Abstract:
There is a need to deploy the IP (Internet Protocol) video surveillance camera over both Ethernet cable and coax cable. The present invention presents the IP video surveillance camera with dual Ethernet cable interface and coax cable interface by using the presented dual physical layer transceiver. The dual physical layer transceiver includes a conventional E-PHY (Ethernet physical layer transceiver) and a lightweight coax adapter to allow low cost. The coax adapter typically exists in series between the active E-PHY and coax cable, keeps part of functions in E-PHY effective, and adapts the E-PHY signal onto coax cable and vice versa. The conventional E-PHY alone provides the Ethernet cable interface while the conventional E-PHY is combined with the coax adaptor to provide the coax cable interface. Further, the present invention presents methods to relay Ethernet over coax by using a pair of the coax adaptors.

Description:
[0001]    This application refers to the prior provisional application under application No. U.S. 61/993,514 filed on May 15, 2014. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates to the IP (Internet Protocol) video surveillance camera with dual Ethernet cable (cat5/6 UTP cable) and coax cable interface (referred as dual cable interface IP camera, dual interface camera, or Dual-I/F camera). The present invention also relates to transmission of Ethernet over coax cable or transmission of IP over coax cable. 
         [0004]    2. Background 
         [0005]    In the HD (high definition) IP video surveillance systems, typically multiple HD IP cameras are connected with one NVR (network video recorder) or DVR (digital video recorder) via cable networks. Each HD IP camera transmits its video to the NVR over the connecting cables. The NVR often displays the camera videos instantly to monitor live scenes in the field of view of cameras and records the camera videos for later playback as well. 
         [0006]    Many HD IP cameras are deployed over Ethernet cables. The HD IP cameras often employ heavyweight video compression technology such as H.264 to compress the source HD video into the compressed HD video at a bit rate about 10 Mbps or below. The compressed HD video is wrapped in IP packets, and further into forward Ethernet MAC (multiple access control) frames. The forward Ethernet MAC frames are sent to the E-PHY (Ethernet physical layer transceiver), where the Ethernet physical layer frames are generated and translated into the E-PHY TX signal. The E-PHY TX signal is typically sent onto the Ethernet cable, such as the CAT 5/6 UTP cable, towards the NVR on the other end. Meanwhile, the E-PHY in the IP camera also receives the incoming E-PHY RX signal from the Ethernet cable, which originates from the NVR, and recovers the backward MAC frames and sends to the processor system in IP camera. 
         [0007]    Although many IP cameras are deployed over Ethernet cables, there are needs to deploy IP cameras over coax cables too. For example, as coax cables have been commonly installed and accumulate in the conventional CCTV (Closed-Circuit TV) video surveillance applications in decades, there is the need to deploy the IP cameras over the existing coax cable networks in these legacy CCTV systems. For another example, due the Ethernet standard, the IP video transmission over Ethernet cable is limited to 100 meters, which is insufficient to cover many large video surveillance applications. Deployment over coax can extend the distance beyond the 100-meter limit and serve large video surveillance applications. In order to deploy the IP video surveillance system over both Ethernet and coax cable, there is a need for dual cable interface IP camera and the dual physical layer transceiver that provides the dual cable interface. 
         [0008]    Various IP over coax convertors are made to transmit the IP over coax cable. The conventional IP over coax convertors are typically full-blown coax transceivers (referred as coax-PHY), which exist in parallel with the E-PHY and abandon all functions in E-PHY. The prior invention in [1] discloses a SLOC camera that transmits both Ethernet and analog CVBS video signal over coax simultaneously in parallel to the E-PHY typically included in the IP camera. This leads to higher cost. As the video surveillance industry is cost sensitive, there is a need for the dual cable interface physical layer transceiver, which is able to reuse the E-PHY by including the E-PHY as a part of the coax interface, and thus achieves the low cost. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention presents the IP (Internet Protocol) video surveillance camera with dual Ethernet cable (cat5/6 cable) interface and coax cable interface, referred as the dual cable interface IP camera, dual interface IP camera, or Dual-I/F camera. The presented dual cable interface IP camera adopts the dual physical layer transceiver that provides the dual Ethernet cable interface and coax cable interface, referred as dual cable interface physical layer transceiver, dual cable interface PHY, or Dual-I/F PHY. The presented Dual-I/F PHY includes a conventional E-PHY (Ethernet physical layer transceiver) and a low-cost lightweight coax adapter. The coax adaptor typically exists in series between the active E-PHY and coax cable, keeps part of functions in E-PHY effective, and adapts the E-PHY signal onto coax cable and vice versa. The conventional E-PHY alone provides the Ethernet cable interface while the conventional E-PHY is combined with the coax adaptor to provide the coax cable interface. Further, the present invention presents methods to relay Ethernet over coax by using a pair of the coax adaptors. 
