Remote - Winter 2012 - (Page 16)

Applications - Feature Challenges of Remote Management Over Satellite Successful Practices from the Front Lines of Africa Adriaan Vorster, Chief Technology Officer Transtech Africa Global Looking across the African savannah, one can see desolate vistas as far as the eye can see. Considering how dispersed the population centers are over this continent, it’s easy to understand why land-based infrastructure has lagged, and why you’ll see a landscape increasingly dotted with satellite dishes perched high on bluffs and plateaus. Many of these are hubs providing cellular backhaul for Africa’s increasingly vibrant market for wireless voice and streaming data. While satellite has been a boon, bypassing the need for wireline communications, it does present some weak links given its RF nature. So, whether you’re an Internet Service Provider (ISP) providing connectivity to remote townships in Africa, have a fleet of oil rigs throughout the Gulf, or operate SCADA systems for pipelines, managing the remote equipment that makes it up these networks can be all the more complex when it’s over satellite. Let’s consider why first. Unlike over fiber and copper, signals traveling long distances over satellite can experience inherent delays, while also being affected by weather conditions and solar events, all of which can cause network latency, or even worse, total loss of communications. Then there are remote device protocols that often aren’t robust enough to adapt when these degraded conditions occur, leading to the status requests and commands sent out to the devices being lost. Alarms from devices using protocols such as SNMP, which are broadcast-based, send traps out to the world, but can’t confirm the receipt. So, if they’re never received, no one may be aware if there is a problem at the site. Operators are then left in the dark, or mistakenly believe that everything is fine when critical conditions might exist out in the field. They might even inadvertently bring down the site by acting on stale or incorrect information on their screen. Also, let’s not overlook the matter of security. Data from most equipment using Serial protocols do not support encryption, since in most cases they aren’t meant to work over a satellite link. This leaves the door open for unauthorized access, and for those with malicious intent, the ability to gain control of the site via the same satellite access point being used by the operator to control the site. These are of some the challenges faced by Transtech Global in South Africa when building VSAT (Very Small Aperture Terminals) and small to mid-size ground stations for ISPs and SCADA network operators across the continent. With several hundred site installations throughout countries such as Zambia, Congo, Sierra Leone, Niger, South Africa, Kenya and Chad, Transtech has installed remote satellite terminals in some of the most challenging geographic and diverse climates. Physically accessing these sites is costly and can require several days of travel over rugged and sometimes dangerous terrain. When there is a problem out at the remote site, for example a power outage or rain fade condition, network operators need to be able to identify the source of failure, and, if possible, to remotely recover the site, avoiding the costly and lengthy delays of dispatching a technician 16 www.RemoteMagazine.com who may be tens or hundreds of miles away. Without having visibility into the site’s equipment status, there’s also the chance the technician might arrive without the components for a needed repair. Considering that the most significant expense is the cost of leasing bandwidth on the space segment, a major challenge for Transtech was to provide operators with an affordable way to remotely access and manage their equipment over the satellite. That’s enough to control the remote equipment using the least amount of bandwidth possible, yet still maintaining the speed and status updates required to effectively and securely manage the remote site. Trying to poll the equipment from the Network Operations Center (NOC) over the satellite directly was often impossible due to the limited bandwidth, the variety of physical interfaces required, and the large number of requests that had to be sent over the satellite link using a wide variety of protocols. To handle these issues, Transtech elected to use an intelligent controller at the remote sites to handle the equipment polling, selecting the COMPASS Mercury appliance from Kratos. The appliance supports the various protocols and physical interfaces that communicate with the diverse range of equipment at the site. For instance, most of the RF equipment associated with the communications uses a serial protocol over an RS-232, RS-422 and RS-485 port. The network routers and servers use an SNMP protocol over the Ethernet network; and the fire and door alarms are contact closure based. All of these can be accommodated in a single 2U 19 inch rack mounted COMPASS remote site management unit. The COMPASS software, running on the appliance, polls the equipment over whichever physical interface the device supports, using whatever protocol or language the device uses to communicate. Once COMPASS has the data from the devices, it can send it to the NOC over the satellite link. It’s important to consider that the main purpose of networks for SCADA systems and ISPs and is to serve the business and customers, not to use bandwidth to manage the remote equipment. So for a SCADA network, the main satellite channel would be used for the data from the Remote Terminal Units (RTUs) and Programmable Logic Controllers (PLCs) coming back to the SCADA control software, and for an ISP, it would be the email and internet content for communications. In both cases, the operators want to minimize the amount of traffic for controlling the equipment at the remote site for operational and cost purposes. Often times, this control has to be done through the Satellite Engineering Service Channel on the modem which is allocated to very low bandwidth, usually in the range of 4.8 Kbs32 Kbs. To maximize the throughput, the remote software only sends the changed data back to the NOC. So as the system polls the equipment at the remote site, it compares the result to what was last sent to the NOC, and if it hasn’t changed, it doesn’t send anything, helping minimize the traffic over the small pipe. To further adjust the amount of data being sent over the satellite link, a Making Remote Equipment Smart Equipment Protecting Valuable Bandwidth Out in Africa http://www.RemoteMagazine.com

Table of Contents for the Digital Edition of Remote - Winter 2012

Remote - Winter 2012
Editor's Choice
Automated Monitoring Out at the Network Edge
What’s in Your Radio Communication Tackle Box?
When Does Solar Make Sense for Remote Sites?
Utility Networks in Transition
TV White-Space Technology Makes Broadband Affordable for Remote Locations
Challenges of Remote Management over Satellite
SCADA Market: Charting Strong Growth Amidst Industry Speculation
SCADA
Networking
Security
Oniste Power
Environmental Monitoring
Industry News

Remote - Winter 2012