1,720,972 research outputs found
Performance of nonorthogonal FSK for the Internet of Things
No full textIEEE 802.15.4 is a popular standard for low-rate wireless communications used for the Internet of Things (IoT). This IEEE standard contains a variety of physical layers (such as SUN, TVWS, RCC LMR, and LECIM) that make use of different modulations, such as nonorthogonal frequency-shift keying (FSK) and position-based FSK. This paper proposes simple closed-form expressions to evaluate the bit-error rate (BER) performance of nonorthogonal FSK schemes used for the IoT. Both coherent and noncoherent detection cases are investigated in additive white Gaussian noise (AWGN) and frequency-nonselective fading channels. In case of AWGN channels, the proposed BER expressions are obtained by selecting and modifying two terms of a union bound on the error probability. In case of fading channels, the proposed BER expressions are obtained by integration of the conditional BER over the fading statistics. Simulation results confirm the good accuracy of the proposed analytical BER expressions for different channel models (such as AWGN, Nakagami-m, Rice, lognormal) and for different detection techniques (such as noncoherent, coherent, and coherent with a residual phase error). Experimental results with wireless transmission and reception confirm the accuracy of the proposed approach. In addition, this paper also presents a BER expression for coherent detection of position-based FSK. Simulation results demonstrate that the presented BER expression for position-based FSK is more accurate than the BER expressions proposed in the literature
A Fast Algorithm to Find Generic Odd and Even Order Intermodulation Products
No full textNonlinear devices, such as power amplifiers, typically generate spurious signal components known as intermodulations. This phenomenon is particularly important when multiple signals, allocated at different frequencies, pass through nonlinear devices simultaneously. In this paper we extend a known fast counting algorithm (FCA) of intermodulation components and compare it with other counting algorithms. The results obtained show significant improvement on the processing time. The carrier configuration is modelled by using indicator polynomials. We show that the distribution of high order intermodulation products can be computed in a reduced amount of time, by extending the algorithmic results relevant to third order intermodulations. In addition, we notice that in particular situations even order intermodulations are also important. They occupy the adjacent harmonic zones, generally allocated to other services, so that the achievable performance deteriorates. We extend an algorithm which computes the position of even and odd order intermodulations, and we make it faster and computationally more efficient. These results may improve both the optimisation of the spectrum shape and the analysis of the nonlinear effects. Comparisons with some other direct counting algorithms are made in terms of accuracy and speed
Adaptive error protection coding for wireless transmission of motion JPEG 2000 video
No full textThe delivery of video over wireless, error-prone transmission channels requires careful allocation of channel and source code rates, given the available bandwidth. In this paper, we present a theoretical framework to find an optimal joint channel and source code rate allocation, by considering an intra-coded video compression standard such as Motion JPEG 2000 and an error-prone wireless transmission channel. Lagrangian optimization is used to find the optimal code rate allocation, from a PSNR perspective, starting from commonly available source coding outputs, such as intermediate rate-distortion traces. The algorithm is simple and adaptive both on the available bandwidth and on the transmission channel conditions, and it has a low computational complexity. Simulation results, using Reed-Solomon (R-S) coding, show that the achieved performance, in terms of PSNR and MSSIM, is comparable with that of other methods reported in literature. In addition, a simplified and sub-optimal expression for determining the channel code assignment is also provide
Effects of HPA Non Linearity on Frequency Multiplexed OFDM Signals
No full textThe paper analyzes the performance of the downlink channel of a multimedia interactive service system which transmits the desired information by the frequency multiplexing of several OFDM signals compliant with the DVB-T standard. The effects of the nonlinear distortions introduced by a high power amplifier on the system performance are evaluated both in terms of the bit error rate (BER) degradation in AWGN channels and of the spectral regrowth. The performance comparison to the case of a single DVB-T signal as well as the benefits of an ideal predistortion is also considered by comparing analytical results to computer simulation
JPEG XR / JPEG 2000 Coding Complexity profiling and PSNR analysis on 8 bit and 12 bit imagery
No full textDocument wg1n458
