1. A method for transmitting a signal by a transmitter via Nt antennas in a multiple antenna system using multiple subcarriers, the method comprising:
acquiring a plurality of modulation symbol streams by modulating a transmission signal;
phase-shift based precoding the plurality of modulation symbol streams using a matrix of D*U to output Nt symbol streams; and
transmitting the \u2018Nt\u2019 symbol streams via the Nt antennas,
wherein D is a diagonal matrix and U is a unitary matrix,
wherein U and D are determined such that the plurality of modulation symbol streams are cyclically delayed with a unit of a first delay value when feedback information from a receiver is not used,
wherein U and D are determined such that the plurality of modulation symbol streams are cyclically delayed with a unit of a second delay value, when the feedback information from the receiver is used, and
wherein the first delay value is larger than the second delay value.
2. The method of claim 1, wherein D is determined based on a multiplexing rate.
3. The method of claim 1, wherein D has different phase shift angles for each row of the diagonal matrix.
4. The method of claim 1, wherein U is determined based on a multiplexing rate.
5. The method of claim 1, wherein U is predetermined in a form of a codebook.
6. The method of claim 1, wherein:
the phase-shift based precoding is performed in a form of D*U*X when a number of the multiple antennas is 2 and a multiplexing rate is 2;
a number of the plurality of modulation symbol streams is m; and
X is an m*1 matrix consisting of the plurality of modulation symbol streams.
7. The method of claim 1, wherein:
U is predetermined based on a value of Nt and a multiplexing rate (R); and
phase angles of D are linearly increased according to a frequency index.
8. The method of claim 7, wherein the matrix of D*U is represented as:
(
\u2147
j
\u2062
\u2062
\u03b8
1
\u2062
k
0
\u2026
0
0
\u2147
j
\u2062
\u2062
\u03b8
2
\u2062
k
\u2026
0
\u22ee
\u22ee
\u22f1
0
0
0
0
\u2147
j
\u2062
\u2062
\u03b8
N
t
\u2062
k
)
\u2062
(
U
N
t
\xd7
R
)
,
where U has a dimension of Nt*R and \u2018k\u2019 represents the frequency index.
9. A method for receiving a signal by a receiver in a multiple antenna system using multiple subcarriers, the method comprising:
receiving the signal transmitted from a transmitter via Nt antennas;
performing a function that is opposite to a phase-shift based precoding on the received signal using a matrix of D*U; and
demodulating the signal on which the opposite function was performed,
wherein D is a diagonal matrix and U is a unitary matrix,
wherein U and D are the same matrices determined at the transmitter such that a plurality of modulation symbol streams are cyclically delayed with a unit of a first delay value, when feedback information from the receiver is not used,
wherein U and D are the same matrices determined at the transmitter such that the plurality of modulation symbol streams are cyclically delayed with a unit of a second delay value, when the feedback information from the receiver is used, and
wherein the first delay value is larger than the second delay value.
10. The method of claim 9, wherein D is determined based on a multiplexing rate.
11. The method of claim 9, wherein U is determined based on a multiplexing rate.
12. The method of claim 9, wherein U is predetermined within a codebook.
13. The method of claim 9, wherein:
U is predetermined based on a value of Nt and a multiplexing rate (R); and
phase angles of D are linearly increased according to a frequency index.
14. The method of claim 13, wherein the matrix of D*U is represented as:
(
\u2147
j
\u2062
\u2062
\u03b8
1
\u2062
k
0
\u2026
0
0
\u2147
j
\u2062
\u2062
\u03b8
2
\u2062
k
\u2026
0
\u22ee
\u22ee
\u22f1
0
0
0
0
\u2147
j
\u2062
\u2062
\u03b8
N
t
\u2062
k
)
\u2062
(
U
N
t
\xd7
R
)
,
where U has a dimension of Nt*R and \u2018k\u2019 represents the frequency index.
15. An apparatus for transmitting a signal via Nt antennas in a multiple antenna system using multiple subcarriers, the apparatus comprising:
a mapper acquiring a plurality of modulation symbol streams by modulating a transmission signal; and
a precoder performing a phase-shift based precoding on the plurality of modulation symbol streams using a matrix of D*U to output Nt symbol streams,
wherein D is a diagonal matrix and U is a unitary matrix,
wherein U and D are determined such that the plurality of modulation symbol streams are cyclically delayed with a unit of a first delay value when feedback information from a receiver is not used,
wherein U and D are determined such that the plurality of modulation symbol streams are cyclically delayed with a unit of a second delay value, when the feedback information from the receiver is used, and
wherein the first delay value is larger than the second delay value.
16. The apparatus of claim 15, wherein D is determined based on a multiplexing rate.
17. The apparatus of claim 15, wherein D has different phase shift angles for each row of the diagonal matrix.
18. The apparatus of claim 15, wherein U is determined based on a multiplexing rate.
19. The apparatus of claim 15, further comprising:
a memory unit storing U in a form of a codebook.
20. The apparatus of claim 15, wherein:
U is predetermined based on a value of Nt and a multiplexing rate (R); and
phase angles of D are linearly increased according to a frequency index.
