Changes between Version 18 and Version 19 of Projects/Mango_MobiCom_2014_Demo

Timestamp:

Sep 15, 2014, 3:48:28 PM (10 years ago)

Author:

chunter

Comment:

--

Projects/Mango_MobiCom_2014_Demo

@@ -9 +9 @@
   * 4 are quad-antenna monitors capturing per-subcarrier channel estimates for real-time analysis.
 
-Conference attendees join the open AP with their personal Wi-Fi clients (e.g. smartphones/tablets) and use the AP to access the Internet. Once the association process with the AP is complete, the 16-antenna array of WARP boards begins to overhear transmissions from the conference attendees' Wi-Fi clients. The [wiki:802.11/PHY#ReceiverArchitecture OFDM Receiver] in each array element's PHY automatically estimates the channel between the conference attendees' devices and itself. These channels are learned via the two LTS symbols in the preamble of every transmission from the Wi-Fi clients. 
+Conference attendees join the open AP with their personal Wi-Fi clients (e.g. smartphones/tablets) and use the AP to access the Internet. Once the association process with the AP is complete, the 16-antenna array of WARP boards begins to overhear transmissions from the conference attendees' Wi-Fi clients. The [wiki:802.11/PHY#ReceiverArchitecture OFDM Receiver] in each array element's PHY automatically estimates the channel between the conference attendees' devices and itself. These channels are estimated via the two LTS symbols in the preamble of every transmission from the Wi-Fi clients. The array of WARP v3 boards then streams these channel estimates to a custom application for processing and visualization via the [wiki:802.11/wlan_exp WLAN Experiments framework].
 
 
 ||  [[Image(screenshot.png, 320px)]]  ||  [[Image(screenshot2.png, 320px)]]  ||
+||  (1)  ||  (2)  ||
 
+The custom application consumes the per-user, per-antenna, and per-subcarrier channel estimates and produces the two visualizations seen above.
 
-* Custom Python framework coordinates runtime configuration of each node
-* Custom PC application displays real-time channel estimates and SU/MU-MIMO achievable rates
-* Full 802.11 MAC/PHY source available at [http://warpproject.org/802.11 http://warpproject.org/802.11]
+(1) In the first window, the application displays a list of users on the right. For the selected user, the application plots the magnitude of each channel estimate between that user and the 16 array elements. Since this visualization occurs live, the user is able to move their Wi-Fi client around and see the impact of their mobility on the wireless multipath environment.
 
-All code used in the demonstration corresponds to [source:ReferenceDesigns?rev=3857 SVN revision 3857]
+(2) In the second window, the large array of channel is processed to determine the achievable rate that a multi-user AP would be able to achieve if the given channel estimates accurately represented the wireless environment at the time that a MU-MIMO waveform could be sent. Specifically, 4-users are selected using the UI elements on the bottom of the window. Using a [http://en.wikipedia.org/wiki/Moore–Penrose_pseudoinverse Moore-Penrose Pseudoinverse], MU-MIMO beamweights are calculated for the instantaneous snapshot of channel estimates. Using these beamweights, the effective SNR to each user is calculates and the achievable rate for each is calculated using log(1 + SNR). Depending on the channels, this matrix may be near singular, thereby collapsing the MU-MIMO AP's ability to send each user an independent data stream. The users can see this behavior in the rate calculation by moving their devices very close to one another. Furthermore, standard single-user beamforming achievable rates are also plotted for each user for comparison. With every additional antenna, single-user beamforming only has a logarithmic increase in achievable rate, so there are very diminishing returns with large antenna arrays. The promise of MU-MIMO is that the network rate than can be achieved can scale linearly with the number of users once a sufficient number of antennas is used.
+
+All code used in the demonstration corresponds to [source:ReferenceDesigns?rev=3852 SVN revision 3852].
 
 Conference handout: [raw-attachment:Mango_MobiCom_2014_Handout.pdf PDF (660 kB)]