Band assignment is an important function in multi-band heterogeneous networks. Most of the existing works have considered the rate of user equipment (UE) as a key criterion for the band assignment. However, the power consumption at the mmWave band is significantly higher than the Sub-6 GHz band, which is particularly significant because the UE battery power is limited. In this context, we design a novel long short term memory (LSTM) aided energy efficient band assignment system for a moving UE. Corresponding to the realistic scenario, we apply a timeseries split based approach to train and test the model. The proposed policy is validated on the publicly available ‘DeepMIMO’ dataset. Research findings shows that the RMSE of predicted rate using timeseries split approach is much less than the conventional approach. Moreover, with proposed scheme, the median energy efficiency is 56.30% higher as compared to the case when energy usage is not considered in the bandswitching decision, while the median rate with our proposed scheme reduces only by 13.81%.

The high frequency communication bands (mm Wave and sub- THz) promise tremendous data rates, however, they also have very high power consumption which is particularly significant for battery-power-limited user-equipment (UE). In this context, we design an energy aware band assignment system which reduces the power consumption while also achieving a target sum rate of$M$in$T$time-slots. We do this by using 1) Rate forecaster(s); 2) Channel forecaster(s) which forecasts$T$direct multistep ahead using a stacked long-short term memory (LSTM) architecture. We propose an iterative rate updating algorithm which updates the target rate based on current rate and future predicted rates in a frame. The proposed approach is validated on the publicly available ‘DeepMIMO’ dataset. We find that the rate forecaster based approach performs better than the channel forecaster. Furthermore, LSTM based predictions outperforms well celebrated Transformer predictions in terms of normalized root mean square error (NRMSE) and normalized mean absolute error (NMAE). Research findings reveals that the power consumption with this approach is ~300 mW lower compared to a greedy band assignment at a 1.5Gb/s target rate.

Principles of Wireless Communication (PWC) is an upper-level Electrical and Computer Engineering (ECE) elective taught at Olin College, an undergraduate-only engineering institution that is known for its small size and project-based learning (PBL) curriculum. PWC takes a top-down approach to teaching where students develop an understanding of wireless communications principles by transmitting and receiving data across physical and simulated channels. The course is run in a studio-like environment; class time is used collaboratively to complete three labs using MATLAB and software-defined radios (SDRs). After each lab is completed, teams write a report which details their implementation, the theory behind the algorithms they wrote, and relevant quantitative benchmarks like constellation plots, signal-to-noise ratio (SNR) calculations, and bit error rate calculations. Labs 1 and 2 entail implementations of binary phase-shift keying (BPSK) and quadrature phase-shift keying (QPSK) along with multiple-input multiple-output (MIMO) system simulations. Lab 3 culminates in students implementing orthogonal frequency-division multiplexing (OFDM) from first principles and communicating data over the air. OFDM is a standard multicarrier scheme used in WiFi and Long-Term Evolution (LTE) systems among others. By implementing OFDM according to the required specifications, students execute a real-world project and apply self-directed learning techniques to acquire the relevant technical skills much like one would in an industry or research position. Throughout this process, the students gain a deep familiarity with the OFDM algorithm while preparing data at specific points in the processing pipeline for meaningful visualization. While OFDM is often covered in an introductory graduate-level course, in this course offering, undergraduates are exposed to the OFDM algorithm with a top-down, problem-based learning approach that ties together fundamentals of electrical engineering with a real-world context.

We present a hybrid Visible-Light Communication (VLC) and Radio-Frequency (RF) communication system based on an open-source platform, which is integrated at the Medium-Access-Control (MAC) layer. Downlink data transmissions of the system use VLC with a commercially available lighting source, and uplink transmissions use RF. An auxiliary, low-power infra-red (IR) control channel is also implemented on the uplink to transmit acknowledgement signals for VLC data packets. We experimentally demonstrate that the system has low latency, and can achieve end-to-end TCP/IP throughput comparable to single antenna, 20 MHz 802.11 links when operated in isolation, and provide a 70% increase in total throughput when operating concurrently and in the same channel as a legacy 802.11 TCP/IP link. We also show that the RF signals of our system can achieve fair usage of the RF spectrum with an independent 802.11 network with UDP transmissions. In addition to addressing some practical challenges of implementing hybrid, asymmetric VLC-RF systems, our system is open-source, and requires no custom components and can serve as a reference for researchers who wish to construct and analyze hybrid VLC-RF systems.

