The document discusses key concepts in cellular network design including:
- Frequency reuse which involves dividing a service area into cells and assigning different channel groups to adjacent cells to allow channels to be reused.
- Channel assignment strategies including fixed assignment where channels are permanently assigned to cells and dynamic assignment where channels are allocated on demand.
- Handoff strategies for transferring calls between cells as users move, including techniques like guard channels and queuing handoff requests.
- Interference, which is the major limiting factor for capacity, including co-channel interference between cells using the same frequencies and adjacent channel interference from nearby frequencies.
The document discusses key concepts in cellular network design including:
- Frequency reuse which allows the same channels to be reused in different cells by assigning different channel groups to adjacent cells to minimize interference.
- Channel assignment strategies including fixed assignment where channels are permanently assigned to cells and dynamic assignment where channels are allocated on demand considering interference.
- Handoff strategies to transfer calls between cells as users move, prioritizing ongoing calls through guard channels and queuing handoff requests.
- Interference, particularly co-channel interference between cells using the same channels, which is the major limiting factor in capacity and requires sufficient separation between co-channel cells. Signal-to-interference ratio characterizes this interference.
The cellular concept solves spectral congestion issues by reusing radio channels in different hexagonal cells. Hexagonal cells provide full coverage with minimal cells and equal distance between cell centers. Each cell is assigned a group of channels to limit interference between neighboring cells using frequency planning. The capacity of the system increases with the number of times the frequency plan can be reused across different cell clusters.
The document discusses key concepts in mobile communication systems, including:
1. Cellular networks segment coverage areas into cells using multiple carrier frequencies to allow frequency reuse, with different frequencies used in adjacent cells. As user density increases, cells can be split into smaller cells.
2. Frequency reuse is key to cellular systems, allowing the same frequency to be used in different cells as long as they are sufficiently separated. Proper frequency planning is needed to minimize co-channel interference between cells using the same frequency.
3. When a mobile user moves between cells, a handover transfers the call to the new cell to maintain coverage. Handover thresholds and strategies aim to balance call quality and burden on the network.
Cellular systems use multiple low-power transmitters (base stations) rather than a single, high-power transmitter to increase capacity and coverage. Frequency reuse is used to allocate channels to nearby base stations to minimize interference. Handoff strategies are employed to transfer calls between base stations as users move. Interference and power control techniques aim to equalize signal power levels and improve capacity. Traffic engineering principles including Erlang formulas are applied to determine the optimal number of channels needed based on expected call volumes.
1) Cellular networks divide a region into smaller areas called cells to improve capacity and reuse frequencies. Each cell contains a base station that can communicate with user equipment within its coverage area.
2) Frequency reuse allows the same set of frequencies to be reused in different cells by ensuring sufficient distance between cells using the same frequencies. This increases overall network capacity.
3) Handoff allows calls to be transferred between base stations as users move between cells to maintain call quality. Various handoff strategies aim to minimize call drops during handoffs.
2.6 cellular concepts - frequency reusing, channel assignmentJAIGANESH SEKAR
- Cellular networks address the problem of limited spectrum availability by using frequency reuse, where nearby base stations are assigned different channels to avoid interference. Cells are arranged in a hexagonal pattern and the same set of channels are reused in cells sufficiently far from each other.
- There are two main channel assignment strategies - fixed assignment, where each cell has a predetermined set of channels, and dynamic assignment, where channels are allocated on demand by a central controller considering interference levels. Dynamic assignment helps improve spectrum utilization but requires more complex coordination.
- Frequency reuse allows the available spectrum to be reused as needed across multiple cells as long as interference is kept at acceptable levels, increasing network capacity.
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.
The document discusses the cellular concept and frequency reuse in cellular networks. It describes how:
1) The cellular concept addresses the shortcomings of early mobile networks by dividing coverage areas into cells and reusing frequencies through frequency planning, allowing for greater capacity.
2) Each cell is assigned a group of channels, and neighboring cells are assigned different groups to minimize interference. The size of the frequency reuse cluster and number of channels impacts capacity and interference.
3) Handoffs must be performed seamlessly as users move between cells to maintain calls. Different cellular systems use different handoff techniques, such as network-controlled or mobile-assisted handoffs.
The document discusses key concepts in cellular network design including:
- Frequency reuse which allows the same channels to be reused in different cells by assigning different channel groups to adjacent cells to minimize interference.
- Channel assignment strategies including fixed assignment where channels are permanently assigned to cells and dynamic assignment where channels are allocated on demand considering interference.
- Handoff strategies to transfer calls between cells as users move, prioritizing ongoing calls through guard channels and queuing handoff requests.
