Tae‐Jin Lee

IEEE 802.15.4 low-rate Wireless Personal Area Networks (WPAN) are expected to provide ubiquitous networking between small personal/home devices and sensors with low power consumption and low cost features. The technology employs special CSMA/CA to save power consumption for battery-powered small or portable WPAN devices. In this letter, we present a new model for the slotted CSMA/CA of IEEE 802.15.4 Medium Access Control (MAC) and evaluate its throughput limit in order to grasp the characteristi

The energy harvesting paradigm enables the design of new wireless powered cellular networks (WPCNs) for the Internet‐of‐Things (IoT). In a WPCN, if the harvested energy is larger than the consumed energy, an IoT device may utilise the surplus harvested energy to extend the battery lifetime or to enhance the performance. Otherwise, a power saving mechanism is utilised as in traditional wireless cellular networks. In long‐term evolution (LTE) systems, the discontinuous reception (DRX) mechanism ha

Most of the cyber-attacks are caused by malware, and damage from them has escalated from cyber space to home appliances and infrastructure, thus affecting the daily living of the people. As such, anticipative analysis and countermeasures for malware have become more important. Most malware programs are created as variations of existing malware. This paper proposes a scheme for the detection and group classification of malware, some measures to improve the dependability of classification using th

We consider model and performance evaluation of the Bluetooth system supporting point-to-multipoint communications in a piconet. In order to support more than seven slave devices in a piconet, a park mode is considered and modeled. We evaluate the performance, i.e., throughput and delay, using simulations when multi-connections (both A CL and SCO connections) are present in a piconet. We show that the data rate may be less than 10 kbps when SCO connection(s) and more than six ACL connections are

We consider a flow control algorithm to allocate bandwidth in a network subject to throughput and fairness constraints. Our algorithm achieves a max-min fair allocation among contending users, and has desirable properties in that it can operate in a decentralized and asynchronous manner accounting in part for heterogeneity in round trip delays. The algorithm is simple in that (1) the network links make local measurements of capacity and calculate local 'explicit rates' which are fed back to sour

Summary Delay sensitive applications are being actively introduced with the advent of 5G and vehicular communications, and such applications are very sensitive to tail latency. However, tail latency has not been seriously considered so far, especially in IEEE 802.11–based networks. Channel access is scheduled by random Contention Window (CW) values in IEEE 802.11–based networks, and the node with the larger CW waits longer, and it may even observe multiple transmissions from a single contending

In energy harvesting IoT networks, an energy queue state of an IoT device will change dynamically and the number of IoT devices that transmit data to the IoT AP will vary in a frame. So we need a MAC protocol to adjust the frame length taking the amount of energy of IoT devices into consideration. Since the existing Framed slotted ALOHA (F-ALOHA) Medium Access Control (MAC) protocol utilizes the fixed frame size, the resource efficiency can be reduced. In this paper, we propose a Harvested Energ

Summary In a wireless powered communication network (WPCN), sensor nodes harvest energy to transmit information. By a harvest‐then‐transmit (HT) protocol, nodes can be classified into either energy receiving (ER) or data transmitting (DT) nodes depending on the current level of the harvested energy. Since nodes may join or leave a network any time and energy levels vary, the distribution of ER and DT nodes changes over time. As the number of contending DT nodes is highly dynamic, a quick learnin

Abstract The Near Field Communication (NFC) standard is based on the radio‐frequency identification (RFID) standard. Because NFC and High Frequency RFID share the same frequency band, an NFC device cannot operate normally when they coexist. In this letter, we propose a fast identification protocol for the coexistence of NFC and RFID systems. When an RFID reader identifies an NFC device in the tag mode, the RFID reader stops identifying RFID tags and reserves the next slot for the NFC device in t

The MPEG-D unified speech and audio coding (USAC) standardization process was initiated by MPEG to develop an audio codec that is able to provide consistent quality for mixed speech and music contents. The current USAC reference model structure consists of frequency domain (FD) and linear prediction domain (LPD) core modules and is controlled using a signal classifier tool. In this letter, we propose an LPD single-mode USAC structure using an adaptive widowing-based transform-coded excitation mo

Abstract The efficient use of resources in wireless communications has always been a major issue. In the Internet of Things (IoT), the energy resource becomes more critical. The transmission policy with the aid of a coordinator is not a viable solution in an IoT network, since a node should report its state to the coordinator for scheduling and it causes serious signaling overhead. Machine learning algorithms can provide the optimal distributed transmission mechanism with little overhead. A node