Talk:Code-division multiple access

message: From the article:
The data signal with pulse duration of Tb is XOR’ed with the code signal with pulse duration of Tc. (Note: bandwidth is proportional to 1 / T where T = bit time) Therefore, the bandwidth of the data signal is 1 / Tb and the bandwidth of the spread spectrum signal is 1 / Tc. 
Why is the bandwidth proportional to 1 / T? Is that dependent on modulation? Could someone either explain why this is so, or put a link in that sentence to an article that explains why this is so. 
77.67.176.125 (talk) 20:58, 7 March 2012 (UTC)
thread_title:  Why is bandwidth proportional to 1 / T 

message: Seems like their dot product is 4.  — Preceding unsigned comment added by 50.76.46.94 (talk) 15:32, 23 March 2012 (UTC)
thread_title:  Is the diagram of 4 orthogonal signals actually orthogonal? 

message: The text claims that a Soviet mobile phone was 3 cubic metres in size. This can't possibly be correct. That's equivalent to about 106 cubic feet, or the entire interior capacity of a 2007 Ford Crown Victoria. Pburka (talk) 04:13, 10 February 2013 (UTC)
replies: text: I have added the reference to the Kupriyanovich 1957 patent to the article. Can somebody check whether it really describes a mobile phone system using what we call CDMA? I find it rather incredible. While it can be possible that the first work about code-division multiple access principle was published in 1935 by Dmitry Ageev, and that Leonid Kupriyanovich in 1957 made a working prototype of a wireless device allowing to make phone calls, and perhaps that spread-spectrum technology was used in USSR since 1970s, it is hardly true that the 1957 Leonid Kupriyanovich's device used CDMA. There was not electronic component base in 1950s to produce a device with weight of 3 kg with CDMA technology in the eastern block, and there is no reason why even the first prototype should use CDMA. I've spent some time with the text, so I can supply the corrected text of the patent in Russian language. The patent describes the device build from vacuum tubes. Kolarp (talk) 21:27, 9 July 2020 (UTC)
thread_title:  Dubious 

message: In the example box, where does the encoding step come from?
encode0 = 2(1, 0, 1, 1) – (1, 1, 1, 1) = (1, –1, 1, 1)
I see that we multiply the signal by 2 and then subtract a vector of all ones. Where does this come from? It is not clear in the explanation so 2D-V where D is the data vector and V is (1,1,1,1).
Please explain.
Thanks!  — Preceding unsigned comment added by 70.163.0.234 (talk) 13:13, 12 August 2016 (UTC)
thread_title:  Please explain the coding step in the example: 

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replies: text: It's not clear why the archived version is necessary; why is the status of the site from 2011-02-08 of more interest than the status of the site from any other day, including today? Guy Harris (talk) 07:30, 10 August 2017 (UTC)
thread_title:  External links modified 

message: In this article we have, "Due to their very advantageous auto- and crosscorrelation characteristics, these spreading sequences have also been used for radar applications for many decades, where they are called Barker codes (with a very short sequence length of typically 8 to 32)."
The text "length of typically 8 to 32" is misleading.  Listed in the Barker code article, "Only nine Barker sequences are known, all of length N at most 13."  — Preceding unsigned comment added by Rwg1975 (talk • contribs) 13:56, 30 January 2022 (UTC)
thread_title:  Barker Codes 

message: Is spread-spectrum multiple access a synonym for code-division multiple access? (see Talk:Channel_access_method#Code_division_multiple_access_(CDMA)/Spread_spectrum_multiple_access_(SSMA)) ~Kvng (talk) 17:53, 5 June 2022 (UTC)
thread_title:  Spread-spectrum multiple access