The English version this article is after the Chinese.
PicoScenes研发团队荣幸地宣布，PicoScenes现在正式支持HackRF One——最具性价比的支持Wi-Fi感知研究的软件定义无线电（SDR）设备！
这个手掌大小的SDR设备具有20 MHz 8-bit ADC/DAC采样以及10 MHz—7.25GHz射频范围，完整覆盖Wi-Fi 6E 2.4/5/6GHz频段！最让人意外的是它的价格！它仅仅200美元的价格（甚至接近100美元，如果在淘宝购买）相比NI USRP系列SDR设备（2000～20000美元）大幅降低了SDR设备在Wi-Fi感知研究与应用中的门槛。
通过对USRP系列SDR以及HackRF One的先后支持，PicoScenes平台达成了一个里程碑：实质性地扫除了将SDR应用于Wi-Fi感知研究与应用的两个根本障碍：缺乏Wi-Fi基带实现与昂贵的研究成本。
为什么要在Wi-Fi感知研究中使用SDR（或Wi-Fi网卡有什么问题）？
Wi-Fi网卡（NIC）的commercial off-the-shelf (COTS)特性是Wi-Fi感知研究与应用得到广泛关注的重要宣传口号。研究者通过低成本的COTS Wi-Fi网卡获取信道状态信息（CSI）并通过CSI对环境或设备进行感应与定位。 然而，对于研究者来说，COTS Wi-Fi NIC绝大部分时候就是一个不可控的、信息吝啬的黑盒。
- 不可控性反映在，研究者无法调节众多极具研究价值的底层参数，例如前端硬件的参数（频率控制，增益控制，I/Q等），基带的参数（信号灵敏度、AGC以及OFDM基带编解码器等）以及MAC层的参数（ACK、延时、协议控制等）等。
- 信息吝啬反映在，除了CSI大量PHY层的信息都无法获取，例如基带时钟、AGC参数、帧定位参数，载波或采样/频偏Legacy段（L-LTF）的CSI估计、数据段的Pilot子载波等。
- 黑盒特性则反映在，软硬件底层实现细节未知，例如未知的前端构架、未知的硬件对CSI的影响，未知的基带实现，未知的参数，未知的DSP流程，未知的特殊设计，甚至还包括未知的bugs。
以上三方面问题随着Wi-Fi感知研究的深入逐渐放大，现已明显成为阻碍Wi-Fi感知研究进一步突破的瓶颈！
使用PicoScenes驱动SDR的好处
PiocScenes自带的高性能Wi-Fi基带软件实现覆盖主流Wi-Fi协议的所有特性，并且用户可以控制丰富的收发参数，包括802.11a/g/n/ac/ax协议编解码器、最大160MHz带宽、LDPC及BCC编解码器、0至11MCS设置、最大4×4 MIMO、Beamforming甚至相控阵。
除了丰富的可控性，PicoScenes基带实现的Rx路径还返回大量底层信息，如L-LTF段的CSI估计、CFO估计、Pilot子载波的CSI估计、HT/VHT/HE-LTF段的CSI估计、交织器种子、完整的基带信号等。
除了技术特性，PicoScenes还具有极为用户友好并且统一的控制界面。例如，驱动一台IP地址为192.168.10.2的USRP去监听2412MHz（Wi-Fi信道1）的所有Wi-Fi流量，记录并实时显示其CSI，可以用非常短的PicoScenes控制命令表达：“-i usrp192.168.10.2 —freq 2412e6 —mode logger —plot”。 您可以替换以上命令的“ usrp192.168.10.2”为“hackrf0”，就可以切换至使用HackRF One设备。
具体如何使用PicoScenes驱动USRP或HackRF One？
PicoScenes平台的文档网站(https://ps.zpj.io)已经更新了对HackRF One的支持。
我们录制了一个视频demo，已经放在B站
https://www.bilibili.com/video/BV17Z4y127Jx?share_source=copy_web
那么，为什么以前少有Wi-Fi感知研究使用SDR？
如前所述，缺乏Wi-Fi基带实现与昂贵的研究成本是阻碍SDR应用的两个最主要原因。
没有易用的基带实现是致命的问题。更像是一对麦克风和扬声器但在电磁波上运行，SDR并不集成特定无线协议的编解码器电路（俗称基带芯片）；因此，上位机需要运行特定协议的编解码器的软件实现才能充分发挥SDR的灵活性。不幸的是，Wi-Fi协议很复杂，直到现在，并没有除了PicoScenes平台的免费可用的支持全部Wi-Fi协议、全部带宽并支持MIMO的Wi-Fi基带软件实现。显然，没有基带实现，SDR只是一对没有脑子的麦克风和扬声器。
研究领域最广泛使用的NI USRP系列SDR过于昂贵，入门级B210需要2000美元左右，而高端X410则需要20000美元。过分高的设备成本、高应用门槛以及可能的研究风险进一步阻碍了USRP在Wi-Fi sensing研究与应用中的使用。
结论
PicoScenes平台继支持USRP系列SDR之后，现在加入了对HackRF One的支持，极大地降低了（接近10-20倍）SDR设备在Wi-Fi感知研究中应用的价格门槛，实质性地扫清了将SDR应用于Wi-Fi感知研究与应用的两个根本障碍。
We PicoScenes R&D team is proud to announce that PicoScenes now officially supports the HackRF One, the most cost effective Software Defined Radio (SDR) device to support Wi-Fi sensing research!
