Sinam Woo

Knowledge-Based Exponential Backoff Scheme in IEEE 802.15.4 MAC

In wireless personal area network, a channel is shared by a number of nodes. Therefore packet collision may take place and it degrades the throughput performance. To improve the throughput of slotted CSMA/CA in IEEE 802.15.4, we propose knowledge-based exponential backoff (KEB) scheme for enhancing channel utilization solely based on the locally available channel state information. In addition, we propose an analytical model of slotted channel access mechanism with finite retry and derive the theoretical throughput limit. In simulation experiments, we show that the existing MAC scheme, binary exponential backoff (BEB) scheme, operates very far from the theoretical limits due to increased time for negotiating channel access. Also performance results indicate that KEB shows significant improvement in throughput performance over BEB with the knowledge of the network status.

Throughput and delay analysis considering packet arrival in IEEE 802.11

In recent years, Wireless Local Area Networks (WLANs) have become extremely popular. IEEE 802.11 protocol is the dominating standards for WLANs employing the Distributed Coordination Function (DCF) as its Medium Access Control (MAC) mechanism. In the literature, several papers have stuided performance of IEEE 802.11 protocol and assume that a station always have a packet available for transmission. This paper 1 presents a Markov chain model to compute IEEE 802.11 DCF performance taking into account the packet arrival rates. Throughput and packet delay analysis are carried out in order to study the performance of IEEE 802.11 DCF under various traffic conditions. We present the analytical results of throughput and packet delay through network size and arrival rates. Results indicate that throughput and packet delay depends on the number of stations and packet arrival rates.

Local source routing based route optimization in nested mobile networks

Network Mobility (NEMO) is concerned with managing the mobility of an entire network and included one or more Mobile Routers (MRs) which are connected as gateways to the Internet. This paper proposes a mechanism for route optimization in nested NEMO by using local source routing with uni-direction tunneling. Our scheme focuses on minimizing the number of tunnels required outside the NEMO when there are multiple levels of nesting. The simulation results demonstrate that the proposed scheme is well adapted for supporting route optimization over existing NEMO’s bi-directional tunneling scheme.

Implementation and Performance Analysis of an IPv6 Multicast Forwarder for the IXP2400 Network Processor

This paper describes the design and implementation of an IPv6 multicast forwarder as the preliminary step for developing a high-speed IPv6 multicast-enabled router for use in an environment where multicast packets occupy some portion of the total network traffic using the programmable IXP2400 network processor. We validate our implementation and evaluate its performance with hardware experiments. Our experimental results show that the measured forwarding rate is 86% of full line rate in the minimum IPv6 packet size and the latency of IPv6 multicast packet forwarding compared with IPv6 unicast increases 25% in average. These are due to the processing overhead of IPv6 multicast route lookup in IPv6 multicast forwarder microblock, the packet copy in packet replication microblock, and the packet buffer management in packet TX microblock

Service Migration Mechanism Using Mobile Sensor Network

The recent advancement of wireless communication technology provides us with new opportunities, but it initiates new challenges and demands as well. Especially, there is an increasing demand for supporting user mobility and service mobility transparently. In this paper, we propose a new mechanism for service migration based on sensor networks of wireless sensor nodes. This mechanism is composed of a component-based server-side model for service mobility and Mobile IP technology for supporting user mobility among sensor networks.

Performance Evaluation of a NAT subsystem on Programmable Network Processors

It is a challenge to prototype network applications such as NAT that needs compute-intensive packet header processing while keeping the line speed on programmable network processors. In this paper, we design, implement, and evaluate a NAT subsystem capable of runtime adaptation on an experimental board containing a pair of Intel IXP2400 network processors, which operates in switch-over mode (NAT or NAPT) based on the fullness of the available global addresses or user configuration. We evaluate and validate our system through simulations and hardware experiments. It is found that the bottleneck of the system is due to the DRAM access latency. Also, we demonstrate that our NAT subsystem can support more than five hundreds of thousands of concurrent TCP/UDP sessions and sustain the full line rate on two Gigabit Ethernet links. Our experimental results and architecture can contribute to the other designs and implementations of network services over programmable network processors since they have similar architectures, functionalities and components

Marking mechanism for enhanced end-to-end qos guarantees in multiple diffserv environment

Recent demands for real time applications have given rise to a need for QoS in the Internet. DiffServ is one of such efforts currently being developed by IETF. In a DiffServ network, previous researchers have proposed several marking mechanisms that are adapted to operate in intra-domain rather than in multi-domain. In this paper, we propose an enhanced marking mechanism based on a color-aware mode using the conventional tswTCM for flows crossing one or more DiffServ domains in order to guarantee effectively enhanced end-to-end QoS. The key concept of the mechanism is that the marking is carried out adaptively based on the initial priority information stored at the ingress router of the first DiffServ domain and the average queue length for promotion of packets. By statistics based on simulations, we show that the proposed marking mechanism improves an end-to-end QoS guarantee for most cases.

Location Management with Dynamic Anchor Scheme in Wireless ATM Networks

This paper presents a dynamic anchor scheme in wireless ATM (asynchronous transfer mode) networks, which improves the location registers (LR) scheme, in which LR’s are hierarchically structured. This dynamic anchor scheme introduces the CCR (communication-to-computation cost ratio) term in the LR scheme. The proposed scheme reduces computation cost by introducing the active LR. There are at most two active LR’s in a hierarchical arrangement of LR’s and the location of one active LR is static and the location of another active LR called as anchor LR is dynamically selected among the LRs in the hierarchy in order to minimize a total location management cost. The total location management cost is calculated depending on the CCR as well as the CMR (call-to-move ratio). Numerical results show that the proposed scheme can reduce the location management cost compared with the original LR scheme for the different values of the CCR and the CMR.