waashk/dblp huggingface dataset:
a phy-mac cross-layer protocol for ad hoc networks with multiple-antenna nodes. in this paper, we propose a physical (phy) - medium access control (mac) cross-layer protocol for ad hoc networks with antenna-array-equipped nodes that employ single-antenna transmission and multiple-antenna reception. our protocol extends the progressive back-off algorithm (pboa), proposed by toumpis and goldsmith, by integrating medium access and power control with optimum receive beamforming (orb); hence it is named pboa-orb. the protocol performance is evaluated via simulations over a single-hop ad hoc network that is subject to a uniform traffic load. it is shown that pboa-orb significantly enhances both the aggregate throughput and the energy efficiency of pboa by harnessing the interference suppression and array gains of receive beamforming. specifically, for a small number of antennas compared to the number of nodes, the aggregate throughput increases linearly with the number of antennas while the average energy consumption per data packet decreases.
fairness-aware joint routing and scheduling in ofdma-based cellular fixed relay networks. relaying and orthogonal frequency division multiple access (ofdma) are the accepted technologies for emerging wireless communications standards. the activities in many wireless standardization bodies and forums, for example ieee 802.16 j/m and lte-advanced, attest to this fact. the availability or lack thereof of efficient radio resource management (rrm) could make or mar the opportunities in these networks. this paper therefore provides a comprehensive rrm algorithm for ofdma-based multi-cellular fixed relay networks in a way to ensure fairness among users with minimal impact on the network throughput (in contrast, pure opportunistic rrm techniques always favor users with good channel conditions). unlike the majority of works in the literature, our proposed scheme is queue-aware and jointly performs routing, fair scheduling, and load balancing among cell nodes. the routing strategy has inherent learning ability and it dynamically converges to better routes.
sum rates and user scheduling for multi-user mimo vector perturbation precoding. this paper considers the multiuser multiple-input multiple-output (mimo) rayleigh fading broadcast channel. we consider the case where the multiple transmit antennas are used to deliver independent data streams to multiple users via a multi-user technique known as vector perturbation. we derive expressions for the capacity in terms of the average energy of the precoded vector, and use this to derive a closed-form high-snr upper bound, which we show to be tight via simulation. we then turn to the practical issue of user selection. we propose a low-complexity user selection algorithm that attempts to maximize the high-snr sum rate upper bound. simulations show that the algorithm outperforms other user selection algorithms of similar complexity.
distributed space-time code for asynchronous two-way wireless relay networks under frequency-selective channels. in this paper, we consider asynchronous two-way wireless relay networks with amplify-and-forward protocol (aftwrn), where the distributed space-time code (dstc) is utilized without synchronization among relays to assist the communication between two terminals. we analyze the pairwise error probability (pep) behavior of dstc for af-twrn under frequency-selective channels. from our analysis, it is seen that of the paths from one terminal to relays and from relays to another terminal, those with smaller diversity order result in an overall system performance bottleneck. considering both the timing errors among relays and the multipath fading, we then propose a family of distributed convolutional space-time codes (dcstc) for af-twrn such that the full diversity order can be achieved. finally, various numerical examples are provided to corroborate the analytical studies.
loop-free link stability metrics for proactive routing in wireless ad hoc networks. to improve communication quality in wireless ad hoc networks, it is definitely important to select stable links as communication paths. to this end, various mobility metrics are presented in the literature. however, the routing loop problem, which is inevitably involved in link-state proactive routing scheme, has not been discussed well. in this paper, we propose a simple dynamic metrics in respect of link stability, which is loop-free throughout dynamic metric transition. through a theoretical analysis of loop-freeness, we present our new strategy to achieve loop-freeness with sufficiently low cost for ad hoc networks.
a game-based self-organizing uplink tree for voip services in ieee 802.16j networks. in this paper, we propose a game theoretical approach to tackle the problem of the distributed formation of the uplink tree structure among the relay stations (rss) and their serving base station (bs) in an ieee 802.16j wimax network. unlike existing literature, which focused on the performance assessment of the network in the presence of the rss, we investigate the topology and dynamics of the tree structure in the uplink of an 802.16j network. we model the problem as a network formation game, where each rs aims to maximize its utility that accounts for the gains from cooperation in terms of bit error rate (ber) and the delay costs resulting from multi-hop transmission. the proposed utility model is based on the concept of the r-factor which is a parameter suitable for assessing the performance of voip services. for forming the tree structure, we propose a distributed myopic best response dynamics in which each rs can autonomously choose the path that connects it to the bs through other relays while optimizing its utility. using the proposed dynamics, the rss can self-organize into the tree structure, and adapt this topology to environmental changes such as mobility while converging to a nash tree network. simulation results show that the proposed algorithm presents significant gains in terms of average achieved ms utility reaching up to 42.57% compared to the star topology where all rss are directly connected to the bs, and up to 44.78% compared to the case with no rss.
