Even though human movement and mobility patterns have a high degree of freedom and variation, they also exhibit structural patterns due to geographic and social constraints. Using cell phone location data, as well as data from two online location-based social networks, we aim to understand what basic laws govern human motion and dynamics. We find that humans experience a combination of periodic movement that is geographically limited and seemingly random jumps correlated with their social networks. Short-ranged travel is periodic both spatially and temporally and not effected by the social network structure, while long-distance travel is more influenced by social network ties. We show that social relationships can explain about 10% to 30% of all human movement, while periodic behavior explains 50% to 70%. Based on our findings, we develop a model of human mobility that combines periodic short range movements with travel due to the social network structure. We show that our model reliably predicts the locations and dynamics of future human movement and gives an order of magnitude better performance than present models of human mobility.

/pdf/friendship-and-mobility-user-movement-in-location-based-2u0rrxuc9l.pdf

Friendship and mobility: user movement in location-based social networks

We report that human walk patterns contain statistically similar features observed in Levy walks. These features include heavy-tail flight and pause-time distributions and the super-diffusive nature of mobility. Human walks are not random walks, but it is surprising that the patterns of human walks and Levy walks contain some statistical similarity. Our study is based on 226 daily GPS traces collected from 101 volunteers in five different outdoor sites. The heavy-tail flight distribution of human mobility induces the super-diffusivity of travel, but up to 30 min to 1 h due to the boundary effect of people's daily movement, which is caused by the tendency of people to move within a predefined (also confined) area of daily activities. These tendencies are not captured in common mobility models such as random way point (RWP). To evaluate the impact of these tendencies on the performance of mobile networks, we construct a simple truncated Levy walk mobility (TLW) model that emulates the statistical features observed in our analysis and under which we measure the performance of routing protocols in delay-tolerant networks (DTNs) and mobile ad hoc networks (MANETs). The results indicate the following. Higher diffusivity induces shorter intercontact times in DTN and shorter path durations with higher success probability in MANET. The diffusivity of TLW is in between those of RWP and Brownian motion (BM). Therefore, the routing performance under RWP as commonly used in mobile network studies and tends to be overestimated for DTNs and underestimated for MANETs compared to the performance under TLW.

/pdf/on-the-levy-walk-nature-of-human-mobility-tdkmsro9ui.pdf

On the levy-walk nature of human mobility

Vehicular Ad-hoc Networks (VANETs) have been recently attracting an increasing attention from both research and industry communities. One of the challenges posed by the study of VANETs is the definition of a vehicular mobility model providing an accurate and realistic vehicular mobility description at both macroscopic and microscopic levels. Another challenge is to be able to dynamically alter this vehicular mobility as a consequence of the vehicular communication protocols. Many mobility models have been developed by the community in order to solve these two issues. However, due to the large number of available models claiming to be adapted to vehicular traffic, and also due to their different and somehow incomparable features, understanding their true characteristics, their degree of realism with respect to vehicular mobility, and real capabilities is a hard task. In this survey, we first introduce a framework that proposes a guideline for the generation of vehicular mobility models. Then, we illustrate the different approaches chosen by the community for the development of vehicular mobility models and their interactions with network simulators. Finally, we propose an overview and taxonomy of a large range of mobility models available for vehicular ad hoc networks. The objective is to provide readers with a guideline to easily understand and objectively compare the different models, and eventually identify the one required for their needs.

/pdf/mobility-models-for-vehicular-ad-hoc-networks-a-survey-and-1g8mz9v0dy.pdf

Mobility models for vehicular ad hoc networks: a survey and taxonomy

Simulating human mobility is important in mobile networks because many mobile devices are either attached to or controlled by humans and it is very hard to deploy real mobile networks whose size is controllably scalable for performance evaluation. Lately various measurement studies of human walk traces have discovered several significant statistical patterns of human mobility. Namely these include truncated power-law distributions of flights, pause-times and inter-contact times, fractal way-points, and heterogeneously defined areas of individual mobility. Unfortunately, none of existing mobility models effectively captures all of these features. This paper presents a new mobility model called SLAW (self-similar least action walk) that can produce synthetic walk traces containing all these features. This is by far the first such model. Our performance study using using SLAW generated traces indicates that SLAW is effective in representing social contexts present among people sharing common interests or those in a single community such as university campus, companies and theme parks. The social contexts are typically common gathering places where most people visit during their daily lives such as student unions, dormitory, street malls and restaurants. SLAW expresses the mobility patterns involving these contexts by fractal way points and heavy-tail flights on top of the way points. We verify through simulation that SLAW brings out the unique performance features of various mobile network routing protocols.

