Graphic Card - How to choose

If you plan to buy a graphic card then this guide will definitely help you. First of all, usually people would want to buy graphic card when their windows go bogged down.

An example of this would be when you move windows around on the desktop the windows move very slowly. This is an indication that you video RAM is pretty less for you particular motherboard. This only your own experience can tell.

Video RAM is different from the normal memory or RAM as this RAM is particularly important when you play games or do other things like playing movies, Low video ram will make your video movies to freeze and play slowly.

Nowadays graphic card manufacturers are making high video RAM adapters. Previously the graphic cards used to have a RAM of around 13 to 32 MB and also 64 mb.Now there are graphic adaptors of 128 and 256 mb Video RAM.

Having high Video Ram graphic card ensures that your computer doesn’t go very slow on graphical heavy uses like watching movies or playing NFS “Most Wanted”.

Currently I am having a graphic adapter of 32 Mb video Ram .I do know it needs upgrading but currently I think its enough as I don’t use much graphic heavy usages like games and movies.

Also there are varieties of such graphic cards.There are dual VGA output adapters.What this means is that you can extend your desktop onto two screens.This isn’t of much use to the normal computer user but it might be particularly useful if you are in the field of graphical application and technology.

And some have TV – Out capabilities too.This means you can connect to a TV set for viewing movies or some presentation.

Finally make sure you consult some of your friend or computer technician on how to meet your budget and get the best deal for it.

Recent engagements...

Well recently i was a lot busy doing researching on wireless routers and experimenting and tinkering with them.

I have many wireless routers as usually whenever my friends or relatives have a router that is not working, it comes straight into my area of expertise ;-) lol, well i am not an expert but yeah i do work on them.

Having used Linksys,D-Link and others, one of my most recent experience with the best ADSL wireless router has been 3Com's OfficeConnect Wireless ADSL router, my my it just baffled me by its range without any external amplifier, it had around 400 ft open LOS range.

Actually i was thinking i might need to buy a Luxul or Hyperlink tech amplifier, i mean b/g ofcourse i dont prefer just 802.11b as they are somewhat cheaper, but with the coming of the Wireless N, i doubt if i bought a wireless b amplifier, it wouldnt be outdated, so i prefer b+g amps, they tend to be more reliable? well that only time will tell, as right now i am still working on my linksys WRT54GS with dd-wrt firmware ofcourse as you might know its one of *the* best firmwares i have encountered, it also has a UWR(Universal Wireless Repeater), that can repeat any wifi signals in your neighbourhood.

Over clocking – Introduction and is it safe?

Over clocking is the process of operating computer hardware at speeds in excess of their manufacturers’ ratings.

Over clocking allows normal computer users to buy OEM(Original Equipment Manufacturer) computers at lower speeds and then overclock them to much higher speeds, even sometimes better than a brand new OEM at that higher speed.Overclocking a system may be difficult than building a new computer as it usually requires a great patience and a lot of planning.

Over clocking is not something of a secret as you may think, The manufacturers of CPU or Processors are well aware of the over clocking phenomenon. A lot of these companies to little to lock the over clocking phenomenon in processors as a vast majority of people don’t know even know what over clocking is and are pretty naïve in this field.Another reason is that initially some companies did put in a mechanism called clock locking, because of which the users couldn’t over clock the processor.But eventually this venture didn’t turn out to be feasible on the commercial production level and was later finished.

Over clocking can be done in a lot of ways.Some of the retail manufacturers most of the time want to maximize system configurations,hence their motherboards would be extremely feasible and tweak able to over clock.On the other hand there are those OEM manufacturer’s(or pre-built computers like those from HP, SONY and others) often are lacking user-defined options.The main reasons are that these systems are not designed to be custom tailored and are mainly engineered for maximum stability and perfection across a wide range of uses.

Some companies outperform others in this retail – level manufacturing.Taiwan based Abit Computer Corporation is one of those famous and most popular retail level manufacturer whose motherboards are highly customizable to ones needs and support a wide range of options.But the basic thing Is nearly all motherboard manufacturers offer some or the other way, through which we can over clock the computer.

