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CDMA
Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communication channel. This allows several users to share a band of frequencies (see bandwidth). To permit this without undue interference between the users, CDMA employs spread spectrum technology and a special coding scheme (where each transmitter is assigned a code). CDMA optimizes the use of available bandwidth as it transmits over the entire frequency range and does not limit the user's frequency range. It is used as the access method in many mobile phone standards. IS-95, also called "cdmaOne", and its 3G evolution CDMA2000, are often simply referred to as "CDMA", but UMTS, the 3G standard used by GSM carriers, also uses "wideband CDMA", or W-CDMA, as well as TD-CDMA and TD-SCDMA, as its radio technologies. Many carriers (such as AT&T, U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UMTS
The Universal Mobile Telecommunications System (UMTS) is a 3G mobile cellular system for networks based on the GSM standard. UMTS uses Wideband Code Division Multiple Access, wideband code-division multiple access (W-CDMA) radio access technology to offer greater spectral efficiency and bandwidth to mobile network operators compared to previous 2G systems like GPRS and Circuit Switched Data, CSD. UMTS on its provides a peak theoretical data rate of 2 Data-rate units, Mbit/s. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the International Telecommunication Union IMT-2000 standard set and compares with the CDMA2000 standard set for networks based on the competing IS-95, cdmaOne technology. The technology described in UMTS is sometimes also referred to as Freedom of Mobile Multimedia Access (FOMA) or 3GSM. UMTS specifies a complete network system, which includes the radio access network (UMTS Terrestrial Radio Access Network, or U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CDMA2000
CDMA2000 (also known as C2K or IMT Multi‑Carrier (IMT‑MC)) is a family of 3G mobile technology standards for sending voice, data, and signaling data between mobile phones and cell sites. It is developed by 3GPP2 as a backwards-compatible successor to second-generation cdmaOne (IS-95) set of standards and used especially in North America and South Korea. CDMA2000 compares to UMTS, a competing set of 3G standards, which is developed by 3GPP and used in Europe, Japan, China, and Singapore. The name CDMA2000 denotes a family of standards that represent the successive, evolutionary stages of the underlying technology. These are: *Voice: CDMA2000 1xRTT, 1X Advanced *Data: CDMA2000 1xEV-DO ( Evolution-Data Optimized): Release 0, Revision A, Revision B, Ultra Mobile Broadband (UMB) All are approved radio interfaces for the ITU's IMT-2000. In the United States, ''CDMA2000'' is a registered trademark of the Telecommunications Industry Association (TIA-USA). 1X CDMA200 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Channel Access Method
In telecommunications and computer networks, a channel access method or multiple access method allows more than two terminals connected to the same transmission medium to transmit over it and to share its capacity. Examples of shared physical media are wireless networks, bus networks, ring networks and point-to-point links operating in half-duplex mode. A channel access method is based on multiplexing, which allows several data streams or signals to share the same communication channel or transmission medium. In this context, multiplexing is provided by the physical layer. A channel access method may also be a part of the multiple access protocol and control mechanism, also known as medium access control (MAC). Medium access control deals with issues such as addressing, assigning multiplex channels to different users and avoiding collisions. Media access control is a sub-layer in the data link layer of the OSI model and a component of the link layer of the TCP/IP mod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mobile Phone Standards
This is a comparison of standards of wireless networking technologies for devices such as mobile phones. A new generation of cellular standards has appeared approximately every tenth year since 1G systems were introduced in 1979 and the early to mid-1980s. Issues Global System for Mobile Communications (GSM, around 80–85% market share) and IS-95 (around 10–15% market share) were the two most prevalent 2G mobile communication technologies in 2007. In 3G, the most prevalent technology was UMTS with CDMA-2000 in close contention. All radio access technologies have to solve the same problems: to divide the finite RF spectrum among multiple users as efficiently as possible. GSM uses TDMA and FDMA for user and cell separation. UMTS, IS-95 and CDMA-2000 use CDMA. WiMAX and LTE use OFDM. * Time-division multiple access (TDMA) provides multiuser access by chopping up the channel into sequential time slices. Each user of the channel takes turns to transmit and receive signals. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Verizon (mobile Network)
Verizon is an American wireless network operator that previously operated as a separate division of Verizon Communications under the name Verizon Wireless. In a 2019 reorganization, Verizon moved the wireless products and services into the divisions Verizon Consumer and Verizon Business, and stopped using the Verizon Wireless name. Verizon is the largest wireless carrier in the United States, with 146 million subscribers as of March 31, 2025. It currently has the second-largest network in the United States with their LTE network covering 2.68 million sq. miles of the United States. The company is headquartered in Basking Ridge, New Jersey. It was founded in 2000 as a joint venture of American telecommunications firm Bell Atlantic, which would soon become Verizon Communications, and British multinational telecommunications company Vodafone. Verizon Communications became the sole owner in 2014 after buying Vodafone's 45-percent stake in the company. It operates national 5G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CdmaOne
