PILOT_STRENGTH and NUM_PILOTS
Definition: PILOT_STRENGTH is the ratio of received pilot energy, Ec, to total received energy or the total power spectral density, Io. When more than one RAKE-receiver finger will be used to process the multipath from one pilot, PILOT_STRENGTH is the sum of the Ec/Io values on each of the multipath components to be combined by the RAKE-receiver fingers. PILOT_STRENGTH is expressed in dB. NUM_PILOTS is the number of pilots in the active set reported to the base station in the Power Measurement Report Message (PMRM). The symbol NoT is sometimes used to denote Io.
PILOT_STRENGTH and NUM_PILOTS
Example: PILOT_STRENGTH is a 6-bit word in the PMRM. The mobile station mea-sures the pilot strength (Ec/Io) as a fraction, not in dB. It then calculates the largest integer less than or equal to -20log10(Ec/Io). Suppose Ec/Io equals .25, meaning that 25% of the energy in the total bandwidth is due to the pilot. Then -20log10(.25) equals decimal 12.04. Then in decimal form
PILOT_STRENGTH equals 12. In binary form PILOT_STRENGTH equals 001100.
If -20log10(Ec/Io) is less than zero, a physical impossibility, then the value entered for PILOT_STRENGTH is binary 000000. If the calculation of the largest integer less than or equal to -20log10(Ec/Io) is greater than decimal 63, PILOT_STRENGTH is set equal to 111111. This means that the smallest Ec/Io ratio accurately reported is such that -20log10(Ec/Io) is on the order of decimal 63.9999. Solving for Ec/Io yields a value of about decimal .00063.
NUM_PILOTS has 4 bits assigned to it in the PMRM. In fact, 6 pilots is the maximum size of the active set supported by the mobile station.
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