Hi all,
I would like to announce the publication of a new 802.11 that we
developed at the SIGNET lab, University of Padova, Department of
Information Engineering (DEI), downloadable at
http://www.dei.unipd.it/wdyn/?IDsezione=5090
This 802.11 implementation, named dei80211mr, permits the simulation of rate
adaptation algorithm (in the distribution an implementation of ARF is already
included) with an enhanced physical layer with respect to those
in the ns distribution. In particular:
- support for multiple PHY modes is included; in particolar,
dei80211mr supports simulation of the different transmission rates,
modulation and coding schemes defined in the IEEE802.11b/g standards.
- a SINR-based packet level error model is introduced:
+ the RX Threshold variable which was used in the 802.11
implementation included in standard NS to determine successful
receptions has been removed. Instead, Packet Error Rate (PER) is
used to determine random packet losses.
+ PER is calculated using pre-determined curves (PER
vs SINR and packet size); the curves can be specified by the user
via TCL. Some default curves for both 802.11g and 802.11b are
provided.
+ SINR is calculated using received signal strength, noise and
interference
+ interference is calculated using a gaussian model to account for
all transmissions which happen simultaneously to the one which is
considered for reception
+ noise power is set via TCL
- the capture model, i.e. the determination of whether a packet can be
received when there are other concurrent transmissions are
simultaneously ogoing, is now embedded in the above mentioned
interference model (no more Capture Threshold).
- Some well-known bugs of the 802.11 implementation in NS have been
resolved. With reference to [1], we solved the following bugs:
+ direct access denial
+ random backoff time
+ capture model (note: this is different from the point above since,
as per the description in [1], it is actually a synchronization
issue)
- In the wireless channel, the affected nodes distance is no more
determined using the CS threshold, but we used a fixed value in
meters (distInterference_) which can be set at the beginning of the
simulation. The reason is that, since we use a gaussian interference
model, nodes well below the CS threshold often still provide a
non-negligible contribution to interference. The default value for
the affected nodes distance (distInterference_) is very
conservative, so that all nodes are considered for interference
calculation. This default value therefore yields accurate but
computationally intensive simulations. The value can be adjusted via
TCL to achieve different trade-offs between computational load and
simulation accuracy.
- Several useful 802.11 MAC MIB counters described in [3], Annex D, have
been added to the MACMIB C++ class
- dei80211mr can be used within the classical ns-2 MobileNode
dei80211mr is distributed as a dynamic library using the Dynamic Library
patch [2]. Thanks to the functionalities introduced by this patch,
dei80211mr can be used with different versions of ns2. We have tested it
with ns-2.29 and ns-2.31, and we expect it to work with future ns2
releases as well.
[1] Ilango Purushotaman and Sumit Roy,
IEEE802.11 implementation Issues in Network Simulator 2,
Dept. of Electrical Engineering, University of Washington, US
http://ee.washington.edu/research/funlab/
[2] Patch for Loading Dynamic Modules in ns-2,
http://mailman.isi.edu/pipermail/ns-users/2007-June/060486.html
http://www.dei.unipd.it/~rossi/ns2-patch.html
[3] IEEE LAN MAN Standards, Part 11: Wireless LAN
Medium Access Control (MAC) and Physical Layer
(PHY) specifications¿, ANSI/IEEE Std., March 1999.
