This document discusses programming acoustic modems for underwater networking. It describes implementing a basic ALOHA medium access control (MAC) protocol using Teledyne Benthos SM 975 acoustic smart modems. The modems are programmed through a Matlab interface using get, set, execute, and notify commands. Experimental results testing the ALOHA MAC protocol implemented on the modems are also presented.
Wirleless communicatrion notes for 8th sem EC -unit 2SURESHA V
This document discusses common components of cellular networks. It describes the main components as the mobile station (MS), base station system (BSS) including the radio base station (RBS) and base station controller (BSC), and the network switching system (NSS) including the mobile switching center (MSC). The BSS handles radio interface functions and connectivity to the MSC. The MSC is responsible for call routing and mobility management. Other components discussed include the visitor location register (VLR), home location register (HLR), transcoder controller (TRC) and signaling system 7 (SS7).
The document provides an overview of the GSM network architecture, including its three main subsystems: the Mobile Station subsystem, the Base Station Subsystem, and the Network Switching Subsystem. It describes the key elements and interfaces within each subsystem, such as the Mobile Station, Base Transceiver Station, Base Station Controller, Mobile Switching Center, Home Location Register, and Visitor Location Register. The interfaces that connect these elements, such as the A, Abis, and Um interfaces, are also introduced.
Design and analysis 5G mobile network model to enhancement high-density subsc...journalBEEI
To obtain a high data rate that is commensurate with the growing demand for internet services, the fifth generation (5G) cellular networks will use the bandwidth beyond 6 GHz, called millimeters waves (mm-waves), to obtain a higher. The first phase (phase I) of the 5G network design for high user density, where the optimized microcells are deployed at carrier frequency 700 MHz with 20 MHz bandwidth. The second phase (phase II) of the design consists of the deployment of microcells which are operating at 3.6 GHz with 100 MHz bandwidth; this phase is planned to cover 200000 users within the province. The third phase (phase III) of the design is represented by the deployment of picocells, which are planned to operate at 26 GHz frequency and bandwidth 500 MHz; this phase is planned to cover 3,500,000 users within the province. Two types of modulation are adopted for the network (orthogonal frequency division multiplexing (OFDM) and 256 quadrature amplitude modulation (QAM)); the overall performance of the network is studied with regards to the percentage of coverage, power overlapping ratio, frequency interference, and quality of service (QoS).
LTE-Advanced improves upon LTE technology to meet the requirements for ITU's IMT-Advanced specification. This document summarizes the key technology components of LTE-Advanced, including band aggregation, enhanced multiple-input multiple-output antenna techniques, improved uplink transmission, coordinated multipoint transmission and reception, and the use of relay stations. LTE-Advanced aims to provide peak data rates of 1 Gbps downstream and 500 Mbps upstream, reduced latency, increased spectrum efficiency, and high throughput for cell edge users.
This document provides an overview of wireless communication standards including IEEE 802.11x, 802.15x, and 802.16x. It discusses the objectives of the unit which are to explain the differences between wireless LANs, PANs, and MANs. It then goes on to describe the evolution of IEEE 802.11 standards including improvements to data rates, security, and quality of service over time. Key standards such as 802.11a, 802.11b, 802.11g, and 802.11n are explained. Design challenges for wireless LANs like changing topologies and interference are also summarized.
UNIT III
MOBILE COMMUNICATION SYSTEMS
GSM-architecture-Location tracking and call setup- Mobility management- Handover-Security-GSM SMS –International roaming for GSM- call recording functions-subscriber and service data mgt –-Mobile Number portability -VoIP service for Mobile Networks –GPRS –Architecture-GPRS procedures-attach and detach procedures-PDP context procedure-combined RA/LA update procedures-Billing
This document discusses device-to-device (D2D) communication in LTE networks. It describes how D2D allows direct communication between user equipments by bypassing the base station, addressing issues like network coverage, congestion control, and public safety. The document outlines the D2D communication process, including synchronization, discovery, and communication modes. It also describes the ProSe D2D network architecture and direct discovery procedure. D2D communication in LTE aims to improve network coverage, offer last mile connectivity, control congestion, and enable public safety communication during emergencies or disasters.
Wirleless communicatrion notes for 8th sem EC -unit 2SURESHA V
This document discusses common components of cellular networks. It describes the main components as the mobile station (MS), base station system (BSS) including the radio base station (RBS) and base station controller (BSC), and the network switching system (NSS) including the mobile switching center (MSC). The BSS handles radio interface functions and connectivity to the MSC. The MSC is responsible for call routing and mobility management. Other components discussed include the visitor location register (VLR), home location register (HLR), transcoder controller (TRC) and signaling system 7 (SS7).
The document provides an overview of the GSM network architecture, including its three main subsystems: the Mobile Station subsystem, the Base Station Subsystem, and the Network Switching Subsystem. It describes the key elements and interfaces within each subsystem, such as the Mobile Station, Base Transceiver Station, Base Station Controller, Mobile Switching Center, Home Location Register, and Visitor Location Register. The interfaces that connect these elements, such as the A, Abis, and Um interfaces, are also introduced.
Design and analysis 5G mobile network model to enhancement high-density subsc...journalBEEI
To obtain a high data rate that is commensurate with the growing demand for internet services, the fifth generation (5G) cellular networks will use the bandwidth beyond 6 GHz, called millimeters waves (mm-waves), to obtain a higher. The first phase (phase I) of the 5G network design for high user density, where the optimized microcells are deployed at carrier frequency 700 MHz with 20 MHz bandwidth. The second phase (phase II) of the design consists of the deployment of microcells which are operating at 3.6 GHz with 100 MHz bandwidth; this phase is planned to cover 200000 users within the province. The third phase (phase III) of the design is represented by the deployment of picocells, which are planned to operate at 26 GHz frequency and bandwidth 500 MHz; this phase is planned to cover 3,500,000 users within the province. Two types of modulation are adopted for the network (orthogonal frequency division multiplexing (OFDM) and 256 quadrature amplitude modulation (QAM)); the overall performance of the network is studied with regards to the percentage of coverage, power overlapping ratio, frequency interference, and quality of service (QoS).
LTE-Advanced improves upon LTE technology to meet the requirements for ITU's IMT-Advanced specification. This document summarizes the key technology components of LTE-Advanced, including band aggregation, enhanced multiple-input multiple-output antenna techniques, improved uplink transmission, coordinated multipoint transmission and reception, and the use of relay stations. LTE-Advanced aims to provide peak data rates of 1 Gbps downstream and 500 Mbps upstream, reduced latency, increased spectrum efficiency, and high throughput for cell edge users.
This document provides an overview of wireless communication standards including IEEE 802.11x, 802.15x, and 802.16x. It discusses the objectives of the unit which are to explain the differences between wireless LANs, PANs, and MANs. It then goes on to describe the evolution of IEEE 802.11 standards including improvements to data rates, security, and quality of service over time. Key standards such as 802.11a, 802.11b, 802.11g, and 802.11n are explained. Design challenges for wireless LANs like changing topologies and interference are also summarized.
