Relative frequency hops in low-power, wide-area network

Patent metadata

Field	Value
Publication number	US-2020007187-A1
Application number	US-201916437991-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 with mobile device that have unsynchronized local frequency references. The transmitters use hopping sequences defined in term of the relative differences of frequencies, in such a manner that a receiver can determine the hopping sequence of a transmission despite the presence of a large frequency error.

First claim

1 . A wireless communication network comprising a plurality of radio transmitting devices in a frequency band that is divided into a plurality of channels, wherein,
the transmitting devices have each a local frequency reference, and are 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 hopping sequence and, the transmitters being arranged to determine the hopping sequence by incrementing repeatedly a channel of an initial hopping frequency according to a determined succession of increments, thereby obtaining a sequence of channels, each channel in the sequence defining an element of the hopping sequence, and transmit the radio signal through a radio interface.

2 . The wireless communication network of claim 1 , wherein the channels do not overlap.

3 . The wireless communication network of claim 2 , wherein, in the determination of the hopping sequence, the transmitter applies a modulo operation after each increment, to maintain the hopping frequencies within predetermined limits.

4 . The wireless communication network of claim 1 , including at least one receiving gateway arranged for: detecting a signal transmitted from a transmitting device at an initial received frequency; forecasting the hopping frequencies by incrementing repeatedly an initial received frequency according to the determined succession of increments; receiving the signal at the forecast hopping frequencies.

5 . The wireless communication network of claim 4 , wherein the receiving gateway is arranged to determine when a hopping frequency that is expected to fall close to the predetermined limit may be at either of two distinct values according to whether the increment resulted in a frequency judged outside of the predetermined limits by the transmitter, and to listen at both distinct values of frequency.

6 . The wireless communication network of claim 3 , wherein the transmitter device is arranged to omit the transmission of a hop whose hopping frequency falls closer to the predetermined limits than a determined threshold.

7 . The wireless network of claim 1 , wherein the frequency band is divided into sub-bands; the generation of the hopping sequence in the transmitting device includes the determination of a sequence of sub-bands, and each hop is transmitted in a sub-band defined by the sequence of sub-bands at the channel defined by the sequence of channels.

8 . The wireless network of claim 1 , wherein the transmitting device is arranged for selecting a hopping sequence among a plurality of possible sequences.

9 . The wireless network of claim 8 , wherein the selection of a hopping sequence is based on a synchronization state of the frequency reference of the transmitting device.

10 . The wireless network of claim 8 , wherein the selected hopping sequence is signalled through the choice of the first used frequency.

11 . The wireless network of claim 1 , wherein the transmitting device is arranged for signalling the value of one hopping frequency as synthesized based on the transmitting device's own frequency reference.

12 . The wireless network claim 11 wherein the value is implicitly signalled through the choice of the first sub-band.

13 . The wireless network of claim 11 , wherein the value is explicitly signalled by including in the preamble modulated data designating he channel or the frequency used for the first hop or for any hop in the sequence.

Assignees

• Semtech Corp

Inventors

• Seller Olivier Bernard André
• Sornin Nicolas

Classifications

• H04L67/12

  specially adapted for proprietary or special-purpose networking environments, e.g. medical networks, sensor networks, networks in vehicles or remote metering networks · CPC title

• H04B1/715

  Interference-related aspects · CPC title

• H04B1/713 Primary

  using frequency hopping · CPC title

• H04B1/7156

  Arrangements for sequence synchronisation · CPC title

• H04B2001/7152

  with means for suppressing interference · CPC title