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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to cable television apparatus, and more
particularly to a converter with remotely modifiable functionality
provided by downloadable firmware.
As will be apparent from the following specification, the term "firmware"
is used herein to describe functional operating software that is
downloaded to a converter or other device and stored in nonvolatile
memory. Until the downloaded "firmware" is changed, it resides in hardware
(i.e., nonvolatile memory) just like conventional firmware. This concept
of downloaded "firmware" is intended to emphasize that the present
invention provides modifiable functionality in systems that heretofore
could not be modified due to their reliance on permanent firmware.
Cable television converters are currently available that allow a cable
system operator to remotely control subscriber service authorizations from
a central "headend" site. These units, which are commonly referred to as
"addressable converters", allow the cable system operator to control
access to various premium services by sending a control signal from the
headend to individual converters located at subscribers' homes. The
authorization signals are carried on the cable television system, and
enable individual subscribers to view programs that they pay an additional
fee for. In operation, the control signals typically enable the converter
to descramble the premium channels for viewing by the subscriber.
Other addressable systems currently available allow a limited set of
operational parameters to be downloaded to a converter from the headend.
Such operational parameters include, for example, information that maps
displayed channels to tuned channels, time-out periods, barker channel(s),
the converter output channel, the terminal configuration, and
enable/disable functions for subscriber features such as remote hand-held
control, parental control, favorite channel recall, volume control, and
the like. The current state of the art is to download configuration
information for a set of features that have been predetermined at the time
of manufacture or installation of the cable television converter. An
example of such a converter is the Model DPV7200 addressable converter
manufactured by the Jerrold Division of General Instrument Corporation,
Hatboro, Penna., U.S.A.
Other systems with downloadable data capabilities are also known. U.S. Pat.
No. 4,054,911 to Fletcher, et al. relates to an information retrieval
system capable of capturing packets or rows of video displayable data
and/or control program instructions from data continuously transmitted in
a common predetermined format. In the system disclosed in the patent, a
user decides what information is to be retrieved, and takes action to
cause a terminal to retrieve that information. Although a user can vary
the function of the terminal by capturing different transmitted data, it
is the user that determines what video displayable information is to be
received, and how the terminal which receives this information is to
process it. There is no disclosure or provision of means to enable a
system operator to establish the functional operation of individual
terminals on a multi-terminal network.
In commonly owned U.S. Pat. No. 4,712,239 to Frezza, et al. entitled
"Security Arrangement for Downloadable Cable Television Converters",
incorporated herein by reference, a downloadable converter is disclosed
that prevents a false booter image from being downloaded. A false image
could subject the system to various integrity problems, such as enabling
an unauthorized user to view premium programs. In the patented system, a
booter image is received on one channel and a checksum is computed
therefrom. A valid checksum, extracted from tag data transmitted on a
separate channel and associated with a scrambled program signal, is
compared with the computed checksum. If the checksums do not match, a
descrambler in the converter is precluded from descrambling the program
signal. The system disclosed in this patent downloads all of the operating
software to a cable television converter over a dedicated "booter
channel", to which the converter is force tuned when first turned on.
After the download is complete, the converter's data receiver is returned
to the regular data channel, where it remains until the converte is turned
off.
It would be advantageous to provide a method and system for downloading
firmware to a remote terminal, such as a cable television converter, to
allow modification of virtually any or all firmware functions of the
terminal by the system operator. It would be further advantageous for such
a method and system to enable the system operator to replace or modify
options that were predetermined at the time of manufacture or installation
of the terminal. By effecting terminal modifications automatically from a
headend location, such a method and system would eliminate the need for a
technician to travel to a subscriber's home to modify or physically
replace a subscriber's terminal to effect such functional modifications.
The present invention provides such a method and system for remotely
modifying the functionality of a cable television converter or other
terminal.
SUMMARY OF THE INVENTION
In accordance with the present invention, a cable television converter with
remotely modifiable functionality is provided. The converter includes
means for receiving firmware downloaded over a cable television network,
and means coupled to the receiving means for storing the firmware. Means
are provided for verifying the integrity of the firmware, and processor
means coupled to the storing means accesses and executes the firmware to
provide one or more converter functions dictated by the firmware.
