Transmission method with double directivity

Abstract

A transmission method using a massive MIMO (Multiple-Input and Multiple-Output) scheme with an arrangement 108 of N.sub.mN.sub.b antenna elements at the transmitter, arranged in N.sub.m sets of N.sub.b antenna elements or N.sub.b sets of N.sub.m antenna elements based on SC-FDE (Single-Carrier with Frequency Domain Equalization) schemes with large constellations that is compatible with low-cost, highly-efficient, nonlinear amplifiers 106, while allowing spatial multiplexing gains. The transmission structure of this transmission method decomposes in 103 the modulated symbols from 102 associated to a given constellation as the sum of N.sub.m polar components that are modulated as N.sub.m BPSK (Binary Phase Shift Keying) signals. Each of these BPSK signals can be regarded as an OQPSK (Offset Quadrature Phase Shift Keying) signal in the serial format that is specially designed to have good tradeoffs between reduced envelope fluctuations and a compact spectrum.

Claims

1. Transmission method with double directivity comprising the following steps: a. the data stream is split into N.sub.u sub-streams in (101); b. the data bits associated to each of the N.sub.u sub-streams are mapped by a modulator (102) into a symbol sequence of a given constellation (the constellation can be a M-QAM, M-PSK or Voronoi constellation) characterized by the ordered set ={S.sub.0, S.sub.1, . . . , S.sub.M1}, where M is the number of constellation symbols, following the rule
(.sub.n.sup.(1),.sub.n.sup.(2), . . . ,.sub.n.sup.(1),.sub.n.sup.(0))s.sub.n, with (.sub.n.sup.(1),.sub.n.sup.(2), . . . ,.sub.n.sup.(1),.sub.n.sup.(0)) denoting the binary representation of n with =log.sub.2(M) bits; c. the polar mapper (103) decomposes the constellations symbols in N.sub.m polar components, that are the result of the decomposition of signal s.sub.n into M components given by $\begin{array}{c}{s}_n=g_0+g_1{b}_n^{\left(0\right)}+g_2{b}_n^{\left(1\right)}+g_3{b}_n^{\left(0\right)}{b}_n^{\left(1\right)}+g_4{b}_n^{\left(2\right)}+\left(\mathrm{.Math.}\right)\\ =\underset{i=0}{\overset{M-1}{.Math.}}{g}_i\underset{m=0}{\overset{-1}{.Math.}}{\left(b_n^{\left(m\right)}\right)}^{{}_{m,i}}=\underset{i=0}{\overset{M-1}{.Math.}}{g}_i{b}_n^{\mathrm{eq}\left(i\right)},\end{array}$ with (.sub.1,i .sub.2,i . . . .sub.1,i .sub.0,i) denoting the binary representation of i, b.sub.n.sup.(m)=(1).sup..sup.n.sup.(m) denoting the polar representation of the bit .sub.n.sup.(m), b.sub.n.sup.eq(i)=.sub.m=0.sup.1(b.sub.n.sup.(m)).sup.m,i denoting the i.sup.th polar component of s.sub.n and N.sub.m is the number of non-zero g.sub.i coefficients of the referred decomposition equation; d. each of the N.sub.m polar components is modulated as a BPSK signal in (104), whose output is a time continuous BPSK signal, being each of these N.sub.m BPSK signal a serial representation of an OQPSK signal or a GMSK signal; e. each of N.sub.m resulting signals Is submitted to a phase shifter (105) and it is amplified by a nonlinear amplifier (106); f. the N.sub.m signals associated to each sub-stream are transmitted by an arrangement (108) of N.sub.mN.sub.b antennas, arranged in N.sub.m sets of N.sub.b antenna elements or N.sub.b sets of N.sub.m antenna elements; g. each arrangement (108) is composed by one or more sets of N.sub.m antennas (109); h. each arrangement (108) is composed by one or more sets of N.sub.b antennas (110), to allow horizontal beams.

2. Transmission method with double directivity according to claim 1, in which the transmitter uses a massive MIMO (multiple input multiple output) scheme, with the antenna array composed by N.sub.uN.sub.mN.sub.b elements, arranged in N.sub.u sub-arrays, each one composed by N.sub.m sets of N.sub.b antenna elements or N.sub.b sets of N.sub.m antenna elements.

3. Transmission method with double directivity according to claim 1, in which the spacing between the N.sub.m sets of N.sub.b antennas performs constellation shaping of the transmitted constellation.

4. Transmission method with double directivity according to claim 1, in which the N.sub.m signals associated to each one of the N.sub.u sub-streams are combined in the transmission channel.

5. Transmission method with double directivity as in any one of claims 1 and 2, in which each set (108) of N.sub.mN.sub.b antennas associated to the information stream for a user performs beamforming and several sets of N.sub.mN.sub.b antennas (108) in parallel implement; a. spatial multiplexing; b. antenna's interference management; c. spatial multiplexing combined with antenna's interference management.

