Self-concatenated coding for wireless communication systems

In this thesis, we have explored self-concatenated coding schemes that are designed for transmission over Additive White Gaussian Noise (AWGN) and uncorrelated Rayleigh fading channels. We designed both the symbol-based Self-ConcatenatedCodes considered using Trellis Coded Modulation (SECTCM) and bit-based Self- Concatenated Convolutional Codes (SECCC) using a Recursive Systematic Convolutional (RSC) encoder as constituent codes, respectively. The design of these codes was carried out with the aid of Extrinsic Information Transfer (EXIT) charts. The EXIT chart based design has been found an efficient tool in finding the decoding convergence threshold of the constituent codes. Additionally, in order to recover the information loss imposed by employing binary rather than non-binary schemes, a soft decision demapper was introduced in order to exchange extrinsic information withthe SECCC decoder. To analyse this information exchange 3D-EXIT chart analysis was invoked for visualizing the extrinsic information exchange between the proposed Iteratively Decoding aided SECCC and soft-decision demapper (SECCC-ID). Some of the proposed SECTCM, SECCC and SECCC-ID schemes perform within about 1 dB from the AWGN and Rayleigh fading channels’ capacity. A union bound analysis of SECCC codes was carried out to find the corresponding Bit Error Ratio (BER) floors. The union bound of SECCCs was derived for communications over both AWGN and uncorrelated Rayleigh fading channels, based on a novel interleaver concept.Application of SECCCs in both UltraWideBand (UWB) and state-of-the-art video-telephone schemes demonstrated its practical benefits.In order to further exploit the benefits of the low complexity design offered by SECCCs we explored their application in a distributed coding scheme designed for cooperative communications, where iterative detection is employed by exchanging extrinsic information between the decoders of SECCC and RSC at the destination. In the first transmission period of cooperation, the relay receives the potentially erroneous data and attempts to recover the information. The recovered information is then re-encoded at the relay using an RSC encoder. In the second transmission period this information is then retransmitted to the destination. The resultant symbols transmitted from the source and relay nodes can be viewed as the coded symbols of a three-component parallel-concatenated encoder. At the destination a Distributed Binary Self-Concatenated Coding scheme using Iterative Decoding (DSECCC-ID) was employed, where the two decoders (SECCC and RSC) exchange their extrinsic information. It was shown that the DSECCC-ID is a low-complexity scheme, yet capable of approaching the Discrete-input Continuous-output Memoryless Channels’s (DCMC) capacity.Finally, we considered coding schemes designed for two nodes communicating with each other with the aid of a relay node, where the relay receives information from the two nodes in the first transmission period. At the relay node we combine a powerful Superposition Coding (SPC) scheme with SECCC. It is assumed that decoding errors may be encountered at the relay node. The relay node then broadcasts this information in the second transmission period after re-encoding it, again, using a SECCC encoder. At the destination, the amalgamated block of Successive Interference Cancellation (SIC) scheme combined with SECCC then detects and decodes the signal either with or without the aid of a priori information. Our simulation results demonstrate that the proposed scheme is capable of reliably operating at a low BER for transmission over both AWGN and uncorrelated Rayleigh fading channels. We compare the proposed scheme’s performance to a direct transmission link between the two sources having the same throughput

