waashk/dblp huggingface dataset:
minimum sum expected distortion in cooperative networks. in this paper, we consider a wireless cooperative multimedia decode-and-forward network wherein one relay may assist multiple source-destination pairs. by exploiting the global channel state information at the relay, we propose a power allocation, a time allocation and an iterative joint power-time allocation algorithm to minimize the sum expected distortion. firstly, we separately optimize the relay's transmission power and the system transmission time allocated to each source-destination pair such that the sum expected distortion can be minimized. then, we propose an iterative joint power-time allocation algorithm subject to the relay's total power constraint to further improve the distortion performance. the proposed iterative algorithm is guaranteed to converge to an optimal, despite not necessarily globally optimal, point and can achieve the minimum sum expected distortion among all the schemes.
on low-density mimo codes. multiple antenna systems are promising approaches to increase the data rate of wireless communication systems. there, modulated symbols are multiplexed on multiple transmission antennas. typically an outer error correcting code is used additionally to ensure a desired quality of service for a given data rate. an appropriate communications performance can be achieved by iterative decoding, where probabilistic information are exchanged between outer decoder and the mimo demodulator. however, in this case the mimo demodulator has to calculate probabilistic soft-output values for each bit which can be very complex. in this paper we present a new class of linear block codes named low-density mimo codes which reduces the complexity of the mimo soft-demodulator and the outer channel decoder inherently by code design without decreasing the data rate of the overall system. these ldmc codes can have a better communications performance then state of the art solutions with a order of magnitude smaller decoding complexity.
noise-aware wavelength assignment for wavelength switched optical networks. in transparent wson (wavelength switched optical networks), signals are switched optically and propagate thousands of kilometers without electrical regeneration. over such distances, physical impairments, such as crosstalk, ase noise and so on, can accumulate along the path and lead to signal quality degradation. if the admission of a lightpath will either cause its ber to be too high, or sufficiently degrade the performance of the already established lightpaths, it must be blocked. most of recent research only consider the first case, but ignore the second case, which will lead to service interruption. in this paper, a new noise-aware wavelength assignment scheme called nawa has been proposed, which use iies (impairments impact evaluation scheme) to solve both problems mentioned above in a distributed way. simulations have been conducted and numerical results show that: compared with normal impairment-aware solutions, nawa can eliminate the occurrence of service interruption, and achieve better performance in total blocking.
near successive refinement of gaussian vectors in grassmannian space. in this paperwe look at the problem of successively refining the description of a gaussian i.i.d. source in a grassmannian space. this problem is relevant, for example, in the encoding of channel state information for the limited feedback mimo broadcast channel. we show how it is possible to achieve an isotropic distribution of the error vector by applying unitary transformations, which simplifies the problem of finding optimal codebooks for the error quantisation. reconstruction error analysis and numerical tests show how the proposed technique can, in practice, perform very close to the distortion-rate bound and suggest that, in some cases, these successive error descriptions can be optimal refinements of one another.
an optimal sensor network for intrusion detection. wireless sensor networks have been widely used in environment and habitat monitoring, as well as in military applications such as battlefield surveillance. in this paper, we focus on detecting intruders in such surveillance systems. our goal is to optimize the network coverage when the network is deployed to detect an intrusion object with the shape of a disc or a rectangle. we study how the size and shape of the intrusion object influence the configuration of the sensor network. we prove many mathematical results related to detection probability and intrusion coverage intensity and study the asymptotic properties of these detection metrics. we also study the problem of maximizing network lifetime under some qos constraints. we prove the existence of the solution and derive the explicit form of the solution under certain conditions.
to sort or not to sort: optimal sensor scheduling for successive compress-and-estimate encoding. in this paper, we address the problem of energy-efficient decentralized parameter estimation with wireless sensor networks (wsn). more precisely, we adopt the so-called compress & estimate successive encoding scheme and we analyze the impact of the ordering in which the sensor transmissions are scheduled on the resulting estimation accuracy. we consider two scenarios of interest: (i) sensors experiencing different channel gains to the fc (e.g. due to rayleigh fading); and (ii) sensors with different observation qualities. for each scenario, we determine the optimal and worst-case scheduling orders for an arbitrary number of sensors. besides, we propose a suboptimal yet efficient scheduling rule suitable for the case in which sensors experience both different channel gains and observation qualities. performance assessment is carried out by means of computer simulations where we check how sensitive performance can be to the ordering for a varying number of sensors, transmit power and correlation among observations.
