System and methods for home network communications Number:6,941,576 from the United States Patent and Trademark Office (PTO) owispatent

Title: System and methods for home network communications

Abstract: A system that permits use of existing cable TV wiring for home networking is disclosed. Because of the presence of splitters, notch filters, and other components in the cable distribution system, certain of the premises installations in the system can locally communicate over the same frequency as one another, without interference. In a disclosed embodiment, the cable operator determines the attenuation and isolation among different premises in the system, and then assigns home network frequencies to the particular premises, with those premises installations that are sufficiently isolated from one another being assigned the same home network frequency.

Patent Number: 6,941,576 Issued on 09/06/2005 to Amit

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Inventors:	Amit; Mati (Zur-Yigal, IL)
Assignee:	Texas Instruments Incorporated (Dallas, TX)
Appl. No.:	721568
Filed:	November 25, 2003

Current U.S. Class:	725/143; 725/74
Intern'l Class:	H04N 007/16
Field of Search:	725/74,143,78-85,148-150,118-120,127,129 333/100

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References Cited [Referenced By]

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Primary Examiner: Srivastava; Vivek
Attorney, Agent or Firm: Zindani; Abdul, Brady, III; W. James, Telecky, Jr.; Frederick J.

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Parent Case Text

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CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of copending application Ser. No. 09/548,048, filed Apr. 12, 2000, and through that application claims priority under 35 USC §119(e)(1) of Provisional Application No. 60/128,810, filed Apr. 12, 1999.

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Claims

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1. A method of managing communications among a plurality of premise installations in a cable communications distribution system, the cable distribution system including at least one splitter for spreading communicated signals from a headend to a plurality of branches, each of the plurality of branches having at least one premise installation, the method comprising the steps of:

determining an attenuation parameter for each of a plurality of components in the distribution system;

determining an isolation parameter between branches coupled to the at least one splitter;

calculating an overall signal attenuation over a selected frequency band between premise installations on different ones of the plurality of branches; and

responsive to the overall signal attenuation exceeding a minimum isolation threshold value between first and second branches, assigning a frequency within the selected frequency band to a premise installation on each of the first and second branches.

2. The method of claim 1, wherein each of the premise installations includes a splitter.

3. The method of claim 2, wherein the cable communications distribution system includes a fiber optic facility extending from the headend to a street splitter having a fiber-to-coaxial interface.

4. The method of claim 2, wherein at least one of the premise installations includes a notch filter.

5. The method of claim 2, wherein at least one of the splitters of at least one of the premise installations includes an amplifier.

6. The method of claim 1, wherein the determining steps are performed by a priori knowledge of attenuation and isolation parameters of components in the cable distribution system.

7. The method of claim 6, further comprising:

establishing a set of basic rules corresponding to known network configurations, responsive to the determining and calculating steps;

wherein the assigning step is performed responsive to comparing the system to the basic rules.

8. The method of claim 1, wherein the determining step comprises:

operating the cable distribution; and

measuring the attenuation and isolation parameters using spectrum measurement equipment.

9. The method of claim 1, wherein each of the premise installation includes a home cable network modem having a branch calculation operational mode;

wherein the step of determining an isolation parameter comprises:

transmitting a signal from one of the home cable network modems, the transmitted signal comprising a known pattern at a specific power and frequency;

measuring the power of the transmitted signal at each of the home cable network modems; and

building a topology database from the measured isolation among the home cable network modems.

10. The method of claim 1, wherein the frequency band consists of frequencies above 860 MHz.

11. The method of claim 1, wherein at least one of the premise installations includes a transponder, for receiving signals transmitted from within the premise installation at a first frequency, and for retransmitting the received signals at a second frequency;

wherein the assigning step assigns the first and second frequencies to the at least one of the premise installations having the transponder.

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Description

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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The present invention relates to communications systems, and more particularly, to system and methods for home network communications.

