Due to the blooming of Internet of Things (IoT), heterogeneous IoT mobile devices emerge to connect the network infrastructure. Traditional mobile access system faces several challenges arising from these IoT devices: 1) centralized controllers are distant from the end devices, 2) inefficient access control of heterogeneous IoT devices, and 3) insufficient authentication and monitoring for IoT devices. In order to tackle the challenges from IoT devices on mobile access control and scalable access monitoring, we present LEDGE, an agile and secured software-defined edge computing system for resilient access management of mobile IoT. In a nutshell, our LEDGE is a synergy of an efficient location authentication method to secure communication between each IoT mobile device and access point (AP) pair, an optimal AP assignment scheme to satisfy IoT flow requests, a Personal AP protocol for scalable access, and a deep learning model for anomaly detection. We prototype our system, and realistic testbed experiments demonstrate that LEDGE could achieve promising results in mobile IoT.

It is a challenge to design efficient routing protocols for vehicular ad hoc networks (VANETs) because of their highly dynamic properties. We address the vehicular communication problem in urban hybrid networks and present a hybrid routing scheme for data dissemination in VANETs. Location-based crowdsourcing of nearby roadside units (RSUs) has been applied to the infrastructural support of inter-vehicle, vehicle-to-roadside, and inter-roadside communications in hybrid VANETs. The combination of RSU resources and ad hoc networks involves an online probabilistic RSU retrieval algorithm that uses coarse- and fine-grained localization to estimate the number and location of available RSUs; a network coding based multicast routing for dense VANETs using maximum distance separation (MDS) code and local topology information from the forwarding set to achieve robust communication and max-flow min-cut data dissemination; an application of opportunistic routing, using a carry-and-forward scheme to solve the forwarding disconnection problem in sparse VANETs; and a routing switch mechanism to guarantee quality of service (QoS) under various network connectivity and deployment configurations. The performance of our hybrid routing scheme is evaluated using both simulations and real testbed experiments.

WLAN systems based on the IEEE 802.11 could contain hundreds even up to thousands of wireless access points nowadays. However, IEEE 802.11 MAC protocols, including DCF, PCF and EDCA mechanisms, are unable to meet the challenges to provide collision freedom, especially in distributed large scale WLAN systems. We propose a channel access scheduling protocol based on Latin squares, called DCLASS (Distributed Coordination based on Latin SquareS), that provides collision-free CSMA based channel access coordination functions in large scale wireless networks with stringent performance demands. The performance of DCLASS is evaluated using an IEEE standards compliant simulation toolkit, QualNet 4.5, in distributed WLAN systems. The simulation results show the superior performance of DCLASS in contrast to IEEE 802.11 DCF under various scenarios.

Wireless mesh networking (WMN) is an economic means to provide the last-mile Internet access service through ad hoc peer-to-peer communication links. However, WMNs suffer from scalability, performance degradation and service disruption issues due to inherent network mobility. In this paper, we present a mobility management protocol, called HDR (Hierarchical Directory Resolution), using a hierarchical Distributed Hash Table (DHT) approach. Different from prior DHT solutions that were based on consistent hashing algorithms, HDR uses a novel NCR (neighbor-aware contention resolution) algorithm to maintain the DHT lookup functions. Simulation results validate the correctness and advantages of our proposed protocol.

Due to increase in demand for reconfigurability in embedded systems, real-time task scheduling is challenged by non-negligible reconfiguration overheads. If such overheads are not considered, tasks may not be schedulable under given deadlines, and hence, affecting the quality of service. We introduce the problem of real-time periodic task scheduling under transition overhead on heterogeneous reconfigurable systems. We formulate the problem as a network flow problem and provide a mixed integer linear programming solution. We compare our proposed solution with optimal scheduling under maximum fixed transition overhead. We deployed our method on task scheduling for multiple communication protocols on reconfigurable FPGA-like systems. Results show that our proposed scheduling improves the task schedulability by 24.2% in comparison with non-preemptive EDF and by 17.5% in comparison with maximum-transition-overhead scheduling.

