waashk/dblp huggingface dataset:
spatial interference cancellation and pairwise error probability analysis. future wireless communication systems being characterized by tight frequency reuse, adaptive modulation and coding schemes and diversified data services will be interference limited by interfering signals of diverse rates and strengths. keeping in view such a scenario, we propose in this paper the application of a recently proposed low complexity match filter (mf) based detector for spatial interference cancellation in the presence of one strong interferer. we derive an analytical upper bound for the coded pair wise error probability (pep) for the proposed mf based detector using the moment generating function (mgf) based method and prove that this detector not only recuperates the diversity order lost by mmse but also exhibits a coding gain as the interference gets stronger. we also study in this paper the effect of non gaussian interference on coded pep of mmse linear detection and demonstrate the deficit of one order of diversity and a coding loss as the interference gets stronger. our analysis provides insights to explain the relative performance of mmse and proposed mf based detectors as a function of the strength of interference. finally we demonstrate the strength of our new analytical pep upper bounds by simulations.
cfo estimation schemes for differential ofdm systems. this paper proposes two blind carrier frequency offset (cfo) estimation schemes for differentially modulated orthogonal frequency division multiplexing (ofdm) systems. the proposed schemes estimate the fractional part of the cfo with only two consecutive ofdm blocks, and they exploit two implicit properties associated with differentially modulated ofdm (dofdm) systems, i.e., the channel keeps constant over two consecutive ofdm blocks, and the dofdm systems employ an m-ary phase-shift keying constellation. one of the schemes is based on the finite alphabet (fa) constraint and the other one is based on the constant modulus (cm) constraint. they provide a trade-off between the performance and computational complexity. the constrained cramer-rao lower bound is also derived. several numerical examples are presented to validate the efficacy of the proposed schemes.
crbs for the joint estimation of toa and aoa in wideband miso and mimo systems: comparison with siso and simo systems. we derive the crbs (cramer rao bound) for the joint estimation of the toa (time of arrival) and the aoa (angle of arrival) in wideband (wb) miso (multiple input single output) and mimo (multiple input multiple output) systems.we consider both cases of orthogonal and non-orthogonal transmitted signals. we compare the crbs obtained in siso (single input single output), simo (single input multiple output), miso and mimo systems under the assumption that the total transmitted energy is the same for all systems. we show that simo and mimo are equivalent for toa estimation, and miso and siso as well when the transmitted signals are orthogonal. for non-orthogonal signals, mimo is better than simo, and miso is better than siso when the received signals are constructive. for aoa estimation, we show that mimo is better than simo and simo is better than miso when the transmitted signals are orthogonal. for non-orthogonal signals, mimo is much better when the received signals are constructive. the crbs obtained for non-orthogonal signals are very sensitive to the angle. numerical results obtained in a typical scenario are provided.
code book based cl-mimo for dl wimax rel. 1.5: system level performance analysis. in this paper, gains of the codebook based cl-mimo for down link wimax system has been studied using system level simulations. the system level simulation is based on the ieee 802.16m evaluation methodology. the 2×2 and 4×2 antenna configurations, and 3 bits and 6 bits preferred matrix index (pmi) feedback codebooks are considered. both the sub-band and wide band pmi feedback are studied. the results show that the cl-mimo provides substantial gains in cell edge and average sector throughput over ol-mimo system.
dynamic resource allocation for downlink multi-user mimo-ofdma/sdma systems. in this paper, new dynamic resource allocation algorithms are presented for the downlink of multi-user mimo-ofdma/sdma systems. since it is difficult to obtain the optimal solution to the joint optimization problem, the whole procedure is divided into two steps, namely, the subcarrier-user scheduling and the resource allocation. in the first step, a new metric is proposed to measure the spatial compatibility of multiple users each with multiple receive antennas, based on which a new subcarrier-user scheduling algorithm is designed. in the second step, two dynamic resource allocation algorithms are developed to assign radio resources to the scheduled users accordingly. simulation results demonstrate the superiority of the proposed algorithms in terms of the system throughput.
tale in the multi-core era: is java still competitive to host sip applications? multi-core platforms are becoming prevailing in telecom infrastructures, and many sip(session initiation protocol) enabled applications are using java as the development language and runtime environment. it is important to understand the workload characteristics and performance issues of java based sip stack over multi-core platforms. in this paper, two rfc 3261 compliant java based sip stacks, the jain-sip and a proprietary sip stack are studied in depth. especially we focused on the typical performance issues caused by either java language features or the workload of sip protocol, including scalability of sip stack, resource contention issue and gc impact with sip memory usage pattern. some optimization techniques and their drawbacks are also discussed along with the performance evaluation. it turns out that due to the complex combination of sip protocol semantics and java language features, the performance of java based sip stack tends to be far from competitive on multicore platforms. extensive optimization and certain improvements of program structure and object management policy may help, however, may, on the other hand, sacrifice some key values of the java language, e.g. easy development.
