Fig 5 - uploaded by Volker Jungnickel
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QPSK (blue), 16QAM (red) and 64QAM (green) modulated symbols as received by average SIR of 24.5 dB for 40 Volt input signal. Non frequency-flat interference, hardware frequency selectivity and imperfect SIR estimation effects are visible on constellation diagram.
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In this paper we discuss theory, system design and implementation of an acoustical communication system. We aim to transmit data from the bottom of a borehole to the surface with data rates of at least 200 bps. As a technical solution we use acoustic waveguide communication with adaptive OFDM over a baseband frequency spectrum from 0 to 9 kHz. We c...
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... 8 resource blocks (98 sub-carriers) in the low frequencies are not used for transmitting data due to the strong non-linearity and attenuation of the actuator. Figure 5 shows the received data constellations after MMSE equalization within one sub-frame. For simulation we used the average SIR of 24.5 dB, which is assumed to be equal to the interference power, and is thus added before applying the actu- ators frequency response. ...
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Citations
... Meanwhile, stress wave communication is more suitable for underbalanced drilling (UBD) than in mud pulse telemetry or in electromagnetic telemetry [43]. The successful implementation of orthogonal frequency multiplexing (OFDM) based acoustic borehole communication demonstrated the feasibility of stress wave communication through pipeline structures [47,48]. Additionally, other than stress wave-based damage detection and structural health monitoring (SHM) on pipelines [49][50][51], Jin et al. applied stress waves as carriers to transmit information along a steel pipe. ...
Stress wave-based communication has great potential for succeeding in subsea environments where many conventional methods would otherwise face excessive difficulty, and it can benefit logging well by using the drill string as a conduit for stress wave propagation. To achieve stress wave communication, a new stress wave-based pulse position modulation (PPM) communication system is designed and implemented to transmit data through pipeline structures with the help of piezoceramic transducers. This system consists of both hardware and software components. The hardware is composed of a piezoceramic transducer that can generate powerful stress waves travelling along a pipeline, upon touching, and a PPM signal generator that drives the piezoceramic transducer. Once the transducer is in contact with a pipeline surface, the generator integrated with an amplifier is utilized to excite the piezoceramic transducer with a voltage signal that is modulated to encode the information. The resulting vibrations of the transducer generates stress waves that propagate throughout the pipeline. Meanwhile, piezoceramic sensors mounted on the pipeline convert the stress waves to electric signals and the signal can be demodulated. In order to enable the encoding and decoding of information in the stress wave, a PPM-based communication protocol was integrated into the software system. A verification experiment demonstrates the functionality of the developed system for stress wave communication using piezoceramic transducers and the result shows that the data transmission speed of this new communication system can reach 67 bits per second (bps).
... It is noted that unlike UWA channel that is time-variant, the drillstring channel has a relatively slow varying nature and the Doppler effect generally is not considered, but drillstring rotation will negatively produce stronger impact noises and multiple reverberations in passbands [22]. As a result, considering the drillstring channel response pattern, multicarrier modulation technologies have been introduced in the drillstring channel [17,24,25] in combination with the Fig. 1. Schematic view of the channel model. ...
... It is noted that unlike UWA channel that is time-variant, the drillstring channel has a relatively slow varying nature and the Doppler effect generally is not considered, but drillstring rotation will negatively produce stronger impact noises and multiple reverberations in passbands [22]. As a result, considering the drillstring channel response pattern, multicarrier modulation technologies have been introduced in the drillstring channel [17,24,25] in combination with the advantages of overcoming the long delay spread and reducing the intersymbol interference existing in the UWA channel [23]. For example, Mahsa designed an acoustic OFDM transmission scheme with a joint source-channel coding and binary phase shift keying (BPSK) modulation approach to minimize the end-to-end acoustic distortion along drillstring. ...
... However, the achieved transmitted rate and bit error ratio (BER) are not involved in the paper. Then Krueger et al. developed an acoustic waveguide communication system with adaptive OFDM following the 3rd Generation Partnership Project Long Term Evolution specifications over a baseband frequency spectrum form 0 to 9 kHz [24]. The data rates up to 20 kbit/s were achieved in the laboratory by using a 55-m long drillstring made of eight pipes of 6.1-m length and 5-in. ...
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Base station cooperation is recognized as a key technology for future wireless cellular communication networks. Considering antennas of distributed base stations and those of multiple terminals within those cells as a distributed multiple-input multiple-output (MIMO) system, this technique has the potential to eliminate inter-cell interference by joint signal processing and to enhance spectral efficiency in this way. Although the theoretical gains are meanwhile well-understood, it still remains challenging to realize the full potential of such cooperative schemes in real-world systems.
Among other factors, such as the limited overhead for pilot symbols and for the feedback and backhaul, these performance limitations are related to channel and synchronization impairments, such as channel estimation, feedback quantization and channel aging, as well as imperfect carrier and sampling synchronization among the base stations. Because of these impairments, joint data precoding results to be mismatched with respect to the actual radio channel and the gains of base station cooperation are limited.
In order to analyze the signal distortion and the interference among the multiple users, which are caused by mismatched data precoding, it is required to model and investigate impairment effects isolatedly. Therefore, a signal model is provided for base-coordinated orthogonal frequency division multiplexing (OFDM) transmission with channel and synchronization impairments, and closed-form expressions are derived for the mobile users’ signal-to-interference ratio (SIR). Analytical results are numerically verified and lead to practical system requirements. Based on channel modeling and outdoor measurements, inter-site distance limitations for interference-free and time-synchronous transmission are also investigated.
It is further discussed how to synchronize distributed base stations by using commercial oscillators locked to externally provided references, e.g. signals provided by Global Positioning System (GPS). Mitigation techniques including adaptive feedback compression and channel prediction are developed. Adaptive feedback compression keeps the channel mean square error (MSE) below a threshold and achieves more than order of magnitude overhead reduction. Doppler-delay base channel prediction reduces the delay-based MSE by 10 dB, approximately.
For evaluating purposes, the spatial channel model extended (SCME) as well as channel data from outdoor measurements are used. Multi-cellular simulations reveal that the users’ SIR can be enhanced by 10 dB on average. Practically this means that larger feedback delays, higher mobilities and a larger number of users can be supported in coordinated multi-point (CoMP), compared to than previously believed.
Stress waves are increasingly employed in structural health monitoring (SHM) systems of pipelines based on sensor networks. Data transmission among sensors is crucial for the overall stress waves based SHM system. Since conventional communications are hampered by limited transmission ranges when in some environments, such as in soil and water, it is essential to develop an alternative approach to deal with the issues. This paper proposes a stress wave communication networking method that can be implemented among multiple sensors. The proposed work introduces Orthogonal Variable Spreading Factor (OVSF) codes to achieve multiple-access stress wave channels by using piezoelectric transducers. In this paper, both frequency-domain and time-domain channel responses are estimated, and communication schemes are thereby designed to achieve data transmission among multiple sensors based on the features of multiple channels. The experiments are conducted on a T-shape pipeline structure in the laboratory environment, and the results verify the feasibility of the method. Experimental results show that the data rate of each single channel reaches 250 bps.
