Transfer problem (maximum number of Mbit/s)

[dont_know]

I have a spectrum of 900khz that is divided into channels of 4kHz each. That makes 225 channels. Then each channel can transfer 4000 symbols/sec. I will be using the QAM-256 and that allows 8 bits/symbol. That means each channel can transfer 4000*8= 32e3 bit/s. And the channels in total makes 32e3*225=7.2e6 That makes the transfer rate 7.2 Mbit/s. Is that correct? Is it impossible to go up to 24 Mbit with my current settings or am I thinking things wrong here??

Dont_know

 

[WaterRocketBoy]

You are missing the effect of Signal-to-Noise ratio on the capacity of your channel. You can theoretically go to 24 Mbit/s if you have an SNR of > 83 dB on all your 4 kHz channels, and no interference between them... (the practical issues are significant!)

See: http://en.wikipedia.org/wiki/Shannon–Hartley_theorem

... of course, this is the best you could do if there were no other implementation losses, etc.

 

[ravenprp]

Based on the information provided, your calculations seem to be correct. Each channel can transfer 32,000 bits per second and there are a total of 225 channels, which gives a transfer rate of 7.2 Mbit/s. It is not impossible to go up to 24 Mbit/s with your current settings, but it would require either increasing the bandwidth or using a more advanced modulation scheme. Additionally, other factors such as noise and interference can also affect the actual transfer rate. It is important to consider all these factors when designing a communication system.