It is description about trunking theory that is used to develop trunked system that can allocate a limited number of channels to a large number of users.
Diversity Techniques in Wireless CommunicationSahar Foroughi
This document discusses diversity techniques for wireless communication, including cooperative diversity. It begins by introducing wireless systems and the impairments they face like fading. It then covers various diversity techniques like space, frequency, and time diversity that provide multiple transmission paths to reduce fading. Cooperative diversity is described as allowing single-antenna devices to achieve MIMO-like benefits by sharing antennas. The document outlines cooperative transmission protocols and challenges at different network layers in implementing cooperation. In conclusion, diversity techniques improve performance by providing multiple signal replicas to overcome fading, while cooperation enables reliability and throughput gains with challenges to address across protocol layers.
This document discusses spread spectrum techniques. It begins with a brief history, noting that spread spectrum was invented in the 1940s as a way to prevent enemy detection of radio signals, and gained popularity due to its resistance to jamming. The document then provides an overview of spread spectrum systems, classifications (direct sequence, frequency hopping, time hopping), applications (resistance to interference and jamming, security, CDMA), and comparisons of techniques and their advantages/disadvantages.
IS-95 CDMA is an air interface standard that uses code division multiple access (CDMA). It employs various techniques to improve system capacity and performance, including bandwidth recycling, power control, soft handoffs, diversity combining, and variable rate vocoding. Key aspects of IS-95 include the use of quadrature phase shift keying modulation at a 1.2288 Mcps chip rate, forward error correction coding, and multiple logical channels (pilot, sync, paging, traffic) defined using orthogonal Walsh codes.
The document discusses various propagation mechanisms that affect radio signals, including reflection, diffraction, scattering, and their effects on signal strength over distance. It also covers propagation models like free space path loss, two-ray ground reflection model, and log-distance path loss for estimating average received signal power at a given distance. Fresnel zones and knife-edge diffraction are explained as factors in signal propagation around obstructions. Log-normal shadowing is described as a statistical model to account for variations from the average path loss.
The key characteristic of a cellular network is the ability to reuse frequencies to increase both coverage and capacity. Cellular networks divide geographic areas into smaller cells and assign different frequency groups to neighboring cells to minimize interference and allow for frequency reuse. This allows the same frequencies to be reused in different cells separated by a sufficient distance.
MIMO uses multiple antennas at both the transmitter and receiver to improve wireless communication performance. It takes advantage of multipath propagation by using spatial diversity or spatial multiplexing. With spatial diversity, the same information is transmitted from different antennas to improve reliability and coverage. With spatial multiplexing, different data streams are transmitted from different antennas to increase data rates. MIMO can significantly increase capacity, quality, and spectral efficiency compared to single-input systems. It is used in technologies like 3G, 4G, and will be important for 5G networks.
The document discusses small-scale fading and multipath propagation in wireless communications. It describes how multipath propagation leads to fading effects as multiple versions of the transmitted signal combine at the receiver. Channel sounding techniques are used to measure the power delay profile and characterize the time dispersion parameters of mobile radio channels, including mean excess delay, RMS delay spread, and maximum excess delay. Direct pulse systems, spread spectrum correlators, and frequency domain analysis are channel sounding methods discussed.
Diversity Techniques in Wireless CommunicationSahar Foroughi
This document discusses diversity techniques for wireless communication, including cooperative diversity. It begins by introducing wireless systems and the impairments they face like fading. It then covers various diversity techniques like space, frequency, and time diversity that provide multiple transmission paths to reduce fading. Cooperative diversity is described as allowing single-antenna devices to achieve MIMO-like benefits by sharing antennas. The document outlines cooperative transmission protocols and challenges at different network layers in implementing cooperation. In conclusion, diversity techniques improve performance by providing multiple signal replicas to overcome fading, while cooperation enables reliability and throughput gains with challenges to address across protocol layers.
This document discusses spread spectrum techniques. It begins with a brief history, noting that spread spectrum was invented in the 1940s as a way to prevent enemy detection of radio signals, and gained popularity due to its resistance to jamming. The document then provides an overview of spread spectrum systems, classifications (direct sequence, frequency hopping, time hopping), applications (resistance to interference and jamming, security, CDMA), and comparisons of techniques and their advantages/disadvantages.
IS-95 CDMA is an air interface standard that uses code division multiple access (CDMA). It employs various techniques to improve system capacity and performance, including bandwidth recycling, power control, soft handoffs, diversity combining, and variable rate vocoding. Key aspects of IS-95 include the use of quadrature phase shift keying modulation at a 1.2288 Mcps chip rate, forward error correction coding, and multiple logical channels (pilot, sync, paging, traffic) defined using orthogonal Walsh codes.
