STATE. WiFi TECHNOLOGY GUIDELINE

Transcription

1 STATE WiFi TECHNOLOGY GUIDELINE (Version 1) Prepared By : Bahagian Kejuruteraan Jabatan Perkhidmatan Komputer Negeri Date : Nov 2013

2 1. INTRODUCTION OBJECTIVE WIFI LAN COMPONENT...1 STATION ACCESS POINT WIRELESS ROUTER BASE STATION WIRELESS BRIDGE WIRELESS REPEATER 4. WIFI ANTENNA FUNDAMENTAL ANTENNA CLASSIFICATION....2 DIRECTIONAL OMNI-DIRECTIONAL 4.2 ANTENNA PROPERTIES...4 DIRECTIVITY GAIN IMPEDANCE AND STANDING WAVE RATIO FREQUENCY AND WAVELENGTH RADIATION PATTERN POLARISATION 5. WiFi NETWORKING STANDARD RADIO SPECTRUM RADIO FREQUENCY MODULATION FREQUENCY HOPPING SPREAD SPECTRUM DIRECT SEQUENCY SPREAD SPECTRUM ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING MULTIPLE-IN MULTIPLE-OUT 8. DESIGNING OUTDOOR WIRELESS NETWORK...10 FRESNEL ZONE FRESNEL ZONE RADIUS AND EARTH CLEARANCE EARTH CURVATURE ANTENNA's TOWER HEIGHT 9. DEVICE TRANSMISSION RANGE APPLICATION INDOOR HOME / SMALL OFFICE CORPORATE OFFICE HOTSPOT OUTDOOR POINT-TO-POINT POINT-TO-MULTIPOINT POINT-TO-POINT RELAY 11. SECURITY RISKS CLOSING...19

3 1. INTRODUCTION WiFi is short for Wireless Fidelity. It is one of the most popular and widely used wireless technologies to communicate digitally over radio waves. It allows an electronic device such as computers, cell phones, etc to exchange data wirelessly via radio waves. WiFi is an easy way to access the internet, you can be mobile and yet able to communicate worldwide. You need to get an appropriate WiFi device for your desired application. For example to browse the Internet you will need a WiFi enabled computer and bring the computer within range of a WiFi Internet hotspot, you will be able to get connected to the Internet. For connecting dispersed buildings located next to each other or kilometers away, appropriate outdoor antenna can be used to establish the communication link quite easily. 2. OBJECTIVE The objective of this document is to provide a brief explanation of WiFi technology fundamentals and provide a guideline for State government department/agency to follow in designing and implementing WiFi infrastructure for their office. 3. WiFi LAN COMPONENT WiFi local area network (WLAN) is consisted of several type of devices each with different role and specific function while some of the devices may operate more than one function. The devices and it's function(s) are explained briefly below : I) STATION In a WiFi local area network (WLAN), endpoint devices such as laptop computer, tablet computer, smart phone, etc that is equipped with a wireless network adapter is called Station. All stations share a single radio frequency communication channel to communicate with each other. Transmissions on this channel are received by all stations within range. Transmission of signal is based on best-effort delivery mechanism. Each station's radio frequency is constantly tuned in on the radio communication channel to receive/deliver data packets. A Station can be configured and operate in either Infrastructure or Ad-hoc mode. In Infrastructure mode, stations use Access Point to connect to each other or to a wired network, which in turns typically connected to Internet. In Ad-hoc mode, stations communicate directly with one another without the use of an Access Point. Some wireless devices share their Internet connection by configuring into ad-hoc mode and becoming hotspot. II) ACCESS POINT Access Point is a wireless device with built-in antenna and network adapter. It is a transmitter and receiver of radio signals that allow WiFi wireless devices to connect to a WLAN. It acts as a communication hub for users of a WiFi wireless device to connect together. It has a coverage range of about 90 meters (about 300 feet) indoor using a single Access Point to as large as several square kilometers by using multiple overlapping Access Points.