There are mainly two ways of over clocking, hardware or software.

Over clocking your processor will make it often unstable, and to attain stability of the system at that high speeds is usually done by increasing your processors core voltage.Beware that increasing voltage levels can be potentially hazardous and must be done with care and planning.Most of the current micron processor architecture i.e. is the 0.18- and 0.25- can usually operate within a variation that is about ± 10% from the original OEM configurations.

It is common knowledge that if you increase the voltage levels then there will be some increase in heat, you must take care that there is proper cooling of the processor.Otherwise you could end up having a spoilt processor and and don’t think processors come cheap, a new P4 3 Ghz HT processors comes around 250$ or so.Processor coolers,heat sinks,liquid cooling systems , all play an integral part of an over clocked PC , as compared to a normal OEM computer.The reason is that over clocking can make you computer to become unstable if the proper temperature levels are not maintained inside the processor, even though most processors have a tolerable range of temperature, for durable long term running temperature is an important and integral part and must be considered.

Cooling of the computer can be done in many ways, some of the traditional ways are:

Case Cooling : This refers to the normal CPU fan which most of us have in our computers.

Heat Transfer Compounds : This usually involves applying a thermal interface material between the processor core and the heat sink,this enhances heat transfer to a large extent.

But there are other new ways of cooling which are gaining much more popularity due to their innovative ways of cooling.

Known better as alternative ways of cooling these cooling systems are not based on the forced –air technique.Though be forewarned these technologies are not very cheap and often comes at high prices.These techniques are only employed by high – end manufacturers.Although these techniques are extremely effective they are hit by a major disadvantage is the boot – time startup time delay, as most of these devices lack a real - time response system, hence the cooling device must reach a certain temperature before the computer can be powered up.In order to remove this delay,some high –end manufacturers have employed complex systems using electrical relay circuits and timind devices to cut – short the booting time.

Some of these alternative cooling techniques are :

Peltier Cooling : The peltier cooling systems are gaining popularity due to their low cost , but there are other hidden secondary costs also that most people do noe realize.These type of cooling systems work on the Peltier thermoelectric effect(ok for those who are new to this, in layman’s terms its like when you apply current to a thermocouple it starts to cool on one side and gets warm on the other side), theres a thin ceramic like disc that acts like a heat pump, once an electric current is applied across it.

Vapor Phase Cooling : Vapor phase cooling is in its mechanism of working very similar to the working of a air conditioner,and car air conditioning too.Its based on the active refrigeration technology, in which a gaseous substabce, usuallu Freon is made to pass through an exchanger device to provide the effect of cooling.Two companies famous for this vapor cooling system are KryoTech and VapoChill

Liquid Cooling : Liquid cooling involves a pump which circulates water through a radiator element and then throughout the system.Fans are employed to cool the radiator for maxium thermal effeiciency.

Submersion Cooling : Submersion cooling systems are gaining widespread popularity in over clocking enthusiasts.Submersion means literally dumping the complete system into a liquid substance.The liquid can then be chilled to zero degrees or below and with it the computer.Submersion cooling is expensive and cost upto thousands of dollars. Fluorinert liquid from the Electronics Manufacturing Division of 3M is the most attractive submersion cooling fluid.However it is expensive and permits are required to purchase it..And Fluorinert evaporates easily so it requires a vat or cooling system to prevent it from evaporating.

Beep Beep …..

I recently had encountered a very strange problem with my P4 computer which I bought I 2003.When ever I powered on the PC it used to beep twice and then my View sonic monitor used to report No Signal. I was very much confused as I am a bit of a geek in hardware stuff. I really had to troubleshoot a lot. It took me nearly a month to figure it out after reading a lot of books and also asking some other technical experts. But it doesn’t mean that I took so much time so some body else might take the same time. I am very busy in house hold work so I used to spend very few time working out the problem. So if you are also experiencing similar problem like even when the computer is on the monitor says “No Signal” and also that the computer beeps twice whenever you power up the computer. This problem is more common in assembled PC’s rather than branded, because I also have a HP Pavilion 8760C I bought from Best Buy and it still hasn’t given me this problem.

