[Ns-developers] wifi phy API rework

[Mathieu Lacage]

hi,

A long long time ago, I started work on the ns-3 wifi code to make it
easier than it is now to implement and use multiple PHY model
implementations from the MAC layer. I finished this a couple of days ago
in http://code.nsnam.org/mathieu/ns-3-wifi.

I believe that the API is complete and the implementation reasonable so,
I would like to move forward with this code. i.e., reviews would be
welcome, especially from the helper API maintainer.

API:
  - src/helper/wifi-helper.h: does not handle the PHY layer anymore.
WifiHelper::Default constructs a wifi helper in a coherent state. 
  - src/helper/yans-wifi-phy-helper.h: provides a PHY helper for the
only PHY model implemented for now (the so-called yans model).
  - src/devices/wifi/wifi-channel.h: base class
  - src/devices/wifi-phy.h: base class
  - src/devices/wifi/yans-wifi-channel.h: yans model implementation
  - src/devices/wifi/yans-wifi-phy.h: yans model implementation
  - src/devices/wifi/wifi-phy-state-helper.h: phy state machine. Used by
YansWifiPhy. Could be used by others.
  - src/devices/wifi/interference-helper.h: interference calculations.
Used by YansWifiPhy. Could be used by others.
  - src/devices/wifi/error-rate-model.h: calculate PER from mode, snr,
and packet size. Used by YansWifiPhy, could be used by others.

Right now, there is still a small piece missing: I need to make
ErrorRateModel be an abstract base class to integrate the 'nsmiracle'
error rate model which federico maguolo sent me almost a year ago.

The example code in examples/ has been updated to use this new API.

regards,
Mathieu