Outage Probability in GSM-GPRS Cellular Systems With and Without Frequency Hopping

General Packet radio service (GPRS) is designed for transmitting packet data and supposed to take its radio resource from the pool of unused channels by GSM voice services. Obviously, the introduction of GPRS has impact on the voice services. In this paper, we present a method to calculate the outage probability of the GSM-GPRS network for both the non-frequency hopping and the frequency hopping systems. This method takes into account the Rayleigh fading, power control (with error), discontinuous transmission, and frequency hopping (if applied). The outage probability of voice services affected by the introduction of GPRS is discussed. The number of unused voice channels allocated to GPRS depends on the difference between the outage level of the existing GSM network and the maximum acceptable level. The frequency hopping system can accommodate more GPRS traffic than the non-frequency hopping system. The power control error has more impact on the system performance when more channels are allocated to GPRS. Beyond our expectations, for the non-frequency hopping system, the channels provided to GPRS are not much different between the high channel occupancy and low channel occupancy of voice services. However, for the frequency hopping system, the system can provide more channels to GPRS at low channel occupancy. The cell service area decreases by about 10%∼20% for each additional channel allocated to GPRS. Key word: GPRS, outage probability, quality of service.