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Understanding circuit-level manipulations that affect the brain’s capacity for plasticity will inform the design of targeted interventions that enhance recovery after stroke. Following stroke, increased contralesional activity (e.g. use of the unaffected limb) can negatively influence recovery, but it is unknown which specific neural connections exert this influence, and to what extent increased contralesional activity affects systems- and molecular-level biomarkers of recovery. Here, we combine optogenetic photostimulation with optical intrinsic signal imaging to examine how contralesional excitatory activity affects cortical remodeling after stroke in mice. Following photothrombosis of left primary somatosensory forepaw (S1FP) cortex, mice either recovered spontaneously or received chronic optogenetic excitation of right S1FP over the course of 4 weeks. Contralesional excitation suppressed perilesional S1FP remapping and was associated with abnormal patterns of stimulus-evoked activity in the unaffected limb. This maneuver also prevented the restoration of resting-state functional connectivity (RSFC) within the S1FP network, RSFC in several networks functionally distinct from somatomotor regions, and resulted in persistent limb-use asymmetry. In stimulated mice, perilesional tissue exhibited transcriptional changes in several genes relevant for recovery. Our results suggest that contralesional excitation impedes local and global circuit reconnection through suppression of cortical activity and several neuroplasticity-related genes after stroke, and highlight the importance of site selection for targeted therapeutic interventions after focal ischemia.

In this article, we investigate the problem of distributed coherent beamforming in wireless networks where multiple distributed transmitters adjust the phases of their signals to form a directional and targeted communication link to a client receiver. The quality-of-service (QoS) and security are key components of robust and secure wireless networks. Although the security can be improved by exploiting information about potential adversaries, such information may not be available in practical networks since the adversaries are often passive. Therefore, we introduce transmission strategies which not only send a confidential message by forming a beam towards the client but also broadcast interference with the aim of obfuscating adversaries without having any information about them. Since the interference may degrade the QoS of the client, the transmitters radiating the interference steer a null to the client to alleviate the interference. We develop two algorithms. The first assumes that a subset of the transmitters send the confidential message in the direction of the client via coherent beamforming. Then, the others transmit interference while creating a null towards the client. In the second, each node transmits both the confidential message and interference simultaneously. Two different client feedback scenarios are considered, two-bit and rich feedback. Both of the proposed algorithms can be performed in a fully distributed manner without any knowledge about potential adversaries. Numerical simulations in both microwave and low-very high frequency (low-VHF) bands validate the effectiveness of the proposed schemes.

We present new applications on $q$-binomials, also known as Gaussian binomial coefficients. Our main theorems determine cardinalities of certain error-correcting codes based on Varshamov-Tenengolts codes and prove a curious phenomenon relating to deletion sphere for specific cases., Comment: 17 pages, 2 figures

In this paper, we study a wireless network where multiple distributed transmitters control the phases of their signals so that they can be constructively combined at a client receiver. Unlike centralized beamforming with co-located and phase-synchronized antennas, geographically separated transmitters experience phase offsets caused by the individual local oscillators. In practical scenarios, the transmitters should not be placed too close to each other in order to alleviate mutual coupling effects and extend the coverage region. In this regard, we model the spatial distribution of the transmitters as a β -Ginibre point process that models the repulsive feature. We investigate two types of transmission strategies: (i) Transmitter selection in which the client selects the transmitter providing the highest received power at the client, and (ii) Coherent beamforming in which multiple transmitters send their signals simultaneously to the client in the presence of phase offsets among the transmitters. We introduce the exact expression of the coverage probability of the transmitter selection method. Also, we derive an approximation of the coverage probability of the coherent beamforming scheme by leveraging two scaling factors that respectively capture the impacts of the phase offsets and the degree of repulsion on the coverage probability. From numerical simulations, we validate the accuracy of our analysis.

This paper focuses on the development of energy efficient hybrid networks consisting of radio frequency (RF) base stations (BSs) and visible light communication (VLC) BSs. More specifically, since the quality-of-service and energy cost are key parameters in designing energy efficient networks, this paper optimizes the RF BS and VLC BS intensities to minimize the area power consumption (APC) under an outage probability constraint. Using stochastic geometry, approximations of the outage probability of VLC networks, which are applicable to an arbitrary field-of-view at photodiodes and present low computational complexities, are first introduced. Leveraging the derived analytical results, a low complexity algorithm to find the VLC BS intensity that minimizes the APC of VLC networks is then proposed. Furthermore, algorithms to identify the intensities of RF BSs and VLC BSs for energy efficient hybrid RF/VLC networks via one-dimensional search methods are also developed. The numerical simulations corroborate the tightness of the approximations on the outage probability and confirm that the proposed algorithms exhibit almost identical performances as the algorithms that exhaustively search the optimal BS intensities. Finally, it is shown that the hybrid RF/VLC networks achieve a lower outage probability with a reduced APC compared to the RF-only networks and VLC-only networks.

In this paper, we investigate a wireless network where multiple distributed transmitters adjust the phases of their signals so that they can be constructively added at an intended receiver (client). Unlike conventional beamforming with co-located and phase-synchronized antennas, geographically separated transmitters may have phase offsets induced by individual local carrier oscillators, that pose a challenge for coherent distributed beamforming. This is especially true for transmitters that are far apart, when distributed clock synchronization protocols may be more difficult to implement. There may also be a desired spatial repulsion among the positions of the transmitters in order to mitigate mutual coupling effects and extend the coverage region. In this regard, we analyze the performance of distributed beamforming with phase offsets by modeling the spatial distribution of the transmitters as a $\beta$-Ginibre point process that models the repulsive behavior. We consider two transmission strategies: (i) Transmitter selection in which the client chooses the transmitter providing the highest received power at the client, and (ii) Coherent beamforming in which multiple transmitters simultaneously send their signals to the client. From numerical simulations, we examine the impact of the phase offsets on the performance and confirm the accuracy of our analysis. It is shown that even with significant phase offset errors, employing coherent beamforming can be an effective strategy.