         [0010]    In an embodiment of the present invention where E-PHYs in the dual cable interface PHYs at both camera end and DVR end operate in the 100Base-TX full-duplex mode, the coax adaptors in the dual cable interface PHYs at both ends of the coax cable operate in the full-duplex full-speed mode too, exactly matching the E-PHYs. As an aspect of the present invention, the MAC frame buffering and associated network delay are avoided. 
         [0011]    Each coax adaptor is connected via the two-way E-PHY signal with its E-PHY. In the 100Base-TX full-duplex mode, each E-PHY generates a separate E-PHY TX signal to be sent onto one pair of UTP wires, and receives a separate E-PHY RX signal from another pair of UTP wires, both included in the E-PHY signal. 
         [0012]    In the embodiment of the present invention, the near-end coax adaptor converts the near-end E-PHY TX signal into the near-end EoC (Ethernet over Coax) TX signal, and sends it onto the coax cable toward the far-end coax adaptor. From the camera&#39;s point of view, the near-end refers to camera end, and far-end refers to the DVR end. From the DVR&#39;s point of view, the near-end refers to DVR end, and far-end refers to the camera end. Meanwhile, the near-end coax adaptor also receives the EoC RX signal transmitted by far-end coax adaptor through the coax cable. Since the EoC TX output signal and the EoC RX input signal are both connected to the same coax cable, the EoC RX signal from far-end is inevitably mixed together with the near-end EoC TX signal and a mixed EoC signal is formed. 
         [0013]    Furthermore, in the embodiment of the present invention, both the near-end and the far-end coax adaptors may transmit freely, in the same frequency band, at same time, without any multiplexed access mechanism applied to control the transmission of the either end. Therefore, the near-end generated EoC TX signal and the EoC RX signal coming from far-end cannot be separated by any multiplexed access mechanism. However, in the embodiment of the present invention, as each coax adaptor knows the clean near-end EoC TX signal it generates in itself, the echo canceller, which is a type of digital adaptive filter, is adopted to estimate the portion of the known near-end EoC TX signal included in the mixed EoC signal. Then the echo canceller subtracts the estimated portion the known near-end EoC TX signal away from the mixed EoC signal, and thus obtains the unknown EoC RX signal from the far-end. 
         [0014]    Following the echo canceller, the obtained EoC RX signal is compensated for the cable attenuation, decoded coax encoding and re-encoded Ethernet encoding if needed, fully translated into the E-PHY RX signal and sent to the E-PHY. 
         [0015]    In one embodiments of the present invention, the EoC signal is carried through the Ethernet connector, typically an RJ-45 connector to connect with the external coax cable. The RJ-45 connector has four pairs of pins. In an embodiment, the E-PHY operates in 100Base-TX full-duplex mode, where two pairs of pins of the RJ-45 connector are in use, one pair to carry E-PHY TX signal, the other pair to carry the E-PHY RX signal. There are two pairs of pins left unused. Any unused pair of pins can be selected to carry the EoC signal. This is compatible to IEEE 802.3 standard. In another embodiment of the present invention, a pair of pins used by E-PHY can also be selected to carry the EoC signal, as the connection over Ethernet cable and over coax cable do not exist simultaneously but alternatively. This is incompatible with IEEE 802.3 standard. In yet another embodiment of the present invention, the EoC signal is carried through a separate coax connector, such as the BNC connector, to connect with the external coax cable. 
