Masashi YOSHIDA Minoru TERADA Tetsuya MIKI
This paper presents sector based flooding (SBF) and adaptive sector-based flooding (ASBF) that are flooding methods for mobile ad hoc networks using position information. SBF, which divides the communication area of a sender node into sectors, allows only the node nearest to a sector representative position in each sector to rebroadcast a packet. SBF is divided into two methods, SBF-1 and SBF-2; the difference is the number of criteria used to decide whether to rebroadcast or to drop the packet. In ASBF, each node selects a flooding method from among SBF-1, SBF-2, and pure flooding, depending on its local node density. The node density is obtained from the distance between the sector representative position and its nearest node. Simulation results show that SBF reduces the number of packet transmissions generated in flooding and ASBF has high packet reachability with few packet transmissions.
Masanori TAKATA Masaki BANDAI Takashi WATANABE
This paper addresses the issue of deafness in MAC (Medium Access Control) protocols for wireless ad hoc networks using directional antennas. Directional antennas are expected to provide significant improvements over omni-directional antennas in ad hoc networks, such as high spatial reuse and range extension. Recently, several MAC protocols using directional antennas, typically referred to as directional MAC protocols, have been proposed for ad hoc networks. However, directional MAC protocols inherently introduce new kinds of problems arising from directivity. One major problem is deafness, caused by a lack of state information of neighbor nodes, whether idle or busy. This paper proposes DMAC/DA (Directional MAC with Deafness Avoidance) to overcome the deafness problem. DMAC/DA modifies the previously proposed MAC protocol, MDA (MAC protocol for Directional Antennas), to reduce the number of control messages and also maintain the ability to handle deafness. In DMAC/DA, WTS (Wait To Send) frames are simultaneously transmitted by the transmitter and the receiver after the successful exchange of directional RTS (Request To Send) and CTS (Clear To Send) to notify the on-going communication to potential transmitters that may experience deafness. The experimental results show that DMAC/DA outperforms existing directional MAC protocols, such as DMAC (Directional MAC) and MDA, in terms of throughput, control overhead and packet drop ratio under the different values of parameters such as the number of flows and the number of beams. In addition, qualitative evaluation of 9 MAC protocols is presented to highlight the difference between DMAC/DA and existing MAC protocols.
Yasuhisa TAKIZAWA Peter DAVIS Makoto KAWAI Hisato IWAI Akira YAMAGUCHI Sadao OBANA
The location information of ubiquitous objects is one of the key issues for context-aware systems. Therefore, several positioning systems to obtain precise location information have been researched. However, they have scalability and flexibility problems because they need completely configured space with a large number of sensors. To avoid the problems, we proposed a self-organizing location estimation method that uses ad hoc networks and Self-Organizing Maps and needs no prepared space with a large number of sensors. But, as in other similar precise localization methods, the proposed method needs advanced distance measurements unavailable to conventional wireless communication systems. In this paper, the self-organizing location estimation method's modification for distance measurement that uses received signal strength available to conventional wireless communication systems but which fluctuates uncertainly, is described and location estimation accuracy with the modified method is shown.
Choonhwa LEE Sumi HELAL Wonjun LEE
This letter presents a new gossip-based ad hoc service discovery protocol that uses a novel decentralized, peer-to-peer mechanism to provide mobile devices with the ability to advertise and discover services in an efficient way. Our performance study shows that the proposed protocol appropriately addresses the need of proximal service discovery over a dynamic wireless medium.
Han NAMGOONG Dongman LEE Dukyun NAM
The Minimum Connected Dominating Set (MCDS) reduces the number of messages to destinations and the finding MCDS is considered as a NP-hard problem. Alzoubi's approximation algorithm is known as the best in terms of message-optimal CDS construction, but not for mobility management. We present a message-efficient mobility management scheme based on distributed spanning trees. The proposed method may generate more messages than Alzoubi's for message delivery, but it consumes significantly fewer messages for mobility management (to the ratio of 2.5). Thus, when highly mobile networks are assumed, the proposed scheme outperforms Alzoubi's in terms of total number of messages.