21. The apparatus of claim 20, wherein the matrix of D*U is represented as:
(
\u2147
j
\u2062
\u2062
\u03b8
1
\u2062
k
0
\u2026
0
0
\u2147
j
\u2062
\u2062
\u03b8
2
\u2062
k
\u2026
0
\u22ee
\u22ee
\u22f1
0
0
0
0
\u2147
j
\u2062
\u2062
\u03b8
N
t
\u2062
k
)
\u2062
(
U
N
t
\xd7
R
)
,
where U has a dimension of Nt*R and \u2018k\u2019 represents the frequency index.
22. An apparatus for receiving a signal in a multiple antenna system using multiple subcarriers, the apparatus comprising:
one or more antennas for receiving the signal transmitted from a transmitter via Nt antennas;
a precoder performing a function that is opposite to a phase-shift based precoding on the received signal using a matrix of D*U; and
a demapper demodulating the signal on which the opposite function was performed,
wherein D is a diagonal matrix and U is a unitary matrix,
wherein U and D are the same matrices determined at the transmitter such that a plurality of modulation symbol streams are cyclically delayed with a unit of a first delay value, when feedback information from the apparatus is not used,
wherein U and D are the same matrices determined at the transmitter such that the plurality of modulation symbol streams are cyclically delayed with a unit of a second delay value, when the feedback information from the apparatus is used, and
wherein the first delay value is larger than the second delay value.
23. The apparatus of claim 22, wherein D is determined based on a multiplexing rate.
24. The apparatus of claim 22, wherein U is determined based on a multiplexing rate.
25. The apparatus of claim 22, further comprising:
a memory unit storing U in a form of a codebook.
26. The apparatus of claim 22, wherein:
U is predetermined based on a value of Nt and a multiplexing rate (R); and
phase angles D are linearly increased according to a frequency index.
27. The apparatus of claim 26, wherein the matrix of D*U is represented as:
(
\u2147
j
\u2062
\u2062
\u03b8
1
\u2062
k
0
\u2026
0
0
\u2147
j
\u2062
\u2062
\u03b8
2
\u2062
k
\u2026
0
\u22ee
\u22ee
\u22f1
0
0
0
0
\u2147
j
\u2062
\u2062
\u03b8
N
t
\u2062
k
)
\u2062
(
U
N
t
\xd7
R
)
,
where U has a dimension of Nt*R and \u2018k\u2019 represents the frequency index.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A device for mounting a child seat in a car comprising a frame with two frame tubes having at their ends attachment devices for connecting the frame to car mounted brackets and a slide movable along the frame tubes, the slide having a support surface for supporting the child seat and two or more hooks of which at least one is movable for coupling the child seat on the slide characterized in that the support surface can support a first circular flange of the child seat and the hooks have a circular shape andor are placed in a circle for gripping the first circular flange.
2. The device in accordance with claim 1 whereby the upper surface is parallel to the frame tubes and preferably immediately above their upper surface.
3. The device in accordance with claim 1 whereby the movable hooks have a first position whereby the child seat can be positioned on or removed from the support surface and a second position whereby the hooks can hold the first circular flange against the support surface, and a mechanism for positioning the movable hooks in the first position and the second position.
4. The device in accordance with claim 1, whereby the hooks can grip the first circular flange with their outside circumference.
5. The device in accordance with claim 1 whereby there are three or more hooks.
6. The device in accordance with claim 5 whereby the movable hooks can move in three or more radial directions.
7. The device in accordance with claim 1 whereby the movable hooks can slide along a linear guide between the first position and the second position.
8. The device in accordance with claim 1 whereby the slide has at the locations of the hooks one or more second flange parts so that in the second position the hooks grip both the first circular flange and a second flange part.
9. The device in accordance with claim 1 whereby the movable hooks have spring means for moving it to the first position and holding means for holding it in the second position.
10. The device in accordance with claim 1 whereby a cam disc rotatable around a first axis and preferably placed in the centre of the hooks can move the movable hooks, the cam disc having cam surfaces, each of which presses against a side plane of the movable hook.
11. The device in accordance with claim 10 whereby the cam surfaces are shaped such that the spring means prevent rotation of the cam disc when the movable hooks are in the second position.
12. The device in accordance with claim 10 whereby the cam disc is rotated by a handle rotatable around a second axis and provided with means for coupling the rotation of the cam disc and the handle.
13. The device in accordance with claim 1 whereby the slide has a mounting position whereby it is located away from the attachment devices and is provided with blocking means for preventing the slide to move from the mounting position towards the attachment devices.
14. The device in accordance with claim 13 whereby the blocking means comprise pins that can extend from each frame tube.
15. The device in accordance with claim 14 whereby each pin is connected to a first sensor determining whether the attachment device is connected to the car mounted anchorage.
16. The device in accordance with claim 13, whereby by the frame tubes are provided with notches and the slide with a catch for preventing the slide to move in the direction away from the attachment devices.
17. The device in accordance with claim 16 whereby the catch is connected to a second sensor for determining whether a child seat is placed on the support surface andor the circular flange is fully positioned on the support surface.
18. The device in accordance with claim 13 whereby the frame tubes each have a button for disconnecting the attachment device from the car mounted bracket, which button is covered andor deactivated by the slide when the slide is not in the mounting position.
19. The device of claim 1 further including a child seat mounted on said device whereby the child seat has a circular flange that can rest on the support surface and that can be gripped by the hooks.
20. The device of claim 19 whereby the circular flange has on its inner diameter a cylindrical surface that can rotate around the hooks.