Link-level Analysis Research Articles

Link Level Analysis of NR V2X Sidelink Communications

Link Level Analysis of NR V2X Sidelink Communications

How does street environment affect pedestrian crash risks? A link-level analysis using street view image-based pedestrian exposure measurement

Street space plays a critical role in pedestrian safety, but the influence of fine-scale street environment features has not been sufficiently understood. To analyze the effect of the street environment at the link level, it is essential to account for the spatial variation of pedestrian exposure across street links, which is challenging due to the lack of detailed pedestrian flow data. To address these issues, this study proposes to extract link-level pedestrian exposure from spatially ubiquitous street view images (SVIs) and investigate the impact of fine-scale street environment on pedestrian crash risks, with a particular focus on pedestrian facilities (e.g., crossing and sidewalk design). Both crash frequency and severity are analyzed at the link level, with the latter incorporating two distinct aggregation metrics: maximum severity and medium severity. Using Hong Kong as a case study, the results show that the link-level pedestrian exposure extracted from SVIs can lead to better model fit than alternative zone-level measurements. Specifically, higher pedestrian exposure is found to increase the total pedestrian crash frequency, while reducing the risk of serious injuries or fatalities, confirming the “safety in numbers” effect for pedestrians. Pedestrian facilities are also shown to influence pedestrian crash frequency and severity in different ways. The presence of crosswalks can increase crash frequency, but denser crosswalk design mitigates this effect. In addition, two-side sidewalks can increase crash frequency, while the absence of sidewalks leads to higher risks of crash severity. These findings highlight the importance of fine-scale street environment and pedestrian facility design for pedestrian safety.

An Analysis of Various Design Pathways Towards Multi-Terabit Photonic On-Interposer Interconnects

In the wake of dwindling Moore’s Law, to address the rapidly increasing complexity and cost of fabricating large-scale, monolithic systems-on-chip (SoCs), the industry has adopted dis-aggregation as a solution, wherein a large monolithic SoC is partitioned into multiple smaller chiplets that are then assembled into a large system-in-package (SiP) using advanced packaging substrates such as silicon interposer. For such interposer-based SiPs, there is a push to realize on-interposer inter-chiplet communication bandwidth of multi-Tb/s and end-to-end communication latency of no more than 10 ns. This push comes as the natural progression from some recent prior works on SiP design, and is driven by the proliferating bandwidth demand of modern data-intensive workloads. To meet this bandwidth and latency goal, prior works have focused on a potential solution of using the silicon photonic interposer (SiPhI) for integrating and interconnecting a large number of chiplets into an SiP. Despite the early promise, the existing designs of on-SiPhI interconnects still have to evolve by leaps and bounds to meet the goal of multi-Tb/s bandwidth. However, the possible design pathways, upon which such an evolution can be achieved, have not been explored in any prior works yet. In this paper, we have identified several design pathways that can help evolve on-SiPhI interconnects to achieve multi-Tb/s aggregate bandwidth. We perform an extensive link-level and system-level analysis in which we explore these design pathways in isolation and in different combinations of each other. From our link-level analysis, we have observed that the design pathways that simultaneously enhance the spectral range and optical power budget available for wavelength multiplexing can render aggregate bandwidth of up to 4 Tb/s per on-SiPhI link. We also show that such high-bandwidth on-SiPhI links can substantially improve the performance and energy-efficiency of the state-of-the-art CPU and GPU chiplets based SiPs.

Hybrid Beamforming in 5G mmWave Networks: A Full-Stack Perspective

This paper studies the cross-layer challenges and performance of Hybrid Beamforming (HBF) and Multi-User Multiple-Input Multiple-Output (MU-MIMO) in 5G millimeter wave (mmWave) cellular networks with full-stack TCP/IP traffic and MAC scheduling. While previous research on HBF and MU-MIMO has focused on link-level analysis of full-buffer transmissions, this work reveals the interplay between HBF techniques and the higher layers of the protocol stack. To this aim, prior work on the full-stack evaluation of mmWave cellular networks has been extended by including the modeling of MU-MIMO and HBF. Our results reveal novel relations between the networking layers and the HBF MU-MIMO performance at the physical layer. Particularly, throughput can be increased in 5G networks by means of Space Division Multiple Access (SDMA). However, in order to achieve such benefits it is necessary to take into account certain trade-offs and the implementation complexity of a full-stack HBF solution.