The document discusses various propagation mechanisms that affect radio signals, including reflection, diffraction, scattering, and their effects on signal strength over distance. It also covers propagation models like free space path loss, two-ray ground reflection model, and log-distance path loss for estimating average received signal power at a given distance. Fresnel zones and knife-edge diffraction are explained as factors in signal propagation around obstructions. Log-normal shadowing is described as a statistical model to account for variations from the average path loss.
The key characteristic of a cellular network is the ability to reuse frequencies to increase both coverage and capacity. Cellular networks divide geographic areas into smaller cells and assign different frequency groups to neighboring cells to minimize interference and allow for frequency reuse. This allows the same frequencies to be reused in different cells separated by a sufficient distance.
MIMO uses multiple antennas at both the transmitter and receiver to improve wireless communication performance. It takes advantage of multipath propagation by using spatial diversity or spatial multiplexing. With spatial diversity, the same information is transmitted from different antennas to improve reliability and coverage. With spatial multiplexing, different data streams are transmitted from different antennas to increase data rates. MIMO can significantly increase capacity, quality, and spectral efficiency compared to single-input systems. It is used in technologies like 3G, 4G, and will be important for 5G networks.
The document discusses small-scale fading and multipath propagation in wireless communications. It describes how multipath propagation leads to fading effects as multiple versions of the transmitted signal combine at the receiver. Channel sounding techniques are used to measure the power delay profile and characterize the time dispersion parameters of mobile radio channels, including mean excess delay, RMS delay spread, and maximum excess delay. Direct pulse systems, spread spectrum correlators, and frequency domain analysis are channel sounding methods discussed.
Mobile computing unit2,SDMA,FDMA,CDMA,TDMA Space Division Multi Access,Frequ...Pallepati Vasavi
This document discusses various terminology related to the MAC sublayer, including:
1. The station model consisting of independent stations that generate frames for transmission.
2. The single channel assumption where a single channel is available for all communication.
3. The collision assumption where if two frames are transmitted simultaneously they will overlap and be garbled.
It then covers concepts such as carrier sensing, hidden and exposed terminals, and near and far terminals that create challenges for wireless networks. Finally, it introduces various multiple access methods including SDMA, FDMA, TDMA, and CDMA.
This document discusses various diversity techniques used in wireless communications to combat fading. It describes types of diversity including time, frequency, multiuser, and space diversity. It also outlines combining techniques such as selection combining, maximal ratio combining and equal gain combining that are used to improve the signal by combining signals from multiple diversity branches. The document concludes by discussing multiple input multiple output (MIMO) systems and orthogonal frequency division multiple access (OFDMA) schemes that exploit diversity and multiuser diversity.
The document provides an overview of the public switched telephone network (PSTN). It discusses that the PSTN is the interconnected telephone system that uses copper wires to make circuit-switched calls. It then covers the evolution of the PSTN from its invention in 1876 to present digital switches, the use of bandwidth allocation and numbering schemes, and call setup which involves signaling and switching systems to route calls.
OFDM is a digital modulation technique that splits a data stream into several narrowband channels at different frequencies. This reduces interference and crosstalk compared to traditional single-carrier modulation. Fading effects are also reduced since the loss of a subset of bits can be recovered with coding. Windowing and cyclic prefixes are used to reduce interference between channels and intersymbol interference. The cyclic prefix provides a guard interval and allows transforming the linear convolution of the channel to circular convolution in the frequency domain, simplifying processing. While the cyclic prefix reduces data capacity, it provides robustness against multipath effects.
Introduction To Wireless Fading ChannelsNitin Jain
The document summarizes key concepts related to wireless fading channels, including:
1. Multipath fading causes fluctuations in signal strength over small physical distances due to constructive and destructive interference from multiple signal paths.
2. Rayleigh fading occurs when there is no line-of-sight path between transmitter and receiver, resulting in fast, large fluctuations in signal strength over small physical distances.
3. Doppler spread and coherence time describe how quickly the wireless channel varies over time due to mobility, with fast fading occurring if the channel changes significantly within a symbol period.
This document discusses key concepts in telecommunications network planning and traffic engineering. It covers:
- Types of random processes used to model network usage patterns like call arrival rates and durations.
- How traffic engineering balances factors like grade of service, resources, blocking vs. delay systems based on traffic amounts.
