by Terry Stanfield
Hard Knock lessons from a vet of CCTV systems big and little
When you’re looking at designing an IP camera system traditional rules for wiring the cameras and recording the cameras go out the window. Below I have listed 3 design characteristics that have modified from normal coaxial-based camera systems to IP based camera systems.
Rule one : Infrastructure Design
a couple of years ago I was presented with a large camera system that required over ninety cameras in a building that was over 750,000 square ft. The challenge, using traditional camera design, was wiring each camera back to a central location where the command console was located. In some examples, camera locations were over 1,500ft from the command center. Since coaxial cables limitation for RG59 and RG6 cable are between eight hundred and 1000ft, solving the distance limitation problem was vital. Using the methods open to me at the time, I had a choice between fiber optic wire or UTP ( unshielded twisted pair ) cable. Although fiber optics typically will produce a clearer picture with less distortion, it was cost prohibitive for the project. I chose UTP wire and with an active receiver at the command console and passive transmitter at the camera. This provided for cable runs of nearly 3000ft. UTP wire is just CAT3 or CAT5 cable ( frequently referred to as Ethernet cable ), which is employed for telephone and information networks. One of the 4 pairs of wires sends video down the cable. The twisting of the cable provides its unique benefits. This gives the cable its name of unshielded twisted pair. At the time, now more than four years ago, this was the best answer for the application as it met the standards for transmitting the video and met the customer’s budget.
IP Video changes everything.
Using IP cameras presents an absolutely new set of rules for transmitting video. Where before we were able to transmit a video signal up to 1000ft using coaxial cable we are now restricted to only 300ft or a hundred meters. At first, this may seem to be a drawback. To anyone that’s acquainted with designing a computer network it is apparent that this layout is essentially a benefit. Imagine the application below: You have 5 cameras you would like installed. They’re all located along a back wall of the building looking out to the shipping and receiving area. The recorder is found at the front of the building in an IT closet. Under traditional video design, all five cameras would have a coaxial wire installed from the camera to the recorder. In this example, we could say the distance is a mean of 500ft from the recorder to a camera. Five cameras at 500ft each would force 2,500ft of coaxial wire. Using a network solution the following cabling would be required. A single cable, typically fiber, would be pulled from the front of the building to the back. At every end of the fiber, there would be a termination point. The termination point at the front of the building would be considered the Main Distribution Frame or MDF. The point at the rear of the building would be the Intermediate Distribution Frame or IDF. An IDF is defined as a location between the MDF and the end device, in this example the camera. All of the cameras would be cabled to the IDF location. For our example, we’ll say it’s a median of 100ft from each camera to the IDF. We would need 500ft of network wire. Conclusion is that instead of pulling 2500ft of coaxial wire you are installing 500ft of CAT5e cable and 500ft of fiber.
The gigantic Bonus behind IP Video
The chief benefit behind a network solution is scalability, leading to important long, and short term cost benefits. When you have five locations all with five cameras and all 500ft from the recorder, the costs add up quickly with traditional systems. In this position the cost savings can really start to add up. Going back to our example for a minute, we could say you want to add a new camera to view the interior shipping door. The infrastructure is already prepared. Now all that is’s needed is pulling a single CAT5e wire from the new camera location to the IDF. Maybe this is only 50ft away. Using the old design, you’d need to drag another 500ft of coaxial wire back to the recorder. This adds up to a cable savings and a big labor cost reduction.
Rule 2 : PoE – The’Power’ of a Single Cable
PoE or Power over Ethernet is simply the transmission of power together with data over a standard Ethernet wire. In a Power over Ethernet system, a PoE network switch makes available up to 15Watts of power to the end device. This can be a phonephone, camera or any other device that sits on a network and requires less than 15 watts of power. When coming up with an IP camera system you need to look for cameras that use this technology. There are two basic benefits when using PoE for your system layout.
