Multiplex communications – Channel assignment techniques – Combining or distributing information via code word channels...
Reexamination Certificate
1998-10-20
2001-11-06
Ton, Dang (Department: 2661)
Multiplex communications
Channel assignment techniques
Combining or distributing information via code word channels...
C375S130000
Reexamination Certificate
active
06314107
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
This invention relates to the field of communications systems and, in particular, to the field of transmission of message signals in a communications system.
II. Background of Invention
It is well known in the art of cellular communications systems to mix message signals to be transmitted with spreading code vectors such as Walsh code vectors. This permits the message signals to be combined, transmitted, and then separated from each other at the receiver after transmission. It is possible to separate the received signals because the spreading code vectors are orthogonal and they provide a theoretical interference of zero between the signals that are combined.
In order to perform these operations it is known to randomly assign one of the available spreading codes to each new originating call or each new handoff call added to the communications system. However, random assignment of spreading codes in this manner may result in large peaks in the transmit power level of the combined signals.
A serious consequence of the power level peaks is that the power amplifier that amplifies the combined signals can be temporarily driven into a nonlinear region and saturated, thus, distorting the input signal. This can cause interference between the combined signals, particularly between signals on adjacent channels. The interference between the combined signals can cause degradation of the separated and recovered signals.
This problem can be solved by providing a power amplifier with an increased capacity. Such a power amplifier is not driven into its nonlinear region by the peaks in the power level of the combined signals. However, this is an expensive and inefficient solution to the problem because the increased capacity of the power amplifier is not used during the remaining ninety-nine percent of the time.
Thus, it is desirable to provide a system and method for smoothing the transmit power level of the combined signals caused by random assignment of spreading codes in order to cause fewer peaks and drive the power amplifier into its nonlinear region less frequently.
SUMMARY OF THE INVENTION
A method is taught for transmitting message signals in a communication system. The disclosed method applies, in particular, to the assignment of spreading codes (such as Walsh codes) to new calls entering the communication system. As a matter of convenience, the discussion below will consider the Walsh code as the choice for spreading code, although the ideas are easily extensible for any other spreading code. The method includes dividing the Walsh codes into bins and determining the number of active Walsh codes in the bins. Selecting a Walsh code in accordance with the Walsh code number determination and assigning the selected Walsh code to the new call are set forth. The Walsh codes have indices and the Walsh codes are divided into bins according to the indices. The Walsh codes are divided into cycles according, to the indices and if the number of bins is n the Walsh codes are divided into bins in accordance with the value of their indices modulo n. The minimum number of active Walsh codes in the bins is determined and the Walsh code is selected in accordance with the minimum number of active codes. A plurality of the bins can contain the minimum number of active Walsh codes. The method also sets forth selecting a bin of the plurality of bins containing the minimum number of active Walsh codes and selecting a Walsh code from the selected bin. A subset of the bins containing the minimum number of active Walsh codes is selected and a first predetermined bin with a preference lower than a preference for the remaining bins of the subset of the bins is selected.
REFERENCES:
patent: 5619526 (1997-04-01), Kim et al.
patent: 5691974 (1997-11-01), Zehavi et al.
patent: 5757767 (1998-05-01), Zehavi
patent: 5815526 (1998-09-01), Rice
patent: 5910950 (1999-06-01), Ten Brink
patent: 5940434 (1999-08-01), Lee et al.
patent: 6009089 (1999-12-01), Huang et al.
patent: 6028884 (2000-02-01), Silberger et al.
patent: 9503652 (1995-02-01), None
Bharghavan, V. “A Dynamic Addressing Scheme for Wireless Media Access” IEEE pp. 756-760 (1995).
Braithwaite, R. Neil “Nonlinear Amplification of CDMA Waveforms: An Analysis of Power Amplifier Gain Errors and Spectral Regrowth” 48thIEEE Vehicular Technology Conference, Canada, May 18-21, 1998, pp. 2160-2166.
Greenhaus Bruce
Katbab Abdollah
Qualcomm Incorporated
Sam Phirin
Ton Dang
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