performance analysis of the dd ml mimo channel tracking algorithm. in this paper, performance analysis of the decision directed (dd) maximum likelihood (ml) multiple-input multiple-output (mimo) channel tracking algorithm is presented. the ml channel tracking algorithm presents efficient performance especially in the dd mode of the operation. because of the nonlinear decision device, analysis of the dd based algorithms is very difficult. in this paper, first the decision error rate is computed for the known channel tracking error and then the channel tracking error is evaluated for the known decision error rate. the presented analysis is compared with the simulation results for different doppler frequency shifts and snrs, and it is shown that the analysis and simulation results are in a good match even for high rank mimo channels and high doppler shifts.
cross-layer design of networked control systems. the wireless connection of spatially separated sensors, controllers and actuators poses challenging problems to the control system, due to packet drops, delays and measurements quantization, as well as to the wireless network resource allocator. this pushes for a cross-layer design of communication and estimation/control systems. assuming a tcp-like protocol between controller and actuator, we solve the problem of optimum control around a target state for a stable system in case of both packet drops and signal quantization. generalization for unstable systems is also given for large bandwidth transmissions. next, we derive the limiting behavior of the system in the infinite horizon and propose a general framework for cross-layer optimization of signal quantization and network resource allocation. as an example of application, we consider a simple scalar, stable system and compare network resource allocation in the presence of i) low-cost sensors using a fix modulation and ii) long-term future sensors capable of rate adaptation. interestingly, almost optimal control is achievable by small bandwidth transmissions using a simple bpsk, supporting the use of low-cost sensors in applications dealing with state control in stable systems.
an effective cross-layer packet scheduling and routing algorithm for delay-sensitive media transmission over manet. this work presents a tightly-coupled packet scheduling and routing algorithm to effectively transmit delay-sensitive media over mobile ad hoc network. first, packet urgency, node urgency, and route urgency are defined based on the end-to-end delay requirement of each packet and the number of hops over a route. packet scheduling algorithm and packet drop policy are designed to maximize the number of packets delivered in the tolerable delay bound and minimize their node urgency at each node simultaneously. finally, the routing algorithm is implemented to search for a route with the minimum route urgency.
dynamic lightpath allocation in translucent wdm optical networks. the optical reach (the distance an optical signal can travel before the signal quality degrades to a level that necessitates regeneration) ranges from 500 to 2000 miles. to establish a lightpath of length greater than the optical reach, it is necessary to regenerate optical signals. in a translucent optical network, there are regeneration points, where the signal undergoes optical-electronic-optical (o-e-o) conversion. in this paper we have proposed routing algorithms for translucent networks in a dynamic lightpath allocation environment in which requests for communication arrive continuously. in response to each request for communication, the objective is to establish, if possible, a path, from the source to the destination of the request for communication, so that a lightpath may be established, using the path that requires the fewest stages of regeneration. in practical transparent networks, a lightpath must satisfy the wavelength continuity constraint. however, in a translucent network, this constraint can be relaxed at the regeneration points. we have proposed an integer linear program, to give the optimum results for small networks, as well as an efficient heuristic for this problem that works for larger networks. we have evaluated the heuristic through extensive simulations to establish that the heuristic produces close-to-optimal solutions in a fraction of the time needed for the optimal solutions. our extensive evaluations demonstrate the relative impact of a set of network resources, such as (i) the number of regenerators, (ii) the optical reach of the regenerators and (iii) the number of wavelengths, on the network performance, measured in terms of the call blocking probability. to the best of our knowledge this is the first study that undertakes such an evaluation for translucent networks.
component based performance modelling of wireless routing protocols. we propose a component based methodology for modelling and design of wireless routing protocols. componen-tization is a standard methodology for analysis and synthesis of complex systems, or software. the feasibility of the component based design relies heavily on the compositionality property (i.e. system-level properties can be computed from properties of components). to provide a component based design methodology and to test compositionality for routing protocols, we have to develop a component based model of the wireless network. we present the main components of the routing protocol that should be modelled and focus on three main components: neighborhood discovery, selector of topology information to disseminate, and the path selection components. for each component, we identify the inputs, outputs, and a generic methodology for modelling. throughout the paper, we use the optimized link state routing (olsr) protocol as a case study to demonstrate the effectiveness of our approach. using the neighborhood discovery component, we present our design methodology and design a modified enhanced version of this component, and compare its performance to the original olsr design.