Quantitative Engineering Analysis is an eight-credit, two semester, experiential project-based course at F. W. Olin College of Engineering, for second and third semester engineering students. The course is designed to improve students facility and confidence in choosing and using the power tools of analysis in solving engineering problems. The goal of this workshop is to expose faculty from other institutions to the student experience in the first semester of this class, where participants will work through a number of activities based on activities done by students in the course. These goals align with the goals of FIE as we aim to expose participants to innovative teaching practice on multiple fronts including experiential, project-based learning of fundamental mathematics, physics and engineering material, approaches to teaming for students as well as interdisciplinary faculty, and scaffolding self-directed learning. Additionally, we will work with participants to initiate designs of activities which draw on these ideas that are adapted to the contexts of their home institutions.

This work-in-progress, innovative-practice paper describes the creation and first two iterations of an experimental course which aims to develop a process-focused approach to integrated quantitative engineering analysis in early stage engineering students. The goal of this two-semester course is to improve the confidence and competence of our students in choosing and applying the tools of quantitative analysis to solve practical problems throughout their time in college and beyond, including in other course projects, senior capstone experiences, internships and in their careers. The course is led by an interdisciplinary team of faculty, in a project-based format, including in the presentation of fundamental concepts in mathematics. The course is run studio style, with emphasis placed on the process of engineering, improving students' self-directed learning skills, and encouraging peer and near-peer learning. Overall, we observed a high level of engagement in the course, with student-chosen final projects that involved significant analysis and self-directed learning of new tools and approaches.

We consider a user-centric co-operative cellular network, where base stations (BSs) close to a mobile co-operate to detect its signal using a (joint) linear minimum-mean-square-error receiver. The BSs are at arbitrary positions and mobiles are modeled as a planar Poisson point process (PPP). Combining stochastic geometry and infinite-random-matrix theory, we derive a simple expression for the spectral efficiency of this complex system as the number of antennas grows large. This framework is applied to BS locations from PPPs and hexagonal grids and is validated through Monte Carlo simulations. The results reveal the influence of tangible system parameters, such as mobile and BS densities, number of antennas per BS, and number of co-operating BSs on achievable spectral efficiencies. Among other insights, we find that for a given BS density and a constraint on the total number of co-operating antennas, all co-operating antennas should be located at a single BS. On the other hand, in our asymptotic regime, for the same number of co-operating antennas, if the network is limited by the area density of antennas, then the number of co-operating BSs should be increased with a fewer antennas per BS.

We derive a closed-form expression for the throughput in the uplink of a cooperative massive MIMO system. We consider a network where a cluster of base stations co-operate to detect signals from mobiles using a linear minimum-mean-square error receiver. A user-centric clustering approach is assumed, where the cluster that detects the signals from each mobile is composed of the K base stations that are closest to the mobile. The analysis combines stochastic geometry and infinite random matrix theory. We assume that base stations and mobiles are distributed as independent Poisson Point Processes on the plane. Using an asymptotic analysis, a closed-form expression for the spectral efficiency is derived, which is verified by simulations to be accurate even for a moderate number of antennas. This result helps us understand the influence of tangible system parameters such as mobile and base-station densities, number of antennas per base station, and number of co-operating base stations on spectral efficiencies. Our findings show that for a given number of cooperating antennas, it is optimal to have all cooperating antennas in a single base station. But, if the area density of antennas is also limited, then the number of co-operating base stations should be increased instead.

The uplink of interference-limited cellular networks with base stations that have large numbers of antennas and use linear Minimum-Mean-Square Error (MMSE) processing with power control is analyzed. Simple approximations, which are exact in an asymptotic sense, are provided for the spectral efficiencies (b/s/Hz) of links in these systems. It is also found that when the number of base-station antennas is moderately large, and the number of mobiles in the entire network is large, correlations between the transmit powers of mobiles within a given cell do not significantly influence the spectral efficiency of the system. As a result, mobiles can perform simple power control (e.g. fractional power control) that does not depend on other users in the network, reducing system complexity and improving the analytical tractability of such systems.

