LINK PLANNING AND LINK BUDGETTING

In a basic communication consisting of two radios,each with it's associated antenna and separated by a distance(x),the radio require a certain minimum signal to be collected by the antennas and passed on to their input socket.Link budget calculation refers to the determination of the feasibility of the link between two antennas.This feasibility depends on the quality of the equipment being used and on the diminishment of the signal due to distance,called path loss.
The power available for a particular wireless link can be characterised by the following factors:

• Transmit Power.It is usually expressed in dB and ranges from 30mw to 200mw or more,oftenly it is dependant on transmission rate.


• Antenna Gain. Antennas are passive devices that create the effect of amplification by virtue of their physical shape.They have the same characteristics when receiving and transmitting.Parabolic antenna have a gain of 19-24 dBi,omnidirectional antennas have 5-12dBi while sectorial antennas have roughly a 12-15 dBi gain.


• Minimum Received Signal Level.This is also referred to as the sensitivity of the received.The minimum RSL is always expressed as a negative dBm and is the lowest power of the signal the radio can distinguish. The minimum RSL is dependant on the rate , and as a general rule the lowest rate (1mbps) has the greatest sensitivity.


• Cable Losses.Some energy is inevitably lost in the cables,connectors and other devices,going from the radios to the antennas.The loss depends on the type of cable and used and on its length.

To go ahead and calculate the link budget for a particular one is required to calculate the antenna gain,Losses

Antenna gain is given by:Antenna gain of radio 1 plus Antenna gain of radio 2 if there are two radios in the system.

Losses are given by:cable losses in radio 1 plus cable losses in radio 2plus free space loss

Then finally the Link budget between radio 1 and 2 is given by:

Radio 1TX power plus Antenna gain Minus Losses.And for a feasible link this should be less than the sensitivity of radio 2 and viceversa.

WAVES AND WIRELESS COMMUNICATION

A wave is a disturbance that propagates through space or space time,often transferring energy.Every wave posses frequency,speed and wavelength.Frequency refers to the number of cycles passing througth a certain point per unit time,wavelength on the other hand refers to the distance between two corresponding points on the waves.
Waves play a very important role as far as wireless communication is concerned.For a example when one is talking to somebody a distance away using a cell phone,the sound waves with which one speaks are converted into an electrical signal within the cellphone,then the antenna of the cellphone converts the electrical signal into electromagnetic waves which are propagated in space either uni directionally or omnidirectional depending on the type of antenna in use.The antenna on the receiving end captures the electromagnetic waves and converts them into electrical waves which are further converted into audible sound waves by the earpiece of the cellphone.
During this process the signal strength or the amount of energy being transferred by the wave is very critical,hence it is the desire of every engineer,technician or whoever is establishing any form of wireless communication to minimise losses in the signal strength.There are a number of threats to signal strength ,however,as they are transmitted through through the air.Objects can cause radio waves to lose signal power by their shielding effect and absorption,usually objects containing some amount of water posses greater absorption effect than dry objects.In other words humidity is direct proportion to absorption.The other factor affecting signal power of radio waves is reflection.Radio waves reflect off the surface of metals,no wonder metals find wide application in antenna production.Interference has it's own role to play as far as enhancing signal power is concerned.Destructive interference has a negative impact on signal strength while constructive interference has positive impact towards signal strength in the sense that it boost signal power of the radio waves by increasing its amplitude.
Moreover,when it comes to frequency,the higher the frequency the higher the absorption in the same vain it's true that the lower the frequency the higher the refraction.The easier way of finding out whether an object is harmful to the radio waves is by putting it in a microwave.If it gets warm then it has an absorption effect on radio waves,hence harmful to the signal.If on the other hand it remains cool then it is safe to radio waves.

