Knowing what your transmission can or cannot do

ADVANTAGES
PoE
There are many advantages that come with PoE technology. A major advantage of PoE technology is the ability to power devices and transmit data via the same Ethernet cable.

“This simplifies installation, reduces installation and maintenance costs, and improves the stability of the security system. Costs are saved in terms of installing power points, conduits, and cables. Installation is simplified as a single Ethernet cable supplies both power and data. Moreover, management is simplified as power management is centralized,” explained Calvin Wong, Sales Director of OT Systems, on the advantages of PoE technology. It also saves space, due to fewer cables required for the transmission infrastructure, and it saves on labor costs, as only one cable is required for both power and data. Finally, it also provides safety benefits, as it supplies low-voltage power.

EoC
In EoC transmission, the biggest advantage is the ability to utilize existing coaxial cables in the security system. This saves on costs, as installation is most often the most costly component of any security installation. Furthermore, transmission distance is also longer.

VDSL2 is the most commonly used form of EoC transmission and Wong cites the following as an advantage. It allows for up to two kilometers of transmission, although the data rate decreases with increasing distance, down to 1.5Mbps.

When SLOC is used, an additional advantage is that it supports a hybrid surveillance system with both analog and network cameras, in addition to power over coaxial. Hence, this would be appealing to end users who may still want to keep some of their existing analog cameras, or install analog cameras in less critical locations.

PLC
Although PLC is limited to existing power lines and is mostly used in standalone buildings, such as homes or offices, they do have several advantages over others. As with EoC transmission, PLC transmission does not require the installation of additional wires to set up a security system. However, EoC requires a previous security system to be in place, while PLC can be set up without having any prior system in place. It is a simple solution for distributing connectivity in buildings, which would definitely have existing power lines. Installation is also easy as there is no need to configure compatible security cameras.

Furthermore, there are other attractive advantages. “PLC supports the highest data rate at 200Mpbs and the transmission distance can be up to 500 meters, depending on factors such as data rate and cable quality. It supports data encryption at 128-bit AES, and is suitable for applications where a high level of security is required. It also supports multipoint connection, such as multiple coaxial into one coaxial cable or daisy-chained,” said Wong.

LIMITATIONS
Despite the advantages, limitations still exist. An understanding of the limitations with each technology would help system integrators and installers better meet end-user requirements.

PoE
In PoE technology, the most obvious limitation is that distance is limited to around 100 meters, unless repeaters/ extenders are used. In addition, “at the moment, the maximum power provided by power supply equipment (PSE) is 60W, which means that some heavy duty powered devices (PDs) cannot be powered by PoE, such as cameras that require higher power inputs,” noted Wong.

Also, “it is important to realize that the entire system is being powered by one (or a few) source(s) such as the PoE switch, media converter or PoE injector. It is always best practice to use sufficient UPS back up to provide network resiliency in case of a power failure,” said Richard Malstrom, IFS Product Marketing Manager for Lenel & Interlogix at UTC Climate, Controls & Security.

EoC
While EoC transmission can operate over longer distances, the use of repeaters introduces noise into the signal. Hence, transmission is limited by the signal-to-noise ratio. EoC transmission supports point-topoint connection only, making it less flexible if more complex security infrastructure is needed. Both SLOC and VDSL2 support a lower data rate, compared to other transmission mediums. SLOC may only support up to two I.3-megapixel IP cameras and VDSL2 may only support up to four 1.3-megapixel IP cameras.

PLC
The advantage of PLC also limits it. In surveillance systems, PLC is limited by the power lines and locale. However, their potential for smart metering and home automation is substantial and this is where PLC would most likely be most utilized. With the smart home market growing, we can expect to see more of PLC transmission, with data transmission of the security camera being one component of it.

Drawing it all together
 
There may be advantages and limitations to each transmission method, but the key is to understand the environment of the project site and end-user requirements. Following this, it is also crucial that end users are aware of realistic expectations. Finally, the most important glue to an optimal transmission is careful calculations.

Manufacturers understand their products best and are on hand to offer advice on calculations and system design. “Many of our customers will show us their transmission design, based on their calculations. If there is a more cost-effective way, or if alterations need to be made for better video transmission, we will recommend them to our clients. This way, end users can obtain the best results from our products,” said Ben Chiang, Business Development Manager at EtherWAN on the importance of calculations. “Alternatively, other system integrators might request that we come up with two or three designs for them to choose from. As each solution will have its own advantages and limitations, such as higher costs vs. better performance, the system integrator and the end user will decide on one that best suits the budget, schedule, and needs. It is also possible for a design to have no drawbacks, but that would be the most expensive, of course.”