EP1743484A2

EP1743484A2 - System and method for cable localization

Info

Publication number: EP1743484A2
Application number: EP05703155A
Authority: EP
Inventors: Dan Revital; Edmond Shapiro; Andrew Valentine
Original assignee: NDS Ltd
Current assignee: Synamedia Ltd
Priority date: 2004-03-24
Filing date: 2005-01-31
Publication date: 2007-01-17
Also published as: WO2005089057A2; KR20060130736A; WO2005089057A3; EP1743484A4

Abstract

A method and system for determining cable network topology for a plurality of set-top boxes connected to the cable network, the method comprising using existing information transmitted within the cable network for a non-location purpose to determine an absolute physical location of at least one set-top box within the topology. Related methods and apparatus are also described.

Description

SYSTEM AND METHOD FOR CABLE LOCALIZATION

FIELD OF THE INVENTION

The present invention relates to a system and a method for cable

localization.

BACKGROUND OF THE INVENTION

Many different types of content are currently distributed to users over a

cable television system, in which a set-top box for a television set is typically

physically connected to a cable network. The cable network connects these

boxes to central head-ends, which transmit the content itself. Although this

system requires that the cable be laid, usually underground, it is nonetheless a

cost effective and efficient method to distribute content. In addition, such cable

networks are now also used for broadband connections, which enable

households to receive high bandwidth Internet connections. Such high

bandwidth connections are becoming increasingly popular with consumers,

thereby reinforcing the popularity of cable networks.

However, in order for cable networks to operate efficiently, the physical

location of the set-top box, relative to the appropriate cable head-end, must be

detemiined. Such localization is important for new services and applications,

such as targeted advertisements for example, which are preferably transmitted

only to a particular area or location. Unlike the IP addressing system, which

is used for the Internet for example, the topology of current cable networks does not include routing techniques or specifically assigned addresses.

Instead, cable networks use transport streams from the cable head-end

through the network to the set-top boxes. Different transport streams may be

used for transmission from the same head end to set-top boxes at different

physical locations, such that the transport streams themselves do not represent a

permanent addressing mechanism, again unlike the IP system. A typical

physical implementation of a cable network will include an HFC (hybrid fiber

coaxial) connection from the cable head-end to a node, which is like a

substation. This type of cabling is more expensive than older coaxial cable and

may transmit many different frequencies (typically 500-2000). From the node

to the set-top boxes, often older coaxial cables are used, which cables are more

limited in number of frequencies (typically about 120). Each frequency

represents a transport stream; however, all frequencies which are transmitted on

the cable connection to the set-top box are also transmitted to each connected

set-top box, because of the lack of addressing in the system.

One potential solution is to use a smart card for each set-top box to

determine the location of the box within the cable network. This smart card

would be sent to each subscriber at a particular postal address; since the postal

address would be known, the smart card could transmit information to the cable

head-end about the physical location of the set-top box. However, such a

system would clearly be open to fraud and abuse, at least with regard to this

aspect of the system.

Furthermore, the location of the node or substation for the cable network may differ even between neighboring houses. The granularity requirement for

the cable network is quite high, much higher than for satellite television

transmission. For example, the footprint of the satellite may cover an entire

country, continent, or other large area. By contrast, cable networks require the

precise location of small groups of set-top boxes (physical locations) to be

determined, on the order of about 2000 set-top boxes or less. Therefore, an

external mechanism to determine the absolute physical location of set-top

boxes is required.

Another attempted solution to this problem required a GPS (global

positioning system) device to be attached to each set-top box. The GPS device

could then determine the physical location of the set-top box. For example, US

Patent No. 6,108,365 to Philip A. Rubin and Associates, Inc. describes a

system in which the GPS determines the location of the set-top box, which also

receives location-specific signals from the central control, based upon the

expected location of the set-top box. US Patent No. 6,009,116 also to Philip A.

Rubin and Associates, Inc. describes a similar system. However, this solution

is clearly expensive and impractical.

Yet another attempted solution to this problem is to embed information

in the transport stream itself. For example, some VOD (video on demand)

vendors have a solution for implementing VOD over cable networks, which

involves storage of proprietary information in the storage location used by the

transport stream identifier in a normal broadcast in order to be able to identify

the specific set top box that is to receive the VOD content; however the inclusion of this information may lead to ambiguity because more than one

transport stream might have the same identifier. Therefore, this solution is

clearly not desirable.

Important reasons for being able to determine the location of a set-top

box within a cable network system include but are not limited to the

requirement for different channel assignments in some areas. For historical and

regulatory reasons, particularly in crowded urban or suburban areas, a

particular channel assignment must be maintained. For example, the weather

reporting could be assigned to channel 1, while sports are assigned to channel

2. Many of these fixed channel assignments arose from their implementation

for analog broadcast transmissions, before the advent of digital cable. In order

to retain these assignments, a mapping table is used by the set-top box.

Therefore, different tables must be sent to set-top boxes in different

neighborhoods. Again, knowledge of the absolute physical location of the set-

top box within the cable network is required.

Another example is the requirement in some areas for a "blackout" of

particular programming, even if neighboring areas are allowed to receive it.

For example, games or matches in sports are often restricted by physical area;

if a sports team fails to sell enough tickets to a "home" game in its city, the

team may have an agreement with a television broadcaster to not transmit the

game to local set-top boxes. However, since many programs are broadcast

nationally through cable television, a mechanism is required to prevent a set-

top box in the city of the sports team from receiving the game. Such a "blackout" can only be implemented if the absolute physical location of the set-

top box within the cable network system is known.

Thus, clearly a solution to the problem of being able to determine the

location of a set-top box within a cable network system is required. However,

all of the currently proposed solutions are also clearly unsatisfactory.

SUMMARY OF THE INVENTION

None of the background art solutions teaches or suggests a mechanism

to determine the absolute physical location of a set-top box without requiring

additional hardware. In addition, none of the background art solutions teaches

or suggests a solution which is low cost, efficient and also enables the location

to be determined through a mechanism that is at least partially external to the

set-top box itself.

