3.1 NEC WiMAX Base Station Transceiver System (BTS)
The NEC WiMAX base-station hardware is a 5U rack based system which consists of multiple Channel Cards (CHC) and a Network Interface Card. The shelf can be populated with up to three channel cards, each supporting one sector for a maximum of three sectors. The BS operates in the 2.5 Ghz or the 3.5 Ghz bands and can be tuned to use either 5, 7 or 10 Mhz channels. At the MAC frame level, 5 msec frames are supported as per the 802.16e standard. The TDD standard for multiplexing is supported where the sub-channels for the Downlink (DL) and Uplink (UL) can be partitioned in multiple time-frequency configurations. The base-station supports standard adaptive modulation schemes based on QPSK, 16QAM and 64QAM. The interface card provides one Ethernet Interface (10/100/1000) which will be used to connect to the high performance PC used to control the device. The base station has been tested for radio coverage and performance in realistic urban environments and is being used in early WiMAX deployments – typical coverage radius is ~3-5Km, and peak service bit-rates achievable range from 15-30 Mbps depending on hardware configuration of the line cards, operating mode and terrain.