Broadcast Nature Of Wireless Medium Research Articles

Detecting Rogue Access Points Using Client-agnostic Wireless Fingerprints

The broadcast nature of wireless media makes WLANs easily attacked by rogue Access Points (APs) . Rogue AP attacks can potentially cause severe privacy leakage and financial loss. Hardware fingerprinting is the state-of-the-art technology to detect rogue APs since an attacker would find it difficult to set up a rogue AP with specific hardware fingerprints. However, existing hardware fingerprints not only depend on the AP but also depend on the client, significantly limiting their application scenarios. In this work, we investigate two novel client-agnostic fingerprints, which can be extracted using commercial off-the-shelf WiFi devices, to detect rogue APs. One is the power amplifier non-linearity fingerprint and the other is the frame interval distribution fingerprint . These two fingerprints remain consistent over time and space for the same AP but vary across different APs even with the same brand, model, and firmware. We use the fingerprint similarity between the candidate AP and the authorized AP for device authentication in typical indoor environments. We have also proposed a threshold-improved authentication scheme to improve the robustness of our system in dynamic environments. Our schemes can be implemented without modifying the infrastructural APs and can work well with new clients without rebuilding the fingerprint database. We evaluate our scheme in both in-lab and field scenarios, by analyzing 18 million WiFi packets. Results show that our scheme achieves an overall 96.55% positive detection rate and a 4.31% false alarm rate. Moreover, the threshold-improved authentication scheme can further reduce the false alarm rate by 13.0%-44.8% for dynamic environments.

Practical Network Coding Technologies and Softwarization in Wireless Networks

Network coding is an elegant and novel technique to improve network throughput and performance. It is considered as a critical technology to facilitate ever-increasing demands of future wireless networks. It exploits the broadcast nature of wireless media and cooperatively codes packets from different senders to provide reliable, secure, and efficient transmissions. Current research focuses on either transmission delay, coding complexity, forwarding security, or end-to-end throughput. Network coding-aided solutions can recover lost packets without feedback, eliminate latency, reduce the routing cost on diverse paths, or optimize the capacity of unstable wireless networks. However, devices or smart sensors usually have limited computational capacity and some applications could not tolerate high decoding delay, which prevents network coding from being widely deployed in the real world. In recent years, many research methods consider simplifying decoding matrix or coding algorithm to alleviate the shortcoming of network coding and further satisfy the extreme demands of the future wireless network. This article summarizes complexity-optimized methods and explains the interaction effect of coding opportunities and decoding overhead. We propose a taxonomy of practical network coding methods and illustrate three practical directions on cutting computational complexity and enhancing progressive decoding. We also conclude the benefit and cost of current network coding algorithms along with the outline of future research.

On the Analysis of Content Dissemination with Reactive Content Pushing in Cache-Enabled D2D Networks

Device-to-device (D2D) communication has huge potential to offload ever increasing cellular traffic. As a premise, devices should store as many popular contents as possible. For augmenting the number of cached contents, in this paper, we propose a reactive content pushing (RCP) mechanism in cache-enabled D2D networks, in which some devices overhear the transmitted contents utilizing the broadcast nature of wireless medium. Since no proactive content pushing is involved, it doesn’t generate interference to the D2D links for normal content requests and its implementation is quite simple. By modeling the D2D network by Poisson point process (PPP), we derive the probabilities that users are in the defined states and the law of evolution of content caching distribution. Moreover, based on the PPP model, we derive the expressions of the successful offloading probability, the average delay and the upper bound of average energy consumption of a request. Simulation results demonstrate the accuracy of the theoretical results and the superiority of the RCP mechanism compared with general content dissemination process.

