Greetings,

This project implements the complete IEEE802.11 protocol, including PHY, MAC, and rate adaptation approaches upon GNURadio/USRP software-defined radio platform. The project integrates the existing open-source projects (See literature [2,3]) and makes them a unity that works under the latest GNURadio platform. In addition, mainstream rate adaptation approaches Minstrel and Adaptive Auto Rate Fallback (AARF) are implemented. The rate adaptation module continuously collects the data transmission status, i.e, whether acknowledgement frames are received after data transmission, and decides the next data transmission rate to be used according to such statistics. The new data rate is then being transferred to the PHY module and applied in the subsequent frame encoding and modulation.

To use this project, please cite the following literatures:

[1] Implementation of rate adaptation approach and complete system integration

@inproceedings{lu2016scheduling, title={Scheduling Dynamic Wireless Networks with Limited Operations}, author={Haoyang Lu and Wei Gao}, booktitle={IEEE International Conference on Network Protocols}, year={2016}, organization={IEEE} }

[2] The PHY implementation is based on (https://github.com/bastibl/gr-ieee802-11/)

@inproceedings{bloessl2013ieee, title={An IEEE 802.11 a/g/p OFDM Receiver for GNU Radio}, author={Bloessl, Bastian and Segata, Michele and Sommer, Christoph and Dressler, Falko}, booktitle={Proceedings of the second workshop on Software radio implementation forum}, pages={9--16}, year={2013}, organization={ACM} }

[3] The MAC implementation is based on (http://www.uwicore.umh.es/mhop-software.html)

@inproceedings{gutierrez2010ieee, title={An IEEE 802.11 MAC Software Defined Radio implementation for experimental wireless communications and networking research}, author={Gutierrez-Agullo, Juan R and Coll-Perales, Baldomero and Gozalvez, Javier}, booktitle={Wireless Days (WD), 2010 IFIP}, pages={1--5}, year={2010}, organization={IEEE} }

Installation

Please go through [2] for installation and settings.

The software is tested on Ubuntu 16.04 and GNU Radio Companion 3.7.11.1. To check your GNURadio version, use

gnuradio-companion --version

Usage

Use one terminal and one command

Open a terminal and run

    ./wifi_exp.sh

You can configure the parameters in this shell script, which invokes four separate Python scripts. You can also run those four files one by one, as shown below.

Run python scripts individually

1. Open a terminal and run

    ./ul_buffer.py

This program stores the packets to be sent and those received into TX and RX buffers, respectively. mac_wifi.py continuously checks if the TX buffer is non-empty, i.e., there is packet to deliver, and stores the received packets into the RX buffer. The buffer sizes would be displayed once changed.

2. Open another terminal and run

    ./ul_traffic.py

This program generates n packets every t seconds and sends them to the TX buffer in 1. For test purpose, the generated packets are TEST_k (k=1,2,3,4). Note: only run ul_traffic.py after the ul_buffer.py starts, as the latter is on the server side of the socket communication.

3. Open a new terminal and run

    ./phy_wifi.py

This is the physical layer implementation, which is based on the hierarchical flow graph wifi_phy_hier.grc. PHY sends valid received packets for MAC for further process, and takes care of the packet transmission. The simulated MAC address of the USRP node is decided by the node number, which can be specified using parameter -n, e.g., ./phy_wifi.py -n 1.

4. Open a terminal and run

    ./mac_wifi.py

This program simulates the MAC layer behaviors, such as Clear Channel Assessment (CCA), waiting for the ack. It will ask phy_wifi.py for node ID and delivers its packets to Node (node + 1), such as Node 1 -> Node 2 -> Node 3 ... So if you configure one USRP as Node 1 and another as Node 2, you would only receive ACK on Node 1, as all traffic on Node 2 targets Node 3. To allow bidirectional data transfer between Node 1 and Node 2, you can modify dest_mac in the source code.

Troubleshooting

• If you see ImportError: No module named wifi_phy_hier when running ./phy_wifi.py, open example\wifi_phy_hier.grc in GNURadio and generate the flow graph. You should be able to see wifi_phy_hier.py is generated under ~/.grc_gnuradio/.

• If you see return _fft_swig.fft_vcc_make(fft_size, forward, window, shift, nthreads) RuntimeError: std::exception when running ./phy_wifi.py, use sudo ./phy_wifi.py. (A read-only .gr_fftw_wisdom under the home folder may be the reason of using sudo command. You can simply change its permissions to get rid of the boring sudo privilege.)

• Python [Errno 98] Address already in use. Kill the process that occupies the socket.

    kill -9 $(lsof -ti tcp:xxxx)

Where xxxx is the socket port. If the error still exists, try

    ps -fA | grep python
    kill -9 xxxx

where xxxx is the PID of the running python scripts.

Tricks

Use tmux to manage multiple terminals.

Further information

If you have any further questions or suggestions, please feel free to contact Haoyang Lu ([email protected]), University of Pittsburgh.