Home networking is a key technology for the evolving home infotainment market, and is expected to itself become a large market over the next decade. Home networks will connect among computing devices (personal computers, palm computers, network computers, etc.), entertainment devices (TV, VCR, DVD player, video camera, audio systems, etc.), I/O devices (printer, scanner, head-sets, keyboards, remote controls, mouse, loud-speakers, etc.), home appliances, and modems (such as cable modems, DSL modems, and PSTN modems) for connecting the home network to external networks including the Internet. The home network will enable a wide range of application such as internet sharing, peripheral sharing, file and application sharing, and home automation. The home network will distribute the computation power of the computer from the study room to the living rooms.

Home networking solutions over existing telephone wiring (e.g., HomePNA) generally allow ordinary voice telephone calls to be carried over the wire, while at the same time providing up to several megabits of data throughput. Because the existing telephony wiring is already in place, these solutions provide an extremely easy and cost-effective way to create a data network in the home. Some solutions require the installing of a gateway where the Public Service Telephone Network (PSTN) interfaces with the wiring in the house. This gateway can also serve as a Voice-over-IP (VoIP) telephony gateway.

Another class of proposed home networking uses the normal AC electrical power wiring in the home for data transmission. Electrical power wiring has been used in the past for low bit-rate data applications such as home automation. Technologies for achieving multi megabit throughput on existing residential electrical wiring are under investigation in the industry. However, this approach has significant challenges, given that electrical wiring is not designed for data transmission. Also, a privacy concern exists where multiple homes are generally served off the same electrical transformer, requiring appropriate encryption to be deployed. Because the electrical wiring is the most ubiquitous in the home and because virtually every digital device in the home connects to the electrical wiring, the use of existing electrical wiring is an attractive way to create a data network in the home.

Wireless technologies, such as short-range wireless (e.g., Bluetooth) and medium range wireless (e.g., HomeRF and IEEE 802.11), are expected to provide several megabits of throughput, and are also proposed as a home network solution. However, their effectiveness can vary, depending on the size of the house, the proximity of other wireless networks, and other sources of noise.

By way of further background, the IEEE 1394 (i.LINK) standard defines a wired serial interface among digital devices. This inexpensive, easy-to-use and high-speed bus handles multimedia bandwidth requirements and provides a universal interface for a variety of devices. By allowing seamless data exchange between devices such as workstations, personal computers and digital televisions, VCRs, camcorders and set-top boxes, it enables a new generation of computers and consumer electronic devices to operate in a common environment. Originally developed as an interface to replace SCSI, IEEE 1394 offers bi-directionality, high data transfer rates and isochronous data transfers. It provides "hot plug" capability i.e. the ability to connect or disconnect equipment with the power on. It also enables devices that require audio, video and control signals to be connected with a single cable. This standard, also referred to as "Fire-wire", requires special wires. The range between two adjacent components is limited, requiring amplifiers to supply the connectivity throughout a house.

For new homes, it is anticipated that standard Category 5 Ethernet wiring can supplement twisted-pair telephone wiring. The added cost of including this extra wiring during construction is relatively low and the benefits reaped can be great, because 100BaseT and other high-speed network types work well over this cable. In existing homes, however, it can be cumbersome to install Cat5 wiring throughout the home.

Another class of existing wiring in the home is TV wiring, consisting of coaxial cables that connect an antenna or a cable TV source to cable outlets or jacks at specific points in the home. Typically, the connection points of coaxial TV wiring are implemented by passive RF splitters. The signals transmitted over the in-home TV wiring may include regular video channels, data channels for fast Internet access (using e.g., DOCSIS cable modem), voice channels for telephony over cable, pay-per-view, control signals and more. Coaxial cable is an excellent communication medium, having a high bandwidth due to its shielding properties.

Coaxial cable TV wiring connect the incoming antenna or cable TV signals, typically via passive splitters, to the cable outlets at specific points in the home. These signals carried over the in-home coaxial TV wiring may include regular video channels, data channels for fast Internet access (using e.g., DOCSIS cable modem), voice channels for telephony over cable, pay-per-view, control signals and more.

Technically, to use the in-home TV wiring for home networking applications, one may connect standard cable modems through the cable TV (CATV) system. In this approach, data from one cable modem can be transmitted to the other cable modem via the CATV head-end. However, this configuration has the drawbacks that it loads the system, possibly beyond the typical headend system capacity, and that it introduces large delays that cannot be tolerated by at least some of the applications. Therefore, it is unlikely that cable operators will adopt this configuration.

