`
`(12) United States Patent
`Landry et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,151,575 B1
`Dec. 19, 2006
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`(54)
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`WIRELESS EXTENSION FOR CABLE
`TELEVISION SIGNALS
`Inventors: Michael William Landry, San Diego,
`CA (US); Itzhak Gurantz, San Diego,
`CA (US)
`Assignee: Entropic Communications, Inc., San
`Diego, CA (US)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 503 days.
`Appl. No.: 10/621,884
`
`Notice:
`
`Filed:
`
`Jul. 17, 2003
`Related U.S. Application Data
`Provisional application No. 60/397,056, filed on Jul.
`18, 2002.
`Int. C.
`(2006.01)
`H04N 5/38
`(2006.01)
`H04N 7/8
`U.S. Cl. ........................... 348/723; 725/81: 725/78
`Field of Classification Search ................ 348/723,
`348/724, 725; 725/81, 82,78, 85
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,682,195 A * 10/1997 Hendricks et al. ............ 725/31
`6,263,503 B1* 7/2001 Margulis ..................... 725/81
`2002/0038459 A1
`3/2002 Talmola et al. ............... 725/81
`
`* cited by examiner
`Primary Examiner Michael H. Lee
`(74) Attorney, Agent, or Firm—Michael W. Landry
`
`(57)
`
`ABSTRACT
`
`A wireless link provides an extension to cable television
`signals for a television receiver that does not have access to
`a coaxial cable. Analog and digital cable channels are
`processed and transmitted over the wireless link. Security of
`the signal is provided by transmitting encrypted data and
`decrypting at the receiving node. The conditional access
`encryption inherent in the data can insure communication
`security or encryption may be performed at the transmitting
`node.
`
`5 Claims, 9 Drawing Sheets
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`U.S. Patent No. 7,589,642
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`U.S. Patent
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`
`Dec. 19, 2006
`Dec. 19, 2006
`
`Sheet 1 of 9
`Sheet 1 of 9
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`US 7,151,575 B1
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`Sheet 9 Of 9
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`Fig.9
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`
`
`1.
`WIRELESS EXTENSION FOR CABLE
`TELEVISION SIGNALS
`
`US 7,151,575 B1
`
`RELATED APPLICATIONS
`
`This application claims priority from United States pro
`visional patent application entitled “Wireless extension to
`coaxial television signal Ser. No. 60/397,056 filed Jul. 18,
`2002.
`
`10
`
`BACKGROUND
`
`15
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`25
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`30
`
`35
`
`1. Field of the Invention
`The present invention relates to transmitting analog and
`digital television signals over a wireless link.
`2. Prior Art
`Coaxial cable has a large signal bandwidth enabling
`transmission of many channels, which allows cable televi
`sion service providers to offer a broad range of programming
`to subscribers. Many cable television systems offer analog
`TV channels and digital TV channels. Analog channels are
`occupied with programming of established over the air
`stations, programming Supported by advertising, or pro
`gramming desired by most Subscribers. Some premium
`services are offered on analog channels that use scrambling
`or blocking to unauthorized users. Digital channels offer
`better utilization of the frequency spectrum, potentially
`higher quality images, and robust security against unautho
`rized reception. Many premium services are transmitted on
`digital channels. Digital programming is commonly trans
`mitted using Motion Picture Experts Group (MPEG) encod
`ing and formatting. The bit rate of an MPEG encoded video
`signal may be approximately 1.5 Mbits/S to 15 Mbits/S and
`generally includes a digital audio signal. An in-home receiv
`ing system must Support reception of both analog and digital
`channels from the cable system.
`Wiring must be installed in homes and each television
`must be connected to the cable to receive the cable system
`signal. Installing wiring in an existing structure when adding
`new television receivers or moving their location presents a
`cost burden and inconvenience to the user.
`FIG. 1 shows a typical wiring configuration of a home
`wired with coaxial cable. The cable signal enters the home
`45
`at a point of entry (POE). A splitter divides the signal power
`and drives coaxial cables run to each room. A set top box
`may be used to convert the signal, or the cable may be
`connected directly to a cable ready television receiver. A
`coaxial cable must be run to each room where a television
`50
`is used.
`U.S. Pat. No. 5.936,660 by Gurantz entitled “Digital
`Video Converter Box for Subscriber/Home with Multiple
`Television Sets', incorporated herein by reference, discloses
`a distribution technique for digital video programming to
`multiple television receivers. This reference includes a Sug
`gestion of a wireless RF link to transmit the video program
`to the television. This reference does not address the need to
`distribute both analog and digital video programming in the
`home. This reference discloses the use of a single chassis
`containing conditional access for all televisions and elimi
`nates set-top converter boxes at each television. Authoriza
`tion of each television signal is done at the central distribu
`tion point before transmission to the television set. The focus
`of the reference is primarily for distribution over cable and
`does not address the need for secure transmission over the
`wireless RF link.
