IIT Mandi develops new spectrum sensor to improve wireless communication

Dr Shrestha said that radiofrequency waves, or “spectrum” as they are known in the telecommunication field, are used for wireless communication and the wireless radiofrequency spectrum is a limited resource allocated by the government to telecom companies through a licensing process. The rapid growth in wireless communication technology seen in recent years and the projected exponential increase due to mass adoption of technology such as fifth-generation new-radio (5G-NR) and the Internet of Things (IoT) are expected to result in a massive demand for the spectrum bands, he added.

Pointing out the need for research in the area of spectrum optimization, he said, “Given the fixed-spectrum allocation policy of many governments around the world, including ours, it becomes important to use the available spectrum intelligently. Cognitive Radio Technology is considered one of the best ways to optimise spectrum use.”

Not all parts of the spectrum band licensed to a telecom company (called primary user or PU) are used all the time by the PU. The idea of Cognitive Radio Technology is that a wireless device such as a cell phone, used by the secondary user (SU) can be fitted with a special sensor that can detect “spectrum holes” (spectrum parts that are not used by the PU) and use them when the main channel is unavailable or crowded, Dr Shrestha said. “This forms the basis of a dynamic-spectrum access policy that can overcome shortages of available spectrum at a given time. The spectrum-hole detecting sensor that is built into the SU’s device is called a Stand-Alone Spectrum Sensor (SSSR),” he added.

Discussing the relevance of the team’s research, Dr Shrestha said, “The SSSR’s detection capability is often less than satisfactory due to various problems such as signal-to-noise ratio (SNR)-wall problems. This leads to the unreliability of performance when the SSSR is used in real-time.”

“The team’s research work seeks to circumvent the above problem. The technology is one where instead of equipping the SU’s wireless device with an SSSR, the received parts are transmitted from the spectrum band to a Data Fusion Centre (DFC). The DFC then digitises these parts and processes them using a single cooperative spectrum sensor (CSR)” he said.

Mr Rohit B. Chaurasiya, elucidated on the matter further, “We have proposed implementation-friendly algorithms for cooperative spectrum sensing with lower computational complexity and have also developed multiple new hardware architectures for CSR and their submodules.”

This digital CSR ASIC-chip developed by IIT Mandi delivers excellent detection reliability of the PU under real-world channel scenarios with the best hardware efficiency and fast sensing time. The CSR chip can be used with any handheld mobile wireless communication device for accessing the unused spectrum. Specifically, it can be used in future 5G and 6G wireless communication technologies for enhancing spectral efficiency, he added.

He said that in addition, this will enable massive deployment of IoT-based networks where numerous connected devices can use spectrum holes for break-less communication. The specific uses of cooperative spectrum-sensing technology in India cannot be understated and will help in establishing broadband services in remote and rural parts of the country.