- Interference, particularly co-channel interference between cells using the same channels, which is the major limiting factor in capacity and requires sufficient separation between co-channel cells. Signal-to-interference ratio characterizes this interference.
The cellular concept solves spectral congestion issues by reusing radio channels in different hexagonal cells. Hexagonal cells provide full coverage with minimal cells and equal distance between cell centers. Each cell is assigned a group of channels to limit interference between neighboring cells using frequency planning. The capacity of the system increases with the number of times the frequency plan can be reused across different cell clusters.
The document discusses key concepts in mobile communication systems, including:
1. Cellular networks segment coverage areas into cells using multiple carrier frequencies to allow frequency reuse, with different frequencies used in adjacent cells. As user density increases, cells can be split into smaller cells.
2. Frequency reuse is key to cellular systems, allowing the same frequency to be used in different cells as long as they are sufficiently separated. Proper frequency planning is needed to minimize co-channel interference between cells using the same frequency.
3. When a mobile user moves between cells, a handover transfers the call to the new cell to maintain coverage. Handover thresholds and strategies aim to balance call quality and burden on the network.
Cellular systems use multiple low-power transmitters (base stations) rather than a single, high-power transmitter to increase capacity and coverage. Frequency reuse is used to allocate channels to nearby base stations to minimize interference. Handoff strategies are employed to transfer calls between base stations as users move. Interference and power control techniques aim to equalize signal power levels and improve capacity. Traffic engineering principles including Erlang formulas are applied to determine the optimal number of channels needed based on expected call volumes.
1) Cellular networks divide a region into smaller areas called cells to improve capacity and reuse frequencies. Each cell contains a base station that can communicate with user equipment within its coverage area.
2) Frequency reuse allows the same set of frequencies to be reused in different cells by ensuring sufficient distance between cells using the same frequencies. This increases overall network capacity.
3) Handoff allows calls to be transferred between base stations as users move between cells to maintain call quality. Various handoff strategies aim to minimize call drops during handoffs.
2.6 cellular concepts - frequency reusing, channel assignmentJAIGANESH SEKAR
- Cellular networks address the problem of limited spectrum availability by using frequency reuse, where nearby base stations are assigned different channels to avoid interference. Cells are arranged in a hexagonal pattern and the same set of channels are reused in cells sufficiently far from each other.
- There are two main channel assignment strategies - fixed assignment, where each cell has a predetermined set of channels, and dynamic assignment, where channels are allocated on demand by a central controller considering interference levels. Dynamic assignment helps improve spectrum utilization but requires more complex coordination.
- Frequency reuse allows the available spectrum to be reused as needed across multiple cells as long as interference is kept at acceptable levels, increasing network capacity.
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.
The document discusses the cellular concept and frequency reuse in cellular networks. It describes how:
1) The cellular concept addresses the shortcomings of early mobile networks by dividing coverage areas into cells and reusing frequencies through frequency planning, allowing for greater capacity.
2) Each cell is assigned a group of channels, and neighboring cells are assigned different groups to minimize interference. The size of the frequency reuse cluster and number of channels impacts capacity and interference.
3) Handoffs must be performed seamlessly as users move between cells to maintain calls. Different cellular systems use different handoff techniques, such as network-controlled or mobile-assisted handoffs.
This presentation provides an overview of the cellular concept and key related topics:
- Cells are small geographical service areas defined by a base station and radio channels. Multiple cells are grouped into clusters to fully utilize available frequencies through frequency reuse.
- Handoff is the process of transferring voice and control signals between cells as a mobile moves between cells during a call. Successful and infrequent handoffs are important.
- Interference is reduced through frequency reuse and strategies like cell splitting and sectoring. Cell splitting divides cells into smaller areas served by low-power base stations to increase channel reuse and capacity. Sectoring uses directional antennas to reduce interference from co-channel cells.
The cellular concept divides a large service area into smaller cells served by low-power base stations to improve capacity and spectrum reuse. Each base station is allocated a group of radio channels for its cell. Areas are divided into hexagonal cells served by a central base station to allow frequencies to be reused efficiently while minimizing interference between adjacent cells. Handoff allows calls to be transferred between base stations as users move between cells to maintain call quality.
Wireless cellular networks divide geographic areas into smaller sections called cells to improve capacity and coverage. Each cell uses a subset of available frequencies and is served by a base station. As users move between cells, their active connections are handed off between base stations through a process managed by the mobile switching center. Cell sizes and the frequency reuse plan must be optimized to balance capacity, coverage, and interference between cells using the same frequencies.
