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Heterogeneous wireless systems such as a combination of mobile broadband wireless access (MBWA) and wireless local area network (WLAN) are candidates to attain the large capacity in the next generation mobile communication systems. For capacity expansion, small cells of multiple wireless network are deployed densely in these systems. Because a number of the cells overlap, users must discover a lot...
In this paper, we propose a distributed load balancing algorithm with adaptive bias adjustment for LTE/LTE-A HetNets. We have formulated the problem as a local sum utility maximization. The distributed algorithm is capable of fairly distributing the load among base stations with a minimum level of coordination. The performance of the algorithm was evaluated with a network topology subject to the conditions...
We consider in this paper an uplink coordinated beamforming problem for multi-cell heterogeneous networks (HetNets) whereby base stations are densely and co-channel deployed. A joint user-base station association, power control and beamforming scheme is presented for HetNets to minimize the power consumption. Such joint optimization is formulated as a mixed-integer second-order conic programming (MI-SOCP)...
Communications play an important role during public safety operations. Since the current communication technologies heavily rely on the backbone network, the failure of base stations (BSs) due to natural disasters or malevolent attacks causes communication difficulties for public safety and emergency communications. Recently, the use of unmanned aerial vehicles (UAVs) such as quadcopters and unmanned...
In cognitive Radio, Energy Detection(ED) is the easiest method to detect idle spectrum due to the simple implementation. However, it is difficult to identify the transmitter when several systems are sharing the spectrum in the same time. In order to improve the spectrum utilization, the spectrum shared by the secondary users may be detected as idle spectrum with keeping the detection performance of...
Efficient discovery of multiple small cells is important to features such as small cell on/off, load balancing, CoMP (Coordinated Multi-point Transmission), e-ICIC (enhanced-Inter-Cell Interference Coordination) in LTE (Long Term Evolution) hyper-dense networks. However, severe interference in the Hyper-Dense Networks imposes great difficulty on efficient discovery of small cells. This paper proposes...
In this paper, a medium access protocol suitably adapted for the operation of Long term evolution (LTE) in unlicensed band (LTE-U) is proposed. The MAC design considers the impact of LTE-U on the devices operating in unlicensed band, such as WiFi and legacy LTE. The LTE-U design differences from the legacy LTE system, an inherently a synchronized, tightly controlled system are explored. The performance...
In this paper, we propose an interference power constraint method using measurement-based spectrum database for high efficient spectrum sharing. The spectrum database is constructed from measurement radio environment information measured by secondary users (SUs) with mobility, and stores radio environment maps (REMs). This paper focuses on a databaseaided communication parameter adaption method which...
We have proposed a concept of a new Quality of Experience (QoE) oriented wireless local area network (WLAN) on which many applications can run with sufficient quality even in congested environment. The proposed system is designed by taking users’ QoE as a key metric. In this paper, we propose a practical functional flow featuring a new channel access control scheme based on loadable capacity prediction...
Large scale growth of wireless networks and the scarcity of the electromagnetic spectrum are imposing more interference to the wireless terminals which jeopardize the Quality of Service offered to the end users. In order to address this kind of performance degradation, this paper proposes a novel experimentally verified cognitive decision engine which aims at optimizing the throughput of IEEE 802...
Energy efficiency has become one of the key performance indicators for 5G wireless networks. Coordinated multipoint (CoMP) transmission/reception and multiinput single-output (MISO) are two technologies which can achieve higher energy efficiency in heterogeneous networks (HetNets) compared to conventional single-input single-out (SISO) systems. CoMP improves energy efficiency by joint transmission...
3D cell structure, where small cells are threedimensionally deployed on macro cells, is considered as one of the effective cell structures to accommodate data traffic growing rapidly in recent years. In this cell structure, inter-cell interference among small cells is one of the major issues. As a technique for mitigating inter-cell interference among small cells, we propose a network coordinated...
In heterogeneous networks of low power Pico Base Station (PBS) overlaid with Macro Base Station (MBS), cell range expansion (CRE) which add a positive bias in PBS for cell association is proposed to offload user equipments (UEs) to PBSs. In this way UEs in CRE region that associated to PBS with weak signal power may experience strong cross-tier interference from MBS. To manage this interference, almost...
Device-to-device (D2D) communication is envisioned as a promising technology in future cellular networks. In this paper, we investigate the delay-aware resource allocation and power control algorithm for delay-sensitive D2D communications underlaying cellular networks. With the objective to minimize the average delay and average drop rate, we formulate the optimization problem as an infinite horizon...
This paper investigates the interactions between a secondary user (SU) with frequency hopping and a jammer with spectrum sensing in heterogenous cognitive radio networks. The power control interactions are formulated as a multi-stage anti-jamming game, in which the SU and jammer repeatedly choose their power allocation strategies over multiple channels simultaneously without interfering with primary...
Device to device (D2D) communication is expected to be an important aspect in future 5G communication systems. To this end, D2D has been identified as an important topic in the EU flagship project METIS, wherein commercial D2D use cases are also considered. In principle, direct D2D communication offers the double benefit of low latency and high data rate at the same time. Interference mitigation and...
As a natural scarcity in wireless networks, radio spectrum becomes a major investment in network deployment. How to improve the channel utilization (CU) of the spectrum is a challenging topic in recent research. In network environment, the utilization of a channel is measured by the effective CU (ECU), ie., the effective time in transmission or being sensed busy over its total operation time. However,...
Cellular communications have witnessed an exponential growth over the last few years. The challenges the industry faces for the next decade arise the need for significant changes, i.e., new paradigms away from just incremental advances in the current technologies. Network densification and high frequency communications are widely-recognized as cornerstones of this revolution. Understanding the needs...
Carrier Aggregation (CA) is a promising solution to enhance peak throughput in LTE-Advanced or Small Cells Networks (SCN). Thanks to this technique, a terminal becomes able to transmit on one or multiple component carriers. However, many issues in terms of radio resource allocation and mobility should be addressed. In this paper, we aim at improving carrier component allocation during inter-cell handovers...
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