Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-12-03
2003-01-28
Le, Thanh Cong (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S522000
Reexamination Certificate
active
06512925
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to communications. More particularly, the present invention relates to a novel and improved method and apparatus for gating the transmission of signals in a wireless communication system.
II. Description of the Related Art
The use of code division multiple access (CDMA) modulation techniques is one of several techniques for facilitating communications in which a large number of system users are present. Other multiple access communication system techniques, such as time division multiple access (TDMA) and frequency division multiple access (FDMA) are known in the art. However, the spread spectrum modulation technique of CDMA has significant advantages over these modulation techniques for multiple access communication systems. The use of CDMA techniques in a multiple access communication system is disclosed in U.S. Pat. No. 4,901,307, entitled “SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS”, assigned to the assignee of the present invention, of which the disclosure thereof is incorporated by reference herein. The use of CDMA techniques in a multiple access communication system is further disclosed in U.S. Pat. No. 5,103,459, entitled “SYSTEM AND METHOD FOR GENERATING SIGNAL WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM”, assigned to the assignee of the present invention, of which the disclosure thereof is incorporated by reference herein.
CDMA by its inherent nature of being a wideband signal offers a form of frequency diversity by spreading the signal energy over a wide bandwidth. Therefore, frequency selective fading affects only a small part of the CDMA signal bandwidth. Space or path diversity is obtained by providing multiple signal paths through simultaneous links from a mobile user through two or more cell-sites. Furthermore, path diversity may be obtained by exploiting the multipath environment through spread spectrum processing by allowing a signal arriving with different propagation delays to be received and processed separately. Examples of path diversity are illustrated in U.S. Pat. No. 5,101,501 entitled “METHOD AND SYSTEM FOR PROVIDING A SOFT HANDOFF IN COMMUNICATIONS IN A CDMA CELLULAR TELEPHONE SYSTEM”, and U.S. Pat. No. 5,109,390 entitled “DIVERSITY RECEIVER IN A CDMA CELLULAR TELEPHONE SYSTEM”, both assigned to the assignee of the present invention and incorporated by reference herein.
A method for transmission of speech in digital communication systems that offers particular advantages in increasing capacity while maintaining high quality of perceived speech is by the use of variable rate speech encoding. The method and apparatus of a particularly useful variable rate speech encoder is described in detail in U.S. Pat. No. 5,414,796, entitled “VARIABLE RATE VOCODER”, assigned to the assignee of the present invention and incorporated by reference herein.
The use of a variable rate speech encoder provides for data frames of maximum speech data capacity when said speech encoding is providing speech data at a maximum rate. When a variable rate speech coder is providing speech data at a less that maximum rate, there is excess capacity in the transmission frames. A method for transmitting additional data in transmission frames of a fixed predetermined size, wherein the source of the data for the data frames is providing the data at a variable rate is described in detail in U.S. Pat. No. 5,504,773, entitled “METHOD AND APPARATUS FOR THE FORMATTING OF DATA FOR TRANSMISSION”, assigned to the assignee of the present invention, of which the disclosure thereof is incorporated by reference herein. In the above mentioned patent application a method and apparatus is disclosed for combining data of differing types from different sources in a data frame for transmission.
In frames containing less data than a predetermined capacity, power consumption may be lessened by transmission gating a transmission amplifier such that only parts of the frame containing data are transmitted. Furthermore, message collisions in a communication system may be reduced if the data is placed into frames in accordance with a predetermined pseudorandom process. A method and apparatus for gating the transmission and for positioning the data in the frames is disclosed in U.S. Pat. No. 5,659,569, entitled “DATA BURST RANDOMIZER”, assigned to the assignee of the present invention, of which the disclosure thereof is incorporated by reference herein.
A useful method of power control of a mobile in a communication system is to monitor the power of the received signal from the mobile station at a base station. The base station in response to the monitored power level transmits power control bits to the mobile station at regular intervals. A method and apparatus for controlling transmission power in this fashion is disclosed in U.S. Pat. No. 5,056,109, entitled “METHOD AND APPARATUS FOR CONTROLLING TRANSMISSION POWER IN A CDMA CELLULAR MOBILE TELEPHONE SYSTEM”, assigned to the assignee of the present invention, of which the disclosure thereof is incorporated by reference herein.
In a communication system that provides data using a QPSK modulation format, very useful information can be obtained by taking the cross product of the I and Q components of the QPSK signal. By knowing the relative phases of the two components, one can determine roughly the velocity of the mobile station in relation to the base station. A description of a circuit for determining the cross product of the I and Q components in a QPSK modulation communication system is disclosed in U.S. Pat. No. 5,506,865, entitled “PILOT CARRIER DOT PRODUCT CIRCUIT”, assigned to the assignee of the present invention, the disclosure of which is incorporated by reference herein.
There has been an increasing demand for wireless communications systems to be able to transmit digital information at high rates. One method for sending high rate digital data from a remote station to a central base station is to allow the remote station to send the data using spread spectrum techniques of CDMA. One method that is proposed is to allow the remote station to transmit its information using a small set of orthogonal channels, this method is described in detail in copending U.S. Pat. No. 08/886,604, entitled “HIGH DATA RATE CDMA WIRELESS COMMUNICATION SYSTEM”, assigned to the assignee of the present invention and incorporated by reference herein.
SUMMARY OF THE INVENTION
The present invention is a novel and improved method and apparatus for controlling the transmission power in a plurality of base stations simultaneously communicating with a mobile station in soft handoff. In a power controlled communication system where multiple transmitters at different physical locations are employed to transmit the same signal to a given receiver, the receiver measures the quality of the composite received signal from all transmitters and feeds back this observed quality to the transmitters. In the exemplary implementation, the feedback is a single stream of up or down commands from the receiver that is received by all transmitters involved. However, the reliability of the reception is not uniform across transmitters. Further, the reliability of the feedback to any given transmitter can change over time. As a result,the transmitters follow their individually received feedback and transmit at different power level at the same time.
It is usually advantageous to align the transmit power levels for a given receiver from all participating transmitters according to a desired pattern. For example, the transmitters can also send a fixed pilot channel at the same power level. Equating the traffic channel transmit levels imply the same traffic to pilot ratios across transmitters and the best maximal ratio combining can be achieved at the receiver by taking the inner product of the pilot and traffic. Another example is when the transmitters transmitter have different maximum power and send out pilot channel at different power levels. In this case, the alignmen
Chen Tao
Holtzman Jack M.
Patel Shim
Razoumov Leonid
Saints Keith
Baker Kent D.
Beladi S. Hossain
Corsaro Nick
Qualcomm Incorporated
Wadsworth Philip R.
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