Harvesting Time Frequency Space Diversity With Coded Modulation For Underwater Acoustic Communications
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| Author | : Konstantinos Pelekanakis |
| Publisher | : |
| Total Pages | : 360 |
| Release | : 2009 |
| Genre | : |
| ISBN | : |
(Cont.) Both systems are combined with specific space-time block codes (STBC) when two or three transmit antennas are used. Moreover, pilot-symbol-aided channel estimation is performed by using a robust 2-D Wiener filter, which copes with channel model mismatch by employing appropriate time and frequency correlation functions. The following result was obtained by testing the aforementioned systems using both simulated and experimental data from RACE '08: the BICM scheme performs better when the UWA channel exhibits limited spatial diversity. This result implies that coded modulation schemes emphasizing higher Hamming distances are preferred when there is no option for many receive/transmit hydrophones. The TCM scheme, on the other hand, becomes a better choice when the UWA channel demonstrates a high spatial diversity order. This result implies that coded modulation schemes emphasizing higher free Euclidean distances are preferred when multiple receive/transmit hydrophones are deployed.
| Author | : Homa Eghbali |
| Publisher | : |
| Total Pages | : 151 |
| Release | : 2013 |
| Genre | : |
| ISBN | : |
Since the early 1880's, wireless broadband communications have been growing at explosive rates. While the personal communication systems have almost exhausted the spectrum, higher and higher data rates are required to support the ever demanding wireless services. Recently, to improve the spectral efficiency, diversity gains, and interference and power management for wireless multimedia and internet services, by combining the signals at both ends and effectively creating multiple parallel spatial data pipes, the multiple-input multiple-output (MIMO) technology has become a convenient framework. Motivated by these practical concerns, this thesis addresses the analysis and design of diversity techniques for terrestrial and underwater acoustic communication channels, in two parts. Part I studies novel relay selection strategies and diversity techniques for single carrier frequency domain equalization (SC-FDE) multi-relay cooperative networks, considering maximum-likelihood (ML) and minimum mean-square error (MMSE) receivers. We further extend our analysis to two-way relaying (TWR) networks, while incorporating different power control techniques. Building on our results on the diversity and error performance of the single relay and TWR cooperative systems, we extend our analysis to design of MMSE-based optimum beamforming matrices at user and relay terminals in a multi-user, multi-antenna TWR cooperative system. We further present a joint user-relay antenna selection algorithm by applying the estimation of distribution algorithm (EDA). The final contribution of the first part of this thesis is to extend our analysis to large relay networks and address the prohibitive computational and implementation complexity cost of the exhaustive search algorithms for joint transceiver/relay beamforming matrix design in large amplify-and-forward (AF) MIMO TWR networks, while incorporating the orthogonal matching pursuit (OMP) algorithm. The second part of this thesis focuses on the performance of differentially encoded space-time and space-frequency block coding techniques for terrestrial and underwater communication channels.
| Author | : Violeta Skoro Kaskarovska |
| Publisher | : |
| Total Pages | : 136 |
| Release | : 2015 |
| Genre | : Adaptive signal processing |
| ISBN | : |
High data rate acoustic communications become feasible with the use of communication systems that operate at high frequency. The high frequency acoustic transmission in shallow water endures severe distortion as a result of the extensive intersymbol interference and Doppler shift, caused by the time variable multipath nature of the channel. In this research a Single Input Multiple Output (SIMO) acoustic communication system is developed to improve the reliability of the high data rate communications at short range in the shallow water acoustic channel. The proposed SIMO communication system operates at very high frequency and combines spatial diversity and decision feedback equalizer in a multilevel adaptive configuration. The first configuration performs selective combining on the equalized signals from multiple receivers and generates quality feedback parameter for the next level of combining. The second configuration implements a form of turbo equalization to evaluate the individual receivers using the feedback parameters as decision symbols. The improved signals from individual receivers are used in the next iteration of selective combining. Multiple iterations are used to achieve optimal estimate of the received signal. The multilevel adaptive configuration is evaluated on experimental and simulated data using SIMO system with three, four and five receivers. The simulation channel model developed for this research is based on experimental channel and Rician fading channel model. The performance of the channel is evaluated in terms of Bit Error Rate (BER) and Signal-to-Noise-and-Interference Ratio (SNIR). Using experimental data with non-zero BER, multilevel adaptive spatial diversity can achieve BER of 0 % and SNIR gain of 3 dB. The simulation results show that the average BER and SNIR after multilevel combining improve dramatically compared to the single receiver, even in case of extremely high BER of individual received signals. The results demonstrate the ability of the proposed multilevel adaptive combining approach to significantly improve the performance of the shallow water acoustic channel, while preserving the same transmission power and channel bandwidth.
