WIRELESS NETWORKING (Part 5)

Some Wireless Network Specifications

Here we will learn some technology specifications that can be used as a base reference in the development of network infrastructure without wires, whether indoor or outdoor, even MAN.

A. Fixed Wireless

is a wireless technology where the sender and receiver occupy a fixed location such as home or office. Applying this technology is MMDS (Multichannel Multipoint Distribution Service), LMDS (Local Multipoint Distribution Services), Point-to-Point Microwave, or WLAN.

A.1 MMDS (Multichannel Multipoint Distribution Service)

operate in the spectrum of 2.5 - 2.7 GHz with a width of 200 MHz. Throughput which can be given is 1-2 Mbps. The distance that can be taken is 35 mile from the radio port controller (RPC) which is based on the strength of signal.

A.2 LMDS (Local Multipoint Distribution Services)

a microwave communication systems with models of point-to-multipoint who works on a frequency of 20 GHz. Bandwidth provided to 500 Mbps. Typically used for short distances that require bandwidth high, such as campuses, companies, etc..

Example:

A.3 Point-to-point microwave

is a technology line-of-sight is very influenced by multipath and the absorption of some other object, such as MMDS and LMDS

A.4 Wireless LAN

Connection type Wireless LAN

● W-LAN Outdoor - used for connecting devices in the outdoors, follow the 802.16 standard

● W-LAN Indoor - used for connecting devices in the indoors, follow the 802.11 standard

Use of wireless technology for local networks, can follow standardization of IEEE 802.11x, where x is a sub standard which consists of:

• 802.11 - 2.4 GHz speed up to 2Mbps

• 802.11a - 5GHz speeds up to 54Mbps

• 802.11a 2X - 5GHz speeds up to 108Mbps

• 802.11b - 2.4 GHz speeds up to 11Mbps

• 802.11g - 2.4 GHz speeds up to 22Mbps

• 802.11n - 2.4 GHz speeds up to 120Mbps

802.11 MAC is known DFWMAC (distributed foundation wireless MAC). Flowchart of the algorithm is:

Here are the types of W-LAN devices

Examples of W-LAN device specifications

● Output Power

• 5150 ~ 5700 GHz

15 dBm (+ / - 2 dB) for 6 Mbps

12 dBm (+ / - 2 dB) for 54 Mbps

• 5745 ~ 5850 GHz

15 dBm (+ / - 2 dB) for 6 Mbps

10 dBm (+ / - 2 dB) for 54 Mbps

● Antenna Gain

2.81dBi Max.

● Receiver Sensitivity

Min. -67dBm for 54 Mbps @ 10% PER

Min. -73dBm for 36 Mbps @ 10% PER

● Power Consumption

520 mA at transmit mode

310 mA at receive mode

Use of specification 802.16 (wireless broadband) to the network outdoor is very expensive, so there is no harm if we also using the 802.11 specification for these outdoor networks. There a few things to note:

● Radio 802.11b only has 11 channels

● The installation must follow the rules of Line of Sight

● Requires the tower if two points are at different levels

● Use a small power should really be taken into account

● Must overcome the interference that occurs Using the PCMCIA in the computer

Using the Access Point to connect to external antenna

802.11 is used in indoor known as the HotSpot and standards WiFi

● One access point can not serve more than 50 clients

● Installation of access points should not interfere with each other frequencies (Remember: there are only 3 frequencies are not mutually stacked)

WIRELESS NETWORKING (Part 4)

RF Channelling

All RF communications require a fairly small segment of the total RF spectrum is available. One segment is called the channel (Channel). To allow for multiple signals are used simultaneously, each channel requires a separate frequency with the help of FDMA. The frequency of one channel is the center frequency of a single spectrum canal. The width of the channel spectrum is called the channel bandwidth.

The use of such channel, highly depends on the type communication. In the CB radio (handy talky), using a type halfduplex, so it is quite necessary one channel only. In multi-channel systems, such as mobile phones, used for supports full-duplex type. In order to implement full-duplex, then The second channel is made in addition to the main channel, which allows two-way can dirambatkan simultaneously. Another example is the two-channel receiver in a stereo system (the left channel and right channel) FM radio. With the increasingly widespread use of RF for many purposes, then the channel utilization is considered, so that later emerged concept of frequency reuse (Frequency Reuse). Examples of the use of frequencies between the radio station in Yogyakarta with at jakarta could use the same single frequency. This probably because of the distance that had exceeded the scope of the ability of the FM signal.