Near-capacity fixed-rate and rateless channel code constructions

Fixed-rate and rateless channel code constructions are designed for satisfying conflicting design tradeoffs, leading to codes that benefit from practical implementations, whilst offering a good bit error ratio (BER) and block error ratio (BLER) performance. More explicitly, two novel low-density parity-check code (LDPC) constructions are proposed; the first construction constitutes a family of quasi-cyclic protograph LDPC codes, which has a Vandermonde-like parity-check matrix (PCM). The second construction constitutes a specific class of protograph LDPC codes, which are termed as multilevel structured (MLS) LDPC codes. These codes possess a PCM construction that allows the coexistence of both pseudo-randomness as well as a structure requiring a reduced memory. More importantly, it is also demonstrated that these benefits accrue without any compromise in the attainable BER/BLER performance. We also present the novel concept of separating multiple users by means of user-specific channel codes, which is referred to as channel code division multiple access (CCDMA), and provide an example based on MLS LDPC codes. In particular, we circumvent the difficulty of having potentially high memory requirements, while ensuring that each user’s bits in the CCDMA system are equally protected. With regards to rateless channel coding, we propose a novel family of codes, which we refer to as reconfigurable rateless codes, that are capable of not only varying their code-rate but also to adaptively modify their encoding/decoding strategy according to the near-instantaneous channel conditions. We demonstrate that the proposed reconfigurable rateless codes are capable of shaping their own degree distribution according to the nearinstantaneous requirements imposed by the channel, but without any explicit channel knowledge at the transmitter. Additionally, a generalised transmit preprocessing aided closed-loop downlink multiple-input multiple-output (MIMO) system is presented, in which both the channel coding components as well as the linear transmit precoder exploit the knowledge of the channel state information (CSI). More explicitly, we embed a rateless code in a MIMO transmit preprocessing scheme, in order to attain near-capacity performance across a wide range of channel signal-to-ratios (SNRs), rather than only at a specific SNR. The performance of our scheme is further enhanced with the aid of a technique, referred to as pilot symbol assisted rateless (PSAR) coding, whereby a predetermined fraction of pilot bits is appropriately interspersed with the original information bits at the channel coding stage, instead of multiplexing pilots at the modulation stage, as in classic pilot symbol assisted modulation (PSAM). We subsequently demonstrate that the PSAR code-aided transmit preprocessing scheme succeeds in gleaning more information from the inserted pilots than the classic PSAM technique, because the pilot bits are not only useful for sounding the channel at the receiver but also beneficial for significantly reducing the computational complexity of the rateless channel decoder

Transmit antenna subset selection in spatial modulation relying on a realistic error-infested feedback channel

In this paper, we study the performance of spatial modulation (SM) employing Euclidean distance based antenna selection (EDAS) operating in a realistic error-infested feedback channel, which has hitherto only been studied under ideal feedback channel conditions. Specifically, we model the feedback channel by a bit-flip probability ?delta and study its impact on the forward link employing EDAS. We show that the erroneous feedback channel severely degrades the performance of EDAS-aided SM (EDAS-SM) system by imposing an error floor in the forward link. Furthermore, we quantify the error floors associated both with the spatial and with the conventional symbols with the aid of asymptotic symbol error rate analysis. The expressions derived for the error floors in the forward link are utilised for optimizing the feedback signalling, which are shown to help reduce the error floor levels. Furthermore, a pilot-aided selection verification (PSV) algorithm is proposed for mitigating the effects of antenna-set mismatch between the transmitter and the receiver, which eliminates the error floor in the forward link. Simulations are conducted in order to validate the theoretical results presented in the paper. Furthermore, the bit-error ratio (BER) performance of the EDAS-SM is compared to that of the conventional antenna selection (C-AS) both in the PSV as well as in the no selection verification scenarios. It is observed that EDAS-SM outperforms C-AS in both the scenarios considered. Specifically, at a BER of 10^-5, EDAS-SM is observed to give a 3dB signal-to-noise ratio gain compared to the C-AS, when operating at a spectral efficiency of 7 bits per channel use in the face of a feedback BER of delta = 0.05

Transmit Antenna Subset Selection in Spatial Modulation Relying on a Realistic Error-Infested Feedback Channel