- Key metrics like erlangs, traffic intensity, busy hour, traffic volume that are used to quantify network usage and demand.
- Concepts like grade of service, blocking probability, and how they measure network performance during busy periods.
This document provides an overview of signal processing techniques used in wireless systems, including diversity and equalization. It discusses various diversity techniques like spatial, temporal, frequency, angular, and polarization diversity as well as macro and micro diversity. It also explains different types of combining diversity including selection, maximal ratio combining, and equal gain combining. The document concludes with sections on linear equalizers such as zero forcing and MMSE, as well as nonlinear equalizers using algorithms like LMS and RLS.
This document discusses mobile radio propagation and propagation models. It begins by introducing how radio channels are random and time-varying. It then covers the free space propagation model and how received power decreases with distance. Reflection, diffraction, and scattering are described as the main propagation mechanisms. The two-ray ground reflection model is presented to model propagation over large distances. Diffraction is explained using the knife-edge diffraction model. Fresnel zones and diffraction gain are also defined.
- The document discusses wireless channel propagation and fading. It covers topics like large-scale fading (path loss and shadowing), small-scale fading (time-selective and frequency-selective fading), and statistical characterization of fading channels.
- Small-scale fading is caused by multipath propagation and results in rapid fluctuations in the strength of the received signal over short periods of time or travel distances. It can be time-selective or frequency-selective depending on delay spread and Doppler spread.
- Common distributions for modeling fading amplitudes are Rayleigh for non-line-of-sight environments and Rician when there is a dominant line-of-sight path. The document presents models for generating both Rayleigh and Rician fading
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.
Channel planning is critical for wireless network deployment. Poor planning can lead to unreliable networks with low capacity and performance. Assigning appropriate radio channels to each base station while determining frequency reuse ratios and cell separation distances is an important but difficult process. Cellular systems do not always follow homogeneous path loss models. Control channels are vital and generally use more conservative frequency reuse than voice channels. Cell breathing occurs as CDMA cell sizes dynamically shrink and grow depending on the number of users in the cell. Near-far problem and reverse link power control are also important CDMA concepts.
Packet radio protocols allow multiple subscribers to access a shared channel for transmitting data packets. They use contention-based random access techniques like ALOHA. Pure ALOHA protocol has low efficiency due to partial packet collisions. Slotted ALOHA synchronizes transmissions to time slots to prevent partial collisions, improving efficiency. Performance is evaluated using metrics like throughput, which is highest at optimal channel load and drops off above and below this point.
2.5 capacity calculations of fdma, tdma and cdmaJAIGANESH SEKAR
The document discusses the capacity calculations of cellular systems using FDMA, TDMA, and CDMA. For FDMA systems, capacity is limited by co-channel interference and calculated based on channel bandwidth, frequency reuse factor, and signal-to-interference ratio. TDMA systems improve capacity over analog systems through techniques like timeslot allocation and adaptive channel assignment. CDMA systems can reuse the entire spectrum in all cells, and capacity is interference-limited rather than bandwidth-limited. Capacity is increased in CDMA through sectorization, monitoring voice activity, and controlling transmit power.
Small-scale fading in wireless channels is caused by multipath propagation. There are three main effects: rapid signal strength changes over small distances/times, random Doppler shifts from multipath signals, and time dispersion of echoes. Multipath results from reflection, diffraction and scattering off surroundings. Several methods measure multipath structure including direct RF pulse systems, spread spectrum sliding correlators, and frequency domain channel sounding using vector network analyzers. These techniques help determine power delay profiles and understand time-varying multipath effects.
DAMA is a technique used to assign satellite channels to users on an as-needed basis. It allows a satellite to communicate with different earth stations simultaneously without interference. With DAMA, communication channels are assigned based on requests from user terminals to a network control system. Once allocated, a channel is reserved for a user's session and not available to others until it is finished. This improves efficiency over systems that permanently allocate channels.
TDMA divides the radio spectrum into time slots and allows only one user to transmit or receive data during each time slot. It uses a buffer-and-burst transmission method, making it well-suited for digital systems. TDMA systems employ TDMA/TDD or TDMA/FDD for duplexing and multiple access. A TDMA frame includes a preamble for identification and synchronization, and multiple time slots containing user data, trail bits, and guard bits between slots. TDMA provides high transmission rates, simpler handoff, and is more cost-effective than FDMA, though it requires minimum guard times between slots to avoid interference.