6. Transmission method with double directivity according to claim 1, in which two kinds of directivities are implemented, one that affects the constellation shape of the transmitted constellation and another associated to the beamforming that affects the radiation pattern of the set of antennas.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The various aspects of embodiments disclosed here, including features and advantages of the present invention outlined above are described more fully below in the detailed description in conjunction with the drawings where like reference numerals refer to like elements throughout, in which:

(2) FIG. 1 shows a diagram of the transmitter's structure where the modulator 102, based on large dimension constellation (e.g., M-QAM), maps into symbols of a constellation the bits from the high bit rate data stream from 101. The resulting symbols are subsequently converted into N.sub.m antipodal sequences by the polar decomposition converter 103. These antipodal sequences are the inputs of BPSK modulators 104, whose outputs are continuous time BPSK signals, that are the phase shifter's input 105, and amplified by N.sub.m nonlinear amplifiers 106 before being transmitted by N.sub.m antennas placed vertically 109. Each of these N.sub.m signals will be transmitted by N.sub.b antenna elements placed horizontally 110, with appropriate phase shifts to provide directive beams. The arrays are composed by identical antennas 111;

(3) FIG. 2 illustrates a detailed diagram of the arrangement of the antenna array 108 from FIG. 1 where N.sub.m antennas are placed vertically with a separation distance d from each other and N.sub.b antenna elements placed horizontally with spacing /2;

(4) FIG. 3 illustrates a detailed diagram of the vertical arrangement 109 of a set of N.sub.m antennas that provides constellation shaping as seen by the receiver; and

(5) FIG. 4 illustrates a detailed diagram of the horizontal arrangement 110 of a set of N.sub.b antennas.

DETAILED DESCRIPTION OF THE INVENTION

(6) The present application describes a transmission method using a multi-antenna transmitter combined with a frequency-domain receiver for broadband mm-wave systems based on large and dense constellations. This transmitter is compatible with efficient, low-cost, nonlinear amplifiers, while allowing spatial multiplexing gains. Referring to the figures, it will now be described technology using different embodiments of the same technology, which is not intended to limit the scope of protection of this application. The embodiments are composed by a method of sequential steps as described below.

(7) The transmission method uses SC-FDE schemes, combined with offset modulations with large constellations, for high spectral efficiency mm-wave communications. To allow highly efficient, strongly nonlinear power amplifiers, the variable envelope signals associated to large constellations are decomposed as the sum of several polar components [8], each one modulated as a serial OQPSK signal [9] with reduced envelope fluctuations that is amplified and transmitted by a separate antenna within a massive MIMO scheme.

(8) The basic structure of the transmitter considered in this application is depicted in FIG. 1. In the present method, the signal associated to a given constellation is decomposed as the sum of N.sub.m polar components that are modulated as N.sub.m BPSK signals and it should be noted that each of these BPSK signals can be regarded as an OQPSK signal in the serial format that is specially designed to have good tradeoffs between reduced envelope fluctuations and a compact spectrum.

(9) The method disclosed in the present application employs a massive MIMO scheme with N.sub.mN.sub.b antenna elements at the transmitter represented by 108, arranged in N.sub.m sets of N.sub.b antenna elements or N.sub.b sets of N.sub.m antenna elements. As with conventional beamforming schemes N.sub.b antenna elements are employed to define directive beams for spatial multiplexing purposes and/or interference management. However, the N.sub.m elements associated to each of the N.sub.b beamforming elements are employed to allow an efficient amplification of the signals associated to a large constellation, which is substantially different from conventional massive MIMO schemes. The high rate data stream is split into N.sub.u sub-streams in 101 that will be transmitted in parallel thanks to the spatial multiplexing capabilities of the antenna arrays employed for beamforming purposes (typically N.sub.u<N.sub.b). The data bits associated to each of the N.sub.u sub-streams are mapped by a modulator 102 into a given constellation (e.g., a QAM constellation) characterized by the ordered set ={s.sub.0, s.sub.1, . . . , s.sub.M1}, where M is the number of constellation symbols, following the rule
(.sub.n.sup.(1),.sub.n.sup.(2), . . . ,.sub.n.sup.(1),.sub.n.sup.(0))s.sub.n,
with (.sub.n.sup.(-1),.sub.n.sup.(2), . . . ,.sub.n.sup.(1),.sub.n.sup.(0)) denoting the binary representation of n with =log.sub.2(M) bits. In the polar decomposition block 103, the constellations symbols are mapped in N.sub.m polar components, that are the result of the decomposition of signal s.sub.n in M components given by

