Research & Implementation Of Handoff In IP-based Cdma2000-1x System

This dissertation is devoted to the researches of some key issues from the point of view of implementation according to the IP-based cdma2000 1 x system known as CMT, including soft handoff and hard handoff.There is only an ATM-based interface protocol between WAS and WAU in the existing cdma2000 protocol family, which called Abis-interface protocol. In this paper, a design of IP-based Abis-interface and its call flows is presented. Among these issues, the significant one is how to design the sequence of the messages in IP-based Abis-interface.In soft handoff, data is required to arrive synchronously in order to combine. However, the uncertainty of the transmission delay in IP network is inherent. The contradiction between them is a key problem in realization. This paper presents a double-loop feedback algorithm to resolve this problem, which adopting uplink and downlink feedback loop separately. It realizes the data synchronization by compensating sending time using the feedback information.The mobile station needs to obtain the real-time information of its neighbor list in the process of soft handoff. Based on the vote model, we provide an algorithm to create the real-time neighbor list according to the pilot strength information. The simulation results indicate that the performance of the algorithm is exceeding those traditional neighbor list-updating methods.The performance of the soft handoff is determined by the values of its parameters to a great extent. Some researches and simulations to a certainty degree are performed, mainly on the TADD and T_DROP thresholds. The results have a directive effect on the parameter's setting in actual systems.It is more complicated to design the hard handoff in cdma2000-1x system, as the overlay of the wireless network is various. We design a scheme of the hard handoff according to the different wireless environments, which adapts to the CMT system. The main part is the control algorithm of the hard handoff including the startup, the execution, and the back management.