This repository contains compact MATLAB simulations for the NSDI 2021 paper Verification and Redesign of OFDM Backscatter. The code is organized to make the TScatter signal model easy to inspect first, and then to show the same ideas inside an 802.11n HT SISO packet-level simulation.
Paper: USENIX NSDI 2021 paper page
| Folder | Purpose | Main scripts |
|---|---|---|
Proof-of-Concept_Simulation |
Mathematics-only proof-of-concept simulations. No 802.11n protocol stack. | Full_TScatter_PoC.m, Lite_TScatter_PoC.m |
802.11n_HT_SISO |
Packet-level 802.11n HT 20 MHz SISO simulations for both Full and Lite TScatter. | Full_TScatter_80211n_SISO.m, Lite_TScatter_80211n_SISO.m |
The math PoC scripts expose the core equations directly:
y = exp(j beta) H_b W D(v) W^{-1} H_f x
z = (H_f H_b)^{-1} y
z = exp(j beta) A v
The Full PoC uses 64 useful time samples, 48 unknown sample-level tag phases, and 16 known/predefined phases. The Lite PoC uses one tag phase per OFDM block.
The packet-level scripts in 802.11n_HT_SISO use MATLAB WLAN Toolbox
components in the style of the MathWorks 802.11n TGn packet-error-rate
example:
wlanWaveformGenerator
Tx -> tag TGn channel
TScatter modulation on HT-Data
tag -> Rx TGn channel
receiver-side CFO injection
wlanPacketDetect
wlanCoarseCFOEstimate / frequencyOffset
wlanSymbolTimingEstimate
wlanFineCFOEstimate / frequencyOffset
wlanHTLTFDemodulate
wlanHTLTFChannelEstimate
wlanHTDataRecover
Reference example: 802.11n Packet Error Rate Simulation for 2x2 TGn Channel.
The packet-level tag decoders use same-realization calibration packets to
estimate frequency-selective H_f and/or H_f H_b compensation terms. This
keeps the simulation close to the paper-level channel model while still using
MATLAB's realistic 802.11n receiver pipeline.
- MATLAB
- WLAN Toolbox
- Communications Toolbox, for functions such as
awgnandfrequencyOffset
The current scripts were smoke-tested with MATLAB R2024b.
From MATLAB, run:
cd Proof-of-Concept_Simulation
Full_TScatter_PoC
Lite_TScatter_PoC
cd ../802.11n_HT_SISO
Full_TScatter_80211n_SISO
Lite_TScatter_80211n_SISOExpected high-SNR smoke-test behavior:
Full_TScatter_PoC -> 0/48 tag errors
Lite_TScatter_PoC -> 0/8 tag errors
Full_TScatter_80211n_SISO -> 0/48 tag errors
Lite_TScatter_80211n_SISO -> 0/8 tag errors
The 802.11n scripts also print ordinary PSDU bit errors after tag modulation. Those errors are not the TScatter tag-decoding metric; they show what a standard WiFi receiver sees before any TScatter-aware payload repair.
If you use this code or build on TScatter, please cite:
@inproceedings {tscatter,
author = {Xin Liu and Zicheng Chi and Wei Wang and Yao Yao and Pei Hao and Ting Zhu},
title = {Verification and Redesign of {OFDM} Backscatter},
booktitle = {18th USENIX Symposium on Networked Systems Design and Implementation (NSDI 21)},
year = {2021},
isbn = {978-1-939133-21-2},
pages = {939--953},
url = {https://www.usenix.org/conference/nsdi21/presentation/liu-xin},
publisher = {USENIX Association},
month = apr
}This repository also includes CITATION.cff so GitHub can show a
machine-readable "Cite this repository" entry.
This repository is released under the MIT License. See LICENSE.
