Sharif Digital Repository

Split-Row technique is proved to be one of the most effective methods to reduce the routing complexity of fully-parallel LDPC decoders. This technique is based on the idea of splitting each check node processor to multiple smaller processors. This paper introduces a new method, to increase the power-efficiency of Split-Row LDPC decoders. The proposed method is called trust to the truthful check node (TTCN), enabling the decoder to only depend on a portion of check node processors at specific decoding iterations. This leads to an average reduction of 30%-40% in the check node dynamic power consumption. This is achieved by means of trust to a minority of check node processors and gating the... 

In this paper, we investigate the performance of two strategies: simultaneous sliding window decoding (SimSlide) and simultaneous backward decoding (SimBack) when generalizing partial decode-and-forward to the relay networks. We show that these two methods yield the same achievable rates for relay networks but in comparison with sequential decoding, they yield higher rates. This is due to the fact that simultaneously decoding the different parts of the source message yields fewer bounds and this ultimately results a comprehensive and higher rate. We also introduce a special class of semi-deterministic relay networks and obtain its capacity by the proposed achievable rate  

Symmetric relaying is a method of relaying in which the relays can decode the message of other relays in the network in addition to the source message. In this paper an achievable rate is presented for a symmetric two-relay network based on partial decoding. The strategy make use of familiar techniques such as product binning, regular encoding/sliding window decoding and regular encoding/backward decoding. The proposed rate is shown to subsume the previously proposed rate for feed-forward relay network based on decode-and-forward. This rate is also used to establish the capacity of a generalisation of Aref network called 'semi-deterministic relay network with no interference at the relays'... 

Compress-and-Forward (CF) is a well-known coding strategy proposed for relay channels. Few works which were done about the generalization of the CF strategy to the relay networks, are based on irregular encoding/successive decoding. In this paper, a new generalization of the CF strategy to the relay networks based on regular encoding/backward decoding is presented. In general, backward decoding has been shown to yield higher rates in comparison with successive decoding. Here we will investigate the performance of backward decoding in our problem and show that our achievable rate includes the previously proposed rates  

In this paper, we propose a new achievable rate for two-level relay networks by introducing a new strategy named simultaneous partial and backward decoding. In the proposed method, benefitting from regular encoding/backward decoding strategy, different message parts transmitted in the network are simultaneously decoded at the relays and the receiver. The proposed strategy is shown to achieve better rates than the previously proposed methods based on decode-and-forward and partial decode-and-forward. © 2009 IEEE  

Partial decoding scheme is a scheme in which each relay decodes only part of the transmitted message. Obviously, the achievable rates proposed by the partial decoding scheme subsume the achievable rates proposed by the full decoding scheme. The other motivation of using partial decoding scheme is that there are some special classes of relay networks such as semi-deterministic and orthogonal relay networks such that their capacities are obtained via this scheme. The authors propose a comprehensive partial decoding scheme based on regular encoding/sliding window decoding analysis to propose a new achievable rate for two-level relay networks. In contrast with the previously proposed methods,... 

In this paper, we present an MPEG-2 video decoder implemented in our ODYSSEY design methodology. We start with an ASIP tailored to the JPEG decompression algorithm. We extend that ASIP by required software routines such that the extended ASIP can now perform MPEG2 decoding while still benefiting from hardware units common between JPEG and MPEG2. This demonstrates the ability of our approach in extending an already manufactured ASIP, which was tailored to a given application, such that it implements new, yet related applications. The implementation platform is a VirtexII-Pro FPGA. The hardware part is implemented in VHDL, and the software runs on a PowerPC processor. Experimental results show... 

In this study, the three-user interference channel (IFC) with common information is considered, where each receiver decode not only the private message from the intended transmitter but also the common messages from the non-intended transmitters by applying a simultaneous decoding scheme. An achievable rate region is presented using rate splitting and superposition encoding at the transmitters and simultaneous joint decoding at the receivers in which the transmitters cooperatively send the split messages which allows the interference cancellation at the receivers. The implicit form of the achievable rate region is also extended to K-user IFC with common information. Finally the inner bound... 

The authors study a two-user state-dependent generalised multiple-access channel (GMAC) with correlated states. It is assumed that each encoder has 'non-causal' access to channel state information (CSI). They develop an achievable rate region by employing rate-splitting, block Markov encoding, Gelfand-Pinsker multicoding, superposition coding and joint typicality decoding. In the proposed scheme, the encoders use a partial decoding strategy to collaborate in the next block, and the receiver uses a backward decoding strategy with joint unique decoding at each stage. The author's achievable rate region includes several previously known regions proposed in the literature for different scenarios... 

In this paper, we investigate reliable transmission of three correlated discrete memoryless sources over a two-relay network. In our considered model, one of the sources is available at the sender whereas, the other two sources are known to the first and the second relay. We present both joint and separate source-channel coding schemes, and derive the corresponding sets of sufficient conditions for reliable sources transmission. The manner of cooperation in both schemes is Decode-and-Forward strategy. In the joint approach, we generalize the correlation preserving mapping technique to our model using nested backward decoding. Our proposed separate approach is based on Slepian-Wolf source... 

