Laihyuk Park

CoR-MAC: Contention over Reservation MAC Protocol for Time-Critical Services in Wireless Body Area Sensor Networks

Reserving time slots for urgent data, such as life-critical information, seems to be very attractive to guarantee their deadline requirements in wireless body area sensor networks (WBASNs). On the other hand, this reservation imposes a negative impact on performance for the utilization of a channel. This paper proposes a new channel access scheme referred to as the contention over reservation MAC (CoR-MAC) protocol for time-critical services in wireless body area sensor networks. CoR-MAC uses the dual reservation; if the reserved time slots are known to be vacant, other nodes can access the time slots by contention-based reservation to maximize the utilization of a channel and decrease the delay of the data. To measure the effectiveness of the proposed scheme against IEEE 802.15.4 and IEEE 802.15.6, we evaluated their performances with various performance indexes. The CoR-MAC showed 50% to 850% performance improvement in terms of the delay of urgent and time-critical data according to the number of nodes.

Deafness-aware MAC protocol for directional antennas in wireless ad hoc networks

The use of directional antennas is a promising technique for the provision of high-speed wireless local and personal area networks such as IEEE 802.11ac, IEEE 802.11ad, and IEEE 802.15.3c. In this paper, we propose a new directional MAC protocol for wireless ad hoc networks that is referred to as deafness-aware MAC (DA-MAC). Although a significant number of directional MAC protocols have been proposed, they have not comprehensively resolved the deafness problem. Our proposed DA-MAC protocol can distinguish the deafness problem from collisions by employing logical data and control channels. We provide a discrete-time Markov chain model to analyze the impact of deafness for both an existing technique and DA-MAC. Through extensive simulations, we show that our DA-MAC protocol can significantly outperform the other existing techniques with respect to the throughput, deafness duration, energy consumption, and transmission fairness.

Using social Internet of Things (SIoT) demand side management on the plant

Demand-side management program is important for future smart grid. Most of the DSM program developed in the past interact customer and utility company. We suggest the Factory Management System using Social Internet of Things. It is not interaction between customer and utility company but interaction between things and things. Therefore we propose a autonomous demand-side management system and a system architecture.

Performance analysis of circular directional MAC protocol

There have been great attentions on directional MAC (D-MAC) protocol recently in wireless ad hoc networks. Even if directional MAC has benefits such as spatial reuse and thus increased throughput, it has significant problems that have not been effectively rectified including hidden terminal and deafness problems. To tackle the hidden terminal and deafness problems, we propose a new D-MAC protocol that uses circular RTS (CRTS) and circular CTS (CCTS). We evaluate the performance of our protocol using ns-2 simulator. Performance evaluation shows that our proposed D-MAC protocol can reach up to 800% throughput gain with scenario 2 (24 nodes) against scenario 1 (3 nodes).

Optimization of ISM Band interference coordination between WLAN and IEEE 802.15.4 using NAV on PAN Coordinator

2.4GHz Industrial Scientific Medical(ISM) Band is shared by both WLAN and IEEE 802.15.4. Therefore, WLAN and IEEE 802.15.4 get interfered by each other where WLAN and IEEE 802.15.4 deploy locally. Especially, IEEE 802.15.4 devices are more influenced by the interference from LWAN devices because WLAN devices transmit data with higher power than IEEE 802.15.4 devices. In this paper, we proposed a possible algorithm for interference coordination in the Heterogeneous Network (HetNet) and optimized an important parameter, NAV, of the proposed mechanism. Our goal is to mitigate the interference problem and to make IEEE 802.15.4 work properly while minimizing the loss of WLAN by making PAN Coordinator conduct the role of both WLAN and IEEE 802.15.4 devices.

Deafness-aware MAC protocol for directional antennas

In this paper, we propose a new directional MAC protocol referred to as deafness-aware MAC (DA-MAC) distinguishing the deafness from the collision. Although a significant number of directional MAC protocols have been proposed including [1]-[3], they have not comprehensively resolved the deafness problem. With the expense of an additional narrow-band antenna, we provide distinction between the deafness and the collision. Through performance analysis, we show our DA-MAC protocol can significantly outperform the existing techniques with respect to the throughput, energy consumption, and deafness duration.

SPARM: Spatially Pipelined ACK Aggregation for Reliable Multicast in Directional MAC

In this paper, we propose an ACK-based reliable multicast protocol for directional antennas referred to as spatially pipelined ACK aggregation for reliable multicast (SPARM). To resolve the problems of ACK implosion and ACK collection latency, the SPARM exploits (1) spatial reuse and (2) pipelining of ACK aggregation. In the SPARM, receivers sequentially aggregate their ACKs while the sender multicasts a data frame to the next beam, both removing the ACK implosion problem and reducing ACK collection latency. Also, we prove that the aggregation process does not interfere with the sender multicasting to the next beam. Performance evaluation shows that the proposed SPARM has full reliability and outperforms the existing schemes with respect to the throughput by about 200%.

Greedy Technique for Smart Grid Demand Response Systems

최근 몇 년간, 전력 소비의 급격한 증가로 인하여 전력 수급의 불안이 전 세계적으로 발생하였다. 또한 전력 예측의 불확실성 및 전력 발전량이 급격히 증가하게 되었다. 이러한 문제를 해결하기 위한 방안으로 전력망과 IT 기술을 결합한 스마트 그리드기술은 각광을 받고 있다. 스마트 그리드는 전력 최대 부하율을 낮추...

Mobility-Aware Interference Avoidance Scheme for Vehicular WLANs

Communication technology of future networks is predicted to provide a large variety of services including WiFi service in vehicular network. In this paper, we assume that vehicles are embedded with WiMAX antenna and in-vehicle terminals receive WiMAX traffic through WiFi interface. This assumption will impose severe performance degradation due to interference among mobile BSSs when WiFi access points (APs) are densely located. Existing interference avoidance techniques cannot properly resolve the above problems and do not cope with dynamically moving vehicular scenario since they focus only on the fixed network topology. In this paper, we propose a mobility-aware interference avoidance scheme for WiFi services. The proposed scheme computes the interference duration by exploiting mobility vector and location information of neighboring APs. If the interference duration is not negligible, our scheme searches for another channel in order to avoid interference. However, if the interference duration is negligible, our scheme continues to use the channel to reduce switching overhead. To measure the effectiveness of the proposed scheme against other existing techniques, we evaluated performance by using OPNET simulator. Through the simulation, we obtained about 60% reduction in the maximum interference frequency and about 67% improvement in throughput. Furthermore, our scheme provides fair channel usage.