Transmission rate of information

Discussion in 'Homework Help' started by Guitarras, Apr 10, 2011.

  1. Guitarras

    Thread Starter New Member

    Dec 10, 2010
    14
    0
    Hi.

    Here is a simple question of transmission rates and bandwidth.

    A signal source is sampled, quantified and coded in PCM. Each sample is coded into words of three impulses of information and a adicional synchronism impulse. The impulses of information can assume one of four possible levels. The transmission is made through a channel with 6KHz of bandwidth, using raised cosine impulses with roll-off factor of 50%.

    Determine the maximum transmission rate of the impulses PCM, the matching transmission rate of information and the maximum bandwidth allowed for the analog source. (Solution: Rmax=8000 impulses/s; Rinformation=12 Kbps; Wmax=1KHz)

    My attempt:

    Raised Cosine a=0.5
    Wtransmission=(Rmax/2)*(1+a)
    Rmax=(2*6K)/(1+0.5)=8000 impulses/s

    1 sample have 4 impulses (3 of information + 1 synchronism). Each impulse of information can assume 1 of 4 levels.
    Rinformation=(3/4)*8000*4=24 Kbps

    Shannon's Theorem fsampling >= 2*fmax
    fsampling=(8000 impulses/s) / (4 impulses/sample) = 2000 samples/s
    fmax <= fsampling/2
    fmax <= 2000/2 = 1000 Hz

    Can someone explain me how to solve this problem?

    Thanks in advance.
     
  2. Guitarras

    Thread Starter New Member

    Dec 10, 2010
    14
    0
    I figured out how to solve this.

    We have 3 impulses of information in 4 impulses (one sample). Each impulse of information can assume 1 of 4 levels. For example, 00 01 10 11. Well, we need 2 bits.
    Rinformation=(3/4)*8000*2=12Kbps

    /Solved
     
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