Connectivity analysis for mmWave V2V networks : exploring critical distance and beam misalignment

In this paper, we investigate the analytical connectivity performance of Vehicle-to-Vehicle communications when using millimeter wave carrier frequencies, by taking into account its challenges of high path loss and beam misalignment. The connectivity analysis is carried out in two dimensions; first, an analytical and parametric critical transmission range is developed, based on system parameters such as vehicle density and Signal-to-Interference-Plus-Noise ratio threshold, and second, the beam misalignment probability caused by the in-lane lateral displacement of vehicles is determined. The analysis is carried out for antennas with half power beamwidths of 3◦, 6◦, 10◦, 20◦ and 45◦, resulting in different beamwidth regimes depending upon road curvature and vehicle density. For low/medium vehicle density on low-curvature roads, the sensitivity of the network connectivity to the beamwidth is relatively small. On the other hand, the narrowest beamwidth is the best performer in terms of maximizing connectivity in low/medium vehicle density scenarios on high-curvature roads, and the wider beamwidth is the best performer for high vehicle density on low-curvature roads

Capacity Maximisation for Hybrid Digital-to-Analog Beamforming mm-Wave Systems

Millimetre waves (mm-Waves) with massive multiple input and multiple output (MIMO) have the potential to fulfill fifth generation (5G) traffic demands. In this paper, a hybrid digital-to-analog (D-A) precoding system is investigated and a particle swarm optimisation (PSO) based joint D-A precoding optimisation algorithm is proposed. This algorithm maximises the capacity of the hybrid D-A mm-Wave massive MIMO system. The proposed algorithm is compared with three known hybrid D-A precoding algorithms. The analytical and simulation results show that the proposed algorithm achieves higher capacity than the existing hybrid D-A precoding algorithms

Revisiting the Energy-Efficient Hybrid D-A Precoding and Combining Design For mm-Wave Systems

Hybrid digital to analog (D-A) precoding is widely used in millimeter wave systems to reduce the power consumption and implementation complexity incurred by the number of radio frequency (RF) chains that consume a lot of the transmitted power in this system. In this paper, an optimal number of RF chains is proposed to achieve the desired energy efficiency (EE). Here, the optimization problem is formulated in terms of fractional programming maximization, resulting in a method with a twofold novelty: First, the optimal number of RF chains is determined by the proposed bisection algorithm, which results in an optimized number of data streams. Second, the optimal analog precoders/combiners are designed by eigenvalue decomposition and a power iteration algorithm, followed by the digital precoders/combiners which are designed based on the singular value decomposition of the proposed effective uplink and downlink channel gains. Furthermore, the proposed D-A systems are designed carefully to attain a lower complexity than the existing D-A algorithms while achieving reasonable performance. Finally, the impact of utilizing a different number of quantized bits of resolution on the EE is investigated. Simulation results show that the proposed algorithms outperform existing algorithms in terms of EE, spectral efficiency, and computational complexity

3D Beamforming for 5G Millimeter Wave Systems Using Singular Value Decomposition and Particle Swarm Optimization Approaches

Millimeter wave (mmWave) systems are one of the proposed solutions for the fifth generation (5G) mobile network. However, mmWave system experiences strong path loss due to higher frequencies. To solve this problem, such a system demands a narrow beampattern to reduce the loss of the mmWave signal energy due to the high path loss. One of the significant challenges to be addressed before their deployment is designing three dimensional (3D) beamforming algorithms, which are required to be directional. In this paper, we first propose two 3D beamforming algorithms with aim of tracking users in both the azimuth and elevation planes. Our proposed beamforming algorithms operates based on the principles of singular value decomposition (SVD) and particle swarm optimization (PSO). Furthermore, these beamforming algorithms are designed to have limited or negligible side lobes, which cause less interference to the other users operating in the same cell. In order to achieve this objective, Kaiser Bessel (KB) filter is adopted which helps in mitigating side lobes in the synthesized beampattern. Based on our analysis, we gain some valuable insights. The proposed algorithms are shown to perform well in achieving considerable capacity and lower side lobs

Impact of overlapped AoAs on the achievable uplink rate of hybrid beamforming for massive MIMO mm-Wave Systems for industrial environments

In this paper, we develop novel precoder and combiner schemes for multi-user hybrid digital-to-analog (D-A) beamforming for uplink massive multiple-input multiple-output millimeter wave (mm-Wave) systems, where the number of radio frequency chains is much smaller than the number of antennas each transceiver is equipped with. Industry 4.0 targets to accelerate the digitalization of manufacturing processes by allocating fixed and mobile robotics which use wireless communication. Such development requires high data throughput for which the utilization of short distance wireless communication such as mm-Wave system is crucially required. Based on our measurements, the probability of mm-Wave propagation waves to be reflected and refracted from metallic surfaces are shown to be significantly high. Consequently, uplink transmissions from different users such as robotics, machines, and sensors can go through paths sharing the same physical scatters, some transmission paths of different users may have overlapped angle of arrivals (AoAs) at the base station. Under such circumstance, the correlation between the channel vectors also increases considerably, which affects the achievable uplink rate severely. Therefore, the intrinsic focus is on substantially maximizing the desired signal while reducing the system interference. The proposed analog precoders and combiners are designed by using the power iteration and the Riemannian optimization method based on Stiefel manifold algorithms, respectively. The proposed digital combiner adapts the minimum mean-square error by judiciously exploiting the effective uplink analog channel gains. Furthermore, the channel estimation is investigated through a newly designed two-step procedure. In each scattering point, there is the strongest power point which is detected and then used to improve the accuracy by employing an angular domain scheme. The impact of this paper will be the boosting of the achievable uplink rate in industrial environme..