UNIT III
MOBILE COMMUNICATION SYSTEMS
GSM-architecture-Location tracking and call setup- Mobility management- Handover-Security-GSM SMS –International roaming for GSM- call recording functions-subscriber and service data mgt –-Mobile Number portability -VoIP service for Mobile Networks –GPRS –Architecture-GPRS procedures-attach and detach procedures-PDP context procedure-combined RA/LA update procedures-Billing
This document discusses device-to-device (D2D) communication in LTE networks. It describes how D2D allows direct communication between user equipments by bypassing the base station, addressing issues like network coverage, congestion control, and public safety. The document outlines the D2D communication process, including synchronization, discovery, and communication modes. It also describes the ProSe D2D network architecture and direct discovery procedure. D2D communication in LTE aims to improve network coverage, offer last mile connectivity, control congestion, and enable public safety communication during emergencies or disasters.
This document provides an introduction and overview of mobile ad hoc networks (MANETs). It discusses how MANETs are self-configuring networks formed by mobile nodes without a fixed infrastructure. The key characteristics of MANETs include using wireless communication, nodes acting as both hosts and routers, limited bandwidth and variable capacity links, energy-constrained operation, and dynamic network topology. The document also outlines some common applications of MANETs and provides an overview of different routing protocols used in MANETs, including proactive, reactive, and hybrid protocols. It gives a brief description of distance-vector and link-state routing approaches.
UNIT II
WIRELESS NETWORKS
Wireless LAN – IEEE 802.11 Standards – Architecture – Services – Mobile Ad hoc Networks- WiFi and WiMAX - Wireless Local Loop
LTE-Advanced is an evolution of LTE that provides higher data rates of up to 1 Gbps download and 500 Mbps upload through carrier aggregation and advanced MIMO technologies. It has lower latency of under 50ms for handovers and uses self-optimizing networks to automatically configure itself. Key technologies include carrier aggregation, enhanced MIMO, Coordinated MultiPoint transmission and reception, and support for heterogeneous networks. LTE-Advanced fulfills the requirements for 4G networks and sees applications in high-definition video streaming, cloud services, mobile health, and smart grids. Further developments will aim to improve spectrum efficiency and meet future capacity demands.
This document provides an overview of wireless personal area networks (WPANs), including Bluetooth, ZigBee, and Ultra-Wideband. It describes the key features and applications of each technology, how their protocols are structured, and how they compare to each other. Bluetooth supports data rates up to 2 Mbps over short ranges and is used in devices like phones, laptops, and printers. ZigBee focuses on low power consumption and supports thousands of nodes in a mesh network for uses like smart homes and buildings. Ultra-Wideband provides high data rates over short ranges and is used in applications like TVs, DVD players, and mobile devices.
This document discusses multiple access techniques for wireless communications, including FDMA, TDMA, and CDMA. It provides details on how each technique works and its advantages and disadvantages. FDMA divides the frequency band into channels that can be assigned to individual users. TDMA divides each channel into time slots that can be assigned to users. CDMA allows all users to use the whole available bandwidth simultaneously by using unique codes to distinguish users.
The tutorial is designed for all those readers who are planning or pursuing the CDMA course to make their career in this field. However, it is also meant for the common readers who simply want to understand − what is CDMA Technology?
Mobile Networking and Ad hoc routing protocols validationIOSR Journals
This document discusses mobile networking and ad hoc routing protocols. It begins with an overview of cellular phone networks and their growth in usage. It then describes mobile ad hoc networks and some of the challenges in designing routing protocols for them. The document evaluates two model checking tools, SPIN and UPPAAL, and discusses their ability to verify properties of ad hoc routing protocols through formal validation methods.
The document provides an overview of Long Term Evolution (LTE), the leading 4G mobile broadband technology. It discusses the key drivers behind the evolution to 4G including increasing user demands for speed and bandwidth. It then summarizes the evolution of wireless technologies from 1G to 4G LTE. Key features of LTE that make it superior include peak download speeds of 300Mbps, low latency, support for flexible bandwidths and large cell sizes. The document outlines the LTE network architecture consisting of the radio access network with eNodeBs and the core network known as the Evolved Packet Core. It describes the functions of various core network nodes like the MME, HSS, S-GW and P-GW.
1) Transcoder Free Operation (TrFO) and Tandem Free Operation (TFO) allow for improved voice quality and reduced delay in UMTS and GSM networks respectively by removing transcoding steps from voice calls.
2) With TrFO, mobile-to-mobile calls in a UMTS network can use wideband codecs without transcoding, improving quality. TFO removes tandem transcoders from GSM calls by tunneling compressed audio between transcoding units.
3) Events like handovers can temporarily interrupt TrFO/TFO and require renegotiation or fallback to standard transcoding to maintain call quality.
SS7 (Common Channel Signaling System 7) is a global standard defined by the ITU for telecommunications networks to exchange signaling information for call setup and routing over a digital network. It allows for wireless and wireline calls as well as enhanced services. SS7 uses out-of-band signaling over dedicated channels between network elements called signaling points, including SSPs, STPs, and SCPs. SS7 messages are transmitted over these signaling links and routing points using a layered protocol stack.
A mobile station in GSM comprises several functional groups including the mobile terminal, terminal adapter, terminal equipment, and subscriber identity module. The network and switching subsystem is the main component of the public mobile network and controls switching, mobility management, and interconnection. It includes components like the mobile switching center, home location register, and visitor location register. The mobile switching center plays a central role in switching functions and mobility support.
The document summarizes the hybrid wireless-optical broadband-access network (WOBAN) architecture. It discusses how WOBAN combines the benefits of wireless and optical networks by using an optical network like a passive optical network (PON) at the back end connected to wireless base stations. This saves on network deployment costs compared to fully wired networks. The document then reviews challenges for WOBAN including algorithms for network setup and placement of optical network units, examining the network's routing properties, and designing fault-tolerant behavior. It provides context on industry efforts to deploy related broadband access solutions and municipal mesh networks.
As a consequence of the proliferation of smart phones and tablets, data traffic is growing significantly, both on the radio access links and the backhaul infrastructure of mobile operators’ networks. And although LTE and LTE Advanced offer higher data traffic throughput than that of 3G, given to their wider allocated bandwidths, the combined capacities of even these networks is not sufficient to meet projected future capacity demands.
The conventional solution to increasing the capacity of LTE mobile networks includes splitting macro-cells and/or adding more sites. Both of these solutions require high CAPEX and OPEX, so mobile operators are seeking new and cost effective ways of increasing their network capacity. One solution is to deploy small-cell base stations (BSs) within their existing macro-cellular networks, an approach referred to as Heterogeneous Networks.
It is well known that a HetNet not only increases the network capacity, but also provides better coverage and enhances the user’s experience. These benefits are achieved by offloading data traffic dynamically from MCBSs to SCBSs using an algorithm based on several parameters such as the characteristics of the traffic, the required QoS and network
Unit 5 : wireless communication : GSM System operationsAshutha K
The document summarizes the key steps in GSM call setup, which includes 10 operations: interrogation, radio resource connection establishment, service request, authentication, ciphering mode setting, IMEI number check, TMSI allocation, call initiation, assignment of a traffic channel, and user alerting signaling. The radio resource connection establishment involves 10 steps including paging the mobile station, establishing a signaling connection, determining available channels, and assigning a traffic channel for the call. Authentication ensures the identity of the mobile station through random numbers and encryption keys.
The document provides a summary of the history and evolution of internet and wireless broadband technology. It discusses the early concepts of computer networking starting in the 1960s, the development of ARPANET in the late 1960s, and the introduction of TCP/IP in the early 1970s which led to the modern internet. It then covers the emergence of dial-up internet access in the late 1970s and 1980s, and the evolution of cellular network technologies from 1G to 4G. Finally, it provides an overview of LTE and LTE-Advanced wireless broadband technologies and their capabilities.
Co-channel and adjacent-channel interference evaluation of an outdoor telecom...Konstantinos Stamatakis
The objective of the present paper is to evaluate the
impact of adjacent and co-channel interference on the
performance of some standard report systems that exists in an
outdoor telecommunications cabinet - base station (BS) (also
known as KV, from the acronym of the German word
Kabelverzweiger) and devices that technicians frequently use.
Specifically, the interference analyzed is between devices, such as
Bluetooth handset, laptop and measurement tools, that are
usually used during inspections and repairs by technicians and
wireless reporting systems installed inside BS that provide
information about BS’s condition and real time connection with
the help desk back office
The document discusses how software defined networking (SDN) could be applied to cellular networks to simplify network management and enable new services. It proposes several extensions to SDN controllers, switches, and base stations to address challenges in supporting mobility, scalability, and real-time control in cellular networks. Specifically, it suggests expressing policies based on subscriber attributes rather than addresses, using local switch agents for real-time control, and enabling remote control of virtualized base station resources from the SDN controller.
LTE Advanced is an enhancement of the LTE mobile communication standard that aims to improve spectrum efficiency, flexibility, and throughput. Key features of LTE Advanced include support for wider bandwidths up to 100MHz, advanced MIMO technologies with up to 8 antenna ports, improved cell edge performance using Coordinated Multi-Point transmission, and integration of relay nodes to enhance coverage. LTE Advanced is designed to meet the ITU requirements for 4G networks by providing peak data rates of at least 1 Gbps for high mobility communication.
The document summarizes the key concepts from the course "Mobile Computing" taught in the sixth semester of the Bachelor of Engineering program in Computer Science and Engineering at RAMCO Institute of Technology. It covers the basics of mobile computing including definitions, applications, components of wireless communication systems, mobile communication architectures, and generations of mobile technologies from 1G to 5G. It also describes multiplexing techniques such as space division multiplexing, frequency division multiplexing, and time division multiplexing that allow multiple users to share communication channels and medium.
The document summarizes Rockford IT's services, which include managed IT services, hosting solutions, communication solutions, IT security solutions, and disaster recovery solutions. They provide flexible and tailored solutions to meet customers' exact needs with expert support. Rockford IT aims to recommend the best solutions and suppliers so customers can focus on their core business while their infrastructure is reliable and secure.
This document provides information about a school including images of students working and participating in class along with news briefs about school sports teams. It also displays the school logo and name.
This document provides an introduction and overview of mobile ad hoc networks (MANETs). It discusses how MANETs are self-configuring networks formed by mobile nodes without a fixed infrastructure. The key characteristics of MANETs include using wireless communication, nodes acting as both hosts and routers, limited bandwidth and variable capacity links, energy-constrained operation, and dynamic network topology. The document also outlines some common applications of MANETs and provides an overview of different routing protocols used in MANETs, including proactive, reactive, and hybrid protocols. It gives a brief description of distance-vector and link-state routing approaches.
UNIT II
WIRELESS NETWORKS
Wireless LAN – IEEE 802.11 Standards – Architecture – Services – Mobile Ad hoc Networks- WiFi and WiMAX - Wireless Local Loop
LTE-Advanced is an evolution of LTE that provides higher data rates of up to 1 Gbps download and 500 Mbps upload through carrier aggregation and advanced MIMO technologies. It has lower latency of under 50ms for handovers and uses self-optimizing networks to automatically configure itself. Key technologies include carrier aggregation, enhanced MIMO, Coordinated MultiPoint transmission and reception, and support for heterogeneous networks. LTE-Advanced fulfills the requirements for 4G networks and sees applications in high-definition video streaming, cloud services, mobile health, and smart grids. Further developments will aim to improve spectrum efficiency and meet future capacity demands.
This document provides an overview of wireless personal area networks (WPANs), including Bluetooth, ZigBee, and Ultra-Wideband. It describes the key features and applications of each technology, how their protocols are structured, and how they compare to each other. Bluetooth supports data rates up to 2 Mbps over short ranges and is used in devices like phones, laptops, and printers. ZigBee focuses on low power consumption and supports thousands of nodes in a mesh network for uses like smart homes and buildings. Ultra-Wideband provides high data rates over short ranges and is used in applications like TVs, DVD players, and mobile devices.
This document discusses multiple access techniques for wireless communications, including FDMA, TDMA, and CDMA. It provides details on how each technique works and its advantages and disadvantages. FDMA divides the frequency band into channels that can be assigned to individual users. TDMA divides each channel into time slots that can be assigned to users. CDMA allows all users to use the whole available bandwidth simultaneously by using unique codes to distinguish users.
The tutorial is designed for all those readers who are planning or pursuing the CDMA course to make their career in this field. However, it is also meant for the common readers who simply want to understand − what is CDMA Technology?
Mobile Networking and Ad hoc routing protocols validationIOSR Journals
This document discusses mobile networking and ad hoc routing protocols. It begins with an overview of cellular phone networks and their growth in usage. It then describes mobile ad hoc networks and some of the challenges in designing routing protocols for them. The document evaluates two model checking tools, SPIN and UPPAAL, and discusses their ability to verify properties of ad hoc routing protocols through formal validation methods.
The document provides an overview of Long Term Evolution (LTE), the leading 4G mobile broadband technology. It discusses the key drivers behind the evolution to 4G including increasing user demands for speed and bandwidth. It then summarizes the evolution of wireless technologies from 1G to 4G LTE. Key features of LTE that make it superior include peak download speeds of 300Mbps, low latency, support for flexible bandwidths and large cell sizes. The document outlines the LTE network architecture consisting of the radio access network with eNodeBs and the core network known as the Evolved Packet Core. It describes the functions of various core network nodes like the MME, HSS, S-GW and P-GW.
1) Transcoder Free Operation (TrFO) and Tandem Free Operation (TFO) allow for improved voice quality and reduced delay in UMTS and GSM networks respectively by removing transcoding steps from voice calls.
2) With TrFO, mobile-to-mobile calls in a UMTS network can use wideband codecs without transcoding, improving quality. TFO removes tandem transcoders from GSM calls by tunneling compressed audio between transcoding units.
3) Events like handovers can temporarily interrupt TrFO/TFO and require renegotiation or fallback to standard transcoding to maintain call quality.
