Subjective video quality and video decoding complexity are jointly optimized in order to determine the video encoding parameters that will result in the best Quality of Experience (QoE) for an end user watching a vide...
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Subjective video quality and video decoding complexity are jointly optimized in order to determine the video encoding parameters that will result in the best Quality of Experience (QoE) for an end user watching a video clip on a mobile device. Subjective video quality is estimated by an objective criteria, video quality metric (VQM), and a method for predicting the video quality of a test sequence from the available training sequences with similar content characteristics is presented. Standardized spatial index and temporal index metrics are utilized in order to measure content similarity. A statistical approach for modeling decoding complexity on a hardware platform using content features extracted from video clips is presented. The overall decoding complexity is modeled as the sum of component complexities that are associated with the computation intensive code blocks present in state-of-the-art hybrid video decoders. The content features and decoding complexities are modeled as random parameters and their joint probability density function is predicted as Gaussian Mixture Models (GMM). These GMMs are obtained off-line using a large training set comprised of video clips. Subsequently, decoding complexity of a new video clip is estimated by using the available GMM and the content features extracted in real time. A novel method to determine the video decoding capacity of mobile terminals by using a set of subjective decodability experiments that are performed once for each device is also proposed. Finally, the estimated video quality of a content and the decoding capacity of a device are combined in a utility-complexity framework that optimizes complexity-quality trade- offto determine video coding parameters that result in highest video quality without exceeding the hardware capabilities of a client device. The simulation results indicate that this approach is capable of predicting the user viewing satisfaction on a mobile device.
Multi-Input Multi-Output (MIMO) has become a popular technique to increase spectral efficient. Meanwhile, the design of cost-effective receiver for LTE-A system remains a challenging task. The sphere detection algorit...
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ISBN:
(纸本)9781612846835
Multi-Input Multi-Output (MIMO) has become a popular technique to increase spectral efficient. Meanwhile, the design of cost-effective receiver for LTE-A system remains a challenging task. The sphere detection algorithm performs exact Maximum Likelihood (ML) detection algorithm, however, its decoding complexity is greatly impacted by the initial radius of decoding. A new type of sphere decoding algorithm based on threshold is proposed in this paper. This new algorithm, considering the influence of signal-to-noise ratio and channel condition number on detection algorithm, has lower sphere decoding complexity and ensures performance of sphere decoding. This algorithm has been applied to the LTE-TDD wireless integrated test instrument and has shown perfect performance.
Turbo Convolutional Codes (TCC) are widely used to reduce Bit Error Rate (BER) for Second Generation (2G) and Third Generation (3G) wireless networks. However, TCC require large decoding complexity. Recently, Low Dens...
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ISBN:
(纸本)9781467319881
Turbo Convolutional Codes (TCC) are widely used to reduce Bit Error Rate (BER) for Second Generation (2G) and Third Generation (3G) wireless networks. However, TCC require large decoding complexity. Recently, Low Density Parity Check Codes (LDPC) have been included in standards for 3G wireless networks. But encoding complexity of LDPC is larger than that of TCC. Modified Turbo codes (MTC) are low complexity turbo-like codes with error performance which is equivalent to that of Turbo codes. However, MTC require 2-dimensional interleavers with large spreading factor and dispersion. In this paper, it is shown that BER of MTC is almost equivalent to TCC. Moreover, MTC decoders require 50% less computations than those of TCC and LDPC. Spreading factor and dispersion for various interleavers are compared. It is observed that 2-stage interleaver achieves large spreading factor and dispersion.
H.264/advanced video coding (AVC) decoding complexity modeling and applications are examined in this paper. We focus on complex modeling of spatial and temporal compensations achieved by a rich set of inter and intra-...