4 III) WIRELESS ROUTER Wireless Router is used to join multiple LANs with a WAN. It normally serves as a gateway for WLAN traffic to Internet. It inspects the incoming data packets for source and destination network ip addresses, then forwards the data packets according to the designated routes in the routing table to its destination. IV) BASE STATION Base station is a wireless device functioning as a central hub for wireless network communication. It is installed at fixed location to provide wireless access and generally covers a much larger area than Access Point to serve more clients. V) WIRELESS BRIDGE A Wireless Bridge is a hardware component used to connect two or more network segments which are physically and logically seperated. For point-to-point connection, Wireless Bridge device works in pairs, one on each side of the Wireless Bridge. There can be point-to-multiple point connection using a central device. VI) WIRELESS REPEATER Data transmissions can only span a limited distance before the quality of the radio signal degrades. A Wireless Repeater is an active hub placed within the range of a Wireless Router or Access Point to regenerate wireless radio signals and relay the radio signals to extend the distance over which the data can travel. 4. WIFI ANTENNA FUNDAMENTAL Antenna is an electrical device consists of metallic conductors electrically connected to the receiver and transmitter. It converts electric power into electromagnetic/radio signals and vice versa. In transmission, a radio transmitter supplies specific radio frequency electric current to the antenna and radiates the energy as electromagnetic/radio signals where listening devices's antenna pick up and converts them back to electric current for receiver. Some WiFi antenna may be mounted externally while others are embedded inside the device's hardware enclosure. Antenna connectors used by IEEE wireless devices include N-Type, RP-SMA, SMA, etc. 4.1 ANTENNA CLASSIFICATION Antennas generally are classified by the direction in which they radiate electromagnetic/radio signals. DIRECTIONAL Directional antennas are commonly used for outdoor point-to-point network connections. This type of antenna receives or radiates in a particular direction or directional pattern.

5 I) Parabolic & Disc Antenna as shown in figure 1 below is a highly directional antenna type that transmits and receives radio signals in a very narrow angle. It is designed for long distance and point-to-point network connections. It consists reflector surface with an active element at its focus. The reflector surface is used to collect or project radio waves of very narrow beamwidth which provide minimum interferance with another wireless network, very long signal distance, faster link and improve security. Figure 1 Parabolic & Disc Antenna II) Panel Antenna as shown in figure 2 below is a directional antenna used for both point-to-point and point-to-multipoint network connections. It is an ideal solution when aesthetics appearance is critical due to it's flat plastic or fiberglass cover. Figure 2 Panel Antenna III) Yagi-Uda Antenna as shown in figure 3 below is a semi-directional antenna used for point-to-point or point-to-multiple point network connections over long distance. It is made up of array of *dipoles (elements) parallel to each other. The first element (longest) is the reflector, second is the driven element and other elements are directors. Yagi with more directors has the greater gain. Figure 3 Yagi-Uda Antenna

6 OMNI-DIRECTIONAL I) Omni-Directional Antenna shown in figure 5 is a common base antenna used for point-to-multipoint distribution of electromagnetic/radio signals to other wireless computers or devices.this type of antenna radiates radio frequency equally horizontally and very little above and below the antenna. Because of this, if the gain of the antenna is increased, the distance it can cover will be increased but decrease the directions above and below the antenna. Figure 4 Omni-Directional Antenna 4.2 ANTENNA PROPERTIES An antenna has several fundamental properties which affect the selection of the right antenna for applications purpose : I) DIRECTIVITY Directivity is the direction of the radio waves as it leave the antenna. It is a measurement of how 'directional' an antenna radiates it's radio signals. Directivity is a function of angle and measured in degrees and are called beamwidths. As the gain of an antenna increases, the angle of the radiation pattern decreases. An antenna that radiates equally in all directions, as in the case of the theoritical isotropic antenna with 360 degree vertical and horizontal beamwidth, would have zero directionality, and the directivity of this type of antenna would be 1 (or 0 db). II) GAIN Gain is a measurement of the strength of an antenna signal power that radiates radio signals in a desired direction against the theoretical isotropic omnidirectional antenna. The signal power level produced by an antenna is compared to the isotropic antenna in decibels-isotropic unit (dbi). If an antenna is rated as 10 dbi, it has a gain of 10 times that of a isotropic antenna. Higher gain antenna is more effective in radiation pattern in desired direction. Therefore high gain antenna is normally for point-to-point long distance connections. Gain of an antenna is reciprocal, i.e. the gain of any antenna when receiving is equal to it's gain for tansmitting. An antenna is a passive device that does not add power to the signal, it merely redirects the energy it receives from the transmitter, therefore the direction where energy is directed to will receive more energy, and less energy in other directions. A device's transmission power affects the capability of the device to transmit or receive electromagnetic signals. It is typically measured in unit of dbm (milliwatts), therefore a larger dbm value indicating capabilty of the device to transmit or receive electromagnetic signals over greater distance.

