Transmission Media

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Abstract
This is an illustration of the importance of transmission media, their uses, architecture, evolution, and technological advances. The goal is to convey the message of a transmission, through research of historical findings, all the while keeping incite on future developmental projections. Time has proven the justification of continuous enhancement in data transmission, and even though communication can be illustrated across many productive means, productivity is only as good as it is efficient.

Transmission Media

Communication networks have been the means of efficiency and productivity for generations, and the evolution of communication networking has grown significantly over those years. The importance on implementing effective communication, when dealing with large or complex applications, has been in demand ever since the word “network” was first spoken. Although the importance of networking is known, the method of how we communicate is what truly makes networking a productive means. Aside from body language, spoken word, and smoke signals; digital communications are both the hindsight and foresight of networking technology. We can see how networking is very important, but the bigger spectrum rests in how we network, and what methods are used. It’s a far cry from smoke signals, but current technology gears toward the methods, rates, and structure of network transmissions. This approach to expedited/multifunctional transmission media ultimately affects both ends of the network, making it the primary concern for network efficiency and productivity.

The evolution of transmission media, also known as medium, has a significant impact on the overall networking process, and has gone through many transformations over the inception of digital media. The oldest medium is metallic wire, usually copper, and in the mid-1800s telegraph signals were the first form of telecommunication to be carried over this wire (Noll). The most noted / documented event of historical medium was in 1844 by Samuel F. B. Morse when he demonstrated a digital telegraph using the words “What hath God wrought?” This marked the beginning, and use, of Morse code through digital transmission medium, and gave notice to the importance of utilizing such a tool for many applications. The recognition of such a communication revolutionized the industry. More time and effort went into the research and development of creating this medium more effectively.

It was during the time of the civil war and during the Presidency of Abraham Lincoln, when telecommunication methods such T-Mail, helped end the war against the confederates. The President of the United States telegraphed a colonel in the field during the Civil War Battle of Second Manassas (Bull Run) in 1862. Abraham Lincoln was using the new medium of electronic communications in an unprecedented manner to revolutionize the nature of national leadership (Wheeler). Because information traveled at much higher rates than on foot, government / military became more involved and helped drive the medium industry to a completely new level. Because transmission media directly correlates to the physical aspect of a network, this was about the time when physical pathways drew across the country in an effort to strengthen governmental support, industrial infrastructure, and mass communication. This would invoke a mass telecommunications era, but life went on after that.

More resources other than Morse code and voice communications, have introduced themselves to the physical pathways that were constructed around the country, and even at this point, around the world. Computer technology had also grown significantly at this point in time. Mainframes and relay computers were being developed to take on heavy calculations, and perform a multitude of tasks. This ability sparked a drive to create a computer that could do the same functions, but on a personal level. Others wanted to be able to utilize the same resources minus the extremely high cost of owning and operating such a machine. Large business owners and government projects made up the majority of the end users during the inception of computer technology. Eventually you could communicate with a mainframe with what is known as a dummy terminal. This terminal allowed you to select input and view output by sending requests to the mainframe, which was either in the next room or in another building at some other location.

Eventually, terminals weren’t enough. The demand for performing calculations, communicating, as well as sharing information sky rocketed with the anxiety of pressured researchers. Networking picked up after the succession of the federal organization ARPANET, which stood for Advanced Research Projects Agency Network. ARPA was created in 1958 by President Eisenhower, which became known as the first actually working network (Meuller). Slowly, ARPANET evolved into what we now know of as the internet. With that being said, the usage, features, and capabilities are endless. The only problem now, is that you need a reasonable means of communicating this data across a network in a timely and efficient manner. Although Lincoln won the civil war with the help of metallic wire, this was by no means an effective way of transmitting data via a network.

Copper wire was the initial media transmitter due to its candid ability to carry a signal. This is still known today, but the physic of the cabling harness, as well as the way it’s manufactured, has a large part in how it performs. Over time, copper wiring has evolved into many fashions and applications of transmission media. The telecommunications industry utilized Category 1 cabling, which became known as Cat1 prior to 1983, and was the typical voice communications line. This form of medium utilized some of the same concepts as its originator, but was manufactured indifferently. Cat1 introduced unshielded twisted pair (UTP), which is the physical twist of the copper wiring to reduce electromagnetic interference. This medium acted as a sufficient method of voice communication, but was not suitable for data communication. Both the Electronic Industries Association (EIA) and Telecommunications industries Association (TIA) developed independent specifications for UTP wiring (Miller). CAT1 as well as the very similar CAT2, which was used mostly for alarm systems, never met the specifications of either association, leaving it to fall back in the banks of time.

