[Ns-developers] GSoC: WiMAX Projects

[Nitin Dua, IIT G]

Hi Amine,

Thanks for the help. How is this for an abstract?

"I propose to implement in ns-3 WiMAX module a mechanism for
fragmenting/de-fragmenting of Protocol Data Units (PDUs) to the optimal
size when the error rate for the Forward Error Correction (FEC) block is
known. The FEC block error rate (BLER) shall be estimated by implementing
Gilbert-Elliot bit-error model. Using FEC BLER, the PDU error rate can be
computed which is further used to estimate the optimal PDU size."

Suggested modifications are most welcome.

Also I would like to read the paper[1] regarding error estimates but not
able to find it on the web. May be you could help me with this.
[1]- E. O. Elliot. Estimates of error rates for codes on burst-noise
channels. Bell Systems Technical Journal,
42:1977–1997, September 1963.

Please reply soon,
Thanks,
Nitin


> Hi Nitin,
>
>> estimated error. Do you think implementation of such a scheme in ns-3
>> wimax module will be feasible?
>
> I think such a mechanism is very interesting for the WiMAX module,
> however, in
> the current version of the code there is no error model implemented yet.
> You
> can maybe implement a basic error model (Gilbert model?)  and then design
> and
> implement  a mechanism which computes the optimal size of the PDU based on
> the estimated error.
>
> Thanks
> Amine
>
> On Tuesday 31 March 2009 21:31:05 Nitin Dua, IIT G wrote:
>> Dear Amine,
>>
>> I had some queries regarding the mail below which you sent a few days
>> back.
>>
>> > Hi,
>> >
>> > I'am Mohamed Amine ISMAIL a Ph.D student at the INRIA. Actually I am
>> > working
>> > on the wimax module for ns-3.
>> >
>> > The current WiMAX module provides the main functionalities of the
>> WiMAX
>> > standard. The core part of the MAC layer includes the generation of
>> the
>> > MAC
>> > frames (in TDD mode) and the construction and transmission of the key
>> MAC
>> > control messages (DL-MAP, UL-MAP, DCD, UCD, RNG-REQ and RNG-RSP).
>> >
>> > The Link Manager component at the SS and BS side handles the network
>> > entry and initialisation procedure that a new SS follows upon entering
>> > the WiMAX network. This procedure includes the scanning process  and
>> the
>> > initial ranging process.
>> >
>> > Once the network entry process is successful, the SS is assigned with
>> a
>> > set of
>> > connections. This includes two connections for the management messages
>> > and a
>> > number of transport connections for the data traffic. Both SS and BS
>> > maintain
>> > their own connection managers. For the BS the connection manager
>> handles
>> > the
>> > creation and management of all the connections associated to SSs
>> > registered
>> > with the BS. For SS the connection manager manages connection
>> associated
>> > to
>> > the SS. The SS Manager component is maintained by the BS to access all
>> > the SSs currently registered to BS.
>> >
>> > The service flows are set up during the installation of the
>> application.
>> > Once
>> > registered with BS the SS then requests for creation of an already set
>> up
>> > service flow from BS, and BS then creates the service flow, registers
>> the
>> > QoS
>> > parameters associated to it, and allocates service flow to SS. This
>> whole
>> > process is done through the exchange of DSA (DSA-REQ, DSA-RSP and
>> > DSA-ACK) messages.
>> >
>> > The module supports all four scheduling services. Each service flow is
>> > associated to exactly one transport connection and one scheduling
>> > service. The QoS parameters associated to a service flow actually
>> define
>> > the scheduling service it belongs to. Standard QoS parameters for UGS,
>> > rtPS, nrtPS and BE services, as specified in Tables 111a to 111d of
>> the
>> > 802.16e amendment, are supported.
>> >
>> >
>> > The current WiMAX module provides two different versions of the PHY
>> > layer. The first one is a basic PHY implementation which simply
>> forwards
>> > bursts received by the MAC layer ignoring any underlying PHY layer
>> > details. The second one is a more complete OFDM PHY layer, it uses
>> > external
>> > mathematics and signal processing library IT++ together with the
>> LAPACK,
>> > BLAS
>> > and FFTW libraries. no propagation/error model has been considered,
>> hence
>> > one
>> > of the future works is also to add support for a propagation/error
>> model.
>>
>> Is it that the optimal size for the PDU is not considered at all. I came
>> across this paper
>> http://ieeexplore.ieee.org/iel5/4483765/4488105/04488131.pdf?arnumber=44881
>>31 which talks about finding an optimal size of the PDU based on the
>> estimated error. Do you think implementation of such a scheme in ns-3
>> wimax module will be feasible? I am sure there may exist other tested
>> schemes. I would like to integrate such fragmenting/defragmenting PDU
>> techniques in ns-3 over this summer. Please send me any resources you
>> are
>> aware of.
>>
>> > Actually we are working on an IPCS classifier. The classifier  is used
>> to
>> > map
>> > the incoming packet to the appropriate service flow based on a set of
>> > criteria. The service flows are created at the scenarios setup and a
>> bind
>> > function is developed to associate an IP traffic to a service flow
>> based
>> > on
>> > the IP src,IP dst, protocol, port src, and port dst. The IPCS analyses
>> > the headers of the incoming IP packets from the upper layer and map
>> them
>> > to the
>> > appropriate connexion.
>> >
>> > An other ongoing work is the development of the pcap tracing function
>> for
>> > the
>> > wimax packets.
>> >
>> >
>> > The module currently lacks the implementations of :
>> >
>> > - fragmentation/defragmentation of PDU(s)
>> > - dynamic burst profile management
>> > - Propagation/error model
>> > - more sophisticated algorithm for the scheduler
>> > - more efficient algorithm for the bandwidth management mechanism
>> >
>> >
>> >
>> > Regards
>> > Amine
>>
>> Thanks & Regards,
>> Nitin
>
>
>