X-TCP: A Cross Layer Approach for TCP Uplink Flows in mmWave Networks

Millimeter wave frequencies will likely be part of the fifth generation of mobile networks and of the 3GPP New Radio (NR) standard. MmWave communication indeed provides a very large bandwidth, thus an increased cell throughput, but how to exploit these resources at the higher layers is still an open research question. A very relevant issue is the high variability of the channel, caused by the blockage from obstacles and the human body. This affects the design of congestion control mechanisms at the transport layer, and state-of-the-art TCP schemes such as TCP CUBIC present suboptimal performance. In this paper, we present a cross layer approach for uplink flows that adjusts the congestion window of TCP at the mobile equipment side using an estimation of the available data rate at the mmWave physical layer, based on the actual resource allocation and on the Signal to Interference plus Noise Ratio. We show that this approach reduces the latency, avoiding to fill the buffers in the cellular stack, and has a quicker recovery time after RTO events than several other TCP congestion control algorithms.Comment: 6 pages, 5 figures, accepted for presentation at the 2017 16th Annual Mediterranean Ad Hoc Networking Workshop (MED-HOC-NET

Cost Estimate Modeling of Transportation Management Plans for Highway Projects, Research Report 11-24

Highway rehabilitation and reconstruction projects frequently cause road congestion and increase safety concerns while limiting access for road users. State Transportation Agencies (STAs) are challenged to find safer and more efficient ways to renew deteriorating roadways in urban areas. To better address the work zone issues, the Federal Highway Administration published updates to the Work Zone Safety and Mobility Rule. All state and local governments receiving federal aid funding were required to comply with the provisions of the rule no later than October 12, 2007. One of the rule’s major elements is to develop and implement Transportation Management Plans (TMPs). Using well-developed TMP strategies, work zone safety and mobility can be enhanced while road user costs can be minimized. The cost of a TMP for a road project is generally considered a high-cost item and, therefore, must be quantified. However, no tools or systematic modeling methods are available to assist agency engineers with TMP cost estimating. This research included reviewing TMP reports for recent Caltrans projects regarding state-of-the-art TMP practices and input from the district TMP traffic engineers. The researchers collected Caltrans highway project data regarding TMP cost estimating. Then, using Construction Analysis for Pavement Rehabilitation Strategies (CA4PRS) software, the researchers performed case studies. Based on the CA4PRS outcomes of the case studies, a TMP strategy selection and cost estimate (STELCE) model for Caltrans highway projects was proposed. To validate the proposed model, the research demonstrated an application for selecting TMP strategies and estimating TMP costs. Regarding the model’s limitation, the proposed TMP STELCE model was developed based on Caltrans TMP practices and strategies. Therefore, other STAs might require adjustments and modifications, reflecting their TMP processes, before adopting this model. Finally, the authors recommended that a more detailed step-by-step TMP strategy selection and cost estimate process be included in the TMP guidelines to improve the accuracy of TMP cost estimates

Improved Handover Through Dual Connectivity in 5G mmWave Mobile Networks

The millimeter wave (mmWave) bands offer the possibility of orders of magnitude greater throughput for fifth generation (5G) cellular systems. However, since mmWave signals are highly susceptible to blockage, channel quality on any one mmWave link can be extremely intermittent. This paper implements a novel dual connectivity protocol that enables mobile user equipment (UE) devices to maintain physical layer connections to 4G and 5G cells simultaneously. A novel uplink control signaling system combined with a local coordinator enables rapid path switching in the event of failures on any one link. This paper provides the first comprehensive end-to-end evaluation of handover mechanisms in mmWave cellular systems. The simulation framework includes detailed measurement-based channel models to realistically capture spatial dynamics of blocking events, as well as the full details of MAC, RLC and transport protocols. Compared to conventional handover mechanisms, the study reveals significant benefits of the proposed method under several metrics.Comment: 16 pages, 13 figures, to appear on the 2017 IEEE JSAC Special Issue on Millimeter Wave Communications for Future Mobile Network

Rat-running through Walmer Estate, University Estate and Upper Woodstock during the PM peak period

Urban sprawl remains as a remnant of previous Apartheid legacy policies and has a daily impact on the majority of South African commuters: large, densely populated residential areas (i.e. informal settlements) are generally located on the periphery of towns or cities, far away from areas of employment. As a result, a large number of commuters have to travel great distances to-and from work on a daily basis, and those making use of private vehicles have to accept very high levels of congestion for a large part of their journey. Certain motorists, therefore, carefully select routes, in an attempt to bypass some of this congestion experienced on the arterials and highways, to minimise their travel time and many times this is achieved through the practice of rat-running. This minor dissertation proposes to quantify the number of rat-runners and to identify the routes that the motorists use when moving through a pre-defined study area, with a view towards developing an effective solution to this problem. To achieve this, it is necessary to explore the root causes behind rat-running and investigate what has been done elsewhere to, successfully, mitigate this problem. This information was used to derive a number of proposed mitigating measure alternatives, applicable to the study area's current rat-running where, after a final decision, a preferred solution and the way forward was established. Problem Description The existing Cape Town CBD is positioned in a unique location: the topography of the City, i.e. the position of Table Mountain (and other mountain ranges) and the Atlantic Sea (coastline) means that the majority of the population lives to the east of the CBD, with very few residential opportunities available to the west. As such, there are a limited number of road-based routes to access and exit the City's Central CBD, to and from these east-lying areas which results in significant peak period congestion issues on the City's road network. In fact, results from a study undertaken by GPS manufacturer Tomtom (2014) show that the Cape Town road network is the most congested in the country. It is anticipated that the above-mentioned conditions make it attractive/possible for vehicles leaving the CBD during the PM peak period to rat-run through the immediately adjacent suburban areas, in an attempt to bypass the excessive levels of congestion currently experienced on the major routes. This practice creates major health, safety and economic problems for the affected communities and is a cause for major unhappiness as a result of the associated deterioration in their overall quality of life

