Snow on sea ice is a sensitive indicator of climate change and is considered a key reason for amplified warming in the Arctic. The passive microwave remote sensing is an important method for Snow Depth (SD) observation. Therefore, understanding the influence of SD on observed brightness temperature (TB) is necessary for SD retrieval using microwave radiometer. Taking the FengYun-3D/Microwave Radiation Imager (FY3D/MWRI) as an example, this paper simulates the influence of SD on observed TBs from different channels using the MicroWave MODel (MWMOD) in the Arctic. Several conditions are considered for both first year ice (FYI) and multi-year ice (MYI), including various sea ice concentrations and water vapor contents in the atmosphere. The correlation between SD and TB is also briefly analyzed. It provides a theoretical reference for the retrieval of SD using microwave radiometer.

Multiple channels in Wireless Sensor Networks (WSNs) are often exploited to support parallel transmission and to reduce interference. However, the extra overhead posed by the multi-channel usage coordination dramatically challenges the energy-constrained WSNs. In this paper, we propose a Regret Matching based Channel Assignment algorithm (RMCA) to address this challenge, in which each sensor node updates its choice of channels according to the historical record of these channels’ performance to reduce interference. The advantage of RMCA is that it is highly distributed and requires very limited information exchange among sensor nodes. It is proved that RMCA converges almost surely to the set of correlated equilibrium. Moreover, RMCA can adapt the channel assignment among sensor nodes to the time-variant flows and network topology. Simulations show that RMCA achieves better network performance in terms of both delivery ratio and packet latency than CONTROL, MMSNand randomized CSMA. In addition, real hardware experiments are conducted to demonstrate that RMCA is easy to be implemented and performs better.

Energy saving is an important issue in Mobile Ad Hoc Networks (MANETs). Recent studies show that network coding can help reduce the energy consumption in MANETs by using less transmissions. However, apart from transmission cost, there are other sources of energy consumption, e.g., data encryption/decryption. In this paper, we study how to leverage network coding to reduce the energy consumed by data encryption in MANETs. It is interesting that network coding has a nice property of intrinsic security, based on which encryption can be done quite efficiently. To this end, we propose P-Coding, a lightweight encryption scheme to provide confidentiality for network-coded MANETs in an energy-efficient way. The basic idea of P-Coding is to let the source randomly permute the symbols of each packet (which is prefixed with its coding vector), before performing network coding operations. Without knowing the permutation, eavesdroppers cannot locate coding vectors for correct decoding, and thus cannot obtain any meaningful information. We demonstrate that due to its lightweight nature, P-Coding incurs minimal energy consumption compared to other encryption schemes.

Recently, distributed data storage has gained increasing popularity for reliable access to data through redundancy spread over unreliable nodes in wireless sensor networks (WSNs). However, without any protection to guarantee the data integrity and availability, the reliable data storage cannot be achieved since sensor nodes are prone to various failures, and attackers may compromise sensor nodes to pollute or destroy the stored data. Therefore, how to design a robust sensor data storage scheme to efficiently guarantee the data integrity and availability becomes a critical issue for distributed sensor storage networks. In this paper, we propose a distributed fault/intrusion-tolerant data storage scheme based on network coding and homomorphic fingerprinting in volatile WSNs environments. For high data availability, the proposed scheme uses network coding to encode the source data and distribute encoded fragments with original data pieces. With secure, compact, and efficient homomorphic fingerprinting, our scheme can fast locate incorrect fragments and then initialize data maintenance. Extensive theoretical analysis and simulative results demonstrate the efficacy and efficiency of the proposed scheme.

