1,721,269 research outputs found
Multi-antenna aided secrecy beamforming optimization for wirelessly powered HetNets
No full textThe new paradigm of wirelessly powered two-tier heterogeneous networks (HetNets) is considered in this paper. Specifically, the femtocell base station (FBS) is powered by apower beacon (PB) and transmits confidential information to a legitimate femtocell user (FU) in the presence of a potential eavesdropper (EVE) and a macro base station (MBS). In this scenario, we investigate the secrecy beamforming design under three different levels of FBS EVE channel state information (CSI), namely, the perfect, imperfect and completely unknown FBS-EVE CSI. Firstly, given the perfect global CSI at the FBS, the PB energy covariance matrix, the FBS information covariance matrix and the time splitting factor are jointly optimized aiming for perfect secrecy rate maximization. Upon assuming the imperfect FBS-EVE CSI, the worst-case and outage-constrained SRM problems corresponding to deterministic and statistical CSI errors are investigated, respectively. Furthermore, considering the more realistic case of unknown FBS-EVE CSI, the artificial noise (AN) aided secrecy beamforming design is studied. Our analysis reveals that for all above cases both the optimal PB energy and FBS information secrecy beamformings are of rank-1. Moreover, for all considered cases of FBS-EVE CSI, the closed-form PB energy beamforming solutions are available when the cross-tier interference constraint is inactive. Numerical simulation results demonstrate the secrecy performance advantages of all proposed secrecy beamforming designs compared to the adopted baseline algorithms.<br/
Distributed irregular codes relying on decode-and-forward relays as code components
No full textA near-capacity distributed coding scheme is conceived by incorporating multiple relay nodes for constructing a virtual Irregular Convolutional Code (IRCC). We first compute the relay channel’s capacity and then design IRCCs for the source and relay nodes. Extrinsic Information Transfer (EXIT) charts are utilized to design the codes for approaching the achievable capacity of the relay channels. Additionally, we improve the transmit power efficiency of the overall system by invoking both power allocation and relay selection. We found that even a low-complexity repetition code or a unit-memory convolutional code is capable of forming a near-capacity virtual IRCC. The performance of the proposed Distributed IRCC (DIRCC) scheme is shown to be perfectly consistent with that predicted from the EXIT chart. More specifically, the DIRCC scheme is capable of operating within 0.68 dB from the corresponding lower bound of the relay channel capacity, despite the fact that each relay node is exposed to realistic decoding errors due to communicating over imperfect source-relay channels
Efficient Rate-Splitting Multiple Access for the Internet of Vehicles: Federated Edge Learning and Latency Minimization
Full text linkRate-Splitting Multiple Access (RSMA) has recently found favour in the
multi-antenna-aided wireless downlink, as a benefit of relaxing the accuracy of
Channel State Information at the Transmitter (CSIT), while in achieving high
spectral efficiency and providing security guarantees. These benefits are
particularly important in high-velocity vehicular platoons since their high
Doppler affects the estimation accuracy of the CSIT. To tackle this challenge,
we propose an RSMA-based Internet of Vehicles (IoV) solution that jointly
considers platoon control and FEderated Edge Learning (FEEL) in the downlink.
Specifically, the proposed framework is designed for transmitting the unicast
control messages within the IoV platoon, as well as for privacy-preserving
FEEL-aided downlink Non-Orthogonal Unicasting and Multicasting (NOUM). Given
this sophisticated framework, a multi-objective optimization problem is
formulated to minimize both the latency of the FEEL downlink and the deviation
of the vehicles within the platoon. To efficiently solve this problem, a Block
Coordinate Descent (BCD) framework is developed for decoupling the main
multi-objective problem into two sub-problems. Then, for solving these
non-convex sub-problems, a Successive Convex Approximation (SCA) and Model
Predictive Control (MPC) method is developed for solving the FEEL-based
downlink problem and platoon control problem, respectively. Our simulation
results show that the proposed RSMA-based IoV system outperforms the
conventional systems
A low-complexity energy minimization based SCMA detector and its convergence analysis
No full textSparse code multiple access (SCMA) has emerged as a promising non-orthogonal multiple access (NOMA) technique for next generation wireless communication systems. Since the signal of multiple users is mapped to the same resources in SCMA, its detection imposes a higher complexity than that of the orthogonal schemes, where each resource slot is dedicated to a single user. In this paper, we propose a low complexity receiver for SCMA systems based on the radical variational free energy framework. By exploiting the pairwise structure of the likelihood function, the Bethe approximation is utilized for estimating the data symbols. The complexity of the proposed algorithm only increases linearly with the number of users, which is much lower than that of the maximum a posteriori (MAP) detector associated with exponentially increased complexity. Furthermore, the convergence of the proposed algorithm is analyzed and its convergence conditions are derived. Simulation resultsdemonstrate that the proposed receiver is capable of approaching the error probability performance of the conventional message passing based receiver.</p
Near-capacity turbo trellis coded modulation design based on EXIT charts and union bounds
No full textBandwidth efficient parallel-concatenated Turbo Trellis Coded Modulation (TTCM) schemes were designed for communicating over uncorrelated Rayleigh fading channels. A symbol-based union bound was derived for analysing the error floor of the proposed TTCM schemes. A pair of In-phase (I) and Quadrature-phase (Q) interleavers were employed for interleaving the I and Q components of the TTCM coded symbols, in order to attain an increased diversity gain. The decoding convergence of the IQ-TTCM schemes was analysed using symbol-based EXtrinsic Information Transfer (EXIT) charts. The best TTCM component codes were selected with the aid of both the symbol-based union bound and non-binary EXIT charts, for designing capacity-approaching IQ-TTCM schemes in the context of 8PSK, 16QAM, 32QAM and 64QAM modulation schemes
Peritraumatic startle response predicts the vulnerability to develop PTSD-like behaviors in rats: a model for peritraumatic dissociation
No full textPeritraumatic dissociation, a state characterized by alteration in perception and reduced awareness of surroundings, is considered to be a risk factor for the development of post-traumatic stress disorder (PTSD). However, the predictive ability of peritraumatic dissociation is questioned for the inconsistent results in different time points of assessment. The startle reflex is an objective behavioral measurement of defensive response to abrupt and intense sensory stimulus of surroundings, with potentials to be used as an assessment on the dissociative status in both humans and rodents. The present study examined the predictive effect of acoustic startle response (ASR) in different time points around the traumatic event in an animal model of PTSD. The PTSD-like symptoms, including hyperarousal, avoidance, and contextual fear, were assessed 2-3 weeks post-trauma. The results showed that (1) the startle amplitude attenuated immediate after intense footshock in almost half of the stress animals, and (2) the attenuated startle responses at 1 h but not 24 h after stress predicted the development of severe PTSD-like symptoms. These data indicate that the startle alteration at the immediate period after trauma, including 1 h, is more important in PTSD prediction than 24 h after trauma. Our study also suggests that the startle attenuation immediate after intense stress may serve as an objective measurement of peritraumatic dissociation in rats
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