A device that lets you make voice calls from a battery powered hand held unit. Modern cellphones are also Java powered computers with Internet access. This lets you do web browsing, especially to sites designed for cell phones with trimmed down WAP (Wireless Application Protocol) content, email, and applications that talk to servers.
Today’s cellphones are actually hand held computers with wireless data access. They can do voice, text messaging, and run specialised applications.
In an emergency, sometimes cellphone networks become overloaded and you can’t get through. In that case, use text messaging. It uses a microscopic amount of air time.
To write cellphone software, you need a cellphone OS (Operating System) simulator that runs on your desktop. It is basically a stripped down Java with special classes useful to cellphones. You want to download Java ME and MIDP 2.0, both free from Sun.
Analog phones use NAMPS. Time Division MUX (Multiplexor) phones use iDEN or GSM (the world standard). Spread-spectrum digital phones in North America use CDMA.
If you have a T-Mobile, Cingular, or recent new M-mode type service with AT&T (American Telephone & Telegraph), then you have GSM (Global System for Mobile Communications) service. GSM phones are not compatible with CDMA (Code Division Multiple Access) wireless.
In Canada Rogers and Fido are GSM.
If you are signed up with Verizon Wireless or Sprint PCS, you are using CDMA. CDMA phones are not compatible with GSM.
In Canada, Bell and Telus run CDMA.
The world is now flipping to 3G/4G, which is faster and uses bandwidth more efficiently. Even video is possible. Japan and Korea have already done so. The new Apple iPhone 3G uses it. Rogers in Canada is now supporting it partly to support the iPhone.
The evolution will be to lower and lower power with more and more broadcast nodes, perhaps eventually getting down to LAN (Local Area Network) WiFi (Wireless Fidelity) levels and coverage. This downsizing allows faster traffic, more efficient use of the air, and less damage from radio waves. This strategy increases total bandwidth because if each broadcast pollutes a smaller volume of air, it leaves more air to transmit other broadcasts simultaneously.
To define the capabilities of a given cellphone you need to know its configuration and profile. The configuration defines the virtual machine and the bare minimum APIs (Application Programming Interfaces) that must be present. The specification includes the minimum amount of memory, the minimum processor type and processor speed, as well as the minimum processor type and speed.
A profile refers to the APIs for a specific domain. For example, the MIDP (Mobile Information Device Profile) profile defines the API (Application Programming Interface) for mobile phones and wireless PDAs (Personal Digital Assistants). A device might implement more than one profile.
PCS (Personal Communication Services) is an advanced type of cellphone service that uses smaller cells and therefore requires a larger number of antennas to cover a geographic area. PCS phones use frequencies between 1.85 and 1.99 GHz. The idea is to create more bandwidth to handle the exploding volume of traffic and lower the power requirements of the phones.
WiFi wireless Internet Access gives up to 54MBps via IEEE (Institute of Electrical & Electronics Engineers) 802.11. This is primarily an Internet access protocol for laptop computers and handhelds. It is also used for in-home wireless networks that connect to the Internet via a router that connects to the ISP (Internet Service Provider) via traditional DSL (Digital Subscriber Loop) or cable.
Verizon wireless gives 400KBPs download Internet access.
A WiFi phone is one designed to hook into a wireless Internet connection. It is much cheaper to use than a traditional cellphone since it requires no air time to a cellphone tower. It uses ordinary nearby PCs (Personal Computers) connected to the Internet as its cellphone towers. Further it has much higher bandwidth. You might use one to tie into your home Internet to hook into a VOIP (Voice Over Internet Protocol) system like Vonage and then go to an WiFi-equipped Internet café to use it too.
Ironically, the way to get higher data transmission speeds, and support more customers, is to make the cell phone power lower, and the range smaller, using weaker cellphone towers, but more closely spaced. This is how 4G gets more bandwidth. How could this be? The air is limited in its ability to carry signals. If you use powerful phones, they saturate the air for miles around, preventing others from using that same air. All users surrounding a cellphone tower have to share the same volume of air. Early phone systems handled this by broadcasting on different frequencies, analogous to some people shouting in high pitched voices and others in low pitches. Modern phones handle this by automatically rapidly taking turns many times a second, sending a single packet of digitised sound (much the way an Ethernet LAN works). However, the pie is limited. If you use weaker phones, you saturate a much smaller area, leaving the rest for other people to use. With WiFi, you saturate a space only about the size of an apartment building. You could look at 4G as one step closer to universal WiFi access.
I suspect future phones will be self-adjusting, broadcasting powerfully in rural regions where there are only a few widely spaced towers, and less powerfully in suburbs, and flipping to nearby WiFi in urban areas or in your own home using almost no power at all. If this baffles you, imagine that cellphones worked by shouting for you to the cellphone tower. The further away the tower, the louder it has to shout, and the more it interferes with everyone else. It should be clear now.
5G cellphones that allow 200 Mb/S is coming soon. WiFi is about 300 Mb/S, but it is constantly improving too.
About 1 in six cellphone customers experience fraudulent billing, and surprise much it comes from the cellphone carrier, not petty criminals. Verizon Wireless just paid the largest voluntary fine in FCC (Federal Communications Commission) history — $25 million — for sticking their customers with millions in bogus mystery charges.
The two most common scams are charging tens of thousands of dollars for roaming or downloading a few megabytes, both of which cost the carrier only pennies. I would never sign up for any sort of cellphone billing plan other than a pre-paid card. Presumably, the worst they can rip you off then is the cost of the card, but you had better study the fine print. In Canada, one of the scams is to charge you for international roaming when you go near the US border and a US tower handles your call.
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