Nowadays VoIP (Voice over IP) develops quickly. H.323 is the most popular and mature architecture for VoIP, in which Gateway is one of the most important components. In this paper, two main aspects of the Gateway are discussed. They are the processing of simultaneous initialization of multiple calls and the compatibility with other H.323 standard endpoints and different H.323 versions. At last, the test of our Gateway is shown and the result is discussed.
In this paper, firstly, we introduce the protocol of VoIP, and analyze the process of a call establishment based on H.323, including RAS, H.225, and H.245 phases. Then, we focus on implementing ALG, which allow an application on a host in one address realm to connect to its counterpart running on a host in different realm transparently. An ALG may interact with NAT to set up state, use NAT state information, modify application specific payload and perform whatever else necessary to get the application running across disparate address realm. In addition, this section presents many important data structures and algorithms, for example, the algorithm to check for match of remote IP address and port, the algorithm for classifier to look at both outbound as well as an inbound packets, and etc. Finally, the paper describes and analyzes the results of experiments, and we obtain some significant parameters, namely, call setup latency and packet forwarding latency. The experiments and applications demonstrate it feasible for ALG to realize NAT for VoIP.
KEYWORDS: Digital signal processing, Stochastic processes, Mathematical modeling, Integration, Signal processing, Internet, Computer programming, Control systems, Computer architecture, Performance modeling
With rapid development of computer network and a wide application of Internet, IP telephony has been realized. Currently, one of the most important research areas of IP telephony system is to develop the IP telephony gateway. In this paper, a new idea of design on an Integrated IP Telephony Gateway is proposed, and the hardware of Integrated IP Telephony is discussed in detail. The software architecture of the Integrated IP telephone gateway is studied, and this paper focus on the voice compression module and SPOX schedule module. In addition, Stochastic Petri Net Model of an Integrated IP Telephony Gateway is set up, and its performance analyzed through the Stochastic Petri Net model. Array of Petri Net Model is computed, and educes the mathematical relationship of CPU efficiency and structure parameters of the IP telephony gateway.
KEYWORDS: Digital signal processing, Digital filtering, Control systems, Computer programming, Internet, Analog electronics, Computer architecture, Data storage, Telecommunications, Data processing
A new idea of design on an Integrated IP Telephone Gateway is stated in this paper. Some key techniques are analyzed and discussed in detail. A Centered Echo Chancellor based on TMS320C6201 DSP is implemented, and many optimization methods for voice compression code are concluded to enhance the performance of the gateway. Finally, the performance parameters of the Integrated IP Telephony Gateway are summarized in this paper.
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