On a mobile phone communication, also applied the concept of frequency reuse This, first pioneered by the AMPS (Advanced Mobile Phone Service). Time Division Multiple Accessing (TDMA) TDMA is used to add capabilities FDMA. Each channel is divided into several time slots, where each one slot used by one user. An example is the GSM (Global System for Mobile Communication) is a type of TDMA. Code Division Multiple Access (CDMA) CDMA is the latest technology for multiple access. CDMA is not divide a set of frequencies used to be several channels. CDMA gives a unique code for each signal and then combines all the signals into one large channel. CDMA wireless technology known as 3G phones because of very efficient in bandwidth usage and also very secret because uniquely encoded communications.

WIRELESS NETWORKING (Part 3)

Line-of-sight


Straight path is clear of obstacles between the receiver and sender called line-of-sight. For high frequencies require line-of-sight more better than low frequency.

There are two terms

● Optical Line-of-sight, the two stations can optically see each other

● Radio line-of-sight, no reflection or

line-of-sight Calculation is necessary when you build wireless network outside the building (outdoor). You can find how to calculate Link budget for outdoor Propagation in this blog. we can used excell to provide a calculator to help you calculate radio links outdoor.

There are 4 parameters that are used to calculate the W-LAN systems outdoor work well:

● System Operating Margin (SOM), associated with strength sender, the type of antenna, coaxial cable length and distance.

As an illustration of calculation, on the 802.11b specification, the recipient (Receiver) has a sensitivity of -80 to -85 dBm. On the client side, normally we use a directional antenna, such as antenna parabola with the addition of 19-24 dBm. Loss of signal for coaxial cable between 2-3 dB. To cover the operating margin (SOM) 10-15 dB is highly dependent on type of antenna used on the Access Point. If using an antenna (Discussed next) omnidirectional with the addition of 10-12 dB, we get a coverage area of 4-5 km. If using a sectoral antenna (Directional).with the addition of 12-14 dB, we can cover 6-8 Km.


Free Space Loss (FSL): lost power after a distributed radio at a certain distance.

Example:
FSL for a distance of 5 km at a frequency of 2.4 GHz is 114 dB. Normally (by Onno W. Purbo) per distance of 1 km at 2.4 GHz will have the FSL in the range of 100dB.


Fresnel Zone Clearance (FZC), to see the need for high antenna to go through obstacle.

Fresnel Zone is an area not there are barriers between the two terminal. Usually for the 1st 80% Fresnel Zone. formula:

R = 43.3 sqrt (d / 4f)

Where:
R : Radius Freznel Zone
d : Path length 2 node

f : frequency

Here is a table FZC to 1-7 km distance to the terminal Wi-Fi operates at 2.4 GHz

Antenna bearing, tilt down the antenna and the coverage radius antennas need to know to cover an area.

Where Hb is the height of the BTS antenna and receiver antenna height Hr is and A is the angle in radians.

For example: for a BTS with a height of 30 m to cover distance of 3 km, take the angle of degrees to achieve 0:35 receiving antenna height of 10 m. In some cases we need the approximate area of coverage can be calculated by the formula:

Where H is the height of the BTS, A is the antenna tilt angle, BW is the width of coverage (beam).

For example:

 to an access point with antenna height 30 m, and beam width 10 degrees with 0.2 degree angle, we will achieve the inner 150 m radius and outer radius of 8.7 km.

Antenna

The antenna is needed if we install a wireless network infrastructure for outdoor. The antenna will change from electric signals into electromagnetic signals. The amount of energy that can be amplified by the antenna on the side recipient or the sender is called the antenna gain.

Directional Antenna

antenna which amplifies the signal from the sender to dirambatkan on one or two directions. There are two categories: parabolic and phased arrays. Parabolic used for medium or long distances and can provide gain

between 18-28 dBi. Example:

Yagi Phased Array

This antenna is suitable for short distances with a gain of 7-15 dBi

● Sectoral Antenna

is a phased array type that divides the coverage area of a circle into several sectors to help the channel allocation and use of  repeated. A sectoral antenna has a beam of approximately 120 degrees that divides one area of the circle into 3 areas.

By used sectoral antenna would be more efficient rather than the use of omnidirectional installation.

