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Multiple-input multiple-output (MIMO) systems with implicit feedback utilize uplink channel state information (CSI) for downlink transmit beamforming, relying on over-the-air channel reciprocity. We develop real-time hardware for multiuser MIMO transmission with implicit feedback based on orthogonal frequency division multiplexing (OFDM), with field programmable gate arrays (FPGAs). This paper presents...
Millimeter wave (mmWave) frequencies offer the potential for very large capacity increases from traditional cellular frequencies because of the incredible amount of available spectrum (e.g., 10 GHz in the E-band alone). Additionally the latest channel measurements and research have shown that mmWave frequencies are useable for a 5G-type local area access system. However, employing mmWave frequencies...
Transmission over a half-duplex relay channel with secrecy and quality-of-service (QoS) constraints is studied. It is assumed that data is stored in buffers prior to transmission and transmitters operate with a constraint on the buffer overflow probability. Using the effective capacity formulation, secrecy throughput is derived for the half duplex two-hop fading relay system operating in the presence...
A distributed antenna system, where antennas at a base station are spatially distributed over the cell, can improve throughput at the cell edge compared to a centralized antenna system. However, the peak capacity degrades when a remote antenna unit has a few antenna elements due to rank deficiency. In general, the number of antennas at the base station is limited by the number of pilot sequences....
In recent years, there has been an increasing awareness to traffic localization techniques driven by the emergence of heterogeneous networks (HetNet) with small cells deployment and the green networks. The localization of hotspot data traffic with a very high accuracy is indeed of great interest to know where the small cells should be deployed and how can be managed for sleep mode concept. In this...
We develop an auction-based algorithm for joint allocation of resources, namely power profiles at the source and relay nodes and subcarrier assignment profile for multiple users amplify and forward (AF) orthogonal frequency division multiple access (OFDMA) system. The proposed algorithm is based on sequential single item auction, where each user submits a bid based on either the marginal increase...
Coordinated multiple point transmission (CoMP) technology becomes popular due to its potential for improving the performance of cell-edge UEs who undergo strong inter-cell interference (ICI). To fully exploit the potential CoMP gain, the appropriate method to converge cells into cluster is a prerequisite. However, the majority of existing research are based on theoretical hexagonal cell grid model...
As traditional wireless cellular networks are facing a rapid growth of traffic demand, future networks may consist of a large number of small cells which are densely deployed. However, networks in dense environment is exposed to strong inter-cell interference problem which is critical to networks capacity. To solve the problem, we use the Graph Coloring Algorithm (GCA) to divide the small cells into...
In this paper, a hybrid network combining visible light communication (VLC) with a radio frequency (RF) wireless local area network (WLAN) is considered. In indoor scenarios, a light fidelity (Li-Fi) access point (AP) can provide very high throughput and satisfy any illumination demands while wireless fidelity (Wi-Fi) offers basic coverage. Such a hybrid network with both fixed and mobile users has...
The objective of this study is to analyze a new disruptive deployment of wireless sensors in order to cope with the explosive demand for bandwidth while taking into account energy consumption considerations. The work is grounded on the idea of massive network densification by drastically increasing the number of sensors in a given area in a Time Division Duplex (TDD) mode. Using ideas from the recent...
In order to tackle rapidly increasing traffic, the 5th generation (5G) mobile communication system will introduce small cells using higher frequency bands with wider bandwidth to achieve super high bit rate transmission of several tens Gbps. Massive MIMO beamforming (BF) is one of promising technologies to compensate for larger path-loss in the higher frequency bands. Joint analog fixed BF and digital...
Two-tier heterogeneous wireless networks are considered in this paper where nodes in the first tier are distributed as a Poisson Point Process (PPP). Nodes in the second tier are distributed as a Poisson Clustered Process (PCP). Nodes in the second tier have imperfect channel state information (CSI) of the first tier node whose Voronoi cell they are in. On one hand, cross-tier interference is coordinated...
In LTE, the Interference over Thermal Noise (IoT) level is useful for operator to determine the link budget for coverage optimization. However, it is difficult to achieve the desired IoT operating point with the inter-cell power control solution in LTE. In this paper, a novel dynamic inter-cell power control scheme is proposed with enhanced X2 signaling to achieve the desired IoT operating point,...
Spectrum leasing is one of the cognitive radio models, where a primary user leases its spectrum resources for secondary user in exchange for cooperation. In [1] cooperative communication with beamforming (BF) in spectrum leasing was proposed for primary secure communications. However, interference is caused to the primary user from secondary user with its scheme. Therefore, we focus on cooperative...
Macrocell cellular networks utilizing relay nodes with low transmission power have emerged as a new paradigm to meet the fast increasing capacity and coverage demands in Fourth-Generation-Long-Term Evolution (4G-LTE). For such a network, an efficient radio resource allocation scheme is critical to achieve a desirable mobile quality of service (QoS). This paper investigates a stepwise radio resource...
Polar codes are a class of codes discovered recently, which are proved to have capacity-achieving performance. The hardware implementations of successive cancellation (SC) decoding and List SC decoding are increasing dramatically now. However, throughput of these hardware structures remain to be improved on the one hand. On the other hand, stochastic computation is now wildly used because it uses...
In this paper, we study the problem of cooperative communications in cognitive radio systems where the secondary user has limited relaying room for the overheard primary packets. More specifically, we characterize the stable throughput region of a cognitive radio network with a finite relaying buffer at the secondary user. Towards this objective, we formulate a constrained optimization problem for...
This paper proposes a new cooperative protocol which involves cooperation between primary and secondary users. We consider a cognitive setting with one primary user (PU) and multiple secondary users (SUs). The time resource is partitioned into discrete time slots. Each time slot, one of the SUs is scheduled for transmission according to time division multiple access scheme, and the remainder of the...
In 3GPP Release-12 specification, the adoption of small cells in long term evolution (LTE) networks is considered as a promising solution to meet the growing traffic demand for mobile data usage. However, energy consumption becomes a crucial challenge for network operators to deploy more small cells in heterogeneous networks in order to fulfill the requirement for achieving high data rates. In this...
Inserting attenuators between transceivers and antennas is proposed to improve spatial channel reuse in carrier sense multiple access with collision avoidance based WLANs. Using attenuators enables the access points or stations to decrease the powers of transmission signals and received signals, which equivalently results in the increase of the carrier sense threshold. Thus, the attenuation value...
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