The (test) specifications of radio access technologies for certification are usually limited to
the assumption there is no other device or other RF source active at the very same frequen-
cy of operation. For example, traditional EMC tests generally exclude frequency bands in
which the equipment under test (EUT) uses wireless communications.

Even newer technologies, which in principle provide coexistence mechanisms, cover problems almost only within their own radio access technology. In addition, there are often only less stringent regulatory
requirements for this:
• Frequency Hopping Spread Spectrum
(FHSS)
• Listen before talk (LBT)
• Limitation of the duty cycle
• Carrier sense multiple access (CSMA)

Thus, the test remains limited to the individual technology – although the complexity in wireless coexistence increases with the degree of utilization of the shared spectrum. This becomes problematic in the case of unlicensed frequency bands (e.g., ISM), in which proprietary radio access systems that
are not well known are also permitted. In contrast, the problem does not arise in licensed frequency bands.

Coexistence has a fundamental influence on the low-interference use of devices using wireless technologies. Unexpected incidents can be avoided by evaluating the wireless coexistence. For this purpose, the usual tests for product certification are important – but not sufficient anymore.

Therefore, they should be supplemented by tests according to the ANSI C63.27 standard. It takes into account the intended product environment and helps to assess satisfaction with dedicated KPIs, verification of the FWP and QoS to ensure user satisfaction. True to the motto “prevention is better than cure”, the wireless coexistence of devices should be taken into account. This testing is already
mandatory for the use of medical devices in the USA. cetecom advanced carries out the corresponding coexistence tests on request, also complementary to the basic certification process.