Image Number 4 for United States Patent #5590156.
A technique for extending the instantaneous dynamic range available in a wideband digital basestation for use in a wireless communication network. The basestation processes the bandwidth allocated to it in two or more sub-bands. The sub-bands are each processed by a digital tuner section consisting of an amplifier, analog-to-digital (A/D) converter, and digital filter bank. The digital filter bank may make use of multirate digital signal recovery techniques for efficient implementation. In operation, a received signal strength indication (RSSI) is first determined for each subscriber unit requesting access to the basestation. A channel assignment controller then assigns a transmit frequency to the subscriber unit depending upon this RSSI. In particular, subscriber units exhibiting a relatively stronger RSSI are to transmit on a frequency assigned to a first digital tuner section, while subscriber units having a relatively weak RSSI are assigned to a second digital tuner section. The gains of the first and second tuner sections of each other adjusted independently, to insure that the relatively strong signals are not clipped by the first tuner section, and that the relatively weak signals may be correctly detected by the second tuner section. The net effect is to provide a much greater overall system dynamic range. The invention can be used to advantage in both existing AMPS type cellular systems as well as CDMA systems.
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