Wireless….

Hello guys, how are you doing? hope everything's good. Lets see something about wireless. Now a days every individual is using wireless as there prime mode of communication. Let's take a simple example of our daily life scenario, All of us are using mobile phone's or WiFi for there way of interaction between each other. So have we ever thought how these all things are working? I guess 99% of us had never even thought about this? Mostly what we people do is we just get to know something new tech has launched and we want that but never thinks what it is or how does it works..... Ok now lets see what is wireless.... let me give a brief... I think it will be a good idea to give a brief and then start Wireless if we say wireless its not just a simple topic.... Its like sea or even bigger than that. I guess the best way to put it is like this what ever transfer of any information which is being transported from a initial point to the end point without the use of wired infrastructure or simple no cables.... But then again you guys can ask is it fully wireless? Will there be no strings attached? No cris-crossing? But i would like to say to that will be No and Yes To the end users they will not be able to see any strings or the chaps who will be using these services (Wireless) the strings will not be visible. Actually we wont be able to eradicate the full usage of strings or the traditional cables.... Because in the backend infra we have to use it other wise so far we don't have any solution for this i guess.... getting the equipments equipped and getting it interconnected. Ok So what is wireless doing here ? You might be asking this i guess..... Ok here what wireless does is, it helps to get connected the chaps devices to the access point. Ok now you might ask what is an access point? It is a device which helps the wired data to be converted into a wireless data. So basically you can call it as a converter but its not just a converter.

For most of the people when they here wireless they only think of WiFi or Bluetooth. But its wrong. Its not only WiFi or bluetooth. There are a lots of wireless technologies.

Now let me go a little technical here, please dont mind i have to go a little tech here. For example in case of different wireless technologies, Its mainly classified into two 1) Short range 2) Long range 1) Short range

ANT+

ANT and ANT+ are proprietary wireless sensor network technologies used in the collection and transfer of sensor data. As a type of personal-area network (PAN), ANT’s primary applications include sports, wellness, and home health. For example, it’s used in heart-rate monitors, speedometers, calorimeters, blood pressure monitors, position tracking, homing devices, and thermometers. Typical radios are built into sports watches and equipment like workout machines.

The technology divides the 2.4-GHz industrial, scientific, and medical (ISM) band into 1-MHz channels. The radios have a basic data rate of 1 Mbit/s. A time division multiplexing (TDM) scheme accommodates multiple sensors. ANT+ supports star, tree, mesh, and peer-to-peer topologies. The protocol and packet format is simple. And, it boasts ultra-low power consumption and long battery life.

Bluetooth

Bluetooth (www.bluetooth.org, www.bluetooth.com) is another PAN technology. The Bluetooth Special Interest Group (SIG) manages the standard. IEEE 802.15.1 also covers it. Bluetooth primarily is used in wireless headsets for cell phones. It’s also used in some laptops, printers, wireless speakers, digital cameras, wireless keyboards and mice, and video games. Bluetooth Low Energy, which has a simpler design, targets health and medical applications. It effectively competes with ANT+.

Bluetooth operates in the 2.4 -Hz ISM band and uses frequency-hopping spread spectrum with Gaussian frequency shift keying (GFSK), differential quadrature phase shift keying (DQPSK), or eight-phase-shift differential phase-shift keying (8DPSK) modulation. The basic data gross rate is 1 Mbit/s for GFSK, 2 Mbits/s for DQPSK, and 3 Mbits/s for 8DPSK. There are also three power classes of 0 dBm (1 mW), 4 dBm (2.5 mW), and 20 dBm (100 mW), which essentially determines range. Standard range is about 10 meters and up to 100 meters at maximum power with a clear path.

Bluetooth is also capable of forming simple networks of up to seven devices. Called piconets, these PANs aren’t widely used. The peer-to-peer communications mode is the most common. The Bluetooth SIG defines multiple “profiles” or software applications that have been certified for interoperability among vendor chips, modules, and software.

Cellular

With services from most network carriers, cellular radio provides data transmission capability for machine-to-machine (M2M) applications. M2M is used for remote monitoring and control. Cellular radio modules are widely available to build into other equipment. Most of the standard technologies are used, such as GSM/GPRS/EDGE/WCDMA/HSPA.

1. Put a cell phone in your product. The Sierra Wireless AirPrime SL808x series is a full UMTS/WCDMA/HSDPA data cell phone designed to be embedded into other products. The module measures 25 by 30 mm, and it can transfer data downloads up to 3.6 Mbits/s. 2. The CEL MeshConnect module using Ember EM357 devices makes ZigBee wireless applications fast and easy to implement.

LTE capability is also being made available for higher-speed applications like HD video surveillance. Otherwise, data rates are usually low (< 1 Mbit/s). The working range is from 1 to 10 km, which is the range of most cell sites today.

IEEE 802.15.4

IEEE 802.15.4 is designed to support peer-to-peer links as well as wireless sensor networks. The standard defines the basic physical layer (PHY), including frequency range, modulation, data rates, and frame format, and the media access control (MAC) layer. Separate protocol stacks are then designed to use the basic PHY and MAC. Several wireless standards use the 802.15.4 standard as the PHY/MAC base, including ISA100, Wireless HART, ZigBee, and 6LoPAN.