Coming to the point, the real cause is that all of our PC’s have a graphic card to which we connect the monitor cable. This card is usually fit onto the AGP slot on the motherboard. The graphic card due to some reason gets loose and then your motherboard reports that in audible tones. The two beeps signal that the graphic card has failed to initialize. This usually happens when you graphic card gets moved inside the AGP slot.So what you have to do is open the computer, and tighten the graphic card.Once you power up hopefully you should not have the problem again.

In my case, my motherboard is an Intel and the processor is also Intel Pentium.So the problem was easy to resolve as Intel motherboards are widely popular compared to other motherboards like Mercury, AMD and other manufacturers.

Lastly, please take care while opening and working on your computer as mishandling any part may destroy the IC’s on both the motherboard and the components.Take caution of ESD as it maybe potentially dangerous for your motherboard.Motherboard are very ESD sensitive.Make sure to use anti-static methods for working on your motherboard.

What to do with that silly old computer

Today I junked out my old computer which was a Pentium MMX (for newbie’s it’s a Pentium machine older than the Pentium 1).I thought of putting Linux on it for practicing Linux but unfortunately some time before I had thrown out the processor while doing some examining. But I did manage to recover all the screws from it (yeah it was a Dell machine) and nothing more. Many of us have such PC’s lying around in our houses sitting and doing nothing. If you have more than one working computer in your house then you could probably install Linux on such an old PC and then put in 2 NIC’s (Network Interface Card) and use it as a firewall or router.Dont underestimate the protection that a firewall or router gives to your home network. and best of all most of the time you don’t even have to have a hard drive. The beauty of Linux is that you can run it right from the floppy and have it up and running as a router. Its at least better that throwing your PC away in the trash. Also what you could do is that use the old PC and get it exchanged, a lot of us must be aware of those exchange programs that run frequently wherein you bring in your own PC and then after paying some adjustment you get the new PC. Although be aware that these are generally not value for money and you could be pretty easily fooled into thinking that you are getting the best deal.

Wired or Wireless Networking - And Router Details

Great, so you have decided to go wireless.That’s a great decision.But it has its own implications as well.Wireless networking, recently has been gaining widespread popularity especially because of the convenience through which we can network computers.

First of all before we go into much detail let me introduce for naïve computer users that basically when you have to or more computers, and they are to be networked, then what you require is a router.Router are special computer devices which act as concentrators or you can say mediators so that is easier to communicate multiple computers over a LAN.

Presuming you already have more than one computer, I also think that then you must be having a router.Routers come in a lot of wide varieties, nowadays.Choosing a router can be difficult for the naïve user.First, you must make out what type of Internet connection do you have ? Whether it’s a cable access or dsl..or dial – up.Because nowadays routers are available which can act as cable modems as well as perform their router functionality.Similarly they are also DSL routers which can act as an DSL gateways between you computer network and your ISP.

Going wireless has a lot of advantages, the principle one being the flexibility to roam.If you have a computer and a laptop at your home,using a wireless router you can sit in your lawn and access the Internet,check your email or do stock trading.Its really cool technology.Also just like those cordless phone there are different channels and you can change the channels if you get some interference.

But wireless has its own disadvantages.First and foremost is the range factor.Most of the manufacturers of Routers specify a very feasible range but most of the time, this is not the same range one would get on normal usage.There are some factors for it, wireless routers work on the RF technology,thus thick walls and other obstacles significantly decrease the signal strength.Other factors include bouncing of the signal when it strikes thick surfaces leading to loss of signal again.Nowadays there are some long range cordless phones which operate in the 2 Ghz band unlike the old ones which usually operate in the 900 Mhz band.The problems with these new 2 Ghz cordless phones are that wireless routers operate at the same frequency, thus causing interference.Also the microwave which has become almost a household necessity also interferes with these wireless signals.

