High Capacity Wireless Networks Research Articles

Advancements in Terahertz Communication: Harnessing the 300GHz Band for High-Efficiency, High-Capacity Wireless Networks

Advancements in Terahertz Communication: Harnessing the 300GHz Band for High-Efficiency, High-Capacity Wireless Networks

Optimized CNN and adaptive RBFNN for channel estimation and hybrid precoding approaches for multi user millimeter wave massive MIMO

ABSTRACT The millimetre-wave (mmWave) communication satisfies the demand for high data rates due to the characteristic of wide bandwidth. Using massive multiple-input multiple-output (MIMO) technology, a significant propagation loss of mmWave communication is effectively compensated. However, it is challenging to provide a specialised radio frequency chain for each antenna due to the constrained physical area with closely spaced antennas and prohibitive power consumption in mmWave massive MIMO systems. This paper presents novel approaches for effective channel estimation and hybrid precoding in mmWave communication systems. To address the challenges of channel estimation, a convolutional neural network (CNN) is utilised, and network parameters are optimised using enhanced whale optimization algorithm (EWOA). The proposed CNN-based channel estimation method aims to accurately estimate the channel in mmWave systems with enhanced efficiency and reduced complexity. By training CNN using EWOA optimisation algorithm, the network parameters are fine-tuned to improve accuracy and generalisation capability of channel estimation process. Furthermore, hybrid precoding is achieved using adaptive radial-basis function neural networks (adaptive RBFNNs) which enables efficient precoding while minimising complexity. Moreover, the adaptive RBFNN approach determines the optimal precoding weights based on channel state information, resulting in a improved performance and a reduced computational overhead. The performance analysis is validated using the MATLAB/Simulink software and offers to provide effectual and reliable mmWave communication systems, facilitating the realisation of high-speed and high-capacity wireless networks.

Metamaterial-Based LTCC Compressed Luneburg Lens Antenna at 60 GHz for Wireless Communications

In this study, a metamaterial-based LTCC compressed Luneburg lens was designed, manufactured and measured. The lens was designed at 60 GHz to utilize the unlicensed mm-wave spectrum available for short-range high-capacity wireless communication networks. The transformation optics method was applied to ensure the compression of the Luneburg lens antenna and thus maintain a low-profile structure. The two different types of unit cells for low and high permittivity regions were considered. The parametric study of the effect of compression on lens performance was presented. The antenna is implemented with a standard high-permittivity LTCC process, and details of the manufacturing process for the metamaterial lens are discussed. The low-profile lens is thinner than 2 mm and measures 19 mm in diameter. A size reduction of 63.6% in comparison with a spherical lens was achieved. The near-field to far-field mm-wave measurement technique is presented, and the measurement results show a peak antenna gain of 16 dBi at 60 GHz and a beam-scanning capacity with 1 dB scan loss within a 50° field of view.

Wavelength & mm-Wave Flexible Converged Optical Fronthaul With a Low Noise Si-Based Integrated Dual Laser Source

A widely tunable hybrid InP-Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> dual laser module (DLM) with low linewidth and relative intensity noise (RIN) is used to develop a wavelength and frequency flexible optical fronthaul system for high-capacity wireless networks. The wavelength flexible (over C-band) delivery of 5G signals over an analog radio-over-fiber (A-RoF) system, incorporating wireless transmission at 60 GHz is demonstrated. A phase noise (PN) and frequency offset (FO) cancelling receiver is used to overcome phase/frequency noise from the DLM due to thermal fluctuations, and this reduces the received (error vector magnitude) EVM to as low as 5%. Using the same DLM we demonstrate the mm-wave frequency flexible (over sub-V-band) delivery of 5G and WiGig signals over a simplified converged fronthaul link. The experimental results show excellent performance with bit error ratio (BER) values as low as 8.46×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> and 1.11×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> , and lowest EVMs of 2.4% and 6.1%, achieved for sub-V-band 5G and WiGig signals, respectively. In addition to highlighting the high flexibility of the DLM, this work also presents an approach to deploy this source in future optical-wireless access networks paving way for beyond 5G and 6G technologies.

