Analysis of handoff algorithms using both absolute and relative measurements

An analytic model has been previously developed for evaluating the performance of handoff algorithms based on relative signal strength measurements, i.e., the difference of signal strength from two base stations (BS). In this paper we have extended this analysis by including an additional criterion based on absolute signal strength in the handoff decision algorithm. The absolute signal strength is the averaged value of the received signal level from current serving BS measured by the mobile unit. Recommended, e.g., in the GSM system, this value has to be below a fixed threshold to initiate a handoff (a necessary, not sufficient condition). In this way the mobile unit should be assigned to a new BS if the absolute signal strength from the old BS drops below the threshold and the relative signal strength between the new and old BS reaches the hysteresis level. The model is proved to be sufficiently accurate by comparison with simulation. The effect of adding absolute signal strength is illustrated