Telecommunications – Carrier wave repeater or relay system – With frequency conversion
Reexamination Certificate
1999-02-03
2001-09-18
Chang, Vivian (Department: 2682)
Telecommunications
Carrier wave repeater or relay system
With frequency conversion
C455S014000
Reexamination Certificate
active
06292652
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mobile telecommunication system, more particularly, to a repeater having frequency conversion in a mobile telecommunication system for generating a dummy frequency assignment signal for repeating a frequency conversion or providing a hard handoff based on a traffic signal having traffic and overhead information.
2. Prior Art
In a code division multiple access(CDMA) mobile telecommunication system, a repeater is used to embody a smooth communication environment and to enlarge coverage thereof. Since the cost of such a repeater is relatively small according to equipment investment and management and is easily installed, it is widely used to enlarge coverage in a wave shadow area such as a mountainous district or a large size building, in a weak wave area such as a subway, or in an area in which service is provided.
A typical repeater amplifies and transmits a weak signal generated by a mother base station. Since a repeating frequency between a base station and a repeater is identical with a service frequency, an oscillating phenomenon is generated in the repeater. Therefore, in order to prevent the oscillating phenomenon, an isolation device should be provided. However, up to now, since service has been performed in a low gain of the repeater, it is limited to enlargement of coverage.
Currently, in order to improve any limitation according to enlargement of coverage, a frequency converting repeater is being widely used. Such a frequency converting repeater receives a dummy frequency assignment signal transmitted from a mother base station and converts it into a traffic signal of the mother base station. Thus, the frequency converting repeater provides service to a wave shadow area or a weak wave area by means of the traffic signal so that an oscillating phenomenon which is generated in a conventional repeater can be prevented.
U.S. Pat. No. 3,750,173 (issued to Norbert E. Tackman on Jul. 13, 1973) discloses a frequency translating repeater using single-sideband techniques.
FIG. 1
shows a conventional frequency converting apparatus in a base station.
The conventional frequency converting apparatus includes a traffic frequency device S
1
, a dummy frequency assignment device S
2
, a linear power amplifier(LPA)
122
, and a low noise amplifier(LNA)
128
.
The traffic frequency device S
1
includes a first channel card
102
, a first analog conversion unit(ACU)
104
, and a first baseband combiner and radio(BCR)
106
. The first channel card
102
generates a digital traffic signal of a baseband having traffic information and overhead information. The overhead information includes pilot channel information, paging channel information, and sync channel information.
The first ACU
104
converts the digital traffic signal of a baseband from the first channel card
102
into an analog signal. The first BCR
106
converts the analog traffic signal of a baseband from the first ACU
104
into an intermediate frequency traffic signal and converts the intermediate frequency traffic signal into a forward traffic signal F
1
.
The dummy frequency assignment device S
2
includes a second channel card
112
, a second ACU
114
, and a second BCR
116
. The second channel card
112
generates a digital dummy frequency assignment signal of a baseband having overhead information. The second ACU
114
converts the digital dummy frequency assignment signal of a baseband from the second channel card
112
into an analog signal. The second BCR
116
converts the analog dummy frequency assignment signal of a baseband from the second ACU
114
into an intermediate frequency signal and converts the intermediate frequency signal into a forward dummy frequency assignment signal F
2
. The LPA
122
amplifies the forward traffic and dummy frequency assignment signals F
1
and F
2
from the first and second BCR
106
and
116
, respectively, and transmits them through an antenna
124
. Accordingly, both the traffic signal F
1
and dummy frequency assignment signal F
2
from the LPA
122
are transmitted through a first antenna
122
to thereby perform a hard handoff between frequency assignments of base stations. The LNA
128
low-noise amplifies reverse traffic and dummy frequency assignment signals F
1
and F
2
transmitted through an antenna
126
and outputs them to the first and second BCRs
106
and
116
.
However, in the conventional frequency converter in a base station, in order to provide a dummy frequency assignment signal which has the same information as that of traffic frequency signal and has a frequency different from that of the traffic frequency signal, a channel card, an analog conversion unit, and a baseband combiner and radio for providing the dummy frequency assignment signal should be added. Accordingly, that requires additional expenses.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention, for the purpose of solving the above mentioned problems, to provide a carrier changing apparatus capable of generating a dummy frequency assignment signal for repeating frequency conversion or providing a hard hand off based on a traffic signal.
In order to attain the object, according to the present invention, there is provided a carrier changing apparatus, said apparatus comprising:
a transmitting carrier changer for transmitting an input forward traffic signal having traffic and overhead information and generating a forward dummy frequency assignment signal based on the forward traffic signal; and
a receiving carrier changer for receiving and outputting a reverse traffic signal having traffic and overhead information from a mobile station and generating a delayed reverse traffic signal based on a reverse dummy frequency assignment signal from the mobile station.
Preferably, the transmitting carrier changer includes a first directional coupler for dividing the input forward traffic signal into two paths to generate first and second divided forward traffic signals; and a transmitting carrier changing section for changing the second divided forward traffic signal from the first directional coupler into the forward dummy frequency assignment signal. More preferably, the receiving carrier changer includes a second directional coupler for dividing the reverse traffic and dummy frequency assignment signals from the mobile station into two paths; and a receiving carrier changing section for changing the reverse dummy frequency assignment signal from the second directional coupler into the delayed reverse traffic signal.
Also, there is provided a carrier changing apparatus, said apparatus comprising:
a directional coupler for dividing an input traffic signal having traffic and overhead information into two paths to generate first and second divided traffic signals; and
a carrier changing section for changing the second divided traffic signal from the first directional coupler into a dummy frequency assignment signal.
Preferably, the directional coupler includes an input port for receiving the input forward traffic signal; a first coupled port connected to an input terminal of the carrier changing section; a first termination port mounted spaced from the first coupled port by a first predetermined distance; a second coupled port connected to an output terminal of the transmitting carrier changing section; a second termination port mounted spaced from the second coupled port by a second predetermined distance; and an output port for outputting the traffic signal received by the input port and the dummy frequency assignment signal from the transmitting carrier changing section.
More preferably, the carrier changing section includes a first band pass filter for band pass filtering the traffic signal of a radio frequency from the directional coupler at a first predetermined bandwidth; a first amplifier for amplifying an output signal of the first band pass filter; an intermediate frequency module for converting an output signal of the first amplifier into an intermediate frequency signal; a first sur
Chang Vivian
Haas George E.
Quarles & Brady LLP
Ramos-Feliciano Eliseo
Shinsegi Telecomm, Inc.
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