waashk/dblp huggingface dataset:
design and evaluation of a multilevel decoder for satellite communications. in this paper, we propose a multilevel coding (mlc) scheme suitable for satellite communications, where different qos levels are required. we introduce a novel characterization of schemes based on mutual information, called multi-stage decoder (msd) charts, to aid in the design and evaluation of multilevel coding systems. this characterization method finds the optimal set of code rates for the mlc scheme for a set of required snr operation points. on the other hand, fixing the code rates to find out the operation points of snr is also possible. performance of common mapping strategies used in mlc schemes, as block labeling and ungerböck labeling, are evaluated using msd charts. an established transmission scheme for satellite broadcasting, european satellite digital radio (esdr) standard, is compared with the proposed mlc scheme, showing that the mlc scheme is able to work in lower snr regions and provides more flexibility in designing the levels.
adaptive intra-symbol smse waveform design amidst coexistent primary users. an analytic approach is presented for optimizing spectrally modulated, spectrally encoded (smse) waveforms using independent selection of intra-symbol (within a symbol) subcarrier power and modulation order. the smse framework is well-suited for cognition-based, software defined radio (sdr) applications. by exploiting statistical knowledge about the spectral and temporal behavior of interfering signals, the inherent smse framework flexibility is leveraged to substantially increase system throughput while limiting coexistent interference. results for a coexistent scenario are provided in which the analytic optimization of the smse waveform is demonstrated in the presence of multiple direct sequence spread spectrum (dsss) signals. the results reveal significant performance benefits that demonstrate the potential of the smse framework to dynamically adapt to changing environmental conditions-key functionality required for future sdr implementations.
2nd order cyclostationarity of ofdm signals: impact of pilot tones and cyclic prefix. this paper deals with 2nd order cyclostationarity of orthogonal frequency division multiplex (ofdm) signals. a new generalized formula for the spectral correlation density (scd) function is derived. compared to related work in the literature, our derivation is not restricted to the case that all sub-carriers of an ofdm signal carry statistically independent data. the reason for that is that correlated data in terms of pilot tones are typically introduced on different carriers for channel estimation and synchronization purposes. the new formula allows us to analyze the impact of such pilot tones on the scd. in addition, it gives extra information about the impact of the cyclic prefix.
on the efficiency of dynamic routing of connections with known duration. in this paper we devise an highly-efficient load balancing algorithm, called lb-hta, for the dynamic provisioning of connections with known duration in wdm networks. we introduce a time-dependent link-weight assignment that captures future congestion of links, leveraging the knowledge of connection durations. by means of an extensive set of simulative experiments, we compare our approach to other traditional, yet holding-time agnostic, dynamic routing algorithms. for a typical us nationwide network, lb-hta obtains significant saving in blocking probability for practical scenarios. moreover, we address two key-questions regarding holding-time-aware dynamic routing. three main traffic models are considered here, namely i) dynamic traffic, ii) dynamic traffic with known durations and iii) scheduled traffic: how much the knowledge of connection durations improves the performance with respect of a holding-time- agnostic solution? is the obtained solution close to the most effective solution provided by scheduled traffic? in order to exhaustively evaluate the performance of lb-hta, we consider as benchmark the solution obtained under the well-known scheduled traffic model (ti-st) and also under an approximated, but more effective, approach for traffic scheduling, called time-variant scheduled traffic (tv-st). for both ti-st and tv-st, integer linear program (ilp) formulations are proposed and results compared with dynamic routing algorithms.
non-coherent receiver with fractional sampling for impulsive uwb systems. we propose a low complexity noncoherent receiver operating at twice the symbol-rate for systems where each data symbol consists of multiple frames/chips. the receiver does not require explicit timing and channel estimation. it implements simple delayed-autocorrelation, followed by sampling at twice the symbol-rate. simulation results show the receiver achieves performance close to a conventional one with perfect timing.
robust cyclic space-frequency filtering for bicm-ofdm with outdated csit. in this paper, we introduce robust cyclic space-frequency (csf) filtering for systems combining bit-interleaved coded modulation (bicm) and orthogonal frequency division multiplexing (ofdm). the proposed robust csf filtering scheme exploits outdated channel state information at the transmitter (csit) and takes into account the reliability of the csit via a bayesian model. based on an upper bound on the worst-case pairwise error probability we formulate the optimization problem for the robust csf filters which can be solved exactly for certain special cases. for the general case, we obtain an approximate solution by solving a related problem with additional constraints. this approximate solution can be further improved with a gradient algorithm for the original problem. simulation results confirm the excellent performance of bicm-ofdm with robust csf filtering.