Technology, Assembly, and Test of a W-Band Traveling Wave Tube for New 5G High-Capacity Networks

The folded waveguide (FWG) traveling wave tube (TWT) developed in the frame of the Horizon 2020 TWEETHER project for enabling a novel ${W}$ -band (92–95 GHz) high capacity wireless network for 5G is presented. The FWG TWT was designed by particle-in-cell (PIC) simulations. The technology and the results in terms of measured RF losses and beam transmission from the realized beam tester are presented. Amplification on the first TWT breadboard has been observed but with a poor multireflection pattern resulting from spurious burrs inside the FWG. It indicates, however, that the FWG technology offers great manufacturing simplification compared to conventional helix TWTs, thus enabling a low-cost device with large series production suitable for the wide market of wireless communications.

Optimized Deployment of Millimeter Wave Networks for In-Venue Regions With Stochastic Users’ Orientation

Millimeter wave (mmW) communication is a promising solution for providing high-capacity wireless network access. However, the benefits of mmW are limited by the fact that the channel between a mmW access point and the user equipment can stochastically change due to severe blockage of mmW links by obstacles such as the human body. Thus, one main challenge of mmW network coverage is to enable directional line-of-sight links between access points and mobile devices. In this paper, a novel framework is proposed for optimizing mmW network coverage within hotspots and in-venue regions, while being cognizant of the body blockage of the network’s users. In the studied model, the locations of potential access points and users are assumed as predefined parameters while the orientation of the users is assumed to be stochastic. Hence, a joint stochastic access point placement and beam steering problem subjected to stochastic users’ body blockage is formulated, under desired network coverage constraints. Then, a greedy algorithm is introduced to find an approximation solution for the joint deployment and assignment problem using a new “size constrained weighted set cover” approach. A closed-form expression for the ratio between the optimal solution and approximate one (resulting from the greedy algorithm) is analytically derived. The proposed algorithm is simulated for three in-venue regions: the meeting room in the Alumni Assembly Hall of Virginia Tech, an airport gate, and one side of a stadium football. The simulation results show that, in order to guarantee network coverage for different in-venue regions, the greedy algorithm uses at most three more access points (APs) compared to the optimal solution. The results also show that, due to the use of the additional APs, the greedy algorithm will yield a network coverage up to 11.7% better than the optimal, AP-minimizing solution.

Performance Analysis of 20 Gbit/s–40 GHz MDM-Ro-FSO Link Incorporating DPSK Modulation Scheme

Abstract The congestion in the radio frequency spectrum has posed a serious challenge for mobile service providers. Radio-over-free space optics (Ro-FSO) technology has been considered as a front runner to deal with the problem of spectrum congestion and to provide future generation high-capacity wireless networks. This work proposes designing and numerical analysis of differential phase shift keying (DPSK) modulation-based 20 Gbit/s–40 GHz hybrid mode division multiplexing-radio-over-free space optics (MDM-Ro-FSO) link up to 40 km transmission range under clear weather. Quality Factor (Q Factor), log of bit error rate (BER), signal to noise ratio (SNR), and received power are the key metrics used to probe the proposed system performance. The impact of increasing divergence angle and different fog weather conditions on the proposed system performance is also numerically evaluated. Further, the decomposition analysis of different spatial modes at the receiving unit is carried out in this work.

Design of sub-THz traveling wave tubes for high data rate long range wireless links

The development of high capacity wireless networks, to satisfy the increasing demand of mobile high-speed internet, is stimulating the exploitation of the wide frequency bands in the millimeter and THz range. Above 100 GHz, the high atmosphere attenuation is the major obstacle for wireless links of adequate length, due to the low power available from solid state amplifiers. Traveling wave tubes (TWT) are promising devices capable og generating multi-watt power at sub-THz frequency. In this paper, the design and performance of a TWT in the 210–250 GHz band with about 1 W output power will be described, to power a 40 Gigabits per second optical transmitter for 1 km point-to-point link. A novel approach for a simple and low-cost fabrication, based on the use of the double corrugated waveguide is proposed.

