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In this paper, we consider a layered decoding algorithm for a performance improvement of LDPC. The proposed algorithm is based on a serial scheduling algorithm for the layered decoding of LDPC in which we consider check node degree, variable node degree, and the edge connection between the each node. Simulation results show that the proposed method improves about 0.2dB SNR gain compared with random...
“Soft is better than hard” — this sentence explains the meaning of one of the most important innovations in coding theory during the 90's: the usage of soft output in Soft Input Soft Output decoding and the appearance of Turbo Codes. The same principle may be applied to the verification mechanisms of cryptographic check values: instead of standard or hard verification, soft verification can be used...
Cooperative relaying has played an important role in the rapid evolution of wireless communications. The cooperative performance strongly depends on the selected relays. In this paper, an improved Least Maximum Pathloss (LMP) method is analyzed for the relay node selection. Both the direct transmission as well as the traditional LMP and the improved LMP under the condition of cooperative amplify-and-forward...
This paper presents an extrinsic data compression method for double-binary turbo codes. Frame and extrinsic data memory occupy more area in turbo decoder implementations with the frame size increasing. Besides, non-binary turbo codes have much more extrinsic memory usage than single-binary turbo codes. This proposed compression method utilizes an operation in radix-4 single-binary turbo decoder and...
The performance analysis of discrete-rate adaptive modulation (AM) for MIMO-OFDM systems with space-frequency block code (SFBC) in Rayleigh fading channels is presented. The fading gain value in each subchannel is partitioned into a number of regions by which the modulation is adapted in terms of the region the fading gain falls in. The fading gain region boundaries are attained for attaining maximum...
In iterative IDMA scheme, the users are distinguished with various chip-level interleaving sequences instead of user-specific signature sequences as in conventional code-division multiple-access (CDMA) scheme. A set of interleavers is considered to be practical if it has zero correlation with each other and also easy to generate as well requires minimal bandwidth during communication process. A properly...
In this paper, we propose a novel method suitable for unequal error protection(UEP) and unequal recovery time (URT) properties, namely the Duplicating-Expanding Window Fountain(D-EWF) codes. We implement duplicating windows and expanding windows techniques to improve the performance of both more important bits (MIB) and less important bits (LIB). We analyze the proposed method over binary erasure...
To achieve high data rate Multi-Carrier Code Division Multiple Access (MC-CDMA) is one suitable choice for next generation wireless communication system. MC-CDMA is the combination of CDMA and OFDM schemes, resulting into getting the advantages of both the schemes. Capacity planning is one of the major issues in designing of wireless communication system. In wireless communication system capacity...
In this paper, a generalized construction of quasi-cyclic low-density parity-check (QC-LDPC) codes for unequal error protection (UEP) is proposed based on the masking technique. We can obtain UEP QC-LDPC codes as long as the Tanner graph of the masking matrix satisfies a general condition which can include our previous UEP construction as a special case. A sufficient condition to have flexible choice...
This paper processes the theoretical analysis about the interference when digital or analogy jammer occurrs in spread spectrum communication system. Bit-error-rate (BER) performance is simulated to evaluate the influence caused by different spread codes and jammer signals. Moreover, some new methods to improve the performance of spreading system are discussed.
The novelty of this study is the extension of the relationship among error vector magnitude (EVM), bit-error-rate (BER) and signal-to-noise ratio (SNR) for an AWGN channel to the communication systems subject to nonlinearity in such channels. Particularly, this introductory work attempts to make a connection between the nonlinearity characteristics (i.e., both joint and individual AM-AM and AM-PM...
A new technique for constructing the Quasi Cyclic Low density Parity Check (QC-LDPC) codes based on splitting rows into sub rows method is proposed. The proposed QC-LDPC code, at BER of 10−6 achieves 0.1dB coding gain over the PEG-LDPC codes. Moreover, in the high Eb / N0 region, the proposed code with girths 16 and 20 respectively, achieve 0.056 dB and 0.27 dB at a BER of 10−5 over the randomly constructed...
This paper investigates the multiuser diversity introduced by opportunistic user selection in the cognitive radio parallel access channel (CR-PAC), where multiple cognitive users request to access the spectral resources of the licensed user. Assuming a simple cognitive user selection strategy based on maximizing the received signal-to-interference-plus- noise ratio (SINR), we study the statistics...
This paper provides an analytical framework to study the performance of linear companding techniques proposed in the OFDM literature, thus settling the numerous controversial claims that are based solely on simulation results. Linear companding transforms are widely employed to reduce the peak-to- average-power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. Two main linear...
A circulant permutation search algorithm is present in this paper, which can be employed to search appopriate circulant permutation to construct QC-LDPC codes with desired girth. The algorithm is based on a tree expansion mechanism and a select-and-discard procedure. By proposed method, a practical (3, 4) code with code length n=37368 and girth g=18 is constructed. The experiment shows that the codes...
In this paper we determine and modify the values of the two parameters in the companding transform function proposed previously. The CCDF of the compressed signals is derived and it shows good PAPR reduction ability. BER of the modified scheme is simulated, which shows that when combined with oversampling, the scheme can achieved good BER performance. Power spectrum density of the compressed signals...
A multi-edge framework for unequal error protecting (UEP) LT codes is derived by distinguishing between the edges connected to each protection class. Under the framework introduced, two existing techniques for the design of unequal error protecting LT codes can be evaluated and explained in a unified way. Furthermore, a simple and flexible design technique is proposed for UEP LT codes with good performance.
This paper considers maximum a posteriori (MAP) decoding of the maximum transition run (MTR) codes, over two-head digital magnetic recording system. Decoding is based on Bayesian algorithm and computes a posteriori log-likelihood ratios (LLR) from codewords of the MTR code. In this paper we present simulation results for performance of the joint soft detection-decoding of a concatenation of MTR code...
A serial concatenated scheme for Overlapped Code Division Multiplexing (OvCDM) system is proposed, characterized in that one or more OvCDM codes are as component codes in serial concatenated OvCDM to make up such a concatenated code with higher spectrum efficiency. The serial concatenated OvCDM uses iterative decoding algorithm based on LOG-MAP Algorithm with soft input soft ouput (SISO). As the simulation...
Compared with the conventional AF-based single-relay cooperative networks, there is nearly double spectrum efficiency in the AF-based two-path relay cooperative networks. However, there are few channel estimation methods for that. In this paper, we propose this channel estimation scheme. Firstly, we find the necessary channel state information (CSI) based on the FIC (full interference cancelation)...
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