Transmission Media

Transmission media is the path between the sender and the receiver. Transmission media is classified as 1) guided (such as cable and twisted wire) and 2) unguided (which is usually referred to as wireless transmission). Additionally, the medium is controlled by the error-detection process (error detection and correction) to ensure transmission accuracy. A parity check is an approach to error detection. In ASCII transmissions, the value bit is selected so that each 7-bit character is attached a 1 for even or odd parity. The receiving end will check, and if a 1 is inverted to 0, an error is detected. In addition, lost frames and damaged frames can occur when data is sent in-frame sequence. Error control techniques include positive acknowledgment, retransmission after a time-out, negative acknowledgment, and retransmission. Additionally, as an example of satellite transmission media, Kepler’s law is reviewed for calculating the period a signal reaches earth for satellite transmissions. The orbit section and assignment were extracted from Forouzan (2007, p. 479). SLP 2 reviews sections 7 and 9 of the Data Communication and Networking e-textbook. Orbit An artificial satellite needs to have an orbit—the path in which it travels around the Earth. The orbit can be equatorial, inclined, or polar. The period of a satellite, the time required for a satellite to make a complete trip around the Earth, is determined by Kepler’s law, which defines the period as a function of the distance of the satellite from the center of the Earth. Example 1 What is the period of the Moon, according to Kepler’s law? Period:::: C x distance1.5 Here C is a constant approximately equal to 1/100. The period is in seconds and the distance in kilometers. Solution The Moon is located approximately 384,000 km above the Earth. The radius of the Earth is 6,378 km. Applying the formula, we get: Example 2 According to Kepler’s law, what is the period of a satellite that is located at an orbit approximately 35,786 km above the Earth? Solution Applying the formula, we get: This means that a satellite located at 35,786 km has a period of 24 h (hours), which is the same as the rotation period of the Earth. A satellite like this is said to be stationary to the Earth. The orbit is called a geosynchronous orbit. SLP 2 Assignment Lookup the altitude of a Globalstar satellite on the Internet. Use Kepler’s formula to check the accuracy of a given period and altitude for a Globalstar satellite. Use the following exponent calculator to estimate the period. http://www.rkm.com.au/CALCULATORS/CALCULATOR-powers.html Submit the assignment answer in a 2- to 3-page Word document (excluding cover page and references) and explain how you arrived at the period using the Kepler’s formula. SLP Assignment Expectations The report should: Demonstrate a clear understanding of the subject and address all key elements of the assignment. Show analysis, synthesis, and evaluation of the required material. Demonstrate writing proficiency at the academic level of the course; address the Learning Outcomes of the assignment. Use and cite relevant and credible sources to support assertions. The report is well organized and follows the structure of a well-written paper. APA style format is applied for all citations.

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