802.11n与ZigBee共存:子载波置零多输入多输出物理层模型

Physical layer model for 802. 11n-Zig Bee coexistence:subcarrier-nulling multi-input multi-output

针对802.11n与Zig Bee共享ISM频段造成的Wi Fi与Zig Bee信道重叠,进而导致网络间相互干扰使得网络性能下降,以及当前载波侦听多路访问/冲突避免（CSMA/CA）可能导致的频谱资源利用率较低的问题,提出一个采用子载波置零技术的2×2非相干多输入多输出（MIMO）物理层模型。该模型中,为了避免共信道干扰,Wi Fi发送端在发送数据前首先对其当前使用的信道中可能存在的Zig Bee信号进行检测,若检测到Zig Bee信号则对已被占用的频谱对应的子载波置零,使用余下频谱不重叠子载波进行通信。接收端对发送端使用的子载波进行识别,并完成后续工作。通过使Wi Fi与Zig Bee信号频谱分离来消除信号间干扰,解决两者共存问题,实现Wi Fi与Zig Bee数据并行传输。在由GNURadio/USRP软件无线电设备和Zig Bee节点搭建的实验床上进行的实验结果表明,采用子载波置零技术的2×2非相干MIMO可以获得全带宽发送状态下50%~70%的吞吐量,同时在数据并行传输过程中Zig Bee的正确收包百分比达到90%以上。

In view of the problem of a sharp fall on network performance due to network interference caused by channel overlapping aroused by ISM （ Industrial Scientific Medical） band shared between WiFi and ZigBee, and severe spectrum underutilization induced by the current CSMA,/CA （ Carrier Sense Multiple Access with Collision Avoidance） mechanism, a subcarrier-nulling 2 × 2 noncoherent antenna MIMO （ Multi-Input Multi-Output） PHY （ Physical Layer） model was proposed in this paper. In this model, to avoid co-channel interference, a WiFi transmitter needs to detect ZigBee signals appearing in its adopted channel before data transmission, and if any, this transmitter will null the subcarriers within the spectrum occupied by ZigBees, and take advantage of the rest subcarriers to transmit its packets. The receiver needs to identify the subcarriers used by the transmitter, and finish the follow-up work. By this means, interference will he eliminated by signal spectrum separation, thus achieving the goal of heterogeneous network coexistence and making parallel data transmission available. The experiments were run on the test bed composed of GNURadio/USRP platform and ZigBee nodes, and the experiment results show that subcarrier-nulling enabled 2 × 2 noncoherent antenna MIMO to gain 50% - 70% throughput of that in the full bandwidth scenario, and during parallel data transmission ZigBee＇ s valid received packets ratio is at least 90%.