The accurate identification of wireless devices is critical for enabling automated network access monitoring and authenticated data communication in large-scale networks; e.g., IoT networks. RF fingerprinting has emerged as a potential solution for device identification by leveraging the transmitter unique manufacturing impairments of the RF components. Although deep learning is proven efficient in classifying devices based on the hardware impairments, trained models perform poorly due to channel variations. That is, although training and testing neural networks using data generated during the same period achieve reliable classification, testing them on data generated at different times degrades the accuracy substantially. To the best of our knowledge, we are the first to propose to leverage MIMO capabilities to mitigate the channel effect and provide a channel-resilient device classification. For the proposed technique we show that, for Rayleigh channels, blind partial channel estimation enabled by MIMO increases the testing accuracy by up to 40% when the models are trained and tested over the same channel, and by up to 60% when the models are tested on a channel that is different from that used for training.

Recent deep neural network-based device classification studies show that complex-valued neural networks (CVNNs) yield higher classification accuracy than real-valued neural networks (RVNNs). Although this improvement is (intuitively) attributed to the complex nature of the input RF data (i.e., IQ symbols), no prior work has taken a closer look into analyzing such a trend in the context of wireless device identification. Our study provides a deeper understanding of this trend using real LoRa and WiFi RF datasets. We perform a deep dive into understanding the impact of (i) the input representation/type and (ii) the architectural layer of the neural network. For the input representation, we considered the IQ as well as the polar coordinates both partially and fully. For the architectural layer, we considered a series of ablation experiments that eliminate parts of the CVNN components. Our results show that CVNNs consistently outperform RVNNs counterpart in the various scenarios mentioned above, indicating that CVNNs are able to make better use of the joint information provided via the in-phase (I) and quadrature (Q) components of the signal.

Recently, Collective Perception Messages (CPM) that carry additional information about the surrounding environment beyond Basic Safety Messages (BSM) or Cooperative Awareness Messages (CAM) have been proposed to increase the situational awareness for Connected and Automated Vehicles (CAV) in Intelligent Transportation Systems. However, blindly trusting perception information from neighbors that cannot be locally verified is dangerous given the safety impact that erroneous or malicious information might have. This paper addresses the data trust challenge of CPMs, proposing a misbehavior detection scheme called MISO- V (Multiple Independent Sources of Observations over V2X) that leverages the inherently overlapping nature of the perception observations from multiple vehicles to verify the semantic correctness of the V2X data and improve the data trust and robustness of V2X systems. CPM-enabled CAVs are implemented and MISO-V performance is evaluated in CARLA-based simulation tool, where falsified V2X packets presenting a ghost car are injected in a suburban T-junction scenario with other cars. The results show that MISO- V is very effective in detecting the ghost car attacks and removing the impact of such misbehavior from influencing the receiver and offers a conservative and sensible approach towards trustworthy Collective Perception Services for CAV s.

The viability of device to device (D2D) communication on uplink resources [1] as also the benefits accruing from network control over such communication, on licensed spectrum [2], are quite well understood today. We investigate the merits of a particular system instantiation based on these two tenets. The challenge of scheduling communication between two devices using remote schedulers at one or more base stations is addressed with minimal changes to the current signaling mechanisms in a 3GPP LTE based framework. This system maintains as tight a control over device to device communication as is currently maintained over device to infrastructure communication. Furthermore the benefits of such a system range from optimized routing and resource allocation to metered charging for data exchanged on the D2D link to lawful intercept to dynamic local broadcast. We also provide a comparison of this system with the available option of D2D communications over unlicensed spectrum using Wi-Fi.

Enhanced Inter-cell Interference Co-ordination (eICIC) is a time-domain multiplexing technique for improving the performance of legacy co-channel Heterogeneous Networks (HetNets). eICIC offers several benefits, including a more equitable distribution of user traffic across the macro and embedded pico cells (i.e., load balancing), in turn leading to better pico cell utilizations and better edge user throughputs. eICIC uses two mechanisms to achieve load balancing: (i) a cell selection bias to increase the pico coverage area, enabling the pico to attract more users, and (ii) macro muting ("Almost Blank Sub-frame", ABS) to improve SINRs of range extended pico users. Network load in the cellular system varies continuously as a result of user mobility and traffic dynamics (the varying amount of data pending for a user - arising from packet arrivals and eventual departures). Previous work did not consider dynamically changing network conditions in HetNets. Hence, they studied the benefits of eICIC over legacy HetNets arising from static optimization of eICIC parameters. Our approach is dynamic, and further improves performance by keeping the HetNet continuously optimized for improved user experience, by adapting the ABS in response to dynamic variations in network load. We present several analytical formulations, which allow for simple optimizations and an intuitive understanding of the desired system response to load variation. Exhaustive system simulations illustrate the performance gains along different dimensions, such as spectral efficiency, fairness, mean file transfer times, number of file transmissions, number of file drops, and mean queue lengths. Furthermore, we study the impact of different mobility scenarios, traffic mixes, and adaptation rate. We also provide a brief discussion of practical considerations in implementing Dynamic eICIC.

