Comparison between Semi-soft and Hard handover in a Cellular IP networks

Due to the lack of the capacity per user connected to one access point (AP), the hotspot network providers are forced to constantly increase a number of APs to accommodate the customer´s growing capacity needs. For that reason, APs cover a small area, so mobile hosts must initiate frequent handovers. During the handover mobile hosts can not receive data, which results in a packet loss and in performance degradation of higher layer protocols, especially TCP (transmission control protocol). Cellular IP (CIP) is a protocol which supports semi-soft handover and shows a good performance of TCP in the throughput aspect. In this paper, as a part of our research we have implemented a CIP protocol in OPNET modeling environment. We present simulation results showing handover performance and its influence on the higher layer protocols, especially TCP. Also, we have pointed out several reliability issues in the CIP and suggested improvements that correct mentioned problems. It is shown that CIP is an efficient solution in frequent handover environment