RBA: Detection and Protection Analysis Using Region-Based Algorithm in Ultra-Dense Networks

Due to broadcast nature of wireless medium, increased density of users, base stations (BSs) and small cell size in the ultra-dense network (UDN), the users are susceptible to be attacked by malicious eavesdroppers (EDs). However, UDN is provisioned with exceptionally adequate performance for all diversity of users along with the appearance of low power small cells in abundance. This paper deals with the secure transmission in UDN for high speed (or vehicular) users under the influence of single or multiple EDs. Thereby to ensure secure communication, we design a detection algorithm based on pattern matching for high-speed users by computing the secrecy rate loss (SRL) and simultaneously estimating the ranks to determine the sensitive area for attack. We then also develop the mathematical approach through the formation of a correlation matrix. We formulate the secure and energy efficient algorithm called region-based algorithm (RBA), which will protect users by encrypting the information transmitted in the sensitive area of attack. Simulation results reveal that the proposed algorithm is energy efficient and secure. RBA outperforms the conventional approach of encryption and also helps in saving energy (reserved for encryption) more than 90%. We also propose the optimal utilization of saved encryption energy to further improve the secrecy rate of moving users in the region of attack. The simulation results verify our theoretical approach and proposed approach well meets the target QoS in the attacked zone, to overcome the impact of ED.

Joint Opportunistic Routing and Intra-Flow Network Coding in Multi-Hop Wireless Networks: A Survey

Opportunistic routing and network coding are two promising techniques that have been proposed for wireless networks. These techniques have significantly improved the performance of multi-hop wireless networks by utilizing the broadcast nature of wireless media and optimizing the capacity of lossy wireless networks. Recent research has shown that the combination of opportunistic routing and network coding in a single joint protocol outperforms each of them individually. This article explains the motivation and interaction effect of the joint protocols. We provide a taxonomy of joint protocols and illustrate the benefit and cost by highlighting their fundamental components and comparing different solutions. We also present a conclusion along with the outline of future research direction.

To overhear or not to overhear: a dilemma between network coding gain and energy consumption in multi-hop wireless networks

Any properly designed network coding technique can result in increased throughput and reliability of multi-hop wireless networks by taking advantage of the broadcast nature of wireless medium. In many inter-flow network coding schemes nodes are encouraged to overhear neighbours traffic in order to improve coding opportunities at the transmitter nodes. A study of these schemes reveal that some of the overheard packets are not useful for coding operation and thus this forced overhearing increases energy consumption dramatically. In this paper, we formulate network coding aware sleep/wakeup scheduling as a semi Markov decision process (SMDP) that leads to an optimal node operation. In the proposed solution for SMDP, the network nodes learn when to switch off their transceiver in order to conserve energy and when to stay awake to overhear some useful packets. One of the main challenges here is the delay in obtaining reward signals by nodes. We employ a modified Reinforcement Learning (RL) method based on continuous-time Q-learning to overcome this challenge in the learning process. Our simulation results confirm the optimality of the new methodology.

Dynamic association and participant based adaptive streaming in small base station for live video conference on 5G networks

AbstractTargeting to handle the explosive growth of mobile media streaming, the emerging fifth‐generation systems need to manage control plane and data plane appropriately. The control plane is used for node association in the heterogeneous cellular network and data plane for media streaming with heterogeneous user equipment. To satisfy the aforementioned requirements, we proposed a solution to alter the control plane and data plane by systematic usage of in‐network resource available in wireless edge (eg, macro, pico, and femto) small base stations (SBSs) for the deployment of smart association policies and media processing technique that improve the efficiency in fifth‐generation wireless networks. On the other hand, due to the broadcast nature of wireless medium, we introduce the media processing agent (MPA) that would reside in SBSs to process the media on the fly and then deliver streams adaptively to the participants. MPA can identify the presenter among the participant to create the server channel with media server and the observer can service from MPA itself. To better exploit the participant's node association with the nearby SBSs, association policies are enhanced with concerns on dynamic association with SBSs. In addition, we describe a heuristic algorithm that provides significant performance gains compared with the existing centralized processing schemes. Numerical results are presented with realistic parameters for the media processing speed, and the quality of delivery demonstrate up to 20% reduction in central processing unit usage over existing (centralized) media processing schemes.

