waashk/dblp huggingface dataset:
interference subtraction with supplementary cooperation in wireless cooperative networks. in wireless networks, the broadcast nature of wireless transmission enables cooperation by sharing the same transmissions with nearby receivers and thus can help improve spatial reuse and boost network throughput along a multi-hop routing. the performance of wireless networks can be further improved if prior information available at the receivers can be utilized to achieve perfect interference subtraction. in this paper, we investigate performance gain on network throughput for wireless cooperative networks by using a simple mud scheme, called overlapped transmission, in which multiple transmissions are allowed only when the information in the interfering signal is known at the receiver. it is shown that the scheme of cooperative transmission with overlapping increases network throughput by 24% compared to that of direct transmission with overlapping. we then propose a new cooperation scheme called supplementary cooperation, which improves the performance gain of direct transmission with overlapping by 42%. analytical results are developed to show that in a general network scenario, supplementary cooperation achieves bit error rate (ber) reduction of 34.87%, compared with the conventional cooperative transmission. furthermore, we proposed a criterion for finding the best cooperative route to achieve maximum network throughput in a general network.
a discrete channel model for capturing memory and soft-decision information: a capacity study. a discrete (binary-input 2q-ary output) communication channel with memory is introduced with the objective to judiciously capture both the statistical memory and the soft-decision information of time-correlated fading channels modulated via binary phase-shift keying and coherently demodulated with an output quantizer of resolution q. it is shown that the discrete channel can be explicitly described in terms of its binary input process and a 2q-ary noise process. it is also shown that the channel is symmetric and admits a simple expression for its capacity when its noise is stationary ergodic. the 2q-ary noise process is next modeled via a generalized version of the recently studied binary queue-based channel (2007) to produce a mathematically tractable stationary ergodic m'th order markovian noise source with 2q + 2 parameters. numerical results indicate that the capacity of the discrete channel with q = 2, 3 is substantially improved over the cases of perfect channel interleaving (which yields an equivalent memoryless channel) and of hard-decision demodulation (q = 1). these results point to potentially large performance gains achievable by designing coding schemes for this discrete channel that exploit both its memory and soft-decision information, as opposed to ignoring either of them.
burst erasure correction capabilities of (n, n-1) convolutional codes. for (n, k, m) systematic polynomial convolutional encoders, there exists an upperbound on the length of a correctable burst of erasures in terms of code parameters. in this paper, we restrict ourselves to the case k = n-1 and provide a necessary and sufficient condition to achieve the upperbound in terms of the encoder coefficients. in addition, for selected values of m, we present explicit (n, n-1, m) systematic polynomial convolutional encoders that achieve the upperbound.
efficiently constructing candidate set for network topology design. network topology seriously affects network cost, path length, distribution of link load, and reliability, for example, so we need to consider these multiple criteria with different units simultaneously when designing network topology. the analytic hierarchy process (ahp) is a way to make a rational decision considering multiple criteria. using ahp, we can reflect the relative importance of each criterion on the evaluation result, so we have applied it to network topology evaluation. when evaluating network topologies using ahp, we need to construct the set of topology candidates prior to the evaluation. however, the time required to construct this set greatly increases as the network size grows. in this paper, we propose to apply a binary partition approach for constructing a topology candidate set with dramatically reduced calculation time. to reduce the calculation time, we introduce an upper limit for the total link length. although the results of ahp are affected by introducing the upper limit of total link length, we show that desirable topologies are still selected in ahp.
intercell interference measured in urban areas. we report on measurements at 2.53 ghz with 20 mhz bandwidth in two triple-sectored urban macro-cell deployments in berlin and dresden, germany. these measurements assist the design of multiuser and cooperative transmission and detection techniques promising to reduce the interference in future cellular systems. we study the geometry factor and the top-n power statistics in the non-cooperative case and compare the results with a commonly used spatial channel model. furthermore we observe that the median delay parameters in a coherent single frequency network deployment are roughly 1.5 times higher than in an isolated cell while the maximum excess delays are similar in both cases. finally we study the correlation of the channel response for different antenna spacings at the base station. when the sector antennas are close together, the correlation is generally high which is also predicted by the channel model, but with spacings of about 20 m the correlation significantly decreases.
