Red
MAX
™
Base Station
user manual
Doc. #70-00058-01-01-DRAFT
Proprietary Redline Communications © 2006
November
29,
2006
Page 23 of 106
2.7.4 Scheduling
The base station enforces QoS settings for each service flow by controlling all uplink and
downlink traffic scheduling. This provides non-contention based traffic model with
predictable transmission characteristics. By analyzing the total of requests of all
subscribers, the base station ensures that uplink and downlink traffic conforms with the
current service level agreements (SLAs). Centralized scheduling increases predictability
of traffic, eliminates contention, and provides the maximum opportunity for reducing
overhead.
A regular period is scheduled for subscribers to register with the base station. These
subscribers may be newly commissioned or have been deregistered due to service outage
or interference on the wireless interface. This is the only opportunity for multiple
subscribers to transmit simultaneously.
Real-Time Polling Service (rt-PS)
The base station schedules a continuous regular series of transmit opportunities for the
subscriber to send variable size data packets. The grant size is based on the current data
transfer requirement. Typical applications include streaming MPEG video or VOIP with
silence suppression. This is efficient for applications that have a real-time component and
continuously changing bandwidth requirements.
Non-Real-Time Polling Service (nrt-PS)
The base station schedules regular transmit opportunities for the subscriber station to
send variable size data packets. Typical applications may include high bandwidth FTP.
The polling period may typically be one second or less, even during periods of network
congestion.
Best Effort (BE)
The base station schedules transmit opportunities for the subscriber to send traffic based
on unused bandwidth after all higher level traffic scheduling requirements are serviced.
Typical applications may include Internet access and email. Best effort service flows can
be assigned a priority of 0 to 7.
Unsolicited Grant Service (UGS)
The base station schedules a continuous series of transmit opportunities for the subscriber
station to send fixed size data packets. This schedule supports real-time applications
including VoIP or TDM transport. The UGS pre-scheduled grants guarantee reserved
bandwidth and reduce latency introduced by repetitive grant requests. The service flow
will not transmit packets larger than nominal grant interval.
Traffic Scheduling Algorithm
The base station scheduling algorithm uses two scheduling passes. On the first pass, the
scheduler attempts to allocate bandwidth to meet the minimum rates for all active service
flows. If there is available bandwidth remaining at the end of the first pass, the scheduler
executes a second pass and attempts meet all specified maximum rates. During both
passes, bandwidth allocations are assigned based on the following order of assessment: