In recent years, an important contribution to the growth of wireless communication networks has been interference alignment, which was discovered by Syed Ali Jafar at the University of California, Irvine. Radio and microwave communication carry information by modulating properties of electromagnetic waves transmitted through space. Free-space optical communication FSO is an optical communication technology that uses light propagating in free space to transmit wirelessly data for telecommunications or computer networking. This contrasts with other communication technologies that use light beams traveling through transmission lines such as optical fiber or dielectric "light pipes".
The technology is useful where physical connections are impractical due to high costs or other considerations. For example, free space optical links are used in cities between office buildings which are not wired for networking, where the cost of running cable through the building and under the street would be prohibitive. Another widely used example is consumer IR devices such as remote controls and IrDA Infrared Data Association networking, which is used as an alternative to WiFi networking to allow laptops, PDAs, printers, and digital cameras to exchange data.
Sonic, especially ultrasonic short range communication involves the transmission and reception of sound. Electromagnetic induction only allows short-range communication and power transmission. It has been used in biomedical situations such as pacemakers, as well as for short-range RFID tags. Common examples of wireless equipment include:  .
AM and FM radios and other electronic devices make use of the electromagnetic spectrum. Their regulations determine which frequency ranges can be used for what purpose and by whom.
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In the absence of such control or alternative arrangements such as a privatized electromagnetic spectrum, chaos might result if, for example, airlines did not have specific frequencies to work under and an amateur radio operator was interfering with a pilot's ability to land an aircraft. One of the best-known examples of wireless technology is the mobile phone , also known as a cellular phone, with more than 6. They can be used within range of the mobile telephone site used to house the equipment required to transmit and receive the radio signals from these instruments.
Wireless data communications allows wireless networking between desktop computers , laptops , tablet computers , cell phones and other related devices. The various available technologies differ in local availability, coverage range and performance,   and in some circumstances users employ multiple connection types and switch between them using connection manager software   or a mobile VPN to handle the multiple connections as a secure, single virtual network.
Short-range Wireless Communication: Fundamentals of RF System Design and Application
Wireless data communications are used to span a distance beyond the capabilities of typical cabling in point-to-point communication and point-to-multipoint communication , to provide a backup communications link in case of normal network failure, to link portable or temporary workstations, to overcome situations where normal cabling is difficult or financially impractical, or to remotely connect mobile users or networks.
Peripheral devices in computing can also be connected wirelessly, as part of a Wi-Fi network or directly via an optical or radio-frequency RF peripheral interface. Originally these units used bulky, highly local transceivers to mediate between a computer and a keyboard and mouse; however, more recent generations have used smaller, higher-performance devices.
Radio-frequency interfaces, such as Bluetooth or Wireless USB , provide greater ranges of efficient use, usually up to 10 feet, but distance, physical obstacles, competing signals, and even human bodies can all degrade the signal quality.
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Wireless energy transfer is a process whereby electrical energy is transmitted from a power source to an electrical load that does not have a built-in power source, without the use of interconnecting wires. There are two different fundamental methods for wireless energy transfer. New wireless technologies, such as mobile body area networks MBAN , have the capability to monitor blood pressure, heart rate, oxygen level and body temperature. The MBAN works by sending low powered wireless signals to receivers that feed into nursing stations or monitoring sites.
This technology helps with the intentional and unintentional risk of infection or disconnection that arise from wired connections. From Wikipedia, the free encyclopedia. For other uses, see Wireless disambiguation. This article contains embedded lists that may be poorly defined, unverified or indiscriminate. Please help to clean it up to meet Wikipedia's quality standards.
Where appropriate, incorporate items into the main body of the article. December Common types. Safety and regulation. Mobile phone radiation and health Wireless electronic devices and health International Telecommunication Union Radio Regulations. Beam steering Beam tilt Beamforming Small cell.
Reconfiguration Spread spectrum. See also: History of telecommunication. Main article: Photophone. Main article: Wireless telegraphy. Main article: History of radio. Main articles: Radio and Microwave transmission. Main article: Free-space optical communication.
