UIC researchers develop novel way to improve wireless communications
By Andrea Poet
UIC researchers have developed a novel way to improve wireless communications, increasing the rate and the range of communications and designing circuits with low power consumption. Their method is detailed in the paper “Active Two-Way Backscatter Modulation: An Analytical Study,” which was recently published in the journal IEEE Transactions on Wireless Communications.
The team uses backscatter modulation, a technique most often used for short, one-way communications, and modified it for two-way use, increasing both the range and rate of communications.
To send a message over the air using wireless communications, an oscillatory wave needs to be generated, then modulated. Using backscatter modulation, you can eliminate the need for an oscillator, as smaller radio frequency identification (RFID) tags are employed. RFID tags have been in use for some time; they are used to track inventory, control access to parking lots, or even track race participants via their bib numbers. These small tags operate without an internal power source, receiving energy via electromagnetic waves from the reader’s antenna. The tag uses some of the energy it receives to send back a reply to the reader. Traditionally, because of the lack of power supply, the reading range for an RFID tag is short, therefore the tag must be fairly close to the reader.
“People think of backscatter as a technique only for short range, one-way communication,” said Besma Smida, associate professor of electrical and computer engineering at UIC and one of the paper’s authors. “We made it two-way, which opens the door to all types of Internet of Things (IoT) applications. Maybe you want a sensor to send data or order an antenna to change directions — now we have data that can go both directions.”
To improve the range of communications, which is typically limited to 3 to 6 feet using backscatter modulation, the researchers designed a power-efficient circuit using a geometry optimization approach.
“We derived the equation and simplified it into a plot, which is easier to use,” said Seiran Khaledian, the lead author on the paper, a Ph.D. candidate at UIC and an antenna designer at Motorola Mobility. “You just choose a constellation point and that will give you the value of the load you have to use. Basically, you can design your circuit based on our plot.”
This technique will open the door to all types of sensors, which will be particularly useful with the IoT and for indoor communications.
“You have these small devices that have sensing capabilities that you can put everywhere and that don’t use much power. You don’t need a huge battery, and you can use some energy harvesting through sunlight or the electromagnetic wave themselves. You can put the sensors out in the world or the city and forget about battery life,” Smida said. “Anytime you want to communicate with them you generate the wave so the transmitter will generate the message, send it to a small sensor, and through backscatter technique they will send back the data.”
The paper’s other authors include Farhad Farzami, a UIC alumnus and senior RF engineer at Motorola Mobility; Hamza Soury, a post-doctoral fellow with the electrical and computer engineering department at UIC; and Danilo Erricolo, a professor with the electrical and computer engineering department and director of the Andrew Electromagnetics Laboratory at UIC.