Patent Publication Number: US-2005135611-A1

Title: Method and system for wireless digital communication

Description:
RELATED APPLICATIONS  
      This is a continuation-in-part of and claims priority from U.S. patent applications Ser. Nos. 10/666,724 and 10/937,162, incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates generally to wireless digital communication systems.  
     BACKGROUND  
      The wireless spectrum between 57 GHz and 64 GHz (hereinafter “60 GHz band”) is unlicensed by the U.S. Federal Communications Commission, to give organizations the opportunity, unfettered by excessive regulations, to use this spectrum for implementing wireless local area networks (LANs). The wireless LANs, in turn, can be used in a large number of applications owing to the characteristics of the 60 GHz spectrum, which include short range, high directivity (and, hence, inherent security), and large data bandwidth.  
      Originally used for covert satellite-to-satellite communications (the Earth&#39;s atmosphere severely attenuates signals with frequencies around 60 GHz), current applications for 60 GHz wireless LANs include communications between a bank customer and an automatic teller machine, “last-mile” extension of wider area networks, and many other applications in which wireless, high bandwidth, yet localized and inherently secure data communication is desired. As an example, in the first of the above-referenced U.S. patent applications, a system is disclosed for sending high definition (HD) video in High Definition Multimedia Interface (HDMI) format from a laptop computer on a table in a room to a video projector mounted on the ceiling using a high bandwidth 60 GHz link. At this frequency the signal is so short range and directional that the video may be transmitted in an uncompressed form such that so much data is transmitted each second that bootlegging the content is essentially untenable.  
      Regardless of the particular application, the present invention makes the following critical observations. In some applications, a transmitter and receiver might communicate certain high bandwidth data such as multimedia on a 60 GHz forward channel and certain low bandwidth data such as control data on a lower frequency reverse channel. As recognized herein, while the forward channel is inherently secure owing to the high frequency and directionality, the reverse channel, at a lower frequency and not amenable to as precisely controlled directionality, is not as inherently secure.  
     SUMMARY OF THE INVENTION  
      A system includes a transmitter of multimedia data and a receiver of multimedia data. The transmitter wirelessly transmits the multimedia data on a forward channel link in the sixty GigaHertz (60 GHz) band. Also, the transmitter and receiver exchange encryption information on the forward channel link. In accordance with present principles, the encryption information is used to protect data transmitted between the transmitter and receiver on a reverse channel link, which may be at approximately 2.4 GHz.  
      In one implementation the encryption information includes an encryption key, and the transmitter and/or receiver uses the key to encrypt control information prior to sending the control information over the reverse channel link. Alternatively, the encryption information can be established by a unique identifier that is combined with control information prior to sending the control information over the reverse channel link. In specific embodiments the unique identifier may be “OR&#39;ed” with the control information prior to sending the control information over the reverse channel link.  
      In another aspect, a method for transmitting data includes establishing a forward channel link and a reverse channel between a wireless transmitter and a wireless receiver. The forward channel link is inherently more directional and shorter range than the reverse channel link. The method also includes communicating encryption information over the forward channel link. Data may be altered using the encryption information and then communicated over the reverse channel link.  
      In yet another aspect, a computer includes means for communicating unencrypted multimedia data and encryption information using a wireless forward channel link in the 60 GHz band, as well as means for altering control information using the encryption information. Means are provided for communicating altered control information over a reverse channel link that is not in the 60 GHz band. The altered control information cannot be easily used by a recipient without access to the encryption information.  
      The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which:  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a block diagram showing the present system;  
       FIG. 2  is a block diagram of the detailed architecture;  
       FIG. 3  is a flow chart of one logic scheme that may be implemented by any of the processors disclosed herein; and  
       FIG. 4  is a flow chart of another logic scheme that may be implemented by a processor in accordance with he present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring initially to  FIG. 1 , a system is shown, generally designated  10 , which includes a source  12  of multimedia data, and in particular HD video. The source  12  may be a laptop computer or other multimedia computer or server that, for instance, a user may place on a table  14  in a room  16  to display the multimedia on a screen or wall  18  using, e.g., a multimedia player  20  such as a video projector that receives the multimedia over a wireless forward channel link  22 , for displaying the multimedia on the screen or wall  18  as indicated by the arrow  24 . Additional sources and/or receivers can be present in the system  10 . For example, a second source  12   a  can communicate with a second receiver  20   a  over a forward channel link  22   a . Each source may communicate with its receiver over a reverse channel link as well. While multimedia data is envisioned as being communicated over a forward channel link, other types of data are contemplated herein.  
