This paper addresses energy conservation, a fundamental issue of paramount importance in heterogeneous mobile ad hoc networks (MANETs) consisting of powerful nodes (i.e., P-nodes) as well as normal nodes (i.e., B-nodes). By utilizing the inherent device heterogeneity, we propose a cross-layer designed Device-Energy-Load Aware Relaying framework, named DELAR, to achieve energy conservation from multiple facets, including power-aware routing, transmission scheduling and power control. In particular, we design a novel power-aware routing protocol that nicely incorporates device heterogeneity, nodal residual energy information and nodal load status to save energy. In addition, we develop a hybrid transmission scheduling scheme, which is a combination of reservation-based and contention-based medium access control schemes, to coordinate the transmissions. Moreover, the novel notion of "mini-routing" is introduced into the data link layer and an Asymmetric MAC (A-MAC) scheme is proposed to support the MAC-layer acknowledgements over unidirectional links caused by asymmetric transmission power levels between powerful nodes and normal nodes. Furthermore, we present a multi-packet transmission scheme to improve the end-to-end delay performance. Extensive simulations show that DELAR can indeed achieve energy saving while striking a good balance between energy efficiency and other network performance metrics.

The recent Federal Communications Commission regulations for ultra-wideband (UWB) transmission systems have sparked a surge of research interests in the UWB technology. One of the important application areas of UWB is wireless sensor networks. The proper operations of many UWB sensor networks rely on the knowledge of physical sensor locations. However, most existing localization algorithms developed for sensor networks are vulnerable to attacks in hostile environments. As a result, attackers can easily subvert the normal functionalities of location-dependent sensor networks by exploiting the weakness of localization algorithms. In this paper, we first analyze the security of existing localization techniques. We then develop a mobility-assisted secure localization scheme for UWB sensor networks. In addition, we propose a location-based scheme to enable secure authentication in UWB sensor networks.

Node compromise is a serious threat to wireless sensor networks deployed in unattended and hostile environments. To mitigate the impact of compromised nodes, we propose a suite of location-based compromise-tolerant security mechanisms. Based on a new cryptographic concept called pairing, we propose the notion of location-based keys (LBKs) by binding private keys of individual nodes to both their IDs and geographic locations. We then develop an LBK-based neighborhood authentication scheme to localize the impact of compromised nodes to their vicinity. We also present efficient approaches to establish a shared key between any two network nodes. In contrast to previous key establishment solutions, our approaches feature nearly perfect resilience to node compromise, low communication and computation overhead, low memory requirements, and high network scalability. Moreover, we demonstrate the efficacy of LBKs in counteracting several notorious attacks against sensor networks such as the Sybil attack, the identity replication attack, and wormhole and sinkhole attacks. Finally, we propose a location-based threshold-endorsement scheme, called LTE, to thwart the infamous bogus data injection attack, in which adversaries inject lots of bogus data into the network. The utility of LTE in achieving remarkable energy savings is validated by detailed performance evaluation.

This paper studies key management, a fundamental problem in securing mobile ad hoc networks (MANETs). We present IKM, an ID-based key management scheme as a novel combination of ID-based and threshold cryptography. IKM is a certificateless solution in that public keys of mobile nodes are directly derivable from their known IDs plus some common information. It thus eliminates the need for certificate-based authenticated public-key distribution indispensable in conventional public-key management schemes. IKM features a novel construction method of ID-based public/private keys, which not only ensures high-level tolerance to node compromise, but also enables efficient network-wide key update via a single broadcast message. We also provide general guidelines about how to choose the secret-sharing parameters used with threshold cryptography to meet desirable levels of security and robustness. The advantages of IKM over conventional certificate-based solutions are justified through extensive simulations. Since most MANET security mechanisms thus far involve the heavy use of certificates, we believe that our findings open a new avenue towards more effective and efficient security design for MANETs

The shared wireless medium of mobile ad hoc networks facilitates passive, adversarial eavesdropping on data communications whereby adversaries can launch various devastating attacks on the target network. To thwart passive eavesdropping and the resulting attacks, we propose a novel anonymous on-demand routing protocol, termed MASK, which can accomplish both MAC-layer and network-layer communications without disclosing real IDs of the participating nodes under a rather strong adversary model. MASK offers the anonymity of senders, receivers, and sender-receiver relationships in addition to node unlocatability and untrackability and end-to-end flow untraceability. It is also resistant to a wide range of attacks. Moreover, MASK preserves the high routing efficiency as compared to previous proposals. Detailed simulation studies have shown that MASK is highly effective and efficient.

