Motorola PTP 500 User's Guide download pdf (Page 47)

3 Product Features

3.9 Telecoms Circuits

The PTP 500 link provides native support for one E1 link, or one T1 link. The link relays

unstructured E1 or T1 data and provides accurate timing transfer.

3.9.1 Lowest Telecoms Modulation Mode

In narrow channel bandwidth and lower modulation modes, the link may have insufficient

capacity to relay the E1/T1 payload; in this case, the wireless link continues to carries timing

information in order to maintain accurate clock synchronization. The relay of telecoms data

resumes automatically when the link reaches a suitable modulation mode.

Links that are able to operate consistently in a high modulation mode can take advantage of

lower link latency. This option is configured by setting the "Lowest Telecoms Modulation

Mode" during installation. Appropriate settings for this control may be determined by using the

LINKPlanner tool. The reduction in latency is achieved by disabling the relay of telecoms data

in lower modulation modes, and this necessarily results in somewhat lower availability for the

telecoms circuit. The loss of availability can be estimated using the LINKPlanner.

The unit will override the user setting of Lowest Telecoms Modulation Mode if the selected

mode has insufficient capacity to carry the telecoms data, or if the mode demands very high

latency and requires more buffering than the link can provide. When the effective mode differs

for Single and Dual Payload operation two modes will be displayed: "Lowest Dual Payload

Modulation Mode" and "Lowest Single Payload Modulation Mode".

3.9.2 Fixed Frequency Operation

In the PTP 500 link, data errors may occur during channel changes on an operational link. It

may be appropriate to minimize channel-change-related errors in a link carrying Telecoms

traffic by preventing channel changes initiated by i-DFS. This can be achieved by barring all

channels except one in the Spectrum Management page, or alternately by selecting Fixed

Frequency mode. These steps disable interference avoidance mechanisms, and should not

be taken if the risk of errors due to interference is more severe than the risk due to channel

changes.

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Motorola PTP 500 User's Guide Page 47