By way of further background, conventional cable modems may be used to connect any type of home networking system to external (out of the home) networks, such as the Internet.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a system and methods for communication between subscribers' devices over cable infrastructure that are designed to carry video signals, using pass-band frequency bands, without transmission through a CATV headend device.

It is a further object of this invention to allow very high-speed digital and analog communications within the home and from the home to external devices or networks using low cost devices.

It is a further object of this invention to provide home networking solutions that utilize in-home TV wiring for supplying high rate connectivity between any two home networking nodes, without loading the city cable TV (CATV) network.

It is a further object of this invention to provide such a system and method that utilize the pre-existing CATV inlets and coaxial cable infrastructure that are already present in many residential homes, to obtain the benefits of the coaxial cable as an excellent communication medium, with high bandwidth and excellent noise shielding.

It is a further object of this invention to provide a method and system that allows home networking over these coaxial cables, allowing for very high data rates and a low cost implementation.

By way of definition, the term "Home Cable Network", or "HomeCN", as used throughout this specification, will refer to the system of this invention.

In the prior art (e.g. the DOCSIS 1.0 spec), a CATV infrastructure is utilized for communication between a subscribers' devices (e.g. cable modem) and a headend, thus, two subscribers' devices can communicate via the headend. In contrast, the system and method of the present invention is based on direct communications between two subscribers' devices, without transferring the data via a headend, thus allowing for high data rates between units in a home without reducing the capacity of the regional CATV network.

In the prior art, coaxial cables have been used for local area networks (LAN) and for analog communications. In contrast, the system and method of the present invention is designed for cable networks that carry video, or other information, from a headend or an antenna, and thus it is different from prior art LAN over coaxial cables. Furthermore, the method employs a new digital modulation scheme based on pass-band RF signaling, which is fundamentally different than prior art LAN and analog modulation over coaxial cables.

The present invention enables installation of modems, connected to different types of nodes of the CATV, to enable communication between these nodes. The present invention provides a way to transfer data between these nodes, when the data is not required to be transferred to the headend.

This invention provides these benefits and advantages in a low cost manner, which is very important to mass market implementation.

A summary of some of the principles of the system and methods according to the preferred embodiments of the invention follow:

