HFN is utilized among the base station and the portable to restrict the quantity of bits that are utilized for sequencing over the radio interface. HFN is a timer at the next level to SFN. HFN ranges somewhere in the range of 0 and 1023. The value increments by 1 when SFN arrives at 1023 and reset to 0. The number may likewise be utilized as a feature of the security process.