(10) $\begin{array}{c}{s}_n=g_0+g_1{b}_n^{\left(0\right)}+g_2{b}_n^{\left(1\right)}+g_3{b}_n^{\left(0\right)}{b}_n^{\left(1\right)}+g_4{b}_n^{\left(2\right)}+\left(\mathrm{.Math.}\right)\\ =\underset{i=0}{\overset{M-1}{.Math.}}{g}_i\underset{m=0}{\overset{-1}{.Math.}}{\left(b_n^{\left(m\right)}\right)}^{{}_{m,i}}=\underset{i=0}{\overset{M-1}{.Math.}}{g}_i{b}_n^{\mathrm{eq}\left(i\right)},\end{array}$
with (.sub.1,i .sub.2,i . . . .sub.1,i .sub.0,i) denoting the binary representation of i, b.sub.n.sup.(m)=(1).sup..sup.n.sup.(m) denoting the polar representation of the bit .sub.n.sup.(m), b.sub.n.sup.eq(i)=.sub.m=0.sup.1(b.sub.n.sup.(m)).sup.m,i denoting the i.sup.th polar component of s.sub.n and N.sub.m is the number of non-zero g.sub.i coefficients of the referred decomposition equation.

(11) Next each of the N.sub.m polar components is modulated as a BPSK signal in a modulator 104, whose output is a time continuous BPSK signal. To allow high spectral efficiency as well as the use of power-efficient, nonlinear amplifiers, each of these N.sub.m BPSK signals will be a serial representation of an OQPSK signal [9], specially designed to have good tradeoffs between reduced envelope fluctuations and compact spectrum (e.g., a GMSK signal). The corresponding signals can them be amplified by a set 107 of N.sub.m efficient, low-cost, nonlinear amplifiers 106 before being transmitted by an arrangement 108 of N.sub.mN.sub.b identical antennas 111. To allow spatial multiplexing effects combined with beamforming gains, each of these N.sub.m signals will be transmitted by N.sub.b antenna elements 110, with appropriate phase shifts to provide directive beams, while each vertical sub-array 109 of N.sub.m antennas performs constellation shaping as seen by the receiver, accordingly the combination of polar components expressed by

(12) $\begin{array}{c}{s}_n=g_0+g_1{b}_n^{\left(0\right)}+g_2{b}_n^{\left(1\right)}+g_3{b}_n^{\left(0\right)}{b}_n^{\left(1\right)}+g_4{b}_n^{\left(2\right)}+\left(\mathrm{.Math.}\right)\\ =\underset{i=0}{\overset{M-1}{.Math.}}{g}_i\underset{m=0}{\overset{-1}{.Math.}}{\left(b_n^{\left(m\right)}\right)}^{{}_{m,i}}=\underset{i=0}{\overset{M-1}{.Math.}}{g}_i{b}_n^{\mathrm{eq}\left(i\right)},\end{array}$

(13) For this, in each one of the N.sub.m branches, the signal obtained at the output of BPSK modulator 104 suffers a phase rotation in the phase shifter 105 and is amplified by the nonlinear amplifier 106. Thus, in each branch, the signal at the BPSK modulator's output is multiplied by a complex coefficient in the phase shifter 105 and then amplified by a nonlinear amplifier 106, which can operate in saturated mode or closed to it. This signal is sent to the corresponding horizontal set 110 of transmission antennas, that in the limit can be composed by only one antenna if beamforming is not used.

(14) The amplification stage 107 is composed by N.sub.m amplifiers 106 in parallel with each amplifier connected to an antenna sub-array 110 with N.sub.b antennas arranged horizontally. The transmission structure is then composed by a set of N.sub.m nonlinear amplifiers and N.sub.m sets of N.sub.b antenna elements or N.sub.b sets of N.sub.m antenna elements. As with conventional beamforming schemes N.sub.b antenna elements are employed to define directive beams for spatial multiplexing purposes and/or interference management. It should be mentioned that there are no combination losses, since the outputs of the N.sub.m amplifiers are combined at the channel. Since the antenna sub-array 109 associated to the N.sub.m antenna elements performs constellation shaping as seen by the receiver [11], the N.sub.m elements of 109 should be placed vertically, and as close as possible (ideally less than /2). On the other hand, the N.sub.b antenna elements of 110 should be placed horizontally, with spacing /2, to allow horizontal beams, where they are mostly needed.

(15) All antennas are equal, i.e. they have same radiation pattern. The N.sub.m antennas of the transmitter of FIG. 1 may be equally spaced vertically, being positioned along a line as illustrated in the linear array shown in FIG. 3. The set of N.sub.mN.sub.b in a planar array the transmit antennas are positioned with different spacing for the two dimensions as shown for the case of the planar spatial arrangement depicted in FIG. 2.

(16) Since the BPSK components signals in the several amplifiers and antennas are uncorrelated, the resulting radiation diagram of the vertical sub-array with N.sub.m elements remains omnidirectional in the broad sense. Changes of the diagram due the superposition of the radiation patterns of the various antennas are introduced by each set of N.sub.b antenna elements with the spatial arrangement of FIG. 4. In this case, the excitation of the antennas aims a steering diagram as in the classical approach, being the directivity introduced at the radiated power.

(17) Even though embodiments of the various aspects have been described, many different alterations, modifications and the like thereof will become apparent for those skilled in the art. The described embodiments are thereof not intended to limit the scope of the present disclosure.