Step Global has developed a solution for remote area GPS tracking by interfacing the Trimble TM3000 asset tracking device with an Iridium short burst data modem.
When GSM (GPRS and SMS) communications is unavailable, the TM3000 will switch over to the Iridium modem for transmitting its reports to an Internet-based applications server. This solution provides for continuous tracking from anywhere in the world and is especially useful for remote area tracking requirements.
TM3000 Asset Tracking Devices
Trimble’s TM3000 asset tracking device is an open and flexible platform that can be adapted to a broad range of asset or vehicle monitoring, management and recovery services. The
TM3000 asset tracking device integrates a GSM/GPRS modem, a GPS receiver, 3-axis accelerometer, extensive digital and analogue inputs and outputs, 2 RS232 ports, battery backup, rugged automotive grade power regulator, extensive data log, Over-The-Air configuration, an independent application sub-system and an array of peripheral interfaces in a small, robust, cost-effective package.
Remote area tracking functions that can be achieved with the TM3000 deployed in assets/vehicles include:
- Locate the position of assets/ vehicles at all times
- Monitor vehicle conditions
- Warn operators on safety conditions
- Remotely operate systems on board the vehicle
- Communicate from monitoring centre to vehicle operator
- Measure fuel consumption
- Measure engine idle times
- Monitor vehicle operator’s driving behaviour for excessive braking, swerving and acceleration
- Remotely monitor operation of peripheral equipment attached to vehicle
- Accurately capture FBT information
- Security alerts on out of hours’ operation
- Alert on unauthorised use of vehicles
- Accurately measure driver hours and alert on excessive hours
The RST425 data modem is a robust data terminal providing simple short burst data communications from all types of devices with serial communications to the global Iridium satellite network from or to anywhere on earth.
The Iridium network of Low Earth Orbit satellites provides truly global voice and data communications from any location – land, air or sea. Suitable for remote area communications, Iridium delivers essential communications services to and from remote areas where no other form of communication is available.
Iridium Short Burst Data services (data only) allow users to simply and conveniently gain access to data packet data services anywhere on earth.
The TM3000 to Iridium Modem Interface
The RST425 houses an Iridium SBD (Short Burst Data) 9601 modem with a regulated power supply. It has external connections for power, an Iridium antenna and a DB9 connector for its RS-232 communications.
The Iridium communications infrastructure is very similar to standard GSM infrastructure in the way that data is communicated to external equipment: a mobile phone number for SMS, an email address or an IP address. For tracking applications the data is sent to an IP address of the server service that provides the back-end monitoring.
The TM3000 interfaces to the RST425 via its secondary RS232 port. The TM3000 manages the communications over the RST425. The process steps that the TM3000 takes to ensure robust communication are:
- TM3000 constantly monitors GSM connectivity
- If TM3000 does not have a good GSM connection when a report is due to be transmitted to the tracking server, then the TM3000 will mark that report as being unsent by GSM
- TM3000 will then check that it has a good Iridium connection. If it does, then it will send the unsent GSM report as an Iridium condensed report over Iridium SBD service to the tracking server
- If the TM3000 does not have a good GSM or Iridium connection then it will store all unsent reports in a buffer, until it has a reliable communication path.
- If the TM3000 has been sending reports over Iridium SBD service, these reports will remain marked as unsent GSM. When the TM3000 has a reliable GSM connection it will then send all reports marked as unsent GSM reports to the server over GSM. The reason that it does this is because the reports sent over Iridium have been condensed.
- All reports sent over the Iridium SBD service are marked as Iridium reports. The application server is then able to recognise these reports, decode the compressed message and store it in the database as a standard report. The application server can display as part of its report that the message was transmitted over Iridium.
Since the cost for Iridium airtime is significantly higher compared to that of GPRS or SMS data costs, the TM3000 condenses the standard message to a more cost-effective length. All essential data is still transmitted in the condensed format.
The TM3000 can also be configured to have a reduced report frequency for Iridium versus GSM to keep Iridium airtime costs low without losing any tracking detail.