/pdf/slaw-a-new-mobility-model-for-human-walks-2871oh7dj1.pdf

SLAW: A New Mobility Model for Human Walks

A system and method identifies mobile applications that can have an adverse effect on a mobile device or mobile network. In an implementation, a server monitors behavioral data relating to a mobile application and applies a model to determine if the application has an adverse effect or has the potential to cause an adverse effect on a mobile device or a network the mobile device may connect to. A mobile device may monitor behavioral data, apply a model to the data, and transmit a disposition to the server. The server may aggregate behavioral data or disposition information from multiple devices. The server may transmit or make available the disposition information to a subscriber through a web interface, API, email, or other mechanism. After identifying that an application may have an adverse effect, the server may enact corrective actions, such as generating device or network configuration data.

System and method for adverse mobile application identification

Understanding user mobility is critical for simula- tions of mobile devices in a wireless network, but current mobility models often do not reflect real user movements. In this paper, we provide a foundation for such work by exploring mobility characteristics in traces of mobile users. We present a method to estimate the physical location of users from a large trace of mobile devices associating with access points in a wireless network. Using this method, we extracted tracks of always-on Wi-Fi devices from a 13-month trace. We discovered that the speed and pause time each follow a log-normal distribution and that the direction of movements closely reflects the direction of roads and walkways. Based on the extracted mobility characteristics, we developed a mobility model, focusing on movements among popular regions. Our validation shows that synthetic tracks match real tracks with a median relative error of 17%.

/pdf/extracting-a-mobility-model-from-real-user-traces-5gpwbzudyr.pdf

Extracting a Mobility Model from Real User Traces

In order to access a web site, for example one identified by a domain name, a client device must determine the network location, or IP address, of the webs site. In one example, the corresponding IP address of the domain name has been stored locally at the client device but has expired. The client device may send a request to network location of the expired IP address while concurrently sending a request to a domain name server for updated IP address information. If the updated IP address received from the server is the same as the expired IP address, the client device may request the web site information from the previously established connection. If the updated IP address is not the same as the expired IP address, the client device may abort the connection with the expired IP address and establish a new connection with the updated IP address.

Method for reducing DNS resolution delay

An apparatus prints on a continuous web moving in a process direction. A fiducial marker prints on a portion of the web a repeating pattern of fiducial marks at a predetermined spacing along the process direction. At least two printing stations are operatively disposed downstream of the fiducial marker, each printing station including a printhead for placing marking material suitable for a partial image on the web. A photosensor reads a fiducial mark on the web moving relative to the printing station.

Registration system for a web printer

This paper presents a MPEG-4 video codec (MoVa) that is based on an ARM core and AMBA. The MoVa includes an ARM embedded microprocessor and several hardwired modules, using pseudo-advanced microprocessors bus architecture (AMBA). The MoVa performs 30 frames/s of QCIF (SQCIF) or 15 frames/s of CIF at 27 MHz and meets the requirements for MPEG-4 SP@L2. Co-verification, HDL simulator and logic synthesis tools are used for hardware-software design and verification. It contains 1.7 million gates with a power consumption of about 0.5 W at 3.3 V.

MPEG-4 video codec on an ARM core and AMBA

Dependability of service (DoS) has become an important requirement for real-time applications, such as remote medical services, business-critical network meetings and command-and-control applications. The Dependable Real-Time Protocol (DRTP), in which each dependable real-time connection is realized with one primary and one or more backup channels, has been shown to be an effective way of providing DoS. How to route both primary and backup channels for each dependable real-time connection is of vital importance to the success of failure recovery and to overhead reduction in providing DoS. In this paper, we propose and evaluate three different schemes for routing the primary and backup channels of each dependable real-time connection. Specifically, we present methods based on link-state information and bounded flooding to discover routes for the primary and backup channels while satisfying the required quality of service (QoS). The costs of the link-state and flooding algorithms are reduced significantly by using the fact that the probability of success in failure recovery can be estimated with simple link-state information, and by bounding the flooded region within an ellipse with the two communication end-points as loci. Our in-depth simulations have shown that the proposed routing schemes are highly effective, providing a fault tolerance of 87% or higher with a network capacity overhead of less than 85%.

Songkuk Kim

Papers

Extracting a Mobility Model from Real User Traces

Method for reducing DNS resolution delay

Registration system for a web printer

MPEG-4 video codec on an ARM core and AMBA

Design and evaluation of routing schemes for dependable real-time connections