Hyung-Kun Park

Channel prediction-based channel allocation scheme for multichannel cognitive radio networks

Cognitive radio (CR) has been proposed to solve the spectrum utilization problem by dynamically exploiting the unused spectrum. In CR networks, a spectrum selection scheme is an important process to efficiently exploit the spectrum holes, and an efficient channel allocation scheme must be designed to minimize interference to the primary network as well as to achieve better spectrum utilization. In this paper, we propose a multichannel selection algorithm that uses spectrum hole prediction to limit the interference to the primary network and to exploit channel characteristics in order to enhance channel utilization. The proposed scheme considers both the interference length and the channel capacity to limit the interference to primary users and to enhance system performance. By using the proposed scheme, channel utilization is improved whereas the system limits the collision rate of the CR packets.

A Distributed-Request-Based DiffServ CAC for Seamless Fast-Handoff in Mobile Internet

The next-generation wireless networks are evolving toward an IP-based network that can provide various multimedia services seamlessly. To establish such a wireless mobile Internet, the registration domain supporting fast handoff is integrated with the DiffServ mechanism. In this paper, a Distributed-request-based CDMA DiffServ call admission control (CAC) scheme is proposed for the evolving mobile Internet. Numerical examples show that the forced termination ratio of handoff calls is guaranteed to be much less than the blocking ratio of new calls for a seamless fast-handoff while proposed scheme provides quality of service guarantee for each service class efficiently.

Packet Scheduling Scheme for Multiple Services in Mobile WiMAX System

In Mobile WiMAX system, it is important to allocate resources appropriately in order to the efficient utilization of resources among a variety of real-time and non real-time services. Although a lot of the real-time and non real-time packet scheduling schemes in OFDMA system have been proposed, it need to be modified to apply to Mobile WiMAX system. Since Mobile WiMAX supports five kinds of service classes, it is important to take QoS constraints of each class into consideration. In this paper, we propose an efficient packet scheduling scheme to support various services by considering the QoS constraints of each class. Proposed scheme selects a service class first considering characteristics of each class and next choose an appropriate user in the selected class. Simulation results show that the proposed scheme support QoS of each class efficiently.

A power-, delay- and emergency-efficient protocol of ubiquitous sensor network systems for silver town applications

A power- and delay-efficient routing algorithm and emergency-efficient protocol of ubiquitous wireless sensor network systems for silver town applications is presented. For this protocol, a fixed node (without any limited resources) is established at one point which can communicate with one-hop to both the sink node and the mobile sensor nodes in the dark region (in which mobile sensor nodes cannot communicate to the sink node). The fixed nodes are operated like the fixed cluster head. The simulated lifetime of the proposed routing algorithm is longer than those of LEACH and HEED and the simulated time delay of the proposed routing algorithm is faster than those of LEACH and HEED when the three protocols are applied to a specific silver town environment.

Channel Selection Scheme using Statistical Properties in the Cognitive Radio Networks

In a CR (cognitive radio) network, channel selection is one of the important issues for the efficient channel utilization. When the CR user exploits the spectrum of primary network, the interference to the primary network should be minimized. In this paper, we propose a spectrum hole prediction based channel selection scheme to minimize the interference to the primary network. To predict spectrum hole, statistic properties of primary user`s traffic is used. By using the predicted spectrum hole, channel is selected and it can reduce the possibility of interference to the primary user and increase the efficiency of spectrum utilization. The performance of proposed channel selection scheme is evaluated by the computer simulation.

Distributed Proportional Fair Scheduling for IEEE802.11 Wireless LANs

In the time varying wireless channel, opportunistic scheduling is one of the important techniques to achieving the rich diversities inherent in wireless communications. However, most existing scheduling schemes require centralized scheduling and little work has been done on developing distributed algorithms The proportional fair scheduling is one of the representative opportunistic scheduling for centralized networks. In this paper, we propose distributed proportional fair scheduling (DPFS) scheme for wireless LAN network. In the proposed DPFS scheme, each receiver estimates channel condition and calculates independently its own priority with probabilistic manner, which can reduce excessive probing overhead required to gather the channel conditions of all receivers. We evaluate the proposed DPFS using extensive simulation and simulation results show that DPFS obtains higher network throughput than conventional scheduling schemes while maintaining fairness among users.

Modified proportional fair scheduling for Cognitive Radio networks

Channel selection is one of important issues in Cognitive Radio (CR) networks and it is closely related to the channel characteristics and primary users behavior. In this paper, we proposed a modified proportional fairness scheduling which not only consider the fairness and the throughput but also take the primary user characteristics of each channel into account.

Channel Allocation Scheme considering Inter-Link Interference for Cognitive Radio Networks

In a multi-hop CR (Cognitive Radio) network, each node find a path to destination node through several links. If links have the same frequency channel, there can be a serious interference among the links and it can reduce the network capacity. In multi-channel CR networks, each channel has different capacity according to the inter-link interference, and each channel has different traffic properties of primary users. In this paper, we propose channel scheduling scheme to minimize channel interferences and collision with primary users. Simulation results show the improvement of channel capacity and collision rate with primary users.

Partial multipath routing for mobile ad-hoc networks

In a mobile ad-hoc network, to establish a stable routing path is one of the important technical issues to transmit data from source to destination by multi-hop transmission. Mobile ad-hoc network has time varying channels, and traffic congestion or unstable link condition can be severe problems. To solve those problems, multipath routing protocols were proposed. Conventional multipath routing, however, requires much more nodes and power consumption. In this paper, we propose partial multipath routing with interference avoidance. The proposed routing does not establish another full routing path but establish a partial multipath to complement some poor links, and the routing paths have enough distance from each other to reduce path interference.

Routing algorithm using channel based hop counting for wireless ad-hoc networks

A wireless ad-hoc network is a decentralized wireless network and a routing protocol is important to support efficient data transmission in wireless ad-hoc network. Conventional routing schemes considered the number of hops to determine the routing path. However, channel condition is an important factor to determine successful data transmission. In this paper, we propose a routing algorithm that consider successful transmission rate of each link. The advantage of the proposed algorithm is that it can be easily applied to conventional routing algorithms by using channel-based hop count.