03. Chapter- Three Elements of Cellular Radio System Design1.pdfsamiulsuman
The document summarizes key elements of cellular radio system design including low power transmitters, frequency reuse, co-channel interference reduction, handoff mechanisms, and cell splitting. It discusses how frequency reuse allows the same channels to be used in different cells to increase capacity but can cause co-channel interference. Handoff mechanisms allow calls to be transferred between cells as users move. Cell splitting involves installing new base stations to reduce interference and increase capacity in busy areas.
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 provides an overview of fundamental concepts in cellular engineering. It discusses the goals of cellular systems to have high capacity and large coverage area through efficient use of limited spectrum. Key concepts explained include frequency reuse, where the same radio channels are reused in different cells to serve more users; channel assignment strategies like fixed and dynamic allocation; and techniques to enhance capacity like cell splitting, sectoring, and microcell zones. The handoff process is also summarized, which allows seamless transfer of calls between base stations as users move between cells.
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.
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.
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.
This document provides an overview of wireless communication and cellular systems. It discusses key concepts such as frequency reuse, cell footprint, handover, interference, and system capacity. It explains how cellular networks divide a service area into smaller cells served by low-power base stations to improve capacity. Neighboring cells are assigned different frequency groups to reduce interference. The same frequencies can be reused in cells far enough apart. Handover allows calls to be transferred between cells as users move. The document also covers channel assignment strategies and methods for expanding system capacity through cell splitting or reducing the frequency reuse factor.
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 cell sites served by lower-power base stations. Neighboring cells are assigned different groups of channels to minimize interference. This frequency reuse allows the same frequencies to be used in multiple cells across an area.
Frequencies management,Channel assignments,
Frequency reuse, System capacity and its improvement: Cell spliting and sectoring, Handoffs & its types, prioritizing handoff, Umbrella cell approach, Cell dragging, Roaming, Co channel and adjacent channel interference, Improving coverage- Repeaters for range extension and microcell zone concept, Examples
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.
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.
Cellular Concepts by Mian Shehzad Iqbal,
Earlier systems used single high power
transmitter. So no frequency reuse
• Cellular concept solve the problem of spectral
congestion and user capacity without any major
technological changes.
• Replaces single high power transmitter with
many low power transmitters.
• Each base station is allocated portion of
available channels.
• Distribution to neighbors so that minimize
interference.
Hexagonal shape is only logical shape.
Actual coverage of cell is known as
footprint and is determined by
measurements and prediction models.
Cell must be designed to serve the
weakest mobile at edge in footprint.
MSC plays major role by monitoring reuse
distance, cost function and other issues. • MSC
needs to collect real time data on channel
occupancy, traffic distribution and radio signal
strength indications (RSSI) this increases the
storage and computational load but provides the
advantage of increased channel utilization and
decreased probability of blocked calls.
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 document discusses key concepts in cellular network design including:
1) The cellular concept divides a large service area into smaller cells served by low-power base stations to improve capacity compared to single transmitter systems.
2) Frequency reuse planning involves assigning different channel groups to neighboring cells to minimize interference while maximizing frequency reuse.
3) Handoff strategies are used to transfer calls between cells as users move, and guard channels and queuing can help reduce dropped calls.
4) Techniques like cell splitting, sectoring, and smaller cell zones can help improve coverage and capacity in congested areas without requiring additional spectrum.
The document discusses the cellular concept in wireless networks. Key points include:
- Cells have a hexagonal shape and neighboring cells reuse frequencies to avoid interference and increase capacity.
- Frequency reuse allows more simultaneous calls by allocating the same set of frequencies to different neighboring cells.
- Cell size is a tradeoff between interference and system capacity - smaller cells mean lower power needs but more cells and handoffs.
The document discusses key concepts in cellular system design including frequency reuse, cell size, system capacity, and handoff strategies. The cellular concept allows efficient reuse of a fixed number of channels across a large coverage area by dividing the area into smaller cells and reusing frequencies in cells sufficiently distant from each other to prevent interference. System capacity is determined by the number of available channels, cluster size which impacts frequency reuse distance and interference levels, and the number of times a cluster can be replicated across the coverage area. Handoff strategies aim to transfer calls seamlessly between cells as users move and involve monitoring signal levels, assigning priority to handoffs over new calls, and reserving guard channels.
TIME DIVISION MULTIPLEXING TECHNIQUE FOR COMMUNICATION SYSTEMHODECEDSIET
Time Division Multiplexing (TDM) is a method of transmitting multiple signals over a single communication channel by dividing the signal into many segments, each having a very short duration of time. These time slots are then allocated to different data streams, allowing multiple signals to share the same transmission medium efficiently. TDM is widely used in telecommunications and data communication systems.
