Tag Archives: Wi-Fi

The Latest in Li-Fi

Newly developed technologies are allowing wireless networks to operate several hundred times faster than Wi-Fi—one of them is Li-Fi or Light Fidelity. Simply by switching on a light bulb, it is possible to encode data within the visible light spectrum rather than allow them to ride on radio waves as traditional wireless technologies such as Wi-Fi do.

So far, research labs had confined Li-Fi within their closed doors. Of late, however, several new products using the Li-Fi technology has started to appear on the market. While the majority of the wireless industry focused their attention on developing 5G or the fifth generation wireless technology, PureLiFi presents a new dongle for laptops and computers that uses the latest light fidelity technology. Another startup company, Oledcomm from France, offers their Internet lighting system for hospitals and offices.

Light bulbs use LEDs, which are semiconductor devices able to switch at very high speeds, unlike the incandescent or fluorescent bulbs, which are rather slow in turning on and off. Li-Fi technology interrupts the electric current through the LEDs at high speeds, making them flicker and at the same time, encoding the light they produce with parallel streams of data. The analogy here is the process is very much like producing the Morse code in a digital manner, the difference being the flickering is much faster than the human eye can follow.

Dongles, smartphones, and other devices with built-in photo detectors can receive this light encoded with data. This manner of communication is not new, as remote controls have been using this technology using infrared lights. The remote sends tiny data stream commands to toys and televisions, and they interpret the information, process it, and change their functioning accordingly. Li-Fi uses visible light spectrum, as it can reach intensities capable of transmitting much larger amounts of data than infrared light can. For instance, it is common to find Li-Fi networks operating at speeds around 200 gigabytes per second.

The only downside to Li-Fi is it works on line-of-sight. As light does not bend around corners, the transmitter and receiver must physically see each other to communicate effectively. According to Harald Haas, the professor of mobile communications who introduced the world to Li-Fi, this handicap is easy to overcome by fitting a small microchip in every potential illumination device. The microchip would serve to combine two basic functionalities in an LED light bulb—illumination and wireless data transmission—one need only place the microchip embedded LED light bulbs in sight of one another to act as repeaters in between the transmitter and the receiver.

Haas spun out PureLiFi, whose initial products had a throughput of 10 Mbits per second, making them comparable to Wi-Fi versions available at the time. Since then, PureLiFi has advanced the technology to produce LiFi-X, an access point connecting LED bulbs and dongles and providing 40 Mbits per second for both downloads and uploads speeds.

Another company from Estonia, Velmenni, has already demonstrated Li-Fi technology in their products that offer speeds around one Gbits per second. Oledcomm has developed kits for retrofitting Li-Fi into existing LED light bulbs, useful for communication within supermarkets and retail stores.

What is E-Smog and How to Detect it?

Many people claim advancement in technology and the proliferation of electronic devices is creating a sea of electromagnetic waves around us, and this eSmog is actually a cause for many of the illnesses we are afflicted with nowadays. While eSmog causing bad health is up for debate, some people seem to be more sensitive to it than others are. However, the presence of electromagnetic waves around us cannot be ruled out, with greater concentrations around devices such as computers, mobile phones, Wi-Fi routers, cordless phone bases, and in fact, anything electronic and powered up. Therefore, an instrument that measures the level of electromagnetic fields around it is in order.

Today, it is practically impossible for us to live life without our electronic devices and everyday technology that produce electromagnetic fields. Although we cannot see the electromagnetic fields that surround us, an instrument that can measure its presence is useful for us to know, say, whether a brick wall has reduced the level, and to what extent.

We all need our Wi-Fi, Zigbee, Bluetooth, television, radio, mobile phones, and other gadgets. To know the level of eSmog each of them is producing, you can use the kit TAPIR—an eSmog detector. You can assemble this tiny instrument from the seven small PCBs in the kit. TAPIR comes with an antenna and two types of electromagnetic detectors.

