Dynamic Power Control
System operation in a point-to-multipoint system is critically dependent on the use of power control algorithms. These algorithms automatically adjust the transmit power from the various devices and make sure that the system operates with a high degree of reliability, while generating the least amount of interference. The PacketWave® system features several sophisticated power control algorithms, which are not matched by any other vendor in the industry.
Upstream Power Control: The objective of upstream power control is to compensate for varying link attenuations from different SUs, such that the received power at the BSU does not vary with SU location. Hence an SU that is located farther away transmits with higher power, while a SU that is closer transmits with lower power.
Downstream Power Control: The downstream power control feature is unique to the Aperto® product. Other products send downstream transmissions at full power, irrespective of the SU location. The Aperto BSU on the other hand, varies the signal power as a function of the link attenuation to the SU, so that transmissions to a nearby SU are a lower power level as compared to a more distant SU. Downstream power control has been shown to be very effective in reducing co-channel interference, it leads to an average improvement of 4.5 dB in the carrier to interference ratio, in a multi-cell deployment.
Dynamic Power Control: This is another unique feature in the Aperto product. The system constantly monitors the level of link attenuation to and from each SU. If it detects any change in attenuation, for example due to a new obstruction in the line of sight, it then compensates for it by dynamically increasing (or decreasing) the transmit power. The time required to do so is of the order of tens of milliseconds.