Showing papers on "Bandwidth expansion published in 2011"

Analog Joint Source-Channel Coding Using Non-Linear Curves and MMSE Decoding

Abstract: We investigate the performance of a discrete-time all-analog-processing joint source-channel coding system for the transmission of memoryless sources over average power constrained AWGN channels. First, N:1 bandwidth compression systems are analyzed and optimized. At the encoder, N samples of an i.i.d. source are directly mapped into one channel symbol using a non-linear curve. Different from previous work in the literature, we introduce an additional degree of freedom at the encoder, MMSE decoding instead of ML decoding is considered, and we focus on both high and low channel signal-to-noise ratio (CSNR) regions. By using MMSE decoding, the proposed system presents a performance very close to the theoretical limits, even at low CSNR, as long as the system parameters are properly optimized. Then, N:K bandwidth compression systems are constructed by parallel combination of an M:1 system and a 1:1 uncoded system, and the optimal power allocation between the two constituent systems is derived in order to maximize the overall output signal-to-distortion ratio (SDR). Finally, 1:2 bandwidth expansion systems using mapping functions similar to those used in 2:1 system are investigated. Different from digital systems, the proposed scheme does not require long block lengths to achieve good performance, and shows graceful degradation when the CSNR is lower than the one used for the design.

Energy-Efficient Scheduling and Bandwidth-Energy Efficiency Trade-Off with Low Load

Abstract: This paper presents a novel adaptation of the score-based scheduling principle along with a method for trading-off bandwidth for energy efficiency for use in Long Term Evolution (LTE) systems. The score-based principle is adapted to make use of both a relative and absolute energy efficiency metric. This results in flexible energy efficient scheduling that preserves the quality of service (QoS), as well as reduces the interference in the system. The general principle behind bandwidth expansion is to extend a user's bandwidth by a factor of alpha. The currently achieved QoS is maintained by switching to a lower order modulation scheme and adjusting any other link parameters as necessary. Both, a purely theoretical and an empirical approach are used to evaluate the performance of the concept. Through a theoretical derivation, it is established that the higher the user's employed modulation order is, the greater the possible gains are from employing such a transmission mode. The calculated improvement ranges from approximately 43% to 98%, or approximately 2 to 50 times reduction in transmission energy. A realistic simulation tool is developed to empirically validate the theoretical results. When an expansion of bandwidth by a factor of 2 is simulated, the bandwidth expansion mode (BEM) is more efficient in 83% of the time, and energy is reduced 2.6 times on average, while retaining the established QoS.

On the Performance of Hybrid Digital-Analog Coding for Broadcasting Correlated Gaussian Sources

Abstract: We consider the problem of sending a bivariate Gaussian source S=(S1,S2) across a power-limited two-user Gaussian broadcast channel. User i (i=1,2) observes the transmitted signal corrupted by Gaussian noise with power σi2 and desires to estimate Si. We study hybrid digital-analog (HDA) joint source-channel coding schemes and analyze the region of (squared-error) distortion pairs that are simultaneously achievable. Two cases are considered: 1) broadcasting with bandwidth compression, and 2) broadcasting with bandwidth expansion. We modify and adapt HDA schemes of Wilson et al. and Prabhakaran et al. , originally proposed for broadcasting a single common Gaussian source, in order to provide achievable distortion regions for broadcasting correlated Gaussian sources. For comparison, we also extend the outer bound of Soundararajan et al. from the matched source-channel bandwidth case to the bandwidth mismatch case.

Hybrid digital-analog source-channel coding with one-to-three bandwidth expansion

Abstract: We consider the problem of bandwidth expansion for lossy joint source-channel coding over a memoryless Gaussian channel. A low delay 1∶3 bandwidth expansion hybrid digital-analog coding system, which combines a scalar quantizer and a 1∶2 nonlinear analog coder, is proposed. It is shown that our proposed system outperforms the 1∶3 generalized hybrid scalar quantizer linear coder in terms of signal-to-distortion ratio (SDR). A lower bound on the system SDR is also derived.

Codebook Design and Hybrid Digital/Analog Coding for Parallel Rayleigh Fading Channels

Abstract: Low-delay source-channel transmission over parallel fading channels is studied. In this scenario separate source and channel coding is in general highly suboptimal. A scheme based on hybrid digital/analog joint source-channel coding is therefore proposed, employing scalar quantization and polynomial-based analog bandwidth expansion. Simulations demonstrate substantial performance gains.

Bandwidth expanding method and device

Abstract: The invention provides a brand new bandwidth expanding method, which comprises: dividing time domain signals in a t1 to t2 time period into high-frequency time domain signals and low-frequency time domain signals by pretreatment; converting the high-frequency time domain signals and the low-frequency time domain signals into high-frequency frequency domain signals and low-frequency frequency domain signals respectively by time-frequency conversion; and calculating at least one bandwidth expansion gain corresponding to the t1 to t2 time period according to part of the low-frequency frequency domain signals and part of high-frequency frequency domain signals

Reducing Multi-user Interference through Rotation Matrix

Abstract: A new method through rotation matrix in MIMO system is proposed in this paper, which increases the distance of code-words and decreases the pair wise error probability. Compared with some traditional ways, this method is bandwidth-efficient. A detection method MMSE-ML is used for the simple algorithm. The computer simulation results confirmed that in high SNR, this method can efficient decrease multi-user interference without any coding or bandwidth expansion. Using MMSE-ML detection, 3.2E-3 BER reached at 22 dB SNR.

Efficient Image Transmission Through Analog Error Correction

Abstract: This paper presents a new paradigm for image transmission through analog error correction codes. Conventional schemes rely on digitizing images through quantization (which inevitably causes significant bandwidth expansion) and transmitting binary bit-streams through digital error correction codes (which do not automatically differentiate the different levels of significance among the bits). To strike a better overall performance in terms of transmission efficiency and quality, we propose to use a single analog error correction code in lieu of digital quantization, digital code and digital modulation. The key is to get analog coding right. We show that this can be achieved by cleverly exploiting an elegant "butterfly" property of chaotic systems. Specifically, we demonstrate a tail-biting triple-branch baker's map code and its maximum-likelihood decoding algorithm. Simulations show that the proposed analog code can actually outperform digital turbo code, one of the best codes known to date. The results and findings discussed in this paper speak volume for the promising potential of analog codes, in spite of their rather short history.