an economic model for pricing tiered network services. we consider networks offering tiered services and corresponding price structures, a model that has become prevalent in practice.we develop an economic model for such networks and make contributions in two important areas. first, we formulate the problem of selecting the service tiers and present an approximate yet accurate and efficient solution approach for tackling this nonlinear programming problem. given the set of (near-) optimal service tiers, we then employ game-theoretic techniques to find an optimal price for each service tier that strikes a balance between the conflicting objectives of users and service provider. this work provides a theoretical framework for reasoning about and pricing internet tiered services. our results also indicate that tiering solutions currently adopted by isps do not perform well.
capacity evaluation of a land mobile satellite system utilizing multiple element antennas. land mobile satellite (lms) systems can exploit multiple-input-multiple-output (mimo) techniques in order to achieve high transmission rates. this paper evaluates theoretically the capacity of single-input-multiple-output (simo) system utilizing uniform linear arrays at the receiver terminal for satellite applications. the theoretical study is performed at three different frequency bands. sufficient capacities are achieved varying between 5 and 6.2 b/s/hz at l and s bands being almost independent from the elevation angle. in ku band the capacity is highly variable with the elevation angle, taking values between 2 and 5.9 b/s/hz, whereas the maximum capacity values are observed in a blocked environment. at l and s bands the capacity is uncorrelated with distance for element spacing up to 1.5 cm and varies between 5.5 and 6 b/s/hz. in ku band the capacity is highly variable with the element spacing and maximizes for distances between 1 and 1.5 cm.
discernibility analysis and accuracy improvement of machine learning algorithms for network intrusion detection. network intrusion detection based on machine learning algorithms has demonstrated high performance in execution time and overall classification accuracy. however, very poor identification skill is showed for certain specific attack types, especially for the unknown attack types appeared in the test data only. we use the parallel coordinates plot (pcp), one kind of visualization technique for multi-dimension data analysis, to comparatively analyze the data distribution characteristic for both training and test datasets. on the other hand, we make use of rough sets theory to investigate the discernibility in respect of whole training dataset, randomly sampled dataset and reduct attributes set. furthermore, based on the higher classification accuracy for data with unknown attack types by using rough sets method, the decision rules extracted from both c4.5 and rough sets method are combined to improve the detection capability of classification model.
bit-interleaved coded modulation for hybrid rf/fso systems. in this paper, we propose a novel architecture for hybrid radio frequency (rf)/free-space optics (fso) wireless systems. in particular, we show that a hybrid system robust to all weather conditions is obtained by joint bit-interleaved coded modulation (bicm) of the bit steams transmitted over the rf and fso sub-channels. an asymptotic performance analysis reveals that a properly designed convolutional code can exploit the diversity offered by the independent sub-channels. furthermore, we develop a code design criterion and provide an efficient code search procedure. simulation results show that hybrid rf/fso systems with bicm outperform previously proposed hybrid systems employing a simple repetition code and selection diversity.
performance evaluation of optical ofdm systems with nonlinear clipping distortion. this paper investigates the effects of nonlinear biasing and clipping (bac) on a random optical orthogonal frequency-division multiplexing (ofdm) signal with direct detection. we look at the problem of theoretical performance evaluation of such a system. specifically, we derive an approximation for the symbol error rate (ser). the nonlinear bac process is modeled as a linear deterministic gain plus a random additive clipping noise. the total effective snr is presented as a function of biasing power, modulation constellation and receiver snr. analytical results are in good agreement with simulations in various cases.
sub-noise primary user detection by cross-correlation. an ideal cognitive radio must be able to detect primary user signals under unfavorable conditions. especially when the hidden node problem occurs, a cognitive radio is required to detect the presence of signals under the noise floor. this paper addresses the question to what extent sub-noise detection is practically usable in a cognitive radio. three methods based on cross-correlation are analyzed and compared.
low complexity markov chain monte carlo detector for channels with intersymbol interference. in this paper, we propose a novel low complexity soft-in soft-out (siso) equalizer using the markov chain monte carlo (mcmc) technique. direct application of mcmc to siso equalization (reported in a previous work) results in a sequential processing algorithm that leads to a long processing delay in the communication link. using the tool of factor graph, we propose a novel parallel processing algorithm that reduces the processing delay by orders of magnitude. numerical results show that, both the sequential and parallel processing siso equalizers perform similarly well and achieve a performance that is only slightly worse than the optimum siso equalizer. the optimum siso equalizer, on the other hand, has a complexity that grows exponentially with the size of the memory of the channel, while the complexity of the proposed siso equalizers grows linearly.
