User guide

Canopy System User Guide Understanding Bandwidth Management
pmp-0229 (Mar 2013)
83
This Registration Grant includes the air delay (distance) between the AP and SM. The SMs are at
various distances from the AP, and each of them uses its air delay value to determine when to
begin its uplink transmission. This results in uplink transmissions from multiple SMs at various
distances all being in sync when the AP receives them.
Data Transfer Capacity
Modules use Time Division Duplex (TDD) on a common frequency to divide frames for uplink
(orange) and downlink (green) usage, as shown in Figure 24.
Time
Figure 24: TDD dividing frames
Maximum Information Rate (MIR) Parameters
Point-to-multipoint links use the following four MIR parameters for bandwidth management:
• Sustained Uplink Data Rate (kbps)
• Uplink Burst Allocation (kb)
• Sustained Downlink Data Rate (kbps)
• Downlink Burst Allocation (kb)
You can independently set each of these parameters per AP or per SM.
Token Bucket Algorithm
The software uses a token bucket algorithm that
• stores credits (tokens) for the SM to spend on bandwidth for reception or transmission.
• drains tokens during reception or transmission.
• refills with tokens at the sustained rate set by the network operator.