Pulse or digital communications – Systems using alternating or pulsating current – Plural channels for transmission of a single pulse train
Reexamination Certificate
1999-06-11
2003-04-15
Corrielus, Jean (Department: 2631)
Pulse or digital communications
Systems using alternating or pulsating current
Plural channels for transmission of a single pulse train
C375S295000, C370S208000
Reexamination Certificate
active
06549581
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a transmitter and a method as well as to a transmitting system for the wireless transmission of informational data and particularly to a technique for interference cancellation in OFDM communication.
BACKGROUND OF THE INVENTION
One technique to minimize interference in wireless transmission, particularly in OFDM systems, is the so-called random orthogonal transform (ROT). The principles of ROT are described in the European patent application 98 104 287.2 of Sony Corporation which is only to be regarded to be prior art according to Article 54(3) EPC. The enclosure of said application is herewith incorporated by reference. In the following, the basic technique according to this application will be explained in detail with reference to
FIGS. 8
to
10
.
In
FIG. 8
, reference numerals
105
A,
105
B denote respectively portable telephone device. Reference numerals
106
A and
106
B denote base stations of a wireless transmission system. As shown in
FIG. 8
, the portable telephone device
105
A uses a predetermined channel to be engaged in radio communication with the base station
106
A in the cell
101
A. At the same time, the same channel is used in the adjacent cell
101
B so that the portable telephone device
105
B is engaged in radio communication with the base station
106
B. At that time, for example, in the portable telephone devices
105
A and
105
B both QPSK modulation (Quadrature Phase Shift Keying; Four Phase Transition Modulation) is used as a modulation method of the sent data. The signal series of the modulated sending signal are defined as x
(A)
2
, modulated sending signal are defined as x
(A)
1
, x
(A)
2
, x
(A)
3
, . . . x
(A)
k−1
, x
(A)
k
, x
(A)
k+1
, . . . and x
(B)
1
, x
(B)
2
, x
(B)
3
, . . . x
(B)
k−1
, x
(B)
k
, x
(B)
k+1
, . . .
The portable telephone device
102
A groups N (N is an integer which is 1 or more) sending signal series x
(A)
n
(n=1, 2, 3, . . . ). The grouped sending signal series x
(A)
k
, . . . x
(A)
k+N
and a predetermined Nth normal orthogonal matrix M
A
are multiplied in order as shown in the following equation.
[Equation 1]
[
y
k
(
A
)
⋮
y
k
+
N
(
A
)
]
=
M
A
[
X
k
(
A
)
⋮
X
k
+
N
(
A
)
]
(
1
)
As a consequence, an orthogonal conversation is added to the sending signal series x
(A)
n
(n=1, 2, 3, . . . ) and a resulting sending signal series y
(A)
n
(n=1, 2, 3, . . . ) are sent in order.
On the other hand, at the base station
106
A which is a receiving side, when a sending signal CA is received from the portable telephone device
105
A of the communication partner, N received signal series y
(A)
n
(n=1, 2, 3, . . . ) are grouped, and the grouped received signal series y
(A)
k
, . . . y
(A)
k+N
are successively multiplied with an inverse matrix M
A
−1
of the Nth normal orthogonal matrix M
A
used on the sending side as shown in the following equation.
[Equation 2]
[
X
k
(
A
)
⋮
X
k
+
N
(
A
)
]
=
M
A
-
1
[
y
k
(
A
)
⋮
y
k
+
N
(
A
)
]
=
M
A
-
1
M
A
[
x
k
(
A
)
⋮
x
k
+
N
(
A
)
]
=
[
x
k
(
A
)
⋮
x
k
+
N
(
A
)
]
(
2
)
As a consequence, the signal series X
(A)
n
(n=1, 2, 3, . . . ) is restored which is equal to the signal series x
(A)
n
(n=1, 2, 3, . . . ) before orthogonal conversion.
In the similar manner, at the time of sending data, the portable telephone device
105
B groups the N sending signal series x
(B)
n
(n=1, 2, 3, . . . ). The grouped sending signal series x
(B)
k
, . . . X
(B)
k+N
and the predetermined Nth normal orthogonal matrix M
B
are multiplied in order for each group as shown in the following equation.