• 1. Subscribers' devices communicate directly (not via the headend) using RF signaling over the coaxial cable. These signals will typically propagate between the devices via reflections from other devices, e.g. splitters or amplifiers, that are installed in the line.
• 2. When the home coaxial cables are connected to a local or regional CATV network, communications are in an out-of-band frequency (i.e., a band that is otherwise not in use, e.g., above 860 MHz), or in part of the downstream band (e.g., within the range of 100-860 MHz) that is allocated (e.g., by the cable operator) for home networking applications.
• 3. When the home coaxial cables are connected to a local or regional CATV network, frequencies are re-used between portions of the CATV plants, so that the same frequency range is allocated to different users in a CATV plant, relying on the isolation between those users due to the attenuation of the cable plant.
• 4. The frequency re-use can be improved by adding filters within the signal path in the local or regional CATV network. The quality of the signal transmitted by one subscriber device to another subscriber device can be further improved by deliberately using splitters with high reflections.
• 5. The home devices may also be capable of connecting to the CATV headend, in the manner as a DOCSIS or DVB cable modem or set-top box. This headend connection may be simultaneous with connections to other devices in the home. Alternatively, the home device may switch between cable modem functionality, on one hand, and connecting to the other in-home devices, on the other hand. Parts of the home device that connect to the headend can be used for both home networking and for cable modem functionality, thus reducing the implementation cost of the home networking functionality. An architecture is proposed in which the home network includes as few as one device that operates both as a cable modem and as a home-networking device. In this architecture, other devices in the home can communicate only over the home network; these other home devices communicate outside the home through the device having the cable modem functionality. Other devices that have home networking and cable modem functionality may also handle a direct connection to other devices in the home. It is contemplated that the home networking functionality can be implemented in cable modems, and particularly in host-based cable modems, as installed in personal computers and that use the processor of the personal computer to perform some of the cable modem and the home cable networking functionality. More generally, the home networking devices may be installed in various kinds of devices that employ general purpose computers (such as a laptop computer, a network computer, a TV, a DVD device, or even certain cellular phones); in this implementation, the general purpose processor performs home networking functionality, thus reducing the implementation cost of home networking capability.
• 6. In an example of a particular implementation of the method, the home coaxial cables are connected to a local or regional CATV network. Each home device addresses the headend, which in turn assigns carrier frequency and bandwidth to each home network. The maximum power level for each device on the home network is assigned by a home networking device that exists in each specific sub-network. In another implementation of the method, the devices search for a non occupied frequency sub-band within a band that is pre-assigned for home networking, and once such a sub-band is found they use it for their needs. When a home CN device is initialized it is trying to "join its home network", that is trying to communicate with other devices in the same home and adopt their frequency band and protocol.
• 7. In an exemplary particular implementation of the method, the devices in a home network are based on the IEEE 802.11 MAC layer. This collision avoidance multiple access protocol is in common use, and supports priority levels.
• 8. In an exemplary particular embodiment of this invention, a special splitter device is present at the input to the user premises, to provide higher quality home networking capabilities. Alternatively, a passive filter may be connected to a conventional splitter, to inhibit interference between signals in that home subnetwork and other neighboring home subnetworks. In either case, the invention provides a "single home" operational mode that allows for low cost equipment and frequency re-use. Alternatively, an active device can be provided that receives signals from a TV antenna or a regional CATV network, also receives signals from subscribers' devices via the home coaxial lines, and functions as a repeater for communications signals between subscribers' devices as well as between subscribers' devices and the headend of the regional CATV network, while still allowing transparent transition of TV antenna or CATV signals into the home.
• 9. In a particular embodiment of the present invention, the home coaxial network interconnects portions of the home (e.g. rooms or floors), and has terminals as inputs and outputs for wireless connections within these portions.
• 10. In a particular embodiment of the present invention, one or more of the home cable network devices have an interface to another communication link, such as IEEE1394 link (I.LINK), extending the range of the home coaxial network.
• 11. In a particular embodiment of the present invention, one or more of the home cable network devices have an interface to another communication link, such as Bluetooth, extending the range of the home coaxial network by supplying pico-cells.
• 12. In cases where direct communications among home devices is not feasible (e.g., due to a highly balanced splitter that has very low reflections), the home devices may have a fallback option of communicating via a regional CATV headend.
• 13. The data transmitted in the coaxial home network may be secured (i.e. encrypted).

As used herein, while the term "home network" (or "subnetwork") connotes a local network, it does not necessarily have to be in a home. For example, the home networks may be deployed in an office environment, or in a multi-family residential complex containing several homes (e.g. an apartment building or condominium).

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The preferred embodiments of the invention as well as other features and advantages thereof will be best understood by reference to the detailed description which follows, read in conjunction with the accompanying drawings, wherein:

FIG. 1 shows a home that has four nodes inside the home and is connected to a regional CATV10 plant;

FIG. 2 shows an example of a preferred embodiment of the home network method and system connected to a regional CATV plant;

FIG. 3 shows an example of the present invention, not connected to a CATV;

FIG. 4 shows an example of HomeCN with a hub;

FIG. 5 presents a frequency allocation that may be employed by the present invention;

FIG. 6 shows an HFC infrastructure;

FIG. 7 shows a network with a notch filter;

FIG. 8 shows HCNM interfaces;

FIG. 9 shows representative HCN data flows;

FIG. 10 shows a power supply;

FIG. 11 shows a dual frequency architecture;

FIG. 12 shows layer two transporting over a home network using dual frequency components;

FIG. 13 shows a Bluetooth home network;

FIG. 14 shows neighborhood wiring;

FIG. 15 shows building wiring;

FIG. 16 and FIG. 17 show home wirings;

FIG. 18 and FIG. 19 depict examples of an HCNM and HNCU.

FIG. 20 is an electrical diagram, in block form, of a home network architecture that operates according to a two-frequency mode.