SS7 (Common Channel Signaling System 7) is a global standard defined by the ITU for telecommunications networks to exchange signaling information for call setup and routing over a digital network. It allows for wireless and wireline calls as well as enhanced services. SS7 uses out-of-band signaling over dedicated channels between network elements called signaling points, including SSPs, STPs, and SCPs. SS7 messages are transmitted over these signaling links and routing points using a layered protocol stack.
A mobile station in GSM comprises several functional groups including the mobile terminal, terminal adapter, terminal equipment, and subscriber identity module. The network and switching subsystem is the main component of the public mobile network and controls switching, mobility management, and interconnection. It includes components like the mobile switching center, home location register, and visitor location register. The mobile switching center plays a central role in switching functions and mobility support.
The document summarizes the hybrid wireless-optical broadband-access network (WOBAN) architecture. It discusses how WOBAN combines the benefits of wireless and optical networks by using an optical network like a passive optical network (PON) at the back end connected to wireless base stations. This saves on network deployment costs compared to fully wired networks. The document then reviews challenges for WOBAN including algorithms for network setup and placement of optical network units, examining the network's routing properties, and designing fault-tolerant behavior. It provides context on industry efforts to deploy related broadband access solutions and municipal mesh networks.
As a consequence of the proliferation of smart phones and tablets, data traffic is growing significantly, both on the radio access links and the backhaul infrastructure of mobile operators’ networks. And although LTE and LTE Advanced offer higher data traffic throughput than that of 3G, given to their wider allocated bandwidths, the combined capacities of even these networks is not sufficient to meet projected future capacity demands.
The conventional solution to increasing the capacity of LTE mobile networks includes splitting macro-cells and/or adding more sites. Both of these solutions require high CAPEX and OPEX, so mobile operators are seeking new and cost effective ways of increasing their network capacity. One solution is to deploy small-cell base stations (BSs) within their existing macro-cellular networks, an approach referred to as Heterogeneous Networks.
It is well known that a HetNet not only increases the network capacity, but also provides better coverage and enhances the user’s experience. These benefits are achieved by offloading data traffic dynamically from MCBSs to SCBSs using an algorithm based on several parameters such as the characteristics of the traffic, the required QoS and network
Unit 5 : wireless communication : GSM System operationsAshutha K
The document summarizes the key steps in GSM call setup, which includes 10 operations: interrogation, radio resource connection establishment, service request, authentication, ciphering mode setting, IMEI number check, TMSI allocation, call initiation, assignment of a traffic channel, and user alerting signaling. The radio resource connection establishment involves 10 steps including paging the mobile station, establishing a signaling connection, determining available channels, and assigning a traffic channel for the call. Authentication ensures the identity of the mobile station through random numbers and encryption keys.
The document provides a summary of the history and evolution of internet and wireless broadband technology. It discusses the early concepts of computer networking starting in the 1960s, the development of ARPANET in the late 1960s, and the introduction of TCP/IP in the early 1970s which led to the modern internet. It then covers the emergence of dial-up internet access in the late 1970s and 1980s, and the evolution of cellular network technologies from 1G to 4G. Finally, it provides an overview of LTE and LTE-Advanced wireless broadband technologies and their capabilities.
Co-channel and adjacent-channel interference evaluation of an outdoor telecom...Konstantinos Stamatakis
The objective of the present paper is to evaluate the
impact of adjacent and co-channel interference on the
performance of some standard report systems that exists in an
outdoor telecommunications cabinet - base station (BS) (also
known as KV, from the acronym of the German word
Kabelverzweiger) and devices that technicians frequently use.
Specifically, the interference analyzed is between devices, such as
Bluetooth handset, laptop and measurement tools, that are
usually used during inspections and repairs by technicians and
wireless reporting systems installed inside BS that provide
information about BS’s condition and real time connection with
the help desk back office
The document discusses how software defined networking (SDN) could be applied to cellular networks to simplify network management and enable new services. It proposes several extensions to SDN controllers, switches, and base stations to address challenges in supporting mobility, scalability, and real-time control in cellular networks. Specifically, it suggests expressing policies based on subscriber attributes rather than addresses, using local switch agents for real-time control, and enabling remote control of virtualized base station resources from the SDN controller.
LTE Advanced is an enhancement of the LTE mobile communication standard that aims to improve spectrum efficiency, flexibility, and throughput. Key features of LTE Advanced include support for wider bandwidths up to 100MHz, advanced MIMO technologies with up to 8 antenna ports, improved cell edge performance using Coordinated Multi-Point transmission, and integration of relay nodes to enhance coverage. LTE Advanced is designed to meet the ITU requirements for 4G networks by providing peak data rates of at least 1 Gbps for high mobility communication.
The document summarizes the key concepts from the course "Mobile Computing" taught in the sixth semester of the Bachelor of Engineering program in Computer Science and Engineering at RAMCO Institute of Technology. It covers the basics of mobile computing including definitions, applications, components of wireless communication systems, mobile communication architectures, and generations of mobile technologies from 1G to 5G. It also describes multiplexing techniques such as space division multiplexing, frequency division multiplexing, and time division multiplexing that allow multiple users to share communication channels and medium.
The document summarizes Rockford IT's services, which include managed IT services, hosting solutions, communication solutions, IT security solutions, and disaster recovery solutions. They provide flexible and tailored solutions to meet customers' exact needs with expert support. Rockford IT aims to recommend the best solutions and suppliers so customers can focus on their core business while their infrastructure is reliable and secure.
This document provides information about a school including images of students working and participating in class along with news briefs about school sports teams. It also displays the school logo and name.
Este documento fornece instruções sobre como calcular a cinemática direta e inversa para um manipulador de três graus de liberdade. Ele apresenta as matrizes para calcular a posição (X, Y, Z) da ponta do manipulador usando a cinemática direta e destaca que os resultados da cinemática direta são necessários para calcular a cinemática inversa.
1. O documento apresenta informações sobre máquinas de transporte para uma disciplina sobre o tema ministrada pelo professor Alexandre Silva, incluindo referências bibliográficas, introdução aos equipamentos de transporte vertical e horizontal, e detalhes sobre diversos tipos de equipamentos como gruas, guindastes e talhas.
2. São apresentadas definições de termos técnicos de acordo com a NBR 8400 e simbologia para representar equipamentos.
3. São descritos os procedimentos para classificar as estruturas dos equipamentos em grupos levando em conta fatores
Saurabh Pathak is seeking a position as a Trainee Recruitment Consultant. He has a MBA in Marketing and Finance from Liverpool John Moores University and work experience as an Assistant Manager for DixonsCarphone Stores Group International, where he gained experience in recruitment, interviewing candidates, and managing staff. His skills include excellent communication, sales experience, meeting targets, and the ability to work well in teams, making him qualified for the Trainee Recruitment Consultant role.