This paper studies public-key management, a fundamental problem in providing security support for mobile ad hoc networks. The infrastructureless nature and network dynamics of ad hoc networks make the conventional certificate-based public-key solutions less suitable. To tackle this problem, we propose a novel anonymous and certificateless public-key infrastructure (AC-PKI) for ad hoc networks. AC-PKI enables public-key services with certificateless public keys and thus avoids the complicated certificate management inevitable in conventional certificate-based solutions. To satisfy the demand for private keys during network operation, we employ the secret-sharing technique to distribute a system master-key among a preselected set of nodes, called D-PKG, which offer a collaborative private-key-generation service. In addition, we identify pinpoint attacks against D-PKG and propose anonymizing D-PKG as the countermeasure. Moreover, we determine the optimal secret-sharing parameters to achieve the maximum security.

Due to the broadcast nature of radio transmissions, communications in mobile ad hoc networks (MANETs) are more susceptible to malicious traffic analysis. In this paper we propose a novel anonymous on-demand routing protocol, termed MASK, to enable anonymous communications thereby thwarting possible traffic analysis attacks. Based on a new cryptographic concept called pairing, we first propose an anonymous neighborhood authentication protocol which allows neighboring nodes to authenticate each other without revealing their identities. Then utilizing the secret pairwise link identifiers and keys established between neighbors during the neighborhood authentication process, MASK fulfills the routing and packet forwarding tasks nicely without disclosing the identities of participating nodes under a rather strong adversarial model. MASK provides the desirable sender and receiver anonymity, as well as the relationship anonymity of the sender and receiver. It is also resistant to a wide range of adversarial attacks. Moreover, MASK preserves the routing efficiency in contrast to previous proposals. Detailed anonymity analysis and simulation studies are carried out to validate and justify the effectiveness of MASK.

Wireless sensor networks are often deployed in unattended and hostile environments, leaving individual sensors vulnerable to security compromise. The paper proposes the novel notion of location-based keys for designing compromise-tolerant security mechanisms for sensor networks. Based on location-based keys, we develop a node-to-node authentication scheme, which is able not only to localize the impact of compromised nodes within their vicinity, but also to facilitate the establishment of pairwise keys between neighboring nodes. Compared with previous proposals, our scheme has perfect resilience against node compromise, low storage overhead, and good network scalability. We also demonstrate the use of location-based keys in combating a few notorious attacks against sensor network routing protocols.

Wireless sensor networks (WSNs) are appealing in obtaining fine-granular observations about the physical world. Due to the fact that WSNs are composed of a large number of low-cost but energy-constrained sensor nodes, along with the notorious time-varying and error-prone nature of wireless links, scalable, robust, and energy-efficient data disseminating techniques are requisite for the emerging WSN applications such as environment monitoring and surveillance. To meet this challenging demand, we propose a hybrid data dissemination framework for WSNs in this paper. In particular, we conceptually partition a whole sensor field into several functional regions and apply different routing schemes to different regions in order to provide better performance in terms of reliability and fair energy usage. For this purpose, we also propose a novel zone flooding scheme, essentially a combination of geometric routing and flooding techniques. Our scheme features low overhead, high reliability, good scalability, and notable flexibility. Simulation studies are carried out to validate the effectiveness and efficiency of our scheme.

Due to MAC collisions and mobility, quality of service (QoS) provisioning in mobile ad hoc networks is very challenging. In this paper, we propose an innovative scheme to grant high priority to communications between some important nodes in TDMA based ad hoc networks. In addition to bandwidth reservation in previous QoS routing approaches, our scheme adopts a new approach: bandwidth prereservation. Some bandwidth is prereserved at intermediate nodes in a quadrangle-shaped area formed between important nodes. The key idea is to utilize each node's geographic location information and minimize potential scheduling conflicts for transmissions. In this way, time slot collisions in adjacent wireless links along a path can be reduced so that more high priority connections can be accepted into the network. Extensive simulations show that our scheme can successfully provide better communication quality at a relatively low price.

Due to the salient characteristics such as the time-varying and error-prone wireless links, the dynamic and limited bandwidth, the time-varying traffic pattern and user locations, and the energy constraints, it is a challenging task to efficiently support heterogeneous traffic with different quality of service (QoS) requirements in mulithop mobile ad hoc networks. In the last few years, many channel dependent mechanisms are proposed to address this issue based on the cross-layer design philosophy. However, a lot of problems remain before more efficient solutions are found. One of the problems is how to alleviate the conflict between throughput and fairness for different prioritized traffic, especially how to avoid the bandwidth starvation problem for low priority traffic when the high priority traffic load is very high. In this paper, we propose a novel scheme named courtesy piggybacking (CP) to address this problem. With the recognition of inter-layer coupling, our courtesy piggybacking scheme exploits the channel dynamics and stochastic traffic features to alleviate the conflict. The basic idea is to let the high priority traffic help the low priority traffic by sharing unused residual bandwidth with courtesy. Another noteworthy feature of the proposed scheme is its implementation simplicity: the scheme is easy to implement and is applicable in networks using either reservation-based or contention-based MAC protocols.