Another very well known and utilized medium was coaxial cable, which could be used for many applications. This medium consisted of the traditional style copper wiring, but incorporated a plastic insulation, which separated and included a braided metal shield. Then, the shield was coated with another protective plastic coating in order to protect the shield. All-in-all, the braided mesh prevents electromagnetic inference from occurring, and is not affected by the placement of the wiring. Many different types of coaxial cabling existed, and possibly still exist today. ThinNet, also known as 10Base-2, was approximately .25” in diameter, and was good for carrying a signal at about 185 meters. ThickNet, also known as 10Base-5, was approximately .5” in diameter, and was good for carrying a signal at about 500 meters (Miller). Coaxial is used for radio transmitters and receivers, computer networks, and cable television signals. The biggest issue with coax is that because it only utilizes one thick copper wire, it lacks in flexibility.

The most commonly used medium in most networks today would be Category 3 – 7, and each category representing a different frequency. Cat3 runs at 16 MHz, Cat4 runs a slight higher at 20 MHz, Cat5 quadrupled it to 100 MHz, Cat6 is at 250 MHz, and Cat7 runs at 600Mhz (White). Each cable has its own unique features. Some cables can reach further distances, integrate more stringent crosstalk features, be manufactured differently, or can even be backward compatible. The crosstalk feature is very important as well as very similar to UTP, meaning that it reduces the chances for crosstalk between two wires by ultimately avoiding any electromagnetic signals in either wire. Another elfacto in the decision making process of physical network medium is the cost of these intricate cables. Some of these cables can cost as much as one dollar a foot. And, although they are expensive these cables can only handle certain distances before they lose their signal. Category5-7 are the top players in transmission media, so it becomes a cost benefit analysis as to whether or not the medium is geared toward the networks application or not.

Very similar to UTP is a medium know as Shielded Twisted Pair (STP). STP is almost like the combination of both coaxial cable and Untwisted Pair cabling. It carries the transmission features of UTP, with the shielding of coaxial cable. Ultimately, it reduces the probability of electromagnetic interference when transmitting to and from the medium. The older cable designs were known to be called RJ-11 cables, and were used for telecommunications. The newer version UTP/STP designs became known as RJ-45 cables, and universal called Ethernet, which is common in the majority of all computers today. The connectors for these cables differ in respect that you can select the application and modify the cable to meet the criteria, but only for certain cables. Connectors such as a DB-15 cables can utilize vampire clips, which are clips that bite into single wired cable (Barnett). You would not otherwise utilize this connection with a UTP or STP cables because it carries multiple wires, and would ultimately ground their connections.

Coaxial cable lacks the flexibility that the other cables have because of its physical aspects. Coaxial would lose its connection and not know where to locate the break because it was so heavily protected. Well, the same applies to a more advanced medium technology, which utilizes a completely different method of transmission. It’s called fiber optic and is exactly that; it’s made up of fiber, and utilizes optic technology. This method has the highest bandwidth of any medium, however it is more expensive and more difficult to install. It can span 2 kilometers, and comes in two basic types, multi-mode and single-mode. The difference is, that this medium carries signals via a light ray, and is propagated through the optical core. The mode is the angle at which it travels. So multi-mode would represent multiple transmissions, and a non-coherent light source to follow the optical core. Single-mode allows the light to travel at one angle, which increases its range and reliability. One of the biggest downsides to a fiber optic media is that the core is made up of either plastic or glass, and is known to fail if not handled properly.

Transmission media is a great combination of quality, substance, and delivery, but not all medium needs to occur physically in order to function like a network. One of the many useful applications of such a network would be the transmission through radio waves. Wireless media works on the electromagnetic spectrum, and is expressed in cycles per second called hertz (Hz) just as the physical aspect of medium does. A radio transmits at variable cycles between 10Khz and 1Ghz, and is broken into bands. These bands are known as amplitude modulation (AM), frequency modulation (FM), and very high frequency (VHF). AM represents some of the first successfully produced quality audio over telephone lines, but could also be transmitted over a radio carrier wave. This carrier wave is a waveform that is modified with an input signal for the purpose of conveying information. FM does merely the same as AM but vary in its instantaneous frequency.