cdmaOne, most often simply referred to as CDMA, is a 2G digital cellular technology. It was the commercial name for Interim Standard 95 (IS-95), a technology that was developed by Qualcomm and later adopted as a standard by the Telecommunications Industry Association in TIA/EIA/IS-95 release published in 1995. cdmaOne used code-division multiple access (CDMA), a multiple access scheme for digital radio, to send voice, data and signaling data (such as a dialed telephone number) between mobile telephones and cell sites. CDMA transmits streams of bits ( PN codes). CDMA permits several radios to share the same frequencies. Unlike time-division multiple access (TDMA), a competing system used in 2G GSM, all radios can be active all the time, because network capacity does not directly limit the number of active radios. Since larger numbers of phones can be served by smaller numbers of cell-sites, CDMA-based standards have a significant economic advantage over TDMA-based stand ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Global Positioning System
The Global Positioning System (GPS) is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. It does not require the user to transmit any data, and operates independently of any telephone or Internet reception, though these technologies can enhance the usefulness of the GPS positioning information. It provides critical positioning capabilities to military, civil, and commercial users around the world. Although the United States government created, controls, and maintains the GPS system, it is freely accessible to anyone with a GPS receiver. Overview The GPS project was started by the U.S. Department of Defense in 1973. The first prototype spacecraft was launched in 1978 an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthogonal Frequency-division Multiplexing
In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission used in digital modulation for encoding digital (binary) data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital communication, used in applications such as digital television and audio broadcasting, DSL internet access, wireless networks, power line networks, and 4G/ 5G mobile communications. OFDM is a frequency-division multiplexing (FDM) scheme that was introduced by Robert W. Chang of Bell Labs in 1966. In OFDM, the incoming bitstream representing the data to be sent is divided into multiple streams. Multiple closely spaced orthogonal subcarrier signals with overlapping spectra are transmitted, with each carrier modulated with bits from the incoming stream so multiple bits are being transmitted in parallel. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spread Spectrum
In telecommunications, especially radio communication, spread spectrum are techniques by which a signal (electrical engineering), signal (e.g., an electrical, electromagnetic, or acoustic) generated with a particular Bandwidth (signal processing), bandwidth is deliberately spread in the frequency domain over a wider frequency band. Spread-spectrum techniques are used for the establishment of secure communications, increasing resistance to natural Interference (communication), interference, Noise (electronics), noise, and radio jamming, jamming, to prevent detection, to limit Spectral flux density, power flux density (e.g., in satellite downlinks), and to enable multiple-access communications. Telecommunications Spread spectrum generally makes use of a sequential noise-like signal structure to spread the normally narrowband information signal over a relatively wideband (radio) band of frequencies. The receiver correlates the received signals to retrieve the original information ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Offset Carrier Modulation
Binary offset carrier modulation (BOC modulation) was developed by John Betz in order to allow interoperability of satellite navigation systems. It is currently used in the US GPS system, Indian IRNSS system and in Galileo and is a square sub-carrier modulation, where a signal is multiplied by a rectangular sub-carrier of frequency f_\text equal to or greater than the chip rate. Following this sub-carrier multiplication, the spectrum of the signal is divided into two parts, therefore BOC modulation is also known as a split-spectrum modulation. Their major advantages are, that one can shape the spectrum to allow inter-system-compatibility and better theoretically achievable tracking capabilities, due to higher frequencies if downmixed to the complex baseband. On the other hand, a huge variety of different implementations or instantiations was set up, making it difficult to get the whole picture. Early (and sometimes recent) publications dealing with that topic usually do not incl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dmitry Vasiliyevich Ageev
Dmitry Vasilyevich Ageyev (; 21 February 1911 in Saint Petersburg, Russian Empire – 31 July 1997 in Nizhny Novgorod Nizhny Novgorod ( ; rus, links=no, Нижний Новгород, a=Ru-Nizhny Novgorod.ogg, p=ˈnʲiʐnʲɪj ˈnovɡərət, t=Lower Newtown; colloquially shortened to Nizhny) is a city and the administrative centre of Nizhny Novgorod Oblast an ..., Russia) was a Soviet and Russian scientist and educator in the field of radio engineering. He developed the theory of code division of signals during the radio reception, which is the basis for the construction of cellular networks on CDMA technology. Along with Vladimir Kotelnikov, he was one of the founders of the theory of optimum noise immunity that he developed throughout life, starting with a thesis at his institute. References 1911 births 1997 deaths Engineers from Saint Petersburg Communication theorists Soviet engineers {{Russia-scientist-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
9-1-1
911, sometimes written , is an emergency telephone number for Argentina, Canada, the Dominican Republic, Fiji, Jordan, Mexico, Pakistan, Maldives, Palau, Panama, Iraq, the Philippines, Sint Maarten, the United States, and Uruguay, as well as the North American Numbering Plan (NANP), one of eight N11 codes. Like other emergency numbers, dialing 911 for purposes other than reporting an emergency is a crime in most jurisdictions. Penalties for abuse or misuse of 911 can range from probation or community service to fines and jail time. Offenders can also be ordered to undergo counseling and have their use of telephones restricted or suspended for a period of time as a condition of probation. In over 98 percent of locations in Argentina, Sint Maarten, Panama, Belize, Anguilla, Costa Rica, Ecuador, Jordan, Ethiopia, Liberia, Saudi Arabia, Philippines, Uruguay, the United States, Iraq, Palau, Mexico, Tonga and Canada, dialing ''911'' from any telephone will link the caller to an em ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