In wireless sensor networks (WSNs), localization has many important applications, among which wireless sensor retrieval bears special importance for cost saving, data analysis and security purposes. Localization for sensor retrieval is especially challenging due to the fact that the number and locations of these sensors are both unknown. In this paper, we propose two probabilistic localization algorithms that iteratively identify the locations of multiple wireless sensors in WSNs, one of which calculates location information offline, and the other online. In both algorithms, we implement a two-step localization process — the first step is called Grid-LEGMM (grid location estimation based on the Gaussian mixture model), a coarse-grain location search using grids by choosing the proper number and locations of the wireless sensors that maximize a likelihood estimation, and the second step is called EM-LEGMM (expectation maximization based on the Gaussian mixture model), which uses the EM-method to refine the results of Grid-LEGMM. An additional step in the online localization algorithm is a credit-based filtering mechanism that removes spurious sensor locations. The performance of both offline and online localization algorithms are analyzed using the Cramer–Rao lower bound (CRLB), and evaluated using simulations and real testbed experiments.

Localization has many important applications in wireless sensor networks. A variety of wireless technologies, such as acoustic, infrared, and ultra-wide band (UWB) media have been applied for localization purposes. This paper consists of two parts. The first part presents new UWB-based communication protocols for received signal strength (RSS) information collection, namely, a robust UWB coding method called U-BOTH (UWB based on Orthogonal Variable Spreading Factor and Time Hopping), an ALOHA-type channel access method and a message exchange protocol to collect location information. The second part presents the localization algorithm, which is applied in coal mine environments. The localization algorithm first derives the corresponding UWB path loss model, then applies the maximum likelihood estimation (MLE) method to compute the distances to the reference sensors using the RSS information, and to estimate the coordinate of the moving sensor using least squares (LS) method. The performance of the system is validated using theoretic analysis and simulations. Results show that U-BOTH transmission technique can effectively reduce the bit error rate under the path loss model, and the corresponding ranging and localization algorithms can accurately compute object locations in coal mine environments.

The radio spectrum in wireless communication systems is being allocated up quickly with ever increasing demands in wireless industries. Cognitive radio is a way of opportunistically sharing the scare spectrum among primary and secondary users of the spectrum. The key challenge in deploying cognitive radio networks is to find out the spectrum holes in the primary wireless systems in order to allow the secondary users to operate. In this paper, we present novel localization algorithms based on grid-search and EM (expectation maximization) methods under the GMM (Gaussian mixture model) to find out the positions of the base stations and identify the spatial spectrum holes for cognitive radio deployments. Under this approach, we model the problem as localizing multiple unknown radio sources using a mobile measurement station, which is different from the problem modeling of many previous localization solutions. We evaluate our localization algorithms using both simulations and experiments.

Software Defined Radio (SDR) base stations can compensate for failures in disaster scenarios by assimilating different communication technologies. FPGAs play an important role in the platform of an SDR base station because of flexibility and DSP processing power that they deliver. The flexibility of FPGAs comes at the high cost of reconfiguration time overhead which can be a serious deterrence because of QoS requirements of real time traffic. In this paper we propose a solution to reduce reconfiguration time overhead at system-level where we are provided the configuration of each wireless system. Following that we step further and integrate our solution in to a floorplanner to generate placements for wireless systems which can systematically hide or reduce reconfiguration time overhead. Our experiments show the effectiveness of our approach

Location-based service provisioning is of great interests to wireless Internet service providers. However, the essential mechanism, location authentication, can easily become the target of network hackers for free-riding and attacks. We identify two aspects for improvements at the network providers to enforce location authentication for network access control location-based key distribution and run-time location verification, and propose solutions to enforce network access control based on location, which we refer to as LENA (Location-Enforced Network Access). First, we designed a location authentication and authorization protocol based on Diffie-Hellman algorithm, which securely authenticates the location claims of mobile wireless devices, and distributes shared keys for data encryption purpose. Secondly, we employ a mobility management protocol to guarantee that the mobile devices are physically at where they claim to be when they access the network. These two steps can separately enforce location based network access control, or be combined. LENA climinates the dependence on expensive hardware devices in order to localize the mobile devices, and solves a couple of possible attacks to the system. The computations, communication, and the memory requirement are evaluated and validated using simulations.