This chapter investigates resource management in 5G and beyond (5G+) heterogeneous networks (HetNets) for multi-homing connections. In such HetNets, channels from different networks vary at different timescales, which impacts resource allocation for multi-homing connections. We consider one application scenario for a 5G+ HetNet that integrates radio frequency (RF) and visible light base stations (BSs). In such a setting, RF channel gains vary faster than VLC channels due to small scale fading. Hence, to properly manage the HetNet resources at different timescales, we leverage multi-agent Q-learning to interact with the dynamics of wireless environments and present an online two-timescale power allocation policy that optimizes the transmit powers at the RF and optical BSs to ensure quality-of-service (QoS) satisfaction. Simulation results demonstrate the effectiveness of the introduced Q-learning based power allocation policy.

The current developments in the fifth generation and beyond (5G+) mobile networks focus on moving from the increasingly congested radio frequencies (RF) to higher frequency bands such as millimeter wave (mmWave), Terahertz, and Visible Light bands. Among these high frequency options, visible and infrared lights represent a strong candidate owing to the widely deployed lighting systems. Due to their distinct wave propagation characteristics, efficient integration of RF with such high frequency bands is needed for better reliability and high throughput. This introductory chapter presents an overview on RF and light (optical)-based wireless networks. This chapter highlights existing research efforts along with the limitations that should be addressed from planning and operational perspectives to enable a smooth integration of RF and optical networks in mobile environments.

This chapter investigates resource management in 5G and beyond (5G+) heterogeneous networks (HetNets) for multi-mode connections. To ensure a reliable link with quality-of-service (QoS) guarantee in terms of network delay and throughput, vertical handovers are triggered within the HetNet. A cross-layer data-driven approach is adopted to reach optimal handover decisions and tackle the challenges associated with mobility and reliability. We consider the application scenario of a HetNet consisting of an overlapped coverage of radio frequency (RF) and optical wireless communication (OWC) to support human connectivity in the 5G+ indoor HetNets. Using the dataset presented in the previous chapter, we present a data-driven algorithm that predicts abrupt outages in line-of-sight (LOS) optical links and evaluates the optical channel quality through deep learning. Given the resulting LOS link outage prediction in OWC, a reinforcement learning-based approach is introduced to implement optimal vertical handover decisions with QoS guarantee. This handover decision algorithm learns to make a trade-off between the outage risk and the cost of excessive handovers. Numerical results demonstrate considerable improvement in overall latency and handover rate under indoor mobility for bi-directional links.

High frequency bands in 5G and beyond (5G+) heterogeneous networks (HetNets) are challenged by link instabilities induced by users’ mobility, which are attributed to the wave propagation characteristics in such bands. Hence, good understanding of channel characteristics in dynamic high frequency bands plays a vital role in developing robust resource management strategies in 5G+ HetNets. Unfortunately, it is quite difficult to collect accurate indoor channel data in dynamic environments. In addition, indoor trajectory datasets are not publicly available. In order to address such limitations, this chapter introduces an analytical framework to model realistic human mobility patterns in dynamic indoor environments. The presented model abstracts the nature of human behavior by integrating both macro and micro mobility patterns. These patterns are then used to realize the spatio-temporal characteristics of wireless channels under long-term environment-confined mobility. We apply this framework to characterize the wireless indoor channel for optical wireless networks whose downlink adopts visible light and uplink adopts infrared light. Our results demonstrate that the indoor layout and the user’s environment-confined mobility pattern significantly impact the line-of-sight (LOS) dynamics but present limited impact on non-LOS components. The presented framework can be used to generate realistic wireless channel datasets that could be further employed to develop data-driven resource management strategies in 5G+ HetNets.

This chapter focuses on the deployment of energy efficient 5G and beyond (5G+) heterogeneous networks (HetNets) that employ both radio frequency (RF) and high frequency bands. Since the quality-of-service and energy cost are key parameters in designing energy efficient networks, in this chapter the base station (BS) densities for different frequency bands are optimized to minimize the area power consumption (APC) by taking into account an outage probability constraint. The considered setting assumes integration of RF BSs with optical BSs. Using stochastic geometry tools, approximations of the outage probability of optical visible light communication (VLC) networks, which are applicable to an arbitrary field-of-view (FOV) at photodiodes (PDs) and present low computational complexity, are first proposed. Leveraging the derived analytical results, a low complexity algorithm to find the optical BS density that minimizes the APC of VLC networks is then recommended. Reduced complexity algorithms that rely on one-dimensional searching approaches and that identify the optimal densities of RF BSs and optical BSs to secure energy efficiency of RF-optical HetNets are also proposed. Numerical simulations corroborate the tightness of the approximations proposed for the outage probability and confirm that the introduced algorithms exhibit almost identical performance as the algorithms that exhaustively search the optimal densities of BSs. It is shown that the RF-optical HetNets achieve a lower outage probability and a more reduced APC compared to the RF-only networks and VLC-only networks.