Achieving adaptive broadcasting performance tradeoff for energy-critical sensor networks: A bottom-up approach

Low-duty-cycle mode is widely adopted in energy-critical wireless sensor networks (WSNs). Such mode greatly reduces the energy waste caused by idle listening. However, it brings many new challenges for broadcasting. This paper mainly focuses on the minimum cost broadcast problem for low-duty-cycle WSNs. We propose a novel opportunistic broadcasting transmission model, which makes full use of the broadcast nature of wireless media to reduce the total energy consumption for broadcasting. The key idea is to allow nodes to defer their wake-up slots to opportunistically overhear the broadcasting messages sent by their neighbors, which could reduce the total energy consumption for broadcasting but increase the average end-to-end broadcasting delay. In this paper, we define a generalized broadcasting cost function, which can make a flexible tradeoff between average end-to-end broadcasting delay and total energy consumption for broadcasting, to adaptively meet various broadcasting performance requirements. Our target is to utilize the opportunistic broadcasting transmission model to design an efficient broadcasting schedule for low-duty-cycle WSNs, so that the broadcasting cost function is minimized. First, we define the Receiver-Constrained Minimum Cost Single-hop Broadcast Problem (RC-MCSB) and propose an optimal solution with a polynomial running time. Next, we extend the solution of RC-MCSB problem to our target problem and present a novel and efficient bottom-up solution. The simulation results have verified the significant performance advantage of our proposed bottom-up solution over the existing top-down solutions and the other solutions.

Physical Layer Security Schemes for Full-Duplex Cooperative Systems: State of the Art and Beyond

Due to the broadcast nature of wireless medium, wireless communication is highly vulnerable to eavesdropping attack. Traditionally, secure wireless data transmission has relied on cryptographic techniques at the network layer which incur high computational power and complexity. As an alternative, physical layer security (PLS) is emerging as a promising paradigm to protect wireless systems by exploiting the physical characteristics of the wireless channels. Among various PLS approaches, the one based on cooperative communication is favorable and has got a lot of interest from the research community. Although PLS schemes with half-duplex relays have been extensively discovered, the issue of PLS in cooperative systems with full-duplex (FD) relays is far from being comprehensively understood. In this paper, we first present the state of the art on PLS approaches proposed for FD cooperative systems. We then provide a case study in which a source-based jamming scheme is proposed to enhance the secrecy performance of a cooperative system with an untrusted FD relay. Finally, we outline several interesting yet challenging future research problems in this topic.

Fundamental Storage-Latency Tradeoff in Cache-Aided MIMO Interference Networks

Caching is an effective technique to improve user perceived experience for content delivery in wireless networks. Wireless caching differs from traditional web caching in that it can exploit the broadcast nature of wireless medium and hence opportunistically change the network topologies. This paper studies a cache-aided MIMO interference network with 3 transmitters each equipped with M antennas and 3 receivers each with N antennas. With caching at both the transmitter and receiver sides, the network is changed to hybrid forms of MIMO broadcast channel, MIMO X channel, and MIMO multicast channels. We analyze the degrees of freedom (DoF) of these new channel models using practical interference management schemes. Based on the collective use of these DoF results, we then obtain an achievable normalized delivery time (NDT) of the network, an information-theoretic metric that evaluates the worst-case delivery time at given cache sizes. The obtained NDT is for arbitrary M, N and any feasible cache sizes. It is shown to be optimal in certain cases and within a multiplicative gap of 3 from the optimum in other cases. The extension to the network with arbitrary number of transmitters and receivers is also discussed.

