Hyeong Ho Lee

Neighbor caching in multi-hop wireless ad hoc networks

We propose a neighbor caching strategy to overcome the overhead of multi-hop wireless communications. Neighbor caching makes a node able to expand its caching storage instantaneously by storing its data in the storage of idle neighbors. We also present the ranking based prediction that selects the most appropriate neighbor which data can be stored in. The ranking based prediction is an adaptive algorithm that adjusts the frequency of neighbor caching and makes neighbor caching flexible according to the idleness of nodes.

Performance Analysis of Statistical Voice/Data Multiplexing Systems with Voice Storage

In this paper the performances of four statistical voice/data multiplexers are analyzed and compared. The structures of these multiplexers are based on the newly proposed queueing, frame management, and integrated flow control methods. For the queueing purpose, two separate finite voice and data buffers are used to queue voice and data packets independently. For frame management, four versions of master frame management are considered. As for the integrated flow control algorithm, speech coding techniques such as variable rate coding and embedded coding are considered. To evaluate the performances of the multiplexers, analytical formulations are made from the equivalent queueing models of the proposed systems. Then, numerical results on the performance of the multiplexers are obtained by using the Gauss-Seidel iteration method. These results show that there exist tradeoffs between data and voice traffic performances for a given input traffic load and the output channel rate.

A dynamic wavelength allocation scheme with status information for fixed- and variable-length messages

We propose a new multiple access protocol to support both fixed- and variable-length messages, in a wavelength division multiple access (WDM) based local network using a passive star coupler. The proposed protocol is the dynamic wavelength allocation scheme based on a contention-based reservation protocol. In the proposed protocol, a whole message can be transmitted after the first reservation of the control channel is successfully completed. To reserve the subsequent slots, the status information is used, instead of the control channel. Moreover, the data channels are dynamically allocated to the nodes that win the reservation. Thus, the proposed protocol can reduce the probability of the control and data channel conflicts, and uses the same data channel while transmitting a whole message.

Shortest and Oldest First Non-interleaving Packet Switching Scheduling Algorithm

A packet-aware non-interleaving scheduling algorithm is proposed and examined in this paper. The non-interleaving scheduling algorithm eliminates the complexity of packet reassembly at the output queue. The characteristics of packet latency and queue occupancies are investigated in comparison with the cell-interleaving scheduling algorithm. The simulated results show that the packet-aware non-interleaving scheduling could be a feasible or better choice for packet switch implementations in the latency, output buffer requirement and implementation complexity viewpoints. The simulated results are obtained using self-similar traffic generated based on the measured Internet backbone traffic that reflects the predominance of short packets.

A new line code for 10-Gigabit Ethernet: MB810

The 10-Gigabit Ethernet (10GbE) is emerging as an alternative for solving the bottleneck of wide area network (WAN) links. Currently, the choice of line codes is being an issue in the 10GbE standardization. We review the candidates for the 10GbE line code, and propose a new line code, MB810, for 10GbE. Its spectrum is bounded within the Nyquist band and has no DC component. This code can improve the transmission rate-distance limitation of the optical fiber. We describe the design concept of the MB810 and its design procedure, and compare its characteristics with the NRZ and 8B/10B codes.

Structures of an ATM switching system with MPLS functionality

MultiProtocol Label Switching (MPLS) is a new IP over ATM technology that can be deployed in private networks as well as in public backbone networks operated by Internet service providers or telecommunication operators. From the viewpoint of telecommunication, we propose several structures of an ATM switching system having MPLS functionality that swaps a label at the packet forwarding engine and controls a label switched path at the MPLS controller. The proposed structures are discussed, and compared with each other according to their features. We also introduce the new ATM switching system named HANbit ACE 64 system that supports the MPLS functionality.

IEEE 802 standardization on heterogeneous network interworking

As various radio access technologies and multi-mode terminals incorporating multiple network interfaces appear, research and development interest on heterogeneous network interworking increases. IEEE 802 groups have standardized technologies on interworking between heterogeneous IEEE 802 networks and between an IEEE 802 network and a cellular network. This paper analyzes technologies on heterogeneous network interworking of IEEE 802 standards and provides trends and requirements of future technology on heterogeneous network interworking.

Providing flexible redundancy for an ATM access switch system

ATM switches require stringent reliability and availability even for access nodes. Carrier class ATM switches fulfill this requirement by employing expensive and sophisticated fault tolerant architectures. However, access switch systems are relatively cheap and compact. Most access switches support fundamental system reliability by providing redundancy for common parts of a system (e.g., switch fabric, power etc.). In addition to providing reliable connection to the core switch systems, access switch systems also need to support various customer premises services. Depending on the need of the network provider, highly reliable line redundancy is more important than the switching capacity of the access system or vice versa. This paper presents an implementation of an ATM switch that provides flexible line card redundancy and scalable switching capacity. Switching capacity of the system is scalable up to 10 Gbps from 5 Gbps depending on the configuration of line card redundancy.

SROS: a dynamically-scalable distributed real-time operating system for ATM switching network

We introduce a noble fault-tolerant distributed real-time operating system, SROS (Scalable Real-time Operating System), that is successfully implemented and working in an ATM switching system for B-ISDN. SROS is based on a micro-kernel for the purpose of achieving portability, scalability and reusability. In addition, to reduce system development period and to preserve call service continuity during system/application software upgrade, SROS adopts a dynamic code binding (DCB) method that enables system/application software upgrade without system halt or service disconnection. We also propose a cool development environment suitable for an embedded, distributed real-time system. This environment, together with SROS mechanisms, greatly cuts down the system development time.

Radio resource management based on IEEE 802.21 Media Independent Service Framework

As various radio access technologies and multi-mode terminals incorporating multiple network interfaces have appeared, interferences between wireless access networks have increased. This paper proposes radio resource management in heterogeneous radio access networks based on IEEE 802.21 Media Independent Service (MIS) Framework. The proposed schemes use MIS framework of IEEE 802.21 standard as a common platform to support radio resource management in heterogeneous networks.