an adaptive resource/performance trade-off for resolving complex queries in p2p networks. structured peer-to-peer (p2p) systems are increasingly important for scalable data dissemination and search. current distributed approaches for resolving complex search queries, like multi-attribute and range queries, typically require multiple query messages to resolve a single search request. to reduce the message overhead and the search latency, some approaches like the multi-attribute addressable network (maan) use static replication. however, this results in high main memory requirements and large data transfers each time a device joins the p2p network. those drawbacks can be tolerated for p2p networks that mainly consist of fixed, powerful nodes like pcs but are intolerable for resource-constrained nodes with high churn, like mobile devices. as mobile devices will play a significant role in accessing and distributing data in the future, we propose and evaluate an improved search mechanism for such a scenario. compared to maan, our approach significantly reduces the memory footprint and bandwidth requirements (up to a factor of five in our sample scenario). at the same time, the good latency properties of maan are remained on average. this is achieved via a dynamic replication scheme which introduces an adjustable trade-off between memory footprint and search latency. thereby, our approach makes efficient, distributed resolution of complex queries in resource-constrained p2p networks feasible.
a mathematical optimization approach for radio network planning of gsm/umts co-siting. 3g umts networks are being widely deployed by several cellular operators worldwide that already have existing gsm networks. in this paper, we model the problem of gsm/umts co-siting as a nested mixed integer optimization problem which takes as input an area of interest with existing gsm sites and obtains as output the optimal number and locations of umts sites to be deployed (new and co-sited with gsm sites) in order to optimize target objectives. the goal is to minimize the cost of umts network deployment by reusing as many existing gsm sites as possible while guaranteeing that every cell is covering a target capacity load which is a percentage of the downlink pole capacity. we propose an algorithm taking into account both integer and continuous variables to solve the formulated optimization problem as a function of the user distribution and the existing fixed gsm site locations. results for different scenarios show that it is optimal to reuse a subset of the existing gsm sites in addition to deploying new umts sites.
novel shaping and complexity-reduction techniques for approaching capacity over queuing timing channels. this paper discusses practical codes for communication via packet timings across network queuing systems - an instantiation of the "bits through queues" result for timing channels. it has recently been shown that sparse-graph linear codes followed by shaping techniques, combined with message-passing decoding, can enable practical timing channel codes with low symbol error rates near the capacity. the previous work had two main drawbacks. first, the shaping technique was only effective for very large finite field sizes. secondly, the complexity of the message-passing decoder was quadratic in the block length. in this work, 1) we develop an alternative shaping technique using random dithers with provably good statistical guarantees; 2) we exploit little's law from queuing theory along with a large deviations argument to reduce the message-passing decoder's complexity from quadratic to linear in block length. we illustrate the effectiveness of this approach on simulated queuing systems with low symbol error rates near the capacity.
reconfigurable peer-to-peer connectivity overlays for information assurance applications. the paper offers tree-structured connectivity between the peer entities over an infrastructure network as an abstraction to embody the application-oriented processing functions on peer-to-peer information flows. tree reconfigurations are triggered when failures or security violations occur in the connectivity path between the peer nodes (e.g., increase in path delays, dos attack on a node). reconfigurations are also initiated when the application-level properties of information flows change (e.g., lower data accuracy for non-important contents). for information assurance settings, a tree structure elegantly supports the desired properties of separation and non-inference between the low-level network entities and the application entities. a connectivity management algorithm reconfigures a tree satisfying the desired topological properties (e.g., low geographic spread, low peer-to-peer distances). the algorithm provides redundancy in the connectivity paths along the temporal dimension (on top of a rich connectivity in the physical infrastructure -- as in overlay networks). application case studies of tree-structured connectivity with qos and security goals are also described.