The standard defines three basic frequency ranges. The most widely used is the worldwide 2.4-GHz ISM band (16 channels). The basic data rate is 250 kbits/s. Another range is the 902- to 928-MHz ISM band in the U.S. (10 channels). The data rate is 40 kbits/s or 250 kbits/s. Then there’s the European 868-MHz band (one channel) with a data rate of 20 kbits/s.

All three ranges use direct sequence spread spectrum (DSSS) with either binary phase-shift keying (BPSK) or offset quadrature phase-shift keying (QPSK) modulation. The multiple access mode is carrier sense multiple access with collision avoidance (CSMA-CA). The minimum defined power levels are –3 dBm (0.5 mW). The most common power level is 0 dBm. A 20-dBm level is defined for longer-range applications. Typical range is less than 10 meters.

IEEE 802.22

Also known as the Wireless Regional Area Network (WRAN) standard, IEEE 802.22 is one of the IEEE’s newest wireless standards. It’s designed to be used in the license-free unused broadcast TV channels called white space. These 6-MHz channels occupy the frequency range from 470 MHz to 698 MHz. Their availability varies from location to location. The standard isn’t widely used yet, though. White space radios use proprietary protocols and wireless standards.

Because of the potential for interference to TV stations, 802.22 radios must meet strict requirements and use cognitive radio techniques to find an unused channel. The radios use frequency-agile circuitry to scan for unused channels and to listen for potential interfering signals. They also use a TV white space database to determine the optimum place to be for the best results without interfering with other communications.

This standard is designed for fixed wireless broadband connections. The basestations talk to multiple fixed-location consumer radios for Internet access or other services. They would compete with cable TV and phone companies and/or provide broadband connectivity in rural areas underserved by other companies. While mobile operation is possible, most radios will be fixed.

The standard uses orthogonal frequency-division multiplexing (OFDM) to provide spectral efficiency sufficient to supply multiple user channels with a minimum of 1.5-Mbit/s download speed and 384-kbit/s upload speed. The maximum possible data rate per 6-MHz channel ranges from 18 to 22 Mbits/s. The great advantage of 802.22 is its use of the VHF and low UHF frequencies, which offer very long-range connections. With the maximum allowed 4 W of effective isotropic radiated power (EIRP), a basestation range of 100 km (almost 60 miles) is possible.

ISA100a

Developed by the International Society of Automation, ISA100a is designed for industrial process control and factory automation. It uses the 802.15.4 PHY and MAC but adds special features for security, reliability, feedback control, and other industrial requirements.

Infrared

Infrared (IR) wireless technology uses light instead of radio for its connectivity. Infrared is low-frequency, invisible light that can serve as a carrier of high-speed digital data. The primary wavelength range is 850 to 940 µm. The transmitter is an IR LED, and the receiver is a diode photodetector and amplifier. The light wave is usually modulated with a high-frequency signal that is, in turn, coded and modulated by the digital data to be transmitted.

Most TV sets and consumer electronic devices use an IR remote control, which has a range of several meters and a narrow angle (<30°) of transmission. Various protocols and coding schemes are used. Also, IR devices must have a clear line-of-sight path for a connection.

There is a separate standard for data transmission called IrDA. The Infrared Data Association sets and maintains its specifications. IrDA exists in many versions mainly delineated by their data rate. Data rates range from a low of 9.6 to 115.2 kbits/s in increments to 4 Mbits/s, 16 Mbits/s, 96 Mbits/s, and 512 Mbits/s to 1 Gbit/s. New standards for rates of 5 and 10 Gbits/s are in development. The range is less than a meter.

IR has several key benefits. First, since it’s light instead of a radio wave, it isn’t susceptible to radio interference of any kind. Second, it’s highly secure since its signals are difficult to intercept or spoof.

IR once was widely used in laptops, PDAs, some cameras, and printers. It has mainly been replaced by other wireless technologies like Bluetooth and Wi-Fi. It is still widely used in consumer remote controls, but new RF remote controls are gradually replacing the IR remotes in some consumer equipment. Some designs include both IR and RF.

ISM Band

Most of these standards use the unlicensed ISM bands set aside by the Federal Communications Commission (FCC) in Part 15 of the Code of Federal Regulations (CFR) 47. The most widely used ISM band is the 2.4- to 2.483-GHz band, which is used by cordless phones, Wi-Fi, Bluetooth, 802.15.4 radios, and many other devices. The second most widely used band is the 902- to 928-MHz band, with 915 MHz being a sweet spot.

Other popular ISM frequencies are 315 MHz for garage door openers and remote keyless entry (RKE) applications and 433 MHz for remote temperature monitoring. Other less used frequencies are 13.56 MHz, 27 MHz, and 72 MHz. For full consideration of all available bands, see Part 15, which is a must-have document for anyone designing and building short-range wireless products. It’s available through the U.S. Government Printing Office.

For many simple wireless applications that do not require complex network connections, security, or other custom features, simple proprietary protocols can be designed. Many vendors of ISM band transceivers offer standard protocol support and development systems that can be used to develop a protocol for a specific application.

Near-Field Communications

Near-field communications (NFC) is an ultra-short-range technology that was designed for secure payment transactions and similar applications. It maximum range is about 20 cm, with 4 to 5 cm being a typical link distance. This short distance greatly enhances the security of the connection, which is also usually encrypted. Many smart phones include NFC, and many others are expected to get it eventually. The goal is to implement NFC payment systems where consumers can tap a payment terminal with their cell phone instead of using a credit card.