Security is a critical issue in a mobile ad hoc network (MANET). We propose and investigate a novel scheme, security protocol for reliable data delivery (SPREAD), to enhance the data confidentiality service in a mobile ad hoc network. The proposed SPREAD scheme aims to provide further protection to secret messages from being compromised (or eavesdropped) when they are delivered across the insecure network. The basic idea is to transform a secret message into multiple shares by secret sharing schemes and then deliver the shares via multiple independent paths to the destination so that even if a small number of nodes that are used to relay the message shares are compromised, the secret message as a whole is not compromised. We present the overall system architecture and investigate the major design issues. We first describe how to obtain message shares using the secret sharing schemes. Then we study the appropriate choice of the secret sharing schemes and the optimal allocation of the message shares onto each path in order to maximize the security. The results show that the SPREAD is more secure and also provides a certain degree of reliability without sacrificing the security. Thirdly, the multipath routing techniques are discussed and the path set optimization algorithm is developed to find the multiple paths with the desired property, i.e., the overall path set providing maximum security. Finally, we present the simulation results to justify the feasibility and evaluate the effectiveness of SPREAD.

Wireless sensor networks (WSNs) are appealing in obtaining fine-granular observations about the physical world. Due to the fact that WSNs are composed of a large number of low-cost but energy-constrained sensor nodes, along with the notorious timer-varying and error-prone natures of wireless links, scalable, robust, and energy-efficient data disseminating techniques are requisite for the emerging WSN applications such as environment monitoring and surveillance. In this paper we examine this emerging field from a view of supply chain management and propose a hybrid data dissemination framework for WSNs. In particular, we conceptually partition a whole sensor field into several functional regions based on the supply chain management methodology, and apply different routing schemes to different regions in order to provide better performance in terms of reliability and energy usage. For this purpose, we also propose a novel zone flooding scheme, essentially a combination of geometric routing and flooding techniques. Our hybrid data dissemination framework features low overhead, high reliability, good scalability and flexibility, and preferable energy efficiency. Detailed simulation studies are carried out to validate the effectiveness and efficiency of our scheme.

Due to the salient characteristics such as the time-varying and error-prone wireless links, the dynamic and limited bandwidth, the time-varying traffic pattern and user locations, and the energy constraints, it is a challenging task to efficiently support heterogeneous traffic with different quality of service (CoS) requirements in multihop mobile ad hoc networks. In the last few years, many channel-dependent mechanisms are proposed to address this issue based on the cross-layer design philosophy. However, a lot of problems remain before more efficient solutions are found. One of the problems is how to alleviate the conflict between throughput and fairness for different prioritized traffic, especially how to avoid the bandwidth starvation problem for low-priority traffic when the high-priority traffic load is very high. In this paper, we propose a novel scheme named Courtesy Piggybacking to address this problem. With the recognition of interlayer coupling, our Courtesy Piggybacking scheme exploits the channel dynamics and stochastic traffic features to alleviate the conflict. The basic idea is to let the high-priority traffic help the low-priority traffic by sharing unused residual bandwidth with courtesy. Another noteworthy feature of the proposed scheme is its implementation simplicity: The scheme is easy to implement and is applicable in networks using either reservation-based or contention-based MAC protocols.

We propose a novel media access control (MAC) architecture to support differentiated service (DiffServ) in IEEE 802.11 WLAN. By employing the MAC-core as base and different adaptors as add-ons in this architecture, the resulting MAC can provide prioritized services with different delays and throughputs. Our simulation studies show that the resulting MAC protocols based on this architecture can achieve low access delay and high throughput for high priority traffic while maintaining fairness.

It is well-known that distributed delay-constrained least-cost (DCLC) unicast routing problem is NP-complete. In this paper we propose an efficient distributed algorithm, namely, selection function based DCLC (SF-DCLC), based on a novel selection function for the DCLC problem. The proposed SF-DCLC algorithm requires limited network state information at each network node and is always able to find a loop-free path satisfying the delay bound if such paths exist. Simulation study show that the SF-DCLC is not as sensitive to the delay bound and network size as some other DCLC routing algorithms, and attains very low cost-inefficiency (less than 3% to the optimal One) in various network scenarios we simulate. The most attractive feature of SF-DCLC is that SF-DCLC has very high probability to find the optimal solution or a near-optimal solution in polynomial time with low computational complexity and message complexity.