This document provides information about cellular networks and cellular technology. It discusses how cellular networks work using a network of cells with radio signals and base stations to allow communication between mobile devices. It also describes some key aspects of cellular networks including frequency reuse, multiple access methods like FDMA and TDMA, signal encoding, handovers between cells, and provides an example of cellular networks using mobile phone networks.
Cellular networks divide geographic areas into smaller cells to increase capacity and reuse frequencies. Each cell has a base station that transmits and receives from mobile devices within its cell. As mobile devices move between cells during calls, the network performs handovers to transfer the call seamlessly between base stations. Common cellular technologies include GSM, CDMA, and LTE that use techniques like FDMA, TDMA, and CDMA to allow frequency reuse and multiple access across cells.
The document discusses cellular technology and mobile phone networks. It provides details on:
- How early mobile phones worked and the development of modern cellular networks.
- The basic components and functions of a cellular network including radio base stations, mobile switching centers, and connections to the public telephone network.
- Concepts of cellular networks like frequency reuse, cells, and handovers that allow calls to be switched between cells as users move.
- Factors that influence cellular network performance like frequency choice, interference, and coverage depending on frequency used.
Wireless cellular networks divide geographic areas into cells served by base stations to allow for frequency reuse. As users travel between cells, their calls are handed off seamlessly. Cellular systems improve capacity by allocating unique frequency groups to each cell and reusing the same frequencies in cells sufficiently distant from each other. Larger networks connect multiple base stations and mobile switching centers to facilitate roaming and complete calls between mobile and fixed users.
Cellular network wikipedia, the free encyclopediaSarah Krystelle
A cellular network divides a geographic area into sections called cells, with each cell served by a fixed base station. This allows portable devices like mobile phones to communicate within the network and across multiple cells. When a device moves between cells, its connection is automatically handed off to the new cell's base station to maintain continuous coverage. Cellular networks reuse frequencies in non-adjacent cells to increase capacity and coverage across a wide area.
Data Communications,Data Networks,computer communications,multiplexing,spread spectrum,protocol architecture,data link protocols,signal encoding techniques,transmission media,asynchronous transfer mode,routing,cellular networks
This document discusses several key concepts in mobile computing and cellular networks. It begins by explaining spectrum management and the concepts of frequency division multiple access (FDMA) and time division multiple access (TDMA). It then provides a brief history of early radiotelephone systems and their limitations. The document goes on to explain the three basic communication modes, the three components of a basic cellular system, and factors that influence radio propagation in a mobile environment such as multipath. It concludes by discussing the need for multiple access techniques, and explaining the differences between circuit switching and packet switching.
Today's cellular telephone systems operate by dividing geographic areas into cells served by base stations. Each cell is assigned certain radio frequencies that are reused in non-neighboring cells to increase coverage and capacity. When a mobile user moves between cells, the call is handed off from one base station to another through a mobile switching center to avoid disconnection. Modern cellular networks use digital technologies like CDMA, TDMA and FDMA to provide voice, text, and data services to users through cellular infrastructure.
Cellular networks divide geographic areas into smaller cells to increase capacity and reuse frequencies. Each cell has a base station that transmits and receives from mobile devices within its cell. As mobile devices move between cells during calls, the network performs handovers to transfer the call seamlessly between base stations. Common cellular technologies include GSM, CDMA, and LTE that use techniques like FDMA, TDMA, and CDMA to allow frequency reuse and multiple access across cells.
The document discusses cellular technology and mobile phone networks. It provides details on:
- How early mobile phones worked and the development of modern cellular networks.
- The basic components and functions of a cellular network including radio base stations, mobile switching centers, and connections to the public telephone network.
- Concepts of cellular networks like frequency reuse, cells, and handovers that allow calls to be switched between cells as users move.
- Factors that influence cellular network performance like frequency choice, interference, and coverage depending on frequency used.
Wireless cellular networks divide geographic areas into cells served by base stations to allow for frequency reuse. As users travel between cells, their calls are handed off seamlessly. Cellular systems improve capacity by allocating unique frequency groups to each cell and reusing the same frequencies in cells sufficiently distant from each other. Larger networks connect multiple base stations and mobile switching centers to facilitate roaming and complete calls between mobile and fixed users.
Cellular network wikipedia, the free encyclopediaSarah Krystelle
A cellular network divides a geographic area into sections called cells, with each cell served by a fixed base station. This allows portable devices like mobile phones to communicate within the network and across multiple cells. When a device moves between cells, its connection is automatically handed off to the new cell's base station to maintain continuous coverage. Cellular networks reuse frequencies in non-adjacent cells to increase capacity and coverage across a wide area.
Data Communications,Data Networks,computer communications,multiplexing,spread spectrum,protocol architecture,data link protocols,signal encoding techniques,transmission media,asynchronous transfer mode,routing,cellular networks
This document discusses several key concepts in mobile computing and cellular networks. It begins by explaining spectrum management and the concepts of frequency division multiple access (FDMA) and time division multiple access (TDMA). It then provides a brief history of early radiotelephone systems and their limitations. The document goes on to explain the three basic communication modes, the three components of a basic cellular system, and factors that influence radio propagation in a mobile environment such as multipath. It concludes by discussing the need for multiple access techniques, and explaining the differences between circuit switching and packet switching.
Today's cellular telephone systems operate by dividing geographic areas into cells served by base stations. Each cell is assigned certain radio frequencies that are reused in non-neighboring cells to increase coverage and capacity. When a mobile user moves between cells, the call is handed off from one base station to another through a mobile switching center to avoid disconnection. Modern cellular networks use digital technologies like CDMA, TDMA and FDMA to provide voice, text, and data services to users through cellular infrastructure.
Introduction to Cellular Mobile System,
Performance criteria,
uniqueness of mobile radio environment,
operation of cellular systems,
Hexagonal shaped cells,
Analog Cellular systems.
Digital Cellular systems
This document provides an overview of cellular network technology. It discusses key concepts such as how a cellular network divides geographic coverage into cells served by base stations, allowing frequencies to be reused across cells. It also summarizes techniques for distinguishing signals like frequency division multiple access (FDMA) and code division multiple access (CDMA). The document concludes with explanations of frequency reuse patterns, directional antenna use, broadcast messaging, paging, and handovers as mobile devices move between cells.
TDMA, CDMA, FDMA, and SDMA are different multiple access techniques used in mobile communications. TDMA divides each channel into time slots and allocates slots to different users. CDMA encodes each conversation with a pseudo-random sequence and all users share the full spectrum. FDMA divides the bandwidth into individual frequency bands, each assigned to a single user. SDMA uses smart antennas to create spatial pipes between the base station and mobile users to improve performance.
The document outlines the key concepts and units covered in a course on wireless and cellular communications. Unit 1 discusses cellular system design fundamentals including frequency reuse, interference, and capacity. Unit 2 covers speech coding techniques and radio channel characterization. Unit 3 discusses modulation techniques, diversity techniques, and OFDM. Unit 4 introduces MAC protocols for wireless networks. Unit 5 introduces satellite communication systems. Reference books on wireless communication principles and standards are also listed.
cellular concepts in wireless communicationasadkhan1327
The document discusses the concept of frequency reuse in cellular networks. It explains that a limited radio spectrum is used to serve millions of subscribers by dividing the network coverage area into cells and reusing frequencies across spatially separated cells. Each cell is allocated a portion of the total available frequencies, and neighboring cells are assigned different frequencies to minimize interference. The frequency reuse factor is defined as the ratio of the minimum distance between co-channel cells to the cell radius. Larger frequency reuse factors provide better isolation between co-channel cells but reduce network capacity. The document also covers additional topics like different channel assignment strategies, handoff methods, interference calculation and optimization of frequency reuse networks.
Mobile networks use radio frequencies to allow cellular devices to connect to a network of base stations. Base stations transmit and receive signals in frequency bands between 850-1900 MHz. As devices move between base station coverage areas, the network performs handoffs to transfer the connection seamlessly. Higher generations of cellular networks like 3G and 4G provide improved data speeds but still must handle user mobility effectively.