In this paper, we study the performance of spatial modulation (SM) employing Euclidean distance-based antenna selection (EDAS) operating in a realistic error-infested feedback channel, which has hitherto only been studied under ideal feedback channel conditions. Specifically, we model the feedback channel by a bit-flip probability delta and study its impact on the forward link employing EDAS. We show that the erroneous feedback channel severely degrades the performance of EDAS-aided SM (EDAS-SM) system by imposing an error floor in the forward link. Furthermore, we quantify the error floors associated both with the spatial and with the conventional symbols with the aid of asymptotic symbol error rate analysis. The expressions derived for the error floors in the forward link are utilized for optimizing the feedback signaling, which are shown to help reduce the error floor levels. Furthermore, a pilot-aided selection verification (PSV) algorithm is proposed for mitigating the effects of antenna-set mismatch between the transmitter and the receiver, which eliminates the error floor in the forward link. Simulations are conducted in order to validate the theoretical results presented in this paper. Furthermore, the bit-error ratio (BER) performance of the EDAS-SM is compared with that of the conventional antenna selection (C-AS) both in the PSV as well as in the no selection verification scenarios. It is observed that EDAS-SM outperforms C-AS in both the scenarios considered. Specifically, at a BER of 10(-5), EDAS-SM is observed to give a 3-dB signal-to-noise ratio gain compared with the C-AS, when operating at a spectral efficiency of 7 bits per channel use in the face of a feedback BER of delta = 0.05

Dateset for Transmit Antenna Subset Selection in Spatial Modulation Relying on a Realistic Error-Infested Feedback Channel

Dataset supports: Mysore Rajashekar, R., Hari, K. V. S., &amp; Hanzo, L. (2017). Transmit Antenna Subset Selection in Spatial Modulation Relying on a Realistic Error-Infested Feedback Channel. IEEE Access. In this paper, we study the performance of spatial modulation (SM) employing Euclidean distance based antenna selection (EDAS) operating in a realistic error-infested feedback channel, which has hitherto only been studied under ideal feedback channel conditions. Specifically, we model the feedback channel by a bit-flip probability $\delta$ and study its impact on the forward link employing EDAS. We show that the erroneous feedback channel severely degrades the performance of EDAS-aided SM (EDAS-SM) system by imposing an error floor in the forward link. Furthermore, we quantify the error floors associated both with the spatial and with the conventional symbols with the aid of asymptotic symbol error rate analysis. The expressions derived for the error floors in the forward link are utilised for optimizing the feedback signalling, which are shown to help reduce the error floor levels. Furthermore, a pilot-aided selection verification (PSV) algorithm is proposed for mitigating the effects of antenna-set mismatch between the transmitter and the receiver, which eliminates the error floor in the forward link. Simulations are conducted in order to validate the theoretical results presented in the paper. Furthermore, the bit-error ratio (BER) performance of the EDAS-SM is compared to that of the conventional antenna selection (C-AS) both in the PSV as well as in the no selection verification scenarios. It is observed that EDAS-SM outperforms C-AS in both the scenarios considered. Specifically, at a BER of $10^{-5}$, EDAS-SM is observed to give a 3dB signal-to-noise ratio gain compared to the C-AS, when operating at a spectral efficiency of 7 bits per channel use in the face of a feedback BER of $\delta=0.05$.</span

NASA Tech Briefs, May/June 1986

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Using MapReduce Streaming for Distributed Life Simulation on the Cloud

Distributed software simulations are indispensable in the study of large-scale life models but often require the use of technically complex lower-level distributed computing frameworks, such as MPI. We propose to overcome the complexity challenge by applying the emerging MapReduce (MR) model to distributed life simulations and by running such simulations on the cloud. Technically, we design optimized MR streaming algorithms for discrete and continuous versions of Conway’s life according to a general MR streaming pattern. We chose life because it is simple enough as a testbed for MR’s applicability to a-life simulations and general enough to make our results applicable to various lattice-based a-life models. We implement and empirically evaluate our algorithms’ performance on Amazon’s Elastic MR cloud. Our experiments demonstrate that a single MR optimization technique called strip partitioning can reduce the execution time of continuous life simulations by 64%. To the best of our knowledge, we are the first to propose and evaluate MR streaming algorithms for lattice-based simulations. Our algorithms can serve as prototypes in the development of novel MR simulation algorithms for large-scale lattice-based a-life models.https://digitalcommons.chapman.edu/scs_books/1014/thumbnail.jp

