Hyun-Kook Kahng

A Correlated Load Aware Routing Protocol in Mobile Ad Hoc Networks

In this paper, we investigate the load distribution in ad hoc networks for reducing the possibility of power depletion and queuing delay at a node with heavy load environments. We examine the efficiency of dominant ad hoc routing protocols from a point of load balancing. Based on the results from various simulations, we design a new Correlated Load-Aware Routing (CLAR) protocol that considers the traffic load, through and around neighboring nodes, as the primary route selection metric. Simulation results show that CLAR outperforms other popular protocols and is better suited for the heady load networks with low mobility.

MRED: a new approach to random early detection

In order to reduce the increasing packet loss rates caused by an exponential increase in network traffic, the IETF (Internet Engineering Task Force) is considering the deployment of active queue management techniques such as RED (random early detection). While active queue management in routers and gateways can potentially reduce packet loss rates in the Internet, this paper has demonstrated the inherent weakness of current techniques and shows that they are ineffective in preventing high loss rates. The inherent problem with these queue management algorithms is that they all use queue lengths as the indicator of the severity of congestion. In order to solve this problem, a new active queue management algorithm called MRED is proposed. MRED computes the packet drop probability based on our heuristic method rather than the simple method used in RED. Using simulation, MRED is shown to perform better than existing queue management schemes.

Dynamic Agent Advertisement of Mobile IP to Provide Connectivity between Ad Hoc Networks and Internet

Although the Ad Hoc On-Demand Routing Protocol (AODV) is well designed for the ad hoc network, it does not deal with Internet connectivity. While some of solutions are proposed for integrating the ad hoc networks with global Internet, there are some limitations and drawbacks. In this paper, we propose the dynamic agent advertisement to reduce the control packets overhead and the power consumption due to a redundant packet processing. We use ns2 to compare the proposed approach with the existing solutions in terms of the overhead and throughput for packet transmission.

An Experimental Performance Evaluation of the Stream Control Transmission Protocol for Transaction Processing in Wireless Networks

In this paper, we show that the Stream Control Transmission Protocol(SCTP) could be an efficient alternative to the Transmission Control Protocol(TCP) for processing wireless multimedia transaction with multiple in-line objects in a transaction. This comes from three improvements of SCTP over TCP: the standard feature of selective acknowledgment, a different set of the initial and maximal values for retransmission counter and timer, and the multi-streaming feature. Among them, the multi-streaming feature of SCTP has the most profound impact on the overall performance in terms of throughput and delay in wireless networks with high probability of burst errors.

Multiscale quadtree model fusion with super-resolution for blocky artefact removal

Digital elevation model (DEM) integration by optimally fusing multiple measurements having different characteristics can play an important role in estimation and prediction of environmental changes and natural disasters. Multiscale or multiresolution modelling used for this purpose has attracted attention in terms of its rich modelling capability as well as computational efficiency. In particular, a multiscale Kalman smoother (MKS) with tree structure graph can provide a powerful, efficient algorithm based on the Markov property. However, due to the stair-like correlation from the tree structure, unrealistic artefacts can be generated in the fusion result. This is especially prominent on geographic surfaces or ocean surfaces that have naturally smooth characteristics. In this article, a super-resolution (SR) algorithm is applied to remove blocky artefacts. Using the algorithm, new measurements are generated in the area where blocky artefacts can arise. The measurement is then fused with vector-valued MKS. The results show that this novel image fusion scheme provides a smaller root mean square error (RMSE) as well as better visual inspection.

SCTP Mobility Highly Coupled with Mobile IP

This paper presents results, which have obtained by extensive simulations for Mobile IP (MIP) and Stream Control Transmission Protocol (SCTP) from the perspective of mobility support in wireless Internet. After illustrating the problem in the existing Mobile SCTP and SCTP over Mobile IP for diverse cases, we propose SCTP highly coupled with MIP for realizing seamless mobility. In this thesis we use ns2 with SCTP module to compare the throughput and end-to-end delay for packet transmission associated with the Mobile SCTP, SCTP over Mobile IP, and the proposed approach. Simulation results show that our proposed approaches achieve better performance than other proposals.