NFC uses the 13.56-MHz ISM frequency. At this low frequency, the transmit and receive loop antennas function mainly as the primary and secondary windings of a transformer, respectively. The transmission is by the magnetic field of the signal rather than the accompanying electric field, which is less dominant in the near field.

NFC is also used to read tags that are powered up by the interrogation of an NFC transmitted signal. The unpowered tags convert the RF signal into dc that powers a processor and memory that can provide information related to the application. Numerous NFC transceiver chips are available to implement new applications, and multiple standards exist:

· ISO/IEC 14443A

· ISO/IEC 14443B

· JIS X6319-4

· ECMA 340, designated NFCIP-1

· ISO/IEC as 18092

· ECMA 352, called NFCIP-2, and ISO/IEC 23917

RFID

Radio-frequency identification (RFID) is used primarily for identification, location, tracking, and inventory. A nearby reader unit transmits a high-power RF signal to power passive (unpowered) tags and then read the data stored in their memory.

RFID tags are small, flat, and cheap and can be attached to anything that must be tracked or identified. They have replaced bar codes in some applications. RFID uses the 13.56-MHz ISM frequency, but other frequencies are also used including 125 kHz, 134.5 kHz, and frequencies in the 902- to 928-MHz range. Multiple ISO/IEC standards exist.

6LoWPAN

6LoWPAN means IPv6 protocol over low-power wireless PANs. Developed by the Internet Engineering Task Force (ITEF), it provides a way to transmit IPv6 and IPv4 Internet Protocols over low-power wireless point-to-point (P2P) links and mesh networks. This standard (RFC4944) also permits the implementation of the Internet of Things on even the smallest and remote devices.

The protocol provides encapsulation and header compression routines for use with 802.15.4 radios. The IETF is said to be working on a version of this protocol for Bluetooth. If your wireless device must have an Internet connection, this is your technology of choice.

Ultra Wideband

Ultra Wideband (UWB) uses the 3.1- to 10.6-GHz range to provide high-speed data connectivity for PCs, laptops, set-top boxes, and other devices. The band is divided up into multiple 528-MHz wide channels. OFDM is used to provide data rates from 53 Mbits/s to 480 Mbits/s. The WiMedia Alliance originally defined the standard.

Devices use ultra-low power to prevent interference with services in the assigned band. This restricts range to a maximum of about 10 meters. In most applications, the range is less than a few meters so the highest data rates can be used. UWB is used primarily in video applications such as TV sets, cameras, laptops, and video monitors in docking stations.

Wi-Fi

Wi-Fi is the commercial name of the wireless technology defined by the IEEE 802.11 standards. Next to Bluetooth, Wi-Fi is by far the most widespread wireless technology. It is in smart phones, laptops, tablets, and ultrabooks. It’s also used in TV sets, video accessories, and home wireless routers. It’s deployed in many industrial applications as well. Wi-Fi is now showing up in cellular networks where carriers are using it to offload some data traffic like video that clogs the network.

Wi-Fi has been around since the late 1990s when a version called 802.11b because popular. It offered up to 11-Mbit/s data rates in the 2.4-GHz ISM band. Since then, new standards have been developed including 802.11a (5-GHz band), 802.11g, and 802.11n using OFDM to get speeds up to 54 and 300 Mbits/s under the most favorable conditions.

More recent standards include 802.11ac, which uses multiple-input multiple-output (MIMO) to deliver up to 3 Gbits/s in the 5-GHz ISM band. The 802.11ad standard is designed to deliver data rates up to 7 Gbits/s in the unlicensed 60-GHz band. You will hear of 802.11ad referred to as WiGig, its commercial designation. Its main use is video transfer in consumer electronic systems with HDTV and in high-resolution video monitors.

Wi-Fi is readily available in chip form or as complete drop-in modules. The range is up to 100 meters under the best line-of-sight conditions. This is a great option where longer range and high speeds are needed for the application.

Wireless HART

HART is the Highway Addressable Remote Transducer protocol, a wired networking technology widely used in industry for sensor and actuator monitoring and control. Wireless HART is the wireless version of this standard. The base of it is the 802.15.4 standard in the 2.4-GHz band. The HART protocol is a software application on the wireless transceivers.

WirelessHD

WirelessHD is another high-speed technology using the 60-GHz unlicensed band. It also is supported by the IEEE 802.15.3c standard. It can achieve speeds to 28 Gbits/s over a range that tops out at about 10 meters in a straight, unblocked path. It is designed mainly for wireless video displays using interfaces like HDMI or DisplayPort, HDTV sets, and related consumer devices like DVRs and DVD players.

WirelessUSB

WirelessUSB is a proprietary standard from Cypress Semiconductor. It is not the same as Wireless USB, which is a wireless version of the popular wired USB interface standard. Wireless USB generally refers to Ultra Wideband. WirelessUSB NL uses the 2.4-GHz band with GFSK modulation. Data rates up to 1 Mbit/s are possible. This ultra-low-power technology is designed primarily for human interface devices (HIDs) like keyboards, mice, and game controllers. It uses a simple protocol.

Another version of WirelessUSB designated LP uses the same 2.4-GHz band but employs direct-sequence spread-spectrum (DSSS) at a lower speed (up 250 kbits/s) for greater range and reliability in the presence of noise. The LP version can also implement the GFSK 1-Mbit/s feature if desired. The maximum power level is 4 dBm, and a 16-bit cyclic redundancy code (CRC) is used for error detection. Versions of the transceivers can be had with an on-chip Cypress PSoC microcontroller.

