7/28/2019 How Many Cells
1/1
How Many Cells?
When trying to figure out how many of these 53-byte cells we can
transport per second we
need to look at the capacity of the link.
An E1 line can transport 2.048 Mbps, in the form of 32
timeslots. Two of these timeslots are
used for signalling and set-up, leaving 30 for the transport of
the ATM cells, or 2.048 * (30/32)
= 1.92 Mbps for transport.
Next we convert to bytes, and see that the E1 line can transport
240 kBps. Seeing as each
ATM cell is 53 bytes long it is a simple calculation to see that
the E1 line can transport:
240000 / 53 = 4528 ATM cells per second.
An STM-1 line can transport 155.55 Mbps, with a throughput of
149.76 Mbps once the
overheads are discounted. Again we convert to bytes, calculating
a throughput of 18720
kBps. From this an STM-1 line can transport 18720000 / 53 =
353207 ATM cells per
second.
RNC
SGSN
MGW
E1 links 4528ATM cps STM-1 links 353207 ATM cps