7 III) IMPEDANCE AND STANDING WAVE RATIO (SWR) Impedance is a measure of the opposition to electrical flow in electronic components. It is measured in ohms. The antenna impedance represents the power that is absorbed by the antenna as well as the power that is dispersed by it as it comes into contact with an electromagnetic wave. If the feedline impedance does not equal the feed point impedance, the driven element cannot transfer the RF energy effectively from the transmitter, thus reflecting it back to the feedline resulting in a Standing Wave Ratio (SWR). For efficient transfer of energy, the impedance of the radio, the antenna, and the transmission line connecting the radio to the antenna must be the same. A high SWR is an indication that the signal is reflected prior to being radiated by the antenna. A SWR of 2:1 or less is considered good. Most commercial antennas, however, are specified to be 1.5:1 or less. IV) FREQUENCY AND WAVELENGTH Radio waves radiate from a source based on the transmitter power and antenna. It travels at the speed of light through space. Each wave has a certain shape and length. The distance between two identical points (for example two adjacent high points as shown in figure 5) of one cycle of the wave is the wavelength. The length is usually specified in meters, centimeters or millimeters. The difference in wavelength tells different kind of electromagnetic energy. The higher the frequency of the radio signal, the shorter the wavelength. An antenna must be tuned to the same frequency band as the radio system to which it is connected to and operates in, otherwise reception and/or transmission will be impaired. The frequency of an antenna must also be of the same frequency with all wireless devices such as access point, router in order for the wireless system to function properly. Figure 5

8 V) RADIATION PATTERN Radiation pattern depicts the strength of the signal power radiated by an antenna as a function of the direction away from the antenna. Shown below are radiation patterns from antennas with different power gain. Figure 6 is a theoretical isotropic antenna radiation pattern with energy radiated equally in all directions. Figure 7 is the radiation pattern for a typical omni-directional antenna in the shape of a donut which provides 360 degree signal coverage. Omni-directional antennas are typically used in indoor offices, retail stores, cafes, home networks, etc. Figure 8 shows a typical high gain directional radiation pattern for directional antenna with forward gains to desired direction. Directional antenna focuses the wireless signal in a specific direction. High gain directional antennas can transmit and receive wireless signals over long distant in kilometers given clear line of sight and strong device transmission power. Figure 6 Theoretical Isotropic Omni-directional Antenna Radiation Pattern Figure 7 Typical Omni-directional Antenna Radiation Pattern Figure 8 Typical High Gain Directional Antenna Radiation Pattern

9 VI) POLARISATION A radio wave is composed of electric and magnetic fields propagating perpendicular to each other. Polarization refers to the orientation of the electric field as energy radiates away from an antenna. Radio wave is commonly propagate horizontally, vertically or dual polarised as shown in figure 9 below. Dual polarised antenna utilises dual polarity via seperate input ports where antenna transmits or receives two signals on the same frequency simultaneously, increasing the throughput of the data thus higher transmission speed. In outdoor n MIMO systems, the seperation of two inputs allow the two MIMO radio signal streams to coexist without interferance. Figure 9 Two antennas with similar polarisation will inter-operates most effectively. A horizontally polarised antenna will not communicate with a vertically polarised antenna. Polarity on both ends of a communication link must be the same else they will not be able to communicate. Figure 10 below shows the correct antenna alignment methods. Figure 10

10 5. WIRELESS NETWORKING STANDARD WiFi is the name for the popular wireless networking technology for networking that conforms to the IEEE standards. Products that follow specifications are differentiated by their Frequency Band, Data Rate, Range, Modulation as listed at Table 1 below : IEEE Standards a b g n ac (Draft) Frequency Band 2.4 GHz 5 GHz 2.4 GHz 2.4 GHz 2.4/5 GHz 5 GHz Max. Data Rate 2 Mbps 54 Mbps 11 Mbps 54 Mbps 600 Mbps > 1 Gbps Indoor Range 50 ft 100 ft 100 ft 125 ft 225 ft Outdoor Range 300 ft 400 ft 450 ft 450 ft 820 ft To be announced To be announced Modulation DSSS,FHSS OFDM DSSS OFDM,DSSS OFDM OFDM MIMO Stream Table 1 6. RADIO SPECTRUM Radio spectrum refers to the part of the electromagnetic spectrum corresponding to radio frequencies within the range of about 3Hz to 300GHz. To prevent interference and allow for efficient use of the radio spectrum, different parts of the radio spectrum are set aside and designated as band for different radio transmission technologies and applications. Table 2 below listed the frequency band 9 and 10 for wireless LAN shared with other technologies and applications. Band Name Band Frequency Uses Ultra High Frequency (UHF) Super High Frequency (SHF) MHz Television Broadcasts, Microwave Devices /Communications, Radio Astronomy, Mobile Phones, Wireless LAN, Bluetooth, ZigBee, GPS and two-way Radios GHz Radio Astronomy, Microwave Devices / Communications, Wireless LAN, most modern Radars, Communications Satellites, Amateur Radio Table 2 Spectrum assignments and operational limitations are different worldwide. For 2.4 GHz band, number of channels allowed for the US is A Wi-Fi signal occupies five channels in the 2.4 GHz band. Any two channel numbers that differ by five or more such as channels 2 and 7 do not overlap. WiFi devices should be set to nonoverlapping channel number to avoid signal interference.

