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DUS 31 » History » Version 3

laforge, 11/03/2020 03:31 PM

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h1. DUS 31
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{{>doc}}
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The DUS 31 is the first digital unit (we know) which supported multi-standard on the same DU.  As you can run both LTE and GSM on the same unit, it basically combines a DUL and a DUG.
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The GSM back-haul is no longer exposed via E1/T1 TDM lines, but uses _Ericsson PacketAbis over IP_, which is basically the L2TP/HDLC based protocol stacking that the [[SIU 02]] or the [[TCU]] would have traditionally generated.
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h2. Mass Storage
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The unit has an internal 8GB USB Mass Storage device, as a _Micron Embedded USB Mass Storage Drive (e230)_. You can think of it as a USB thumbdrive, but not with an exterenal USB A plug, but with a 9-pin 2-row 2.54mm pitch receptacle, which can be plugged directly onto USB 2.0 headers on mainboards.
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The partition table looks as follows:
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<pre>
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Disk ./dus31.dd: 7.56 GiB, 8120172544 bytes, 15859712 sectors
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Units: sectors of 1 * 512 = 512 bytes
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Sector size (logical/physical): 512 bytes / 512 bytes
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I/O size (minimum/optimal): 512 bytes / 512 bytes
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Disklabel type: dos
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Disk identifier: 0x00000000
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Device      Boot   Start      End  Sectors   Size Id Type
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./dus31.dd1            4  1999999  1999996 976.6M 21 unknown
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./dus31.dd2      2000000 13999999 12000000   5.7G 21 unknown
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</pre>
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h2. LMT cable
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The DUS31 combines the serial UART (traditionally "LMT A") and the management ethernet port (traditionally "LMT "B) in a single RJ45 connector.  You need a special breakout cable to split those two signals.   As it is a purely mechanical/electrical adapter without any active parts, it's relatively easy to build one DIY.
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TODO: connector layout
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We have created a small OSHW circuit board design of a break-out board, its design files can be found at https://git.osmocom.org/osmo-small-hardware/tree/dus-lmt-breakout
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