Seog-Gyu Kim

Performance Evaluation of Synchronous and Asynchronous MAC Protocols for Wireless Sensor Networks

In the wireless sensor networks (WSNs), Synchronous approaches share the schedule information that specifies the cycle of active and sleep period by the control packets. On the other hand, asynchronous approaches do not exchange the synchronization information to send or receive data. Instead, they employ preamble sampling to do that. In this paper, we compare and analyze synchronous and asynchronous MAC protocols for WSNs with our two proposed schemes (AD-MAC and AS-MAC). Our proposed schemes present an enhanced adaptive duty cycling and high low power listening algorithm for energy efficiency, respectively.The performance of those two MAC mechanisms with our proposed protocols will be investigated through simulation and analysis to design the effective MAC protocol in WSNs.

An Enhanced Cross-Layer Protocol for Energy Efficiency in Wireless Sensor Networks

In wireless sensor networks, the simplified and energy efficient protocol should be designed in order to maximize the network lifetime because of its stringent resource constraints, ultra power limitation, and tiny embedded devices. In this paper, we propose an enhanced cross-layer protocol for energy efficiency in wireless sensor networks by integrating medium access control and routing protocol. Our proposed protocol utilizes a synchronous medium access control scheme by using the adaptive duty cycling technique to improve energy efficiency and solve long end-to-end delay problem. We also design a tree-based energy aware routing algorithm to prolong the network lifetime in our protocol. Simulation results show that the proposed protocol outperforms other existing algorithms in terms of energy efficiency and latency.

HUHG: High Utilization and Hybrid Granting algorithm for EPON

The In recent year, EPON (Ethernet PON) system is expected to be more efficient solutions for High speed, broadband access networks in Next generation access network due to the convergence of low-cost Ethernet equipment and low-cost fiber infrastructure. However, upstream channel control algorithm is essential to share upstream bandwidth in EPON. Therefore, many studies about EPONs are interested in the problems of efficient bandwidth utilization and supporting QoS (Quality of Service). In this paper, we suggest HUHG (High Utilization and Hybrid Granting) algorithm of supporting high bandwidth utilization and QoS for different service classes. This algorithm improves bandwidth utilization as diminishing or removing idle time of upstream channel scheduling using characteristics of fixed EF (Expedited Forwarding) cycle. This algorithm also minimizes the packet delay and delay jitter of EF service class. We conduct detailed simulation experiments using OPNET to study the performance and validate the effectiveness of the proposed algorithm.

Advanced MAC protocol with energy-efficiency for wireless sensor networks

This paper proposes E2-MAC, a contention-based energy-efficient Medium Access Control (MAC) Protocol for wireless sensor networks. Energy efficiency is primary goal in wireless sensor networks. Existing MAC protocols for sensor networks attempt to solve energy consumption problem caused by idle listening using an active/sleep duty cycle. Since there are various traffic conditions, however, they may not always provide improvements in energy consumption. We propose a MAC protocol algorithm that stores data in a buffer and transmits data when the buffer exceeds a threshold value so that energy efficiency is always guaranteed for any network traffic conditions. Analytical results show that our proposed algorithm has significant improvements in energy consumption compared to the existing MAC protocols for sensor networks.

High Utilization and Hybrid Granting algorithm for EPON

In recent years, numerous studies have been attempted to solve problems of efficient bandwidth utilization and supporting QoS(Quality of Service) of EPON(Ethernet Passive Optical Network) system. This paper examines advanced scheduling algorithm which improves bandwidth utilization and supports QoS for different service classes of EPON system. This algorithm improves bandwidth utilization by diminishing or removing idle time of upstream channel scheduling using characteristics of fixed EF(Expedited Forwarding) cycle and also minimizes the packet delay and delay jitter of EF service class by splitting EF sub-cycle and AF sub-cycle. We conduct detailed simulation experiments using OPNET to evaluate the performance and validate the effectiveness of the proposed algorithm.