Therefore, there is an unmet need for, and it would be highly useful to

have, a system and a method for determining the absolute physical location of a

set-top box within a cable network system. By "absolute physical location" it

is meant the physical (rather than logical) location of the set-top box according

to a certain degree of granularity (precision). The method and system of the

present invention, in certain preferred embodiments thereof, meet this need by

determining the absolute physical location of a set-top box within a cable

network system.

The method and system of the present invention, in certain preferred

embodiments thereof, operate to determine the relative cable network topology,

with regard to the location of individual set-top boxes within the topology, at

least partially according to existing information that is already passed within

the system, for example through OOB (out-of-band) messages, which are not

sent with the transmitted content. The information is external to the set-top

boxes, which do not need to be preconfigured and/or configured with an

internal or additional device (such as a smartcard for example). Rather, the information is passed during routine transmissions between the set-top box and

the cable head-end. Thus, unlike other background art methods described

previously, the present invention, in certain preferred embodiments thereof,

does not require special information to be inserted into transport streams

between the set-top box and the cable head-end. The present invention, in

certain preferred embodiments thereof, is preferably implemented with a

system which is capable of two-way transmissions between the set-top box and

the cable head-end and/or another network component under at least some

circumstances. According to a preferred embodiment, the present invention uses the

upstream channel identifier assignment mechanism to identify set-top boxes by

location, optionally and more preferably combined with a mapping mechanism

which optionally and most preferably derives information from the ability of a

set-top box to identify an assigned DOCSIS upstream channel identifier, and to

retrieve the LEP (localization entry-points) mapped to this upstream channel

identifier. This LEP is then used for determining further localization dependent

identifiers and assignments. Such an upstream channel identifier is used for

cable networks featuring two-way transmission, in which each set-top box also

preferably features an embedded cable modem. Alternatively, mapping of the set-top box may optionally be performed

by using the cable-headend assigned out-of-band downstream channel to the

set- top box. It should be noted that generally, inband and out of band channels

may be distinguished as follows, across different types of technologies. Inband refers to the primary use of a standard or type of technology for

communication, while out of band refers to any additional use, for example for

sending control signals and/or other messages. Transport streams are inband,

while the downstream channel and upstream channel are out of band for the

purposes of the present application. This out of band channel or channels is

then used to determine other types of location information about the set-top

box.

For example, the head-end may broadcast a plurality of LEPs. A newly

connected set-top box would receive a particular LEP, by virtue of the set-top

box's location within the network. Preferably each LEP would be mapped to a

particular node and/or other subset of the cable network system. The cable

head-end could then optionally broadcast a table, containing mapping

information, for which the LEP would be the key. Preferably the LEP is

mapped one-to-one with the upstream channel identifier in a two-way system.

The set-top box would therefore be self-located within the system, although it

would not be able to verify this location by a return message to the cable head¬

end without the optional embodiment of two-way transmissions. The LEP

could also be used for other types of self-location functions by the set-top box. The mapping (and hence localization of the set-top box) enables such

services as targeted advertisements to be provided, since the advertisement

server is able to use the mapping information to determine which set-top

box(es) should receive a particular advertisement. For example, an

advertisement would optionally and preferably be targeted to a particular neighborhood (group of set-top boxes), as the physical location or area which is

to receive the advertisement could preferably be selected according to the

mapping information.

The present invention, in certain preferred embodiments thereof, has the

benefit of being strongly resistant to cheating or unauthorized manipulation,

because an incorrect upstream channel identifier and/or using an incorrect out-

of-band downstream channel would prevent the set-top box from operating

properly.

The system and method of the present invention, in certain preferred

embodiments thereof, may optionally be used with any appropriate type of

cable network system, as well as with any appropriate type of transmission

protocols and/or applications which operate over such a system. Various

illustrative examples are given herein of the operation of such protocols and

applications with regard to the system of NDS Limited (United Kingdom);

however, it is understood that these examples are given for the purposes of

description only and are not meant to be limiting in any way.

US Patent Nos. 5,282,249 and 5,481,609, describe effective security

mechanisms for the system of NDS Limited with which the present invention,

in certain preferred embodiments thereof, may optionally operate and which are

hereby incorporated by reference as if fully set forth herein. The disclosed

system enables a signal containing media content to be broadcast widely, yet

only to be played back or otherwise displayed by authorized users. This signal

could contain a television program for example. The signal is scrambled, such that the authorized users are able to descramble the signal and play back or

otherwise display the media content only with the proper security device, such

as a smart card for example. Thus, widely received media content is still

protected from access by unauthorized users. The scrambled television data streams described in US Patent Nos.

5,282,249 and 5,481,609 feature both scrambled data representing television

signals and coded control messages, also known as ECMs. These ECMs contain, in a coded form, data necessary for generating a control word (CW) which may be

used to descramble the scrambled data representing television signals. The

disclosed system enables a signal containing media content, such as a television program for example, to be transmitted widely, yet only to be played back or

otherwise displayed by authorized users.

Data necessary for generating a control word is known in the

background art to take many different forms and may include, in general, at

least any of the following: a control word; an encrypted control word packet

which is intended to be decrypted before use; and a seed to a generating

function such as, for example, a one-way function which generates the control

word upon input of the seed.

While US Patent Nos. 5,282,249 and 5,481,609 describe an analog

system, that is, a system in which analog television data streams are broadcast

to television sets, it is appreciated that similar ECM methods may also be used

for digital television data streams. Generally, the scrambling techniques used

for scrambling analog television signals such as, for example, the well-known

"cut-and-rotate" technique, are chosen for their particular applicability to analog signals. However, scrambling of digital television signals preferably

employs other techniques, which are well-known in the art and which are more

appropriate to digital signals. One example of such a technique is the

application of the well-known DES algorithm to the digital television signals.

Other examples include the well-known triple DES algorithm and the DVB

(digital video broadcasting) CSA (common scrambling algorithm).