Joint Resource Allocation in Secure OFDMA-Based Networks Taking a Base Station as a Two-Way Relay

Due to the broadcast nature of wireless media, all nodes in the coverage of a transmitter are capable of capturing its signals, thus wireless transmission is sensitive to wiretapping. Several existing schemes place an emphasis on secrecy rate improvement, under the protocols of amplify-and-forward or decode-and-forward, when there are only relay users in the network. We set up a novel communication model in which normal and two-way relay users coexist in the same cell, taking the base station as a relay. Our objective is to maximize the total secrecy rate, taking subcarrier pairing, subcarrier assignment and power allocation into account, when there is one eavesdropper in one cell of the cellular network. Although this problem is very intricate, we reformulate it as a convex optimization problem by means of Lagrange duality. In order to reduce the computational complexity, equal power allocation is proposed. Lastly, the experimental results show the proposed resource allocation scheme can obtain a higher secrecy rate than traditional schemes.

Cooperative Privacy Preserving Scheme for Downlink Transmission in Multiuser Relay Networks

This paper studies the privacy-preserving for downlink transmission in multiuser relay networks, where a source communicates with multiple users via a relay employing the amplify-and-forward protocol. Within any scheduling unit, only one user (desired user) is chosen for data reception, and the other users (undesired users) are viewed as potential eavesdroppers due to the broadcast nature of wireless medium. To prevent information leakage, we propose a physical-layer cooperative privacy preserving scheme, whose key idea is to schedule a cooperating user in addition to the desired user to deliver artificial noise (AN). By exploiting the characteristics of channels, the cooperating user carefully designs the AN transmitted during two time slots such that the AN can be canceled out at the desired user, but cannot be removed at the undesired users. As a result, the end-to-end signal-to-noise-ratio of any undesired user is heavily degraded, while that of the desired user is not seriously affected, thus preserving the data confidentiality of the desired user. To maximize the instantaneous secrecy rate, an opportunistic user selection criterion is developed. The lower bound of the ergodic secrecy rate (ESR) as well as the approximate upper bound of the secrecy outage probability is derived. The asymptotic performance of ESR is also analyzed via extreme value theory. Furthermore, to motivate users with heterogeneous channel conditions to participate in cooperation and guarantee the fairness among users, a user-grouping-based selection method is proposed. To evaluate the performance of this method, a novel concept called system fairness factor is introduced and studied. Theoretical analysis and simulation results show that, thanks to the proposed cooperative privacy preserving mechanism, the system ESR grows with the increasing number of users, and much higher secrecy rate and lower secrecy outage probability can be achieved compared with the existing schemes in the literature.

Opportunistic broadcasting for low-power sensor networks with adaptive performance requirements

To reduce the energy waste caused by idle listening, sensor nodes in wireless sensor networks (WSNs) usually work with low-duty-cycle mode. However, such mode brings many new challenges, especially for broadcasting applications. This paper proposes to exploit the broadcast nature of wireless media to further save energy for broadcasting in low-duty-cycle WSNs, by adopting a novel opportunistic broadcasting transmission model. The key idea is to allow nodes to defer their wake-up time slots to opportunistically overhear the broadcasting messages sent by their neighbors, improving the energy efficiency at the cost of the increase of average broadcasting delay. Instead of regarding delay or energy as the single optimization objective, in this paper, we present a broadcasting cost function, which provides an adaptive control on the tradeoff between delay and energy to cover various performance requirements. Our target is thus to find the optimal broadcasting schedule to minimize the broadcasting cost, based on the opportunistic broadcasting transmission model. To this end, we first model the target problem under the single-hop case as a dynamic programming problem and prove it is solvable in polynomial time, then extend it to the multi-hop case and come up with an efficient solution. Extensive simulation results reveal that our solution always has a better performance over the other solutions under whatever configurations.