Intorduction to cellular communicationZaahir Salam
This document provides an introduction to cellular communications. It discusses how mobile networks use separate radio channels and pairs of frequencies for communication between mobile devices and cell sites. It also describes how early mobile systems used one powerful transmitter while modern cellular networks use many low-power transmitters and a cellular structure. Key aspects of cellular network design are also summarized such as cells, clusters, frequency reuse, and handovers.
This document provides an overview of cellular networks. It discusses key concepts like cells, base stations, frequency reuse, and multiple access methods. It describes how location of mobile devices is managed through location updating and paging. It also covers handoff which allows active calls to continue seamlessly as users move between different cells.
Cellular communication systems have evolved through multiple generations from analog 1G to digital 4G systems. A cellular network is divided into geographical areas called cells served by base transceiver stations. Cells are grouped into clusters where frequencies are reused to allow for more subscribers. When making a call, the cellular phone registers with the local base station which routes the call through switching centers to establish communication with the intended recipient. Modern cellular networks support additional services beyond voice like texting, internet access, and location tracking through technologies like GSM that employ protocols like TDMA for efficient frequency usage.
The document discusses the growth of cellular networks worldwide and in Pakistan. It provides statistics on the rising number of mobile subscribers globally, with Asia Pacific projected to account for half of all subscribers by the end of the decade. It then describes key components of cellular networks including mobile phones, base stations, mobile switching centers, and the use of frequency reuse to increase network capacity by dividing coverage areas into cells and assigning different frequency groups to adjacent cells.
Mobile computing allows for anytime, anywhere computing through portable devices that can access wireless networks. However, mobile computing faces several challenges compared to traditional distributed systems, including resource scarcity due to limitations of mobile devices, variable connectivity, bandwidth and interfaces, and increased security vulnerabilities. These issues must be addressed through systems that can adapt to varying resources and environmental conditions, handle intermittent connectivity and mobility across domains, and maintain scalability.
This document discusses handoff in mobile communication networks. It begins with defining handoff as the transition of signal transmission from one base station to an adjacent one as a user moves. It then discusses various handoff strategies such as prioritizing handoff calls over new calls, monitoring signal strength to avoid unnecessary handoffs, and reserving guard channels for handoff requests. The document also covers types of handoffs, how handoff is handled differently in 1G and 2G cellular systems, challenges like cell dragging, and concepts like umbrella cells to minimize handoffs for high-speed users.
The document defines cellular radio systems as radio communication networks divided into small geographic areas called cells. Each cell contains a low-power transmitter/receiver base station that can communicate with mobile units within its cell. As a mobile unit moves between cells, it automatically switches to the nearest base station. The mobile telephone switching office coordinates calls between cells and landline networks. Key components include mobile units, base stations, and the switching office. Channels include control channels for signaling and voice channels for calls.
The document provides an overview of cellular mobile communications including:
1) The historical development from isolated mobile systems to modern cellular networks with handoff capabilities and connections to public networks.
2) The key components of a cellular system including mobile stations, base transceiver stations, base station controllers, and mobile switching centers.
3) How the cellular concept enables frequency reuse through the use of lower power transmissions in smaller coverage areas called cells, allowing the same frequencies to be reused in separated cells.
This document provides an overview of mobile communication and cellular technologies. It begins with learning objectives which are to refresh basics of cellular technologies, understand functioning in a cellular environment, and explain technical aspects of cellular telecommunications. The document then outlines the course agenda which will cover topics like access methods, multiple access techniques, mobile services, evolution of cellular communication standards like GSM and CDMA, cellular networks, and wireless data technologies. It dives into concepts like electromagnetic waves, frequency division multiple access, time division multiple access, duplexing, cellular architecture with frequency reuse, and elements of mobile communication systems.
This presentation contains the basic of cellular system.
in which direction the cellular system works and how it changes the network from one bast station to another is simply explained.
how Hand-off occur between two base station is shown via figure to understand well.
the cell system in mobile network and the cell spliting, sectoring, microcell zone concept is also explained well.
Please take a look.
may be it is helpfull for you.
Thank you.
The cellular concept was developed to solve the problem of spectral congestion and increase user capacity without major technological changes. It involves replacing single, high power transmitters with many low power transmitters covering small areas. Neighboring cells are assigned different channel groups to minimize interference, and the same channels are reused at different locations. When designing cellular systems, providing good coverage and services in high density areas requires considering factors like geographical separation and shadowing effects that allow frequency reuse.
The document discusses cellular network architecture and interference. It describes how cellular networks divide geographic coverage areas into hexagonal cells serviced by low-power base stations to reuse frequencies and increase capacity. Interference between cells using the same frequency is a major limiting factor and can be reduced by increasing the distance between co-channel cells. The document also discusses types of interference like co-channel and adjacent channel interference and techniques to mitigate interference like increasing cluster size and implementing power control.
Cellular wireless networks use three basic devices: a mobile station, base transceiver, and mobile switching office. The base transceiver includes an antenna and controller. The switching office connects calls between mobile units. Two channel types are available: control channels for call setup/maintenance, and traffic channels that carry voice/data. Cells use low-powered transmitters and each cell has its own antenna and base station. Frequency reuse allows the same frequencies to be used in different cells. As users move between cells, handoffs change their assignment from one base station to another.
Cellular networks divide geographic areas into cells served by low-power base stations to reuse frequencies. Adjacent cells are assigned different frequencies to avoid interference. As capacity demands increase, networks employ techniques like frequency borrowing, cell splitting, cell sectoring, and microcells. Cellular standards like GSM use TDMA to allow multiple users per cell by dividing the air interface into time slots. CDMA spreads user data over a wide bandwidth using unique codes and allows soft handoff between cells. Third generation networks support high-speed data and multimedia services.
This document discusses desktop and application virtualization concepts and deployment strategies. It provides an overview of MCPc and their approach, which includes assessing cloud readiness, designing and implementing cloud migrations, and providing ongoing managed cloud services. Case studies of education customers who deployed virtual desktops through Citrix or VMware are also presented to demonstrate benefits like cost savings, management improvements, and supporting remote learning.
1. The document discusses the evolution of wireless mobile communication networks from 1G to 5G.
2. 1G networks were the first generation of analog cellular networks introduced in the 1980s. They supported only voice calls with speeds up to 2.4 kbps.
3. 2G networks introduced digital cellular technology in the late 1980s, allowing for improved voice quality, data services like texting, and more efficient use of spectrum. GSM became the dominant 2G standard globally.
Introduction to Cellular Mobile System,
Performance criteria,
uniqueness of mobile radio environment,
operation of cellular systems,
Hexagonal shaped cells,
Analog Cellular systems.
Digital Cellular systems
This document provides an overview of cellular network technology. It discusses key concepts such as how a cellular network divides geographic coverage into cells served by base stations, allowing frequencies to be reused across cells. It also summarizes techniques for distinguishing signals like frequency division multiple access (FDMA) and code division multiple access (CDMA). The document concludes with explanations of frequency reuse patterns, directional antenna use, broadcast messaging, paging, and handovers as mobile devices move between cells.
TDMA, CDMA, FDMA, and SDMA are different multiple access techniques used in mobile communications. TDMA divides each channel into time slots and allocates slots to different users. CDMA encodes each conversation with a pseudo-random sequence and all users share the full spectrum. FDMA divides the bandwidth into individual frequency bands, each assigned to a single user. SDMA uses smart antennas to create spatial pipes between the base station and mobile users to improve performance.
The document outlines the key concepts and units covered in a course on wireless and cellular communications. Unit 1 discusses cellular system design fundamentals including frequency reuse, interference, and capacity. Unit 2 covers speech coding techniques and radio channel characterization. Unit 3 discusses modulation techniques, diversity techniques, and OFDM. Unit 4 introduces MAC protocols for wireless networks. Unit 5 introduces satellite communication systems. Reference books on wireless communication principles and standards are also listed.
cellular concepts in wireless communicationasadkhan1327
The document discusses the concept of frequency reuse in cellular networks. It explains that a limited radio spectrum is used to serve millions of subscribers by dividing the network coverage area into cells and reusing frequencies across spatially separated cells. Each cell is allocated a portion of the total available frequencies, and neighboring cells are assigned different frequencies to minimize interference. The frequency reuse factor is defined as the ratio of the minimum distance between co-channel cells to the cell radius. Larger frequency reuse factors provide better isolation between co-channel cells but reduce network capacity. The document also covers additional topics like different channel assignment strategies, handoff methods, interference calculation and optimization of frequency reuse networks.