multiple-ring based modeling and simulation of wideband space-time-frequency mimo channels. in this paper, based on the concept of the tapped delay line (tdl) structure, we first propose a new wideband multiple-ring multiple input multiple output (mimo) channel reference model for macro-cell scenarios. it is shown that the proposed model can easily match any given or measured power delay profile (pdp) and has the ability to jointly consider the angle of arrival (aoa), angle of departure (aod), and time of arrival (toa). from the proposed model, we derive the closed-form expression of the 3-dimensional (3-d) space-time-frequency (stf) correlation function (cf) for each tap, considering the interaction of the temporal, spatial, and frequency correlations. finally, based on the proposed reference model, a deterministic simulation model is then proposed.
green dsl: energy-efficient dsm. dynamic spectrum management (dsm) has been recognized as a key technology for tackling multi-user crosstalk interference for dsl broadband access. up to now, dsm design has mainly been focusing on maximization of data rates. however, recently, reducing the total power has become a main target, as it power consumption has been identified as a significant contributor to global warming. in this paper we extend traditional dsm design towards a much wider energy-efficient scope and show how to tackle the corresponding optimization problems. the impact of this 'green dsl' approach is evaluated for practice with some surprisingly good numerical results. furthermore bounds are provided on the trade-off between data rate performance and power saving.
carrier-sense arq: squeezing out bluetooth performance while preserving standard compliancy. in this paper, we propose a simple and standard compliant retransmission mechanism, called carrier-sense automatic repeat request (cs-arq), which aims at improving system performance, both in terms of throughput and energy efficiency, by avoiding useless data packet retransmissions. more specifically, in case of missed acknowledgment (ack), the source makes use of its carrier-sensing capabilities to decide whether retransmitting the data packet or soliciting the ack retransmission from the destination. the scheme is modeled by means of a two-state markov chain that permits to determine closed-form expressions for the throughput and energy efficiency figures. the analysis reveals that the cs-arq mechanism is actually capable of significantly enhancing the system performance, in particular in some critical scenarios, while preserving standard compliancy.
adaptive puncturing for coded ofdma systems. a scheme is proposed for adaptively changing the code rate of coded ofdma systems via changing the puncturing rate within a single codeword (scw). in the proposed structure, the data is encoded with the lowest available code rate then it is divided among different resource blocks (tiles) where it is punctured adaptively based on some measure of the channel quality for each tile. the proposed scheme is compared against using multiple codewords (mcws) where the transmitter divides the data over tiles and encodes them separately. we investigate two different adaptive modulation and coding (amc) selection methods. the first is a recursive scheme that operates directly on the snr whereas the second operates on the effective snr value that is obtained using mutual information effective snr mapping (miesm). we then compare our scheme to per-frame adaptation (pfa) where we fix the modulation and coding scheme (mcs) over a given frame. we show via simulations that when using the recursive rate selection method the scw scheme significantly outperforms the mcws and the pfa. it is also shown that applying the miesm rate selection method, the pfa improves significantly, yet the scw scheme is the best performer. we also introduce a novel interleaving method prior to puncturing that improves the performance for certain restricted adaptation mechanisms.
end-host authentication and authorization for middleboxes based on a cryptographic namespace. today, middleboxes such as firewalls and network address translators have advanced beyond simple packet forwarding and address mapping. they also inspect and filter traffic, detect network intrusion, control access to network resources, and enforce different levels of quality of service. the cornerstones for these security-related network services are end-host authentication and authorization. using a cryptographic namespace for end-hosts simplifies these tasks since it gives them an explicit and verifiable identity. the host identity protocol (hip) is a key-exchange protocol that introduces such a cryptographic namespace for secure end-to-end communication. although hip was designed with middleboxes in mind, these cannot securely use its namespace because the on-path identity verification is susceptible to replay attacks. moreover, the binding between hip as an authentication protocol and ipsec as payload transport is insufficient because on-path middleboxes cannot securely map payload packets to a hip association. in this paper, we propose to prevent replay attacks by allowing packet-forwarding middleboxes to directly interact with end-hosts. also we propose a method for strengthening the binding between the hip authentication process and its payload channel with hash-chain-based authorization tokens for ipsec. our solution allows on-path middleboxes to efficiently leverage cryptographic end-host identities and integrates cleanly into existing standards.
speeding up homomorpic hashing using gpus. homomorphic hash functions (hhfs) have been applied into peer-to-peer networks with erasure coding or network coding to defend against pollution attacks. unfortunately hhfs are computationally expensive for contemporary cpus. this paper proposes to exploit the computing power of graphic processing units (gpus) for homomorphic hashing. specifically, we demonstrate how to use nvidia gpus and the computer unified device architecture (cuda) programming model to achieve 38 times of speedup over the cpu counterpart. we also develop a multi-precision modular arithmetic library on cuda platform, which is not only key to our specific application, but also very useful for a large number of cryptographic applications.
