Multi-mode communication device

Details Multi-mode communication device Multi-mode communication device

1998-10-01

2003-03-18

Ton, Dang (Department: 2661)

Multiplex communications

Communication over free space

Combining or distributing information via code word channels...

C370S335000, C370S441000, C370S442000, C370S479000, C455S552100

Reexamination Certificate

active

06535499

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-mode communication device which establishes a communication path through an application of appropriate communication control in response to a given multiplex-attachement scheme when the given multiplex-attachment scheme is selected from a plurality of multiplex-atachement schemes, inclusive of a code-division-multiplex-attachment scheme, to be employed in a radio-transmission path.
2. Description of the Related Art
Because of a recent development in electrical-power-transfer control, a code-division-multiplex-attachment scheme is now applicable to mobile-communication systems despite of the fact that lengths of radio-transmission paths and a propagation loss greatly vary in such systems. Hereinafter, code-division-multiplex-attachment scheme is referred to as a CDMA scheme.
Such mobile-communication system employing a CDMA scheme is less susceptible to interference and noise than are systems employing other multiplex attachment schemes such as a frequency-division-multiplex-attachment scheme (hereinafter, referred to as an FDMA scheme) and a time-division-multiplex-attachement scheme (hereinafter, referred to as a TDMA scheme). Use of the CDMA scheme also provides for a greater security of information, and permits recurrent use of frequency bands by allowing a number of terminals to share a broad range of frequency bands. Against such a background, research efforts are directed to a practical application of various schemes.
In mobile communication, a large portion of investment is generally directed to radio-communication stations and equipment for facilitating communication with switch systems. A mobile communication service is generally required to service a large number of terminals where these terminals are spread across a large geographical area, and have a drifting location thereof. Under such conditions, a newly installed mobile communication system is often used together with existing systems which have been in operation before the installation of the new system.
In areas where traffic is relatively small (such areas are hereinafter called non-urban areas), however, it is not justifiable to run a plurality of systems of different schemes when considering costs and other factors. In such areas, unlike in urban areas, only a new system, once installed, is generally allowed to run.
In surroundings as described above, a subscriber needs a dual-mode terminal device which is applicable to any one of the CDMA scheme, the FDMA scheme, and the TDMA scheme if the subscriber desires communication service in both the urban areas and the non-urban areas. Such dual-mode terminal devices are now gradually becoming available in the market, and are directed to combinations of major communication schemes.
FIG. 1
is a block diagram showing a configuration of a dual-mode-terminal device used in the related art.
In
FIG. 1
, the power-supply node of an antenna
71
is connected to an antenna node of the air-cable sharing device
72
, and the air-cable sharing device
72
has a receiver output thereof supplied to a signal input of a DSP (digital signal processor)
77
via a high-frequency amplifier
73
, a frequency converter
74
, a middle-frequency amplifier
75
, and an orthogonal demodulator
76
arranged in a series.
A signal output of the DSP
77
is supplied to a transmitter side of the air-cable sharing device
72
via a orthogonal modulator
78
, a middle-frequency amplifier
79
, a frequency converter
80
, a frequency-band amplifier
81
, and a power amplifier
82
connected in a series. A processor
83
has a first output port thereof connected to a control input of a synthesizer
84
. The synthesizer
84
has two outputs which are respectively supplied to the frequency converters
74
and
80
. The processor
83
has second and third output ports connected to control inputs of synthesizers
85
-R and
85
-T, respectively. Respective outputs of the synthesizers
85
-R and
85
-T are supplied to the orthogonal demodulators
76
and
78
. Fourth and fifth output ports of the processor
83
are respectively connected to the control inputs of the middle-frequency amplifiers
75
and
79
. The DSP
77
has an output port thereof connected to the control inputs of the frequency-band amplifier
81
and the power amplifier
82
.
The middle-frequency amplifier
75
includes a switch
86
-
1
, band-pass filters
87
-F and
87
-C, and a switch
86
-
2
. The switch
86
-
1
receives a signal having a middle-frequency range from the frequency converter
74
directly, or indirectly after appropriate processing is applied to the signal. The band-pass filters
87
-F and
87
-C are provided along respective paths extending from the switch
86
-
1
. The switch
86
-
2
connects an output from either the band-pass filter
87
-F or
87
-C to a subsequent stage. The switches
86
-
1
and
86
-
2
have a control input thereof which receives a binary signal from the fourth output port of the processor
83
.
In this related-art configuration, the processor
83
instructs the DSP
77
to establish a channel in a radio-communication zone corresponding to the CDMA scheme when the terminal enters an effective range of the radio-communication zone from outside any service area or when the terminal is newly switched on. Further, the processor
83
controls the synthesizers
84
,
85
-R, and
85
-T to generate a respective radio frequency (for example, 980 MHz, 100 MHz, and 150 MHz, respectively), which is appropriate for the established channel utilizing the CDMA scheme. Also, the processor
83
instructs the switches
86
-
1
and
86
-
2
to selectively activate a path corresponding to the band-pass filter
87
-C.
The frequency converter
74
receives a radio wave from a radio-communication station (not shown) when the radio wave arrives at the antenna
71
and is forwarded via the air-cable sharing device
72
and the high-frequency amplifier
73
. The frequency converter
74
generates a middle-frequency-range signal distributed around a frequency of 100 MHz. This signal corresponds to a differential between the received radio wave and a signal generated by the synthesizer
84
.
The middle-frequency amplifier
75
amplifies the middle-frequency-range signal by using the band-pass filter
87
-C, which has a frequency band corresponding to the band assigned to the CDMA scheme. The orthogonal demodulator
76
applies orthogonal demodulation to the middle-frequency-range signal based on a signal generated by the synthesizer
85
-R. As a result, two base-band signals i and q, which are orthogonal to each other, are generated.
The DSP
77
has a build-in firmware, and applies signal processing equivalent to that of a sliding correlator in accordance with instructions given by the processor
83
. As part of the process for establishing a channel, under the control of the processor
83
, the DSP
77
attempts to establish synchronization between dispersed codes internally generated and a compressed phase differential of the received radio wave.
The processor
83
gives an instruction to start establishing another channel corresponding to another scheme(for example, the FDMA scheme) other than the CDMA scheme when the attempt to establish synchronization fails in view of certain criteria.
Further, an instruction is given to the switches
86
-
1
and
86
-
2
to effect amplification of the middle-frequency-range signal of the frequency converter
74
by activating the path corresponding to the band-pass filter
87
-F since the band-pass filter
87
-F has a frequency band corresponding to the FDMA scheme. Hereinafter, only specifically relevant matters will be described when describing operations relating to the schemes other than the CDMA scheme since such operations have little bearing on the present invention.
If the attempt to establish synchronization succeeds, the DSP
77
notifies the processor
83
of this fact, and attends to a channel-control procedure under the guidance of the processor
83
. During this proce

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