Publications

Haya H Al Muhannadi
/ Categories: Publications

Joint rate, power, and decoding order optimization of multiuser MIMO systems

Author(s): Mesbah, W (Mesbah, Wessam); Alnuweiri, H (Alnuweiri, Hussein)

We consider multiuser MIMO systems with some of the users having target-rate requirements while the other users are working on best-effort data transmission. Both multiple-access channels (MAC) and broadcast channels (BC) are considered. We show that the best-effort users can achieve higher rates when the data streams of any user are not restricted to be decoded consecutively and when time-sharing between different decoding orders is allowed. For MIMO-MAC, we show that the problem can be formulated as a convex optimization problem, and hence efficient algorithms can be used to obtain the globally optimal solution. We also show that in some cases it is possible to reduce the transmission power of some users without affecting the optimal solution, and we show that the power minimization problem is convex. We also exploit the MAC-BC duality in order to solve the same problem for the MIMO-BC channel.


Source: IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 10(6): 1681-1686 JUN 2011

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DeSIGN: Guided Practice for Sign Language

DeSIGN: Guided Practice for Sign Language

Children learn and practice their vocabulary through interaction with parents and friends as well as through formal instruction at school. However, for deaf children, sign language is the main method of communication. Despite the importance of strong vocabulary skills for understanding text, effective verbal communication and integration into society, the average deaf student graduates from American high schools with a fourth grade reading level. This can be partially attributed to the fact that 90% of deaf children are born to hearing parents who are rarely fluent in sign language.

Calcium channels determine how life begins, and ends
Calcium channels determine how life begins, and ends

Calcium channels determine how life begins, and ends

Ongoing work at Weill Cornell Medical College in Qatar (WCMC-Q) is investigating how intracellular calcium (Ca2+) signaling pathways are involved in the very beginning of life as they prepare the egg for fertilization and the initiation of embryogenesis. The National Priorities Research Program-funded work also has wider implications. Since all cells use Ca2+ signals, these studies could impact the treatment of various pathological conditions including infertility, hypertension, and cancer.
Cells in the human body need to be able to sense their environment in order to respond to cues to perform some function. Intercellular signaling, using hormones sent from one part of the body to another, allow, for example, the brain to tell your hand to pick up a pen as neurons in the brain fire action potentials to trigger the relevant muscle actions. For other cells, the message may be to divide or to die if infected by a virus.

Taking gas-to-liquid technology to the next level
Taking gas-to-liquid technology to the next level

Taking gas-to-liquid technology to the next level

In the 1920s, two German scientists—Franz Fischer and Hans Tropsch—developed revolutionary chemical reactions that could transform gas into liquid. These reactions proved particularly valuable to natural gas-based fuel processing. Since the Fischer-Tropsch days, engineers around the world have been working on ways to tweak these gas-to-liquid (GTL) reactions to produce more products, more efficiently and with less environmental impact. An international research team headquartered at Texas A&M University at Qatar (TAMUQ) is making remarkable progress along these lines.

Researchers discover a remarkably easy way to make filters at the nano scale
Researchers discover a remarkably easy way to make filters at the nano scale

Researchers discover a remarkably easy way to make filters at the nano scale

From your average spaghetti strainer to the screen on your windows, filters are a part of our every-day life. In their simplest form, they keep debris out of air and water. Yet as filter technology advances, so does the level of precision around what we can keep out.
Today, it’s possible to create membranes that filter a range of substances on a nano (microscopic) scale, and a QNRF, NPRP grant-funded project has made significant progress in doing just that. A member of the team and advanced research fellow in experimental physics in the Biological and Soft Sciences Department at the University of Cambridge, Dr. Easan Sivaniah, explained:

Researchers build the case for wind and wave studies in Qatar
Researchers build the case for wind and wave studies in Qatar

Researchers build the case for wind and wave studies in Qatar

For the first time, fine detail about the wind and wave conditions around the coast of Qatar has been recorded. By arranging the most sophisticated equipment available on the edge of a 500-meter pier extending into the Gulf, a research team at Texas A&M University at Qatar (TAMUQ) has collected detailed readings of air and wave currents around the peninsula. Their findings highlight a dearth of information on coastal conditions that have the potential to offer vital insights into many sectors.
“The actual research started in trying to understand the relationship between the wind and waves,” said Dr. Reza Sadr, Assistant Professor in the Mechanical Engineering Department at TAMUQ. “Why do we need this? Because there are very poor models to track wind current and predict ocean waves, and this information affects, among other things, marine life, the offshore oil and gas industry and renewable energy initiatives.”
Around the world, the methods for measuring the patterns of wind and waves, also known as the atmospheric surface layer (ASL), are so far based on weather and wind models combined with analysis of the ocean dynamics. Dr. Sadr said that these models, however, need to be fortified with more sophisticated data and analysis for each region in the globe.

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