ZigBee

ZigBee is the standard of the ZigBee Alliance. It is a software protocol and technology that uses the 802.15.4 transceiver as a base. It provides a complete protocol stack designed to implement multiple types of radio networks that include point-to-point, tree, star, and point-to-multipoint. Its main feature is the ability to build large mesh networks for sensor monitoring. And, it can handle up to 65,000 nodes.

ZigBee also provides profiles or software routines that implement specific applications for consumer home automation, building automation, and industrial control. Examples include building automation for lighting and HVAC control, as well as smart meters that implement home-area network connections in automated electric meters.

Low-power versions are used in health care for remote patient monitoring and similar applications. A lighting profile is available for LED lighting fixtures and their control. There is also a ZigBee remote control profile to implement an RF rather than infrared remote control for consumer TV and other devices. ZigBee is used in factory automation and can be used in many M2M and Internet of Things applications as well.

Z-Wave

Z-Wave is a proprietary wireless standard originally developed by Zensys, which is now a part of Sigma Designs. Recently, the International Telecommunications Union (ITU) included the Z-Wave PHY and MAC layers as an option in its G.9959 standard, which defines a set of guidelines for sub-1-GHz narrowband wireless devices.

Z-Wave is a wireless mesh networking technology. A Z-Wave network can have up to 232 nodes. The wireless transceivers operate in the ISM band on a frequency of 908.42 MHz in the U.S. and Canada but use other frequencies depending on the country’s rules and regulations. The modulation is GFSK. Data rates available include 9600 bits/s and 40 kbits/s. Output power is 1 mW or 0 dBm. In free space conditions, a range of up to 30 meters is possible. The through-wall range is considerably shorter. The main application for Z-Wave has been home automation and control of lighting, thermostats, smoke detectors, door locks, appliances, and security systems.

Critical Design Factors

The performance of a wireless link is based on pure physics as modified by practical considerations. In building a short-range wireless product or system, the important factors to consider are range, transmit power, antenna gains if any, frequency or wavelength, and receiver sensitivity. Basic guidelines include:

· Lower frequencies extend the range if all factors are the same. This is strictly physics. A 900-MHz signal will travel farther than a 2.4-GHz signal. A 60-GHz signal has substantially less range than a 5-GHz signal.

· Lower data rates will also extend the range and reliability for a given set of factors. Lower data rates are less susceptible to noise and interference. Always use the lowest possible data rate for the best results.

· Be sure to factor in other possible losses such as those in a coax transmission line, filters, impedance matching, or other circuits.

· Losses through trees, walls, or other obstacles should also be considered.

· Add fade margin to your design to overcome unexpected environmental conditions, noise, or interference. This ensures your system will have sufficient signal strength over the range to compensate for unknowns. Increase fade margin if the signal must pass through walls and other obstructions.

· Keep in mind that antennas can have gain. By making the antenna directional, its beam is more focused with RF power and the effect is the same as raising the transmit or receive power. Half-wave dipoles and quarter-wave verticals aren’t considered to have gain unless compared to a pure isotropic source.

Your first calculation is to determine possible path loss for a typical situation. Assume the longest possible distance the signal needs to travel and use it to determine other factors. Then calculate the path loss. The formula is:

dB loss = 37 dB + 20log(f) + 20log(d)

In this formula, f is the operating frequency in MHz and d is the range in miles. For example, the path loss of a 900-MHz signal over 2 miles is:

dB loss = 37 + 20log(900) + 2-log(2) = 37 + 59 + 6 = 102 dB

Remember, this is the free space loss meaning a direct line-of-sight transmission with no obstacles. Trees, walls, or other possible barriers will significantly increase the path loss.

Next, manipulate the following formula to ensure a link connection:

Receive sensitivity (minimum) = transmit power (dBm) + transmit antenna gain (dB) + receive antenna gain (dB) – path loss (dB) – fade margin (dB)

Fade margin is an estimate or best guess. It should be no less than, say, 5 dB, but it could be up to 40 dB to ensure 100 % link reliability. Other losses like transmission line loss should also be subtracted.

The resulting figure should be greater than the receiver sensitivity. Receiver sensitivities range from a low of about –70 dBm to –130 dBm or more. Assume a transmit power of 4 dBm, antenna gains of 0 dB, and the 102-dB path loss calculated above. Assume a fade margin of 10 dB. The link characteristics then are:

4 + 0 + 0 – 102 – 10 = –108 dB

To obtain a reliable link, the receiver sensitivity must be greater than –108 dBm.

Typical Applications

The use of wireless as expanded geometrically over years thanks to new wireless standards and very low-cost transceiver chips and modules. Generally, there is little need to invent a new standard or protocol, and there is less need to be an RF and wireless expert. Wireless has become an easy and relatively low-cost addition to almost any new product where a wireless feature can enhance performance, convenience, or marketability.

In the automotive space, remote keyless entry (RKE) and remote start are the most widespread. Wireless remote reading of tire pressures is one interesting feature on some vehicles. GPS navigation has also become a widespread option on many cars. Radar, a prime wireless technology, is finding considerable application in speed control and automated braking.

Home consumer electronic products are loaded with wireless. Virtually all entertainment products such as HDTVs, DVRs, and cable and satellite boxes have remote controls. They’re still primarily IR, but RF wireless is now being incorporated. Other wireless applications include baby monitors, toys, games, and hobbies.

