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Wireless Access (wireless + access)

Distribution by Scientific Domains

Engineering	83%

Selected Abstracts

Broadband wireless access based on VSF-OFCDM and VSCRF-CDMA and its experiments

EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 3 2004
Hiroyuki Atarashi
This paper presents broadband packet wireless access schemes based on variable spreading factor (VSF)-orthogonal frequency and code division multiplexing (OFCDM) in the downlink and variable spreading and chip repetition factors (VSCRF)-CDMA in the uplink for the systems beyond IMT-2000. In our design concept for wireless access in both links, radio parameters such as the spreading factor (SF) are optimally controlled so that the system capacity is maximized according to the cell configuration, channel load and radio channel conditions, based on the tradeoff between efficient suppression of other-cell interference and the capacity increase in the target cell by exploiting orthogonality in the time and frequency domains. We demonstrate that the peak throughput of greater than 100,Mbps and 20,Mbps is achieved by the implemented base station and mobile station transceivers using the 100-MHz and 40-MHz bandwidths in the downlink and uplink respectively. Moreover, the simulation results show the possibility of the peak throughput of approximately 1,Gbps for short-range area applications using the 100-MHz bandwidth OFCDM downlink by applying four-branch multiple input multiple output (MIMO) multiplexing with 16,QAM data modulation and punctured turbo coding. Copyright © 2004 AEI [source]

Layered view of QoS issues in IP-based mobile wireless networks

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2006
Haowei Bai
Abstract With the convergence of wireless communication and IP-based networking technologies, future IP-based wireless networks are expected to support real-time multimedia. IP services over wireless networks (e.g. wireless access to Internet) enhance the mobility and flexibility of traditional IP network users. Wireless networks extend the current IP service infrastructure to a mix of transmission media, bandwidth, costs, coverage, and service agreements, requiring enhancements to the IP protocol layers in wireless networks. Furthermore, QoS provisioning is required at various layers of the IP protocol stack to guarantee different types of service requests, giving rise to issues related to cross-layer design methodology. This paper reviews issues and prevailing solutions to performance enhancements and QoS provisioning for IP services over mobile wireless networks from a layered view. Copyright © 2006 John Wiley & Sons, Ltd. [source]

WTCP: an efficient mechanism for improving wireless access to TCP services

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 1 2003
Karunaharan Ratnam
Abstract The transmission control protocol (TCP) has been mainly designed assuming a relatively reliable wireline network. It is known to perform poorly in the presence of wireless links because of its basic assumption that any loss of a data segment is due to congestion and consequently it invokes congestion control measures. However, on wireless access links, a large number of segment losses will occur more often because of wireless link errors or host mobility. For this reason, many proposals have recently appeared to improve TCP performance in such environment. They usually rely on the wireless access points (base stations) to locally retransmit the data in order to hide wireless losses from TCP. In this paper, we present Wireless-TCP (WTCP), a new mechanism for improving wireless access to TCP services. We use extensive simulations to evaluate TCP performance in the presence of congestion and wireless losses when the base station employs WTCP, and the well-known Snoop proposal (A comparison of mechanisms for improving TCP performance in wireless networks. In ACM SIGCOMM Symposium on Communication, Architectures and Protocols, August 1996). Our results show that WTCP significantly improves the throughput of TCP connections due to its unique feature of hiding the time spent by the base station to locally recover from wireless link errors so that TCPs round trip time estimation at the source is not affected. This proved to be critical since otherwise the ability of the source to effectively detect congestion in the fixed wireline network is hindered. Copyright © 2003 John Wiley & Sons, Ltd. [source]

From anytime, anywhere to all-the-time, everywhere: Learning objects, broadband and wireless reshape digital libraries for learning and research.

PROCEEDINGS OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE & TECHNOLOGY (ELECTRONIC), Issue 1 2003
Sponsored by SIG STI
Learning objects are among the latest types of materials to be included in digital libraries. These are small portions of lesson material designed to be used in multiple configurations for multiple instructional applications, ranging from distance learning to interactive simulation. As broadband and wireless technologies change the expectations and performance patterns of the user, learning objects change the nature of content and the way that it must be managed. The size and diversity of digital collections affect the options through which these materials can be accessed. Many libraries are offering wireless access to their networks and many individuals are accessing digital libraries off-site using broadband technologies. Each of these trends affects decisions made for collection development, portal design and network design, and those decisions dictate specific technological requirements for access. This panel session highlights management and infrastructure issues of digital libraries as they relate to learning objects, broadband and wireless technologies. [source]