This document discusses the key parameters in designing a transceiver system. It describes the components in the transmitter and receiver paths that impact the link budget, including transmitter power output, gains and losses, noise figure, and signal-to-noise ratio. Key transmitter components are the power amplifier, transmission line, and antenna. Key receiver components are the antenna, low-noise amplifier, and additional amplifiers. The document provides equations to calculate link budget parameters like effective isotropic radiated power, received signal power, and noise level.
The document discusses the Rake receiver, which is used to counter the effects of multipath fading in wireless communications. It works by using multiple "fingers" to collect different time-shifted versions of the original signal transmitted over multiple paths. Each finger correlates and extracts one of the multipath components. The outputs are then weighted and combined to provide a better estimate of the transmitted signal. This allows the Rake receiver to equalize the effects of multipath and improve the signal-to-noise ratio. While useful for CDMA, W-CDMA and other technologies, Rake receivers are also more complex and expensive than conventional receivers.
1) Cellular radio systems use trunking to allow many users to share a limited number of channels. Trunking allocates channels to users on demand, returning channels when calls end.
2) The grade of service (GOS) measures a trunked system's ability to provide users access during peak hours, and is defined as the probability of a call being blocked or delayed. GOS is used to determine the minimum number of channels needed.
3) There are two main types of trunked systems - ones where blocked calls are cleared and ones where blocked calls are queued. The Erlang B and C formulas are used to calculate GOS for these systems respectively based on traffic intensity and number of channels
Telephone traffic engineering involves collecting and analyzing traffic data to determine the appropriate size of a telephone network. It studies metrics like busy hour, calling rate, traffic intensity, and grade of service. Traffic units like Erlangs are used to measure traffic load. The basic goals are to determine the optimal configuration and sizing of networks to balance cost effectiveness against normal and peak traffic loads. Traffic engineering helps ensure networks can handle call volumes without too many blocked calls during busy periods.
Mobile computing unit2,SDMA,FDMA,CDMA,TDMA Space Division Multi Access,Frequ...Pallepati Vasavi
This document discusses various terminology related to the MAC sublayer, including:
1. The station model consisting of independent stations that generate frames for transmission.
2. The single channel assumption where a single channel is available for all communication.
3. The collision assumption where if two frames are transmitted simultaneously they will overlap and be garbled.
It then covers concepts such as carrier sensing, hidden and exposed terminals, and near and far terminals that create challenges for wireless networks. Finally, it introduces various multiple access methods including SDMA, FDMA, TDMA, and CDMA.
This document discusses various diversity techniques used in wireless communications to combat fading. It describes types of diversity including time, frequency, multiuser, and space diversity. It also outlines combining techniques such as selection combining, maximal ratio combining and equal gain combining that are used to improve the signal by combining signals from multiple diversity branches. The document concludes by discussing multiple input multiple output (MIMO) systems and orthogonal frequency division multiple access (OFDMA) schemes that exploit diversity and multiuser diversity.
The document provides an overview of the public switched telephone network (PSTN). It discusses that the PSTN is the interconnected telephone system that uses copper wires to make circuit-switched calls. It then covers the evolution of the PSTN from its invention in 1876 to present digital switches, the use of bandwidth allocation and numbering schemes, and call setup which involves signaling and switching systems to route calls.
OFDM is a digital modulation technique that splits a data stream into several narrowband channels at different frequencies. This reduces interference and crosstalk compared to traditional single-carrier modulation. Fading effects are also reduced since the loss of a subset of bits can be recovered with coding. Windowing and cyclic prefixes are used to reduce interference between channels and intersymbol interference. The cyclic prefix provides a guard interval and allows transforming the linear convolution of the channel to circular convolution in the frequency domain, simplifying processing. While the cyclic prefix reduces data capacity, it provides robustness against multipath effects.
Introduction To Wireless Fading ChannelsNitin Jain
The document summarizes key concepts related to wireless fading channels, including:
1. Multipath fading causes fluctuations in signal strength over small physical distances due to constructive and destructive interference from multiple signal paths.
2. Rayleigh fading occurs when there is no line-of-sight path between transmitter and receiver, resulting in fast, large fluctuations in signal strength over small physical distances.
3. Doppler spread and coherence time describe how quickly the wireless channel varies over time due to mobility, with fast fading occurring if the channel changes significantly within a symbol period.
This document discusses key concepts in telecommunications network planning and traffic engineering. It covers:
- Types of random processes used to model network usage patterns like call arrival rates and durations.
- How traffic engineering balances factors like grade of service, resources, blocking vs. delay systems based on traffic amounts.