Methods of transmitting a scrambled digital signal, including ECMs and

EMMs, are described in the MPEG-2 standard, ISO/IEC 13818-1, 15 April

1996 and subsequent editions. Another attempted solution to the problem of content protection is

described in published European Patent Application No. EP 0858184 and

corresponding US Patent 6,178,242, which disclose a digital recording

protection system and which are hereby incorporated by reference as if fully set

forth herein. The disclosed system enables the digital content to be sent in a

scrambled format, such that the digital content cannot be read and/or displayed

without a key. The key is obtained from a control message, which is only sent

to authorized users. Preferably, the key is obtained from coded information

contained within the Entitlement Control Message, or ECM, for generating a

code word associated with the ECM. Thus, only authorized users are able to

correctly read and/or display the digital content.

In addition, the system and method described in European Patent

Application No. EP 0858184 enable the authorized user to record and playback

or otherwise display the digital content, while preventing the user from producing and distributing multiple playable copies of the digital content to

other, non-authorized users. Therefore, the authorized user is able to fully use

and enjoy the digital content, while the content itself is still protected from

unauthorized use. The present invention, in certain preferred embodiments thereof, may

optionally operate with the previously described background art systems as

follows. An EMM (entitlement message) may need to be sent to subscribers,

for example for targeted advertisement applications, in order for the set-top box

to be able to use the correct ECM for decoding the content. A general

broadcast of all EMM's to all set-top boxes would require too much bandwidth.

It is therefore desirable to select EMM's for broadcast according to the cable

topology. For example, EMM's may be transmitted according to the node

alone or according to a group of nodes, or according to the hub. All of these

components represent portions of the cable network, such that the EMM's only

need to be sent to the relevant portion of the set-top boxes in the network and

not to all set-top boxes. Thus, the ability of the present invention to determine

the physical location of the set-top box may optionally be used to increase the

efficiency of transmitting EMM's and/or other messages to the set-top boxes.

The disclosures of all references mentioned above and throughout the

present specification are hereby incorporated herein by reference.

For preferred embodiments of the present invention, a software

application could be written in substantially any suitable programming

language, which could easily be selected by one of ordinary skill in the art. The programming language chosen should be compatible with the

computational device according to which the software application is executed.

Examples of suitable programming languages include, but are not limited to, C,

C++, Java and Assembly. In addition, preferred embodiments of the present invention could be

implemented as software, firmware or hardware, or as a combination thereof.

For any of these implementations, the functional steps performed by the

method could be described as a plurality of instructions performed by a data

processor. In addition, for the software implementation, the functional steps

performed by the method could be described as a plurality of instructions

performed by a computer software product.

Hereinafter, "Applied Cryptography" by Bruce Schneier, John Wiley

2nd ed. 1996, is incorporated by reference as if fully set forth herein, for the

teachings regarding cryptography and techniques for implementation thereof. There is thus provided in accordance with a preferred

embodiment of the present invention a method for determining cable network

topology for a plurality of set-top boxes connected to the cable network,

including using existing information transmitted within the cable network for a

non-location purpose to determine an absolute physical location of at least one

set-top box within the topology.

Further in accordance with a preferred embodiment of the present

invention the cable network features two-way transmissions, such that the using

the existing information includes listening for an identifier by the at least one set-top box, and transmitting the identifier in an upstream transmission by the

at least one set-top box for identifying the at least one set-top box.

Still further in accordance with a preferred embodiment of the present

invention the listening for the identifier includes receiving mapping

information by the at least one set-top box, and listening to at least one

transmission frequency selected according to the mapping information.

Additionally in accordance with a preferred embodiment of the present

invention the mapping information includes a LEP for analysis of the mapping

information. Moreover in accordance with a preferred embodiment of the present

invention the LEP is used as a key for the mapping information.

Further in accordance with a preferred embodiment of the present

invention the using the existing information includes transmitting a message on

an OOB (out of band) channel. Still further in accordance with a preferred embodiment of the present

invention transmitting an EMM to a portion of the cable network topology

according to the LEP.

Additionally in accordance with a preferred embodiment of the present

invention transmitting a targeted advertisement to the at least one set-top box

according to the at least one LEP.

Moreover in accordance with a preferred embodiment of the present

invention receiving a FIPS code according to the LEP, and determining an

emergency message according to the FIPS code. Further in accordance with a preferred embodiment of the present

invention associating a transport stream with a region for a user according to

the LEP.

Still further in accordance with a preferred embodiment of the present

invention assigning a LEP according to a UCID (upstream channel identifier)

for at least one set-top box for localizing the at least one set-top box.

Additionally in accordance with a preferred embodiment of the present

invention determining at least one location-based or location-sensitive

assignment according to the LEP. Moreover in accordance with a preferred embodiment of the present

invention determining at least one location-based or location-sensitive message

according to the LEP.

Further in accordance with a preferred embodiment of the present

invention providing an advertisement to the at least one set-top box according

to the LEP.

Still further in accordance with a preferred embodiment of the present

invention the assigning the LEP is performed by a DSG Server, communicating

with a DSG Client at the at least one set-top box.

There is also provided in accordance with another preferred embodiment

of the present invention a plurality of transmission channels, wherein each set-

top box is capable of listening to at least one transmission channel but not to all

transmission channels, the system including a cable network component for

transmitting data to the transmission channels, wherein the transmitted data differs between at least two of the transmission channels, a map for mapping

information concerning a relative location of at least one set-top box within the

topology, wherein the map is transmitted to the at least one set-top box and

wherein the transmitted data forms a key to the map, such that the at least one

set-top box is capable of determining the relative location within the topology

according to the map and the key.

Further in accordance with a preferred embodiment of the present

invention the cable network features two-way transmissions between the cable

network component and the plurality of set-top boxes, such that the

transmission channels including an upstream channel and a downstream

channel, the upstream channel featuring an upstream channel identifier, and

wherein the at least one set-top box determines a capability of communicating

on the upstream channel according to the upstream channel identifier, the at

least one set-top box transmitting the upstream channel identifier to the cable

network component and the upstream channel identifier forming a portion of

the mapping information for the map.