Mobile networks use radio frequencies to allow cellular devices to connect to a network of base stations. Base stations transmit and receive signals in frequency bands between 850-1900 MHz. As devices move between base station coverage areas, the network performs handoffs to transfer the connection seamlessly. Higher generations of cellular networks like 3G and 4G provide improved data speeds but still must handle user mobility effectively.
Intorduction to cellular communicationZaahir Salam
This document provides an introduction to cellular communications. It discusses how mobile networks use separate radio channels and pairs of frequencies for communication between mobile devices and cell sites. It also describes how early mobile systems used one powerful transmitter while modern cellular networks use many low-power transmitters and a cellular structure. Key aspects of cellular network design are also summarized such as cells, clusters, frequency reuse, and handovers.
This document provides an overview of cellular networks. It discusses key concepts like cells, base stations, frequency reuse, and multiple access methods. It describes how location of mobile devices is managed through location updating and paging. It also covers handoff which allows active calls to continue seamlessly as users move between different cells.
Cellular communication systems have evolved through multiple generations from analog 1G to digital 4G systems. A cellular network is divided into geographical areas called cells served by base transceiver stations. Cells are grouped into clusters where frequencies are reused to allow for more subscribers. When making a call, the cellular phone registers with the local base station which routes the call through switching centers to establish communication with the intended recipient. Modern cellular networks support additional services beyond voice like texting, internet access, and location tracking through technologies like GSM that employ protocols like TDMA for efficient frequency usage.
The document discusses the growth of cellular networks worldwide and in Pakistan. It provides statistics on the rising number of mobile subscribers globally, with Asia Pacific projected to account for half of all subscribers by the end of the decade. It then describes key components of cellular networks including mobile phones, base stations, mobile switching centers, and the use of frequency reuse to increase network capacity by dividing coverage areas into cells and assigning different frequency groups to adjacent cells.
Mobile computing allows for anytime, anywhere computing through portable devices that can access wireless networks. However, mobile computing faces several challenges compared to traditional distributed systems, including resource scarcity due to limitations of mobile devices, variable connectivity, bandwidth and interfaces, and increased security vulnerabilities. These issues must be addressed through systems that can adapt to varying resources and environmental conditions, handle intermittent connectivity and mobility across domains, and maintain scalability.
This document discusses handoff in mobile communication networks. It begins with defining handoff as the transition of signal transmission from one base station to an adjacent one as a user moves. It then discusses various handoff strategies such as prioritizing handoff calls over new calls, monitoring signal strength to avoid unnecessary handoffs, and reserving guard channels for handoff requests. The document also covers types of handoffs, how handoff is handled differently in 1G and 2G cellular systems, challenges like cell dragging, and concepts like umbrella cells to minimize handoffs for high-speed users.
The document defines cellular radio systems as radio communication networks divided into small geographic areas called cells. Each cell contains a low-power transmitter/receiver base station that can communicate with mobile units within its cell. As a mobile unit moves between cells, it automatically switches to the nearest base station. The mobile telephone switching office coordinates calls between cells and landline networks. Key components include mobile units, base stations, and the switching office. Channels include control channels for signaling and voice channels for calls.
The document provides an overview of cellular mobile communications including:
1) The historical development from isolated mobile systems to modern cellular networks with handoff capabilities and connections to public networks.
2) The key components of a cellular system including mobile stations, base transceiver stations, base station controllers, and mobile switching centers.
3) How the cellular concept enables frequency reuse through the use of lower power transmissions in smaller coverage areas called cells, allowing the same frequencies to be reused in separated cells.
This document provides an overview of mobile communication and cellular technologies. It begins with learning objectives which are to refresh basics of cellular technologies, understand functioning in a cellular environment, and explain technical aspects of cellular telecommunications. The document then outlines the course agenda which will cover topics like access methods, multiple access techniques, mobile services, evolution of cellular communication standards like GSM and CDMA, cellular networks, and wireless data technologies. It dives into concepts like electromagnetic waves, frequency division multiple access, time division multiple access, duplexing, cellular architecture with frequency reuse, and elements of mobile communication systems.
This presentation contains the basic of cellular system.
in which direction the cellular system works and how it changes the network from one bast station to another is simply explained.
how Hand-off occur between two base station is shown via figure to understand well.
the cell system in mobile network and the cell spliting, sectoring, microcell zone concept is also explained well.
Please take a look.
may be it is helpfull for you.
Thank you.
The cellular concept was developed to solve the problem of spectral congestion and increase user capacity without major technological changes. It involves replacing single, high power transmitters with many low power transmitters covering small areas. Neighboring cells are assigned different channel groups to minimize interference, and the same channels are reused at different locations. When designing cellular systems, providing good coverage and services in high density areas requires considering factors like geographical separation and shadowing effects that allow frequency reuse.
The document discusses cellular network architecture and interference. It describes how cellular networks divide geographic coverage areas into hexagonal cells serviced by low-power base stations to reuse frequencies and increase capacity. Interference between cells using the same frequency is a major limiting factor and can be reduced by increasing the distance between co-channel cells. The document also discusses types of interference like co-channel and adjacent channel interference and techniques to mitigate interference like increasing cluster size and implementing power control.
Cellular wireless networks use three basic devices: a mobile station, base transceiver, and mobile switching office. The base transceiver includes an antenna and controller. The switching office connects calls between mobile units. Two channel types are available: control channels for call setup/maintenance, and traffic channels that carry voice/data. Cells use low-powered transmitters and each cell has its own antenna and base station. Frequency reuse allows the same frequencies to be used in different cells. As users move between cells, handoffs change their assignment from one base station to another.
Cellular networks divide geographic areas into cells served by low-power base stations to reuse frequencies. Adjacent cells are assigned different frequencies to avoid interference. As capacity demands increase, networks employ techniques like frequency borrowing, cell splitting, cell sectoring, and microcells. Cellular standards like GSM use TDMA to allow multiple users per cell by dividing the air interface into time slots. CDMA spreads user data over a wide bandwidth using unique codes and allows soft handoff between cells. Third generation networks support high-speed data and multimedia services.
This document discusses desktop and application virtualization concepts and deployment strategies. It provides an overview of MCPc and their approach, which includes assessing cloud readiness, designing and implementing cloud migrations, and providing ongoing managed cloud services. Case studies of education customers who deployed virtual desktops through Citrix or VMware are also presented to demonstrate benefits like cost savings, management improvements, and supporting remote learning.
1. The document discusses the evolution of wireless mobile communication networks from 1G to 5G.
2. 1G networks were the first generation of analog cellular networks introduced in the 1980s. They supported only voice calls with speeds up to 2.4 kbps.
3. 2G networks introduced digital cellular technology in the late 1980s, allowing for improved voice quality, data services like texting, and more efficient use of spectrum. GSM became the dominant 2G standard globally.
The document discusses multiple access techniques for satellite communications. It describes frequency division multiple access (FDMA), time division multiple access (TDMA), and code division multiple access (CDMA). FDMA divides the available radio spectrum into narrow frequency channels. TDMA divides each radio channel into time slots. CDMA allows all users to access the full bandwidth at all times by using orthogonal spreading codes. The document provides examples of these different multiple access techniques and compares their approaches.
FDMA (frequency division multiple access) is a technology that divides the frequency band allocated for wireless communication into multiple channels, with each channel assigned to a single user. It allows more than one user to share the radio frequency spectrum by allocating different frequency channels. In FDMA, each call is placed on a separate frequency channel. It separates the spectrum into uniform chunks of bandwidth for voice channels. While capable of digital transmission, FDMA is not efficient for digital transmission.
