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How is the BTS connected to the BSC?

  1. Feb 6, 2014 #1
    I have a bachelors in electrical engineering but doing an internship at a telecom place. My opinion after 3 weeks is that the telecom industry doesn't require much science background, I feel. I started at BTS sites installing GSM and 3G (CDMA) antennas, ran feeders/fiber optics into the radio frequency units (RFU) of the BTSs. I was later part of the transmission team that installed microwave link antennas. Here I found something I could relate to from my electromagnetics classes (antenna radiation pattern diagrams) even when the guys installing them had no idea what they meant. All they cared about was establishing a line of sight with another parabolic antenna. Later I moved to the BSC where I saw how links were made to the different BTSs via the LAPDm protocol.
    The part I didn't understand is how are the BTS and the BSC interfaced. I kept hearing about E1 connection. I know what the E1 link is; that it has 32 channels; that it has a data rate of 2Mbps etc. What I don't seem to understand is:
    1) Why is E1 used and not ethernet for example ?
    2) How is the E1 connected ?
    3) How many TRX can the E1 support ?

    I went to the BSC cabinet rooms and was shown a rack of ports which are used to connect to the E1s.
    4) How does a specfic port at the BSC know which E1 it is connecting to when the typologies used are ring and cascade ?

    I have limited knowledge on E1s. I have searched google but couldn't find anything to explain my questions. Please provide answers if you can.

  2. jcsd
  3. Feb 6, 2014 #2


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