- Key metrics like erlangs, traffic intensity, busy hour, traffic volume that are used to quantify network usage and demand.
- Concepts like grade of service, blocking probability, and how they measure network performance during busy periods.
This document provides an overview of signal processing techniques used in wireless systems, including diversity and equalization. It discusses various diversity techniques like spatial, temporal, frequency, angular, and polarization diversity as well as macro and micro diversity. It also explains different types of combining diversity including selection, maximal ratio combining, and equal gain combining. The document concludes with sections on linear equalizers such as zero forcing and MMSE, as well as nonlinear equalizers using algorithms like LMS and RLS.
This document discusses mobile radio propagation and propagation models. It begins by introducing how radio channels are random and time-varying. It then covers the free space propagation model and how received power decreases with distance. Reflection, diffraction, and scattering are described as the main propagation mechanisms. The two-ray ground reflection model is presented to model propagation over large distances. Diffraction is explained using the knife-edge diffraction model. Fresnel zones and diffraction gain are also defined.
- The document discusses wireless channel propagation and fading. It covers topics like large-scale fading (path loss and shadowing), small-scale fading (time-selective and frequency-selective fading), and statistical characterization of fading channels.
- Small-scale fading is caused by multipath propagation and results in rapid fluctuations in the strength of the received signal over short periods of time or travel distances. It can be time-selective or frequency-selective depending on delay spread and Doppler spread.
- Common distributions for modeling fading amplitudes are Rayleigh for non-line-of-sight environments and Rician when there is a dominant line-of-sight path. The document presents models for generating both Rayleigh and Rician fading
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.
Channel planning is critical for wireless network deployment. Poor planning can lead to unreliable networks with low capacity and performance. Assigning appropriate radio channels to each base station while determining frequency reuse ratios and cell separation distances is an important but difficult process. Cellular systems do not always follow homogeneous path loss models. Control channels are vital and generally use more conservative frequency reuse than voice channels. Cell breathing occurs as CDMA cell sizes dynamically shrink and grow depending on the number of users in the cell. Near-far problem and reverse link power control are also important CDMA concepts.
Packet radio protocols allow multiple subscribers to access a shared channel for transmitting data packets. They use contention-based random access techniques like ALOHA. Pure ALOHA protocol has low efficiency due to partial packet collisions. Slotted ALOHA synchronizes transmissions to time slots to prevent partial collisions, improving efficiency. Performance is evaluated using metrics like throughput, which is highest at optimal channel load and drops off above and below this point.
2.5 capacity calculations of fdma, tdma and cdmaJAIGANESH SEKAR
The document discusses the capacity calculations of cellular systems using FDMA, TDMA, and CDMA. For FDMA systems, capacity is limited by co-channel interference and calculated based on channel bandwidth, frequency reuse factor, and signal-to-interference ratio. TDMA systems improve capacity over analog systems through techniques like timeslot allocation and adaptive channel assignment. CDMA systems can reuse the entire spectrum in all cells, and capacity is interference-limited rather than bandwidth-limited. Capacity is increased in CDMA through sectorization, monitoring voice activity, and controlling transmit power.
Small-scale fading in wireless channels is caused by multipath propagation. There are three main effects: rapid signal strength changes over small distances/times, random Doppler shifts from multipath signals, and time dispersion of echoes. Multipath results from reflection, diffraction and scattering off surroundings. Several methods measure multipath structure including direct RF pulse systems, spread spectrum sliding correlators, and frequency domain channel sounding using vector network analyzers. These techniques help determine power delay profiles and understand time-varying multipath effects.
DAMA is a technique used to assign satellite channels to users on an as-needed basis. It allows a satellite to communicate with different earth stations simultaneously without interference. With DAMA, communication channels are assigned based on requests from user terminals to a network control system. Once allocated, a channel is reserved for a user's session and not available to others until it is finished. This improves efficiency over systems that permanently allocate channels.
TDMA divides the radio spectrum into time slots and allows only one user to transmit or receive data during each time slot. It uses a buffer-and-burst transmission method, making it well-suited for digital systems. TDMA systems employ TDMA/TDD or TDMA/FDD for duplexing and multiple access. A TDMA frame includes a preamble for identification and synchronization, and multiple time slots containing user data, trail bits, and guard bits between slots. TDMA provides high transmission rates, simpler handoff, and is more cost-effective than FDMA, though it requires minimum guard times between slots to avoid interference.