per-tone equalizer design and analysis of filtered multitone communication systems over time-varying frequency-selective channels. although orthogonal frequency division multiplexing (ofdm) communication systems that use inverse discrete fourier (idft) for multicarrier modulation and discrete fourier transform (dft) for demodulation are dominantly adopted in the current broadband standards, there have been some reports in recent years that discuss the shortcomings of ofdm in highly mobile and/or multiple access environments. to resolve these problem, a number of authors have proposed a shift from ofdm to filterbank-based multicarrier techniques. this paper is also along the same line. we present a thorough study of filtered multitone (fmt)in time-varying frequency selective channels. we derive close-form equations for the optimum parameters of per tone fractionally spaced equalizers and also signal to interference plus noise ratio (sinr) and use these to evaluate fmt in typical wireless mobile environments.
distributed quality-lifetime maximization in wireless video sensor networks. owing to the availability of low-cost and low-power cmos cameras, wireless video sensor networks (wvsn) has recently become a reality. however video encoding is still a costly process for energy and capacity constrained sensor nodes and its optimal joint control with the communication protocols has a direct impact on the network lifetime. in this paper we propose a distributed quality-lifetime control algorithm where quality is simply measured by the visual signal quality. in order to formulate the quality-lifetime problem, we consider the power-rate-distortion (p-r-d) model of the video encoder together with the rate control, medium access and routing functions of the underlying communication protocol and formulate the problem as a generalized network utility maximization (gnum) problem. then we construct a distributed solution based on duality and proximal point methods with necessary convergence analysis. simulation results support that optimal quality-lifetime control is possible through the proposed distributed algorithm, where the desired point of operation is simply adjusted by the sink via a configuration parameter.
wireless location privacy protection in vehicular ad-hoc networks. advances in mobile networks and positioning technologies have made location information a valuable asset in vehicular ad-hoc networks (vanets). however, the availability of such information must be weighted against the potential for abuse. in this paper, we investigate the problem of alleviating unauthorized tracking of target vehicles by adversaries in vanets. we propose a vehicle density-based location privacy (dlp) scheme which can provide location privacy by utilizing the neighboring vehicle density as a threshold to change the pseudonyms. we derive the delay distribution and the average total delay of a vehicle within a density zone. given the delay information, an adversary may still be available to track the target vehicle by some selection rules. we investigate the effectiveness of dlp based on extensive simulation study. simulation results show that the probability of successful location tracking of a target vehicle by an adversary is inversely proportional to both the traffic arrival rate and the variance of vehicles' speed. our proposed dlp scheme also has a better performance than both mix-zone scheme and amoeba with random silent period.
vertex packing decoding. in this work, we present a new framework for developing decoding algorithms for linear block codes. we define a new graphical model, called configuration graph and show that maximum likelihood (ml) sequence decoding can be performed by finding a maximum vertex packing on a configuration graph. we present examples of low-cost decoding algorithms developed using this graphical model and show that remarkable performance improvements can be achieved especially by combining these algorithms with belief propagation (bp) decoding for low density parity check (ldpc) codes.
improved decision-directed recursive least squares mimo channel tracking. this paper presents a comparative study of different recursive least squares algorithms to track a rayleigh flat fading mimo channel. we investigate the effect of the initialization and training of these algorithms on their performance. we propose a new training scheme which can deliver a lower mean squared estimation error without loss of bandwidth efficiency.
on the interaction between channel coding and hierarchical modulation. classical systems using hierarchical modulation (such as dvb-sh) involve a "high-priority" (hp) and a "low-priority" (lp) bit stream that are separately and independently encoded before being mapped on non-uniformly spaced constellation points, leading to different levels of error protection. however, an inherent drawback of this scheme is the severe performance degradation of the less protected lp stream. in this paper, we propose a concatenated encoding scheme that mixes the two streams in order to make the encoding of the lp stream dependent on the well protected hp stream. consequently, at the receiver side, the reliable information on hp bits provided by the hp decoder is naturally involved in the decoding process of the lp stream and acts as "soft pilots". we have exploited this feature inside a soft decoding mechanism in order to improve the lp decoding performance while keeping the hp decoding performance unchanged. numerical results presented in the case of the dvb-sh standard show that the proposed system outperforms the classical approach in terms of lp bit error rate without a considerable increase in the receiver complexity.
joint transmit and receive analog beamforming in 60 ghz mimo multipath channels. analog beamforming (abf) with one scalar weight per antenna is an attractive technique for low-cost, low-power 60 ghz multi-antenna wireless communication systems. however, the design of the corresponding joint transmit and receive (tx/rx) abf optimization algorithms is still challenging in the case of multipath channels due to the constraint of having only one scalar weight per antenna. in this paper, we aim at maximizing the average signal to noise ratio (snr) at the input of the equalizer and analytically derive close-to-optimal tx/rx scalar weights. we show that the required channel state information (csi) for joint tx/rx abf weights computation is the inner product between all tx/rx channel impulse response pairs. taking the channel length into account, a training-based estimation strategy of this csi is proposed. simulation results carried out in a typical 60 ghz multipath environment show that the proposed scheme outperforms the existing abf schemes in term of ber performances.
