| Summary: | 碩士 === 國立交通大學 === 資訊工程系 === 89 === GPRS, General Packet Radio Service, is a technique, which allows network operators to offer a packet-oriented data communications service based on GSM infrastructure. Initial GSM telecommunications system mainly provides voice service and circuit switched connection. However, it is limited by the small bandwidth at the speed 9.6k Bits/s. Therefore, GPRS, a new telecommunications technique, is developed to solve the problem. GPRS comes with the features as fast data transfer speed and always-on-line connection. It also combines with mobile communication and the Internet new functions. To use GPRS by current GSM operators, the main cost is on the hardware by adding two new nodes (SGSN and GGSN) and on software upgrade. Original GSM equipment can be continually used by the operators.
Though GPRS has great advantages described as above, its network node route still has the triangle transmission problem, that causes the inefficiency of packet data transfer and the increase of traffic load on the Internet. For GPRS triangle transmission problem, there are two reasons. First, it is necessary to pass GGSN nodes when MS end users perform intra data transfer. Second, in GPRS architecture with two more GGSN nodes, there's also a triangle transmission problem after MS implements handover with Inter SGSN routing area update. Therefore, the paper provides two approaches to solve the transmission problem. First approach is hierarchy GGSN solution for the architecture that only has one GGSN node. It solves the problem by adding a node between GGSN and SGSN to enhance SGSN packet route service. Second approach is distributed GGSN solution for GPRS with two GGSN nodes at least. It solves the problems by adding columns from senders and then storing PDP context to help data route. It needs to consider register, RA update, handoff and data transfer protocol. It also requires to modify original GPRS network protocol and packet route to optimize routing for GPRS.
Meanwhile, we use computer to simulate our approaches to verify new protocol and routing efficiency. According to our simulation results, both of hierarchy GGSN and distributed GGSN solutions can reduce GGSN load when we transfer data. Consequently, GGSN node can support more users and GPRS network can improve its efficiency.
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