This document discusses the key parameters in designing a transceiver system. It describes the components in the transmitter and receiver paths that impact the link budget, including transmitter power output, gains and losses, noise figure, and signal-to-noise ratio. Key transmitter components are the power amplifier, transmission line, and antenna. Key receiver components are the antenna, low-noise amplifier, and additional amplifiers. The document provides equations to calculate link budget parameters like effective isotropic radiated power, received signal power, and noise level.
The document discusses the Rake receiver, which is used to counter the effects of multipath fading in wireless communications. It works by using multiple "fingers" to collect different time-shifted versions of the original signal transmitted over multiple paths. Each finger correlates and extracts one of the multipath components. The outputs are then weighted and combined to provide a better estimate of the transmitted signal. This allows the Rake receiver to equalize the effects of multipath and improve the signal-to-noise ratio. While useful for CDMA, W-CDMA and other technologies, Rake receivers are also more complex and expensive than conventional receivers.
1) Cellular radio systems use trunking to allow many users to share a limited number of channels. Trunking allocates channels to users on demand, returning channels when calls end.
2) The grade of service (GOS) measures a trunked system's ability to provide users access during peak hours, and is defined as the probability of a call being blocked or delayed. GOS is used to determine the minimum number of channels needed.
3) There are two main types of trunked systems - ones where blocked calls are cleared and ones where blocked calls are queued. The Erlang B and C formulas are used to calculate GOS for these systems respectively based on traffic intensity and number of channels
Telephone traffic engineering involves collecting and analyzing traffic data to determine the appropriate size of a telephone network. It studies metrics like busy hour, calling rate, traffic intensity, and grade of service. Traffic units like Erlangs are used to measure traffic load. The basic goals are to determine the optimal configuration and sizing of networks to balance cost effectiveness against normal and peak traffic loads. Traffic engineering helps ensure networks can handle call volumes without too many blocked calls during busy periods.
The document discusses various topics related to mobile and wireless communication including:
1) Cell capacity and reuse, defining how capacity increases as the cluster size decreases but interference also increases.
2) Traffic theory, defining concepts like arrival rate, holding time, load, and blocked calls. Formulas for blocking probability and Erlang B & C are provided.
3) Channel assignment strategies including fixed and dynamic assignment and how their impact on performance.
Teletraffic engineeringTeletraffic engineers use their knowledge (2).pptxMdSharifUddinShajib
Teletraffic engineers use their knowledge of statistics including queuing theory, the nature of traffic, their practical models, their measurements and simulations to make predictions and to plan telecommunication networks such as a telephone network or the Internet. These tools and knowledge help provide reliable service at lower cost.
Traffic analysis and characterization is used to analyze communication networks and model their performance. It applies probability theory to understand the random nature of network traffic, which arises from random call arrivals and holding times. Key aspects of traffic that are analyzed include arrival rates, holding times, destination distributions, user behavior, occupancy levels, busy hour patterns, and call completion rates. Units of traffic like Erlangs and Cent Call Seconds are used to measure traffic intensity. Models like negative exponential and Poisson distributions help characterize random inter-arrival times.
M & WC unit 1.pptx very good condition and success20EC040
The document discusses various handoff strategies used in cellular networks. It explains that handoff is required when a mobile moves between base stations to transfer an ongoing call to a new channel and base station. It describes different types of handoff like hard handoff in TDMA networks and soft handoff in CDMA networks. It also discusses factors like minimizing unnecessary handoffs, ensuring successful handoffs, and making handoffs imperceptible to users.
Lecture 3 trunking theory and other issues with cellsUmairKhalil16
In a trunked system, channels are pooled and shared among users on an as-needed basis. The Erlang B and Erlang C formulas can be used to determine the blocking probability and delay probability respectively for a given number of channels and traffic intensity. Additional considerations in cellular systems include handoffs which allow calls to continue as users move between cells, sectoring to reduce interference through directional antennas, and power control to minimize transmission power and interference between users.
The document discusses cellular system capacity and the Erlang B formula. It provides examples of calculating the number of supported users for different channel configurations using the formula. Key points:
- The Erlang B formula calculates the blocking probability given traffic intensity and number of channels
- Sectoring increases SIR but reduces trunking efficiency by sharing channels among more sectors
- For a 400 channel, 20MHz system with SIR>15dB and blocking <5%, 120 degree sectoring with a cluster size of 3 supports the most users at around 38,000. Smaller cluster sizes increase channels per sector and supported users.