Localization has many important applications in wireless sensor networks (WSNs). A variety of technologies, such as acoustic, infrared. and UWB (ultra-wide band) media have been utilized for localization purposes. In this paper, we propose a helistic, buttom-up design of a UWB-based communication architecture and related protocols for localization in WSNs. A new UWB coding method, called U-BOTH (UWB ased on Orthogonal Variable Spreading Factor and Time Hopping), is utilized for minimum interference communication, and an ALOHA-type channel access method and a message exchange protocol are used to collect distance information in WSNs. We derive the corresponding UWB path loss model in order to apply the maximum likelihood estimation (MLE) method to compute the distances between neighbor nodes using the RSSI information. Then, we propose NMDS-MLE (Non-metric Multidimensional Scaling and Maximum Likelihood Estimation) localization algorithms based on the two types of distance information: estimated distance and Euclidean distance. The performance of the system is validated using theoretic analysis and simulations.

The traditional networking builds on layered protocol architecture to isolate the complexities in different layers. It has been realized that real-life wireless sensor networks (WSNs) must be considered holistically across different layers for optimum performance. We consider a special case of WSNs that is deployed in underground tunnels. Underground communications present unique signal propagation characteristics due to the geographic and geological features, which in turn impact the underground network deployment and multi-hop routing patterns. We propose an efficient routing algorithm, called BRIT (bounce routing in tunnels), for underground WSNs, and evaluate BRIT against the bottomline AODV in terms of network throughput, packet loss rate, stability and latencies using simulations. The contributions of the paper include a hybrid signal propagation model in three dimentional underground tunnels, an assortment of sensor deployment strategies in tunnels, an integrated routing metric (forwarding speed), and a route suppression mechanism.

Network-based attacks can be either persistent or sporadic. Persistent attack flows can be relatively easy to trace by mechanisms such as probabilistic packet marking, traffic logging, data mining etc. Sporadic attacks are sometimes easily detected by the Intrusion Detection Systems (IDSs) at the victims, but are hard to trace back to the attack origins. We propose CAPTRA, a CoordinAted Packet TRAceback mechanism, for wireless sensor networks (WSNs) that takes advantage of the broadcasting nature of the packet transmissions. By remembering packets in multi-dimensional Bloom filters distributed in overhearing sensors and later retrieving the information, CAPTRA identifies the path of the packet transfers using a series of REQUEST-VERDICT-CONFESS message exchanges between the forwarding and overhearing nodes. CAPTRA requires only small memory footprint on the sensors due to the usage of Bloom filters, and allows sensors to asynchronously refresh the Bloom filters so that the network traffic is continuously monitored. CAPTRA is simulated using J-Sim, and a few key parameters are tuned for the best tracing performance.

Location-based service provisioning is of great interests to wireless Internet service providers (WISPs) to deliver attractive value-added services, such as service advertisements, product marketing, to the special network users according to their geographic coordinates, along with Internet access benefits. It is usually the case that the basic location information is derived from direct interactions between the infrastructure network and the wireless mobile devices. Unfortunately, the Internet access service easily becomes the target of free-riders and attackers by exploiting the location authentication protocols, and collusively forging their location claims. We propose a location authentication and authorization protocol, LBAC (location-based network access control), to securely authenticate the location claims of mobile wireless users, and to securely distribute the shared keys for data encryption purposes. In LBAC, location areas are defined by the shared points of multiple wireless access points. The fact that a mobile node is located at certain places is authenticated by the mobile node collecting all the key information from the corresponding access points. Using Diffie-Hellman algorithm, LBAC authenticates location claims, and derives the keys for each mobile node and access point pair. LBAC eliminates the dependence on global positioning system (GPS) or ultrasonic devices in order to localize the mobile devices. We enumerate possible attacks to the system and analyze their countermeasures. The computational, communicational and the memory requirement are also evaluated

