[Ns-developers] 802.11 10Mhz Channel

[Ramon Bauza]

Hello everyone,

I am Ramon Bauza, a researcher at Miguel Hernandez University (Spain).
Currently, I am involved in the EU FP7 project iTETRIS which aims at
creating an integrated traffic and wireless simulation platform that will
allow evaluating traffic management strategies and communication protocols
in vehicular environments. The iTETRIS project employs SUMO and ns-3 as
traffic simulation and wireless simulation platforms respectively.

Our research group at UMH, it is charge of implementing the 802.11p (WAVE)
standard in ns-3. 802.11p is based on 802.11a, being the channel bandwidth
and thus also the data rates the main differences between both (802.11p uses
a 10Mhz whereas 802.11a uses 20Mhz). After implementing 802.11p in ns-3, we
will also look into and implement propagation models for vehicular
environments that consider LOS/NLOS visibility conditions,
vehicle-to-vehicle and vehicle-to-infraestructure communications, and
shadowing and multipath fading effects.

In order to model a 10Mhz channel in ns-3, some additions/modifications
should be done (some weeks ago I posted a message in the user mailing list
regarding this
http://groups.google.com/group/ns-3-users/browse_thread/thread/f27b1ddcf9f1d532#).
Apart from 802.11p, I think other 802.11 standards employ 10MHz channels and
thus probably the modeling of 10Mhz channels would also be useful for the
ns-3 community working on 802.11-related topics. In fact, the IEEE Std
802.11TM-2007 standard considers 10Mhz channel spacing using OFDM. If you
consider that the modeling of 10Mhz channels may be beneficial for other
users we would be glad to merge the 10Mhz modeling in the main branch.

Below, I compile the needed functions and modifications we plan to introduce
in ns-3 at the PHY layer for modeling a 10Mhz channel:

+ wifi-phy-standard.h

  Add WIFI_PHY_STANDARD_80211_10Mhz in the enum WifiPhyStandard

+ wifi-phy.h and wifi-phy.cc

  Declare and define the following new functions:

    static WifiMode Get3mb10Mhz (void);
    static WifiMode Get4_5mb10Mhz (void);
    static WifiMode Get6mb10Mhz (void);
    static WifiMode Get9mb10Mhz (void);
    static WifiMode Get12mb10Mhz (void);
    static WifiMode Get18mb10Mhz (void);
    static WifiMode Get24mb10Mhz (void);
    static WifiMode Get27mb10Mhz (void);

+ yans-wifi-phy.h and yans-wifi-phy.cc

  Declare and define the void Configure80211_10Mhz (void) function.
  Modify the void SetStandard (enum WifiPhyStandard standard) function so
that the user can also select a 10Mhz channel.

+ interference-helper.h and interference-helper.cc

  Declare and define void Configure80211_10MhzParameters (void);

One function that should be modified is
InterferenceHelper::CalculateTxDuration (uint32_t size, WifiMode
payloadMode, WifiPreamble preamble) const since it assumes that the symbol
duration is always 4us (20 Mhz channel). This function should employ a
symbol duration according to the channel used (10Mhz or 20Mhz). One possible
solution to solve this would be to have a new variable in the class
InterferenceHelper which allows differentiating the channel used. This
variable could be of type WifiPhyStandard. In the function Time
InterferenceHelper::CalculateTxDuration, this new variable would be examined
and the packet txon duration will be calculated based on the bandwidth
channel.

Please, I would like to have your comments on this in order to proceed with
the implementation.

Thank you in advance.
Best regards,
Ramon.

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Ramon Bauza
Ubiquitous Wireless Communications Research Laboratory
Uwicore, http://www.uwicore.umh.es
Signal Theory and Communications Division
University Miguel Hernández (Spain)
Tel: +34 96522 2031
Fax: +34 96665 8903
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