Researchers at Carnegie Mellon University are developing new ways to improve tracking technology so that airline passengers won’t have to look for bags at the lost and found counter.
Most airports use a radio-frequency identification (RFID) tags to track the movement of baggage through the airport. This approach contains two parts: a mobile tag and a stationary reader. The reader remains at a fixed checkpoint within the airport; the tag is attached to the baggage and serves as a unique label. As a suitcase moves through the airport, it passes certain baggage checkpoints. When the tag comes within range of the reader, the two parts of the system communicate with each other, transmitting and receiving signals. Through this communication, the reader can confirm that a baggage has made it to each checkpoint.
Checkpoints are placed at specific points throughout the airport, often appearing periodically along the path the baggage must take from check-in to boarding. Unfortunately, each reader has a range of only 15 to 45 ft, much shorter than the distance between checkpoints. In other words, there are blind spots along the path where no checkpoint can confirm that a bag is nearby. Once bags are outside of that range, they become essentially “lost,” even though they are most likely still somewhere along the proper path.
Many warehouses, such as those used by retailers, pair merchandise with RFID tags so it can be tracked during shipping, and some retail stores place tags on clothing to keep tabs on inventory and prevent shoplifting. These items are often in similar blind spots created by RFID readers.
Ways around this problem have been proposed, with some focusing on changing the readers themselves, and others changing the tags to get better ranges. However, both options require installation of new RFID tags and readers.
Recently, researchers in the lab of CMU’s Swarun Kumar have updated the current software to increase the range.
“From a deployment perspective, upgrading software on existing readers is much less expensive than purchasing and installing new, often-bulkier hardware,” says Kumar, an assistant professor in the Department of Electrical and Computer Engineering.
“Our proposal, called PushID, uses a technique called beamforming that focuses energy from many different readers on to one tag. By carefully modifying signals from each reader, we ensure their energy adds up at the tag’s location,” Kumar says. “Our key innovation is finding where the battery-free tags beam energy to, because they have absolutely no energy in the first place to advertise their locations.”
To determine where tags are in the environment, the readers give out specialized signals that intelligently smear energy through the environment in search of a tag. If a tag is within the range, it transmits a signal in return. The reader receives this transmitted reply and once again sends out a signal of its own. By repeating this process every few milliseconds, the readers quickly identifies the tags in the environment and can determine their precise locations.
This iterative process also lets PushID to account for obstacles in the environments, such as furniture, signs, and walls. The presence of even a single obstacle can dramatically change how energy adds up or cancels out across tag locations. PushID lets the RFID system account for the effect of these obstacles, thereby ensuring the tag’s location is properly identified. Readers can also account for mobility, letting the system follow a tag as it moves through the environment.
Unlike current RFID tags, which have a range of 55 to 45 ft, PushID expands that range to almost 200 ft. And for a given environment, PushID covers 97% of the area within four seconds; without it, only 33% of the total area is covered.
Although PushID is operational as it stands, the team has already identified improvements. The range can be expanded if the team can choose where new readers are installed. Additionally, the team hopes to incorporate its technology with other devices on the market to further increase range.
Currently, PushID works at a store-scale: 200 ft covers a warehouse or retail store, but it is not enough for larger areas. In the future, the team aims to expand the technology to a city scale and broaden its applications.
“The technology may one day let us track our phones and clothes, every item we don’t want to lose, throughout entire cities,” says Jingxian Wang, the Ph.D. student in ECE who spearheaded the project.
