Path division multiple access radio apparatus having...

Details Path division multiple access radio apparatus having... Path division multiple access radio apparatus having...

1999-09-24

2003-10-21

Kincaid, Lester G. (Department: 2685)

Multiplex communications

Communication over free space

Having a plurality of contiguous regions served by...

C370S319000

Reexamination Certificate

active

06636493

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radio apparatus having transmission directivity and a method of controlling the same, and more particularly, it relates to a radio apparatus employed in an adaptive array radio base station and a method of controlling the same.
2. Description of the Related Art
An adaptive array radio base station employing an array antenna has been recently put into practice as a radio base station for a mobile communication system such as a portable telephone. The operation principles of such adaptive array radio base stations are described in the following literature, for example:
B. Widrow, et al. “Adaptive Antenna Systems,” Proc. EEE, vol. 55, No. 12, pp. 2143-2159 (December 1967).
S. P. Applebaum, “Adaptive Arrays,” EEE Trans. Antennas & Propag., vol. AP-24, No. 5, pp. 585-598 (September 1976).
O. L. Frost, III, “Adaptive Least Squares Optimization Subject to Linear Equality Constraints,” SEL-70-055, Technical Report No. 6796-2, Information System Lab., Stanford Univ. (August 1970).
B. Widrow and S. D. Stearns, “Adaptive Signal Processing,” Prentice-Hall, Englewood Cliffs (1985).
R. A. Monzingo and T. W. Miller, “Introduction to Adaptive Arrays,” John Wiley & Sons, New York (1980).
J. E. Hudson, “Adaptive Array Principles,” Peter Peregrinus Ltd., London (1981).
R. T. Compton, Jr., “Adaptive Antennas-Concepts and Performance,” Prentice-Hall, Englewood Cliffs (1988).
E. Nicolau and D. Zaharia, “Adaptive Arrays,” Elsevier, Amsterdam (1989).
FIG. 10
is a model diagram schematically showing the operation principle of such adaptive array radio base stations. Referring to
FIG. 10
, an adaptive array radio base station
1
includes an array antenna
2
formed by n antennas #
1
, #
2
, #
3
, . . . , #n. A first area
3
with slant lines shows the range capable of receiving radio waves from the radio base station
1
. A second area
7
with slant lines shows the range capable of receiving radio waves from another radio base station
6
adjacent to the radio base station
1
.
In the area
3
, a portable telephone
4
serving as a terminal of a user A transmits/receives a radio signal to/from the adaptive array radio base station
1
(arrow
5
). In the area
5
, on the other hand, a portable telephone
8
serving as a terminal of another user B transmits/receives a radio signal to/from the radio base station
6
(arrow
9
).
If the radio signal employed in the portable telephone
4
of the user A is by chance equal in frequency to that employed in the portable telephone
8
of the user B, the radio signal from the portable telephone
8
of the user B may act as an undesired interference signal in the area
3
depending on the position of the user B, to be mixed into the radio signal between the portable telephone
4
of the user A and the adaptive array radio base station
1
.
In this case, the adaptive array radio base station
1
receives the radio signals from the users A and B in a mixed state if taking no measures, to disadvantageously disturb communication with the user A.
In order to eliminate the signal from the user B from the received signals, the adaptive array radio base station
1
employs the following structure and processing:
FIG. 11
is a block diagram showing the structure of an adaptive array
100
. Referring to
FIG. 11
, the adaptive array
100
is provided with n input ports
20
-
1
to
20
-n, in order to extract a signal of a desired user from input signals including a plurality of user signals.
Signals received in the input ports
20
-
1
to
20
-n are supplied to a weight vector control part
11
and multipliers
12
-
1
to
12
-n through switching circuits
