Method for transmitting data packets on carrier frequency with linear variation and transmitter implementing this method

Abstract

A method for transmitting data packets having a heading followed by a data field. The data of the field is transmitted by groups of symbols. According to the OFDM technique, subcarriers modulated by the groups are generated. A frequency modulation of a carrier signal delivered by a linear ramp generator is produced with a set of modulated subcarriers. When the signal is received, mixing with a linear ramp results in subcarriers which are separated and then demodulated for supplying data. This is useful for transmitting data packets particularly in wide band networks.

1. A process for transmitting data in packets, the packets comprising a header at a first carrier frequency, followed by an information field at a second carrier frequency, a start of transmission of the information field being tied to a start of transmission of the header of the corresponding packet, comprising:
 obtaining data packets to be transmitted the packets comprising a header to be transmitted at a first carrier frequency, followed by an information field to be transmitted at a second carrier frequency, wherein a start of transmission of the information field is tied to a start of transmission of the header of the corresponding packet, and wherein transmission at the second carrier frequency starts with the information field; 
 usingproviding N distinct and simultaneous subcarriers for concurrent transmission of data in the information field, where N is an integer greater than 1; 
 splitting the data to be transmitted in the information field into successive groups of N M symbols; 
 assigning the N symbols M symbols respectively to the N subcarriers by OFDM multiplexing; 
 modulating the N subcarriers respectively by the N symbols M symbols thereby obtaining a modulating signal made of the N subcarriers; 
 generating a transmit signal at the second carrier frequency varying over time according to a linear ramp for optimizing bandwidth use; 
 modulating the transmit signal at the second carrier frequency by the modulating signal; and 
 mixing the transmit signal, upon reception, corresponding to the information field with a ramp signal corresponding to the transmit signal at the second carrier frequency to obtain a received signal corresponding to the modulating signal and to extract from the received signal data of the information field. 
 
     
     
       2. The process according to  claim 1 , wherein the modulating the N subcarriers comprises:
 constructing from a table of samples having values representative of the N subcarriers modulated by the data of each of said successive groups, thereby directly generating the subcarriers; 
 summing samples of like temporal index; and 
 converting a result of summation of the samples from digital to analog, thereby obtaining a modulating signal. 
 
     
     
       3. A transmitter for transmitting data in packets, the packets comprising a header to be transmitted at a first carrier frequency, followed by an information field to be transmitted at a second carrier frequency, a start of transmission of the information field being is tied to a start of transmission of the header of the corresponding packet, and wherein transmission at the second carrier frequency starts with the information field, wherein the transmitting comprises using providing N distinct and simultaneous subcarriers for concurrent transmission of data in the information field, where N is an integer greater than 1, splitting the data to be transmitted in the information field into successive groups of N symbols M symbols, assigning the N symbols M symbols respectively to the N subcarriers by OFDM multiplexing, modulating the N subcarriers respectively by the N symbols M symbols thereby obtaining a modulating signal made of the N subcarriers, generating a signal at the second carrier frequency varying over time according to a linear ramp, modulating the signal at the second carrier frequency by the modulating signal, and
 mixing the signal, upon reception, corresponding to the information field with a ramp signal corresponding to the signal at the second carrier frequency to obtain a signal corresponding to the modulating signal and to extract from the signal data of the information field, the transmitter comprising: 
 a computing device, configured to compute groups of symbols representative of data to be transmitted in a field; 
 a first modulator, configured to generate a the modulating signal by OFDM for the N subcarriers; 
 a ramp generator configured to generate a carrier signal, wherein the carrier signal has a frequency variant over time according to a the linear ramp for optimizing bandwidth use; and 
 second modulator, configured to receive signals generated by the first modulator and the ramp generator. 
 
     
     
       4. The transmitter according to  claim 3 , wherein the first modulator comprises:
 a digital generator of modulated subcarriers; 
 a summation device; and 
 a digital to analog converter, wherein the digital generator, the summation device, and the digital to analog converter are arranged in series. 
 
     
     
       5. A receiver for transmitting data in packets, the packets comprising a header to be transmitted at a first carrier frequency, followed by an information field to be transmitted at a second carrier frequency, wherein a start of transmission of the information field being is tied to a start of transmission of the header of the corresponding packet, and wherein transmission at the second carrier frequency starts with the information field, wherein the transmitting comprises using providing N distinct and simultaneous subcarriers for concurrent transmission of data in the information field, where N is an integer greater than 1, splitting the data to be transmitted in the information field into successive groups of N symbols M symbols, assigning the N symbols M symbols respectively to the N subcarriers by OFDM multiplexing, modulating the N subcarriers respectively by the N symbols M symbols thereby obtaining a modulating signal made of the N subcarriers, generating a signal at the second carrier frequency varying over time according to a linear ramp, modulating the signal at the second carrier frequency by the modulating signal, and
 mixing the signal, upon reception, corresponding to the information field with a ramp signal corresponding to the signal at the second carrier frequency to obtain a signal corresponding to the modulating signal and to extract from the signal data of the information field, the receiver comprising: 
 a mixer, comprising:
 a first input for receiving a signal; 
 a second input; and 
 an output; 
 
 a ramp generator, wherein the ramp generator is configured to deliver a signal having a frequency variant over time according to a the linear ramp, for optimizing bandwidth use, to the second output of the mixer; 
 a frequency time/operator; and 
 a subcarrier demodulation circuit. 
 
     
     
       6. A process for transmitting data, the process comprising:
 modulating two or more subcarriers by the data to be transmitted using an OFDM technique a to obtain a modulating signal made up of the two or more subcarriers, the data to be transmitted comprising data packets, the packets comprising a header to be transmitted at a first carrier frequency, followed by an information field to be transmitted at a second carrier frequency, wherein a start of transmission of the information field is tied to a start of transmission of the header of the corresponding packet, and wherein transmission at the second carrier frequency starts with the information field;   generating a carrier signal at a frequency varying over time according to a linear ramp for optimizing bandwidth use, and   modulating the carrier signal by the modulating signal.   
     
     
       7. The process of claim 6, wherein modulating two or more subcarriers by the data to be transmitted using an OFDM technique comprises:
 using N subcarriers for transmitting the data, where N is an integer greater than 1;   splitting the data to be transmitted into successive groups of M symbols;   assigning the M symbols respectively to the N subcarriers by OFDM; and   modulating the N subcarriers respectively by the M symbols thereby obtaining a modulating signal made of the N subcarriers.   
     
     
       8. The process of claim 7, wherein modulating the N subcarriers respectively by the N symbols further comprises:
 constructing from a table of samples having values representative of the N subcarriers modulated by the data of each said successive groups, thereby directly generating the subcarriers;   summing samples of like temporal index; and   converting a result of summation of the samples from digital to analog, thereby obtaining a modulating signal.   
     
     
       9. A transmitter for transmitting data, the transmitter comprising:
 a first modulator configured to generate a modulating signal for two or more subcarriers using the data to be transmitted and an OFDM technique, the data to be transmitted comprising data packets the packets comprising a header to be transmitted at a first carrier frequency, followed by an information field to be transmitted at a second carrier frequency, wherein a start of transmission of the information field is tied to a start of transmission of the header of the corresponding packet, and wherein transmission at the second carrier frequency starts with the information field;   a ramp generator configured to generate a carrier signal, wherein the carrier signal has a frequency variant over time according to a linear ramp for optimizing bandwidth use; and   a second modulator configured to modulate the carrier signal by the modulating signal for the two or more subcarriers.