Redline Communications Inc. AN100UXA 用户手册
User
AN-100U/UX Base Station
Manual
70-00058-01-04
Proprietary Redline Communications © 2010
Page 107 of 136
April 19, 2010
Q = (Min. Reserved Rate * Frame Duration / 8) * ( L + 1 )
5. When packets have been transmitted in a wireless frame, the connection will not
receive any bandwidth allocation during the next L-1 sequential wireless frames. This
delay ensures the total throughput for the connection does not exceed the Max.
Sustained Rate.
delay ensures the total throughput for the connection does not exceed the Max.
Sustained Rate.
Generally, the scheduler should be able to send data for an rtPS connection in every
wireless frame when
wireless frame when
Max. Latency < 3 X Frame Duration.
The following tests may be
applied to validate that the desired latency can be achieved:
The downlink latency requirements can be achieved only when both of the following
conditions are true (w
here UL ratio may be from 0.15 to 0.75)
:
i) Burst_Size_Bytes <= Q * (L+1)
ii) Max. Latency >= Min [Frame Duration * 2, Frame Duration * (%UL ratio +1.5)]
6. Latency settings are ignored under the following condition:
(
Max. Latency < 3 * Frame Duration
)
The following formulas can be used to estimate the expected latency. Use the table
below to determine the time required to transmit the data.
below to determine the time required to transmit the data.
Latency
Min
= 2.4 ms + (T
FrameRate
* UL %) + (PDU
Ref
/ 1000 * T
Rate
)
Latency
Max
= Latency
Min
+ T
FrameRate
Table 53: Approximate Time to Transmit 1K Bytes @ Modulation/Coding
Modulation
&
Coding
Bytes/
OFDM
OFDM
Symbol
Time to Send 1K Bytes (ms)
CP=3.5 MHz
CP=1/4
CP=3.5 MHz
CP=1/16
CP=7 MHz
CP=1/4
CP=7 MHz
CP=1/16
64 QAM 3/4
108
0.74
0.64
0.37
0.31
64 QAM 2/3
96
0.83
0.71
0.42
0.35
16 QAM 3/4
72
1.1
0.94
0.56
0.47
16 QAM 1/2
48
1.7
1.4
0.83
0.71
QPSK 3/4
36
2.2
1.9
1.1
0.94
QPSK 1/2
24
3.3
2.8
1.7
1.4
BPSK 1/2
12
6.7
5.7
3.3
2.8
Example: Consider a connection with the following settings:
Min. Reserved Rate = 409,600 bps
Frame Duration = 10 ms
Max. Latency = 65 ms
L = RoundDown (55 ms / 10 ms) - 2 = 3
Q = (409,600 bps * 10 ms / 8) * (3 +1) = 2,048 bytes
The scheduler assigns a quantum of 2,048 bytes (versus 512 bytes when latency is not
specified). This allows up to four times the data throughput and related packets can be
transmitted together in the same wireless frame. No bandwidth will be allocated to this
connection for the next three consecutive wireless frames, and then the pattern repeats.
The latency and bandwidth settings can be adjusted to ensure a 'best fit' for the
application.
specified). This allows up to four times the data throughput and related packets can be
transmitted together in the same wireless frame. No bandwidth will be allocated to this
connection for the next three consecutive wireless frames, and then the pattern repeats.
The latency and bandwidth settings can be adjusted to ensure a 'best fit' for the
application.