Started from 7 December I attend supported course which is: Cisco Certified Network Associate (CCNA) Fast Track, as a recommended course from my supervisor.Then as i have been told, i will be assigned for new tasks which needs CCNA course to be solved...

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Part 1

General overview about GSM wireless network

The GSM wireless network can be partitioned into two major segments which are:

-          Radio Access Network (RAN)

-          Core Network (CN)

Figure down explain more

The way of registering a handset in the GSM system works like explain down:

The handset listen for a SID (System identification number) which being broadcasted by the nearest BTS (Base transceiver station), while the BTS received SID, the handset send its IMEI (international mobile equipment identity) as well MIN (Mobile identity number) then goes through the BSC (base station controller ) where the transmission is determined whether it’s voice or data. The BSC and BTS together called BSS (Base station subsystem).

Then directly goes to the MSC (Mobile switching center) where subscribers get authenticated, validated also the process of subscribers database SIM details which are HLR (Home location register) and VLR (Visitor location register) get checks in here, so the time that subscriber services confirmed, it goes back to the handset the same way. Although these all happen so fast that customers don’t even notice.  

An alternate part in the system is the GMSC (Gateway Mobile Switching Center) which routes calls targeted to another carrier’s wireless network or the PSTN (Public Switch Telephone Network). Also there is a VLR (Visitor Location Register) which is used to load balancing as it stores subsets of information from the HLR when the subscriber is not in his home area.

For data service, GPRS (General Packet Radio Service), the SGSN (Serving GPRS Support Node) perform as the MSC, then goes to the GGSN (Gateway GPRS Support Node), then depending on the APN (Access Point Name), it will go out to the Internet in varied ways. For the APNs there are three which commonly used

-          GOAM.com: is used for plain text browsing and accesses the internet by WAP gateway.

-          Internet.com: used for HTML browsing, accesses the Internet by a NAT Server.

-          Media.com: used for multimedia messaging, accesses the Internet by a WAP Gateway, then a MMSC (Multimedia Service Centre) or SMTP server (for email).

Part 2

Analysis the survey to find a new antenna location at BIT BOS area in Sana’a:

Figure below shows BIT BOS area:

An antenna is one of the most critical issues in any RF communications system. The antenna performance determines the quality and the Continuum of data flow in both directions. Selection of the antenna is often deferred to the first phases of a program and the quality of the selection is usually driven by value (quality, performance and price) not by price. The actual performance of the antenna in the system is always verified until after the system is installed, if at all.

It is important to make a level of common understanding among the system designer, the system integrator, the user and the antenna supplier regarding the required antenna performance. The joint goal of this team is to maximize the performance of the total system while minimizing cost.

In here is outlining the major questions regarding antenna parameter which should be answered prior to making a final antenna selection.

First, what kind of radiation pattern is desired?

This is the first major of antenna selection. The only way to increase gain is to concentrate power in a narrower beam width .The narrower the beam width, the greater the gain of the antenna. A good conceptual example of this concentration is the vertical Omnidirectional antenna. It is used for line-of-sight communications with mobile stations.

Second, what is the maximum allowable VSWR?

VSWR (voltage-standing-wave-ratio) which represents the degree with which an antenna is "matched" to the system impedance. Most modern antennas do not require any tuning for o optimum performance. VSWR is one of the easiest parameters to measure and VSWR meters are becoming very popular antenna installation tools. Most modern antennas, receivers and transmitters are designed for peak performance when operating into a 50 Ohm transmission line. If the VSWR is too high, the transmitter power may be reduced as well as the strength of the received signal.

Third, what polarization is required?

The common types of system polarization are vertical, horizontal or elliptical. Selecting the proper polarization for the system can enhance the overall performance by minimizing the interference from adjoining systems. For example, by installing system orthogonal to other systems in the area, you can provide up to 20 dB of isolation

Fourth, where will the antenna be mounted?

 Real impact comes when estimate the total environment and whether the antenna will perform and survive once installed. Moreover, the impact of local zoning ordinances and regulations on installing antennas should not be underestimated. The integral strength of the design must be considered such as its ability to withstand wind, ice, heat or cold and other extremes. In addition assess the ability of the major components such as the feed, the radome and connectors to withstand stress.

Fifth, how to choose the appropriate location for outdoor antenna

1-      The location should be high so the signals can cover the wanted area.

2-      The location should be not in a crowded area due to the signal’s effects on the human being, if so’ the signal power should not be high.

3-       To avoid annoying interference happening, the used frequency slots must be deferent from any other frequency that can reach that area.

4-      The antenna carrying capacity is at most 16 users calling at the same time, means if the antenna location in crowded area we should lower the frequency signal power, so that allow to reuse the same frequency slot in new different area without happening interference: as the signal power of the first location could not reach to new location where same slot of frequency is used.

Sixth, the challenges that we faced during the survey is

1-      Locations owners afraid of the antenna side effects as well the neighbors, so we need to convince them that there is no side effects could happen.

Seventh, why do we need to establish new antenna and how to know that:

The need for establishing new antenna has come from variety reasons such as:

-          Overcrowded population, in the worse case of antenna’s capacity it become able to connect with 48 users all of them calling at the same time, here I meant antenna with three sectors so, the individual sector is able to be connected with 16 user.

-          Enhance indoor signaling.

-          High data traffic, this figured out by many ways, below is the technique that we performed  before the analysis data department decide to establish new antenna :

After every cellular network design and implementation there should be network evaluation ,and to do network evaluation there are many ways, the efficient one that we performed is evaluate the network by drive test.

 Drive test is, evaluation method performed in mobile radio networks regardless of technology GSM,LTE,CDMA..Etc this way used vehicle or motor to collect the data, the vehicle or the motor contains the measurement tools “Tems investigating software, GPS, two  mobile phones” which doing data collection for network ,then after collecting the data there is step called analysis. Drive test data analysis this step is to identify problems that network has such as dropped calls, interference, high data traffic …etc .

Drive test hardware and software used in the test:

·         Laptop or notebook or other similar device with Tems investigation software installed

·          Two mobile phone or at least one

·         One GPS

·         Scanner if there is or it’s optional

The following figure shows the Standard connections:

The main objective of this test is to collect data, the data is collected by collection software and store in one or more output files below is the figure shows the job for each connection:

·         GPS: collecting data of latitude and longitude of each point / measurement data, time, speed… etc.  It is also perfect as a guide for following the correct routes.

·         MS: mobile data collection, such as signal strength  etc

·         Scanner: collecting data throughout the network, since the mobile radio is a limited and does not handle all the necessary data for a more complete analysis.

The min required to do a drive test, is a mobile device with a Tems investigation software to collect data and a GPS. Currently, there are cell phones that do everything. They have a GPS, as well as a collection of specific software. They are very practical, but still quite expensive.

Drive test investigation are:

·         Integration of new Sites or change parameters of Existing Sites.

·         Performance network and analysis.

·         Comparing, for example between two GSM networks performance.

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References

1-vijay k garg wireless communication and networking

2-http://www.tabula.com/applications/wireless.php

3-http://www.ascom.com/nt/en/index-nt/tems-products-3/tems-investigation-5.htm#overview

*For the videos and photos i will upload later coz i have problem with syncing videos form my phone*