Coarse (~1s) time synchronization between distributed ground-nodes will be an essential part of ensuring that tag transmissions detected by multiple ground-nodes can be identified as coming from the same source transmitter by the positioning server.
The Raspberry Pi does not have an integrated RTC or other means of long-term synchronization between ground-nodes.
Two possible choices are:
NTP (Network Time Protocol) via the USB modems
GPS modules
As in #18, the issue comes down to access to a cellular/internet network. In option 1, access to the internet is a requirement for establishing a common time base across ground nodes. As stated in #18, internet access cannot be guaranteed in the intended deployment areas of the system. In option 2, only access to a GPS signal is required, and very precise time synchronization is possible (indeed, GPS units may help not only with coarse-scale time synchronization [sub 1 second synchronization], but has the potential to replace the need for positioning beacons for fine-scale time synchronization [sub 1 usecond synchronization]. GPS units, however, may be expensive and power hungry.
We need to conduct a detailed search into the optimal hardware implementation for implementing a common time base across distributed ground-nodes.
Coarse (~1s) time synchronization between distributed ground-nodes will be an essential part of ensuring that tag transmissions detected by multiple ground-nodes can be identified as coming from the same source transmitter by the positioning server.
The Raspberry Pi does not have an integrated RTC or other means of long-term synchronization between ground-nodes.
Two possible choices are:
As in #18, the issue comes down to access to a cellular/internet network. In option 1, access to the internet is a requirement for establishing a common time base across ground nodes. As stated in #18, internet access cannot be guaranteed in the intended deployment areas of the system. In option 2, only access to a GPS signal is required, and very precise time synchronization is possible (indeed, GPS units may help not only with coarse-scale time synchronization [sub 1 second synchronization], but has the potential to replace the need for positioning beacons for fine-scale time synchronization [sub 1 usecond synchronization]. GPS units, however, may be expensive and power hungry.
We need to conduct a detailed search into the optimal hardware implementation for implementing a common time base across distributed ground-nodes.