Talk:Communication channel

--203.129.193.45 04:50, 21 December 2005 (UTC)--203.129.193.45 04:50, 21 December 2005 (UTC)--203.129.193.45 04:50, 21 December 2005 (UTC)i moved communications channel to here as part of re-structuring the various pages on channels. i would support re-establishing communications channel as its own page (and linking it from this one) if the specific-to-telecom details get fleshed out more. as of now, it seems acceptable to include such information on this general-com page.

Untitled

among other cleanups, i removed this line (which was on channel):

One of possibly millions of often times pointless wavelengths decoded by a television system.

am i wrong to see it as a duplicate meaning? what is 'pointless' implying? it is quite possible i have misunderstood.

my edits here are solely from the basis of cleanup, i am far from an expert. anyone who knows more is strongly encouraged to fix any mistakes, including re-opening communications channel.

also, i guess this article should not be in category:telecommunications stubs since some of it is about non-telecom. am i right about this?

Burgher 20:50, 9 Jun 2005 (UTC)

I've added a definition of Channel from Shokrollahi's "LDPC Codes: An Introduction" (see references). This is the clearest, most concise explanation of a channel I have seen. I've pasted it verbatim, so it will probably need to be worked into the article better. I figured the value and clarity of this definition outweighed any temporary lack of flow. Please be sure to retain the simplicity in any further editing!

I'm currently unclear whether Shokrollahi's definition is restricted to a memoryless channel, or can it be extended by defining each 'alphabet member' to be a sequence of symbols. Anyone care to clarify? Perhaps the definition also requires links to articles explaining 'alphabet' and other technical terms, or a rewrite to eliminate those terms?

Johal

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ton 04:48, 12 December 2005 (UTC)

guys plz expalin the meanin ofa channel.. does it to be considered as a range of frequency ...i mean during the radio trnsmission ...

Please explain the difference btn elements and chaneels of communication

Article is a misnomer, resulting in confusion

This article fails to distinguish between the many different meanings of "channel" within various subfields of communications. The result is confusion since it is never clear which definition of channel is being used. Is it a radio channel, a television channel, an audio channel, an information theoretic channel, ...? Indeed the article arbitrarily swaps between meanings.

As a first step, I propose that an article Channel (information theory) should be created. "Channel" has a precise meaning in information theory, summarised in Shanon's paper. The new article could describe "channel" as it is understood in information theory. It could talk about channel capacity, with a link to the main article. It could talk about how the theoretical concept of channel in information theory relates to real life. It might then go on to explain the idea of channel modeling (give full details in an article on channel modeling) and simulation. Perhaps list all the various of classes of channel models with links to articles (or keep this for a channel modeling article?). Maybe mention channel coding?

Separate articles could also be created for other uses of the word "channel" in communications.

In time Channel (communications) could become either a disambiguation page or a cursory overview of the various meanings of channel in a communications sense with links to articles. John Dalton (talk) 04:25, 2 January 2009 (UTC)

That might work. But before starting a new article, make sure it's the best way. An alternative would be to make two major sections in this article, for information theoretic channels and physical channels. There's already a Channel (broadcasting) that you can offload lots of TV and radio stuff to. Dicklyon (talk) 04:34, 2 January 2009 (UTC)

Popular channel models

I am missing an article summarizing particularly popular channel models, including their capacity. Should this be done here? Or in channel capacity? Or some article on its own?

Popular examples: discrete memoryless channels: binary symmetric channel and binary erasure channel, time-continuous analog channel: (Additive White) Gaussian noise channel (AWGN), etc.

Particularly missing: what means discrete vs. analog channel, memoryless channel, symmetric vs. asymmetric channel

Thoughts? Nageh (talk) 22:11, 9 January 2010 (UTC)

Great suggestion. The channel model section of this article is perfect for that. Please improve this rather poor article. However, i think equations can be left out of this article. Theoretical information theory should be placed in the end of this article because very few are interested in that, or understand it. Central concepts of a beginners course in computer networks or telecommunications should be mentioned early in this article, for example simplex and duplex channels. Mange01 (talk) 15:35, 10 January 2010 (UTC)

Thanks for your comment. It was more intended as a hint for other people to write about it. ;) I don't feel qualified enough to do it myself, and I'm lacking the references. Hope somebody else picks it up! Nageh (talk) 16:49, 10 January 2010 (UTC)

Thanks, Mange01, I think the recent changes are a step forward! Nageh (talk) 21:22, 18 January 2010 (UTC)

Redirect from channel noise

I created a redirect for channel noise to this article, because neither noise (electronics) nor noise (radio) exactly fits. This needs to be better addressed by the current article. Nageh (talk) 13:27, 20 February 2010 (UTC)

Hmm. I don't see why noise (telecommunications) (nowadays merged into noise (electronics)) would not fit. What is the difference between channel noise and other forms of noise in telecommunications? Mange01 (talk) 23:02, 28 March 2010 (UTC)

My gripe with dealing with noise in telecommunications within Noise (electronics) is that noise in electronics is more specific than noise in telecommunications, which actually refers to channel noise. For example, in telecommunications, noise can also appear in optical channels, maybe even acoustic channels, and even in higher layers (e.g., buffer overrun in packet routers resulting in erasures). One suggestion was to merge telecommunication aspects of noise into the article noise, but in the end I think it should be a separate article. I still need to think about how this could be done, e.g., through a split of the current article as you suggested. Nageh (talk) 07:52, 29 March 2010 (UTC)

Suggested split, disposition

This article has no clear focus and context. Sometimes it is about specific radio channels, sometimes about physical transmission medium, sometimes about theoretical channel models and channel properities in either telecommunications, computer networking or wireless communications, and it is not always clear which of these. A suggestion is to split it into several articles, for example:

• Radio channel (Currently redirected to radio)
• Channel model. Channel (communications) could be redirected here.

