ppxscal/embedding_network huggingface dataset:
On unequal error protection of finite-length LDPC codes over BECs: a scaling approach
Authors: Amir H. Djahanshahi, P. H. Siegel, L. B. Milstein
Venue: Proceedings of the 2009 IEEE international conference on Symposium on Information Theory - Volume 3 (2009)

In this paper, we explore a novel approach to evaluate the inherent UEP (unequal error protection) properties of irregular LDPC (low-density parity-check) codes over BECs (binary erasure channels). Exploiting the finite-length scaling methodology, suggested by Amraoui et. al., we introduce a scaling approach to approximate the bit erasure rates of variable nodes with different degrees in the waterfall region of the peeling decoder. Comparing the bit erasure rates obtained from Monte Carlo simulation with the proposed scaling approximations, we demonstrate that the scaling approach provides a close approximation for a wide range of code lengths (between 1000 and 8000). In view of the complexity associated with the numerical evaluation of the scaling approximation, we also derive simpler upper and lower bounds.
Secret-key sharing based on layered broadcast coding over fading channels
Authors: Xiaojun Tang, Ruoheng Liu, Predrag Spasojevic, H. Vincent Poor
Venue: Proceedings of the 2009 IEEE international conference on Symposium on Information Theory - Volume 4 (2009)

A secret-key sharing strategy based on layered broadcast coding is introduced for slow fading channels. In the model considered, Alice wants to share a key with Bob while keeping the key secret from a passive eavesdropper, Eve. Both Alice-Bob and Alice-Eve channels are assumed to undergo slow fading, and perfect channel state information (CSI) is assumed to be known only at the receivers during the transmission. Layered coding facilitates adapting the reliably decoded rate at Bob to the actual channel state without CSI available at Alice. The index of a reliably decoded layer is sent back to Alice via a public and error-free channel, which is exploited by Alice and Bob to generate the secret key. In this paper, the secrecy key rate is derived. In addition, the optimal power distribution over coded layers is characterized. It is shown that layered coding can increase the secrecy key rate significantly compared with single-level coding.
An overview of mobility management over IEEE802.16e
Authors: Lamia Chaari, Lotfi Kamoun
Venue: Proceedings of the 16th international conference on Telecommunications (2009)

Providing diverse broadband services economically every time, even to mobile subscribers will be a major challenge for the telecommunication community. IEEE 802.16 networks are going to provide broadband wireless access as a fixed wireless broadband solution. However, the IEEE 802.16e as an amendment to 802.16d which expands the standard to allow mobile subscriber station. As handover is an important aspect of mobile wireless communications, we have studied and analyzed concepts, functionalities and keys aspects to provide mobility over IEEE802.16e. This paper looks particularly at the advanced features introduced by the IEEE802.16e standard for mobility in WiMax systems in order to prove that the enhanced IEEE 802.16e system has the capability to fulfill the requirements regarding the mobility management of future telecommunication systems.
Peer assisted streaming of scalable video via optimized distributed caching
Authors: Öztan Harmanci, Sandeep Kanumuri, Ulas C. Kozat, Umut Demirçin, Reha Civanlar
Venue: Proceedings of the 6th IEEE Conference on Consumer Communications and Networking Conference (2009)

In this paper, we propose a method for peer assisted on demand delivery of scalable video using an optimal, distributed caching algorithm for cache constrained peers. We assume that there are one or more content delivery servers that are provisioned to support delivery of the base layer for all of the peers, and the enhancement layer is only supported for a fraction of peers. It has been shown that in such an application, peer assisted content distribution improves the delivery of the content. In this paper, we use peer assisted delivery of the enhancement layer and show that in a cache constrained video-on-demand environment, availability of the cached content becomes a bottleneck. By using peer arrival rates and supply-demand analysis of the peers, we propose better caching policies at each peer. One proposed policy (referred to as "static optimal") optimizes the utility of the currently available caching opportunities. The other proposed policy (referred to as "dynamic programming" solution) on the other hand performs utility optimization by further considering the future caching opportunities during the streaming operation. Experimental results show that the proposed methods allow more peers to access the enhancement layer; hence, more peers experience improved video quality compared to traditional caching methods.
Techno-economic study for a mobile WiMAX solution in an emerging market: a case study for Luanda
Authors: Bruno Lopes, Rui L. Aguiar, A. Manuel De Oliveira Duarte
Venue: Proceedings of the 16th international conference on Telecommunications (2009)