Mobility agent with sip registrar for VoIP services

The Session Initiation Protocol (SIP) is likely to play a key role in the convergence of Internet and the conventional cellular networks. Several issues related to mobility management in SIP enabled networks remain to be resolved. While other work has compared and contrasted mobility management in SIP and Mobile IP (MIP), in this paper we investigate possible integration techniques that combine the mobility management capabilities of both protocols. After illustrating some of the issues with each protocol when used in isolation in various mobile VoIP scenarios, we propose an integrated model (MIP+SIP), that reduces the disruption time during handovers. Our combination of network and application layer mobility management models reduces the global signaling load and provides fast handoff for ongoing conversations. Simulation results show that our proposed mechanisms achieve better performance than isolated SIP and MIP mobility management. Simulation results presented in this paper are based on the ns2 mobility package[6], which we extended with new capabilities to model SIP components (i.e., user agents, redirect servers, proxy servers, registrars) and SIP-based VoIP traffic.

IPv6 global connectivity for 6LoWPAN using short ID

6LoWPAN is for IPv6 packets to be sent to and received from over IEEE 802.15.4 based networks for applications which require wireless internet connectivity at lower data rates for devices. However it is well known that the management of addresses for devices that communicate across the two dissimilar domains of IPv6 and IEEE802.15.4 is complicated. Routing itself is another problem especially between the IPv6 domain and the IEEE802.15.4 domain. IEEE802.15.4 standard packet size is 127 bytes, among which IEEE 64 bit extended addresses may be used. After an association, 16 bits are used as an unique ID in a PAN L2, Still only 102 bytes are available for payload at MAC layer. Now considering the devices need to communicate with other nodes via IPv6 domain, 256 bits of the source and destination addresses seem to be cumbersome in a limited MAC payload fields. Here we propose an IP address translation mechanism. When a device in IEEE802.15.4 domain needs to communicate with other nodes in IPv6 domain, it acquires its source ID and destination ID for source IP address and destination IP address, respectively from an IP translation-capable gateway. The device will send the packet using those IDs to the gateway, and then the gateway will translate it to normal IPv6 packet. This paper will show the detailed procedures and its performance.

Multicast Session Management and QoS Management for Multicast Group Communications

Conventional multicast group communications need a dynamic mechanism for group management according to the join/leave of receivers and for the modification of membership information and a QoS management for a reliable multicast group communication. The Group Management Protocol (GMP) is an application-layer control protocol to supports the group management and the membership management for the multicast group communications but GMP does not support the QoS management. Also, RSVP supports the QoS for a reliable multicast group communication but RSVP is limited for managing the group membership. Therefore, we need to manage the group membership together with the QoS for the multicast group communications. In this paper, we propose a reliable multicast session management protocol called Multicast Session Management Protocol (MSMP). MSMP should coordinate the group management and the QoS management. MSMP is an application layer control protocol for managing QoS. MSMP consists of a session management function and a QoS management function.

Voice traffic characterization models in VoIP transport network

The motivation for characterization of VoIP traffic is that VoIP quality is mainly affected by some impairments in transport network in terms of delay, jitter and packet loss It is shown at the paper that the prediction of transport network resource to satisfy the VoIP QoS is important to find an perceptual optimization of playout buffer, and is able to provide effecient way to compute resource consumption in VoIP transport network This paper shows two models to caharcterize VoIP traffic in transport network, and proposes the novel mechanism to compute an amount of resource consumption The mechanism evaluates its availability of VoIP call arrived newly in order to sustain a stable VoIP quality level The applicability of the proposed mechanism in the paper will be stressed in terms of computational efficiency of dynamic real time computation algorithm.