`
`40
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`2
`It is desirable to overcome the cable wiring difficulty to
`enable the analog and digital programming available from
`the cable service to be sent to any television receiver in the
`home.
`
`SUMMARY OF THE INVENTION
`
`A wireless connection is created between a coaxial cable
`outlet and a television receiver at a remote location. In a
`sending unit, a tuner responsive to a remote control interface
`selects an RF channel for reception. The RF channel may be
`an analog TV channel with a single program or a digital
`channel that comprises several programs. The sending unit
`comprises two signal processing paths to enable selection of
`either channel type. A digital demodulator and MPEG
`demultiplexer extract one or more MPEG programs from a
`digital channel MPEG stream. An MPEG encoder converts
`an analog channel to an MPEG program. A selector applies
`the MPEG program from one of the two paths to a modulator
`and transmitter. A wireless link transmits the MPEG infor
`mation. At the remote location, a receiving unit converts the
`transmitted signal to an MPEG stream and an MPEG
`decoder produces a signal to drive a television set. A remote
`control uses an IR or RF wireless command link to select the
`channel tuned. The device may include conditional access to
`enable receiving protected programming. Conditional
`access information is transmitted over the wireless link, if
`needed. Frequency selection, power control, device identi
`fication, and network identification is used to maintain
`privacy and avoid interference between links operating
`within range of each other.
`The wireless link may operate using a custom protocol or
`may be used with a wireless network standard Such as
`IEEE-802.11. While MPEG encoding is used as an example,
`other digital video encoding techniques can be used with the
`invention.
`In one embodiment, conditional access incorporated into
`the cable programming provides the security for the wireless
`link. In another embodiment, encryption is added by the
`transmitting node to insure link security. The conditional
`access information is transmitted over the link to the
`receiver.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a diagram of a prior art cable wiring configu
`ration.
`FIG. 2 is a diagram of a cable wiring configuration using
`a wireless extension to a cable outlet in accordance with the
`present invention.
`FIG. 3 is a block diagram a wireless link in accordance
`with the present invention.
`FIG. 4 is a block diagram of a wireless link using multiple
`tuners and receivers according to the present invention.
`FIG. 5 is a block diagram of an alternate embodiment of
`a wireless link that recodes the signal from both digital and
`analog channels.
`FIG. 6 is a block diagram of an alternate embodiment of
`a wireless link where conditional access is decoded in the
`sending unit and transmitted as a parallel channel to the
`receiving unit.
`FIG. 7 is a block diagram of a wireless link that encrypts
`digital data transmitted over the wireless link.
`FIG. 8 is block diagram of a modulator and transmitter.
`FIG. 9 is a block diagram of a receiver.
`
`
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`US 7,151,575 B1
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`3
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`4
`vision as baseband signals or modulated to a standard TV
`channel frequency before coupling to the television.
`Remote control 360 is preferably located near television
`320 and is commanded by the user to select channels. The
`remote control signal is communicated to sending unit
`remote interface 230.
`Wireless link access is limited, since the conditional
`access is in the receiving unit. This provides security to
`prevent unauthorized receiving units from accessing the
`program data.
`FIG. 4 shows an embodiment of the invention using
`multiple tuners in the sending unit. This allows one cable
`drop connection to connect to the sending unit and extract
`multiple channels for transmission over the wireless link.
`Framing 270 combines the several streams of digital data
`and adds frame formatting, which includes address infor
`mation that allows receiving units 358 and 359 to select the
`proper signal. Remote control interface receives 230
`receives a signal from either remote controls 360 or 361.
`This configuration allows transmitting several signals over
`the link, each independent signal containing addressing to
`determine which of several receiving units decode the
`signals. Two or more tuner and signal processing paths may
`be included in a sending unit. The remote control units can
`operate on different UHF frequencies or the same frequency
`with an occasional collision in signals. A remote control
`identifier is sent with the remote control data to insure that
`the correct remote control signal is controls the proper
`respective tuner.
