waashk/dblp huggingface dataset:
a unified framework for interference modeling for multi-user wireless networks. the paper addresses the problem of interference modeling for wireless networks. two axiomatic frameworks are known from the literature: (1) standard interference functions introduced by yates in [jsac 1995], and (2) general interference functions proposed by the authors in their previous work. in this paper, both frameworks are analyzed and compared. it is shown that (1) is contained in the more general framework (2). this means that certain structure results, which were recently derived for (2) can also be applied to (1). a focus of this paper is on convexity and concavity properties, which are important because they often lead to interesting algorithmic opportunities. the results provide a bridge between both frameworks, which have been studied separately in the past.
on the multi-rate division with limited feedback for one source multiple destinations wireless transmission systems. multiuser diversity is inherent in wireless networks due to independent channel variations of different users. it requires that the transmitter has the knowledge of the channel state information (csi) of each user in the downlink. too much feedback will bring a heavy load to the system in some cases. this paper investigates the problem of exploiting multiuser diversity in a one source multiple destinations wireless transmission system with limited feedback. a strategy for obtaining the optimal multiple rate level and the maximum achievable sum rate is proposed in this paper. moreover, the scheduling outage probability, the probability that rates of all users are below a threshold, is also analyzed. for one-bit feedback, a tight bound of the achievable rate is obtained. it is shown that the achievable rate nearly capture the order of the double-logarithmical of the number of users in full csi systems. numerical results are also presented. the achievable sum rate is close to the full csi capacity via limited feedback as the number of users is large enough.
channel spectral flattening in time domain equalizer design for ofdm systems. time domain equalization (teq) methods based on the maximum shortening signal-to-noise ratio (mssnr) criterion is one of the most commonly used criterion for shortening impulse responses as it is computationally efficient and simple. however, the mssnr method tends to design a teq with a bandpass-like frequency response, resulting in a spectrally uneven effective channel response. as as result, bit-loading have to be performed to improve the bit rate of the system. additionally, when residual intersymbol interference (isi) is low compared to noise power, the spectral shape of the effective channel does not have much impact on the bit rate. however, the negative effect of the channel spectral unevenness on achievable bit rate increases as the noise power decreases. in this paper, a design method is proposed to maximize effective channel spectral flatness to increase the bit rate of the system.
low complexity coordinated beamforming in 2-user mimo systems. in this paper, we propose a new noniterative coordinated beamforming scheme to obtain full multiplexing gain in 2-user mimo systems. in order to find the beamforming and combining matrices, we solve a generalized eigenvector problem and describe how to find generalized eigenvectors according to the gaussian broadcast channels. selected simulation results show that the proposed method yields the same sum-rate performance as the iterative coordinated beamforming method with a lower complexity non-iterative computation of the beamforming and combining matrices. we also show that the proposed method can easily exploit selective gain by choosing the best combination of generalized eigenvectors.
spatial and temporal packet recovery schemes for dvb-h systems through ip-relay wireless networks. the dvb-h standard has been defined to provide digital video broadcast to mobile handheld devices. however, without a request channel, a handheld device may encounter data loss and thus it requires an additional recovery architecture to relieve this problem. in this paper, we follow the dvb-ipdc standard and propose combining a dvb-h system with an ip-relay wireless network. a handheld device losing dvb-h data can thus request the relay network for retransmission. under this architecture, we identify two critical issues, group packet loss (gpl) and broadcast data handover (bdh). the gpl problem occurs when there are bursty requests for retransmissions of the same data with high spatial and temporal locality, causing network congestion. the bdh problem occurs when these requesting devices move out of their current serving cells. in this paper, we propose a bulk request recovery (brr) scheme to solve these problems by exploiting spatial and temporal locality of recovery requests. our scheme can efficiently reduce duplicate requests and schedule retransmissions of lost packets, so both gpl and bdh problems are relieved. simulations results are also presented to verify the effectiveness of our result.
performance analysis of cooperative communication systems with imperfect channel estimation. this paper investigates the effects of channel estimation errors on the symbol-error-rate (ser) performance of a cooperative communication system operating in an amplify-and-forward (af) mode. a pilot symbol assisted modulation scheme with linear minimum mean square estimation (lmmse) is used for the channel estimation. an accurate and easy-to-evaluate ser expression is presented for uncoded cooperative communication systems with quadrature amplitude modulation (qam) and phase-shift keying (psk) constellations. numerical simulations are conducted to verify the correctness of the proposed analytical formulation. it is shown that the performance loss caused by channel estimation errors increases mainly with the normalized maximum doppler frequency.