These problems though wont effect you most of the time.I would prefer the wireless router instead of the wired one for is flexibility.Wireless routers also nowadays are becoming a lot cheaper than what they were before.Routers require an external power supply which usually is supplied alongwith the standard router package.

Routers are not that difficult to configure, most of them have a web based interface.Most routers have a web server installed on it and can automatically configure your LAN.

Installing a router, both wired and wireless routers are pretty much easy.All you have to do is make the proper connections, like suppose you have a dsl(adsl) then just connect the router to the phone line and the other Ethernet connections to the computers to be networked and also power up the router, the rest is done by the router itself like addressing Dynamic IP addresses using its built in DHCP server functionality.

But the above mentioned way of installation can vary depending upon what kind of router you have and also what kind of internet connection you have at your place.

If you want to connect your wireless router to your wireless desktop then you have to buy another peripheral device for the desktop called a wireless network card.This is very similar and infact almost the same other than its wireless function as the normal Ethernet NIC(Network Interface Card).

But if you want to connect your wireless laptop(most laptops nowadays have wireless card built in) to your wired desktop then you can do it easily.

If your laptop is a bit old, and you want wireless internet, the all you have to do is get yourself a pcmcia wireless card or as its becoming common nowadays, the new USB wireless adapters.

Lastly, its always good to have a always on connection, as far as a router is concerned(both wired and wireless routers) its best if you have adsl connection or a cable connection.Having a dial – up and then networking can be more tedious as for this type, you would have to put one computer as the server and others as clients.Unlike the router(for adsl & cable connection) which behaves like the go between, between your PC and your ISP.

How to setup a network in your house – Ethernet LAN to the HPNA

Nowadays almost every single house has a computer, and also since in the recent years the prices of computers have declined rapidly and are very cheap today, many of us have more than one computer at our houses.And if you have more than one computer in your house and you haven’t networked them up, then you are missing something here.

Networking two or more computers saves a lot of time, effort and also money!.Let me explain in this article how you can save a lot of money just by networking.

Imagine the following situation, Dad has a computer in his room and the kids have their own computers and mom has a laptop, and there’s only one printer in the house, anytime any one in the family has to print something they have to store it on a CD or floppy and then go to the dad’s room and print it out.Also there is a lot of problem in sharing files.

Networking all the computers through a router can save a lot of troubles.When you setup a network in your house, and the printer is also networked, then anyone can use the printer without moving away from their own computer.Also if you want to move any files from your computer to your kids computer, then you can easily and fastly do it through the network.

Networking is most of the time done through the Ethernet standard, but there are other mediums as well.HPNA which stands for Home Phone Line Network Adapter is another technology which utilizes the existing phone line to transfer high speed data with maximum transmission speed of up to 10 mbps.For utilizing HPNA you need a HPNA adapter which you connect it on one side to the computer and on the other side to the telephone line, and vice versa for the other machine as well.HPNA had some popularity in the past few years around year 2000, but nowadays since the prices of different types of routers has already declined a lot, there is not much demand of HPNA.Another thing is that routers(utilizing Ethernet network technology) are much more faster than these HPNA technology, Ethernet routers typically transfer data at a speed of up to 100 mbps.

Ethernet standard is also known as 10/100 mbps Fast Ethernet, recently a new type of even a faster type of Ethernet has been introduced, known as Giga LAN, these Giga LAN
Enabled routers and compatible NIC(Network Interface Cards) can transfer speeds of up to 1 Gbps.This is revolutionary speed, I really don’t know where the limit.

Networking two computers is best done using a cross over cable(CAT 5 UTP).This cable is different from the cable that is used to connect from a computer to a router, that type is also a CAT 5 UTP, but its straight over.

Setting up a network of two computers is relatively easy and doesn’t usually require you to buy a router, unless you plan to go wireless, then you will need to buy a wireless router.Going wireless is pretty good as wireless routers give a lot of flexibility.