Routing in wireless ad hoc networks are vulnerable to traffic analysis, spoofing and denial of service attacks due to open wireless medium communications. Anonymity mechanisms in ad hoc networks are critical security measures used to mitigate these problems by concealing identification information, such as those of nodes, links, traffic flows, paths and network topology information from harmful attackers. We propose ODAR, an On-Demand Anonymous Routing protocol for wireless ad hoc networks to enable complete anonymity of nodes, links and source-routing paths/trees using Bloom filters. We simulate ODAR using J-Sim, and compare its performance with AODV in certain ad hoc network scenarios

With the proliferation of wireless communication technologies and mobile computing devices, research interest has grown for location-aware systems and services. We propose LAAC, a novel location-aware access control protocol based on a coarsely defined location area that is enclosed by overlapping areas of multiple access points. Accordingly, a location key for location claim is derived from the overlapping access points' beacon information. In addition, the fact that a mobile device derives the location key enables us to track the location of the mobile device. LAAC does not require additional hardwares such as GPS or ultrasonic devices in order to localize the mobile devices. We enumerate possible attacks to the system and analyze their countermeasures. The computational and communicational costs and the memory requirement are evaluated, and the simulation results are presented

In mobile wireless systems, the quest to support delay-stringent multimedia applications challenges most existing solutions to the mobility support and traffic management problems. An infrastructure supported approach is required to provide non-disrupted services with seamless roaming capabilities. We propose a mobility management scheme called personal AP, to support station mobility efficiently. In personal AP mobility support system, the mobility context of each mobile station is defined by the relevant state information at the currently associated access point, including the MAC layer association states at the access point. When the mobile station roams, the access point context follows the mobile station from one physical access point to another, thus creating the "ghost" access point following the mobile station and eliminating the mobile station from re-associating with new access points. Personal AP system improve the seamless roaming support by avoid the lengthy re-association process commonly seen in IEEE 802.11 systems. The essential idea of personal AP is applicable in other wireless systems as well.

In hybrid wired and wireless systems, mobile hosts constantly changes points of attachment to the wired networks, causing frequent disruptions to the ongoing network traffic. An infrastructure supported approach is required to meet the stringent delay and jitter requirements in non-disrupted services. We propose a mobility management scheme, called personal AP, to support seamless roaming. In personal AP systems, the network attachment information, i.e., the association states, of a mobile station is extracted, and handed off from one physical access point to another along with the mobile station, thus eliminating the mobile station from reassociating with new access points. Simulation results show that personal AP can greatly reduce the handoff latencies, and is suitable to support delay-sensitive multimedia applications

In this paper, we propose a novel approach that combines the multi-rate adaptation and topology management mechanisms so as to provide the highest network throughput under very low control overhead. Under topology management, a connected dominating set (CDS) of the network topology is elected and maintained for routing protocols as the backbone of the network. A MAC protocol using multi-rate transmission capability in the physical media is further applied to provide high network throughput so that a low data-rate wireless link is substituted with a high data-rate two-hop wireless link by employing an intermediate node. The efficiency of the combined optimization algorithms is validated by network performance analysis and extensive simulations with DSR (dynamic source routing) as the routing protocol. The analytical and simulation results demonstrate that our solution significantly reduces the routing control overhead, improves the network data forwarding performance.

Finite battery energy and limited bandwidth resources are the two major constraints in ad hoc networks. Therefore, researchers have persistently sought for optimization algorithms to reduce the control overhead and to increase bandwidth utilization efficiency, using mechanisms such as topology control and management, multi-rate adaptation etc. to cut down the energy expenditure in ad hoc networks. However, the energy conservation and network throughput improvement are handled separately in many cases. In this paper, we propose a unified framework that combines the multi-rate adaptation and clustering mechanisms so as to provide the optimal network throughput under very low control overhead. The framework incorporates two control mechanisms into the networking stack. The first mechanism is based on a novel clustering algorithm, called PATM (priority-based adaptive topology management), that constructs the backbone of the network topology for routing protocols. The second mechanism is a medium access control protocol, called RMAC (relay-based MAC), that provides high data transmission rates between adjacent backbone nodes. The efficiency of the unified framework is evaluated using theoretical analysis and extensive simulations with DSR (dynamic source routing) as the underlying routing protocol. We demonstrate that our solution not only significantly reduces the routing control overhead, but also substantially improves the network throughput.