The uplink of a wireless network with base stations distributed according to a Poisson Point Process (PPP) is analyzed. The base stations are assumed to have a large number of antennas and use linear minimum-mean-square-error (MMSE) spatial processing for multiple access. The number of active mobiles per cell is limited to permit channel estimation using pilot sequences that are orthogonal in each cell. The cumulative distribution function (CDF) of the spectral efficiency of a randomly located link in a typical cell of such a system is derived when accurate channel estimation is available. A simple bound is provided for the spectral efficiency when channel estimates suffer from pilot contamination. The results provide insight into the performance of so-called massive Multiple-Input-Multiple-Output (MIMO) systems in spatially distributed cellular networks.

In this paper, the impact of interferers that are not synchronized in frequency is investigated in multi-antenna OFDM systems. Exact closed-form expressions for the outage probabilities are derived for two spatial linear receivers: the matched-filter (MF) receiver and the linear minimum-mean-square-error (LMMSE) receiver, assuming correlated frequency-selective Rayleigh fading channels and carrier frequency offsets (CFOs) between each interferer and the receiver. It is found that the CFOs have a negligible impact on the performance of the MF receiver, but a non-negligible impact on the performance of the LMMSE receiver for a range of realistic parameters. This theoretical analysis reveals valuable insights into practical implementation of such systems, and enables system designers to quantify the impact of the CFOs on the performance of the MF receiver and the LMMSE receiver.

A technique is presented to characterize the signal-to-interference-plus-noise ratio (SINR) of a representative link with a multiantenna linear minimum-mean-square-error receiver in a wireless network with transmitting nodes distributed according to a doubly stochastic process, which is a generalization of the Poisson point process. The cumulative distribution function of the SINR of the representative link is derived, assuming independent Rayleigh fading between antennas. Several representative spatial node distributions are considered, including networks with both deterministic and random clusters, strip networks (used to model roadways, for example), hardcore networks and networks with generalized path-loss models. In addition, it is shown that if the number of antennas at the representative receiver is linearly increased with the nominal node density, the signal-to-interference ratio converges in distribution to a random variable that is nonzero in general and a positive constant in certain cases. This result indicates that to the extent that the system assumptions hold, it is possible to scale such networks by increasing the number of receiver antennas linearly with the node density. The results presented here are useful in characterizing the performance of multiantenna wireless networks in more general network models than what are currently available.

A technique is presented to characterize the Signal-to-Interference-plus-Noise Ratio (SINR) on a wireless link with a multi-antenna linear Minimum-Mean-Square Error (MMSE) receiver in the presence of spatially clustered interferers. The interferers could be distributed as either a single, randomly located cluster or a Poisson cluster process. Explicit expressions are provided for both the Thomas and Matern cluster processes of interferers which can be evaluated numerically using standard numerical integration tools. These results generalize previously derived results for non-homogenous Poisson networks (where the spatial non-homogeneity is deterministic) to networks where the non-homogeneity is random.

The spectral efficiency of a representative uplink of a given length, in interference-limited, spatially-distributed wireless networks with hexagonal cells, simple power control, and multiantenna linear Minimum-Mean-Square-Error receivers is found to approach an asymptote as the numbers of base-station antennas N and wireless nodes go to infinity. An approximation for the area-averaged spectral efficiency of a representative link (averaged over the spatial base-station and mobile distributions), for Poisson distributed base stations, is also provided. For large N, in the interference-limited regime, the area-averaged spectral efficiency is primarily a function of the ratio of the product of N and the ratio of base-station to wireless-node densities, indicating that it is possible to scale such networks by linearly increasing the product of the number of base-station antennas and the relative density of base stations to wireless nodes, with wireless-node density. The results are useful for designers of wireless systems with high inter-cell interference because it provides simple expressions for spectral efficiency as a function of tangible system parameters like base-station and wireless-node densities, and number of antennas. These results were derived combining infinite random matrix theory and stochastic geometry.

