Link layer

About: Link layer is a research topic. Over the lifetime, 3548 publications have been published within this topic receiving 55750 citations.

Protocols and Architectures for Wireless Sensor Networks

Abstract: Preface. List of Abbreviations. A guide to the book. 1. Introduction. 1.1 The vision of Ambient Intelligence. 1.2 Application examples. 1.3 Types of applications. 1.4 Challenges for WSNs. 1.5 Why are sensor networks different? 1.6 Enabling technologies. PART I: ARCHITECTURES. 2. Single node architecture. 2.1 Hardware components. 2.2 Energy consumption of sensor nodes. 2.3 Operating systems and execution environments. 2.4 Some examples of sensor nodes. 2.5 Conclusion. 3. Network architecture. 3.1 Sensor network scenarios. 3.2 Optimization goals & figures of merit. 3.3 Design principles for WSNs. 3.4 Service interfaces of WSNs. 3.5 Gateway concepts. 3.6 Conclusion. PART II: COMMUNICATION PROTOCOLS. 4. Physical Layer. 4.1 Introduction. 4.2 Wireless channel and communication fundamentals. 4.3 Physical layer & transceiver design considerations in WSNs. 4.4 Further reading. 5. MAC Protocols 133 5.1 Fundamentals of (wireless) MAC protocols. 5.2 Low duty cycle protocols and wakeup concepts. 5.3 Contention-based protocols. 5.4 Schedule-based protocols. 5.5 The IEEE 802.15.4 MAC protocol. 5.6 How about IEEE 802.11 and Bluetooth? 5.7 Further reading. 5.8 Conclusion. 6. Link Layer Protocols. 6.1 Fundamentals: Tasks and requirements. 6.2 Error control. 6.3 Framing. 6.4 Link management. 6.5 Summary. 7. Naming and Addressing. 7.1 Fundamentals. 7.2 Address and name management in wireless sensor networks. 7.3 Assignment of MAC addresses. 7.4 Distributed assignment of locally unique addresses. 7.5 Content-based and geographic addressing. 7.6 Summary. 8. Time Synchronization. 8.1 Introduction to the time synchronization problem. 8.2 Protocols based on sender/receiver synchronization. 8.3 Protocols based on receiver/receiver synchronization. 8.4 Further reading. 9. Localization and Positioning. 9.1 Properties of positioning. 9.2 Possible approaches. 9.3 Mathematical basics for the lateration problem. 9.4 Single-hop localization. 9.5 Positioning in multi-hop environments. 9.6 Impact of anchor placement. 9.7 Further reading. 9.8 Conclusion. 10. Topology control 295 10.1 Motivation and basic ideas. 10.2 Flat network topologies. 10.3 Hierarchical networks by dominating sets. 10.4 Hierarchical networks by clustering. 10.5 Combining hierarchical topologies and power control. 10.6 Adaptive node activity. 10.7 Conclusions. 11. Routing protocols. 11.1 The many faces of forwarding and routing. 11.2 Gossiping and agent-based unicast forwarding. 11.3 Energy-efficient unicast. 11.4 Broadcast and multicast. 11.5 Geographic routing. 11.6 Mobile nodes. 11.7 Conclusions. 12. Data-centric and content-based networking 395. 12.1 Introduction. 12.2 Data-centric routing. 12.3 Data aggregation. 12.4 Data-centric storage. 12.5 Conclusions. 13. Transport Layer and Quality of Service. 13.1 The transport layer and QoS in wireless sensor networks. 13.2 Coverage and deployment. 13.3 Reliable data transport. 13.5 Block delivery. 13.6 Congestion control and rate control. 14. Advanced application support. 14.1 Advanced in-network processing. 14.2 Security. 14.3 Application-specific support. Bibliography. Index.

TinySec: a link layer security architecture for wireless sensor networks

Abstract: We introduce TinySec, the first fully-implemented link layer security architecture for wireless sensor networks. In our design, we leverage recent lessons learned from design vulnerabilities in security protocols for other wireless networks such as 802.11b and GSM. Conventional security protocols tend to be conservative in their security guarantees, typically adding 16--32 bytes of overhead. With small memories, weak processors, limited energy, and 30 byte packets, sensor networks cannot afford this luxury. TinySec addresses these extreme resource constraints with careful design; we explore the tradeoffs among different cryptographic primitives and use the inherent sensor network limitations to our advantage when choosing parameters to find a sweet spot for security, packet overhead, and resource requirements. TinySec is portable to a variety of hardware and radio platforms. Our experimental results on a 36 node distributed sensor network application clearly demonstrate that software based link layer protocols are feasible and efficient, adding less than 10% energy, latency, and bandwidth overhead.

An empirical analysis of the IEEE 802.11 MAC layer handoff process

Abstract: IEEE 802.11 based wireless networks have seen rapid growth and deployment in the recent years. Critical to the 802.11 MAC operation, is the handoff function which occurs when a mobile node moves its association from one access point to another. In this paper, we present an empirical study of this handoff process at the link layer, with a detailed breakup of the latency into various components. In particular, we show that a MAC layer function - probe is the primary contributor to the overall handoff latency. In our study, we observe that the latency is significant enough to affect the quality of service for many applications (or network connections). Further we find variations in the latency from one hand-off to another as well as with APs and STAs used from different vendors. Finally, we discuss optimizations on the probe phase which can potentially reduce the probe latency by as much as 98% (and a minimum of 12% in our experiments). Based on the study, we draw some guidelines for future handoff schemes.

Broadcast storm mitigation techniques in vehicular ad hoc networks

Abstract: Several multihop applications developed for vehicular ad hoc networks use broadcast as a means to either discover nearby neighbors or propagate useful traffic information to other vehicles located within a certain geographical area. However, the conventional broadcast mechanism may lead to the so-called broadcast storm problem, a scenario in which there is a high level of contention and collisions at the link layer due to an excessive number of broadcast packets. While this is a well-known problem in mobile ad hoc wireless networks, only a few studies have addressed this issue in the VANET context, where mobile hosts move along the roads in a certain limited set of directions as opposed to randomly moving in arbitrary directions within a bounded area. Unlike other existing works, we quantify the impact of broadcast storms in VANETs in terms of message delay and packet loss rate in addition to conventional metrics such as message reachability and overhead. Given that VANET applications are currently confined to using the DSRC protocol at the data link layer, we propose three probabilistic and timer-based broadcast suppression techniques: weighted p-persistence, slotted 1-persistence, and slotted p-persistence schemes, to be used at the network layer. Our simulation results show that the proposed schemes can significantly reduce contention at the MAC layer by achieving up to 70 percent reduction in packet loss rate while keeping end-to-end delay at acceptable levels for most VANET applications.

Extending Networking into the Virtualization Layer.

Abstract: The move to virtualization has created a new network access layer residing on hosts that connects the various VMs. Virtualized deployment environments impose requirements on networking for which traditional models are not well suited. They also provide advantages to the networking layer (such as software flexibility and welldefined end host events) that are not present in physical networks. To date, this new virtualization network layer has been largely built around standard Ethernet switching, but this technology neither satisfies these new requirements nor leverages the available advantages. We present Open vSwitch, a network switch specifically built for virtual environments. Open vSwitch differs from traditional approaches in that it exports an external interface for fine-grained control of configuration state and forwarding behavior. We describe how Open vSwitch can be used to tackle problems such as isolation in joint-tenant environments, mobility across subnets, and distributing configuration and visibility across hosts.