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Over the air testing of multiple antenna systems has attracted great attention in recent years. The research and standardization work have been focused on evaluating user equipment (UE) in two dimension (2D) radio propagation channel models. This paper proposes two future direction of over the air testing: 1) performance evaluation of WiFi devices under realistic propagation scenarios and 2) 3D radio...
Parallel file systems are important infrastructures for both cloud and high performance computing. The performance of metadata operations is critical to achieve high scalability in parallel file systems. Nevertheless, traditional parallel file systems are lack of scalable metadata service. To alleviate these problems, some previous research distributes metadata to separated large-scale clusters and...
The data scale in many data centers is growing explosively with emerging applications and usages of big data technologies. Data distribution is a key issue in large-scale distributed storage systems to place petabytes of data or even beyond, among tens or hundreds of thousands of storage devices. In the meantime, heterogeneous storage systems, such as those having devices with hard disk drives (HDDs)...
A Virtual Private Network (VPN) is a technology that is used to securely connect private network passing through a public network such as the Internet. Using a VPN, a computer, tablet, or smartphone is able to securely connect with others in the Internet as if they were part of a private network. Using this technology may also bring security threats like spoofing, snipping, and hacking as the data...
This paper provide an overview of behaviour of transition mechanisms, with and without VPN Protocols. Performance metrics related to networks have been gathered from test-bed implementations. The two transition mechanisms we will be evaluating are 4to6 and 6to4. Both of these mechanism have certain advantages and disadvantages. VPN protocols, PPTP and IPsec were configured on the transition mechanism...
In this paper, we propose a multi-layer multicast routing protocol for multi-hop mobile ad hoc cognitive radio (CR) networks. The proposed protocol employs a probabilistic approach in performing the channel assignment and path selection process based on the concept of minimum spanning tree (MST). Our protocol accounts for the unique features of CR operating environment. Simulations experiments are...
We derive the Multiple-Input Multiple-Output (MIMO) efficiency of the Zero-Forcing (ZF) receiver algorithm in Random Line-Of-Sight (Random-LOS). We make use of the Probability-of-Detection (PoD) curves based on the ideal digital threshold receiver model in the derivations. We show that the MIMO efficiency in this case, is mainly determined by two factors: the smallest channel gain of the two available...
High-velocity data imposes high durability overheads on Big Data technology components such as NoSQL data stores. In Apache Cassandra, a widely used NoSQL solution with high scalability and availability, write-ahead logging is used to support Commitlog operations, which in turn provides fault tolerance to applications. However, current write-ahead logging techniques are limited by the excessive overhead...
Distributed key-value stores have become indispensable for large scale low latency applications. Many cloud services have deployed in-memory data grids for their enterprise infrastructures and support multi-tenancy services. But it is still difficult to provide consistent performance to all tenants for fluctuating workloads that need to scale out. Many popular key-value stores suffer from performance...
Software-defined networking (SDN) is moving from its initial deployment in small-scale data center networks to large-scale carrier-grade networks. In such environments, high availability and scalability are two of the most prominent issues and thus extensive work is ongoing. In this paper, a well-known open source project, OpenDaylight (ODL) is analyzed in terms of network state database partition/synchronization...
802.11 (WiFi) networks have become increasingly important for our daily lives. However, previous work has shown that enterprise WiFi performance is often unsatisfactory and that over-utilization and interference from rogue APs are the two primary reasons. To address the above problem, this paper proposes to improve the capacity of WiFi infrastructures by increasing the enterprise AP deployment density,...
Multiple asynchronous devices, that exploit a pool of radio resources to communicate, form a key 5G communication scenario. Considering multicarrier transmission for this scenario, the expected multiuser synchronization errors at a receiving node, may be compensated by inserting guard subcarriers between transmissions from different devices. We analyze the radio resource overhead due to the use of...
In our previous work, we had proposed a distributed storage system which aims to optimize the locations of data blocks on the basis of their access frequency. In order to relocate data blocks at an appropriate node, each node should collect fresh information about storage utilization of other nodes. However, frequent information exchange might become the cause of network congestion. In this paper,...
The paper presents a methodology proposal for testing and evaluation of communication systems in Smart Grids, especially for Power Line Communication (PLC) systems. The PLC technology is widely used in power grid as a part of Advanced Metering Infrastructure (AMI) allowing mainly data transfers between a management system at utility and customer-premises smart meters. However, the PLC technology on...
For IoT applications that require near real-time wireless connections, the traditional TCP protocol is not adept enough due to the size of its packet header, its conservative Additive Increase Multiplicative Decrease (AIMD) congestion control algorithm and its slow start strategy. This paper mainly evaluates three kinds of reliable UDP-based transport protocols namely, RUBDP, UDT, and PA-UDP, for...
This paper deals with the problem of severe wireless performance degradation when multiple wireless technologies are concurrently utilized in a same user device. This type of usage is already frequent in most smartphones and laptops, such as streaming Bluetooth audio while using a Wi-Fi download, and is more intensifying with IoT device deployment which triggers the coexistence of heterogeneous wireless...
A hybrid scheme of femtocell and distributed antenna system (DAS) is proposed that utilizes a subband dedicatedly assigned to each of multiple femtocells for system capacity gain and a subband shared for DAS simulcasting for cell-edge interference reduction. This paper presents a fundamental downlink performance evaluation and analysis of the in-building wireless system. Proportional fair (PF) scheduling...
TV White Spaces (TVWS) and associated spectrum sharing mechanisms represent key means of realizing necessary prime-frequency spectrum for future wireless communication systems. We have been leading a major trial of TVWS technology within the Ofcom TV White Spaces Pilot. As one aspect of the work of our trial, we have investigated solutions for aggregation in TVWS and as part of that the performance...
The traffic growth as well as the diversity in Quality of Service (QoS) requirements are drastically increasing the challenges in achieving effective network management. The need to handle dynamic QoS requests exacerbates such challenges and dictates novel solutions able to make network management more flexible and adaptable to traffic changes. To this aim, in this paper we propose a novel approach...
We provide a case study of current inefficiencies in how traffic to well-known cloud-storage providers (e.g., Dropbox, Google Drive, Microsoft OneDrive) can vary significantly in throughput (e.g., a factor of 5 or more) depending on the location of the source and sink of the data. Our case study supplements previous work on resilient overlay networks (RON) and other ideas. These inefficiencies exist...
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