symbol periods

Discussion in 'Wireless & RF Design' started by jlatshaw, Nov 24, 2014.

  1. jlatshaw

    Thread Starter New Member

    Jul 20, 2013
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    Hi,
    I was reading this article about Zigbee, and I noticed a lot of mentions about symbols and symbol periods. My question is, how do symbols relate to packets of information?

    Also, do you know how many bits of information are typically sent over the course of a packet/ symbol?

    Thanks,
    James
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,142
    1,790
    Good question. Boolean logic uses two symbols, referred to as HIGH and LOW, ON and OFF, or '1' and '0'. A binary, or two valued logic system is not the only one possible. In a three valued logic system you might use the symbols '0', '2', and '4' as the do in the 802.4 standard. The information content of a three values system is log to the base 2 of 3. To figure out what Zigbee is doing you will have to dig deeper.
     
  3. jlatshaw

    Thread Starter New Member

    Jul 20, 2013
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    0
    Thank you for your response!
    So basically, one symbol is equal to one bit of information?

    On the table on that article, I see that it says:
    aBaseSlotDuration 60 symbol periods

    Does this mean that a packet is 60 symbols long?

    And is a packet the same as a super frame?

    Thank you so much,
    James
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,142
    1,790
    Not necessarily. One symbol can encode multiple bits. One symbol equals one bit ONLY for a system with two unique symbols. If there a 64 uniques symbols the the information content is 6 bits per symbol. Get the idea?
     
  5. jlatshaw

    Thread Starter New Member

    Jul 20, 2013
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    Ok, yes that does make sense. Alright, so I think I might understand it now. Back to the table on that webpage, I see there's a mention of:
    PHY acknowledgement frame length 11 octets
    PHY beacon frame length 23--100 octets
    PHY data frame length 15--133 octets


    I believe that an octet is a group of 6 bits, so this would imply that the actual packet (or super frame) is 11+100+133 octets or 1.464 kb in length. Am I right about this?
    And if this is all true, then I would just have 11+100+133=244 symbols per packet, right?

    Thank you so much for your time,
    James
     
  6. jlatshaw

    Thread Starter New Member

    Jul 20, 2013
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    Sorry, I just realized an octet is 8 bits. So instead of 1.464kb I meant 1.952 kb.
     
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