Frequency Reuse and Coding for Gprs Multi-slot Operation

Due to the growing interest in mobile data applications, the Global System for Mobile communications (GSM) has been extended by the General Packet Radio Service (GPRS). It allows the transmission of packet data at moderate bit rates using random access channels within the existing GSM infrastructure. This paper analyses the impact of using multiple channels in a GSM system for GPRS packet transmission. Different combinations of frequency reuse and channel coding are evaluated for 1, 4 and 8 Packet Data Channels (PDCHs) per cell. A tight frequency reuse of 1, together with a strong error coding scheme was found to provide the highest capacity. The increased trunking efficiency for a system with 8 PDCHs yields a capacity gain of about 64% over a system with only 1 channel. The results indicate that mixing circuit and packet switched traffic causes inefficient use of system resources. Since GSM voice services usually require a frequency reuse of 3 or 7, a separate overlaying network for GPRS provides better resource utilization and maximizes the number of users fulfilling the specified Quality of Service (QoS) requirements.