In recent years WiMAX has been presented by its promoters as a complete solution for the broadband access market. Since it is a wireless technology, it can easily serve the most remote and difficult areas. Even more important, the mobile version of WiMAX added the potential of sustainable growth and later adaptation of all its services to compete at the fixed and mobile markets. This paper attempts to analyze the relevance of WIMAX for emerging markets where the demand for broadband services is growing at a very fast pace, and Wireline infrastructures either do not exist or are not in an appropriate state of conservation. To support the study, a techno-economic analysis was performed for the region of Luanda, Angola, taking into consideration geographic and demographic conditions, different service packages, tariffs, roll-out strategies, and sensitivity to adoption rates. The results show that WiMAX can be a feasible and profitable solution specially suited for emerging markets.
Analyzing multi-fiber reconstruction in high angular resolution diffusion imaging using the tensor distribution function
Authors: Liang Zhan, Alex D. Leow, Siwei Zhu, Ming-Chang Chiang, Marina Barysheva, Arthur W. Toga, Katie L. McMahon, Greig I. de Zubicaray, Margaret J. Wright, Paul M. Thompson
Venue: Proceedings of the Sixth IEEE international conference on Symposium on Biomedical Imaging: From Nano to Macro (2009)

High-angular resolution diffusion imaging (HARDI) can reconstruct fiber pathways in the brain with extraordinary detail, identifying anatomical features and connections not seen with conventional MRI. HARDI overcomes several limitations of standard diffusion tensor imaging, which fails to model diffusion correctly in regions where fibers cross or mix. As HARDI can accurately resolve sharp signal peaks in angular space where fibers cross, we studied how many gradients are required in practice to compute accurate orientation density functions, to better understand the tradeoff between longer scanning times and more angular precision. We computed orientation density functions analytically from tensor distribution functions (TDFs) which model the HARDI signal at each point as a unit-mass probability density on the 6D manifold of symmetric positive definite tensors. In simulated two-fiber systems with varying Rician noise, we assessed how many diffusion-sensitized gradients were sufficient to (1) accurately resolve the diffusion profile, and (2) measure the exponential isotropy (EI), a TDF-derived measure of fiber integrity that exploits the full multidirectional HARDI signal. At lower SNR, the reconstruction accuracy, measured using the Kullback-Leibler divergence, rapidly increased with additional gradients, and EI estimation accuracy plateaued at around 70 gradients.
A new approach to improve multiplexing gain in decentralized networks via frequency hopping and repetition coding
Authors: Kamyar Moshksar, Amir K. Khandani
Venue: Proceedings of the 2009 IEEE international conference on Symposium on Information Theory - Volume 2 (2009)

This paper addresses a distributed signaling scheme to improve the multiplexing gain (MG) in a wireless decentralized network with a fixed number u > 1 of frequency sub-bands to be shared among K transmitter-reciever pairs. In a decentralized network, users are not aware of the code-books of each other. Hence, in the high SNR regime, interference highly degrades the achievable rates of users as canceling the interference is impossible. On the other hand, decentralized networks have no fixed underlying infrastructure, i.e., there is no central management to assign certain non-overlaping portions of the spectrum to different users. As such, choosing the same sub-band by different users may result in losing the data transmitted on this subband. These shortcomings motivate us to propose a decentralized scheme that enables all users to coexist fairly, while utilizing the spectrum efficiently. We introduce a distributed signaling scheme (using i:i:d: Gaussian code-books) called Repetition-Frequency Hopping (RFH) where all users keep transmitting the same set of independent signals over different portion of the spectrum along a certain repetition frame. Due to the dynamic nature of interference, sensing the spectrum to locate the interference is practically not possible. This makes the interference plus noise probability density function (PDF) be mixed Gaussian. We obtain upper and lower bounds on the rates of users that coincide as SNR tends to infinity. This enables us to derive a general formula for the sum-rate multiplexing gain in the network. We show that it is possible to achieve higher multiplexing gains in such systems if the length of the repetition frame along the time-axis is large enough. In fact, in many cases, there is a certain amount of repetition that leads to the highest multiplexing gain per user.
Spatial correlation characteristics of antenna systems using uniform concentric ring arrays
Authors: Ju-Hong Lee, Shou-I Li
Venue: Proceedings of the 16th international conference on Digital Signal Processing (2009)