      When the forward channel links are in the 60 GHz band, they are inherently secure because their high frequency forecloses transmission through walls and enables very precise control of the directionality of the transmitted beams. However, the lower frequency reverse channel links may not be as inherently directional, short range, and, hence, as inherently secure, and so the invention set forth below is provided.  
      In the non-limiting embodiment shown, the player  20  advantageously may be mounted on a ceiling  26  of the room  16  by, e.g., one or more mounting brackets or struts  28 , either in front of or behind the screen  18  depending on the type of player. Owing to the presently envisioned wireless link, no wiring except for power need be installed in the ceiling  26 , and the player  20  need not include an MPEG or other video decompression module.  
      Alternatively, the multimedia player may include a cathode ray tube (CRT), liquid crystal display (LCD), plasma display panel (PDP), or TFT for displaying the multimedia data. The source of multimedia data may be a set-top box like device capable of decoding compressed multimedia content as received from a satellite, cable, terrestrial broadcast, internet streaming, or other source. The data communication described herein may use digital visual interface (DVI) protocols.  
      In accordance with present principles, the link  22  is a forward channel link that carries a frequency which is sufficiently high that the signal on the link substantially cannot be received outside the room. Also, multimedia may be transmitted in an uncompressed form on the link  22  such that so much data is transmitted each second that bootlegging the content is essentially untenable, although some data compression less preferably may be implemented. The data may also be transmitted in compressed form if desired. As discussed further below, the link  22  preferably operates at a fixed (unvarying, single-only) frequency of approximately sixty GigaHertz (60 GHz), and more preferably in the range of 57 GHz-64 GHz, and the link  22  has a data rate, preferably fixed, of up to two Giga bits per second (2.0 Gbps). Various modulation schemes may increase the data rate, e.g., when DQPSK is used the data rate may be 2.2 Gbps, and the link may have a data rate of approximately 2.5 Gbps. The link may have a fixed bandwidth of up to seven GigaHertz (7 GHz). Error correction appropriate for wireless transmission (e.g., Reed-Solomon encoding) as well as appropriate re-multiplexing (e.g., by re-multiplexing twenty four lines of video and appropriate control signals into two in the case of QPSK modulation) may be implemented in some applications accordance with wireless transmission principles known in the art.  
       FIG. 2  shows further details of the system  10 . The non-limiting source  12  includes a processor  30  that accesses a data storage device  32  such as a hard disk drive, CD, or DVD to send multimedia data to a forward channel encoder  34  for encoding in accordance with principles known in the art. The encoded data is modulated at approximately 60 GHz by a 60 GHz forward channel modulator  36  and upconverted by an upconverter  38  for transmission over the link  22  at about 60 GHz through a first source antenna  40  that is configured as appropriate as a 60 GHz antenna. Using the above-described wide channel and a simpler modulation scheme such as but not limited to DQPSK, QPSK, BPSK or 8-PSK, a high data rate yet simple system can be achieved. For example, when DQPSK is used, a data rate of twice the symbol rate can be achieved. For 8-PSK a data rate of 3.3 Gbps may be achieved. If desired, a copy protect system such as high definition copy protection (HDCP) can be used with the multimedia content in accordance with HD principles known in the art.  
      The multimedia signal is received at a first player antenna  42  (configured for 60 GHz operation) on the player  20 . In accordance with principles known in the art, the signal is downconverted at a forward channel downconverter  44  and demodulated from 60 GHz at a forward channel 60 GHz demodulator  46 , and then decoded at a forward channel decoder  48  that can undertake error correction and multiplexing functions. The decoded signal may be stored in a data storage device  50  of a processor  52  of the player  20 . It will be recognized by those skilled in the art that the components  34 - 38  of the player  12  establish at least a portion of a wireless transmitter and the components  44 - 48  of the player  20  establish at least a portion of a wireless receiver.  
