A Low-Complexity High-Performance Preprocessing Algorithm for Multiuser Detection using Gold Sequences

• The optimum multiuser detection problem can be formulated as a maximum likelihood problem, which yields a binary quadratic programming problem to be solved. Generally this problem is NP-hard and is therefore hard to solve in real time. In this paper, a preprocessing algorithm is presented which makes it possible to detect some or all users optimally for a low computational cost if signature sequences with low cross correlation, e.g., Gold sequences, are used. The algorithm can be interpreted as, e.g., an adaptive tradeoff between parallel interference cancellation and successive interference cancellation. Simulations show that the preprocessing algorithm is able to optimally compute more than 94,% of the bits in the problem when the users are time-synchronous, even though the system is heavily loaded and affected by noise. Any remaining bits, not computed by the preprocessing algorithm, can either be computed by a suboptimal detector or an optimal detector. Simulations of the time-synchronous case show that if a suboptimal detector is chosen, the bit error rate (BER) rate is significantly reduced compared with using the suboptimal detector alone.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Reglerteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Control Engineering (hsv//eng)

Nyckelord

Code division multiple access

Computational complexity

Error statistics

Interference suppression

Maximum likelihood detection

Multiuser detection

Quadratic programming

Sequences

CDMA channel models

Gold sequences

NP-hard problem

Binary quadratic programming problem

Bit error rate

Low cross correlation

Low-complexity high-performance preprocessing algorithm

Maximum likelihood problem

Optimal detector

Optimum multiuser detection problem

Parallel interference cancellation

Suboptimal detector

Successive interference cancellation

Time-synchronous users

TECHNOLOGY

TEKNIKVETENSKAP

Automatic control

Reglerteknik

Publikations- och innehållstyp

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