User's Manual

3 Detailed Description
40 APCD-LM043-4.0
In determining the order in which to poll the EUMs, the CCU tries to
• ensure consecutive polls of an EUM occur within the range defined by the EUM's
grade of service,
• maintain the average time between polls defined by the grade of service, and
• divide the total number of polls among EUMs consistent with the grades of service of
the EUMs being polled.
SinceitisinefficienttopollanEUMifthereisnodatatosendeitherway,anEUMcanbe
polled less often if it has not recently transmitted or received traffic. The GOS parameter set
essentially provides for independent control of the polling characteristics for both active EUMs
(those that have recently had traffic) and for inactive EUMs (those that have recently had no
traffic), where “recently” is defined by the GOS parameter set.
In addition to efficiently managing the usage of the radio link and providing differentiated
service capabilities, the polling MAC inherently smooths the upstream (EUM-to-CCU) packet
arrival times. It also has a smoothing effect on the downstream traffic arrivals, which positively
impacts network performance by reducing
• surges in data traffic,
• transients in queue occupancy, and
• packet discards.
GOS Configuration Files
Each GOS is defined by configuration files that are stored in the CCU. The CCU can maintain
up to five GOS configuration files, consisting of
• up to four assignable GOS configuration files, and
• one GOS configuration file for broadcast messages.
The operator assigns each EUM to one of the four assignable GOS configuration files, which
have the fixed labels of Gold, Silver, Bronze, and Best Effort. Although the labels are fixed, the
actual service level is determined by the configuration file that is associated with label.
Although only four assignable GOS configuration files can exist simultaneously in the CCU,
each of these files can be readily changed by FTPing a new configuration file to the CCU, to
replace the existing one. This change can be done while the CCU is active and takes effect
immediately.
As specific requirements are identified, WaveRider creates and makes available sets of
predefined configuration files. To illustrate the operation of the GOS configuration files, the
performance of the factory default GOS service levels is summarized in Table 8. This default
GOS configuration file is tailored for networks consisting of both residential and business-class
users.