Section 1 TRACER Description
Direct Sequence
A direct sequence transmitter spreads the signal by mixing the data with the output of a pseudorandom number generator which changes state at a rate higher than the data rate. This rate is called the “chipping” rate. The TRACER chipping rate is twelve times the data rate.
Coding
Many different pseudorandom sequences exist. The sequences are called pseudorandom because, although they appear
Channel Selection
The FCC has allocated 83.5 MHz of spectrum in the 2.4 GHz band and 125 MHz in the 5.8 GHz band in which TRACER operates. A TRACER system fully uses the available bandwidth – transmitting in one half and receiving in the other. Figure
2400 MHz | 2441 MHz | 2483.5 MHz |
| or |
|
5725 MHz | 5787 MHz | 5850 MHz |
Figure 1-2. Bandwidth Division
The transmitter at one end of a link (TxA) will transmit in the lower half of the spectrum. Consequently, the receiver at the other end will receive in the lower half of the band and transmit in the upper half. Thus, a system will operate in one of two frequency plans
Forward Error Correction
With the addition of overhead data, error detection and correction capability can be added to a data stream. Error correction can be accomplished by allowing the receiver to request to retransmit of the erred block once detected. The TRACER, on the other hand, implements forward error correction (FEC) which adds enough overhead data for the receiver to detect and correct errors in the data stream. This capability comes at the cost of bandwidth. The addition of FEC decreases the required
2 | TRACER 2 x E1 User’s Manual |