Multipath spread is one of the most important factors which limit data transfer with high bit rate. Data transfer with high bit rate is possible in the range of gigahertz. The main problem in this frequency range is m...
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ISBN:
(纸本)9781479944095
Multipath spread is one of the most important factors which limit data transfer with high bit rate. Data transfer with high bit rate is possible in the range of gigahertz. The main problem in this frequency range is multipath spread. Orthogonal frequency division multiplexing (OFDM) technique divides the transferring symbols between several subcarriers and transfers them simultaneously. Accordingly this technique is very resistant against the adverse effects of multipath spread. As a result of the increasingly grow of systems with high capacity, the uses of this technique increases cumulatively. OFDM system along with MIMO has been offered for the next generations of cell phones. Channel coding plays an important role in improving the efficiency of OFDM. Due to the special structure of OFDM, using channel coding in it, compared with uni-subcarrier systems, has special features which enhance the efficiency of the system. For this reason, this system is also called coded OFDM or COFDM. In this article in addition to studying the OFDM technique, we will consider the role of the delay spread of the channel in increasing the coding interest of the channel and the efficiency of OFDM system.
Numerical simulation of UWB noise communications with spectrum spreading is performed. It is detected that the intersystem jamming appearing in result of code spectrum modulation. Noise performance of UWB communicatio...
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ISBN:
(纸本)9789663354125
Numerical simulation of UWB noise communications with spectrum spreading is performed. It is detected that the intersystem jamming appearing in result of code spectrum modulation. Noise performance of UWB communication system is investigated for a single-ray channel with additive Gaussian white noise. The new method of intersystem jamming reduction is proposed when nonmultiple time delays of noise informative signals are used.
In this work we consider incremental redundancy hybrid ARQ (HARQ) transmission of data packets over independent block-fading channels. In HARQ, the transmitter, upon request (NACK), resends the "NACKed" pack...
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ISBN:
(纸本)9781479935123
In this work we consider incremental redundancy hybrid ARQ (HARQ) transmission of data packets over independent block-fading channels. In HARQ, the transmitter, upon request (NACK), resends the "NACKed" packet in the next available block. Conventionally, the original and retransmitted packets occupy one block, each. In our approach, we allow the transmitter to share the resources between the new and the retransmitted packets. To implement such a multi-packet transmission we consider the superposition coding and the time-sharing modulation as possible encoding schemes for simultaneous transmission of both packets. Targeting the maximization of the throughput, we cast the problem into the framework of Markov decision process (MDP), where the decisions about the optimal transmission strategy are taken using information about the state of the receiver in the previous transmissions. Numerical examples obtained in a Rayleigh block-fading channel show that proposed transmission
The author revises his concept of Packet Appending for Bit-Interleaved Coded modulation with Iterative Decoding (PA-BICM-ID) and proposes a new receiver design in which some demapper operations are called in every ite...
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ISBN:
(纸本)9781479925810
The author revises his concept of Packet Appending for Bit-Interleaved Coded modulation with Iterative Decoding (PA-BICM-ID) and proposes a new receiver design in which some demapper operations are called in every iterative decoding pass, as previously, but the rest is called only in the first iteration, thereby reducing the computational cost. Afterwords, it is shown that PA-BICM-ID can considerably improve the performance of such systems that originally employ low-order modulation. The decoding convergence is examined by means of the EXtrinsic Information Transfer (EXIT) chart, whereas the overall system performance over uncorrelated Rayleigh fading channel is analyzed using computer simulation.
Interference detection and suppression schemes are proposed for coded OFDM systems in the presence of narrow-band interference. Previously proposed interference detection schemes perform with a recursive forward error...
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ISBN:
(纸本)9781479935123
Interference detection and suppression schemes are proposed for coded OFDM systems in the presence of narrow-band interference. Previously proposed interference detection schemes perform with a recursive forward error correcting (FEC) decoding, thus its calculation is heavy. The proposed scheme is based on an expectation maximization (EM) algorithm to detect the interference before the FEC decoding process. The complexity is reduced because the FEC decoding is performed only once. Simulation results indicate that the proposed scheme achieves almost the same bit error rate performance as the conventional scheme, while decreasing the times of the FEC decoding.