### How TDM Works
1. **Time Slots Allocation**: The core principle of TDM is to assign distinct time slots to each signal. During each time slot, the respective signal is transmitted, and then the process repeats cyclically. For example, if there are four signals to be transmitted, the TDM cycle will divide time into four slots, each assigned to one signal.
2. **Synchronization**: Synchronization is crucial in TDM systems to ensure that the signals are correctly aligned with their respective time slots. Both the transmitter and receiver must be synchronized to avoid any overlap or loss of data. This synchronization is typically maintained by a clock signal that ensures time slots are accurately aligned.
3. **Frame Structure**: TDM data is organized into frames, where each frame consists of a set of time slots. Each frame is repeated at regular intervals, ensuring continuous transmission of data streams. The frame structure helps in managing the data streams and maintaining the synchronization between the transmitter and receiver.
4. **Multiplexer and Demultiplexer**: At the transmitting end, a multiplexer combines multiple input signals into a single composite signal by assigning each signal to a specific time slot. At the receiving end, a demultiplexer separates the composite signal back into individual signals based on their respective time slots.
### Types of TDM
1. **Synchronous TDM**: In synchronous TDM, time slots are pre-assigned to each signal, regardless of whether the signal has data to transmit or not. This can lead to inefficiencies if some time slots remain empty due to the absence of data.
2. **Asynchronous TDM (or Statistical TDM)**: Asynchronous TDM addresses the inefficiencies of synchronous TDM by allocating time slots dynamically based on the presence of data. Time slots are assigned only when there is data to transmit, which optimizes the use of the communication channel.
### Applications of TDM
- **Telecommunications**: TDM is extensively used in telecommunication systems, such as in T1 and E1 lines, where multiple telephone calls are transmitted over a single line by assigning each call to a specific time slot.
- **Digital Audio and Video Broadcasting**: TDM is used in broadcasting systems to transmit multiple audio or video streams over a single channel, ensuring efficient use of bandwidth.
- **Computer Networks**: TDM is used in network protocols and systems to manage the transmission of data from multiple sources over a single network medium.
### Advantages of TDM
- **Efficient Use of Bandwidth**: TDM all
Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapte...University of Maribor
Slides from talk presenting:
Aleš Zamuda: Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapter and Networking.
Presentation at IcETRAN 2024 session:
"Inter-Society Networking Panel GRSS/MTT-S/CIS
Panel Session: Promoting Connection and Cooperation"
IEEE Slovenia GRSS
IEEE Serbia and Montenegro MTT-S
IEEE Slovenia CIS
11TH INTERNATIONAL CONFERENCE ON ELECTRICAL, ELECTRONIC AND COMPUTING ENGINEERING
3-6 June 2024, Niš, Serbia
This presentation provides an overview of the cellular concept and key related topics:
- Cells are small geographical service areas defined by a base station and radio channels. Multiple cells are grouped into clusters to fully utilize available frequencies through frequency reuse.
- Handoff is the process of transferring voice and control signals between cells as a mobile moves between cells during a call. Successful and infrequent handoffs are important.
- Interference is reduced through frequency reuse and strategies like cell splitting and sectoring. Cell splitting divides cells into smaller areas served by low-power base stations to increase channel reuse and capacity. Sectoring uses directional antennas to reduce interference from co-channel cells.
The cellular concept divides a large service area into smaller cells served by low-power base stations to improve capacity and spectrum reuse. Each base station is allocated a group of radio channels for its cell. Areas are divided into hexagonal cells served by a central base station to allow frequencies to be reused efficiently while minimizing interference between adjacent cells. Handoff allows calls to be transferred between base stations as users move between cells to maintain call quality.
Wireless cellular networks divide geographic areas into smaller sections called cells to improve capacity and coverage. Each cell uses a subset of available frequencies and is served by a base station. As users move between cells, their active connections are handed off between base stations through a process managed by the mobile switching center. Cell sizes and the frequency reuse plan must be optimized to balance capacity, coverage, and interference between cells using the same frequencies.
03. Chapter- Three Elements of Cellular Radio System Design1.pdfsamiulsuman
The document summarizes key elements of cellular radio system design including low power transmitters, frequency reuse, co-channel interference reduction, handoff mechanisms, and cell splitting. It discusses how frequency reuse allows the same channels to be used in different cells to increase capacity but can cause co-channel interference. Handoff mechanisms allow calls to be transferred between cells as users move. Cell splitting involves installing new base stations to reduce interference and increase capacity in busy areas.
