Many sensor network application scenarios include mobile nodes, such as a moving sink. Evaluation of such applications in a testbed is challenging as the testbed has to support mobile nodes. Here, we present Sensei-UU, a sensor network testbed that supports mobile sensor nodes. The testbed is inexpensive, relocatable and possible to reproduce by other researchers. Its primary design objectives are to support experiments with repeatable mobility and relocating the testbed deployment to different locations. Mobile sensor nodes are carried by robots that use floor markings for navigation and localization. The testbed can be used to evaluate applications in which sensor nodes move in the order of meters rather than millimeters, e.g. when a human carries a mobile phone that collects data while passing stationary sensor nodes. To investigate the repeatability of robot movements, we measure the achieved precision and the timing of the robots, and find that our robot localization is accurate to ±1 cm. Furthermore, we investigate variations in radio signal strengths between mobile and stationary nodes. We study the impact of imprecise movements, external sources of interference and environmental influences. We conclude that Sensei-UU supports experiments in which these variations are acceptably low to capture small-scale fading phenomena in IEEE 802.15.4.

Longest prefix matching is frequently used for IP forwarding in the Internet. Data structures used must be not only efficient, hut also robust against pathological entries caused by an adversary or misconfiguration. In this paper, we attack the longest prefix matching problem by presenting a new algorithm supporting high lookup performance, fast incremental updates and guaranteed compression ratio. High lookup performance is achieved by using only four memory accesses. Guaranteed compression ratio is achieved by combining direct indexing with an implicit tree structure and carefully choosing which construct to use when updating the forwarding table. Fast incremental updates are achieved by a new memory management technique featuring fast variable size allocation and deallocation while maintaining zero fragmentation. An IPv4 forwarding table data structure can be implemented in software or hardware within 2.7 Mb of memory to represent 2/sup 18/ routing entries. Incremental updates require only 752 memory accesses in worst case for the current guaranteed compression ratio. For a hardware implementation, we can use 300 MHz SRAM organized in four memory banks and four pipeline stages to achieve a guaranteed performance of 300 million lookups per second, corresponding to /spl sim/ 100 Gbit/s wire speed forwarding, and 400,000 incremental updates per second. In measurements performed on a 3.0 GHz Pentium 4 machine using a routing table with more than 2/sup 17/ entries, we can forward over 27 million IPv4 packets per second, which is equivalent to wire speeds exceeding 10 Gbit/s. On the same machine and with the same routing table, we can perform over 230,000 incremental updates/second.

We study how Pastry performs in a heterogeneous network environment of varying size. The large traffic overhead for management traffic makes the overlay nonfunctional if it grows too large. This can be circumvented by partitioning the routing tables at the cost of increased path lengths and response times.

With current Internet protocols, users may experience low and unpredictable forwarding quality at wireless links. This is due to varying link properties caused by changing radio conditions. Decreased forwarding quality can cause severe degradation in utilization. This is undesirable since forwarding capacity often is expensive at wireless links because of the limited radio spectrum. Allowing the application and transport layers to communicate with wireless link layers can improve the forwarding quality and utilization. We propose to enable inter-layer communication by adding hints and notifications (HAN) to the Internet architecture. Hints can be introduced and used without notifications, while notifications need hints or a similar mechanism to operate. By using IP options and ICMP messages to implement HAN, a backward-compatible partial deployment is possible. With HAN, the network layer becomes truly wireless friendly and the radio spectrum can be used efficiently while supporting both real-time and traditional data applications.

Internet and cellular technologies are merging to decrease transport costs and enable IP-based applications to hundreds of millions of cellular users. Real time voice services will continue to be dominant in future cellular systems and to reduce system costs it is desirable to base all services, including voice, on IP. However, the radio spectrum must be efficiently used to provide mass-market services at reasonable prices, but Internet protocol headers are large in size. Moreover, data discarding policies are poorly suited to the error-proneness of cellular links. Protocol overhead for IP-based voice services can be reduced by compressing headers, e.g. with the compressed real time protocol (CRTP). CRTP, however, does not perform well over cellular links since it is not robust in the face of errors. ROCCO, a header compression scheme suitable for cellular systems, delivers more packets to the user than CRTP at realistic error rates with a better average compression ratio. Voice services in cellular systems should also be able to use damaged speech data. This can be done using the UDP Lite protocol which provides a more flexible checksumming policy that enables delivery of data possibly usable to the application. This paper shows that CRTP/UDP fails to deliver sufficient service quality at the error rates of a cost-efficient cellular system and that ROCCO combined with UDP Lite can provide an IP-based voice service over such cellular systems.