Search results for "Data_CODINGANDINFORMATIONTHEORY"
showing 10 items of 196 documents
Online channel adoption in supermarket retailing
2021
Abstract Introducing a new online channel is a crucial decision for brick-and-mortar retailers that requires insight and forecasts into customers' adoption and subsequent behaviour. The aim of this study is to analyse the dynamics in the behavioural heterogeneity of (new) multichannel supermarket customers when the online channel is introduced. A Latent Class Analysis (LCA) was conducted on 1151 adopters of the new online channel of a supermarket retailer to segment customers. We employed an extended “Recency, Frequency and Monetary (RFM)” model that includes customers’ purchases prior to the introduction of the new channel. Results show that adopters of a new channel are not a homogenous g…
A Single radio based channel datarate-aware parallel rendezvous MAC protocol for cognitive radio networks
2009
Channel hopping based parallel rendezvous multichannel MAC protocols have several advantages since they do not need a control channel, require only one transceiver, and produce higher system capacity. However, channel hopping sequences in existing parallel rendezvous MAC protocols have been designed as irrelevant to channel datarates, leading to under-utilization of channel resources in multi-rate multi-channel networks. Considering that datarates among channels may be different, we propose a dynamic parallel rendezvous multichannel MAC protocol for synchronized cognitive radio networks in which the secondary users adjust their own distinct hopping sequences according to the datarates of th…
Energy-efficient resource allocation for OFDMA two-way relay networks with imperfect CSI
2015
Most of the existed works on the radio resource allocation (RRA) problem commonly assume the channel-state information (CSI) can be perfectly obtained by the transmission source. However, such assumption is not practical in the realistic wireless systems. In this work, we consider the practical implementation issues of resource allocation in orthogonal frequency division multiple access (OFDMA) two-way relay networks: the inaccuracy of channel-state information (CSI) available to the source. Instead, only the estimated channel status is known by the source. In this context, a joint optimization of subcarrier pairing and allocation, relay selection, and transmit power allocation is formulate…
Fixed Costs Per Shipment
2011
Exporting firms do not only decide how much of their products they ship abroad but also at which frequency. Doing so, they face a trade-off between saving on fixed costs per shipments (by shipping large amounts infrequently) and saving on storage costs (by delivering just in time with small and frequent shipments). The firm's optimal choice defines a mapping from size and frequency of shipments to fixed costs per shipment. We use a unique dataset of Swiss cross-border trade on the transaction level to analyze the size and shape of the underlying fixed costs. The data suggest that for the average Swiss exporter the fixed costs per shipment are economically important: 0.82 percent of the valu…
Joint LMMSE equalizer for HSDPA in full-rate space time transmit diversity schemes
2005
This contribution presents a joint linear minimum mean square error (LMMSE) equalizer for full-rate space-time transmit diversity multi-code schemes based on W-CDMA, featuring two and four transmit antennas. Specifically, high-rate, high load systems are targeted, in order to analyze the high speed downlink packet access (HSDPA) of 3GPP Release 6. We derive an equivalent transmission scheme to equalize the received sufficient statistic in a single stage. To reduce the effects of multipath and multiuser interference, and to provide spatial and frequency diversity at the receiver, an LMMSE equalizer is employed. Computer simulations confirm that the proposed schemes achieve robust performance…
Testing the H.264 error-resilience on wireless ad-hoc networks
2004
The purpose of this paper is to provide a framework to tune and evaluate the performance of the H.264 codec in 802.11b wireless ad-hoc networks. The codec's error-resilience features are measured under stress conditions typical to these networks, and the most critical parameters are presented. We present solutions concerning the random packet loss problem and show how to quickly recover from packet loss bursts.
On the Provisioning of Mobile Digital Terrestrial TV Services to Vehicles With DVB-T
2012
[EN] Most of the DVB-T (Digital Video Broadcasting -Terrestrial) networks deployments worldwide have been designed for fixed rooftop antennas and high transmission capacity, not providing good coverage level for vehicular mobile reception. This letter analyzes how to combine different technical solutions, so far studied individually, in order to increase the robustness of the transmission for vehicular reception to provide in-band mobile services. In particular, we consider: receive antenna diversity, hierarchical modulation, and Application Layer Forward Error Correction (AL-FEC). Performance evaluation results have been obtained by means of simulations, laboratory tests, and field measure…
Mobile radio channel models for present and future wireless communication systems
2008
From the beginnings of mobile communication, there is a high demand for realistic models for mobile fading channels. The reason for the demand is that channel models are essential for the performance evaluation, parameter optimisation, and test of mobile communication systems. Design methods for mobile fading channels are therefore of great importance for system engineers who are involved in the development of present and future mobile communication systems. In this presentation, an overview will be given about several design methodologies commonly used for the design of mobile radio channel models in present and future wireless communication systems. All presented channel models have in co…
BEP analysis of M-ary PSK modulation schemes over double Rice fading channels with EGC
2010
In this article, the performance of M-ary phase shift keying (PSK) modulation schemes over mobile-to-mobile (M2M) fading channels with equal gain combining (EGC) in cooperative networks is analyzed. Narrowband M2M fading channels under line-of-sight (LOS) propagation conditions are modeled as double Rice processes. A dual-hop amplify-and-forward relay network, where LOS components can exist in the transmission links between the source mobile station and the destination mobile station via K mobile relays, is studied. Here, the average bit error probability (BEP) is utilized to evaluate the performance of Mary PSK modulation schemes. A simple analytical approximation for the average BEP of M-…
Enabling Retransmissions for Achieving Reliable Multicast Communications in WSNs
2016
To ensure end-to-end reliable multicast or broadcast transmissions in IEEE 802.15.4 based wireless sensor networks WSNs) is a challenging task since no retransmission and acknowledgment mechanisms are defined in such WSNs. In this paper, we propose three retransmission enabled multicast transmission schemes in order to achieve reliable packet transmissions in such networks. Different from the legacy CSMA/CA principle, these schemes allow a sending or forwarding node to retransmit a packet if necessary and enable implicit or/and explicit acknowledgment for multicast services. Simulations are performed in order to assess the performance of these schemes in terms of number of retransmissions, …