Environmental drivers of spatiotemporal variation in the movement, performance, and genetic structure of brown trout and Atlantic salmon

Environmental conditions vary spatially and temporally, providing organisms with both challenges and opportunities. Animals have evolved a spectacular variety of migratory behaviours to take advantage of environmental variation, particularly in cases where this variation is predictable. The spatiotemporal pattern of migratory movements displayed by a population or species can be thought of as the evolutionary outcome of trade-offs amongst life history traits. As such, the study of animal movement in relation to environmental heterogeneity can yield valuable insights into the proximate and ultimate drivers of migratory behaviours as well as the behavioural mechanisms underpinning genetic structure. Against this background, the overarching aim of this thesis is to investigate the role of environmental heterogeneity in shaping locally-adapted migratory behaviours, finescale genetic structure and physiological performance in populations of wild brown trout (Salmo trutta) and Atlantic salmon (Salmo salar). Using telemetry data from passive integrated transponder (PIT) tags, I investigated the fine scale spatiotemporal patterns of spawning-related movements of brown trout between a feeding lake and two spawning streams (one inflowing, one outflowing, separated by < 100 m) over two spawning seasons. The timing of seasonal, daily and diel movements was strongly associated with variation in photoperiod, stream height and moon phase. Movement activity was highest at night, and particularly on nights with minimal lunar illumination and high water levels, suggesting that trout synchronise their spawning movements with environmental conditions that minimise their visibility to predators. Males began their movements between the lake and vii streams significantly earlier in the spawning season than females (protandry) and were generally more active. A substantial proportion of trout entered both spawning streams during the spawning periods, providing potential sources of gene flow between the two streams. However, Bayesian analyses revealed the existence of subtle genetic differentiation between juvenile trout sampled in the two streams and indicated that gene flow was strongly asymmetrical in a predominantly downstream (i.e. inflow to outflow) direction. Thus, natal dispersal between the two streams appears to be more common amongst trout that hatch in the inflow than the outflow. These findings have important implications for genetic diversity and local adaptation of fish stocks in fluvial and lacustrine environments. The collection of PIT-derived data in fluvial habitats is often hindered by the fragility of PIT antennae when exposed to high flows and flotsam. In Chapter 3 I present a novel PIT antenna design I developed for use in flood-prone spatey rivers. This design allows flotsam to pass without causing significant damage to antennae and was crucial for collecting the data used in Chapters 4 and 5 and in Appendix A. The performance of migratory populations can be strongly influenced by factors that affect the physiology or survival of migrants in any encountered habitat. I therefore investigated whether the acanthocephalan endoparasite Pomphorhynchus laevis causes a habitat-specific (i.e. freshwater or saltwater) pathology in Atlantic salmon smolts. Peculiarly for the species, the Irish strain of P. laevis uses salmonids, instead of cyprinids, as its preferred definitive hosts. Despite observing high prevalence of the parasite amongst wild smolts and high infection intensities in some individuals, I found no evidence of a pathological effect of infection in fresh or salt water. viii However, I did demonstrate that this freshwater parasite can survive in smolts in salinities similar to those found in coastal waters for at least 72 hours. Thus, the coastal roaming behaviour of Irish sea trout may have facilitated the colonisation of Irish river systems, resulting in the exceptionally widespread distribution of the parasite in Ireland. Collectively, these results contribute to our knowledge of how environmental heterogeneity influences the movement, performance, distribution and genetic structure of organisms in aquatic environments. As modern environmental changes occur at an unprecedented pace, such knowledge may provide us with the ability to anticipate, and perhaps even ameliorate, the impacts that anthropogenic activities have on migratory species