Method and apparatus for regulation of the effective noise figure in a CDMA receiver

Abstract

The present invention relates to a method for effecting regulation of the effective noise figure of a CDMA (Code Division Multiple Access) receiver. The regulation process can be used to control the receiver during the activation / deactivation of a cell / sector in a CDMA wireless system and during normal operation when the service area of the cell / sector needs to enlarge or shrink. In a most preferred embodiment the CDMA receiver includes a source of pseudo-random noise that is injected in the received signal, downstream of the signal digitization stage. A power detector measures the power in the received digitized signal and a program logic determines the amount of noise figure degradation to be applied. The actual noise power regulation is effected by multiplying the output of the noise generator by a weighing factor. In a multi-channel CDMA system, each channel is provided with an independent system to regulate the effective noise power figure degradation, thus allowing to effect a noise figure regulation on a channel by channel basis.

Description

[0001] This invention relates in general to wireless communications and, more particularly to a method and apparatus for regulating the effective noise figure of a CDMA receiver in a base station. The regulation may be effected to control the blossoming / breathing or wilting functions of a CDMA communication system.[0002] In a CDMA wireless system the activation or deactivation of a cell / sector affects the network. The sudden activation of the cell / sector causes a sudden increase in the total forward link power. This may temporarily degrade the forward link performance of the network and possibly cause the calls in other cells / sectors close to the activating cell / sector to be dropped due to the sudden increase of channel interference from the activating cell / sector. In addition, the sudden deactivation of a cell / sector will result in calls in the cell / sector been dropped. To avoid this problem, when a cell / sector is activated in a CDMA wireless system, the transmitted power of the tr...

AI Technical Summary

Benefits of technology

[0013] The effective noise figure regulation may be effected in the analog processing unit or the digital processing unit of each channel. In a specific embodiment the channels of the receiver process independent CDMA signals separated by frequency. Most preferably, the effective noise power regulation means is located in the digital processing unit of the channel. The effective noise power regulation means includes a source of noise, such as a synthesized pseudo-random noise that is injected in the signal path. For easier control it is preferred to inject the signal at the digital baseband stage. At the baseband stage, the noise can be injected in the signal before or after the channel select filter. To determine the amount of noise to inject into the signal path for a given effective noise figure change, a power detector is used to measure the actual receiver noise power. Based on the information supplied by the power detector, the noise source can be controlled to effectively regulate the receiver effective noise figure degradation.

Problems solved by technology

This may temporarily degrade the forward link performance of the network and possibly cause the calls in other cells / sectors close to the activating cell / sector to be dropped due to the sudden increase of channel interference from the activating cell / sector.

In addition, the sudden deactivation of a cell / sector will result in calls in the cell / sector been dropped.

1. inaccurate control due to gain and / or noise figure instability (over temperature, aging, non-linearity, etc.)

2. this method is not suitable for effecting noise power regulation on a channel by channel basis in a multichannel CDMA receiver in which the channels share the same RF section and early stages of IF section.

Images