[ns] Measuring channel access probabilty
Hi, In a wireless network testbed, packet statistics at the receiver include the list of packets that reached the receiver node. Each packet has a source id and the transmission timestamp. Assuming a single hop network, how do we calculate the channel access probability of a node here? Note that theoretically, for a permanently backlogged network, channel access probability = 2/(CW+1). However, it is difficult to measure CW in our setting. Thanks for your help. Regards, Debarshi
[ns] Observations and Query on holdoff exponents in IEEE 802.16 mesh
Hi,
We were performing some experiments in NS-2 using the IEEE 802.16 / WiMAX
mesh patch (http://cng1.iet.unipi.it/wiki/index.php/Ns2mesh80216) on tuning
the holdoff exponents for distributed coordinated scheduler in IEEE 802.16
mesh.
*Setup: *
We considered a chain of odd number of nodes.
For example, a chain of 7 nodes looks like:
n1 - n2 - n3 - n4 - n5 - n6 - n7
*Holdoff Time: *
The holdoff time (in slots) of a node is the number of slots it has to wait
between two successive control channel access.
The expected holdoff time E[t_k] of node k is given by:
E[t_k] = 2^(base_k + x_k) + E[s_k]
where base_k is the holdoff time base, x_k is the holdoff exponent and
E[s_k] is the expected number of slots in which node k fails before it wins
the competition for control channel access.
The above relation follows from the following paper:
*M. Cao, W. Ma, Q Zhang, X. Wang and W. Zhu, “Modeling and Performance
Analysis of the Distributed Scheduler in IEEE 802.16 Mesh Mode,” Proc. 6th
ACM MobiHoc, Urbana-Champaign, May 2005
*
*Method to reduce holdoff time:*
Now for a linear chain, it is useful to set
base_k = floor(ln (N_k))
where N_K is the number of two-hop neighbors of node k.
This idea is suggested in
S.Y. Wang, C.C. Lin, H. Chu and T.W. Hsu, “Improving the Performances of
Distributed Coordinated Scheduling in IEEE 802.16 Mesh Networks,” IEEE
Transactions on Vehicular Technology, 57(4): 2531-2547, July 2008
In the above paper, Wang et al. also suggested that hold off exponents
should be set to zero.
Thus for the chain of 7 nodes, holdoff bases are {1, 1, 2, 2, 2, 1, 1} and
the holdoff exponents are {0, 0, 0, 0, 0, 0, 0}.
*Our observations:*
For the chain of 7 nodes, we used the same values for holdoff bases, that
is, {1, 1, 2, 2, 2, 1, 1} but used the set {0, 0, 1, 0, 1, 0, 0} for the
exponents.
Note: There is a provision to set the holdoff exponents manually via a tcl
script in the patch mentioned above.
Then we carried out all the experiments reported in the above paper by Wang
et al., that is, we measured TCP throughput, UDP throughput and round trip
time (RTT).
We found that our setting produced slightly better results.
Similar observations were made for longer chains of odd lengths when the
exponents of the third node from the left and the third node from the right
are set to one and all other exponents are set to zero.
*This observation appears very surprising since the delay is supposed to
increase for larger exponents.*
Can anyone please throw some light on this?
Your feedback is appreciated.
Regards,
Debarshi
Regards,
Debarshi
[ns] IEEE 802.11 VoIP patch for NS-2
Hi, Can anyone please provide an NS-2 patch and test scripts for VoIP over IEEE 802.11? We are looking for a patch that has the optimizations proposed in D. Niculescu, S. Ganguly, K. Kim, and R. Izmailov, “Performance of VoIP in a 802.11-based Wireless Mesh Network”,http://samrat.name/papers/wireless/infocom06-voip.pdfProceedings of IEEE INFOCOM, 2006, Barceleno. Regards, Debarshi
[ns] Patch for ETX and mETX routing metrics for wireless mesh networks
Hi, Is there an NS-2 patch for ETX and mETX routing metrics for wireless mesh networks? Regards, Debarshi
Re: [ns] where is the hdr_flags constructed?
