Multi-directional Warning Message Dissemination Protocol Based on Motion Vector Clustering for VANETs

Problem. Most broadcast suppression protocols in vehicular ad hoc networks (VANET) mainly focus on one-dimensional message dissemination model for both highway and urban scenarios. Due to the non-line-of-sight (NLOS) problem occuring frequently in urban scenario, protocols mostly rely on either infrastructure or the vehicle that is passing through the intersection to forward the message in multiple directions manner. However, these one-dimensional message dissemination models fail to take into account realistic road topologies and traffic distribution. As a result, they tend to miss some possible dissemination directions. Method. Vehicles travelling on the same road share similar motion pattern due to the constraint of road topology. Each motion pattern represents a road topology as well as a potential dissemination direction. By identifying motion pattern of one-hop neighbors, the proposed motion vector protocol (MVP) enables a vehicle not only to identify potential dissemination directions without the support from infrastructure or a road map but also to make suppression decisions without any additional information from periodic beacons. Results. The total number of transmissions for simple flooding (each node broadcasts once) compared with MVP ranges respectively as follows: 90.2-269.7 and 40.6-72.3. Also, the number of saved rebroadcasts for simple flooding compared with MVP ranges respectively as follows: 0%-0% and 57%-73%. In the case of reachability, the simple flooding compared with MVP ranges 100%-100% and 100%-100% respectively. Finally, the average latency of the entire dissemination for simple flooding and MVP ranges 0.01446-0.01286s and 0.1127-0.1565s respectively. Conclusions. The experimental results show that MVP achieves high reachability, while still significantly reducing rebroadcast redundancy. One distinctive feature of MVP is that it is capable of operating on complex road topology such as a roundabout, curve road, branch road, etc., with multi-directional traffic in it

Testing Game Theory in the Field: Swedish LUPI Lottery Games

Game theory is usually difficult to test precisely in the field because predictions typically depend sensitively on features that are not controlled or observed. We conduct one such test using field data from the Swedish lowest unique positive integer (LUPI) game. In the LUPI game, players pick positive integers and whoever chose the lowest unique number wins a fixed prize. Theoretical equilibrium predictions are derived assuming Poisson- distributed uncertainty about the number of players, and tested using both field and laboratory data. The field and lab data show similar patterns. Despite various deviations from equilibrium, there is a surprising degree of convergence toward equilibrium. Some of the deviations from equilibrium can be rationalized by a cognitive hierarchy model

Observation of Ultrahigh Mobility Surface States in a Topological Crystalline Insulator by Infrared Spectroscopy

Topological crystalline insulators (TCIs) possess metallic surface states protected by crystalline symmetry, which are a versatile platform for exploring topological phenomena and potential applications. However, progress in this field has been hindered by the challenge to probe optical and transport properties of the surface states owing to the presence of bulk carriers. Here we report infrared (IR) reflectance measurements of a TCI, (001) oriented $Pb_{1-x}Sn_{x}Se$ in zero and high magnetic fields. We demonstrate that the far-IR conductivity is unexpectedly dominated by the surface states as a result of their unique band structure and the consequent small IR penetration depth. Moreover, our experiments yield a surface mobility of 40000 $cm^{2}/(Vs)$, which is one of the highest reported values in topological materials, suggesting the viability of surface-dominated conduction in thin TCI crystals. These findings pave the way for exploring many exotic transport and optical phenomena and applications predicted for TCIs