Soft-Output Demapper with Approximated LLR for DVB-T2 Systems
No full textBit-interleaved coded modulation (BICM) is at the heart of the second generation digital terrestrial television systems (DVB-T2), which achieves a large spectral efficiency by means of high-order quadrature amplitude modulation (QAM) and low-density parity-check (LDPC) codes. This paper proposes a simple but effective approximation for the log-likelihood ratio (LLR) of the bits estimated by the soft-output QAM demapper. The proposed approximation, which keeps few dominant terms of the LLR expression, needs low additional complexity with respect to the conventional Max-Log approximation. Simulation results for DVB-T2 in multipath channels show a performance gain with respect to the Max-Log approach, especially for QAM with large modulation order
Design and Validation of a Software Defined Radio Testbed for DVB-T Transmission
No full textThis paper describes the design and validation of a Software Defined Radio (SDR) testbed, which can be used for Digital Television transmission using the Digital Video Broadcasting - Terrestrial (DVB-T) standard. In order to generate a DVB-T-compliant signal with low computational complexity, we design an SDR architecture that uses the C/C++ language and exploits multithreading and vectorized instructions. Then, we transmit the generated DVB-T signal in real time, using a common PC equipped with multicore central processing units (CPUs) and a commercially available SDR modem board. The proposed SDR architecture has been validated using fixed TV sets, and portable receivers. Our results show that the proposed SDR architecture for DVB-T transmission is a low-cost low-complexity solution that, in the worst case, only requires less than 22% of CPU load and less than 170 MB of memory usage, on a 3.0 GHz Core i7 processor. In addition, using the same SDR modem board, we design an off-line software receiver that also performs time synchronization and carrier frequency offset estimation and compensation
Adaptive Error Protection for the Streaming of Motion JPEG 2000 Video over Variable Bit Error Rate Channels
No full textIn this paper we present a technique that can be used for optimizing the streaming of Motion JPEG 2000 video when the communication channel can be abstracted as a binary symmetric channel (BSC), characterized by a certain slowly variable rate of transmission errors. The video is packetized and every packet is protected with a Reed-Solomon forward error correction (FEC) code and then sent on the communication channel. The FEC helps to recover from erased/error-affected source information bytes at the receiver-decoder. The optimized amount of error protection is chosen by using an uncomplicated mathematical expression, given the knowledge of the channel status. In particular, we show the results of simulations that outline the robustness of this technique and its clear advantage over more trivial solutions
TCP/IP Services Over ATM Satellite Link – Integration With DVB-S Services Using the Multiresolution Modulation
No full textWe propose to exploit the energy margin that can exist in satellite links to deliver multimedia traffic using multiresolution modulation techniques over the DVB-S. We propose an asymmetrical architecture, formed by a satellite forward link and a narrowband terrestrial reverse link, based on the N-ISDN. The ATM cell transport technique is adopted to support different QoS for different fluxes. In order to deliver the TCP/IP traffic, the additional delay on message delivery time suggests to modify the slow start and the congestion avoidance of the TCP. Our approach is based on the combination of a fixed window flow control at the transport layer with the ATM congestion control. The analysis shows that the system performance is satisfactory if some bounds on the transmit buffer size are respected and the spacing of the resource management cells is within a given range of values
DSP Based OFDM Demodulator and Equalizer for Professional DVB-T Receivers
No full textThis work treats the design of base-band processing subsystems for professional DVB-T receivers using 1600 MIPS, fixed point DSPs. We show the results about the implementation of OFDM demodulation, channel estimation and equalization functional blocks, for the 2k/8k modes. The adoption of general purpose DSPs provides a great flexibility in the development of different configurations of the receiver. Furthermore, it enables the feasibility of adaptive equalization schemes, where the quality of the channel estimation varies according to both channel characteristics and speed of the channel variations. The 16/32 bit fixed point architecture leads to a very low implementation loss, and a carefull optimization of the pipeline architecture of the processor allows the receiver to obtain short processing delays. The flexibility of the software approach along with the obtained performance make the proposed implementation very interesting in professional and high-end receivers for interactive, multimedia applications of DVB-T
- …