But if you want to setup a network of more than two computers, then you will need to buy a router, whether a wireless router or wired one, that is up to you.And also you have to buy the standard Ethernet cables(CAT 5 UTP).

Choosing which router to go with is not very tricky.Routers come in a variety of types and which one to choose will depend surely on your needs.If you need to setup a wireless network, then you would need to buy a wireless router.But if you plan to go for the wired router, its much cheaper and a bit easier to install also.

Some popular manufacturers of routers are D-Link, Linksys( a CISCO subsidiary),3 COM, Netgear and many others which I don’t remember.These routers are extremely good and are designed for stability.Routers usually operate only within a specific range of temperature, the reason because since routers have to be powered on 24/7 they must be taken care of, as excessive temperature can damage the router.

If you don’t want to spend a lot of cash on routers(both wired and wireless routers), then I suggest you head to www.ebay.com which is a popular site for second hand goods and also some brand new(sealed) products at extremely low rates.These discount routers are very good as well, but one must buy them after carefully reviewing the item.Also some shops have special offers and discount prices on routers.

If you want to setup a wireless network for all the computers, including the desktops, then you would have to buy a wireless client card for each computer along with the router.These wi-fi cards are usually PCI cards, but nowadays the USB wi-fi cards are becoming very common.You don’t even have to open the computer, simply plug in the USB wireless device and then you’re hooked on to the wireless network.The USB wireless devices are so small, like the popular pen or flash drives that can be hooked into a key chain.

But a disadvantage of these USB wireless devices is that they need a custom software to be managed, unlike the PCI(for Desktops) and PCMCIA(for laptops) which just require a driver and then they can be configured through Windows Xp itself.

Grid antennas and Yagi's

I research new wifi technologies, and i bench test wireless RF amplifiers and misc.

I recently bought a couple of grid antennas and Yagi antennas, and low loss cable to test long range wireless networking and the maximum range that could be achieved using these highly directional wifi antennas.

First of all i would like to tell that wifi grid reflector antennas are not for normal wifi, they are highly directional, and have a very narrow beamwidth, which makes it highly unfeasible for a general purpose omnidirectional wifi usage.

If you want to estabilish a Point-2-Point long range wifi link, as in a BackHaul or others, then this is probably the best situation, i mean although you need to make sure that the path is LOS(Line os Sight), and that the fresnel Zone is not blocked, as in long range wireless networking, the Fresnel Zone effect is all the more significant.And you can also add a few amplifiers if you are getting a veyr weak signal at the other end, and your Free path loss is very high.Make sure though that you dont exceed the FCC 15.204 Legal limits.

The antennas i bought were a hyper link HG24 24Dbi grid antenna and a hyperlink 14.5 Dbi Radome enclosed Wifi Yagi.They far outperformed all those cheap antennas we get on ebay.Another good company for wifi antennas is Andrews which makes excellent wifi grid antennas.

Setting it up was not that difficult, the more difficult being configuring the parameters, to fine tune the sensitivity.

Also a Spectrum Analyzer or SWR power meter is extremely helpful as you dont want extra power to be transmitted, and stay well below the FCC legal limits, the Spectrum Analyzer will help you to Site survey the area and also will show the signal levels of the incoming RF wifi signal.

Wireless networking in Linux

I was discussing recently with my friend about setting up a wireless network on Linux systems.Although wired networking on Linux flavors is a breeze, wifi networking isnt necessarily like that.

First of all you need to make sure that the Wifi PCI card that you intend to buy must support or have Linux drivers, or else you wont be able to use it at all!

The best place to check that is madwifi, but this is mainly for atheros based chipsets, and not others,usually these will be supported by dd-wrtx86, like the Dlink DWL-G520.

Installing wifi chipset driver also requires some knowledge of linux, usually USB based wifi devices are more difficult to install rather than the normal Wifi PCI adapter.

Wifi Interference

Recently, i have noticed a lot of wifi interference in my area, dont know whether its due to the area being more popluated, or something else, this is really one disadvantage of long distance wifi, although short range, in homes wont be affected much, apart from the microwaves and the 2.4 gigs cordless fones.

