物联网环境下多子载波频域竞争技术研究

In IoT, many communication protocols (such as WiFi and Zigbee) dictate that a node should first perform a time-domain channel contention process and then a data transmission process. As the physical-layer date rate increases rapidly, the contention time overhead may be up to 46.5% of the total transmission time. The recent frequency-domain contention (FDC) mechanism can significantly reduce the time overhead of conventional time-domain contention mechanisms and hence is a hot technology of improving throughput efficiency. Although promising, FDC introduces many new problems (e.g., synchronization difficulty due to the inherent multiple-transmission-multiple-reception characteristic, tradeoff between the winner’s arbitration time and the collision probability in contention, and the fast solution of hidden/exposed terminal problems matching with the scale of FDC’s contention time). These problems become more serious in multi-subcarrier contention or high-density networks. In this project, we plan to conduct the following research: (1) analyze the selection and detection schemes of contention subcarriers so as to lower the adverse impact of the synchronization error in multiple-transmission-multiple-reception environments, (2) design a multi-subcarrier contention mechanism with time/frequency-interleaving decision, so as to support large user populations, reduce the winner’s arbitration time and minimize the collision probability, and (3) design effective centralized and distributed schemes, so as to solve frequency-domain hidden/exposed terminal problems timely and effectively. This project will promote the practicality of FDC greatly.

在物联网中，许多通信协议（如WiFi和Zigbee）规定节点首先应执行时域信道竞争，然后再进行数据传输。随着物理层传输速率的快速增长，信道竞争时间开销占总传输时间可高达46.5％。频域竞争机制可以显著地减少时域竞争的时间开销，因此是提高吞吐效率的热门技术。虽然优点显著，但它也引入了新的问题，比如：同时多发多收的环境使得同步困难；仲裁时间与竞争冲突概率之间的折中；隐藏/暴露终端问题的方案须适应频域竞争时间的尺度。这些问题在多子载波竞争或密集网络中越发严重。在本项目中，我们计划进行以下研究：（1）多发多收环境下分析竞争子载波选取策略与检测技术，以降低同步误差的影响;（2）设计一个具有时频域交错决策的多子载波竞争机制，支持密集用户访问，在减少仲裁时间的同时最小化冲突概率;（3）设计集中式和分布式方案，及时有效地解决频域隐藏/暴露终端问题。该项目将大大提高频域竞争机制的实用性。

在物联网中，广泛使用的无线网络协议如WiFi和Zigbee常常采用传统的低效的时域竞争技术。频域竞争机制可以显著地减少时域竞争的时间开销，因此是提高吞吐效率的重要技术。本项目聚焦多子载波频域竞争技术。主要的研究任务：分析多发多收环境下竞争子载波选取与检测技术；设计支持密集用户访问的多子载波竞争协议；设计多子载波竞争仲裁方案，以有效地解决其特有的子集包含问题、冲突问题等；对多子载波竞争机制的性能如冲突概率、吞吐量、延时等进行建模。本项目按计划执行，实现了在论文、专利、学生培养等预期目标。本研究将为设计实用的多子载波竞争协议打下了坚实的基础。