Redline Communications Inc. AN100UXA 用户手册
User
AN-100U/UX Base Station
Manual
70-00058-01-04
Proprietary Redline Communications © 2010
Page 101 of 136
April 19, 2010
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6.1
Overview
There are several challenges when transporting traffic over a WiMAX interface:
1. Some jitter and delay is necessarily introduced by the half-duplex operation of the
TDD (time division multiplex) wireless interface.
2. Designating quality of service (e.g., priority, throughput, and latency) settings for
specific connections affects all other traffic.
3. Additional factors include state of the wireless interface, uplink/downlink ratio, frame
size, management traffic, queue sizes, distribution of bandwidth between
subscribers, and special services including subchannelization.
subscribers, and special services including subchannelization.
This document describes the function of the RedMAX wireless traffic scheduling
algorithm, the types of traffic being scheduled, and the effects of Quality of Service
(QoS) settings.
algorithm, the types of traffic being scheduled, and the effects of Quality of Service
(QoS) settings.
For each connection type, the minimum rate, maximum rate, and latency are important
factors used in scheduling traffic. Understanding the characteristics of each connection
type and associated settings can help operators configure the system for optimum
operation.
factors used in scheduling traffic. Understanding the characteristics of each connection
type and associated settings can help operators configure the system for optimum
operation.
Notes:
Throughout this document, service flows are referred to as 'connections'.
In all cases except uplink UGS, unused connection bandwidth is always recovered for
use by other connections or services.
6.2
Scheduling Factors
The base station schedules the transmission of all data sent over the wireless interface.
This centralized scheduling eliminates contention, increases predictability, and provides
the maximum opportunity for reducing overhead. The scheduling algorithm is functionally
the same in the base station and subscriber, except that subscribers must request and
receive uplink bandwidth grants from the base station before transmitting uplink traffic.
Subscribers are not guaranteed to receive requested bandwidth.
This centralized scheduling eliminates contention, increases predictability, and provides
the maximum opportunity for reducing overhead. The scheduling algorithm is functionally
the same in the base station and subscriber, except that subscribers must request and
receive uplink bandwidth grants from the base station before transmitting uplink traffic.
Subscribers are not guaranteed to receive requested bandwidth.
6.2.1 Bandwidth Margin
The sector wireless bandwidth capacity is evaluated in real-time by monitoring the
modulation and coding rates for all subscribers. The sector capacity is compared to the
total committed bandwidth requirements (Min. Sustained Rate) for all UGS, rtPS, and
nrtPS connections and the results are reported as uplink and downlink bandwidth
margins. These values can be monitored using SNMP and HTTP (Wireless Status
page). The margin values are updated to reflect changing conditions on the wireless link
(e.g., interference) and of connections being added and deleted.
modulation and coding rates for all subscribers. The sector capacity is compared to the
total committed bandwidth requirements (Min. Sustained Rate) for all UGS, rtPS, and
nrtPS connections and the results are reported as uplink and downlink bandwidth
margins. These values can be monitored using SNMP and HTTP (Wireless Status
page). The margin values are updated to reflect changing conditions on the wireless link
(e.g., interference) and of connections being added and deleted.