Link and System-Level NOMA Simulator: The Reproducibility of Research

This study focuses on the design of a MATLAB platform for non-orthogonal multiple access (NOMA) based systems with link-level and system-level analyses. Among the different potential candidates for 5G, NOMA is gaining considerable attention owing to the many-fold increase in spectral efficiency as compared to orthogonal multiple access (OMA). In this study, a NOMA simulator is presented for two and more than two users in a single cell for link-level analysis; whereas, for system-level analysis, seven cells and 19 cells scenarios were considered. Long-term evolution (LTE) was used as the baseline for the NOMA simulator, while bit error rate (BER), throughput and spectral efficiency are used as performance metrics to analyze the simulator performance. Moreover, we demonstrated the application of the NOMA simulator for different simulation scenarios through examples. In addition, the performance of multi-carrier NOMA (MC-NOMA) was evaluated in the presence of AWGN, impulse noise, and intercell interference. To circumvent channel impairments, channel coding with linear precoding is suggested to improve the BER performance of the system.

Comparative link-level analysis and performance estimation of channel models for IIoT (Industrial-IoT) wireless communications

In the industrial scenarios, modern gadgets should communicate independently and in a robust and productive manner with one another, depending on an enormous degree on wireless communication channels, which will expand and enhance the current wired communication links. The wireless communication channels experience several channel impairments, for example, attenuation because of propagation losses, random fluctuations because of fading and shadowing impacts over the channel and the non-line-of-sight (NLOS) because of obstacles on the communication channel. Hence adequate channel modeling is necessary. Several pieces of research exist on channel models to model industrial environments, but a comprehensive analysis and measurement of their characteristics are still missing from the current literature. This paper has performed analyses and measurements on a vast number of wireless channel models applicable to the IIoT in terms of multiple analytical approaches in several sections of the paper. Performance estimation approaches, such as received signal strength, packet loss probability, and RMS (Root Mean Square) error, RMS delay spread are investigated with a focus on channel models and three prominent IoT technologies are also included. The research might be able to address the demand for adequate IIoT channel modeling with included channel models and all analytical approaches presented.

Link-Level Analysis of a Multiservice Indoor Distributed Antenna System [Wireless Corner

In this article, the link-level performance of a multiservice indoor distributed antenna system (MS-IDAS) in an indoor-hotspot scenario is studied. A low-profile broadband antenna is proposed as the access point (AP) antenna, and then it is used as an identical array element for constructing two-and three-port multipleinput, and multiple-output (MIMO) antennas. The proposed MS-IDAS antenna covers various IEEE 802.11 standards within 2-6 GHz, and its link-level simulations are performed at 5 GHz for the 802.11n protocol. The error-rate performances of the three-element MIMO antenna is analyzed in WINNER indoor scenarios by using simulated-channelimpulse response (CIR). In a typical indoor-hotspot room with dimensions of 20 m x 20 m x 10 m, the wallmounted MS-IDAS antenna shows better coverage than the ceilingmounted case. In addition, the proposed MIMO antenna outperforms a uniform linear-dipole array with the same interelement distance in terms of error-rate performance.