Security outage probability analysis of cognitive networks with multiple eavesdroppers for Industrial Internet of Things

The Industrial Internet of Things (IIoT) has been recognised as having the potential to benefit a range of industrial sectors substantially. However, widespread development and deployment of IIoT systems are limited for some reasons, the most significant of which are a shortage of spectrum resources and network security issues. Given the heterogeneity of IIoT devices, typical cryptographic security techniques are insufficient since they can suffer from challenges including computation, storage, latency, and interoperability. This paper presents a physical layer security analysis of the underlying cognitive radio networks for IIoT. Through consideration of the spectrum, IIoT devices can opportunistically utilise the primary spectrum, thereby improving spectrum efficiency and allowing access by an increased number of devices. Specifically, we propose two cognitive relay transmission (CRT) schemes, optimal single CRT (O-SCRT) and multiple CRT (MCRT), to improve transmission reliability further. Since it is challenging to obtain channel state information in the wiretap link, we provide a sub-optimal single CRT scheme and derive closed-form expressions of security outage probability by invoking both selection combination and maximal ratio combination techniques at the eavesdropper. To provide a benchmark, the round-robin single CRT scheme is also analysed. Simulation results are provided to verify our analysis and show that O-SCRT provides the best system security outage performance

Hybrid Precoding Algorithms for Millimeter-Wave Massive MIMO Systems

The large available spectrum efficiency and wider bandwidth at millimeter wave (mm-Wave) frequencies can enable the gigabit-per-second data rates needed for next generation wireless systems. To compensate for the high propagation loss at mm-Wave bands, multiple-input multiple-output (MIMO) with a large number of antennas are usually employed to enable beamforming. Therefore, a combination of the large number of antennas which can be called massive MIMO technology with mm-Wave bands are considered as one solution for substantially increasing the data rate for future wireless communication systems. The theoretical benefits of large antenna array systems are based on the fact that the number of radio frequency (RF) chains is equivalent to the number of antennas in the conventional wireless communication system which is known as the fully digital system. Nevertheless, implementing a large number of RF chains can be problematic since it increases the system cost, power consumption, high complexity and lowers power efficiency The overall objective of this thesis is to provide simple and effective hybrid D/A precoding and combing for mm-Wave large antenna array systems. Firstly, hybrid D/A precoding with a small number of RF chains is being considered for mm-Wave large antenna array systems. Currently, two types of antenna structures, fully-connected antenna array and partially-connected antenna array structures are adopted in the literature. Considering that each antenna array structure has its own practical advantage, in this thesis, by addressing both structures hybrid D/A precoding algorithms are proposed with target of maximizing the system's spectral efficiency with low computational complexity. For a fully-connected antenna array structure, the precoding design is formulated as an optimization problem to minimize the Euclidean distance between the hybrid D/A and the fully digital system. For a partially-connected antenna array structures, the hybrid D/A precoding is formulated as a joint D/A optimization to maximize the spectral efficiency of the system. This work further develops hybrid D/A precoding designs for mm-Wave multi-user systems based on maximizing the sum rate of the system directly. It will be shown that the proposed algorithms outperform the existing hybrid D/A precoding algorithms for the two types of structures, in terms of the spectral efficiency. Secondly, energy efficient and low complexity hybrid D/A system for mm-Wave large antenna array systems is proposed to reduce the power consumption at the system. The energy efficiency criteria is formulated as fractional programming maximization problem. The target is to find the optimal number of RF chains as the RF chains consume a high energy at the system. Therefore, the effective optimal number of RF chains of the system is found by proposing a simple search algorithm. Then, two methods are proposed for designing low complexity analog and digital precoders and combiners. The presented solutions for the hybrid D/A system are shown to be effective, as these approaches can achieve high energy efficiency, and low computational complexity as compared to the existing algorithms in hybrid D/A paradigms. Ultimately, the proposed D/A precoders and combiners based on the fully-connected antenna array attain an asymptotically optimal achievable spectral efficiency to that of the fully digital system. Thirdly, uplink multi-user hybrid D/A precoding and combining design for mm-Wave large antenna array systems is investigated. The intrinsic focus of this work is to reduce the interference of the system in the analog and digital precoders and combiners. Considering the possibility that uplink transmissions from different users can go through the paths sharing the same physical scatters, some transmission paths of different users may have overlapped angle of arrivals (AoAs) at the base station. Under this circumstance, the correlation between the channel vectors also increases highly, which affects the achievable uplink rate severely. The underlying concentrate of this work is to reduce the interference caused by users sharing the same scatterers during simultaneous uplink transmission. Therefore, in this thesis, by taking account the channel correlation between users sharing the overlapped AoAs, the genuine focus is on substantially maximizing the desired signal of a piratical user while reducing the system interference. Furthermore, the channel estimation is investigated by designing a two-step procedure. The strongest power point in each scattering point is detected and the accuracy is improved by employing an angler domain scheme. Extensive simulations demonstrate that the achievable uplink rate of our proposed algorithms surpasses the achievable uplink rate of the existing algorithms in hybrid D/A paradigms in the practical scenarios