11 7. RADIO FREQUENCY MODULATION Radio frequency modulation is the encoding of information suited to the characteristics of a high frequency radio transmission channel in a carrier wave by varying the frequency of the radio signal. The main purpose of frequency modulation is to squeeze as much data as possible into the limited radio spectrum. There are several techniques with different level of efficiency that can be employed to achieve this purpose. I) FREQUENCY HOPPING SPREAD SPECTRUM (FHSS) The FHSS modulation technique uses available transmission channels in carrier wave to transmit and receive data and rapidly switches between channels. If interference affects only a few of the channels, interference is minimized. IEEE wireless networks use FHSS for modulation. II) DIRECT SEQUENCY SPREAD SPECTRUM (DSSS) DSSS spreads the carrier signal across the entire 22MHz (2.401 to GHz) frequency range of its channel. At the same time it is transmitting the data over this channel, it also generates a noise signal. This noise signal can be reversed or subtracted from the data signal, therefore the effect of interference is reduced. DSSS has an advantage over FHSS in that it has better resistance to interference. It is used primarily by IEEE b networks operating in the 900MHz, 2.4GHz, and 5GHz spectrums. IEEE g/n networks also sometimes use DSSS. III) ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING (OFDM) OFDM takes the data that needs to be transmitted and breaks it into a large number of subcarrier streams that can then all be multiplexed into a single data stream. This multiplexing process gives OFDM an advantage over DSSS because it allows higher throughput, and it can be used both in the 2.4GHz and 5GHz frequency range. OFDM is used with IEEE a/g/n networking. IV) MULTIPLE-IN MULTIPLE-OUT (MIMO) MIMO allows multiple antennas to be used when sending and receiving data. MIMO allows multiple signals to be multiplexed or aggregated, thereby increasing the throughput of data. To improve the reliability of the data stream, MIMO is usually combined with OFDM. When using multiple antennas, you can achieve higher transmission speeds of over 100 Mbps. MIMO is used in IEEE n networks and is the main reason the network is able to achieve high speed.

12 8. DESIGNING OUTDOOR WIRELESS NETWORK When designing an outdoor wireless network, line of sight between two antennas is very critical to the network traffic performance. To create an outdoor point-to-point or point-to-multipoint link, any obstructions between the antennas would cause degradation of the radio signal. There are three main categories of line of sight, i) Line of Sight with no obstacles (LoS), ii) near Line of Sight with partial obstacles such as trees or buildings (nlos) and iii) Non Line of Sight with full obstruction (NLoS). When a signal travels from transmitter to receiver, it travels in three possible ways i.e. directly to the receiver; downward and reflects off objects such as the ground and then to the receiver; or to left or right and reflected back by objects such as hill and then to the receiver. Figure 11 LOS, nlos and NLOS Radio signals will get reflected by solid objects such as ground, vehicles, etc. It has more difficulty in passing through trees, this is due to water content in tree as radio signal absorbs quite well into water. Figure 12 FRESNEL ZONE WITH OBSTRUCTIONS

13 FRESNEL ZONE Radio frequency line of sight condition is defined by Fresnel zone. Fresnel zone is an oval-shaped area around the line of sight between the transmtting and receiving radio antennas. This area must be cleared of obstacles else the radio signals strength will be weaken. Figure 13 FRESNEL ZONE 1 AND 2 Figure 13 above shows the imaginery cylinders for Fresnel zone 1 (F1) and Fresnel zone 2 (F2) with main and reflected signals travel within F1 zone. The reflection can happen at any location between the transmitter and receiver. When a signal is reflected, it will take longer distance to travel to the receiver antenna. Figure 14 FRESNEL ZONE 1 RADIUS r The F1 zone radius r at point P which is the widest point is calculated such that the difference in path length between the main signal and a reflected signal arrive at the receiving antenna in phase. The two signals will be added together and enhance the receiver's antenna performance. The F2 zone is where the main signal and the reflected signal arrived at the receiving antenna out of phase, therefore cancel out each other. Since the F2 zone is detrimental to receive signal, antenna heights are often determined so that F1 zone has an unobstructed path and obstructions such as hills or bodies of water, etc fall within F2 zone.