FIGS. 21a through 21c are electrical diagrams, in schematic and block form, illustrating examples of attenuation and isolation parameters for components in the home network system.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 presents the structure of an existing regional CATV network, into which the present invention can be implemented. The typical home coaxial cable infrastructure is consists of a Cable Source 101 which is connected to the home splitter 102 (which may be Customer Premises Equipment, or CPE, in the CATV sense). Some wires connect the interfaces at the home to splitter 102. The components that can connect to the network are TV 103, and a VCR 104 that is connected to TV 103.

Cable Modems (CM) 105, which may be implemented according to the known DOCSIS standard, couples a personal computer to splitter 102 as shown. Cable Telephone Device 106 connects some telephones to the cable infrastructure (e.g. for communications using VoIP protocol over DOCSIS channel).

An amplifier 107 can be added in the entrance of the home/house to increase signal power. If CM equipment exists at home in the network, amplifier 107 should be bi-directional amplifier, amplifying the signal to home side (downstream, or DS) in the 100 MHz-860 MHz frequency range, and amplifying the signal to the headend side (upstream, or US) in the 5 MHz-44 MHz frequency range).

There are some major types of HomeCN components in the home network, as will be described relative to FIG. 2. The Home Cable Networking Interface (HCNI) is a sub-component that supplies a Home Cable Networking interface, and is a sub-component part of specific equipment (e.g. PC, TV, DVD) 204, 205. The Home Cable Networking Unit (HCNU) is a component that supplies connection to the Home Cable Networking, as a separate unit that contains one or more interfaces to the home equipment (e.g. 10BaseT, USB, wireless), and may provide bridging or routing between the home cable network to other interfaces (networks) 207, 212. A Home Cable Networking Modem (HCNM) is a component that includes an HCNU and a cable modem (e.g. a DOCSIS cable modem), supplying a connection to the home cable network and to the CATV headend. This component is usually implemented as a separate unit that also contains one or more other interfaces (e.g. 10BaseT, USB, wireless), and also provides routing among the home cable network, the cable network, and the other interfaced networks 206.

FIG. 2 shows an example of a preferred embodiment of the disclosed method and system. As shown in FIG. 2, an example of a home cable network ("HomeCN" or "HCN") that has five nodes 204-207, 212 in the CATV network, and that is connected to the regional CATV plants via cable 201. Notch filter 202 is a band reject filter that blocks a certain RF range that will be used by home networking devices 204-207, 212. This filter 202 improves the isolation between the home network and other homes as well as the regional network. In many cases, it is believed that the use of filter 202 will be optional, because it is contemplated that the disclosed system and method will properly function within the isolation levels of the CATV network without the additional notch filtering of filter 202. RF splitter 203 splits the signal coming from and to the regional CATV plant 201, to the signals coming to and from units 204-207, 212, respectively. The signals arriving to RF splitter 203 from the home units 204-207, 212 are partially reflected back to these home units 204-207. It may be recommended to use splitters that deliberately have high reflection levels (although we believe that the method and system can operate with typical commercial splitters). Video Cassette Recorder (VCR) 204 and TV set 205 include Home Cable Networking Interface (HCNI) devices. Personal Computer (PC) 208 is connected to a Home Networking Cable Modem (HNCM) device 206, which supplies both the Home Networking functionality and the Cable Modem functionality. The HCNM is also connected to a phone 215 to supply VoIP functionality. A personal computer that includes HCNI can be connected directly to the HCN. The HCNU+wireless units 207, 212 are connected to the CATV and have a wireless output (e.g. Bluetooth, HomeRF or infra-red) that connects to devices within the vicinity of the device 207, such as wireless telephone unit 209, 213, and notebook computer 210. The HCNU devices are capable of transmitting and receiving digital communications signals among themselves. These signals propagate in the CATV wires and are reflected by the RF splitter 203. The HCNM device is further capable of operating as a DOCSIS cable modem and communicating with a headend of a regional CATV plant 201. The HNCI's, the HCNU's and the HNCM are using Home Cable Network Protocol HCNP.

The HomeCN can also be used to supply full home coverage by the Bluetooth network. To enable this coverage, some HCNU+Bluetooth components 207, 212 that are connected to HomeCN should exist in the home. In this way, a person that travels from room to room with a wireless phone 209, 213 or a notebook computer 210 can remain connected to the network, over the nearest Bluetooth station.

