4.3. Ranging codes

It is a requirement for navigation systems that the distance of the transmitting satellite from the receiver be estimated by the latter. From this measured distance, position fixing is done. Plus, in CDMA-based systems, signals from multiple satellites need to be received by the receiver simultaneously in the same carrier frequency without interference between them. These requirements must be fulfilled in addition to the basic criterion of secured transmission of the data.
All these may be easily achieved by using a simple technique: by multiplying the data bits with a pseudo random binary sequence. This is a term we are using for the first time. We will learn it in the next section in more details.
Broadly, the pseudo random ...

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