Demands on high data rate applications are increasing and consequently demands on spectral resources are increasing as well. Although electromagnetic spectrum is recently said to be in a scarcity situation, several studies have shown that this scarcity is mainly due to the legacy command-and-control regulation rather than due to physical scarcity of spectrum. For this reason researchers have started investigating techniques to better manage the usage of spectrum. Among these techniques there exist the methods allowing the primary/secondary usage of spectrum, or secondary market. Secondary market techniques mainly manage sensing, accessing and aborting the spectrum usage by the secondary users. Techniques developed for secondary market context are also referred to as algorithms for Cognitive Radio (CR) networks. Regulators worldwide took measures to promote the deployment of primary/secondary context.
MULTIPLE-INPUT MULTIPLE-OUTPUT (MIMO) SYSTEMS
A major interest of the group (up to 2009) was to study and promote space-time signal processing and multiple-transmitter multiple-receiver (MTMR) antenna technology in wireless communication systems. This is also known as multiple-input multiple-output (MIMO) technology. While a variant of this approach was proposed as an option for third generation (3G) mobile systems, multiple antennas will be mandatory in next generation wireless communication systems. MTMR antenna systems are important since they increase potential data rate or capacity through multiplexing gain and enhance link quality through diversity benefit. We have applied this technology to different systems including indoor communications, cellular mobile radio terminals, satellite systems and High Altitude Platforms (HAPs).
HIGH ALTITUDE PLATFORMS
High Altitude Platforms (HAPs) is an emerging novel technology which is preserving many of the advantages of both satellite and terrestrial systems and recently started to attract considerable attention in Europe through the European Community COST 297 Action, in which Professor Abbas Mohammed is the Swedish representatives and member of the management committee to the Action. HAPs are airships, balloons or planes, operating in the stratosphere, at altitudes of typically 17-22 km. At this altitude (which is well above commercial aircraft height), they can maintain a quasi-stationary position, and support payloads to deliver a range of communication services including emergency communications.
The main goal in this research area is to investigate novel signal processing techniques for mitigating interference sources in order to enhance the performance and precision in radio navigation systems. In particular, Professor Abbas Mohammed has discovered new signal processing techniques for the identification of skywave interference in long range navigation (Loran-C) receivers and demonstrated them in a prototype receiver working in real-time. This work has received the Best Paper Award from the International Loran Association (ILA), USA.
RADIOWAVE PROPAGATION AND CHANNEL MODELLING
The performances of many radio communication and navigation systems are critically dependent on matching the system design to radio frequency propagation characteristics and the propagation environment. Thus, our research aims to contribute to a better understanding of environment effects on radio wave propagation within the individual systems and the coexistence scenarios with other systems in order to offer improvements to existing systems and propose new applications.
2002-2010: Graduate School of Telecommunications (GST)
GST is a collaboration consortium in Reserach and Education between 4 swedish Universities (KTH, BTH, HiG, MU). We had 10 PhD students funded by GST. Prof. Mohammed is the BTH Director of GST and Council Board member of the consortium.
The below European Union (EU) within Information & Telecommunications Technologies (ICT) Research
EU IP Project: Cognitive Radio Networks for Beyond 4G. Submitted in 2012 but ufortunately it was not funded.
EU ICT Project IC0902 (2010-2014): Cognitive Radio and Networking for Cooperative Coexistence of Heterogeneous Wireless Networks
International Project WUN (2008-Present): Worldwide Universities Network on Cognitive Communications
EU ICT Project IC0802 (2009-2013): Propagation Tools and Data for Integrated Telecommunications, Navigation and Earth Observation Systems
EU ICT Project 297 (2005-2009): High Altitude Platform Systems for Communications and Other Services
EU ICT Project 296 (2005-2009): Mitigation of Ionospheric Effects on Radio Sysytems
EU ICT Project 280 (2000-2005): Channel Modelling and Propagation Impairment Mitigation for Millimetre Wave Radio Systems
EU FP4 Advanced Communications Technologies and Services (ACTS)