Article reviewed on Jul 24, Tweet Share Email. Android Switching from iOS. In This Article. Leading Mobile Network Providers. Types of Mobile Networks. GSM vs. Was this page helpful? Thanks for letting us know! Email Address Sign up There was an error. Please try again. You're in! Thanks for signing up. There was an error. Tell us why! More from Lifewire. Updated for What Is a Cellphone? Cellphones, Coverage, and Networks. Your Privacy Rights. To change or withdraw your consent choices for Lifewire.
At any time, you can update your settings through the "EU Privacy" link at the bottom of any page. Cell phones operate within cells , and they can switch cells as they move around. Cells give cell phones incredible range. Someone using a cell phone can drive hundreds of miles and maintain a conversation the entire time because of the cellular approach. In simplex radio, both transmitters use the same frequency. Only one party can talk at a time. In duplex radio, the two transmitters use different frequencies, so both parties can talk at the same time.
Cell phones are duplex. In the next section, you'll get a good look inside a digital cell phone. Inside a Cell Phone On a "complexity per cubic inch" scale, cell phones are some of the most intricate devices people play with on a daily basis.
Modern digital cell phones can process millions of calculations per second in order to compress and decompress the voice stream. The parts of a cell phone If you take a cell phone apart, you find that it contains just a few individual parts: An amazing circuit board containing the brains of the phone An antenna A liquid crystal display LCD A keyboard not unlike the one you find in a TV remote control A microphone A speaker A battery The circuit board is the heart of the system.
Here is one from a typical Nokia digital phone: The front of the circuit board The back of the circuit board In the photos above, you see several computer chips. Let's talk about what some of the individual chips do. The analog-to-digital and digital-to-analog conversion chips translate the outgoing audio signal from analog to digital and the incoming signal from digital back to analog. The digital signal processor DSP is a highly customized processor designed to perform signal-manipulation calculations at high speed.
The microprocessor The microprocessor handles all of the housekeeping chores for the keyboard and display, deals with command and control signaling with the base station and also coordinates the rest of the functions on the board.
The ROM and Flash memory chips provide storage for the phone's operating system and customizable features, such as the phone directory. The radio frequency RF and power section handles power management and recharging, and also deals with the hundreds of FM channels. Finally, the RF amplifiers handle signals traveling to and from the antenna. The display and keypad contacts The display has grown considerably in size as the number of features in cell phones have increased.
Most current phones offer built-in phone directories, calculators and even games. And many of the phones incorporate some type of PDA or Web browser. The Flash memory card on the circuit board The Flash memory card removed Some phones store certain information, such as the SID and MIN codes, in internal Flash memory, while others use external cards that are similar to SmartMedia cards.
The cell-phone speaker, microphone and battery backup Cell phones have such tiny speakers and microphones that it is incredible how well most of them reproduce sound. As you can see in the picture above, the speaker is about the size of a dime and the microphone is no larger than the watch battery beside it. Speaking of the watch battery, this is used by the cell phone's internal clock chip. What is amazing is that all of that functionality -- which only 30 years ago would have filled an entire floor of an office building -- now fits into a package that sits comfortably in the palm of your hand!
In order to encourage competition and keep prices low, the U. One of the carriers was normally the local-exchange carrier LEC , a fancy way of saying the local phone company.
Carriers A and B are each assigned frequencies : for voice and 42 for data. A pair of frequencies one for transmit and one for receive is used to create one channel. The frequencies used in analog voice channels are typically 30 kHz wide -- 30 kHz was chosen as the standard size because it gives you voice quality comparable to a wired telephone.
The transmit and receive frequencies of each voice channel are separated by 45 MHz to keep them from interfering with each other. Each carrier has voice channels, as well as 21 data channels to use for housekeeping activities like registration and paging. Even though it uses digital technology, it is still considered analog. Along Comes Digital Digital cell phones use the same radio technology as analog phones, but they use it in a different way.
Analog systems do not fully utilize the signal between the phone and the cellular network -- analog signals cannot be compressed and manipulated as easily as a true digital signal. This is the reason why many cable companies are switching to digital -- so they can fit more channels within a given bandwidth.
It is amazing how much more efficient digital systems can be. Digital phones convert your voice into binary information 1s and 0s and then compress it see How Analog-Digital Recording Works for details on the conversion process. This compression allows between three and 10 digital cell-phone calls to occupy the space of a single analog call.
FSK uses two frequencies , one for 1s and the other for 0s, alternating rapidly between the two to send digital information between the cell tower and the phone. Clever modulation and encoding schemes are required to convert the analog information to digital, compress it and convert it back again while maintaining an acceptable level of voice quality.
All of this means that digital cell phones have to contain a lot of processing power! Cellular Access Technologies There are three common technologies used by cell-phone networks for transmitting information: Frequency division multiple access FDMA Time division multiple access TDMA Code division multiple access CDMA Although these technologies sound very intimidating, you can get a good sense of how they work just by breaking down the title of each one.
The first word tells you what the access method is. The second word, division , lets you know that it splits calls based on that access method. FDMA puts each call on a separate frequency. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson but not the third party web trend services to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.
This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site. Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.
Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider.
Marketing preferences may be changed at any time. If a user's personally identifiable information changes such as your postal address or email address , we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service informit. Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT.
If you choose to remove yourself from our mailing list s simply visit the following page and uncheck any communication you no longer want to receive: www. While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest pearson. California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice.
The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services. This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information.
This privacy statement applies solely to information collected by this web site. Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information. We may revise this Privacy Notice through an updated posting.
We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way.
Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions. This chapter describes how cellular networking works — and how these networks relate to the other wireless networks you employ on a daily basis.
This chapter is from the book. NOTE The cells in a cellular network vary in size, depending on how many calls are conducted within that geographic area. Overview Pearson Education, Inc. Collection and Use of Information To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including: Questions and Inquiries For inquiries and questions, we collect the inquiry or question, together with name, contact details email address, phone number and mailing address and any other additional information voluntarily submitted to us through a Contact Us form or an email.
Surveys Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites.
0コメント