You can make out all the disturbance that is coming into your wifi network very easily by buying a Spectrum Analyzer or SWR meter.The spectrum analyzer will analyze the RF wifi signals in your area and show you the noise and from which channel it is coming.Spectrum Analyzers are not that expensive, anywhere from the 100$ to very expensive ones, offering advanced analyzing capabilites.But personally i recommend the 100$ price range Spectrum Analyzers, as they will do.

If you intend to do long range wifi networking, then do ensure that you have atleast one yagi antenna and amplifiers of around 250mW on both ends, as this will boost up the signal.

Smart antenna

Smart Antenna (also known as adaptive antenna) refers to a system of antenna arrays with smart signal processing algorithms that are used to identify the direction of arrival (DOA) of the signal, and use it to calculate beamforming vectors, to track and locate the antenna beam on the mobile/target. The antenna could optionally be any sensor.

Smart antenna techniques are used notably in acoustic signal processing, track and scan RADAR, radio astronomy and radio telescopes, and mostly in cellular systems like W-CDMA and UMTS.

Smart antennas have two main functions

1.DOA estimation
2.Beamforming

DOA estimation

The smart antenna system estimates the direction of arrival of the signal, using any of the techniques like MUSIC (Multiple Signal Classification) or ESPRIT (Estimation of Signal Parameters via Rotational Invariant Techniques) algorithms,Matrix Pencil method or their derivatives. They involve finding a spatial spectrum of the antenna/sensor array, and calculating the DOA from the peaks of this spectrum. MUSIC involves calculation of eigenvalues and eigenvectors of an autocorrelation matrix of the input vectors from the receiving antenna array. These calculations are computationally intensive. Matrix Pencil is very efficient in case of real time systems, and under the correlated sources.

Beamforming

Beamforming is the method used to create the radiation pattern of the antenna array by adding constructively the phases of the signals in the direction of the targets/mobiles desired, and nulling the pattern of the targets/mobiles that are undesired/interfering targets. This can be done with a simple FIR tapped delay line filter. The weights of the FIR filter may also be changed adaptively, and used to provide optimal beamforming, in the sense that it reduces the MMSE between the desired and actual beampattern formed. Typical algorithms are the steepest descent, and LMS algorithms. Beamforming is a latest technology being used for various purposes.

Types of Smart Antennas

Two of the main types of smart antennas include switched beam smart antennas and adaptive array smart antennas. Switched beam systems have several available fixed beam patterns. A decision is made as to which beam to access, at any given point in time, based upon the requirements of the system. Adaptive arrays allow the antenna to steer the beam to any direction of interest while simultaneously nulling interfering signals.

Extension of Smart Antennas

Smart antenna systems are also a defining characteristic of MIMO systems, such as the proposed IEEE 802.11n standard. Conventionally, smart antennas is an unit of a wireless communication system and performs spatial singal processing with multiple antennas. Multiple antennas can be used at either the transmitter or receiver. Recently, the technology has been extended to use the multiple antennas at both the transmitter and receiver, which is called especially as MIMO. As extended Smart Antennas technologies, MIMO supports spatial information processing, relative that conventional researches on Smart Antennas have foucsed on how to provide a beamforming advantage by the use of spatial signal processing in wireless channels. Spatial information processing includes spatial information coding suh as Spatial multiplexing and Diversity Coding, as well as beamforming.

Wireless mesh network

Wireless mesh networking is mesh networking implemented over a wireless LAN.

Whereas the Internet is mostly a wire-based, co-operative electronic communication infrastructure similar to the international postal agreement, in that messages are mutually delivered and relayed within their separate domains free of charge (i.e. if you relay my messages within your domain I'll relay yours within mine), Mesh is a wireless co-operative communication infrastructure between a massive amount of individual wireless transceivers (i.e. a wireless mesh) that have Ethernet type capabilities.