UNDERSTANDING THE IMPACT OF INCIDENTS AND INCIDENT MANAGEMENT PROGRAMS ON FREEWAY MOBILITY AND SAFETY

Despite significant technological achievements over past decades, and institutional support for Intelligent Transportation System (ITS), it is not possible to prevent all traffic incidents. Numerous incidents occur every day along U.S. freeways and traffic incident management (TIM) programs have been proposed and implemented to mitigate their impact. This dissertation proposes various tools to aid in the evaluation of proposed TIM programs, contributing, thus, to the general study area of freeway incident management. In addition, moving violations specific to concurrent flow lane operations are conceived as a type of transient incident. Their impact on mobility and safety is considered. Techniques to address four key areas are proposed. First, a methodology that considers the dynamics of incident impact given a primary incident's properties and prevailing traffic conditions for identifying secondary incidents from a database is proposed. This method is computationally efficient and overcomes deficiencies of other existing techniques, with utility in any context in which the study of secondary incidents is warranted. A three-stage time-saving process is developed for conducting TIM program benefit evaluations. The process aids in sampling a relatively small set of good quality incident scenarios that can represent historical incident data and overcomes the computational burden encountered when evaluating TIM program's benefit by simulation. Modeling techniques are proposed for simulating violations associated with the operation of concurrent flow lanes. Results from a case study show significant impact to mobility that grows nonlinearly with increasing violation rate. Such illegal traffic maneuvers contribute to increased speed variation and congestion, ultimately affecting safety. Finally, diversion strategies that exploit existing capacity of managed lanes for the purpose of reducing the impact of an incident in the general purpose lanes are evaluated. Simulation modeling methodologies were developed for modeling freeway incidents and studied diversion strategy implementations. Experimental findings indicate benefits of diversion that are contrary to qualitatively developed recommendations in the literature

Full-duplex wireless communications: challenges, solutions and future research directions

The family of conventional half-duplex (HD) wireless systems relied on transmitting and receiving in different time-slots or frequency sub-bands. Hence the wireless research community aspires to conceive full-duplex (FD) operation for supporting concurrent transmission and reception in a single time/frequency channel, which would improve the attainable spectral efficiency by a factor of two. The main challenge encountered in implementing an FD wireless device is the large power difference between the self-interference (SI) imposed by the device’s own transmissions and the signal of interest received from a remote source. In this survey, we present a comprehensive list of the potential FD techniques and highlight their pros and cons. We classify the SI cancellation techniques into three categories, namely passive suppression, analog cancellation and digital cancellation, with the advantages and disadvantages of each technique compared. Specifically, we analyse the main impairments (e.g. phase noise, power amplifier nonlinearity as well as in-phase and quadrature-phase (I/Q) imbalance, etc.) that degrading the SI cancellation. We then discuss the FD based Media Access Control (MAC)-layer protocol design for the sake of addressing some of the critical issues, such as the problem of hidden terminals, the resultant end-to-end delay and the high packet loss ratio (PLR) due to network congestion. After elaborating on a variety of physical/MAC-layer techniques, we discuss potential solutions conceived for meeting the challenges imposed by the aforementioned techniques. Furthermore, we also discuss a range of critical issues related to the implementation, performance enhancement and optimization of FD systems, including important topics such as hybrid FD/HD scheme, optimal relay selection and optimal power allocation, etc. Finally, a variety of new directions and open problems associated with FD technology are pointed out. Our hope is that this treatise will stimulate future research efforts in the emerging field of FD communication

Cross Border Transportation Patterns at the Western Cascade Gateway: Implications for Mitigating the Impact of Delay on Regional Supply Chains

The Pacific Highway border crossing in Blaine, Washington, is the fourth busiest commercial crossing on the northern border and the most significant commercial crossing for Western Canada and the U.S. (USDOT/FHWA 2006). The primary commodities that flow across this border are agricultural/food, wood, and paper products (WCOG Manifest Data). These commodities are not viewed as particularly time critical, as they do not move in a strictly scheduled environment, although in fact a significant proportion of these goods are highly perishable. Both of these factors are significantly different than along the eastern portion of the northern border, where goods are flowing across the border in a time sensitive business environment that requires more precise delivery time estimates. These regional characteristics are important in understanding the current U.S. commercial vehicle transportation phenomenon and the impacts of delays, as well as in developing improvements and anticipating the consequences of change both at border crossings and within the Cascade border region as a whole