Redline Communications Inc. SC1000E 用户手册

Doc #70-00100-01-00-DRAFT 

Proprietary Redline Communications © 2009  

Page 51 of 60 

January 7, 2009 

16 QAM 1/2 

15.3 / 30.4 

6.2 / 12.5 

3.1 / 3.0 

1.2 / 1.3 

QPSK 3/4 

7.6 / 15.3 

4.7 / 9.4 

1.5 / 1.5 

0.9 / 0.9 

QPSK 1/2 

7.6 / 15.3 

3.1 / 6.2 

1.5 / 1.5 

0.6 / 0.6 

BPSK 1/2 

3.9 / 7.6 

1.6 / 3.1 

0.8 / 0.8 

0.3 / 0.3 

 

Important: To minimize inter-sector RF interference, synchronization must be 
used to coordinate RF transmissions of base stations. 

The IEEE 802.16 standard calls for the use of GPS (Global Positioning System) 
receivers to provide the precise time reference for synchronization of WiMAX networks. 
Operating in TDD mode, the base station and the subscribers transmit at the same 
frequency, and require precise synchronization between downlink and uplink 
transmissions. Proper coordination of these activities is required to minimize interference 
and ensure the best overall system performance. 

The base station uses the GPS 1 PPS signal to set the frequency of the TCM onboard 
clock. This TCM reference clock is used when broadcasting a radio frame 
synchronization signal to all BBM and RRH modules. If the 1 PPS signal becomes 
unavailable at any base station, that TCM enters 'holdover mode' to maintain the highest 
accuracy until the GPS signal can be restored. 

GPS reference clock systems require that a receiver be placed at each base station and 
that the GPS antenna have line-of-sight satellite access. Ideally, a GPS antenna should 
be mounted on a rooftop with a full 360º view of the sky, but often an antenna mounted 
on the side of a building or a tower with a 180º view of the sky is adequate. 

The base station provides the following synchronization schemes. 

The GPS component is an integrated GPS receiver/antenna module. Signal input is 
through an RS-232 cable connected to the Serial 1 port on the TCM front panel. 
Recommended for short cable runs (~20m).