Currently deployed cellular data systems limit any user to downlink reception only from a single base station. Recent standardization work on newer revisions of the HRPD and HSPA air-interface technologies relaxes this constraint by allowing multiple base stations to transmit independent data streams targeted towards a single user. We characterize the regions of performance gain for this technology, and investigate further improvements using advanced terminal receivers. The scheme is shown to be an effective load-balancing adaptation to bursty traffic at low to moderate loads. Furthermore, with a Successive Self Interference Cancellation capability at the device and Co-ordinating Scheduling at the base stations, further performance gains are demonstrated by favorably trading-off link adaptation loss for larger interference cancellation gains. 3 different schedulers are considered to intuit the ideal scheduler. Improvements are quantified when load is varied by increasing data usage per user, rather than increasing the number of users.

In this paper, gains of the codebook based CL-MIMO for down link WiMax system has been studied using system level simulations. The system level simulation is based on the IEEE 802.16 m evaluation methodology. The 2 times 2 and 4 times 2 antenna configurations, and 3 bits and 6 bits preferred matrix index (PMI) feedback codebooks are considered. Both the sub-band and wide band PMI feedback are studied. The results show that the CL-MIMO provides substantial gains in cell edge and average sector throughput over OL-MIMO system.

The detection of a binary phase-shift keying signal distorted by like-modulated cochannel interference and noise using a noise-plus-interference whitening matched filter (WMF) is considered. The interfering signals are assumed to be independent and Rayleigh-faded. It is shown that in a synchronous channel, the signal-to-interference-plus-noise ratio (SINR) at the output of a WMF can not exceed that of the conventional matched filter (CMF) receiver. It is observed that in a synchronous channel, an interference WMF degrades the performance both through decreasing the SINR and introducing intersymbol interference (ISI). In contrast, in an asynchronous channel an optimal WMF can improve the SINR relative to the CMF receiver. It is shown that for a standard raised-cosine pulse the maximum achievable SINR gain over the CMF receiver is 1.76 dB. The SINR of the WMF receiver in asynchronous CCI is also evaluated for the case when a linear equalizer is used to mitigate the ISI caused by the WMF.

Precise outage probability performance analysis of a micro- cellular system with selection and switched diversities is considered. The micro-cellular system is assumed to follow a flat slow Nakgami/Raleigh fading model wherein the fading channels from the desired transmitter to all the receiver antennas are independent and identically distributed Nakagami channels, and all the fading channels for the interfering signals are independent, identically distributed Rayleigh channels. Three selection and switching criteria, namely, desired signal power, signal-to-interference power ratio and total output power are considered. Unlike previous results, the system model under investigation takes into account the pulse shaping and the random delays and phase offsets of the interfering users. Two Nyquist pulse shapes, spectrum-raised-cosine and Beaulieu–Tan–Damen pulse shapes are considered. Analytical outage probability expressions derived for an arbitrary number of interferers, arbitrary diversity order and arbitrary value of desired user fading parameter. The outage performance of the selection criteria are compared. The optimum switching thresholds for different switching criteria are formulated.

Precise outage probability performance analysis of a microcellular system with selection and switched diversities is considered. The microcellular system is assumed to follow a flat, slow Nakagami/Rayleigh fading model wherein the fading channels from the desired transmitter to all the receiver antennas are independent and identically distributed Nakagami channels, and all the fading channels for the interfering signals are independent, identically distributed Rayleigh channels. Three selection and switching criteria, namely, desired signal power, signal-to-interference power ratio, and total output power are considered. Unlike previous results, the system model under investigation takes into account the pulse shaping, the random delays, and the phase offsets of the interfering users. Two Nyquist pulse shapes, spectrum-raised-cosine and Beaulieu-Tan-Damen pulse shapes, are considered. Analytical outage probability expressions are derived for an arbitrary number of interferers, arbitrary diversity order, and arbitrary value of desired user fading parameter. The outage performances of the selection criteria are compared. The optimum switching thresholds for different switching criteria are formulated.