There are also wireless thermostats, remote thermometers and other weather monitors, garage door openers, security systems, and energy metering and affiliated monitors. Many homes now have wireless Internet access with a Wi-Fi router. There may even be a cellular femto cell to boost mobile coverage in the home. Cell phones, cordless phones, Bluetooth, and Wi-Fi are widespread.

Commercial applications include wireless temperature monitoring, wireless thermostats, and lighting control. Some video surveillance cameras use a wireless rather than coax link. Wireless payment systems in cell phones promises to revolutionize commerce.

In industry, wireless has gradually replaced wired connections. Remote monitoring of physical characteristics such as temperature, flow, pressure, proximity, and liquid level is common. Wireless control of machine tools, robots, and industrial processes simplifies and facilitates economy and convenience in industrial settings. M2M technology has opened the door to many new applications such as monitoring vending machines and vehicle location (GPS). The Internet of Things is mostly wireless. RFID has made it possible to more conveniently track and locate almost anything.

Checklist For Selecting A Wireless Application

The following list outlines the almost obvious factors to consider in selecting a wireless technology:

· Range: How far is it from the transmitter to the receiver? Is the distance fixed or will it vary? Estimate maximum and minimum distances.

· Duplex or simplex: Is the application one way (simplex) or two-way (duplex)? For some monitoring applications, a one-way path is all that’s needed. The same goes for some remote control applications. The need for control and feedback from transmitter to receiver or vice versa implies the need for a two-way system.

· Number of nodes: How many transmitters/receivers will be involved? In simpler systems, only two nodes are involved. If a network for devices is involved, determine how many transmitters and receivers are needed and define the necessary interaction between them.

· Data rate: What speed will data occur? Is it low speed for monitoring and control or high speed for video transfer? The lowest speed is best for link reliability and noise immunity.

· Potential interference: Will there be other nearby wireless devices and systems? If so, they may interfere with or block the connection. Noise from machinery, power lines, and other interference sources should also be considered.

· Environment: Is the application indoors or outdoors? If outdoors, are there physical obstacles like buildings, trees, vehicles, or other structures that can block or reflect a signal? If indoors, will the signals have to pass through walls, floors or ceilings, furniture, or other items?

· Power source: Will ac power be available? If not, assume battery operation. Consider battery, size, life, recharging needs, battery replacement intervals, and related costs. Will adding wireless significantly increase the power consumption of the application? Is energy harvesting or solar power a possibility?

· Regulatory issues: Some wireless technologies require an FCC license. Most of the wireless technologies for short-range applications are unlicensed. Only the unlicensed technologies are discussed here.

· Size and space: Is there adequate room for the wireless circuitry? Keep in mind that all wireless devices need an antenna. While the circuitry may fit in a millimeter-sized chip, the antenna could take up much more space. Usually some discrete impedance matching components are also needed. If a separate antenna is required, then a coax transmission line will be needed as well.

· Licensing fees: Some wireless technologies may require the user to join an organization or pay royalties to use the technology.

· User type and experience: Will the user be a consumer with no wireless competency or an experienced technician or engineer? Will installation and operation require expertise? System complexity may be beyond the user’s capability. Ease of installation, setup, operation, and maintenance are crucial factors.

· Security: If security from hacking and other misuses is an issue, the use of encryption and authentication may be necessary. Most wireless standards or protocols have security measures that may be used as applications determine.