[Equation 3]
[
y
k
(
B
)
⋮
y
k
+
N
(
B
)
]
=
M
B
[
x
k
(
B
)
⋮
x
k
+
N
(
B
)
]
(
3
)
As a consequence, the orthogonal conversion is added to the sending signal series x
(B)
n
(n=1, 2, 3, . . . ), and the resulting sending signal series y
(B)
n
(n=l, 2, 3, . . . ) are sent in order. For reference, the Nth normal orthogonal matrix M
B
which is used in the portable telephone device
5
B and the Nth normal orthogonal matrix M
A
which is used in the portable telephone device
105
A are matrixes which are completely different from each other.
At the base station
106
B which is a receiving side, when the sending signal CB from the portable telephone device
5
B of the communication partner is received, the N received receiving signal series y
(B)
n
(n=1, 2, 3, . . . ) are grouped, and the grounded y
(B)
k
, . . . y
(B)
k+N
and the inverse matrix M
B
−1
of the Nth normal orthogonal matrix M
B
used at a sending side are multiplied in order for each group as shown in the following equation.
[Equation 4]
[
X
k
(
B
)
⋮
X
k
+
N
(
B
)
]
=
M
B
-
1
[
y
k
(
B
)
⋮
y
k
+
N
(
B
)
]
=
M
B
-
1
M
B
[
x
k
(
B
)
⋮
x
k
+
N
(
B
)
]
=
[
x
k
(
B
)
⋮
x
k
+
N
(
B
)
]
(
4
)
Consequently, the signal series X
(B)
n
(n=1, 2, 3, . . . ) which is equal to the signal series x
(B)
n
(n=1, 2, 3, . . . ) which is equal to the signal series x
(B)
n
(n=1, 2, 3, . . . ) before the orthogonal conversion is restored.
By the way, at the base station
106
A, only the sending signal CA sent by the portable telephone device
105
A reaches, but the sending signal CB sent by the portable telephone device
105
B also reaches depending on the situation. In that case, the sending signal CB from the portable telephone device
105
B acts as an interference wave I. When the signal level of the sending signal CB is large as compared with the sending signal CA from the portable telephone device
105
A, trouble is caused to communication with the portable telephone device
105
A. In other words, as the base station
106
A, it is not recognized that the signal is a sending signal from either of the portable telephone devices
105
A or
105
B so that it is feared that the sending signal CB form the portable telephone device
105
B is received by mistake.
In such a case, the base station
6
A groups the N received signal series y
(B)
n
(n=1, 2, 3, . . . ) received from the portable telephone device
5
B so that the demodulation processing is performed by multiplying the inverse matrix M
A
−1
to the grouped signal series y
(B)
k
, . . . y
(B)
k+N
as shown in the following equation as in the normal receiving processing.
[Equation 5
[
X
k
(
A
)
⋮
X
k
+
N
(
A
)
]
=
M
A
-
1
[
y
k
(
B
)
⋮
y
k
+
N
(
B
)
]
=
M
A
-
1
M
B
[
X
k
(
B
)
⋮
X
k
+
N
(
B
)
]
(
5
)
However, as seen from the equation (5), the receiving signal series y
(B)
n
(n=1, 2, 3, . . . ) from the portable telephone device
5
B is a result obtained from a multiplication of the orthogonal matrix M
B
which is different from the orthogonal matrix M
A
so that the diagonal reverse conversion is not obtained even when the inverse matrix M
A
−1
is multiplied with the result that the original signal series x
(B)
n
(n=1, 2, 3, . . . ) is not restored. In this case, the received signal series becomes a signal series which is the original signal series x
(B)
n
(n=1, 2, 3, . . . ) orthogonally converted with another orthogonal matrix consisting of M
A
−1
M
B
, so that the signal becomes ostensibly a noise signal, and even when the signal series is QPSK demodulated, the sending data of the portable telephone device
5
B is not restored.
In this manner, in the case of the radio communication system to which the pre
Corrielus Jean
Frommer William S.
Frommer & Lawrence & Haug LLP
Megerditchian Samuel H.
Sony International (Europe) GmbH
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