Still further in accordance with a preferred embodiment of the present

invention the transmitted data is transmitted for a purpose other than

determining the relative location. Additionally in accordance with a preferred embodiment of the present

invention the transmitted data includes a LEP (localization entry point).

There is also provided in accordance with a still another preferred

embodiment of the present invention a plurality of two-way transmission channels, each transmission channel featuring an upstream channel having an

upstream identifier and a downstream channel, wherein each set-top box is

capable of listening to at least one transmission channel but not to all

transmission channels, the system including a cable network component for

receiving a communication from at least one set-top box, wherein the at least

one set-top box identifies the upstream identifier of the upstream channel being

received by the at least one set-top box and transmits the upstream identifier to

the cable network component, and a map for mapping information concerning a

relative location of the at least one set-top box within the topology according to

the upstream identifier, wherein an absolute physical location of each

transmission channel within the topology is known.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with

reference to the accompanying drawings, wherein:

FIG. 1 is a schematic block diagram of an exemplary system according

to the present invention;

FIG. 2 shows a schematic block diagram of an exemplary hierarchy

according to the present invention; and

FIG. 3 shows an exemplary method for determining the physical

location of the set-top box with two-way transmissions within the cable system,

according to transmission of a LEP.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention, in preferred embodiments thereof, is of a method

and system for determining the physical location of individual set-top boxes,

preferably at least partially by using existing information that is already passed

within the system. The information is preferably external to the set-top boxes,

which do not need to be preconfigured and/or configured with an internal or

additional device (such as a smartcard for example). Rather, the information is

passed during routine transmissions between the set-top box and the cable

head-end. Thus, unlike other background art methods described previously, the

present invention, in preferred embodiments thereof, does not require special

information to be inserted into the content transport streams between the set-top

box and the cable head-end, although OOB (out-of-band) message channels

may optionally be used for message transmission. The present invention, in

preferred embodiments thereof, is preferably implemented with a system which

is capable of two-way transmissions between the set-top box and the cable

head-end and/or another network component under at least some

circumstances.

According to a preferred embodiment, the present invention uses the

upstream channel identifier assignment mechanism to identify set-top boxes by

location. Such an upstream channel identifier is used for cable networks

featuring two-way transmission, in which each set-top box optionally and

preferably also features an embedded cable modem.

Set-top boxes which operate on a cable network featuring two-way transmissions preferably receive an upstream channel identifier from the cable

head-end upon registration, which occurs when first connecting to the network

and/or rebooting the set-top box; this mechanism is used for example in

networks implemented according to the DOCSIS standard (see for example

SCTE 22-1, SCTE 23-1, or SCTE 79-1, from the SCTE (Society of

Telecommunications Engineers)). The location of the head-end is known;

furthermore, the head-end controls a known physical area, which corresponds

well with the limits of the required area within which the set-top box location

needs to be determined. A group of set-top boxes, typically (but not

necessarily) corresponding to a few hundred boxes in the same physical area,

have the same upstream channel identifiers when the network is implemented

according to the DOCSIS standard. Preferably, this group is associated with a

particular node; typically (although not necessarily) a head-end controls a

plurality of nodes, directly or indirectly (for example through a hub as

described in greater detail below). However, it should be understood that the

present invention, in preferred embodiments thereof, is also operative when the

identifier is sent to a single set-top box or a small group of set-top boxes, as

long as the set-top boxes sharing the upstream channel identifier are located

within a physical area which is sufficiently small for the purposes of the present

invention, according the requirements for localization which in turn depend

upon the use of the present invention.

The cable head-end preferably configures the list of upstream channel

identifiers that are used by DOCSIS in advance, for transmission of localization maps based on these upstream channel identifiers by the DSG Server. The DSG

Server is responsible for generating the DSG Tunnel contents that are sent to

the set-top box over a DOCSIS downstream channel. The present invention, in

preferred embodiments thereof, is preferably implemented such that necessary

information (such as various region identifiers) for the set-top boxes is also

placed in the DSG Server.

A map is then preferably determined for mapping between these pre¬

defined upstream channel identifiers and the physical location of the set-top

boxes. Such a map (containing mapping information) is preferably performed

in advance, by populating data into the DSG Server database tables.

The mapping information, or at least a portion thereof, is sent to the set-

top box through the DSG standard messaging function, such as by using DCDs

(Downstream Channel Descriptors) for example.

According to preferred embodiments of the present invention, upon

initial registration of and/or restarting the set-top box, the set-top box locates an

out of band downstream channel. The set- top box is assigned an upstream

channel identifier (UCID) by the CMTS for example, or some other type of

server (depending upon the particular implementation of the present invention)

which is preferably located at the cable head-end and/or hub. This process

could also be implemented according to reference standards SCTE 55-1 or

SCTE 55-2 for example, or according to DHCP or any other appropriate out of

band method, as can be appreciated by one of skill in the art. More preferably, each UCID is predetermined to be relevant to a

particular physical location as previously described.

Next the DSG Server sends the LEP keyed by the UCID to the set-top

box. The LEP is a logical location rather than a physical location within the

cable network. For a two-way cable network transmission system, a unique

LEP is preferably identified with each upstream channel, such that the

minimum size of any type of region (see below for examples of different types

of regions) is equal to the physical area and also the number of set-top boxes

serviced by a single upstream channel. The set-top box receives the LEP. The

DSG Server sends location dependent information and assignments keyed by

the LEP to the set-top box.

Mapping between the upstream channel identifier and the LEP enables

the absolute physical location of the set-top box to be determined and mapped.

The cable head-end sends mapping information to every set-top box, preferably

as a multicast of all sets of information for all possible upstream channel

identifiers that could be used in the physical area served by the head-end. The

set-top box then preferably accepts the mapping information according to the

upstream channel identifiers and/or according to the LEP. The LEP can

optionally and preferably be used as a key for the assignment of many other

location-dependent identifiers, optionally and more preferably for the provision

of such services as targeted advertising as previously described.

