waashk/dblp huggingface dataset:
cooperative bridges: topology control in cooperative wireless ad hoc networks. cooperative communication (cc) is a technology that allows multiple nodes to simultaneously transmit the same data. it can save power and extend transmission coverage. however, prior research work on topology control considers cc only in the aspect of energy saving, not that of coverage extension. we identify the challenges in the development of a centralized topology control scheme, named cooperative bridges, which reduces transmission power of nodes as well as increases network connectivity. we observe that cc can bridge (link) disconnected networks. we propose two algorithms that select the most energy efficient neighbor nodes, which assist a source to communicate with a destination node; an optimal method and a greedy heuristic. in addition, we consider a distributed version of the proposed topology control scheme. our findings are substantiated by an extensive simulation study, through which we show that the cooperative bridges scheme substantially increases the connectivity while consuming a similar amount of transmission power compared to other existing topology control schemes.
when watchdog meets coding. we consider the problem of misbehavior detection in wireless networks. a commonly adopted approach is to exploit the broadcast nature of the wireless medium, where nodes monitor their downstream neighbors locally using overheard messages. we call such nodes the watchdogs.we propose a lightweight misbehavior detection scheme which integrates the idea of watchdogs and error detection coding.we show that even if the watchdog can only observe a fraction of packets, by choosing the error detection code properly, an attacker can be detected with high probability while achieving throughput arbitrarily close to optimal. such properties reduce the incentive for the attacker to attack. we then consider the problem of locating the misbehaving node and propose a simple protocol, which locates the misbehaving node with high probability. the protocol requires exactly two watchdogs per unreliable relay node.
the capacity of heterogeneous wireless networks. although capacity has been extensively studied in wireless networks, most of the results are for homogeneous wireless networks where all nodes are assumed identical. in this paper, we investigate the capacity of heterogeneous wireless networks with general network settings. specifically, we consider a dense network with n normal nodes and m = nb (0 < b < 1) more powerful helping nodes in a rectangular area with width b(n) and length 1/b(n), where b(n) = nw and -1/2 < w ≤ 0. we assume there are n flows in the network. all the n normal nodes are sources while only randomly chosen nd (0 < d < 1) normal nodes are destinations. we further assume the n normal nodes are uniformly and independently distributed, while the m helping nodes are either regularly placed or uniformly and independently distributed, resulting in two different kinds of networks called regular heterogeneous wireless networks and random heterogeneous wireless networks, respectively. in this paper, we attempt to find out what a heterogeneous wireless network with general network settings can do by deriving a lower bound on the capacity. we also explore the conditions under which heterogeneous wireless networks can provide throughput higher than traditional homogeneous wireless networks.
simple efficient tcam based range classification. in recent years, hardware based packet classification has became an essential component in many networking devices. ternary content-addressable memories (tcams) are one of the most popular solutions in this domain, allowing to compare in parallel the packet header against a large set of rules, and to retrieve the first match. however, using tcam to match a range of values is much more problematic and dramatically reduces the cost effectiveness of the solution. in this paper we study ways to use simple built-in tcam mechanisms in order to increase the efficiency of range coverage. while current techniques have a worst expansion ratio of 2ċw-4, we present an efficient algorithm enabling to encode any range with at most w tcam entries (where w in the number of bits), without using additional processing, extra bits, and without any external encoding. the same paradigm can be applied to multiple raging rules as well, resulting in significant improvement over current known techniques. moreover, our simulation results indicate that these techniques can be used to reduce the actual tcam size of hardware networking devices under realistic scenarios.
on the feasibility and efficacy of protection routing in ip networks. with network components increasingly reliable, routing is playing an ever greater role in determining network reliability. this has spurred much activity in improving routing stability and reaction to failures, and rekindled interest in centralized routing solutions, at least within a single routing domain. centralizing decisions eliminates uncertainty and many inconsistencies, and offers added flexibility in computing routes that meet different criteria. however, it also introduces new challenges; especially in reacting to failures where centralization can increase latency. this paper leverages the flexibility afforded by centralized routing to address these challenges. specifically, we explore when and how standby backup forwarding options can be activated, while waiting for an update from the centralized server after the failure of an individual component (link or node). we provide analytical insight into the feasibility of such backups as a function of network structure, and quantify their computational complexity. we also develop an efficient heuristic reconciling protectability and performance, and demonstrate its effectiveness in a broad range of scenarios. the results should facilitate deployments of centralized routing solutions.
