Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1999-07-26
2002-12-31
Le, Thanh Cong (Department: 2684)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S069000, C455S453000, C370S342000, C370S318000
Reexamination Certificate
active
06501958
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 arising from an application entitled, METHOD FOR CONTROLLING FORWARD POWER UTILIZING AN ERASURE INDICATOR BIT INA CDMA SYSTEM, earlier filed in the Korean Industrial Property Office on Jul. 29, 1998, and there duly assigned Serial No. 1998-30483.
FIELD OF THE INVENTION
The present invention relates to a method used in a mobile communication system for controlling base station forward transmission power utilizing erasure indicator bit (EIB) message, and in particularly to a forward power control method for improving call quality and subscriber capacity of the system using EIB message to adjust the gain of the base station forward transmission power and the rate of the reducing the digital gain of its forward transmission power based on a newly predetermined power control parameter messages stored in the base station.
DESCRIPTION OF THE RELATED ART
As it is well known, a near-far problem arises in the channel quality between a base station and a faraway mobile station. In view of this, a forward power control has been studied to overcome the near-far problem. The forward power control is performed when a frame error at a base station exceeds a predetermined threshold level, in which case the transmission power of the base station to the mobile station is adjusted. The power control on the forward link increases or decreases the transmit power level of base station so that all channels can maintain good call quality when fading or interference occurs, especially in the boundary of a cell where the noise interference is high.
The power control is used to adjust the transmit power of the base station for each traffic channel. When the mobile station is affected by the signals traveling through propagation paths or other multi-path characteristic interference, the transmission power control is performed such that the received power levels of signals transmitted from the mobile stations and receive by the base station, or the SIR (Signal-to-interference power ratio) associated with the received power levels are kept constant at the base station.
Without the power control, the distance of the mobile station located in a neighboring area between base stations is so faraway from the corresponding base station that the transmit power from the base station is weakened. Consequently, a call set-up rate is low and even if the call set-up is successful, the voice quality is poor due to the severe interference in the neighboring base stations.
It will be appreciated by those skilled in the relevant art based on the detailed description provided herein that in a typical forward power control known in the art include a mobile station unit for measuring the quality of a communication signal received by the mobile station from a base station and a unit for producing a base station transmission power control data/forward power control signal, and the base station include a unit for measuring a receiving the forward power control signal, a unit for calculating a power level command based on the received forward power control signal based on control parameters stored in the base station, and a unit for producing a mobile station transmission power control data specifying a mobile station transmission power in accordance with the received.
In power control technique, the mobile station measures the frame error rate (FER) of the forward link by 20 milliseconds (ms) and transmits a forward power control signal to the base station. The base station compares the forward power control signal to a predetermined FER threshold value, and based on such comparison changes the transmission power level by increasing/decreasing the power level allocated to the traffic channel at an increment/decrement rate.
They are different types of forward control signal that is used depending on the system employed. There are power measurement report message (PMRM) used as a forward power control signal in the digital cellular system and erasure indicate bit (EIB) used in the personal communication system (PCS). The PCS makes it possible to report the status of the forward link every frame by adding a bit of EIB to the front of the reverse traffic channel. EIB indicates whether the received frame from the base station to mobile station contains an erasure. For an example, an EIB binary value of “0” can indicate a properly received frame, while a value of “1” can indicates an erased frame or bad frames. That is, in the event that mobile station is unable to successfully decode in response to forward frames, mobile station generates EIB messages having a value of “1” for each erased frame, and transmits these messages back to base station over the reverse link signal.
Base station processes the EIB and determines the gain of its forward link signal based on the EIB messages it receives on the reverse link signal from the mobile station. Base station transmits the forward link signal at a decreasing transmission gain or at an increased gain whenever an EIB message indicating an error is received, and increases or decreases the forward transmission power level transmitted by base station in the subsequent forward frame. By producing the power control signal in such away, it is possible to keep track of the change in the traffic channel more quickly than employing the PMRM method used in the PCS system. The base station receives these forward power control signal from the mobile station via reverse link and extracts the transmission power control bit, and determines its transmission power in accordance with the transmission power control bit.
As described in the above, the forward power control employing the EIB, the base station forward transmission power is depended on power control parameters messages stored in the base station, that is characteristic of the distance between the base station and the mobile station so that the power of the transmitted radio signals as received by the mobile station is not interfering with other cells. The related power control parameters are as follows: ‘Step_til_down’ for decreasing the digital gain by one per frame if the current traffic channel gain is greater than or equal to a ‘slow_down_level,’ and for decreasing the digital gain by one per every two frames if the current traffic channel gain is less than the ‘slow_down_level,’ ‘Down_delta’ for decreasing the digital gain, ‘Nominal_gain’ refers to an initial gain of the primary traffic channel when a call is established between the mobile station and the base station, ‘Max_tx_gain’ refers to a maximum gain of traffic channel, ‘min_tx_gain’ refers to a minimum gain of traffic channel, ‘Big_up_delta’ for increasing the digital gain, ‘small_up_delta’ for increasing the digital gain that is smaller than the digital gain for the ‘Big_up_delta,’ and, ‘Slow_down_level’ refers to a value at the level that is bottom one-third down between levels of the max_tx_gain and min_tx_gain.
In operation of the forward power control using the above power control parameters,
FIG. 1
illustrates the digital gain increment of the traffic channel in which the PCS increases the digital gain of the traffic channel in case where the value of EIB is 1. Whenever a frame generating EIB message of ‘1’ is received, it adjusts the gain value to either the ‘small_up_delta’ and the ‘big_up_delta’ depending on the sequence of received EIB messages. For an example, when twelve frames having a string of EIB messages of ‘1’ or ‘0’ are received as illustrated in FIG.
1
and
FIG. 2
, the gain is increased as high as ‘5’ initially when EIB message of the first frame corresponds to ‘1,’ and then the subsequently received EIB message of ‘1’ increases the digital gain to as high as ‘2’ three times. That is, the gain is increased with a specific pattern, ‘5, 2, 2, 2’ in sequence. After that, if subsequent repetitive receptions of the EIB message of “1” is received, the value of the subsequent digital gain is adjusted according to the pattern sh
Hwang Yun-seok
Wee Pyeong-hwan
Cha Steve
Cha & Reiter
Cong Le Thanh
Harry Andrew T
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