A technique to compute the Cumulative Distribution Function (CDF) of the Signal-to-Interference-plus-Noise-Ratio (SINR) for a wireless link with a multi-antenna, Linear, Minimum-Mean-Square-Error (MMSE) receiver in the presence of interferers distributed according to a non-homogenous Poisson point process on the plane, and independent Rayleigh fading between antennas is presented. This technique is used to compute the CDF of the SINR for several different models of intensity functions, in particular, power-law intensity functions, circular-symmetric Gaussian intensity functions and intensity functions described by a polynomial in a bounded domain. Additionally it is shown that if the number of receiver antennas is scaled linearly with the intensity function, the SINR converges in probability to a limit determined by the “shape” of the underlying intensity function. This work generalizes known results for homogenous Poisson networks to non-homogenous Poisson networks.

An asymptotic technique is presented to characterize the bits/symbol achievable on a representative wireless link in a spatially distributed network with active interferers at correlated positions, N receive diversity branches, and linear Minimum-Mean-Square-Error (MMSE) receivers. The models analyzed include analogs to Matern type I and type II networks. It is found that for our network models, with large N, the correlation between interferer positions does not significantly influence the bits/symbol resulting in simple approximations for the data rates achievable in such networks with moderately large numbers of diversity branches.

An asymptotic technique is presented for finding the spectral efficiency of multiantenna links in spatially distributed wireless networks where transmitters have channel-state-information (CSI) corresponding to their target receiver. Transmitters are assumed to transmit independent data streams on a limited number of channel modes which limits the rank of transmit covariance matrices. An approximation for the spectral efficiency in the interference-limited regime as a function of link-length, interferer density, number of antennas per receiver and transmitter, number of transmit streams, and path-loss exponent is derived. It is found that targeted-receiver CSI, which can be acquired with low overhead in duplex systems with reciprocity, can increase spectral efficiency several fold, particularly when link lengths are large, node density is high, or both. Additionally, the per-link spectral efficiency is found to be a function of the ratio of node density to the number of receiver antennas, and it can often be improved if nodes transmit using fewer streams. These results are validated for finite-sized systems by Monte-Carlo simulation and are asymptotic in the regime where the number of users and antennas per receiver approach infinity.

An asymptotic technique is developed to find the Signal-to-Interference-plus-Noise-Ratio (SINR) and spectral efficiency of a link with N receiver antennas in wireless networks with non-homogeneous distributions of nodes. It is found that with appropriate normalization, the SINR and spectral efficiency converge with probability 1 to asymptotic limits as N increases. This technique is applied to networks with power-law node intensities, which includes homogeneous networks as a special case, to find a simple approximation for the spectral efficiency. It is found that for receivers in dense clusters, the SINR grows with N at rates higher than that of homogeneous networks and that constant spectral efficiencies can be maintained if the ratio of N to node density is constant. This result also enables the analysis of a new scaling regime where the distribution of nodes in the network flattens rather than increases uniformly. It is found that in many cases in this regime, N needs to grow approximately exponentially to maintain a constant spectral efficiency. In addition to strengthening previously known results for homogeneous networks, these results provide insight into the benefit of using antenna arrays in non-homogeneous wireless networks, for which few results are available in the literature.

Receivers with N antennas in single-hop, ad-hoc wireless networks with nodes randomly distributed on an infinite plane with uniform area density are studied. Transmitting nodes have single antennas and transmit simultaneously in the same frequency band with power P that decays with distance via the commonly-used inverse-polynomial model with path-loss- exponent (PLE) greater than 2. This model applies to shared spectrum systems where multiple links share the same frequency band. In the interference-limited regime, the average spectral efficiency of a representative link E[C] (b/s/Hz/link) is found to grow as log(N) and linearly with PLE, and its variance decays as 1/N. The average signal-to-interference-plus-noise-ratio (SINR) on a representative link is found to grow faster than linearly with N. With multiple-input-multiple-output (MIMO) links where transmit nodes have multiple antennas without Channel- State-Information, it is found that E[C] in the network can be improved if nodes transmit using the optimum number of antennas compared to the optimum selfish strategy of transmitting equal-power streams from every antenna. The results are extended to random code-division-multiple-access systems where the optimum spreading factor for a given link length is found. These results are developed as asymptotic expressions using infinite random matrix theory and are validated by Monte-Carlo simulations.