      In addition to carrying the multimedia data proper, the forward channel link  22  may carry encoding information such as encoding keys and/or a unique identifier that may be multiplexed within the multimedia data, so that the decoder  48  can decode the streams and obtain the encoding information. The encoding information may be used as set forth further below. If desired, the forward channel link  22  can be a full duplex link, so that the player  20  can communicate information back to the source  12 . For example, the player  20  may communicate capabilities and if necessary its own encryption information to the source  12 . Or, the player  20  can communicate reception conditions so that the transmission power of the source  12  and/or directivity of the first source antenna  40  can be established to minimize power while maximizing reception. Automatic gain control and automatic antenna beam control adjustment thereby can be effected by the processor  30  of the source  12 .  
      Additionally, a reverse link  54  such as but not limited to Bluetooth, 802.11, 802.15, infrared, PLC, HPNA, or any other suitable link such as a wireless link operating at 2.4 GHz is provided.  
      It is to be understood that although 60 GHz is not required for both the forward and reverse link, since the data rate requirement particularly for the reverse link does not merit the expense, both a half-duplex and full-duplex 60 GHz transceiver are envisioned. Thus, a full duplex 60 GHz version can be used for establishing both the forward and reverse links, and the forward channel can be established by one 60 GHz sub-band (e.g., 60-61 GHz) and the reverse channel can be established by another 60 GHz sub-band, e.g., 61-62 GHz. In any case, encryption can be used particularly when private or confidential data is to be exchanged.  
      In one non-limiting implementation the source  12  includes a reverse channel transceiver  56  that sends and receives control signals over a second source antenna  58  and that stores/processes the control signals in a control signal module  60 . The module  60  may be a software-implemented module accessed by the processor  30  of the source  12  as shown. Similarly, because a reverse channel link is used, the player  20  includes a control signal transceiver  62  that sends and receives signals over a second player antenna  64  and that stores/processes the information in a control signal module  66 . The module  66  may be a software-implemented module accessed by the processor  52  of the player  20  as shown. The control signals may be, e.g., audio and video display function information including trick play features, communication capabilities, reception conditions so that the transmission power of the source  12  and/or directivity of the first source antenna  40  can be established to minimize power while maximizing reception, and encryption information as set forth further below.  
      In the second of the above-referenced patent applications, it was recognized that when the reverse links between transmitter-receiver pairs are 2.4 GHz radio links, they might interfere with each other and/or communicate with the wrong transmitter. Accordingly, the second of the above-referenced patent applications proposes a receiver (or the associated source) sending an identifier that is unique to the pair to the source (or associated receiver) on the 60 GHz forward channel, with subsequent communications from the source (or associated receiver) being ignored unless the unique identifier was echoed back as part of the communication. As recognized herein, however, while echoing back the unique identifier in the clear effectively resolves miscommunication, the reverse channel 2.4 GHz link remains inherently less secure than the 60 GHz forward channel link.  
      Accordingly, turning to  FIG. 3 , in one implementation the unique identifier mentioned above and described in the second of the above-referenced patent applications is sent over the forward (60 GHz) channel link  22   a  from, e.g., the transmitter  12   a  to the receiver  20   a , it being understood that the receiver  20   a  alternatively could generate and send the unique identifier to the transmitter  12   a . Moving to block  72 , when one of the receiver or transmitter has data such as control signals to communicate on the reverse channel (e.g., 2.4 GHz) link, the data is “OR&#39;ed” (using, e.g., a wired “OR”) or otherwise combined with the unique identifier, and then transmitted at block  74 . The recipient executes the reverse of the combination performed at block  72  to render the information in usable form.  
      Instead of using an “OR” or other function of the unique identifier,  FIG. 4  shows that one or more encryption keys for, e.g., Data Encryption Standard (DES) or Advanced Encryption Standard (AES) encryption can be sent at block  76  over the forward (60 GHz) channel link  22   a  from, e.g., the transmitter  12   a  to the receiver  20   a , it being understood that the receiver  20   a  alternatively could generate and send the keys to the transmitter  12   a . Moving to block  78 , when one of the receiver or transmitter has data such as control signals to communicate on the reverse channel (e.g., 2.4 GHz) link, the data is encrypted using the keys, and then transmitted at block  80 . The recipient decrypts the information using the keys.  
      While the particular METHOD AND SYSTEM FOR WIRELESS DIGITAL COMMUNICATION as herein shown and described in detail is fully capable of attaining the above-described objects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and is thus representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more”. It is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited as a “step” instead of an “act”. Absent express definitions herein, claim terms are to be given all ordinary and accustomed meanings that are not irreconcilable with the present specification and file history.