14 FRESNEL ZONE RADIUS AND EARTH CLEARANCE The important component of Fresnel Zone Radius is the clearance between the Fresnel zone cylinder and the surface of the earth as shown in figure 15. As a rule of thumb, if the ratio of Fresnel zone F1 earth clearance / Fresnel zone radius is greater than 60%, the path is considered clear line of sight for radio signal propagation. Figure 15 The size of the Fresnel zone is determined by the frequency f used to transmit the radio signal and the distance between two sites D concerned. The radius of the widest point of the F1 zone can be calculated by using formular below : where r = radius in metres D = total distance in kilometres f = frequency transmitted in gigahertz EARTH CURVATURE Radio signal transmission over long distance faces the issue of the Earth curvature. Therefore outdoor antennas often be installed on towers to raise them high enough to avoid the curvature of the Earth. A cylindrical volume of space must be unobstructed around the direct line-of-sight between the two antennas. Figure 16 FRESNEL ZONE WITH OBSTRUCTIONS

15 ANTENNA'S TOWER HEIGHT To determine the required height of an antenna tower, it is necessary to have at least 60% radius of the Fresnel Zone F1, take into effect of the Earth's curvature, and add the height of the tallest obstacle object in line of sight as depicted in figure 17 below. Figure 17 For a given distance between two antennas, the table below lists the approximate value for each of these factors : Distance Between Two Antennas Fresnel Zone 1 Approximate Value (60% at 2.4 GHz b/g) - F Earth Curvature Approximate Value - E Height Of Obstruction Object - O 1 Mile 2 feet 3 feet o 3 Miles 23 feet 4 feet o 5 Miles 30 feet 5 feet o 8 Miles 40 feet 8 feet o 10 Miles 44 feet 13 feet o 15 Miles 55 feet 28 feet o 20 Miles 65 feet 50 feet o 25 Miles 72 feet 78 feet o Table 3 The table above shows that a wireless link between two antennas separated by 10 miles with no obstruction would approximately require an antenna tower with a minimum height of 57 feet for an b/g radio. In practice the heights would typically be higher. This is because the tower height must be raised by o feet to compensate for the height of the obstruction object such as buildings, trees or other obstacles in the line-of-sight between the two towers.

16 9. DEVICE TRANSMISSION RANGE The range a wireless device can reach is often not mentioned in the device's specification. The formula for calculating the theoretical transmission distance between two wireless devices which is derived from the Friis Transmission Equation is shown below : pt is the transmission power for the transmitting wireless device in dbm. With greater transmission power will enable the transmitting device greater transmission range; pr is the receiver sensitivity for the receiving wireless device in dbm. With greater receiver sentivity will enable the receiving wireless device to receive weaker signals; gt is the transmission antenna gain in dbi, indicating how much is the radio signal boosted by the antenna; gr is the receiver antenna gain in dbi, indicating how much is the radio signal boosted by the antenna; f is the frequency the IEEE device use. IEEE b/g/n devices use 2.4 GHz band while a/n/ac devices use 5 GHz band; r is the transmission range; The theoretical transmission distance between two wireless devices can be calculated using the formula with example below. Suppose you are using g wireless devices with specifications stated below : Transmitting Antenna Receiving Antenna Antenna Gain (gt) = 15 dbi Antenna Gain (gr) = 15 dbi Tx Power (pt) = 21 dbm Rx Sensitivity (pr) = -74 dbm Frequency = 2442 MHz (2.442 GHz for g) The transmission range between two antennas is approximately r = KM In the real world many variable affects the performance of the antenna such as obstructions, mismatched impedance, electronic interference, etc. Wireless communication between two devices will also be affected if two devices have different Transmission power and Receiving sensitivity specifications.

