Offshore: Microwave Radio use in Explosive Situations

BATS-Aviat stabilized microwave antenna system certified ATEX and IECEx Zone 1 for use in explosive environmentsIn oil and gas exploration, danger’s part of the business. In particular, offshore drilling is hazardous (e.g., water inundation, drill-hole blowouts). However, there are acceptable levels of risk, and the industry participants take those into account when they work in the field. But one item that should not be a hazard is the microwave radio installations rigs and other platforms use to communicate to shore.

As all know, microwave radios use a certain amount of electricity in order to operate. And microwave radios, waveguides and antennas emit energy when they transmit. However, onboard an offshore rig or other types of floating production, storage and offloading (FPSO) vessels flammable gasses are always present and have the possibility of becoming explosive in the presence of operating microwave radio equipment.

Until recently there were few solutions that could offer protection against the high chance of calamity associated with using microwave aboard an FPSO. Now there is a solution that has passed ATEX and IECEx Zone 1 certifications for mitigating the danger of explosive gasses: the BATS DVM ExP2 has passed both major safety body equipment requirements for operation in potentially explosive atmospheres.

Pressurized radome keeps flammable gas away from Eclipse radios
The BATS pressurized radome enclosed antenna aiming and tracking system (AATS) combined with one or two Aviat ODU 600s connected with a 0.9m or smaller antenna is the only microwave radio solution for potentially explosive atmospheric situations that is certified for use as per these two leading safety regimes. The system purges any potential flammable gas from the radome and once pressurized keeps any flammable gas out and away from the powered microwave radio.

Gas cannot get inside due to the positive pressure of the system. The only way gas could enter is if there is no longer positive pressure within the dome. In that case, everything in the dome is automatically shut off. The system is designed so that there is no possible way for gas to enter the system and any electronics to be active. All microwave and stabilization systems are plugged into a hardwire PDU/alarm system that automatically shuts power off at the source in the event of a loss of pressure.

Only antenna alignment system based on two technologies
Combined with its AATS capabilities to align microwave antennas onboard floating platforms to shore, a BATS-Aviat microwave radio antenna solution can stabilize the microwave signal on a vessel or platform as it moves—due either to sea motion or sway. This system uses two types of alignment technologies: GPS and Signal Quality Tracking Algorithms (SQTA).

With SQTA, the microwave radio beam is tested for the center of the beam, which is aimed directly at the center of the receiver. This algorithm runs continuously resulting in a dynamically aimed system through the BATS sync system, keeping the link on beam as much as possible as the ocean conditions change and move the floating platform. Systems that rely exclusively on GPS to accomplish microwave antenna alignment between ship and shore—and vessel to vessel—are very inexact, achieving lower quality links that may be off-center with only a portion of the signal strength and capacity of an on-beam signal.

In addition, in emergency shutdown (ESD) situations, it is unwise to have heavy reliance on GPS because if the floating platform is powered down, the GPS units will also lose power. A BATS-Aviat solution has its own internal power and using the signal tracking algorithm, it can maintain a last line of communication to shore or a companion rig when everything else onboard is shutdown.

For more information on the BATS-Aviat microwave radio antenna alignment solution, please download the datasheet.

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All-Outdoor Microwave Radios: Site Considerations

One of the great things about the microwave radio market today is the diversity of products available to network operators. But like many situations where there is a glut of options, it tends to put more stress on making the right choice.

An operator looking at products in the microwave radio sector will notice that there are three general categories of product to choose from: all-indoor, split-mount and all-outdoor, and within each, they are myriad different flavors.

All-outdoor radios are the most recent addition to the microwave radio party, and for the sake of easy reference, I’ll refer to them as ODRs (outdoor radios). These self-contained systems incorporate the traffic interfaces, switching/multiplexing elements, radio modem and radio transceiver—all packaged in a weatherproof outdoor housing. By contrast, an outdoor unit (ODU) used in split-mount systems only contains the radio transceiver, which connects to a radio modem embedded in an indoor unit (IDU). In a split-mount radio system, the IDU also provides the traffic interfaces and switching/multiplexing elements.

The rationale for ODRs is straightforward—networks are getting denser, new sites are getting smaller and established sites more densely populated. Space for equipment such as IDUs is at a premium and costs of upgrading sites with bigger equipment shelters is often not viable or possible due to site constraints. As a result, more network devices are being repackaged for deployment outdoors on supporting structures such as towers, walls or masts. Advances in electronics have made microwave radios viable for all-outdoor treatment, so ODRs came into being.

They did so to a fanfare of claims that pointed to fantastic gains in terms of operator TCO (total cost of ownership). No doubt, an ODR can deliver cost benefits, but it is important to fully scope and quantify those benefits, because although ODRs represent simplification in terms of product architecture, most networks have remained stubbornly complex. In practical terms, this means for each type of site in the network an operator needs to closely examine the gains an ODR might generate vs. a split-mount radio, for example. Our experience is that ODRs provide the most operator benefits at sites where:

  • One gigabit Ethernet (GbE) interface is adequate
  • Only a single local device will be connected (such as an LTE basestation)
  • There are no requirements to aggregate traffic from “downstream” sites
  • Out-of-band management facilities are not required
  • Non-protected (1+0) link configuration is adequate

Once operators consider sites with requirements beyond this scope—usually the majority—then ODRs (somewhat ironically) start to generate complexity and cost. This becomes manifest in the form of multiple Ethernet cable runs, multiple power cable runs, multiple PoE injectors, multiple lightning protection devices and, in some cases, the need for a separate outdoor Ethernet switch.

Even at modestly complex sites, the overhead costs ODRs can generate mean that a split-mount radio will often be a more effective option and deliver better TCO, assuming space can be found. On that note it is worth highlighting that IDUs already deployed at such sites are often modular and can be scaled without consuming any additional rack space, and the most advanced fixed (i.e., non-modular) IDUs only consume a half-rack unit of space.

On the surface, the case for ODRs can seem compelling but before jumping in, I would encourage operators to carefully examine how marketing claims translate into meaningful (real) TCO gains.

I am convinced ODRs represent a new and potentially very useful product category for microwave radio, but they are not a panacea; our experience (at Aviat Networks) is that optimum TCO is based on a mix of split-mount and all-outdoor radios (i.e., one “size” does not fit all).

So there you have it, in the right environment, an ODR can offer a winning formula but in other situations, it may not work so well. An old saying comes to mind: Knowledge is knowing a tomato is a fruit, but wisdom is knowing not to put a tomato in a fruit salad.

Next time, we will examine ODRs in more detail, how they differ and how to choose the best option for your network.

Jarlath Lally
Product Marketing Manager
Aviat Networks

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