This document provides an overview and summary of a training course on Agenda, GSM & MPA. The course agenda covers definitions and history of GSM, GSM services, system architecture including components like the HLR, VLR, BTS, BSC and MSC. It also discusses the GSM functional model including call management, mobility management and radio resource management. The document then summarizes the GSM radio interface, protocols like DTAP and interfaces like A-bis and A. It provides high-level descriptions of GSM standards and evolution over time.
VSAT (Very Small Aperture Terminal) technology allows for wireless communication via satellite using small dish antennas. A VSAT network consists of a central hub with a large antenna that communicates with multiple remote VSAT sites. The hub controls and monitors the network, sending data to the satellite which amplifies and redirects the signals to the VSATs. VSAT offers advantages like flexibility, lower installation costs than terrestrial networks, and ability to access areas without terrestrial infrastructure. Common applications of VSAT include corporate networks, internet access, distance education, and retail/banking networks. VSAT uses multiple access techniques like TDMA to allow efficient sharing of satellite bandwidth among sites.
CDMA is a digital cellular standard that allows multiple users to access the same radio frequency channel simultaneously through the use of unique code sequences. Users are separated by spreading their transmitted signals across the frequency band using pseudo-random codes. CDMA provides advantages over other multiple access techniques like FDMA and TDMA such as increased capacity, soft handoffs between cells, and covert operation due to its noise-like signals. The IS-95 standard introduced CDMA to cellular networks and specified the use of orthogonal codes to separate signals and a 1.25 MHz channel bandwidth to support multiple simultaneous voice calls.
Mobile communication - GSM/CDMA/WIMAX TechnologiesAman Abhishek
Mobile communication allows communication without a physical connection and flexibility to move anywhere during communication. It uses technologies like GSM and CDMA. Mobile communication has become one of the fastest growing industries. A mobile handset allows making and receiving calls over radio links while moving. It contains components like a battery, SIM card and antenna. A SIM card identifies the subscriber to the network. In mobile communication, a cell is the smallest area, subscribers pay for use, and base stations connect mobile units to switching centers. As users move, handoffs transfer calls between base stations to maintain connectivity.
This summary provides an overview of the history and technology of mobile, cellular, and personal communications systems:
Mobile radio systems evolved from two-way radios used by public services to cellular networks that enabled widespread mobile phone use. Cellular networks overcome issues with conventional mobile networks by reusing frequencies in adjacent hexagonal cells controlled by base stations and switching offices. Personal communications systems (PCS) operate in different frequency bands than early cellular networks and use digital technologies like TDMA and CDMA to further improve spectrum efficiency. These advances have enabled mobile networks to support additional features and the growth of wireless communication.
The document provides an overview of cellular network concepts and architecture. It discusses how early cellular networks used a single, high-power base station, which led to capacity issues. The core idea of cellular networks was to use multiple, lower-power base stations divided into cells to increase capacity. Key concepts include cell tessellation, handoffs between cells as users move, frequency reuse between cells to avoid interference, and network architecture components like base stations, switches, and subscriber databases.
The document provides information about cellular networks and technologies. It discusses how cellular networks use cells served by base stations to provide radio coverage over a wide area. This allows many portable transceivers like mobile phones to communicate through the network. It then describes some key components of cellular networks like base stations, mobile switching offices, and mobile devices. The document also summarizes different cellular network access technologies including AMPS, TDMA, and CDMA.
Cellular phones allow users to make calls from mobile devices by connecting to nearby transmitter towers through radio signals. The document discusses the history and evolution of cellular phones from early analog models weighing 2 pounds that offered 30 minutes of talk time to modern digital cellular networks that support data services in addition to calls. It also describes key components of cellular networks like base stations, switching centers, and databases that help cellular providers manage subscriber identities and locations to route calls and support roaming.
This document provides an overview of cellular networks. It begins with an introduction that defines a cellular network as a radio network composed of radio cells served by base stations. It then discusses how cellular networks work by allowing mobile devices to connect to the nearest base station and hand off connections between stations as the device moves between cells. Finally, it covers benefits like increased network capacity and coverage area as well as examples of cellular technologies used in modern mobile phone networks.
Comparison between gsm & cdma najmul hoque munshiNajmulHoqueMunshi
This document compares and contrasts GSM and CDMA cellular communication technologies. It begins with an introduction to cellular concepts and architectures. It then describes GSM, including that it uses TDMA and operates at 900/1800 MHz bands. The GSM architecture includes components like the BTS, BSC, HLR, VLR, and AuC. It then describes CDMA, including that it uses spread spectrum technology and references GPS for timing. The CDMA architecture spreads each user's signal over the entire bandwidth using unique codes. Finally, it lists the main differences between GSM and CDMA, such as their use of different multiple access technologies and CDMA providing better security through encryption.
1. The document discusses various topics related to mobile communication and networks including definitions of key terms like base station, control channel, and handoff.
2. It explains concepts like frequency reuse, which allows the same set of frequencies to be reused in different cells by limiting each cell's coverage area.
3. Channel assignment strategies and handoff strategies are covered, distinguishing between fixed and dynamic channel assignment and soft and hard handoffs.
4. Propagation models are summarized, including free space propagation models which predict signal strength over large transmitter-receiver distances with clear line of sight.
Time division multiplexing (TDM) is a technique used in telecommunications to transmit multiple signals over a shared medium. It involves dividing a signal into multiple time slots and assigning each slot to a different signal. TDM was initially developed for telegraphy in 1870 and is now widely used. It is used in digital networks like TDM telephone networks and synchronous digital hierarchy (SDH) networks to efficiently allocate bandwidth to multiple signals or data streams. Common examples of TDM include digitally transmitting multiple telephone calls over the same cable or interleaving left and right stereo signals in an audio file.
Early Mobile Telephone System Architecture.docxPaulMuthenya
This document discusses several key aspects of cellular network architecture and technology:
- Traditional mobile networks used one powerful transmitter, while cellular networks use many low-power transmitters divided into cells to increase capacity and allow handoffs between transmitters.
- Modern networks divide both rural and urban areas into cells using specific deployment guidelines.
- Mobile networks employ different multiple access techniques including FDMA, TDMA, and CDMA to allow multiple users to access the network simultaneously.
The document discusses the history and development of 3G mobile communication technology, specifically UMTS. It provides details on:
- The evolution from 1G to 2G mobile networks and the need for 3G to support higher data rates and multimedia services.
- The standardization of UMTS through ETSI and ITU, focusing on the two selected radio transmission technologies - UTRA FDD and TDD.
- The architecture of 3G UMTS networks, including frequency reuse techniques used to maximize capacity within limited spectrum availability.
The document provides an overview of the Global System for Mobile Communication (GSM) standard. It describes GSM as an integrated European mobile system that enables international roaming. The key objectives of GSM are outlined as well as the basic system elements, including mobile stations, base station systems, and mobile switching centers. The document also discusses concepts such as frequency reuse, cellular networks, handover, and multiple access methods used in GSM like TDMA.
STANDARD ASCENSION TOWERS GROUP was established on Dec 08 2015 as a domestic business corporation. Larry Jordan Buffalo NY. Founded 5 Stems llc a telecommunication infrastructure construction company Minority and vet owned. BS Florida Tech, MBA/PHD Colorado Tech.
STANDARD ASCENSION TOWERS GROUP was established on Dec 08 2015 as a domestic business corporation. Larry Jordan II Buffalo NY. Founded 5 Stems llc a telecommunication infrastructure construction company Minority and vet owned. BS Florida Tech, MBA/PHD Colorado Tech.
A project report_at_cell_phone_detector - copyPranoosh T
This document provides an overview of a cell phone detector circuit project. It acknowledges the contributions of faculty and staff who supported the project. It then presents an abstract that describes the key capabilities of the circuit: it can sense activated cell phones from 1.5 meters away and detect calls, SMS, and video transmission even on silent mode. The circuit uses a 0.22uF capacitor to capture RF signals and an op-amp configured as a current-to-voltage converter to detect the signals and trigger an alarm.