Opportunistic Shortcut Tree Routing in ZigBee Networks

The shortcut tree routing has been proposed to provide near optimal routing path as well as maintaining the advantages of the ZigBee tree routing, such as resource-free multi-hop routing capability. However, in spite of the efforts to provide an efficient and reliable protocol, the unicast routing itself has the fundamental limitation in wireless environment due to lossy, time-varying, and broadcast nature of wireless medium. For example, even one lossy link on a path may result in the failure of end-to-end packet delivery in wireless network environment. In this paper, we propose the opportunistic shortcut tree routing that combines the shortcut tree routing and the opportunistic routing. Instead of specifying a next hop node, the opportunistic shortcut tree routing allows the receiving nodes to compete to forward a packet with the priority of remaining hops. Since it has inherited advantages of both routing protocols, it can provide reliable packet delivery service without any resources for multi-hop routing and forwarder candidate selection for opportunistic routing. The performance evaluation proves that the opportunistic approach significantly enhances diverse network performances, while suppressing duplicate forwarding effectively with a metric of the remaining hops and the one-hop neighbor table.

LDAT: LFTM based data aggregation and transmission protocol for wireless sensor networks

Wireless sensor network consists of a large number of resource constrained sensor nodes. These sensor nodes communicate over wireless medium to perform a variety of information processing functionality. Due to broadcast nature of wireless medium, security is one of the major concerns and overlapping sensing range of sensor nodes results in redundancy in sensing data. Moreover, a large amount of energy is consumed by the base station to process these redundant data. To conserve energy and enhance the lifetime of sensor nodes, redundancy is eliminated at intermediate nodes by performing data aggregation. Wireless sensor networks are generally deployed in untrusted and hostile environments which results in compromised nodes. Thus, security and reliability of the transmitted data get reduced. Compromised nodes can inject false data, drop all the data, selectively forward data to an attacker, copy legal nodes to join routing paths, and disrupt data transmission during the data aggregation operation. In this paper, a novel scheme for data aggregation based on trust and reputation model is presented to ensure security and reliability of aggregated data. It will help to select secure paths from sensor nodes to the base station; thereby the accuracy of aggregated data will be increased significantly. Simulations show that the proposed protocol LDAT has less energy consumption and more accuracy as compared to some existing protocols which are based on functional reputation.

Exploiting Caching and Multicast for 5G Wireless Networks

The landscape toward 5G wireless communication is currently unclear, and, despite the efforts of academia and industry in evolving traditional cellular networks, the enabling technology for 5G is still obscure. This paper puts forward a network paradigm toward next-generation cellular networks, targeting to satisfy the explosive demand for mobile data while minimizing energy expenditures. The paradigm builds on two principles; namely caching and multicast . On one hand, caching policies disperse popular content files at the wireless edge, e.g., pico-cells and femto-cells, hence shortening the distance between content and requester. On other hand, due to the broadcast nature of wireless medium, requests for identical files occurring at nearby times are aggregated and served through a common multicast stream. To better exploit the available cache space, caching policies are optimized based on multicast transmissions. We show that the multicast-aware caching problem is NP-hard and develop solutions with performance guarantees using randomized-rounding techniques. Trace-driven numerical results show that in the presence of massive demand for delay tolerant content, combining caching and multicast can indeed reduce energy costs. The gains over existing caching schemes are 19% when users tolerate delay of three minutes, increasing further with the steepness of content access pattern.

Toward Efficient 5G Transmission: SER Performance Analysis for Asynchronous Physical-Layer Network Coding

People’s pursuit of higher quality communication has never ceased, which challenges the layout of 5G networks. Physical-layer network coding (PNC), as a key technology for 5G, supplies a powerful platform through leveraging the broadcast nature of wireless media. However, the symbol error rate (SER) of PNC is not well investigated, which would seriously influence user’s quality of experience due to packet loss in wireless environment. In this paper, considering both phase and symbol misalignments, we perform analysis on SER of asynchronous PNC. By assuming part of information is known to the relay, and we derive the lower bound for SER. Afterward, through applying the concept of error vector and eliminating redundant terms, we derive the upper bound for SER. Both the lower and upper bounds are applicable to either multiuser detection-based network coding or belief propagation-based maximum a posteriori decoding. Finally, Monte Carlo simulation verifies our results and demonstrates that the bounds are relatively tight. The analytical results derived in this paper can facilitate future studies of practical and theoretical issues on PNC.

