Low-power, frequency-hopping, wide-area network with random medium access

Patent metadata

Field	Value
Publication number	US-2020007186-A1
Application number	US-201916438022-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. The network includes mobile devices with unsynchronized local clocks that transmit including, in a preamble portion, a plurality of sync words, each combined with at least one instance of a sequential index. The hopping frequencies at which the sync word are transmitted are different. This arrangement helps detection and synchronization of the signals, despite the unavoidable frequency mismatches and collisions.

First claim

1 . A radio-transmitting device comprising a radio interface operating in a predetermined frequency band, operatively arranged for modulating a carrier having a frequency in the frequency band, while switching the frequency of the carrier among several hopping frequencies in the frequency band, according to a hopping sequence, to obtain a spread-spectrum modulated signal,
wherein the spread-spectrum modulated signal includes, in a preamble portion, a plurality of sync words, each combined with at least one instance of a sequential index, the sync words being transmitted at different frequencies, and a data portion following the preamble portion and including a plurality of frequency hops.

2 . The radio-transmitting device of claim 1 , wherein each hopping frequency in the hopping sequence is deterministically derivable from the frequency of the immediately preceding hop in the hopping sequence, for example by a permutation operation.

3 . The radio-transmitting device of claim 1 , wherein the sequential indexes are arranged in a countdown sequence.

4 . The radio-transmitting device of claim 1 , wherein frequency hops in the preamble contain a sync word between two copies of the sequential index.

5 . The radio-transmitting device of claim 1 , wherein frequency hops in the preamble contain additional information designating a data rate for the data portion and/or an indication designating a hopping sequence among a plurality of possible hopping sequences.

6 . The radio-transmitting device of claim 1 , wherein the sync words are identical or different.

7 . The radio-transmitting device of claim 1 , wherein the modulated signal inside each frequency hop has a bandwidth, and wherein part of the frequency hops are shifted by a frequency offset that is a half or a predetermined fraction of said bandwidth, wherein the sequence of integer and fractional steps is deterministic.

8 . The radio-transmitting device of claim 1 , including a local frequency reference, and operatively arranged to obtain a synchronization status indicative of the frequency error of the local frequency reference, and to adjust a sync word repetition number and/or a sync word repetition rate based on the synchronization status.

9 . The radio-transmitting device claim 8 , operatively arranged to obtain an estimation of a transmission success rate and to adjust a sync word repetition number and/or a sync word repetition rate based on the estimation of a transmission success rate.

10 . The radio-transmitting device of claim 9 , operatively arranged to adjust a sync word repetition number and/or a sync word repetition rate upon reception of a command.

11 . A plurality of the radio transmitting devices of claim 1 in a communication network that includes at least one receiver, the receiver being arranged for detecting in the modulated signal a sync word and an associated sequential index, to determine the hopping sequence and align with the hopping sequence based on the sync word and on the sequential index, to determine from the sequential index the position of the data portion, and to demodulate the data portion.

12 . A radio-receiving device comprising a radio interface operating in a predetermined frequency band, operatively arranged for demodulating a carrier having a frequency in the frequency band, whereby the frequency of the carrier jumps between several hopping frequencies in the frequency band, according to a hopping sequence, and for obtaining a demodulated signal including, in a preamble portion, a plurality of sync words, each combined with at least one instance of a sequential index, the sync words being transmitted at different frequencies, and a data portion following the preamble portion and including a plurality of frequency hops, and for determining from said sequential index the position of the data portion.

Assignees

• Semtech Corp

Inventors

• Seller Olivier Bernard André
• Sornin Nicolas

Classifications

• H04B1/7156 Primary

  Arrangements for sequence synchronisation · CPC title

• H04B2001/71365

  using continuous tuning of a single frequency source · CPC title

• H04B1/715

  Interference-related aspects · CPC title

• H04B2001/7152

  with means for suppressing interference · CPC title

• H04B1/7136 Primary

  Arrangements for generation of hop frequencies, e.g. using a bank of frequency sources, using continuous tuning or using a transform · CPC title