In bit patterned magnetic recording (BPMR), The two-dimensional (2D) interference composed of inter-symbol and inter-track interference is a major problem especially at high areal density (AD). One way to alleviate th...
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ISBN:
(纸本)9786163618238
In bit patterned magnetic recording (BPMR), The two-dimensional (2D) interference composed of inter-symbol and inter-track interference is a major problem especially at high areal density (AD). One way to alleviate the destructive effect of 2D interference is to deploy a 2D coding scheme on an input data sequence before recording in order to avoid some data patterns that easily cause an error at the data readback process. However, some coding schemes generate high complexity. Consequently, this paper proposes a new low-complexity modulation code with redundant bits to eliminate the data patterns leading to severe 2D interference and compare overall system performance. Experimental results indicate that the system with the proposed code is superior to that without coding, especially when the AD is high and/or the position jitter is large.
We address the problem of multiuser power and bandwidth allocation for Orthogonal Frequency Division Multiple Access (OFDMA) networks employing a Type-II Hybrid Automatic Repeat reQuest (HARQ) mechanism, practical Cod...
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ISBN:
(纸本)9781479944828
We address the problem of multiuser power and bandwidth allocation for Orthogonal Frequency Division Multiple Access (OFDMA) networks employing a Type-II Hybrid Automatic Repeat reQuest (HARQ) mechanism, practical coding and modulation Schemes (MCSs) and Bit Interleaved Coded modulation (BICM). The problem is formulated as minimizing the sum power required to satisfy a goodput constraint for each link while its post-HARQ Packet Error Rate (PER) does not exceed a certain threshold. Assuming statistical Channel State Information (CSI), we propose a computationally-efficient algorithm to compute the corresponding optimal resource allocation. We finally provide a practical selection of the MCSs that significantly boosts the performance of the proposed resource allocation algorithm.
We study the problem of designing a rate-1 block-precoder to minimize bit/symbol error rate when storing a given source on a magnetic recording channel. A block-precoder of length b-bits is defined by a permutation pi...
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We study the problem of designing a rate-1 block-precoder to minimize bit/symbol error rate when storing a given source on a magnetic recording channel. A block-precoder of length b-bits is defined by a permutation pi on 2(b) blocks. We show that the problem of finding a permutation for the block-precoder that minimizes bit/symbol error rate is equivalent to solving the quadratic assignment problem, a known combinatorial optimization problem that is NP-complete. We exploit the symmetry group of the b-dimensional hypercube to reduce the search space, allowing a branch-and-bound technique to find the optimal 5-bit precoders. We also implement a local search algorithm that can find good precoders for larger blocklengths. We design precoders for MTR-constrained user bits and unconstrained parity bits with a reverse-concatenation architecture, and we evaluate the resulting SNR gains in a turbo equalization scheme.
This paper presents performance analysis and cross-layer design approaches for hybrid ARQ (HARQ) protocol in wireless networks which employ adaptive modulation and coding (AMC) at the physical layer and are subject to...
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This paper presents performance analysis and cross-layer design approaches for hybrid ARQ (HARQ) protocol in wireless networks which employ adaptive modulation and coding (AMC) at the physical layer and are subject to time-correlated fading channels. Utilizing a Markov channel model which accounts for the temporal correlation in successive parity transmissions by the adaptive rate HARQ protocol, we derive the system throughput and the packet loss probability based on a rate compatible punctured convolutional (RCPC) code family. As an application, we then present a cross-layer AMC design which takes into account the performance gain of the HARQ protocol at the link layer. The results illustrate that including AMC in the HARQ protocol leads to a substantial throughput gain, but the channel correlation strongly diminishes the performance of the HARQ protocol in terms of throughput and packet loss rate.
Adaptive modulation and coding (AMC) is attracting research interest in wireless multicast broadcast services (MBS). AMC increases the system throughput by utilizing possible good channel states instead of using robus...
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Adaptive modulation and coding (AMC) is attracting research interest in wireless multicast broadcast services (MBS). AMC increases the system throughput by utilizing possible good channel states instead of using robust modulation and coding schemes. A model for the AMC in an MBS system with multiple MBS groups is provided, and stochastic analysis using Markov chain is also applied for modeling analysis. Simulation results show extremely high correspondence to the proposed mathematical model.
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