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Muhammad Zeeshan Waheed: Signal models and digital cancellation of passive intermodulation distortion in radio communication systems

Tampere University
LocationKorkeakoulunkatu 1, 33720 Tampere
Hervanta campus, Tietotalo building, auditorium TB109
Date30.8.2024 9.00–13.00
Entrance feeFree of charge
Photo: Elina Lassila
As the demand for higher data rates and internet-dependent devices grows, spectral congestion increases. This has led to innovative solutions that improve spectral efficiency, enabling high data rate without the need for additional spectrum resources. In his study, M.Sc Muhammad Waheed developed novel solutions for modelling and suppressing passive intermodulation distortion in modern telecommunication systems, demonstrating that these methods can significantly reduce passive intermodulation induced self-interference and enhance overall system performance by mitigating the unwanted distortions.

In his doctoral dissertation MSc Muhammad Zeeshan Waheed explored innovative methods to enhance the efficiency of wireless communication systems, focusing on the challenges posed specifically by passive intermodulation (PIM) distortion. 

Waheed's research addresses a critical issue in modern telecommunication systems, such as 5G and beyond: the interference caused by PIM distortion. 

“PIM occurs when multiple signals mix in the non-linear components of the communication system, creating unwanted interference that can degrade the performance of the receiver”, Waheed says. 

Mitigating interference with new models and digital cancellation techniques

The interference caused by PIM distortion is particularly problematic in systems using carrier aggregation (CA) technology, which combines multiple frequency bands to increase data rates.

“The methods I developed can significantly reduce PIM-induced self-interference, which is a major hurdle in achieving higher spectral efficiency," Waheed says.

Waheed’s dissertation presents new models and digital cancellation techniques that mitigate this interference, thus enhancing the overall performance of the communication system. 

“These solutions are not only effective but also practical, as they use the existing transmit data to model and cancel out the unwanted PIM signals in the receiver”, Waheed says.

One of the key findings of the research is that by accounting for the non-linear distortions caused by amplifiers, the amount of interference cancellation can be improved by an additional 4-5 dB. This improvement is substantial, considering that PIM-induced self-interference can be nearly 20 dB above the noise floor even with state-of-the-art components.

Enhanced connectivity to help sustain the growth of internet-dependent technologies

Waheed's work is highly relevant in today's context of ever-increasing connectivity demands.

“As we continue to integrate more devices into our wireless networks, ensuring efficient use of the spectrum becomes crucial," he explains. ”My research offers practical applications that can be implemented in current and future telecommunication systems, thereby helping to sustain the rapid growth of internet-dependent technologies.”

Waheed's dissertation contributes valuable insights and solutions to the field of wireless communications, making it possible to achieve higher data rates and better performance without the need for additional spectrum. This has significant implications for both the industry and the public, as it supports the ongoing expansion of reliable and fast wireless connectivity.

Muhammad Zeeshan Waheed came to Finland in 2015 to pursue a master’s degree in wireless communication systems at Tampere University. After completing his degree in 2017, he began working for Nokia while simultaneously continuing his doctoral studies part-time.

Over the course of seven years, Waheed dedicated himself to his research, culminating in his innovative dissertation on enhancing spectral efficiency in wireless communications by devising methods for the digital cancellation of PIM distortion.

Currently, Waheed serves as an SoC Architect at Nokia, applying his expertise to advance the field of telecommunications.

Public defence on Friday 30 August

The doctoral dissertation of Muhammad Zeeshan Waheed in the field of Wireless Communication titled Passive Intermodulation Distortion in Radio Communication Systems: Signal Models and Digital Cancellation will be publicly examined at the Faculty of Information Technology and Telecommunication Science, Tampere University, at 12:00 on Friday 30.8.2024 at Hervanta Campus, Tietotalo building, auditorium TB 109. The Opponent will be Professor Timo Rahkonen from University of Oulu. The Custos will be Professor Mikko Valkama from Tampere University.

The doctoral dissertation is available online.