on capacity region of two-way multi-antenna relay channel with analogue network coding. this paper studies the wireless two-way relay channel (twrc), where two source nodes, s1 and s2, exchange information through an assisting relay node, r. it is assumed that r receives the sum signal from s1 and s2 in one time-slot, and then amplifies and forwards the received signal to both s1 and s2 in the next time-slot. by applying the principle of analogue network coding (anc), each of s1 and s2 cancels the so-called "self-interference" in the received signal from r and then decodes the desired message. assuming that s1 and s2 are each equipped with a single antenna and r with multi-antennas, this paper analyzes the capacity region of an anc-based twrc with linear processing (beamforming) at r. the capacity region contains all the achievable bidirectional rate-pairs of s1 and s2 under the given transmit power constraints at s1, s2, and r. we present the optimal relay beamforming structure as well as an efficient algorithm to compute the optimal beamforming matrix based on convex optimization techniques.
pollution resilience for dns resolvers. the dns is a cornerstone of the internet. unfortunately, no matter how securely an organization provisions and guards its own dns infrastructure, it is at the mercy of others' provisioning when it comes to resolutions its resolvers perform on behalf of its clients - even one compromised dns server in the internet can mislead an organization's clients to fake look-alike phishing web sites or malware-serving sites, among other things. in this paper, we propose a self-defense mechanism where the dns resolvers collect a small amount of additional information for the dns responses they receive and maintain a history of previous responses to guard their clients against misleading information from compromised dns servers in the internet. any organization can choose to enhance its resolvers with our mechanism unilaterally, unlike dnssec, which can ensure correctness of information only if the remote dns server deploys it.
a first order logic security verification model for sip. it is well known that no security mechanism can provide full protection against a potential attack. there is always a possibility that a security incident may happen, mainly as a result of a new or modified attack that the employed countermeasures cannot handle or identify. it is therefore useful to perform a deferred analysis of logged network data, in an attempt to identify abnormal behavior/traffic that flags some type of security incident that has not been detected by the security countermeasures. such an analysis of logged data for critical real time applications, like voip services, is certainly a valuable tool for enhancing the security level of the provided service. in this paper we introduce a practical tool that can be employed for the analysis of logged voip data and thus validate the effectiveness of the security mechanisms and the conformance with the corresponding security policy rules. for the analysis of the data we capitalize on our security model for voip services [25] that is based on first order logic concepts, while the protégé api and the semantic web rule language (swrl) are also exploited. the proposed tool has been evaluated in terms of an experimental environment, while the results obtained confirm the validity of its operation and demonstrate its effectiveness.
virtual calibration for rssi-based indoor localization with ieee 802.15.4. localization systems based on received signal strength indicator (rssi) exploit fingerprinting (based on extensive signal strength measurements) to calibrate the system parameters. this procedure is very expensive in terms of time as it relies on human operators. in this paper we propose a virtual calibration procedure which only exploits the measurements of the rssi between pairs of anchors. in particular, we propose two procedures for virtual calibration and we evaluate their performance with respect to an ad-hoc calibration campaign by performing measures in an indoor environment with an ieee 802.15.4 sensor network.
general order selection allocation for decentralized multiple access networks. decentralized multiple access networks require dynamic spectrum allocation to efficiently and fairly allocate resources among multiple users. in this paper, we consider the problem of spectrum allocation from the standpoint of diversity combining, and in particular as an explicit case of selection combining (sc). general order selection allocation (gosa) was previously proposed by the authors as a low-complexity spectrum allocation scheme for decentralized multiple access networks. in this paper, noting that previous analytical results on the error performance of gosa are for independent identically distributed (i.i.d.) rayleigh fading, we carry out a thorough and exact analysis of gosa for the i.i.d. nakagami-m fading scenario. in particular, based on new results on the exact and asymptotic average error probability of the γ-th order statistic, we obtain exact and asymptotic closed-form expressions for the error performance of gosa. numerical results show that the performance of the algorithm is close to that of the highly complex optimal search method.