extending the inter-domain pce framework for authentication and authorization in gmpls networks. ietf is working on the design of new architectures and signaling solutions to support inter-as (autonomous system) gmpls-te (generalized multi protocol label switching with traffic engineering) for multi-domain, multi-carrier connection setup with guaranteed quality of service (qos). in addition, the path computation element (pce) working group is developing the framework for inter-domain path computation. however, many issues are still open regarding the joint path computation and path setup signaling solutions for inter-carrier authentication and authorization (aa). in this paper, we propose the first security solution which integrates inter-domain aa features in the pce path computation framework. specifically, we define a new architecture for inter-domain qos path provisioning based on an extension of the pce framework to include features that allow domains interested in inter-domain resources to get aa for end-to-end path provisioning over multiple domains belonging to different carriers. in addition, we introduce a mechanism to tie policies controlling path setup with the aa mechanisms introduced in the pce framework. while at present provisioning of inter-domain paths is based on rather static settlements between neighboring domains that make end-to-end qos provisioning a challenge, we propose an aa framework that allows domains interested in setting an inter-domain qos path to have guarantees about resource provided by each domain along the path from source to destination. simulation results show the performance of the model proposed in networks having different size and connectivity.
optimization of split-and-combine relaying. relays play an important role for increasing rate and reducing energy consumption of wireless networks. in this paper we consider a three-node network (source, relay, destination) in which we want to minimize total energy consumption for a given transmission rate. we analyze and optimize the split-combine-relaying (scr) protocol that for many typical parameter settings performs better than traditional decode-and-forward. scr splits a data packet into two fragments, which are then transmitted in two phases. in the first phase of transmission, the source sends the first fragment to the relay. in the second phase of the transmission, the source sends the second fragment to the destination, while, at the same time, the relay forwards the first fragment to the destination. we provide an optimization framework to decide the amount of data in each fragment, the amount of time spent in each of the phases, and the corresponding transmission powers. we also show that an extension of scr that employs slepian-wolf coding of the fragments leads to further reduction of energy consumption.
power optimal signaling for fading multi-access channel in presence of coding gap. in a multi-access fading channel, dynamic allocation of bandwidth, transmission power and rates is an important aspect to counter the detrimental effect of time-varying nature of the channel. most of the existing work on dynamic resource allocation assumes capacity achieving codes for various signaling schemes like tdma, fdma, cdma and successive decoding. for the capacity achieving codes, the rate achievable by the user is log(1 + snr), where snr denotes the signal to noise ratio of the user at the receiver side. however, codes that are used in practice have a finite gap to capacity, i.e., the achievable rate is log(1 + snr/γ) γ > 1. the exact value of γ depends on the coding strategy and the desired bit error rate. many existing resource allocation techniques that are optimal for capacity achieving codes perform sub-optimally in presence of the coding gap. for example, successive decoding does not always minimize the sum power required for providing the desired rate to each of the users for γ > 1. the problem of minimizing the sum power while guaranteeing the required rate to each of the users is important for both real-time and non real-time applications, and is addressed here. we obtain the resource allocation that is optimal for the above problem in presence of the coding gap.
dtia: an architecture for inter-domain routing. this paper proposes an architecture for inter-domain routing, called dtia - dynamic topological information architecture. dtia separates the issues of reachability and routing, and this paper addresses the first one. one major requirement has been not to change ip packets and the commercial relations in the internet. dtia is based on the knowledge of a static network formed by the autonomous systems (as) and an algorithm to manage link failures. we use the concept of a region as a mechanism to sustain scale. dtia supports the most important functionalities of bgp: some of them are built in and others can be implemented on top of the reachability level or the routing level. the main concerns we aim to solve are taking advantage of multihoming, increase the robustness in terms of convergence, reduce the churn rate and range of routing events, and due to forwarding packets by as identifiers and topologic links (as opposed to prefix policy defined) reduce the growth of the routing table.
on the capacity region of the gaussian multiple access channel with noisy feedback. we provide a new outer bound on the capacity region of the two-user gaussian multiple access channel (mac) with awgn-corrupted feedback. our outer bound is based on the idea of dependence balance due to hekstra and willems [1]. evaluating our outer bound is non-trivial as it involves taking a union over joint densities of three random variables, one of which is an auxiliary random variable. we resolve this difficulty by proving that it is sufficient to consider jointly gaussian random variables when evaluating our outer bound. as the feedback noise variances become large, our outer bound collapses to the capacity region of the gaussian mac without feedback, thereby yielding the first non-trivial result for a gaussian mac with noisy feedback. furthermore, as the feedback noise variances tend to zero, our outer bound collapses to the capacity region of the gaussian mac with noiseless feedback, which was established by ozarow [2]. for all non-zero, finite values of the feedback noise variances, our outer bound strictly improves upon the cut-set outer bound.
