The Truth about Quality-of-Service in LPWAN
A Comparative Study of MYTHINGS vs LoRa Technology
In Industrial IoT, network Quality-of-Service (QoS) is hands-down a top priority. Because industrial applications are often mission-critical, failing to get the message through, particularly in times of emergency, can result in costly and even disastrous consequences. Think of situations like material tanks going empty, workers falling from heights or a spike of flammable gases in the atmosphere.
To ensure important data is accessible when needed the most, QoS of the communication network is paramount. A primary QoS indicator is packet error rate (PER) which signifies the percentage of failed transmissions out of total sent messages. In industrial applications, a PER of less than one percent is typically demanded. This study will prove that MYTHINGS delivers significantly higher interference resilience than LoRa technology.
Quality-of-Service in LPWAN
Given their unique range, power and cost advantages, Low Power Wide Area Networks (LPWAN) are expected to answer the growing demand for low-power, reliable industrial M2M communications. That being said, QoS remains a challenge for most LPWAN solutions. This is mainly due to two reasons – their operations in the license-free spectrum and the use of simple asynchronous communication, typically pure ALOHA (a node accesses the channel and sends a message whenever there is data to send). While bringing significant power benefits, uncoordinated transmissions in asynchronous networks greatly increase the chance of packet collisions and data loss. As wireless IoT deployments and radio traffic in the license-free sub-GHz bands rapidly grow, legacy LPWANs potentially come with serious QoS and scalability challenges caused by co-channel interference.
Several mitigation mechanisms are available as add-on deployment options in the Medium Access Control (MAC) layer to reduce packet collisions and improve QoS in LPWAN. One is the acknowledgment of received messages, in which a retransmission attempt is triggered if no packet acknowledgment is present. Another is the Listen-Before-Talk function wherein a node senses ongoing transmission in the radio environment before sending a message.
The problem with these mitigation mechanisms is their persistent trade-off on battery life. They introduce extra communication overhead that considerably increases on-air time and power consumption of every message, not to mention higher complexity and cost of the transceiver design. Adding acknowledgement also raises the chance of failed messages, since a transmitting base station can’t listen for incoming messages. As such, mitigation mechanisms are often bypassed in real-world LPWAN deployments, especially when long battery life is desired. When retransmission is absent, Packet Error Rate becomes the key parameter to gauge QoS in LPWAN.
A Comparative Study of MYTHINGS vs LoRa Technology
To resolve the trade-off between QoS and power efficiency, an LPWAN’s modulation scheme and its underlying physical layer technology must be purpose-built for interference immunity. Most, if not all LPWAN technologies swear by their reliable performance in the crowded license-free spectrum. But, it remains a big question to what extent the statement holds true and how different technologies compare. To accurately picture the difference in interference immunity among different LPWAN solutions, an impartial study has been conducted to evaluate the performance of MYTHINGS vs LoRa technology in the same IIoT-equivalent scenario.
As a widely adopted LPWAN solution, LoRa technology employs Chirp Spread Spectrum (CSS) modulation scheme that claims to provide robustness against interference and multipath conditions. On the other hand, MYTHINGS is an emerging wireless connectivity software platform that implements TS-UNB – a unique LPWAN technology recognized by ETSI for its interference resilience and scalability.
Both MYTHINGS and LoRa networks operate in the sub-GHz frequency bands and employ pure ALOHA. To ensure a fair comparison, in this study, the LoRa system is set to Spreading Factor 12 which offers the highest range and interference immunity.
The following infographic encapsulates key information on the test setup, execution and results.
The study has shown that not all LPWANs are created equal and network QoS under interference can drastically vary from one technology to another. While MYTHINGS could quickly zero out packet loss under heavy interference conditions, packet loss on the LoRa network remained considerably above the 1% permissible threshold. High PER signifies poor QoS and a great unpredictability in message reception. In mission-critical IIoT applications, such a network can fail exactly when you need it the most. A solution purpose-built for interference resilience like MYTHINGS, provides you with a robust and future-proof IoT architecture that enables seamless network expansion while guaranteeing optimal performance. LoRa Technology vs. MYTHINGS technology report.