Archive Innovation Management - A Future Key Position in Media Innovation or ...FIAT/IFTA
The document discusses the results of a questionnaire and study on the qualifications, skills, and characteristics needed for the potential future role of Archive Innovation Management (AIM). The study received over 180 responses from 17 countries. It found that communication, archival workflows and reuse of content, and awareness of new trends and innovations were among the top essential skills. English language competence, media economics, and project management were among the skills considered least valuable. The document argues AIM will require strong communication skills, digital and archival expertise, social competence, and awareness of media innovation developments to serve the international media archive community.
Simulation model of dc servo motor controlEvans Marshall
This document describes a simulation model of a DC servo motor control system using the TrueTime simulator and WirelessHART communication protocol. The model includes three nodes - a sensor, controller, and actuator - connected via a WirelessHART network. The document provides details on configuring the TrueTime kernel blocks for each node, implementing the control algorithm, and setting up the WirelessHART network simulation. Simulation results are presented showing the data transfer between the nodes for controlling the motor position.
Design of optimal system level for embedded wireless sensor unitIAEME Publication
This document describes the design of an optimal wireless sensor unit system for embedded applications. It presents an architecture that allows for flexible and efficient implementation of communication protocols to optimize performance under power constraints. The key aspects of the design include a central microcontroller connected to an RF transceiver, secondary storage, sensors, and power management. Hardware accelerators are used alongside the microcontroller to improve protocol efficiency while maintaining flexibility. The system is evaluated through implementation of sample communication protocols and demonstrations of system-level optimizations, such as a protocol that reduces receiver power consumption by 90% through preamble-based transmission.
This document summarizes a research paper on medium access control (MAC) protocols for wireless sensor networks. It discusses how MAC protocols are needed to manage shared access to communication channels in wireless sensor networks and outlines some key characteristics and requirements for efficient MAC protocols, including energy efficiency, scalability, and supporting variable traffic loads. It then reviews some traditional MAC protocols, including time division multiple access (TDMA), frequency division multiple access (FDMA), and code division multiple access (CDMA). The full paper provides a more in-depth survey and comparison of schedule-based and contention-based MAC protocols designed specifically for wireless sensor networks.
This project aims to design an embedded irrigation control system that allows farmers to remotely control water pumps via SMS messages. The system uses a GSM modem to receive SMS commands and control an irrigation pump. This allows farmers to start and stop water pumps without being physically present, saving time, effort and resources. The system was implemented using an ATmega8 microcontroller, GSM modem, relay and other basic electronic components. It is powered by a 5V regulated power supply and allows farmers without literacy skills to easily operate irrigation from any mobile phone.
These slides explain the Protocol Framework for 5G mmWave Backhaul Network, as a part of a project presentation for the course Telecom Architecture at Northeastern University.
In this paper, we examine WiMAX – based network and evaluate the performance for quality of service (QoS) using an idea of IEEE 802.16 technology. In our models, the study used a multiprocessor architecture organized by the interconnection network. OPNET Modeler is used to simulate the architecture and to calculate the performance criteria (i.e. throughput, delay and data dropped) that
slightly concerned in network estimation. It is concluded that our models shorten the time quite a bit for
obtaining the performance measures of an end-to-end delay as well as throughput can be used as an
effective tool for this purpose.
The improvement of end to end delays in network management system using netwo...IJCNCJournal
The document summarizes research on improving end-to-end delays in a network management system using network coding. Specifically, it applies network coding to manage radio and television broadcast stations in a wireless network. The study shows that a proposed "Fast Forwarding Strategy" using network coding outperforms a classical routing strategy in reducing end-to-end delays from source to destination. It analyzes end-to-end delays theoretically using network calculus and conducts a practical study on a network of broadcast stations, finding the proposed strategy reduces delays compared to the classical strategy.
TECHNICAL WHITE PAPER: NetBackup Appliances WAN OptimizationSymantec
In a world of ever increasing data flow as well as globalization of data centers the effectiveness and utilization of the networks connecting sites is of the highest importance to end users. Even with network enhancement and improvement, the ability of the infrastructure to keep pace with the flow of data has proved not to be in lockstep. To optimize the flow of data verses increasing the pipe that is flows along is seen as critical to keeping operations running and costs minimal. This paper discusses the new WAN Optimization technology that has been introduced in the NetBackup 5220 and 5020 appliances.
This document outlines the WAN Optimization feature enhancements introduced on the NetBackup 5220 and NetBackup 5020 and applies to:
• NetBackup 5220 & 5230 appliances with version N2.5 and above installed
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This document provides an overview of key concepts in computer networks and communication. It defines what a network is, discusses the need for networking and sharing of resources, and outlines the evolution of early networks like ARPANET and NSFNET into the modern Internet. It also covers network topologies, transmission media, switching techniques, common network devices, and communication protocols.
Design and implementation of heterogeneous surface gateway for underwater aco...IJECEIAES
Underwater Acoustic Sensor Networks (UASNs) are used for diverse purposes such as pollution monitoring, disaster prevention and industrial sensing in the oceans. Especially, UASNs are mainly focusing on monitoring various underwater environmental data and delivering the data to a monitoring center where nearby or far from the deployed area. To reliably deliver the data, a surface gateway should convert acoustic signal to RF (Radio Frequency) signal. In this paper, we devise a multiple interfaces-based surface gateway that can connect both a cellular network and a Zigbee network. Depends on the service requirement, the surface gateway can easily adopt each wireless interface and relay the data to a low power ZigBee network or a long range CDMA network.
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Routers are networking devices that forward packets between logical networks. They are used to extend or segment large internetworks and connect TCP/IP networks and local area networks to the Internet. Routers have advanced features for quality of service, traffic filtering, and encryption. Switches offer intelligence beyond basic hubs and can read MAC addresses to selectively forward frames to specific ports. Bridges divide a network into segments and filter traffic between segments based on MAC addresses. Gateways connect networks that use different protocols by operating at the network layer.
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International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
The document contains detailed description for displaying a Message on LED Notice board through SMS service Wirelessly, if facing any problem you can mail me at rajneeshkumarsalgotra@gmail.com with Subject GSM Wireless Notice Board Report_Your Name
A network connects two or more computers. Common network types are local area networks (LANs), which connect computers in a small area like a building, and wide area networks (WANs), which connect computers over a large geographical area through multiple LAN connections. Networks can be configured using different topologies like bus, star, or ring and use protocols like Ethernet or Token Ring to transmit data. Common network devices include hubs, switches, routers, and firewalls. Networks can be categorized based on their topology, protocols, and architecture.
1. 1
Programming Acoustic Modems for Underwater
Networking
Andrew Tu, Student Member, IEEE, Brian Wilcox Student Member, IEEE,, Mark German, Yashar
M. Aval, Member, IEEE, and Stefano Basagni, Senior Member, IEEE
Abstract—Underwater acoustic communication and networks
have attracted significant attention in recent years, with ap-
plications ranging from ocean monitoring to off-shore sensor
control, and port surveillance. Experimental data are required
to test and develop effective underwater networking protocols
before underwater networks can be successfully deployed for real
world applications. Unfortunately, there are very few permanent
underwater acoustic testbeds currently in operation, making it
difficult for full scale tests to be conducted. To meet the demands
for experimental data, we are working to deploy a permanent
underwater acoustic network at the Northeastern University
Marine Science Center in Nahant, MA. At the final stage, the
network will consist of at least five SM 975 Teledyne Benthos
acoustic smart modems, with one wirelessly connected to the
shore through a smart buoy of our design. This paper describes
the interface for programming these modems and how we used it
to implement a fundamental protocol to be used as performance
benchmark for more advanced underwater solutions.