detecting low-power primary signals via distributed sensing to support opportunistic spectrum access. cognitive radio operation with opportunistic spectrum access has been proposed to utilize spectrum holes left unused by a primary system owning the spectrum license. the key of cognitive radio operation is the ability to detect weak primary signals and to control the transmission of cognitive users in a way that interference between the two systems is minimized. in this paper we evaluate how a sensor network deployed to provide distributed spectrum sensing can assist cognitive operation. specifically, we consider sensor networks with regular topology, where a high level of cooperation also means that sensors far from the source of the primary signal are involved in the sensing process. assuming energy detection and hard-decision combining we derive worst case probabilities of missed detection and false alarm, determine the necessary level of cooperation among the sensors and evaluate how the sensor density and the sensing time affect the performance of distributed sensing.
peer-to-peer application recognition based on signaling activity. because of the enormous growth in the number of peer-to-peer (p2p) applications in recent years, p2p traffic now constitutes a substantial proportion of internet traffic. the ability to accurately identify different p2p applications from the network traffic is essential for managing a number of network traffic issues, such as service differentiation and capacity planning. however, modern p2p applications often use proprietary protocols, dynamic port numbers, and packet encryptions, which make traditional identification approaches like port-based or signature-based identification less effective. in this paper, we propose an approach for accurately recognizing p2p applications running on monitored hosts based on signaling behavior, which is regulated by the underlying p2p protocol; therefore, each application possesses a distinguishing characteristic. we consider that the signaling behavior of each p2p application can serve as a unique signature for application identification. our approach is particularly useful for three reasons: 1) it does not need to access the packet payload; 2) it recognizes applications based purely on their signaling behavior; and 3) it can identify particular p2p applications. the performance evaluation shows that 92% of a real-life traffic trace can be correctly recognized within a 5-minute monitoring period.
reducing average power in wireless sensor networks through data rate adaptation. the use of variable data rate can reduce network latency and average power consumption, and automatic rate selection is critical for improving scalability and minimizing network overhead. in the ieee 802.15.4 standard the snr can be inferred through the radio reported link quality or received signal strength, and an extension to the standard leads to highly dynamic and accurate rate selection. using data from an experimental study of 44 ieee 802.15.4 nodes in an industrial mesh network, snr is extracted to show sufficient margin exists for higher data rate communication. a variable rate signaling scheme with automatic rate selection is proposed to provide links at the standard 250kb/s as well as 500kb/s, 1000kb/s and 2000kb/s with a minimum of hardware changes. using the experimental data to generate a model of the real world system, total network energy is compared using legacy and variable rate signaling showing over 40% savings.
zero forcing processing in two hop networks with multiple source, relay and destination nodes. in this paper, we consider two hop networks with multiple source, relay and destination nodes. in particular, we investigate systems with different processing capabilities at the relay and destination nodes. we derive new closed-form outage probability expressions when zero forcing processing is used at the i) relay, ii) relay and destination and iii) destination nodes only. our results indicate significant decreases in outage probability for certain node configurations. we confirm our results through comparison with monte carlo simulations.
demonstration of ipv6 network mobility in aeronautical communications network. this paper presents the development of a laboratory demonstrator within newsky, a project co-funded by the european commission within its 6th research framework programme (fp6). host and network mobility are some of the essential network functionalities required for efficient operation of a network-centric aeronautical communication system. this paper deals with the feasibility demonstration of mobile ipv6 (mipv6) and network mobility (nemo) protocols to suitable provide mobility support for the future air traffic management (atm) network.
controlling error propagation in network-coded cooperative wireless systems. in cooperative communications, error propagation at relays degrades the diversity order of the system. to combat that effect, it has been suggested to implement a reliability threshold at the relay to control error propagation. the relay calculates log-likelihood ratio (llr) values for the bits sent from the source. these values are subjected to a threshold to selectively forward bits that are most reliable and discard bits that are less so, resulting in less errors propagating to the destination. we investigate the application of this technique to a network-coded two-way relay channel, where the relay is assisting two sources simultaneously. we investigate two modes of thresholding at the relay: at the individual-bit level and at the combined-bit level. we analyze the bit-error rates of both thresholding modes and optimize the threshold for both. we show significant gains using thresholding over an unthresholded network-coded system. based on system simulations, we conclude that utilizing separate thresholds yields better results than utilizing a combined threshold scheme.
