Wildlife researchers and managers who use wireless telemetry devices generally have three choices for retrieving data: A) Short Range Radio, B) Satellite Uplink and C) Cellular/GSM. Each have their own pros and cons including A) data throughput, B) restrictions on the weight your animal can bear , and C) energy constraints. At CTT™, we want to reduce the significance of these limitations through the Internet of Wildlife®. The remainder of this post is dedicated to differences in these wireless technologies.
Short range radio and satellite transmitters are generally smaller than their cellular counterpart. Satellite and short range radios have less electrical complexity which translates to smaller devices. Cellular modules are typically enclosed in a metal casing to minimize RF interference. This case cannot be removed without violating FCC certifications, therefore the modem itself can weight several grams. The amount of energy required for cellular connections also means heavier batteries.
Cellular modems are the most robust transmitters of wildlife movement data. They can directly interface with web servers, which can make the latency between data collection and delivery to the user very low. Another advantage to cell modems is data integrity. Complex protocols are in place between the cell modem and tower that ensure information is not lost. These protocols are typically missing or must be developed and implemented for short range radios, thus increasing complexity, cost, or the chance of data being lost. Most satellite radios are one directional, meaning there is no way for the radio to know if transmitted data were received.
Satellite radios provide global data connectivity, however there can be times of the day when no satellite is available to receive your data. Short range radios and cell modems must be in proximity to a base station (cell tower) for a connection. Due to increasing cellular/GSM popularity, areas without coverage are rapidly decreasing. Our cellular devices can store months of information, then transmit it when a network becomes available. Eagles with CTT transmitters have been able to connect to cell towers from 40 miles away as they were soaring. Short range radios usually require a base station to be installed near migratory paths or study sites.
Complex protocols are in place between the cell modem and tower that ensure information is not lost.
Service and Data Availability
Satellite may be required because of limited or non-existent cellular service in your research area. Consider if your animals will be out of cellular coverage for extended times. With a GSM-only transmitter, you will have to wait until they return to GSM coverage to get your data. Additionally, GSM units, like satellite transmitters, upload their data on pre-defined schedules. With satellite service like Argos, you have several opportunities each day to transmit info as satellites pass overhead. Satellite providers typically have a longer delay in getting your transmitter and tag data to you, so be sure you can live with this. Additionally, satellite is generally asynchronous, so your tags and transmitters broadcast, but there is no assurance of full and proper receipt of your data.
With terrestrial radio, you can get multiple uploads each day if you like, even near real-time, giving you far more timely data availability. This can be a huge advantage in protecting species like pachyderms that are often poached.
Short range radio systems are usually lower costs than cellular or satellite radios. If service is available, you can put GSM in the base station and pay a lot less than GSM service for each transmitter. However, the trade off is that you will see a lower volume of data from the transmitter(s) to the receiver. The bandwidth limitations of radio transmitters apply to the link between the telemetry units and the receiver. GSM can be a solid value in terms of timeliness and carrying capacity, while satellite’s greatest value is in near universal availability.
The main determinants of which network your movement ecology research project will use will depend on the weight carrying capacity of your animal, the network service available, the pace at which you need to receive data, data volume, and your budget. You can find out exactly what is your best choice by asking here.