`FIG. 5 shows an embodiment of the invention using an
`alternate encoding technique for the video signal. MPEG
`decoder 240 converts the demultiplexed MPEG stream to an
`analog signal. Signal selector 239 routes the selected analog
`or decoded digital signal to encoder 242, which outputs a
`digital signal to the modulator and transmitter. The alternate
`encoding technique is useful when the wireless link is
`optimally utilized with a data rate different from that offered
`by the MPEG encoding. The link may have more or less
`available bandwidth than required by an MPEG encoded
`signal, thus an alternate coding may be used. The wireless
`link may be restricted in bandwidth and another video
`compression technique is needed. Such as Wavelet transform
`encoding. An example Wavelet compression device is an
`Analog Devices Inc. ADV601 video codec. Wavelet trans
`form compression can achieve a high compression ratio with
`good image quality. Decoder 342 is the complementary
`Video decoder that converts the encoded signal to a signal
`suitable for driving the television.
`FIG. 6 shows an alternative where the conditional access
`(CA) information is decoded from the tuner output by CA
`decoding 280. This is applicable when the CA signaling is
`transmitted out of band from the tuned channel or the data
`is not embedded in the MPEG stream. The CA information
`is combined with the digital video information to be trans
`mitted over the wireless link. The receiving unit communi
`cates the CA information to CA unit 384 to enable access to
`the video data.
`Unauthorized devices are denied network access and are
`prevented from receiving information unless commanded
`from the network controller. In one embodiment, data is
`transmitted in the clear and the operation of the client device
`disables the receipt and processing of the restricted infor
`mation if the address of the message indicates that it is not
`intended for the client. This provides a moderate level of
`security because the operation of the device is controlled by
`hardware and software functions that are not generally
`accessible to a user.
`
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`Referring to FIG. 2, splitter 100 divides power among
`several cables, which are connected to set top boxes (STB)
`110 or directly to televisions 122. STB 110 tunes a channel
`and delivers a signal to television 120. Wireless link sending
`unit 200 receives the cable signal, tunes a specific channel
`and transmits digital information using transmitting antenna
`210. Receiving antenna 310 receives the signal, receiver 300
`tunes and decodes the link signal, and Supplies a signal to
`television 320.
`Referring to FIG. 3, tuner(s) 220 preselects, amplifies, and
`down converts one or more cable channels, typically 6 MHz
`wide each. The tuning process performed by tuner 220 is
`15
`Substantially the same for analog and digital channels; the
`channel tuned can be an analog channel or a digital channel.
`The tuner output can be at an intermediate frequency (IF) or
`baseband. Alternatively, two separate tuners can be used,
`one optimized for analog channels and one optimized for
`digital channels. Digital demodulator 232 processes the
`tuner output signal if the channel is a digital signal. MPEG
`encoder 234, which includes a video decoder, processes the
`signal if the tuner output is an analog channel and creates a
`digital MPEG signal. Both signal processing paths can
`attempt to process the signal. Digital demodulator 232
`outputs an MPEG multiplex data stream to MPEG demul
`tiplexer 236 that selects one or more programs from the
`stream. Under control of control unit 230, data selector 238
`routes one of the signal path digital data streams to modu
`30
`lator and transmitter 250. Modulator/transmitter 250 con
`tains a digital modulator, up converter, and power amplifier
`to drive transmitting antenna 210 with an RF signal. Tuner
`220 can tune more than one channel and MPEG demux 236
`can select more than one program.
`Remote control interface and control unit 230 is respon
`sive to wireless remote control signal, preferably either an
`infrared (IR) or RF signal or both. Any common UHF
`remote control signal and protocol is suitable for this inter
`face. Remote control interface contains logic to select an
`analog or digital signal processing path. Alternatively, it is
`possible to re-multiplex the output of the MPEG encoder
`with one or more of the MPEG demultiplexed channels from
`the digital tuned channel to form an MPEG stream. The
`determination of which channels are analog or digital can be
`based on a channel lineup programmed in the sending unit
`or by determining, using control logic circuitry, which signal
`processing path has detected a lock on the tuner output
`signal. A lock detector is an included function in a digital
`demodulator and an MPEG decoder encoder.
`User settings including channel selection, power level,
`network and device identification, encryption keys, and
`other user selected parameters can be made through
`Switches, remote control commands, or a data programming
`interface such as USB, RS-232, or Ethernet.
`Receiving antenna 310 receives the wireless link signal
`and couples the signal to receiver 350, which amplifies,
`down converts, and demodulates the RF signal. A digital
`output signal is produced that drives MPEG demultiplexer/
`decoder 340. Conditional access (CA) unit 382 is used to
`decrypt any encrypted fields of the MPEG data to enable
`decoding. MPEG data can include embedded conditional
`access information to enable unlocking the signal or the CA
`information may be transmitted in other portions of the
`digital data stream. MPEG decoder 340 produces a video
`and audio signal suitable for display on a television receiver.