pick your layers wisely - a quality assessment of h.264 scalable video coding for mobile devices. multi-dimensional video scalability as defined in h.264/svc is a promising concept to efficiently adapt encoded streams to individual device capabilities and network conditions. however, we still lack a thorough understanding of how to automate scaling procedure in order to achieve an optimal quality of experience (qoe) for end uses. in this paper we present and discuss the results of a subjective quality assessment we performed on mobile devices to investigate the effects of multi-dimensional scalability on human quality perception. our study reveals that qoe degrades nonmonotonically with bitrate and that scaling order preferences are content-dependent. we confirm previous studies which found common objective metrics to fail for scalable content, but we also show that even scalability-aware models perform poor. our results are supposed to help improving the design of quality metrics and adaptive network services for scalable streaming applications.
optimal relay assignment and power allocation in selection based cooperative cellular networks. we consider a system with a single base station communicating with multiple users over orthogonal channels while being assisted by multiple relays. several recent works have suggested that selection, i.e., a single relay helping the source, is the best option in terms of the resulting complexity and overhead. however, in a multiuser setting, optimal relay assignment is a combinatorial problem. in this paper, using the sum rate as our design metric, we develop a convex optimization problem that provides an extremely tight upper bound on performance. we also provide a heuristic to find a close-to-optimal relay assignment. simulation results using realistic channel models demonstrate the efficacy of the proposed scheme.
a study on collaborative beamforming with protocol defects in wireless ad hoc networks. to conduct collaborative beamforming in wireless ad hoc or sensor networks, several protocols must be executed, including the localization protocol, time synchronization protocol, and data dissemination protocol. in practice, however, these protocols are often limited by their complexities for achieving the ideal perfect performance. therefore, protocol defects such as location errors, time synchronization errors, and message losses often appear in collaborative beamforming with distributed operations. in this paper, we introduce an analytical framework to analyze the impact of protocol defects on the performance of collaborative beamforming. we show numerical results of the proposed model, and explain how the proposed model can be used to mitigate the impact of protocol defects for collaborative beamforming in wireless networks.
reduced-rank adaptive least bit error-rate detection in hybrid direct-sequence time-hopping ultrawide bandwidth systems. in this paper we consider the low-complexity detection in hybrid direct-sequence time-hopping ultrawide bandwidth (ds-th uwb) systems. a reduced-rank adaptive lber detector is proposed, which is operated in the least bit error-rate (lber) principles within a detection subspace obtained with the aid of the principal component analysis (pca)- assisted reduced-rank technique. our reduced-rank adaptive lber detector is free from channel estimation and does not require the knowledge about the number of resolvable multipaths as well as that about the multipaths' strength. in this paper the bit error-rate (ber) performance of the hybrid ds-th uwb system is investigated, when communicating over the uwb channels modelled by the saleh-valenzuela (s-v) channel model. our study and simulation results show that this reduced-rank adaptive lber detector constitutes a feasible detection scheme for deployment in practical pulse-based uwb systems.
bluebat: towards practical bluetooth honeypots. it is still difficult to assess the real danger posed by bluetooth-propagated malware. bluebat is an effort to build and deploy a practical honeypot for capturing in-the-wild samples and empirically study malware prevalence. this paper describes the design and implementation of a first prototype, focusing on bluetooth worms propagating over the obex push service. we develop and perform initial field testing of different types of sensors, in order to achieve an optimal collection capability. we analyze the results of the field tests, and demonstrate various design constraints. also, from these preliminary tests, we cast some doubts on the prevalence of in-the-wild bluetooth worms, and hint at some reasons why such threat could be more limited than previously thought.
rate allocation for the multi-source downlink channel with minimax optimization. we consider the downlink transmission with multiple sources. each source transmits over an orthogonal channel by using cooperative broadcasting. each destination is required to receive and decode a given amount of information. a destination can receive different partitions of information from multiple sources. the sources cooperate and allocate the flow rates along each link to minimize the maximum individual transmit power of each source. to simplify the computations involved in the optimization process, we suggest a sub-optimal algorithm. simulation results indicate that our optimal scheme gives improvements between 4.2db and 5.6db over the single-source scheme, where a destination selects only one source for transmission, in our considered networks and rate requirements. our sub-optimal algorithm suffers a loss of below 0.4db compared with the optimal one. the expressions involved in the sub-optimal algorithm are less complicated and it requires m iterations, where m is the number of destinations, and a bisection search in each iteration.
dynamic coexistence of frequency hopping networks using parallel and gaussian allocations. this paper studies the coexistence of several independent and dynamic wireless networks using the frequency hopping technique in the unlicensed radio band. we propose a new hopping scheme that allows more networks to collocate effectively, but does not violate federal restrictions regarding frequency constraint (related to the minimum number of frequencies in a hopping set) and time constraint (related to the maximum duration of using a particular frequency). the coexisting networks follow the gaussian distribution in choosing transmission frequencies from parallel hopping spaces without the overhead of extra message exchange. simulation results include comparison with other contemporary approaches and establish the viability of the proposed scheme.
