Ferenc Balázs

Non-coherent multi-user detection based on quantum search

3G and 4G mobile systems are based on CDMA technology. In order to increase the efficiency of CDMA receivers a large amount of effort is invested to develop suitable multi-user detector techniques. However, at this moment there are only suboptimal solutions available because of the rather high complexity of optimal detectors. One of the possible receiver technologies can be the quantum assisted computing devices which allows high level parallelism in computation. The first commercial devices are estimated by 2004, which meets the advent of 3G and 4G systems. We introduce a novel quantum computation based quantum multi-user detection (QMUD), employing Grovers (see Bell Labs, April 1999)search algorithm, which provides optimal solution. The proposed algorithm is robust to any kind of noise/suboptimal solutions.

The Generalized Quantum Database Search Algorithm

In this paper, we analyze and enhance previously achieved results related to the generalized Grover search algorithm in terms of arbitrary initial pure state, arbitrary unitary transformation, arbitrary phase rotations, and arbitrary number of marked items. This allows us to construct an unsorted database search algorithm which can be included inside a quantum computing system. Because of its constructive nature this algorithm is capable of handling any kind of amplitude distribution at its input, provides absolute success in case of measurement and allows its output to be connected to another algorithm.

A tight bound for probability of error for quantum counting based multiuser detection

This paper describes a novel quantum computation based multiuser detection (QMUD) scheme in static and also in dynamical changing environments. The well known Grover database search based quantum counting algorithm is implemented in our proposed detector. Furthermore the exact error probability calculation referring to the static one and an upper bound for the dynamic model was shown.

Maximum Likelihood Based Quantum Set Separation

In this paper we introduce a method, which is used for set separation based on quantum computation. In case of no a-priori knowledge about the source signal distribution, it is a challenging task to find an optimal decision rule which could be implemented in the separating algorithm. We lean on the Maximum Likelihood approach and build a bridge between this method and quantum counting. The proposed method is also able to distinguish between disjunct sets and intersection sets.

QUANTUM COMPUTATION BASED PROBABILITY DENSITY FUNCTION ESTIMATION

Signal processing techniques will lean on blind methods in the near future, where no redundant, resource allocating information will be transmitted through the channel. To achieve a proper decision, however, it is essential to know at least the probability density function (PDF), which to estimate is classically a time consumpting and/or less accurate hard task that may make decisions to fail. This paper describes the design of a quantum assisted PDF estimation method also by way of an example, which promises to achieve the exact PDF by proper setting of parameters in a very rapid way.

The SONG (SOlutions for Next Generation Mobile Systems) Project

The SONG project was formed in 2001, when research team of Mobile Communications and Computing Laboratory (MCL) at Budapest University of Technology and Economics (BUTE) joined the Inter-University Centre for Telecommunications and Informatics (ETIK). ETIK consists of academic research teams form BUTE and Eotvos Lorand University of Sciences (ELTE) and industrial partners among the leaders of information technology in Hungary. Industrial members are: Ericsson Communications Systems Hungary Ltd., KFKI Computer Systems Sc., Hungarian Telecommunications Sc., Sun Microsystems Hungary Ltd., Westel Mobile Telecommunications Sc., Compaq Computer Hungary Ltd., Antenna Hungaria Sc., Computer Science and Automation Research Institute of the Hungarian Academy of Sciences.