Map-matching is the process of aligning a sequence of observed user positions with the road network on a digital map. It is a fundamental pre-processing step for many applications, such as moving object management, traffic flow analysis, and driving directions. In practice there exists huge amount of low-sampling-rate (e.g., one point every 2--5 minutes) GPS trajectories. Unfortunately, most current map-matching approaches only deal with high-sampling-rate (typically one point every 10--30s) GPS data, and become less effective for low-sampling-rate points as the uncertainty in data increases. In this paper, we propose a novel global map-matching algorithm called ST-Matching for low-sampling-rate GPS trajectories. ST-Matching considers (1) the spatial geometric and topological structures of the road network and (2) the temporal/speed constraints of the trajectories. Based on spatio-temporal analysis, a candidate graph is constructed from which the best matching path sequence is identified. We compare ST-Matching with the incremental algorithm and Average-Frechet-Distance (AFD) based global map-matching algorithm. The experiments are performed both on synthetic and real dataset. The results show that our ST-matching algorithm significantly outperform incremental algorithm in terms of matching accuracy for low-sampling trajectories. Meanwhile, when compared with AFD-based global algorithm, ST-Matching also improves accuracy as well as running time.

/pdf/map-matching-for-low-sampling-rate-gps-trajectories-4hstm6zk4l.pdf

Map-matching for low-sampling-rate GPS trajectories

The present invention provides a firewall that achieves maximum network security and maximum user convenience. The firewall employs “envoys” that exhibit the security robustness of prior-art proxies and the transparency and ease-of-use of prior-art packet filters, combining the best of both worlds. No traffic can pass through the firewall unless the firewall has established an envoy for that traffic. Both connection-oriented (e.g., TCP) and connectionless (e.g., UDP-based) services may be handled using envoys. Establishment of an envoy may be subjected to a myriad of tests to “qualify” the user, the requested communication, or both. Therefore, a high level of security may be achieved. The usual added burden of prior-art proxy systems is avoided in such a way as to achieve fall transparency-the user can use standard applications and need not even know of the existence of the firewall. To achieve full transparency, the firewall is configured as two or more sets of virtual hosts. The firewall is, therefore, “multi-homed,” each home being independently configurable. One set of hosts responds to addresses on a first network interface of the firewall. Another set of hosts responds to addresses on a second network interface of the firewall. In one aspect, programmable transparency is achieved by establishing DNS mappings between remote hosts to be accessed through one of the network interfaces and respective virtual hosts on that interface. In another aspect, automatic transparency may be achieved using code for dynamically mapping remote hosts to virtual hosts in accordance with a technique referred to herein as dynamic DNS, or DDNS.

Firewall providing enhanced network security and user transparency

A data transmission system is disclosed which optimizes transfer and updates of information between systems by providing difference information between the systems. The system transmits data packages having instructions for manipulating user data. The data packages include a header identifying the respective packages, as well as transaction objects for effecting a change to user data on a device having object instructions.

Data transfer and synchronization system

A system and method of advanced identification information to be created and distributed to users of wireless communication devices, such as mobile phones. Subscribers can define their own personas as collections of information which define the users. Subscribers can then publish their persona(s) to their friends' and associates' mobile phones, and update the others' address books with the subscriber's contact information. Users can specify different personas to be presented to different users.

Advanced contact identification system

A content delivery network is enhanced to provide for delivery of cacheable markup language content files such as HTML. To support HTML delivery, the content provider provides the CDNSP with an association of the content provider's domain name (e.g., www.customer.com) to an origin server domain name (e.g., html.customer.com) at which one or more default HTML files are published and hosted. The CDNSP provides its customer with a CDNSP-specific domain name. The content provider, or an entity on its behalf, then implements DNS entry aliasing (e.g., a CNAME of the host to the CDNSP-specific domain) so that domain name requests for the host cue the CDN DNS request routing mechanism. This mechanism then identifies a best content server to respond to a request directed to the customer's domain. The CDN content server returns a default HTML file if such file is cached; otherwise, the CDN content server directs a request for the file to the origin server to retrieve the file, after which the file is cached on the CDN content server for subsequent use in servicing other requests. The content provider is also provided with log files of CDNSP-delivered HTML.

HTML delivery from edge-of-network servers in a content delivery network (CDN)

An apparatus and method for enhancing the infrastructure of a network such as the Internet is disclosed. Multiple edge servers and edge caches are provided at the edge of the network so as to cover and monitor all points of presence. The edge servers selectively intercept domain name translation requests generated by downstream clients, coupled to the monitored points of presence, to subscribing Web servers and provide translations which either enhance content delivery services or redirect the requesting client to the edge cache to make its content requests. Further, network traffic monitoring is provided in order to detect malicious or otherwise unauthorized data transmissions.

Peder J. Jungck

Papers

Apparatus and method for domain name resolution