High-throughput Communication Research Articles

Hybrid Optical RF Airborne Communications

The use of hybrid free-space optical (FSO)/radio-frequency (RF) links to provide robust, high-throughput communications, fixed infrastructure links, and their associated networks have been thoroughly investigated for both commercial and military applications. The extension of this paradigm to mobile, long-range networks has long been a desire by the military communications community for multigigabit mobile backbone networks. The FSO communications subsystem has historically been the primary limitation. The challenge has been addressing the compensation of propagation effects and dynamic range of the received optical signal. This paper will address the various technologies required to compensate for the effects referenced above. We will outline the effects FSO and RF links experience and how we overcome these degradations. Results from field experiments conducted, including those from the Air Force Research Laboratory Integrated RF/Optical Networked Tactical Targeting Networking Technologies (IRON-T2) program, will be presented.

Construction of vertex-disjoint paths in alternating group networks

The existence of parallel node-disjoint paths between any pair of nodes is a desirable property of interconnection networks, because such paths allow tolerance to node and/or link failures along some of the paths, without causing disconnection. Additionally, node-disjoint paths support high-throughput communication via the concurrent transmission of parts of a message. We characterize maximum-sized families of parallel paths between any two nodes of alternating group networks. More specifically, we establish that in a given alternating group network AN n , there exist n?1 parallel paths (the maximum possible, given the node degree of n?1) between any pair of nodes. Furthermore, we demonstrate that these parallel paths are optimal or near-optimal, in the sense of their lengths exceeding the internode distance by no more than four. We also show that the wide diameter of AN n is at most one unit greater than the known lower bound D+1, where D is the network diameter.

SafeMesh: A wireless mesh network routing protocol for incident area communications

Reliable broadband communication is becoming increasingly important during disaster recovery and emergency response operations. In situations where infrastructure-based communication is not available or has been disrupted, an Incident Area Network needs to be dynamically deployed, i.e. a temporary network that provides communication services for efficient crisis management at an incident site. Wireless Mesh Networks (WMNs) are multi-hop wireless networks with self-healing and self-configuring capabilities. These features, combined with the ability to provide wireless broadband connectivity at a comparably low cost, make WMNs a promising technology for incident management communications. This paper specifically focuses on hybrid WMNs, which allow both mobile client devices as well as dedicated infrastructure nodes to form the network and provide routing and forwarding functionality. Hybrid WMNs are the most generic and most flexible type of mesh networks and are ideally suited to meet the requirements of incident area communications. However, current wireless mesh and ad-hoc routing protocols do not perform well in hybrid WMN, and are not able to establish stable and high throughput communication paths. One of the key reasons for this is their inability to exploit the typical high degree of heterogeneity in hybrid WMNs. SafeMesh, the routing protocol presented in this paper, addresses the limitations of current mesh and ad-hoc routing protocols in the context of hybrid WMNs. SafeMesh is based on the well-known AODV routing protocol, and implements a number of modifications and extensions that significantly improve its performance in hybrid WMNs. This is demonstrated via an extensive set of simulation results. We further show the practicality of the protocol through a prototype implementation and provide performance results obtained from a small-scale testbed deployment.

Design and implementation of low-energy turbo decoders

Turbo codes have been chosen in the third generation cellular standard for high-throughput data communication. These codes achieve remarkably low bit error rates at the expense of high-computational complexity. Thus for hand held communication devices, designing energy efficient Turbo decoders is of great importance. In this paper, we present a suite of MAP-based Turbo decoding algorithms with energy-quality tradeoffs for additive white Gaussian noise (AWGN) and fading channels. We derive these algorithms by applying approximation techniques such as pruning the trellis, reducing the number of states, scaling the extrinsic information, applying sliding window, and early termination on the MAP-based algorithm. We show that a combination of these techniques can result in energy savings of 53.2%(50.0%) on a general purpose processor and energy savings of 80.66%(80.81%) on a hardware implementation for AWGN (fading) channels if a drop of 0.35 dB in SNR can be tolerated, at a bit error rate (BER) of 10/sup -5/. We also propose an adaptive Turbo decoding technique that is suitable for low power operation in noisy environments.