a generalised multi-receiver radio network and its decomposition into independent transmitter-receiver pairs: simple feasibility condition and power levels in closed form. we consider a generalised multi-receiver radio network under a quality-of-service (qos) constraint that involves generalised carrier-to-interference ratios. this model includes as special cases many well-known schemes, such as those discussed by yates (jsac, 13(7):1341-1348, 1995). a simple feasibility condition for the qos targets, and a power-vector that yields those targets are given in closed form for the case in which additive noise is negligible and the key functions are homogeneous of degree one. the condition has the simple form, k_i <= q_i, where "i" identifies a terminal, "k_i" its desired qos level, and "q_i" its quality of service when all power levels equal unity. if the feasibility condition is satisfied, the power levels p_i = k_i / q_i yield or exceed the desired levels of quality. the generalised multi-receiver network can be conservatively represented by an equivalent set of independent transmitter-receiver pairs, with q_i equal to the channel gain of the pair that represents "i". macro-diversity and multiple-connection reception are some of the specific models discussed as examples.
distributed and power efficient routing in wireless cooperative networks. most ad hoc mobile devices in wireless networks operate on batteries and power consumption is therefore an important issue for wireless network design. in this paper, we propose and investigate a new distributed cooperative routing algorithm that realizes minimum power transmission for each composed cooperative link, given the link ber (bit error rate) constrained at a certain target level. the key contribution of the proposed scheme is to bring the performance gain of cooperative diversity from the physical layer up to the networking layer. specifically, the proposed algorithm selects the best relays with minimum power consumption in distributed manner, and then forms cooperative links for establishing a route with appropriate error performance from a source to a destination node. analytical results are developed to show that our cooperative transmission strategy (mpsdf) achieves average energy saving of 82.43% compared to direct transmission, and of 21.22% compared to the existing minimum power cooperation strategy. furthermore, the proposed power efficient routing algorithm can also reduce the total power consumption by a couple db compared to existing cooperative routing algorithms. monte-carlo simulation results are also provided for performance evaluation.
using area hierarchy for multi-resolution storage and search in large wireless sensor networks. we consider multi-resolution storage, a technique for providing scalable adaptive data fidelity, necessary for many applications of large wireless sensor networks (wsns). although the previously proposed design of multi-resolution storage, based on quad trees and geographic routing, is conceptually simple, it exhibits inherent problems if applied to real-world wsns. to address these problems, we revisit some of the networking assumptions and propose an alternative design that employs an overlay combining area and landmark hierarchies. simulations and initial experiments with a prototype embedded implementation indicate that our solution can be scalable and can work on real hardware, which motivates further research.
de-registration based s-cscf load balancing in ims core network. ip multimedia subsystem (ims) provides a common control layer over which the services can be easily accessed by fixed and mobile users. in order to guarantee performance to both service providers and end service subscribers, careful management and maintenance within the control layer must be fulfilled. in this paper, we propose a solution that utilizes a controlling entity to track the utilization of hotspot session initiation protocol (sip) server (i.e., s-cscf) and to initiate de-registration procedure so that a sufficient number of subscribers at the overloaded s-cscf are re-associated with the other s-cscf(s) for subsequent session services. the proposed solution redistributes and smoothes the future traffic load over individual s-cscf in an automatic manner. the goodness of the proposal is assessed through simulations using opnet.
a 3-d markov chain queueing model of ieee 802.11 dcf with finite buffer and load. we introduce a 3-dimensional markov chain that integrates the ieee 802.11 dcf contention resolution and queueing processes into one model. important qos measures, delay and loss, plus throughput and queue length, can be obtained for a realistic systems with finite buffer under finite load. we present an efficient method for solving the steady state probabilities of the markov chain. simulations confirm the accuracy of our model, and demonstrate that the model provides new insights into the 802.11 dcf protocol.
performance of dual-hop transmissions with fixed gain relays over generalized-k fading channels. we present the end-to-end performance of dual-hop wireless communication systems with non-regenerative fixed gain relays operating over independent not necessarily identically generalized-k (kg) fading channels. new closed-form expressions are derived for the moments of the end-to-end signal-to-noise ratio (snr), while the corresponding moment-generating function (mgf) is accurately approximated with the aid of padé approximants theory. useful performance criteria are studied; the average end-to-end snr and the amount of fading, which are expressed in closed form, the average bit-error probability for several coherent, noncoherent, and multilevel modulation schemes, and the outage probability, which are both accurately approximated using the well-known mgf approach. furthermore, novel closed-form expression is obtained for the gain of semi-blind relays over kg fading channels. the proposed mathematical analysis is complemented by various performance evaluation results, which demonstrate the accuracy of the theoretical approach.