Nonvolatile memory means are coupled to the processor means for storing
default operation software for the converter. Means responsive to the
verifying means cause the processor means to execute the default operation
software, instead of the downloaded firmware, in the event the integrity
of the firmware is not verified.
Data receiving means may be provided for obtaining instructions downloaded
over a cable television network. Downloaded firmware is received and
stored by the converter only in response to specific instructions received
by the data receiving means.
The firmware receiving means and data receiving means can comprise a
frequency agile data receiver, together with means for selectively tuning
the receiver, to receive instructions on a first channel and downloaded
firmware on a second channel. Timer means return the receiver to the first
channel if the receiver has been tuned to the second channel for a
predetermined time period. The predetermined time period may be specified
in instructions received on said first channel, and the length of the time
period may be dependent on an amount of firmware to be received. In this
manner, a converter will not become stuck on the second channel by error,
and be rendered unable to receive further instructions on the first
channel.
The downloaded firmware received and stored by the converter can implement
a functional layout on a keyboard associated with the converter. Firmware
can also implement a feedback function, such as an LED
(light-emitting-diode) display or on-screen display to assist a user in
operating the converter. A control function for a video recorder coupled
to the converter can also be implemented by the firmware. Similarly, the
firmware can implement a communication protocol for the converter, a
descrambling technique for the converter, an on-screen display to be
provided by the converter to a television coupled thereto, and/or a user
interface to services provided over the cable television network.
In a preferred embodiment of the present invention, firmware is transmitted
in an encrypted form, and the instructions contain a key for decrypting
the firmware. The firmware may also be received by the converter in a
plurality of segments, with the instructions identifying the number of
segments to be received for a complete firmware download. Means can be
provided for determining if all of the segments have been validly
received, and for receiving replacement segments if one or more segments
of the firmware have not been validly received. Receipt of firmware can be
prevented if the number of segments identified by the instructions is
greater than a predetermined limit.
Cable television headend apparatus is provided for downloading firmware to
an addressable, remotely modifiable cable television converter. Means are
provided for transmitting addressable converter data on a first data
channel of a cable television network. Means are provided for transmitting
firmware on a second data channel of the cable television network. An
address specific to a particular converter is provided in the addressable
converter data, which enables specific data to be received by the
converter. Instructions are provided in the specific data, to cause the
converter to receive firmware transmitted on the second channel.
The cable television headend apparatus can further include means for
verifying that firmware downloaded to the converter has been successfully
received by the converter. Billing means maintain records of the cable
television services each converter on the system is authorized to receive,
and the various functions the converter is to have, and can assign a
particular firmware package to be downloaded to a particular converter on
the basis of the functions specified for that converter.
A method for providing a cable television converter with functions dictated
by downloaded firmware is also provided. Converter control data is
received from a remote location via a cable television network. A
designated firmware package is captured from a set of firmware packages
carried on the cable television network, in response to instructions
contained in the converter control data. The designated firmware package
is stored in a memory provided in the converter, and is executed to
provide at least one converter function dictated thereby.
The firmware packages may be carried on the cable television network in
encrypted form, and decrypted using a key contained in the converter
control data. In one embodiment, the converter control data is received on
a first data channel and the firmware packages are captured from a second
data channel on the cable television network. The first channel is
monitored to receive converter control data, and the second channel is
tuned to capture firmware upon receipt of appropriate instructions on the
first channel. Reception is returned to the first channel after the
firmware is captured. If the firmware has not been captured within a
predetermined time period, reception switches back to the first channel
from the second channel.
Also in accordance with the present invention, a remotely modifiable user
terminal is provided which comprises means for receiving a plurality of
cyclically transmitted firmware segments, the segments together comprising
a firmware package. Means coupled to the receiving means verify each
segment upon receipt thereof, and means are provided for storing each
verified segment. A determination is made as to whether a complete
firmware package has been stored in the storing means at the completion of
a firmware transmission cycle. If not, then reception, verification, and
storage of transmitted firmware segments continues during a subsequent
firmware transmission cycle. Reception of the firmware segments is
terminated upon a finding that a complete firmware package has been
stored. Means can further be provided for precluding the execution of
firmware segments until a complete firmware package has been stored.
