The Issue of Device Densification in NB-IoT Networks
(Spanish Version Available ) NB-IoT (NarrowBand Internet of Things) networks have seen rapid adoption in recent years to connect IoT devices that need to exchange small data packets occasionally and require long battery life (on the order of 10 years of operation).
However, with the exponential massification of use cases for NB-IoT in smart cities, smart meters, asset tracking and infrastructure monitoring among others; the density of NB-IoT nodes deployed in limited geographical areas has increased considerably. This increase in NB-IoT device density poses a series of technical challenges to ensure reliability, low latency, and maximum battery life.
Technical Issues Behind Densification
The main problems arising from densification of NB-IoT devices in a small space are:
Analysis of the Impact on Battery Life
One of the most critical effects of this issue is the significant reduction in the battery life of NB-IoT devices densely deployed in a limited area.
With a higher collision and interference rate, the percentage of messages successfully received on the first transmission attempt decreases. The need to repeatedly retransmit the same messages until delivery is confirmed means that the NB-IoT communication module must remain powered on longer, in transmitting state and consuming energy from the battery.
Considering that most NB-IoT devices have a specification of 10 or more years of battery life, this premature consumption increase due to densification jeopardizes achieving the desired requirement.
Recent research shows that in densified NB-IoT environments, battery consumption can grow by up to 40% compared to consumption in a cell with low node density. Clearly, this effect shortens the operational life and would require battery replacements sooner than expected.
Potential Improvements and Technological Solutions
There are some potential ways to alleviate or mitigate this problem of reduced battery life due to densified NB-IoT cells. The main alternatives are:
However, research to mitigate the problems of shared resources in dense IoT environments is still incipient. More efforts and collaboration between operators, equipment manufacturers and specialized research groups in this field are required.
Real-World Challenges in Cellular IoT Power Management
As someone with years of experience deploying IoT solutions, I have found that one of the main energy management problems stems from rigid adherence to standards by operators and module vendors without considering real-world complexities.
The lack of proper energy and network management measures can lead to huge operational costs for management companies, where the underlying expense remains hidden beneath layers of unforeseen issues.
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A clear example is the religious use of technologies like PSM and eDRX power saving modes. Devices are forced by operators to establish parameters for the connection, but if the network becomes saturated and the device is unable to reconnect within its TAU window, it will be rejected and required to fully reattach.
If such connection retries are not contemplated, managing large fleets across geographical areas can be catastrophic. Imagine having to replace 1000 water meters, considering legal concessions, contracts, and above hardware costs if new units are needed.
In my experience, both operators and module makers advertise battery lifetimes and energy efficiency capabilities that may not hold up under challenging real-world situations. Too much faith is placed on network resilience against interference, coverage gaps and congestion.
The industry is making gradual improvements as technologies like NB-IoT and LTE-M incorporate power optimization mechanisms into the standards themselves. However, exaggerated marketing claims continue to place unrealistic reliability expectations on companies handling massive IoT deployments.
Better transparency, thorough field testing before commitments, and anticipating edge case flaws in the technology's robustness is key. Upfront evaluation of energy performance across diverse environments can avoid profit-damaging experiences down the line. Stay tuned for more insider knowledge on pragmatic adoption of cellular IoT.
In Conclusion
The densification of NB-IoT devices is far from stopping due to multiple emerging use cases in IoT leveraging this technology. But the associated challenges, especially reduced battery life, must be tackled jointly between various stakeholders. There is hope in evolutionary technological solutions for NB-IoT to minimize energy overconsumption in densified environments. And thus ensure future scalability of LPWAN networks.
There are several sources of interesting information on the issues of device densification in NB-IoT networks:
The Nokia document "NB-IoT - Enabling New Business Opportunities" presents good analysis on the challenges of implementing large-scale NB-IoT, including high device density.
In the research paper "Scaling NB-IoT - Technical Possibilities and Requirements" from Fraunhofer Institute researchers, aspects such as interference, latency and battery consumption are analyzed when increasing density.
The IEEE held a specialized conference "ICC 2019 - IoT Density" where several papers addressed densification issues specifically in NB-IoT, such as efficient management of radio resources.
In the 5GAA (5G Automotive Association) industry alliance there are reports such as "C-V2X Ecosystem Build-up Issues" that examine QoS in dense environments for cellular-based vehicular communications.
The IMDEA Networks Institute has several interesting publications on scheduling and interference management in NB-IoT with increased device density.
Major NB-IoT chipset providers such as Qualcomm, HiSilicon, Unisoc also investigate optimizations in this area.
All focused specifically on the challenges of adequately scaling densified IoT over existing LTE networks.
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