Tutorial 25 – Spread spectrum and CDMA

Description: Spread spectrum and CDMA

Download: CDMA.pdf

2 comments on “Tutorial 25 – Spread spectrum and CDMA
  1. hemanth says:

    this material is very good for understanding i really liked the tutorials very much and i request you to post more tutuorials on communication

  2. Zefyr says:

    First off, I really appreciate the effort and lucidity with which these topics have been addressed. It really helps to get a physical feel for such mathematical topics which is important.
    I have a question about EVDO. From what I’ve read on the forward link, this uses TDM. There also seems to be some spread spectrum but I do not understand it.But is there a spreading gain also?
    I don’t understand for example how the 38.4 Kbps rate using config of (1024,16,1024) is generated. The generic transmit block diagram shows the incoming data bits being split into 16 streams each at 76 ksym/sec and then each spread by a factor of 16 and then summed. Is this spreading or just 16-ary Walsh coding?
    So how do I know what the spreading gain for the 38.4 Kbps stream is versus a higher bit rate stream. If incoming streams are always at 1.228 Mcps/sec and then split into 16 streams and spread- is this really any spreading gain??
    Also how is a single packet sent over 16 slots. Is it just repetition coding- that does not seem like it would provide the negative SNRs.

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