Rajiv Laroia’s development of Flash-OFDM was integral to transitioning cellular voice access systems to the wireless data access systems that have mobilized our access to the Internet via smartphones, tablets, and wireless modems. He realized that the nature of Internet data traffic demanded a redefinition of wireless connectivity and thus developed Flash-OFDM (fast low latency access with seamless handoff—orthogonal frequency division multiplexing). Unlike voice calls, which require a persistent but relatively low rate connection, Internet traffic requires intermittent bursts at high rates, and the system needed to be agile enough to quickly reassign air-link resources according to widely and rapidly varying traffic demands. The key to Flash-OFDM is that the overall channel resource is divided into very fine-grained time-frequency slots that each user can access orthogonally without interference from another. Prior to Flash-OFDM, cellular wireless connectivity was circuit-switched. He saw that the migration from cell phones to smartphones was creating capacity demand that could not be met by circuit-switched networks and developed a packet-switched architecture. In patented work, he described a wireless system in which terminals support various states of operation (on-state, hold-state, sleep-state, and access-state). In the hold-state a mobile device is put into a low-power, passive state to free up system resources and preserve battery life but can quickly transition into a communicating state. Other patented work addressed assigning traffic resources by mapping active users to data resources so that users would not maintain an active uplink, fractional frequency reuse, and beacon signals that allow detection of hand-off candidates and timing correction at long range for efficient hand off between cells and across frequencies. These aspects of Flash-OFDM, plus many other concepts developed by Laroia and his teams, helped form the basis for the LTE and 4G systems that are powering today’s mobile broadband communications.
An IEEE Fellow and recipient of the 2018 Eduard Rhein Technology Award, Laroia is the founder and chief technology officer of The Light Company, Far Hills, NJ, USA.