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 Bipolar encoding is a line coding technique used in digital communication systems to transmit binary data over communication channels. It's also known as Alternate Mark Inversion (AMI) or Pseudoternary encoding.
-In bipolar encoding, each binary 1 is represented by alternating voltage levels, while binary 0 is represented by no change in voltage. Unlike other line coding schemes, such as unipolar encoding where only one voltage level is used to represent binary 1, bipolar encoding alternates between positive and negative voltage levels to represent binary 1s. This helps in maintaining a balance between positive and negative voltages, which is beneficial for systems sensitive to DC components.
-Here's how bipolar encoding works:
-. **Polarity Alternation**: Each binary 1 is represented by alternating positive and negative voltage levels. The first binary 1 is represented by a positive voltage level, the next binary 1 by a negative voltage level, and so on. Binary 0s do not cause a change in voltage.
-. **Zero Substitution**: To ensure sufficient signal transitions for clock recovery and error detection, bipolar encoding uses a technique called zero substitution. In zero substitution, each consecutive sequence of zeros is replaced with a sequence of zeros with no voltage change (neutral state), followed by a signal transition to maintain clock synchronization.
-. **DC Balance**: Bipolar encoding ensures that the average DC voltage level over time remains close to zero by balancing the number of positive and negative voltage levels used to represent binary 1s.
-Bipolar encoding offers several advantages:
-- Efficient use of bandwidth: It requires only two voltage levels, positive and negative, which allows for efficient use of the available bandwidth.
-- DC balance: It maintains a balance between positive and negative voltage levels, making it suitable for transmission systems that are sensitive to DC components.
-- Error detection: It allows for the detection of errors caused by signal distortion or noise, as any deviation from the expected transitions can be detected.
-Bipolar encoding is commonly used in various communication systems, including T1 and E1 digital transmission systems, as well as in older versions of Ethernet. However, it's important to note that bipolar encoding requires additional hardware or software to convert between binary and bipolar representations, which can add complexity and overhead to digital systems.