This article proposes a quantitative approach to optimizing the 5G core (5GC) network refactoring as an example. Our previous study formulated the refactoring problem to minimize queuing delay and resource allocation cost directly in the M/M/k model and utilized the optimization tool, GUROBI, to derive an optimal refactored 5GC architecture, abbreviated as GUR-5GC. However, it is time-consuming; this approach for refactoring optimization is not feasible for dynamic scaling design. We design two quantitative indicators, message exchange reduction (MER) and merging utilization degradation (MUD), to evaluate the impacts of merging certain network functions. Moreover, the problem of calculating the two quantitative indicators can be reduced to a string-matching problem. Then, we reconstructed the optimization model formulation by using MER and MUD indicators in the objective functions instead of the queuing delay and resource allocation cost, since the optimization tool (CPLEX) Mathematical Programming (MP) and Constraint Programming (CP) models could not solve the original problem. Then, we utilized the CPLEX MP Model optimizer integrated with Pareto optimality to derive the CPLEX-based Refactored 5GC (CPR-5GC). In addition, we use a CURE-based (clustering) algorithm with MER and MUD by performing the quantitative analysis to derive the CURE-based Refactored 5GC (CUR-5GC) architecture. Finally, we analyzed the performance of the 5GC, GUR-5GC, CPR-5GC, and CUR-5GC. Moreover, we evaluate them in terms of queuing delay and scaling side effects. The performance results show that CPR-5GC and CUR-5GC outperform the original 5GC and are close to the GUR-5GC; the two heuristic algorithms for 5GC refactoring are feasible and practical.

Evolved Packet Core (EPC) is a framework for providing converged voice and data on a 4G network. Recently Control and User Plane Separation of EPC nodes (CUPS) is proposed to improve the scalability of the EPC network, and enhance data traffic in mobile core networks [1]. Network Function Virtualization (NFV) abstracts and modularizes the network functions from network entities [2]. In this way, operators can create, scale, and deploy network entities according to real-time traffic conditions. This paper proposes a quantitative approach for refactoring the control plane of CUPS-based EPC as the foundation to minimize signaling delay and improve resource utilization of the NFV-based mobile core network.

The CAMEL and the IMS are representative service platforms in the circuit switched (CS) and packet switched (PS) domain. The integration of the CAMEL and the IMS will bring tremendous benefits to the network operators and end users. Many researchers invest in investigating the mechanism of invoking the CAMEL service from the PS domain, however, there are few studies about the mechanism of invoking the IMS service from the CS domain. This paper proposes a CAMEL service invocation function (CAMEL-SIF) as a gateway for service invocation from CS domain to IMS. The CAMEL-SIF works as an overlay on the top of the current CS infrastructure that enables operators to deploy it without any change in the existing CS core. It is responsible for translating the CAP message into the SIP message, and vice versa. The translation is based on the call state and message diagram (CSM) and mapping tables. The CSM is in charge of maintaining the call state and determining the corresponding messages. The mapping tables indicate the mapping between the parameters in CAP and the headers in SIP. The trigger Filter Criteria (tFC) and the execution Filter Criteria (eFC) are employed to resolve ambiguity and arm the event detection point respectively. Our study improves the completeness of service invocation architecture in the service integration of the CS domain and the IMS. We also discuss the appropriate allocation of the CAMEL-SIF for reducing the service invocation delay.

The key exchange protocol is the most important cryptography mechanism to protect end-to-end communications by the secret session key encryption. This paper focuses on the four-party key exchange protocol in a environment in which two clients (or UEs) are registered under two distinct servers. We propose a Three-Way Key Exchange and Agreement Protocol, denoted by TW-KEAP. It makes two communication parties have a secret session key to protect their subsequent communications on an efficient way, and intends the servers to involve with the key exchange procedure to derive the session key for the lawful interception support. Security analyses show that it provides mutual authentication, replay attack protection and perfect forward secrecy. Furthermore, the TW-KEAP has not only the shortest total service time based on the experimental results but also the shortest queuing delay from the queuing model analyses, as compared with current alternatives.

