Identifying Fiscal Policy (In)effectiveness from the Differential Counter-Cyclicality of Government Spending in the Interwar Period

Differences across decades in the counter-cyclical stance of fiscal policy can identify whether the growth in government spending affects output growth and so speeds recovery from a recession. We study government-spending reaction functions from the 1920s and 1930s for twenty countries. There are two main findings. First, surprisingly, government spending was less counter-cyclical in the 1930s than in the 1920s. Second, the growth of government spending did not have a significant effect on output growth, so that there is little evidence that this feature of fiscal policy played a stabilizing role in the interwar period.fiscal policy, business-cycle history, Great Depression, interwar period

Memory and Complexity Analysis of On-the-Fly Coding Schemes for Multimedia Multicast Communications

A new class of erasure codes for delay-constraint applications, called on-the-fly coding, have recently been introduced for their improvements in terms of recovery delay and achievable capacity. Despite their promising characteristics, little is known about the complexity of the systematic and non-systematic variants of this code, notably for live multicast transmission of multimedia content which is their ideal use case. Our paper aims to fill this gap and targets specifically the metrics relevant to mobile receivers with limited resources: buffer size requirements and computation complexity of the receiver. As our contribution, we evaluate both code variants on uniform and bursty erasure channels. Results obtained are unequivocal and demonstrate that the systematic codes outperform the nonsystematic ones, in terms of both the buffer occupancy and computation overhead

Mitigating Receiver’s Buffer Blocking by Delay Aware Packet Scheduling in Multipath Data Transfer

Reliable in-order multi-path data transfer under asymmetric heterogeneous network conditions has known problems related to receiver's buffer blocking, caused by out of order packet arrival. Consequently, the aggregate capacity from multiple paths, which theoretically should be available to and achievable by the multi-path transport protocol, is practically severely underutilized. Several mitigation techniques have been proposed to address this issue mostly by using various packet retransmission schemes, load-balancing and bandwidth-estimation based mechanisms. In comparison to the existing reactive techniques for buffer block mitigation, we propose a novel and yet simpler to implement, delay aware packet scheduling scheme for multipath data transfer over asymmetric network paths, that proactively minimizes the blocking inside receiver's buffer. Our initial simulation results show that, in comparison to the default round robin packet scheduler, by using our proposed delay aware packet scheduling scheme, we can significantly improve the overall performance of a multi-path transport protocols while notably minimizing the receiver's buffer usage. Therefore, our proposal is particularly beneficial for multi-homed hand-held mobile devices with limited buffering capacity, which, due to their multi-homing and heterogeneous wireless network features (i.e. availability of 3G and Wi-Fi) are also one of the most common use cases for multi-path transport

On the Limit of Fountain MDC Codes for Video Peer-To-Peer Networks

Video streaming for heterogeneous types of devices, where nodes have different devices characteristics in terms of computational capacity and display, is usually handled by encoding the video with different qualities. This is not well suited for Peer-To-Peer (P2P) systems, as a single peer group can only share content of the same quality, thus limiting the peer group size and efficiency. To address this problem, several existing works propose the use of Multiple Descriptions Coding (MDC). The concept of this type of video codec is to split a video in a number of descriptions which can be used on their own, or aggregated to improve the global quality of the video. Unfortunately existing MDC codes are not flexible, as the video is split in a defined number of descriptions. In this paper, we focus on the practical feasibility of using a Fountain MDC code with properties similar to existing Fountain erasure codes, including the ability to create any number of descriptions when needed (on the fly). We perform simulations using selected pictures to assess the feasibility of using these codes, knowing that they should improve the availability of the video pieces in a P2P system and hence the video streaming quality. We observe that, although this idea seems promising, the evaluated benefits, demonstrated by the PSNR values, are limited when used in a real P2P video streaming system