`The video and audio signal may be connected to the tele
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`In order to have a higher level of security and prevent
`interception of the signal by unauthorized users, data can be
`transmitted with encryption that requires a decryption key in
`order to receive and process the data. In a key-based
`encryption system, both the sender and receiver must pos
`sess the same key, or keys derived from a common source.
`An unauthorized user would not possess the decryption key
`and would not have access to the data. A number of well
`known techniques for encrypting data and transmitting keys
`can be employed. The keys can be manually programmed
`into the sender and receiver or keys exchanged between
`units using well known public key algorithms. Encryption
`using private key techniques include CAST 128 bit, IDEA
`128 bit, DES, Triple-DES 168 bit. Public key exchange
`techniques include Diffie-Hellman, ElGamal, RSA, and
`PGP. Encryption can also be performed by simple scram
`bling operation.
`Encryption is discussed generally in Stinson, Douglas R.,
`Cryptography Theory and Practice, CRC Press, Inc. 1995
`The following documents, each of which is incorporated
`herein by reference, further disclose encryption techniques
`suitable for use with the present invention:
`U.S. Pat. No. 4,200,770 Cryptographic Apparatus and
`Method, Hellman et al.
`U.S. Pat. No. 4,218,582 Public Key Cryptographic Appara
`tus and Method, Hellman et al.
`U.S. Pat. No. 5.299,263 Two-Way Public Key Authentica
`tion and Key Agreement for Low-cost Terminals, Beller et
`al.
`U.S. Pat. No. 4,424.414 Exponentiation Cryptographic
`Apparatus And Method, Hellman et al.
`U.S. Pat. No. 4,405,829 Cryptographic Communications
`System and Method, Rivest et al. (RSA)
`Digital Signature Standard (DSS), Federal Information
`Processing Standards Publication 186-1, Dec. 15, 1998,
`National Technical Information Service, U.S. Department of
`Commerce, Springfield, Va. 22161. FIPS PUB 186-1.
`40
`Conditional access techniques are described in the fol
`lowing references; each is incorporated herein by reference:
`U.S. Pat. No. 6.292,568, Akins, III, et al., Representing
`entitlements to service in a conditional access system: U.S.
`Pat. No. 6,157,719, Wasilewski, et al., Conditional access
`system.
`Conditional access information is transmitted in various
`ways from the cable head end to the home. Among the
`techniques for transmitting CA information are: a parallel
`out of band channel, in-band signaling using vertical blank
`ing interval (VBI) or subcarriers, embedded in digital video
`information. When needed, the CA information is sent by the
`transmitting node of the link to the receiving node to be used
`by the CA unit for unlocking the signal.
`FIG. 7 shows an alternative embodiment in which encryp
`tion is performed on the wireless link data in the sending unit
`and decryption is performed in the receiving unit. Encryp
`tion unit 290 performs encryption prior to transmitting the
`data. An encryption key is provided by the control unit,
`which receives the key or key selection information from a
`user setting interface.
`The receiving unit can be programmed with a user
`selected unique key over the user settings interface of the
`sending unit. A corresponding key is programmed into the
`receiving unit over a user setting interface 391. The remote
`control can be used to load keys into the sending or receiving
`units.
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`Alternatively, a private key can be programmed into the
`receiving unit through user setting interface 391. A public
`key is computed in the receiving unit and transmitted to the
`sending unit to be used for encryption of the digital data. A
`wireless link communicating from the receiving unit to the
`sending unit would be employed for this purpose, which
`requires only a low data rate capability.
`FIG. 8 shows details of a modulator and transmitter
`suitable for use with the invention. Digital data modulation
`and transmitting is well known. The video data is preferably
`transmitted as digital data. Encryption may be performed on
`the data. Modulator 251 maps the digital data to analog
`symbols suitable for the modulation type used. Up converter
`253 translates the symbol signal to an RF frequency. To
`enable operation of several units within communication
`range of each other, the RF frequency is selectable by the
`user setting under control of control unit 252. The frequency
`choices can be within any available or authorized band,
`preferably an unlicensed band commonly used for short
`range low power links.
`Power level of the transmitter can be adjustable to avoid
`interference with other links. Power amplifier 254 has a
`power level setting controlled by control unit 252. Power
`amplifier 254 drives antenna 210 to transmit the wireless
`link signal.
