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The use of statistical eigen-beamforming is effective in spatially correlated fading environments, but it may suffer from interference near the sector boundary when applied to the downlink with universal frequency reuse. This interference effect may not sufficiently be handled by a minimum mean square error (MMSE) receiver unless a sufficient number of receive antennas are employed. In this paper,...
In wireless sensor networks (WSN) location awareness is required to use the communication advantages of adaptive antenna arrays (AAA) and use energy efficiency location based routing protocols. In this work, we introduce a simple and practical location estimation technique which uses AAAs at the central node in WSNs. This localization technique can be used at the setup phase in the location based...
Recently, a new class of space-time trellis codes was proposed as having the best performance. These codes are dasiabalancedpsila because they use the points of the constellation with the same probability. In this correspondence, we propose a new and simpler method than existing method to design these class for QPSK modulation and several transmit antennas. New and better balanced codes for 3 and...
Propagation model tuning is a fundamental part of everyday GSM cellular engineering practice. The model tuning is usually accomplished through elaborate and costly tests based on CW measurements. This paper evaluates alternatives to CW testing where measurements are collected using GSM scanners and GSM high dynamic range receivers. The results of the analysis reveal that GSM receivers provide a viable...
In this paper we proposed a novel self-organized message dissemination algorithm, namely the cluster-based broadcast (CB), for the emergency electronic brake light (EEBL) application in vehicular ad-hoc networks (VANET). The proposed cluster-based broadcast algorithm converts multihop broadcast message forwarding into multiple of single-hop broadcast clusters, which offers higher reliability, lower...
WLAN, based on the IEEE 802.11 standard has been extensively studied since its release. In addition to infrastructure access to WLAN, mesh networks currently attract a lot of attention. This comes from the envisioned advantages of wireless mesh networks, such as cheap installation costs, extended coverage, robustness, easy maintenance, and self-configuration possibilities. In this paper we focus on...
There are two basic duplexing schemes for present and future mobile radio networks, frequency-division duplex (FDD) and time-division duplex (TDD). In general each of these methods has its benefits and drawbacks. However, both schemes have their scenarios where they perform best. In future mobile radio systems typical wireless data communication will not only occur in metropolitan area scenarios like...
The EU FP6 ANGEL project considers the usage of IEEE 802.15.4-based wireless sensor network technology in medical applications. Some key requirements found in this class of applications are not well supported by IEEE 802.15.4. In this paper we propose a wrapper layer on top of IEEE 802.15.4 that adds, amongst others, a mechanism combining priority queueing and per-packet parameter control to provide...
60 GHz wireless networks have the potential to support high data rate applications, but have short range transmission limitations due to larger propagation losses and reduced diffraction around obstacles. On the other hand, directional antennas are easier to implement at millimeter wavelengths and can provide benefits such as spatial reuse and higher transmission range. This paper proposes a network...
Digital video broadcasting for handheld terminals (DVB-H) is assuming an aver growing importance for digital video transmission over wireless terminals In this context, services are transmitted in ldquopacketsrdquo or ldquoburstsrdquo periodically repeating in time and interspaced by ldquooff-timerdquo periods. To improve this time sliced transmission effectiveness, a novel technique, the variable...
In this paper a mathematical model for the non-beacon enabled mode of the IEEE 802.15.4 Multiple access control (MAC) protocol, is provided. A wireless sensor network (WSN) composed of nodes which transmit data to a sink through direct links, is considered. Upon reception of a query from the sink, the nodes transmit their packets by using the carrier sensing multiple access with collision avoidance...
Media-based services often require a multicast-enabled transport that guarantees quasi error free transmission under strict delay constraints. In packet based networks, furthermore, both multicast and delay constraints deeply influence the architecture of erasure error recovery. Therefore, we propose a general architecture and study its optimization in this paper. Since the Gilbert-Elliot (GE) erasure...
We consider a situation where a transmitter has a batch of packets in its buffers and wants to transmit these in one go and in a semi-reliable fashion to an arbitrary subset of its neighbors over error-prone channels. We design schemes that let the transmitter node control the sleeping activities of the receivers (in order to save energy) and which adapt the sequence in which receivers are addressed...
In this paper, the tail-biting convolutional code (TBCC) performance of the 802.16e Orthogonal Frequency-Division Multiple Access (OFDMA) frame control header (FCH) is studied It is known that the performance and the weight spectrum of a TBCC depend on the paylod size. Therefore, the search for optimal generator polynomials should be done accordingly. In 802.16e, a rate-1/2, memory-6 TBCC that has...
In this paper we design interleavers for bit-interleaved coded modulation (BICM) based on popular convolutional codes and quadrature amplitude modulation with Gray mapping. We analyze the so-called modular interleavers where the outputs of the convolutional encoder are appropriately matched with the input bits of the modulator. To quantify the achievable improvements we develop bounds on the coded...
The hybrid hierarchical architecture (HHA) represents a particular case of wireless hybrid network, where sensor nodes transmit their samples to an infrastructure network through multiple hops. In the HHA, gateway terminals implementing both cellular and infrastructure-less air interfaces, allow integration of the two separate paradigms characterising the wireless sensor network (WSN) and the cellular...
In the last years many different technologies and air interfaces have been standardized. B3G systems will allow the integration and coexistence of these diverse technologies in a common environment. It is a priority objective of this scenario of have a flexible terminal that can dynamically select the most appropriate RAT and reconfigure itself from the physical to the application layer. This reconfiguration...
Opportunistic Routing gained lots of attention as a way to improve the performance of wireless multi-hop relay mesh networks. The key characteristic is its ability to take advantage of the numerous, yet unreliable wireless links in the network. The most important part of every opportunistic routing protocol is the forwarder selection algorithm. Most of the currently known protocols assume that signal...
In this contribution we present the results of a study on satellite to outdoor channel modeling for satellite systems with multiple satellites. Our model for several satellites is based on a first order Markov channel state model for joint processes. The probability density function (PDF) of the signal amplitude within each state is fitted to the Loo distribution. The parameters of our model are based...
In the wireless local area network (WLAN) standard IEEE 802.11b, complementary code keying (CCK) modulation has been adopted for the high data rate transmission mode. In this paper, complexity reduction for block decision-feedback equalization (bDFE), tailored for CCK transmission over frequency-selective channels, is considered. Since the CCK signal may be viewed as a linear block code with respect...
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