MY LEARNING EXPERIENCE AT LITA

When my head of department shared the thought of coming to macha,it was not appealing to me.To a great extent i could have come due to the fact that non of the companies i applied to responded positively towards my applications for vacation employment.Some how the desire to earn a little bit of money during this period of would have denied me an opportunity to learn what i have learned at macha in this small period of time.I don't regret coming to this place,it is an ideal place for any body young or old who wants to train in computers,networks and indeed stewardship.
I would like to hail Lita for the wonderful experience and exposure to the world of Computer Engineering and of course the the unlimited exposure to Internet 24-7.At least during this time of my learning at Lita i could always see practically how to go about certain operations.Learning at macha is not just about theory it is also about practical and practical based on the things that you have done.There are times or i should say we have always learnt it the hard way back on campus,whereby,you are required to do labs on the stuff you have not covered in lectures.It's not easy after all but as a student you must always find your way out and this leads to students cooking lab results.This has a great negative implication on the calibre and quality of university graduates on campus.I don't,however, under estimate the quality of education at the highest learning institution of this land but for the sake of quality, i suggest labs should appear synchronously with the theory.If it works wonders here at macha it can do much more for our only university in science based schools.
The other difference i would like to stress out here is the increasing cost of Internet on campus
and the entire city at large.It's not surprising to see a lot of people getting involved with Internet cafes on campus its due to an increasing demand of information by students doing there last year projects.This is not the case here at macha students are entitled to unlimited exposure to the Internet at any time ,this way i have always had an opportunity to add on the knowledge acquired during lectures.Moreover,it was a luxury for me to do a single course which demanded two to three hours of my time a day,this is not the case at unza in the school of engineering,each student is required to do a maximum of five courses per semester.This is quiet hectic,it drains ones energy and zeal to make it even more interesting you are required to do a minimum of seven labs in each and write an exam at the end of it all its hard but there is no remedy for failure any way. All in all,i would like to say congratulations to Jon and the rest of the guys at Lita, you are charging it to the game.

MORE ON LINKSYS TECHNOLOGY

The other aspect of linksys technology which i have discovered this week is it's wide spread use in bridging.Bridging is a unique AP-CLIENT network.This type of network provides a high level of security and better throughput for example a single client is able to enjoy a bandwidth of about 54mbps.However,when another client router is added to this network each receives 27mbps of data this is a reduced band width in comparison to the previous arrangement.This is inline with a standard rule in bridging which states that the more the number of clients on a network the less the bandwidth or speed.Bridging helps prevent other illegal users from accessing ones internet and consequently reduces traffic and conjetion on the network.The specific routers used in bridging carry the code WAP...,it should be noted here that bridging can be done between WAP routers or between a WAP and WRT router only and not between WRT routers.The procedure of establishing a bridge involved use of MAC Addresses to uniquely configure an AP-CL relationship.The AP was assigned the client MAC Address while the CL was given the AP MAC Address.Both the client and access point modes were set to client bridge mode.Each ethernet network device had one specific MAC address for its connection.The routers are assigned unique MAC addresses at the time of manufacture which was easily entered in the appropriate spaces on the setup page.On the contrary to obtain the MAC Address of the computer a command ipconfig /all was typed and entered,the page was then displayed from which the MAC address also refered to as the physical address was selected.After all these settings were configured the status and survey icons were clicked to check the status of the network, the signal strength being transmitted by the AP and the signal strength being received by the client.It was discovered that the signal strength was about 71% which was not bad.Another vital tool used in troubleshooting this network is the ping command.To do this exercise the start button was clicked,then went to run,and then typed cmd andthen click ok.At this point a black page was displayed the word ping was typed followed by the IP address of the

gadget being troubleshooted.when enter details of how many packets of data which were successfully transmitted and received were displayed.This way troubleshooting was easily archieved.

THIS WEEK'S ACTIVITIES AT LITA

Basically,this was a week of practical work both for us as UNZA students and the local students.The objective of our project this week was to establish a unza network using the DD-WRT54G routers which are an upgraded version of the original WRT54G routers.The routers come with inbult software and a separate CD-ROM .The photo on the top left of this page shows two blue electronic boxes with antanaes,these are the boxes refered to as routers.One of these boxes was configured as an access .When using the inbult software to configure the router,the router was first connected to a computer using an ethernet CAT5 cable and then connected to the power supply.The routers setup page was accessed by opening a web page and typing the default IP Address of that particular router which can be changed for security reasons.Once the setup page was displayed Clicked on the wireless icon which displayed a page which allowed us to set the wireless mode to AP i.e access point meaning that this router would be the one transmitting signals all around.The wireless network mode was set to G-ONLY since all our cards and routers supported G.Then the wireless Network Name(SSID) was changed from linksys to UNZA implying that any laptop , router or indeed any other machine with a wireless card would recognise our network by this name.These setting were saved by clicking on the save button.Upon saving saving the settings we could automatically see the unza network on one of the laptops.

In addition, another task was to access the internet wiredly using ethernet cables.To do this exercise we first had to configure the router to posses both the WAN(wide area network) and LAN(local area network) address,in this case the router was assigned 10.1.1.90 and 192.168.2.1 .The router uses the WAN IP address to access the internet and the LAN IP address to connect to several other PCs ,in this exercise the router was connected to one PC.For this communication to be possible,however,the PC had to be assigned an IPaddress,subnet address and the gateway address.On the LAN side of the AP(ROUTER) the gateway address was the IPaddress of the router itself because it was performing the role of the gateway at the same time while on the WAN side, the the gateway address was 10.1.1.1. The DNS IP address was that of the gateway throughout.The DNS (domain name server) is the server that translates the domain names into IP addresses and the DHCP(dynamic host control panel) is the server which tells the computer what its IP address,subnet and gateway is.Upon serving these setting internet was accessed on the host PC.