I. INTRODUCTION
With over 70% of Earth surface covered in water, underwa-
ter communications and networking are critical technological
developments with countless applications in the research and
commercial sectors. Wireless underwater networks will enable
the remote monitoring and control of sensors and equipment
that can be used to collect marine data and analyze their
patterns, thus fostering new applications for the sustainable ex-
ploitation of this still unknown realm of our planet. Prevailing
forms of terrestrial wireless communications, especially radio,
are ill adept for long distance underwater transmissions. As
such, acoustic communication provides a crucial component
towards implementing large scale underwater networks.
Currently, there are very few permanent testbeds for under-
water acoustic networks (UANs) in the world, severely limiting
experimental results on the design of effective networking
protocols. Our end goal is to build a permanent testbed
that will enable easier, more efficient testing of protocols
for UANs at all layers of the protocol stack. Northeastern
University is set to design, develop and deploy a permanent
testbed at its Marine Science Center campus in Nahant, MA.
The network, called NU MONET for Northeastern University
Marine Observatory NETwork, will consist of at least five
SM 975 Teledyne Benthos acoustic smart modems with one
modem connected to the shore via a radio link to program and
control the network and to relay data to the final user. We call
A. Tu, B. Wilcox, M. German, Y. M. Aval and S. Basagni are with the
Department of Electrical and Computer Engineering, Northeastern University,
Boston, MA, USA. Corresponding authors e-mail: tu.a@husky.neu.edu.
Fig. 1: The NU MONET to be deployed in Nahant, MA.
The connections between the modems are underwater acoustic
links (white lines in the picture). One modem acts as the
network gateway to the terrestrial Internet via a smart buoy (of
our design). The connection between the buoy and the shore
station is radio (ZigBee-based; black line in the picture).
this node the entry point, as it connects the UAN to the shore.
A sketch of the planned NU MONET is depicted in Fig. 1.
This paper concerns programming the Teledyne Benthos
modems as a fundamental step towards building the NU
MONET. Modem programming largely depends on the Appli-
cation Programming Interface (API) provided with the devices.
Teledyne Benthos modems, for instance, come with BenthoNet
as the interface for implementing basic networking func-
tionalities (see Section II). Other approaches to underwater
network programming go well beyond the modem relatively
limited interface, and concern the use of suites for integrated
simulation, emulation and testbed trials of protocols at all
levels of the networking stack. Examples of this approach are
provided by tools such as SUNSET [1] and DESERT [2].
The SUNSET (Sapienza University Networking framework
for underwater Simulation, Emulation and real-life Testing)
framework was developed by a team at the University of Rome
“La Sapienza.” The package is designed to allow developers
to easily conduct simulations, emulations and field tests of
underwater communication protocols [1]. DESERT (DEsign,
Simulate, Emulate and Realize Test-beds for Underwater net-
work protocols) is a set of C++ libraries extending the NS-
2. 2
MIRACLE simulation framework to support the development
and implementation of UANs [2]. The key idea of both
packages is that of using the same code for emulation and
simulations of underwater protocol and also, once the physical
layer is provided by actual modems, to run that same code
for experimentation in the water. These software packages are
designed to be largely platform independent, in that given the
appropriate driver, they can be used irrespective of the specific
modem. The approach to modem programming described in
this paper is of the first kind, i.e., built on the specific interface
of the Teledyne Benthos modems. In particular, we develop
Matlab-based building blocks for controlling the modem from
an outside device running Matlab (i.e., a laptop or other small-
factor computer that can be deployed underwater with the
modem itself), and with which we can implement different
communication protocols. Our blocks range from low-level,
driver-like interfaces between Matlab and the hexadecimal-
based commands of the modems, to more “autonomous”
blocks taking care of basic networking primitives, such as
sending and receiving data, topology set-up, etc. As a case
study, we show how we use these building blocks to implement
one of the simplest medium access control (MAC) protocols,
namely, ALOHA, for which we show results obtained in water
that are based on our implementation.
The rest of the paper is organized as follows. Section II
describes the SM 975 Teledyne Benthos acoustic smart mo-
dem. In Section III we show how to control the modem via
Matlab-based programming. In the following Section IV we
demonstrate our programming primitives for implementing
ALOHA and show some experimental results obtained through
our implementation. Finally, Section V concludes the paper.
II. THE SM 975 TELEDYNE BENTHOS ACOUSTIC MODEM
The SM 975 Teledyne Benthos Acoustic Smart Modem is
one of the fundamental components of our project. The modem
electronics are housed within a vacuum sealed glass sphere,
nestled within a two piece polyethylene hardhat. The vacuum
seal allows the modem to descend to depths up to 6,700 meters
underwater. An omnidirectional transducer extends from the
top glass hemisphere and through a cutout in the hardhat.
The bottom of the hardhat has an electrolytic dissolving “burn
wire” which allows the remote release of the modem from
the sea floor.1
Users can interact and control the modem via a
proprietary serial port/power connection near the modem base.
The modem contains a 28 Ah battery allowing the modem
to run on battery life for up to one year between charges
depending on usage. A sketch of the SM 975 is shown in
Fig. 2.
The low frequency acoustic modem can emit sounds be-
tween 9-14 kHz and has two modes of operation. The first
mode uses coherent detection and employs phase shift keying
(PSK) modulation to deliver baud rates of up to 15,360
bits/sec, while the second mode is based on incoherent detec-
tion and employs frequency shift keying (FSK) modulation,
delivering baud rates up to 2,400 bits/sec. Note that while
1The modem is positively buoyant and will ascend to the surface when
released.
Fig. 2: A cut-away view of the SM 975 Teledyne Benthos
Smart Modem.
FSK modulation cannot deliver data rates as high as PSK
modulation, it has improved reliability as compared to PSK
modulation, which makes it a practical solution for more
challenging channels.
The Teledyne modems come pre-loaded with BenthoNet, a
software API that enables basic primitives for packet trans-
mission and reception as well as simple networking func-
tionalities, including automatic acknowledgment replies and
automatic re-transmission of data packets. We have disabled
most of these functionalities as they are not dynamically
controllable. This has allowed us to implement channel access
protocol with greater control over key parameters.
III. PROGRAMMING THE SM 975
The SM 975 modem is interfaced through a serial port to
an external computer, i.e., a laptop or a small form-factor
computer such as the BeagleBone Black [3]. Through this
interface, we control and program the modem via a series
of Matlab functions and scripts. We organize the code for the
SM 975 in a series of layers as shown in Fig. 3.
