Optical wireless networks with Omnet++/INET

[Nathan Vo]

Hello, I'm trying to model and simulate an optical wireless network especially for satellite communications. Are there any current working projects or plans on adapting the INET framework to use optical wireless links also? If not, can someone steer me in the right direction?

Thanks.

[Alfonso Ariza Quintana]

You can use the actual electromagnetic model with parabolic antennas, you need to set a quite narrow lobules an modify the attenuation model, you ca use the obstacles model to model the differences in the attenuation between different layers in the atmosphere.

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[Nathan Vo]

By narrow lobules, did you mean the beamWidth? So far for the antennas, I basically made a copy of the parabolic antenna model and renamed it to telescope. I made a radio model based off the ieee80211 radio model using the scalar analog models with added pointing loss parameters. But this limits what type of bitrate I can set to in the NIC settings due to the ieee80211 specifications not to mention what other things I'm missing due to the ieee80211 standards..should I start with the ideal radio model instead?

[Momoko Sakura]

No, this is an authentication protocol used in LTE network to user accessing

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[Alfonso Ariza Quintana]

You can use wifi, but you need to modify the sifs/difs and the error model. To increase the bit rate in the wifi model is possible, if you use the ideal radio, you have a channel without errors and collisions

 

 

Enviado desde Correo para Windows 10

 

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[Nathan Vo]

I think you replied to the wrong post?

[Nathan Vo]

How do I modify the sifs/difs? The current available errors models are BerTableErrorModel, NistErrorModel, and YansErrorModel.. and the bitrate for wifi is capped at 54Mbps for available opModes "a", "b", "g(erp)", "g(mixed)", "n", "p" but I need to do more than 1 Gbps, do I have to introduce a new opMode?

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[Alfonso Ariza Quintana]

Inet integration already supports 802.11ac 6.9Gb/s. The default error model is Nist and it includes the error model for qpsk 256 and qpsk1024 (future 802.11ax). The timers are computed in the Ieee80211VhtMode files. Inetmanet 3.5 also includes the 802.11ac model.

 

It is necessary to modify the attenuation model. 802.11ac uses 5GHz to compute the attenuation.

[Nathan Vo]

Are there any examples that uses 802.11ac?

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[Alfonso Ariza Quintana]

https://github.com/aarizaq/inetmanet-3.x/tree/inetmanet-3.5/examples/wireless/lan80211ac

[Nathan Vo]

Ah I see, it seems only the InetManet and Inet Integration versions have "ac" support, the official inet version is still missing that even in the latest version, I wonder why.

[Nathan Vo]

Alfonso, I've been testing the throughput with "ac" mode 693.3Mbps for adhoc hosts but normal traffic only reach a peak of 80000 bps, what reason would cause this?

[Alfonso Ariza Quintana]

693 Mb/s is the maximum physical bit rate, but the time that you need to transmit the data of frame is a lot smaller that the time necessary to transmit the frame, the frame has a physical header, after the transmission it must wait a ACK, after the reception of ACK it must wait a difs time, after a transmission the node must start a backoff procedure ….

 

If you consider all of this, you can see that the throughput that you can obtain is lower that the maximum bi rate. And if you are using small packets, even more.

[Nathan Vo]

I see.. so in your opinion, if I want to model an optical wireless satellite network with >1Gbps..what are the exact steps I need to do to accomplish this?

[Alfonso Ariza Quintana]

You can increase the throughput if you use bigger packets, you should check with packets with a size close to the maximum MTU

[Nathan Vo]

I think the maximum MTU is 1500, but according to the timing table, you need something around 15000000 to even come close to the maximum physical throughput of ac mode.

[Levente Mészáros]

The WiFi throughout is affected by several things not just the net bitrate. For example, RTS/CTS, aggregation, fragmentation, MTU size, block acknowledgement, guard interval, txop, PHY mode to name a few. In ac mode the maximum MTU is around a few megabytes IIRC.

Best regards,

Levente