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Vehicle GPS tracking devices
Created on January 5th, 2017

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Jo Smith
(josmith)
joined Nov 2016
location Shenzhen,China
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Jan 5th 2017 at 18:37 PM
Direct communication between vehicles allows information exchange without requiring any fixed infrastructure or base stations. The location and velocity of vehicles is constantly changing, and the RF communication range is of fairly short distance; therefore, the set of vehicles that can directly communicate will constantly change over a short period of time. This dictates that the physical layer and the network must be capable of operating in an ad hoc, decentralized manner, although coordination and synchronization through GPS ( GPS tracking device for cars ) time signals are possible. Any two nodes must be able to communicate securely whenever they are within communication range.

In a V2V network we can distinguish two modes of communication, usually designated as:

• Single hop: Two vehicles are close enough to communicate directly with each
other (either broadcast or point to point) with low latency.

• Multihop: Vehicles that can not directly communicate may forward messages through intermediate nodes.

Multihop communication has been the subject of much research, but no standard has emerged, and in fact the technical difficulties of establishing routing and acknowledgment protocols along with potentially high latency may limit its use to very specific applications such as medium range emergency notification or other sparse broadcast communication applications.
GPS Tracker For Car


Many early experiments in V2V communication were carried out with standard wireless LAN technologies, and some success was achieved at ranges of up to several hundred meters. But the technical difficulties inherent in vehicle and traffic situations, including the high relative velocities (Doppler effects), a safety critical low latency requirement, operation in an urban environment (multipath), and spectrum competition from other users in unlicensed frequency bands renders this an unrealistic solution for commercial deployment. The IEEE 802.11p/WAVE standards have recently emerged as the current consensus for the implementation of V2V and local V2I communications.

Positioning of the vehicle is provided by a Differential GPS (DGPS)—Inertial Navigation System ( vehicle GPS tracking systems ). This vehicle position updates the vehicle positioning computer to make corrections to bring the vehicle back to its pre-programmed track. While the vehicle generally operates in an automated mode (autoheading and preprogrammed track), its operation can be immediately over-ridden by moving the rudder joystick or the throttle at the surface console.

There are existing standards for digital communication using subcarriers of standard AM and FM radio broadcast stations. Applications include channel and programming information, commercial paging systems, weather, news, and traffic information, stock market quotes, and GPS differential correction services. The data rate is quite low (on the order of 1 Kbps) and the services often require paid subscriptions. Many of these applications are declining in popularity due to the availability of other, faster technologies. Satellite radio offers a similar unidirectional capability at much higher data rates, for example, Sirius Traffic, a subscription service for real-time traffic data.

As we have previously mentioned, cellular telephone and broadband data services have become ubiquitous. Pricing, at least for individual users, is still rather high, but vehicle OEM and other providers have negotiated pricing arrangements for particular services. Perhaps the best known is the GM On Star service, which provides driver information including directions, stolen vehicle location, crash detection and emergency services notification, and other services. BMW Assist is a similar service. To date, these services have been implemented by specific vehicle manufacturers and are not available outside their vehicle brands.

More information at http://www.jimilab.com/. Should you have any other question, please contact us at http://www.jimilab.com/contact/.


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