on sensor placement for directional wireless sensor networks. a directional sensor network is formed by directional sensors which may be oriented toward different directions. the sensing region of a directional sensor can be viewed as a sector in a two-dimensional plane. therefore, a directional sensor can only choose one sector (or direction) at any time instant. planning of directional sensor networks has received very little attention in the literature. in this paper, we discuss directional sensor placement which is a critical task in the planning of directional sensor networks. we also present an integer linear programming model whose goal is to minimize the number of directional sensors that need to be deployed to monitor a set of discrete targets in a sensor field. numerical results demonstrate the viability and effectiveness of the model.
analysis of selective retransmission techniques for differentially encoded data. this paper presents an analytical framework for the study of hybrid arq techniques aimed at the transmission of multimedia content with differential encoding. we propose a markov model of a selective repeat hybrid arq transmission scheme, where we assume that packets have different properties in terms of size, information content, and retransmission limit, so as to capture the differential encoding which characterizes such multimedia data.we consider a non-zero round-trip time channel modeled through a discrete-time markov chain. we provide an analytical tool for the evaluation of two main performance metrics, namely, throughput and goodput. the model is extremely flexible and allows evaluation of several channel conditions and comparison of different types of arq (plain arq, type i and ii hybrid arq). our results can be used as an effective tool to define design guidelines of multimedia transmission systems and to understand their performance trends.
pilot design of mimo-ofdm with beamforming. reference symbols (pilots) support coherent detection, but add overhead and consume transmit power. a sophisticated pilot design needs to trade-off the attainable channel estimation accuracy with the induced losses in bandwidth & power efficiency. mimo transmission, transmit beamforming, and spatial multiplexing further complicate pilot design. in this paper a unified analytical framework is developed to evaluate the attainable spectral efficiency of different pilot types for mimo-ofdm employing fixed transmit beamforming.
a load-balanced route selection for network coding in wireless mesh networks. cope [1] appears as the first wireless network coding approach which can improve the throughput of wireless mesh networks (wmns). but the established routes in cope may result in fairly limited coding opportunities and low throughput gain. although excessive intersections of flows can bring forth more coding opportunities, they may make some nodes overloaded, and decrease the throughput. furthermore, detecting coding opportunities may induce the high routing delay. to solve these problems, we propose hlcr, a heuristic load-balanced coding-aware routing mechanism, and its novel path metric called heuristic path metric for coding and load-balancing (hpmcl) in wmns. hpmcl evaluates a path considering network load, expected number of transmissions and potential coding opportunities. thus hlcr can efficiently find high throughput paths having coding opportunities and achieve good load balance with low cost by the hpmcl metric and other effective measures. our simulation results in ns-2 show that hlcr scheme can gain higher network throughput compared with cope.
blind frame synchronization of product codes based on the adaptation of the parity check matrix. we present in this paper a blind frame synchronization method based on the adaptation of the parity check matrix of the code. the blind synchronizer is initially based on the calculation of the log-likelihood ratios (llr) of the syndrome elements, obtained using the parity check matrix of the code. before applying our synchronization procedure, we propose in this paper to rearrange the parity check matrix of the code according to the reliability of the received symbols as previously introduced for decoding linear block codes with high density parity check matrix. simulation results show that the frame error rate (fer) curves obtained after applying the proposed synchronization method to product codes are very close to the ones with perfect synchronization. in addition to its powerful synchronization properties, the main advantage of the proposed synchronization algorithm is its capability of being introduced as a part of the decoder so that no additional material is required for the synchronization step.
a novel interactive streaming protocol for image-based 3d virtual environment navigation. image-based rendering (ibr) has attracted recent attention mainly due to its low requirements for generating new scenes based on a sequence of reference images. ibr has paved the way for a new class of application, the free viewpoint television (ftv), which allows the viewer to interactively control the camera and move freely within a scene. ibr can also be used to render complex 3d virtual environments on graphics-constrained devices, such as cellphones and pdas. in this paper, we propose a new protocol that offers the user a richer virtual experience by pre-streaming the necessary imagery data to generate new views as the user wanders within a 3d environment. we introduce the idea of key partial panoramas, i.e., panorama segments that cover movements in any direction by simply strafing from an appropriate key partial panorama and streaming the amount of lost pixels. we have implemented our protocols and evaluated them against two well-known approaches. experimental results show that our solution outperforms the selected approaches, by minimizing the delay between image updates and by allowing for a more complex navigation scheme.
