Hyung-Weon Cho

Dynamic frequency hopping channel management in cognitive radio ad-hoc networks

In this paper we propose a novel out-of-band spectrum sensing and dynamic channel management scheme for frequency hopping-based cognitive radio ad-hoc networks. At the beginning of each channel hopping time, member nodes perform spectrum sensing of the next hopping channel. Based on the proposed collision free primary detection notification, the member nodes determine whether they execute a hopping time extension of the current channel or not. When the primary detected hopping channel is re-idled, the hopping pattern recovery procedure is performed. In this paper we evaluate the performance of the proposed dynamic sensing and hopping channel extension mechanism for the various wireless network conditions. As a result, the proposed method can increase channel utilization and provide reliable channel management operation.

Genetic algorithm based sensing and channel allocation in cognitive ad-hoc networks

We present a novel out-of-band spectrum sensing and channel allocation scheme for frequency hopping based cognitive radio networks using genetic algorithm. Based on the optimized solution derived from GA, a set of nodes for sensing the next hopping channel and a set of nodes for transmitting data on current channel are derived. The channel allocation is performed according to individual traffic demand of each node. Simulation results show that the proposed scheme can achieve reliable spectrum sensing and efficient channel allocation.

Initial rendezvous protocol using multicarrier operation for ad-hoc cognitive radio networks

In cognitive radio technology, the overall capacity of communications systems can be improved without allocating additional bands by allowing secondary system to utilize the licensed band when a primary system who has right to use the band does not use it. In this paper, we consider how to set up a common channel for data communication in an ad-hoc networks consisting of a cluster head and member nodes using a cognitive radio technology. We propose a new initial rendezvous protocol that uses the system activation signal which has angle difference patterns with multicarrier operations.

Common channel initialization protocol in cognitive radio ad-hoc networks

Due to the increasing demand for spectrum resources, cognitive radio network and dynamic spectrum access get a lot of attention for efficiently utilizing the limited spectrum resources. To set up cluster-based CR ad-hoc common channels, conventional methods require relatively long time to successfully exchange the initialization messages. In this paper, we propose a fast and reliable common channel initialization protocol for CR ad-hoc networks. In the proposed method, cluster head sequentially broadcasts a system activation signal through its available channels with a predetermined correlation pattern. To detect the cluster heads broadcasting channels and to join the cluster, each member node takes FFT and computes autocorrelation of FFT bin sequence for each available channel of the member node. The join request and channel decision procedure are also presented in this paper. In the simulation study, the performance of the proposed method is evaluated.

Minimum jitter probability routing for DiffServ wireless mesh networks

In this letter, a minimum jitter probability (MJP) route selection algorithm for wireless mesh networks (WMNs) is proposed. To create the MJP algorithm, the inter-arrival packet jitter probability mass function (PMF) for differentiated service (DiffServ) priority classes is derived, which considers the effect of retransmissions due to packet errors in WMNs. Simulation results show the effectiveness of the proposed MJP algorithm compared to the popular minimum hop (MH) and expected transmission count (ETX) WMN routing schemes.

Selective Subspace Interference Alignment for Cognitive Radio Systems

This paper presents a selective interference alignment for cognitive radio system with spectrum leasing. The proposed method selects users who cause severe interference to other basestations that have required SINR. Since few users are selected to apply subspace interference alignment, the total complexity of the system is not high compared with that of the system who utilizes subspace interference alignment to all users. In addition, all users can transmit without considering interference. The computer simulation shows the proposed method exhibits 350% throughput enhancement at a two cell case, and 400% increase at a three cell case.