Browsing by Subject "Digital communication systems"

Now showing 1 - 3 of 3

Open Access
Binary sequences with low aperiodic autocorrelation for synchronization purposes
(IEEE, 2003) Kocabaş, Ş. E.; Atalar, Abdullah
An evolutionary algorithm is used to find three sets of binary sequences of length 49-100 suitable for the synchronization of digital communication systems. Optimization of the sets are done by taking into consideration the type of preamble used in data frames and the phase-lock mechanism of the communication system. The preamble is assumed to be either a pseudonoise (PN) sequence or a sequence of 1's. There may or may not be phase ambiguity in detection. With this categorization, the first set of binary sequences is optimized with respect to aperiodic autocorrelation which corresponds to the random (PN) preamble without phase ambiguity case. The second and third sets are optimized with respect to a modified aperiodic autocorrelation for different figures of merit corresponding to the predetermined preamble (sequence of 1's) with and without phase ambiguity cases.
Open Access
Input sequence estimation and blind channel identification in HF communication
(IEEE, 2000) Khames, Mariam; Miled, B. H.; Arıkan, Orhan
A new algorithm is proposed for reliable communication over HF tropospheric links in the presence of rapid channel variations. In the proposed approach, using fractionally space channel outputs, sequential estimation of channel characteristics and input sequence is performed by utilizing subspace tracking and Kalman filtering. Simulation based comparisons with the existing algorithms show that the proposed approaches significantly improve the performance of the communication system and enable us to utilize HF communication in bad conditions.
Open Access
Simulation of a digital communication system
(IEEE, 2005-09) Güngör, A.; Arıkan, F.; Arıkan, Orhan
In this paper, basic components of a digital communication system are simulated by a computer program. The simulation program is modular and flexible to incorporate any future additions and updates. The simulation program allows the user to choose from various channel models, transmitter and receiver antenna systems, modulation and channel coding techniques. A communication system is defined by various parameters including the source, coding, modulation, antenna systems. In order to facilitate the input of these parameters and follow the flow of the simulation, the Graphical User Interface (GUI) is designed for convenience to the user. The input parameters can both be entered from the GUI or from prepared user files. The major contribution of this simulation system to the existing communication simulators is the addition of flexible antenna systems both at the transmitting and receiving ends. With this simulation program, the antenna arrays can be located anywhere on Earth, on any platform and array elements can be placed on the platform by any desired orientation. The simulation program results are compared with both theoretical computations and commercial simulator results and excellent agreement is observed in both cases.