Inter-vehicular communication for collision avoidance using Wi-Fi Direct

Inter vehicular collision avoidance systems warn vehicle drivers of potential collisions. The U.S Department of Transportation (USDOT) National Highway Traffic Safety Administration, in February 2014 has decided to enable vehicular communication among lightweight vehicles to exchange warning messages to prevent accidents. Dedicated Short Range Communications (DSRC) is a communication standard that allows short-range communication between vehicles and infrastructure, exchanging critical safety information to avoid collision. DSRC safety applications include forward collision warning, sudden brake warning and blind spot warning among many other warnings. It is also important to exchange location information between vehicles and pedestrians to avoid accidents. To exchange safety messages using DSRC, dedicated equipment is required. Pedestrians may not benefit from DSRC, as they may not carry dedicated DSRC safety equipment with them. Wi-Fi Direct technology can be used as an alternate to DSRC to exchange safety messages. Wi-Fi Direct enabled smartphones can exchange important safety information without the need of additional equipment. Peer-to-Peer (P2P) connections are formed between Wi-Fi Direct devices to exchange safety information. The Group Owner acts as the access point through which all clients communicate. This work examines how Wi-Fi Direct can be used in vehicular environment to exchange basic safety information between smartphones of vehicle drivers. Wi-Fi Direct and DSRC transmission delays are calculated are calculated. The results show, with more devices in a Wi-Fi Direct group the congestion in the network increases due to unnecessary retransmissions through the group owner. As mitigation, a broadcast method is proposed to reduce the delay. The results illustrate that the P2P group can now accommodate more vehicles and the delay is lesser. The calculations are extended to compute the transmission delay when P2P groups of same size exchange safety messages. The results help analyse the limitations of the system

System-Level Performance Analysis and Optimization of IEEE 802.11ah -- the New Sub-1 GHz Wi-Fi

Internet of Things (IoT) is a concept which will have major effects on our future lives. It will introduce a novel dimension to the world of information and communication technology where connectivity will be available anytime, anywhere for anything. This will implicitly introduce billions of devices and stations that need to communicate within the IoT network. Consequently, it is necessary to design new wireless technologies to support them. IEEE 802.11ah is one of these technologies which exploit IEEE 802.11 standard advantages while benefiting from certain changes specifically made to satisfy IoT requirements like being able to handle this amount of devices and being power efficient. IEEE 802.11ah which operates in sub-1 GHz band is expected to assure 1 km coverage with at least 100 Kbps data rate and it should support beyond 2000 stations. This thesis evaluates the performance of IEEE 802.11ah and some of its features in various scenarios using a system-level simulator developed in this research work. Comparing the developed simulator's results with two analytical models, one introduced in the literature and one developed in this thesis, proves the high accuracy of the simulator in modeling the IEEE 802.11ah network. The performance analysis shows that for IoT use cases with relatively low packet size (256 bytes), it is better not to use RTS/CTS access scheme. Based on the presented results, it is concluded that frequency management mechanisms, link adaptation algorithms and Restricted Access Window (RAW) mechanism, should be used in most of the practical cases to have higher energy efficiency and improve the general system performance

Performance Enhancement Mechanism of IEEE 802.11AH Machine Communication System

As the Internet gets more populated and the number of devices increase dramatically, demanding connectivity anytime, anywhere and for everything, the urge for a novel concept is raised. Consequently, Internet of Things (IoT) is introduced to shed a light on the vision of the future Internet with tremendous amount of "things" interconnected to each other while utilizing various technologies for different applications. As a wide range of wireless technologies are developed and are extensively used worldwide, IEEE 802.11 working group for WLAN standards is developing a new amendment referred as IEEE 802.11AH targeting mainly the IoT based applications. The new amendment has inherited many characteristics from the legacy IEEE 802.11 while benefiting from new enhanced features defined specifically for IoT and Machine to Machine communications (M2M) systems. Ultimately, IEEE 802.11AH which has been defined to operate in sub-1 GHz band, is expected to support high number of simultaneous connections up to 6000 devices for a 1 km coverage range. This thesis implements some of the enhanced features for IEEE 802.11AH and conducts the corresponding evaluation based on a developed simulator. The aforementioned simulator has been compared to a Markov chain based analytical model, developed in this research. The results have shown that the developed system level simulator is following the results from the modeled network with high accuracy. The developed system level simulator has been used in performance evaluation of the IEEE 802.11AH main features like the restricted access window (RAW) and sectorization schemes in the case of single and multiple APs deployments scenarios. It is concluded that the implementation of these features, help to improve IEEE 802.11AH overall performance. The performance measures considered in this evaluation are throughput, energy efficiency and average delay in sending successful packets, respectively. Moreover, for resolving the coverage requirements there is a trade-off in using single AP or multi AP configuration. Implementing more APs results in more network capacity while causing additional interference to the network. The RAW and sectorization mechanisms can fortunately reduce this interference by minimizing the hidden node probability and mitigating against the overlapping BSS resulting problems