Teledyne Benthos modems interact with the user via mes-
sages of four different types: “get,” “set,” “execute,” and “no-
tify.” Get is used to read parameters from the modem (e.g., its
local address, which is a positive integer in {0, 1, 2, . . . , 63});
set is used for changing a parameter (e.g., setting the local
address to a different number), and execute asks the modem
to perform a certain task (e.g., send a ping). These three
commands are always generated by the user. The notify
message, on the other hand, is generated by the modem and
carries the modem response to the computer (e.g., the response
to a get request), or is used to indicate that an event has
3. 3
Tda_
Td_
HEX Code
SM 975 Acous5c Smart Modem
Tdt_
Fig. 3: The Matlab-based NU MONET code architecture for
the SM 975. The users work with the “tdt ” layer that uses
functions in lower layers to accomplish tasks.
occurred (e.g., notify the user about the reception of a packet
from another modem). These four message types form the
entirety of communication modes to and from the modem.
Commands are sent to the modem in a string of hexadecimal
bytes through the serial port connection. The available com-
mands are laid out in the proprietary manuals accompanying
the SM 975 modems. In order to interface more easily with
the modems, we implemented a Matlab base level code (i.e., a
Matlab function) to send and receive bytes to/from the modem.
This code takes in a command (e.g. “td get(s,“localAddr”,
1)”) and converts it to the appropriate hexadecimal byte string.
These functions are prefixed by “td ” for “Teledyne” and serve
as the basis for any communication with the modem.
With the base layer established, we build up a new layer
that utilize the “td ” functions to perform more automated
tasks. Functions in this layer of communication are prefixed
by “tda ,” where the appended “a” stands for autonomous. For
instance, these functions may combine “td get,” “td notify,”
and some additional logic for extracting information like the
local address from the modem into a usable variable in a
protocol code. Desired information returned in the modem
response is extracted by the function and stored in memory.
On top of the “td ” and “tda ” layers we define a new
layer, termed “tdt ” where the extra “t” is short for “timer.”
This layer is based on Matlab timers set to periodically trigger
the execution of specific functions. Functions defined at the
“tdt ” layer are used to implement several building blocks for
protocol implementation and testing. We describe here five
fundamental basic blocks. They concern sending a packet,
receiving a packet, building the list of a node neighbors,2
namely, a node “address book,” functions for traffic man-
agement, and a GUI interface that we built in Matlab for
run time control of relevant modem status parameters (e.g.,
the length of its data queue). Every block utilizes queues to
2 Two nodes are said to be neighbors if they can communicate directly to
each other, i.e., when there is a physical channel between them that they can
use to exchange information.
which packets are pushed and pulled. The queues, and a set of
global variables acting as “bridges” between blocks, allow the
functions to pass information back and forth. For example, a
new data packet generated by the traffic management block is
pushed into the global transmit queue, from which the sending
block will pop and transmit packets.
In the rest of this section we describe these blocks and
structures in details.
The data production and transmission block utilizes the
transmission queue to pass and store packets. The transmission
queue is a series of parallel queues with each queue specific
to a modem in the address book. Having several parallel
queues specific to a modems affords more versatility than one
large queue for all data packets. By separating the packets
by modem, the sending function can randomly select a non-
empty queue to pull packets from and send. In the event that
connection to a modem is lost (thus resulting in delays and
dropped messages), the sending function can continue to oper-
ate normally via another queue without getting stuck waiting
on the retransmission of the lost packet. Furthermore, if a
modem is dropped from the network, any packets generated
for that modem can be deleted more easily, without having to
sift among many packets with different destinations.
We have functions for generating data packets (for instance,
for testing purposes) which also include pertinent time stamps
and diagnostic information. A data generating function is
associated with its own timer. This function can be customized
to implement different traffic generation patterns, such as
Constant Bit Rate traffic, or random traffic generated according
to a distribution relevant to a specific application. When a data
packet is produced for transmission and its destination node is
chosen, it is inserted into the transmit queue for that selected
destination.
When the tx timer function is called, the lengths of all the
transmission queues are evaluated. If the sum of these lengths
is greater than 0, (i.e., there are messages ready to be sent),
the function generates random numbers between 1 and the
current size of the address book to be used as indexes. The
queue lengths of the randomly produced indexes are checked
until an index with queue length greater than 0 is found. The
function extracts the oldest message to be sent from the queue
at the given index (i.e., the first message in that queue) and
sends it, moving the message after transmission to a buffer
queue and shifting all messages in the transmission queue
forward. When an acknowledgment (ACK) is received from
the recipient, the packet is deleted from the buffer. If an ACK
is not received within a designated timeout, the modem will
attempt to retransmit the message from the buffer up to a
certain number of times, which is protocol dependent.
All notifications that a modem receives or generates sits in
the serial buffer pending processing by the notification timer
function “tdt notify.” When “tdt notify” is called, the function
immediately checks the length of the serial buffer to see if a
new packet has been generated. If the length is greater than
0, (i.e., bytes for a notification packet have been generated
by the modem and are sitting in the buffer), tdt notify reads
the available bytes into a packet. A signature is generated
and assigned to the packet as it is processed. The signature,
4. 4
comprised of key elements of the packet, is used to efficiently
discriminate and act upon packets depending on the contained
data. The information received is interpreted by “tdt notify”
upon which it is either pushed to the appropriate queue or
passed along to another function for further processing. The
data stored in queues will be pulled by the corresponding timer
function. This process can also work in reverse mode, in which
“tdt notify” reads from the queues of the other functions, and
forwards the information to the modem.
Each modem has an address book containing the addresses,
distances and other pertinent information of every modem
within transmission range. New modems can be added to an
address book in one of three ways. The first is through a
“ping” message broadcast to all modems within transmission
range. Any modems who hear the ping respond with their own
address and distance at a random time (up to time tping). After
the timeout period, the ping originator produces a notification
containing the addresses and distances of all the modems who
responded. The function “Tdt notify” identifies this notifica-
tion based on its signature, and passes the packet into another
function, “tdt AddToAddrBook,” with a flag indicating a ping
response. The flags “Ping,” “justAddr,” or “Range” specify
how the information is being presented to the function so that
it can be properly extracted. In particular, “Ping” may contain
multiple addresses and distances, “justAddr” only contains a
single integer pertaining to the extracted address, and “Range”
contains both address and distance updates. The other ways ad-
dresses can be added to the address book involve overhearing
modems talking to one another. When a message is transmitted
from a modem, the modem also sends several system messages
with information such as timestamps, range updates, and
acoustic information. Any modem that overhears these mes-
sages generate notifications indicating their receipt, but ignore
the actual data packets unless they are addressed specifically to
them. Through signature identification, “tdt notify” can pass
information from certain packets to “tdt AddToAddrBook”
tagged with either “justAddr” or “Range,” depending on the
nature of the receipt. When packet information is passed to
“tdt AddToAddrBook,” the address is first checked against the
current entries in the address book. If an address already exists
in the address book, the function simply updates the modems
distance (if applicable). If the address is new, all pertinent
information (address, distance, time last heard from, etc.) will
be added to the address book.
