Numerical round-off error in cellular phone services billing system

Cellular phone services billing for per minute tariff plan and 1-second pulse involve floating point division and multiplication operation to calculate per call bill. Monthly customer billing involves addition operations on per call bills, which are floating point numbers. Round-off errors occur due to floating point numbers’ computer representation limitations and for storing limited significant figures during billing. The study analyzed post-paid itemized bills of a cellular phone service operator in Bangladesh and identified that accumulated round-off error for active post-paid subscribers is significantly high for subscriber group of large number. The research recommends a per second tariff plan to completely eliminate round-off error which also reduces floating point number operations.