Skip to content Skip to navigation

Connexions

You are here: Home » Content » Digital Transmission over Baseband Channels

Navigation

Content Actions
  • Download module PDF
  • Add to ...
    Add the module to:
    • My Favorites
    • A lens
    • An external social bookmarking service
    • My Favorites (What is 'My Favorites'?)
      'My Favorites' is a special kind of lens which you can use to bookmark modules and collections directly in Connexions. 'My Favorites' can only be seen by you, and collections saved in 'My Favorites' can remember the last module you were on. You need a Connexions account to use 'My Favorites'.
    • A lens (What is a lens?)

      Definition of a lens

      Lenses

      A lens is a custom view of Connexions content. You can think of it as a fancy kind of list that will let you see Connexions through the eyes of organizations and people you trust.

      What is in a lens?

      Lens makers point to Connexions materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

      Who can create a lens?

      Any individual Connexions member, a community, or a respected organization.

    • External bookmarks
  • E-mail the author

Recently Viewed

This feature requires Javascript to be enabled.

Digital Transmission over Baseband Channels

Module by: Behnaam Aazhang

Summary: I have no idea whatsoever.

Until this point, we have considered data transmissions over simple additive Gaussian channels that are not time or band limited. In this module we will consider channels that do have bandwidth constraints, and are limited to frequency range around zero (DC). The channel is best modified as gt g t is the impulse response of the baseband channel.

Consider modulated signals x t = s m t x t s m t for 0≤t≤T 0 t T for some m∈12…M m 1 2 … M . The channel output is then

r t =∫-∞∞ x τ gt-τdτ+ N t =∫-∞∞ S m τgt-τdτ+ N t r t τ x τ g t τ N t τ S m τ g t τ N t (1)

The signal contribution in the frequency domain is

∀f: S m ˜ f= S m fGf f S m ˜ f S m f G f (2)

The optimum matched filter should match to the filtered signal:

∀f: H m opt f= S m f¯Gf¯ⅇ-ⅈ2πft f H m opt f S m f G f 2 f t (3)
This filter is indeed optimum (i.e., it maximizes signal-to-noise ratio); however, it requires knowledge of the channel impulse response. The signal energy is changed to
E s ˜ =∫-∞∞| S m ˜ f|2df E s ˜ f S m ˜ f 2 (4)
The band limited nature of the channel and the stream of time limited modulated signal create aliasing which is referred to as intersymbol interference. We will investigate ISI for a general PAM signaling.

Comments, questions, feedback, criticisms?

Send feedback