Examples of wireless communication systemsveeravanithaD
This document discusses different wireless communication systems including paging systems, cordless telephone systems, and cellular telephone systems. Paging systems send brief numeric, alphanumeric or voice messages to subscribers and use base stations to transmit pages over radio carriers. Cordless telephone systems allow wireless communication within a limited range of a base station connected to a landline. Cellular systems provide wireless coverage over a large geographic area using a network of base stations and a mobile switching center to handoff calls between cells and connect to the public switched telephone network.
Examples of wireless communication systems, paging systems, cordless telephone systems, cellular telephone systems,evolution of mobile phone, MSC, MTSO, PSTN, Mobile communication, wireless link, subscriber,
The document discusses different medium access control (MAC) schemes for wireless networks. It describes some key challenges with applying carrier sense multiple access with collision detection (CSMA/CD) to wireless networks due to signal strength degradation over distance and hidden and exposed terminal problems. It then covers space division multiple access (SDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), and code division multiple access (CDMA) schemes and discusses their applications to wireless multiple access and duplexing. Specific TDMA schemes like fixed and dynamic TDMA as well as Aloha and slotted Aloha are also summarized.
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Cellular technology
1. NATIONAL COLLEGE OF SCIENCE AND TECHNOLOGY
Amafel Bldg. Aguinaldo Highway Dasmariñas City, Cavite
ASSIGNMENT 1
CELLULAR TECHNOLOGY
Cauan, Sarah Krystelle P. October 03, 2011
Communications 1/ BSECE 41A1 Score:
Engr. Grace Ramones
Instructor
2. CELLULAR NETWORK
A cellular network is a radio network distributed over land areas called cells, each served
by at least one fixed-location transceiver known as a cell site or base station. When joined
together these cells provide radio coverage over a wide geographic area. This enables a
large number of portable transceivers (e.g., mobile phones, pagers, etc.) to communicate
with each other and with fixed transceivers and telephones anywhere in the network, via
base stations, even if some of the transceivers are moving through more than one cell
during transmission.
Cellular networks offer a number of advantages over alternative solutions:
increased capacity
reduced power use
larger coverage area
reduced interference from other signals
An example of a simple non-telephone cellular system is an old taxi driver's radio system
where the taxi company has several transmitters based around a city that can communicate
directly with each taxi.
CONCEPT
In a cellular radio system, a land area to be supplied with radio service is divided into
regular shaped cells, which can be hexagonal, square, circular or some other irregular
shapes, although hexagonal cells are conventional. Each of these cells is assigned multiple
frequencies (f1 - f6) which have corresponding radio base stations. The group of
frequencies can be reused in other cells, provided that the same frequencies are not reused
in adjacent neighboring cells as that would cause co-channel interference.
3. The increased capacity in a cellular network, compared with a network with a single
transmitter, comes from the fact that the same radio frequency can be reused in a different
area for a completely different transmission. If there is a single plain transmitter, only one
transmission can be used on any given frequency. Unfortunately, there is inevitably some
level of interference from the signal from the other cells which use the same frequency.
This means that, in a standard FDMA system, there must be at least a one cell gap between
cells which reuse the same frequency.
In the simple case of the taxi company, each radio had a manually operated channel
selector knob to tune to different frequencies. As the drivers moved around, they would
change from channel to channel. The drivers knew which frequency covered approximately
what area. When they did not receive a signal from the transmitter, they would try other
channels until they found one that worked. The taxi drivers would only speak one at a time,
when invited by the base station operator (in a sense TDMA).
Directional antennas
Although the original 2-way-radio cell towers were at the centers of the cells and were
omni-directional, a cellular map can be redrawn with the cellular telephone towers located
at the corners of the hexagons where three cells converge. Each tower has three sets of
directional antennas aimed in three different directions with 120 degrees for each cell
(totaling 360 degrees) and receiving/transmitting into three different cells at different
frequencies. This provides a minimum of three channels (from three towers) for each cell.
The numbers in the illustration are channel numbers, which repeat every 3 cells. Large
cells can be subdivided into smaller cells for high volume areas
Broadcast messages and paging
Practically every cellular system has some kind of broadcast mechanism. This can be used
directly for distributing information to multiple mobiles, commonly, for example in mobile
telephony systems, the most important use of broadcast information is to set up channels
for one to one communication between the mobile transceiver and the base station. This is
called paging.
The details of the process of paging vary somewhat from network to network, but normally
we know a limited number of cells where the phone is located (this group of cells is called a
Location Area in the GSM or UMTS system, or Routing Area if a data packet session is
involved). Paging takes place by sending the broadcast message to all of those cells. Paging
messages can be used for information transfer. This happens in pagers, in CDMA systems
for sending SMS messages, and in the UMTS system where it allows for low downlink
latency in packet-based connections.
Movement from cell to cell and handover
4. In a primitive taxi system, when the taxi moved away from a first tower and closer to a
second tower, the taxi driver manually switched from one frequency to another as needed.
If a communication was interrupted due to a loss of a signal, the taxi driver asked the base
station operator to repeat the message on a different frequency.
In a cellular system, as the distributed mobile transceivers move from cell to cell during an
ongoing continuous communication, switching from one cell frequency to a different cell
frequency is done electronically without interruption and without a base station operator
or manual switching. This is called the handover or handoff. Typically, a new channel is
automatically selected for the mobile unit on the new base station which will serve it. The
mobile unit then automatically switches from the current channel to the new channel and
communication continues.
The exact details of the mobile system's move from one base station to the other varies
considerably from system to system (see the example below for how a mobile phone
network manages handover).
Example of a cellular network: the mobile phone network
The most common example of a cellular network is a mobile phone (cell phone) network. A
mobile phone is a portable telephone which receives or makes calls through a cell site
(base station), or transmitting tower. Radio waves are used to transfer signals to and from
the cell phone.
Modern mobile phone networks use cells because radio frequencies are a limited, shared
resource. Cell-sites and handsets change frequency under computer control and use low
power transmitters so that a limited number of radio frequencies can be simultaneously
used by many callers with less interference.
A cellular network is used by the mobile phone operator to achieve both coverage and
capacity for their subscribers. Large geographic areas are split into smaller cells to avoid
line-of-sight signal loss and to support a large number of active phones in that area. All of
the cell sites are connected to telephone exchanges (or switches) , which in turn connect to
the public telephone network.
In cities, each cell site may have a range of up to approximately ½ mile, while in rural areas,
the range could be as much as 5 miles. It is possible that in clear open areas, a user may
receive signals from a cell site 25 miles away.
Since almost all mobile phones use cellular technology, including GSM, CDMA, and AMPS
(analog), the term "cell phone" is in some regions, notably the US, used interchangeably
with "mobile phone". However, satellite phones are mobile phones that do not
communicate directly with a ground-based cellular tower, but may do so indirectly by way
of a satellite.
5. There are a number of different digital cellular technologies, including: Global System for
Mobile Communications (GSM), General Packet Radio Service (GPRS), Code Division
Multiple Access (CDMA), Evolution-Data Optimized (EV-DO), Enhanced Data Rates for GSM
Evolution (EDGE), 3GSM, Digital Enhanced Cordless Telecommunications (DECT), Digital
AMPS (IS-136/TDMA), and Integrated Digital Enhanced Network (iDEN).
Structure of the mobile phone cellular network
A simple view of the cellular mobile-radio network consists of the following:
A network of Radio base stations forming the Base station subsystem.
The core circuit switched network for handling voice calls and text
A packet switched network for handling mobile data
The Public switched telephone network to connect subscribers to the wider
telephony network
This network is the foundation of the GSM system network. There are many functions that
are performed by this network in order to make sure customers get the desired service
including mobility management, registration, call set up, and handover.
Any phone connects to the network via an RBS (Radio Base Station) at a corner of the
corresponding cell which in turn connects to the Mobile switching center (MSC). The MSC
provides a connection to the public switched telephone network (PSTN). The link from a
phone to the RBS is called an uplink while the other way is termed downlink.
Radio channels effectively use the transmission medium through the use of the following
multiplexing schemes: frequency division multiplex (FDM), time division multiplex (TDM),
code division multiplex (CDM), and space division multiplex (SDM). Corresponding to
these multiplexing schemes are the following access techniques: frequency division
multiple access (FDMA), time division multiple access (TDMA), code division multiple
access (CDMA), and space division multiple access (SDMA).