This type of infrastructure can be decentralized (with no central server) for less scalable applications or centrialized controlled for high scalable applications (with a central server), both are relatively inexpensive, and very reliable and resilient, as each node need only transmit as far as the next node. Nodes act as repeaters to transmit data from nearby nodes to peers that are too far away to reach, resulting in a network that can span large distances, especially over rough or difficult terrain. Mesh networks are also extremely reliable, as each node is connected to several other nodes. If one node drops out of the network, due to hardware failure or any other reason, its neighbours simply find another route. Extra capacity can be installed by simply adding more nodes. Mesh networks may involve either fixed or mobile devices. The solutions are as diverse as communications in difficult environments such as emergency situations, tunnels and oil rigs to battlefield surveillance and high speed mobile video applications on board public transport or real time racing car telemetry.

The principle is similar to the way packets travel around the wired Internet — data will hop from one device to another until it reaches a given destination. Dynamic routing capabilities included in each device allow this to happen. To implement such dynamic routing capabilities, each device needs to communicate its routing information to every device it connects with, "almost in real time". Each device then determines what to do with the data it receives — either pass it on to the next device or keep it. The routing algorithm used should attempt to always ensure that the data takes the most appropriate (fastest) route to its destination.

The choice of radio technology for wireless mesh networks is crucial. In a traditional wireless network where laptops connect to a single access point, each laptop has to share a fixed pool of bandwidth. With mesh technology and adaptive radio, devices in a mesh network will only connect with other devices that are in a set range. The advantage is that, like a natural load balancing system, the more devices the more bandwidth becomes available, provided that the number of hops in the average communications path is kept low. Additional information by can be seen at the original patent description for mesh wireless networks at http://www.delphion.com/details?&pn=WO09608884A1 giving the mesh technology designs.

There are three distinct generations of wireless mesh products today. In the first generation one radio provides both backhaul (packet relaying) and client services (access to a laptop). In the second generation, one radio relayed packets over multiple hops while another provided client access. This significantly improved backhaul bandwidth and latency. Third generation wireless mesh products use two or more radios for the backhaul for higher bandwidth and low latency. Third generation mesh products are replacing previous generation products as more demanding applications like voice and video need to be relayed wirelessly over many hops of the mesh network.

Wireless Distribution System

A Wireless Distribution System is a system that enables the interconnection of access points wirelessly. As described in IEEE 802.11, it allows a wireless network to be expanded using multiple access points without the need for a wired backbone to link them, as is traditionally required.

An access point can be either a main, relay or remote base station. A main base station is typically connected to the wired Ethernet. A relay base station relays data between remote base stations, wireless clients or other relay stations to either a main or another relay main station. A remote base station accepts connections from wireless clients and passes them to relay or main stations. Connections between "clients" are made using MAC addresses rather than by specifying IP assignments.

All base stations in a Wireless Distribution System must be configured to use the same radio channel, and share WEP keys if they are used. They can be configured to different service set identifiers.

WDS may also be referred to as repeater mode because it appears to bridge and accept wireless clients at the same time (unlike traditional bridging). It should be noted, however, that throughput in this method is inversely proportional to the number of "hops", as all traffic uses the same channel. For example, client traffic going through one relay station before it reaches the main access point will see at most half the maximum throughput that a directly connected client would experience.

Canopy (wireless)

Motorola Canopy is a point-to-multipoint wireless networking system designed for WISPs (wireless internet service providers) based on a star network topology.

Canopy relies on a central access point (AP) placed on a hilltop or tower. These APs usually have 6 panels, allowing for omni-directional coverage of an area. Customers of the system receive service through subscriber modules (SMs) aimed towards the AP. The SMs must be mounted on a tall point of a building to get a reliable connection, else ground clutter will weaken the signal. Under ideal circumstances, no further equipment is required to receive service within a 3.5 mile radius of the AP, but most WISPs install dishes, reflectors and other high gain antennas to increase received signal strength. Some WISPs use altered APs to further increase gain and narrow the signal beam width.

