Nabih Jaber

Reconfigurable simulator using graphical user interface (GUI) and object-oriented design for OFDM systems

Abstract In this paper, a design of a new object-oriented simulation environment and graphical user interface (GUI) for versatile orthogonal frequency division multiplexing (OFDM) systems is presented. This is achieved using high-level design, parallelism and usability for the simulation environment. GUI interface can serve as a learning/research tool for students or practiced professionals to investigate particular designs. It is evident that OFDM systems intended to be used in dynamic environments must be tested under various conditions in order to be designed for optimality. Hence, a simulation design is proposed coupling the GUI, parallelism, and high-level object-oriented design techniques to be beneficial to the researcher. A high-level design and GUI layouts of the proposed simulator is shown in details. Important OFDM parameters needed for reconfiguration of transmitter components, channel condition parameters, and receiver components are discussed. In addition, this paper provides a simple technique to implement simulation partitioning for increased parallel performance of reconfigurable object-oriented OFDM simulators. This simple technique applies to scenarios where there is disproportionate simulation duration between different OFDM configurations. It is shown to decrease total simulation time considerably.

New combined WiMAX/DSRC infrastructure design for efficient vehicular networking

In this article, a new infrastructure of a combined Worldwide Interoperability for Microwave Access (WiMAX) and Dedicated Short-Range Communications (DSRC) link layer is proposed with the purpose of reducing simultaneous WiMAX connections. WiMAX offers wide area connectivity of vehicles to ground-based base stations, while DSRC offers relatively shorter communication that allows for vehicles in proximity of each other to communicate directly. The proposed design uses the fact that WiMAX amendments support the concept of a WiMAX relay node, and substitutes the WiMAX relay nodes with nodes that are capable of both WiMAX and DSRC communications. This change allows for the number of WiMAX connections to be concentrated while supporting more subscribing users via WiMAX tunnelled over DSRC relay. The focus of this design is on the use case of providing broadband Internet access to a large number of DSRC capable vehicles in a WiMAX served region. The design uses DSRC as a WiMAX tunnel, but with changes to the WiMAX protocol, specifically network entry and handover processes are redesigned to have different behaviour only when operating over DSRC. Network entry over DSRC modifications are described and illustrated with comparison to existing WiMAX standards. Handover process facilitated over both WiMAX and DSRC layers are described, illustrated and are also standard compliant. Unified modeling language is used to assist with the explanations of the components to improve understanding of the design in relation to existing WiMAX standards. In addition to standard WiMAX operability, the design can also support WiMAX data subscription using a software-defined WiMAX radio via DSRC relay connectivity. This proposed design improves WiMAX communication by reducing the number of WiMAX connections between vehicles. We plotted the throughput of various cluster sizes of WiMAX only mobile relay, versus our proposed DSRC-enabled WiMAX mobile relay in order to show the efficiency benefit of our design. We also provide a simulated curve of percentage improvement efficiency for varying amount of active users. We show that as the total number of users in the system increases, our proposed system significantly improves the overall system efficiency, especially in heavily congested traffic.

Improvement in vehicular networking efficiency using a new combined WiMAX and DSRC system design

WiMAX is a competing standard for next generation wireless broadband internet access. With the latest revision of the standard, Mobile WiMAX, it is becoming ready for use in highly mobile applications, such as handheld devices and in-vehicular internet access. Research has shown, however, that WiMAX suffers overhead problems with high numbers of simultaneous active connections. This paper proposes a new combined technology system that uses the DSRC vehicle-to-vehicle links to cluster concentrate the WiMAX connections. An efficiency equation model is developed, and the simulation results show that the new proposed system improves efficiency of WiMAX by over 30%, while at the same time promoting the adoption of DSRC for safety and intelligent transportation system applications. Hence, it is shown that integrating WiMAX and DSRC would significantly save the bandwidth usage for WiMAX.

Complete architecture and demonstration design for a new combined WiMAX/DSRC system with improved vehicular networking efficiency

Abstract This paper provides a detailed architecture and demonstration system for a new combined Worldwide Interoperability for Microwave Access (WiMAX) and Dedicated Short Range Communications (DSRC) network layer design for providing Internet access to vehicles. The overall design consists of subscriber station (SS) vehicles, cluster head relay station (RS) vehicles, WiMAX base stations (BSs), and Internet access gateways (IAGs). Here RSs serve as intermediate relays for serving virtual WiMAX connections to SS vehicles, relying on a WiMAX backend network for Internet connectivity. Simulation results show that our proposed system significantly improves the overall system efficiency as compared to the conventional WiMAX-only system, motivating a design of a complete WiMAX/DSRC Internet access architecture. The first main focus of this paper is on the layer 3 network protocol (L3NP) operating between the access concentrator (AC) in the SS instances and the Network Server (NS) component of an IAG, which provides Internet service to user applications. The second main focus of this paper is on the WiMAX backend network protocol (WBNP) and backend connection networking for handling traffic between the BS nodes and the IAG node providing the L3NP service to the vehicles. Finally, the third main focus of this paper is on the demonstration system design which takes all of the above mentioned elements, namely SS, RS, BS, and IAG modules, network entry functionality, to network protocol settings and behaviour, and implements them in an object-oriented design for accurate scenario performance and feasibility testing. The demonstration system implements tunnelling of protocols in the same way as an actual implementation, but uses virtual network devices for each module to facilitate communications. We provide example use cases for using our proposed architecture design with our provided demonstration system to serve as a useful tool to vehicular communications and networking engineers/researchers, that can be reconstructed and adapted as needed for derivative designs and scenarios.