这个仓库包含 NSDI 2021 论文 Verification and Redesign of OFDM Backscatter 的精简 MATLAB 仿真代码。仓库的目标是先用最小数学脚本把 TScatter 的信号模型讲清楚， 再把同样的机制放进 802.11n HT SISO 的 packet-level 仿真链路里验证。
论文入口：USENIX NSDI 2021 paper page
| 文件夹 | 作用 | 主脚本 |
|---|---|---|
Proof-of-Concept_Simulation |
纯数学 proof-of-concept 仿真，不使用 802.11n 协议栈。 | Full_TScatter_PoC.m, Lite_TScatter_PoC.m |
802.11n_HT_SISO |
Full 和 Lite TScatter 在 802.11n HT 20 MHz SISO 上的 packet-level 仿真。 | Full_TScatter_80211n_SISO.m, Lite_TScatter_80211n_SISO.m |
数学 PoC 直接展示核心矩阵关系：
y = exp(j beta) H_b W D(v) W^{-1} H_f x
z = (H_f H_b)^{-1} y
z = exp(j beta) A v
Full PoC 使用 64 个 useful time samples，其中 48 个 sample-level tag phases 是未知量，16 个 phase 是已知/预定义量。Lite PoC 则是每个 OFDM block 一个 tag phase。
802.11n_HT_SISO 文件夹里的脚本使用 MATLAB WLAN Toolbox 的真实接收流程，
结构参考 MathWorks 的 802.11n TGn packet-error-rate 示例：
wlanWaveformGenerator
Tx -> tag TGn channel
HT-Data 上插入 TScatter modulation
tag -> Rx TGn channel
接收端 CFO 注入
wlanPacketDetect
wlanCoarseCFOEstimate / frequencyOffset
wlanSymbolTimingEstimate
wlanFineCFOEstimate / frequencyOffset
wlanHTLTFDemodulate
wlanHTLTFChannelEstimate
wlanHTDataRecover
参考示例： 802.11n Packet Error Rate Simulation for 2x2 TGn Channel。
packet-level 的 tag decoder 使用 same-realization calibration packet 来估计
频率选择性的 H_f 和/或 H_f H_b 补偿项。这样既保留论文中的信道补偿模型，
又使用了 MATLAB 较真实的 802.11n 接收链路。
- MATLAB
- WLAN Toolbox
- Communications Toolbox，例如
awgn和frequencyOffset
当前脚本已经在 MATLAB R2024b 下做过 smoke test。
在 MATLAB 中运行：
cd Proof-of-Concept_Simulation
Full_TScatter_PoC
Lite_TScatter_PoC
cd ../802.11n_HT_SISO
Full_TScatter_80211n_SISO
Lite_TScatter_80211n_SISO高 SNR 默认设置下，预期 smoke-test 结果是：
Full_TScatter_PoC -> 0/48 tag errors
Lite_TScatter_PoC -> 0/8 tag errors
Full_TScatter_80211n_SISO -> 0/48 tag errors
Lite_TScatter_80211n_SISO -> 0/8 tag errors
802.11n 脚本还会打印 tag modulation 后普通 PSDU 的 bit errors。这个不是 TScatter tag decoding 的指标；它只是说明标准 WiFi receiver 在不知道 tag phase 时会看到 payload 被扰动。真正应该看的指标是最后的 tag error count。
如果你使用这个代码或者基于 TScatter 做后续研究，请引用：
@inproceedings {tscatter,
author = {Xin Liu and Zicheng Chi and Wei Wang and Yao Yao and Pei Hao and Ting Zhu},
title = {Verification and Redesign of {OFDM} Backscatter},
booktitle = {18th USENIX Symposium on Networked Systems Design and Implementation (NSDI 21)},
year = {2021},
isbn = {978-1-939133-21-2},
pages = {939--953},
url = {https://www.usenix.org/conference/nsdi21/presentation/liu-xin},
publisher = {USENIX Association},
month = apr
}这个仓库也包含 CITATION.cff，这样 GitHub 可以显示机器可读的
“Cite this repository” 信息。
本仓库使用 MIT License 发布。详见 LICENSE。