Hardware and Sorftware: Major Techniques that Allocate Capacity for Wirless WAN Communications

4. Radio: most common form of wireless transmission, typical of home routers and most wireless devices to use this form. Infared uses low frequency light waves to carry data using line-of-sight.

The Radio was introduced to society because of the telegraph and the telephone. These inventions don’t do the same things but their similar branch of technology. “Radio technology began as “wireless telegraphy”. “It all started with the discovery of radio waves, electromagnetic waves that have the capacity to transmit music, speech, pictures and other data invisibly through air.” [Bellis] Majority of technology uses electromagnetic waves to send data information or TV broadcasts. During the 1860’s, Scottish physicist, James Clerk Maxwell predicted the existence of radio waves; and in 1886, German physicist, Heinrich Rudolph Hertz showed how fast the variation of electric current could be placed into space in the form of

the radio is something everyone has in their cars and or at home. The Radio is very popular and will probably always will be because the radio is used for many things like for communication, music, and weather. The radio has been around since 1895 and it was made by an Italian inventor named Guglielmo Marconi. It has improved over the years in many ways, also it has a very long history of how it is made, and finally it is very complex on how to make a radio. Marconi's radio did not receive voice or music. Rather, it received buzzing sounds created by a spark gap transmitter sending a signal using Morse code.

5. (DSSS), Direct Sequence Spread Spectrum , frequency Hopping Spread Spectrum (FHSS) and Infrared and Orthogonal Frequency Division Multiplexing(OFDM)

Radio waves, a form of electromagnetic radiation, have had a significant impact on our daily life because of their use as a form of communication. Radio waves have long wavelengths and have low energy photon particles. Because they have low energy photons, they have lower frequencies when compared to other forms of electromagnetic radiation, such as x- rays that have a higher frequency despite having short wavelengths. Today, radio waves are used as a method to transmit and receive information. Technology that makes use of radio waves includes telephones, television and more popularly known the radio, which picks up signals from a radio antenna that is equipped with a resonator that filters the signals received and as its name implies it resonates only with radio waves of a certain frequency; this allows people to listen to different sounds at different frequencies. Radio waves can be emitted by objects in space, such as planets, while radio waves that occur on Earth can come from lightning.

Today we are in Fourth Generation; it is categorized based on its characteristic services and features like transmission signals, data transmission rate, bandwidth frequency and nature of the services provided. First generation (1G) is introduced in 1980, so each generation had been comes at the end of every decade. First generation used analog signals, circuit switching and FDMA with 30 kHz channels occupying the 824MHz 894MHz frequency band .First generation supports only voice transmission .The data was not reliable; there were interrupted communication and few other problems in First Generation [1]. Second Generation (2G) technology was established in 1990, which used digital signals for transmission and two digital modulation schemes TDMA and CDMA with circuit switched network . Second Generation uses the existing radio spectrum to provide the services. It was developed to overcome the previous generation’s drawbacks, and to have data and voice transmission. But this generation also has few drawbacks like

But then also there are some disadvantages related to OFDM-CDMA systems. To differentiate among different users OFDM-CDMA uses different orthogonal codes and due to this orthogonality distortion occurs among users in frequency selective channel (especially in uplink transmission), which may cause problem of MAI. For MAI problem, MUD is a promising technique which is very complex in practical application. The detectors for OFDM-IDMA system like the linear MMSE detector and other de-correlator have the quadratic complexity with the number of users say K [22]. This quadratic complexity occurs to resolving the correlation operations involved in spreading sequences. The computational prohibitive occur for practical implementation if value of K is large.

Beholding the unmatchable technology of transmitting & receiving electric waves wirelessly by Hertz during late 1880’s, today is recognized as the fundamental building block of radio.

LTE supports Frequency division duplex (FDD) and also time division duplex (TDD). TDD can is done for cases where cell size needs to be reduced significantly. We consider FDD here because it is widely used for implementation. However as number of users are increasing we will be going for TDD in the future. The technology is such developed that device may operate in TDD with one node and FDD with other node at the same time. For our case, we consider FDD as it is currently being used to a large extent.

WiMAX is the development of new technologies of the fourth generation (4 g) in the field of Broadband Wireless Access (BWA) to meet the needs of high-speed Internet access with better capabilities compared previous technologies were present, such as WiFi and cellular systems like GPRS, EDGE, 3G, 4G,and 5G.

The Third Generation Partnership Project (3GPP) Evolved Universal Terrestial Radio Access (E-UTRA) Long Term Evolution (LTE) principles are a piece of 3G advancements. Multi-input,multi –output (MIMO) has turned into a key innovation to enhance communication over a wireless channel. With constrained spectrum, MIMO procedures attain to least target cell spectral proficiency, peak spectral effectiveness and cell edge client spectral efficiency which are the base necessities indicated by the ITU.

While allowing simultaneous access to multiple users to the medium OFDMA has been shown to reduce multi-path fading, within air interfaces in the IEEE 802.16 standard.

Antennas are key components of any wireless communication system and it is a device that provides a way for radiation or receiving electromagnetic waves. IEEE standard definitions for antenna (IEEE Std 145-1983) defines antenna as a means for radiating or receiving radio wave. Figure 3.1 shows an antenna as transition device. The arrows displayed in Figure 3.1 shows the electric field lines

OFDM or Orthogonal Frequency Division Multiplexing is a transmission scheme that is widely used in broadcast and wireless communication technologies. Some of the applications employing OFDM include Digital Audio Broadcast (DAB), Digital Video Broadcasting Terrestrial (DVB-T2), Wireless-LAN, Worldwide Interoperability for Microwave Access (WiMAX) and 4G Long Term Evolution (LTE) radio technologies [1, 2]. Two of the main reasons to use OFDM are to increase date rates and robustness against frequency-selective fading. In the rest of this document an overview of OFDM transmission theory is given.

The base station of WiMAX has higher broadcasting power, antennas and enhanced additional algorithms. WiMAX technology serves the network through towers that enable communication access over many miles. The broadband service of WiMAX is available only those areas which are coverage by their network.