lightweight static analysis to detect polymorphic exploit code with static analysis resistant technique. the general method in which attackers obtain the control authority of the remote host is through the exploit code. as network security systems have mounted the desired signatures about exploits, they have reduced damage due to the spreading and reoccurrence of the exploits. however, to avoid signature-based detection techniques, exploits employing techniques such as polymorphism and metamorphism have become more prevalent. especially in the case of polymorphism, because there are many automation engines even if there is no special knowledge in order to make various exploits easily, the polymorphism researches need to be more actively studied. we present a new static analysis method for detecting the decryption routine of polymorphic exploit code. most of decryption routines store the program counter value of remote host on a stack and use the value as the address for accessing the memory that the encrypted original code is positioned. the proposed method traces the processing steps of decryption routine as using the static analysis method. in the results of experiment, the proposed method can detect polymorphic exploit codes that the static analysis resistant techniques are used, and shows more efficient than the emulation-based method in the processing performance.
a linear time synchronization algorithm for underwater wireless sensor networks. large propagation delay and node movement are considered to be two significant attributes that differentiate an underwater wireless sensor network (uwsn) from a ground wireless sensor network (wsn). considering the effects of both propagation delay and movement, we propose a time synchronization algorithm suitable for a uwsn. an underwater node can move out of and into another node's range frequently. with the proposed algorithm, no time synchronization is necessary if the time stamps of the received data packets are within the tolerance. in this fashion, the network underwater does not need to perform global time synchronizations periodically, which reduces the time used to synchronize clocks among sensor nodes. the simulation results show the time cost for synchronization is linear to the data packets exchanged.
cross-layer design for mimo spatial multiplexing in correlated ricean fading. in this paper, we investigate a cross-layer transmit antenna selection (t-as) approach for multiple-input multiple-output spatial multiplexing (mimo-sm) systems employing decision-feedback detector (dfd), over spatially correlated ricean channels. the selected transmit antennas are those that maximize the link layer throughput of mimo channels. a closed-form expression for the system throughput with perfect channel state information (csi) is derived. extensive simulation results are provided for the system performance assessment, showing that the cross-layer t-as scheme always assigns the transmission to the antenna combination which sees better channel conditions, resulting in a substantial improvement over the optimal capacity-based t-as approach.
bicmb-ofdm link resource adaptation. an efficient and flexible air interface is the necessary condition for enabling high data rates next generation wireless systems. a practical answer to this need consists in exploiting channel state information at the transmitter for an adaptive and efficient use of the available radio link resources. this paper contributes with a novel strategy for the allocation of the sub-carrier transmit power in the case of a wireless system featuring: i) bit-interleaved coded modulation (bicm); ii) orthogonal frequency division multiplexing (ofdm); iii) multiple antenna profile (mimo). the proposed power-allocation algorithm aims at maximizing the so-called goodput performance metric for packet transmissions employing automatic repeat request (arq) schemes. in addition, it is also proven to be near-optimum in maximizing the input/output mutual information of the mimo-ofdm subchannels. numerical simulations over typical wireless indoor scenarios confirm the effectiveness of the procedure when applied in the context of mimo-bicm-ofdm systems.
effective capacity of superposition coding based mobile multicast in wireless networks. effective capacity is a useful technique to characterize the system throughput with statistical delay-constrained quality of service (qos) guarantees. in this paper, we integrate effective capacity theory into superposition-coding (spc) based multicast transmission to devise the efficient channel-aware multicasting scheme in wireless networks. specifically, we propose to optimize the effective capacity for multicast transmissions subject to the specified loss-rate constraint and the statistical delay qos requirement in terms of the qos exponent. we use superposition coding in wireless multicast to handle heterogeneous channel fading across multicast receivers, and apply the pre-drop strategy to gain more flexible rate control. under our proposed framework, we derive the optimal pre-drop strategy and the optimal power/rate allocation for each layer of superposition coding. simulation analyses present insightful observations on tradeoff between effective capacity and the qos requirements, and demonstrate the superiority of the spc-based scheme over the existing time-sharing (ts) based multicast scheme.
integration of ims and dvb-rcs for interactive content delivery. this paper describes issues related to the integration of ims and dvb-rcs satellite networks. dvb-rcs is studied as an access network variant for ims in addition to the already known cellular, wireless and cable access networks. although combining ims and dvb-rcs seems a practical solution for communication and content delivery several issues must be addressed in order to make the integration effective. the main areas of research are quality of service integration and multicast integration. specifically, integration of the ims qos architecture (pcc) and the control protocol (c2p) of satellite communication is studied, and also how ip multicast can be integrated with the satellite content distribution mechanism.