The kit has a PCB panel, actually made of seven parts. You can assemble the PCBs and make them form the enclosure for TAPIR. The PCBs are numbered—starting with the top piece, the left sidepiece with a switch, the bottom piece with the components, the right side piece with the headset connector, the negative battery connection piece, the positive battery connection piece, and the end piece. A headset plugged into the connector allows the user to hear the device detecting eSmog. The intensity of sound increases with the level of eSmog TAPIR detects. You need a single AAA battery to power the kit.

TAPIR—acronym for Totally Archaic but Practical Interceptor of Radiation—is a wideband ultrasensitive eSmog detector. Once you have connected it to the antenna and the headphones, and switched it on, you can move it around an electronic device. This allows you to hear different noises depending on the type and frequency of the field the device is emitting.

Making the two antennae for the TAPIR is important for it to function properly. All around us, there are two types of electromagnetic fields—the E-field or electrical field, and the H-field or the magnetic field—and two separate antennae are necessary to allow TAPIR to detect the two fields.

The E-field antenna consists of a length of solid insulated wire. The kit includes the wire, and you will need only half of it to form the antenna. Insulate one end of the wire with heat-shrink tubing and bend it to form a loop. At the other end of the wire, solder the cinch connector shell to complete the antenna.

A coil is enclosed with the kit, and you can solder this coil to two pieces of insulated wires. Solder the free ends of the wires to the second cinch connector, and your H-field antenna is ready.

Connect with a New Type of Li-Fi

Many of us are stuck with slow Wi-Fi, and eagerly waiting for light-based communications to be commercialized, as Li-Fi promises to be more than 100 times faster than the Wi-Fi connections we use today.

As advertised so far, most Li-Fi systems depend on the LED bulb to transmit data using visible light. However, this implies limitations on the technology being applied to systems working outside the lab. Therefore, researchers are now using a different type of Li-Fi using infrared light instead. In early testing, this new technology has already crossed speeds of 40 gigabits per second.

According to the Li-Fi technology, a communication system first invented in 2011, data is transmitted via high-speed flickering of the LED light. The flickering is fast enough to be imperceptible to the human eye. Although lab-based speeds of Li-Fi have reached 224 gbps, real-world testing reached only 1 gbps. As this is still higher than the Wi-Fi speeds achievable today, people were excited about getting Li-Fi in their homes and offices—after all, you need only an LED bulb. However, there are certain limitations with this scheme.

LED based Li-Fi presumes the bulb is always turned on for the technology to work—it will not work in the dark. Therefore, you cannot browse while in bed in the dark. Moreover, as in regular Wi-Fi, there is only one LED bulb to distribute the signal to different devices, implying the system will slow down as more devices connect to the LED bulb.

Joanne Oh, a PhD student from the Eindhoven University of Technology in the Netherlands, wants to fix these issues with the Li-Fi concept. The researcher proposes to use infrared light instead of the visible light from an LED bulb.

Using infrared light for communication is not new, but has not been very popular or commercialized because of the need for energy-intensive movable mirrors required to beam the infrared light. On the other hand, Oh proposes a simple passive antenna that uses no moving parts to send and receive data.
Rob Lefebvre, from Engadget, explains the new concept as requiring very little power, since there are no moving parts. According to Rob, the new concept may not be only marginally speedier than the current Wi-Fi setups, while providing interference-free connections, as envisaged.

For instance, experiments using the system in the Eindhoven University have already reached download speeds of over 42 gbps over distances of 2.5 meters. Compare this with the average connection speed most people see from their Wi-Fi, approximately 17.5 mbps, and the maximum the best Wi-Fi systems can deliver, around 300 mbps. These figures are around 2000 times and 100 times slower respectively.

The new Li-Fi system feeds rays of infrared light through an optical fiber to several light antennae mounted on the ceiling, which beam the wireless data downwards through gratings. This radiates the light rays in different direction depending on their wavelengths and angles. Therefore, no power or maintenance is necessary.