Polar codes are novel and efficient error-correcting codes with low encoding and decoding complexities. These codes have a channel-dependent generator matrix, which is determined by the code dimension, code length and transmission channel parameters. A variant of the McEliece public-key cryptosystem based on polar codes, called the PKC-PC, is studied. Since the structure of the polar codes' generator matrix depends on the parameters of the channel, the authors have used an efficient approach to conceal their generator matrix. The proposed approach is based on a random selection of rows of the matrix by which a random generator matrix is constructed. Using the characteristics of polar codes... 

In this paper, we present a JPEG decoder implemented in our ODYSSEY design methodology. We start with an object-oriented JPEG decoder model. The total operation from modeling to implementation is done automatically by our EDA tool-set in about 10 hours. The resultant system is a JPEG decoder ASIP whose hardware part is implemented on FPGA logic blocks and software part runs on a MicroBlaze processor. This ASIP can be extended by software routines to implement the motion JPEG or MPEG2 decoding algorithms. We implemented our system on ML402 FPGA-based prototype board. Experimental results show that our ASIP implementation is comparable to other approaches while our approach enables quick and... 

In this work, we study the problem of linear index coding from graph homomorphism point of view. We show that the decision version of linear (scalar or vector) index coding problem is equivalent to certain graph homomorphism problem. Using this equivalence expression, we conclude the following results. First we introduce new lower bounds on linear index of graphs. Next, we show that if the linear index of a graph over a finite filed is bounded by a constant, then by changing the ground field, the linear index of the graph may change by at most a constant factor that is independent from the size of the graph. Finally, we show that the decision version of linear index coding problem is... 

In this paper, a novel scaling based information hiding approach robust against noise and gain attack is presented. The host signal is assumed to be stationary Gaussian modeled with a first-order autoregressive process. For data embedding, the host signal is divided into two parts. One part is manipulated while the other part is kept unchanged for parameter estimation. The decoding scheme using the ratio of samples is suitable for highly correlated signals in which the decoding process is difficult. By calculating the distribution of the ratio, the performance of the maximum likelihood decoder is analytically studied. The proposed algorithm is applied to several artificial Gaussian... 

In this paper, we propose an efficient method for demodulating pulse position modulation (PPM) signals based on Reed-Solomon decoding algorithm. It is shown that the proposed technique outperforms other demodulating methods such as those based on Lagrange, Spline, and Iterative algorithms. Furthermore, the proposed method is generalized to the case that the PPM signal is corrupted by additive white Gaussian noise. © 2004 Elsevier B.V. All rights reserved  

A symmetric semideterministic relay network is introduced, generalizing Aref networks. In the considered model, there is no interference at the relays, but the links from the source and the relays to the sink are interfering and nondeterministic. An achievable rate is determined for an arbitrary number of relays, based on symmetric relaying and simultaneous partial and backward decoding at the sink. The information expressions of the achievable rate match those of the standard cut-set bound, but the set of probability distributions is substantially different. We also study a wireless example of the defined network where nondeterministic links are replaced with fading AWGN channels, and... 

A new achievable rate based on a partial decoding scheme is proposed for the multilevel relay network. A novel application of regular encoding and backward decoding is presented to implement the proposed rate. In our scheme, the relays are arranged in feed-forward structure from the source to the destination. Each relay in the network decodes only part of the transmitted message by the previous relay. The proposed scheme differs from general parity forwarding scheme in which each relay selects some relays in the network but decodes all messages of the selected relays. It is also shown that in some cases higher rates can be achieved by the proposed scheme than previously known by Xie and... 

A new high-performance architecture for decoding the irregular Low-Density Parity-Check (LDPC) codes with respect to the iterative message-passing decoding algorithm is explored. The proposed method is based on reducing the logic delays in the iterative processing of the bit nodes and check nodes leading to the increment of maximum possible frequency. The simulations show the efficiency of the proposed method in low/high-complexity graph matrices, though it is more effective in high-complexity ones. About 28% reduction of the combinational delay in the bit/check processors is explored without much impacting the area consumption. ©2007 IEEE  

Maximum likelihood naturally arises as the target criterion for detection in many applications as well as in layered space-time communications. Nevertheless, the existing algorithms for maximum-likelihood decoding have computational complexity that is not feasible for implementation in practical systems. Applying the Expectation-Maximization algorithm to the Maximum Likelihood detection of layered space-time codes, we iteratively maximize the conditional log-likelihood of a single layer, rather than maximizing the intractable likelihood function of all layers. Computer simulations demonstrate the efficiency of the proposed detection scheme, in comparison to the well known nulling and... 

In this paper, we introduce a new class of sigature matrices for overloaded synchronous CDMA systems that have a very low complexity decoder. While overloaded systems are more efficient from the bandwidth point of view, the Maximum Likelihood (ML) implementation for decoding is impractical even for moderate dimensions. Simulation results show that the performance of the proposed decoder is very close to that of the ML decoder. Indeed, the proposed decoding scheme needs neither multiplication nor addition and requires only a few comparisons. Furthermore, the computational complexity and the probability of error vs. Signal to Noise Ratios (SNR) are derived analytically