Channels with Cooperation Links that May Be Absent

It is well known that cooperation between users in a communication network can lead to significant performance gains. A common assumption in past works is that all the users are aware of the resources available for cooperation, and know exactly to what extent these resources can be used. Unfortunately, in many modern communication networks the availability of cooperation links cannot be guaranteed a priori, due to the dynamic nature of the network. In this work a family of models is suggested where the cooperation links may or may not be present. Coding schemes are devised that exploit the cooperation links if they are present, and can still operate (although at reduced rates) if cooperation is not possible.Comment: Accepted for publication in the IEEE transaction on Information Theory, June 201

Relay Channels with Unreliable Helpers

The relay channel with unreliable helper is introduced and studied. The model is that of a classical relay channel where the input from the relay to the channel has an extra primitive link whose presence is not assured a priori. The extra link represents a helper who may decide not to cooperate in transmission. The goal is to devise robust coding schemes that exploit all the relay links when they are present, but can also operate, possibly at reduced rates, when the extra primitive link (helper) is absent. The capacity region of this class of problems is defined, and fully characterized for degraded relay channels. The degraded Gaussian relay channel with unreliable relay link is solved.Comment: 9 pages, 4 figures. Part of the results were presented at the 2023 International Symposium on Information Theory, June 25-30 2023, Taipei, Taiwa

Secure Communication with Unreliable Entanglement Assistance

Secure communication is considered with unreliable entanglement assistance, where the adversary may intercept the legitimate receiver's entanglement resource before communication takes place. The communication setting of unreliable assistance, without security aspects, was originally motivated by the extreme photon loss in practical communication systems. The operational principle is to adapt the transmission rate to the availability of entanglement assistance, without resorting to feedback and repetition. Here, we require secrecy as well. An achievable secrecy rate region is derived for general quantum wiretap channels, and a multi-letter secrecy capacity formula for the special class of degraded channels

Coastal geomorphology, processes and erosion at the tourist destination of Ferryland, Newfoundland and Labrador

The community of Ferryland is located on the southeastern coast of the Avalon Peninsula. The town traditionally relied on a fishing-based economy until the collapse of the fishery in the early 1990s. The present economy emphasizes sustainable development in the tourism sector with focus on archaeology, geotourism and other recreational uses. This paper discusses coastal erosion and impacts on sites and infrastructure using methods including: local knowledge, Real Time Kinematic (RTK) surveying and other survey techniques, seawater level measurement, meteorological data from a locally-installed station, custom-made drifter tube buoys, photography, HD video, and investigation using various modes of transport including inflatable boat. The major findings of the study include that the residents and stakeholders are genuinely interested in and knowledgeable of coastal erosion. The causes of coastal erosion include: large waves, surge, longshore currents, harbour oscillations, mass wasting, and location of infrastructure causing alterations of these processes. Freeze-thaw Cycles (FTC), rainfall, and gravity loosen and transport rock, till, and fill materials downslope. Large waves and currents transport the materials alongshore or into the nearshore. Harbour oscillations causing high velocity currents (> 2 m/s) are responsible for shoreline erosion and damage to property in The Pool. Historical resources such as gun batteries and ordnance pieces which date to the 1700s are being lost or threatened through coastal erosion of till and rock cliffs. Improper drainage and maintenance is responsible for erosion of roads and supporting shoulders, necessitating mitigation measures. Sediment transport and deposition during and after large wave and surge events lead to undercutting of infrastructure and increased risk of washover of existing infrastructure. Erosion is ongoing at Bois Island and Ferryland Head Isthmus through slope processes and undercutting; The Pool and the lower Colony of Avalon site through harbour oscillations and related undermining; the tombolo and the main breakwater through wave attack; and Meade’s Cove including the East Coast Trail through wave attack and undercutting. The floor of the latrine in the lower Colony of Avalon site indicates that sea level was approximately 1.25m below present in the 1620s, a relative sea level rise rate of 3.2 mm/y. The recommendations include suggested mitigation to reduce impacts specific to each site

Myopic Coding in Multiterminal Networks

This paper investigates the interplay between cooperation and achievable rates in multi-terminal networks. Cooperation refers to the process of nodes working together to relay data toward the destination. There is an inherent tradeoff between achievable information transmission rates and the level of cooperation, which is determined by how many nodes are involved and how the nodes encode/decode the data. We illustrate this trade-off by studying information-theoretic decode-forward based coding strategies for data transmission in multi-terminal networks. Decode-forward strategies are usually discussed in the context of omniscient coding, in which all nodes in the network fully cooperate with each other, both in encoding and decoding. In this paper, we investigate myopic coding, in which each node cooperates with only a few neighboring nodes. We show that achievable rates of myopic decode-forward can be as large as that of omniscient decode-forward in the low SNR regime. We also show that when each node has only a few cooperating neighbors, adding one node into the cooperation increases the transmission rate significantly. Furthermore, we show that myopic decode-forward can achieve non-zero rates as the network size grows without bound

Optimal Power Allocation for a Successive Refinable Source with Multiple Descriptions over a Fading Relay Channel Using Broadcast/Multicast Strategies