Nonlinear Self-Interference Cancellation for Full-Duplex Radios: From Link-Level and System-Level Performance Perspectives

One of the promising technologies for Long Term Evolution is full-duplex radio, an innovation that is expected to double spectral efficiency. To realize full-duplex in practice, the main challenge is overcoming self-interference, and to do so, researchers have developed self-interference cancellation techniques. Since most wireless transceivers use power amplifiers, especially in cellular systems, researchers have revealed the importance of nonlinear self-interference cancellation. In this article, we first explore several nonlinear digital self-interference cancellation techniques. We then propose a low-complexity pre-calibration- based nonlinear digital self-interference cancellation technique. Next, we discuss the issues about reference signal allocation and the overhead of each technique. For performance evaluations, we carry out extensive measurements through a real-time prototype and link-/system-level simulations. For link-level analysis, we measure the amount of cancelled self-interference for each technique. We also evaluate system-level performance through 3D ray-tracing-based simulations. Numerical results confirm the significant performance improvement over a half-duplex system even in interference-limited indoor environments.

Performance Analysis of Asynchronous Multicarrier Wireless Networks

This paper develops a novel analytical framework for asynchronous wireless networks deploying multicarrier transmission. Nodes in the network have different notions of timing, so from the viewpoint of a typical receiver, the received signals from different transmitters are asynchronous, leading to a loss of orthogonality between subcarriers. We first develop a detailed link-level analysis based on OFDM, based on which we propose a tractable system-level signal-to-interference-plus-noise ratio (SINR) model for asynchronous OFDM networks. The proposed model is used to analytically characterize several important statistics in asynchronous networks with spatially distributed transmitters, including (i) the number of decodable transmitters, (ii) the decoding probability of the nearest transmitter, and (iii) the system throughput. The system-level loss from lack of synchronization is quantified, and to mitigate the loss, we compare and discuss four possible solutions including extended cyclic prefix, advanced receiver timing, dynamic receiver timing positioning, and semi-static receiver timing positioning with multiple timing hypotheses. The model and results are general, and apply to ad hoc networks, cellular systems, and neighbor discovery in device-to-device (D2D) networks.

How tube strikes affect macroscopic and link travel times in London

The purpose of this study was to investigate the impact of the five strikes on the London Underground (metro) rail system, which occurred in 2009 and 2010, on macroscopic and road link travel times. A consequence of these strikes was an increase in road traffic flows above usual levels. This provides an opportunity to observe the operation of the road network under unusually high flows. The first objective involves the examination of strike effects on inbound (IT) and outbound traffic (OT) within central, inner and outer London. Travel time data obtained from automatic number plate recognition cameras are used within the first part of the analysis. The second more detailed objective was to investigate in spatio-temporal effects on travel times on five road links. Correlation analyses and general linear models are developed using both traffic flow and travel time data. According to the results of the study, the morning IT had approximately twice as much delay as the OT. Central London experienced the highest delays, followed by inner and outer London. As would be expected, the unique full-day strike in 2009 yielded the worst impact on the network with the highest percentage increase in total travel time (60%) occurring during the morning peak in the IT in inner London. The results from the link-level analysis showed statistical significance amongst the examined links indicating heterogeneous effects from one link to another. It was also found that travel time changes may be more effectively captured through time-of-day terms compared to hourly traffic flows.

Opportunities and Challenges of Using Plasmonic Components in Nanophotonic Architectures

Nanophotonic architectures have recently been proposed as a path to providing low latency, high bandwidth network-on-chips. These proposals have primarily been based on micro-ring resonator modulators which, while capable of operating at tremendous speed, are known to have both a high manufacturing induced variability and a high degree of temperature dependence. The most common solution to these two problems is to introduce small heaters to control the temperature of the ring directly, which can significantly reduce overall power efficiency. In this paper, we introduce plasmonics as a complementary technology. While plasmonic devices have several important advantages, they come with their own new set of restrictions, including propagation loss and lack of wave division multiplexing (WDM) support. To overcome these challenges we propose a new hybrid photonic/plasmonic channel that can support WDM through the use of photonic micro-ring resonators as variation tolerant passive filters. Our aim is to exploit the best of both technologies: wave-guiding of photonics, and modulating using plasmonics. This channel provides moderate bandwidth with distance independent power consumption and a higher degree of temperature and process variation tolerance. We describe the state of plasmonics research, present architecturally-useful models of many of the most important devices, explore new ways in which the limitations of the technology can most readily be minimized, and quantify the applicability of these novel hybrid schemes across a variety of interconnect strategies. Our link-level analysis shows that the hybrid channel can save from 28% to 45% of total channel energy-cost per bit depending on process variation conditions.

