FDMA TDMA CDMA SDMA PDF

Traditionally, analog radio modulation methods such as AM and FM limited the amount of information conveyed within a given channel, and each channel could only host a single conversation at any one time -a pair of users, one transmitting and one receiving. Digital radio, using various modulation schemes, is moving to alleviate this problem by increasing the amount of information that can be conveyed on a channel. Digital radio has developed ways in which more than one conversation can be accommodated multiplexed inside the same physical RF channel. There are three common ways of achieving this: 1. For example, one

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Traditionally, analog radio modulation methods such as AM and FM limited the amount of information conveyed within a given channel, and each channel could only host a single conversation at any one time -a pair of users, one transmitting and one receiving. Digital radio, using various modulation schemes, is moving to alleviate this problem by increasing the amount of information that can be conveyed on a channel.

Digital radio has developed ways in which more than one conversation can be accommodated multiplexed inside the same physical RF channel. There are three common ways of achieving this: 1. For example, one This technique has been around for decades and is used with either analog or digital radios. The drawback of this is the more sub-channels you try to fit in to the original channel, the more likely that the users will suffer interference on the call.

This is because the reduced channel spacing makes it harder to filter only the intended sub-channel and reject all the others at the receiver. Consequently, dividing a single narrowband The transmitted RF frequency is identical in each slot, but each slot is still capable of carrying a separate conversation.

In the diagram, the channel is split in to four time slots, so in each slot the speech is transmitted in a quarter of the time taken to say it. In the diagram, the channel is split in to four code slots. Each slot is still capable of carrying a separate conversation because the receiver only reconstructs information sent from a transmitter with the same code. However this does create a problem, as transmissions on the same frequency with different codes are still received and decoded but simply re-appear as noise.

This means the greater the number of users, the higher the noise level on the system, which of course can affect coverage. To get updates as our posts get published, subscribe via email below: Email Address.

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Comparison – FDMA, TDMA and CDMA

Moreover, if we take a look at non-adjacent spectra the theoretical isolation is infinite and thus the average of the adjacent SSCs would be of CDMA achieves higher protection by means of the cross-correlation of the employed codes. In the case of FDMA there is only one code and thus we have to talk about auto-correlation instead of cross-correlation. If we consider now the spectral separation and code separation effects together, we can see that from this point of view FDMA would provide an additional protection of 22 dB with respect to the CDMA approach. As we can recognize, the implicit assumption behind is that the jammers are narrowband. While the protection against jammers was at the beginning of GNSS of particular importance and drove most of the decisions that Russia and the USA took to build their respective satellite navigation systems, nowadays it is possible to build very wideband jammers.

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Différence entre FDMA, TDMA et CDMA

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