Wireless communication system with macro diversity
A wireless communication system, comprising one or several nodes (A) equipped by a wireless radio interface that is adapted for transmitting digital messages modulated in the form of a series of frequency chirps, for example, LoRa-modulated radio signals. The message is received simultaneously by several base stations (C, D, E), and a server (S) is arranged for dividing the frames by the diverse stations and recombining a corrected frame for the intended recipient (B) based on error codes. Advantageously, the base stations being adapt their timing error compensation strategy when the error codes indicate a corruption of the message.
1. A wireless communication system, comprising one or several nodes equipped by a wireless radio interface that is adapted for transmitting to a recipient digital messages modulated in the form of a series of frequency chirps organized in frames of determined length and comprising error codes,
a plurality of base stations arranged for receiving and demodulating the digital messages,
a server arranged to receive the frames received from each base station and originating from the one or several nodes, the server being operatively arranged for dividing the frames received from the plurality of base stations in blocks, recombining a corrected frame comprising blocks received by diverse base stations, based on the error codes, transmitting the corrected frame to the recipient.
2. The communication system of claim 1 , wherein each base station in the plurality of base stations is arranged for determining and tracking a timing error between a time reference of the one or several nodes and a time reference of the base station, and for compensating the timing error when demodulating the message originating from the node, the plurality of base stations being arranged for adapting the compensation of the timing error when the error codes indicate a corruption of the message.
3. The communication system of claim 2 , wherein the plurality of base stations have a first control unit for the compensation of the timing error, and a second control unit for the compensation of the timing error, the second unit being less sensitive than the first unit to impulses that are essentially shorter than the duration of a frame, the adaptation of the compensation consisting in selecting the second control unit.
4. The communication system of claim 3 , wherein the first control unit and/or the second control unit include a thermal drift model for the time reference of the one or several nodes.
5. The communication system of claim 3 , wherein the second control unit applies a constant frequency offset correction.
6. The communication system of claim 1 , wherein the plurality of base stations operate at the same frequency.
7. A wireless communication system, comprising one or several nodes equipped by a wireless radio interface that is adapted for transmitting to a recipient digital messages modulated in the form of a series of frequency chirps organized in frames of determined length and comprising error codes, a plurality of base stations arranged for receiving and demodulating the digital messages, a server arranged to receive the frames received from each base station and originating from the one or several nodes, the server being operatively arranged for dividing the frames received from the plurality of base stations in blocks, recombining a corrected frame comprising blocks received by diverse base stations, based on the error codes, transmitting the corrected frame to the recipient, wherein each base station in the plurality of base stations is arranged for determining and tracking a timing error between a time reference of the one or several nodes and a time reference of the base station, and for compensating the timing error when demodulating the message originating from the node, the plurality of base stations being arranged for adapting the compensation of the timing error when the error codes indicate a corruption of the message.
8. The communication system of claim 7 , wherein the plurality of base stations have a first control unit for the compensation of the timing error, and a second control unit for the compensation of the timing error, the second unit being less sensitive than the first unit to impulses that are essentially shorter than the duration of a frame, the adaptation of the compensation consisting in selecting the second control unit.
9. The communication system of claim 8 , wherein the first control unit and/or the second control unit include a thermal drift model for the time reference of the one or several nodes.
10. The communication system of claim 8 , wherein the second control unit applies a constant frequency offset correction.
11. The communication system of claim 7 , wherein the plurality of base stations operate at the same frequency.