Other applications of preferred embodiments of the system and method

of the present invention, which require the determination of the absolute physical location of the set-top box include but are not limited to, determination

of the region for "black-out" purposes; determination of time zone; and

determination of location for FIPS codes (for example for DEAS (digital

emergency alert system), FIPS PUB 6-4 in the FCC decision coded as "47 CFR

FCC Part 11"). As previously described, "black-out" regions occur when a

content provider (and/or other regulatory authority) has determined that certain

content should not be provided to certain regions, for example when a sporting

event is being shown at a particular city or other region, in which case the

broadcast is often blocked for that city or region. With regard to time zone, countries such as the USA contain multiple

time zones and the region being served by the head-end may span more than

one time zone. It is therefore necessary for the set-top box to be configured

with the correct UTC (time zone) offset for the time zone in which the set-top

box is located. FIPS codes are used for broadcasting messages in case of (national or

regional) emergencies, for example for the DEAS (digital emergency alert

system), for which the FIPS codes are according to FIPS PUB 6-4 in the FCC

decision coded as "47 CFR FCC Part 11". In the case of emergency alerts,

optionally and preferably the set-top box filters the location information (FIPS

code) within the alert so that it may discard alert messages that are not relevant

to the geographical location of the set-top box. In order to provide such

filtering, the set-top box is required to be configured with the FIPS code for its

geographical region. For more information on FIPS codes see www.itl.nist.gov/fipspubs/fip6-4.htm and also FIPS PUB 6-4 in the FCC

decision coded as "47 CFR FCC Part 11", hereby also incorporated by

reference as if fully set forth herein.

Another optional but preferred embodiment of the present invention is

for EMM segregation, such that bandwidth is not wasted by transmitting

EMMs to all portions of the cable network topology, but only to those portions

that are relevant.

The principles and operation of preferred embodiments of the present

invention may be better understood with reference to the drawings and the

accompanying description, which are provided for the purposes of explanation

only and without intending to be limiting in any way.

Referring now to the drawings, Figure 1 is a schematic block diagram of

an illustrative system according to the present invention. Although the

operation of the system is described with regard to television program content,

it is understood that this is for the purposes of illustration only and is without

any intention of being limiting in any way.

As shown, a system 100 according to a preferred embodiment of the

present invention for a cable network features a cable head-end 102, shown as a

regional head-end. Head-end 102 controls and manages content transmission

over a geographical region, which typically (although not necessarily) extends

to a few thousand cable connections. Head-end 102 optionally and preferably

features a DSG Server 107 according to this exemplary, non-limiting

implementation of the present invention, although as previously described, the present invention could optionally and alternatively be implemented according

to any suitable out of band method, as can be appreciated by one of skill in the

art. Head-end 102, and preferably DSG Server 107 within head-end 102,

optionally and preferably features a targeted advertising server 106. Head-end 102 is connected to a hub 104, which preferably includes a

CMTS 108 as shown. Although only one hub 104 is shown, head-end 102 may

optionally be connected to a plurality of hubs 104 (not shown). Hub 104 in

turn is connected to a plurality of nodes 110, of which a number are shown for

the purposes of illustration and without any intention of being limiting. Each node 110 is connected to a plurality of set-top boxes 112, which

are typically (although not necessarily) about a few hundred in number. Each

node 110 serves a much more limited geographical area than each hub 104,

which in turn serves a more limited geographical area than each head-end 102.

Hub 104 optionally communicates with each node 110 through a high

bandwidth fiber link 114, which is capable of carrying a high number of

different frequencies of transport streams. Typically (although not necessarily),

each node 110 in turn communicates with set-top boxes 112 through a lower

bandwidth cable connection 116, which may for example be coaxial cable.

Therefore, each node 110 optionally communicates to set-top boxes 112 with a

lower number of frequencies for transport streams than are available to hub

104. Of course, these are all non-limiting, illustrative examples of the physical

layer.

System 100 is preferably implemented according to a standard, such as the DOCSIS cable standard for example, which enables two-way transmissions

under at least certain circumstances, for example between set-top box 112 and a

CMTS 108, which normally resides in hub 104 but may optionally reside in

head-end 102. Such transmissions pass through node 110, which then relays

them to hub 104.

The present invention, in preferred embodiments thereof, enables the

absolute physical location of each set-top box 112 within system 100 to be

determined, without any additional device being added to set-top box 112,

according to information already passed between CMTS 108 and set-top box

112.

The present invention, in preferred embodiments thereof, optionally and

preferably operates by using OOB (out-of-band) messages for communication

with set-top boxes 112 and head-end 102 and or hub 104. OOB messages are

preferred because in certain markets such as the US, both analog and digital

channels are delivered by cable; in-band messages cannot be delivered on

analog channels, but only when set-top box 112 is connected to a digital

channel. OOB messages perform a number of different functions, including

subscriber service authorizations and providing system information for set-top

box 112, which are both implemented by sending one-way messages (from

head-end 102 and/or hub 104 to set-top box 112). Subscriber service

authorizations include EMMs (Entitlement Management Messages), which are

used to deliver various authorizations to set-top box 112 (for example and

without intending to be limiting, a smart card within set-top box 112, not shown) in order to permit set-top box 112 to receive and access content for

which the subscriber is authorized.

Other types of one-way messages include, but are not limited to, channel

and frequency maps, digital emergency alert messages (FIPS codes) and

software download version tables.