We investigate the spatial correlation characteristics of uniform concentric ring arrays (UCRAs) deployed in antenna systems. The spatial correlation functions are derived for UCRAs with two different geometric structures and two common types of angular energy distributions, i.e., the uniform distribution and truncated Gaussian distribution. It is found that the spatial correlation is a function of antenna sensor spacing, the geometric structure of a UCRA, and the angular energy distribution. Simulation results are given for illustration and comparison.
Optimally efficient multicast in structured peer-to-peer networks
Authors: Dirk Bradler, Jussi Kangasharju, Max Mühlhäuser
Venue: Proceedings of the 6th IEEE Conference on Consumer Communications and Networking Conference (2009)

The Distributed Tree Construction (DTC) algorithm is designed for optimally efficient multicast tree construction over structured peer-to-peer networks. It achieves this by creating a spanning tree over the peers in the multicast group, using only information available locally on each peer. Furthermore, we show that the tree depth has the same upper bound as a regular DHT lookup which in turn guarantees fast and responsive runtime behavior. Our DTC algorithm is DHT-agnostic and works with most existing DHTs. We evaluate the performance of DTC over several DHTs by comparing the performance to existing application-level multicast solutions, we show that DTC sends 30-250% fewer messages than common solutions.
Cooperation in the MAC channel using frequency division multiplexing
Authors: Momin Uppal, Anders Høst-Madsen, Zixiang Xiong
Venue: Proceedings of the 2009 IEEE international conference on Symposium on Information Theory - Volume 2 (2009)

This paper considers cooperation in the low power/SNR regime for the multiple access channel. We assume that transmitters have no channel state information, and consider the outage capacity. We further assume that the nodes operate in half duplex. The nodes are multiplexed by assigning to each node a unique frequency band via frequency division multiplexing (FDM). A node transmits only on this band while listening on the others. We perform outage wideband analysis on FDM based cooperation, and show perhaps surprisingly that FDM loses very little in performance compared to the idealized situation where nodes can operate in full duplex. We then develop practical rateless coding methods for FDM using Raptor codes.
Low complexity synchronizer architecture based on common autocorrelator for digital video broadcasting system
Authors: Jang Woong Park, Myung Hoon Sunwoo, Pan Soo Kim, Dae-Ig Chang
Venue: Proceedings of the 16th international conference on Digital Signal Processing (2009)

This paper presents an efficient synchronizer architecture using a common autocorrelator for Digital Video Broadcasting via Satellite, Second generation (DVB-S2). To achieve the required performance under the worst channel condition and to implement the efficient H/W resource utilization of functional synchronization blocks, we propose a new efficient common autocorrelator structure. The proposed architecture can decrease about 92% of multipliers and 81% of adders compared with the direct implementation. Moreover, the proposed architecture has been thoroughly verified in Xilinx™ Virtex IV mid R&S™ SFU (Signaling and Formatting Unit) broadcast test equipment.
Hybrid coding for Gaussian broadcast channels with Gaussian sources
Authors: Rajiv Soundararajan, Sriram Vishwanath
Venue: Proceedings of the 2009 IEEE international conference on Symposium on Information Theory - Volume 4 (2009)

This paper considers a degraded Gaussian broadcast channel over which Gaussian sources are to be communicated. When the sources are independent, this paper shows that hybrid coding achieves the optimal distortion region, the same as that of separate source and channel coding. It also shows that uncoded transmission is not optimal for this setting. For correlated sources, the paper shows that a hybrid coding strategy has a better distortion region than separate source-channel coding below a certain signal to noise ratio threshold. Thus, hybrid coding is a good choice for Gaussian broadcast channels with correlated Gaussian sources.
Adoption of electronic trading at the International Securities Exchange
Authors: Bruce W. Weber
Venue: Decision Support Systems (2006)

