Choosing IoT connectivity technology needs careful consideration of multiple technical and commercial factors linked closely to individual use cases. Different applications favour different technologies so that what the product is designed to do is a critical factor in the design decisions. This series of articles discusses what a successful LPWAN technology looks like.
Last time out we considered network range and discovered that in fact it doesn’t matter a whole lot, at least not to the user. This time around we’re going to focus on reliability.
If you’re following this series you’ll recall that I have grouped technologies into three categories – LAN/PAN at one end, 3GPP options at the other and an increasingly busy centre ground roughly described as LPWAN. This is the focus of these articles with the goal being to provide guidance on which is right for your application. No single technology is right for every product or use case so it is certainly not the intention of these articles to advocate a particular commercial proposition. Instead I am discussing the implications of the technology choice in terms of particular parameters.
Choosing connectivity technology is complex – there are a lot of features and benefits, often conflicting, to weigh in the balance. So these articles distil the key characteristics that define an IoT connectivity technology to identify those important to your particular use cases. We think that the strength of an IoT connectivity technology can be defined in terms of the following eight parameters. Today we’re focusing on the fourth in this list – reliability.
- Quality of Service
- Battery life
- Proprietary vs Standard
By reliability we normally mean messages getting through consistently day after day, throughout the lifetime of the device. There is also an element of QoS in that the messages should be received within a desired time frame.
There are a number of factors that could prevent message transmissions including:
- Hardware failure
- Software bugs that either become worse over time or cause issues such as re-starts
- Growing network congestion
- Worsening reception perhaps due to increased interference or deteriorating antenna
Most important in delivering a reliable network is acknowledgement of messages. A device, or the network, will then know if a message fails to get through, or takes longer than anticipated and can flag this issue to users or network managers. This enables problems to be resolved quickly and deteriorations in performance to be identified and diagnosed. It also allows devices to re-transmit messages until they do get through, helping to provide a reliable service even in unfavourable conditions.
Software bugs, glitches or security loopholes can occur at any time. We’ve become accustomed to weekly updates and patches to Microsoft Windows and Android Apps. While IoT devices should need far less frequent updates, they will nevertheless need to have software changes from time to time as networks and services evolve. Only those systems that can efficiently and quickly upgrade the device software will maintain reliability across the years. And reliable software upgrades require bidirectional capability.
Network congestion can be overcome in many ways, but one of the best approaches is to have a highly efficient system such that congestion may never occur, and when it does it results in graceful degradation rather than system failure.
LPWAN requirements for reliability
Choosing a low power wide area network technology has traditionally involved a compromise – high performance, high cost and high power consumption from cellular based technologies operating in licensed spectrum or more modest performance from a low cost, low power technology in licence exempt bands. Today the decision will typically be driven by the use case; where cost and power consumption are not critical and where Quality of Service and reliability are priorities then the larger amounts of licensed spectrum with less restriction on transmit power suggests 3GPP technologies. But Weightless-P represents a game changer with its ‘clean slate’ design philosophy. By leveraging proven concepts from cellular technologies with a robust and tailored MAC and PHY, Weightless-P brings carrier grade performance at a low cost, low complexity price point. Indeed, Weightless-P supports licensed spectrum operation meeting mandatory selectivity/blocking performance requirements ensuring good coexistence in licensed bands without any protocol changes. Across all spectrums, including sub-GHz bands, Weightless-P offers industrial grade reliability.
What Weightless offers:
- Fully acknowledged communications
- Auto-retransmission upon failure
- Frequency and time synchronisation
- Supports narrowband channels (12.5KHz) with frequency hopping for robustness to multi-path and narrowband interference
- Channel coding
- Supports licensed spectrum operation