On the influence of the propagation environment on throughput performance in indoor wireless network

Providing high capacity wireless networks that are able to support high throughput requirements within the constraint of finite bandwidth resource is crucial and has been the motivation of this work. Received signal quality may vary under different propagation environments due to variation in user location and base station deployment strategy. The investigation and analysis of throughput performance for downlink orthogonal frequency division multiplexing (OFDM) indoor wireless network is presented in this paper. This investigation requires a cross-layer model that takes into account the received signal quality in the physical layer and resource allocation in the medium access control layer. Results have shown that the coverage performance for an indoor wireless network that adopts the aligned configuration (AC) outperforms the offset configuration (OC) by 18% under a low throughput threshold using either maximum rate or equal allocation scheduling. At high throughput threshold, OC outperforms the AC by up to 33% given that MR is used as the scheduling scheme.

Data-Driven Deployment and Cooperative Self-Organization in Ultra-Dense Small Cell Networks

Ultra-dense small-cell network is widely acknowledged as a key enabler for high capacity wireless networks. Some of the key challenges that ultra-dense networks face are profitable deployment distribution under complex traffic loads and efficient radio resource management (RRM) in excessive interference environments. Poor small-cell deployment locations can lead to excessive interference without clear profit margins and inefficient resource utilization. As such, data-driven small-cell deployment and self-organizing RRM of small-cell clusters are regarded as the two main technologies that can improve ultra-dense small-cell services. This paper first reviews the latest research in data-driven small-cell deployment using structured and unstructured social media data. A combination of irregular clustering techniques is used to identify hotspots, and natural language processing algorithms are used to identify blackspots. This paper then reviews recent advances in self-organization of small-cell RRM and analyzes how data can improve self-organization performance. Moreover, the idea of cooperative self-organization is introduced to further promote the self-organization capability. Finally, two ultra-dense small-cell RRM case studies are presented to demonstrate the performance which improves of cooperative self-organization.

MABC: Power-Based Location Planning with a Modified ABC Algorithm for 5G Networks

The modernization of smart devices has emerged in exponential growth in data traffic for a high-capacity wireless network. 5G networks must be capable of handling the excessive stress associated with resource allocation methods for its successful deployment. We also need to take care of the problem of causing energy consumption during the dense deployment process. The dense deployment results in severe power consumption because of fulfilling the demands of the increasing traffic load accommodated by base stations. This paper proposes an improved Artificial Bee Colony (ABC) algorithm which uses the set of variables such as the transmission power and location of each base station (BS) to improve the accuracy of localization of a user equipment (UE) for the efficient energy consumption at BSes. To estimate the optimal configuration of BSes and reduce the power requirement of connected UEs, we enhanced the ABC algorithm, which is named a Modified ABC (MABC) algorithm, and compared it with the latest work on Real-Coded Genetic Algorithm (RCGA) and Differential Evolution (DE) algorithm. The proposed algorithm not only determines the optimal coverage of underutilized BSes but also optimizes the power utilization considering the green networks. The performance comparisons of the modified algorithms were conducted to show that the proposed approach has better effectiveness than the legacy algorithms, ABC, RCGA, and DE.

A Genetic Algorithm with Location Intelligence Method for Energy Optimization in 5G Wireless Networks

The exponential growth in data traffic due to the modernization of smart devices has resulted in the need for a high-capacity wireless network in the future. To successfully deploy 5G network, it must be capable of handling the growth in the data traffic. The increasing amount of traffic volume puts excessive stress on the important factors of the resource allocation methods such as scalability and throughput. In this paper, we define a network planning as an optimization problem with the decision variables such as transmission power and transmitter (BS) location in 5G networks. The decision variables lent themselves to interesting implementation using several heuristic approaches, such as differential evolution (DE) algorithm and Real-coded Genetic Algorithm (RGA). The key contribution of this paper is that we modified RGA-based method to find the optimal configuration of BSs not only by just offering an optimal coverage of underutilized BSs but also by optimizing the amounts of power consumption. A comparison is also carried out to evaluate the performance of the conventional approach of DE and standard RGA with our modified RGA approach. The experimental results showed that our modified RGA can find the optimal configuration of 5G/LTE network planning problems, which is better performed than DE and standard RGA.