Location-based and/or location-sensitive services, on the other hand,

preferably feature two-way messages; indeed, more advanced such services

require two-way messages. Accurately determining the physical location of

set-top box 112 also is preferably performed by using two-way messages for

implementations with system 100 featuring two-way transmissions. Therefore,

the implementation of two-way communication, such as for advanced location-

based and/or location-sensitive services for example, also enables OOB

messages to be used for determining the absolute physical location of set-top

box 112. The present invention, according to a preferred embodiment, optionally

and preferably operates by enabling set-top box 112 to connect to system 100

through an upstream channel, identified by an upstream channel identifier

within system 100. According to a first preferred implementation with a LEP,

system 100 is a two-way transmission system, such that the LEP functions as

follows. A unique LEP is identified with each upsfream transport channel, such

that the minimum size of any type of region (see below for examples of

different types of regions) is equal to the physical area and also the number of

set-top boxes 112 serviced by a single upstream transport channel. In order to be able to provide the LEP to a newly connected set-top box

112, preferably a map is prepared which describes the relationships between

cable head-end 102, an upstream channel identifier and a LEP for each hub

104. Hub 104 optionally and preferably contains a DSG Agent 120 for

interacting with DSG Server 107. The mapping is therefore more preferably

performed for each DSG Agent 120, and is also more preferably stored in the

MIB (management information database; not shown) associated with each DSG

Agent 120.

DSG Server 107 preferably has its own identifier, termed herein the

region identifier, which is preferably used to determine regional time zones and

other information when performing the mapping functions. Other types of

regions which may be important include but are not limited to, billing vendor

regions (for example from acquisition of multiple smaller cable vendors by a

larger vendor), franchise regions which may be required by regulatory

authorities in relation to particular groups of channels and/or channel

numbering as previously described, and municipal regions (state and/or county

and/or city, or other groupings) which are related to broadcast of emergency

messages. Some of these regions may be concurrent with the region of hub

104; others may need to be identified within the topology of system 100 itself. The map preferably includes a relationship between one upstream

channel identifier and one LEP, such that each upstream channel identifier

maps to only one LEP, while one LEP optionally maps to many upstream

channel identifiers. Of course, a one-to-one mapping between each LEP and each upstream channel identifier may optionally be performed.

At least a portion of the mapping information is then transmitted to each

set-top box 112, for example by being sent to the associated cable modem

embedded in set-top box 112 (not shown). Hub 104 optionally may send only

the portion of the mapping information that is relevant for the particular set-top

box 112, or alternatively may send all mapping information.

Optionally, the mapping information is sent over a DSG Tunnel. A

DSG Tunnel is an IP datagram stream, originating at DSG Server 107. The

DSG Tunnel carries OOB messages to set-top boxes 112 over the downstream

DOCSIS channel, and is preferably identified by an Ethernet MAC address

which is assigned by the content provider related to cable head-end 102. The

present invention, in preferred embodiments thereof, preferably includes the

feature that some of the information sent over a DSG Tunnel can be associated

with a region identifier. One optional implementation of such a LEP is for targeted advertising,

as an example of a location based and/or location-sensitive service. Each node

110 preferably has an associated node identifier, which needs to be mapped to

the group of set-top boxes 112 being served by that node 110. Head-end 102

features targeted advertising server 106 as previously described, which

provides targeted advertisements to a subscriber of a particular set-top box 112

according to the physical location of set-top box 112. As previously described,

the advertisement(s) may optionally be targeted according to a neighborhood or

other physical area in which set-top box 112 is located. Also as previously described, head-end 104 is capable of

communicating with a number of different nodes 110, and needs to be able to

identify which node 110 should receive the targeted content (such as targeted

advertising). Broadcasting any type of localized content to all nodes 110 is

inefficient and wasteful.

When set- top box 112 is first connected, initially set-top box 112 is

assigned a UCID by CMTS 108. Then the LEP is retrieved based on UCID to

LEP mapping sent by DSG Server 107, and then (concurrently or sequentially)

set-top box 112 receives the mapping information between LEP and other

localization identifiers. The LEP may optionally be received and processed by

a DSG Client 113 as shown.

The present invention, in preferred embodiments thereof, is preferably

implemented such that necessary information (such as various region identifiers

and upstream channel identifiers) for set-top boxes 112 is also placed at DSG

Server 107.

DSG Server 107 then determines at least the upstream channel identifier,

and optionally and more preferably determines other information as well, such

as other region identifiers as previously described. The information also

optionally and preferably includes the location of the OOB configuration table

for retrieving mapping information. The information may optionally be

selected according to a rule base for example. DSG Server 107 preferably uses

the UCID (upstream channel identifier) to select appropriate mapping

information. The mapping information is then preferably transmitted to set-top box 112.

This optional implementation, with DSG Server 107, may also

optionally be used in combination with the LEP implementation described

previously. The process begins as previously described, except that DSG

Server 107 now selects the appropriate LEP, according to the location

(physical/geographical area) of set-top box 112 and the OOB configuration

table. Set-top box 112 then receives the LEP and parses it to use the LEP as an

index for the configuration tables, which may be retrieved or alternatively

transmitted to set-top box 112. In any case, once the LEP has been broadcast to a set-top box 112,

various implementations may optionally use this information to automatically

derive additional region information. For example, the LEP key may

optionally be used to derive information from a mapping table, related to region

specific details such as billing regions, franchise regions, targeted advertising

selection and emergency alert municipalities (see also Figure 2 for a

description). The mapping table could optionally be broadcast from cable

head-end 108 with information relevant to all LEPs associated with cable head¬

end 108.

Optionally and preferably, a plurality of nodes 110 may be contained

within a group that is smaller than the group associated with hub 104, which

smaller group is termed herein a population group. Each population group

preferably has an associated population identifier. Population groups may

optionally be used for such purposes as transmitting a multicast message, such as for the conditional access system of NDS Limited (United Kingdom).

Also optionally and preferably, an upstream channel is associated with

only one time zone, although an upstream channel may optionally be associated

with more than one extended FIPS code area (the term "extended" optionally

refers to the subdivision of emergency areas by geographic regions in the

emergency alert table). An upstream channel is preferably only associated with

one region identifier.

