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Utilizing Single Pair Ethernet in Video Surveillance Applications

To help maximize security, the surveillance infrastructure in industrial, office and residential buildings is steadily increasing. Over the past decade, camera technology has seen tremendous advances in image sensors, video processing, connectivity, and video analytics through artificial intelligence. Most cameras use the Mobile Industry Processor Interface (MIPI) to connect the image sensor to the video processor to upgrade the camera with image sensors of various resolutions. Figure 1 shows the various elements that make up a video surveillance camera system.

To help maximize security, the surveillance infrastructure in industrial, office and residential buildings is steadily increasing. Over the past decade, camera technology has seen tremendous advances in image sensors, video processing, connectivity, and video analytics through artificial intelligence. Most cameras use the Mobile Industry Processor Interface (MIPI) to connect the image sensor to the video processor to upgrade the camera with image sensors of various resolutions. Figure 1 shows the various elements that make up a video surveillance camera system.


Figure 1: Basic Internet Protocol (IP) surveillance cameras

The continued demand for high-resolution images and video has driven improvements and innovations in image sensors, increasing resolutions from 320 x 240 pixels to 4,096 x 2,160 pixels and beyond, an increase of approximately tenfold. The increase in pixel count also means that more data needs to be transferred from the image sensor to the video processor via the MIPI interface. In order to support high-quality video transmission, the Ethernet physical layer (PHY) in IP cameras also needs to be increased from 10Mbps to 1Gbps. Because of this, the ability of a video processor to run video compression algorithms that minimize the amount of data transmitted over an Ethernet cable becomes important.

A 4K resolution image sensor with a frame rate of 30fps produces uncompressed video at a data rate of 9.56Gbps. Although MIPI is designed to support such high or even higher rates, it is not economically feasible to transmit data and store uncompressed high-resolution video at these rates over Ethernet (requiring massive storage space). Using efficient video compression algorithms such as H.265, data rate requirements can be reduced to less than 10Mbps even when compressing to medium quality using 4K image sensors. While image sensor companies try to make higher-resolution sensors, standards bodies such as the International Electrotechnical Commission, the International Organization for Standardization, and the International Telecommunication Union are working on video compression algorithms that limit the rate of video data over Ethernet in some work scenarios. below 10Mbps.

The standard Ethernet interface in IP cameras is limited by specifications and only supports cable transmission distances of 100m; however, there is a new technology that can increase the minimum cable length to 1,000m. The distance from the IP camera to the network video recorder can be 1km or more, and connecting through standard Ethernet at the above distance requires the use of repeaters or fiber optic cables. An alternative is to use coax (RG-59) for longer distances, but this requires passive adapters to convert the Ethernet signal from CAT 5e to coax and vice versa. The cost per 100m of coaxial cable tends to be higher than the cost of standard Ethernet cable.

Recently, the Institute of Electrical and Electronics Engineers (IEEE) defined a new Ethernet standard, IEEE 802.3.cg, to enable 10Mbps operation and associated power delivery over a single pair of balanced conductors. More specifically & 10BASE-T1L: The IEEE 802.3 PHY specification applies to 10Mbps Ethernet LANs over a single pair of balanced conductors over a cable transmission distance of at least 1,000m (long transmission distances can be achieved using 18 AWG wire for point-to-point connections). Since single-pair cables can now support both data transmission and power delivery, the adoption of IEEE 802.3.cg provides significant cost savings and easier installation in video surveillance applications.

10BASE-T1L PHYs use full-duplex communication over a single pair of balanced conductors, with an effective data rate of 10Mbps in each direction simultaneously. The 10BASE-T1L PHY uses three-level pulse amplitude modulation (PAM3) and transmits at 7.5 Mbaud on the link segment. A 33-bit scrambler helps improve electromagnetic compatibility. The MII transmit data (TXD) is encoded using 4B3T encoding (ie, 4 binary to 3 ternary) so that the running average (DC reference) of the transmitted PAM3 symbols is within range. Using the management data input/output interface to set the 10BASE-T1L PHY’s transmitter output voltage to 1.0Vpp or 2.4Vpp differential helps achieve longer communication distances over different cables.

The DP83TD510E is an ultra-long transmission distance PHY transceiver that complies with the IEEE 802.3cg 10Base-T1L specification. The device operates from a single 3.3V supply and supports 2.4V p2p and 1V p2p voltage modes as defined by the IEEE 802.3cg 10Base-T1L specification. The PHY has a very low noise coupled receiver architecture and can support cable lengths up to 2,000m. The device provides Media Independent Interface (MII), Simplified MII, Simplified Gigabit MII, and RMII low-power 5MHz master modes to interface with the processor’s MAC. The DP83TD510E diagnostic tools include Time Domain Reflectometry (TDR), Active Link Cable Diagnostics (ALCD), Signal Quality Indicators (SQI), multiple loopback interfaces and an integrated PRBS packet generator to simplify debugging and development during development. On-site fault condition detection.

Single-pair Ethernet (SPE) networks also support Power Over Data Line (PoDL) along the same single-pair cable through a low-pass filter in video surveillance applications, as shown in Figure 2.


Figure 2: PoDL example in video surveillance

Table 1 lists the various power levels supported by the IEEE 802.3.cg standard. The maximum power that can be supplied to the load is 52W, which is defined as class 15. IEEE 802.3.bu covers power classes below 10.

Table 1: Power classes supported by the IEEE 802.3.cg standard

Source: IEEE Ethernet Standard

Classes 8 and 9 (48V regulated power supply device) or 14 and 15 (50V to 58V maximum) can support the power classes required for IP cameras, which may require up to 52W to operate. This power is sufficient for most camera systems, even those with built-in heaters. For buildings requiring upgrades, a standard Ethernet to SPE converter can be used as an intermediate solution. Figure 3 provides a connection example for an IP camera system.


Figure 3: IP webcam connection

Future IP camera products are expected to support SPE for easier installation, and network video recorders will also provide ports for power equipment. Achieving higher-compression video over a simplified SPE network enables better surveillance without adding complexity and cost.

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