Privacy threat is one of the critical issues in multi-hop wireless networks, where attacks such as traffic analysis and flow tracing can be easily launched by a malicious adversary due to the open wireless medium. Network coding has the potential to thwart these attacks since the coding/mixing operation is encouraged at intermediate nodes. However, the simple deployment of network coding cannot achieve the goal once enough packets are collected by the adversaries. On the other hand, the coding/mixing nature precludes the feasibility of employing the existing privacy-preserving techniques, such as Onion Routing. In this paper, we propose a novel network coding based privacy-preserving scheme against traffic analysis in multi-hop wireless networks. With homomorphic encryption on Global Encoding Vectors (GEVs), the proposed scheme offers two significant privacy-preserving features, packet flow untraceability and message content confidentiality, for efficiently thwarting the traffic analysis attacks. Moreover, the proposed scheme keeps the random coding feature, and each sink can recover the source packets by inverting the GEVs with a very high probability. Theoretical analysis and simulative evaluation demonstrate the validity and efficiency of the proposed scheme.

Privacy threat is a very serious issue in multi-hop wireless networks (MWNs) since open wireless channels are vulnerable to malicious attacks. Source unobservability is an attractive and desirable security property for many privacy-sensitive applications, and dummy messages are most commonly used to achieve this property. However, dummy messages may incur severe performance degradation or even service denial due to the explosion of network traffic. In this paper, we propose a novel scheme, called SUNC (Source Unobservability by Network Coding), to prevent traffic explosion while achieving source unobservability. With SUNC, specially designed dummy messages can be absorbed at intermediate nodes, and, thus, traffic explosion can be naturally prevented. In addition, SUNC can offer forwarder blindness, which is an important privacy property for thwarting internal attackers. Security analysis and performance evaluation demonstrate the efficacy and efficiency of the proposed SUNC.

It is widely recognized that the packet loss burstiness over wireless channels has a significant impact on the performance of network protocols. The analysis of packet loss burstiness, however, is very challenging, and there is a lack of well-established analytical models to provide fundamental insights for characterizing the burstiness. To address the issue, in this paper, we develop a generic analytical model to study the packet loss burstiness. In the model, we use the correlation length of packet loss rate as a metric to represent the packet loss burstiness mathematically, and we formulate the metric by investigating the correlations between packet losses. In addition, a closed-form expression of packet loss rate is derived for protocol design. We apply the model to design an adaptive packetization scheme, which can enhance the channel throughput by over 10%. Simulation results are given to validate the proposed model and scheme.

Multiple channels in Wireless Sensor Networks (WSNs) are often exploited to support parallel transmission and reduce interference. However, there are many challenges, such as extra communication overhead, posed to the energy constraint of WSNs by the multi-channel usage coordination. In this paper, we propose a Regret Matching based Channel Assignment algorithm (RMCA) to address those challenges. The advantage of RMCA is that it is highly distributed and requires very limited information exchanges among sensor nodes. It converges almost surely to the set of correlated equilibrium. Moreover, RMCA can adapt the channel assignment among sensor nodes to the time-variant flows and network topology. Simulations show that RMCA achieves good network performance in terms of both delivery ratio and packet latency.

In this paper, we formulate multi-channel assignment in Wireless Sensor Networks (WSNs) as an optimization problem and show it is NP-hard. We then propose a distributed Game Based Channel Assignment algorithm (GBCA) to solve the problem. GBCA takes into account both the network topology information and transmission routing information. We prove that there exists at least one Nash Equilibrium in the channel assignment game. Furthermore, we analyze the sub-optimality of Nash Equilibrium and the convergence of the Best Response in the game. Simulation results are given to demonstrate that GBCA can reduce interference significantly and achieve satisfactory network performance in terms of delivery ratio, throughput, channel access delay and energy consumption.

Though providing an intrinsic secrecy, network coding is still vulnerable to eavesdropping attacks, by which an adversary may compromise the confidentiality of message content. Existing studies mainly deal with eavesdroppers that can intercept a lim-ited number of packets. However, real scenarios often consist of more capable adversaries, e.g., global eavesdroppers, which can defeat these techniques. In this paper, we propose P-Coding, a novel security scheme against eavesdropping attacks in network coding. With the lightweight permutation encryption performed on each message and its coding vector, P-Coding can efficiently thwart global eavesdroppers in a transparent way. Moreover, P-Coding is also featured in scalability and robustness, which enable it to be integrated into practical network coded systems. Security analysis and simulation results demonstrate the efficacy and efficiency of the P-Coding scheme.