SPAIS: A novel Self-checking Pollution Attackers Identification Scheme in network coding-based wireless mesh networks

Pollution attacks refer to ones where attackers modify and inject corrupted data packets into the wireless network with network coding to disrupt the decoding process. In the context of network coding, the epidemic effect of pollution attacks can degrade network throughput significantly because of the mixing nature of network coding. To address this issue, a number of schemes to identify malicious nodes have been developed in the past. Nonetheless, these schemes have their limitations and cannot effectively deal with pollution attacks. In this paper, we propose a novel light-weight Self-checking Pollution Attackers Identification Scheme (SPAIS), which can identify the pollution attackers effectively and efficiently. By making full use of the broadcast nature of wireless media and the insight that a well-behaved node can monitor its downstream neighboring nodes locally by cooperating with other nodes, SPAIS hierarchically organizes the network as levels such that the nodes in the same level can monitor their downstream level nodes cooperatively. Through the combination of theoretical analysis and extensive simulations, our experimental data demonstrates that SPAIS can more effectively identify pollution attackers with a lower cost in comparison with the existing candidate schemes. For example, even if the quality of network connections is not in good condition and the malicious nodes send only one corrupted packet, the pollution attackers can be identified with a high probability.

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Low-duty-cycle mode is widely adopted in energy-critical wireless sensor networks (WSNs). Such mode greatly reduces the energy waste caused by idle listening. However, it brings many new challenges for broadcasting. This paper mainly focuses on the minimum cost broadcast problem for low-duty-cycle WSNs. We propose a novel opportunistic broadcasting transmission model, which makes full use of the broadcast nature of wireless media to reduce the total energy consumption for broadcasting. The key idea is to allow nodes to defer their wake-up slots to opportunistically overhear the broadcasting messages sent by their neighbors, which could reduce the total energy consumption for broadcasting but increase the average end-to-end broadcasting delay. In this paper, we define a generalized broadcasting cost function, which can make a flexible tradeoff between average end-to-end broadcasting delay and total energy consumption for broadcasting, to adaptively meet various broadcasting performance requirements. Our target is to utilize the opportunistic broadcasting transmission model to design an efficient broadcasting schedule for low-duty-cycle WSNs, so that the broadcasting cost function is minimized. First, we define the Receiver-Constrained Minimum Cost Single-hop Broadcast Problem (RC-MCSB) and propose an optimal solution with a polynomial running time. Next, we extend the solution of RC-MCSB problem to our target problem and present a novel and efficient bottom-up solution. The simulation results have verified the significant performance advantage of our proposed bottom-up solution over the existing top-down solutions and the other solutions.

Security-embedded opportunistic user cooperation with full diversity

As a promising technique for wireless networks, cooperative communications is coming to maturity in both theory and practice. The main merit of the cooperation technique is its capability in providing additional transmission links to harvest the spatial diversity gain at the physical layer. However, due to the broadcast nature of wireless medium, the diversity gain can be also freely achieved at the potential eavesdropper if the cooperation is performed blindly. To solve this problem, we propose a security-embedded opportunistic user cooperation scheme (OUCS) in this paper. The OUCS first defines a concept called secrecy-providing capability (SPC) for both the source and the cooperative relays. By comparing the values of SPC of these nodes, the OUCS jointly decides whether to cooperate and with whom to cooperate from the perspective of physical layer security. The secrecy outage performance of the OUCS is then derived. From the results we prove that full diversity can be achieved (i.e., the diversity order is N + 1 for N cooperative relays), which outperforms existing alternatives. Finally, numerical results are provided to validate the theoretical analysis.