ABSTRACT: This paper considers a multi-user MIMO broadcast wireless channel where a MAC layer scheduler is used to improve system efficiency and provide quality of service improvements (fairness) to users. In particular, an alpha-rule scheduler is considered that uses rate estimates from users to make user selection decisions. The main challenge faced by the scheduler is that users need to estimate the interference caused by other users before transmit antenna allocation has been done. The paper examines two techniques for estimating data rates. The first technique assumes no interfering signals are present and the second technique includes the dominant interfering signal. We show that the scheduler can be tuned to significantly increase fairness with little reduction in mean sum rate to users and we show that both mean sum rate and fairness can be increased by including the dominant interfering signal to estimate data rates.
Communications Theory Workshop, 2009. AusCTW 2009. Australian; 03/2009
ABSTRACT: This paper considers a signalling scheme for a multi-user wireless broadcast system where the base station has multiple transmit antennas and users can have multiple receive antennas. Independent data streams are transmitted in this system by allocating different transmit antennas to different selected users where multiple transmit antennas may be allocated to each selected user. The signalling scheme is used to select the particular users to receive data in a transmission block and to allocate transmit antennas to those users. We examine two partial feedback schemes for selecting users: one that we call norm-based and the other that we call SINR-based. We also present a novel transmit-antenna selection scheme for allocating multiple transmit antennas to selected users based on the Gram-Schmidt orthogonalisation algorithm. The signalling scheme presented in this paper reduces the amount of channel information required by the base station. We study the performance of the user selection and transmit-antenna selection schemes when linear receivers are used at the receiver side for decoding the transmitted signal. In particular, we consider zero-forcing (ZF) and minimum mean square-error (MMSE) receivers. We examine the sum capacity performance of the system compared to schemes with no feedback and using random antenna selection. We show that the best performance is achieved with norm-based user selection, Gram-Schmidt antenna selection and MMSE receivers.
Telecommunication Networks and Applications Conference, 2008. ATNAC 2008. Australasian; 01/2009
ABSTRACT: This paper considers wireless broadcast systems with multi-antenna base stations. Preceding at the transmitter reduces interference between users allowing independent data streams to be sent to multiple users simultaneously. With typically more users than transmit antennas, efficient selection of user subsets is important. The paper compares the effectiveness of several user selection algorithms and identifies situations where they are suboptimal. The impact of zero-forcing (ZF) and dirty paper coding (DPC) precoding are considered. A modification to two current algorithms is proposed that reduces computational time while retaining effectiveness. Simulation is used to assess the modifications and suggest methods of setting parameters. The paper examines the variability of allocated data rates and shows how it affects the performance of weighted alpha rule schedulers, which trade-off efficiency with fairness. It is shown that reducing the variability of allocated rates can have a significant reduction on mean scheduler queue sizes.
Wireless Broadband and Ultra Wideband Communications, 2007. AusWireless 2007. The 2nd International Conference on; 09/2007
ABSTRACT: The design of Abstract Syntax Notation One (ASN.1) coders and
compilers using recursive descent techniques from its theoretical basis
in compiler theory to software engineering considerations is examined.
LL(1) compiler theory is used to develop parser tables and state
transition diagrams for recursive descent decoders. A generic decoder is
developed which includes specific ANS.1 specification information in
tables generated using YACC and LEX. The decoder requires small amounts
of code and can be used for general ASN.1 syntax specifications without
modification, making it suitable for rapid prototyping applications. The
storage of data is achieved by means of lists rather than conventional
TENCON '92. ''Technology Enabling Tomorrow : Computers, Communications and Automation towards the 21st Century.' 1992 IEEE Region 10 International Conference.; 12/1992