[Paper Review] 868 MHz Wireless Sensor Network - A Study

Pushpam Aji John, Rudolf Agren+3 more|arXiv (Cornell University)|Sep 2, 2016

Energy Efficient Wireless Sensor Networks5 references3 citations

TL;DR

This study evaluates 868 MHz wireless sensor networks using XBee radios in an urban university environment, demonstrating superior range and lower interference compared to 2.4 GHz bands. The network achieved reliable 300m line-of-sight coverage with minimal packet loss, suggesting 868 MHz is viable for large-scale outdoor deployments despite environmental signal degradation from weather and fading.

ABSTRACT

Today 2.4 GHz based wireless sensor networks are increasing at a tremendous pace, and are seen in widespread applications. Product innovation and support by many vendors in 2.4 GHz makes it a preferred choice, but the networks are prone to issues like interference, and range issues. On the other hand, the less popular 868 MHz in the ISM band has not seen significant usage. In this paper we explore the use of 868 MHz channel to implement a wireless sensor network, and study the efficacy of this channel

Motivation & Objective

• To assess the feasibility of using the 868 MHz ISM band for long-range wireless sensor networks in real-world urban environments.
• To compare 868 MHz performance against the crowded 2.4 GHz band, particularly regarding interference, range, and packet loss.
• To evaluate signal propagation, RSSI strength, and environmental impact on radio transmission in a deployed WSN.
• To investigate the role of weather conditions (rain, humidity, fog) and multipath fading in causing packet loss.

Proposed method

• Deployed a custom 868 MHz WSN using XBee modules on Arduino-based Seediuno Stalker boards with ATMega328P microcontrollers.
• Equipped sensor nodes with temperature, humidity, oxygen, and particulate matter sensors, transmitting 100-byte payloads every 3 minutes.
• Used a pcDuino-based base station running Lubuntu and Python to capture, timestamp, and forward packets to an IoT cloud platform.
• Conducted a 1-week experiment with all radios active (no duty cycling), transmitting at 300mW (24dBm) power.
• Measured Packet Error Rate (PER) as the number of missing packets per hour (20 packets expected per hour).
• Analyzed RSSI and packet loss across three nodes at varying distances and environmental conditions, including weather data from local stations.

Experimental results

Research questions

• RQ1 Can 868 MHz wireless sensor networks achieve reliable long-range communication in outdoor, urban environments with obstacles and weather variations?
• RQ2 How does environmental weather (rain, humidity, fog) affect packet loss and signal strength in 868 MHz WSNs compared to 2.4 GHz bands?
• RQ3 To what extent do multipath fading and non-line-of-sight conditions degrade performance in 868 MHz WSN deployments?
• RQ4 Is there a measurable correlation between atmospheric conditions (temperature, dew point, pressure) and radio link reliability at 868 MHz?

Key findings

• The 868 MHz WSN achieved reliable line-of-sight coverage up to 300 meters with average RSSI above 40% and no observed packet loss in this range.
• Only one node, located in a separate building with an air pocket between it and the base station, exhibited significant packet loss, suggesting environmental obstruction as a key factor.
• Packet loss correlated with adverse weather conditions such as high humidity, rain, and fog, likely due to absorption and scattering losses in the radio wave path.
• Signal degradation was attributed to both atmospheric absorption (L_abs) and scattering (L_scat), with total wave loss modeled as L_tot = L_abs + L_scat.
• The study found that environmental factors like weather and fading were more impactful than indoor climate variations, which remained stable across the test period.
• Despite interference from 4G/LTE UE devices being a known issue, no such interference was observed during the experiment, suggesting 868 MHz may offer better coexistence in certain scenarios.