1. Apparatus for surfing instruction, comprising:
a motorized surfboard with a propulsion system and a wireless receiver configured to control the activation state of the propulsion system, and
an instructor’s wireless transmitter in communication with the wireless receiver to control the propulsion system,
where the instructor’s wireless transmitter is configured to control a motion of the motorized surfboard through water from a position off the motorized surfboard.
2. The apparatus of claim 1, further comprising a rider’s wireless transmitter in communication with the wireless receiver to control the propulsion system from a position on the motorized surfboard.
3. The apparatus of claim 2, where the rider’s wireless transmitter is wearable and comprises actuators positioned on a rider’s transmitter-operating hand.
4. The apparatus of claim 2, where:
the wireless receiver is configured to recognize an override signal taking precedence over any other wireless signal received, and
the instructor’s wireless transmitter is configured to transmit the override signal following an instructor’s demand.
5. The apparatus of claim 2, further comprising a wireless communication link between the rider’s wireless transmitter and the instructor’s wireless transmitter.
6. The apparatus of claim 5, where the wireless communication link comprises a voice channel.
7. The apparatus of claim 1, further comprising:
a board-data transmitter embedded in the motorized surfboard, configured to transmit information collected by integrated sensing elements, and
a board-data receiver configured to receive the information from the board transmitter and accessible to at least one of the instructor and the rider,
a processing element configured to interpret the information from the board-data receiver, and
an output device to present the information interpreted by the processor in a human-comprehensible form.
8. The apparatus of claim 7, further comprising a storage element connected to the processor and configured to store the information interpreted by the processor.
9. The apparatus of claim 7, where
the information comprises one of the group consisting of fuel level, battery charge level, motor power level, board speed, temperature, and board pitch or roll angle, and
the output device comprises one of the group consisting of a real-time display, a display associated with the storage element, an audio speaker, and a haptic transducer.
10. The apparatus of claim 1, further comprising an auxiliary wireless transmitter remote from, but communicating with, at least one of the group consisting of the motorized surfboard, the rider’s wireless transmitter, and the instructor’s wireless transmitter.
11. A method for surfing instruction using the apparatus of claim 1, comprising:
placing the motorized surfboard of claim 1 in a natural or human-made body of water;
arranging for a student to mount the motorized surfboard;
using the instructor’s wireless transmitter of claim 1 to activate the propulsion system of claim 1 and cause the motorized surfboard, carrying the mounted student, to move across the surface of the water.
12. The method of claim 11, further comprising instructing or observing the student in the practice of at least one of surfing balance, paddling, wave-catching, takeoff, pop-up, weight-shifting, or maneuvering on the motorized surfboard as the propulsion system moves the motorized surfboard across the surface of the water.
13. The method of claim 11, where the water is too calm for unmotorized surfing.
14. The method of claim 13, further comprising at least one of:
operating the propulsion system at variable speeds according to the student’s skill level,
operating the propulsion system in a pulsed or otherwise variable mode to simulate the changing forces of waves and currents, and
directing the propulsion system to work against the student’s paddling to build strength for paddling against incoming waves.
15. The method of claim 11, further comprising recording at least one of
the instructions given to the student,
the student’s comments, and
the student’s performance.
16. The method of claim 11, further comprising at least one of
monitoring information from a board-data transmitter, and
recording information from the board-data transmitter to review with or without the student at a later time.
17. The method of claim 11, further comprising:
providing a rider’s wireless transmitter to the student, and
teaching the student to control the propulsion system using the rider’s wireless transmitter while riding the motorized surfboard.
18. The method of claim 17, further comprising communicating with the student over a wireless link between the instructor’s wireless transmitter and the rider’s wireless transmitter while the student is on or near the motorized surfboard.
19. The method of claim 17, further comprising taking control of the motorized surfboard from the student by activating an override switch on the instructor’s wireless transmitter.
20. The method of claim 11, where the water has waves of a suitable size for unmotorized surfing, and further comprising at least one of:
using the propulsion system to propel the motorized surfboard against breaking waves to reach a zone of sloping swells,
using the propulsion system to reach a necessary speed for catching a wave, and
controlling the propulsion system to help the student evade hazards in the water.
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 method for the decoding of a received signal comprising symbols distributed in space, time andor frequency by a space-time or space-frequency encoding matrix, wherein the method implements a space-time decoding step and at least one iteration, each iteration comprising the following sub-steps:
diversity pre-decoding, which is the inverse of a diversity pre-encoding carried out when said signal is emitted, delivering pre-decoded data;
estimation of the symbols forming said signal, from said pre-decoded data, delivering estimated symbols; and
diversity pre-encoding identical to said diversity pre-encoding implemented at emission, applied to said estimated symbols, to give an estimated signal, except for the last iteration.
2. The method according to claim 1 comprising:
the space-time decoding, which is the inverse of the space-time encoding implemented at emission, delivering a decoded signal;
equalization of said decoded signal, delivering an equalized signal;
conversion of a matrix of the equalized signals into a diagonal matrix, obtained from a total encodingchanneldecoding matrix taking account of at least said encoding matrix, and of a decoding matrix that is the conjugate transpose of said encoding matrix;
the diversity pre-decoding, which is the inverse of the diversity pre-encoding implemented at emission of said signal, delivering the pre-decoded data;
the estimation of the symbols forming said signal, from said pre-decoded data, delivering the estimated symbols;
the diversity pre-encoding, identical to said diversity pre-encoding implemented at emission, applied to said estimated symbols, to give the estimated signal; and
at least one iteration of an interference cancellation step implementing the following sub-steps:
subtraction, from said equalized signal, of said estimated signal multiplied by an interference matrix, delivering an optimized signal;
diversity pre-decoding of said optimized signal, that is the inverse of the diversity pre-encoding implemented at emission of said signal, delivering improved pre-decoded data;
estimation of the symbols forming said optimized signal, from the improved pre-decoded data, delivering new estimated symbols; and
diversity pre-encoding identical to said diversity pre-encoding implemented at emission, applied to said new estimated symbols to give a new estimated signal, except for the last iteration.