17 10. APPLICATION Application for WiFi technology is wide for both indoor and outdoor environment. Typical scenarios of usage are explained briefly below : Radio signal propogation can take multipath from a transmitter to receiver. The main signal and the reflected, diffracted (bend around the obstacle) or refracted signal can be added up and increase the signal level or get corrupted at the receiver depending whether they arrive in phase or out of phase. Multipath is more common in the indoor environment due to it's enclosed environmwent. INDOOR Indoor radio signal propogation capability can be hindered by the building materials used to construct the office walls, floors and ceilings. Wooden walls can be penetrated easily without affecting much the signal coverage whereas concrete walls with reinforced steel would pose more difficulties for signal to penetrate. Metal walls would cause signal to reflect back. I) HOME / SMALL OFFICE Router incorporated modem and Access Point can be setup to provide Internet access to wireless client devices at home or small office environments. The placement of Access Point is very important to the effective transmission of the radio signal. Omi-directional antenna equipped Access Point is normally installed to provide 360 degree horizontal coverage for home / small office usage. Figure 18 II) CORPORATE OFFICE WiFi local area network (WLAN) can be setup as part of an enterprise office network where laying of cables over office space is not suitable, therefore installation of Access Point at strategic locations can be an alternative. It is usually deployed as an extension to wired network that offer mobile connection and access to network resources at common areas, meeting room, etc. Directional antenna can be considered to be installed to direct radio signals to desired direction so that long range distance such as hallways, corridors can be covered effectively.

18 Figure 19 III) HOTSPOT A Hotspot is a site that offers free public Internet access through wireless local area network (WLAN). A WiFi client device such as smart phone, laptop computer, etc can connect to the Internet when within range of a WLAN. Setting up of a Hotspot is as simple as configuring an Access Point which uses Omni-directional antenna in conjunction with a router and an Internet connection. The coverage of one or more (interconnected) Access Point can extend from an area as small as a few rooms to as large as many square kilometers. Figure 20

19 OUTDOOR Point-To-Point and Point-To-Multipoint antennas are used as the building block for outdoor wireless network design where different geographical environments exist which poses different network design challenge to establish an effective and efficient communcation link. Antenna is set in bridging mode to connect two or more networks located at different buildings/sites. Bridging of networks can be either a point-to-point or point-tomultipoint configuration. The coverage can be over long distance of as far as multiple kilometers away as long as there is line of sight coupled with the device's strong transmission power. I) POINT-TO-POINT Point-To-Point WiFi link is the most straight forward wireless network design where two seperate buildings/sites can be linked up using directional antenna with one building acting as the base station connected to carrier network for Internet access and another building as the remote client station. Figure 21 Point-To-Point Directional Antenna (Bridge Mode) II) POINT-TO-MULTIPOINT Point-To-MultiPoint antenna can be used in a design to link up multiple buildings with one centrally located building designated as the base station. The base station building will be installed with Point-To-Multipoint Omni_directional antenna whereas the other buildings will each use Point-To-Point directional antenna pointing to the base station's Omni-directional antenna.

20 Figure 22 III) POINT-TO-POINT RELAY In this design, a pair of Point-to-Point directonal antenna is installed at a suitably located building as the relay point to link up two remote buildings. The relay point is to overcome connectivity issue caused by obstructions between the two remote buildings. Figure 23

21 11. SECURITY RISKS WiFi network can be less secure than wired network because an intruder does not need to connect to the network physically. Open-air nature of wireless communications has made level of network security even more complex. Wireless radio signals a lot of time pass through walls and into nearby streets or parking lots. Wireless radio signal propogates through the air are much easier to intercept, beside the carelessness or ignorant of human nature. Various WiFi encryption technologies were developed for use to mitigate the risks. One of these is the WPA/2 encryption service whereby network traffic signals between clients and Access Point can be encrypted so that the contents are adequately protected. Beside encryption, some wireless devices have network access control features such as MAC address filtering so that only user access with the registered MAC is allowed to get connected. 12. CLOSING This guideline provides a brief overview on the WiFi technology and related electrical and radio properties which affect the performance of the wireless devices. Multipath radio signals that travel from transmitter to receiver is common for indoor environment due to obstructions caused by walls, ceilings, etc, therefore the placement of antenna and the type used has direct impact to the performance of the WLAN. Outdoor WiFi communication link's performance depends very much on the condition of the line of sight between two antennas as it is critical to effective propagation of radio signals from transmitter to receiver. WiFi technology is a relatively cheaper and easier to implement due to the unlicensed frequency spectrum it uses as compared to other wireless technologies such as WiMAX which require license for implemention. With the coming of the latest IEEE standard i.e ac, with significant increase in the transmission speed has made WiFi technology a viable option beside WiMAX as the last mile solution to connect Customer Premise Equipments (CPE) to Base Station for Internet connectivity.