Into the Ethernet

Manufacturers take advantage of powerful communication platform

• By Ray Shilling
• Oct 02, 2008

Over the past several years, much attention has been paid to the development and deployment of IP-based video surveillance systems. However, the rate of adoption has been slowed in part by the heavy bandwidth consumption of video streams and their resulting adverse impact on the network.

Undaunted by these restraints, manufacturers of access control systems with relatively low data rates have been gradually introducing network-based offerings of their own. The idea is to take advantage of the powerful and ubiquitous TCP/IP communication platform, without consuming large quantities of bandwidth.

Furthermore, an IP network is relatively affordable to deploy and universally understood. Therefore, installation and configuration challenges associated with proprietary technologies are all but eliminated.

However, in many cases, a wire-line network connection is not readily available at all locations where access control points may be required. Few buildings -- even those constructed in the past decade -- include network connections (RJ-45 ports) at their doors and gates. As a result, wireless technologies are increasingly being considered to deploy these Ethernet-based edge devices.

Important Considerations
There are many factors to consider when designing and deploying a wireless Ethernet-based access control system:

Selecting the right products. The single most important factor in ensuring the successful deployment of a wireless Ethernet access control system is selecting the right product and transmission frequency for the application.

For example, if the installation includes short-range indoor transmission to a few doors, a wireless Ethernet product will suffice. However, if the system includes a long-range connection to remote buildings or across larger distances to gates in the facility, then the choice of products is narrowed considerably. Other factors to consider are the ease of installation and long-term maintenance and support of the product suite. Also, purchasing the lowest cost hardware may not always be the answer, especially if the product has a steep learning curve and/or the technical support offered by the manufacturer is sub-par.

Antenna selection. An often-overlooked aspect of the wireless system is the antenna. For longer distances, or in crowded RF environments, it is imperative that a directional antenna be used whenever possible. This increases the signal- to-noise ratio, and therefore both the transmission and receive power of the radio, and allows the system to function well now and in years to come as the RF envrionment changes.

Tamper-proofing your installation. Radio transceivers are not -- by themselves -- a primary target for vandals. However, the best way to keep an investment safe is to put it out of reach of the public. Install the equipment up a pole or on top of a building. This is generally more favorable from an RF transmission standpoint as well.

In-band interference. The majority of Ethernet radios sold in North America today use one of three ISM bands: 900 MHz, 2.4 GHz and 5.8 GHz. These are unlicensed bands, and anyone is free to deploy FCC-certified products. For larger projects, conduct a site survey with a portable spectrum analyzer prior to implementation to assess the nature of the particular band chosen. If it turns out to be crowded, the in-band noise floor will be high and the signal-to-noise ratio will be unfavorable, thereby adversely affecting the wireless range and performance. Alternatively, since spectrum analyzers are expensive, end users also can select a radio transceiver that has the ability to scan the ISM band in which it operates and assess the spectrum viability.

Near-band interference. Another potential pitfall is RF noise interference from sources spectrally adjacent to the ISM band. For example, the FCC-reserved space for the 900 MHz band is 902 to 928 MHz. Unfortunately, several legacy paging systems use the space immediately above this in the 929 to 931 MHz range. While this frequency is not actually in the ISM band, the near-band interference can be significant since the output power from the paging tower is often several orders of magnitude higher than the lower power commercial off-theshelf wireless Ethernet systems running in the ISM band itself. To address this, notch filters preferentially discard all frequencies except the band in which you are operating. This allows the installer to add an inline component to neutralize the adverse effects of this interference.

Training. Many wireless Ethernet manufacturers offer free technical training, either with online webinars or, in some cases, on site and in person, in conjunction with their network of manufacturers’ reps. End users should participate in this training before attempting to install a large-scale wireless access control system.

Technical support. If an end user is new to the technology and the selected product suite, it is important to have access to the manufacturer’s technical support team during the early stages of the job. Beginning the project late on a Friday afternoon and planning to work through the weekend may not be in your best interest until you are comfortable with the process and potential issues.

