T E Overview :Technology vs Capacity

Technology vs Capacity Every system has its inherent capacity limits, dictated by the channel bandwidth and the number of calls per slot. The most common cellular system technologies and their bandwidth/traffic capacity are:   AMPS TDMA IS-54 GSM CDMA IS-95 Channel Bandwidth 30 KHz 30 KHz 200 KHz 1.23 MHz Time Slots 3 8 # Calls Supported 1 3 6 13 Erlangs 0.02 0.602 3.63 7.4 #Erlangs/MHz 0.67 20.06 4.54 6.02 Note that CDMA does not have hard time slots, but rather a number of users a single carrier can support. The number of slots (or calls) supported is usually between 13 and 24, and the number of Erlangs per sector is around 7.4. Sector Effect on Capacity As the number of sectors increase, the radio trunk groups split into smaller groups and become less efficient. The diagram shows these sector types: You Try It! A subscriber group generates 60 Erlangs of traffic. The GOS objective is 2%. How is the trunking efficiency changed if: Subscribers are served by a single trunk group or cell? It is a 3-sector cell with equal Erlangs in each sector? It is a 6-sector cell with equal Erlangs in each sector? Continue with Traffic Capacity.