efficient resource allocation with flexible channel cooperation in ofdma cognitive radio networks. recently, a cooperative paradigm for single-channel cognitive radio networks has been advocated, where primary users can leverage secondary users to relay their traffic. however, it is not clear how such cooperation can be exploited in multi-channel networks effectively. conventional cooperation entails that data on one channel has to be relayed on exactly the same channel, which is inefficient in multi-channel networks with channel and user diversity. moreover, the selfishness of users complicates the critical resource allocation problem, as both parties target at maximizing their own utility. this work represents the first attempt to address these challenges. we propose flec, a novel design of flexible channel cooperation. it allows secondary users to freely optimize the use of channels for transmitting primary data along with their own data, in order to maximize performance. further, we formulate a unifying optimization framework based on nash bargaining solutions to fairly and efficiently address resource allocation between primary and secondary networks, in both decentralized and centralized settings. we present an optimal distributed algorithm and sub-optimal centralized heuristics, and verify their effectiveness via realistic simulations.
network positioning from the edge - an empirical study of the effectiveness of network positioning in p2p systems. network positioning systems provide an important service to large-scale p2p systems, potentially enabling clients to achieve higher performance, reduce cross-isp traffic and improve the robustness of the system to failures. because traces representative of this environment are generally unavailable, and there is no platform suited for experimentation at the appropriate scale, network positioning systems have been commonly implemented and evaluated in simulation and on research testbeds. the performance of network positioning remains an open question for large deployments at the edges of the network. this paper evaluates how four key classes of network positioning systems fare when deployed at scale and measured in p2p systems where they are used. using 2 billion network measurements gathered from more than 43,000 ip addresses probing over 8 million other ips worldwide, we show that network positioning exhibits noticeably worse performance than previously reported in studies conducted on research testbeds. to explain this result, we identify several key properties of this environment that call into question fundamental assumptions driving network positioning research.
mset: a mobility satellite emulation testbed. satellite systems are ideal for distributing the same content to a large number of users, as well as providing broadband connectivity in remote areas or backup in case of terrestrial network failures. unlike terrestrial networks, satellite networks face a unique set of challenges, such as signal fading and interference from multiple transmitters combined with long propagation delays. a well known challenge is that these unique characteristics can have an adverse impact on various protocols, making it necessary to study protocol behavior in satellite networks. the challenge of our research, and the focus of this paper, is to develop an architecture for a high-fidelity and scalable emulation testbed tailored for mobile satellite communications research. the testbed is designed to provide multi-beam, multi-satellite, tdma, and mobility functionality. our validation studies demonstrate that the testbed is capable of achieving delay, loss, and jitter that can be associated with a mobile satellite link.
demand-oblivious routing: distributed vs. centralized approaches. until recent years, it was more or less undisputed common-sense that an accurate view on traffic demands is indispensable for optimizing the flow of traffic through a network. lately, this premise has been questioned sharply: it was shown that setting just a single routing, the so called demandoblivious routing, is sufficient to accommodate any admissible traffic matrix in the network with moderate link overload, so no prior information on demands is absolutely necessary for efficient traffic engineering. demand-oblivious routing lends itself to distributed implementations, so it scales well. in this paper, we generalize demand-oblivious routing in a new way: we show that, in contrast to the distributed case, centralized demand-oblivious routing can eliminate link overload completely. what is more, our centralized scheme allows for optimizing the routes with respect to arbitrary linear or quadratic objective function. we realize, however, that a centralized scheme can become prohibitively complex, therefore, we propose a hybrid distributed-centralized algorithm, which, according to our simulations, strikes a good balance between efficiency, scalability and complexity.
an efficient algorithm for constructing maximum lifetime tree for data gathering without aggregation in wireless sensor networks. data gathering is a broad research area in wireless sensor networks. the basic operation in sensor networks is the systematic gathering and transmission of sensed data to a sink for further processing. the lifetime of the network is defined as the time until the first node depletes its energy. a key challenge in data gathering without aggregation is to conserve the energy consumption among nodes so as to maximize the network lifetime. we formalize the problem of tackling the challenge as to construct a min-max-weight spanning tree, in which the bottleneck nodes have the least number of descendants according to their energy. however, the problem is np-complete. a ω(log n/log log n)- approximation algorithm mitt is proposed to solve the problem without location information. simulation results show that mitt can achieve longer network lifetime than existing algorithms.
