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To enlarge the cell capacity of mobile network, LTE network offloads its traffic to WLAN network. However, User Equipment (UE) can run out of batteries rapidly due to the independent operation of multi-Radio Access Technologies (RAT), LTE and WLAN. In this paper, we propose new Multi-RAT power saving scheme, Single-RAT Monitoring which remove the duplication of periodic wake up operation. Because...
In this paper, we model power consumption of a heterogeneous network consisting of overlapped cellular and WiFi networks. Then, we propose a novel WiFi offloading model for maximizing per-user energy effciency in terms of bps per Joule. In the proposed WiFi offloading model, the heterogeneous network gathers user information and decides which portion of generated per-user traffic should be transmitted...
We investigate the maneuvering control of a UAV-based relay for efficient communication with mobile ground nodes. The objective of the maneuvering control is to maximize the minimum ergodic link capacity which is achieved by any ground node. We propose an efficient maneuvering control scheme of a UAV-based relay which does not require any location or direction information of ground nodes. The proposed...
In heterogeneous networks (HetNets), small cells are overlaid within a large cell in order to increase capacity and coverage beyond the initial deployment of a large cell. Previous studies assumed that small cells are deployed only in the cell edge area of a large cell to support low-SINR users in that area. However, in a future communication environment, we need more small-cells to support much higher...
In order to reduce the power consumption of cellular base stations (BSs), the following BS architectures have been developed: micro cell BSs, and remote radio head (RRH)-based BSs. In this paper, we propose a novel BS power consumption model for comparing the power consumption and energy efficiency of above three different BS architectures. The RRH-based BS architecture outperforms the conventional...
In this paper, we propose a novel network-assisted user-centric WiFi-offloading model for maximizing per-user throughput in a heterogeneous network. In the proposed WiFi-offloading model, the heterogeneous network collects network information, such as the number of users in WiFi networks and their traffic load. Then, the network decides the specific portion of traffic to be transmitted via WiFi networks,...
In order to alleviate a mobile data explosion problem, WiFi offloading has been proposed. The key issue is how many access points (APs) are needed to accommodate a proper number of users per WiFi AP without severe performance degradation. Although WiFi networks can provide higher throughput as more and more APs are deployed, it may not be a reasonable solution if we consider an increase in the corresponding...
Low-powered and light-weight sensor nodes will be deployed for e-health services in wireless body area networks (WBANs). Recently, the Institute of Electrical and Electronic Engineering (IEEE) introduced a new standard, IEEE 802.15.6 for wireless body area communications. The goal of this standard is to specify several physical layers (PHY) and medium access control (MAC) layer protocols for variety...
Energy efficiency in wireless communications is one of important research issues. Previous studies on reducing the energy consumption of IEEE 802.11 WLAN systems mainly focused on the energy consumption of a single-link transmission only. However, due to its carrier sensing property, all the WLAN stations in the network receive the transmitted frames. Hence, this single-link transmission not only...
Power saving mechanisms with sleep-mode operations have been used in IEEE 802.16e in order to extend the battery lifetime of mobile devices. The standard sleep-mode operation needs to meet a given delay constraint. However, it may incur unnecessary energy consumption due to frequent state transitions. In this paper, we propose a new energy-efficient sleep-mode operation while meeting a given delay...
In this paper, we propose a mobile grouping procedure to cooperate, and propose three different cost metrics for grouping: the remaining battery energy, WLAN physical (PHY) data-rate, and the number of MSs in the expected cooperation group. Moreover, we propose three cooperative MS-grouping schemes based on the above three metrics in order to extend the battery lifetime of MSs with both WLAN and Bluetooth...
Unmanned aerial vehicle (UAV) network is a network consisting of lying UAVs with communication capabilities. There are many technical challenges and problems due to a highly dynamic and mobile UAV network environment. In this paper, we focus on an inter-node interference problem. To overcome the interference problem and guarantee the communication quality, we propose an adaptive beamforming antenna...
The IEEE 802.11 standard supports multiple PHY rates. However, the IEEE 802.11 DCF in a multiple-rate environment may cause a performance anomaly. There have been many studies about the performance analysis and improvement of single- and multi-rate WLAN systems. However, there were a few studies about a generalized analysis on throughput and channel utilization for successful transmissions in multi-rate...
In emerging ubiquitous wireless environments, mobile devices can have multiple communication modules such as WLAN and ZigBee. Since IEEE802.15.4 ZigBee devices and IEEE802.11b WLAN devices share the same 2.4 GHz ISM band, a ZigBee network operating in a low power environment can be severely interfered by overlapped WLAN networks with much larger bandwidth due to higher transmission power. To overcome...
Emerging ubiquitous wireless networks are being spread widely. Ubiquitous wearable computers (UWCs) which may contain various communication protocol modules such as WLAN, Bluetooth, ZigBee, Wibro, and CDMA can be a solution in this era to support the ubiquitous wireless network environment. In ubiquitous wireless environments, ubiquitous wearable computers (UWCs) with multiple communication modules...
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