Mange01 (talk) 23:00, 28 March 2010 (UTC)

Hm... if we split the article then we should probably outsource aspects of channels which are related to a specific technology, e.g., Radio channel or Channel (radio).

Channel (communications) could then discuss channels and channel models from a generic point of view. Redirects to it could be Channel model and Channel noise. Then it could include a section in the end with references to channel types characterized by their technology, including radio channel.

But let me try to summarize what we have so far:

• Channel models, which characterize error properties based on the distinction between analog and digital channels. Interference channel probably goes here as well.
• Channel types, which characterize the connectivity: point-to-point (unicast/dedicated), point-to-multipoint (multicast, broadcast/shared), multiple-access channel, simplex, half-simplex, duplex channels, back link/return link, forward link, uplink, downlink.
• Channel types, which specify technological properties of physical channels: fibre channel, radio channel, baseband/passband channel. An introductory section on this may include the distinction between physical, logical, and virtual channels.
• Channel types, which specify their usage: multiplexed channel.

Maybe in the end it's not bad at all having everything on one page. I don't know... let me know what you think. Nageh (talk) 19:54, 29 March 2010 (UTC)

A good start. The above is discussed pretty well in the channel model section and below. But we should not restrict ourself to physical layer and information theory/tele transmission aspects. There are also computer networking aspects, like virtual and logical channels, multiplex channels, etc.

The overview is the section that I currently have most problem with. Is it supposed to list a number of application examples, or to serve as disambiguation list to alternative definitions? Could it help if we devide this list into different contexts, for example OSI layers or applications areas?

The definitions should clarify the relationship to similar concepts, for example path, connection, link, carrier, signal, bit stream, circuit, message sequence, frequency band, multiplex, ensemble, physical network, subnet, data flow, socket, etc. We need sources for that. Mange01 (talk) 20:47, 29 March 2010 (UTC)

The current Overview section can go as an Examples section at the end of the article. Maybe we can start with Channel Characterizations as summarized above? ... Have to think about it.

Not sure how you would categorize channels according to OSI layers or application areas.

Nageh (talk) 21:53, 29 March 2010 (UTC)

(Unindent) It is not clear to me eather what to do about the overview, and the dispostion. Definitions should be placed early. Examples of interest to a large audience should also be placed early. Very theoretical stuff only of interest in the academic world, such as simulation models, should be placed late.

Layered categorization of channels and their context

This is a first attempt for OSI layer based division of channel types, with the aim of clarifying in what context different channel types can be found. Feel free to further develop the suggestion here at the discussion page.

• Physical layer channels:
  • Physical transmission medium, e.g. wires, point-multipoint medium (broadcasting medium), point-point medium, shared medium (e.g. bus networks, hub networks).
  • Multiplexing channels: time division channels, frequency channels, spread spectrum|code-division multiplex channels
• Data link layer channels:
  • MAC sublayer: Virtual channels (eg. in ATM).
    • Shared channel access: TDMA channels, FDMA channels, CDMA channels, OFDMA channels.
    • Addressing services: Unicasting, broadcasting, multicasting channels.
  • LLC sublayer: logical links, also known as logical channels
• Network layer:
  • IP: The channel concept corresponds to a packet flow or a routing path.
  • X.25: Virtual channels.
  • Addressing services: Unicasting, broadcasting, multicasting channels.
• Transport layer: Statistical multiplexing channels
  • TCP: virtual channels, also known as virtual connections, byte streams, TCP sessions or socket-to-socket connections.
  • UDP: socket-to-socket communication path or packet flow.

Mange01 (talk) 16:38, 1 April 2010 (UTC)

Don't think a layer based division would be good as a main categorization. Several concepts are intersecting with my above categorization, which I think has a clearer separation, and amongst different layers (e.g., virtual channel, multiplexing, point-to-(multi)point).

For example, if you say this is a multiplexing channel you do not refer to a specific layer but rather to a channel implementing the concept of multiplexing. Or if you speak of a virtual channel you mean any channel within a shared medium above the PHY. Note that the latter concept is even present in multimedia files, where you e.g. can have one (or more) audio channels and one video channel. And in stereo audio, you have a left and a right audio channel.

So I think, while not as a main classification, it could work as an additional classification in the form of: Channel types corresponding to (OSI) layering concepts.

Nageh (talk) 10:25, 3 April 2010 (UTC)

Okay. THis is a suggestion for rough disposition:

1. Section 1 "Overview" can be renamed "definitions and application examples", and overlapping texts should be removed. Definitions form the literature can be added.

2. Section 2 is "Channel types", where the above OSI based division can be merged with your text.

3. Section 3 is "Channel attributes and performance measures". (Alternatively this may be part of the channel model section.)

4. Section 4 is "Mathematical channel models". Basically my text. Two sub-sections: Digital (or binary) channels, and analog channels.

Mange01 (talk) 12:27, 9 April 2010 (UTC)