The next and almost always used transmission media of our generation is the microwave medium. The oldest microwave transmission is the terrestrial microwave system, and this system transmits tightly focused beams of radio signals from one ground-base microwave antenna to another (Miller). Applications such as wireless telecommunications utilize this radio broadcasting service from multiple towers, interconnected, to strengthen the signal and extend the range of service. The down side to utilizing a terrestrial metropolitan telecommunication system such as this, is that it requires a direct line of sight connection in order to fulfill the transmission. Terrestrial microwave systems operate in the low-gigahertz range, typically at 4-6 GHz and 21-23 GHz, and costs are highly variable depending on requirements. Long-distance microwave systems can be quite expensive but might be less costly than alternatives. When line-of-sight transmission is possible, a microwave link is a one-time expense that can offer greater bandwidth than a leased circuit.

Another microwave satellite medium that has been in effect, and is still in effect, is satellite transmission. Very similar to terrestrial systems, although the signal travels from earth ground to a satellite in orbit, and back to earth ground. This utilizes the same line of sight transmission, but covers further distances. Because satellite medium travels far distances, it subcategorized in distance between uplink, which is time required in sending data to satellite, and downlink, which is time required to receiving data from the satellite. The combination to and from the satellite is summed up as propagation dely. An orbital satellite can reach distances up to 22,300 miles above earth ground and as low as 100 miles above earth ground.

There are four ranges of satellite transmission; low earth orbit (LEO), middle earth orbit (MEO), geosynchronous earth orbit (GEO), and highly elliptical earth orbit (HEO). LEO is the closest with a range of 100 miles to 1000 miles, and must travel very quickly to resist the pull of gravity at approximately 17,000 miles per hour. There are about 300 LEO satellites orbiting space. A MEO satellite is approximately 6,000 to 12,000 miles above the earth in an elliptical orbit around the poles of the earth, and because they are polar orbit they can cover more area with fewer satellites. A GEO is 22,240 miles above the earth. It is craft inserted into orbit over the equator, traveling at approximately 6,880 miles per hour following the earth’s rotation. Typical GEO uses are Television satellites, Long Distance Communications satellites, Internet, and Global Positioning Systems (GPS). HEO satellites are elliptical and cover the Polar Regions where the geostationary satellites cannot reach (Miller). Cellular telephones and imagery mapping all occur at these transmission mediums.

The evolution of transmission media, on both the voice and data communications end, has enabled us to understand the historical value of current and future networking transmission lines. We began the revolutionary era with only a single wire entity, and utilized our most current resources. This illustrated media across a non bearing path, and has made the transformation of transmission an appreciated outcome. The importance in networking technology has been known throughout history, but without efficient communications our use of networks would be far from productive. From the beginning with a hand-to-hand acknowledgment of appreciation, to a mass of communication networks, circumventing the globe. We have learned and innovatively adapted from our experiences, and would never have recognized the importance of transmission media without the importance of its usefulness.

References

Barnett, D., Groth, D., & McBee, J. (2004). Cabling the complete guide to network wiring (3rd ed.). San Francisco: SYBEX.

Burd, S. D., & Leigh, W. E. (20052006). Systems architecture (5th ed.). Boston, Mass.: Thompson/Course Technology.

Meyers, M. (2004). Network+ certification exam guide (3rd ed.). Emeryville, CA: McGraw-Hill/Osborne.

Miller, R. J., & Askmo, P. J. (2004). Network+ certification: exam N10-002. Upper Saddle River, N.J.: Pearson/Prentice Hall.

Mueller, S. (2006). Upgrading and repairing PCs (17th ed.). Indianapolis, Ind.: Que ;.

Noll, A. M. (2007). The evolution of media . Lanham: Rowman & Littlefield Publishers.

Wheeler, T. (2006, November 20). How the Telegraph Helped Lincoln Win the Civil War. History News Network. Retrieved February 14, 2011, from http://hnn.us/articles/30860.html

White, C. M. (2011). Data communications and computer networks: a business user’s approach (6th ed.). Boston, MA: Course Technology.

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