1- Write a detailed comparison between cabled network and wireless network.

The basic difference between a wired and a wireless network is self-explanatory. A wired network uses wires to communicate whereas a wireless network uses radio waves. let us look at what are the other differences and how one technology gets an edge over the other. * Wired networks are easy to set up and troubleshoot where wireless networks are comparatively difficult to set up, maintain, and troubleshoot. * Wired networks make you immobile while wireless ones provide you with convenience of movement. * Wired networks prove expensive when covering a large area because of the wiring and cabling while wireless networks do not involve this cost. * Wired networks have better transmission speeds than wireless ones. * In a wired network, a user does not have to share space with other users and thus gets dedicated speeds while in wireless networks, the same connection may be shared by multiple users.
Wired and Wireless networks are very common in the workplace as well as in the home. The wired Computer Networks provide a secure and faster means of connectivity but the need of mobility for example anywhere, anytime and anyone access is tilting the network users towards wireless technology. Wireless technology has high mobility. Technology has been created to store, transmit and receive data through networks at very high rates of speed. Users can now store detailed information at a very low cost. In the future, the speed of networks will increase as they have in past years. The cost of networks will continue to decline and using a network will be essential for every organization. As computing technology increases in power, and decreases in size, the price of creating a high-powered full featured network will decrease rapidly.

2- Describe the following terms related to Antennas

(a) Line of Sight

Line of sight (LoS) is a type of propagation that can transmit and receive data only where transmit and receive stations are in view of each other without any sort of an obstacle between them. FM radio, microwave and satellite transmission are examples of line-of-sight communication.
Long-distance data communication is more effective through wireless networks but geographical obstacles and the curvature of the earth bring limitations to line-of-sight transmission. However, these issues can generally be mitigated through planning, calculations and the use of additional technologies.
For example, mobile phones use a modified line-of-sight transmission, which is made possible through a combination of effects like diffraction, multipath reflection, local repeaters and rapid handoff.
(b) Fresnel Zone

The Fresnel zone is a three dimensional elliptic shaped region surrounding the line of sight path from the transmitter to the receiver. If a reflective object is placed anywhere on the edge of the ellipse, it will cause a reflected signal that, due to propagation delay, is delayed 180 degrees (in carrier phase) with the line of sight signal at the receiving antenna. If the Fresnel ellipse is cut perpendicular to the line of sight path anywhere along the line of sight path, a circle is formed with a radius known as the Fresnel radius. Note that Fresnel zones and Fresnel radius are frequency dependant because they are defined by the wavelength and propagation delay of the carrier.

(c) Antenna Gain

Antennas have a gain that is usually referenced to an isotropic source or a dipole.
The gain is referenced to the ratio of the power level out of the antenna of interest to one of the above reference antennas. Gain referenced to an isotropic source is expressed in dBi while gain referenced to a dipole is commonly expressed in dB. All antennas in this document have their gain expressed in dBi. Antennas have perfect reciprocity. The have the same characteristics whether used as a transmitting or receiving antenna. The gain is identical for both applications.
Gain is expressed as the ratio of the antenna power out (transmitting) or in (receiving) to the reference antenna power out or in. Assume a reference antenna is used to receive a signal from a transmitter. Then the antenna of interest is used.

(d) Intentional Radiator

international Radiator is a device that broadcasts radio energy (not infrared or ultrasonic energy) to perform its function. Intentional radiators are things like cell phones, CB radios, walkie-talkies, wireless connections, Bluetooth connections, and short range broadcast equipment, wireless key-access systems. These devices intentionally use the radio spectrum and therefore always require FCC equipment authorization.

(f) Equivalent Isotropically Radiated Power (EIRP)

is the apparent power transmitted towards the receiver, if it is assumed that the signal is radiated equally in all directions, such as as a spherical wave emanating from a point source; in other words, the arithmetic product of the power supplied to an antenna and its gain. Begin by testing the transmitter with a good dummy load and a good calibrated watt meter

3- Are wireless network a health hazard? Give proof to your findings.

A common concern about base station and local wireless network antennas relates to the possible long-term health effects that whole-body exposure to the RF signals may have. To date, the only health effect from RF fields identified in scientific reviews has been related to an increase in body temperature (> 1 °C) from exposure at very high field intensity found only in certain industrial facilities, such as RF heaters. The levels of RF exposure from base stations and wireless networks are so low that the temperature increases are insignificant and do not affect human health.
The strength of RF fields is greatest at its source, and diminishes quickly with distance. Access near base station antennas is restricted where RF signals may exceed international exposure limits. Recent surveys have indicated that RF exposures from base stations and wireless technologies in publicly accessible areas (including schools and hospitals) are normally thousands of times below international standards.
In fact, due to their lower frequency, at similar RF exposure levels, the body absorbs up to five times more of the signal from FM radio and television than from base stations. This is because the frequencies used in FM radio (around 100 MHz) and in TV broadcasting (around 300 to 400 MHz) are lower than those employed in mobile telephony (900 MHz and 1800 MHz) and because a person's height makes the body an efficient receiving antenna. Further, radio and television broadcast stations have been in operation for the past 50 or more years without any adverse health consequence being established.

While most radio technologies have used analog signals, modern wireless telecommunications are using digital transmissions. Detailed reviews conducted so far have not revealed any hazard specific to different RF modulations.

Cancer: Media or anecdotal reports of cancer clusters around mobile phone base stations have heightened public concern. It should be noted that geographically, cancers are unevenly distributed among any population. Given the widespread presence of base stations in the environment, it is expected that possible cancer clusters will occur near base stations merely by chance. Moreover, the reported cancers in these clusters are often a collection of different types of cancer with no common characteristics and hence unlikely to have a common cause.
Scientific evidence on the distribution of cancer in the population can be obtained through carefully planned and executed epidemiological studies. Over the past 15 years, studies examining a potential relationship between RF transmitters and cancer have been published. These studies have not provided evidence that RF exposure from the transmitters increases the risk of cancer. Likewise, long-term animal studies have not established an increased risk of cancer from exposure to RF fields, even at levels that are much higher than produced by base stations and wireless networks.

Other effects: Few studies have investigated general health effects in individuals exposed to RF fields from base stations. This is because of the difficulty in distinguishing possible health effects from the very low signals emitted by base stations from other higher strength RF signals in the environment. Most studies have focused on the RF exposures of mobile phone users. Human and animal studies examining brain wave patterns, cognition and behaviour after exposure to RF fields, such as those generated by mobile phones, have not identified adverse effects. RF exposures used in these studies were about 1000 times higher than those associated with general public exposure from base stations or wireless networks. No consistent evidence of altered sleep or cardiovascular function has been reported.
Some individuals have reported that they experience non-specific symptoms upon exposure to RF fields emitted from base stations and other EMF devices. As recognized in a recent WHO fact sheet "Electromagnetic Hypersensitivity", EMF has not been shown to cause such symptoms. Nonetheless, it is important to recognize the plight of people suffering from these symptoms.
From all evidence accumulated so far, no adverse short- or long-term health effects have been shown to occur from the RF signals produced by base stations. Since wireless networks produce generally lower RF signals than base stations, no adverse health effects are expected from exposure to them.

Conclusions
Considering the very low exposure levels and research results collected to date, there is no convincing scientific evidence that the weak RF signals from base stations and wireless networks cause adverse health effects.