Performance Evaluation of Interference Bound Backhaul Links in High Capacity Wireless Networks

An innovative architecture employing wireless backhaul in hierarchical wireless networks is considered in this paper to provide high throughput densities. Multi-beam antennas, combined with aggressive frequency reuse have recently been exploited to increase the throughput density in densely deployed wireless networks. However, large number of narrow beams cause not only co-channel interference but also inter-cell interference. To mitigate this problem, amplitude tapering in multi-beam antennas is investigated in this paper. Results show that tapered beams significantly improve the carrier to interference ratio from 5 to 8 dB and consequently achieve downlink throughput density over 0.65 Gbps/km $$^2$$ 2 . An overall throughput density of 1.2 Gbps/km $$^2$$ 2 is expected when taking both up- and downlinks into account.

Constrained least squares detector for OFDM/SDMA-based wireless networks

The two major obstacles toward high-capacity indoor wireless networks are distortion due to the indoor channel and the limited bandwidth which necessitates a high spectral efficiency. A combined orthogonal frequency division multiplexing (OFDM)/spatial division multiple access (SDMA) approach can efficiently tackle both obstacles and paves the way for cheap, high-capacity wireless indoor networks. The channel distortion due to multipath propagation is efficiently mitigated with OFDM while the bandwidth efficiency can be increased with the use of SDMA. However, to keep the cost of an indoor wireless network comparable to its wired counterpart's cost, low-complexity SDMA processors with good performance are of special interest. In this paper, we propose a new multiuser SDMA detector which is designed for constant modulus signals. This constrained least squares (CLS) receiver, which deterministically exploits the constant modulus nature of the subcarrier modulation to achieve better separation, is compared in terms of performance and complexity with the zero forcing (ZF) and the minimum mean square error (MMSE) receiver. Additionally, since the CLS detector relies on reliable channel knowledge at the receiver, we propose a strategy for estimating the multiple input multiple output (MIMO) channels. Simulations for a Hiperlan II-based case-study show that the CLS detector significantly outperforms the ZF detector and comes close to the performance of the MMSE detector for QPSK. For higher order M-PSK, the CLS detector outperforms the MMSF detector. Furthermore, the estimation complexity for the CLS detector is substantially lower than that for the MMSE detector which additionally requires estimation of the noise power.

Adaptive loading for OFDM/SDMA-based wireless networks

The two major obstacles toward high-capacity indoor wireless networks are distortion due to the indoor channel and the limited availability of bandwidth which necessitates a high spectral efficiency. A combined orthogonal-frequency division multiplexing/spatial-diversity multiple access (OFDM/SDMA) approach can effectively tackle both obstacles. The channel distortion due to multipath propagation is easily mitigated with OFDM while the bandwidth efficiency can be increased with the use of SDMA. In order to keep the network's cost acceptable, simplified SDMA processors are preferred over the exponentially complex optimal maximum-likelihood processors. However, these simplified processors perform significantly worse than the optimal ones in terms of average bit error rate (BER). In this paper, we show that by adapting the constellation sizes applied on the individual subcarriers to the channel conditions, the performance of OFDM/SDMA processors can be significantly enhanced. In the uplink, we derive simple closed-form equations for the optimal constellation sizes for both a simple linear minimum mean-square error (MMSE) detector and for a nonlinear MMSE decision feedback equalizer (DFE) detector. Furthermore, for each detector, we introduce a simplified loading algorithm which lowers the computational and signaling complexity substantially at a small performance penalty. In the downlink, we study the dual precoders of the uplink detectors, respectively, the linear MMSE precoder and the nonlinear Tomlinson-Harashima (TH) MMSE-based precoder. For both precoders, we derive expressions for the optimal and the simplified constellation sizes. Additionally, we show that in time-division duplexing systems, the constellation distribution of a set of dual detectors/precoders is identical for up- and downlink, which effectively halves the computational complexity of adaptive loading. In the fully loaded uplink, the proposed adaptive loading algorithm results in a gain of 9 dB for a BER=10/sup -3/ for the linear MMSE detector and a gain of 4.5 dB for the nonlinear MMSE-DFE detector. In the fully loaded downlink, a gain of 6.3 dB is achieved for the MMSE precoder and 5.5 dB for the TH-MMSE precoder.