The efficiency of a communication network depends not only on its control protocols, but also on its topology. We propose a distributed topology management algorithm that constructs and maintains a backbone topology based on a minimal dominating set (MDS) of the network. According to this algorithm, each node determines the membership in the MDS for itself and its one-hop neighbors based on two-hop neighbor information that is disseminated among neighboring nodes. The algorithm then ensures that the members of the MDS are connected into a connected dominating set (CDS), which can be used to form the backbone infrastructure of the communication network for such purposes as routing. The correctness of the algorithm is proven, and the efficiency is compared with other topology management heuristics using simulations. Our algorithm shows better behavior and higher stability in ad hoc networks than prior algorithms.

We present the hybrid activation multiple access (HAMA) protocol for ad hoc networks. Unlike previous channel access scheduling protocols that activate either nodes or links only, HAMA is a node-activation channel access protocol that also maximizes the chance of link activations using time- and code-division schemes. HAMA only requires identifiers for the neighbors within two hops from each node to schedule channel access. Using this neighborhood information, each node determines whether to transmit in the current time slot on a dynamically assigned spreading code. A neighbor protocol supplements HAMA with up-to-date two-hop neighborhood information by reliably propagating the one-hop neighbor updates through a novel random access technique. The throughput and delay characteristics of HAMA in randomly-generated multihop wireless networks are studied by analyses and simulations. The results of the analyses show that HAMA achieves higher channel utilization in ad hoc networks than a distributed scheduling scheme based on node activation, similar throughput as a well-known scheduling algorithm based on complete topology information, and much higher throughput than the ideal CSMA and CSMA/CA protocols.

Directional antennas can adaptively select radio signals of interest in specific directions, while filtering out unwanted interference from other directions. Although a couple of medium access protocols based on random access schemes have been proposed for networks with directional antennas, they suffer from high probability of collisions because of their dependence on omnidirectional mode for the transmission or reception of control packets in order to establish directional links. We propose a distributed receiver-oriented multiple access (ROMA) channel access scheduling protocol for ad hoc networks with directional antennas, each of which can form multiple beams and commence several simultaneous communication sessions. Unlike random access schemes that use on-demand handshakes or signal scanning to resolve communication targets, ROMA determines a number of links for activation in every time slot using only two-hop topology information. It is shown that significant improvements on network throughput and delay can be achieved by exploiting the multi-beam forming capability of directional antennas in both transmission and reception. The performance of ROMA is studied by simulations, and compared with a well-know static scheduling scheme that is based on global topology information.

Three types of collision-free channel access protocols for ad hoc networks are presented. These protocols are derived from a novel approach to contention resolution that allows each node to elect deterministically one or multiple winners for channel access in a given contention context (e.g., a time slot), given the identifiers of its neighbors one and two hops away. The new protocols are shown to be fair and capable of achieving maximum utilization of the channel bandwidth. The delay and throughput characteristics of the contention resolution algorithms are analyzed, and the performance of the three types of channel access protocols is studied by simulations.

It is shown that a unidirectional link of a network can be used for routing only if it has an inclusive cycle, which provides a path to carry routing updates from the downstream node to the upstream node joint by the unidirectional link. A new routing algorithm for networks with unidirectional links is then presented, which incrementally disseminates link-state information and selectively utilizes unidirectional links in networks. The new algorithm is verified to be correct and its complexity is analyzed. Simulations on a 20-node unidirectional network show that the new algorithm is more efficient than topology broadcasting.