A TDD-OFDMA framework is designed for broadband wireless access. The main features of our design are predefined MAP structure, scalable OFDMA system with frequency overlay and MIMO mode switching scheme. An extensive system level simulation study has been carried out in the practical channel conditions. Our results show that the average sector throughput can be improved by 25~50%, and the size of MAP message is reduced by more than 50%.

Accurate average bit-error rate analysis of asynchronous bandlimited binary direct-sequence code-division multiple-access (DS-CDMA) systems in Nakagami-m fading is studied. The fading is assumed to be flat and slow. The spectrum raised-cosine (SRC) and Beaulieu-Tan-Damen (BTD) pulse-shapes are employed. A new method which combines the characteristic function (CF) method with the improved Gaussian approximation (GA) is proposed for evaluating the BER of bandlimited DS-CDMA. A substantial computational complexity reduction is achieved. The well-known standard GA, Holtzman's simplified improved GA, and improved Holtzman's GA methods are also considered. The accuracies of the approximation methods are assessed using Monte Carlo simulation. For a system employing a deterministic sequence for the desired user and random sequences for the active interfering users, a CF method is employed to derive precise BER results. The new BTD pulse outperforms the SRC pulse in all situations

A whitening matched filter receiver for multiple access interference suppression is considered for a bandlimited DS-CDMA system in Nakagami fading. The whitening matched filter, while maximizing the signal-to-noise-plus-interference ratio, introduces intersymbol interference in the decision statistic. A fractionally spaced linear MMSE equalizer is introduced to combat the intersymbol interference. The Beaulieu-Tan-Damen pulse and the conventional spectrum raised-cosine pulse are employed as chip pulse shapes. Asynchronous timing and slow flat fading are assumed. The precise BER expressions are derived using characteristic function and Fourier series methods.

Accurate average bit error rate analysis of diversity receivers for asynchronous bandlimited binary DS-CDMA systems operating over Nakagami-m fading channels is studied. Predetection equal gain combining (EGC) and selection combining (SC) are considered. The fading is assumed to be flat and slow, and random spreading sequences are considered. The spectrum raised cosine (SRC) and Beaulieu-Tan-Damen (BTD) pulse shapes are employed. The improved Gaussian approximation for multiple access interference is employed with characteristic function and Fourier series methods for the performance analysis. Our results are valid for arbitrary diversity order and arbitrary Nakagami fading parameter and the computational complexity does not grow with the diversity order. The new Beaulieu-Tan-Damen pulse outperforms the spectrum raised-cosine pulse in all situations examined.

Cochannel interference mitigation in bandwidth efficient BPSK systems operating in slow, flat fading microcellular environments is considered. The desired and interfering users undergo Nakagami-m and Rayleigh fading, respectively. A whitening matched filter and fractionally spaced linear minimum mean square error equalizer are employed in the receiver. While whitening maximizes the signal-to-noise-plus-interference ratio, the whitening matched filter introduces intersymbol interference in the decision statistic. A minimum mean square error equalizer is used to combat the intersymbol interference. Important observations regarding the performance of the proposed receiver structure are made. The performance with Beaulieu-Tan-Damen pulse shaping is always better than with spectrum raised-cosine pulse shaping. The performance is considerably better than the conventional matched filter receiver under a variety of fading conditions for the desired user. The performance gain decreases with the severity of the fading of the desired user. When the cochannel interference is synchronous, the performance can approach the optimum single user performance by appropriately choosing the tap spacing and length of the equalizer.

Accurate performance analysis of asynchronous bandlimited binary DS-CDMA systems in Nakagami-m fading is considered. The fading is assumed to be flat and slow. The spectrum raised-cosine and Beaulieu-Tan-Damen pulse shapes are employed. A new accurate approximation for computing the bit error rate of bandlimited DS-CDMA systems employing random spreading sequences is proposed. A substantial computational complexity reduction is achieved. The well-known standard Gaussian approximation, Holtzman's simplified improved Gaussian approximation, and the improved Holtzman's Gaussian approximation are also considered. The accuracies of the approximations are assessed using Monte-Carlo simulation. For a system employing a deterministic sequence for the desired user and random sequences for the active interfering users, a characteristic function method is employed to derive exact BER results. The new Beaulieu-Tan-Damen pulse outperforms the spectrum raised-cosine pulse in all situations examined.