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 provides an overview of fundamental concepts in cellular engineering. It discusses the goals of cellular systems to have high capacity and large coverage area through efficient use of limited spectrum. Key concepts explained include frequency reuse, where the same radio channels are reused in different cells to serve more users; channel assignment strategies like fixed and dynamic allocation; and techniques to enhance capacity like cell splitting, sectoring, and microcell zones. The handoff process is also summarized, which allows seamless transfer of calls between base stations as users move between cells.
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.
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.
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.
This document provides an overview of wireless communication and cellular systems. It discusses key concepts such as frequency reuse, cell footprint, handover, interference, and system capacity. It explains how cellular networks divide a service area into smaller cells served by low-power base stations to improve capacity. Neighboring cells are assigned different frequency groups to reduce interference. The same frequencies can be reused in cells far enough apart. Handover allows calls to be transferred between cells as users move. The document also covers channel assignment strategies and methods for expanding system capacity through cell splitting or reducing the frequency reuse factor.
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 cell sites served by lower-power base stations. Neighboring cells are assigned different groups of channels to minimize interference. This frequency reuse allows the same frequencies to be used in multiple cells across an area.
Frequencies management,Channel assignments,
Frequency reuse, System capacity and its improvement: Cell spliting and sectoring, Handoffs & its types, prioritizing handoff, Umbrella cell approach, Cell dragging, Roaming, Co channel and adjacent channel interference, Improving coverage- Repeaters for range extension and microcell zone concept, Examples
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.
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.
Cellular Concepts by Mian Shehzad Iqbal,
Earlier systems used single high power
transmitter. So no frequency reuse
• Cellular concept solve the problem of spectral
congestion and user capacity without any major
technological changes.
• Replaces single high power transmitter with
many low power transmitters.
• Each base station is allocated portion of
available channels.
• Distribution to neighbors so that minimize
interference.
Hexagonal shape is only logical shape.
Actual coverage of cell is known as
footprint and is determined by
measurements and prediction models.
Cell must be designed to serve the
weakest mobile at edge in footprint.
MSC plays major role by monitoring reuse
distance, cost function and other issues. • MSC
needs to collect real time data on channel
occupancy, traffic distribution and radio signal
strength indications (RSSI) this increases the
storage and computational load but provides the
advantage of increased channel utilization and
decreased probability of blocked calls.
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 document discusses key concepts in cellular network design including:
1) The cellular concept divides a large service area into smaller cells served by low-power base stations to improve capacity compared to single transmitter systems.
2) Frequency reuse planning involves assigning different channel groups to neighboring cells to minimize interference while maximizing frequency reuse.
3) Handoff strategies are used to transfer calls between cells as users move, and guard channels and queuing can help reduce dropped calls.
4) Techniques like cell splitting, sectoring, and smaller cell zones can help improve coverage and capacity in congested areas without requiring additional spectrum.
The document discusses the cellular concept in wireless networks. Key points include:
- Cells have a hexagonal shape and neighboring cells reuse frequencies to avoid interference and increase capacity.
- Frequency reuse allows more simultaneous calls by allocating the same set of frequencies to different neighboring cells.
- Cell size is a tradeoff between interference and system capacity - smaller cells mean lower power needs but more cells and handoffs.
The document discusses key concepts in cellular system design including frequency reuse, cell size, system capacity, and handoff strategies. The cellular concept allows efficient reuse of a fixed number of channels across a large coverage area by dividing the area into smaller cells and reusing frequencies in cells sufficiently distant from each other to prevent interference. System capacity is determined by the number of available channels, cluster size which impacts frequency reuse distance and interference levels, and the number of times a cluster can be replicated across the coverage area. Handoff strategies aim to transfer calls seamlessly between cells as users move and involve monitoring signal levels, assigning priority to handoffs over new calls, and reserving guard channels.
TIME DIVISION MULTIPLEXING TECHNIQUE FOR COMMUNICATION SYSTEMHODECEDSIET
Time Division Multiplexing (TDM) is a method of transmitting multiple signals over a single communication channel by dividing the signal into many segments, each having a very short duration of time. These time slots are then allocated to different data streams, allowing multiple signals to share the same transmission medium efficiently. TDM is widely used in telecommunications and data communication systems.
### How TDM Works
1. **Time Slots Allocation**: The core principle of TDM is to assign distinct time slots to each signal. During each time slot, the respective signal is transmitted, and then the process repeats cyclically. For example, if there are four signals to be transmitted, the TDM cycle will divide time into four slots, each assigned to one signal.