information combining for relay networks. analyzing the capacity of relay networks is often based on the max-flow min-cut theorem providing an upper bound on the true capacity which is generally still unknown. this paper analyzes the achievable rates of a simple relay network by a semi-analytical approach considering ideal capacity achieving codes of appropriate rates and optimum symbol-by-symbol soft-output decoding at the relay. applying the information combining technique, regions are illustrated where the upper bound provided by the max-flow min-cut theorem can be reached. moreover, the results show that the lower bound obtained by the constraint of error-free decoding at the relay can be exceeded in many scenarios. simulations with a nearly capacity achieving half-rate repeat accumulate code confirm the semi-analytic results.
ofdma-tdd networks with busy burst enabled grid-of-beam selection. interference aware user scheduling in fixed grid-of-beam (gob) transmission is envisaged to significantly benefit from the receiver initiated busy burst (bb) protocol. fixed gob scheduling relies on the knowledge of the location of the intended users as well as the vulnerable users which effectively is provided by the bb protocol via exploitation of channel reciprocity. this paper studies the hybrid bb and gob (bb+gob) approach in a manhattan environment. the new proposed hybrid interference avoidance scheme with an underlying score based scheduler is evaluated by means of system level simulations, and is compared against a pure gob approach with the same scheduler as well as the bb based interference avoidance techniques applied to omnidirectional antennas. the results show an improvement in both system throughput and fairness (defined as cell edge user throughput). in particular, system throughput of up to 238.5 mbps/cell or user throughput of up to 8.88 mbps/user for the lower 10%-ile of users are shown to be feasible. in particular, the hybrid bb+gob scheme exhibits a 16-fold improvement at the lower 10%-ile compared to pure gob technique.
improving throughput in high bandwidth-delay product networks with random packet losses. it is well known that the standard tcp has become a performance bottleneck in the networks with large bandwidth-delay products. the situation gets worse if high-speed wireless links are part of the networks, due to the frequent random losses over the wireless links. this is because the standard tcp increments its congestion window too slowly in the absence of packet losses and decrements it too drastically in response to packet losses. a natural solution is to make tcp more aggressive. this approach has been exercised in the recent tcp development such as hstcp and multcp which have the capability of using a single logical connection to emulate the behaviour of a set of multiple standard tcp connections. in the meantime, tcp parallelisation uses a set of parallel tcp connections to transfer data for an application process. then, a question arises - can the single-connection based approach achieve the similar performance as tcp parallelisation in the environments where random packet losses prevail. our analysis shows that tcp parallelisation has the better performance and is more efficient for performance improvement.
improved vector perturbation with modulo loss reduction for multiuser downlink systems. in this paper, we present an improved precoding technique which reduces a modulo loss in vector perturbation (vp) with low complexity for the downlink of a multiuser multiple-input multiple-output (mimo) system. at low snr regime, the vp suffers from the modulo loss due to the increased number of nearest neighbors. for the original vp, the sphere encoder searches perturbation vectors in the infinite lattice. in contrast, the proposed scheme restricts the search range utilizing the distribution of the perturbation vector depending on transmitted data. as a result, we can achieve significant complexity savings at the transmitter and the receiver while providing better performance compared to the conventional sphere encoder. simulation results show that the proposed scheme provides a 0.2 db gain over the conventional vp at a bit error rate (ber) of 10-3 for the case of four transmit antennas and four users with 4qam. also, the proposed scheme reduces the maximum number of candidate search by 95% in comparison to the original vp.
distributed interference pricing for the mimo interference channel. we study distributed algorithms for updating transmit precoding matrices for a two-user multi-input/multi-output (mimo) interference channel. our objective is to maximize the sum rate with linear minimum mean squared error (mmse) receivers, treating the interference as additive gaussian noise. an iterative approach is considered in which given a set of precoding matrices and powers, each receiver announces an interference price (marginal decrease in rate due to an increase in interference) for each received beam, corresponding to a column of the precoding matrix. given the interference prices from the neighboring receiver, and also knowledge of the appropriate cross-channel matrices, the transmitter can then update the beams and powers to maximize the rate minus the interference cost. variations on this approach are presented in which beams are added sequentially (and then fixed), and in which all beams and associated powers are adjusted at each iteration. numerical results are presented, which compare these algorithms with iterative water-filling (which requires no information exchange), and a centralized optimization algorithm, which finds locally optimal solutions. our results show that the distributed algorithms perform close to the centralized algorithm, and by adapting the rank of the precoder matrices, achieve the optimal high-snr slope.