HotMobile 2008: Postconference Report

HotMobile 2008 presented a two-day program on mobile computing systems and applications. The authors focuses on the sessions on sensors, modularity, wireless, security, systems, and screens. The mobile device is the most amazing invention in history and that it has had the largest impact on human kind. Because mobile phones combine mobile devices with ongoing developments in software and communication technologies, they have the potential to change the way people think and act

Secure Cloud Controlled Software Defined Radio Network For Bandwidth Allocation

The purpose of this research is to investigate the impact of mobility of wireless devices for opportunistic spectrum access and communications using National Instrument Universal Software Radio Peripherals devices. The overall system utilizes software defined radio networks for frequency allocation, cloud connectivity to maintain up-to-date information, and moving target defense as a security mechanism. Each USRP device sends its geolocation to query the spectrum database for idle channels. The cloud cluster was designed for complex data storage and allocation using a smart load balancer to offer ultra-security to users. This project also explores the advantages of data protection and security through moving target defense. To achieve this, the system would use an array of antennas to split the data into different parts and transmit them across separate antennas. This research provides the design to each of the mentioned projects for the implementation of a fully developed system

When Distributed Consensus Meets Wireless Connected Autonomous Systems: A Review and A DAG-based Approach

The connected and autonomous systems (CAS) and auto-driving era is coming into our life. To support CAS applications such as AI-driven decision-making and blockchain-based smart data management platform, data and message exchange/dissemination is a fundamental element. The distributed message broadcast and forward protocols in CAS, such as vehicular ad hoc networks (VANET), can suffer from significant message loss and uncertain transmission delay, and faulty nodes might disseminate fake messages to confuse the network. Therefore, the consensus mechanism is essential in CAS with distributed structure to guaranteed correct nodes agree on the same parameter and reach consistency. However, due to the wireless nature of CAS, traditional consensus cannot be directly deployed. This article reviews several existing consensus mechanisms, including average/maximum/minimum estimation consensus mechanisms that apply on quantity, Byzantine fault tolerance consensus for request, state machine replication (SMR) and blockchain, as well as their implementations in CAS. To deploy wireless-adapted consensus, we propose a Directed Acyclic Graph (DAG)-based message structure to build a non-equivocation data dissemination protocol for CAS, which has resilience against message loss and unpredictable forwarding latency. Finally, we enhance this protocol by developing a two-dimension DAG-based strategy to achieve partial order for blockchain and total order for the distributed service model SMR

Enhanced stability of cluster-based location service mechanism for urban vehicular ad hoc networks

Vehicular Ad Hoc Networks (VANETs) are gaining tremendous research interest in developing an Intelligent Transportation System (ITS) for smart cities. The position of vehicles plays a significant role in ITS applications and services such as public emergency, vehicles tracking, resource discovery, traffic monitoring and position-based routing. The location service is used to keep up-to-date records of current positions of vehicles. A review of previous literatures, found various locationbased service mechanisms have been proposed to manage the position of vehicles. The cluster-based location service mechanisms have achieved growing attention due to their advantages such as scalability, reliability and reduced communication overhead. However, the performance of the cluster-based location service mechanism depends on the stability of the cluster, and the stability of the cluster depends on the stability of the Cluster Head (CH), Cluster Member (CM) and cluster maintenance. In the existing cluster-based location service schemes, the issue of CH instability arises due to the non-optimal cluster formation range and unreliable communication link with Road Side Unit (RSU). The non-optimal cluster formation range causes CH instability due to lack of uniqueness of Centroid Vehicle (CV), uncertainty of participating vehicles in the CH election process and unreliability of the Cluster Head Election Value (CHEV). Also, the unreliable link with RSU does not guarantee that CH is stable with respect to its CMs and RSU simultaneously. The issue of CM instability in the existing cluster-based location service schemes occurs due to using instantaneous speed of the CH and fixed CM affiliation threshold values. The instantaneous speed causes the CM to switch the clusters frequently and fixed CM affiliation threshold values increase isolated vehicles. The frequent switching of isolated vehicles augment the CM instability. Moreover, the inefficient cluster maintenance due to non-optimal cluster merging and cluster splitting also contributes to cluster instability. The merging conditions such as fixed merging threshold time and uncertain movement of overlapping CHs within merging threshold time cause the cluster instability. Furthermore, the unnecessary clustering during cluster splitting around the intersection due to CH election parameters also increases cluster instability. Therefore, to address the aforementioned cluster instability issues, Enhanced Stability of Cluster-based Location Service (ESCLS) mechanism was proposed for urban VANETs. The proposed ESCLS mechanism consists of three complementary schemes which are Reliable Cluster Head Election (RCHE), Dynamic Cumulative Cluster Member Affiliation (DCCMA) and Optimized Cluster Maintenance (OCM). Firstly, the aim of the RCHE scheme was to enhance the stability of the CH through optimizing the cluster formation range and by considering communication link reliability with the RSU. Secondly, the DCCMA scheme focussed on improving the stability of the CMs by considering the Cumulative Moving Average Speed (CMAS) of the CH and dynamic CM affiliation threshold values, and finally, the OCM scheme enhanced the cluster stability by improving cluster merging conditions and reducing unnecessary clustering in cluster splitting. The results of the simulation verified the improved performance of the ESCLS in terms of increasing the location query success rate by 34%, and decreasing the query response delay and localization error by 24% and 35% respectively as compared to the existing cluster-based location service schemes such as HCBLS, CBLS and MoGLS. In conclusion, it is proven that ESCLS is a suitable location service mechanism for a wide range of position-based applications of VANETs that require timely and accurate vehicle locations