Cellular handover in mobile phone networks
As the phone user moves from one cell area to another cell whilst a call is in progress, the
mobile station will search for a new channel to attach to in order not to drop the call. Once
a new channel is found, the network will command the mobile unit to switch to the new
channel and at the same time switch the call onto the new channel.
With CDMA, multiple CDMA handsets share a specific radio channel. The signals are
separated by using a pseudonoise code (PN code) specific to each phone. As the user moves
from one cell to another, the handset sets up radio links with multiple cell sites (or sectors
of the same site) simultaneously. This is known as "soft handoff" because, unlike with
traditional cellular technology, there is no one defined point where the phone switches to
the new cell.
6. In IS-95 inter-frequency handovers and older analog systems such as NMT it will typically
be impossible to test the target channel directly while communicating. In this case other
techniques have to be used such as pilot beacons in IS-95. This means that there is almost
always a brief break in the communication while searching for the new channel followed by
the risk of an unexpected return to the old channel.
If there is no ongoing communication or the communication can be interrupted, it is
possible for the mobile unit to spontaneously move from one cell to another and then
notify the base station with the strongest signal.
Cellular frequency choice in mobile phone networks
The effect of frequency on cell coverage means that different frequencies serve better for
different uses. Low frequencies, such as 450 MHz NMT, serve very well for countryside
coverage. GSM 900 (900 MHz) is a suitable solution for light urban coverage. GSM 1800
(1.8 GHz) starts to be limited by structural walls. UMTS, at 2.1 GHz is quite similar in
coverage to GSM 1800.
Higher frequencies are a disadvantage when it comes to coverage, but it is a decided
advantage when it comes to capacity. Pico cells, covering e.g. one floor of a building,
become possible, and the same frequency can be used for cells which are practically
neighbours.
Cell service area may also vary due to interference from transmitting systems, both within
and around that cell. This is true especially in CDMA based systems. The receiver requires a
certain signal-to-noise ratio. As the receiver moves away from the transmitter, the power
transmitted is reduced. As the interference (noise) rises above the received power from the
transmitter, and the power of the transmitter cannot be increased any more, the signal
becomes corrupted and eventually unusable. In CDMA-based systems, the effect of
interference from other mobile transmitters in the same cell on coverage area is very
marked and has a special name, cell breathing.
One can see examples of cell coverage by studying some of the coverage maps provided by
real operators on their web sites. In certain cases they may mark the site of the transmitter,
in others it can be calculated by working out the point of strongest coverage.
Coverage comparison of different frequencies
7. CELL SIGNAL ENCODING
To distinguish signals from several different transmitters, frequency division multiple
access (FDMA) and code division multiple access (CDMA) were developed.
With FDMA, the transmitting and receiving frequencies used in each cell are different from
the frequencies used in each neighbouring cell. In a simple taxi system, the taxi driver
manually tuned to a frequency of a chosen cell to obtain a strong signal and to avoid
interference from signals from other cells.
The principle of CDMA is more complex, but achieves the same result; the distributed
transceivers can select one cell and listen to it.
Other available methods of multiplexing such as polarization division multiple access
(PDMA) and time division multiple access (TDMA) cannot be used to separate signals from
one cell to the next since the effects of both vary with position and this would make signal
separation practically impossible. Time division multiple access, however, is used in
combination with either FDMA or CDMA in a number of systems to give multiple channels
within the coverage area of a single cell.
8. MULTIPLE ACCESS
Multiple Access refers on how the subscriber are allocated to the assigned frequency
spectrum.
Frequency reuse
The increased capacity in a cellular network, comparing to a network with a single
transmitter, comes from the fact that the same radio frequency can be reused in a different
area for a completely different transmission. If there is a single plain transmitter, only one
transmission can be used on any given frequency. Unfortunately, there is inevitably some
level of interference from the signal from the other cells which use the same frequency.
This means that, in a standard FDMA system, there must be at least a one cell gap between
cells which reuse the same frequency.
The frequency reuse factor is the rate at which the same frequency can be used in the
network. It is 1/n where n is the number of cells which cannot use a frequency for
transmission.
Code division multiple access based systems use a wider frequency band to achieve the
same rate of transmission as FDMA, but this is compensated for by the ability to use a
frequency reuse factor of 1. In other words, every cell uses the same frequency and the
different systems are separated by codes rather than frequencies.
Depending on the size of the city, a taxi system may not have any frequency reuse in its
own city, but certainly in other nearby cities, the same frequency can be used. In a big city,
on the other hand, frequency reuse could certainly be in use.
Frequency Division Multiple Access or FDMA is a channel access method used in multiple-
access protocols as a channelization protocol. FDMA gives users an individual allocation of
one or several frequency bands, or channels. It is particularly commonplace in satellite
communication. FDMA, like other Multiple Access systems, coordinates access between
multiple users. Alternatives include TDMA, CDMA, or SDMA. These protocols are utilized
differently, at different levels of the theoreticalOSI model.
Disadvantage: Crosstalk may cause interference among frequencies and disrupt the
transmission.
In FDMA all users share the satellite simultaneously but each user transmits at single
frequency.
FDMA can be used with both analog and digital signal.
9. FDMA requires high-performing filters in the radio hardware, in contrast
to TDMA and CDMA.
FDMA is not vulnerable to the timing problems that TDMA has. Since a predetermined
frequency band is available for the entire period of communication, stream data (a
continuous flow of data that may not be packetized) can easily be used with FDMA.
Due to the frequency filtering, FDMA is not sensitive to near-far problem which is
pronounced for CDMA.
Each user transmits and receives at different frequencies as each user gets a unique
frequency slot
FDMA is distinct from frequency division duplexing (FDD). While FDMA allows multiple
users simultaneous access to a transmission system, FDD refers to how the radio channel is
shared between the uplink and downlink (for instance, the traffic going back and forth
between a mobile-phone and a mobile phone base station). Frequency-division
multiplexing (FDM) is also distinct from FDMA. FDM is a physical layer technique that
combines and transmits low-bandwidth channels through a high-bandwidth channel.
FDMA, on the other hand, is an access method in the data link layer.
FDMA also supports demand assignment in addition to fixed assignment. Demand
assignment allows all users apparently continuous access of the radio spectrum by
assigning carrier frequencies on a temporary basis using a statistical assignment process.
The first FDMA demand-assignment system for satellite was developed byCOMSAT for use
on the Intelsat series IVA and V satellites.
There are two main techniques:
Multi-channel per-carrier (MCPC)
Single-channel per-carrier (SCPC)
10. Time division multiple access (TDMA) is a channel access method for shared medium
networks. It allows several users to share the same frequency channel by dividing the
signal into different time slots. The users transmit in rapid succession, one after the other,
each using its own time slot. This allows multiple stations to share the same transmission
medium (e.g. radio frequency channel) while using only a part of its channel capacity.
TDMA is used in the digital 2G cellular systems such as Global System for Mobile
Communications (GSM), IS-136, Personal Digital Cellular (PDC) and iDEN, and in the Digital
Enhanced Cordless Telecommunications (DECT) standard for portable phones. It is also
used extensively in satellite systems, combat-net radio systems, and PON networks for
upstream traffic from premises to the operator. For usage of Dynamic TDMA packet mode
communication.
TDMA is a type of Time-division multiplexing, with the special point that instead of having
one transmitter connected to one receiver, there are multiple transmitters. In the case of
the uplink from a mobile phone to abase station this becomes particularly difficult because
the mobile phone can move around and vary the timing advance required to make its
transmission match the gap in transmission from its peers.
TDMA in 2G systems
Most 2G cellular systems, with the notable exception of IS-95, are based on TDMA. GSM, D-
AMPS, PDC, iDEN, and PHS are examples of TDMA cellular systems. GSM combines TDMA
with Frequency Hopping and wideband transmission to minimize common types of
interference.
