Multiuser detection method and device

• US 20020097784A1
• Filed: 12/11/2001
• Published: 07/25/2002
• Est. Priority Date: 12/13/2000
• Status: Active Grant

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Brunel, Loic
• Granted Patent: US 7,130,353 B2
• Time in Patent Office: Days
• US Class Current: 375/147
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04L 25/03331 Arrangements for the joint estimation of multiple sequences
• CPC Class Codes: H04L 25/03993 Noise whitening
• CPC Class Codes: H04L 5/026 using code division

Abstract

Method of detecting a plurality of symbols (d_k(i)) transmitted by or for a plurality K of users, each symbol belonging to a modulation constellation and being the subject of a spectral spreading before being modulated on a plurality L of carriers, the said method comprising a step of demodulation (420) and a step of spectral despreading (430) of the received signal (r(i)) in order to supply a vector (y₂(i), {tilde over (y)}₂(i)) characteristic of the said signal, and a step (450) of searching, within an array of points (Λ₂,Ω₂) generated by the symbols of the said modulation constellations, for at least the closest neighbor of the said vector.

Claims

1. Method of detecting a plurality of symbols (d_k(i)) transmitted by or for a plurality K of users, each symbol belonging to a modulation constellation and being the subject of a spectral spreading before being modulated on a plurality L of carriers, the said method comprising a step of demodulation (420) and a step of spectral despreading (430) of the received signal (r(i)) in order to supply a vector (y₂(i), {tilde over (y)}₂(i)) characteristic of the said signal, characterised in that it comprises a step (450) of searching, within an array of points (Λ

₂,Ω

₂) generated by the symbols of the said modulation constellations, for at least the closest neighbour of the said vector.

2. Detection method according to claim 1, characterised in that the said search step is limited to a set of points on the array belonging to a predetermined area around the said characteristic vector.

3. Detection method according to claim 1, characterised in that the said search step is limited to a set of points on the array belonging to a predetermined area around the origin of said array.

4. Detection method according to claim 2 or 3, characterised in that the said predetermined area is a sphere.

5. Detection method according to one of the preceding claims, characterised in that the transmitted symbols having been spread spectrally by means of sequences with real values, the said characteristic vector is decomposed into a first vector with real components and a second vector with real components and in that the search step consists of determining the closest neighbour to the said first vector and the said second vector within an array (Λ

,Ω

) of points with real coordinates of dimension K.

6. Detection method according to one of claims 1 to 4, characterised in that, the said characteristic vector being considered to be a vector with real components of size 2.K, the said search step consists of determining the closest neighbour within an array (Λ

₂,Ω

₂) of points with real coordinates of dimension 2.K.

7. Detection method according to claim 6, characterised in that the said search step is implemented on a plurality of real components of the said characteristic vector, the search being limited for each of the said components to an interval defined by a lower bound and an upper bound, the said bounds being chosen so that the said interval does not include points relating to symbols which cannot belong to the modulation constellation.

8. Detection method according to one of the preceding claims, characterised in that the spectral demodulation step is followed by a step of despreading and equalisation of the symbols obtained by demodulation of the signal received at the different carriers, supplying a vector (y₂(i)) of symbols equalised for the different users.

9. Detection method according to claim 8, characterised in that the said characteristic vector ({tilde over (y)}₂(i)) is obtained from the vector of equalised symbols by means of a matrix-type processing (440) aimed at substantially decorrelating the different noise components thereof.

10. Detection method according to one of the preceding claims, characterised in that the said search step is extended to that of a set of adjacent points to the said characteristic vector and in that the transmitted symbols are estimated flexibly from the symbols generating the said adjacent points and the distances separating the said adjacent points from the received point.

11. Device for detecting a plurality of symbols (d_k(i)) transmitted by or for a plurality K of users, each symbol belonging to a modulation constellation and being the subject of a spectral spreading before being modulated on a plurality L of carriers, the device comprising means for implementing the method claimed according to one of the preceding claims.

12. Receiver for an MC-CDMA mobile telecommunication system comprising a detection device according to claim 11.