Wireless communication technologies have evolved from Guglielmo Marconi's early radio demonstrations in 1897. In the 1960s-1970s, Bell Laboratories developed the cellular concept, which enabled wireless communication networks to serve entire populations. This led to the development of cellular mobile systems using radio frequency technology. Cellular systems use a hexagonal cell structure and frequency reuse to improve spectrum efficiency and service capacity. They employ technologies such as handoff, dynamic channel assignment, and prioritization of handoffs to manage calls as users move between cells.
This document contains 61 multiple choice questions related to mobile computing and wireless communication technologies. It covers topics such as signals, modulation, multiplexing, cellular networks, GSM, GPRS, mobile IP, WAP, and satellite communication systems. The questions define key terms, ask about protocols and standards, and require calculations related to wireless networks and services.
Spread spectrum is a technique that spreads user data signals across a larger frequency band to provide resistance to narrowband interference. It works by converting a narrowband signal into a broadband signal at the sender, then reconverting it back to narrowband at the receiver while spreading any interference. Two common spread spectrum techniques are direct sequence spread spectrum (DSSS), which spreads signals using a chipping sequence, and frequency hopping spread spectrum (FHSS), which splits the bandwidth into smaller channels and hops between them.
This document discusses key concepts in cellular systems including frequency reuse, interference management, and capacity improvement techniques. The main points are:
1. Cells reuse radio frequencies to allow large numbers of users by allocating different frequency groups to neighboring cells. This reduces interference within tolerable limits.
2. Interference is managed through techniques like frequency planning, channel assignment strategies, and power control. The balance of interference and capacity is important.
3. System capacity can be improved through cell splitting, sectoring cells with directional antennas, using different cell sizes, and coverage zone techniques. Managing interference is crucial to improving cellular network capacity.
Bandwidth Utilization Multiplexing and Spectrum SpreadingMeenakshi Paul
This document provides an overview of bandwidth utilization techniques including multiplexing and spread spectrum. It discusses multiplexing techniques like frequency-division multiplexing (FDM), wavelength-division multiplexing (WDM), and time-division multiplexing (TDM). It also covers spread spectrum techniques such as frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS). The key advantages of these techniques are that they allow for more efficient use of bandwidth and increase resistance to interference and jamming.
This document outlines the key concepts and components of a wireless communications course, including:
- The 5 units that will be covered: wireless channels, cellular architecture, digital signaling for fading channels, multipath mitigation techniques, and multiple antenna techniques.
- An overview of the cellular architecture unit, which will cover topics like multiple access techniques, capacity calculations, cellular concepts, frequency reuse, channel assignment, handoff, interference and more.
- Information on the textbooks that will be used.
This document discusses multiple access techniques used in wireless communication. It focuses on frequency division multiple access (FDMA) which allows multiple users to share the same frequency channel by assigning different, non-overlapping frequency sub-bands to each user. FDMA divides the available bandwidth into separate channels, with each user assigned their own channel containing a narrow frequency band. Guard bands are left between channels to prevent overlap and interference. The document provides examples of FDMA used in analog cellular systems and describes its advantages, including continuous transmission and simple hardware requirements.
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.
Optimizing Gradle Builds - Gradle DPE Tour Berlin 2024Sinan KOZAK
Sinan from the Delivery Hero mobile infrastructure engineering team shares a deep dive into performance acceleration with Gradle build cache optimizations. Sinan shares their journey into solving complex build-cache problems that affect Gradle builds. By understanding the challenges and solutions found in our journey, we aim to demonstrate the possibilities for faster builds. The case study reveals how overlapping outputs and cache misconfigurations led to significant increases in build times, especially as the project scaled up with numerous modules using Paparazzi tests. The journey from diagnosing to defeating cache issues offers invaluable lessons on maintaining cache integrity without sacrificing functionality.
Redefining brain tumor segmentation: a cutting-edge convolutional neural netw...IJECEIAES
Medical image analysis has witnessed significant advancements with deep learning techniques. In the domain of brain tumor segmentation, the ability to
precisely delineate tumor boundaries from magnetic resonance imaging (MRI)
scans holds profound implications for diagnosis. This study presents an ensemble convolutional neural network (CNN) with transfer learning, integrating
the state-of-the-art Deeplabv3+ architecture with the ResNet18 backbone. The
model is rigorously trained and evaluated, exhibiting remarkable performance
metrics, including an impressive global accuracy of 99.286%, a high-class accuracy of 82.191%, a mean intersection over union (IoU) of 79.900%, a weighted
IoU of 98.620%, and a Boundary F1 (BF) score of 83.303%. Notably, a detailed comparative analysis with existing methods showcases the superiority of
our proposed model. These findings underscore the model’s competence in precise brain tumor localization, underscoring its potential to revolutionize medical
image analysis and enhance healthcare outcomes. This research paves the way
for future exploration and optimization of advanced CNN models in medical
imaging, emphasizing addressing false positives and resource efficiency.