We developed a GUI in Matlab to display the contents
of the address books of a node, the lengths of its queues
and other status information. The GUI is updated every .5
seconds through a timer. Two curves are depicted that graph
the length of the tx queue with respect to time and the end-
to-end delay for each received data packet. Additionally, the
GUI offers several buttons and sliders to input and change
modem settings mid run. This includes how often packets
are generated (slider), toggles for enabling data generation,
sending pings, and buttons to clear the TX queue, and send
packets.
IV. CASE STUDY: ALOHA
We demonstrate the use of our primitives for programming
the SM 975 by implementing a basic MAC protocol for
channel access, namely, ALOHA.
The ALOHA protocol is one of the earliest and most basic
random access protocols proposed for wireless broadcast chan-
nels. In the original version of this protocol, packets are sent
in their entirety immediately upon generation, indiscriminately
and without limiting factors [4]. ACKs are sent back to the
sending nodes to confirm the successful delivery of a packet.
In the event of packet collision, the sending nodes will im-
mediately attempt to retransmit their packets with probability
p, opting to remain silent with probability of 1 − p. The
randomness in packet retransmission decreases the probability
of repeated collisions. Nodes will attempt to retransmit a total
of retransmission attempts times before discarding the packet.
Fig. 4 shows the set of actions performed within each of the
SM 975 modems for generating a data packet and transmitting
it according to our Matlab implementation of ALOHA.
Data produced by data produc.on
.mer
Tx queues Modem
1
0
packets
Modem
2
0
packets
Modem
3
1
packets
Modem
n
0
packets
Tx .mer
Td_exec – remote send data
Transmission
Buffer (awai.ng ACK)
Retransmissions
>= 3
Delete packet
ACK
Yes
No ACK
No
…
Fig. 4: The path of a data packet from production to deletion
after transmission in our implementation of ALOHA.
The data production timer generates a packet and places
it in one of the transmission queues (tx queue) of a selected
destination, which is any one of the other n−1 modems. In our
experimentation below data packets are generated according
to a Poisson distribution, while the data packet destination is
any of the other modems, selected randomly and uniformly.
All transmissions and retransmissions are coordinated through
the tx timer. When the tx timer is called, the generated packet
is transmitted by passing it into a “td exec” remote send data
command, which converts it into the appropriate hex string for
the modem. After transmission, the packet is moved from the
tx queue into a buffer queue until an ACK is received from
the recipient. If an ACK is not received within a designated
timeout, it is assumed that the packet did not reach its intended
destination and the modem will attempt to retransmit the
packet. The modem will then attempt to resend the packet
with probability p. We set the (re)sending probability p to
1/(2n − 1), where n is the number of nodes in the address
5. 5
book. The packet is then transferred to the end of the buffer
queue while it awaits an ACK. This process repeats until the
message is transmitted successfully and the sender receives an
ACK from the recipient, at which point the packet is deleted
from the sender memory. The packet can also be dropped and
deleted from memory if it fails to be successfully transmitted
within a predefined number of attempts (set to three in our
experimental evaluation and in Fig. 4).
We use our implementation to conduct underwater exper-
iments with three SM 975 acoustic smart modems running
ALOHA. We deployed the modem in an indoor rectangular
tank filled with fresh water positioned in a line (Fig. 5).
Fig. 5: Three TB SM 975 acoustic modems. In this lab setting
the devices are controlled by laptops outside the tank.
We investigate the metrics of packet delivery ratio, i.e., the
percentage of packet successfully delivered to their intended
destination, as well as the end-to-end delay incurred by packets
from the moment they are created to when they are delivered.
The results of the performance evaluation of ALOHA are
shown in Fig. 6.
0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12 0.13 0.14 0.15
packet generation rate [packets/s]
0
0.2
0.4
0.6
0.8
packetdeliveryratio
0
20
40
60
80
averagedelay[s]
packet deliver ratio
average delay
Fig. 6: Packet delivery ratio and end-to-end delay for the
ALOHA MAC protocol in the setting of Fig. 5.
We observe that as the rate of packet generation increases,
the packet delivery ratio decreases while the end-to-end delay
greatly increases. As for its terrestrial counterpart, the sim-
plistic nature of ALOHA used underwater leads to very low
channel utilization.3
This is the consequence of not having
an effective collision detection/avoidance mechanisms, like
those used by CSMA/CD and /CA-based protocols. Curiously,
the higher propagation delay of the underwater channel helps
improving channel utilization. In fact, two senders at different
distances from the same receiver and transmitting a packet at
the same time are less likely to incur collision at the receiver
than if the networks was terrestrial (radio), where the speed of
light will instead lead to certain collision. We did not benefit
from this effect, however, as our current testbed setting allows
very similar distances between modems.
V. CONCLUSIONS AND FUTURE WORKS
We used Matlab-based programming to develop a series
of building blocks for controlling and programing Teledyne
Benthos SM 975 Acoustic Smart Modems. We demonstrate
how to use these blocks by implementing a basic channel-
access networking protocol, ALOHA, and running underwater
experiments. Eventually, we plan to use these basic building
blocks for developing more complex modern protocols de-
signed specifically for use in UANs. We have started imple-
menting one such protocol (TARS) and hope to begin testing
soon. Once we have established a stable base of protocols,
we hope to expand our small scale underwater testing to the
ocean, and collect more realistic results for further analysis.
In addition to programming the modems, we are also work-
ing on other portions of the NU MONET in preparation for
a full deployment of five modems at the Northeastern Marine
Science Center campus in Nahant, MA, over the Summer of
2016. This includes the design and construction of a “smart
buoy” that will serve as the wireless link to the shore and
provide power to the modems.
ACKNOWLEDGMENTS
This research was supported in part by the National Science
Foundation through the grant “MRI: Development of the
Northeastern University Marine Observatory NETwork (NU
MONET)” (CNS 1428567). In particular, Tu, Wilcox and
German were supported by REU grants associated to this MRI.
REFERENCES
[1] C. Petrioli, R. Petroccia, and D. Spaccini, “SUNSET version 2.0:
Enhanced framework for simulation, emulation and real-life testing of
underwater wireless sensor networks,” in Proceedings of ACM WUWNet
2013, Kaohsiung, Taiwan, November 11–13 2013, pp. 1–8.
[2] R. Masiero, S. Azad, F. Favaro, M. Petrani, G. Toso, F. Guerra, P. Casari,
and M. Zorzi, “DESERT underwater: an NS-miracle-based framework to
DEsign, simulate, emulate and realize test-beds for underwater network
protocols,” in Proceedings of IEEE OCEANS 2012, Yeosu, Korea, May,
21–24 2012, pp. 1–10.
[3] What is beaglebone black? [Online]. Available:
https://beagleboard.org/black
[4] N. Abramson, “The ALOHA System—another alternative for computer
communications,” in Proceedings of AFIPS 1970, 1970, pp. 281–285.
[5] L. G. Roberts, “ALOHA packet system with and without slots and cap-
ture,” Stanford Research Institute, Advanced Research Projects Agency,
Network Information Center, Stanford, CA, Tech. Rep. ASS note 8, June
1972.
3 It is notoriously known that the maximum channel utilization of un-slotted
ALOHA in radio networks with saturated traffic is about 18% [5].