The above mentioned are some of the major things in short range.... Ok now lets start with Long range . I am using some reference from some of the famous sites.... Introduction Since the development of the IEEE 802.11 radio standard (marketed under the Wi-Fi brand name), the technology has become markedly less expensive and achieved higher bit rates. Long range Wi-Fi especially in the 2.4 GHz band (as the shorter range higher bit rate 5.8 GHz bands become popular alternatives to wired LAN connections) have proliferated with specialist devices. While Wi-Fi hotspots are ubiquitous in urban areas, some rural areas use more powerful longer range transceivers as alternatives to cell (GSM, CDMA) or fixed wireless (Motorola Canopy and other 900 MHz) applications. The main drawbacks of 2.4 GHz vs. these lower-frequency options are: poor signal penetration - 2.4 GHz connections are effectively limited to line of sight or soft obstacles far less range - GSM or CDMA cell phones can connect reliably at > 16 km (9.9 mi) distances. The range of GSM, imposed by the parameters of Time division multiple access, is set at 35 km. few service providers commercially support long distance Wi-Fi connections Despite a lack of commercial service providers, applications for long range Wi-Fi have cropped up around the world. It has also been used in experimental trials in the developing world to link communities separated by difficult geography with few or no other connectivity options. Some benefits of using long range Wi-Fi for these applications include: unlicensed spectrum - avoiding negotiations with incumbent telecom providers, governments or others smaller, simpler, cheaper antennas - 2.4 GHz antennas are less than half the size of comparable strength 900 MHz antennas and require less lightning protection availability of proven free software like OpenWrt, DD-WRT, Tomato that works even on old routers (WRT54G for instance) and makes modes like WDS, OLSR, etc., available to anyone. Including revenue sharing models for hotspots. Nonprofit organizations operating widespread installations, such as forest services, also make extensive use of long-range Wi-Fi to augment or replace older communications technologies such as shortwave or microwave transceivers in licensed bands. Applications Business Provide coverage to a large office or business complex or campus. Establish point-to-point link between large skyscrapers or other office buildings. Bring Internet to remote construction sites or research labs. Simplify networking technologies by coalescing around a small number of Internet related widely used technologies, limiting or eliminating legacy technologies such as shortwave radio so these can be dedicated to uses where they actually are needed. Bring Internet to a home if regular cable/DSL cannot be hooked up at the location. Bring Internet to a vacation home or cottage on a remote mountain or on a lake. Bring Internet to a yacht or large seafaring vessel. Share a neighborhood Wi-Fi network. Nonprofit and Government Connect widespread physical guard posts, e.g. for foresters, that guard a physical area, without any new wiring In tourist regions, fill in cell dead zones with Wi-Fi coverage, and ensure connectivity for local tourist trade operators Reduce costs of dedicated network infrastructure and improve security by applying modern encryption and authentication. Military Connect critical opinion leaders, infrastructure such as schools and police stations, in a network local authorities can maintain Build resilient infrastructure with cheaper equipment that an impoverished war-torn region can afford, i.e. using commercial grade, rather than military-class network technology, which may then be left with the developed-world military Reduce costs and simplify/protect supply chains by using cheaper simpler equipment that draws less fuel and battery power; In general these are high priorities for commercial technologies like Wi-Fi especially as they are used in mobile devices. Scientific research See also: Wireless sensor network A long range seismic sensor network was used during the Andean Seismic Project in Peru. A multi-hop span with a total length of 320 kilometres was crossed with some segments around 30 to 50 kilometers. The goal was to connect to outlying stations to UCLA in order to receive seismic data in real time. Large-scale deployments The Technology and Infrastructure for Emerging Regions (TIER) project at University of California at Berkeley in collaboration with Intel, uses a modified Wi-Fi setup to create long-distance point-to-point links for several of its projects in the developing world. This technique, dubbed Wi-Fi over Long Distance (WiLD), is used to connect the Aravind Eye Hospital with several outlying clinics in Tamil Nadu state, India. Distances range from five to over fifteen kilometres (3–10 miles) with stations placed in line of sight of each other. These links allow specialists at the hospital to communicate with nurses and patients at the clinics through video conferencing. If the patient needs further examination or care, a hospital appointment can then be scheduled. Another network in Ghana links the University of Ghana, Legon campus to its remote campuses at the Korle bu Medical School and the City campus; a further extension will feature links up to 80 km (50 mi) apart. The Tegola project of the University of Edinburgh is developing new technologies to bring high-speed, affordable broadband to rural areas beyond the reach of fibre. A 5-link ring connects Knoydart, the N. shore of Loch Hourne, and a remote community at Kilbeg to backhaul from the Gaelic College on Skye. All links pass over tidal waters; they range in length from 2.5 km to 19 km. Increasing range in other ways Further information: 802.11 non-standard equipment and Radio propagation Specialized Wi-Fi channels For more details on this topic, see List of WLAN channels. In most standard Wi-Fi routers, the three standards, a, b and g, are enough. But in long-range Wi-Fi, special technologies are used to get the most out of a Wi-Fi connection. The 802.11-2007 standard adds 10 MHz and 5 MHz OFDM modes to the 802.11a standard, and extend the time of cyclic prefix protection from 0.8 µs to 3.2 µs, quadrupling the multipath distortion protection. Some commonly available 802.11a/g chipsets support the OFDM 'half-clocking' and 'quarter-clocking' that is in the 2007 standard, and 4.9 GHz and 5.0 GHz products are available with 10 MHz and 5 MHz channel bandwidths. It is likely that some 802.11n D.20 chipsets will also support 'half-clocking' for use in 10 MHz channel bandwidths, and at double the range of the 802.11n standard. 