Figure 2 shows a schematic block diagram of these different regions in

relation to a LEP (localization entry-point) as described above. A hierarchy

200 includes a LEP 202, from which the set-top box (not shown) automatically

locates itself within the cable network system (also not shown). From the

correct upstream channel identifier 204, the set-top box preferably first

determines LEP 202. Next, the set-top box determines the time zone 206,

regional identifier 208 (for the hub, also not shown), the FIPS code 210 (for

filtering non-relevant emergency messages), and optionally other types of

regions as discussed above (not shown). Another type of information to be

selected preferably includes appropriate targeted advertising through

advertisement insertion identifier 212 as shown, thereby supporting location-

based advertising. Figure 3 describes an optional but preferred implementation of a method

according to the present invention, for determining the physical location of a

set-top box within a cable network featuring two-way transmissions within the

cable system, according to transmission of a LEP. In stage 1, the set-top box locates an out of band downstream channel

(for example according to DOCSIS if the cable network is implemented

according to this standard, and otherwise according to a method which could

easily be determined by one of skill in the art for a particular cable network). In stage 2, the set-top box is assigned an upstream channel identifier

(UCID) by the CMTS (see Figure 1).

In stage 3, the DSG Server is preferably pre-assigned a mapping

between UCID and LEP. It transmits (preferably through a multicast) this

mapping as mapping information for example, optionally and more preferably

to all set-top boxes which may optionally use this UCID.

In stage 4 the set-top box retrieves the LEP from the mapping

information, using its previously assigned UCID as a key. Preferably, the DSG

Server sends location dependent information and assignments keyed by LEP to

the set-top box (stage 5). The mapping information may optionally be sent in the form of a table

with the following optional, exemplary structure. It should be noted that this

structure is given for the purposes of description only, without any intention of

being limiting. This table would optionally be multicast by the head end on a

well-known port (1314). The repetition period for broadcast may optionally be

from about 2 to about 3 minutes for example.

Each section represents the user data area of the datagram, as for the

content of a UDP packet. The table may optionally feature multiple sections. The set-top box preferably only processes a section if the hash value has been authenticated.

Each LEP is optionally identified by a number. Preferably, LEP 0

applies to all set-top boxes and optionally carries default configuration

information that applies to the entire set-top box population. This information

is then preferably amended when the set-top box parses its specific LEP.

Therefore, the information in each section is preferably arranged in ascending

order of lep_id (identifiers for the LEP), in order for the LEP information to be

parsed in the correct order.

Once the initial localization information has been acquired, the set-top

box preferably continues to listen on the port for a change in the version

number. If the hash and CRC fields are authenticated, the new localization

information is preferably used to re-configure the set-top box.

Table 1: Cable Localization Table

Syntax No. of Bits Identifier table_id 8 Uimsbf section_syntax_indicator 1 Bslbf reserved_future_use 1 Bslbf

Reserved 2 Bslbf section__length 12 Uimsbf

Unused 16 Uimsbf

Reserved 2 Bslbf Syntax No. of Bits Identifier version number 5 Uimsbf current next indicator 1 Bslbf section number 8 Uimsbf last section number 8 Uimsbf

Nonce 4400 BBssllbbff for (i=0;i<N;i++){ lep_id 16 Uimsbf region_id 16 Uimsbf tot_region_id 6 Bslbf

Reserved 2 Bslbf fips_loop_length 8 Uimsbf for (j=0;j<N;j++){ state_code 8 Uimsbf county_subdivision 4 Uimsbf

Reserved 2 Bslbf county_code 10 Uimsbf

}

HMAC-hash 128 Uimsbf Syntax No. of Bits Identifier

CRC_32 32 Rpchof

The meanings of the fields are given below: table_id: This 8-bit field indicates the specific private table. The value

for this table is 0x82 (hex 82). section_syntax_indicator: This value is ' 1 ' according to the standard

for being a longer form. section_length: This is a 12 bit field. It specifies the number of bytes of

the section, starting immediately following the section_length field and

including the CRC. The section_length preferably does not exceed 4093 so that

the entire section preferably has a maximum length of 4096 bytes. unused: This 16-bit field is unused in this implementation, and should

be set to all Ts. version number: This 5-bit field indicates the version number of the

section. The version_number shall be incremented by 1 when a change is made

to the information carried in the section. When it reaches value 31, it wraps

around to 0. current next indicator: This value is ' 1 ', indicating 'current'. There is

no 'next' configuration information according to the DVB/SI standard. section_number: This 8-bit field gives the number of the section. last_section_number: This 8-bit field gives the number of the last

section. nonce: This 40-bit field is optional but preferred to prevent the set-top

box from being subject to 'replay' type malicious denial of service attacks.

Typically, it contains the time of creation of this section in Universal Time Co¬

ordinated (UTC) and Modified Julian (Calendar) Date (MJD) (see DVB/SI

standard EN 300 468 annex C). This field is coded as 16 bits giving the 16

LSBs of MJD followed by 24 bits coded as 6 digits in 4-bit Binary Coded

Decimal (BCD).

The set-top box preferably only accepts sections that are more recent

than the last valid section received. Any maliciously inserted section therefore

preferably is required to have a more recent nonce (preventing replays). This

data is therefore preferably only accepted with an authenticated hash field -

therefore the new section can only come from a source that knows the shared

secret. lep_id: The identifier for the LEP for which the following localization

information applies; as noted above, preferably a value of 0 indicates that the

information is relevant to all LEP's. region_id: The Regionld to which the LEP belongs, as used by the OOB

configuration table and NIT. tot_region_id: The tot_region_id is the TOT country_region_id to

which this LEP belongs. fips__loop_Iength: The length in bytes of the following FIPS code loop.

A maximum of some number of FIPS, such as 10 FIPS can be present in the

loop (see for example the standard J-STD-042-2002). state_code: Encoded according to FIPS 6-4. The value of 0 indicates all

states. county_subdivision: Encoded according to the standard J-STD-042-

2202. county_code: Encoded according to FIPS 6-4. The value of 0 indicates

the entire state.

HMAC-hash: This field is the HMAC-MD5 hash of all bytes in the

section up to, but not including the hash itself.

The hash is preferably calculated as described in RFC 2104 (for example

at www.ietf.org/rfc.html), based on repeated use of the MD-5 signature and the

use of a shared secret, to generate a 16 byte digest of the section.

