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Exploiting full-duplex (FD) technology on base stations (BSs) is a promising solution to enhancing the system performance. Motivated by this, we revisit a full-duplex base station (FD-BS) aided OFDMA system, which consists of one BS, several uplink/downlink users and multiple subcarriers. A joint 3-dimensional (3D) mapping scheme among subcarriers, down-link users (DUEs), uplink users (UUEs) is considered...
In this paper, we experimentally validate the functionality of a developed algorithm for spectrum cartography using adaptive Gaussian radial basis functions (RBF). The RBF are strategically centered around representative centroid locations in a machine learning context. We assume no prior knowledge about neither the power spectral densities (PSD) of the transmitters nor their locations. Instead, the...
Unmanned aerial vehicle (UAV) is attractive for localization where global positioning system (GPS) satellites are uncapturable and wireless anchor nodes are unavailable. The advantage of localization using UAVs is their movability, that is, even when only few UAVs are available, if each of them ranges a target node many times from different locations, the localization accuracy can be improved, because...
In this paper, we consider a heterogeneous cellular network with a macrocell and several femtocells. In each femtocell, the femto base station (FBS) serves one femto user (FU), which is capable of simultaneous wireless information and power transfer (SWIPT) energy harvesting (EH) in a power splitting manner. All FBSs suppress their interference to macro users (MUs) via a interference power constraint...
In millimeter-wave communication systems with large-scale antenna arrays, conventional digital beamforming may not be cost-effective. A promising solution is the implementation of hybrid beamforming techniques, which consist of low-dimensional digital beamforming followed by analog radio frequency (RF) beamforming. This work studies the optimization of hybrid beamforming in the context of a cloud...
The perfect Gaussian integer sequences have been recently used in orthogonal frequency division multiplexing (OFDM) systems and code division multiple access (CDMA) systems. This paper proposes a new construction method, called monomial o-polynomials, to generate the perfect Gaussian integer sequences. The resulting sequences have odd periods and high energy efficiency. Furthermore, the number of...
In this paper, minimum MSE based interference alignment (IA) algorithm is developed for the interfering broadcast channel (IBC), which models the multi-cell downlink system, underlying cognitive radio, device-to-device and other scenarios. The IA precoders and decoders are computed to minimize the MSE. Cascade design is used for IA precoder design, where the first component precoder is obtained by...
Cognitive radio (CR) was proposed in wireless communications to improve spectral efficiency based on the concept of opportunistic spectrum access. Because orthogonal frequency division multiplexing (OFDM) has become the major access technique, an efficient spectrum sensing technique targeted at OFDM-based signals is one of the primary requirements of CR networks. To reduce computational complexity,...
Fast initialization of cognitive radio systems is a key problem in a variety of wireless communication systems, particularly for public safety organizations in emergency crises. In the initialization problem, the goal is to rapidly identify an unoccupied frequency band. In this paper, we formalize the initialization problem within the framework of active hypothesis testing. We characterize the optimal...
The millimeter wave communication is largely affected by distance dependent large scale fading. With the recent improvements in accurate localization techniques, location information can be exploited to improve the network capacity in an mm-wave channel instead of the more computationally extensive channel state information (CSI). We discuss how the classical waterfilling algorithm can be applied...
High-accuracy indoor radio positioning can be achieved by using high signal bandwidths to increase the time resolution. Multiple fixed anchor nodes are needed to compute the position or alternatively, reflected multipath components can be exploited with a single anchor. In this work, we propose a method that explores the time and angular domains with a single anchor. This is enabled by switching between...
Initial access at millimeter wave frequencies is a challenging problem due to hardware non-idealities and low SNR measurements prior to beamforming. Prior work has exploited the observation that mmWave MIMO channels are sparse in the spatial angle domain and has used compressed sensing based algorithms for channel estimation. Most of them, however, ignore hardware impairments like carrier frequency...
In this paper, a novel two-phase orthogonal frequency division multiplexing-index modulation (OFDM-IM)-aided cooperative relaying protocol is proposed for overlay cognitive radio (CR) networks, where the primary and secondary networks work concurrently over the same spectrum band. In the proposed scheme, OFDM-IM technique is used at the secondary user (SU) to split the transmission space into the...
Fifth generation (5G) radio networks are expected to provide remarkable improvements in the user experience due to faster data rates and lower latencies, for example. These kind of enhancements are made possible by several technical advances when compared to the existing networks. In particular, densification of network, device-centric network topology and exploitation of smart antennas, among others,...
In multi-cell massive MIMO systems, estimation accuracy can be severely degraded due to pilot sequences reuse in adjacent cells. This causes inter-cell interference called pilot contamination. An additional challenge is the increase in computational load due to the massive amount of data. It is, therefore, desirable to reduce the number of RF chains. In this paper, we focus on the problem of channel...
In this paper, we design a frequency synchronization method for multiuser orthogonal frequency division multiplexing (OFDM) uplink with a large-scale partly calibrated uniform linear array (ULA) at base station (BS). A beamforming parameter is introduced for each user to mitigate the harmful effect of inter-subarray uncertainties. The proposed method performs carrier frequency offset (CFO) estimation...
In this work, decentralized coordinated scheduling in LTE-Advanced downlink networks is studied, where the base stations abstain from transmitting data on particular frequency/time resources in order to reduce the inter-cell interference experienced by users connected to neighboring base stations. The proposed decentralized scheme is derived with regard to low information exchange between the base...
We investigate secure communication over a channel under two different classes of attacks at the same time: a passive eavesdropper and an active jammer. This scenario is perfectly modeled by the concept of arbitrarily varying wiretap channels (AVWCs). It has been shown that uncorrelated codes are not always capable of overcoming the various jamming attacks. On the other hand, correlated random codes...
We identify phase noise as a bottleneck for the performance of digital self-interference cancellers that utilize a single auxiliary receiver — single-tap digital cancellers — and operate in multipath propagation environments. Our analysis demonstrates that the degradation due to phase noise is caused by a mismatch between the analog delay of the auxiliary receiver and the different delays of the multipath...
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