Measurement and modeling of interference for multiple antenna system

Journal ArticleThis paper provides a detailed signal model based on network theory to predict the multi-antenna capacity in the presence of co- and adjacent channel interference. This model expands on previous channel models by including the simultaneous effects of interference, antenna matching, efficiency, directivity and polarization. Single and multi-antenna interference are modeled using both a statistical channel model and a site-specific 3D ray tracer. The network theory based detailed signal model was obtained by adding antenna front end effects at both the transmitter and receiver to the channel models. This model was validated with measurements performed in two underground tunnels. The site-specific model predicted the capacity to within 1 bit/sec/Hz of the measurements while the statistical model was within 1-2 bits/sec/Hz except for a few locations. It was also observed that for small antenna spacing the conjugate match provides higher capacity than the self match

Low Latency Geo-distributed Data Analytics

Low latency analytics on geographically distributed dat-asets (across datacenters, edge clusters) is an upcoming and increasingly important challenge. The dominant approach of aggregating all the data to a single data-center significantly inflates the timeliness of analytics. At the same time, running queries over geo-distributed inputs using the current intra-DC analytics frameworks also leads to high query response times because these frameworks cannot cope with the relatively low and variable capacity of WAN links. We present Iridium, a system for low latency geo-distri-buted analytics. Iridium achieves low query response times by optimizing placement of both data and tasks of the queries. The joint data and task placement op-timization, however, is intractable. Therefore, Iridium uses an online heuristic to redistribute datasets among the sites prior to queries ’ arrivals, and places the tasks to reduce network bottlenecks during the query’s ex-ecution. Finally, it also contains a knob to budget WAN usage. Evaluation across eight worldwide EC2 re-gions using production queries show that Iridium speeds up queries by 3 × − 19 × and lowers WAN usage by 15% − 64 % compared to existing baselines

Measurement and modeling of multiuser multiantenna system in aircraft in the presence of electromagnetic noise and interference

ManuscriptThis paper evaluates the accuracy with which the performance of a multi-user multi-antenna system can be predicted with and without considering co-channel interference and noise (Gaussian, α- stable and Cauchy) using a site-specific 3D ray-tracing algorithm as well as with statistical models with Gaussian and Nakagami-m channel models in small to medium sized aircraft. These models expand on previous statistical channel models such as the hyper-Rayleigh model by including the simultaneous effects of co- and adjacent channel interference, antenna matching, efficiency, directivity and polarization as well as (for the 3D model) site-specific multipath effects. Measurements and comparisons are made in a metallic-bodied Beech Baron BE 58P and a composite structure Rockwell T-39 Sabreliner. It was found that the 3D ray tracing model provides a mean capacity within 1 % of those measured in the two aircraft in the presence of interference and noise. This was closely followed by the Nakagami-m distribution (m=1.4) which was within 1-3% of measured capacity in the presence of interference and within 6% for a combination of interference and noise and the Gaussian model which was within 6% of measured capacity in the presence of interference and within 11% for a combination of interference and noise . The Cauchy noise degraded the capacity more than the other types of noise in the aircraft, providing a lower bound for capacity in an aircraft system

Antenna optimization for vehicular environments

Journal ArticleAbstract? This paper presents a multi-antenna optimization for communication in a Rockwell T-39 Sabreliner, a mid-size aircraft with a metallic body. The aircraft channel at 2.45 GHz is modeled using site specific 3D ray-tracing software. Added effects from system details including the antenna radiation patterns, mutual coupling, etc. are incorporated into a network theory based detailed signal model. The paper considers traditional antennas including dipoles, square patches, PIFAs, and polarization agile patches along with some more complex shaped patches and PIFAs. A random search algorithm was used to optimize capacity for arrays with widely divergent element count, element type, matching, directivity, polarization alignment, efficiency, spatial correlation and coupling. The polarization agile patch provides the best capacity for locations near the aircraft ceiling while the PIFAs with more variety in shape (spiral shapes) provide the best capacity for locations near the floor. This is because the signals reaching the roof and sides contain more polarization diversity than those in the center of the body where the nonconductive floor is located

Low latency via redundancy

Low latency is critical for interactive networked applications. But while we know how to scale systems to increase capacity, reducing latency --- especially the tail of the latency distribution --- can be much more difficult. In this paper, we argue that the use of redundancy is an effective way to convert extra capacity into reduced latency. By initiating redundant operations across diverse resources and using the first result which completes, redundancy improves a system's latency even under exceptional conditions. We study the tradeoff with added system utilization, characterizing the situations in which replicating all tasks reduces mean latency. We then demonstrate empirically that replicating all operations can result in significant mean and tail latency reduction in real-world systems including DNS queries, database servers, and packet forwarding within networks

A novel conductometric titration approach for rapid determination of boron

21-30In laboratories dealing with radioactive samples it is important to minimize both the sample size and also the associated waste generated in an analysis. To meet this objective a rapid conductometric titration technique is developed to determine boron in the moderators of Pressurized Heavy Water Reactors (PHWR’s). Using this novel PC interfaced titration facility a minimum tenfold reduction in sample size is achieved compared to conventional conductometric titration. Determination of boron is based on the conversion of extremely weak boric acid to better conducting boron mannitol complex and titrating the complex against NaOH. Various parameters affecting the analysis, when moving from large to small sample size, are analyzed and optimized. The technique is primarily proposed for the assay of boron (≥0.5 ppm) during reactor startup. Each analysis requires less than 10 min. The detection limit is 0.5 ppm and the precision obtained at this level is 4.6% RSD. The technique is a good alternative to less sensitive carminic acid based spectrophotometric method

A divide and conquer strategy for the maximum likelihood localization of low intensity objects

In cell biology and other fields the automatic accurate localization of sub-resolution objects in images is an important tool. The signal is often corrupted by multiple forms of noise, including excess noise resulting from the amplification by an electron multiplying charge-coupled device (EMCCD). Here we present our novel Nested Maximum Likelihood Algorithm (NMLA), which solves the problem of localizing multiple overlapping emitters in a setting affected by excess noise, by repeatedly solving the task of independent localization for single emitters in an excess noise-free system. NMLA dramatically improves scalability and robustness, when compared to a general purpose optimization technique. Our method was successfully applied for in vivo localization of fluorescent proteins

Tachyon: Reliable, Memory Speed Storage for Cluster Computing Frameworks

Tachyon is a distributed file system enabling reliable data sharing at memory speed across cluster computing frameworks. While caching today improves read workloads, writes are either network or disk bound, as replication is used for fault-tolerance. Tachyon eliminates this bottleneck by pushing lineage, a well-known technique, into the storage layer. The key challenge in making a long-running lineage-based storage system is timely data recovery in case of failures. Tachyon addresses this issue by introducing a checkpointing algorithm that guarantees bounded recovery cost and resource allocation strategies for recomputation under commonly used resource schedulers. Our evaluation shows that Tachyon outperforms in-memory HDFS by 110x for writes. It also improves the end-to-end latency of a realistic workflow by 4x. Tachyon is open source and is deployed at multiple companies.National Science Foundation (U.S.) (CISE Expeditions Award CCF-1139158)Lawrence Berkeley National Laboratory (Award 7076018)United States. Defense Advanced Research Projects Agency (XData Award FA8750-12-2-0331