Understanding Inductive Bias in Machine LearningSUTEJAS
This presentation explores the concept of inductive bias in machine learning. It explains how algorithms come with built-in assumptions and preferences that guide the learning process. You'll learn about the different types of inductive bias and how they can impact the performance and generalizability of machine learning models.
The presentation also covers the positive and negative aspects of inductive bias, along with strategies for mitigating potential drawbacks. We'll explore examples of how bias manifests in algorithms like neural networks and decision trees.
By understanding inductive bias, you can gain valuable insights into how machine learning models work and make informed decisions when building and deploying them.
International Conference on NLP, Artificial Intelligence, Machine Learning an...gerogepatton
International Conference on NLP, Artificial Intelligence, Machine Learning and Applications (NLAIM 2024) offers a premier global platform for exchanging insights and findings in the theory, methodology, and applications of NLP, Artificial Intelligence, Machine Learning, and their applications. The conference seeks substantial contributions across all key domains of NLP, Artificial Intelligence, Machine Learning, and their practical applications, aiming to foster both theoretical advancements and real-world implementations. With a focus on facilitating collaboration between researchers and practitioners from academia and industry, the conference serves as a nexus for sharing the latest developments in the field.
Harnessing WebAssembly for Real-time Stateless Streaming PipelinesChristina Lin
Traditionally, dealing with real-time data pipelines has involved significant overhead, even for straightforward tasks like data transformation or masking. However, in this talk, we’ll venture into the dynamic realm of WebAssembly (WASM) and discover how it can revolutionize the creation of stateless streaming pipelines within a Kafka (Redpanda) broker. These pipelines are adept at managing low-latency, high-data-volume scenarios.
2. CONTENTS
•Problem statement
•Purpose of trunking theory
•Introduction
•Common terms in trunking theory
•Types of trunked systems
•Traffic intensity
•Example problem
3. Problem statement
Limited number of channels
Many users
For example a telephone system has 4 users and 3 channels.
Central
office
user useruseruser
4. Purpose of trunking theory
To determine the required capacity and allocate the proper
number of channels in order to meet GOS.
GOS: grade of service is the measure of user’s ability to
access a trunked system during busiest hour.
5. Introduction
Trunking theory was represented by Erlang in the late 19th
century.
It helps in establishing a trunked system which provides
communication services to a large group of users with limited
number of available channels in the system.
All PSTN/cellular radio systems exploits trunking theory to
cover a large user community with limited number of
circuits/frequency spectrum.
6. In a trunked radio system, each user is allocated a channel on
a per call basis, and upon the termination of the call, the
previously occupied channel is immediately returned to the
pool of channels.
In telephone system, it is used to determine the number of
telephone circuits that need to be allocated for office buildings
with hundreds of telephones.
7. Common terms in trunking theory
Set-up time: Time required to allocate a channel to the
requesting user.
Blocked call: call which can not be completed at the time of
request, also called as lost call.
Holding time: average duration of a typical call, denoted by
“H”.
Load: traffic intensity across the entire trunked system.
Request rate: the average number of requesting call requests
per unit time. It is denoted by “λ”
8. Types of trunked system
There are two types of trunked systems commonly used.
1. Blocked calls cleared: It offers no queuing for call request.
That is, for every requesting user, it is assumed to have no
any set-up time and user is given immediate access to
channel if available. If no channel is available, the
requesting user is blocked and is free to try again later.
2. Blocked calls delayed: it offers a queue to hold the calls
which are blocked. If channel is not available for the
requesting user, the call request may be delayed until a
channel becomes available.
9. Traffic intensity
Traffic intensity is measured in erlangs, 1 erlang is the amount
of traffic intensity carried by a channel that is completely
occupied i.e. one call-minute per minute. It is denoted by “A”
Each user generates a traffic intensity of Au erlangs.
Au= λH
Where λ is the average number of call requests per unit time,
H is the average duration of call
10. Example
There are 3000 calls per hour, each lasting an average of 1.76 min.
what is the traffic intensity?
Solution: Data
average duration of a call (H) = 1.76 min
call request per unit time (λ) = 3000/hour = 3000/60= 50
Since, traffic intensity (A) = H×λ
Therefore, A = 1.76×50= 88 Erlangs.