User Manual

Chapter 1 - System Description The Base Transceiver Station
4Motion 17 System Manual
 Keep-alive signaling towards the BS for enhanced service availability.
When several shelves are collocated, the NPU cascade interface can be used for
shelf interconnection. In this architecture, the NPU that is directly connected to
the backhaul implements a layer-2 connection toward the NPUs in the cascaded
shelves. Bearer, control and management traffic is sent over the cascade
connection. Synchronization and GPS backup power are sent toward the NPUs in
the cascaded shelves through the GPS/SYNC ports.
GPS synchronization cascading will be implemented in a future release.
1.3.3 AU
The Access Unit module performs the WiMAX/IEEE 802.16e BS function
according to the NWG Profile C definitions via digital signal processors (DSPs) and
field-programmable gate array (FPGA) technology. The AU module is designed to
support high-traffic throughput and enable diversity, MIMO and AAS, thereby
extending capacity and range.
The AU implements the following functionality:
 802.16e multi-channel OFDMA PHY
 Up to four-channel support (Tx/Rx)
 Diversity and future AAS
 Flexible channel bandwidth - up to 20 MHz
 Flexible FFT size - up to 2048 points
 Wide variety of reuse patterns
 Advanced channel coding (CTC)
 HARQ
 Rate adaptation
 High-performance CDMA detector
 IF interface to RF ODU
 MAC-PHY interface