The Motorola canopy product is available in 5.7 GHz, 5.4 GHz ETSI, 5.3 GHz, 5.2 GHz, 2.4 GHz and 900 MHz versions. In general, the 900 MHz version is easier to use in outlying areas, because of its ability to penetrate through trees, and reach further. However, this signal does not provide as high speeds as 2.4 or 5.7 would.

The 5.7 GHz is the most popular frequency because it does not interference with existing wifi installations. WISPs that use the 2.4 GHz version can use add-on products to get more gain, allowing communications at distances of up to 15 miles, throughputs of 14 Mbps, and latencies of 7 ms. 5.7 GHz units are also used as backhauls, bringing data to and from the APs.

Point to point connections are capable of throughput ranging from 10 Mbps to 300 Mbps with latencies of 2 ms.

Long Range Wi-Fi

Long range Wi-Fi is used for low-cost, unregulated point-to-point connections, instead of expensive cellular networks, microwave or satellite links.

Introduction

Since the development of the Wi-Fi radio standard, great leaps in the technology's abilities have been made. In one area, range, Wi-Fi has been pushed to an extreme, and both commercial and residential applications of this Long Range Wi-Fi have cropped up around the world. It has also been used in experimental trials in the developing world to link communities separated by difficult geography with little or no connectivity options.

Applications

Business

Provide coverage to a large office or business complex or campus.
Establish Point to point link between large skyscrapers or other office buildings.
Bring Internet to remote construction sites or research labs.

Residential

Bring Internet to a home if regular cable/DSL cannot be hooked up at the location.
Bring Internet to a vacation home or cottage on a remote mountain or on a lake.
Bring Internet to a yacht or large sea-faring vessel.
Share a neighborhood Wi-Fi network.

Increasing range in other ways

Specialized Wi-Fi channels

In most Standard Wi-Fi routers, the three standards, A, B and G, are enough. But in long range Wi-Fi, special technologies are used to get the most out of a Wi-Fi connection. The 802.11-2007 standard adds 10 MHz and 5 MHz OFDM modes to the 802.11a standard, and extend the time of cyclic prefix protection from 800 ns to 3.2 µs, quadrupling the multipath distortion protection. Some commonly available 802.11a/g chipsets support the OFDM 'half-clocking' and 'quarter-clocking' that is in the 2007 standard, and 4.9 GHz and 5.0 GHz products are available with 10 MHz and 5 MHz channel bandwidths. It is likely that some 802.11n D.20 chipsets will also support 'half-clocking' for use in 10 MHz channel bandwidths, and at double the range of the 802.11n standard.

802.11n (Mimo)

802.11n is a feature that now comes standard in many routers, this technology works by using multiple antennas to target one or more sources to increase speed. But in tests, the speed increase was said to only occur over short distances rather than the long range needed for most point to point setups

Power increase

Another way of adding range to your Wi-Fi network is by hooking a power amplifier into your existing antenna. Commonly known as "range extender amplifiers" these small devices add usually around ½ watt of power to the antenna these amplifiers have been tested to give more than 5x the range to your existing network. In the case of the popular Linksys WRT54G The RadioLabs 2.4 GHZ range extender amplifier increases the stock power of the WRT54G from 18dB to 38dB an increase of power by 211%[2]. These power amplifiers offer a cheap, minimal setup that can easily be added to any existing network.

High-gain antennas and protocol hacking

Specially-shaped antennas can be used to increase the range of a Wi-Fi transmission without having to drastically increase transmission power. Parabolic high-gain antennas allow transmitting over distances of several kilometers. The standard 802.11 protocol stacks can also be modified to make them more suitable for long distance, point-to-point usage, at the risk of breaking interoperability with other Wi-Fi devices and suffering interference from transmitters located near the antenna. These two approaches are used by the TIER project (see "Rethinking Wireless in the Developing World").

Alternatively, a low-cost approach can be used to increase the range of a Wi-Fi transmission using very simple enhanced antennas while keeping the standard protocols and hardware (see "www.usbwifi.orcon.net.nz/").