beyond triangle inequality: sifting noisy and outlier distance measurements for localization. knowing accurate positions of nodes in wireless ad-hoc and sensor networks is essential for a wide range of pervasive and mobile applications. however, errors are inevitable in distance measurements and we observe that a small number of outliers can degrade localization accuracy drastically. to deal with noisy and outlier ranging results, triangle inequality is often employed in existing approaches. our study shows that triangle inequality has a lot of limitations which make it far from accurate and reliable. in this study, we formally define the outlier detection problem for network localization and build a theoretical foundation to identify outliers based on graph embeddability and rigidity theory. our analysis shows that the redundancy of distance measurements plays an important role. we then design a bilateration generic cycles based outlier detection algorithm, and examine its effectiveness and efficiency through a network prototype implementation of micaz motes as well as extensive simulations. the results shows that our design significantly improves the localization accuracy by wisely rejecting outliers.
frequency-domain packet scheduling for 3gpp lte uplink. in this paper, we investigate the frequency-domain packet scheduling (fdps) problem for 3gpp lte uplink (ul). instead of studying a specific scheduling policy, we provide a unified approach to tackle this issue. first we formalize a general lte ul fdps problem which is suitable for various scheduling policies. then we prove that the problem is max snp-hard, which implies that approximation algorithms with constant approximation ratios are the best that we can hope for. therefore we design two approximation algorithms, both of which have polynomial runtime. subsequently, we analyze the two algorithms and find their approximation ratios. the first algorithm is easy to follow, since it is based on a simple greedy method. the second one is based on the local ratio technique and it can approximately solve the lte ul fdps problem with a approximation ratio of 2.
bayesian inference for localization in cellular networks. in this paper, we present a general technique based on bayesian inference to locate mobiles in cellular networks. we study the problem of localizing users in a cellular network for calls with information regarding only one base station and hence triangulation or trilateration cannot be performed. in our call data records, this happens more than 50% of time. we show how to localize mobiles based on our knowledge of the network layout and how to incorporate additional information such as round-trip-time and signal to noise and interference ratio (sinr) measurements. we study important parameters used in this bayesian method through mining call data records and matching gps records and obtain their distribution or typical values. we validate our localization technique in a commercial network with a few thousand emergency calls. the results show that the bayesian method can reduce the localization error by 20% compared to a blind approach and the accuracy of localization can be further improved by refining the a priori user distribution in the bayesian technique.
enabling a bufferless core network using edge-to-edge packet-level fec. internet traffic is expected to grow phenomenally over the next five to ten years, and to cope with such large traffic volumes, core networks are expected to scale to capacities of terabits-per-second and beyond. increasing the role of optics for switching and transmission inside the core network seems to be the most promising way forward to accomplish this capacity scaling. unfortunately, unlike electronic memory, it remains a formidable challenge to build even a few packets of integrated all-optical buffers. in the context of envisioning a bufferless (or near-zero buffer) core network, our contributions are threefold: first, we propose a novel edge-to-edge based packet-level forward error correction (fec) framework as a means of combating high core losses, and investigate via analysis and simulation the appropriate fec strength for a single core link. second, we consider a realistic multi-hop network and develop an optimisation framework that adjusts the fec strength on a per-flow basis to ensure fairness between singleand multi-hop flows. third, we study the efficacy of fec for various system parameters such as relative mixes of short-lived and long-lived tcp flows, and average offered link loads. our study is the first to show that packet-level fec, when tuned properly, can be very effective in mitigating high core losses, thus opening the doors to a bufferless core network in the future.
mac-layer time fairness across multiple wireless lans. wireless lans have been densely deployed in many urban areas. contention among nearby wlans is locationsensitive, which makes some hosts much more capable than others to obtain the channel for their transmissions. another reality is that wireless hosts use different transmission rates to communicate with the access points due to attenuation of their signals. we show that location-sensitive contention aggravates the throughput anomaly caused by different transmission rates. it can cause throughput degradation and host starvation. this paper studies the intriguing interaction between location-sensitive contention and time fairness across contending wlans. achieving time fairness across multiple wlans is a very difficult problem because the hosts may perceive very different channel conditions and they may not be able to communicate and coordinate their operations due to the disparity between the interference range and the transmission range. in this paper, we design a mac-layer time fairness solution based on two novel techniques: channel occupancy adaptation, which applies aimd on the channel occupancy of each flow, and queue spreading, which ensures that all hosts and only those hosts in a saturated channel detect congestion and reduce their channel occupancies in response. we show that these two techniques together approximate the generic adaptation algorithm for proportional fairness.