smoothing plls for qam dynamical phase estimation. this paper presents a near-optimum, low-complexity, fixed-interval smoothing algorithm that approaches the performance of an optimal smoother for the price of two low-complexity sequential estimators (two plls). the proposed smoothing pll (s-pll) algorithm is easy to implement and fits the cramer-rao bounds over a wide range of signal-to-noise ratios. moreover we show that, compared to the conventional forward loop, the proposed scheme allows to have a large gain of several dbs and is able to track frequency offsets.
investigation of h.264 video streaming over an ieee 802.11e edca wireless testbed. although a number of investigations have been conducted using ieee 802.11e enabled networks to stream class differentiated video, very few reports are available based on a real testbed. in our work, we set up a wireless testbed for h.264 video streaming through assigning the partitioned video packets onto the dcf mac layer and different access classes of the edca mac layer. we investigate three assignment schemes: 1) dcf is used and all the traffic is treated equally; 2) video traffic is assigned to each of the access classes in turn; and 3) the packets are assigned according to their importance and the class priority. in addition to the video stream we introduce tcp traffic from three clients in the best effort class. we show that video quality can be improved through properly assigning packets to wireless access classes compared to the standard best effort scheme. importantly, we show, based on our testbed results, that the single class assignment can achieve better performance than the multi-class assignment suggested by other researchers. finally we show that virtual contention between traffic classes at the access point is an important issue to address.
a testbed development framework for cognitive radio networks. cognitive radio networking is a promising approach to fulfill the future's need for intelligent, high-performance communication and improve the efficiency of overall spectrum utilization. testbed evaluation of protocols and algorithms is a must for the development of cognitive radio networks. in this paper, we present an integrated testbed framework for cognitive radio networks. the framework includes necessary components for cognitive radio operations: flexible rf front end, software define signal processing, adaptive mac layer and network layer as well as a cross layer management interface. such a design eases the cross layer configuration and performance optimization of cognitive protocol stack, while retaining the advantage of modularity. we design a testbed for ad-hoc cognitive radio network.
exploiting connections between mimo mmse achievable rate and mimo mutual information. we present an interesting and powerful new framework connecting the achievable sum rate of multiple-input multiple-output (mimo) wireless systems employing linear minimum mean-squared error (mmse) receivers, and the ergodic mimo mutual information. this allows the vast literature on ergodic mimo mutual information to be directly applied to the analysis of mmse receivers. as an example, the framework is particularized to spatially-correlated rayleigh fading to yield new exact closed-form expressions for the achievable sum rate, as well as simplified expressions for high and low signal to noise ratios.
low complexity encoder for generalized quasi-cyclic codes coming from finite geometries. we define generalized quasi-cyclic (gqc) codes as linear codes with nontrivial automorphism groups. therefore, gqc codes, unlike quasi-cyclic codes, can include many important codes such as hermitian and projective geometry (pg) codes; this capability is important in practical applications. further, we propose the echelon canonical form algorithm for computing gröbner bases from their parity check matrices. consequently, by applying gröbner base theory, gqc codes can be systematically encoded and implemented with simple feedback shift registers. our algorithm is based on gaussian elimination and requires a sufficiently small number of finite-field operations, which is related to the third power of code-length. in order to demonstrate our encoder's efficiency, we prove that the number of circuit elements in the encoder architecture is proportional to the code-length for finite geometry (fg) ldpc codes (a class of gqc codes). we show that the hardware complexity of a serial-in-serial-out encoder architecture for fg-ldpc codes is related to the linear order of the code-length; less than 2n adder and 2n memory elements are required to encode a binary codeword of length n.
cryptanalysis of substitution cipher chaining mode (scc). in this paper, we cryptanalyze the substitution cipher chaining mode (scc-128) [3], which uses three keys. the first key is the encryption key, which we were able to recover with about 240 cipher executions and 5 × 28 chosen plaintexts. the second key is responsible of generation two layers of masks, we recovered the first layer with 213 chosen plaintext and 221 cipher executions and our attack to recover the second layer costs only one known sector plaintext and 64 cipher executions. the third key is used to generate the encrypted sector id, we were able to recover the encrypted sector id of a sector with 1 known plaintext and 2 cipher executions for each sector.