Younghan Kim

SDN and Virtualization-Based LTE Mobile Network Architectures: A Comprehensive Survey

AbstractSoftware-defined networking (SDN) features the decoupling of the control plane and data plane, a programmable network and virtualization, which enables network infrastructure sharing and the “softwarization” of the network functions. Recently, many research works have tried to redesign the traditional mobile network using two of these concepts in order to deal with the challenges faced by mobile operators, such as the rapid growth of mobile traffic and new services. In this paper, we first provide an overview of SDN, network virtualization, and network function virtualization, and then describe the current LTE mobile network architecture as well as its challenges and issues. By analyzing and categorizing a wide range of the latest research works on SDN and virtualization in LTE mobile networks, we present a general architecture for SDN and virtualization in mobile networks (called SDVMN) and then propose a hierarchical taxonomy based on the different levels of the carrier network. We also present an in-depth analysis about changes related to protocol operation and architecture when adopting SDN and virtualization in mobile networks. In addition, we list specific use cases and applications that benefit from SDVMN. Last but not least, we discuss the open issues and future research directions of SDVMN.

Performance analysis of leaky-bucket bandwidth enforcement strategy for bursty traffics in an ATM network

Abstract In this paper, we analyze the performance of the bandwidth enforcement strategy applied for the bursty traffic. As a bandwidth enforcement strategy, we consider the leaky-bucket (LB) strategy which has been regarded as the most promising and easily implementable strategy. In this analysis, we use an Markov-modulated Poisson process (MMPP) as a model for the burst input traffic. With a token and a token pool as models for the transmission right and the allowed burstiness of the input traffic, respectively, we analyze and obtain the performance of the traffic under the LB bandwidth enforcement strategy. We also present some numerical results to show the effects of the system parameters on the performance of the traffic measured by the cell delay and the cell blocking probability.

IPv6 address allocation in hybrid mobile ad-hoc networks

Address allocation to mobile nodes is an important problem in mobile ad-hoc networks (MANET). Recently, several schemes have been proposed for address allocation in pure MANET environment, but they do not consider the access requirement of mobile nodes to the global Internet. In this paper, we consider the hybrid MANET where the pure MANET is interconnected to the external Internet by some gateways. For global-scope address allocation in this hybrid MANET, we present a new address allocation scheme by modifying the IPv6 stateless address autoconfiguration protocol. The proposed protocol decreases the latency of address allocation period by enhancing the duplicate address detection (DAD) mechanism of the address autoconfiguration protocol.

Measuring Inhomogeneity in Spatial Distributions

The spatial distribution of nodes in wireless networks has important impact on network performance properties, such as capacity and connectivity. Although random sample models based on a uniform distribution are widely used in the research community, they are inappropriate for scenarios with clustered, inhomogeneous node distribution. This paper proposes a well-defined measure for the level of inhomogeneity of a node distribution. It is based on the local deviation of the actual value of the density of nodes from its expected value. Desired properties of the measure are defined and mathematically proven to be fulfilled. The inhomogeneity measure is also compared to human perception of inhomogeneity gained via an online survey. The results reveal that the measure well fits human perception, although there are notable deviations if linear operations are applied.

Performance analysis of statistical multiplexing for heterogeneous bursty traffic in an ATM network

Analyzes the performance of a statistical multiplexer for heterogeneous types of bursty traffic in an asynchronous transfer mode (ATM) network. The authors model each type of bursty traffic with a Markov-modulated Poisson process (MMPP), and represent the different burstinesses of traffic by changing the parameters of the MMPP. Then, they use a finite queue multi-server model for analysis of the statistical multiplexer with multiple output channels. In order to consider the slottized operation of the ATM channel, they also assume that transmission of the cells queued in the buffer occurs at discrete time instants. With these traffic and system models they obtain the cell delay distribution and the cell blocking probability for the superposed heterogeneous types of bursty traffic. They also investigate the performance of each traffic separately by obtaining the cell delay and the cell blocking probability. From numerical results, they show the effects of each traffics characteristic on the performance of the statistical multiplexer. According to these results, it is noted that some efficiencies might be effected by dividing those types of traffic with comparable burstiness into segregated groups and allocate bandwidth to them exclusively. >