         [0016]    In one embodiment of the present invention, an IP camera may generate a CVBS (composite video baseband with synchronization) signal. Either the CVBS signal or the EoC TX signal is selected to pass through the separate coax connector. In a certain embodiment of the present invention, the CVBS signal is selected to pass through the coax adaptor when the existence of far-end coax adaptor is not detected, and the EoC TX signal is selected to pass through when the far-end coax adaptor is detected. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  illustrates an embodiment of the presented a dual cable interface IP camera deployed over coax cable in an IP video surveillance system. 
           [0018]      FIG. 2  illustrates an embodiment of the dual cable interface IP camera and the dual cable interface physical layer transceiver. 
           [0019]      FIG. 3  illustrates an embodiment of the presented coax adaptor. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    The principle and embodiments of the present invention will now be described in detail with reference to the drawings, which are provided as illustrative examples so as to enable those skilled in the art to practice the invention. Notably, the figures and examples below are not meant to limit the scope of the present invention to a single embodiment but other embodiments are possible by way of interchange of some or all of the described or illustrated elements. Wherever convenient, the same reference numbers will be used throughout the drawings to refer to same or like parts. Where certain elements of these embodiments can be partially or fully implemented using known components, only those portions of such known components that are necessary for an understanding of the present invention will be described, and detailed descriptions of other portions of such known components will be omitted so as not to obscure the invention. In the present specification, an embodiment showing a singular component should not be considered limiting; rather, the invention is intended to encompass other embodiments including a plurality of the same component, and vice versa, unless explicitly stated otherwise herein. Moreover, applicants do not intend for any term in the specification or claims to be ascribed an uncommon or special meaning unless explicitly set forth as such. Further, the present invention encompasses present and future known equivalents to the components referred to herein by way of illustration. 
         [0021]      FIG. 1  illustrates an embodiment of the presented a dual cable interface IP camera deployed over coax cable in an IP video surveillance system. The dual cable interface camera  110 , through its dual cable interface PHY  140 , is connected with the video recorder  130  through the dual cable interface PHY  120 , via the coax cable  111 . The monitor  160  is connected with the video recorder  130 . Such connection is called the coax connection or the EoC connection. Alternatively, the Ethernet cable (Cat5/6) can be used to connect the camera  110  to DVR  130  through the dual cable interface PHY  140  and  120 . Such connection is called the Ethernet connection. The Ethernet connection is same as that in the conventional IP video surveillance system. For the purpose of brevity, the coax connection is detailed in following description while the Ethernet connection is skipped. 
         [0022]    Inside the DVR  130 , the dual cable interface PHY  120  receives the EoC signal for HD video stream over the coax channel  111 , recovers the forward Ethernet MAC frames and sends to the NVR  150  via the xMII interface  121 , where xMII refers to the MII (media independent interface) interface or its variant such as RMII, SMII, GMII, RGMII and SGMII. It also receives backward Ethernet MAC frames from the NVR  150  via the xMII interface  121 , converts it to the backward EoC TX signal and sends it onto the coax channel  111 . The NVR  150  is same as the conventional NVR in IP video surveillance system, which usually decode the heavily compressed HD IP video for live monitoring, record the received heavily compressed videos, and playback the recorded videos. The NVR  150  often combines input videos and playback videos together, and generates the combined video signal and sends it to the monitor  160 . 
         [0023]      FIG. 2  illustrates an embodiment of the dual cable interface IP camera  110  and its dual cable interface PHY  140 . The lens system  210  focuses the light rays  211  from the objects in the field of view of the lens system  210  onto the image sensor  220 , and produces the raw digital video  221 . The processor system (also referred as SoC system)  230  converts the raw digital video  221  into one of its supported video formats, such as 1280×720 pixels in 24/30/60 frames per second, or 1920×1080 pixels in 24/30/60 frames per second. This is called the original source HD video. The camera SoC system  230  further heavily compresses the source HD video down to a bit rate about 10 Mb/S or below. This result is called the compressed HD video. The compressed video is then wrapped in IP packets, further in forward MAC frames, and sent to the dual cable interface PHY  140  via the xMII interface  231 . The camera SoC system  230  also receives the MAC frames from the dual interface PHY  140  via the xMII interface  231 . Additionally, the camera SoC system  230  can send the signal  232  to control the lens system. The control signal  232  may include the auto-focus control, the iris control and the PTZ (Pan-Tilt-Zoom) control signal. Some control signal, such as the PTZ control signal, may originate from the video recorder  130 , and may be carried over the channel  111  or a separate wiring such as RS 485 cable. Optionally, the camera SoC system  230  may generates the CVBS signal  233  and send it to the dual interface PHY  140  too. 