optimizing the batch mode of group rekeying: lower bound and new protocols. in group communications, an efficient rekeying scheme plays a key role in providing access control when a membership change happens. for reducing the communication cost in the rekeying operation, one proposed model is to rekey upon individual membership change. it is theoretically proved that given the forward secrecy requirement, the optimal amortized communication cost is at least o(log n) (n is the group size) for an individual rekeying (ir). another model is to rekey upon a batch of multiple membership changes: batch rekeying (br), which largely reduces the rekeying communication cost, and relieves implementation difficulties in the ir model (e.g., extremely intensive rekey messages and key arriving disorders in large-size and highly dynamic groups). unlike ir, however, the communication lower bound in br is not yet explicitly stated. this paper first extends the communication lower bound for ir to the br model. specifically, we prove that given the batch level forward secrecy, the communication costs for updating the whole group subset by subset in a sequence of b batch rekeyings are at least o(b ċ (log2 b - 1)) + o(n). this bound, as a superset, inclusively explains the ir bound as a special case of b = n. second, for achieving the found bound, we provide a departing-time related key topology that works optimally under the bound. third, to further implement the proposed optimal topology, we propose two novel br protocols, one with support of forward secrecies and the other with support of two-way secrecies. through extensive analyses and simulations, the proposed protocols are shown to achieve notable upgrades in major performance metrics: 60% ∼ 70% reduction in communication overheads, 50% ∼ 60% reduction in key storage overheads, and elimination of key tree unbalance.
a collaboration-based autonomous reputation system for email services. this paper presents care, an autonomous email reputation system based on inter-domain collaboration. within the framework of care, each domain independently builds its reputation database based on both the local email history and the information exchanged with other collaborating domains. care examines the trustworthiness of the email histories obtained from collaborators by correlating them with the local email history. to validate the efficacy of care, we have analyzed real email logs, conducted a dns-based estimation experiment, and performed a series of simulations. our experimental results show that care can effectively improve the reliability and performance of email systems.
asymptotic analysis of precoded small cell networks. in this paper, we study precoded mimo based small cell networks. we derive the theoretical sum-rate capacity, when multi-antenna base stations transmit precoded information to its multiple single-antenna users in the presence of intercell interference from neighboring cells. due to an interference limited scenario, increasing the number of antennas at the base stations does not yield necessarily a linear increase of the capacity. we assess exactly the effect of multi-cell interference on the capacity gain for a given interference level. we use recent tools from random matrix theory to obtain the ergodic sum-rate capacity, as the number of antennas at the base station, number of users grow large. simulations confirm the theoretical claims and also indicate that in most scenarios the asymptotic derivations applied to a finite number of users give good approximations of the actual ergodic sum-rate capacity.
neighbor discovery with reception status feedback to transmitters. neighbor discovery is essential for the process of self-organization of a wireless network, where almost all routing and medium access protocols need knowledge of one-hop neighbors. in this paper we study the problem of neighbor discovery in a static and synchronous network, where time is divided into slots, each of duration equal to the time required to transmit a hello message, and potentially, some sort of feedback message. our main contributions lie in detailing the physical layer mechanism for how nodes in receive mode detect the channel status, describing algorithms at higher layers that exploit such a knowledge, and characterizing the significant gain obtained. in particular, we describe one possible physical layer architecture that allows receivers to detect collisions, and then introduce a feedback mechanism that makes the collision information available to the transmitters. this allows nodes to stop transmitting packets as soon as they learn about the successful reception of their discovery messages by the other nodes in the network. hence, the number of nodes that need to transmit packets decreases over time. these nodes transmit with a probability that is inversely proportional to the number of active nodes in their neighborhood, which is estimated using the collision information available at the nodes. we show through analysis and simulations that our algorithm allows nodes to discover their neighbors in a significantly smaller amount of time compared to the case where reception status feedback is not available to the transmitters.
design and analysis of a robust pipelined memory system. many network processing applications require wirespeed access to large data structures or a large amount of flowlevel data, but the capacity of srams is woefully inadequate in many cases. in this paper, we analyze a robust pipelined memory architecture that can emulate an ideal sram by guaranteeing with very high probability that the output sequence produced by the pipelined memory architecture is the same as the one produced by an ideal sram under the same sequence of memory read and write operations, except time-shifted by a fixed pipeline delay of δ. the design is based on the interleaving of dram banks together with the use of a reservation table that serves in part as a data cache. in contrast to prior interleaved memory solutions, our design is robust even under adversarial memory access patterns, which we demonstrate through a rigorous worstcase theoretical analysis using a combination of convex ordering and large deviation theory.