March 29, 2018

Trends in communication analysis: Devices that understand both, spectrum and protocol


Field engineers dilemma

Communication issues in field can be either due to a basic channel physics i.e. inadvertant channel conditions or due to protocol and its respective implementation. A field-engineer would traditionally pack different analysis equipment so they can collect relevant data on both channel and protocol front for post processing. These various equipments would imply connecting a laptop through cable (usually USB-Serial), starting their respective applications and triggering data collection

In addition to diversity of specialized equipment to carry, other non channel related aspects further impact both spectrum and protocol analysis excercise for the PLC case

  • Underground substations, specially in urban areas may have limited physical space for reasonable placement of laptop with connecting cables to analysis device resulting in some very uneasy experiences

  • Outdoor analysis on a rainy day is virtually impossible

Some contemporary anlyzers have started to offer mobile device support addressing some of these practical issues but there are further details which still stay the "Achilles' heel" of a field engineer.

Spectrum analyzer perspective

Spectrum analyzers are usually generic devices, made to measure and display the level of energy on the channel. The generic nature of these equipment requires specific procedures to be applied when using them PLC

  • Owing to basic measurement of energy on channel, any ongoing PLC communication occuring at the time of measurement will need be manually filtered out. This is cumbersome for locations that have a PLC rollout with several active devices

  • Powerline characteristics change as users plug-in and plug-out their appliances on grid resulting various artefacts that impact communication (e.g. impedance, noise). A benign channel at 2 pm in afternoon may look very noisy at 7 pm in evening when most people arrive home from work and a diverse set of electrical equipments get functional. A spectrum analyzer only only takes an instant snapshot while the field engineer is at the location and therefore misses time-of-day related channel characteristics changes

Protocol analyzer perspective

Various chip vendors offer different functionalities in their protocol sniffer devices but these are basic sniffers which once again require additional custom software to post-process data and do not provide a real-time perspective required by a field engineer. Protocol analyzers have become functionally feature rich with front-ends like Wireshark but when it comes to channel analysis, they don not offer anything beyond basic information on received signal strength

Next gen analyzers, doing both channel and protocol analysis

The practical design and state-of-art features of nBox-Tool, coupled with excellent usage experience prompted our customers to ask for spectrum analysis functions in the device. This would not only reduce the inventory of analysis equipments to carry to field but also result in convenience of measurement coming from its mobile device support

Within months, we were working with customers on cases like shown in adjoining picture. Out in field on a rainy day, the nBox-Tool in its IP65 suitcase housing could conveniently sit out in rain with its cables connecting to a closed street cabinet analyzing the powerline channel within. Field engineers could sit in their car in a parking area closeby, connecting with their mobile devices to the nBox-Tool for a realtime analysis of both, the channel spectrum and protocol

At another location that had communication issues, the device was left installed for an entire week, collecting regular snapshots of background noise across the band ranging from 30 KHz to 100 KHz. A week later, upon post processing the collected data, specific times-of-day and days-of-week patterns of channel disturbances were clearly visible, enabling to create a frequency masking profile for optimal functioning.

nBox-Tool in rainy envrionment

The nBox-Tool today is able to perform complete background noise analysis with potential to store weeks of analysis data without requiring any manual interaction, requiring only a standard web-browser on mobile device or laptop to interact with

The scenario brings forward an interesting discussion point on next generation "channel analysis" devices on PLC which:

  • Measure background noise in presence of existing PLC traffic from installed devices
  • Perform protocol analysis both real-time and offline
  • Store weeks of data without requiring manual intervention, facilitating long-term measurements
  • Perform data-crunching to display meaningful analysis displays
  • Require no cabling to connect to a display device/s

We would like to hear your comments and feedback on what you consider to be the future evolution of such devices