low bound of energy-latency trade-off of opportunistic routing in multi-hop networks. during the last decade, many works were devoted to improving the performance of relaying techniques in ad hoc networks. one promising approach consists in allowing the relay nodes to cooperate, thus using spatial diversity to increase the capacity of the system. however, this approach introduces an overhead in terms of information exchange, increasing the complexity of the receivers. a simpler way of exploiting spatial diversity is referred to as opportunistic routing. in this scheme, a cluster of nodes still serves as relay candidates but only a single node in the cluster forwards the packet. this paper proposes a thorough analysis of opportunistic routing efficiency under different realistic radio channel conditions. the study aims at finding the best trade-off between two objectives: energy and latency minimizations, under a hard reliability constraint. we derive an optimal bound, namely, the pareto front of the related optimization problem, which offers a good insight into the benefits of opportunistic routing compared with classical multi-hop routing.
distributed flooding-based storage algorithms for large-scale wireless sensor networks. in this paper we propose distributed storage algorithms for large-scale wireless sensor networks. assume a wireless sensor network with n nodes that have limited power, memory, and bandwidth. each node is capable of both sensing and storing data. such sensor nodes might disappear from the network due to failures or battery depletion. hence it is desired to design efficient schemes to collect data from these n nodes. we propose two distributed storage algorithms (dsa's) that utilize network flooding to solve this problem. in the first algorithm, dsa-i, we assume that the total number of sensors is known to each sensor in the network. we show that this algorithm is efficient in terms of the encoding and decoding operations. furthermore, every node utilizes network flooding to disseminate its data throughout the network using a mixing time of approximately o(n). in the second algorithm, dsa-ii, we assume that the total number of nodes is not known to every sensor; hence dissemination of the data does not depend on n. the encoding operations in this case take o(cµ2), where µ is the mean degree of the network graph and c is a system parameter. we evaluate the performance of the proposed algorithms through analysis and simulation. we show that the performance of the proposed algorithms matches the derived theoretical results.
a mutual information approach for comparing llr metrics for iterative decoders. we develop an approach to compare different log-likelihood ratio (llr) metrics for iterative soft decoding. we show that an llr metric for a function of the received signals is a sufficient statistic to this function about the binary channel input. we also prove that when the function belongs to a set of specific mappings, the corresponding llr metric can feed the maximal mutual information to the decoder. for decoding low density parity check codes with the belief-propagation decoder, we develop a method to estimate the minimal average number of iterations. the results are applied to compare the gaussian metric in [1] and the two-symbol-observation-interval llr metric in [2]. the latter is shown to be superior.
dimensioning of a multi-rate network transporting variable bit rate tv channels. we consider a centralised (client-server) digital tv network with heterogeneous receiver devices of different resolutions, requiring a multi-rate transport system. there exist two main ways to store and transport (streamed) tv channels in such a system: either by providing different single-layer versions of a channel (simulcast transport mode) or by keeping one multi-layered version (encoded e.g. in svc) with extractable substreams. we propose one approximate analytical and two simulation methods to estimate the capacity demand in such a network with variable bit rate channels and we consider two behaviour models. in some tv distribution networks, the video is delivered in constant bit rate. however, this implies that the video quality is varying. in order to provide better quality of service (qos), a network operator must deliver the channels in non-constant bit rate aiming in this way at constant video quality. our models take into account also the correlations between the different resolutions of a channel. starting from real experimental data, we obtain the necessary input to our models and explore two realistic tv network scenarios - with bouquets of 50 and 300 channels, respectively. the results by the three approaches correspond well (relative error of 0.5% at most). in the case of 50 channels, svc outperforms simulcast in terms of required bandwidth, while in the case of 300 channels, svc is outperformed by simulcast. therefore, we conclude that it depends on the system parameters which of both transport strategies will be more beneficial to save network resources.
low-complexity energy-efficient ofdma. energy efficient communications in wireless communications is very important as mobile devices are battery-constrained. for mobile devices in a cellular system, uplink power consumption dominates the wireless power budget, due to the rf power requirements for reliable communications over long distances. our previous work in this area demonstrated significant energy savings in uplink cellular ofdma transmissions, with iterative approaches maximizing the instantaneous bits-per-joule energy efficiency. in this paper, we use a time-averaged bits-per-joule metric to develop low-complexity schemes. specifically, we obtain closed-form solutions for energy-efficient link adaptation in frequency-selective channels. we also derive closed-form approaches for the maximum arithmetic and geometric mean energy-efficient schedulers. simulation results show that the proposed schemes not only have low complexity but also perform close to the globally optimum solutions.