The verifying means can operate by testing a checksum for each firmware
segment as it is received. The terminal may further comprise means for
maintaining a record of the proper checksum for each segment, and means
for periodically retesting the checksums after a complete firmware package
has been stored. Default operation software may be stored for the
terminal, and executed if the checksums are not verified upon retesting.
The complete firmware package may also be verified after it has been
stored, and the default operation software executed if the complete
firmware package is not valid. The default operation software may also be
executed if reception of firmware segments is not completed during a
predetermined time period.
A complete firmware package may include a plurality of modules. Execution
of fewer than all of the modules may be precluded as an additional
security feature.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a functionally modifiable cable television
converter system in accordance with the present invention;
FIG. 2 is a block diagram of the pertinent elements of a converter used in
connection with the system of the present invention;
FIG. 3 is a flowchart illustrating steps taken by the headend when it
receives a new firmware package or an assignment to download firmware to a
converter;
FIG. 4 is a flowchart illustrating the continuous transmission of firmware
over a secondary data channel;
FIG. 5 is a flowchart illustrating the steps taken by a converter in
receiving downloaded firmware; and
FIG. 6 is a flowchart illustrating the periodic reverification of
downloaded software by a converter.
DETAILED DESCRIPTION OF THE INVENTION
Turning to FIG. 1, a cable television system is depicted having headend
components, generally designated 10 and subscriber components, generally
designated 12. The headend communicates with the subscriber via a
distribution cable 36. A firmware development system 16 is used to create
new functional firmware packages for subscriber terminals, such as
converter 40. Firmware development system 16 may be physically located at
the headend, but is more typically located at the facilities of a vendor
which develops new firmware programs for sale to a cable system operator.
New firmware packages may be transferred to an addressable controller 14
located at the headend by magnetic tape 20 which is read by addressable
controller 14, or by communication between the firmware development system
16 and addressable controller 14 via direct connection or modems 18
operating over conventional telephone lines. Those skilled in the art will
recognize that other means may also be available for transferring firmware
from firmware development system 16 to addressable controller 14.
Once firmware is resident in addressable controller 14, it is transmitted
repeatedly over a data channel. The data channel may be either the primary
addressable data channel provided in a conventional cable television
network having addressable converters, or a separate secondary data
channel. In either event, the data channel(s) can transmit the data on an
FSK modulated FM carrier or by any other suitable transmission scheme well
known in the art.
The use of a secondary channel for downloading firmware to converters is
illustrated in FIG. 1. Control signals, including data such as converter
addresses, program authorization codes, and the like is communicated from
addressable controller 14 to a converter 40 via control data modulator 26.
The output of control data modulator 26 is coupled to distribution cable
36 via a tap 34, and data is received therefrom by converter 40 via tap
38. The control data modulator transmits the data signals on a primary
channel, and in accordance with the present invention, the data includes
instructions to converter 40 which cause the converter to receive
specified firmware downloaded from addressable controller 14.
In the two channel embodiment illustrated in FIG. 1, the firmware is
transmitted on a secondary channel by firmware modulator 24, coupled to
the cable network at tap 30. Upon receipt of instructions on the primary
channel, converter 40 switches to the secondary channel for receipt of
designated firmware. An additional data path 28 may optionally b provided
via tap 32 for receipt of data from converter 40 by addressable controller
14. Such data might include, for example, a verification that converter 40
has successfully received a firmware package it has been instructed to
receive. The provision of a return path 28, which provides a "two-way"
cable communication system, is well known in the art.
Billing system 22 is provided at the headend for maintaining accounting
information relating to charges incurred by subscribers on the cable
system. In accordance with the present invention, different firmware
packages downloaded by headend 10 to converter 40 may provide different
converter functions, with higher levels of service providing increased
converter functionality. Billing system 22 keeps track of the level of
service for each subscriber, and assigns particular firmware packages to
subscriber converters on the basis of converter functionality to be
provided to each subscriber.
At the subscriber location 12, a subscriber may have one or more video
appliances 42, 44 coupled to the output of converter 40. For example,
video appliance 42 might be a television set, and video appliance 44 might
be a video recorder ("VCR"). In accordance with the present invention,
firmware downloaded to converter 40 can provide functions relating to a
VCR. An example of such a function is time controlled programming. This
function enables the converter to be programmed to make channel changes at
various times so that the VCR can record different television programs on
different channels automatically and while unattended. Such a function can
also enable "impulse pay-per-view" orders to be programmed into the
converter by a subscriber, so that special premium programs can be
ordered, when the subscriber is not home, and recorded on the subscriber's
VCR for later viewing.