WIRELESS NETWORKING (Part 2)

Radio Signal Propagation


In order for a wireless network to function, signals must have a path from sender to receiver, arriving with the signal strength is still sufficient to be translated. Signal strength can be measured by two units:

• dBm (decibels above 1 mW) in units of Watts or Volt
• S / N Ratio (Singnal-to-Noise) shows the ratio between the power signal and noise power. For digital signal, S / N Ratio is less than at S / N for analog signals.
Another thing to note for the propagation of radio signals is attenuation (attenuation) signals. The weakening can be affected by distance. The picture signal attenuation can be shown with light from two different sources.

Ommidirectional

Directional

The formula for converting Watts to dBm or vice versa:

Electromagnetic waves can not cut trough the earth element, likes: mountains, valleys, so the need to elevate the recipient or sender in the mountains or tall buildings.

The cause of signal attenuation is rain. A signal that has higher frequencies will have a density (wavelength) more shorter. Electromagnetic waves can pass through some objects, but also could be reflected by an object. This reflection is often called baunching or scattering. Baunching can decrease the performance of a system and can also enhance other performance. As an example of a radio broadcast signal PM could be reflected by a layer of Earth's atmosphere.

 Some applications that use low frequencies to using the atmosphere as a reflector to increase the distance scope. But for high frequencies can not be reflected in layers of the atmosphere, because of the high frequency will be absorbed by the atmosphere. So for high frequencies required an artificial reflector, which called satellites. Not all obtained from bounching good result, one of them called multipath scattering in mobile communications.

Multipath Scattering is a signal that reaches the recipient of several path is the result of bounching. If the signal is received outside of the phase, then the signal is canceled. If the signal received in phase but not synchronized, will be received echo signal. Examples of applying this is CDMA (Code Division Multiple Accessing)

WIRELESS NETWORKING (Part 1)

Wireless Network Is the the technology of data transmission from one point to point without physical cable, including radio, cellular, infrared, and satellite.Radio is the transmission and reception of signals with wave electromagnetic wirelessly. Electromagnetic Waves presenting all frequencies. Spectrum Radio Frequency (RF) occupies a range of 9 KHz - 300 GHz.

Wave Anatomy :

And The frequency calculate with:

A radio signal sent to a another point, the signals must be modulated into a frequency signal (carrier), which is a constant and higher frequency of the input signal frequency. Reason modulation is required:

1. For a better transmission, because the radio signals that we send mostly using low frequency
2. To allow multiple signals simultaneously transmitted without disturbing each other (interference). Read the back Frekuency Division Multiplexing (FDM)!

Analog Modulation:

Digital Modulation:

FSK is used in the 802.11 specification for modulation Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS).

Pathloss 5.0 Update Build 15 Nov 2010

Pathloss version 5 - Maintenance update - Build date November 12, 2010


Check the build date of your current installation. Click the Help - About Pathloss 5.0 menu item.



If the build date is May 7, 2009 or newer, then use the link below to download the November 12, 2010 maintenance update.



Pathloss 5 update

This is an InstallShield installation program. The Pathloss program must be closed to run this update



If the build date of the current installation is earlier than May 7, 2009 then the update must be carried out as a new installation as described below.



Pathloss version 5 - Maintenance update using a new installation

Your existing installation must be first be uninitialized and then the program must be removed.



The following steps detail the procedure.



Start the Pathloss program



Click Configure - Pathloss program - Uninitialize program

If you were able to initialize the program on line, then select this option and click the Uninitialize Program button. You will be prompted to proceed with the uninitialization. This step will automatically update the licensing database for the next installation.



If you were not able to initialize the program on line due to the program internet access restrictions, then select the EMail option and click the Uninitialize Program button.

You will first be prompted to proceed with the uninitialization. Once the program has been uninitialized, the dialog on the left will appear. Click the "Copy serial number and uninitialization code" button. This step copies these two item to the clip board.



Create a new Email to cte@pathloss.com and paste (Ctrl V) the serial number and uninstallation code into the EMail body.



When we receive the EMail, the licensing database will be updated for the next installation.



Note that the uninitialization procedure (on line and EMail) creates the file "pluninst.txt" in the tmp_file folder. This file contains the serial number and uninstallation code. This also can be Emailed to update the installation status



Once the program has been uninitialized, remove the Pathloss program using the Control Panel operation "Add or Remove Programs" to remove the Pathloss program.



Finally download and install the latest program build using the procedure supplied with your serial number notification



Important note to VISTA users

It will be necessary to manually delete all files in the directory



C:\Users\\AppData\Local\VirtualStore\Program Files\Pathloss 5\geo_data



before installing the complete program.