3. The method according to claim 2, wherein said space-time decoding and equalization steps andor said equalization and conversion steps are done jointly.
4. The method according to claim 1, wherein said encoded symbols are emitted by means of at least two antennas, which produce different corresponding transmission channels and wherein the method of decoding takes the different corresponding transmission channels comprehensively into account.
5. The method according to claim 2, wherein said equalization step implements an equalization according to one of the techniques belonging to the group comprising:
MMSE type equalization;
EGC type equalization;
ZF type equalization; and
equalization taking account of a piece of information representing a signal-to-noise ratio between the received signal and a reception noise.
6. The method according to claim 2, wherein said steps of symbol estimation implement a soft decision, associating a piece of confidence information with the soft decision and said subtraction step or steps take account of said pieces of confidence information.
7. The method according to claim 2, wherein said received signal comprises a multicarrier signal.
8. The method according to claim 1, wherein said pre-encoding is obtained by one of the following methods:
a spread-spectrum technique; and
linear pre-encoding.
9. The method according to claim 1, wherein the method implements an automatic gain control step before or after said equalization step andor during at least one of said iterations.
10. The method according to claim 1 and further comprising a channel-decoding step, symmetrical with a channel-encoding step implemented at emission.
11. The method according to claim 10, wherein said channel-decoding step implements a turbo-decoding operation.
12. The method according to claim 1 and further comprising at least one de-interlacing step and at least one re-interlacing step, corresponding to an interlacing implemented at emission.
13. The method according to claim 1 and further comprising a step of improvement of a channel estimation, taking account of the estimated symbols during at least one of said iterations.
14. The method according to claim 2 and further comprising transmitting by four antennas the signal to be received, referred to as the received signal, through at least one transmission channel, wherein said total encodingchanneldecoding matrix is equal to:
G
=
\u03b3
\u2061
A
0
0
J
0
A
–
J
0
0
–
J
A
0
J
0
0
A
with:
A=|h1|2+|h2|2+|h3|2+|h4|2
J=2Re{h1h*4\u2212h2h*3},
representing the interference, and
\u03b3
=
1
\uf603
h
1
\uf604
2
+
\uf603
h
2
\uf604
2
+
\uf603
h
3
\uf604
2
+
\uf603
h
4
\uf604
2
+
1
SNR
where
\u2062
:
\u2062
\u2003
\u2062
H
=
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2
h
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h
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–
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1
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–
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1
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h
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h
4
–
h
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–
h
2
h
1
is a matrix grouping the space-time encoding and the transmission channel,
and SNR represents the signal-to-noise ratio.
15. The method according to claim 2 and further comprising transmitting by eight antennas the signal to be received, referred to as the received signal, through at least one transmission channel, wherein said total encodingchanneldecoding matrix is equal to:
G
=
\u2062
\u03b3
\xb7
H
H
\xb7
H
=
\u2062
\u03b3
\u2061
A
0
0
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J
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A
with
\u2062
\u2003
\u2062
A
=
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+
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+
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h
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+
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+
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h
8
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2
\u2062
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\u2062
and
J
=
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Im
\u2062
{
h
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+
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+
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}
and
\u2062
\u2003
\u2062
\u03b3
=
\u2062
1
\uf603
h
1
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+
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h
2
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2
+
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h
3
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+
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2
+
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+
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+
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7
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+
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h
8
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2
+
1
SNR
where
\u2062
\u2003
\u2062
:
\u2062
\u2003
\u2062
H
=
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,
is a matrix grouping the space-time encoding and the transmission channel
and SNR represents the signal-to-noise ratio.
16. The method of claim 14 and further comprising, prior to the step of transmitting, encoding said signal to be received, wherein the encoding implements a space-time encoding such that:
H
=
h
1
h
2
h
3
h
4
h
5
h
6
h
7
h
8
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2
–
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1
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,
17. A receiver for receiving a received signal, comprising symbols distributed in space and time andor frequency by means of a space-time encoding matrix, wherein the receiver comprises means of space-time decoding that is the inverse of the space-time encoding implemented at emission, and:
means of diversity pre-decoding, performing a pre-decoding which is the inverse of a diversity pre-encoding carried out at emission of said signal, delivering pre-decoded data;
means of estimation of the symbols forming said signal, from the pre-decoded data, delivering new estimated symbols;
means of diversity pre-encoding, performing a pre-encoding identical to said diversity pre-encoding implemented at emission, applied to said new estimated symbols, to give a new estimated signal, said means of diversity pre-decoding, estimation, and diversity pre-encoding being implemented at least once for each symbol.
18. A method for the decoding of a received signal comprising symbols distributed in space, time andor frequency by means of a space-time or space-frequency encoding matrix, wherein the method comprises:
diagonalization, obtained from a total encodingchanneldecoding matrix taking account of at least said encoding matrix, of a decoding matrix, corresponding to the matrix that is the conjugate transpose of said encoding matrix;
demodulation, symmetrical with a modulation implemented at emission;
de-interlacing symmetrical with an interlacing implemented at emission;
channel decoding symmetrical with a channel encoding implemented at emission;
re-interlacing, identical with the interlacing implemented at emission;
re-modulation identical with the modulation implemented at emission, delivering an estimated signal; and
at least one iteration of an interference cancellation step comprising a subtraction from an equalized signal of said estimated signal multiplied by an interference matrix, delivering an optimized signal.