FIG. 2 is a block diagram illustrating the pertinent components in one
embodiment of a converter 40 in accordance with the present invention. In
the embodiment illustrated, the converter receives addressable data on one
data channel and downloaded firmware on another data channel. It is noted
that in another embodiment of the invention, both the addressable data and
the firmware can be received over a single data channel. Or, the firmware
may be carried on some other media, such as the public telephone network.
In the two channel embodiment illustrated in FIG. 2, a microprocessor 50
receives data from cable 36 via a frequency agile receiver 52. A
transmitter 61 and return path 62 can be provided from microprocessor 50
back to addressable controller 14 in the event the converter is used with
a two-way cable television system. Like receiver 52, transmitter 61 can be
frequency agile to enable a choice of return transmission frequencies.
A tuner 54, under the control of microprocessor 50, tunes frequency agile
receiver 52 to either a primary channel for receipt of addressable data
(e.g., instructions to capture a particular firmware package) or to a
secondary channel for the receipt of firmware. Although a single secondary
channel is described herein for purposes of illustration, it will be
appreciated that any number of such secondary channels can be provided,
depending on system requirements. Typically, frequency agile receiver will
be tuned to the primary channel, and will only switch to the secondary
channel upon specific instructions contained in data received on the first
channel. In the alternate embodiment where both addressable data and
firmware are received on a single data channel, frequency agile receiver
52 and tuner 54 can be replaced with a fixed frequency data receiver.
The provision of a dedicated secondary data channel as illustrated in FIG.
2 is advantageous. By keeping firmware data off of the primary channel,
the data throughput load on this channel is reduced.
In the two channel embodiment, firmware data is broadcast cyclically on the
second channel, by addressable controller 14 at the headend. In a
preferred embodiment, a plurality of different firmware packages are
broadcast on the secondary channel, each package providing different
converter functions or combinations of functions. Upon receipt of
instructions on the primary channel, microprocessor 50 will cause tuner 54
to switch receiver 52 to the secondary channel for receipt of a designated
firmware package.
Various memory devices are coupled to microprocessor 50, including read
only memory ("ROM") 56, operating random access memory ("RAM") 58, and
nonvolatile firmware RAM 60. ROM 56 contains a program that allows
converter 40 to retrieve and execute a downloaded firmware package. Upon
receiving the proper command from the addressable controller, the
converter aborts any downloaded package currently being executed, accesses
the appropriate data channel for receipt of a designated firmware package
to be downloaded, and receives and loads the firmware into nonvolatile
firmware RAM 60.
ROM 56 also contains default operation software, which is used to restore
the converter to a nominal or "baseline" operation if a bad firmware
download occurs. As explained below, if an error is detected in the
receipt of downloaded firmware, or if the firmware is found to be invalid,
the converter is forced to execute only the default operation software
stored in ROM 56.
A timer 64 is associated with microprocessor 50 to provide a time-out
feature that prevents the converter from getting stuck on the secondary
channel, in the event there is a problem receiving specified firmware.
When billing system 22 assigns a new firmware package to a particular
converter 40, addressable controller 14 is commanded to transmit
instructions to the converter. The instructions are received by
microprocessor 50, and include an identifier specifying which firmware
package to receive, where to find the firmware package (i.e., on the
primary or a specified secondary channel), a predetermined time limit
defining how long the converter should attempt to receive the firmware
before aborting, a key to use in decrypting the data in the event it is
encrypted, and the maximum segment number to be loaded (indicating how
many segments are included in the firmware package to be received). While
the firmware is being received, timer 64 counts down the time-out period
specified in the download command. If the timer expires, microprocessor 50
aborts the download, and returns to the original data channel. The
time-out period specified in the download command can be varied depending
on the amount of firmware to be downloaded.