This palm-sized SDR device features 20 MHz 8-bit ADC/DAC sampling and a 10 MHz – maximum 7.25 GHz RF range, covering the entire Wi-Fi 6E 2.4/5/6 GHz bands! The most surprising thing is its price! Its price of just $200 (or even close to $100 if purchased on Taobao) dramatically lowers the threshold for SDR devices in Wi-Fi sensing research and applications compared to the NI USRP series SDR devices ($2000 to $20000).
By successively supporting the USRP series SDR as well as HackRF One, the PicoScenes platform has reached a milestone: substantially eliminating two fundamental barriers to applying SDR to Wi-Fi sensing research and applications: lack of Wi-Fi baseband implementation and expensive research costs.
Why use SDR in Wi-Fi sensing (or what’s wrong with Wi-Fi NICs)?
The commercial off-the-shelf (COTS) feature of Wi-Fi network cards (NICs) is an important tagline for Wi-Fi sensing research. Researchers obtain channel state information (CSI) through low-cost COTS Wi-Fi NICs and use CSI to sense and locate the environment or devices. However, COTS Wi-Fi NICs are actually an uncontrollable, information-stingy black box for researchers most of the time.
The uncontrollability is reflected in the fact that the researcher cannot adjust many valuable underlying parameters, such as front-end hardware parameters (frequency control, gain control, I/Q, etc.), baseband parameters (signal sensitivity, AGC and OFDM baseband codec, etc.), and MAC layer parameters (ACK, delay, protocol control, etc.), etc.
The information stinginess is reflected in the fact that, except for the CSI, a large amount of PHY layer information is not available, such as baseband clock, AGC parameters, frame positioning parameters, CSI estimation of carrier or sampling/frequency bias Legacy segment (L-LTF), pilot subcarrier of data segment, etc.
The black-box characteristics are reflected in that the underlying hardware and software implementation details are unknown, such as unknown front-end architecture, unknown hardware impact on CSI, unknown baseband implementation, unknown parameters, unknown DSP flow, unknown special design, and even unknown bugs.
These problems are amplified with the deepening of Wi-Fi sensing research, and have now clearly become the bottlenecks that hinder further breakthroughs in Wi-Fi sensing research!
The benefits of using PicoScenes to drive SDR
PiocScenes comes with high-performance Wi-Fi baseband software implementation covering all features of mainstream Wi-Fi protocols, and users can control rich transceiver parameters including 802.11a/g/n/ac/ax protocol codecs, maximum 160MHz bandwidth, LDPC and BCC codecs, 0 to 11 MCS settings, maximum 4×4 MIMO, Beamforming and even phased arrays.
In addition to the rich controllability, the Rx path of the PicoScenes baseband implementation returns a large amount of low-level information, such as CSI estimation for the L-LTF segment, CFO estimation, CSI estimation for the pilot subcarrier, CSI estimation for the HT/VHT/HE-LTF segment, scrambler seed, complete baseband signal, etc.
In addition to the technical features, PicoScenes has an extremely user-friendly and unified control interface. For example, driving a USRP with IP address 192.168.10.2 to listen to all Wi-Fi traffic on 2412 MHz (Wi-Fi channel 1), recording and displaying its CSI in real time, can be expressed in a very short PicoScenes control command: “-i usrp192.168.10.2 –freq 2412e6 –mode logger –plot”. You can replace “usrp192.168.10.2” with “hackrf0” in the above command to switch to using HackRF One devices.
How to use PicoScenes to drive USRP or HackRF One?
The documentation site for the PicoScenes platform (https://ps.zpj.io) has been updated with support for HackRF One.
We also record a short demo showing live CSI plot using HackRF One.
So, why have few Wi-Fi sensing research used SDR before?
As mentioned earlier, the lack of Wi-Fi baseband implementations and the cost of expensive research were the two most important reasons preventing SDR adoption.
The lack of an easy-to-use baseband implementation was the killer issue. More like a pair of microphones and speakers but running on electromagnetic field, SDR does not integrate a codec circuit for a specific wireless protocol (commonly known as a baseband chip); therefore, the host computer needs a software implementation running the protocol-specific codec to fully utilize the flexibility of SDRs. Unfortunately, Wi-Fi protocols are complex, and until now, there has been no freely available Wi-Fi baseband software implementation that supports all Wi-Fi protocols, all bandwidths, and supports MIMO, except for the PicoScenes platform. Clearly, without a baseband implementation, SDRs are just a pair of brainless microphones and speakers.
The most widely used NI USRP series SDRs in the research field are too expensive, with the entry-level B210 costing about $2,000 and the high-end X410 costing $20,000. The excessively high equipment cost, high application threshold, and possible research risks further hinder the use of USRPs in Wi-Fi sensing research and applications.
Conclusion
The PicoScenes platform, following support for the USRP family of SDRs, now includes support for HackRF One, significantly lowering (by a factor of nearly 10-20) the price threshold for the application of SDR devices in Wi-Fi sensing research, substantially eliminating two fundamental obstacles to the application of SDRs to Wi-Fi sensing research and applications.