channel estimation and tracking schemes for the pulse-shaping ofdm systems. robust channel estimation scheme is essential for pulse-shaping ofdm systems in the multipath mobile environment. this paper proposes three types of channel estimation schemes for the general class of pulse-shaping ofdm systems. the first two types are suboptimal low-complexity maximum likelihood estimators. the last type is adaptive kalman filter channel estimator. we numerically evaluate the performance of each estimator using computer simulation.
statistical analysis of ip delay measurements as a basis for network alert systems. measuring packet delay and packet loss through dedicated test packet streams in computer networks allows for the assessment of quality of service on the path the probes traverse. for this reason, active ip performance measurements have been carried out in x-win, germany's national research and educational network, and géant2, its european counterpart, by the win-labor group of the university of erlangen-nuremberg for many years. this paper provides an overview of how network measurements can be interpreted using a variety of statistical concepts in order to gain insight into the state of monitored connections. the focus here is set on the analysis of one-way delay (owd); the approach demonstrates how owd can be used for the identification of network congestions and can serve as a basis for network alert systems by statistically categorizing changes in the performance metric.
spectrally efficient fdm signals: bandwidth gain at the expense of receiver complexity. this paper investigates the transmission of frequency division multiplexed (fdm) signals, where carrier orthogonality is intentionally violated in order to increase bandwidth efficiency. in analogy to conventional ofdm, signal generation relies on an inverse fractional fourier transform (ifrft) that can be implemented with o(n log2 n) algorithmic complexity. optimal maximum likelihood (ml) detection is overly complex due to the presence of substantial intercarrier interference (ici). consequently, we investigate an alternative detection mechanism based on the generalized sphere decoding (gsd) algorithm. we examine the bandwidth efficiency and the error performance in additive white gaussian noise (awgn), for various fdm signal parameters. in particular, we show that it is possible to detect optimally and efficiently fdm signals, with 25% bandwidth gain with respect to analogous ofdm signals. this indicates that the transmission of spectrally efficient non orthogonal fdm signals is tangible.
a design of space-time codes for cpfsk modulation over multipath fading channels. in this paper, we derive space-time code design criteria for continuous phase frequency-shift keying (cpfsk) over multipath fast fading channels, aiming at maximizing the overall space-time diversity. we also propose a space-time coding scheme to meet the dominated design criterion, the rank criterion. our encoding scheme consists of a ring convolutional encoder and a spatial encoder with an extender in it. both the theoretical and simulation results show that with the effective code length ecl of the convolutional encoder, lt transmit antennas, lr receive antennas, and l+1 paths in the fading channel, a maximal overall diversity ecl lt lr (l+1) is achievable.
a user grouping method for maximum weighted sum capacity gain. achieving the capacity region in the mimo broadcast channel requires the use of dirty paper coding (dpc). when it cannot be afforded to satisfy the requirements of all users by dpc based approaches, it is necessary to identify the users which exhibit the highest performance gain compared to simpler approaches. in this paper we present a user grouping method that aims to identify those users with highest weighted sum rate gain. first some users are excluded by a simple criterion leading to a reduced user set, from which the final user group is selected by a more sophisticated criterion.
a cross layer fast handover scheme in vanet. this study presents a cross-layer fast handover scheme for vanet, called vehicular fast handover scheme (vfhs), where the physical layer information is shared with the mac layer, to reduce the handover delay. the key idea of vfhs is to utilize oncoming side vehicles (osvs) to collect physical and mac layers information of passing through rvs and broadcast the information to vehicles that are temporarily disconnected, referred to as broken vehicles (bvs). a bv can thus perform a rapid handover when it enters the transmission range of the approaching rvs. the effectiveness of vfhs is verified using ns2 simulations. simulation results indicate that vfhs significantly decreases handover latency and packet loss.
optimal utility-energy tradeoff in delay constrained random access networks. rate, energy and delay are three main parameters of interest in ad-hoc networks. in this paper, we discuss the problem of maximizing network utility and minimizing energy consumption while satisfying a given transmission delay constraint for each packet. we formulate this problem in the standard convex optimization form and subsequently discuss the tradeoff between utility, energy and delay in such framework. also, in order to adapt for the distributed nature of the network, a distributed algorithm where nodes decide on choosing transmission rates and probabilities based on their local information is introduced.