Markov Models for the Physical Layer Block Error Process in a WCDMA Cellular System

In this paper, we investigate the possibility of using Markov chains to model the error process in the data blocks delivered by the physical layer of wideband code division multiple access a (WCDMA) cellular system. Suitable Markov models (MM) are designed to fulfil the two following objectives: First, an upper layer protocol supplied by the output obtained from the MM should behave as if it were running on the actual physical layer; second, MM parameters should be linked via simple relationships to the main physical layer parameters. Starting from the results on the error statistics obtained from a suitable simulation tool which jointly performs system and link level analysis, we first classify the users on the basis of performance level and burstiness, and then, we provide some guidelines for the design of Markov models in the different system and channel conditions. The performance of an automatic repeat request (ARQ) (Go-Back N) protocol at the link layer is taken as an example to test the accuracy of the proposed models. It is shown that the perspective of using simple error models in the analysis of upper layer protocols is feasible in many cases.

Effects of Discontinuous Transmission on the Performance of a WCDMA Cellular System

In this paper, we investigate some side effects of discontinuous transmission (DTX) on the performance of a wide-band code-division multiple-access (WCDMA) radio interface with signal-to-interference-ratio-based closed-loop power control. More precisely, we study how the DTX mechanism affects the transmission of some user signals. It is shown that the mobile terminals, when they turn on their data channels after some frames without any data to transmit, can cause a sudden increase of the interference level, leading, for some neighboring users, to a temporary performance degradation that lasts until the power control has completely reacted to this event. The main parameters that characterize the dynamics of the DTX mechanism are described and the tradeoffs in the choice of their values are evaluated; we also propose a suitable variation to the DTX mechanism that reduces the unwanted effects. For our investigation, a suitable simulation tool, which integrates the system-level and link-level analysis, has been developed, including most of the actual details and features of the WCDMA physical layer.

Error probability analysis for CDMA systems with closed-loop power control

Fast closed-loop-power-control (CLPC) plays a key role in direct-sequence (DS) code division multiple access (CDMA) systems, aiming at achieving acceptable carrier-to-interference (C/I) ratios in all active links. Assuming a terrestrial mobile access, where the round-trip delay may be smaller than the channel time-coherence, fast CLPC can compensate for fading and reduce the error burstiness, as well. This paper provides analytical expressions for the bit error probability given: the CLPC algorithm specified in terms of loop delay and updating rate, the propagation power delay-profile and the terminal speed. A binary PSK DS spread spectrum radio interface, with RAKE processing of multipath or diversity, is considered. Our link-level analysis, being conditioned to a specified average value of C/I, is focused on the inverse update algorithm, which is aimed at keeping the received power at a constant level. Applications of the derived method, aimed at getting insight about CLPC performance in 3rd generation radio interfaces, is also provided and discussed.

Issues Relating to Use of Travel Models in Benefit-Cost Analysis

Benefit-cost (B/C) analysis is a useful tool to compare the economic worth of transportation alternatives across modes. However, the application of tools such as MicroBENCOST, IDAS, and STEAM for B/C analysis in metropolitan areas raises several important technical issues that can significantly affect the results of the analysis. Several issues relate to use of four-step travel model outputs in estimation of benefits. Use of an inappropriate “No Build” base for comparison can exaggerate benefit estimates, as can a lack of consideration of the impact of induced travel. Link-level analysis can overestimate benefits from travel time savings, and at the system level, only trip-based analysis can adequately address issues relating to the “constant travel time budget” theory. Finally, use of congested speeds output by traffic assignment models can exaggerate travel time savings. These issues and their implications in metropolitan transportation decision making are discussed.