Design and implementation of a cross-platform sensor network for smart grid transmission line monitoring

Slow information feedback and hesitation to relay the information to other power stations was a major contributor to North Americas northeast blackout of 2003. Had fault information been properly passed on, the blackout area would have been much smaller. From experience, it can be seen that having the knowledge of knowing exactly when and what is happening on the power distribution grid is extremely valuable. This paper proposes and develops a practical, self configuring, sampling and forwarding scheme for smart grid transmission line monitoring and presents a hierarchical communication topology. The developed prototype operates successfully and its functionality is documented in detail. In addition, descriptive Unified Modelling Language (UML) diagrams are presented to allow for understanding and implementation of the concepts behind our proposed design.

Passive Cooperative Collision Warning (PCCW) MAC designs for reliable vehicular safety messaging

This paper presents - Passive Cooperative Collision Warning (PCCW), and enhanced-PCCW (EPCCW) protocol designs for safety message reception reliability improvement in Dedicated Short Range Communications (DSRC). PCCW and EPCCW employ a cooperative warning scheme for reduction of collisions, without increasing packet traffic. EPCCW utilizes the physical layer (PHY) properties to create sub-slots for the purpose of further increasing reliability by both avoiding and minimizing probability of collision at slots that would nominally fail. Full analytical derivation of the relative reliability and delay performances for both PCCW and EPCCW protocols is provided. An accurate and complete simulation model is used, which combines an accurate DSRC PHY, MAC and federated mobility model designed using the Simulation of Urban MObility (SUMO) model. Analytical and simulation results agree and show that PCCW and EPCCW protocols significantly improve reliability performance relative to the leading safety messaging protocols. Under high collision scenarios and at optimal number of repetitions, an improvement of up to 40% in reliability is observed, and up to 80% of improvement is achieved at higher load. Improvement in average timeslots delay is also observed that is well within acceptable delay threshold. Thorough simulation results of the proposed protocols are presented under varying message range, coding rates, modulation schemes, channel models, vehicular densities, safety message lifetimes, and transmission frequencies.

Markov analysis of the mobile hidden station problem in MANET

This paper provides Markov analysis of mobile hidden station problem in the medium access control (MAC) layer of vehicular/mobile ad hoc networks (VANET/MANET). If a mobile station enters a collision free zone of any ongoing communication and interferes with this communication, it is called a mobile hidden station, and problems associated with mobile hidden stations is called mobile hidden station problem. The mobile hidden station problem severely degrades the throughput and the delay performances of mobile networks. In order to show the effect of mobile hidden station problem, the Markov models of IEEE 802.11 with and without mobile hidden station problem are developed. The developed models show that mobile hidden station increases collisions at the receivers and decreases the throughput up to 36 percent. This paper shows that mobile hidden station problem must be resolved while designing a MAC layer protocol for VANET/MANET.

Cross layer consideration for improved reliability of vehicular safety messaging

This paper presents a theoretical foundation for a new collision correcting medium access control (MAC) and physical (PHY) cross layer design (CLD) for safety messages in dedicated short range communications (DSRC). The concept relies on repetition messaging and the fact that DSRC safety messages are relatively short in length. Hence our design requires a cache of previously received packets, and pre informed packet repetitions. An example scenario is provided with a step by step description of how our proposed system will behave. Unified modeling language (UML) use case diagram is used to help describe functionality of the CLD. The operation of the collision correcting (CC) channel estimator (CE) and equalizer (EQ) is explained. Simulation results show reception reliability and PER performance is improved when our CLD is used as opposed to standard safety message broadcasting, especially in high repetition scenarios.

Collision correction using a cross-layer design architecture for dedicated short range communications vehicle safety messaging

This paper presents a new physical (PHY) and medium access control (MAC) cross-layer design frame collision correction (CC) architecture for correction of Dedicated Short Range Communications (DSRCs) safety messages. Conditions suitable for the use of this design are presented, which can be used for optimization. At its basic level, the CC at the PHY uses a new decision making block that uses information from the MAC layer for the channel estimator and equalizer. This requires a cache of previously received frames, and pre-announcing frame repetitions from the MAC. We present the theoretical equations behind CC mechanism, and describe the components required to implement the cross-layer CC using deployment and sequence diagrams. Simulation results show that especially under high user load, reception reliability of the DSRC safety messages increases and PER decreases.

Vehicular Broadcast Messaging Reliability Enhancement Protocol for Emergency Vehicle Communications

This paper presents a new reliability enhancement to safety messaging system particularly useful for emergency vehicle (EV) communications. This enhancement makes meeting stringent quality of service (QoS) requirements particularly prevalent in safety applications of Dedicated Short Range Communications (DSRC). We show that emergency- Passive Cooperative Collision Warning (ePCCW) enhances EV performance in particular, and measurement of the effect on surrounding vehicles relative to the desired EVs is also shown. ePCCW protocol is an imperfect distributed protocol, and both analytic and simulation results agree and show a significant improvement in EV communication reliability. Substantial improvement in reliability or probability of success relative to a leading alternative is realized. Highway environment is simulated with mobility modeled using the well known Simulation of Urban MObility (SUMO), and the DSRC Physical layer (PHY) is simulated using an accurate Orthogonal Frequency Division Multiplexing (OFDM) PHY simulator, with varying channel conditions based on mobility model and highway environment. Additionally, the proposed system is shown to have a decreased average timeslots delay that is well within acceptable delay threshold, and provides the best reliability in its class.