It is contemplated that the method and system of this invention will be capable to perform home networking even if the home coaxial wiring is not connected to a regional CATV plant 201, but is instead connected to a TV antenna, or even has no TV function. However, in such cases, the home network will not allow the capability of connecting the home outside through the CATV system, as done by the HMCM unit 206 in this example.

The HomeCN operation modes are determined according to the existence or non-existence of notch filter 202 at the home entrance. The notch filter in the entrance of the home is a one of the basic element in the home network design. If this notch filter exists the HomeCN is disconnected from the regional cable network, therefore it design is more simple (single home network). When this filter not exists the home network is part of the regional network, therefore it design is more complicated, and some additional functionality is required. According to this preferred embodiment of the invention, the HomeCN supports two operation modes:

• Single Home operation mode—This mode requires notch filter 202, or alternatively an amplifier that supplies similar functionality, or can be operated in a system that does not connected to the CATV plant.
• Connected Home operation mode—This mode does not require notch filter 202. This mode is more complex and additional functionality. required in the Connected Home operation mode include: Wider frequency operation, frequency selection (Frequency Division Multiplexing, or FDM), multiple bandwidth, privacy, all capabilities be managed by the headend as will be described below.
  Notch filter 202 can be a passive component or an active component, perhaps including management and other additional functionality. One example of an additional functionality is interrogation of whether notch filter 202 is present. This query can be used by the HCNP to verify the type of operating mode that should be handled, if the components can operate according to either of the two modes. The use of notch filter 202 will typically reduce the price and improve the performance of the home network.

Preferably, the default operation mode is Single Home. The management system configures the components to the appropriate mode after initialization. The Connected Home operational mode is recommended only if it is managed by the headend (CMTS).

FIG. 3 presents a Home Networking network at a customer premises, that does not connected to the Regional Cable infrastructure. Instead, it is connected to a local antenna 301. This system operates in Single Home operational mode.

FIG. 4 presents HomeCN with Local Cable HUB 401 that connects the HCNUs and the HCNIs. This system also operates in Single Home operational mode.

FIG. 5 presents a typical channel allocation, for example, to provide a system that supplies TV channels, DOCSIS CM (US and DS), and HomeCN channels. In this FIG. 5, some of the HomeCN channels have a different width. HomeCN components that are work in the single home operation mode (reduced mode) are always using the 900-906.25 MHz channel. These components do not support the frequency selection capability, and different channel bandwidth capability.

In the alternative, an additional mode, namely "Dual Frequencies Mode" may be available. In this mode, one frequency range is dedicated to the transmitted information and a different frequency range to received information. In this mode, a transponder at the entrance of the home transfers all the signals that are sent in the transmitted frequency-range to the received frequency-range. The major benefit of this method is a reduction in the influence of the in home echo (For more details see Dual Frequencies Mode appendix below). The HomeCN protocol is defined by specifying the two lower communication layers: the physical layer and the data link layer.

For the Connected Home and Single Home modes, the preferred frequencies and the preferred frequency ranges (bandwidth) are selected according to the operational mode:

	Connected Home	Single Home
	operation mode	operation mode

Frequency range	higher then 860 MHz;	900-906	MHz
	usually 900-960 MHz
RF channel spacing	8 MHz or lower,	6.25	MHz
(bandwidth)	according to the
	required rate

The modulation method is QPSK, QAM 16, QAM 64 or QAM 256 according to the channel conditions, and according to the equipment capabilities. The modulator of the home networking device preferably provides QPSK and QAM 16, and may provide QAM 64 and QAM 256. The modulator preferably provides a data rate of 2,560 ksym/sec., and may provide rates of 160, 320, 640, 1,280, and 5,120 ksym/sec. FEC (Forward Error Correction) functionality preferably supports R-S (Reed Salomon) T=0,10, and may support R-S (Reed Salomon) T=0, . . . ,10. Preferably, the Channel Allocation method is FDM, with a specific frequency for each home network in Connected Home operational mode, as allocated by the management system. The structure of the hybrid fiber-coax (HFC) environment is important for understanding the home networking when the system is in Connected Home operation mode, as this structure is used for enabling frequency reuse, as will be described below.

