Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1999-11-12
2003-06-17
Chin, Vivian (Department: 2682)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S552100, C455S069000, C455S070000
Reexamination Certificate
active
06580919
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a code division multiple access (CDMA) cellular mobile communication system comprising a base station and a mobile station and, in particular, to a reverse channel interference correction system and method, when there is an interference wave on a reverse channel in a case where a channel between the base station and the mobile station is connected, in a CDMA closed loop power control for performing a closed loop control for transmission power of the mobile station on the basis of a correction value for increasing an average received power that is generated, as a reference, an average received power in a case where there is no interference wave.
In the manner known in the art, the CDMA cellular mobile communication system carries out a transmission power control on the basis of an open loop control according to Interim Standard (IS)-95 standard of Telecommunication Industry Association/Electronic Industry Association (TIA/EIA) in a case of carrying out a start of a position registration sequence for a mobile station which moves in a cell (service area) of a base station. Inasmuch as a plurality of mobile stations use the same frequency band in the CDMA cellular mobile communication system, it is necessary to increase the number of multiple-mobile stations by decreasing interference power between the mobile station mutually.
As a result, control to an appropriate transmission power value is carried out in the CDMA cellular mobile communication system. In this case, the “appropriate transmission power value” is a minimum transmission power value where a data error rate is not over an allowable value when the base station receives a signal from the mobile station.
Attention will be directed to the transmission power control of the mobile station according to the open loop control on starting of channel connection between the base station and the mobile station. In the manner which later become clear, in a conventional CDMA cellular mobile communication system, the transmission power control of the mobile station according to the open loop control is defined by IS-95-A standard and compensation of the interference on a forward channel is carried out according to IS-95-B standard.
However, in the conventional CDMA cellular mobile communication system, it is difficult to obtain a received bit energy-to-interference ratio Eb/I
0
(which is a ratio of desired received wave power (Eb) to interference wave power (I
0
) per one bit) when a lot of mobile stations communicate with the base station. In this event, its incomplete transmission power control becomes an issue. That is, due to degradation of the received bit energy-to-interference ratio Eb/I
0
(degradation of channel quality when there is the interference wave on the reverse channel) in the base station, it is impossible to maintain its stable channel quality. Accordingly, it is difficult to carry out the channel connection stably and certainly and it has contributed to deterioration in its system connectivity.
As a prior art related to the open loop control of the type, Japanese Unexamined Patent Publication of Tokkai No. Hei 10-56,421 or JP-A 10-56421 is known that provides “CDMA RADIO TRANSMISSION SYSTEM, TRANSMISSION POWER CONTROLLER USED FOR THE SYSTEM AND TRANSMISSION POWER CONTROL MEASUREMENT EQUIPMENT.” JP-A 10-56421 realizes adaptive control of transmission power of a mobile station in response to traffic fluctuation in terms of open loop control by correcting a control error in the open loop control for transmission power control in the code division multiple access (CDMA) radio system. According to JP-A 10-56421, a transmission power controller mounted on a mobile station is provided with a calculating circuit for calculating a desired wave reception power from a received signal, a memory circuit for storing an initial relation between the received power and a transmission power setting value, a correcting circuit for correcting the relation, and a decision circuit for deciding the transmission power set value. In this case, the transmission power controller uses a control signal included in periodically in the received signal to use the relation thereby deciding a transmission power set value from the received power while correcting the relation between the received power and the transmission power set value.
In other words, the open loop control according to JP-A 10-56421 comprises the steps of measuring an average received power or the like of the desired wave from the received signal, of detecting an error between an average received power value and a target value, and of correcting the error. In addition, the transmission power control according to JP-A 10-56421 adaptively controls the transmission power of the mobile station in accordance with an amount of traffic.
In JP-A 10-56421, it is possible to carry out correction of the open loop control on the basis of the error between the target value and the average received power value of the desired wave that is measured from the received signal in the open loop control. However, JP-A 10-56421 may be disadvantageous in that it is complicated in structure because correction of the error between the target value and the average received power value is carried out using a table.
In addition, various other CDMA mobile communication systems related to the present invention are already known. By way of example, Japanese Unexamined Patent Publication of Tokkai No. Hei 5-75,484 or JP-A 5-75484 discloses a transmission power controller which is capable of controlling transmission power at a high speed to reduce interference onto another station and to reduce power consumption. According to JP-A 5-75484, the fluctuation of a reception level is detected by a reception level fluctuation detection section. When number of times of the reception level reaching a level or below within a prescribed time exceeds a reference value, a discrimination section controls switches to calculate P
1
=P
2
−(V
2
−Vt) at a transmission power calculation section, where P
2
is a transmission power of an opposite station obtained from a demodulation output of the received signal, V
2
is a reception level from a detection section and Vt is a required minimum reception level. A modulation section is modulated by a signal representing the P
1
to control a power amplifier so that the transmission power is P
1
. The opposite station is controlled similarly and the transmission power is controlled corresponding to the reception level fluctuation at a high speed by the open loop control. When the reception level fluctuation is less than the reference value, the switches are controlled, a received addition/subtraction request value &agr; and a preceding transmission power P
1
′ are added as P
1
=P
1
′+&agr;, and amplifier is controlled so that the transmission power is equal to the P
1
. &bgr;=Vt−V
2
is calculated by an adder section and the value is used as an adder/subtractor request value and the modulation section is controlled for the purpose of modulation transmission.
Japanese Unexamined Patent Publication of Tokkai No. Hei 9-199,963 or JP-A 9-199963 provides a transmission power control circuit which conducts open loop transmission power control and closed loop transmission power control with high accuracy. According to JP-A 9-199963, provided with a first variable gain control amplifier for varying a gain of an input signal with a control voltage, a transmission power control circuit is provided with a second variable gain control amplifier for varying a gain of an output of the first variable gain control amplifier and an automatic power control circuit for generating a control voltage to control the gain of the second variable gain control amplifier from a distributed transmission output. The automatic power control circuit is provided with at least a comparator circuit for outputting a difference between a transmission output and a reference value, a sample-and-hold circuit for sam
Chin Vivian
Foley & Lardner
NEC Corporation
Sharma Sujatha
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