Hong-Seok CHOI Hee-Jung BYUN Jong-Tae LIM
In this letter, we suggest a rate-based supervisory congestion control scheme for the ad hoc networks that use TCP as the transport protocol. This scheme makes it possible for the TCP sender to distinguish the causes of packet loss. In addition, this scheme guarantees the fair sharing of the available bandwidth among the connections. We show the reliability of our scheme by using the supervisory control framework and simulations confirm the effectiveness of our scheme.
Makoto TAKIZAWA Hiroto AIDA Masato SAITO Yoshito TOBE Hideyuki TOKUDA
In this paper, we present a novel forwarding scheme to enhance communication stability based on geographic routing in mobile ad hoc networks, which is called "Position-based Heuristic Forwarding" (PHF). For alternative solutions to traditional ad hoc routings, many geographic routing algorithms have been proposed. Most of the existing routings impose a certain restriction, planarity, on the graph structure of network for delivering messages to destination definitely. PHF achieves the guaranteed packet delivery over Unit Disk Graph, which is more widely employed graph model for the study of ad hoc networks. Accordingly, to eliminate the restriction of the routing algorithms enhances the probability to deliver messages successfully in networks with high nodes' mobility rate. In the simulation of PHF, we have evaluated the performance comparisons between PHF and its related work, Greedy Perimeter Stateless Routing (GPSR) and Dynamic Source Routing (DSR), which are the prominent geographic and conventional topology-based routing protocols, respectively. The results show that PHF provides higher packet delivery success rate indicating better communication stability and equal or less overhead than these work.
Takeshi MURAKAMI Masaki BANDAI Iwao SASASE
In this paper, we propose Split Multi-path Routing protocol with Load Balancing policy (SMR-LB) to improve TCP performance in mobile ad hoc networks. In SMR-LB, each intermediate node records how many primary paths are attempted to construct as well as which source nodes attempt to construct the primary path. Each intermediate node decides which primary path should be constructed by using the primary path and the source node ID information. As a result, SMR-LB can balance the loads and so reduce the probability of congestion and avoid the continuous link breakage time between the specific source and destination pair. Computer simulation results show that SMR-LB can improve TCP performance compared with the conventional protocols.
This letter presents a simple but accurate analytical model to evaluate the throughput of IEEE 802.11 distributed coordination function in non-saturated conditions. The influence of offered load on the throughput of both basic and RTS/CTS access mechanisms are analyzed and compared. It's shown that basic access scheme can achieve the same maximal throughput as that of RTS/CTS mechanism in non-saturated conditions while the latter is robust to the number of contending stations compared to basic mechanism. The analytical results are validated by extensive simulations.
Chih-Min YU Shiang-Jiun LIN Chia-Chi HUANG
In this paper, we present Blueweb, a new Bluetooth-based multihop network with an efficient scatternet formation algorithm and a hybrid routing protocol. The Blueweb is designed from the original idea of Bluetree. Blueweb's scatternet formation uses two mechanisms. One is the role exchange mechanism in which only slave nodes serve as the role of relay through the whole scatternet. The other one is the return connection mechanism in which we convert the scatternet from a tree-shaped to a web-shaped topology. Meanwhile, a modified source routing protocol is designed for Blueweb in which we combine the proactive method with the reactive method to discover the optimal path for packet transmission. Furthermore, using computer simulations we compared the system performance of Blueweb and Bluetree with both a static model and a uniform traffic model. With the static model we evaluate the scatternet performance and with the uniform traffic model we evaluate the transmission performance. Our simulation results show that Blueweb achieves superior system performance than Bluetree on both scatternet performance and transmission performance.
