Telecommunications – Transmitter – With feedback of modulated output signal
Reexamination Certificate
1999-06-18
2003-09-30
Maung, Nay (Department: 2684)
Telecommunications
Transmitter
With feedback of modulated output signal
C455S522000, C370S342000, C375S146000
Reexamination Certificate
active
06628929
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a transmission power control unit, in particular, to a transmission power control unit for use in a transmitting apparatus for transmitting transmission data with the transmission data multiplexed, such as a radio base station apparatus for use in a code division multiple access (CDMA) communication system.
For example, in a cellular mobile communication system such as the code division multiple access (CDMA) communication system, a service area is divided into a plurality of units called cells in each of which a radio base station apparatus is installed, and the radio base station apparatus carries out transmission and reception with mobile station apparatuses lying the cell in question.
In such a radio base station apparatus, it is necessary to accurately control transmission power so that a transmission signal covers within its own cell without affecting other cells.
Particularly, in the radio base station apparatus for transmitting a plurality of channels with the channels multiplexed, the following problems arise when all of the channels multiplexed are transmitted at equal transmission power. That is, interference occurs in mobile station apparatuses in the vicinity of the radio base station apparatus due to too strong electric wave and it is possible to normally receive the transmission signal in mobile station apparatuses away from the radio base station apparatus due to too weak electric wave. In addition, inasmuch as the radio base station apparatus naturally has a limited transmission power enable to output, it is necessary to assign the limited transmission power to each mobile station apparatus or each channel. Under the circumstances, it is necessary for the radio base station apparatus to adjust the transmission power each channel in accordance with factors such as a distance between each mobile station apparatus and the radio base station apparatus in question.
In addition, in the CDMA communication system, when the channels to be multiplexed increase, the whole transmission power increases. As a result, it is possible to insure a lot of usable channels by accurately controlling the transmission power for each channel at the necessary lowest limit in a plurality of channels multiplexed in consideration of near-far problem. Accordingly, it is desirable to accurately carry out transmission power control for each channel.
In a transmitting apparatus carrying out such a multiplexing, a conventional transmission power control unit necessitates a digital-to-analog converter for converting a digital signal indicative of a digital value into an analog signal indicative of an analog value. This is because to adjust an output of a power amplifier demands the analog value although a control value for carrying out the power control is given by the digital value.
Incidentally, the above-mentioned transmission power control is carried out on the premise that the digital-to-analog converter in the transmission power control unit operates ideally. However, actually, a variation amount of the digital signal and a variation amount of an analog signal to be outputted are not perfectly coincident with each other and the digital-to-analog converter may have a demolished linearity. In addition, the digital-to-analog converter is supplied with a reference voltage or a power supply voltage which may vary. As a result, the conventional transmission power control unit is disadvantageous in that it is impossible to obtain a correct analog amount corresponding to the digital value using the digital-to-analog converter and it is difficult to actually carry out correct transmission power control.
In addition, the conventional transmission power control unit is disadvantageous in that precision in the power control degrades due to the influence of variation of temperature and secular change in a part of analog circuits in the next stage of the digital-to-analog converter.
Furthermore, it is necessary for the CDMA communication system to carry out control of the transmission power each channel as described above. However, the conventional transmission power control unit is disadvantageous in that it is impossible to detect the transmission power each channel that is actually transmitted because each channel is multiplexed on the same radio carrier.
Various CDMA communication systems related to the present invention are already known. An example is disclosed in U.S. Pat. No. 5,737,327 which is issued to Ling et al. on Apr. 7, 1998 and which has a title of “Method and apparatus for demodulation and power control bit detection in a spread spectrum communication system.” According to Ling et al., a receiver circuit receives a spread spectrum communication signal, such as a DS-CDMA signal, including a pilot channel and including a power control designator. The spread spectrum communication signal is despread and decoded. The pilot symbols on the pilot channel are provided to a channel estimator for estimating the channel phase and channel gain of the communication channel. This estimate is provided to a demodulator for demodulating the traffic channel symbols. The pilot symbols are provided to another channel estimator for estimating channel phase and channel gain for the power control designator. This estimate is provided another demodulator for demodulating the power control designator. The traffic channel symbols are delayed a predetermined time in a delay element before demodulating. The power control designator is delayed a short time or not at all in a short delay element before demodulation.
Japanese Unexamined Patent Publication of Tokkai No. Hei 7-235,913 or JP-A 7-235913 discloses a spread spectrum communication equipment and signal intensity detecting device which are capable of informing a user a stable talking standard by measuring the signal power intensity of a base station in a spread spectrum communication mode. According to JP-A 7-235913, in a spread spectrum communication equipment, the gain control signal sent from a detector of an automatic gain control (AGC) circuit is converted into the electric power serving as the signal intensity by another detector and sent to a multiplier. The electric power of the desired pilot channel of a base station is detected out of the output signal received from the AGC circuit by a spread code detector and sent to the multiplier. The multiplier calculates the signal intensity of the desired base station based on the received electric power and sends it to a display part. Then the display part shows the signal intensity.
Japanese Unexamined Patent Publication of Tokkai No. Hei 8-8,877 or JP-A 8-008877 discloses a spread spectrum radio communication system and radio communication equipment used in the system which are capable of eliminating the need of complicated numerical arithmetic operation in a mobile station and the transmission of surrounding signal, of improving communication efficiency, of miniaturizing and lightening a mobile station equipment, and of lowering power consumption. According to JP-A 8-008877, in a base station, the radio transmission characteristics of a forward link are estimated by a parameter estimation part based on the reception state of radio signals arriving from the mobile station through a reverse link, RAKE control information to be set in the RAKE receiver of the mobile station is generated based on the estimated result and the mobile station is informed of the RAKE control information. On the other hand, in the mobile station, the RAKE control information is extracted in a RAKE control information extraction part and a tap coefficient is initially set in the transversal filter of the RAKE receiver based on the RAKE control information.
Japanese Unexamined Patent Publication of Tokkai No. Hei 10-41,919 or JP-A 10-041919 discloses a CDMA system multiplex transmitter which is capable of attaining reception always stably from all channels by inserting a power measurement power control code to a spread code of each channel measuring transmission power of each c
Maung Nay
NEC Corporation
Sobutka Philip J.
LandOfFree
Transmission power control for use in a transmitting... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Transmission power control for use in a transmitting..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Transmission power control for use in a transmitting... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3098788