Burst spread spectrum radio system and method for asset tracking and data telemetry
A system for wireless asset tracking is disclosed. The system includes a plurality of mobile devices. Each mobile device performs two spreading operations with two distinct PN codes, a first PN code and a second PN code. Data is transmitted by each mobile device using a burst direct sequence spread spectrum radio signal. The system also includes at least three base stations. Each base station is configured to receive the burst direct sequence spread spectrum radio signals from the mobile devices which includes decoding the signals by first de-spreading with the second PN code and second de-spreading with the first PN code. Each base station is further configured to add a timestamp to each data packet received. A system for calculating the location of the mobile devices creates location information for each mobile device by calculating the time difference of arrival of received bursts for each base station.
1. A mobile device for use in a wireless asset tracking system, the mobile device comprising:
a transmitter configured to communicate with an antenna for transmitting wireless signals;
a processor;
memory in electronic communication with the processor, wherein the memory includes:
a device identification that identifies the mobile device;
a first PN code;
a second PN code; and
instructions stored in the memory, the instructions being executable for:
spreading transmit data using the first PN code to provide first spread transmit data;
spreading the first spread transmit data using the second PN code to provide second spread transmit data;
transmitting the second spread transmit data using a burst direct sequence spread spectrum radio signal; and
waking out of a low power state through a trigger before spreading.
2. The mobile device of claim 1 , wherein the instructions are further executable for returning back to the low power state after the second spread transmit data has been transmitted.
3. A base station that is configured for wireless communication with a plurality of remote mobile devices for use in a wireless asset tracking system, comprising:
an antenna;
a receiver in electronic communication with the antenna for receiving wireless signals from the remote mobile devices;
a processor;
memory in electronic communication with the processor; and
instructions stored in the memory, the instructions being executable for:
receiving a wireless signal from a remote mobile device;
demodulating the wireless signal to obtain first received data and a first received signal;
decoding the first received data by first de-spreading with a first PN code and second de-spreading with a second PN code to obtain received data;
adding a timestamp to the received data according to the first received signal timing;
transmitting the received data with the timestamp to a system for calculating the location of the mobile device.
4. The base station of claim 3 , wherein the base station is not synchronized with the mobile device before, during or after transmitting.
5. The base station of claim 4 , wherein the base station is not configured to perform any handshaking with the mobile device before, during or after transmitting.
6. The base station of claim 3 , wherein the wireless signal is a burst direct sequence spread spectrum radio signal.
7. The base station of claim 3 , wherein the base station is synchronized to a timing reference, and wherein the timing reference is a GPS receiver, a central radio beacon, or a timing reference transmitted over a wire or optical cable.
8. The base station of claim 3 , wherein the base station further comprises:
a first matched filter;
a bank of frequency shifters that perform complex frequency shifts; and
a bank of second matched filters.
9. A system for wireless asset tracking comprising:
a plurality of devices, wherein each device is configured to transmit its device identification, wherein each device performs two spreading operations with two distinct PN codes, a first PN code and a second PN code, and wherein each device transmits data using a burst direct sequence spread spectrum radio signal;
at least three base stations, wherein each base station is configured to receive the burst direct sequence spread spectrum radio signal, wherein each base station decodes the signal by first de-spreading with the second PN code and second de-spreading with the first PN code, and wherein each base station is further configured to add a timestamp to each received data packet and to forward pertinent despread, demodulated and decoded data with other information including the timestamp to a system for calculating the location of the devices; and
a system for calculating the location of the devices configured to create location information for each device by calculating the time difference of arrival of received bursts for each base station, and wherein the system for calculating the location of the devices is further configured to store the location and telemetry and to further provide an interface for other systems to access the information and the telemetry data.
10. A system for wireless asset tracking as in claim 9 wherein the plurality of devices are stationary, mobile or relatively stationary.
11. A system for wireless asset tracking as in claim 9 wherein the burst direct sequence spread spectrum radio signal is received by only one of the base stations.