Information technology is transforming financial trading, lowering costs, and increasing market transparency. Yet, new electronic trading ventures often fail to attract sufficient activity levels, and close down. Optimark, Tradepoint, Jiway, and BondConnect did not develop sufficient trading volume to survive. In contrast, the International Securities Exchange (ISE), an all-electronic options trading platform has gained trading volumes in the United States in competition with four incumbent markets, including the Chicago Board Options Exchange (CBOE). Compared with floor exchanges, electronic options markets offer immediate trading, direct user access to the market, and reduced costs. The paper describes the ISE and examines newly available data from brokerage firms to comply with the Securities and Exchange Commission's (SEC) Rule 11Ac1-6. The order routing disclosures show that brokerage firms differ widely in the extent of their use of the ISE. Based on a sample of 188 quarterly disclosures from 20 major brokerage firms, OLS, Tobit, and fixed-effects models of ISE use are estimated to explain individual firms' adoption levels. Significant factors are whether the firm is an online discount broker, the firm's membership role in the ISE, and the network externality effect of the ISE market's growth. Firm-specific factors are shown to account for about 60% of ISE adoption explained by the model, with the remaining 40% accounted for by the network effects of growing market liquidity.
Symmetric feedback capacity of the Gaussian interference channel to within one bit
Authors: Changho Suh, David Tse
Venue: Proceedings of the 2009 IEEE international conference on Symposium on Information Theory - Volume 3 (2009)

We characterize the symmetric capacity of the two-user Gaussian interference channel with feedback to within 1 bit/s/Hz. The result makes use of a deterministic model to provide insights into the Gaussian channel. We derive a new outer bound to show that a proposed scheme can achieve the symmetric capacity to within one bit for all channel parameters. One consequence of the result is that feedback provides unbounded gain, i.e., the gain becomes arbitrarily large for certain channel parameters. It is a surprising result because feedback has been so far known to provide no gain in memoryless point-to-point channels and only power gain (bounded gain) in the multiple access channels. The gain comes from using feedback to fully exploit the side information provided by the broadcast nature of the wireless medium.
On channel estimation in fast fading mobile coded MIMO OFDM
Authors: Daniel N. Liu, Michael P. Fitz, Urbashi Mitra
Venue: Proceedings of the 2009 IEEE international conference on Symposium on Information Theory - Volume 2 (2009)

Channel estimation of coded multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) in fast time-varying channels are considered. Maintaining high performance with manageable complexity relies on iterative soft-in soft-out equalization and decoding. Conventional frequency domain channel estimation methods have an irreducible error floor due to unaccounted intercarrier interference (ICI). This paper proposes an efficient and high performance time domain pilot symbol assisted modulation (PSAM) system for channel estimation. Simulation results are reported for the iterative receiver with application to the mobile worldwide interoperability for microwave access (WiMAX).
A fuzzy sets based generalization of contact maps for the overlap of protein structures
Authors: David Pelta, Natalio Krasnogor, Carlos Bousono-Calzon, José L. Verdegay, J. Hirst, Edmund Burke
Venue: Fuzzy Sets and Systems (2005)

The comparison of protein structures is an important problem in bioinformatics. As a protein biological role is derived from its three-dimensional native state, the comparison of a new protein structure (with unknown function) with other protein structures (with known biological activity) can shed light into the biological role of the former. Consequently, advances in the comparison (and clustering) of proteins according to their three-dimensional configurations might also have an impact on drug discovery and other biomedical research that relies on understanding the inter-relations between structure and function in proteins. The contributions described in this paper are: Firstly, we propose a generalization of the maximum contact map overlap problem (MAX-CMO) by means of fuzzy sets and systems. The MAX-CMO is a model for protein structure comparison. In our new model, namedgeneralized maximum fuzzy contact map overlap (GMAX-FCMO), a contact map is defined by means of one (or more) fuzzy thresholds and one (or more) membership functions. The advantages and limitations of our new model are discussed. Secondly, we show how a fuzzy sets based metaheuristic can be used to compute protein similarities based on the new model. Finally, we compute the protein structure similarity of real-world proteins and show how our new model correctly measures their (di)similarity.
NAV/COM hybrid architecture for innovative location based payment systems
Authors: F. Dominici, D. Mazzocchi, P. Mulassano, M. Spelat, G. Boiero, P. Lovisolo
Venue: Proceedings of the 6th IEEE Conference on Consumer Communications and Networking Conference (2009)