A high-capacity wireless network by quad-sector cell and interleaved channel assignment

We propose an improved sectorization scheme, called narrow-beam quad-sector cell (NBQC) for cellular networks, in which each cell is divided into four sectors and each sector is covered by a 60/spl deg/ antenna. The NBQC structure allows easy implementation of the concept of interleaved channel assignment (ICA), which can take full advantage of antenna directivity. With ICA, the NBQC system can enhance the system performance from several perspectives. First, the NBQC has better coverage performance than the current three-sector cellular architecture. Second, we demonstrate that in a typical radio environment, the NBQC system ran achieve a reuse cluster size N=2 with the signal-to-interference ratio (SIR) as high as 11 dB in 90% of the cell area, which is a 3-5-dB improvement over the existing cellular architectures. Third, as compared to the most advanced three-sector clover-leaf cell architecture with reuse cluster size N=3, the NBQC system with ICA can achieve reuse cluster size N=2 with very slight degradation in SIR performance, thereby still improving the system capacity by about 10% over a wide range of ninetieth percentile SIR requirements.

Block Reservation Time Division Multiple Access (BRTDMA) Protocol for a High Capacity Wireless Network

Next generation high capacity wireless networks need to support various types of traffic, including voice, video and data, each of which have different Quality of Service (QoS) requirements for successful transmission. This paper presents an advanced reservation packet access protocol BRTDMA (Block Reservation Time Division Multiple Access) that can accommodate voice and data traffic with equal efficiency in a wireless network. The proposed BRTDMA protocol has been designed to operate in a dynamic fashion by allocating resources according to the QoS criteria of voice and data traffic. Most of the existing reservation protocols offers reservation to voice traffic while data packets are transmitted using contention mode. In this paper we propose a block reservation technique to reserve transmission slots for data traffic for a short duration, which minimizes the speech packet loss and reduce the end-to-end delay for wireless data traffic. The optimum block reservation length for data traffic has been studied in a cellular mobile radio environment using a simulation model. Simulation results show that the BRTDMA protocol offers higher traffic capacity than standard PRMA protocol for integrated voice and data traffic and offers flexibility in accommodating multimedia traffic.

RDRN

This paper reports on the initial implementation of an experimental wireless ATM network architecture called RDRN (Rapidly Deployable Radio Network). The RDRN architecture consists of two types of transportable nodes, remote nodes (RNs) and edge nodes (ENs), which utilize GPS-derived location information to rapidly configure themselves into a high capacity wireless network operating at 1--10 Mb/s over distances as far as 10 kilometers. The initial prototype has been deployed and early experiments have been conducted to validate hardware, software, and protocol design and implementation. In addition to describing the RDRN architecture and protocols, this paper details experiences at the DARPA GLOMO '97 demonstration of the RDRN project.

Shared time division duplexing: an approach to low-delay high-quality wireless digital speech communications

Various strategies to provide low-delay high-quality digital speech communications in a high-capacity wireless network are examined. Various multiple access schemes based on time-division and packet reservation are compared in terms of their statistical multiplexing capabilities, sensitivity to speech packet dropping, delay, robustness to lossy packet environments, and overhead efficiency. In particular, a low-delay multiple access scheme, called shared time-division duplexing (STDD) is proposed. This scheme allows both the uplink and downlink traffic to share a common channel, thereby achieving high statistical multiplexing gain even with a low population of simultaneous conversations. The authors also propose a choice of low delay, high quality speech coding and digital modulation systems based on adaptive DPCM, with QDPSK or pseudo-analog transmission (skewed DPSK), for use in conjunction with the STDD multiple access protocol. The choice of the alternative systems depends on required end-to-end delay, recovered speech quality and bandwidth efficiency. Typically, with a total capacity of 1 MBaud, 2 ms frame and 8 kBaud speech coding rate, low delay STDD is able to support 48 pairs of users compared to 38, 35, and 16 for TDMA with speech activity detection, basic TDMA and PRMA respectively. This corresponds to respective gains of 26%, 37% and 200%.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>