LDPC coded transmissions over the Gaussian broadcast channel with confidential messages

We design and assess some practical low-density parity-check (LDPC) coded transmission schemes for the Gaussian broadcast channel with confidential messages (BCC). This channel model is different from the classical wiretap channel model as the unauthorized receiver (Eve) must be able to decode some part of the information. Hence, the reliability and security targets are different from those of the wiretap channel. In order to design and assess practical coding schemes, we use the error rate as a metric of the performance achieved by the authorized receiver (Bob) and the unauthorized receiver (Eve). We study the system feasibility, and show that two different levels of protection against noise are required on the public and the secret messages. This can be achieved in two ways: i) by using LDPC codes with unequal error protection (UEP) of the transmitted information bits or ii) by using two classical non-UEP LDPC codes with different rates. We compare these two approaches and show that, for the considered examples, the solution exploiting UEP LDPC codes is more efficient than that using non-UEP LDPC codes.Comment: 5 pages, 5 figures, to be presented at IEEE ICT 201

Practical LDPC coded modulation schemes for the fading broadcast channel with confidential messages

The broadcast channel with confidential messages is a well studied scenario from the theoretical standpoint, but there is still lack of practical schemes able to achieve some fixed level of reliability and security over such a channel. In this paper, we consider a quasi-static fading channel in which both public and private messages must be sent from the transmitter to the receivers, and we aim at designing suitable coding and modulation schemes to achieve such a target. For this purpose, we adopt the error rate as a metric, by considering that reliability (security) is achieved when a sufficiently low (high) error rate is experienced at the receiving side. We show that some conditions exist on the system feasibility, and that some outage probability must be tolerated to cope with the fading nature of the channel. The proposed solution exploits low-density parity-check codes with unequal error protection, which are able to guarantee two different levels of protection against noise for the public and the private information, in conjunction with different modulation schemes for the public and the private message bits.Comment: 6 pages, 4 figures, to be presented at IEEE ICC'14 - Workshop on Wireless Physical Layer Securit

Security gap analysis of some LDPC coded transmission schemes over the flat and fast fading Gaussian wire-tap channels

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Evaluation of the Fecal Proteome in Healthy and Diseased Cheetahs (Acinonyx jubatus) Suffering from Gastrointestinal Disorders

Fecal proteomics allows for the identification of proteins and peptides present in stools and is useful in finding possible new biomarkers for diagnosing and/or monitoring gastrointestinal (GI) disorders. In the present study, we investigated the fecal proteome in healthy and diseased cheetahs (Acinonyx jubatus). Captive individuals of this species frequently show gastrointestinal disorders characterized by recurrent episodes of diarrhea, rare episodes of vomiting and weight loss, associated with Helicobacter spp. infection. Fecal proteomic evaluation has been performed by two-dimensional electrophoresis followed by liquid chromatography-tandem mass spectrometry. In healthy cheetahs, the results showed the presence of the following proteins: collagen alpha-1 (II) chain, transthyretin, IgG Fc-binding protein, titin, dystonin, isopentenyl-diphosphate Delta-isomerase 1, sodium/potassium-transporting ATPase subunit alpha-1 and protein disulfide-isomerase A6. The presence of albumin isoforms was found only in diseased cheetahs. The present paper reports the study of the fecal proteome in the cheetah, evidences some differences between healthy and diseased patients and confirms, once again, the potential of fecal proteomics for the study of the GI environment, with promising developments regarding the identification of new diagnostic/monitoring markers

Fecal proteomic analysis in healthy dogs and in dogs suffering from food responsive diarrhea

Different laboratory markers are routinely used in the diagnosis and management of gastrointestinal (GI) disease in dogs. In the present study, starting from feces from both healthy dogs and dogs suffering from food responsive diarrhea (FRD), we tried to find proteins differently expressed in the two groups of dogs, by using a proteomic approach. Interestingly, we found that the immunoglobulin J-chain isoform 1 (species: Canis lupus familiaris) was identified only in diseased dogs (not in healthy). J-chain combines especially IgA monomers to IgA dimers and plays a crucial role for their secretions into mucosal interface. Being the first study of that kind in the dog, it is only possible to hypothesize that their presence could be likely due to an increased activation of the immune system or to a mucosal damage or both in FRD patients. Similarly, it is still impossible to assess whether this protein could be used as diagnostic/prognostic marker of GI disease; however, this study represents a promising first step toward fecal proteomics in canine GI disorders

Fecal Protein Profile in Eight Dogs Suffering from Acute Uncomplicated Diarrhea before and after Treatment

Acute diarrhea is a very frequent condition affecting dogs; nevertheless, little is known about what happens in the GI tract during such conditions. Proteomics allows the study of proteins present in a specific biologic substrate, and fecal proteomic investigations have been recently implemented to study GI diseases in dogs. In the present study, the fecal protein profiles of eight dogs suffering from acute uncomplicated diarrhea at the time of inclusion was investigated for the first time, and then the same patients were followed, replicating two further evaluations at two subsequent time points (after 2 and 14 days from the first presentation), with the aim of gaining possible new insights regarding the pathologic changes in the gastrointestinal environment during such conditions. Two-dimensional gel electrophoresis (2-DE) was performed, followed by mass spectrometry. Nine spots, corresponding to four (groups of) proteins (i.e., albumin, alkaline phosphatase, chymotrypsin-C-like, and some immunoglobulins), showed significant differences at two or more of the three time points investigated, almost all behaving similarly and decreasing at T1 (2 days after the onset of the condition) and significantly increasing at T2 (14 days after the onset), mainly evidencing a reaction of the organism. Further studies including a greater number of patients and possibly different techniques are needed to confirm the present finding

importance of espresso coffee machine parameters on the extraction of chlorogenic acids in a certified italian espresso by using spe hplc dad