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H.264/advanced video coding (AVC) decoding complexity modeling and applications are examined in this paper. We focus on complex modeling of spatial and temporal compensations achieved by a rich set of inter and intra-prediction modes of H.264/AVC. We study the relationship between motion vectors (MV), frame sizes, and distributions of selected reference frames, which are highly related to cache management efficiency and, thus, the decoding complexity. An H.264/AVC encoder equipped with the complexity models can choose the best inter or intra-prediction mode and the best MV or intra-prediction direction while meeting the decoding complexity constraint of the target receiver platform. The proposed complexity models are accurate. The application of complexity models to the H.264/AVC decoding complexity reduction is demonstrated.
Turbo convolutional codes (TCC) are excellent error correcting codes for wireless channels. However, TCC decoders require large decoding complexity. Moreover, complexity of TCC decoder does not reduce even if puncturi...
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Turbo convolutional codes (TCC) are excellent error correcting codes for wireless channels. However, TCC decoders require large decoding complexity. Moreover, complexity of TCC decoder does not reduce even if puncturing is used to change the coding rate. Modified turbo codes require lower decoding complexity than TCC as they use multiple concatenations of simple block codes and convolutional codes. Recently, a class of modified turbo codes called low complexity hybrid turbo codes (LCHTC) and improved low complexity hybrid turbo codes (ILCHTC) have been proposed. It has been shown that LCHTC and ILCHTC achieve bit error rate (BER) which is comparable to TCC and have much lower decoding complexity. Simulation results show that BER performance of ILCHTC is better than that of LCHTC. Rate-1/3 ILCHTC achieve BER of 10(-5) at bit energy-to-noise ratio (E-b/N-0) of 1.9 dB, which is 0.4 dB higher than E-b/N-0 for TCC adopted by third generation partnership project (3GPP). Moreover, ILCHTC and LCHTC decoders require half the number of computations as compared to those required for TCC decoder. In this study, union-bound analysis of ILCHTC is presented to investigate BER performance <10(-6). For large interleaver lengths, analysis of theoretical union bound requires numerous computations. Therefore approximate analysis of union bound is derived from theoretical union bound. It is shown that the analysis of approximate union bound achieves reasonable accuracy. Moreover, approximate union bound can be evaluated with significantly less computational complexity than the theoretical union bound.
作者：
Abedi, A.Univ Maine
Elect & Comp Engn Dept Wireless Sensor Networks Lab Orono ME 04469 USA
Most distributed wireless sensor systems avoid using error correction codes because of the added complexity and power consumption of the decoders. Therefore these uncoded sensor systems are not capable of providing a ...
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Most distributed wireless sensor systems avoid using error correction codes because of the added complexity and power consumption of the decoders. Therefore these uncoded sensor systems are not capable of providing a robust communication link in noisy environments. This leads to a high packet loss, limits the communication range and increases the number of sensors required to cover a region. A novel architecture with several simple sensors and a few sensors with complex decoders is proposed. This approach is power efficient, practical and at the same time provides better coverage and link quality. Several coding schemes are studied with the overall goal of maximised performance, while minimising the decoding complexity, hence saving sensor nodes' power. Furthermore, in both additive white Gaussian noise and frequency-flat Rayleigh fading channels a code is optimised to provide the lowest possible bit error rate for a specific memory constraint. It is demonstrated that overall power consumption for a coded wireless sensor system can be less than its uncoded counterpart, even considering the decoding power consumption. The proposed approach is targeted at real-time wireless environmental monitoring, where the information flow is unidirectional, justifying the usage of complex decoders in a few super-nodes.
Space-time codes built with multiplexed Alamouti components provide multiplexing as well as diversity gain. Their orthogonal structure also leads to simpler decoding algorithms. We consider a 4 x 2 system with multipl...