Ying-Hong WANG Chih-Chieh CHUANG Chih-Feng CHAO
A mobile ad hoc network (MANET) is a self-organizing and adaptive wireless network constructed by the dynamic gathering of mobile nodes (MNs). The communication among MNs in MANETs is carried out without base stations or access points and the transmission of data packets is completed through relays among nodes. Due to the mobility of MNs, the topology of a MANET frequently changes and thus results in the disability of on-the-fly data transmission routes. To cope with the intrinsic properties of MANETs, Dynamic Backup Routes Routing Protocol (DBR2P), a distributed backup routes mechanism for quick reconnection during link failures, is proposed in this paper. DBR2P is an on-demand routing protocol which can set up many backup routes to reach a destination node in a given period of time. The information of backup routes can be saved in a specific on-the-route node and enables backup routes to be found immediately in situation regarding disconnection. When a link fails, routes from the source node to the destination node are analyzed to obtain backup routes and to sustain quick reconnection. As a result, DBR2P could more thoroughly improve the quality of routing than previous routing protocols.
Tomoyuki OHTA Toshifumi KAWAGUCHI Yoshiaki KAKUDA
This paper discusses multicast routing in ad hoc networks. In multicast routing, a node delivers the same message to the other nodes within a multicast group along with a multicast tree. Since nodes are moving around in ad hoc networks, the links between the nodes change frequently. However, the multicast tree must be maintained to deliver the messages regardless of the link changes. This paper gives a description of an autonomous clustering-based hierarchical multicast routing protocol in ad hoc networks. Since the autonomous clustering scheme is adaptive to the node movement, the proposed multicast routing can maintain the multicast tree in despite of link changes. This paper shows the effectiveness of autonomous clustering-based hierarchical multicast routing from the point of view of adaptability to link changes and scalability to multicast members.
Hua-Yi LIN Yueh-Min HUANG Tzone-I WANG
Unlike traditional networks, the characteristics of mobile wireless devices that can dynamically form a network without any infrastructure and wired line mean that mobile ad hoc networks frequently display partition owing to node mobility or link failures. Consequently, an ad hoc network is difficult to provide on-line access to trusted authorities or centralized servers. Despite the existence of well-known security mechanisms, the absence of a stationary central authorization facility in an open and distributed communication environment is a major challenge. Consequently, applying traditional Public Key Infrastructure (PKI) security architecture to mobile ad hoc networks will create secure blind sides. Based on this perspective, this study proposes a novel scalable and robust cluster-organized key management scheme. Distribution of trust to an aggregation of cluster heads using a threshold scheme faculty provides mobile ad hoc networks with robust key management. Furthermore, the proposed approach provides Certificate Authority (CA) with a fault tolerance mechanism to prevent a single point of compromise or failure, and saves CA large repositories from maintaining member certificates, making the proposed approach more suitable for numerous mobile devices. Additionally, this study proposes a Cluster Secure Based Routing Protocol (CSBRP) to integrate into the key management to enhance non-repudiation of routing information and routing performances. Finally, this study introduces a mathematical model to demonstrate that the proposed cluster-based communication outperforms the node-based approach.
Ad hoc networks are becoming an interesting research area, as they inherently support unique network applications for the wireless communications in a rugged environment, which requires rapid deployment and is difficult to be provided by an infrastructure network. Many issues need to be addressed for the ad hoc networks. In this paper, we propose an efficient distributed coordination function on the media access control protocol to enhance the power conservation of mobile hosts by using a power control algorithm and the network throughput of an ad hoc network by using an algorithm for simultaneous frame transmissions. Extensive simulation is studied to evaluate the improvement of the proposed method. The results of the simulation exhibit significant improvement to the standard access control protocol. With slight improvement of network throughput, up to 85% of the consumed energy was able to be saved in compared to the standard protocol and up to 7 times of the energy efficiency was enhanced with the proposed method.
