Discussion Assignment Unit 2 CS 2204-01 Communications and Networking - AY2023-T5 University of the People Majd Alhaddad What are the various problems that could arise in Non-Return to Zero (NRZ) encoding if a continuous stream of 0s or 1s is sent? The first step is to turn nodes and links into usable building blocks by understanding how they are connected in such a way that bits can be transferred from one node to another, where signals propagate through physical links, and the binary data that the source node wants to send is encoded into signals that the links can carry, and then decoded. encoding the signal back into the corresponding binary data at the receiving node, you can ignore the modulation details and assume you are working with two separate signals: high and low, but in practice these signals may correspond to two different voltages on a copper link, or two different levels of power on an optical link, or two different capacities on the radio transmission. Most of the functions in this article are implemented by the network adapter which is a piece of hardware that connects between a node and a link. The network adapter contains a signal component that actually encodes bits into signals at the transmitting node and decodes the signals into bits at the receiving node , where the signals are transmitted through a link between the two signal components, and the bits flow between the network adapters as shown in the following figure: Signal Components Node Network Adapter Signal Network Adapter Node Bits Coming back to the problem of encoding bits into signs, the obvious thing to do is associate 1 with high and 0 with low, and this is exactly what a cryptic enough scheme called non-return to zero, abbreviated to NRZ, uses as an example graphically The NRZ encoded signal (bottom) corresponding to the transmission of a specific string of bits (top): 0 1 0 0 0 0 1 0 1 1 1 1 0 1 0 0 Bits 1 - 1 1 1 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 1 1 NRZI encoding
The problem with NRZ encoding is that there is a series of consecutive ones, which means that the signal remains high on the link for a long period of time. Likewise, the presence of several consecutive zeros indicates that the signal remains low for a long time. There are two main problems caused by long strings of ones or zeros. The first problem leads to a condition called basic wandering, where the receiver keeps precisely the average of the signal it has seen so far, and then uses that average to distinguish between low and high signals, so the receiver concludes that it has just seen a zero. When the signal is well below this mean, likewise a signal