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ISBN:
(纸本)9781424425198
Space-time codes built with multiplexed Alamouti components provide multiplexing as well as diversity gain. Their orthogonal structure also leads to simpler decoding algorithms. We consider a 4 x 2 system with multiplexed Alamouti codes. An exhaustive search maximum likelihood (ML) decoding for a 4 x 2 system is of order M-4, for a modulation scheme with constellation size M. For multiplexed orthogonal designs, an exact fast ML decoding algorithm has recently been reported whose complexity order is M-2 for a 4 x 2 system with QAM constellations. Nevertheless, the quadratic complexity of this fast ML algorithm may still be infeasible in practice for large constellations (e. g. M >= 64 QAM). In this paper, we present a method for designing low complexity sub-optimal decoders based on a combination of search based ML decoding and linear decoding. Our formulation facilitates a direct investigation of the trade-off between performance and complexity. The complexity of our hybrid decoder is flexible and it can be fixed based on the desired performance for a hardware implementation. Although extendable to more general multiplexed Alamouti systems, we focus here on a 4 x 2 space-time-polarization system comprising of two dual-polarized transmit antennas and one dual-polarized receive antenna.
In this paper, we propose a new Distributed Source Coding (DSC) scheme based on Low-Density Parity-Check (LDPC) codes with source revealing rate-adaptation. This scheme consists of LDPC codes which are well designed a...
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ISBN:
(纸本)9781457702518
In this paper, we propose a new Distributed Source Coding (DSC) scheme based on Low-Density Parity-Check (LDPC) codes with source revealing rate-adaptation. This scheme consists of LDPC codes which are well designed at their respective operating rates. The member codes do not need to be designed with any rate-adaptation criterion. Instead, when decoding fails, source revealing method is used. Numerical results show that the proposed scheme performs within average 5.6% of the Slepian-Wolf bound over the entire compression rate region. The decoding complexity also dramatically decreases by 57%.
Faster-than-Nyquist (FTN) signaling is a method of improving bandwidth efficiency by transmitting information beyond Nyquist's orthogonality limit for interference free transmission. Previously have theoretically ...
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ISBN:
(纸本)9780769544472
Faster-than-Nyquist (FTN) signaling is a method of improving bandwidth efficiency by transmitting information beyond Nyquist's orthogonality limit for interference free transmission. Previously have theoretically established that FTN can provide improved bandwidth efficiency. However, this comes at the cost of higher decoding complexity at the receiver. Our work has evaluated multicarrier FTN signaling for its implementation feasibility and complexity overhead compared to the gains in bandwidth efficiency. The work carried out in this research project includes a systems perspective evaluating performance, algorithm hardware tradeoffs and a hardware architecture leading to a silicon implementation of the decoder for FTN signaling. From the systems perspective, co-existence of FTN and OFDM based multicarrier system has been evaluated. OFDM being a part of many existing and upcoming broadband access technologies such as WLAN, LTE, DVB, this analogy is motivated. On the hardware aspect, the proposed architecture can accommodate both OFDM and FTN systems. The processing blocks in transmitter and receiver were designed for reuse and carry out different functions in the transceiver. Furthemore, the hardware could be configured to operate at varying bandwidth efficiencies (by FTN signaling) to exploit the channel conditions. The decoder implementation also considered block sizes and data rates to comply with the 3GPP standard. The decoding is carried out in as few as 8 iterations making it more practical for implementation in power constrained mobile devices. The decoder is implemented in 65nm CMOS process and occupies a total chip area of 0.8mm2.
The inner decoder of the Davey-MacKay (DM) construction for combating insertions, deletions and substitution errors, has high complexity and produces bursts of output likelihoods of greatest uncertainty in the vicinit...
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ISBN:
(纸本)9781457705953
The inner decoder of the Davey-MacKay (DM) construction for combating insertions, deletions and substitution errors, has high complexity and produces bursts of output likelihoods of greatest uncertainty in the vicinity of insertions and deletions. We therefore propose (i) a lookup-table-based implementation of the inner decoder to reduce its complexity, (ii) the use of interleaved LDPC codes as outer codes in the DM construction to spread the uncertain likelihoods produced by the inner decoder over several constituent LDPC codewords. Simulation results show that the proposed lookup table approach reduces the complexity of the inner decoder considerably while a significant improvement in frame error rate (FER) performance can be obtained with small interleaving depths. Our lookup table approach culminates in an iterative decoding scheme which yields improved FER performance over its non-iterative counterparts, yet with only a modest increase in decoding complexity, when the insertion/deletion probability is small.
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