Abstract VoIP over WLAN (VoWLAN) gradually has become a popular application with the fast maturing of both WLAN and Voice over IP (VoIP) technology. However there exists one problem that heavily affects the satisfaction of the users which is that the mobility of the mobile host (MH) can disrupt or even intermittently disconnect an ongoing real‐time session. Therefore the issue of how to reduce the handover delay gets more and more important. This paper proposes a Network‐Initiated SimUltaneouS mobility (NISUS) mechanism to facilitate terminal mobility with the session initiation protocol (SIP) in Voice over 3GPP‐WLAN. We design the E2E tunnel state model running on the packet data gateway (PDG) referring to the CAMEL concept. The NISUS is triggered at the PDG by detecting the state transition of the E2E tunnel state model that represents the occurrence of a handover. Then the PDG sends the handover request to notify the Mobility Server (MS) to perform a third party call control (3PCC) and a third party registration on behalf of the MH in parallel for session re‐establishment. With the help of the MS we ensure the lost signaling messages could be correctly re‐sent to moving hosts. Moreover the Master‐Slave Determination procedures derived from H.245 are proposed for the MS in order to handle the racing conditions fairly when two MSs involved in a simultaneous mobility issue 3PCC calls respectively at about the same time. We demonstrate the NISUS works well in the simultaneous and non‐simultaneous movement cases. Analytical results show that the handover delay can be improved significantly by using the NISUS compared with the mobile‐initiated simultaneous/non‐simultaneous mobility. Copyright © 2010 John Wiley & Sons, Ltd.

The combination of SIP-NEMO and IMS brings benefits of power saving, low complexity and few handoff to both end users and service providers. In this article we investigate the integration of SIP-NEMO in the IMS, and propose two interworking architectures: loosely coupled and tightly coupled. We also present three basic scenarios: registration, session establishment and optimized handoff with context transfer in the two architectures, respectively. The loosely coupled architecture maintains the original characteristics of SIP-NEMO and IMS. Control signals for the call setup are passed through the interrogating network in the IMS. The tightly coupled architecture utilizes the network agent of SIP-NEMO as a back- to-back user agent to integrate SIP-NEMO into IMS with minor modification of the IMS network and provides the security offered by IMS. The discussions on deployment and security issues show that the proposed approaches achieve the integration with minimal changes to the existing standards.

With high mobility rates of vehicles, there may be frequent occurrences of simultaneous handover. Our work focuses on and straightens out the problems resulting from simultaneous handover in SIP-NEMO. This article proposes a proxy-aided simultaneous handover (PASH) mechanism for the architecture of mobile networks operating on vehicles. The system architecture is modified from SIP-NEMO. We design a Fast Route/local routE re-Establishment (FREE) algorithm capable of re-establishing the optimized routing path fast and ensuring signaling messages buffered in local proxy could be sent to the correct destination without loss. Moreover, the Master- Slave Determination procedures derived from H.245 are introduced to handle the racing conditions fairly when two local proxies involved in a simultaneous handover issue re-INVITE requests at about the same time. Analytical results show that the handover delay can be improved significantly using the PASH, compared with the home-aided simultaneous handover.

In this paper, we propose a proxy-based SNR scalable error tracking framework for real-time video transmission where the server is wired connected to Internet and the client is connected to Internet through wireless broadband networks. We assume that all errors (packet losses) result from wireless links, and wired links are assumed to be error-free. The client sends back NACKs with the information about base layer lost packets to the proxy via a feedback channel. Once the NACK is received, the proxy uses the motion data and the side information received from the streaming server to perform error tracking. We compare our approach to the original proxy-based error tracking scheme without scalability support at the same bitrate and bit error rate. Experimental results show that the proposed method can effectively improve performance

The proposed network is a pyramid-like network of hypercubes, called pyramided hypercube. A pyramided hypercube containing m levels and having n-cube as basic configuration is denoted by PH(m,n). A PH(m,n) with fixed degree n+2, possesses logarithmic diameter, optimal fault tolerance, and capability of simple routing. The PH(m,n) can be extended smoothly with a constant predefined building block based on its recursive structure such that there is no change in the basic node configuration as we increase the network size. Moreover, links once connected are left undisturbed when the network grows in size. The PH(m,n) is also Hamiltonian.