For Sirleem

Communications

Advantages and Disadvantages

Time Division Multiple Access (TDMA) is a technique that splits a channel into slots in which each slot is used to transfer an individual segment in sequential ordering. Code Division Multiple Access (CDMA) is known as spread spectrum because it takes a digital version of an analog signal and spread it out over a wider bandwidth. Orthogonal Frequency Division Multiplexing (OFDM) is a modulation method that divides a channel into multiple bands that are spaced out far enough to ensure they do not interfere with one another. There is no limit to the number of divisions possible. Frequency Division Multiple Access (FDMA) does have a limit and divides one channel into multiple bands but only for use by a single user. OFDM is found to allow ten times more user than CDMA. The difference between OFDM and DCMA is dependent on whether voice activity detection methods are used. CDMA performs well in an environment where only a single frequency is used but only in that scenario.

Radio Frequency (RF) Transmission Characteristics

There are four characteristics that exist in every RF signal: wavelength, frequency, amplitude, and phase. A wavelength is the distance between two peaks or valleys of a wave pattern. It continuously cycles between positive and negative. Frequency is the number of times that an event occurs within a specific time period. It is usually measured in hertz (Hz) and is an alternating current that is similar to an electromagnetic wave. So the relationship between a wavelength and frequency is inverse. Amplitude is the maximum displacement of a continuous wave. This is a fancy way of saying that this is the signal’s strength or power. And phase is defined as the relationship between two or more signals that share the same frequency. If two signals are not aligned then they are said to be out of phase. (Kellum, 2009).

Common Frequency Bands Used in RF

The applications in which RF is used is numerous as are available technology mediums today. This is a brief list (Wikipedia, 2014).

Varying Protocols in Wireless Communication

There are several protocols in wireless communications. As time progresses the use for multiple protocols are inevitable. Wireless protocol or wireless application protocol is defined as a protocol for transferring documents, especially web pages, over a computer network (Dictionary, 2014). A WAP usually connects with a WLAN to transmit forms of data. Using WAP enables computers to communication with each other using a set of protocols. These protocols are broken down into different sub protocols. The importance of using different protocols is important because the set of rules set for one protocol, may not work for another protocol. Each wireless protocol works with TCP/IP.

These protocols enable the transfer of data in bits. All wireless protocols encompass this standard protocol to communicate. The reason for this is because; the use of WAP requires the use of TCP/IP. Another protocol that uses TCP/IP is VoIP. VoIP us a technology or set of standards for delivery of telephone calls and other voice communications over the internet, involving conversion of analog voice signals to digital form (Dictionary, 2014). All of the protocols discussed require heavy use of WAP. WAP connects to WLAN that in turn connects with a switch. These switches connect to a hub that often time communicate with a satellites.

Challenges of Using Satellites in End-to-End Communication Links

Satellites provide a number of services. Most services are not directed to the end user. The reason for this is because, of the increased expensed of satellite utilization. Satellites are a form of microwave communication. The satellites communicate with each other with the use of radio frequencies. The only way that satellites are able to communicate is through the use of radio towers. These radio towers prove to be very expensive, hence the reasoning why using satellites are not feasible. Not only do satellites prove to be expensive to the end user, satellites are also unreliable.

The use of satellites has a delayed response time. The use of high speed communication for the end user should be determined by the use of fiber. Although most users are using wired communications, the uses of satellites are heavily used in remote locations. The reason for this is because most wired lines have a limitation on distance. Outside of using satellites for end to end user communications, satellites are heavily efficient when sending data uplinks. The reason for this is because of shared frequencies. The only con with this, is there has to be a clear passage way for the satellite to communicate. There also has to be a tower to transmit communications.

References

Kellum, Jeff. (2009). Safari. Certified Wireless Network Administrator Official Study Guide. Wiley Publishing, Inc. Indianapolis, IN. Retrieved from http://my.safaribooksonline.com/book/certification/cwna/9780470438909/radio-frequency-fundamentals/radio_frequency_characteristics#X2ludGVybmFs X0h0bWxWaWV3P3htbGlkPTk3ODA0NzA0Mzg5MDklMkZwcmVmYWNlJnF1ZXJ5PQ==

Wikipedia. (2014). Radio Frequency. Frequency Table. Retrieved from http://en.wikipedia.org/wiki/Radio_frequency#Frequencies