1
—
1
to
10
-n.
The weight vector control part
11
calculates weight vectors w
1i
to w
1n
with a training signal corresponding to the signal of a specific user previously stored in a memory
14
and an output of an adder
13
. Each subscript i indicates that the weight vector is employed for transmission/receiving to/from an i-th user.
The multipliers
12
-
1
to
12
-n multiply the input signals from the input ports
20
-
1
to
20
-n by the weight vectors w
1i
to w
1n
respectively and supply the results to the adder
13
. The adder
13
adds up the output signals from the multipliers
12
-
1
to
12
-n and outputs the result as a received signal S
RX
(t), which in turn is also supplied to the weight vector control part
11
.
The adaptive array
100
further includes multipliers
15
-
1
to
15
-n receiving an output signal S
TX
(t) from the adaptive array radio base station
1
, multiplying the same by the weight vectors w
1i
to w
1n
supplied from the weight vector control part
11
and outputting the results. The outputs of the multipliers
15
-
1
to
15
-n are supplied to the switching circuits
10
-
1
to
10
-n respectively. The switching circuits
10
-
1
to
10
-n supply the signals received from the input ports
20
-
1
to
20
-n to a signal receiving part
1
R in receiving, while supplying signals from a signal transmission part
1
T to the input/output ports
20
-
1
to
20
-n in signal transmission.
The operation principle of the signal receiving part
1
R shown in
FIG. 11
is now briefly described.
In order to simplify the illustration, it is hereafter assumed that the number of antenna elements is four and the number of users PS from which signals are simultaneously received is two. In this case, signals RX
1
(t) to RX
4
(t) supplied from the antennas to the receiving part
1
R are expressed as follows:
RX
1
(
t
)=
h
11
Srx
1
(
t
)+
h
12
Srx
2
(
t
)+
n
1
(
t
)  (1)
RX
2
(
t
)=
h
21
Srx
1
(
t
)+
h
22
Srx
2
(
t
)+
n
2
(
t
)  (2)
RX
3
(
t
)=
h
31
Srx
1
(
t
)+
h
32
Srx
2
(
t
)+
n
3
(
t
)  (3)
RX
4
(
t
)=
h
41
Srx
1
(
t
)+
h
42
Srx
2
(
t
)+
n
4
(
t
)  (4)
where RX
j
(t) represents a signal received in a j-th (j=1, 2, 3, 4) antenna, and Srx
i
(t) represents a signal transmitted from an i-th (i=1, 2) user.
Further, h
ji
represents a complex factor of the signal from the i-th user received by the j-th antenna, and n
j
(t) represents noise included in the j-th received signal.
The above equations (1) to (4) are expressed in vector forms as follows:
X
(
t
)=
H
1
Srx
1
(
t
)+
H
2
Srx
2
(
t
)+
N
(
t
)  (5)
X
(
t
)=[
RX
1
(
t
),
RX
2
(
t
), . . .
RX
n
(
t
)]
T
  (6)
H
1
=[h
1i
, h
2i
, . . . , h
ni
]
T
, (
i
=1, 2)  (7)
N
(
t
)=[
n
1
(
t
),
n
2
(
t
), . . . ,
n
n
(
t
)]
T
  (8)
In the above equations (6) to (8), [ . . . ]
T
shows transposition of [ . . . ].
In the equations (5) to (8), X(t) represents an input signal vector, H
i
represents a received signal factor vector of the i-th user, and N(t) represents a noise vector respectively.
As shown in
FIG. 11
, the adaptive array
100
outputs a signal composited by multiplying the input signals from the respective antennas by the weighting factors w
1i
to w
1n
as the received signal S
RX
(t). The number n of the antennas is four.
When extracting the signal Srx
1
(t) transmitted from the first user, for example, the adaptive array
100
operates under the aforementioned preparation as follows:
An output signal y
1
(t) from the adaptive array
100
can be expressed by multiplying the input signal vector X(t) by a weight vector W
1
as follows:
y
1(
t
)=
X
(
t
)
W
1
T
  (9)
W
1
=[w
11
, w
21
, w
31
, w
41
]
T
  (10)
The weight vector W
1
has the weighting factor w
j1
(j=1, 2, 3, 4) multiplied by the j-th input signal RX
j
(t) as its element.
Substitution of the input signal vector X(t) expressed in the equation (5) into y
1
(t) expressed in the equation (9) gives the following equation:
y
1(
t
)=
H
1
W
1
T
Srx
1
(
t
)+
H
2
W
1
T
Srx
2
(
t
)+
N
(
t
)
W
1
T
  (11)
When the adaptive array
100
ideally operates, the we

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