programming OFDMA in C++

[jérome78]

Hello,

I try to develop an application which sets up a technique of access multiple OFDMA in C++. Will have solutions already carried out in connection with this subject?

Thanks.

[Banfa]

The only OFDMA I know of is the radio frequency modulation scheme (OFDMA).

As such it's hard to see how you would want to relate that directly to C++ given the little detail in your question since a lot of the grunt work would be done by an RF front end (i.e. in hardware).

[jérome78]

First of all, OFDMA, also referred to as Multiuser-OFDM, is being considered as a modulation and multiple access method. OFDM is a digital modulation technique and not a multi user channel access technique. OFDMA allows multiple users to transmit simultaneously on the different subcarriers per OFDM symbol.

So, I am considering to introduce OFDMA in NS2. NS2 stands for Network Simulator. It's a discrete event simulator for networking research. It work at packet level. The language used onto NS2 is C++ &Tcl.

With OFDMA, the whole bandwith is made up of N subcarriers in the direction frequency, and organized into several sub-channels and S time slots in the direction time.

I look for solutions or examples of simulation of this technique in NS2.

Thanks.

[Banfa]

Thank you for copying that excerpt from wikipedia but I had already found it.

The packet level of a data stream is somewhat above the carrier level. That is you have packets of digital data (usually bytes) being transferred digitally, these are then normally modulated onto a carrier of some sort for transmission, be it RF for wireless or an electrical carrier in wired ADSL etc.

OFDMA operates at the carrier level, it is a method of modulating packets streams from several different users onto the same carrier by assigning sub-carriers to different users.

However you, by your own statement, are dealing with a packet stream not a modulated carrier so I do not see how it would be relevant to your work.

[jérome78]

OFDMA is an access method multiple makes it possible various users at the same time to reach the network.

OFDM is a particular case of frequential multiplexing. It makes it possible to make pass more data by using a broad band-width and by occupying the spectrum effectively.

Like OFDMA, while using OFDM, allows; to allocate a certain number of slots time/frequency at each user. such a user will speak on such subcarriers and at such time.

Moreover, on each subcarriers, a modulation must be defined. This depends on the location of the user and channel's conditions.

How I can know which subcarriers were assigned to each user???

[Banfa]

How I can know which subcarriers were assigned to each user???

I believe that depends on what allocation scheme has been implemented in the specific application.

You could try reading this.

[jérome78]

Thanks. I will try reading it.

[jérome78]

Have you other documents because I don't succeed to understand the method ASM and DSM in your document that you send me ???

Thanks

[Banfa]

Sorry I have no further documentation, I found that by looking on the web (well in Wikipedia)