         [0024]    Inside the dual cable interface PHY  140 , the E-PHY  240  converts the forward MAC frames it receives from the camera SoC system  230  through the xMII interface  231  into the E-PHY TX signal in the two-way E-PHY signal  241 . The E-PHY TX signal is sent to the coax adaptor  250  and the Ethernet connector  260 . The coax adaptor  250  converts the E-PHY TX signal in signal  241  into the EoC TX signal in signal  251 , which is suitable for coax transmission, and sends it to the Ethernet connector  260  or the optional coax connector  270  if it is present in the camera  110 . Meanwhile, the coax adaptor  250  also receives the mixed EoC signal in signal  251 , coming in from either the Ethernet connector  260  or the coax connector  270  if it exists, and recovers the E-PHY RX signal in signal  241 . The E-PHY  240  receives the E-PHY RX signal in signal  241  from the coax adaptor  250 , recovers the backward MAC frames from far-end and sends the backward MAC frames to the camera SoC system  230  via the xMII interface  231 . As stated above, the signal  251  is the mixed EoC signal. Though either the Ethernet connector  260 , or the coax connector  270  if it exists, the mixed EoC signal  251  is connected with the external coax cable  111 . 
         [0025]    As mentioned before, through the dual interface PHY  140  and  120 , either Ethernet connection or EoC connection can be built, but not both at same time. The Ethernet connection and the EoC connection cannot be both logically active at same lime. For example, when both an Ethernet cable with an active E-PHY on the far-end is connected to the Ethernet connector  260  and a coax cable with an active coax adaptor on the far-end is connected to the coax connector  270 , one connection has to be disabled logically or electronically. In certain embodiment, the coax connection is disabled whenever the Ethernet connection is established and active. This gives better Ethernet compatibility. 
         [0026]      FIG. 3  illustrates an embodiment of the presented coax adaptor  250 . On the EoC transmission path (also referred as EoC transmitter or EoC TX), the ETX transcoder  310  receives the E-PHY TX signal  301  in the signal  241  and trans-codes it into the EoC TX signal  311 . 
         [0027]    There are various methods to trans-code the E-PHY TX signal into the EoC TX signal. In an embodiment of the present invention, the coax adaptor simply passes the MLT-3 coded E-PHY TX signal in 100Base-TX mode directly as the EoC TX signal without any change. In another embodiment, the coax adaptor decodes the MIT-3 modulation of the E-PHY TX signal, recovers the 125 MHz 1-bit signal and then re-modulates it into the BPSK signal for coax transmission. In yet another embodiment, the coax adaptor decodes the MLT-3 modulation of the E-PHY TX signal, recovers the 125 MHz 1-bit signal, then applies the trellis coded modulation to the 125 MHz 1-bit signal and produces the high-order of PAM modulated signal such as PAM-4T and PAM-8T for coax transmission. In yet another embodiment of the present invention, the coax adaptor decodes the MLT-3 modulation and the 4B5B encoding, and recovers the 100 MHz 1-bit payload signal. In a simple embodiment, the recovered 100 MHz 1-bit payload signal is re-modulated by BPSK modulation for coax transmission. In an advanced embodiment, the recovered 100 MHz 1-bit payload signal is re-encoded with the selected error correcting encoding and re-modulated to the chosen coax modulation method. As mentioned above, in a preferred embodiment, the re-encoder in the coax adaptor produces the output signal at the symbol rate that matches the bit rate of its incoming signal. This avoids the frame buffering and network delay. 
