ITR: MAC Protocols Specific for Sensor Networks (MACSS)

无线传感器网络是一项新兴的技术，具有广泛的潜在应用前景，包括环境监测、智能空间、医疗系统和机器人探测等。虽然这项技术非常有前途，但它在网络和系统设计方面提出了严峻的挑战。传感器网络在许多方面不同于传统的IP或语音网络，有其独特的特点和要求。虽然802.11和时分多址等媒体访问控制协议是无线IP或语音的理想选择，但目前还没有一种媒体访问控制协议能满足传感器网络的需求。具体地说，我们正在研究：适应性和能效：传感器网络MAC必须在多个维度上自适应，包括能耗、流量负载和部署密度。能量是电池供电的传感器节点的“关键限制”。研究人员正在研究并将提供节能方法的设计，这些方法修改节点的工作周期，以在考虑用户不同的应用流量需求的同时进行节能。一种节能的方法是使用寻呼信道触发主节点无线电，但这需要第二个无线电(具有相应的成本、空间和资金要求)。传感器节点已经必须全天候运行传感器，因此研究人员正在评估传感器的使用(声学、地震等)。作为物理传感器寻呼通道，MAC与物理层的交互：与低功耗、相对简单的无线电、传感器网络应用和MAC协议都非常接近物理层的无线电传播效果。当前传感器应用的一个严重问题是处理链路错误条件，例如分组丢失和不对称通信。节能的MAC层已经跟踪邻居，因此研究人员将提供黑名单服务，允许MAC识别和排除不可用的链路。研究人员还将研究和报告无线电功率控制和应用程序交互，以了解Mac如何控制邻居大小。传感器网络的UNIQUE应用需求：传感器网络在几个不同方面与互联网式对等节点网络有根本不同。第一个不同之处是，传感器网络主要是静止的，但当感知到一些东西时，它们偶尔会变得非常活跃。研究人员将开发一种具有多种模式的MAC协议，以使Mac能够适应这种“不是盛宴就是饥荒”的流量负载。此外，能量节约在节点通信中引入了“方向偏差”；休眠/唤醒计划可能会平等地增加所有方向的延迟，或者允许在一个方向上进行快速通信，而在另一个方向上进行较慢的通信。研究人员将评估可控的MAC级定向偏差如何与应用程序交互，并在可能的情况下利用它。最后，研究社区迫切需要一个公开可用的、可自由修改的传感器MAC协议来进行实验和模拟。对我们的想法的评估需要实施和发展MAC协议。我们将把这个实现提供给其他研究人员，用于现有的传感器网络无线电(在加州大学伯克利分校Mote硬件上的参考实现)和模拟(在ns-2模拟器中的参考实现)。因此，除了开辟传感器网络特定的MAC协议作为一个新的研究子领域之外，这项工作还将为迫切需要合适和可修改的MAC的更广泛的传感器网络研究提供催化剂。

Wireless sensor networking is an emerging technology that has a wide range of potential applications including environment monitoring, smart spaces, medical systems and robotic exploration. While the technology is very promising, it raises serious challenges in networkand system design. Sensor networks differ in many ways from than the traditional IP or voice networks, and have their unique features and requirements. Although MAC protocols such as 802.11 and TDMA are ideal for wireless IP or voice, no MAC protocol today meets the needsof sensor networks.This project will execute a systems-driven research program to address these problems through the development of sensor-network specific MAC protocols. Specifically, we are investigating:ADAPTIVITY AND ENERGY EFFICIENCY: Sensor network MACs must be adaptive in several dimensions, including energy consumption, traffic loads, and deployment density. Energy is *the key limitation* for battery-powered sensor nodes. The researchers are investigating and will provide designs for ENERGY CONSERVATION approaches that modify node duty cycleto conserve energy while considering user varying application traffic requirements. One approach to energy conservation is to trigger primary node radios with a paging channel, but this requires a second radio (with corresponding cost, space, and money requirements). Sensor nodes already must operate sensors full time, so the researchers are evaluating the use of sensors (acoustic, seismic, etc.) as a PHYSICAL SENSOR PAGING CHANNEL.MAC INTERACTION WITH THE PHYSICAL LAYER: With low-power, relatively unsophisticated radios, sensor networks applications and MAC protocols are very close to physical layer effects of radio propagation. A serious problem with current sensor applications is dealing with linkerror conditions such as packet loss and asymmetric communication. Energy-conserving MAC layers already keep track of neighbors, so the researchers will provide a BLACKLISTING SERVICE that allows the MAC to identify and exclude unusable links. The researchers also will study and report on radio POWER CONTROL AND APPLICATION INTERACTIONS to understand how MACs can control neighborhood size.UNIQUE APPLICATION NEEDS OF SENSOR NETWORKS: Sensor networks are fundamentally different from Internet-style networks of peer nodes in several different ways. A first differences is that sensor networks are primarily quiescent, but they occasionally become very active whensomething is sensed. The researchers will develop a MAC PROTOCOL WITH MULTIPLEOPERATING MODES to allow the MACs to adjust to this ``feast or famine'' traffic load. In addition, energy conservation introduces a *directional bias* in node communication; sleep/wake-up schedules can either add latency to all directions equally, or can allow rapid communication in one direction and slower communication in the other. The researchers will evaluate how controllable MAC-LEVEL DIRECTIONAL BIAS INTERACTS WITH APPLICATION, exploiting it where possible.Finally, the research community has a compelling need for a publicly available, freely modifiable Sensor-MAC protocol for experimentation and simulation. Evaluation of our ideas requires implementation and evolution of a MAC protocol. We will provide this implementation to other researchers for use over existing sensor network radios (with a reference implementation on the UC Berkeley Mote hardware) and in simulation (with a reference implementation in the ns-2 simulator).Thus, in addition to opening up sensor-network-specific MAC protocols as a new subfield of research, this work will serve as a catalyst for wider sensor network research that is sorely in need of an appropriate and modifiable MAC.