`In operation, a user can adjust the transmitted power to
`achieve robust transmission to the receiving device. It is
`desirable to use the minimum level of power required in
`order to reduce interference with other similar links. An
`example of operation of the power level setting function has
`the initial power set to lowest power level and commands
`initiated by remote control increase the power level in
`predetermined increments until the picture is viewable. The
`control logic can increase the power level an additional
`amount to provide margin and assure a viewable picture if
`minor adjustments are made to the position of the transmit
`ting or receiving terminal.
`The data formatting and modulation techniques used to
`transmit the encoded video data can be selected from among
`the many techniques well known in the art for transmitting
`and receiving digital data. Examples of modulation tech
`niques include on-off keying (OOK), amplitude modulation
`(AM), amplitude shift keying (ASK), frequency modulation
`(FM), frequency shift keying (FSK), Gaussian minimum
`shift keying (GMSK), binary phase shift keying (BPSK).
`quadrature phase shift keying (QPSK), quadrature partial
`response (QPR), quadrature amplitude modulation (QAM),
`vestigial sideband (VSB), orthogonal frequency division
`multiplex (OFDM), code division multiple access (CDMA),
`ultra-wide band (UWB), and numerous variations of these
`modulation types.
`The sending unit digital modulator and receiving unit
`demodulator incorporate error correction coding and decod
`ing, respectively to insure error free communication over the
`wireless link. Compressed video data is particularly sensi
`tive to data errors. If an error occurs in a critical part of the
`data stream, Small regions of the screen may be affected or
`an entire frame may be affected. Error correction coding can
`be used to insure that error free communication occurs. Error
`correction coding and decoding is well known in the art.
`Examples of error correction coding techniques include
`Reed-Solomon coding (RS), convolutional coding, trellis
`coding, turbo coding, and concatenated combinations of
`these coding techniques such as RS followed by convolution
`coding. Data interleaving can be used to increase the effec
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`US 7,151,575 B1
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`tiveness of error correction coding. Error detection coding
`can be employed using check Sums or cyclic redundancy
`codes (CRC).
`FIG. 9 shows details of a receiver for use in the present
`invention. Tuner 351 preselects, amplifies, and down con
`verts the received signal. Digital demodulator 353 converts
`the signal to digital data Suitable for decoding by the video
`decoder. Control 352 sets tuner frequency and digital
`demodulator parameters.
`The wireless extension can also be used in conjunction
`with direct broadcast satellite (DBS) television service.
`Analog over-the-air television signals can be selected and
`combined with digital satellite channels and transmitted over
`the wireless link to a receiving unit. The wireless sending
`unit can be incorporated into a DBS set top box.
`What is claimed is:
`1. A wireless extension for transmitting analog and digital
`television signals from one location to another comprising:
`a sending unit comprising:
`a remote control interface for receiving a channel
`selection command;
`at least one tuner for receiving both analog and digital
`television signals responsive to the remote control
`interface with an RF input and a tuner output;
`a digital demodulator for receiving the tuner output and
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`producing a digital stream containing MPEG
`encoded program information;
`an MPEG demultiplexerfor receiving the MPEG infor
`mation from the digital demodulator and selecting at
`least one MPEG program to produce a first MPEG
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`Stream;
`an MPEG encoder receiving the tuner output and
`producing a second MPEG stream;
`a selector for selecting between the first MPEG stream
`and the second MPEG stream, wherein an active
`MPEG stream is selected;
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`a digital lock detector in the digital demodulator for
`detecting a digital signal lock condition;
`an analog lock detector in the MPEG encoder for
`detecting an analog signal lock condition;
`control logic circuitry responsive to the digital lock
`detector and the analog lock detector with an output
`to the selector to select an active MPEG stream from
`the stream indicating a lock condition; and
`a modulator and transmitter for producing an RF signal
`to transmit the selected MPEG stream;
`a receiving unit comprising:
`a receiver for receiving the RF signal; and
`an MPEG demultiplexer/decoder for demultiplexing
`the desired program and converting the MPEG pro
`gram to a signal Suitable for driving a television
`receiver.
`2. The wireless extension of claim 1 further comprising:
`in the sending unit a means for encryption of the selected
`MPEG program; and
`in the receiving unit a means for decryption of the
`received signal.
`3. The wireless extension of claim 2 further comprising:
`a public key exchange wherein a public key is transmitted
`from the receiving unit to the sending unit.
`4. The wireless extension of claim 1 further comprising:
`in the receiving unit a conditional access unit that receives
`information to enable decoding of the MPEG program.
`5. The wireless extension of claim 1 further comprising:
`in the sending unit a programmable transmit power level
`circuit responsive to power level commands from the
`remote control.
`
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