GCCP - NS: Grid based Congestion Control protocol with N-Sinks in a Wireless Sensor Network

Wireless Sensor Networks (WSN) have been a current trend in the research field and has many issues when there are multiple mobile sinks. Data dissemination gets critical as their locations have to be repeatedly updated and results in huge consumption of the restricted battery supply in sensor nodes. In this paper, we propose GCCP – NS, a grid based congestion control protocol with N –sinks that solves the data dissemination problem leading to congestion. We construct a dual level grid structure to trail the locations of all the source nodes that reports the information to the mobile sinks by monitoring the network in a hierarchical manner. As an added advantage, it aids in data dissemination based on query flooding from the mobile sinks using quorum based method within each cell in the grid and avoids congestion in an effective manner. Simulation results show that our proposed protocol outperforms the other schemes in terms of packet delivery ratio, energy expenditure and throughput

Data management for cloud supported cooperative driving

Tese de mestrado, Engenharia Informática (Arquitetura, Sistemas e Redes de Computadores) Universidade de Lisboa, Faculdade de Ciências, 2020The increasing number of technologies inserted into vehicles, allowed the common user to have access to a broad number of utilities that allows driving to be easier, safer and more economical. ABS, GPS, Bluetooth and onboard computer are some of the technologies associated with a recent vehicle. On more experimental ones there is obstacle detection, automatic braking and self-driving technologies, which can be supported by a wireless network connection to further improve their capabilities. That connection allows the transformation of each independent vehicle into nodes in an ad-hoc network. The current challenge is to connect all those vehicles and be able to provide the data needed for their correct functioning in a timely manner. That is the challenge this dissertation will seek to analyse: the possibility to create a reliable vehicular information system for cooperative driving based on the cloud. Cloud-based storage can support an ever changing number of vehicles while still satisfying scalability requirements and maintaining ease of access without the need to maintain a physical infrastructure, as that responsibility is laid upon the provider. To understand which service is the best to host the vehicular information system it was analyzed three services from Amazon Web Services (AWS): S3, EC2 and DynamoDB. Ease of utility, latency, scalability and cost were the main requirements tested as they are the most important aspects for a real-time vehicular information system for autonomous vehicles. After deciding which cloud service would be the most appropriate to implement the vehicular information system, two client models were created that fulfilled a set of requirements. They were based in an already existing algorithm named Two-Step Full Replication which utilizes a group of Key-Value Stores services from various clouds to simulate a shared-memory based on multi-writer, multi-reader (MWMR) registers. This algorithm tolerates Byzantine faults by using Byzantine quorum techniques and integrity and authenticity checks. It was defined and implemented the necessary changes on the algorithm to create usable a client for a vehicular information system. The first model called ”Atomic Snapshot Client”, uses the modified Two-Step Full Replication interface with the Atomic Snapshot algorithm. This model guarantees that the read of the system (snapshot) is done atomically without being adulterated by concurrent writes, sacrificing execution latency. The second model is a faster version of the first one with the objective of obtaining faster responses from the system without overly sacrificing data consistency, which is called ”Fast Snapshot Client”. The main change from the first one is the reduction of the guarantees of the atomic registers to regular ones making the reads (scan) and writes (update) simpler and faster, although removing the atomic snapshot feature. With the analysis of the data collected from experiments performed with this model it was possible to observe a relation between the increase of the scan latency time and the total time spent on the execution of the read and write operations on an application with various clients. To solve this problem a simple garbage collector was implemented, which cleans each register when the number of outdated writes that it contains goes over a specified threshold. This solution, although simple, proved to be effective to reduce each scan time. Finally, a vehicular information system based on the AWS S3 service was implemented. It is composed by two types of clients based on the Fast Snapshot Client, named vehicular client and calculator client. The two types of client work together, where the vehicular clients trade information with the calculator. The calculator client scans the registers of the vehicle clients and writes on its registers the processed data for each vehicular client. The vehicle clients need to write all the relevant data they gather and read the register of their respective calculator client and act according to the data read. Each of the clients was tested separately and analysed in order to discuss the viability of this system in a real-world application as well as possible changes to further improve it