The use of a hash is a preferred implementation. The purpose of this

hash function is to prevent 'Denial of Service' attacks by broadcasting a

malicious section. In conjunction with the nonce field, the hash function may also prevent

'replay' attacks.

CRC 32: This is a 32-bit field that contains the CRC value that gives a

zero output of the registers in the decoder as defined according to the DOCSIS

standard. This might be used by the set-top box - the 'hash' field provides a

data integrity check, as does the IP checksum field and so the CRC_32 could be

somewhat redundant. reserved: All reserved fields should be set to all Ts.

Table 2 shows the localization configuration table. This table contains the localization information associated with the given LEP. This information optionally and preferably includes the region identifier, node group identifier and FIPS codes for the LEP. The TOT (Time Offset Table) country region id field from the DVB/SI TOT.

Table 2: Localization Configuration Table

Column Type Values Description

LEPJD NUMBER(5) 0..65535 A unique identifier for this LEP.

REGION JD NUMBER(5) 0..65535 The region in which this LEP resides

TOT_REGION_ID NUMBER(2) 0..63 The TOT country region id for this LEP.

FIPS_STATE_ NUMBER(2) 0..99 The FIPS code for the State. CODE 0 = all states.

FIPS_C UNTY_ NUMBERβ) 0..999 The FIPS code for the County within CODE the State. 0 = all counties

FIPS_COUNTY_ NUMBER(1) 0..9 The country sub-division as specified SUBDIV in [12]. 0 = all or an unspecified portion of county

UI_DESCR VARCHAR2 Description of this LEP. (40)

NOTES VARCHAR2 ,NULL User Notes (1000)

According to other preferred embodiments of the present invention, it may optionally be used for VOD (video on demand). VOD enables a consumer to order a particular movie or other content at a convenient time, without being required to wait for a pre-scheduled transmission of the movie. The mapping information and localization of the set-top box according to the present invention enables such services as VOD to be provided, since the VOD server is able to use the mapping information to determine which transport stream should be assigned for VOD to a particular set-top box. While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations,

modifications and other applications of the invention may be made.

Claims

WHAT IS CLAIMED IS:

1. A method for determining cable network topology for a plurality of set-top

boxes connected to the cable network, comprising: using existing information transmitted within the cable network for a non-location

puφose to determine an absolute physical location of at least one set-top box within the

topology.

2. The method of claim 1, wherein the cable network features two-way

transmissions, such that said using said existing information comprises: listening for an identifier by said at least one set-top box; and transmitting said identifier in an upstream transmission by said at least one set-top

box for identifying said at least one set-top box.

3. The method of claim 2, wherein said listening for said identifier comprises: receiving mapping information by said at least one set-top box; and listening to at least one transmission frequency selected according to said mapping

information.

4. The method of claim 3, wherein said mapping information includes a LEP

(localization entry-point) for analysis of said mapping information.

5. The method of claim 4, wherein said LEP is used as a key for said mapping

information.

6. The method of any of claims 1-5, wherein said using said existing

information comprises transmitting a message on an OOB (out of band) channel.

7. The method of any of claims 4-6, further comprising: transmitting an EMM (entitlement management message) to a portion of the cable

network topology according to said LEP.

8. The method of any of claims 4-7, further comprising: transmitting a targeted advertisement to said at least one set-top box according to

said at least one LEP.

9. The method of any of claims 4-8, further comprising: receiving a FIPS code according to said LEP; and determining an emergency message according to said FIPS code.

10. The method of any of claims 4-9, further comprising: associating a transport stream with a region for a user according to said LEP.

11. The method of any of claims 1-10, further comprising: assigning a LEP (localization entry point) according to a UCID (upstream channel

identifier) for at least one set-top box for localizing said at least one set-top box.

12. The method of claim 11, further comprising: determining at least one location-based or location-sensitive assignment according

to said LEP.

13. The method of claims 11 or 12, further comprising: determining at least one location-based or location-sensitive message according to

said LEP.

14. The method of any of claims 11-13, further comprising: providing an advertisement to said at least one set-top box according to said LEP.

15. The method of any of claims 11-14, wherein said assigning said LEP is

performed by a DSG Server, communicating with a DSG Client at said at least one set-

top box.

16. A system for determining a relative cable network topology for a plurality

of set-top boxes connected to the cable network, the cable network featuring a plurality

of transmission channels, wherein each set-top box is capable of listening to at least one

transmission channel but not to all transmission channels, the system comprising: a cable network component for transmitting data to the transmission channels,

wherein said transmitted data differs between at least two of the transmission channels; a map for mapping information concerning a relative location of at least one set-

top box within the topology, wherein said map is transmitted to said at least one set-top

box and wherein said transmitted data forms a key to said map, such that said at least one

set-top box is capable of determining said relative location within the topology according

to said map and said key.

17. The system of claim 16, wherein the cable network features two-way

transmissions between said cable network component and the plurality of set-top boxes,

such that the transmission channels comprising an upstream channel and a downstream

channel, said upstream channel featuring an upstream channel identifier, and wherein

said at least one set-top box determines a capability of communicating on said upstream

channel according to said upstream channel identifier, said at least one set-top box

fransmitting said upstream channel identifier to said cable network component and said

upstream channel identifier forming a portion of said mapping information for said map.

18. The system of claim 17, wherein said transmitted data is transmitted for a

puφose other than determining said relative location.

19. The system of claim 17, wherein said transmitted data comprises a LEP

(localization entry point).

20. A system for determining a relative cable network topology for a plurality

of two-way transmission channels, each transmission channel featuring an upstream

channel having an upstream identifier and a downstream channel, wherein each set-top

box is capable of listening to at least one transmission channel but not to all transmission

channels, the system comprising: a cable network component for receiving a communication from at least one set-

top box, wherein said at least one set-top box identifies the upstream identifier of the

upstream channel being received by said at least one set-top box and transmits said

upstream identifier to said cable network component; and a map for mapping information concerning a relative location of said at least one

set-top box within the topology according to said upsfream identifier; wherein an absolute physical location of each transmission channel within the

topology is known.