802.11n and MIMO Preliminary 802.11n working became available in many routers in 2008. This technology can use multiple antennas to target one or more sources to increase speed. This is known as MIMO, Multiple Input Multiple Output. In tests, the speed increase was said to only occur over short distances rather than the long range needed for most point to point setups. On the other hand, using dual antennas with orthogonal polarities along with a 2x2 MIMO chipset effectively enable two independent carrier signals to be sent and received along the same long distance path. Power increase or receiver sensitivity boosting A rooftop 1 watt Wi-Fi amp, feeding a simple vertical antenna on the left. Another way of adding range uses a power amplifier. Commonly known as "range extender amplifiers" these small devices usually supply around ½ watt of power to the antenna. Such amplifiers may give more than five times the range to an existing network. Every 6 dB gain doubles range. The alternative techniques of selecting a more sensitive WLAN adapter and more directive antenna should also be considered. Higher gain antennas and adapter placement Specially shaped directional antennas can increase the range of a Wi-Fi transmission without a drastic increase in transmission power. High gain antenna may be of many designs, but all allow transmitting a narrow signal beam over greater distance than a non-directional antenna, often nulling out nearby interference sources. A popular low-cost home made approach increases WiFi ranges by just placing standard USB WLAN hardware at the focal point of modified parabolic cookware. Such "WokFi" techniques typically yield gains more than 10 dB over the bare system; enough for line of sight (LOS) ranges of several kilometers and improvements in marginal locations. Although often low power, cheap USB WLAN adapters suit site auditing and location of local signal "sweet spots". As USB leads incur none of the losses normally associated with costly microwave coax and SMA fittings, just extending a USB adapter (or AP, etc.) up to a window, or away from shielding metal work and vegetation, may dramatically improve the link. Protocol hackingThe standard IEEE 802.11 protocol implementations can be modified to make them more suitable for long distance, point-to-point usage, at the risk of breaking interoperability with other Wi-Fi devices and suffering interference from transmitters located near the antenna. These approaches are used by the TIER project. In addition to power levels it is also important to know how the 802.11 protocol acknowledge each received frame. If the acknowledgement is not received, the frame is re-transmitted. By default, the maximum distance between transmitter and receiver is 1.6 km (1 mi). On longer distances the delay will force retransmissions. On standard firmware for some professional equipment such as the Cisco Aironet 1200, this parameter can be tuned for optimal throughput. OpenWrt, DD-WRT and all derivatives of it also enable such tweaking. In general, open source software is vastly superior to commercial firmware for all purposes involving protocol hacking, as the philosophy is to expose all radio chipset capabilities and let the user modify them. This strategy has been especially effective with low end routers such as the WRT54G which had excellent hardware features the commercial firmware did not support. As of 2011, many vendors still supported only a subset of chipset features that open source firmware unlocked, and most vendors actively encourage the use of open source firmware for protocol hacking, in part to avoid the difficulty of trying to support commercial firmware users attempting this. Packet fragmentation can also be used to improve throughput in noisy/congested conditions. Although packet fragmentation is often thought of as something bad, and does indeed add a large overhead, reducing throughput, it is sometimes necessary. For example, in a congested situation, ping times of 30 byte packets can be excellent, while ping times of 1450 byte packets can be very poor with high packet loss. Dividing the packet in half, by setting the fragmentation threshold to 750, can vastly improve the throughput. The fragmentation threshold should be a division of the MTU, typically 1500, so should be 750, 500, 375, etc. However, excessive fragmentation can make the problem worse, since the increased overhead will increase congestion. Obstacles to long-range Wi-Fi Methods that stretch the range of a Wi-Fi connection may also make it fragile and volatile, due to mundane problems including: Landscape interference Obstacles are among the biggest problems when setting up a long-range Wi-Fi. Trees and forests attenuate the microwave signal, and hills make it difficult to establish line-of-sight propagation. In a city, buildings will impact integrity, speed and connectivity. Steel frames partly reflect radio signals, and concrete or plaster walls absorb microwave signals significantly. Sheet metal in walls or roofs, may efficiently reflect Wi-Fi signals, causing signal loss or multipath problems. Tidal fading When point-to-point wireless connections cross tidal estuaries or archipelagos, multipath interference from reflections over tidal water can be considerably destructive. The Tegola project uses a slow frequency-hopping technique to mitigate tidal fading. 2.4 GHz interference Main article: Electromagnetic interference at 2.4 GHz Microwave ovens in residences dominate the 2.4 GHz band and will cause "meal time perturbations" of the noise floor. There are many other sources of interference that aggregate into a formidable obstacle to enabling long range use in occupied areas. Residential wireless phones, baby monitors, wireless cameras, remote car starters, and Bluetooth products are all capable of transmitting in the 2.4 GHz band. Due to the intended nature of the 2.4 GHz band, there are many users of this band, with as many as 2 or 3 devices per household. By its very nature, "long range" connotes an antenna system which can see many of these devices, which when added together produce a very high noise floor, whereby no single signal is usable, but nonetheless are still received. The aim of a long range system is to produce a system which over-powers these signals and/or uses directional antennas to prevent the receiver "seeing" these devices, thereby reducing the noise floor. Notable links Italy The longest unamplified Wi-Fi link is a 304 km link achieved by CISAR (Italian Center for Radio Activities). link first established on 2007-06-16 it appears to be permanent from Monte Amiata (Tuscany) to Monte Limbara (Sardinia) frequency: 5765 MHz IEEE 802.11a (Wi-Fi), bandwidth 5 MHz Radio: Ubiquiti Networks XR5 Wireless routers: MikroTik RouterBOARD with RouterOS, NStreme optimization enabled Length: 304 km (189 mi). Antenna is 120 cm with handmade waveguide. 