01-10-2012, 05:55 PM
SOS TRANSMISSION
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INTRODUCTION
Cellular phones are turning out to be a menace on the road. This is a major problem for the cellular phone manufacturers. This paper provides a solution which transmits a SOS signal to save the accident victim. It describes in detail a cost-effective foolproof solution.
There are many factors to be considered when designing such a system. In most of the accidents, the victim becomes unconscious. How is a SOS transmitted then? Here, many ideas can be implemented. One such solution is described here. The cell phone is fitted with a transducer, which detects shocks. The cell phone automatically transmits the SOS if the shock level goes beyond a certain percentage. The cell phone must not trigger an accidental SOS. To ensure this, the shock level that triggers the SOS must be high enough. Based on the first condition, if the shock level is made very high, then an accident might not be identified at all.
Having thus identified the situations in the accident, one needs to understand the actual requirements in each case. They are given below.
The solution requires a software robot resident in the cellular phone provider’s server, which can transmit the SOS signal in an intelligent manner and monitor responses for the victim.
i)Similarly, the solution needs a Positioning System to transmit the victim’s whereabouts to others. This has to be a cheap system and should not increase the cell phone receiver’s cost greatly.
ii)The solution requires a high fidelity shock transducer and decoding circuit to identify the shock magnitude.
iii)The SOS has to be transmitted as soon as possible. So all systems must have a very small time delay.
iv)Above all, the new system must fit in with the present system (i.e.,) there must be no difference in the information received between a user who requests this option and one who does not.
The detailed description of the solution will be presented now.
This paper describes an ORIGINAL IDEA to help cellular phone users caught in an accident. The idea has been developed keeping in mind the considerations of cost and compatibility with existing system. The Short Message Service or SMS as it is popularly referred to, is made use of for this purpose.
The solution offered is the Force-Transducer method. The victim is assumed to be unconscious and the accident is detected automatically. Detailed simulation results at a scaled down level are provided for this solution. The threshold level is set based on data collected from the experiments.
One major problem in such design is the technique to find the victim’s position. The Global Positioning System (GPS) is found to be costly. So, an unorthodox design using Radio Direction Finders (RDF) and beacon signals is described. The Goniometer or Crossed Loop Antenna is used for this purpose. This reduces cost effectively when compared with the GPS system.
The paper proceeds to suggest an abstract view of the software robot required to perform the Save Our Souls (SOS) message routing task. It uses a special hierarchical message dispatch system wherein people nearby and more likely to help are contacted. The robot also acts as a proxy to the victim and monitors responses for him.
This paper as a whole gives a cost-effective, high performance system which can be introduced in the market if any of the cellular companies are willing to encourage it.
THE TOY CAR EXPERIMENT:
In case the victim becomes unconscious, the system must be able to automatically detect an accident and transmit the SOS automatically. In order to achieve this, a shock transducer is used to measure the jerk experienced through the accident and trigger the SOS circuit if the force level is very high. This system needs statistical data acquisition to find out the exact threshold level of the force in an accident. It is highly expensive to simulate the accident in real time. So, a scaled down experiment is used. Here, a pair of toy cars of mass 200g is made to collide with each other. The force caused by them is measured by simple piezoelectric transducers. The results of this experiment are tabulated below.
IDENTIFYING THE POSITION OF THE VICTIM:
The problem of knowing where we are has been an interesting and difficult problem through the ages. Years of research have resulted in the Global Positioning System (GPS). This technique uses three satellites and pin points the location by the triangulation process, wherein the user’s position is located as the point of intersection of the three circles corresponding to the satellites. Installing such a system is quite simple. But the major constraint here is the cost. A normal hand-held GPS costs around $100 and weighs quite heavy. Minimizing the above apparatus will increase the cost further. This would mean an extra cost of Rs.10000 to Rs.15000 for the Indian user.
COMPLETE BLOCK DIAGRAM OF THE SYSTEM:
The below diagram depicts the working of the complete system. As seen, the jerk caused by the accident is detected by the shock transducer and the SMS sub-routine is triggered. Along with the message, control signals that inform the base station that an accident has occurred are transmitted. The triggering is achieved by using a high pass filter that detects abrupt changes in the transducer. Simultaneously, the microwave signal for the goniometer is also transmitted. The position is identified as described in the previous section. The user’s id and his position in the polar coordinates are given to the software robot. This robot, then decodes the user’s position to other subscribers based on a priority list.