54,806 research outputs found
Multilevel structured low-density parity-check codes
No full textLow-Density Parity-Check (LDPC) codes are typically characterized by a relatively high-complexity description, since a considerable amount of memory is required in order to store their code description, which can be represented either by the connections of the edges in their Tanner graph or by the non-zero entries in their parity-check matrix (PCM). This problem becomes more pronounced for pseudo-random LDPC codes, where literally each non-zero entry of their PCM has to be enumerated, and stored in a look-up table. Therefore, they become inadequate for employment in memoryconstrainedtransceivers. Motivated by this, we are proposing a novel family of structured LDPC codes, termed as Multilevel Structured (MLS) LDPC codes, which benefit from reduced storage requirements, hardware-friendly implementations as well as from low-complexity encoding and decoding. Our simulation results demonstrate that these advantages accrue without any compromise in their attainable Bit Error Ratio (BER) performance, when compared to their previously proposed more complex counterparts of the same code-length. In particular, wecharacterize a half-rate quasi-cyclic (QC) MLS LDPC code having a block length of 8064 that can be uniquely and unambiguously described by as few as 144 edges, despite exhibiting an identical BER performance over both Additive White Gaussian Noise (AWGN) and uncorrelated Rayleigh (UR) channels, when compared to a pseudorandom construction, which requires the enumeration of a significantly higher number of 24,192 edges
Multilevel structured low-density parity-check codes for AWGN and Rayleigh channels
No full textWe propose a novel class of protograph low-density parity-check (LDPC) codes having a combinatorial rather than a random structure, which are termed multilevel-structured (MLS) LDPC codes. It is demonstrated that they posses a strikingly simple structure and, thus, benefit from reduced storage requirements, hardware-friendly implementations, and low-complexity encoding. Our simulation results provided for both additive white Gaussian noise (AWGN) and uncorrelated Rayleigh (UR) channels demonstrate that these advantages accrue without compromising the attainable bit error ratio (BER) and block error ratio (BLER) performance, when compared with their previously proposed more complex random-construction-based counterparts, as well as with other structured codes of the same length
A model of check exchange
No full textThe authors construct and simulate a model of check exchange to examine the incentives a bank (or a bank clearinghouse) has to engage in practices that limit access to its payment facilities, in particular delaying the availability of check payment. The potentially disadvantaged bank has the option of directly presenting checks to the first bank. The authors find that if the retail banking market is highly competitive, the first bank will not engage in such practices, but if the retail banking market is imperfectly competitive, it will find it advantageous to restrict access to its facilities. Lower costs of direct presentment can reduce (but not eliminate) the range over which these practices are employed. The practice of delayed presentment can either reduce or increase welfare, again depending on the degree of competition in the market. The model suggests that, were the Federal Reserve System to exit the business of check processing, practices such as delayed presentment would b e more prevalent.Check collection systems ; Clearinghouses (Banking)
The NHS Health Check programme: implementation in east London 2009-2011
No full textThis is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work noncommercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http:// creativecommons.org/licenses/by-nc/4.0/Objectives To describe implementation and results from the National Health Service (NHS) Health Check programme. Design Three-year observational open cohort study: 2009–2011. Participants People of age 40–74 years eligible for an NHS Health Check. Setting 139/143 general practices in three east London primary care trusts (PCTs) serving an ethnically diverse and socially disadvantaged population. Method Implementation was supported with education, IT support and performance reports. Tower Hamlets PCT additionally used managed practice networks and prior-stratification to call people at higher cardiovascular (CVD) risk first. Main outcomes measures Attendance, proportion of high-risk population on statins and comorbidities identified. Results Coverage 2009, 2010, 2011 was 33.9% (31 878/10 805), 60.6% (30 757/18 652) and 73.4% (21 194/28 890), respectively. Older people were more likely to attend than younger people. Attendance was similar across deprivation quintiles and was in accordance with population distributions of black African/Caribbean, South Asian and White ethnic groups. 1 in 10 attendees were at high-CVD risk (20% or more 10-year risk). In the two PCTs stratifying risk, 14.3% and 9.4% of attendees were at high-CVD risk compared to 8.6% in the PCT using an unselected invitation strategy. Statin prescription to people at high-CVD risk was higher in Tower Hamlets 48.9%, than in City and Hackney 23.1% or Newham 20.2%. In the 6 months following an NHS Health Check, 1349 new cases of hypertension, 638 new cases of diabetes and 89 new cases of chronic kidney disease (CKD) were diagnosed. This represents 1 new case of hypertension per 38 Checks, 1 new case of diabetes per 80 Checks and 1 new case of CKD per 568 Checks. Conclusions Implementation of the NHS Health Check programme in these localities demonstrates limited success. Coverage and treatment of those at high-CVD risk could be improved. Targeting invitations to people at high-CVD risk and managed practice networks in Tower Hamlets improved performanc
Low-density parity-check codes and their rateless relatives
No full textThis survey guides the reader through the extensive open literature that is covering the family of low-density parity-check LDPC codes and their rateless relatives. In doing so, we will identify the most important milestones that have occurred since their conception until the current era and elucidate the related design problems and their respective solutions
Generalized Low-Density Parity-Check Coding Aided Multilevel Codes
No full textClassic Low-Density Parity-Check (LDPC) codes have recently been used as component codes in Multilevel Coding (MLC) due to their impressive BER performance as well as owing to their flexible coding rates. In this paper, we proposed a Multilevel Coding invoking Generalized Low-Density Parity-Check (GLDPC) component codes, which is capable of outperforming the classic LDPC component codes at a reduced decoding latency, when communicating over AWGN and uncorrelated Rayleigh fading channels
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
Non-binary protograph low-density parity-check codes for space communications
No full textProtograph-based non-binary low-density parity-check (LDPC) codes with ultra-sparse parity-check matrices are
compared with binary LDPC and turbo codes (TCs) from space communication standards. It is shown that larger coding gains are achieved, outperforming the binary competitors by more than 0.3 dB on the additive white Gaussian noise channel (AWGN). In the short block length regime, the designed codes gain more than 1 dB with respect to the binary protograph LDPC codes recently proposed for the next generation up-link standard of the Consultative Committee for Space Data Systems
Check-cashing outlets in a changing financial system
No full textThis paper discusses changes in the financial sector that threaten traditional check-cashing outlets (CCOs). Specifically, the paper focuses on four developments that may radically alter the check-cashing industry over the coming decade: the growing use of electronic payments, the deployment of automated check-cashing machines, the rise of payday lending, and the development of "bank/CCO hybrids."Checks
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