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A novel multiple-input multiple-output (MIMO) channel-diagonalization design is proposed for non-simultaneous two-way relaying (NS-TWR). Unlike conventional TWR, the base station in NS-TWR serves two different users - a transmit-only user and a receive-only user. The receive-only user experiences back-propagating interference (BI). The proposed design, which uses linear receivers, cancels the BI and...
In this paper, we study the interdependency between leakage reduction and transmit power control for rate maximization in leakage based precoding (LBP) for a multi user multiple-input multiple-output (MU-MIMO) scenario. We propose a LBP scheme which provides the rate optimal precoding for each MIMO link under a joint leakage and transmit power constraint and derive an iterative closed form solution...
The paper considers the issue of activating inactive terminals by control signaling in the downlink in a massive MIMO system. There are two basic difficulties with this. First, the lack of CSI at the transmitter. Second, the short coherence interval, which limits the number of orthogonal pilots in the case of many antennas. The proposed scheme deals with these issues by repeating the transmission...
In this paper, we develop a novel framework for optimizing data routes, subcarrier schedules and power allocations in generic half-duplex interference-limited multicarrier networks. In this framework each subcarrier can be both reused and time-shared by multiple nodes. Thus, this framework subsumes designs in which time-sharing and frequency-reuse are considered separately, and can therefore offer...
In this paper we explore the distortion performance of distributed estimation schemes in wireless sensor networks (WSNs) in the presence of an eavesdropper. The sensors use an uncoded amplify and forward scheme to transmit their observations to the fusion center (FC), which at the same time can be overheard by the eavesdropper. Both the FC and the eavesdropper reconstruct a minimum mean squared error...
In future cellular networks, self-organizing relaying terminals (RTs) are expected to play a crucial role in assisting the communication between base stations and wireless terminals (WTs), which include, not only active user terminals, but also machine-type communication devices. In the absence of channel quality indicators, the effective utilization of RTs requires a mechanism by which these RTs...
Millimeter wave (mmWave) cellular systems will enable ultra high data rates by communicating over the large bandwidth available in mmWave frequencies. To overcome the channel propagation characteristics in this frequency band, large antenna arrays need to be deployed at both the base station and mobile users. While these large arrays provide sufficient beamforming gains to meet the required link margins,...
We study secure communication in which two confidential messages are transmitted over a broadcast channel to two legitimate receivers, while keeping an eavesdropper ignorant. Each legitimate receiver is interested in decoding one confidential message, while having the other one as side information. In order to measure the secrecy of the communication, we investigate two different secrecy criteria:...
In this paper, we propose a structured linear interference alignment scheme that can achieve 2 degrees of freedom in the 3-cell downlink network with arbitrary time-invariant channels using only local feedback. The scheme employs a finite number of channel extensions and results in an equivalent channel matrix that is 2-level decomposable. The linear precoders at the transmitters are constructed from...
Multi-subcarrier modulation (MSM), known as a popular free-space optical (FSO) modulation technique, is preferred over the on-off keying (OOK) that typically requires an adaptive threshold and the pulse position modulation (PPM) that relies on accurate synchronisation. MSM is, however, criticized for its low power efficiency, and we thus focus on a power-efficient constellation design to increase...
In order for the large-scale realization of vehicular networks to be feasible, the problem of congestion control must be addressed to ensure the reliability of safety applications. The latter rely on single-hop broadcasts of safety packets in the control channel to acquire up-to-date knowledge of the local neighbourhood. However, high transmission ranges of onboard radios and the highly dynamic mobility...
We consider a multiple antenna full-duplex (FD) bi-directional (point-to-point) communication system with a limited analog domain self-interference cancellation capability. The effect of the residual self-interference resulting from independent and identically distributed (i.i.d.) channel estimation errors and limited dynamic ranges of the transmitters and receivers is studied in the digital domain...
The use of soft information instead of hard bits has been widely adapted in signal processing for digital communication to improve the reliability of data transmission by techniques like turbo equalization, turbo decoding, or LDPC codes. For future mobile networks employing a centralized architecture in which the antenna and the baseband processing are separated by an additional fronthaul channel...
In this paper, we propose a new method for bias correction in the simulation of random wireless ad-hoc networks (WANETs), when the distribution of the node locations is modeled as a Poisson-Point-Process (PPP). The aggregate interference is the main limiting factor in WANETs, and dominates the achievable rate and thus also the network capacity. In the proposed method, a bias correction constant is...
Next generation wireless communication systems are pushing the limits of both energy efficiency and spectral efficiency. This presents a challenge to other functions in the receiver such as frame synchronization. In this paper we examine the trade-off between increased complexity and the improvement in energy and spectral efficiency of code-aided frame synchronization. Parallel and serial approaches...
Two-way relaying networks (TWRNs) allow for more bandwidth efficient use of the available spectrum since they allow for simultaneous information exchange between two users with the assistance of an intermediate relay node. However, due to superposition of signals at the relay node, the received signal at the user terminals is affected by multiple impairments, i.e., channel gains, timing offsets, and...
This paper considers a half-duplex multi-way relay (MWR) network where K users exchange messages among themselves with the assist of a relay. The relay is equipped with N antennas and all the users are each equipped with M antennas. The rate region of the network is first characterized by the cut-set bound, and then the degree-of-freedom (DoF) is computed. It is shown that the maximum DoF of the MWR...
We present a joint estimator of the time-of-arrival (TOA) and angle-of-arrival (AOA) for impulse radio ultra-wideband (IR-UWB) localization systems in which an antenna array is employed at the receiver and multiuser (MUI) interference exists. The proposed method includes 3 steps: (1) time-alignment and averaging to reduce the power level of the MUI and background noise; (2) preliminary TOA estimation...
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