB channel and follows an envelope of the constellation sizes of the 8 different carrier number signals within the AB channel. As an example, within the AB channel carrier number signals  1  and  8  may transmit at a constellation size of 256 QAM, carrier number signals  2 ,  3  and  7  may transmit at a constellation size of 128 QAM, carrier number signals  4  and  6  may transmit at a constellation size of 64 QAM, and carrier number signal  5  may be OFF (i.e., no carrier signal of any constellation size may be transmitted because of the null in the channel characteristics).  
         [0067]     Similarly in  FIG. 10B , a plot  1008  of carrier frequency signals of various bit-loading constellations  1010  versus carrier number  1012  for the AC channel path between node A and node C is shown. Line  1014  represents the AC channel and follows an envelope of the constellation sizes of the 8 different carrier number signals within the AC channel. As an example, within the AC channel carrier number signals  1 ,  2 ,  4 ,  6  and  8  may transmit at a constellation size of 128 QAM, carrier number signal  5  may transmit at a constellation size of 256 QAM, and carrier number signals  3  and  7  may be OFF (again, no carrier signals may be transmitted because of nulls in the channel characteristics).  
         [0068]     In  FIG. 10C , a plot  1016  of the common carrier frequency signals of various bit-loading constellations  1018  versus carrier number  1020  for the A-BC channel path between node A and nodes B and C is shown. In this example, plot  1016  shows that within the A-BC channel, carrier number signals  1 ,  2  and  8  may transmit at a constellation size of 128 QAM, carrier number signals  4  and  6  may transmit at a constellation size of 64 QAM, and carrier number signals  3 ,  5  and  7  are OFF. These carrier number signal values are the result of comparing the carrier number signals from the AB channel in  FIG. 10A  and the corresponding carrier number signals from the AC channel in  FIG. 10B  and choosing the lowest corresponding modulation value for each carrier number. The resulting common carrier frequency signals in  FIG. 10C  graphically represent signals utilizing the common bit-loaded modulation scheme. These signals would be able to transmit information from node A to node B and node C simultaneously.  
         [0069]      FIG. 11  shows a flowchart  1100  illustrating the method performed by the BCN shown in  FIG. 3 . In  FIG. 11 , the process starts in step  1102 . In step  1104 , a transmitting node transmits a probe signal from the transmitting node to a plurality of receiving nodes. In response, the receiving nodes receive the probe signal from the transmitting node. In step  1106 , a receiving node of the plurality of receiving nodes receives the probe signal through the appropriate channel path of transmission. The receiving node then determines the transmission characteristics of the channel path from the transmitting node to the receiving node in step  1108  and in response to the determined transmission characteristics of the channel path, the receiving node determines a bit-loaded modulation scheme for the transmission characteristics of the channel path in step  1110 . It is appreciate by those skilled in the art that the transmission characteristics of the channel path may be determined by measuring the metric values of the channel path. Examples of the metric values may include the signal-to-noise ratio (also known as the “SNR” and “S/N”) and/or the bit-error rate (“BER”) or product error rate (PER), or power level or similar measurement of the received signal at the corresponding remote device. Additionally, other signal performance metric values are also possible without departing from the scope of the invention.  
         [0070]     The receiving node then, in step  1112 , transmits a response signal to the transmitting node, informing the transmitting node of the recently-determined bit-loaded modulation scheme.  
         [0071]     The transmitting node then receives a plurality of response signals, in step  1114 , from the corresponding receiving nodes wherein each of the response signals informs the transmitting node of the corresponding bit-loaded modulation scheme determined by each of the plurality of receiving nodes. In response to receiving the plurality of response signals, the transmitting node, in step  1116 , compares the plurality of bit-loaded modulation schemes from the corresponding received plurality of response signals and, in step  1118 , determines the common bit-loaded modulation scheme. Once the transmitting node determines the common bit-loaded modulation scheme, the transmitting node, in step  1120 , transmits a broadcast signal relaying the common bit-loaded modulation scheme to the plurality of receiving nodes. This broadcast signal may either contain handshake information from the transmitting node to the plurality of receiving nodes or it may actually be a communication message containing information such as video, music, voice and/or other data.  
         [0072]     In decision step  1122 , if all the nodes in BCN have performed the handshake process that determines the common bit-loaded modulation scheme in steps  1102  through  1120 , the handshake process is complete and process ends in step  1124 , at which time the BCN may begin to freely transmit information between the various nodes. If instead, there are still nodes in the BCN that have not performed the handshake process that determines the common bit-loaded modulation scheme in steps  1102  through  1120 , the process then returns to step  1126 . In step  1126 , the BCN selects the next node in the BCN and the process steps  1102  to  1122  repeat again. Once all the nodes in the BCN have preformed the handshake process, the handshake process is complete and process ends in step  1124  at which time the BCN may begin to freely transmit information between the various nodes.  
         [0073]     The process in  FIG. 11  may be performed by hardware or software. If the process is performed by software, the software may reside in software memory (not shown) in the BCN. The software in software memory may include an ordered listing of executable instructions for implementing logical functions (i.e., “logic” that may be implemented either in digital form such as digital circuitry or source code or in analog form such as analog circuitry or an analog source such as an analog electrical, sound or video signal), may selectively be embodied in any computer-readable (or signal-bearing) medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that may selectively fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “computer-readable medium” and/or “signal-bearing medium” is any means that may contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer readable medium may selectively be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples, that is “a non-exhaustive list” of the computer-readable media, would include the following: an electrical connection (electronic) having one or more wires, a portable computer diskette (magnetic), a RAM (electronic), a read-only memory “ROM” (electronic), an erasable programmable read-only memory (EPROM or Flash memory) (electronic), an optical fiber (optical), and a portable compact disc read-only memory “CDROM” (optical). Note that the computer-readable medium may even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance, optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory.  
         [0074]     While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of this invention.

Technology Category: 5