Timer 64 is also used in connection with a self-check that is periodically
performed by the converter to ensure that the firmware has not changed
since the last authorized download. This self-check is a security feature
to guard against infiltration of the converter by a "software pirate" who
attempts to download unauthorized software to the converter, in an effort
to steal services from the cable system.
In accordance with the self-check procedure, timer 64 retests the checksum
for each of the firmware segments at regular intervals after the firmware
has been downloaded. In the event a checksum is found to be invalid,
microprocessor 50 restores the converter to baseline operation by
executing the default operation software contained in ROM 56.
Converter 40 contains various other components with functions that can be
modified by downloaded firmware. For example, a light-emitting-diode
("LED") display or other display 66 may be provided on the converter to
give a user feedback concerning converter operations. Pressing a button on
the converter, or its remote control unit, can cause an LED to light,
verifying that the button has been pressed or that a function to be
activated by the button has occurred. Such a feedback function is useful
to assist a user in operating the converter.
The converter also includes a keyboard 68, the functional layout of which
can be defined and/or modified by firmware downloaded to the converter.
Keyboard 68 may be physically on the converter box, on a remote hand-held
unit for the converter, or a separate keyboard can be provided in both
places.
Converter 40 also includes a descrambler 70 for descrambling premium
programs received via the cable television network. Various descrambling
techniques are well known in the art, and different techniques can be
implemented by downloading different firmware to the converter.
Another feature that can be provided by converter 40 is the display of
information on a user's television set. On-screen display driver 72 is
provided for this purpose. An example of such a display is the channel
number tuned to, or the current time. In addition, on-screen displays can
be used to distribute messages from the cable system operator, e.g., "your
account is past due; please send us a check". An electronic mail, or
"E-mail" feature can also be provided, enabling a subscriber to send and
receive text messages on his television (or other display) via the cable
system. The implementation and/or modification of on-screen displays can
be provided by firmware downloaded to the converter.
In order to provide a measure of protection against illegal use of the
firmware download feature, the firmware is downloaded to the converter in
an encrypted form. The data is decrypted at the converter by a decryption
module 74. A decryption key is transmitted to the converter from the
headend as part of the addressable data instructions that command the
converter to receive a particular firmware package. Encryption and
decryption schemes are well known in the art. Examples of such schemes are
provided in commonly owned U.S. Pat. No. 4,638,356 of William A. Frezza,
entitled "Apparatus and Method for Restricting Access to a Communication
Network", and U.S. Pat. No. 4,710,955 of Marc W. Kauffman, entitled "Cable
Television System with Two-Way Telephone Communication Path". Both of
these patents are incorporated herein by reference.
A viewership monitor 76 can be provided in accordance with the present
invention to enable a cable system operator to determine what programs and
services a subscriber has received using each converter, and/or to
retrieve a list of the functions which have been used on each converter.
Viewership monitor 76 will monitor the operation of the converter, and
store pertinent data relating thereto. By addressing an appropriate
command to the converter, the cable system operator will be able to upload
the data to the headend for analysis.
Other functions that can be implemented by firmware downloaded to the
converter include communication protocols for the converter, and user
interfaces to services provided over the cable television network. For
example, a user may be provided with the capability to order pay-per-view
programs on an impulse basis. The procedure for ordering such programs can
be modified through downloadable firmware. Utility meter reading can also
be provided, by adding an asynchronous data port to the converter and
controlling the retrieval of utility data via downloaded firmware.
A flowchart illustrating a routine which can be used by the addressable
controller in connection with the receipt and downloading of firmware is
provided in FIG. 3. The routine begins at box 80, and at box 82 a
determination is made as to whether a firmware update has been received
from the firmware development system. If so, control passes to box 84 and
the new firmware data is encrypted. At box 86, the encrypted data is
loaded into the secondary data channel transmitter (firmware modulator 24)
and continuously transmitted on the secondary channel together with other
firmware packages that can be provided to converters on the system.
At box 88, a determination is made as to whether a new firmware package
assignment has been made by billing system 22. If so, addressable
controller 14 sends an appropriate command on the primary channel (control
data modulator 26) as indicated at box 90. The command is addressed to the
particular converter that is to receive the firmware, and identifies the
channel the firmware is to be received from, identifies the firmware
package to be received, provides the decryption key necessary to decrypt
the firmware data, identifies the number of segments which make up the
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