• • • TEST & MEASUREMENT • • • Testing in a communications
Phil Beecher, president and chief executive of the Wi-SUN Alliance, says critical to providing reliable connectivity is the testing of products to ensure that they comply with the right standards
T
esting is of course critical in most networking scenarios. At Wi-SUN Alliance, for example, products undergo rigorous
testing by independent authorised testing laboratories to ensure that they meet the specification requirements. We could consider that it essential to implement
the same thorough approach in all aspects of a product implementation. It is well understood that it is far more
expensive to rectify problems with a product once it’s been released into the market than to fix it prior to deployment. Not only is there a cost implication, but there is
also the reputational impact. Malfunctioning equipment isn’t just a headache for customers, who may think twice about placing orders in the future, but also has serious repercussions in sectors such as healthcare and aerospace where safety is critical. Highly stringent testing processes are absolutely
required for these (and similar) industries. However, there is also a commercial
consideration; the cost of testing a product must be proportionate to the selling price. Typically, communications product type testing falls into three key areas:
Conformance testing To ensure a product meets the requirements of a relevant specification or standard, i.e., does the product do everything it’s supposed to?
Interoperability testing To ensure products that have passed conformance testing also work as intended with other relevant equipment. This provides an additional check to cover situations where conformance testing is not viable.
End-to-end testing This ties everything together to make sure all of a product’s hardware and software components function correctly in the final application. Typically, this covers testing across multiple specifications. In a communications environment, end-to-end
testing requires that a product is tested across each of the seven layers of the Open Systems Interconnection (OSI) networking reference model. That means the physical (radio) layer, the data link layer (including medium access control and link control), and the network, transport, session, presentation, and application layers.
Therefore, end-to-end testing is so important.
While conformance or interoperability testing may only deal with a subset of the OSI model, end-to- end testing is holistic – requiring a meticulous layer-by-layer approach. For example, smart grids as a typical scenario in
the kind of communications environment where Wi-SUN protocols are used. Smart grids and metering systems can help energy companies achieve operational efficiencies and deliver a better customer experience. But to maximise the benefits to businesses and end users, they must be built with robust, conformant, and interoperable products, based on recognised open standards. So, if we consider a smart meter for example, a
rigorous testing process will check whether the meter can correctly measure energy consumption, with a variety of loads and supply conditions, that it can communicate reliably and securely, and successfully send relevant data to the utility back-end. In detail, the test coverage should include three important areas:
Metrology Connect the meter to an energy source and an energy load and using appropriate test equipment, run it for an allotted time and under a wide range of load and supply conditions and check that the smart meter has measured the correct energy usage.
Communications Check that a device correctly identifies the network to join, authenticates correctly, communicates reliably and securely over that network, and responds correctly under different communications network conditions.
Data exchange Provide a testing environment to emulate the utility back-office environment, which can then verify that the data sent from the meter is correctly formatted and matches the format expected by the application. Each of these three stages uses a combination
of conformance and interoperability testing. When integrated, they provide an end-to-end test system capable of providing good coverage and reliability. Multi-layered testing is essential, particularly for
managing reputational and financial risk end-to- end. Importantly, it should be run before products or equipment are put into production to expose any issues or weaknesses. However, organisations may also benefit from running production line testing occasionally to prevent any costly mistakes from creeping into the system.
32 ELECTRICAL ENGINEERING • DECEMBER 2022/JANUARY 2023
electricalengineeringmagazine.co.uk
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