In the GSM system, the synchronization of the mobile phones is achieved by sending timing
advance commands from the base station which instructs the mobile phone to transmit
earlier and by how much. This compensates for the propagation delay resulting from the
light speed velocity of radio waves. The mobile phone is not allowed to transmit for its
entire time slot, but there is a guard interval at the end of each time slot. As the
transmission moves into the guard period, the mobile network adjusts the timing advance
to synchronize the transmission.
Initial synchronization of a phone requires even more care. Before a mobile transmits there
is no way to actually know the offset required. For this reason, an entire time slot has to be
dedicated to mobiles attempting to contact the network (known as the RACH in GSM). The
mobile attempts to broadcast at the beginning of the time slot, as received from the
network. If the mobile is located next to the base station, there will be no time delay and
this will succeed. If, however, the mobile phone is at just less than 35 km from the base
station, the time delay will mean the mobile's broadcast arrives at the very end of the time
slot. In that case, the mobile will be instructed to broadcast its messages starting nearly a
whole time slot earlier than would be expected otherwise. Finally, if the mobile is beyond
the 35 km cell range in GSM, then the RACH will arrive in a neighbouring time slot and be
11. ignored. It is this feature, rather than limitations of power, that limits the range of a GSM
cell to 35 km when no special extension techniques are used. By changing the
synchronization between the uplink and downlink at the base station, however, this
limitation can be overcome.
Code division multiple access (CDMA) is a channel access method used by various radio
communication technologies. It should not be confused with the mobile phone
standards called cdmaOne, CDMA2000 (the 3G evolution of cdmaOne) and WCDMA (the 3G
standard used by GSM carriers), which are often referred to as simply CDMA, and use
CDMA as an underlying channel access method.
One of the basic concepts in data communication is the idea of allowing several
transmitters to send information simultaneously over a single communication channel.
This allows several users to share a band of frequencies (see bandwidth). This concept is
called multiple access. CDMA employs spread-spectrum technology and a special coding
scheme (where each transmitter is assigned a code) to allow multiple users to be
multiplexed over the same physical channel. By contrast, time division multiple
access (TDMA) divides access bytime, while frequency-division multiple access (FDMA)
divides it by frequency. CDMA is a form of spread-spectrum signalling, since the modulated
coded signal has a much higher data bandwidth than the data being communicated.
An analogy to the problem of multiple access is a room (channel) in which people wish to
talk to each other simultaneously. To avoid confusion, people could take turns speaking
(time division), speak at different pitches (frequency division), or speak in different
languages (code division). CDMA is analogous to the last example where people speaking
the same language can understand each other, but other languages are perceived
as noise and rejected. Similarly, in radio CDMA, each group of users is given a shared code.
Many codes occupy the same channel, but only users associated with a particular code can
communicate. The technology of code division multiple access channels has long been
known. In the USSR, the first work devoted to this subject was published in 1935 by
professor D.V. Aggeev in the "CDMA". It was shown that through the use of linear methods,
there are three types of signal separation: frequency, time and compensatory. The
technology of CDMA was used in 1957, when the young military radio engineer Leonid
Kupriyanovich in Moscow, made an experimental model of a wearable automatic mobile
phone, called LK-1 by him, with a base station. LK-1 has a weight of 3 kg, 20-30 km
operating distance, and 20-30 hours of battery life ("Nauka i zhizn", 8, 1957, p. 49, "Yuniy
technik", 7, 1957, p. 43-44). The base station, as described by the author, could serve
several customers. In 1958, Kupriyanovich made the new experimental "pocket" model of
mobile phone. This phone weighs 0,5 kg. To serve more customers, Kupriyanovich
proposed the device, named by him as correllator. ("Nauka i zhizn", 10, 1958, p.66,
"Technika-molodezhi", 2, 1959, 18-19) In 1958, the USSR also started the development of
the "Altay" national civil mobile phone service for cars, based on the Soviet MRT-1327
standard. The main developers of the Altay system were VNIIS (Voronezh Science Research
12. Institute of Communications)and GSPI (State Specialized Project Institute). In 1963 this
service started in Moscow and in 1970 Altay service was used in 30 USSR cities.
Space-Division Multiple Access (SDMA) is a channel access method based on creating
parallel spatial pipes next to higher capacity pipes through spatial multiplexing and/or
diversity, by which it is able to offer superior performance in radio multiple access
communication systems. In traditional mobile cellular network systems, the base
station has no information on the position of the mobile units within the cell and radiates
the signal in all directions within the cell in order to provide radio coverage. This results in
wasting power on transmissions when there are no mobile units to reach, in addition to
causing interference for adjacent cells using the same frequency, so calledco-channel cells.
Likewise, in reception, the antenna receives signals coming from all directions including
noise and interference signals. By using smart antenna technology and differing spatial
locations of mobile units within the cell, space-division multiple access techniques offer
attractive performance enhancements. The radiation pattern of the base station, both in
transmission and reception, is adapted to each user to obtain highest gain in the direction
of that user. This is often done using phased arraytechniques.
In GSM cellular networks, the base station is aware of the mobile phone's position by use of
a technique called "timing advance" (TA). The Base Transceiver Station (BTS) can
determine how distant the Mobile Station (MS) is by interpreting the reported TA. This
information, along with other parameters, can then be used to power down the BTS or MS,
if a power control feature is implemented in the network. The power control in either BTS
or MS is implemented in most modern networks, especially on the MS, as this ensures a
better battery life for the MS and thus a better user experience (in that the need to charge
the battery becomes less frequent). This is why it may actually be safer to have a BTS close
to you as your MS will be powered down as much as possible. For example, there is more
power being transmitted from the MS than what you would receive from the BTS even if
you are 6 m away from a mast. However, this estimation might not consider all the MS's
that a particular BTS is supporting with EM radiation at any given time.
13. HISTORY
Radiophones have a long and varied history going back to Reginald Fessenden's invention
and shore-to-ship demonstration of radio telephony, through the Second World War with
military use of radio telephony links and civil services in the 1950s.
The first mobile telephone call made from a car occurred in St. Louis, Missouri, USA on June
17, 1946, using the Bell System's Mobile Telephone Service. The equipment weighed 80
pounds (36 kg), and the AT&T service, basically a massive party line, cost US$30 per month
(equal to $337.33 today) plus 30–40 cents per local call, equal to $3.37 to $4.5 today.
In 1956, the world’s first partly automatic car phone system, Mobile System A (MTA), was
launched in Sweden. MTA phones were composed of vacuum tubes and relays, and had a
weight of 40 kg. In 1962, a more modern version called Mobile System B (MTB) was
launched, which was a push-button telephone, and which used transistors to enhance the
telephone’s calling capacity and improve its operational reliability, thereby reducing the
weight of the apparatus to 10 kg. In 1971, the MTD version was launched, opening for
several different brands of equipment and gaining commercial success.
Martin Cooper, a Motorola researcher and executive is considered to be the inventor of the
first practical mobile phone for handheld use in a non-vehicle setting, after a long race
against Bell Labs for the first portable mobile phone. Using a modern, if somewhat heavy
portable handset, Cooper made the first call on a handheld mobile phone on April 3, 1973
to his rival, Dr. Joel S. Engel of Bell Labs.
The first commercially automated cellular network (the 1G) was launched in Japan by NTT
in 1979, initially in the metropolitan area of Tokyo. Within five years, the NTT network had
14. been expanded to cover the whole population of Japan and became the first nationwide 1G
network. In 1981, this was followed by the simultaneous launch of the Nordic Mobile
Telephone (NMT) system in Denmark, Finland, Norway and Sweden. NMT was the first
mobile phone network featuring international roaming. The first 1G network launched in
the USA was Chicago-based Ameritech in 1983 using the Motorola DynaTAC mobile phone.
Several countries then followed in the early-to-mid 1980s including the UK, Mexico and
Canada.
The first "modern" network technology on digital 2G (second generation) cellular
technology was launched by Radiolinja (now part of Elisa Group) in 1991 in Finland on the
GSM standard, which also marked the introduction of competition in mobile telecoms when
Radiolinja challenged incumbent Telecom Finland (now part of TeliaSonera) who ran a 1G
NMT network.