Method for encoding data in bursts

The invention relates to a method for encoding data in a sequence of bursts (..., Bi-2, Bi-1, Bi, Bi+1,...), wherein each burst includes a block of data symbols and a block of redundancy symbols. The block of redundancy symbols (Ri) of the current burst (Bi) of the sequence is generated by the calculating the sum of a series of encoding values relating to a series of bursts (Bi-2, Bi-1), each encoding value from the series of encoding values being obtained by a respective encoding function applied to the block of data symbols of the burst corresponding to the series of bursts

Functional multisite copolymer by one-pot sequential RAFT copolymerization of styrene and maleic anhydride

A Multisite copolymer with functionalizable units inserted at precise locations was synthesised by one-pot Reversible Addition–Fragmentation Chain-Transfer (RAFT) polymerization and sequential Single Monomer Unit Insertion (SMUI) and Chain Extension (ChainExt) using Styrene (Sty) and Maleic Anhydride (MAnh) as comonomers. The multisite copolymer was based on a polystyrene (PSty) backbone (ca. 5700 g mol−1) with MAnh units inserted locally at four positions in the backbone. First, a well-defined macroCTA (1400 g mol−1 – Đ = 1.07) was synthesised by optimized RAFT polymerization (high conversion, high livingness and low dispersity) of styrene (DP = 10) using industrial grade butyl-2-methyl-2-[(dodecylsulfanylthiocarbonyl)sulfanyl] propionate as chain transfer agent (CTA-Ester – 80% pure). Subsequently, the polystyrene macroCTA was used for one-pot SMUI using a small excess of MAnh monomer (DPtarget = 1.5). The copolymer was chain extended by styrene leading to a polystyrene backbone with MAnh units (1.5 in average) located in the middle of the chain. By repeating SMUI and ChainExt, several units of MAnh were inserted locally along the polystyrene backbone (every 10 units on average) to give a functionalizable multisite copolymer (Đ = 1.35). Long alkyl chains (stearyl) were added by esterification of maleic anhydride moieties to obtain branched architecture

Enabling Private Real-Time Applications by Exploiting the Links Between Erasure Coding and Secret Sharing Mechanisms

A huge amount of personal data is shared in real time by online users, increasingly using mobile devices and (unreliable) wireless channels. There is a large industry effort in aggregation and analysis of this data to provide personalised services, and a corresponding research effort to enable processing of such data in a secure and privacy preserving way. Secret sharing is a mechanism that allows private data sharing, revealing the information only to a select group. A parallel research effort has been invested in addressing the performance of real time mobile communication on lossy wireless channel, commonly improved by using erasure codes. In this thesis, we bring together the theoretically related fields of secret sharing and erasure coding, to provide a rich source of solutions to the two problem areas. Our aim is to enable solutions that deliver the required performance level while being efficient and implementable. The thesis has the following contributions. We evaluate the applicability of a new class of Maximum Distance Separable (MDS) erasure codes to transmission of real time content to mobile devices and demonstrate that the systematic code outperforms the non-systematic variant in regards to computation complexity and buffer size requirements, making it practical for mobile devices. We propose a new Layered secret sharing scheme for real time data sharing in Online Social Networks (OSNs). The proposed scheme enables automated profile sharing in OSN groups with fine-grained privacy control, via a multi-secret sharing scheme comprising of layered shares. The scheme does not require reliance on a trusted third party. Compared to independent sharing of specific profile attributes (e.g. text, images or video), the scheme does not leak any information about what is shared, including the number of attributes and it introduces a relatively small computation and communications overhead. Finally, we investigate the links between MDS codes and secret sharing schemes, motivated by the inefficiency of the commonly used Shamir scheme. We derive the theoretical links between MDS codes and secret sharing schemes and propose a novel MDS code based construction method for strong ramp schemes. This allows the use of existing efficient implementations of MDS codes for secret sharing and secure computing applications. We demonstrate that strong ramp schemes deliver a significant reduction of processing time and communication overhead, compared to Shamir scheme