throughput optimization in high speed downlink packet access (hsdpa). in this paper, we investigate throughput optimization in high speed downlink packet access (hsdpa). specifically, we propose offline and online algorithms for adjusting the channel quality indicator (cqi) used by the network to schedule data transmission. in the offline algorithm, a given target bler is achieved by adjusting cqi based on ack/nak history. by sweeping through different target blers, we can find the throughput optimal bler offline. this algorithm could be used not only to optimize throughput but also to enable fair resource allocation among mobile users in hsdpa. in the online algorithm, the cqi offset is adapted using an estimated short term throughput gradient without specifying a target bler. an adaptive stepsize mechanism is proposed to track temporal variation of the environment. we investigate convergence behavior of both algorithms. simulation results show that the proposed offline algorithm can achieve the given target bler with good accuracy. both algorithms yield up to 30% hsdpa throughput improvement over that with 10% target bler.
an evolutionary approach to end-to-end addressing and routing in all-ethernet wide-area networks. while the introduction of new ethernet-based wide-area solutions, such as provider-backbone bridging traffic engineering-pbb-te, paves a way for ethernet to become a carrier class service, it is restricted to the metro area and hence unable to provision global end-to-end communication. in this paper, we propose a new scheme for all-ethernet wide area networking that involves a unique addressing and routing mechanism, and leads to a scalable, hierarchical and service-oriented transport network architecture. the scalability is achieved by means of abstraction of any irregular physical topology into a regular logical topology, based on the concept of binary trees. the regular logical topology is represented with logical 1x2 ethernet switches as the fundamental building blocks which allow switching using a unique binary addresses in a simple and automated fashion. we propose an evolutionary architecture to provide end-to-end ethernet routes using binary addresses embedded in stacked vlan tags on native ethernet frames, in line with the emerging standards. the results show that a significant simplification of wide-area inter-networking can be achieved, while supporting carrier-grade network performance with all-ethernet features.
supporting vcr-like operations in derivative tree-based p2p streaming systems. supporting user interactivity in peer-to-peer streaming systems is challenging. vcr-like operations, such as random seek, pause, fast forward and rewind, require timely p2p overlay topology adjustment and appropriate bandwidth resource re-allocation. if not handled properly, the dynamics caused by user interactivity may severely deteriorate users' perceived video quality, e.g., longer start-up delay, frequent playback freezing, or blackout altogether. in this paper, we propose a derivative tree-based overlay management scheme to support user interactivity in p2p streaming system. derivative tree takes advantage of well organized buffer overlapping to support asynchronous user requests while brings high resilience to the impact of vcr-like operations. a session discovery service is introduced to quickly locate parent peer. we show that the overhead of vcr-like operations in derivative-tree based scheme is o(log(n)), where n is the number of sessions. simulation experiments further demonstrate the efficiency of the proposed scheme.
caching video contents in iptv systems with hierarchical architecture. in this paper we consider iptv systems with an hierarchical architecture. the lowest elements of the architecture are set-top boxes (stbs) at the user homes; a stb is connected to a central office (co) which is in charge of delivering the video content to the end user. since cos have limited storage capabilities, they may need to retrieve a particular video content that is requested by a user but temporary not stored in the local memory. thus, cos exchange video contents with similar cos in a peer-to-peer fashion. at a higher hierarchical level, video source offices (vsos) offer the video contents that cannot be retrieved at the co level. video content caching strategies at the cos and vsos influence the system performance in terms of traffic exchanged between the network nodes. in this paper we propose two simple strategies that aim at reducing both the intra-and inter-level traffic. the strategies are studied by means of an analytical model that is validated against simulation results. our results show that the hierarchical architecture allow good system performance even with limited overall storage capacity. the proposed strategies, in particular, can be helpful in improving system performance.
implementation of a chaotically encrypted wireless communication system. implementing the synchronization of chaotic systems presents new challenges that are difficult to handle by using currently adopted schemes. the paper proposes an implementation of a synchronization method for a pseudo-true random bit generator (ptrbg) based on chaotic systems. synchronization of the chaotic binary sequences is achieved by using the backward iteration approach. the implementation test bed for the complete wireless communication system is based on a chipcon wireless development kit. assessment of the pseudo- true random bits (ptrb) generated is performed using the nist statistical test suite.
adaptive power allocation in two-way amplify-and-forward relay networks. two-way amplify-and-forward relaying is considered in this paper. we propose adaptive power allocation (pa) algorithms to maximize the instantaneous achievable rate and minimize the system outage probability, respectively. both single-and multi-relay systems are considered. it is shown that the proposed adaptive pa algorithms significantly outperform the uniform pa algorithms. furthermore, exploiting multiple relays obtains higher diversity order and lower outage probability than using only one relay, at the price of a lower achievable information rate. the relay locations and relay selection are also taken into account to further improve the system performance.