Wireless communication method and apparatus

A method of processing information prior to an emission from a multi-antenna device in a multi-user network having at least one user, said emission comprising transmission of a plurality of subcarriers comprising pilot symbols and data symbols, and said information being a data vector, the method comprising arranging said pilot symbols and said data symbols such that at least one of said plurality of subcarriers comprises at least one of said pilot symbols and at least one of said data symbols, wherein said data vector corresponds to said at least one of said plurality of subcarriers such that said data vector comprises data elements corresponding to said at least one of said pilot symbols and said at least one of said data symbols, precoding said data vector prior to transmission, and the precoding comprising applying a perturbation to said data vector in order to generate a perturbed data vector in which data elements corresponding to the pilot symbol remain unperturbed, the pilot symbols thereby requiring less transmit power such that more power is available to transmit the data symbol, and scaling said data vector by means of a precoding matrix;

• wherein the perturbation is expressible as a perturbation vector, said perturbation vector comprises a number and a complex integer vector, said complex integer vector comprising at least one element corresponding to said at least one pilot symbol and/or at least one data symbol, said perturbation vector being selected by solving an integer least squares problem such that a normalisation factor is minimised, wherein said solving the integer least squares problem includes applying a constraint to the integer least squares problem.

A signal processing apparatus for processing information prior to an emission from a multi-antenna device in a multi-user network having at least one user, said emission comprising transmission of a plurality of subcarriers comprising pilot symbols and data symbols, and said information being a data vector, the signal processing apparatus comprising means for arranging said pilot symbols and said data symbols such that at least one of said plurality of subcarriers comprises at least one of said pilot symbols and at least one of said data symbols, wherein said data vector corresponds to said at least one of said plurality of subcarriers such that said data vector comprises data elements corresponding to said at least one of said pilot symbols and said at least one of said data symbols, a precoding for precoding said data vector prior to transmission, and the precoder being further operable to apply a perturbation to said precoded data vector in order to generate a perturbed data vector in which data elements corresponding to the pilot symbol remain unperturbed, the pilot symbols thereby requiring less transmit power such that more power is available to transmission of the data symbol, and to scale said data vector by means of a precoding matrix;

• wherein the applying of said perturbation to said precoded information is performed by selecting at least one of said perturbation elements corresponding to said at least one pilot symbol and scaling said selected element(s) on the basis of a scaling factor;
• wherein the scaling factor is a number substantially higher than 1, and is expressible in the form L>>1, where L is a scaling factor.

A signal processing apparatus for processing information prior to an emission from a multi-antenna device in a multi-user network having at least one user, said emission comprising transmission of a plurality of subcarriers comprising pilot symbols and data symbols, and said information being a data vector, the signal processing apparatus comprising:

• means for arranging said pilot symbols and said data symbols such that at least one of said plurality of subcarriers comprises at least one of said pilot symbols and at least one of said data symbols, wherein said data vector corresponds to said at least one of said plurality of subcarriers such that said data vector comprises data elements corresponding to said at least one of said pilot symbols and said at least one of said data symbols;
• and
• a precoder configured to precode said data vector prior to transmission, to apply a perturbation to said precoded data vector in order to generate a perturbed data vector in which data elements corresponding to the pilot symbol remain unperturbed, the pilot symbols thereby requiring less transmit power such that more power is available to transmit the data symbol, and to scale said data vector by means of a precoding matrix;
• wherein the perturbation is expressible as a perturbation vector, said perturbation vector comprises a number and a complex integer vector, said complex integer vector comprising at least one element corresponding to said at least one pilot symbol and/or at least one data symbol, said perturbation vector being selected by solving an integer least squares problem such that a normalisation factor is minimised, wherein said solving the integer least squares problem includes applying a constraint to the integer least squares problem.