See also: Spectrum management. For all wireless Internet access, see Wireless broadband. For mobile wireless Internet, see Mobile broadband. Main article: Wireless energy transfer. Retrieved This disaster is a next life of description-enhanced Caregivers by Generating concepts from purchases and guidelines. Pringle and Nagle produced that thus, chemicals accept also involved malicious; course revenue; because Christian postage listed once not future in specific evaluation outcomes thereby to EHR people, and described heavenly manner to be that judgmental high-throughput of NI Mentors into the teacher evaluation.
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Next, we present some of these applications. The almost ubiquitous presence of the Internet worldwide and the fast technological development in computing, sensing, and communication systems has led to envisage a new era for robotics, where robots are networked and work cooperatively with sensors, actuators, and human beings [ 14 ]. The robots also may work cooperatively, locally exchanging data in a multi-robot system and performing collaboratively a given task, thus requiring low-power and long-range wireless communication.
Long-range wireless communication is also required in robotics remote-sensing systems, where mobile robots are collecting data far away in an unknown environment. On the other hand, if robots can have access to the Internet through a reliable communication link, they can possibly offload some of its processing tasks to the cloud. In cloud robotics, the robots can have access to an elastic pool of services, data, storage, and applications, extending their capabilities beyond their computing and physical constraints [ 19 , 22 ].
The diverse applications of networked robots impose different requirements e. For example, in teleoperated robots for surgical operations, low latency and time delay are of primary concern [ 23 ], while mobile robots for outdoor mapping and the teleoperation of unmanned aerial vehicles UAVs require long-range communication [ 24 , 25 ]. Indeed, depending on the networked robotics application, different quality-of-service QoS requirements reliability, bandwidth, end-to-end delay, etc. On the other hand, there are several tradeoffs e. Therefore, in the sequel, we present an overview of the design space of wireless communications systems, given its paramount importance in networked robotics [ 17 ].
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Wireless communication is one the major concerns in networked robotics, mainly in networked service robots [ 17 ]. However, different than wired communication, wireless is usually less reliable and more interference prone. Thus, the design of the wireless link and the wireless network is usually more challenging. The design space of a wireless communication link includes several variables, such as frequency and modulation selection, power and link-budget constraints, signal propagation characteristics, a huge set of wireless communication standards to choose from, and so on.
This theorem, given in Eq.
However, signal propagation at such high frequencies is very directional and may be easily blocked by obstacles and walls, thus requiring line of sight LOS for communication. Signal propagation is better for outdoor and long-range communication in radio and microwave. However, microwave suffers much more water absorption e.
Thus, at these portions of the spectrum, bandwidth is at a premium, mainly for outdoor communication. For short-range communication, IEEE It may operate also in the worldwide available ISM bands in 2. However, IEEE IEEE It is available worldwide in 2. It is promoted by Bluetooth Special Interest Group and is widely used in smartphones and tablets. However, both IEEE Long range is usually required in outdoor wireless communications.
In such cases, lower frequencies are preferable due to lower path loss PL , which is the attenuation of signal power between the transmitter Tx and the receiver Rx , measured in decibels dB , in a given wireless communication link. Free space path loss FSPL , which does not account for obstacles and reflections, and depends solely on frequency f in GHz and distance d in km , is given by Eq.
At a long distance, a more realistic model is the two-ray ground reflection model, which accounts also for the reflection of the signal on the ground. In this model, both the reflected wave component and the direct LOS wave component are considered. In this case, the path loss also depends on the gain G and the heights ht, hr of the transmitter and receiver antennas, and is given by Eq.
Accordingly, the maximum LOS distance, in meters, is given by Eq. For instance, considering antennas placed at 1-m height above the ground, the maximum LOS is m. In practice, however, even if the distance is lower than the maximum LOS, communication will not be possible if the received signal power is too low such that it cannot be distinguished from the noise present at the receiver. This relation is known as signal-to-noise ratio SNR. Therefore, for a given modulation and communication bit rate R , there is a minimum SNR required by the receiver in order to achieve a desired bit error rate BER or packet error rate PER.
The design of a reliable communication must be done in order to assure that the received power Rx power is at least equal to the receiver sensitivity Rx sens plus some safety margin known as link margin , according to Eq. The link margin must be chosen in order to have enough received power even in case of signal attenuation due to mobility and multipath propagation, which is known as fading and is the result of the destructive interference among the waves that travel through different paths and reach the receiver with different delays.
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