| Author | : Eduard Valera Zorita |
| Publisher | : |
| Total Pages | : 2 |
| Release | : 2012 |
| Genre | : Frequency multipliers |
| ISBN | : |
This work proposes an adaptive receiver for the space-frequency block coding scheme, in which Alamouti coding is applied over the carriers of an OFDM system with the aim of obtaining transmit diversity in an underwater acoustic channel. The receiver relies on the assumption that the channel transfer function does not change much over two consecutive carriers, and that the channel is slowly time-varying. Building on these assumptions we propose an adaptive channel estimation method based on Doppler prediction and time-smoothing, which effectively reduces the pilot overhead. System performance is demonstrated using real data transmitted over a shallow water channel in the 10-15 kHz acoustic band from a vehicle moving at 0.5-2 m/s, using QPSK and a varying number of carriers ranging from 64 to 1024. Results demonstrate a uniform gain over the single-transmitter case.
| Author | : Subhadeep Pranab Roy |
| Publisher | : |
| Total Pages | : 410 |
| Release | : 2006 |
| Genre | : Equalizers (Electronics) |
| ISBN | : |
| Author | : Aeman Saad Mohammed |
| Publisher | : Sudwestdeutscher Verlag Fur Hochschulschriften AG |
| Total Pages | : 84 |
| Release | : 2010-01 |
| Genre | : |
| ISBN | : 9783838112534 |
The coding for the wireless channel is the main topic of this Book. Mainly, single user transmission over one or more antennas is considered in the first part, where a novel multidimensional labeling with a designed interleaver which outperforms the two dimensional Bit Interleaved Coded Modulation with Iterative Decoding (BICM-ID) in the whole SNR region is presented. Modulation doping is used to compensate for the loss at the low SNR regions. The design is extended to the two transmit antennas case and a multidimensional constellation labeling for Bit Interleaved Space Time Coded Modulation with Iterative Decoding (BI-STCM-ID) is proposed . The transmission over two uncorrelated frequency bands and the construction of a simple 2 x 2 x 2 full-rate full-diversity space time frequency code based on constellation rotation is presented. In the second part the multi-user scenario from information theoretic point of view is briefly presented."
| Author | : |
| Publisher | : |
| Total Pages | : 21 |
| Release | : 2004 |
| Genre | : |
| ISBN | : |
Multiple-input multiple-output (MIMO) communication channels are an active area of research for terrestrial wireless applications. The natural bandwidth limitations of the underwater acoustic channel (UAC) combined with the potential for a rich spatial propagation structure suggest the ocean may be another useful application area for MIMO techniques. An underwater acoustic communications experiment was conducted in the waters surrounding Elba, Italy, using spatially modulated signals. Two frequency regimes (9.5-14.5 kHz and 25-35 kHz) were explored over ranges up to 5 km using vertical line arrays suspended from drifting ships. The UAC had an average depth of 100 m. One-way communication links were established at two sites with one site having a rocky (reverberant) bottom and the other having a muddy (absorbent) bottom. The waveform comprised a single data stream with concatenated codes providing error control. The inner code was a high rate BCH code Trellis-coded modulation was used as the basis for the outer code. Successive coded symbols were multiplexed across the available transducer elements. This coding approach effectively maintains the inherent bandwidth efficiency of MIMO signaling. The receiver was an adaptive recursively updated multichannel decision feedback equalizer operating in conjunction with a digital phase-locked loop A packet-based, transport architecture was used and included a training sequence. A Viterbi algorithm was integrated with the equalizer that supported simultaneous tap-weight update and trellis transversal, thereby affording the decision-directed update partial error control. Using appropriate assumptions, channel capacity using a single transducer was estimated to be 5.4 bits/channel use at the soft bottom site. Capacity was maximized at 15.9 bits/channel use using four transducers. More detailed results will be presented along with performance predictions based on both propagation models and measured channel transfer functions7.
| Author | : Yang Xiao |
| Publisher | : CRC Press |
| Total Pages | : 352 |
| Release | : 2010-05-19 |
| Genre | : Computers |
| ISBN | : 1420067125 |
A detailed review of underwater channel characteristics, Underwater Acoustic Sensor Networks investigates the fundamental aspects of underwater communication. Prominent researchers from around the world consider contemporary challenges in the development of underwater acoustic sensor networks (UW-ASNs) and introduce a cross-layer approach for effec
| Author | : Arogyaswami Paulraj |
| Publisher | : Cambridge University Press |
| Total Pages | : 314 |
| Release | : 2003-05-29 |
| Genre | : Computers |
| ISBN | : 9780521826150 |
An accessible introduction to the theory of space-time wireless communications.
| Author | : |
| Publisher | : |
| Total Pages | : 1460 |
| Release | : 1991 |
| Genre | : Aeronautics |
| ISBN | : |
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