According to the preferred embodiment of the invention, the HFC system typically includes the components that will now be described relative to the exemplary arrangement of FIG. 6. In this arrangement, headend (CMTS) 601 usually with fiber output. Fibers 602 present in this HFC (Hybrid Fiber Coax) environment connect the headend 601 to the cabinets (Fiber Nodes) 603. The cabinets 603 include fiber to coaxial converters (O-E). Coaxial cable interconnects the different components 604, 606, 607, 610, 611, etc. in the system. Amplifiers 605, 608, 609 increase the signal power, and also filter the frequencies that are not amplified. These amplifiers 605, 608, 609 may or may not include splitters. In each case, the splitters 605, 608, 609, 612, 613, 614, 619, 622 receive a single wire as input, and have multiple output lines. The splitters 605, 608, 609, 612, 613, 614, 619, 622 are divided into two types: Active splitters 605, 608, 609 includes the amplifier, in combination with passive splitters that usually only divide the power between the different ports. The active splitters 605, 608, 609 are usually deployed close to the CMTS (headend) side, while passive splitters 612, 613, 614, 619, 622 are usually deployed in the house entrance and in the flats (near to the home end equipment).

However, frequency resources in the network are limited. Several methods are available to increase the frequency resources. According to the preferred embodiment of the invention, one such method, referred to as Frequency Reuse, enables simultaneous usage of the same frequency by different customers at different premises in the network. In this embodiment of the invention, the "branches" method installs or ensures the isolation of customer groups from one another, permitting these customer groups to reuse the same frequency as one another. This method uses the attenuation characteristic of the existing components, whether inherent in the cabling or installed by way of filters. Some amount of management complexity is involved in this approach, and the cable system operator should be aware of the attenuation and isolation characteristics of its physical infrastructure, both for branch calculation and also for understanding of HomeCN home network conditions. These aspects are required for the HomeCN component and protocol design.

It is believed that the branch calculation of this preferred embodiment of the invention is advantageous over other approaches, including the building of network equipment that supports a wider frequency range, because of the higher price and increased complexity of the components that are required to support such a wider frequency range.

As shown in FIG. 6, the HFC infrastructure is similar to a tree. This tree build with connection points that supplies isolation between the sub-trees. The components that exist in the network (e.g. amplifiers, splitters, and filters) tend to attenuate the signal, except for amplifiers that amplify signals, to the extent designed to amplify the required frequency in a given direction. The overall attenuation effectively isolates the sub-trees.

As noted above, the key element for efficient frequency allocation to the HomeCN is frequency reuse. To enable calculation of the frequency reuse in a different sub-trees, the term branch will be used. A branch is defined as a sub-network that can use any home networking frequency without interference from another sub-network that exists in another 'branch' and reuses the same home networking frequency. The branches are the key for frequency reuse. Branch calculation should be done before frequency allocation for each HomeCN in the global HFC infrastructure.

The cable network can be divided to 'branches' because of the signal attenuation between branches in the network tree structure. This attenuation results from the coaxial cables themselves, and also by components that include filters. Some of the splitters also provide good isolation between the sub networks that are connected to these components. Because the HomeCN is based on FDM according to the preferred embodiment of the invention, each home has its own frequency range. The ability to supply a reasonable frequency range for each home is based on the network infrastructure and on the ability to reuse frequencies after dividing the network to 'branches'. The size of the 'branches' can be reduced, and the extent of frequency reuse increased, by adding filters in the network. These filters are usually passive filters that are relatively small and can be added easily by the cable operator, or by the user at the home entrance. This mechanism of adding low cost filters at the entrance of a home or flat can be used to define a single home or flat branch, and enables also the Single Home operation mode.

The 'branches' method is very cost effective, and it increase the robustness of the home networking solution. Specifically, the 'branches' approach enables reuse of the same RF frequencies, which enables the manufactures to reduce the price of the home networking equipment, because home networking equipment can support a smaller range of frequencies. In addition, frequency reuse enables the allocation of a larger frequency range for each home or flat, thus supplying higher network capacity: A detailed description of an example of the implementation of this method will now be described.