IT'S TIME TO WORK!

The world is developing so fast that one can not afford to continue lazing around and being the one to whom services are rendered to.I for one ,I'm not satisfied being an end user,hence,i have taken it upon myself to study more,research more,and at least come up with something people can appreciate and admire in terms of invention.Realistically,i know its not easy to come up with something new, something people have never heard of or seen but it calls for determination and courage.What one conceives in his/her mind is what manifests physically.when one thought of flying he invented an aeroplane,when one wanted to travel by sea a ship was invented.Today we sea a countless series of technologies around the world which has made life on planet earth a lot more easier.

With the invetion of computer technology,scientist are spending sleepless nights trying to create software humans can use to perform various tasks.But not all soft ware on market so far is helpful for development in developing continets such as africa.For example a lot of our young people in colleges and universities spend precious time chating on the internet using a software called skype at the expense of doing their assigments and projects.This is a weakness in itself ,why cant our students be interested in creating the source code instead of being satisfied as end users only? It's this very fact that has compelled me write this article to high light the weakness in our selves and motivate sonebody out there to pull up their socks and get to work.Indeed it's time to get to work ,i'm looking forward to an africa that is production oriented,an africa that will donate funds to other countries,an africa that is economically independent and self relient in all her dealings.And this won't be the case until we change our mind set of receiving and receivig until we receive no more.Infact it's hard as receipients to be responsible over the donor funds we keep receiving every year since we can't generate wealth of our own.

NETWORKING

In the past the world was very big in the sence that communication was very difficult.It was not an easy task for people across the continents to share information.On the contrary the modern world has become very small with the introduction of networks.A network is something connected together sharing information.It consists of different devices connected together sharing data and services.A computer network consists of several computers,printers,servers and other electronic devices connected by links.The world wide web or the internet is the network of networks,it joins several local area networks together to form wide area networks and further joins several wide area networks together to form the world wide web.

The most important feature of the internet is the e-mail.The e-mail allows people in different areas to communicate using the internet.For example im here in macha but im able to communicate with my lecturer updating him on the progress of what im doing. The e-mail is faster and coast effective unlike the old way of sending mails using post offices.

Furthermore,networking allows one to share hardware such as printers in a place of work.People can also share files and can access their offices even at home.

WE SHOW THE PEOPLE THE BEST WAY TO DO IT

It's not surprising to see quality in whatever is done here at macha its all because the people managing link net and all the associated branches believes in showing the local people how to provide the best education,best health services and best information.It was awesome to note that pupils in a grade as low as grade one have access to the computer and have regular computer lessons on a weekly basis.This way pupils grow up with the necessary knowledge on how to browse on the Internet and can do several tasks with the help of a computer.Such is a profound example of an ideal primary school.
At LITA which stands for linknet information technology academy students have a wonder priviledge of mixing their theory with practical work. The place is equiped with internet and alot of computer hardware specimens on which students practice how to assemble PCs.Actually the first assignment i did when i came to macha was to assemble a computer which i've been using all along.This was a fantastic experience for me and its something which i really appreciate most especially after doing computer engineering in the previous semester way back at the university.These facts justify the claim by linknet" we show the people thebest way to do it "

DEVELOPMENT IN MACHA

Despite macha being located in one of the most remote parts of zambia it is one of the fastest developing regions in zambia.It is located within choma a small town in the southern province of zambia.It's amazing to see how people in a" bushy" rural area such as macha communicate using highly effective and fast mode of communication such as the internet.A powerful networt has been established in the area which helps people in the area to carry out their research,share information ,chat via e-mail and communicate with the outside world.
All credit goes to linknet in bringing this tremendous development to rural areas.linknet is an organisation which tailors and maintains communication facilities using both human and natural resource found in that particular area of interest.Mr Van stam the director of linknet strongly believes communiction,electricity,good water supply and a good transpost system are the basic requirements to bring development to rural areas.He believes in providing local solutions to local problems.
Another signficant feature at macha is the linknet information technology academy a special school run by an american expartriate by the name of jonathan backens in his capacity as a lecturer.He is a qualified computer scientist equiping the local people with computer knowledge.