Pérez-Solano Juan J, Claver Jose M, Ezpeleta Santiago
Departament d'Informàtica, Universitat de València, Avd. de la Universitat, 46100 Burjassot, Spain.
Sensors (Basel). 2017 Jul 6;17(7):1582. doi: 10.3390/s17071582.
Radio frequency signals are commonly used in the development of indoor localization systems. The infrastructure of these systems includes some beacons placed at known positions that exchange radio packets with users to be located. When the system is implemented using wireless sensor networks, the wireless transceivers integrated in the network motes are usually based on the IEEE 802.15.4 standard. But, the CSMA-CA, which is the basis for the medium access protocols in this category of communication systems, is not suitable when several users want to exchange bursts of radio packets with the same beacon to acquire the radio signal strength indicator (RSSI) values needed in the location process. Therefore, new protocols are necessary to avoid the packet collisions that appear when multiple users try to communicate with the same beacons. On the other hand, the RSSI sampling process should be carried out very quickly because some systems cannot tolerate a large delay in the location process. This is even more important when the RSSI sampling process includes measures with different signal power levels or frequency channels. The principal objective of this work is to speed up the RSSI sampling process in indoor localization systems. To achieve this objective, the main contribution is the proposal of a new MAC protocol that eliminates the medium access contention periods and decreases the number of packet collisions to accelerate the RSSI collection process. Moreover, the protocol increases the overall network throughput taking advantage of the frequency channel diversity. The presented results show the suitability of this protocol for reducing the RSSI gathering delay and increasing the network throughput in simulated and real environments.
射频信号常用于室内定位系统的开发。这些系统的基础设施包括一些放置在已知位置的信标，它们与要定位的用户交换无线电数据包。当使用无线传感器网络实现该系统时，集成在网络节点中的无线收发器通常基于IEEE 802.15.4标准。但是，作为此类通信系统中媒体访问协议基础的CSMA-CA，在多个用户想要与同一个信标交换无线电数据包突发以获取定位过程中所需的无线电信号强度指示（RSSI）值时并不适用。因此，需要新的协议来避免多个用户尝试与同一个信标通信时出现的数据包冲突。另一方面，RSSI采样过程应该非常快速地进行，因为一些系统无法容忍定位过程中的较大延迟。当RSSI采样过程包括不同信号功率电平或频道的测量时，这一点更为重要。这项工作的主要目标是加快室内定位系统中的RSSI采样过程。为实现这一目标，主要贡献是提出了一种新的MAC协议，该协议消除了媒体访问争用期并减少了数据包冲突的数量，以加速RSSI收集过程。此外，该协议利用频道分集提高了整体网络吞吐量。给出的结果表明该协议适用于在模拟和实际环境中减少RSSI收集延迟并提高网络吞吐量。