Benefit one : only 1 cable is necessary to each camera for both power and video transmission. As opposed to a normal camera system that uses a Siamese wire for both video and power. A Siamese cable has a coaxial RG59 wire and sometimes an eighteen gauge two conductor wire molded together to form a single wire. This gives the appearance and ease of pulling a single cable to each camera. The drawbacks to Siamese wire compared to CAT5 wire is it is noticeably more expressive. Siamese wires contain more copper, which is a costly commodity in today’s market. Siamese wire is also more difficult and cumbersome to install.
Benefit 2 : No additional power supply is necessary for powering the cameras and it only requires a single termination at the camera and switch location. These 2 extra features lead to the same benefits : cost savings and a more flexible and scalable system solution. Scalability and space requirements are becoming an enlarging concern for many IT departments. When adding a network camera system the potential rack space required for the present as well as future can be extremely crucial when planning a system. Using PoE can save space and reduce heavy, rigid bundles of cables.
Rule three : Centralized or Edge Recording
There is no right or wrong when it comes to using edge recording or centralized recording. Most of your call will depend on your own application and existing network infrastructure. A hybrid of the two styles could be the best solution but this could add extra cost and limit your available camera options. In a meeting with a school district, I was asked about which solution was better. I responded that I felt neither was a better solution ; both solutions have their benefits and it is dependent on the application. During my meeting I described the following advantages and downsides of each. Centralized Recording:
Imagine you’ve a company which has five buildings ranging in size between ten thousand to 50,000 square ft. All 5 of your buildings are located within a large business park. Each building has a limited number of fiber optic cables between them. Your company has a main server room found in the biggest of the five buildings. The IT dep. manages the server room and there is limited restricted access to that room. The remaining 4 buildings are accessible through fiber from the server room.
For this example, centralized recording offers you the most inexpensive and scalable solution. Centralized recording works well here. There is a main server room and all the buildings are connected through locally owned fiber. Employing a single recording location is cheap because all the recorded video is stored at a central location. A single server as opposed to five servers ( if using edge recording ) will record the video, leading to a significant savings. In each building, PoE network switches would connect to the cameras. The fiber optic cable would transmit the video back to the central server room for recording. This solution is also extremely scalable. Adding a camera to any location in the 5 buildings is as simple as connecting a camera to the closest PoE switch. In this actual application, centralized recording fits best due to the environment and infrastructure available. A drawback of centralized recording is if a fiber is cut between any one of the buildings and the server, all of the cameras within that building won’t be recorded or be able to be viewed live. In this example, all of the video from these cameras will be lost.
Edge Recording:
In this example, you have a corporate office building and a producing plant. The two buildings are found about one mile except for each other. You’ve a dedicated T1 connection between the 2 locations. The T1 is used to share information transmission between the two sites. Almost all of the installed cameras will be at the manufacturing plant so that company is in a position to monitor the plant remotely. The corporate office will have four to 6 cameras installed to view the main entrance and worker parking area.
For this example, edge recording offers the most cheap solution for your company. Limited connectivity between the two locations is the largest obstacle. A standard IP camera requires about 2Mb per second available bandwidth. The first camera would consume all the available bandwidth of a T1 connection making centralized recording most unlikely. Edge recording doesn’t stop centralized viewing it only prevents the recording of the camera centrally. For this example, you would use 2 network video recorders. You would scale each recorder to fit the number of cameras they’ll be recording. From the client side or remote connection, you would be able to configure the system like it were a single connection. The only difference would be the refresh speed of the remote cameras. In this example, edge recording supplies the most cost effective solution while still meeting the goals of your company. The downside, in this application, is the price of having 2 servers and slower live display rates of the cameras.
The Rule Summary:
By reading this, i hope that you’re able to see how IP video offers a totally different design and new features that weren’t possible or cost prohibitive with a conventional coaxial wire system. There are numerous other benefits when using IP video. The 3 listed above are only some of the benefits that IP video technology has provided to the safety industry.