2. **Synchronization**: Synchronization is crucial in TDM systems to ensure that the signals are correctly aligned with their respective time slots. Both the transmitter and receiver must be synchronized to avoid any overlap or loss of data. This synchronization is typically maintained by a clock signal that ensures time slots are accurately aligned.
3. **Frame Structure**: TDM data is organized into frames, where each frame consists of a set of time slots. Each frame is repeated at regular intervals, ensuring continuous transmission of data streams. The frame structure helps in managing the data streams and maintaining the synchronization between the transmitter and receiver.
4. **Multiplexer and Demultiplexer**: At the transmitting end, a multiplexer combines multiple input signals into a single composite signal by assigning each signal to a specific time slot. At the receiving end, a demultiplexer separates the composite signal back into individual signals based on their respective time slots.
### Types of TDM
1. **Synchronous TDM**: In synchronous TDM, time slots are pre-assigned to each signal, regardless of whether the signal has data to transmit or not. This can lead to inefficiencies if some time slots remain empty due to the absence of data.
2. **Asynchronous TDM (or Statistical TDM)**: Asynchronous TDM addresses the inefficiencies of synchronous TDM by allocating time slots dynamically based on the presence of data. Time slots are assigned only when there is data to transmit, which optimizes the use of the communication channel.
### Applications of TDM
- **Telecommunications**: TDM is extensively used in telecommunication systems, such as in T1 and E1 lines, where multiple telephone calls are transmitted over a single line by assigning each call to a specific time slot.
- **Digital Audio and Video Broadcasting**: TDM is used in broadcasting systems to transmit multiple audio or video streams over a single channel, ensuring efficient use of bandwidth.
- **Computer Networks**: TDM is used in network protocols and systems to manage the transmission of data from multiple sources over a single network medium.
### Advantages of TDM
- **Efficient Use of Bandwidth**: TDM all
Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapte...University of Maribor
Slides from talk presenting:
Aleš Zamuda: Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapter and Networking.
Presentation at IcETRAN 2024 session:
"Inter-Society Networking Panel GRSS/MTT-S/CIS
Panel Session: Promoting Connection and Cooperation"
IEEE Slovenia GRSS
IEEE Serbia and Montenegro MTT-S
IEEE Slovenia CIS
11TH INTERNATIONAL CONFERENCE ON ELECTRICAL, ELECTRONIC AND COMPUTING ENGINEERING
3-6 June 2024, Niš, Serbia
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
CHINA’S GEO-ECONOMIC OUTREACH IN CENTRAL ASIAN COUNTRIES AND FUTURE PROSPECTjpsjournal1
The rivalry between prominent international actors for dominance over Central Asia's hydrocarbon
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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. Outline
l Introduction
l Frequency Reuse
l Channel Assignment Strategies
l Handoff Strategies
l Interference and System Capacity
l Improving Capacity In Cellular Systems
3. Introduction
l Early mobile radio systems
l A single high powered transmitter (single cell)
l Large coverage area
l Low frequency resource utility
l Low user capacity
l The cellular concept
l A major breakthrough in solving the problem of spectral
congestion and user capacity
l Many low power transmitters (small cells)
l Each cell covers only a small portion of the service area.
l Each base station is allocated a portion of the total number of
channels
l Nearby base stations are assigned different groups of channels
so that the interference between base stations is minimized
5. Frequency Reuse
l A service area is split into small geographic areas,
called cells.
l Each cellular base station is allocated a group of
radio channels.
l Base stations in adjacent cells are assigned
different channel groups.
l By limiting the coverage area of a base station, the
same group of channels may be reused by different
cells far away.
l The design process of selecting and allocating
channel groups for all of the cellular base stations
within a system is called frequency reuse or
frequency planning.
6. Frequency Reuse:
Cell Shapes
l Geometric shapes covering an entire region
without overlap and with equal area.
l By using the hexagon, the fewest number of cells
can cover a geographic region, and the hexagon
closely approximates a circular radiation pattern
which would occur for an omni-directional antenna.
square equilateral triangle hexagon
7. Frequency Reuse:
Excitation modes
l Center-excited cell
l Base station transmitter is in the center of the cell.
l Omni-directional antennas are used.
l Edge-excited cell
l Base station transmitters are on three of the six
cell vertices.
l Sectored directional antennas are used.
8. Frequency Reuse:
The concept of Cluster
l Consider a cellular system which has a total of
S duplex channels available for use.
l The S channels are divided among N cells (cluster).
l Each cell is allocated a group of k channels.
l The total number of available radio channels can
be expressed as S=kN.
k
k
k
k
k
k
k
Totally S=kN duplex channels
Cluster: N=7
The N cells which collectively use the
complete set of available frequencies is
called a cluster.
