Redline Communications Inc. AN100UXA 用户手册
User
AN-100U/UX Base Station
Manual
70-00058-01-04
Proprietary Redline Communications © 2010
Page 106 of 136
April 19, 2010
Q = (2,325,120 bps / 8) * 10 ms = 2,907 bytes
Uplink Connections
When an uplink UGS connection becomes active, the base station schedules recurring
unsolicited bandwidth grants for that subscriber. Pre-scheduled grants reduce the
overhead and latency associated with normal uplink poll-request-grant sequences. The
grant size is based on the UGS bandwidth requirement and the interval is based on the
latency requirement.
unsolicited bandwidth grants for that subscriber. Pre-scheduled grants reduce the
overhead and latency associated with normal uplink poll-request-grant sequences. The
grant size is based on the UGS bandwidth requirement and the interval is based on the
latency requirement.
Max. Sustained Rate: Specify the required bandwidth plus 5% (overhead).
Max. Latency: Specify the expected interval between consecutive packets.
The uplink UGS grant is calculated as follows:
Grant Interval
= Max. Latency (milliseconds)
Grant Size = Max. Reserved Rate * Max. Latency
Important: The reserved bandwidth grant is issued at regular intervals, even if there are
no packets queued on the subscriber for this connection. The grant interval is
temporarily extended x4 if no packets are received on this connection for 16 consecutive
wireless frames.
no packets queued on the subscriber for this connection. The grant interval is
temporarily extended x4 if no packets are received on this connection for 16 consecutive
wireless frames.
For example, an application is sending 400 x 610 byte packets each second in the uplink
direction and the required Max. Latency is 50 ms.
direction and the required Max. Latency is 50 ms.
Max. Reserved Rate = (400 p/s x 692 bytes * 8) + 5% = 2,325,120 bps
Grant Interval = 50 ms
Grant size = (2,325,120 bps / 8) * 50 ms = 14,532 bytes
The uplink UGS service flow will receive a grant of 14,532 bytes every 50 ms
6.4.2 Real-Time Polling Service (rtPS)
The rtPS service is next in priority after UGS. This service is designed for real-time
applications that typically send 'bursts' of variable size packets and specify maximum
packet delay (latency). Typical applications include MPEG for remote video surveillance
and VoIP with silence suppression.
applications that typically send 'bursts' of variable size packets and specify maximum
packet delay (latency). Typical applications include MPEG for remote video surveillance
and VoIP with silence suppression.
Min. Reserved Rate: The required Committed Information Rate (CIR). The setting
affects the size of the bandwidth allocation.
affects the size of the bandwidth allocation.
Max. Sustained Rate: The required Peak Information Rate (PIR). Traffic is capped at
this rate, measured per connection over a one-second interval.
this rate, measured per connection over a one-second interval.
Max. Latency: The maximum desired latency for this connection. This affects the size of
the bandwidth allocation and the interval of data transmissions.
the bandwidth allocation and the interval of data transmissions.
Inter-packet delay and jitter are typically introduced when bursts of traffic are too large to
transmit in a single wireless frame. The Max Latency setting is used to adjust the
scheduling characteristics for rtPS connections and control latency. When a latency
value is specified, the scheduler performs traffic shaping to reduce inter-packet latency
and jitter.
transmit in a single wireless frame. The Max Latency setting is used to adjust the
scheduling characteristics for rtPS connections and control latency. When a latency
value is specified, the scheduler performs traffic shaping to reduce inter-packet latency
and jitter.
The modified rtPS scheduling has the following characteristics:
When a latency value is specified, a latency factor (L) is calculated.
L = RoundDown (Max. Latency / Frame Duration ) - 2
4. The latency value is used to modify the quantum (Q), to enable sending a greater
amount of data in a single wireless frame. The intent is to provide opportunities to
transmit related packets in the same wireless frame.
transmit related packets in the same wireless frame.