Pulse or digital communications – Spread spectrum – Frequency hopping
Reexamination Certificate
1998-06-04
2001-09-25
Pham, Chi (Department: 2631)
Pulse or digital communications
Spread spectrum
Frequency hopping
C455S452200
Reexamination Certificate
active
06295310
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims priority under 35 U.S.C. §§119 and/or 365 to Hei 9-155033 filed in Japan on Jun. 12, 1997, the entire contents of which are herein incorporated by reference.
1. Field of the Invention
The present invention relates to a mobile communication system that involves periodic switching of the transmitted frequencies by a frequency hopping technique.
2. Description of the Prior Art
A conventional mobile communication system will be described first with reference to
FIG. 12
which depicts a conventional system in conceptual form.
Reference numeral
10
denotes a mobile station, and
11
a base station. Data is transmitted and received between the base station
11
and the mobile station
10
. Reference numeral
12
denotes a radio cell, which indicates the coverage area surrounding the base station
11
and within which data is exchanged between the base and mobile stations
11
and
10
.
A septuplet of radio cells
12
constitute one area as indicated by hatching in FIG.
12
. The frequencies that are assigned to each of such areas repeat in a cyclic order; that is, the areas are common in the frequencies assigned thereto. Each area made up of seven radio cells will hereinafter be referred to as a repetition area. Further, the number of radio cells forming the repetition area will hereinafter be referred to as a repetition cell number. In the prior art example of
FIG. 12
, the repetition cell number is seven.
Furthermore, the radio cells forming the repetition area are each assigned a plurality of frequencies, which will hereinafter be referred to as a frequency group. And the radio cells making up the repetition area are each assigned seven different frequency groups.
The base station
11
has control over the mobile stations
10
belonging to its radio cell and allocates to each mobile station
10
a hopping sequence for frequency hopping use.
Next, a description will be given of the operation of the conventional mobile communication system conceptually depicted in FIG.
12
.
In
FIG. 12
the base station
11
specifies predetermined hopping sequences for all the mobile stations
10
placed under its control. Based on the hopping sequence specified by the base station
11
, each mobile station
10
performs frequency hopping.
Now, a description will be given, with reference to
FIG. 13
, of hopping sequences c
1
, c
2
, c
3
, c
4
, c
5
and c
6
that are specified for a cell A or B when it is assigned frequencies f
1
, f
2
and f
3
. Let it be assumed that mobile stations M
1
to m
3
are present in the cell A and mobile stations M
4
to m
6
in the cell B.
Suppose that the mobile station M
1
is assigned the hopping sequence c
1
, the mobile station m
2
the hopping sequence c
2
, the mobile station m
3
the hopping sequence c
3
, the mobile station M
4
the hopping sequence c
4
, the mobile station m
5
the hopping sequence c
5
and the mobile station m
6
the hopping sequence c
6
. The mobile stations M
1
to m
6
perform frequency hopping with fixed hopping periods based on the hopping sequences c
1
to c
6
respectively assigned to them. The frequencies f
1
, f
2
and f
3
will hereinafter be called first, second and third frequencies in this order.
Turning next to
FIG. 14
, a description will be made of how frequency hopping takes place, for example, in the mobile stations M
1
to m
3
in the cell A. The abscissa represents time.
The mobile station M
1
uses the frequencies f
1
, f
2
and f
3
when it outputs bursts B
1
, B
2
and B
3
, respectively. The mobile station m
2
uses the frequencies f
2
, f
3
and f
1
when it outputs bursts B
1
, B
2
and B
3
, respectively. The mobile station m
3
uses the frequencies f
3
, f
1
and f
2
when it outputs bursts B
1
, B
2
and B
3
, respectively.
The bursts B
1
to B
3
mentioned herein are pulse-like waves or waveforms created by dividing original data such as speech and adding a header or the like to each divided piece of data. By virtue of the hopping sequences c
1
to c
3
assigned thereto, respectively, the mobile stations M
1
to m
3
in the cell A will not be assigned the same frequency at the same timing. Likewise, the mobile stations M
4
to m
6
in the cell B will not be assigned the same frequency at the same timing.
FIG. 15
depicts in block form the mobile station
10
that forms the conventional mobile communication system. With reference to
FIG. 15
, the configuration of the conventional mobile station
10
will be described.
In
FIG. 15
, reference numeral
20
denotes an antenna. Reference numeral
21
denotes a transmitting part, which is connected via a switch
22
to the antenna
20
. Reference numeral
23
denotes a receiving part, which is also connected via the switch
22
to the antenna
20
. Reference numeral
24
denotes a transmission/received data processing part, which is connected to the transmitting part
21
and the receiving part
23
. Reference numeral
25
denotes a synthesizer part, which is connected to the transmitting part
21
, the receiving part
23
and the transmission/received data processing part
24
. Reference numeral
26
denotes a control part, which is connected to the transmission/received data processing part
24
and the synthesizer part
25
.
Reference numeral
24
i
denotes transmission data, which is input into the transmission/received data processing part
24
. Reference numeral
24
t
denotes transmission burst data, which is provided from the transmission/received data processing part
24
to the transmitting part
21
. Reference numeral
21
t
denotes a transmission signal, which is output from the transmitting part
21
. Reference numeral
23
r
denotes a received signal, which is input into the receiving part
23
. Reference numeral
24
r
denotes received burst data, which is provided from the receiving part
23
to the transmission/received data processing part
24
.
Reference numeral
24
o
denotes received data, which is output from the transmission/received data processing part
24
. Reference numeral
25
t
denotes transmission frequency data, which is provided from the synthesizer part
25
to the transmitting part
21
. Reference numeral
25
r
denotes receive frequency data, which is provided from the synthesizer part
25
to the receiving part
23
. Reference numeral
26
r
denotes hopping sequence data, which is provided from the transmission/received data processing part
24
to the control part
26
. The transmission/received data processing part
24
instructs the control part
26
to perform frequency hopping based on the hopping sequence data
26
r.
Reference numeral
26
t
denotes first switching data, which is provided from the control part
26
and fed into the synthesizer part
25
. The synthesizer part
25
operates on the first switching data
26
t,
performing frequency hopping. Reference numeral
24
g
denotes a timing signal, which is provided from the transmission/received data processing part
24
and fed into the synthesizer part
25
. The timing signal
24
g
is output from the transmission/received data processing part
24
based on the received burst data
24
r.
Next, the operation of the conventional mobile station
10
will be described below.
The mobile station
10
receives signals sent from the base station
11
by the antenna
20
. The received signal
23
r
is applied from the antenna
20
to the receiving part
23
via the switch
22
. When supplied with the received signal
23
r,
the receiving part
23
demodulates it and outputs the received burst data
24
r,
which is fed into the transmission/received data processing part
24
.
The transmission/received data processing part
24
decodes the received burst data and outputs the received data
24
o.
Further, the transmission/received data processing part
24
extracts the hopping sequence data
26
r
from the received burst data
24
r.
The transmission/received data processing part
24
applies the timing signal
24
g
to the synthesizer
25
. Additionally, the transmission/received data processing part
24
is supplied
Shibuya Akihiro
Yamauchi Takahisa
Mitsubishi Denki & Kabushiki Kaisha
Pham Chi
Phu Phuong
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