In the realm of the Internet of Things (IoT), devices transmit data known as packets wirelessly to the cloud for powerful business applications and use cases. A wide range of connectivity protocols exists to support IoT solutions, and while each has its strengths, considerations, and unique properties, a common theme exists among all networks: reliability is critical for performance and data viability. However, packet loss and delays represent common challenges for wireless networks impacting the efficiency of data transmission.
LoRaWAN® (long range wide-area network), a prominent player in the IoT landscape, is designed for transmitting small amounts of data over long distances, especially in challenging environments such as deep indoors, underground, or in outdoor applications. Yet, even with its inherent strengths, ensuring consistent and timely data transmission remains top of mind. In this article, we delve into common causes of late packets and explore mitigation strategies to ensure network reliability and performance.
What are Late Packets and Why are they Important?
In a LoRaWAN network, devices transmit packets at specific intervals, determined by parameters such as the data rate and frequency. These intervals are crucial to ensure efficient network utilization and minimal energy consumption. However, like with any network protocol, packet loss or delays can occur for several reasons including network congestion, interference, and device behavior. Late packets have several implications on the performance and reliability of IoT applications, including:
- Reduced Network Efficiency: Late packets consume airtime that could have been used by other devices. This inefficiency leads to decreased network throughput and increased latency.
- Battery Drain: Transmitting late packets requires additional transmission attempts, resulting in higher energy consumption for sensors – all of which drains battery life, negating one of LoRaWAN's key advantages.
- Data Staleness: The performance of applications relying on real-time or near-real-time data may suffer due to late packets. For instance, in environmental monitoring applications, delayed sensor data might lead to inaccurate, immaterial, or obsolete insights.
Thus, it’s important to optimize network performance to ensure mission-critical data is captured and delivered in a timely fashion.
6 Network Planning Strategies to Mitigate Packet Loss and Delays
The following mitigation strategies and solutions help reduce the likelihood of packet loss or late delivery.
- Optimize Gateway Density: One of the primary reasons for late packets is network congestion. As the number of devices increases, the available airtime for transmitting packets becomes limited or congested. This overcrowding can result in delays as gateways may be in the process of receiving other packets concurrently, leading to competition for channel access. Increasing the density (or amount) of gateways can alleviate network congestion, improving overall coverage and reducing the likelihood of late packets. It’s important, however, to find a balance between fault tolerance, efficiency, and reliability with gateway density.
- Strategize Gateway Placement: While LoRaWAN networks can cover vast areas, the distance between the sensor node and the gateway plays a fundamental role in connectivity. As the distance increases, the signal strength diminishes, making it more susceptible to interference, obstacles, and environmental conditions. This attenuation can result in late or lost packets, especially when devices operate at the edge of the network coverage area. To ensure desirable outcomes in a wireless LAN (WLAN) deployment, begin with a site survey to assess the Radio Frequency (RF) behavior. Determine the building type (e.g. skyscraper, mid-rise, high-rise – each has unique best practices for gateway placements) and the building construction materials, observing potential physical impediments that could impact transmissions. Strategically planning the placement of gateways to optimize their coverage areas can help mitigate signal attenuation and improve chances of timely packet delivery. Keep in mind that the spreading factor (SF) varies based on distance (the greater the distance of the device to the gateway, the higher the spreading factor).
- Employ Collision Avoidance Techniques: LoRaWAN employs a unique modulation scheme and spread spectrum technology to minimize the likelihood of collision, but it doesn't eliminate the possibility entirely. If multiple devices attempt to transmit packets simultaneously or if network interference causes collisions, devices will be forced to retry transmission. Collision avoidance techniques such as randomized backoff times can improve channel access efficiency and help reduce collisions.
- Optimize Adaptive Data Rate: LoRaWAN supports adaptive data rate (ADR), allowing the dynamic adjustment of individual device transmission parameters based on network conditions. By optimizing these parameters, ADR helps mitigate collisions and improve the reliability of data transmission, while enhancing battery life and extending network capacity. Optimizing gateway and device placement is important as well for ADR and SF. LoRa modulation includes six spreading factors ranging from SF7 to SF12 which influence data rate/speed, time-on-air, battery life, and receiver sensitivity. Prioritizing a lower spreading factor like SF7 can ensure the highest bandwidth and lowest airtime which helps with battery efficiency.
- Enable End-Device Confirmed Uplinks: A confirmed uplink is when a LoRaWAN endpoint (or the end-device) requests a LoRaWAN network to confirm receipt of its message, known as an acknowledgement or “ACK.” If the device does not receive an ACK within a specified time frame, it assumes the packet was lost and initiates a retransmission. The packet will be retransmitted until an ACK is received from the LoRaWAN® network server, or a preconfigured maximum number of attempts is reached. Adding this acknowledgement mechanism into the communication process ensures that critical information reaches the network server, reducing the risk of data loss.
- Promote End Application Resiliency: Designing end applications with inherent resiliency enhances their reliability and helps ensure proper, proactive handling of late packets. This includes implementing mechanisms that account for delayed or out-of-order data. For example, utilizing timestamping or sequence numbers in packets enables the detection and correction of inconsistencies caused by late arrivals. By dynamically anticipating, identifying, and addressing late packets, the insights and actions derived from data remain accurate, viable, and meaningful, even in the presence of occasional delays.
Empower Reliable, Responsive IoT Ecosystems
Consistent, reliable network performance is essential to sustain your IoT solution without falter. By implementing adaptive strategies, optimizing network infrastructure, and delivering effective device management, LoRaWAN solution providers can create powerful, responsive, and scalable IoT ecosystems to help customers address today’s needs with an eye to the future. Click here to get started with MachineQ today.
