QUESTION:
Can you suggest a better way of extracting a frame synchronization signal (8kHz)from E1(PDH)?
ANSWER:
The serial bit-stream for E1 corresponds to a bit-rate of 2.048 Mbps. Recovery of the bits from the bipolar (HDB3) signal requires that a clock extraction procedure be employed, namely generation of a 2.048 kHz clock signal so that the bipolar signal can be "sampled" to extract the digital nature (bits) of the information. This bit-stream is then processed to find the framing pattern following which the position of the 32 octets comprising the E1 frame can be identified within the bit-stream. If only the time-base (i.e. the frequency reference) is required, the recovered clock (2.048 MHz) can be used. It can be divided down to any convenient frequency (such as 8 kHz) without losing the inherent reference attribute.
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