Method for demodulating UWB pulse sequences encoded according to an on-off keying modulation scheme

• US 7,817,728 B2
• Filed: 11/30/2004
• Issued: 10/19/2010
• Est. Priority Date: 12/17/2003
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Meunier, Claire, Aubert, Louis-Marie, Paquelet, Stephane
• Primary Examiner(s): Wang; Ted M
• Application Number:
  US10/998,930
• Publication Number:
  US 20050213673A1
• Time in Patent Office: 2,149 Days
• Field of Search: 375/316, 375/324, 375/340, 375/259
• US Class Current: 375/259
• CPC Class Codes: H04B 1/71637 Receiver aspects H04B1/7183 takes precedence
• CPC Class Codes: H04L 27/06 Demodulator circuits; Receiver circuits

Abstract

The present invention relates to a method for transmitting data in the form of at least one pulse sequence Tsgk (for k=1 to K). The method according to the invention includes at least one symbol decoding step in the course of which at least one modulation value Pwk representative of an amount of power carried by each pulse sequence Tsgk is computed and compared to at least one predetermined threshold value Thvk, which will be computed beforehand by equating a first and a second probability density function representing a likelihood for the transmitted signal to carry a first symbol and a likelihood for the transmitted signal to carry a second symbol, respectively. The method according to the invention enables to limit the processing time and power needed for performing the demodulation of a power-modulated UWB signal.

Claims

1. A method for demodulating data transmitted in a telecommunication system including at least one transmitter and one receiver, said transmitter being configured to transmit a signal formed by at least one pulse sequence of Ns pulses over Ns time windows, each pulse being enclosed within a time chip whose position within its relevant time window is defined by a chip number, which method comprises:

decoding during at least one symbol decoding executed in said receiver to compute at least one modulation value representative of an amount of power carried by each pulse sequence; and

comparing the modulation value to at least one predetermined threshold value, wherein

the predetermined threshold value has previously been determined by equating a first and a second probability density function representing a likelihood for the transmitted signal to carry a first symbol and a likelihood for the transmitted signal to carry a second symbol, respectively, so that information carried by pulse sequences may be recovered at the receiver without said receiver having to precisely map the pulse sequences, and

each signal to be transmitted is constituted by a superimposition of a predetermined number of pulse sequences, each pulse sequence having been subjected to symbol encoding and corresponding to one of several sub-bands into which a total bandwidth available for transmission has previously been divided.

2. The method as claimed in claim 1, according to which the threshold value is defined by a polynom of a variable M^1/2, where M is defined by M=(2.B.Ns.Ti+I)/2, B being a bandwidth of the pulse sequence for which the threshold value is computed, and Ti a time duration over which an integration of each pulse belonging to said pulse sequence is performed in order to compute the amount of power carried by said pulse sequence.

3. The method as claimed in claim 2, according to which the polynom defining the threshold value is limited to the second order.

4. The method as claimed in claim 2, according to which a first-order coefficient of the polynom defining the threshold value is given by an ordinate of a curve whose abcissis is formed by an energy ratio related to the transmission of the relevant pulse sequence.

5. The method as claimed in any one of claims 1 to 4, further including at least one symbol encoding to be executed before transmission of said pulse sequence, in the course of which symbol encoding each pulse sequence is multiplied by one of two integer values representative of a symbol to be carried by said pulse sequence.

6. A telecommunication system including at least one transmitter and one receiver, said transmitter being configured to transmit a signal formed by at least one pulse sequence of Ns pulses over Ns time windows, each pulse being enclosed within a time chip whose position within its relevant time window is defined by a chip number in which the receiver comprises:

a symbol decoder configured to compute at least one modulation value representative of an amount of power carried by each pulse sequence; and

a comparator configured to compare said modulation value to at least one predetermined threshold value obtained by equating a first and a second probability density function representing the likelihood for the transmitted signal to carry a first symbol and the likelihood for the transmitted signal to carry a second symbol, respectively, wherein

the transmitter further includes a signal combiner configured to receive a predetermined number of pulse sequences, each pulse sequence having been generated by the symbol encoder and corresponding to one of several sub-bands into which a total bandwidth available for transmission has previously been divided, said signal combiner being configured to combine all said pulse sequences into a signal to be transmitted.

7. The telecommunication system as claimed in claim 6, in which the transmitter includes a symbol encoder configured to multiply each pulse sequence by one of two integer values representative of a symbol to be carried by said pulse sequence.

8. A receiver configured to receive a signal formed by at least one sequence of Ns pulses over Ns time windows, each pulse being enclosed within a time chip whose position within its respective time window is defined by a chip number, which receiver comprises:

a symbol decoder configured to compute at least one modulation value representative of an amount of power carried by each pulse sequence; and

a comparator configured to compare said modulation value to at least one predetermined threshold value obtained by equating a first and a second probability density function representing the likelihood for the transmitted signal to carry a first symbol and the likelihood for the transmitted signal to carry a second symbol, respectively, wherein

each signal to be received is constituted by a superimposition of a predetermined number of pulse sequences, each pulse sequence having been subjected to the symbol encoding and corresponding to one of several sub-bands into which a total bandwidth available for transmission has previously been divided.