In this paper, we study the issue of scheduling transmission opportunities among nodes (peers) to achieve higher network throughput and lower transmission delay for network coding enabled wireless networks. By conducting an in-depth investigation on the scheduling principles, we propose a cooperative Peer-to-peer Information Exchange (PIE) scheme with an efficient and light-weight scheduling algorithm. PIE can not only fully exploit the broadcast nature of wireless channels, but also take advantage of cooperative peer-to-peer information exchange. Qualitative analysis and extensive simulations demonstrate the effectiveness and efficiency of PIE.

Network coding has been widely recognized as a promising information dissemination approach for wireless networks. However, in practical wireless networks enabled with network coding, different peer sending sequences make significant impact on overall network throughput and transmission delay. In this paper, we study the peer scheduling problem, which is defined as how to intelligently schedule the sending sequence among a group of peers to maximize the wireless coding gain. By conducting an in-depth investigation on the peer scheduling principles in wireless network coding, we propose a cooperative Peer-to-peer Information Exchange (PIE) scheme with an efficient and light-weight peer scheduling algorithm. The PIE scheme can not only fully exploit the broadcast nature of wireless channels, but also utilize the advantage of cooperative peer-to-peer information exchange. Finally, the effectiveness and efficiency of the PIE scheme are demonstrated through qualitative analysis and extensive simulations.

Privacy threat is one of the critical issues in network coding, where attacks such as traffic analysis can be easily launched by a malicious adversary once enough encoded packets are collected. Furthermore, the encoding/mixing nature of network coding precludes the feasibility of employing the existing privacy-preserving techniques, such as Onion routing, in network coding enabled networks. In this paper, we propose a novel privacy-preserving scheme against traffic analysis in network coding. With homomorphic encryption operation on global encoding vectors (GEVs), the proposed scheme offers two significant privacy-preserving features, packet flow untraceability and message content confidentiality, for efficiently thwarting the traffic analysis attacks. Moreover, the proposed scheme keeps the random coding feature, and each sink can recover the source packets by inverting the GEVs with a very high probability. Theoretical analysis and simulative evaluation demonstrate the validity and efficiency of the proposed scheme.

In this paper, we propose an efficient privacy-preserving scheme for secure packet transmission at wireless link layer. The proposed scheme is constructed by using hash values in reverse hash chains as interface identifiers. It can successfully and efficiently resist the Media Access Control (MAC) address based attacks, such as flow tracking and traffic analysis, which are launched by either outside or even inside attackers. In addition, some optimization techniques are also introduced to further improve the efficiency of the proposed scheme. The extensive analysis and simulations demonstrate the enhanced security and efficiency of the proposed scheme.

Localized mobility management is critical to achieve low handoff delay and signaling cost. However, the existing solutions may not be suitable for emerging wireless mesh networks (WMNs), which are characterized by the direct interconnectivity between access points. To exploit this feature of WMN, in this paper, we propose a novel localized mobility management scheme, called mobility-aware multi-path (MAMP) forwarding scheme, by utilizing multi-path routing. Our scheme can significantly improve the handoff processing performance at a slightly increased cost of control and management overhead. Extensive performance evaluations demonstrate that MAMP is superior to the existing solutions in terms of handoff delay, signaling amount as well as network scalability. Moreover, the proposed scheme can also achieve a better stability and reliability by adopting multi-path packet forwarding strategy.

As an enhancement mechanism for the end-to-end congestion control, active queue management (AQM) can keep smaller queuing delay and higher throughput by purposefully dropping the packets at the intermediate nodes. Comparing with RED algorithm, although the PI (proportional-integral) controller for AQM designed by C. Hollot improves the stability, the transient performance of the PI controller is not perfect, such as the regulating time is too long. In order to overcome this drawback, in this paper, the PID (proportional-integral-differential) controller is proposed to speed up the responsiveness of AQM system. The controller parameters are tuned based on the determined gain and phase margins. The simulation results show that the integrated performance of the PID controller is obviously superior to that of the PI controller.