         [0028]    In another preferred embodiment of the present invention, the signal is randomized to generate the EoC TX signal with flat spectrum when the payload bit stream is not or not completely uncorrelated. 
         [0029]    In certain embodiment, the MUX  350  can pass either the EoC TX signal  311  or the CVBS signal  233  as its output into the signal  251  depending on whether the EoC connection is established or not. In one embodiment, the coax adaptor  250  establishes the coax connection after the certain pre-defined signal pattern is received from far-end coax adaptor in dual cable interface PHY  120 . Initially after power up and whenever the coax connection is not established, the MUX  350  chooses to pass the CVBS  233  into the signal  251 . Whenever the coax connection is established, the EoC TX signal transmission is enabled and the MUX  350  passes the EoC TX signal  311  through into the mixed EoC signal  251 . 
         [0030]    The portion of EoC TX signal included in the mixed EoC signal  251  is called the near-end EoC TX signal. The EoC TX signal from the far-end of coax penetrates the cable and arrives as the EoC RX signal. As stated above, since no multiplexed access mechanism is applied to control the EoC transmission at either end, the EoC RX signal is mixed together with the near-end EoC TX signal and the mixed EoC signal  251  is formed. 
         [0031]    On the EoC receiving path (also referred as EoC receiver), based on the clean near-end EoC TX signal  311 , the echo canceller  320  takes in the mixed EoC signal  251  and estimates the portion of the near-end EoC TX signal  311  included in the signal  251  by using the typical digital adaptive filtering technology such as the LMS (least mean square) adaptive filler. The echo canceller  320  subtracts the estimated portion away from the mixed EoC signal  251 . The left signal  321  mainly contains the EoC RX signal. The coax equalizer  330  compensates for cable attenuation for the signal  321 , and recovers the far-end EoC TX signal. The coax equalizer  330  is an adaptive filter, and can be either digital filter or analog filter. The ERX transcoder  340  demodulates the coax modulation decodes any coax error correcting encoding added by ETX transcoder  310  at the far-end, re-encodes the Ethernet encoding if that is decoded in far-end ETX transcoder  310 , re-modulated with the Ethernet modulation such MLT-3 if that is demodulated in the far-end ETX transcoder  310 , and recovers the E-PHY RX signal  302  in signal  241 . 
         [0032]    In certain embodiment of the present invention, the coax adaptor in dual interface PHY  120  at video recorder side is identical to coax adaptor  250  in IP camera  110  except a) there is no CVBS to multiplex with the EoC TX signal. b) the EoC TX signal transmission is always enabled, and C) a certain pre-defined signal pattern is periodically sent out to indicate its existence before the coax connection is established. 
         [0033]    Although in the above embodiments of the invention, the dual cable interface PHY is described in the way where the separate conventional E-PHY is paired with the separate coax adaptor, the conventional E-PHY can be and is preferred to be tightly integrated with the presented coax adaptor in a practical design and the internal signals of the E-PHY are accessible to the coax adaptor. This allows more simplifications to further reduce the cost of the dual cable interface PHY without functional changes. In one embodiment, the 125 MHz 1-bit signals before the MLT-3 modulation is accessed, included in signal  241 , and sent to the coax adaptor  250 . The MLT-3 demodulation in ETX Transcoder  310  is avoided. Similar embodiments can be made in receiving path to avoid the MLT-3 re-modulation in ERX Transcoder  340 . In another embodiment, the 100 MHz 1-bit signal before the 4B5B encoding in the E-PHY  240  or its equivalent signal is accessed, included in signal  241  and sent to the ETX transcoder  310  in the coax adaptor  250 . The 4B5B encoder and MLT-3 demodulator in ETX Transcoder  310  are both avoided. Similar embodiments can be made in receiving path to avoid the 4B5B encoder and MLT-3 decoder in ERX Transcoder  340 . 