Cluster size: N=4,7,12
Frequency reuse Factor: 1/N
9. Frequency Reuse:
Reuse Planning
l If a cluster is replicated M times within the
system, the total number of duplex channels,
C, can be given as C = MkN = MS.
l Mathematically, N= i2 + ij + j2
l Where i and j are non-negative integers.
l The nearest co-channel neighbors of a particular
cell can be found by doing what follows:
l move i cells along any chain of hexagons;
l turn 60 degrees counter-clockwise;
l move j cells.
10. Frequency Reuse:
Reuse Planning
l Examples
A
A
A
A
B
B
B
B
C
C
C
C
G
G
G
G
D
D
D
D
F
F
F
F
E
E
E
E
Cluster
N=7
i=2, j=1
Cluster
Cluster
A
A
A
B
B
B
C
C
C
D
D
D
A
B
C
D
A
B
D
A
B
C
D
C
C
B
A
D
Cluster
N=4
i=2, j=0
Cluster
N=4
7-cell reuse 4-cell reuse
12. Channel Assignment Strategies
l Objectives:
l Increasing capacity
l Minimizing interference
l Classification:
l Fixed channel assignment strategies
l Dynamic channel assignment strategies
13. Fixed channel assignment
l Each cell is allocated a predetermined set of
channels.
l Any call attempt within the cell can only be
served by the unused channels in that
particular cell.
l If all the channels in that cell are occupied,
the call is blocked and the subscriber does
not receive service.
14. Dynamic channel assignment
strategies
l Channels are not allocated to different cells
permanently.
l Each time a call request is made, the serving base
station requests a channel from the MSC.
l The switch then allocates a channel to the
requested cell following an algorithm that takes into
account:
l the likelihood of fixture blocking within the cell
l the frequency of use of the candidate channel
l the reuse distance of the channel
l other cost functions.
15. Handoff Strategies
l Handoff:
l When a mobile moves into a different cell while a
conversation is in progress, the MSC
automatically transfers the call to a new channel
belonging to the new base station.
l Processing handoffs is an important task in
any cellular radio system.
16. Handoff Strategies:
Requirements
l Handoffs must be performed:
l Successfully;
l As infrequently as possible;
l Imperceptible to the users.
l How to meet these requirements?
l Specify an optimum signal level to initiate a handoff;
l Decide optimally when to handoff;
l Consider the statistics of dwell time.
17.
18. Handoff Strategies:
Signal strength measurements
l First generation analog cellular systems:
l Signal strength measurements are made by the
base stations and supervised by the MSC.
l Second generation systems:
l Handoff decisions are mobile assisted;
l The MSC no longer constantly monitors signal
strengths.
19. Handoff Strategies:
Managing of handoffs
l Prioritizing Handoffs
l Guard channel: a fraction of the total available channels in
a cell is reserved exclusively for handoff requests from
ongoing calls which may be handed off into the cell.
l Queuing of handoff requests: to decrease the probability of
forced termination of a call due to lack of available
channels.
l Queuing of handoffs is possible due to the fact that there is
a finite time interval between the time the received signal
level drops below the handoff threshold and the time the
call is terminated due to insufficient signal level.
20. Practical Handoff Considerations
l Observations
l High speed vehicles pass through the coverage region of a cell within a
matter of seconds.
l Pedestrian users may never need a handoff during a call.
l Particularly with the addition of microcells to provide capacity, the MSC can
quickly become burdened if high speed users are constantly being passed
between very small cells.
l It is difficult for cellular service providers to obtain new physical cell site
locations in urban areas.
l Another practical handoff problem in microcell systems is known as cell
dragging.
l Solutions
l The umbrella cell approach.
l Newer cellular systems make handoff decisions based on a wide range of
metrics other than signal strength.
l Soft handoff (CDMA cellular networks): The ability to select between the
instantaneous received signals from a variety of base stations is called soft
handoff.
22. Interference and System
Capacity
l Interference is the major limiting factor in the
performance of cellular radio systems:
l a major bottleneck in increasing capacity
l often responsible for dropped calls
l The two major types of system-generated
cellular interference are:
l co-channel interference
l adjacent channel interference
l Power Control for Reducing Interference
23. Co-channel Interference and
System Capacity
l Co-channel Interference
l Cells using the same set of frequencies are called co-
channel cells, and the interference between signals from
these cells is called co-channel interference.
l Unlike thermal noise which can be overcome by increasing
the signal-to-noise ration (SNR), co-channel interference
cannot be combated by simply increasing the carrier power
of a transmitter. This is because an increase in carrier
transmit power increases the interference to neighboring
co-channel cells.
l To reduce co-channel interference, co-channel cells must
be physically separated by a minimum distance to provide
sufficient isolation due to propagation.