Hi All, I am facing a serious problem when I run NS-2 simulations of IEEE 802.11bextending over 200 seconds with cbr traffic rate of each node = 11Mbps and number of nodes = 50. The process is killed after around 100 seconds of simulation. This occurs even if I turn off all traces. Any clues will be helpful. Moreover, some papers on IEEE 802.11 report NS-2 simulations extending for 3000 seconds. I am never able to run simulations over so long a duration on Duo-core Intel processors with 1 GB RAM. If you have any experiences, please help. Thanks in advance. Regards, Debarshi
[ns] [URGENT] Problems in running long-duration simulations in NS-2
Hi All, I am facing a serious problem when I run NS-2 simulations of IEEE 802.11bextending over 200 seconds with cbr traffic rate of each node = 11Mbps and number of nodes = 50. The process is killed after around 100 seconds of simulation. This occurs even if I turn off all traces. Any clues will be helpful. Moreover, some papers on IEEE 802.11 report NS-2 simulations extending for 3000 seconds. I am never able to run simulations over so long a duration on Duo-core Intel processors with 1 GB RAM. If you have any experiences, please help. This is very urgent. Thanks in advance. Regards, Debarshi
[ns] Saturation Throughput of IEEE 802.11b
Hi, Can anyone please provide a script to simulate and measure the saturation throughput of a set of nodes in IEEE 802.11b network in NS-2? A tcl script to set up the topology and determine the saturation throughput are urgently required. Regards, Debarshi
Re: [ns] Fwd: Urgent help required: Unable to build xgraph
Hi All, Please let me know how to build xgraph-12.1 given the issues I am facing. The build is on RHEL (Red Hat Enterprise Linux) 3 (Taroon). Appreciate your response in this regard. Regards, Debarshi On 12/27/06, Debarshi Sanyal [EMAIL PROTECTED] wrote: Thanks you so much, Larry. But during ./configure in xgraph-12.1 directory (or with top-level install script), it reports checking for X... (cached) libraries /usr/X11R6/lib, headers= /usr/X11R6/include At the end, it quips creating Makefile creating autoconf.h autoconf.h is unchanged And yet when I run make, it errors out. I have tried after including the above Xdevelopment headers and libraries in PATH, but the issue persists. Could you please suggest a solution? Thanks a lot, Debarshi On 12/27/06, Larry Brigman [EMAIL PROTECTED] wrote: On 12/26/06, Debarshi Sanyal [EMAIL PROTECTED] wrote: Hi, Festive greetings to you all! I recently installed ns2.29 on Red Hat Linux 9. I am unable to build xgraph although other components of ns2 are getting built correctly. When I run ./configure followed by make in the xgraph directory, it tells: Makefile:255: *** missing separator. Stop. This is the same problem discussed in the mail Why building Xgraph Failed? in ns-users mailing list. But I haven't found the solution there. Could anyone please help me fix this issue? This is very urgent. Pleeesee help !! You will need the Xwindows development headers and libraries to build xgraph.
[ns] Help required: Unable to build xgraph
Hi, Festive greetings to you all! I recently installed ns2 on Red Hat Linux 9. I am unable to build xgraph although other components of ns2 are getting built correctly. When I run ./configure followed by make in the xgraph directory, it tells: Makefile:255: *** missing separator. Stop. This is the same problem discussed in the mail Why building Xgraph Failed? in ns-users mailing list. But I haven't found the solution there. Could anyone please help me to fix this issue? This is very urgent. Thanks you so much for your time. Regards, Debarshi
Re: [ns] Fwd: Urgent help required: Unable to build xgraph
Thanks you so much, Larry. But during ./configure in xgraph-12.1 directory (or with top-level install script), it reports checking for X... (cached) libraries /usr/X11R6/lib, headers= /usr/X11R6/include At the end, it quips creating Makefile creating autoconf.h autoconf.h is unchanged And yet when I run make, it errors out. I have tried after including the above Xdevelopment headers and libraries in PATH, but the issue persists. Could you please suggest a solution? Thanks a lot, Debarshi On 12/27/06, Larry Brigman [EMAIL PROTECTED] wrote: On 12/26/06, Debarshi Sanyal [EMAIL PROTECTED] wrote: Hi, Festive greetings to you all! I recently installed ns2.29 on Red Hat Linux 9. I am unable to build xgraph although other components of ns2 are getting built correctly. When I run ./configure followed by make in the xgraph directory, it tells: Makefile:255: *** missing separator. Stop. This is the same problem discussed in the mail Why building Xgraph Failed? in ns-users mailing list. But I haven't found the solution there. Could anyone please help me fix this issue? This is very urgent. Pleeesee help !! You will need the Xwindows development headers and libraries to build xgraph.