         [0034]    Although in the above embodiments of the invention, the coax adaptor is described in the way it is paired with the conventional E-PHY to make the dual cable interface PHY, a pair of the coax adaptors can be used alone to relay Ethernet over coax cable. In an embodiment, a conventional IP camera with Ethernet cable interface and RJ-45 connector only, is connected to the 1 st  coax adaptor over 1 st  Ethernet cable such as Cat5/6 UTP cable with the two Ethernet connectors, one at each end of the Ethernet cable. The 1 st  coax adaptor is connected to the 2 nd  coax adaptor over a coax cable via two coax connectors, one at each end of the coax cable. The 2 nd  coax adaptor is connected to an Ethernet device such as NVR or Ethernet switch over 2 nd  Ethernet cable via another two Ethernet connectors, one at each end of the 2 nd  Ethernet cable. In this embodiment, the 1 st  coax adaptor coverts two-way the E-PHY signal on the 1 st  Ethernet cable to and from the mixed EoC signal on the coax cable while the 2 nd  coax adaptor coverts two-way the E-PHY signal on the 2 nd  Ethernet cable to and from the mixed EoC signal on the coax cable. 
         [0035]    Further, multiple pairs of the coax adaptors can be used alone to relay an Ethernet connection repeatedly. In an embodiment, a conventional IP camera with Ethernet cable interface and RJ-45 connector only, is connected to the 1 st  coax adaptor over 1 st  Ethernet cable such as Cat5/6 UTP cable via the two Ethernet connectors. The 1 st  coax adaptor is connected to the 2 nd  coax adaptor over 1 st  coax cable via two coax connectors. The 2 nd  coax adaptor is connected to the 3 rd  coax adaptor over 2 nd  Ethernet cable via another two Ethernet connectors. The 3 rd  coax adaptor is connected with 4 th  coax adaptor over the 2 nd  coax cable via another two coax connectors. The 4 th  coax adaptor is connected to an Ethernet device such as NVR or Ethernet switch over 3 rd  Ethernet cable via yet another two Ethernet connectors. In this embodiment, the 1 st  coax adaptor coverts two-way the E-PHY signal on the 1 st  Ethernet cable to and from the mixed EoC signal on the 1 st  coax cable while the 2 nd  coax adaptor coverts two-way the E-PHY signal on the 2 nd  Ethernet cable to and from the mixed EoC signal on the 1 st  coax cable. Similarly, the 3 rd  coax adaptor coverts two-way the E-PHY signal on the 2 nd  Ethernet cable to and from the mixed EoC signal on the 2 nd  coax cable while the 4 th  coax adaptor coverts two-way the E-PHY signal on the 3 rd  Ethernet cable to and from the mixed EoC signal on the 2 nd  coax cable. 
         [0036]    It is to be noted that the camera of prior invention in [1] carries the CVBS analog video signal in baseband and the Ethernet over coax signal of the [1] in two passbands by using FDMA for multiplexed access control via the coax connector. The dual cable interface camera of present invention is functionally and structurally different in that it carries ether analog video signal or Ethernet over coax signal of present invention, but not both at same time, and all signals are carried in same band, typically in baseband, without any multiplexed access control. 
         [0037]    It is to be noted that the camera of prior invention in [2] carries the CVBS analog video signal through the Ethernet connector in an IP camera in a way compatible to IEEE 802.3 standard. The dual cable interface camera of present invention is functionally and structurally different in that it carries the Ethernet over coax signal of the present invent, not CVBS analog video through the Ethernet connector. Further, the EoC signal of present invention can be carried through the Ethernet connector in a way incompatible with the IEEE 802.3 standard as the E-PHY signal and the EoC signal are required not to be carried at same time in present invention. 
         [0038]    The present invention is described according to the accompanying drawings. It is to be understood that the present invention is not limited to such embodiments. Modifications and variations could be effected by those skilled in the art without departing from the spirit or scope of the invention as defined in the appended claims. 
       REFERENCE 
       [0000]    
       
         [1] US 2010/0194899 A1, MIXED FORMAT MEDIA TRANSMISSION SYSTEM AND METHODS, filed on Jan. 30, 2009 
         [2] U.S. Pat. No. 8,208,033 B2, VIDEO OVER ETHERNET, filed on Jul. 9, 2009