a new ns2 module for the simulation of mpls networks with point-to-multipoint lsp support. nowadays, many ip backbone networks adopt separate control and forwarding planes for unicast and multicast traffic flows. indeed, while mpls (multiprotocol label switching) is widely deployed for unicast traffic, ip multicast is the only available solution for the delivery of "one-to-many" traffic flows. with p2mp lsps (point-to-multipoint label switched paths) support, a unified control and forwarding plane may be devised. such a reduction in the number of protocols used in the core of the network as well as in the number of encapsulations in the data plane, results in simplified network operations. the paper discusses the design and the development of the control and data planes extensions needed to provide p2mp lsp support in an mpls node. in particular, such extensions, concerning the p2mp lsps path computation, the rsvp-te signalling protocol, and the forwarding mechanism, have been implemented as new software modules for an ad-hoc developed simulator, based on ns2. finally, tests have been performed to assess the behaviour of the new functionalities introduced in the simulator.
optimization for fractional cooperation in multiple-source multiple-relay systems. in fractional cooperation, many relays simultaneously assist the source, and each relay is responsible to relay only a fraction of the source transmission. in this paper, the problem of fractional cooperation is considered in the presence of multiple sources and multiple relays. in particular, optimization problems are formulated that can be used to allocate the relay resources between multiple sources to either minimize the energy consumed to achieve a given probability of error threshold, or minimize the maximum probability of error experienced by each source node.
throughput improvement through precoding in ofdma systems with limited feedback. in this paper, we study the possibility of throughput improvement through precoding in ofdma based wireless systems with limited channel feedback. precoding can increase the overall system throughput by selecting the use of higher modulation and coding schemes (if there are any) in each physical resource unit (pru) under a maximum bit error rate constraint. for a specific form of precoding that we proposed in [1], we analytically derive a formula for the maximum pru throughput. sufficient conditions guaranteeing that our proposed technique outperforms the conventional technique are derived. finally, numerical results show the amount of throughput gain achieved by our proposed technique.
protecting primary users in cognitive radio networks: peak or average interference power constraint? this paper considers spectrum sharing between a cognitive radio (cr) and a primary radio (pr) where the cr protects the pr transmission by regulating the resultant interference power level at the pr receiver to be below some predefined threshold. the interference-power constraint at the pr receiver is usually one of the following two types: average interference power (aip) constraint that regulates the average power level over different fading states and peak interference power (pip) constraint that limits the peak power level at each fading state. from cr's perspective, aip constraint is more favorable than pip constraint because of its more flexibility for dynamic power allocations. on the contrary, from the perspective of protecting the pr, the more restrictive pip constraint appears at a first glance to be a better option. some surprisingly, this paper shows that in terms of various forms of capacity limits achievable for the pr fading channel, namely, ergodic and outage capacities, aip constraint is also superior over pip constraint. this result is based upon an interesting interference diversity phenomenon, i.e., variable interference power levels at the pr receiver in the aip case are more advantageous over constant ones in the pip case for minimizing the resulted pr capacity losses. therefore, aip constraint leads to larger fading channel capacities over pip constraint for both cr and pr transmissions.
power optimization of device-to-device communication underlaying cellular communication. we address resource sharing of the cellular network and a device-to-device (d2d) underlay communication assuming that the cellular network has control over the transmit power and the radio resources of d2d links. we show that by proper power control, the interference between two services can be coordinated to benefit the overall performance. in addition, we consider a scenario with prioritized cellular communication and an upper limit on the maximum transmission rate of all links. we derive the optimum power allocation for the considered resource sharing modes. the results show that cellular service can be effectively guaranteed while having a comparable sum rate with a none power control case in most of the cell area.
blind multipath mimo channel parameter estimation using the parafac decomposition. in this paper, we consider the problem of estimating the physical parameters that describe a multipath mimo communication channel model characterized by specular reflections due to remote scatterers. using the impulse response channel coefficients, we introduce a channel model based on a 3rd- order tensor structure that admits a parafac decomposition with rank equal to the number of propagation paths. the alternating least squares (als) algorithm is used to estimate the channel spatial and temporal signatures and the multipath parameters are then extracted by means of music-like subspace algorithms, enabling us to recover the transmit and receive angles as well as the path propagation delays of the mimo channel, without ambiguities. computer simulation results are shown to illustrate the performance of the proposed als-music estimation algorithm.
improving the performance of lp decoders for cyclic codes. recently, a linear programming (lp) decoder has been introduced for binary linear codes. although the performance of an lp decoder has a close relationship with the form of the parity check matrix (or equivalently with the tanner graph) of the code, there is no clear approach to choosing a suitable form for lp decoding. in this paper, we focus on the class of cyclic codes, and show that the cyclic structure of the code can be used to expand the parity check matrix and obtain a low redundancy form which is suitable for lp decoding. performance results are given which demonstrate the effectiveness of the proposed algorithm.