35 dBi estimated Venezuela Another notable unamplified Wi-Fi link is a 279 km link achieved by the Latin American Networking School Foundation. Napo's Network, Loreto (March 2007) Pico del Águila - El Baúl Link. frequency: 2412 MHz link established in 2006 IEEE 802.11 (Wi-Fi), channel 1, bandwidth 22 MHz Wireless routers: Linksys WRT54G, OpenWrt firmware at el Águila and DD-WRT firmware at El Baúl. Length: 279 km (173 mi). Parabolic dish antennas were used at both ends, recycled from satellite service. At El Aguila site an aluminum mesh reflector 2.74 m (9 ft) diameter, center-fed, at El Baúl a fiberglass solid reflector, offset-fed, 2.44 by 2.74 m (8 by 9 ft). On both ends the feeds were 12 dBi Yagis. Linksys WRT54G series routers fed the antennas with short LMR400 cables, so the effective gain of the complete antenna is estimated at about 30 dBi. This is the largest known range attained with this technology, improving on a previous US record of 201 km (125 mi) achieved last year in U.S. The Swedish space agency attained 420 km (260 mi), but using 6 watt amplifiers to reach an overhead stratospheric balloon. Peru Antenna's installation at Napo, Loreto (March 2007) Loreto, in the jungle region of Peru, is the location of the longest Wi-Fi-based multihop network in the world. This network has been implemented by the Rural Telecommunications Research Group of the Pontificia Universidad Católica del Perú (GTR PUCP). The Wi-Fi chain goes through many small villages and takes seventeen hops to cover the whole distance. It begins in Cabo Pantoja's Health Post and finishes at downtown Iquitos. Its length is about 445 km. The intervention zone was established in the lowland jungle with elevations under 500 meters above sea level. It is a flat zone and for this reason GTR PUCP installed towers with an average height of 80 meters. The link was established in 2007. GTR PUCP, the regional government of Loreto, and Vicariate San José de Amazonas are working together on maintenance of the network. Frequency channels used: 1, 6 and 11, 802.11g non-interfered channels smartBridges Wireless Routers were used. L-com antennas were used. FAQ for 802.11ac...... Q What is 802.11ac? A 802.11ac is the next generation IEEE standard, expected to be ratified in late 2013 by the IEEE 802.11ac Task Group. 802.11ac builds on the 802.11n standard and enables wireless speeds over 1Gbps. Q What are the main differences between 802.11n and 802.11ac? A 802.11ac operates only in the 5GHz band and makes enhancements to several aspects in 802.11n: – 256 QAM modulation scheme – Support for up to 8 spatial streams – Channel bonding to create 80Mhz and 160Mhz channel widths – Multi-user MIMO (MU-MIMO) Q Is 802.11ac backwards compatible? A Yes, 802.11a/n client devices will be able to connect to 802.11ac access points. Q When will client devices support 802.11ac? A High-end laptops and smart phones as well as USB dongles built for 802.11ac are available on the market today. Q How does 802.11ac compare to 802.11n from a security standpoint? Does it still use WEP and WPA? A Both 802.11n and 802.11ac use the same security protocols, including WEP and WPA. Q How do I know my current devices (laptops, tablets, smartphones, smart tv, etc) are compatible with Wi-fi 802.11ac? A 802.11ac is backwards compatible with 802.11a and n devices in the 5GHz band. Q Isn’t 802.11ac better suited for backbone deployment? A The high bandwidth pipe certainly lends itself to backhaul/backbone applications, and the wide channel sets are less of a problem for backbone situations as the coverage may be highly directional or there may be a mesh of APs where everything needs to be on the same channel anyway and thus the smaller set of non-overlapping channels isn’t a detriment when going to 80 or 160 MHz channels. Q What are the biggest differences between 802.11ac and 802.11ad? A The single biggest difference is that 802.11ac is 5GHz and backwards compatible with 5GHz 802.11a/n devices while 802.11ad operates at 60GHz and has no backwards compatibility with existing technology. Q What is the expected range for 802.11ac? A Range is entirely dependent on date rate, TX/ RX antennas, and the strength of the receiving device’s transmitter. Q Why was the ac designation given in 802.11(ac)? A IEEE standards are lettered sequentially a - z, when the alphabet is concluded, they wrap around with double letters (aa - az, ba - bz, etc.) Q Is 802.11ac a draft or is it an actual standard now? A 802.11ac is still in draft status per the IEEE, however there are no anticipated significant changes to the specifications at this time based on the stage of balloting that the draft is in. Q How many users in the 80MHz or 160MHz band channel can be supported at the same time? A The numbers of users is not dependent on the channel bandwidth but is based on vendor AP implementation. For Zebra access points this tends to be 256 clients per AP. Q Does 11ac help improve the performance of 11n devices in any way? A 802.11ac technology itself does not improve the performance of 802.11n devices, however improvements in chipsets as well as receiver technology advancements made in the development of 802.11ac may result in mild improvements for 11n clients in some environments. Q What are the differences between the AP 8232 and AP 8222? A The AP 8232 is a dual radio 802.11n/802.11ac access point with an expandable design to support plug-in USB modules. The AP 8222 is also a dual radio design, but with a fixed configuration with and internal antennas in an aesthetically pleasing housing. Q What application modules are being made available? A There will be a WIPS sensor radio module and a 3G/4G/ LTE backhaul module available in Q3. Additional modules such as an environmental sensor module and video camera module will follow later in 2013. Q Can I use the AP 8132 modules with the AP 8232? A Yes, AP 8132 modules are compatible with the AP 8232. Q How many radios does the AP 8232 have? A The AP 8232 is a dual-radio design, one radio supporting 802.11a/b/g/n and the other supporting 802.11ac. This allows customers to support new mobile devices as well as legacy clients. Q How many spatial streams does the AP 8232 support? A The AP 8232 is a 3x3 MIMO design with 3 spatial streams. Q Can I operate the AP 8232/AP 8222 at 802.11ac off 802.3af power? A es, there will be a configurable mode of operation that allows for 802.11ac operation while running on 3af power. Q Is the AP 8232 plenum rated? A Yes, the external antenna AP 8232 is plenum rated. Q What is hierarchical management? A Hierarchical management provides a single dashboard in WiNG, available on the NX 9500 controller platform, that allows management of remote controllers, APs, WIPS and other applications all from an integrated easy-to-use, graphical console. It also delivers centralized control over the enterprise Wi-Fi deployment. Q How does application acceleration work? A Application acceleration provides real-time caching of content with the NX 4500/6500 Integrated Service Platforms, improving web browsing and mobile app experiences for shoppers and guests without requiring a major upgrade to the WAN infrastructure. Q Can you address the specifics on how the Multiple User MIMO works — E.G. “Allows multiple streams to be assigned to different clients”? A MU-MIMO allows for a certain amount of parallelism in how data is transmitted to client devices improving system throughput and performance over a traditional MIMO system.