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The 4:th generation communication standard is constantly evolving with more features being added to the standard specifications. Carrier aggregation and higher order MIMO are examples of features used to support higher data rates. The addition of features puts new requirements on wireless devices and this increasing complexity implies that Over-the-Air testing is more important than ever. At the same...
Dense small-cell deployments of 5G networks require a wireless backhaul to efficiently connect the small cells to the macro base station (BS). We envision a wireless backhaul architecture where cells are grouped into clusters. One small cell per cluster plays the role of a cluster head connecting the rest of the small cells to the macro cell via a mmWave MIMO link. We formulate the problem of jointly...
MIMO-OFDM is the generally accepted standard in all WLAN systems. However, this method increases training signals required to estimate the propagation matrix of multi-antenna system. In this study, we investigate methods of shortening VHT-LTF training signal in WLAN systems. Simulation results have shown that 1/2 and 3/4 reduction in VHT-LTF training signal is possible while maintaining a considerable...
This paper presents indoor and outdoor experimental results on the achievable throughput for downlink 8-by-16 multi user (MU)-multiple-input multiple-output (MIMO) using 2 sets of user equipment (UE) and carrier aggregation with 8 component carriers in various measurement areas for 5G radio access. In the presence of four centralized antenna units, the throughput performance is evaluated using the...
At vehicular speeds, the contact time during which a mobile node is in range of a fixed road side unit (RSU) is short. While this is not an issue if the RSU only needs to deliver textual information such as traffic updates, short contact times become problematic when transmitting a large amount of information. For instance, an RSU may need to deliver high volumes of local navigation data for an augmented...
In Cognitive Radio Networks (CRNs), the spectrum underlay approach enables primary and secondary networks to transmit simultaneously, as long as the interference from the secondary network to the primary network is below certain threshold. As the recent advancement of the underlay approach, the transparent coexistence exploiting MIMO interference cancellation was proposed. Previous works assume that...
Real-time beam-steering of highly directive antennas at mmWave spectrum under unpredictable propagation environments remains a highly elusive challenge for the upcoming 5G era. Reconfigurable and multifunctional mobile 5G antenna and RF architectures which are desired to achieve sufficient QoS introduce additional technical and economic costs which may outweigh the benefits. This paper investigates...
The paper studies two resource allocation strategies (GRID, anti-EMI) for multi-user OFDMA systems. These strategies are evaluated after being compared with the Round Robin and the FFR strategy in terms of mean throughput and mean dissipated power. All investigated strategies assign resources without Channel State Information (CSI), while both GRID and anti-EMI inherently combat Co-Channel Interference...
This paper investigates a three-node cooperative wireless powered communication system consisting of a multi-antenna hybrid access point (H-AP), a single-antenna relay and a single-antenna user. The H-AP first beams energy to the energy constrained relay and user in the downlink and then the relay assists the user using the harvested power for information transmission in the uplink. To maximize the...
This paper investigates multi-user multi-input multi- output cognitive wireless powered communication networks (WPCN), in which a secondary WPCN shares spectrum with a primary wireless information transfer system. A typical WPCN consists of two different phases. In the first downlink phase, a hybrid access point (H-AP) transfers energy to charge users, and then in the subsequent uplink phase, the...
Software Defined Networking has been adopted to improve data center network efficiency. In SDN, the controllers are responsible for exchanging information with the switches to perform specific operations such as data forwarding. The transmission of control traffic usually uses networks different from data networks. However, building an additional wired network for the control traffic leads to high...
Mobile gadgets including smartphones and laptops nowadays support both Wi-Fi and Bluetooth together. The two protocols coexist in the 2.4GHz ISM band while sharing a single antenna in order to meet constraints on form-factor. We call this kind of devices "Dual- stack devices" in this paper. Since Wi-Fi and Bluetooth on dual-stack devices work in TDM (Time Division Multiplexing) manner, the...
This paper proposes an energy-efficient resource allocation scheme for a wireless power transfer (WPT) enabled multi-user massive MIMO system with imperfect channel estimation. In the considered system, the users who have data to be transmitted only can be empowered by the WPT in the downlink from a base station (BS) with a large scale of multiple antennas. The problem of optimizing the...
In this paper, we investigate resource optimization for energy-efficient data transmissions in a multi-cell massive multiple-input multiple-output (MIMO) system with zero-forcing (ZF) detectors. We optimize the number of active antennas per BS so as to maximize the energy efficiency (EE) of uplink data transmissions. To model the bit-per-joule EE objective, we consider throughput rate and power expenditure...
System latency is one key metric that guides LTE design. Shortening TTI by reducing subframe length along with backward compatibility design can bring significant latency gains for legacy LTE systems. In general, it is believed that the shorter TTI is, the more gain can be achieved. However, due to the hardware limitation as well as the implementation complexity, it is not easy for ultra-short TTI...
In the future 5G networks, deploying ultra-dense smallcells for enhancing the spectrum utilization and network throughput is expected. Moreover, the advanced techniques proposed in LTE-A, the carrier aggregation (CA) and the coordinated multi-point (CoMP), can further improve the network throughput. For maximizing the network throughput, we introduce the software-defined network (SDN) architecture...
The LTE network is usually deployed with adjacent cells using the same frequency band, which significantly improves the frequency utilization efficiency. However, the cell-edge users may suffer throughput loss due to severe inter-cell interference (ICI). With the rapid grow of user terminals in LTE networks, ICI levels are rising and ICI becoming the dominant factor of the network capacity. Coordinated...
This paper proposes a subframe shift method to provide the full-duplex operation for the full-duplex base station (BS) in the current time-division long term evolution (TD-LTE) systems. For the full-duplex operation using the proposed subframe shift, we also propose a frame structure for the simultaneous transmission and reception of full-duplex BS operating in the current TD-LTE system and a signaling...
In this paper, we consider a decoded-and-forward (DF) energy-harvesting system with multiple antennas in the presence of transmit hardware impairments. The relays are energy-constrained nodes that collect energy from the source signals using time-switching architecture. Two partial relay selection (PRS) schemes that are PRS-1 and PRS-2 are employed for simplifying the relay-selection complexity. In...
In this paper, we investigate the inter-cell interference mitigation through mode selection of coordinated multi-point (CoMP) techniques in downlink LTE-A networks. The proposed scheme selects the single-cell (SC) or coordinated beamforming (CB) or joint processing (JT) transmission mode according to interference level to maximize the sum rate. We propose a low complexity algorithm which takes full...
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