25. Co-channel Interference and
System Capacity
l The co-channel interference ratio is a
function of the radius of the cell (B) and the
distance between centers of the nearest co-
channel cells (D).
l By increasing the ratio of D/R, the spatial
separation between co-channel cells relative
to the coverage distance of a cell is increased.
Thus interference is reduced.
26. Cochannel reuse ratio
l The parameter Q= D/R, called the cochannel reuse
ratio, is related to the cluster size N.
l When the size of each cell is approximately the same, and
the base stations transmit the same power, we have
Q= D/R=(3N)1/3
l A small value of Q provides larger capacity since the
cluster size N is small, whereas a large value of Q
improves the transmission quality, due to a smaller level of
co-channel interference.
l A trade-off must be made between these two objectives in
actual cellular design.
28. Signal-to-interference ratio
(SIR)
l The signal-to-interference ratio (SIR) for a mobile
receiver can be expressed as
l S denotes the desired signal power;
l Ii is the interference power caused by the i-th interfering
co-channel cell base station;
l i0 is the number of cochannel interfering cells.
0
0
i
i
i
S
SIR
I
=
=
∑
30. Signal-to-interference ratio
(SIR)
l The average received power
P at a distance d from the
transmitting antenna is
approximated by
l If all base stations transmit
at the same power level, the
SIR can be given as
l In practice, measures
should be taken to keep the
SIR on a acceptable level.
0
0
n
r
d
P P
d
=
0
0
n
i
n
i
i
R
SIR
D
−
−
=
=
∑
31. Adjacent Channel Interference
l Interference resulting from signals which are
adjacent in frequency to the desired signal is
called adjacent channel interference.
l Adjacent channel interference results from
imperfect receiver filters which allow nearby
frequencies to leak into the passband.
l Near-far effect:
l If an adjacent channel user is transmitting in very
close range to a subscriber's receiver, the problem
can be particularly serious.
32. Adjacent Channel Interference
l Adjacent channel interference can be minimized
through careful filtering and channel assignments:
l By keeping the frequency separation between each
channel in a given cell as large as possible, the adjacent
channel interference may be reduced considerably.
l Channel allocation schemes can also prevent a secondary
source of adjacent channel interference by avoiding the
use of adjacent channels in neighboring cell sites.
l High Q cavity filters can be used in order to reject adjacent
channel interference.
33.
34. Power Control for Reducing
Interference
l In practical cellular radio and personal communication systems
the power levels transmitted by every subscriber unit are under
constant control by the serving base stations.
l This is done to ensure that each mobile transmits the smallest
power necessary to maintain a good quality link on the reverse
channel.
l Power control not only helps prolong battery life for the
subscriber unit, but also dramatically improves the reverse
channel S/I in the system.
l Power control is especially important for emerging CDMA spread
spectrum systems that allow every user in every cell to share the
same radio channel.
35. Improving Capacity In Cellular
Systems
l As the demand for wireless service increases, the
number of channels assigned to a cell eventually
becomes insufficient to support the required number
of users.
l Techniques to expand the capacity of cellular
systems :
l Cell splitting: increases the number of base stations in
order to increase capacity.
l Sectoring: relies on base station antenna placements to
improve capacity by reducing co-channel interference.
l Coverage zone: distributes the coverage of a cell and
extends the cell boundary to hard-to-reach places.
36. Cell Splitting
l Cell splitting is the process of subdividing a
congested cell into smaller cells, each with its
own base station and a corresponding
reduction in antenna height and transmitter
power.
l Cell splitting increases the capacity of a
cellular system since it increases the number
of times that channels are reused.
39. Sectoring
l The technique for decreasing co-channel
interference and thus increasing system
capacity by using directional antennas is
called sectoring.
l The factor by which the co-channel
interference is reduced depends on the
amount of sectoring used.
42. A Novel Microcell Zone Concept
l Zone Concept
l Zone sites are connected to a single base station and share the
same radio equipment.
l The zones are connected by coaxial cable, fiberoptic cable, or
microwave link to the base station.
l Multiple zones and a single base station make up a cell.
l As a mobile travels within the cell, it is served by the zone with
the strongest signal.
l This technique is particularly useful along highways or along
urban traffic corridors.
l This approach is superior to sectoring since antennas are placed
at the outer edges of the cell, and any base station channel may
be assigned to any zone by the base station.
l In comparison with sectoring, the number of handoffs can be
reduced significantly.