Collision mitigation in low-power, frequency-hopping, wide-area network

Patent metadata

Field	Value
Publication number	US-2020007188-A1
Application number	US-201916437895-A
Country	US
Kind code	A1
Filing date	Jun 11, 2019
Priority date	Jul 2, 2018
Publication date	Jan 2, 2020
Grant date	—

Abstract

A hopping spread-spectrum wireless network for IoT applications operating in a predetermined frequency band, with mobile device that have unsynchronized local frequency references and receiving gateways that are capable of detecting whether modulated radio signals will collide in frequency in a collision time interval, and blanking the signals in the collision time. Preferably, the frequency band is subdivided into a sub-bands, and the mobile devices adapt the width of the sub-bands used for transmission based on a synchronization status indicative of the frequency error of the local frequency reference.

First claim

1 . A wireless communication network comprising a plurality of radio transmitting devices and at least one receiving gateway,
the transmitting devices, being arranged to modulate a carrier and, processing the modulated signals into a spread spectrum radio signal by switching the frequency of the carrier among several hopping frequencies in the frequency band, according to a sequence, and transmitting the radio signal through a radio interface, the receiving gateway being arranged for receiving radio signals from said radio transmitting devices, for predicting whether detected modulated radio signals will collide in frequency in a collision time interval, and for blanking or weighting the signals in the collision time interval.

2 . The wireless communication method of claim 1 , wherein the receiving gateway maintains an interference map forecasting received signal level as a function of time and frequency, wherein the receiving gateway is arranged to detect a radio signal, measure its signal level, determine its hopping sequence, and fill the bins of the interference map corresponding to the expected times and frequencies of future packets with the signal level.

3 . The wireless communication method of claim 2 , wherein the receiving gateway is arranged to measure the signal level of a plurality of packets in a hopping sequence that are free from interference, and to adapt the interference map based on the measured instantaneous signal level.

4 . The wireless communication method of claim 2 , wherein the receiving gateway is arranged to determine interference originating from other sources by comparing the signals received with the interference map.

5 . The wireless communication network of claim 1 , comprising a plurality of receiving gateways, operatively arranged for receiving in collaboration a same radio signal from the transmitting node.

6 . The wireless communication network of claim 1 , wherein the radio interface in the transmitting devices operates in a predetermined frequency band comprising a plurality of contiguous or separated transmission sub-bands, the transmitting devices comprising a local frequency reference, and being operatively arranged for: obtaining a synchronization status indicative of the frequency error of the local frequency reference, adapting a width of the sub-bands in dependence of the synchronization status.

7 . The wireless communication network of claim 6 , wherein the width of the transmission sub-band is adapted such that, the higher the frequency error indicated by the synchronization status, the narrower the adapted width is.

8 . The wireless communication network of claim 6 , wherein the synchronization status is obtained based on one or more of: nominal error of the local frequency reference; drift of the local frequency reference; time elapsed since a downlink and/or a correction of the local frequency reference.

9 . The wireless communication network of claim 6 , wherein the receiving gateway is operatively arranged for demodulating signal in received sub-bands that are larger than the adapted width of the transmission sub-bands.

10 . The wireless communication network of claim 1 , wherein the hopping frequencies belong to several sub-bands.

11 . The wireless communication network of claim 1 , wherein the transmitters transmits an element of information on the first hopping frequency of the sequence.

12 . A radio transmitting device comprising a radio interface operating in a predetermined frequency band and a local frequency reference, wherein the frequency band comprises a plurality of contiguous or separated sub-bands, the device being operatively arranged for:
obtaining a synchronization status indicative of the frequency error of the local frequency reference, adapting a width of the sub-bands in dependence of the synchronization status, modulating a carrier having a frequency in the transmission sub-band, to obtain modulated signals that, when measured using the local frequency reference of the transmitting node, are comprised in the adapted width of a sub-band, combining the modulated signals into a spread spectrum radio signal by switching the frequency of the carrier among several hopping frequencies in the frequency band, according to a sequence transmitting the radio signal through the radio interface.

13 . The radio transmitting device of claim 12 , wherein the hopping frequencies belong to several sub-bands.

14 . The radio transmitting device of claim 12 , wherein the transmitters transmits an element of information on the first hopping frequency of the sequence.

15 . The radio transmitting device of claim 14 , wherein the element of information encodes a least significant portion of a channel index designating the first hopping frequency.

16 . The radio transmitting device of claim 12 , wherein the hopping sequence is defined in term of relative intervals, the transmitter being capable of choosing the absolute value of the first hopping frequency, the element of information being encoded in the choice of the first hopping frequency.

17 . The radio transmitting device of claim 12 , wherein the width of the transmission sub-band is adapted such that, the higher the frequency error indicated by the synchronization status, the narrower the adapted width is.

18 . The radio transmitting device of claim 12 , wherein the synchronization status is obtained based on one or more of: nominal error of the local frequency reference; drift of the local frequency reference; time elapsed since a downlink and/or a correction of the local frequency reference.

Assignees

• Semtech Corp

Inventors

• Ning Baozhu
• Seller Olivier Bernard André
• Sornin Nicolas

Classifications

• H04W84/18

  Self-organising networks, e.g. ad-hoc networks or sensor networks · CPC title

• H04B1/715 Primary

  Interference-related aspects · CPC title

• H04B2001/7154

  with means for preventing interference · CPC title

• H04B2001/7152

  with means for suppressing interference · CPC title

• H04B1/7156 Primary

  Arrangements for sequence synchronisation · CPC title