Telecommunications – Carrier wave repeater or relay system
Reexamination Certificate
2000-08-29
2004-02-10
Trost, William (Department: 2686)
Telecommunications
Carrier wave repeater or relay system
C455S571000, C370S492000
Reexamination Certificate
active
06690915
ABSTRACT:
This application claims the priority of Patent Application No. 11-246501 filed Aug. 31, 1999 in Japan, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a booster for receiving, amplifying and transmitting signals to be transferred between a base station and a mobile station, a monitoring equipment of the booster, a booster system, a control method of the booster and a monitoring method of the booster.
2. Description of the Related Art
Conventionally, the gain of a booster is adjusted at the installation of the booster before its operation. Assuming that the gain of a booster is G
b
, the noise figure of the booster is NF
b
, its thermal noise is N
kT
, the noise at a base station without the booster is N
bs
, and the propagation loss between the booster and base station is L, the noise N
bs
′ at the base station when the booster is equipped, is expressed as follows:
N
bs
′=G
b
NF
b
N
kT
/L+N
bs
(1)
It is preferable that the effect of the noise produced by the booster on the base station be sufficiently small, satisfying the following expression.
N
bs
>>G
b
NF
b
N
kT
/L
(2)
When a new base station is installed near the booster, the booster is readjusted to make the effect of the booster on the new base station sufficiently small.
Conventionally, a new base station installed in an area covered by the booster because of poor radio wave intensity in mobile communication can suffer from the noise or interference of the booster. In particular, the system performance of CDMA (Code Division Multiple Access) utilizing the same frequency depends greatly on the interference. Thus, it is preferable that the effect of the interference be reduced as much as possible by decreasing the gain of the booster.
Conventionally, however, because of the fixed gain of the booster, the gain of the booster must be readjusted manually at the spot every time a new base station is installed near the booster.
Generally, comparing the area under the booster where the booster exchanges radio waves with mobile stations in the CDMA with the area under the base station where the base station exchanges radio waves directly with the mobile stations, the area under the base station is greater.
For example, assume that a condition changes from the initial state in which the traffic under the booster is heavy and the traffic under the base station is light to a state in which the traffic under the base station is heavy. To increase the traffic under the base station, the traffic under the booster must be limited by reducing the gain of the booster, for example.
Conventionally, however, because the gain of the booster is fixed, it cannot be reduced.
Furthermore, since the booster is a device for receiving and amplifying radio waves, and transmitting them into space, its failure or malfunction will have a large effect on channel quality. Accordingly, it is preferable to monitor an increasing number of items. In addition, it is desirable to monitor not only amplifiers, but also failures of operation circuits and the like.
For example, when the gain of an uplink signal is much smaller than the gain of a downlink signal, the mobile station increases its transmission power to maintain prescribed quality. Accordingly, it is difficult for the base station to detect a failure of the booster. Thus, it is preferable to install a monitor-control equipment to carry out suitable monitoring of the booster using information about parameters for setting the gain of the booster, information about the condition of the booster and the like which information is transmitted to the monitor-control equipment, thereby detecting and controlling the failure or malfunction of the booster.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to reduce the adverse effect of the booster noise on the base station by controlling the gain of the booster.
Another object of the present invention is to adjust the balance between the traffic under the booster and the traffic under the base station by controlling the gain of the booster.
Still another object of the present invention is to carry out suitable monitoring of a booster by transmitting information about the booster (information about parameters for setting the gain of the booster, information about the condition of the booster and the like) to a monitoring equipment so that the monitoring equipment monitors the booster using these information items.
A method will now be described of reducing the adverse effect of the booster noise on the base station by controlling the gain of the booster.
Assume that the booster amplifies the radio waves (uplink signal) transmitted from the mobile station, and that the propagation loss between base station A and the booster is L
1
[dB]. If the expression N
o
>>N
b
−L
1
is satisfied, where N
o
[dBm] is the noise power at the base station A, and N
b
[dBm] is the noise power of the amplified uplink signal at the booster, it can be said that the N
b
has little effect on the base station A. In other words, it can be said that the booster noise has little effect on the base station A if the following expressions are satisfied.
N
b
<<L
1
+N
o
(3)
G
b
<<L
1
+NF
o
−NF
b
(4)
where G
b
is the gain of the booster, NF
b
is the noise figure of the booster, and NF
o
is the noise figure of the base station A.
Next, assume that a new base station B is installed at a location at which its propagation loss L
2
is less than the propagation loss L
1
. Without the readjustment of the gain of the booster, the effect of the booster noise on the base station B is greater than that on the base station A by an amount of about L
1
−L
2
.
When the propagation loss between the base station B and the booster is L
2
, where L
1
>L
2
, the gain of the booster G
b
should be adjusted to satisfy the following expressions.
N
b
<<L
2
+N
o
(5)
G
b
<<L
2
+NF
o
−NF
b
(6)
Next, a method will be described of adjusting the balance between the traffic under the booster and the traffic under the booster by controlling the gain of the booster.
Assume that the interference quantity in the base station is I
o
, and that the interference quantity of an uplink signal input in the booster is I
b
, the interference quantity in the base station from the uplink signal which is amplified by the booster and transmitted to the base station is I
b
′, and the propagation loss between the base station and the booster is L. If the traffic is limited to that under the booster, the following expression holds.
I
o
=I
b
′=G
b
+I
b
−L
(7)
For example, when the interference quantity I
o
in the base station is large and approximately satisfies the expression above, it can be estimated that the traffic under the booster is heavy, bearing severely upon the traffic under the base station. If the gain of the booster is reduced in such a case, the uplink communication of the CDMA tries to maintain the received level of the base station at a fixed level by carrying out transmission power control. Thus, the reduction in the booster gain little affects the interference quantity and traffic at an initial stage.
However, since the transmission power of the mobile stations has a limit, the interference quantity I
b
′ from the booster to the base station gradually reduces, with the reduction in the received power of the downlink signal, thereby reducing the area under the booster. The decreasing interference quantity in the base station can increase the traffic under the base station.
In summary, since the same frequency is used by a plurality of users in the CDMA, the received level and noise power density of the booster increase with the traffic under the booster. Varying the gain of the booster with the increase can change the area,
Ito Kazuhito
Ito Yasushi
Ly Nghi H.
NTT DoCoMo Inc.
Trost William
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