In 2001, the launch of 3G (Third Generation) was again in Japan by NTT DoCoMo on the
WCDMA standard.[
One of the newest 3G technologies to be implemented is High-Speed Downlink Packet
Access (HSDPA). It is an enhanced 3G (third generation) mobile telephony communications
protocol in the high-speed packet access (HSPA) family, also coined 3.5G, 3G+ or turbo 3G,
which allows networks based on Universal Mobile Telecommunications System (UMTS) to
have higher data transfer speeds and capacity.
A mobile phone allows calls into the public switched telephone system over a radio link.
Early mobile phones were usually bulky and permanently installed in vehicles; they
provided limited service because only a few frequencies were available for a geographic
area. Modern cellular "cell" phones or hand phones make use of the cellular network
concept, where frequencies are re-used repeatedly within a city area, allowing many more
users to share access to the radio bandwidth. A mobile phone allows calls to be placed over
a wide geographic area; generally the user is a subscriber to the phone service and does not
own the base station. By contrast, a cordless telephone is used only within the range of a
single, private base station.
A mobile phone can make and receive telephone calls to and from the public telephone
network which includes other mobiles and fixed-line phones across the world. It does this
by connecting to a cellular network provided by a mobile network operator.
In addition to telephony, modern mobile phones also support a wide variety of other
services such as text messaging, MMS, email, Internet access, short-range wireless
communications (infrared, Bluetooth), business applications, gaming and photography.
Mobile phones that offer these more general computing capabilities are referred to as
smartphones.
The first hand-held mobile phone was demonstrated by Dr Martin Cooper of Motorola in
1973, using a handset weighing 2 1/2 lbs (about 1 kg) In 1983, the DynaTAC 8000x was
15. the first to be commercially available. In the twenty years from 1990 to 2010, worldwide
mobile phone subscriptions grew from 12.4 million to over 4.6 billion, penetrating the
developing economies and reaching the bottom of the economic pyramid.
1G
1G (or 1-G) refers to the first-generation of wireless telephone technology, mobile
telecommunications. These are the analog telecommunications standards that were
introduced in the 1980s and continued until being replaced by 2G digital
telecommunications. The main difference between two succeeding mobile telephone
systems, 1G and 2G, is that the radio signals that 1G networks use are analog, while 2G
networks are digital.
Although both systems use digital signaling to connect the radio towers (which listen to the
handsets) to the rest of the telephone system, the voice itself during a call is encoded to
digital signals in 2G whereas 1G is only modulated to higher frequency, typically 150 MHz
and up.
One such standard is NMT (Nordic Mobile Telephone), used in Nordic countries,
Switzerland, Netherlands, Eastern Europe and Russia. Others include AMPS (Advanced
Mobile Phone System) used in the North America and Australia,[1] TACS (Total Access
Communications System) in the United Kingdom, C-450 in West Germany, Portugal and
South Africa, Radiocom 2000[2] in France, and RTMI in Italy. In Japan there were multiple
systems. Three standards, TZ-801, TZ-802, and TZ-803 were developed by NTT, while a
competing system operated by DDI used the JTACS (Japan Total Access Communications
System) standard.
Antecedent to 1G technology is the mobile radio telephone, or 0G.
16. 2G
2G (or 2-G) is short for second-generation wireless telephone technology. Second
generation 2G cellular telecom networks were commercially launched on the GSM standard
in Finland by Radiolinja (now part of Elisa Oyj) in 1991.[1] Three primary benefits of 2G
networks over their predecessors were that phone conversations were digitally encrypted;
2G systems were significantly more efficient on the spectrum allowing for far greater
mobile phone penetration levels; and 2G introduced data services for mobile, starting with
SMS text messages.
After 2G was launched, the previous mobile telephone systems were retrospectively
dubbed 1G. While radio signals on 1G networks are analog, radio signals on 2G networks
are digital. Both systems use digital signaling to connect the radio towers (which listen to
the handsets) to the rest of the telephone system.
2G has been superseded by newer technologies such as 2.5G, 2.75G, 3G, and 4G; however,
2G networks are still used in many parts of the world.
3G
3G or 3rd generation mobile telecommunications is a generation of standards for mobile
phones and mobile telecommunication services fulfilling the International Mobile
Telecommunications-2000 (IMT-2000) specifications by the International
Telecommunication Union.[1] Application services include wide-area wireless voice
telephone, mobile Internet access, video calls and mobile TV, all in a mobile environment.
To meet the IMT-2000 standards, a system is required to provide peak data rates of at least
200 kbit/s. Recent 3G releases, often denoted 3.5G and 3.75G, also provide mobile
broadband access of several Mbit/s to smartphones and mobile modems in laptop
computers.
17. The following standards are typically branded 3G:
the UMTS system, first offered in 2001, standardized by 3GPP, used primarily in
Europe, Japan, China (however with a different radio interface) and other regions
predominated by GSM 2G system infrastructure. The cell phones are typically UMTS
and GSM hybrids. Several radio interfaces are offered, sharing the same
infrastructure:
o The original and most widespread radio interface is called W-CDMA.
o The TD-SCDMA radio interface was commercialised in 2009 and is only
offered in China.
o The latest UMTS release, HSPA+, can provide peak data rates up to 56 Mbit/s
in the downlink in theory (28 Mbit/s in existing services) and 22 Mbit/s in
the uplink.
the CDMA2000 system, first offered in 2002, standardized by 3GPP2, used especially
in North America and South Korea, sharing infrastructure with the IS-95 2G
standard. The cell phones are typically CDMA2000 and IS-95 hybrids. The latest
release EVDO Rev B offers peak rates of 14.7 Mbit/s downstream.
The above systems and radio interfaces are based on kindred spread spectrum radio
transmission technology. While the GSM EDGE standard ("2.9G"), DECT cordless phones
and Mobile WiMAX standards formally also fulfill the IMT-2000 requirements and are
approved as 3G standards by ITU, these are typically not branded 3G, and are based on
completely different technologies.
A new generation of cellular standards has appeared approximately every tenth year since
1G systems were introduced in 1981/1982. Each generation is characterized by new
frequency bands, higher data rates and non backwards compatible transmission
technology. The first release of the 3GPP Long Term Evolution (LTE) standard does not
completely fulfill the ITU 4G requirements called IMT-Advanced. First release LTE is not
backwards compatible with 3G, but is a pre-4G or 3.9G technology, however sometimes
branded "4G" by the service providers. Its evolution LTE Advanced is a 4G technology.
WiMAX is another technology verging on or marketed as 4G.
4G
In telecommunications, 4G is the fourth generation of cellular wireless standards. It is a
successor to the 3G and 2G families of standards. In 2009, the ITU-R organization specified
the IMT-Advanced (International Mobile Telecommunications Advanced) requirements for
4G standards, setting peak speed requirements for 4G service at 100 Mbit/s for high
18. mobility communication (such as from trains and cars) and 1 Gbit/s for low mobility
communication (such as pedestrians and stationary users).[1]
A 4G system is expected to provide a comprehensive and secure all-IP based mobile
broadband solution to laptop computer wireless modems, smartphones, and other mobile
devices. Facilities such as ultra-broadband Internet access, IP telephony, gaming services,
and streamed multimedia may be provided to users.
4G technologies such as mobile WiMAX and first-release Long term evolution (LTE) have
been on the market since 2006[2] and 2009[3][4][5] respectively. The ITU announced in
December 2010 that WiMax, LTE, and HSPA+ are 4G technologies.[6]
IMT-Advanced compliant versions of the above two standards are under development and
called “LTE Advanced” and “WirelessMAN-Advanced” respectively. ITU has decided that
“LTE Advanced” and “WirelessMAN-Advanced” should be accorded the official designation
of IMT-Advanced. On December 6, 2010, ITU announced that current versions of LTE,
WiMax and other evolved 3G technologies that do not fulfill "IMT-Advanced" requirements
could be considered "4G", provided they represent forerunners to IMT-Advanced and "a
substantial level of improvement in performance and capabilities with respect to the initial
third generation systems now deployed.