Overload Control with Removal Algorithm for Real-time Flows in Wireless Networks

In the real-time multimedia applications, packet delay should meet stringent quality of service (QoS) requirements. Delay earliest due date (EDD) scheduler, originally designed for wireline data networks to operate under a maximum allowed delay, cannot be directly applied to wireless networks, due to the location-dependent errors and time-varying channel conditions. Several modifications of EDD scheduler have been proposed for wireless applications, which typically assume successful admission control, a condition hard to provide for wireless networks. In this paper, we propose a removal algorithm for downlink scheduler that is designed to perform under an overloaded situation. Simulation result shows that our algorithm outperforms the previous ones in the QoS guaranteed flows. Last, we discuss an extension of our works to integrate with admission control

Adaptive Duty Cycling MAC Protocols Using Closed-Loop Control for Wireless Sensor Networks

The fundamental design goal of wireless sensor MAC protocols is to minimize unnecessary power consumption of the sensor nodes, because of its stringent resource constraints and ultra-power limitation. In existing MAC protocols in wireless sensor networks (WSNs), duty cycling, in which each node periodically cycles between the active and sleep states, has been introduced to reduce unnecessary energy consumption. Existing MAC schemes, however, use a fixed duty cycling regardless of multi-hop communication and traffic fluctuations. On the other hand, there is a tradeoff between energy efficiency and delay caused by duty cycling mechanism in multi-hop communication and existing MAC approaches only tend to improve energy efficiency with sacrificing data delivery delay. In this paper, we propose two different MAC schemes (ADS-MAC and ELA-MAC) using closed-loop control in order to achieve both energy savings and minimal delay in wireless sensor networks. The two proposed MAC schemes, which are synchronous and asynchronous approaches, respectively, utilize an adaptive timer and a successive preload frame with closed-loop control for adaptive duty cycling. As a result, the analysis and the simulation results show that our schemes outperform existing schemes in terms of energy efficiency and delivery delay.

Topology Control Method Using Adaptive Redundant Transmission Range in Mobile Wireless Sensor Network

In this paper, we simulate the effect of RTR (Redundant Transmission Range) which is used to maintain network connectivity in mobile wireless networks such as ad-hoc or sensor networks. The simulation result shows that the RTR scheme greatly increases network connectivity time. Based on the simulation result, we propose an A-RTR (Adaptive-RTR) algorithm. A-RTR use variable RTR as node’s moving speed and neighbors’ speed. This algorithm can be used any topology control algorithms and prolong the network connectivity time in mobility environment. Simulation results show good performance not only the network connectivity but also node’s energy consumption.

A Time Backoff-Based Energy-Efficient Geographical Forwarding for Wireless Sensor Networks

A geographical forwarding algorithm is an attractive localized data forwarding scheme for wireless sensor networks (WSNs) due to its directional routing properties and scalability. Also, the inherent constraints of WSNs such as limited battery power and network resources require the simplicity and energy efficiency of protocols. In this paper, we propose a Time Backoff-based energy-efficient Geographical Forwarding (TBGF) for WSNs. TBGF is a combined MAC and routing protocol based on geographical forwarding that achieves energy efficiency and minimization of control overhead. TBGF uses the energy-aware time backoff scheme with the optimal geographical information to make the next forwarding decisions. Our simulation results show that the proposed protocol outperforms other existing schemes in terms of energy efficiency and network performance.

A Fast Resilient Routing Protocol with Energy Efficiency for Wireless Sensor Networks

Generally, single path routing is simple and consumes less energy than multi-path routing, but it will cost a lot to re-delivery when the data delivery fails. However, multi-path routing supports high delivery ratio and load balancing, but its traffic is very high and the redundant traffic is burden to the whole networks. In this paper, we introduce a novel routing scheme for wireless sensor networks, so called, the highly energy aware resilient routing scheme (HEAR). Our scheme establishes partial disjoint multi-paths to support high robustness and energy efficiency.