Method and system for performing multiple access in wireless OFDM cellular systems considering both space and frequency domains

摘要

The method comprising a base station equipped with a large number of antennas according to a two-dimensional rectangular array and a number M of cell users, said rectangular array comprising N1 antenna elements along one axis with a regular spacing dx and N2 antenna elements along a perpendicular axis with a regular spacing dy, said users being characterized by angles (θ,φ) in a spherical coordinate system, where in order to achieve orthogonal multiple access the method comprises: selecting a grid spacing (Δu,Δv) in the (u, v) domain; discretizing the (u, v) domain; constructing a set of signals ST[k,l,f]; calculating time-domain excitations AT[n,m,t]for the antenna elements in the array given by coordinates (ndx,mdy) for generation of the downlink transmit signals; and obtaining the frequency contents SR[k,l,f] of the complex baseband signals received from the M users in the uplink.;The system implements the method of the invention.

主权项

1. A method for performing multiple access in wireless OFDM cellular systems considering both space and frequency domains, comprising at least one base station equipped with a large number of antennas according to a two-dimensional rectangular array and a number M of cell users, said rectangular array comprising N1 antenna elements along one axis with a regular spacing dx and N2 antenna elements along a perpendicular axis with a regular spacing dy, said cell users being characterized by spherical angles (θ,φ) in a spherical coordinate system, characterized in that in order to achieve orthogonal multiple access the method comprises using an orthogonal space-frequency processing unit for:
selecting a grid spacing (Δu, Δv) in a (u, v) domain through the equations:Δ⁢⁢u=λN1⁢dxΔ⁢⁢v=λN2⁢dy,  where λ denotes a wavelength of a system operating frequency, and the (u, v) domain is obtained from the following transformation of the spherical angles (θ,φ):
u=sin(θ)cos(φ)v=sin(θ)sin(φ), discretizing the (u, v) domain according to the following expressions:
uk=k·Δu,k=0, 1, . . . , N1−1vl=l·Δv,l=0, 1, . . . , N2−1,  where a visible region of a grid corresponds to values enclosed within a unit circle according to the equation:
u2+v2≦1; constructing a set of signals ST[k,l,f] according to the following expression:ST⁡[k,l,f]={Si⁡[f];∀(k,l)={(ki,li),i=0,1,…⁢,M-1}0;otherwise,  where Si[f] denote frequency contents of a complex baseband signal aimed at user i, and (ki,li) represent estimated user locations in the discretized (u, v) grid; calculating the time-domain excitations coefficients AT[n,m,t] for the antenna elements in the array given by coordinates (ndx,mdy), for generation of the downlink transmit signals according to the following expression:AT⁡[n,m,t]=1Nc⁢N1⁢N2⁢∑f=0Nc-1⁢⁢∑k=0N1-1⁢⁢∑l=0N2-1⁢⁢ST⁡[k,l,f]⁢exp(j⁢2⁢πNc⁢ft)⁢exp⁡(-j⁢2⁢πN1⁢nk)⁢exp⁡(-j⁢2⁢πN2⁢ml),  where Nc denotes the number of subcarriers in the system bandwidth; and obtaining the frequency contents SR[k,l,f] of the complex baseband signals received from the M users in the uplink, by applying the following transformation over a set of received signals AR[n,m,t] corresponding to each of the antenna elements:SR⁡[k,l,f]=∑t=0Nc-1⁢⁢∑n=0N1-1⁢⁢∑m=0N2-1⁢⁢AR⁡[n,m,t]⁢exp(-j⁢2⁢πNc⁢ft)⁢exp⁡(-j⁢2⁢πN1⁢nk)⁢exp⁡(-j⁢2⁢πN2⁢ml).