Date: 15:00, Friday 15 February 2008
Venue: EMG.20
Name: Dr Kit K Wong, University College London - Adastral Park Campus.
Future-generation wireless system aims to provide ubiquitous seamless connections between mobile terminals such as personal digital assistant (PDA), and computer servers so that users can enjoy high-quality high-speed multimedia services at anytime anywhere without wires. Fundamental physical challenges such as channel fading, however, have put strains on the radio resources that make reliable wireless communications difficult to achieve. In response to this, multiple-input multiple-output (MIMO) antenna systems have emerged as a promising means to provide diversity without bandwidth expansion and increase in transmit power.
Previous approaches tended to design wireless systems with maximal capacity by, for instance, an opportunistic transmission that adapts its rate according to the channel strength. Such designs are, nevertheless, of little relevance for providing real-time delay-sensitive traffic because it would be infeasible to postpone the transmission until the channel improves since the data may expire.
In this talk, it is proposed to model a delay-limited communication channel by a sequence of block transmissions and the delay constraint is novelly characterized by the probability that a target rate is not achieved for a given number of blocks. Under this setting, the cost of transmission in terms of power is minimized for attaining a given probabilistic delay constraint by exploiting the statistical channel state information (CSI) at the transmitter. Assuming a time-division downlink channel, our aim is to minimize the overall transmit power for achieving the users' outage constraint by jointly optimizing the power allocation and the time-sharing (i.e., the number of time slots) of the users.