Identification and authentication procedures are really important aspects when talking about payments. Nowadays, credit and debit cards are the target for thieves since they can be easily cloned. One of the main fraud sources is represented by the Point Of Sale, the well-known POS. The paper describes an innovative payment system studied, developed and tested within the GAL-PMI Project, an initiative funded by the Industry Division of the Piedmont Region. The system provides users with a user-friendly application to perform payments by means of personal mobile devices like PDA or smartphone, using Global Navigation Satellite Systems as the baseline to increase security aspects. The paper gives an overview of this payment system architecture, going through the technlogical infrastructure that is based on navigation and communication capabilities. Finally, the paper presents a real test case, which has been set-up to demonstrate how security aspects can be improved within identification and authentication processes during payments at gas station.
A multimedia delivery architecture for IPTV with P2P-based time-shift support
Authors: Diego Gallo, Charles Miers, Vlad Coroama, Tereza Carvalho, Victor Souza, Per Karlsson
Venue: Proceedings of the 6th IEEE Conference on Consumer Communications and Networking Conference (2009)

From the four basic functionalities of video delivery systems - linear TV, Video on Demand (VoD), time-shifted TV (tsTV), and network Personal Video Recorder (nPVR) - most of today's solutions focus either on linear TV, or on VoD. While linear TV usually uses efficient distribution mechanisms such as multicast, VoD is often realized via centralized, bandwidth-inefficient unicast. Even when file sharing P2P algorithms are used for VoD or nPVR, they can not be applied to tsTV since they require the whole content to exist from the beginning. With this paper, we propose a novel solution that aims at offering all four functionalities in one distributed system. Our architecture uses multicast for the distribution of live content, and a modified P2P protocol for offering VoD, nPVR, and tsTV altogether.
Piggyback cooperative repetition for reliable broadcasting of safety messages in VANETs
Authors: Lin Yang, Jinhua Guo, Ying Wu
Venue: Proceedings of the 6th IEEE Conference on Consumer Communications and Networking Conference (2009)

Vehicle safety communication applications require safety messages to be received by all the targeted vehicles within their lifetime. We propose a piggybacked cooperative repetition approach for reliably broadcasting safety messages in VANETs. Repetitions by neighbors that receive the original transmission can effectively cover the areas that are missed in the original transmissions. Moreover, the repetitions are piggybacked by the newly generated messages so that no extra messages are injected into the network. Our experiments show a significant performance improvement, achieving over 90% reception rate of safety messages at distances up to 200 meters to the sender.
Cooperative multiplexing in the multiple antenna half duplex relay channel
Authors: Vinayak Nagpal, Sameer Pawar, David Tse, Borivoje Nikolic
Venue: Proceedings of the 2009 IEEE international conference on Symposium on Information Theory - Volume 2 (2009)

Cooperation between terminals has been proposed to improve the reliability and throughput of wireless communication. While recent work has shown that relay cooperation provides increased diversity, increased multiplexing gain over that offered by direct link has largely been unexplored. In this work we show that cooperative multiplexing gain can be achieved by using a half duplex relay. We capture relative distances between terminals in the high SNR diversity multiplexing tradeoff (DMT) framework. The DMT performance is then characterized for a network having a single antenna half-duplex relay between a single-antenna source and two-antenna destination. Our results show that the achievable multiplexing gain using cooperation can be greater than that of the direct link and is a function of the relative distance between source and relay compared to the destination. Moreover, for multiplexing gains less than 1, a simple scheme of the relay listening 1/3 of the time and transmitting 2/3 of the time can achieve the 2 by 2 MIMO DMT.