Dmitry S. Osipov

Multiple access system for a vector disjunctive channel

We address the problem of constructing a multiple access system for a disjunctive vector channel, similar to a multiuser channel without intensity information as described in [1]. To solve the problem, a signal-code construction based on nonbinary codes is proposed. For the resulting multiple access system, a lower bound on the relative group rate is derived. The bound coincides asymptotically with an upper bound.

On the optimum choice of a threshold in a frequency hopping OFDMA system

We consider a frequency hopping orthogonal frequency-division multiple access (FH OFDMA) system different from those previously described. To find the probability density function of the variable used by the detector, we propose an approach based on the characteristic function method and Bessel function technique. Based on this approach, we obtain an expression for the desired density function (in the most probable case of a collision of multiplicity two) and an expression for the optimum threshold value, which enables us to compute it to any desired degree of accuracy. Efficiency of our approach is justified by simulation results.

Inner Convolutional Codes and Ordered Statistics Decoding in a Multiple Access System Enabling Wireless Coexistence

The problem of wireless coexistence will become crucial in years to come. Future generation communication systems will have to endure interference induced by communication systems operating within the same frequency bands. Coded DHA FH OFDMA using ordered statistics is well suited for the task. This paper addresses the problem of transmission rate increase in a coded DHA FH OFDMA system. It will be demonstrated that using q-ary convolutional codes constructed from punctured Reed-Solomon codes as inner codes in a coded DHA FH OFDMA provides rates sufficiently higher than those ensured by block inner codes ensuring at the same time reasonable decoding complexity, relatively small codeword length and low probability of error.

Reduced-Complexity Robust Detector in a DHA FH OFDMA System under Mixed Interference

Future generation communication systems will have to endure interference induced by communication systems operating within the same frequency bands. Recently several coded DHA FH OFDMA systems employing rank-based detectors able to solve this problem were proposed. Unfortunately such detectors have relatively high complexity. In what follows a reduced-complexity detector using only column sorting for a coded DHA FH OFDMA employing a nonbinary convolutional inner code is proposed. The proposed detector is compared with the rank convolutional detector in terms of performance, complexity and delay.

On the capacity of a PPM UWB multiple-access system with a single user noncoherent reception

We consider an uncoordinated multiple-access system that employs a modulation technique, in which the probability of suppressing the signal sent by a certain user can be considered negligible, to transmit information via a wireless channel (e.g. time hopping (TH) with pulse position modulation (PPM)).This channel can be considered as an A channel (channel without intensity information) [1]. For this channel a new method of transmission is proposed. The expression for the capacity of a multiple access system employing the proposed transmission method (for the single user reception case) is obtained. Both non-asymptotic and asymptotic formulas are derived and asymptotic behavior of the capacity (for the single user reception case) is studied.

On the user capacity for a multiple-access system in a vector disjunctive channel with errors

We consider a multiple-access system in which each user is given q out of Q available subchannels (q ≪ Q). We investigate capacities of two channels emerging in the system under consideration in the case of single-user reception. These channels can be considered as modifications of the A-channel. In the first case we assume that a signal transmitted by a certain user is always registered by the receiver. Thus, activity of other users is the only obstacle to correct reception of information transmitted by a certain user in the multiple-access system. In the second case we assume that the output of each subchannel is inverted with probability p. Analytical expressions (both asymptotic and nonasymptotic) are derived and investigated.

On jamming-proof signal-code constructions for a multiple access system

In what follows signal-code constructions employing block and convolutional nonbinary inner codes that can perform under severe jamming are proposed. Robustness of the proposed signal-code constructions to jamming is verified by means of simulation.

On the Performance of a FH-MC-CDMA System

In what follows a novel quasisynchronous FH-MC- CDMA system with threshold reception is introduced. An ex- pression for the optimum (in maximum a posteriori sense ) threshold value is obtained. Error and erasure probability values for the system under consideration are estimated.

Asynchronous OFDMA system with woven turbo coded modulation.

In this paper a novel OFDMA system with combined ASK/FSK modulation and outer woven turbo code is introduced. The performance of such a system represented in the form of error probability has been investigated.

Sequential Decoding on Syndrome Trellises for Nonparametric Detection

Abstract The following paper adapts the classical Zigangirov-Jelinek algorithm to the decoding of nonbinary block codes under severe mixed jamming. To ensure reliable communications in this scenario we combine reception techniques based on distribution free statistical tests with sequential decoding on syndrome trellises. It will be shown that the proposed approach can ensure relatively high transmission rate with reasonable complexity.