According to this embodiment of the invention, attenuation and isolation calculations can be done by adding the attenuation of each component and the attenuation of the wire in the required pass and in the required direction. The following table (Table 1) presents the typical attenuation of the basic components

TABLE 1

Attenuation/Isolation Calculation

	Signal Attenuation [dB]
Component Type	For frequency range of 900-960 MHz
Coaxial Wiring	0.21 dB for meter (RJ 59 type). The exact isolation
	depends on wiring quality, and attenuation depends
	on cable length and the signal frequencies used.
Passive 1:N splitter	g - Insertion loss: 10log10(N): Theoretical
(FIG. 21a)	3(N = 2), 6(N = 4), 9(N = 8)
	Example of real values 4.2(N = 2), 8.2(N = 4),
	12.5(N = 8)
	P - backward attenuation of downstream amplifier:
	10log10(N): 3(for N = 2), 6(for N = 4),
	9(for N = 8)
	r - Isolation: typically 20-30 depending on the
	quality
Active splitter,	g - downstream amplifier gain: 10log10(N):
including two	3(for N = 2), 6(for N = 4),
diplexers, amplifiers	9(for N = 8), plus amplifying functionality.
both directions,	p - backward attenuation of downstream
and a 1:N passive	amplifier: - 55 dB. (Lower when
splitter	power supply is disconnected.
(FIG. 21b)	r -: 20-30 corresponding to the quality
	(higher in better quality)
Notch Filter	g - 40-60 dB
(FIG. 21c)	p - 40-60 dB
	r - 0.5 dB or 19 dB according to the design

Components' Parameters

Component	Parameter	Value [dB]	Comment
Wires (RG-59 RG-6	dB/meter	0.21
RG-7 RG-11)

Passive splitter		N = 2	N = 4	N = 8
	Insertion Loss	4.2	8.2	12.5
	Isolation	22	25	30	20-30
	Return Loss	11	11	12
Notch Filter	Return Loss	10

Following some typical calculations based on FIG. 6 and Table 1, for a system that does not include a notch filter:

Typical loss between two apartments

Case 1. Loss between two modems in the same flat

sharing the same splitter [from 615 to 616]:

Wires [meters] 20	4.2
Splitter Isolation (n = 4) [612]	25
Total [dB]	29.2

Case 2. Loss between two modems in

neighbor homes [from 615 to 617]:

Wires [44 meters]	9.24 10 m [home 612] + 2*12 m [flat
	to basement] + 10 m [home 613]
Insertion Loss (n = 4) [612]	8.2
Splitter Isolation (n = 8) [608]	30
Passive splitter Insertion	8.2
Loss (n = 4) [613]
Total [dB]	55.64

The loss between two modems that required to pass amplifier is more then 60 dB, because the amplifier contains filter for the frequencies in the up stream direction.

The capability to calculate the attenuation between two different homes or flats is important for enabling efficient frequency reuse. The cable operator should do the calculation of the "branches". The calculation of the 'branches' can be done by the following methods:

• Numerical Calculations—Calculations that are based on a priori knowledge of the cable operator. The cable operator can do calculations that are based on its network structure and its network components.
• Defining Basic Rules—The operator can define some base rules that usually work, and divide the network to branches according to these rules. Examples of rules include i) each port that connects directly to a filter/amplifier unit specifies a "branch"; and ii) Homes and flats that are connected using passive filters are on the same "branch".
• Measurements using special equipment—The cable operator can use spectrum measurement equipment. This equipment will usually be used to enable the cable operator to define the rules according to its own infrastructure.
• Measurements using HCNM Branch Calculation Mode The cable operator can use a specific mode of the home networking equipment that enables 'branch' calculation. This mode will now be described in detail.

Each HCNM should have a specific HCNM Branch Calculation Mode that enables the management system to calculate each 'branch' member. This mode would permit the operations of: i) locking on a specific frequency and specific frequency range; ii) transmitting a signal of a known pattern at a specific power for a specific period; iii) measuring the power of the input signal, at the known pattern and over the known measurement period. The algorithm is based on the structure of the cable infrastructure. A tree data structure is built in the computer memory. This tree data structure represents the existing infrastructure, and is built according to a set of rules, an example of which includes:

• Tree nodes are the splitters (the splitters can be active or passive). The splitter capability to isolate between two sub-trees is saved as data in these