User guide

Understanding Bandwidth Management Link Characteristics
90
pmp-0229 (Mar 2013)
• The amount of noise and multipath must be low enough to allow the receiver in the 6 dB less
sensitive (2X) state to maintain a high carrier-to-interference (C/I) ratio.
The flexibility of this feature is as follows:
• At the time of registration, signaling is at the 1X rate. However, if the above requirements are
all met, then the SM switches to 2X.
• Thereafter, whenever RF conditions are unfavorable for 2X operation, the SM switches to 1X.
When favorable RF conditions allow, the SM switches back to 2X, if user data is present at
that time.
• Similarly, whenever no user data is present, the SM switches to 1X. When user data flow
resumes, the SM switches back to 2X, if RF conditions allow.
• Both links for the SM (uplink and downlink) are independent for this feature. (One can be
operating at 2X operation while the other is operating at 1X.)
• Other SMs in the sector can be communicating with the AP at the other modulation rate.
• Although subscribers with CSM 120s realize higher bursts, and subscribers with CSM 130s
and CSM 09130s realize both higher burst and higher sustained throughput, the network
operator realizes higher sector throughput capacity in the AP.
The effect of 2X operation on aggregate throughput for the SM is indicated in Table 22.
Table 22: Effect of 2X operation on throughput for the SM
Type of SM
Typical Aggregate Rates
1
Sustained
2
Burst
2
CSM 09130 4 Mbps 4 Mbps
CSM 120 with at least
P9 Hardware Series
7 Mbps 14 Mbps
CSM 54400 14 Mbps 14 Mbps
NOTES:
1. Subject to competition among all SMs in the sector.
2. Can be less if limited by the value of Downlink Data set
in the Radio tab of the Configuration page in the AP.