The Bluetmth technology will enable m e n to c0Mect a wide range of electronic devices such as laplops, headsets, cellular phones etc. Bluetooth devices can connect to form a piconel, which consists of a master and upto 7 slaves. m e master controls the medium access in the piconet using a polling scheme. Two types of connections can be established in a piconet: the Synchronous Connection-Oriented (SCO) link, and the Asynchronous Counectiooless (ACL) link. SCO links provide a circuit-oriented service with constant bandwidth based on a fixed and periodic allocation of slots. They require a pair of slots once every two, four or six slots, depending upon the SCO packet used. ACL Connections, on the other hand, provide a packet-oriented service and span over 1, 3 or 5 slots. The master of the piconet uses: a polling mechanism to divide the piconet bandwldth among the ACL links. Since SCO links require a periodic Pllwtion of a pair of slots, they leave very little of the piconet bandwidth available to ACL links. Moreover, the controlled access of Bluetooth ensum that no ACL link gets starved. Under such an aeegs mechanism, ACL links may be s a c i e n t to carry high-quality voice and SCO links may not he n e e d d Our simulation and hardware experiments show that though the voice quality is affected slightly by using ACL instead of SCO links for voice, TCP connections perform much better if SCO links are not used. This paper. thus, makes a case for using ACL in place of SCO links for carrying voice. This renders SCO links redundant.

No abstract

Abstract-In wireless ad-hoc networks, unidirectional links occur for several reasons: non uniform transmit power, non uniform background noise, and external interference. Several researchers have addressed unidirectional links and the associated unidirectional routing problem. The main focus has been so far on "unicast" routing; the consensus is that unidirectional links should be detected and avoided. In this paper, we consider the multicast case and derive a different conclusion: namely, it pays to exploit unidirectional links rather then avoid them. To prove the point, we select a popular ad hoc multicast protocol, On-Demand Multicast Routing Protocol (ODMRP) and introduce a slightly modified version, ODMRP-ASYM, that can handle unidirectional links. Specifically, ODMRP-ASYM reroutes the Join Reply packet when a unidirectional link is detected on the Join Query path. The option is invoked only when a unidirectional link is detected. The main advantages are: control overhead comparable with ODMRP even in highly asymmetric topologies; virtually no performance degradation in presence of unidirectional links (while ODMRP typically suffers up to 15% drop in delivery performance), and; 2-connectivity maintenance even if no bidirectional path exists between sender and receiver (in this case, unidirectional link avoidance strategies fail). Extensive simulation experiments demonstrate ODMRP-ASYM robustness to unidirectional links and superiority over conventional ODMRP.

Network scalability is one of the critical challenges and requirements in routing protocols for ad hoc networks. This paper presents a novel scalable routing protocol called Geo‐LANMAR. The proposed protocol inherits the group motion support of landmark routing (LANMAR) and applies the geo‐routing concept to deliver packets efficiently. In this framework, the integration between geo‐coordinates and table‐driven IP addressing is introduced. There is also an integration of group management with geo‐forwarding and IP group management. Geo‐LANMAR uses link‐state propagation over a virtual topology built on landmarks, and a fisheye like scheme makes this propagation very efficient. The virtual topology helps recover from voids. For extra efficiency, a novel metric called effective traveled distance (ETD) allows us to predict voids or obstacles. With respect to LANMAR, Geo‐LANMAR reduces advertisement update overhead (O/H) and features robust forwarding. Consequently, Geo‐LANMAR is more scalable to large ad hoc networks with group motion. The performance evaluation of Geo‐LANMAR shows that Geo‐LANMAR gives high scalability for large networks in terms of control O/H, end‐to‐end delay, and packet delivery ratio as compared with other routing protocols such as AODV, LANMAR, and GPSR. Copyright © 2006 John Wiley & Sons, Ltd.

No abstract