Cost-efficient network mobility scheme over proxy mobile IPv6 network

As Wi-Fi handheld devices providing a variety of data and multimedia services become more widespread, and as the global demand for internet access everywhere rapidly increases, energy-efficient network mobility (NEMO) technology is attracting great attention with respect to the latest research in mobile networking. The previous research relating to energy-efficient networks in mobile networking has focused on routing protocol or topology control. In NEMO, cost-efficient protocol design reduces unnecessary costs because of mobility signalling and packet delivery, and saves limited network bandwidth in both wired and especially wireless, which is one of the important issues of energy efficiency. In this study, the authors propose a cost-efficient proxy router-based NEMO scheme (PR-NEMO) providing efficient mobility management and packet delivery method. In PR-NEMO, a mobile network is formed with a unique ID and the information of mobile network nodes (MNNs) within the mobile network anchored at local mobility anchor (LMA) are distributed to attached mobile access gateway (MAG). The authors analyse the performance of the PR-NEMO with the N-PMIPv6 and the rNEMO in terms of total cost; that is, sum of location update cost and packet-tunnelling cost. Numerical results demonstrate that the PR-NEMO is the most cost-efficient scheme, under various conditions, among the three schemes evaluated.

Antidepressant-like effects of Cortex Mori Radicis extract via bidirectional phosphorylation of glucocorticoid receptors in the hippocampus

Excessive and prolonged secretion of adrenal glucocorticoids leads to a wide range of pathophysiological processes, including depression. Glucocorticoids, which act at glucocorticoid receptors (GR), are key regulators of the limbic hypothalamic-pituitary-adrenocortical (HPA) axis. In the present study, the antidepressant-like effects of the alcohol extract Cortex Mori Radicis (CMR) and its role in GR signalling were investigated. Male Wistar rats were administered CMR extract (50, 100, 200mg/kg, p.o.) daily for 5 days and then exposed to the forced swim test (FST). Behavioural analyses showed that CMR extract dose-dependently decreased immobility time during forced swimming. CMR extract also decreased the limbic HPA axis response to the FST, as indicated by an attenuated corticosterone response and decreased c-fos immunoreactivity in the dentate gyrus. Reduced hippocampal GR expression following exposure to the FST was reversed by CMR treatment. Moreover, a prominent increase in GR phosphorylation at S232 and a decrease at S246 were noted following treatment with CMR. This resulted in a high pGR(S232)/(S246) ratio. CMR treatment also produced a downregulation of serine/threonine protein phosphatase 5 levels, producing a strong negative relationship with pGR(S232). Taken together, our findings suggest that the alcohol extract CMR promotes antidepressant-like effects through bidirectional phosphorylation of GR at S232 and S246.

XCAST6: eXplicit multicast on IPv6

XCAST6: eXplicit Multicast on IPv6 is a new type of multicast datagram delivery system that enables multipoint visual communications, the killer-applications of the next-generation Internet. In the last decade, using the current scheme of group-address multicast, a good number of useful applications was developed and tested. However, the deployment of the multicast was very slow. XCAST6 solves these problems embedding an explicit list of destinations into the extension routing header of the IPv6 datagram. Intermediate routers may duplicate and forward the datagram only searching ones unicast routing tables. Moreover, using a semi-permeable capsule technique, users can ensure the reachability of the datagram. Deploying a very few number of XCAST6 routers, we could have operated the multi-point video conference trial on the academic IPv6 network among Japan, North America and Korea to prove employability and usefulness of XCAST6.

A Fast and Efficient Handover Authentication Achieving Conditional Privacy in V2I Networks

This paper proposes a fast and efficient handover authentication with conditional privacy in V2I networks. One of the main challenges for achieving secure V2I communications is to accomplish a fast and efficient handover authentication for seamless IP-based services. Anonymous authentication with authority traceability is another important security issue. The basic idea is that a handover authentication occurs only between a vehicle and a roadside unit to reduce the cost of authentication time and communication overhead. After performing the handover authentication, the roadside unit notifies an AAA server of the authentication result and vehicles pseudonym ID, which does not affect the fast handover authentication. The proposed scheme is more efficient than the existing schemes in terms of authentication time and communication overhead. In addition, our work is the first study on conditional privacy preservation during a handover process in V2I networks.

RESTful Architecture of Wireless Sensor Network for Building Management System

The concept of an “intelligent building” received significant attention from academic, industry and standard development organizations when technically termed a building management system (BMS). Wireless sensor networks (WSNs) and their recent development enhanced monitoring and control applications for the building’s areas. This paper surveys and analyzes advantages of the main current and emerging approaches that may be fit for BMS. Specifically, we discuss challenges including interoperability, integration, overhead, and bandwidth limitation of WSNs in BMS. Based on analyses, we highlight the advantages of an IP-based and RESTful architecture approach as the most suitable solution for BMS using WSNs (BMS-WSN). The paper also describes our future direction and design for BMS-WSN based on these advantages. The purpose is to enable interaction of users with BMS-WSN in the same way as with any website while ensuring energy efficiency. A test-bed implementation and evaluation of a BMS application is also introduced in this paper to demonstrate the feasibility and benefits of IP-based and RESTful architecture for BMS.