Chlorogenic acids (CGA) are a group of phenolic acid derivatives, which are commonly found in coffee at concentrations reaching 0.1-0.2%. A method based on high performance liquid chromatography-diode array detector (HPLC-DAD) is proposed for the simultaneous determination of three chlorogenic acids, i.e. 3-O-caffeoylquinic acid (3-CQA), 5-O-caffeoylquinic acid (5-CQA) and 3,5-di-O-caffeoylquinic acid (3,5-diCQA), in time portions of espresso coffee. Two different espresso coffee machines working with different pressure and temperature curves, and two different blends (i.e. Arabica and Robusta) were used. The method presents good linearities (correlation coefficient greater than 0.99) and recoveries (in the range 67-99%) for the 3 chlorogenic acids. The concentration of total CGAs in a cup of Certified Italian Espresso ranged from 1522.5 to 2223.4 mg kg-1 and CGA isomer contents were, in decreasing order, 5-CQA &gt; 3-CQA &gt; 3,5-diCQA. The concentration of total chlorogenic acids was higher in Espresso coffee (EC) prepared with Aurelia machine rather than with Leva; Arabica blend possessed higher level ot total chlorogenic acids than Robusta samples. </p

Modern coding techniques for reliable and secure communications

Oggigiorno, le comunicazioni wireless sono coinvolte in molte applicazioni e gli obiettivi di sicurezza e affidabilità sono sempre più stringenti. Perciò, in questa tesi vengono proposte nuove soluzioni basate su schemi di codifica moderni in grado di conseguire prestazioni sempre più soddisfancenti. Adottiamo codici Low Density Parity Check (LDPC) e codici polari. Per la versatilità dei codici LDPC, li utilizziamo sia per scopi di affidabilità che di sicurezza. Un canale wire-tap è caratterizzato da un intercettatore che tenta di decodificare le informazioni inviate tra ricevitori autorizzati. In questo scenario, seguendo un approccio di Physical Layer Security, analizziamo il tasso di equivocazione degli intercettatori raggiunto tramite schemi LDPC pratici. Generalizzando questo modello con un canale broadcast con messaggi confidenziali, progettiamo codici LDPC con protezione non uniforme degli errori al fine di migliorare la privacy dei dati. Invece, per scopi di affidabilità, utilizziamo i codici LDPC su un canale satellitare non convenzionale come quello influenzato dalla scintillazione solare. In questo contesto, il rumore introdotto dai fenomeni fisici può portare a una scarsa qualità della comunicazione. Perciò, proponiamo schemi di codifica che migliorano l'affidabilità del collegamento. Infine, studiamo sistemi di comunicazione con trasmissione di blocchi corti. In questo caso utilizziamo i codici polari poiché sono una delle famiglie di codici più importanti in questo scenario. Tuttavia, con pacchetti corti, i codici polari possono avere scarse prestazioni. Per questo motivo in letteratura è stata proposta la loro concatenazione con un codice ciclico. I codici polari concatenati diventano competitivi in questo contesto e pertanto sono stati raccomandati per la nuova generazione di sistemi mobili (5G). Studiando lo spettro dei pesi degli schemi concatenati, proponiamo alcune soluzioni in grado di migliorare ulteriormente l'affidabilità della comunicazione.Nowadays, wireless communications are involved in many applications and the security and reliability targets are increasingly growing. Hence, based on modern coding schemes, in this thesis new solutions able to achieve more and more satisfactory performance are proposed. In particular, we adopt Low Density Parity Check (LDPC) codes and Polar Codes. Due to the versatility of LDPC codes, we use this codes family for both reliability and security scopes. A wire-tap channel is characterized by an eavesdropper that tries to decode the information sent among authorized receivers. In this scenario, by following the physical layer security approach, first we investigate the eavesdropper's equivocation rate achieved through practical LDPC schemes. Then, by generalizing this model with a broadcast channel with confidential messages, we design LDPC codes with unequal error protection capabilities that improve the privacy of data. Instead, for reliability purposes, we use LDPC codes over a non-conventional satellite channel like the one affected by solar scintillation. In this context, the noise introduced by physical phenomena may lead to a low quality in the communication. Hence, by mitigating the performance degradation, in this thesis we propose coding schemes that improve the link reliability. Finally, we study communication systems based on the transmission of short blocks. In this case we use Polar codes since they are one of the most prominent codes family proposed for this scenario. However, in the short packet length regime Polar codes may have poor performance. To overcome this issue, a concatenation with a cyclic code was proposed in the literature. Concatenated Polar codes are competitive in this context and therefore they are recommended in the new generation of mobile systems (5G). Thus, we study the structure of these concatenated schemes from a distance spectrum point of view and propose some solutions able to further improve the reliability of communication