Base Station (BS)

The following diagram shows a general view of the Base Station.

Figure 6. Base Station General View

The Base Station consists of several sectors (up to 12 sectors can cover a single cell). Each sector contains one or more (up to 16) Basic Units (BU), an IF MUX, RFU and an antenna.

Basic Unit (BU)

The main building blocks of the BU are: the modem, the telecom interface cards and the IF module. Each BU converts the IF signal to telecom voice/data towards the telecom port, and vice verse.

The modem is implemented on the motherboard, which is identical on all BUs. The interface cards and the IF module are implemented on daughterboards, and therefore allow maximum flexibility.

Each BU contains up to three interfaces to the telecom switches (ISDN, Frame Relay, etc.). Each BU transmits and receives one FDMA carrier and, by employing TDMA mechanism, handles the traffic of several remote Terminal Station (typically 2-10, maximum 16). All BUs are loosely connected via the IF MUX, for monitoring and control purposes only; in this manner, malfunctioning of a single BU does not affect the others.

IF MUX

The IF MUX combines the IF signals from/to the various BUs into a single coax cable that goes up to the roof top, where the RF and antenna subsystem are located. Up to 16 BU may operate together combined by the same IF-MUX.

RFU

The RFU converts the IF to RF, amplifies the signal to its right level and transmits it through the antenna. It is mounted near the antenna. The system has more than one type of an RFU, each serving a different radio frequency band. WALKair supports 3.5 GHz, 10.5 GHz and 26 GHz bands. All RFUs are isolated from the indoor equipment, and operate with the same BU and IF-MUX.

Date: 2015-01-11; view: 580