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Device-to-Device (D2D) communications can increase the spectral efficiency of future cellular networks when sharing part of the cellular spectrum. Radio resource allocation mechanisms are then necessary to control the interference that D2D and cellular transmissions can generate to each other. Most of the existing allocation schemes rely on the knowledge of the channel gain of all possible links between...
In recent years, advances in wireless local area network (WLAN) systems have led to large increases in the transmission speed. The IEEE 802.11ac standard allows for very high transmissions by using multi-user multiple input multiple output (MU-MIMO) techniques in the physical (PHY) layer. However, the transmission efficiency is decreased by the channel state information (CSI) estimation algorithm...
We propose a decentralized multi-cell aware opportunistic random access (MA-ORA) protocol that almost achieves the optimal throughput scaling in a K-cell random access network with one access point (AP) and N users in each cell. Under our MA-ORA protocol, users opportunistically transmit with a predefined physical layer data rate in a decentralized manner if the desired signal power to the serving...
In this paper, we propose an opportunistic scheduling algorithm for secondary users (SUs) in a dynamic spectrum access network. Scheduling is performed at the beginning of each super-frame where appropriate channel(s) are assigned to the SUs based on the expected throughput that each channel provides. We compute the expected throughput for each channel on specific time slots in a super-frame based...
Due to higher cost and spectrum scarcity, it is expected that an efficient use of spectrum in fifth generation (5G) networks will rather rely on sharing than exclusive licenses, especially when higher frequency allocations are considered. In this paper, the performance of a dense indoor multi-operator small cell network at 10 GHz is analyzed. The main goal is to show the benefits obtained at higher...
The key challenges of high-throughput data delivery in multi-radio multi-channel Wireless Mesh Networks (WMNs) are fluctuating channel conditions, dynamic traffic flows, co-channel interferences, congestion, etc. In this paper, we first formulate a mixed integer non-linear programming (MINLP) optimization framework that chooses, at each router, a number of outgoing link-channel pairs and allocates...
Long term evolution-advanced (LTE-A) supports high-speed communications for cellular systems. It allows different types of base stations to form a heterogeneous network to provide service. However, signal interference between a macrocell and its picocells is inevitable. Thus, LTE-A adopts enhanced intercell interference coordination (eICIC) to conquer the interference problem. In the time-domain eICIC...
The directional nature of communication in millimeter-wave bands suggests that the frequency selectivity of the channel may be limited due to the absence of reflected paths. However, our measurement studies show that reflections often cause significant frequency selectivity in practical scenarios, which we can exploit to increase the otherwise limited range of 60 GHz networks. Specifically, we measure...
One of key technologies of 5th generation mobile networks is introducing small cells, such as femtocells and picocells, to supplement existing macrocells, and this results in high heterogeneity in mobile networks. Cell association, which selects a base station for each user to connect to, is a fundamental issue to optimize the performance and utilization of heterogeneous networks. This paper develops...
We consider a cognitive radio network, where primary users have priority over the spectrum resources, and secondary users can exploit the unused resources through channel sensing. Due to sensing inaccuracy, the secondary traffic may obstruct the primary traffic. A penalty for collision has been used to protect the primary traffic, which is often designed to provide a fixed per-collision compensation...
Multi-User Multiple Input Multiple Output (MU-MIMO) enables a multi-antenna access point (AP) to serve multiple users simultaneously, and has been adopted as the IEEE 802.11ac standard. While several PHY-MAC designs have recently been proposed to improve the throughput performance of a MU-MIMO WLAN, they, however, usually assume that all the concurrent streams are of roughly equal length. In reality,...
Classical opportunistic relay selections always cause unequal power consumption among all relays. For the battery-operated relays in the cooperative networks, uneven power consumption among the relays may reduce the network lifetime and thus deteriorates the network performance. In this paper, a novel multi-relay selection scheme aiming at the increase of the network lifetime is proposed for the decode-and-forward...
The increasing multimedia traffic and limited spectrum resource in Geosynchronous (GEO) satellite systems starve for an efficient Call Admission Control (CAC) scheme, which aims to provide acceptable Quality of Service (Qos) to massive users, however, the throughput may not be guaranteed. In order to maximize the total throughput of communication system, a dynamic CAC scheme, named Maximizing Throughput...
Massive Multiple-Input Multiple-Output (MIMO), small cell, and full-duplex are promising techniques for future 5G communication systems, where interference has become the most challenging issue to be coped with. In this paper, we provide an interference coordination framework for a two-tier heterogeneous network (HetNet) that consists of a massive-MIMO enabled macro-cell base station (MBS) and a number...
This paper presents and analyzes a point-to-multi-point (P2MP) network that uses a number of free-space optical (FSO) links for data transmission from the central node to the different remote nodes. A common backup radio-frequency (RF) link is used by the central node for data transmission to any remote node in case of the failure of any one of FSO links. We develop a cross-layer Markov chain model...
Non-orthogonal multiple access (NOMA) has recently been proposed as a key enabling technology for the fifth generation (5G) wireless networks. Different from the existing works which focus on the performance analysis of NOMA with backlogged traffic, in this paper, we analyze the stable throughput region of downlink NOMA transmission with dynamic traffic arrival for users with different priorities...
The 5G physical layer will support applications with different requirements, such as high data rate, ultra low power consumption and low latency. Recently, there is significant interest in the design and performance of new waveforms for 5G. One of the most important candidates is the Generalised Frequency Division Multiplexing (GFDM) waveform. The new waveform must support a smooth transition from...
This paper studies the throughput performance of a two-way energy harvesting relaying system. Network Coding and Energy Harvesting are promising techniques that can improve the transmission efficiency and the energy efficiency of wireless systems, respectively. In particular, we focus on the energy harvesting system with the power splitting-based relaying (PSR) protocol, and consider both the amplify-and-forward...
In this paper, we investigate the energy-efficient resource allocation problem in the downlink of an Orthogonal Frequency Division Multiple Access (OFDMA) system with multiple users. A iterative algorithm is developed to maximize the overall energy efficiency of the downlink transmission by allocating the resource blocks (RBs) and the transmit power, which is constant for all RBs assigned to a given...
Interference, which can be caused by Secondary Users (SUs) to other Primary Users (PUs) or SUs, is of major concern for Cognitive Radio Networks (CRNs). We study a spectrum allocation problem, where our primary focus is on maximizing the throughput of the CRN while protecting the PUs from interference and controlling the co-channel interference among the SUs. We build a CRN, where initially, all SUs...
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