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Welcome to my VSF Project for the 2006/2007 school year.
Hopefully you're using a modern browser. You may have even been caught if you were using IE, but I really don't want you to miss out on the cool CSS and Javascript effects... Firefox 1.5+, Opera 9+, and Safari 2+ work great, and other Gecko or KHTML/Webkit browsers should do fine too.
Now that you're set, use a link to the left to browse through the project however you wish. I highly recommend that you start at the Introduction page first, but if you want to read the Project Info first and then read the intro that's fine with me. After that, top to bottom should be good.
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Cell Phones.
Chances are you have one, and if not, I'm sure you can name at least a few people who do.
According to the CIA World Factbook, there are more cellular phones in the United Kingdom than there are people! Here in Canada we have about 16 million cell phones, which is one for every two of our 33 million people.
Basic two-way wireless networks had existed for some time, and soon radiophones were created with human operators connecting the "walkie-talkie" to the phone network. In the 60s, the hexagonal cells had been developed, but the phone had to remain within one cell (one transmitter's range) for the entire call. Soon the handoff was developed, which allowed the mobile phone to switch from tower to tower during the conversation, without the call being dropped.
The first automated networks began in the 1980s. This network is usually referred to as 1G, for the first generation. Unfortunately, these devices were analog, and were mostly limited to cars because they were quite large.
Technology advanced, and the second generation of phones was available in the early 90s. GSM is the most common 2G standard, which handles and transmits information digitally. Digital encoding allowed better compression of voice, as well as the transmission of non-voice data, such as Email and SMS.
Today, the 3G market is slowly growing. Third generation phones are capable of much higher bandwidth, sufficient for video, music, or high speed internet, but adoption is slow due to high prices and low availability.
Here in Canada, we often use the term cell phone when referring to mobile phones. The primary goal of the cellular system is to allow many customers to be served over a large area, while still keeping power consumption low.
Having many cells distributed around is an excellent solution to these issues. Most cell sites are placed fairly close together; anywhere from under a kilometre apart in populated cities, to up to around 60 km with powerful transmitters in the country.
Cell phone towers are usually serviced by fibre optic or copper cables leading to the telecom company.
As mentioned in the Introduction, the development of the handoff was very important in the development and mobility of the cell phone.
Handoffs are conducted in order to provide a clear and uninterrupted signal. Reasons for the handoff include:
One of the most important concepts in the cellular phone network is the ability to have many people using the services at the same time. It is not uncommon in some areas to have hundreds of mobile phones being used within one cell, so methods have been devised to allow multiple simultaneous users of a single radio frequency.
The two most common methods used in order to achieve this are CDMA (code division multiple access) and TDMA (time division multiple access).
As is suggested by their names, these two systems differ by either dividing the signal by a code (CDMA) or by time (TDMA).
The principles behind TDMA are simple – each user is allocated a section of time. One user's mobile phone will broadcast on the frequency for a split second, then wait (allowing other users to broadcast), and then transmits again when its timeslot comes up again. With the popular GSM standard, the phones are synchronized by contacting a base, which responds by telling the device to broadcast a certain amount of time earlier. This allows the station to compensate for the delay caused by the finite speed of radio waves.
The way CDMA works is quite a bit more complicated than TDMA, because instead of simply transmitting one after another, many phones may be broadcasting at the same moment. Mathematics is then used to separate the signal.
In order to accomplish this feat, CDMA uses a technique known as "Spread Spectrum" modulation. The transmission bits are thrown around in a way that seems to be random, but can actually be separated by the receiver.
GSM, or the Global System for Mobile Communications, is currently the most used mobile phone standard in the world. It is a 2G standard which uses TDMA for data transmission.
According to the GSM Association, GSM is used by over 2 billion people in over 200 countries, which is more than 80% of mobile phone users! Because of the popularity of GSM, GSM equipped phones can often be used all around the world.
Roaming is a process where a phone connects to a network other than its own. Often, carriers have agreements with each other in order to provide this sort of service; when attempting to connect to a visited network, this network will contact the user's home network to see if the user is allowed to roam, and, if so, it will create a temporary record for the user which it then returns to the home network.
Another major feature of GSM is the SIM (Subscriber Identity Module) card. It contains a small amount of flash memory and may be removed from the phone. Information such as the user's carrier and their phone book are usually stored on the card.
Unfortunately, many phones sold in North American and Europe are "SIM Locked," making it difficult to switch carriers or handsets simply by switching the card. However, this allows carriers to subsidize phones, for example, offering an advanced phone for only $50, as long as the customer signs up for a 2– or 3– year contract.
Ever since the widespread adoption of mobile phones, there have been concerns about the health and safety risks involved in their use.
The safety risks involved with using a cellphone while driving have been heavily debated. Studies have shown that using a handheld phone in the car can be less safe than driving while under the influence of alcohol! When combined with the huge number of people who chat on the phone while driving, cell phones can pose serious risks to others on the road.
Even hands-free systems have been found to be unsafe. When involved in a conversation, it is difficult for the car's driver to pay attention to the road and the person on the other end. Problems also arise because the caller cannot see the condition of the driver or road; as a result, this person may continue talking at a quick pace while the driver is attempting to maneuver through heavy traffic or cross an intersection.
As a result of these studies, many places have begun prohibiting or restricting phone usage while driving. Here in Canada, Newfoundland and Labrador has made it illegal to use a hand-held cell phone while driving.
Cell phones, by nature, produce a large amount of electromagnetic radiation. There is debate as to how harmful this radiation is to human beings, with reports ranging from being harmless to greatly increasing the risk of cancer. Some studies even suggest that the radio waves emitted by mobile phones could damage one's DNA.
In general, many of the health risks are associated with the fact that microwaves are produced by mobile phones, which cause a heating effect on tissue, much the same way a microwave oven heats food.
No conclusions have been drawn as to how dangerous cell phones can actually be. Using a phone that may be held away from one's head/body, such as a car or speaker phone, is generally a good idea in order to minimize any risks.
| Grade category: | 7-9 (Grade 9) |
|---|---|
| Team Size: | 1 or 2 (One) |
| Subject Area: | Engineering (telecommunications) |
| Project Type: | Descriptive |
| Language: | English |
| Summary: | Cellphone Mania is about the continously growing mobile phone market and the technology behind these gadgets that many of us use daily. |
| Software: | Bare Bones Software's TextWrangler and Peter Borg's Smultron (HTML, CSS, and JavaScript editing), Cyberduck (FTP client), Adobe Photoshop (bitmap imagery). Mac OS X v10.4 (Tiger) was used for most of the project's creation. |
| Hardware: | Nothing special; main computer was a first-gen Apple iMac G5. Some photos were taken using a Fujifilm Digital Camera. |
| Idea Source: | I think it was a cell phone commercial; I was looking for VSF ideas and my mother suggested "Cellphone Mania" while we were watching TV. |
| Special Skills: | HTML, CSS, Javascript, Graphic design (Photoshop, Flash). |
| Awards: | None at this point; I created this specifically for the 2007 VSF. |
| Past VSF Project: | Email: Inside and Out for the 2006 VSF. |
Some interface images were used with permission from stock.xchng (sxc.hu).