As each device connecting to the system gets its own ray of light to transfer data at a slightly different wavelength, the connection does not slow down, no matter how many computers or smartphones are connected to it simultaneously.

How Do You Count People Using Wi-Fi?

Other than providing wireless communication facilities, Wi-Fi can have other uses as well. Researchers at the UCSB are now experimenting with a common wireless signal to tell them the number of people present in a designated space. Astonishingly, these people need not be carrying any personal devices on them.

At Professor Yasamin Mostofi’s lab in the UC, Santa Barbara, researchers are demonstrating that wireless signals have more uses than simply providing access to the Internet. With a Wi-Fi signal, they are counting the number of people in a given space. According to the researchers, this technology can lead to diverse applications, such as search-and-rescue operations and energy efficiency.

Mostofi explains the process as estimating the number of people walking about in an area, based on the scattering and received power measurements of a Wi-Fi link. Moreover, it is unnecessary for the people being counted to carry any Wi-Fi enabled telecommunications devices.

In the demonstration, the researchers placed two Wi-Fi cards at the opposite sides of a target area measuring roughly 70-square-meters. They measured the received power of the link between the two cards, and this approach allowed them to estimate the number of people walking about in that area. So far, they have been successful in detecting up to nine people in both outdoor and indoor settings. Mostofi’s research group will be publishing their findings in the special issue on location-awareness for radios and networks in the Selected Areas in Communication of the publication of the Institute of Electrical and Electronics Engineers Journal.

According to Mostofi, the main motivation for this work comes from counting several continuously walking people in a small area by measuring only the power of one link of the Wi-Fi signal.

The researchers count people relying to a large extent on the changes in the received wireless signal. Human bodies scatter wireless signal, and when a person crosses the direct wireless link between the two cards, there is a distinct attenuation of the signal—both effects combining to form multi-path fading. Based on these two key phenomena, and a probabilistic mathematical framework, the researchers have proposed a method of estimating the number of people walking in the space.

With Wi-Fi abounding in most urban settings, the researchers estimate a huge potential for their findings for many diverse applications. For instance, smart homes and buildings can estimate the heating and air-conditioning requirements based on occupancy or the number of people present in a given space at the time. Stores can go for better business planning based on the number of shoppers on specific days of the week.

Occupancy estimation could also help in security and rescue operations. Remote estimation of the number of people stranded at a place can help with the organization and logistics involved in arrangement of the transportation required to rescue them. Mostofi and his team have also done extensive research work in their lab involving estimation of stationary objects and humans through walls using Wi-Fi signals. They ultimately plan to bring the two projects together in the future, so that security and rescue operations can commence with better preparation.

How do Wi-Fi Antennas Work?

Antennas are necessary for transmitting and receiving the radio-frequency energy that forms the basis of Wi-Fi communications. The underlying rule is you need a better antenna to improve coverage. Understanding fundamentals is essential for selecting a proper antenna for your application.

In general, antennas radiate radio waves when fed with the right kind of electrical power. Conversely, an antenna can also covert radio waves received by it into electrical power. There are different forms of antennas, some created intentionally, such as those on your wireless router, and others created naturally, such as the wires on your earbuds, which act as antennas. Antennas are usually directional, meaning they are better in transmitting and receiving radio waves in some directions than in others. However, there are omnidirectional antennas that work nearly equally in all directions.

Wi-Fi antennas are mostly dipole types, or more specifically, half-wave dipoles. They consist of two halves, each equal in length to a quarter of the wavelength they are to transmit or receive. A separate conductor from the feedline feeds each half separately. For example, for a frequency of 2.45GHz, a half-wave dipole antenna would be 61.22mm from one end to the other, while each half measuring 30.61mm. However, other parameters also affect the length of the dipole and the resulting antenna may differ considerably from theoretical calculations.