In contention-based wireless ad hoc networks, power control is an efficient way to improve the spatial reuse by allowing multiple pairs to communicate simultaneously. In this paper, we propose a game-theoretical approach for joint power and rate control in ad hoc networks, where the transmit rate of each link is maximized. Meanwhile we consider the transmit power as the cost, since higher power leads to higher interference and more energy consumption. In particular, we introduce a novel auction-like pricing algorithm in which the cost per unit power steps up until the network settles down at a Nash equilibrium, which is a feasible power and rate allocation, even when the Signal to Interference and Noise Ratio (SINR) requirements are initially infeasible. Numerical results show significant throughput improvement and energy consumption savings compared with the previously proposed algorithm that defers the link with minimum SINR.
Suhua TANG Bing ZHANG Masahiro WATANABE Shinsuke TANAKA
Many routing protocols have been proposed for mobile ad hoc networks. Among these protocols, the on-demand routing protocols are very attractive because they have low routing overhead. However, few of the existing on-demand routing protocols have considered the link heterogeneity, such as the different communication rate, different Packet Error Ratio (PER). As a result, the routes tend to have the shortest hop count and contain weak links, which usually provide low performance and are susceptible to breaks in the presence of mobility. In this paper, we analyze the existing on-demand routing protocols and propose a Link Heterogeneity Aware On-demand Routing (LHAOR) protocol, where the link quality and mobility are considered. Specifically, the Local Update (LU) is proposed and the link metric is inversely related with the Received Signal Strength Indicator (RSSI). By using the LU method and RSSI information, the routes adapt to the topology variation and link quality changes, and reach the local optimum quickly, which contains strong links and has a small metric. Simulation and experiment results show that our LHAOR protocol achieves much higher performance than the classical on-demand routing protocols.
Chai-Keong TOH Petri MAHONEN Mikko UUSITALO
In this paper, we provide various perspectives related to wireless sensor and mobile ad hoc networking research. We reveal their commonalities and differences and suggest the need for participation from the computer science community, in addition to communications and protocols. In particular, we reveal the various issues that demand deeper investigation, collaborative research, and standardization. We introduced the aim, structure, objectives, and goals of the World Wireless Research Forum (WWRF) and highlight the activities conducted by the WWRF Working Group 3. Finally, we discuss the status of various standardization efforts and present new research issues and challenges.
Xiaocong QIAN Baoyu ZHENG Genjian YU
The issue of importance of multiuser detection for CDMA-based mobile ad hoc networks is addressed in this paper. For conventional scheme, each terminal in the network uses matched filter to receive packets, so the performance (e.g., throughput) of the network suffers from multi-access interference (MAI). Different from above scheme, in this paper, each terminal of the ad hoc network is equipped with an adaptive blind linear multiuser detector, so the ability of MAI-resistance is gained. Employing slotted-ALOHA protocol in MAC layer and using fully-connected network model, the throughput of ad hoc network is studied. Theoretic analysis and simulation results show that multiuser detection can remarkably improve throughput performance of ad hoc networks.
Yongkang XIAO Xiuming SHAN Yong REN
TCP performance in the IEEE 802.11-based multihop ad hoc networks is extremely poor, because the congestion control mechanism of TCP cannot effectively deal with the problem of packet drops caused by mobility and shared channel contention among wireless nodes. In this paper, we present a cross-layer method, which adaptively adjusts the TCP maximum window size according to the number of RTS (Request To Send) retry counts of the MAC layer at the TCP sender, to control the number of TCP packets in the network and thus decrease the channel contention. Our simulation results show that this method can remarkably improve TCP throughput and its stability.
The basic carrier sense multi-access control scheme for multicast communications in wireless ad hoc networks suffers from the well know hidden terminal problem. The data packet collision probability is relatively high, and the packet delivery ratio is sensitive to the network topology, nodes distribution and traffic load. In this paper, we generalize the virtual carrier sense collision avoidance approach to reduce packet collisions in multicast communications. The sender and receivers exchange RTS and CTS packets to reserve the channel. When more than one receivers reply with CTS packets, the sender will detect an "expected" collision which may be interpreted as a valid "clear-to-send" signal provided the collision satisfies the given timing requirements. Together with a receiver-initiated local recovery mechanism, the reliability and packet delivery ratio can be improved to close to 100%.