Replacement/spare parts. As with any mission-critical network technology, it is always a good idea to keep spare parts on hand. For example, if you have deployed 25 radio transceivers, antennas and mounting hardware, it might make sense to purchase one or two extra kits in case of a failure.

The most likely cause of system failure is human error. The most important thing to do prior to beginning an installation is to read the user manual. Always use high-quality cabling and connector components. Skimping can cost you hundreds of dollars in labor costs and down time. As with any networking device, check the connectors and cabling to make sure they are seated properly and are in good working condition.

Additional Factors
If there is a poor signal-to-noise ratio, and as a result, the system is dropping Ethernet packets and unable to reliably send data, you should check to see if there is inband or near-band interference in the area, or if your neighbor has installed a high-powered source of RF interference recently. Also determine if you are attempting to transmit too far or through obstacles with an RF spectrum not designed for this purpose. Consider swapping the radios for another frequency that may be better suited for your installation. Also, check to see if the system is using directional antennas. Omnidirectional antennas suffer a double whammy: not only do they have less transmission power, but they also pick up interference from all directions. If you are already using a directional antenna, try upgrading to a more powerful model with more RF gain.

In reviewing the published cost-benefit analyses of wired IP-based access control systems, we see that it generally makes sense to use the existing network infrastructure -- versus installing dedicated cabling -- to transmit access control data from doors and gates back to a central management server or off-site backup. It is for this reason that most industry experts believe that, over time, traditional proprietary access control systems will be replaced by open-standard Ethernet-based systems.

To examine a basic total cost of ownership, use the formula of TCO = [(equipment + installation labor) + disruption in service] + long-term maintenance to compare and contrast wired versus wireless access control solutions. It will reveal that using wireless transmission technologies is not always wise. For example, when network cable is already in place at the door or for short cable runs, the additional cost of the radio and antenna at the control panel or door is not justified. If new cable has to be pulled, then the total cost of cable, labor and disruption of service must be compared to the cost of a radio transceiver and antenna at the panel or door.

There are many compelling reasons to use open standards -- such as Ethernet -- to transmit access control data. Furthermore, in many cases, it makes sense to send an Ethernet packet via a low-cost wireless radio transceiver rather than copper cable or glass fiber. In the end, this cost-benefit analysis must be performed for each project undertaken, which will in turn reveal the appropriate network architecture for the job.

Back to the Future
The ability to use a single radio platform to transmit Ethernet and RS-232/RS-485 serial data is compelling. Therefore, much work is currently being done in integrated Ethernet/serial radio transceivers. Look for the continued release and refinement of this dual-platform approach to add to the current generation of radios capable of handling specific proprietary access control protocols such as Wiegand.

The latest release in the class of 802.11 Ethernet transmission systems is the “N” specification. The 802.11N protocol uses MIMO multipath processing and channel bonding to offer some advantages in range and net throughput over traditional Wi-Fi solutions. Several mainstream manufacturers have released products in this category with more to come over the next several years.

During the last five years, mobile phone technology has evolved to include data transmission at moderate speeds and distances. Integrating this technology into fixed-in-place devices allows the system designer to install 2.5 G and 3 G network cards to send/receive data from a variety of platforms. These technologies are becoming faster and more cost effective.

WiMax, a new technology that began its conceptual development in 2001, is based upon the 802.16 standard and uses fixed-in-place high-powered transmission equipment to send and receive high-speed data. The WiMax forum, which developed and manages the framework, describes WiMAX as “a standards-based technology enabling the delivery of last-mile wireless broadband access as an alternative to cable and DSL.” Connecting to a WiMax network will allow the end user to send and receive moderate to high-speed data rates with the network to connect remote access-control devices.

Since the data rates in question are orders of magnitude lower than in the case of IP video products, the challenges associated with bandwidth consumption also are minimized, and the rate of adoption of networkbased access control systems will continue to grow. The use of wireless transmission to support the remote deployment of Ethernet devices is a natural extension of the technology and will only accelerate the growth of IP-based access control solutions.