Knowing Your Cell Phone

blackberry is the most famous cellphone recently, other than apple i-phone or Nokia or other manufacturer
No one doubts that cell phone is one of the most used consumer electronics worldwide. But have you ever asked yourself how does a cell phone work? What is a cell phone?

The amazing fact about a cell phone is that it is a radio - a very special one. The gurus in the line are Bell (1876), Tesla (1880) followed by Marconi and Bose (late 19th century). It is known that the concept of cell phone was produced by Bell Laboratories with the permission of FCC (Federal Communication Commission), and had everything to do with broadcasting and sending a radio message out over the airwaves.

In cell phone technology cells divide the city, allowing for the facility to be frequently reused throughout the city. Millions can simultaneously avail of it.

In devices that are half-duplex (walkie-talkies and CB radios) two communicators use a single frequency. This means that at a single point of time only one can talk. On the other hand a cell phone being a full duplex tool has two frequencies: one for talking and the other for listening. Thus a real-life conversation can take place. Cell phones glide through 1,664 channels whereas the walkie-talkie group has to be content with only 40. The walkie-talkie and the CB radio respectively reaches out to 1 mile and 5 miles but the cell phones, because of their ability to switch from cell to cell can cover incredible distances, even while driving at top speed. Each cell is approximately 10 square miles.

The cells are usually depicted as hexagons. The unique frequency tiers avoid all possibilities of cross connections. Generally a carrier of cell phone can avail of 832 radio frequencies in a city. Each cell phone uses 395 voice channels (per carrier), that is 56 voice channels per cell. It means 56 persons can simultaneously say hello on the phone. In digital transmission technology the number of channels increases even further. For each cell phone 168 channels is available.

The distinctiveness about cell phones is their low-power transmitters. Most use 2 strengths: 0.6 watts and 0.3 watts. In comparison it is 4 watts for CB radios. The advantage of this is that it can be frequently reused consuming less power. Cell phones are battery operated. The lower the power the smaller the battery. This makes the set handy and light.

For cellular technology a city requires a good number of base stations. This can run into some hundreds of towers. But because of the huge number of users costs per head remain very low. Each carrier has one centre called MTSO or Mobile Telephone Switching Office. Its work is to see to all the connections.

Cell phones each have codes, which enable identification of the phone, its user and its server. When someone tries to reach a phone the first thing is to locate the SID (system identification code) on the control channel, that is find out if the phone is within range or not. A message relays no-service when it is out of range. But when the SID is received then the next step is to find out whether the call is within its own home zone or not. The phone also tracks the location of the phone called on a database. Thus the MTSO knows the cell of the called number and caller. Communication is transmitted through the control channel and it is this link that activates the phone being called and calling.

These are the facts of a cell phone as explained for a layman. It is always advisable to know at least the basics of a cell phone since it has become an integral part of our life.

This article is under GNU FDL license and can be distributed without any previous authorization from the author. However the author's name and all the URLs (links) mentioned in the article and biography must be kept.
Source: Free Articles Autor: robertoms

declining demand for handphone

HELSINKI (Reuters) - Sony Ericsson sparked fresh fear of crumbling consumer demand on Friday when the world's No 4 handset maker said it would sell barely half of the phones it sold last quarter.

Shares across the wireless sector dropped sharply on the news -- compounded by smaller rival Palm's overnight report of slumping quarterly sales -- and by 1229 GMT (8:29 a.m. EDT), Ericsson was down 8.7 percent and Nokia was down 5.5 percent.

Sony Ericsson said it expects to sell just 14 million phones in January-March, hit by weak demand and retailers cutting their inventories. Analysts polled by Reuters in January expected between 15.5 million to 21.8 million phones sold.

"Investors are questioning the whole market now, even though I think the issue for Sony Ericsson is more company specific," said Jari Honko, analyst with eQ Bank.

Overnight, U.S. rival Palm Inc reported a widening loss for the December-February quarter and said revenue sank 70 percent from a year ago.

The cellphone industry has entered its toughest year ever as consumers rein in spending and retailers try to clear inventories of unsold phones after bleak Christmas sales.

"The market, overall, continues to be very challenging," said Gartner analyst Carolina Milanesi.

Fears over the future of the mobile market also sent shares in chipmakers sharply lower, with Infineon down 6.6 percent and STMicro 5 percent lower.

VERY WEAK QUARTER

Sony Ericsson said it expected to make a pretax loss of 340-390 million euros ($459 million-$526 million) in the quarter as it heads into a second year of losses.

"It's a real catastrophe. Those are very big losses and they are probably losing a lot of market share," said Greger Johansson, from analyst firm Redeye.

"It's obvious that the volumes are much lower than the market had thought. And first and foremost, the losses are much, much bigger," he said.

Sony Ericsson, the no. 4 global handset maker after Nokia, Samsung and LG, said it expects gross margins to decline both year-on-year and sequentially.

"What is happening now is that everyone will be forced to cut their forecasts for Sony Ericsson and Ericsson," said analyst Hakan Wranne from Swedbank.

Ben Wood, head of research at CCS Insight said Sony Ericsson was suffering most from the weak portfolio and the challenging market conditions it faces in European markets.

"With competition intensifying it is going to be a tough task to regain momentum until new products appear and economic conditions improve," Wood said.

Sony Ericsson's success has been built on a strong offering of mid-range phones with high-quality cameras and music players, but this part of the cellphone market is seeing the sharpest fall this year as operators dole out subsidies to more expensive phones.

SMARTPHONES TO HOLD

Qualcomm, the world's largest cellphone chip maker, said on Friday it was seeing strong demand for higher-end smartphones in spite of the weak economy.

Analysts, on average, expect sales of feature-jammed smartphones to grow between 10 percent and 20 percent this year.

"Consumer demand for higher-end smartphones remains strong as the demand for wireless Internet, multimedia, and value-added services continues to grow," Jing Wang, a Qualcomm executive vice president, said in an e-mail to Reuters.

"While inventories have contracted, global 3G adoption is continuing to grow as subscribers migrate from second-generation to third-generation networks and manufacturers are shipping more 3G devices this year than last year," he said.

TSMC, which makes chips for Qualcomm and Texas Instruments, said on Friday it would end all unpaid leave for employees from April as orders have risen recently.

The move came after TSMC sharply raised its first-quarter sales and margin forecasts last week, due to rush orders from China, indicating a trend of falling sales that began six months ago had hit bottom.

($1=.7412 Euro)
By Tarmo Virki, European technology correspondent
Additional reporting by Baker Li in Taipei and Stockholm bureau; Editing by David Cowell and Simon Jessop