Examining a Wi-Fi antenna from a 2.4GHz wireless router reveals a hinged base connected to a plastic cover. The hinge allows antenna rotations irrespective of the mounting position of the router. Within the plastic cover, you can see the entire dipole antenna. One-half of the dipole is made of a metal cylinder through which the feeder wire passes. The other half is the wire itself that protrudes to the other side of the cylinder. With the metal cylinder and the wire insulated from each other, they form a dipole of approximately one-quarter wavelength long. Such antennas have a gain of about 2dBi and their radiation pattern is circular.

The antenna connects to the Wi-Fi radio transceiver via a wire feedline – a coaxial cable. This has an insulated inner copper conductor covered with an outer braided shield made of copper wires. A clear plastic cover encases the entire feedline. Wi-Fi devices use these feedlines, also known as coax and designated RG-178, specifically for their small size and relatively low RF losses.

Antennas are usually better in transmitting and receiving radio waves in certain directions. Their ERP or Effective Radiated Power is greater in those directions. Although the total radiated power remains the same, antenna gain refers to the increase in strength in several directions than in others. Therefore, simple horizontal dipoles show gain in two directions – parallel to the radiators on both the front and backsides.

Depending on the country that is using the Wi-Fi signals, there are five different bands of transmission – 2.4GHz, 3.6GHz, 4.9GHz, 5GHz and 5.9GHz, with correspondingly matched antenna lengths. Although the general principles apply to all bands, the most widely used transmission for Wi-Fi signals is the 2.4GHz band. Usually, this extends from 2.4GHz to 2.5GHz.

Devices Running on WiFi Power

Mobile devices are now radically smaller and more powerful than those available in the last decade were. They are also able to tackle more technology-related tasks compared to their erstwhile brethren. However, as their capability grows, they need to consume more power. With the Internet-of-Things and wearable technologies gaining increasing recognition from users, the need to keep them ‘on’ all the time is raising the topic of the best methods to power them.

Imagine that you have multiple sensors embedded around your home, tracking temperature changes by the minute and governing your thermostat to help conserve energy. How nice it would be if all the sensors operated without batteries. For then, you could rest assured that they, in tandem with the thermostat, will be properly monitoring the energy consumption. With battery-operated sensors, you will need to check on the status of each sensor frequently to prevent the system going haywire.

Now, engineers have developed a new communication system that does not require batteries to operate it. Instead, it uses existing Wi-Fi infrastructure and radio frequency signals to provide Internet connectivity to devices. Very soon, your battery-less wristwatch or other wearable devices will be able to communicate directly with other gadgets for storing information about your daily activities on your online profiles.

Earlier research by a group of engineers at the University of Washington had shown that it is possible for low-power devices to run off wireless waves such as those belonging to radio and TV. Their most recent work has taken them a step further. Now these devices, apart from operating without batteries, can send their signals to laptops or smartphones, using only wireless waves to generate the required power.

According to Shyam Gollakota, an assistant professor at the University of Washington, this is an essential step for Internet of Things to really take off. Potentially billions of battery-free devices will need connectivity when embedded in everyday objects. The research can now provide WiFi connectivity to devices and they claim their process consumes several orders of magnitude less power than that typically required for WiFi connectivity.

A tag made by the researchers listens for WiFi signals that a local router exchanges with a laptop or a smartphone. An antenna on the tag selectively reflects or absorbs the signal to encode it. The activity produces tiny changes in the signal strength of the radio waves that other devices can detect and decode.

The method allows central devices such as laptops, tablets and smartphones the ability to communicate with other low-power devices and sensors. The central devices exchange data with sensors that lie within a range of about two meters and do so at the rate of one kilobit per second. For example, a pair of smart socks could relay information about your jog to the jogging app on your phone. Although there is a chance for the radio signals to be buried in noise, the system works because the devices know the specific pattern that they need to look for.

That allows low-power Internet of Things to communicate easily with a large swarm of devices around them because of the prevalence of WiFi.