Compensating for moderate effective throughput at the desktop

This article presents the design and development of a networking system architecture targeted to support high-speed TCP/IP communication over ATM. The discussed architecture has been developed in the form of an integrated system which incorporates state-of-the-art software and hardware subsystems, and an OC-12c ATM adapter (622 Mb/s). Moreover, the design of this embedded system has been based on the Chorus real-time operating system, which, in turn, hosts an accelerated TCP/IP protocol stack over ATM. Furthermore, the embedded system board has been developed according to the PCI specification to easily be plugged into a host platform. In addition, the OC-12c ATM adapter subsystem has been designed and developed in order to also be plugged into the same host. The developed architecture has proven very efficient and reliable, providing high-throughput and low-latency bulk data communications. The measured performance on an OC-3c-based (155 Mb/s) testbed has shown that an optimally implemented TCP/IP stack, hosted by a real-time kernel and coupled with an ATM adapter, offers a robust desktop platform for high-speed end-to-end communications. The main feature of the accelerated TCP/IP protocol stack is the out-of-band processing of control and data information. The protocol accelerator embedded system processes the TCP/IP headers and accomplishes checksum computations, while data is transferred from the host's user memory space directly to the network. Finally, for validation purposes, the prototype system has been incorporated in an existing networking infrastructure targeted to support mass storage applications.

ACS: An adaptive communication system for heterogeneous wide-area ATM clusters

This paper presents an architecture, implementation, and performance evaluation of an adaptive message-passing system for a heterogeneous wide-area ATM cluster that we call the Adaptive Communication System (ACS). ACS uses multithreading to provide efficient techniques for overlapping computation and communication in wide-area computing. By separating control and data activities, ACS eliminates unnecessary control transfers over the data path. This optimizes the data path and improves the performance. ACS supports several different flow control algorithms, error control algorithms, and multicasting algorithms. Furthermore, ACS allows programmers to select at runtime the suitable communication schemes per-connection basis to meet the requirements of a given application. ACS provides three application communication interfaces: Socket Communication Interface (SCI), ATM Communication Interface (ACI), and High Performance Interface (HPI) to support various classes of applications. The SCI is provided mainly for applications that must be portable to many different computing platforms. The ACI provides services that are compatible with ATM connection oriented services where each connection can be configured to meet the Quality of Service (QOS) requirements of that connection. This allows programmers to fully utilize the benefits of the ATM network. The HPI supports applications that demand low-latency and high-throughput communication services. In this interface, ACS uses read/write trap routines to reduce latency and data transfer time, and to avoid using traditional communication protocols. We analyze and compare the performance of ACS with those of other message-passing systems such as p4, PVM, and MPI in terms of point-to-point, multicasting, and application performance. The benchmarking results show that ACS outperforms other message-passing systems and provides flexible communication services for various classes of applications.

A High Performance Message-Passing System for Network of Workstations

With the proliferation of Network of Workstations (NOW) environment, there has been a great demand for a high performance message-passing system to implement High Performance Distributed Computing (HPDC) applications over NOW environment. NYNET (ATM wide area network testbed in New York state) Communication System (NCS) is a multithreaded message-passing system developed at Syracuse University that provides low-latency and high-throughput communication services over the Asynchronous Transfer Mode (ATM) based HPDC environment. NCS provides High Performmance Application Communication Interface (HPI) to support applications that demand high-throughput and low-latency communication services. This paper outlines the general architecture of NCS and presents the implementation approach of NCS HPI over an ATM network. This interface has been developed by modifying Fore Systems‘ ATM Application Programming Interface (API) and its device driver. NCS HPI uses read/writetrap routines to bypass traditional operating system calls and kernel-level communication interface (e.g. UNIX System V Streams). It reduces latency, data transfer time, and avoid using traditional communication protocols (e.g., TCP/IP). This substantially improves the communication performance.