In a wireless fading relay system with multicast/broadcast transmission, one of the most crucial challenges is the optimization of a transmission rate under multiuser channel diversity. Previously reported solutions for mitigating the vicious effect due to multi-user channel diversity have been mainly based on superposition coded multicast, where an optimal power allocation to each layer of modulated signals is determined. Many previous studies investigated a harmonic interplay between the successively re nable (SR) content source and a layered modulation via superposition coding (SPC) over the multicast/broadcast channels. By jointly considering the successive re nement characteristic at the source and the dependency of the layered modulation at the channel, a graceful fexibility can be achieved on a group of users with di erent channel realizations. Here most of the receivers are supposed to obtain the base quality layer information modulated in a lower rate, while the receivers with better channel realizations will obtain more information by re ning the base quality layer information using the enhancement quality layer information. In particular, the optimal power allocation for a SR source over a fading relay channel using broadcast/multicast strategy can be determined such that the minimum distortion of total received information is produced. However, a quality layer of data in a successively refined source may not be decodable if there is any loss of channel codewords, even if the corresponding longterm channel realization is su cient for decoding. To overcome this problem, one of the previous studies introduced a framework of coded video multicast, where multiple description coding (MDC) is applied to an SR content source and is further mapped into a layered modulation via SPC at the channel. Up till now, there has not been a rigorous proof provided on the bene t of manipulating the two coding techniques, (i.e. MDC and SPC), nor has any systematic optimization approach been developed for quantifying the parameter selection. Cooperative relaying in wireless networks has recently received much attention. Because the received signal can be severely degraded due to fading in wireless communications, time, frequency and spatial diversity techniques are introduced to overcome fading. Spatial diversity is typically envisioned as having multiple transmit and/or receive antennas. Cooperation can be used here to provide higher rates and results in a more robust system. Recently proposed cooperation schemes, which take into account the practical constraint that the relay cannot transmit and receive at the same time, include amplify-forward(AF), decode-forward(DF), and compress-forward(CF). In this study, in a fading relay scenario, a proposed framework is investigated to tackle the task of layered power allocation, where an in-depth study is conducted on achieving an optimal power allocation in SPC, such that the information distortion perceived at the users can be minimized. This thesis provides a comprehensive formulation on the information distortion at the receivers and a suite of solution approaches for the developed optimization problem by jointly considering MDC and SPC parameter selection over the fading relay channel

All the King’s Men: British Codebreaking Operations: 1938-43

The Enigma code was one of the most dangerous and effective weapons the Germans wielded at the outbreak of the Second World War. The Enigma machine was capable of encrypting radio messages that seemed virtually unbreakable. In fact, there were 158,900, 000,000,000 possible combinations in any given message transmitted. On the eve of the war’s outbreak, the British had recently learned that the Poles had made significant progress against this intimidating cipher in the early 1930s. Incensed and with little help, the British Government Code & Cipher School began the war searching for a solution. Drawing from their experiences from the First World War, and under the visionary guidance of Alan Turing, Gordon Welchman, and countless others, the British created a new, mechanical approach to breaking the seemingly impossible German code. By breaking the code, they could very well save Britain

"From Quiet Woods to Tide Kissed Shore" : Searching for the Colonial Port of Sunbury, Georgia

This thesis chronicles efforts to examine a unique colonial waterfront complex in Sunbury, Georgia comprised of four distinct colonial wharf sites. To carry out an explanation of these features and Sunbury's overall land-water interface, this thesis utilizes Immanuel Wallerstein's World-Systems Theory in conjunction with extensive historical research and archaeological survey. The project's primary aim will be to identify novel aspects of Sunbury's economy and society through archaeology. Secondary goals include an investigation into the port's role locally and abroad. A corollary to this aim will be to connect the lifespan of the wharf sites to larger forces affecting the town.M.A

“A house recommended”: the sensory archaeology of sexuality, embodiment, and creation of space in a mid-nineteenth-century brothel in Boston, Massachusetts

Few verifiable first-hand accounts of the lives of past sex workers exist. What, then, were their daily lives like? Can archaeology assist us in understanding the daily lived experiences of sex workers, brothel managers, and visitors to the brothel? Despite excellent research in this subject, archaeologists have yet to adequately address the daily lived experiences within sites of prostitution. Using artifacts collected from the privy feature of the 27/29 Endicott Street house lot in Boston’s North End neighborhood, this dissertation examines the relationships among embodiment (or the exterior and interior experiences of the body), sensual experience, and identity through analysis of “assemblages of practice,” or artifacts used together to accomplish specific projects in everyday life (e.g., personal grooming, presentation of self, dining, place-making). Employing theories of embodiment and an archaeology of the senses, my study of the Endicott Street collection contributes a new methodological and theoretical framework for studying the archaeology of prostitution across time, space, and culture. Through the analysis of household artifacts such as teawares and lighting, geographic location in the city, and historical crime reports, I determined that the brothel environment was constructed both to avoid police notice and to provide an atmosphere of genteel anonymity to its customers. Likewise, the embodied experiences of women working here were as much a part of the brothel’s economy as were services offered in addition to sex. Artifact and documentary evidence suggests that the closing of the brothel and the filling of the brothel privy appear to signify the end of financial prosperity at the property. Ultimately, this dissertation finds that the practice of nineteenth-century sex work involved a careful construction of fantasy for brothel customers, and that this fantasy had the potential to provide financial stability and security for the madam of the establishment, if not for the women working as prostitutes