Digital Communication #8. Polar: Manchester & Differential Manchester & Bipolar: AMI & Pseudoternary скачать в хорошем качестве

Digital Communication #8. Polar: Manchester & Differential Manchester & Bipolar: AMI & Pseudoternary

Digital Communication playlist.    • Digital Communication #3. Receiver End: Do...   For access to this presentation materials, membership is required: I need the Material PPT Sent me an email to Technologies.Discussion@gmail.com If you need the whole playlist material, send me email and we discuss. Give me some time to response. Thanks. Manchester Encoding: Transition in the middle of every bit period. Falling edge (+ to ) = '1', Rising edge ( to +) = '0' (IEEE 802.3 standard). Pros: No DC component. Excellent synchronization (guaranteed transition per bit). Cons: Bandwidth requirement is double that of NRZ. Used in: Ethernet (10 Mbps), RFID, NFC. Manchester Manchester encoding is a combination of the RZ (transition at the middle of the bit) and NRZ-L schemes. The duration of each bit is divided into two halves. The voltage remains at one level during the first half and moves to the other level in the second half. The transition at the middle of the bit provides synchronization. Note: The Manchester encoding logic we are using is as follows: For bit 1, there is a transition from -V to +V volts in the middle of the bit period. For bit 0, there is a transition from +V to -V volts in the middle of the bit period. Differential Manchester Encoding: Transition in the middle is always present (for clocking). The presence or absence of a transition at the START of the interval encodes the data. No transition at start = '1', Transition at start = '0'. Pros: More noise-immune than Manchester (data depends on transition, not absolute level). Used in: Token Ring LANs. Differential Manchester Differential Manchester is a combination of the RZ and NRZ-I schemes. There is always a transition at the middle of the bit, but the bit values are determined by the presence or absence of a transition at the start of the bit period. A transition at the start indicates a 0, while no transition indicates a 1. For differential Manchester in this example, we assume the signal level before the start of the data sequence "010011" was positive. Therefore, a transition occurs at the beginning, and the first bit "0" in the current data set "010011" starts from -V. Example data: 010011 Bipolar / Alternate Mark Inversion (AMI) Uses three voltage levels: +V, 0, -V. '0' is represented by zero voltage. '1's (marks) are represented by alternating +V and -V. Pros: No DC component. Long strings of 1s remain synchronized. Error detection: A violation of the alternating rule indicates an error. Cons: Long strings of 0s still cause loss of sync. Used in: Older T1/E1 carrier systems (with additional scrambling). Bipolar schemes - In this scheme there are 3 voltage levels, positive, negative & zero. The voltage level for one data element is at zero, while the voltage level for the other element alternates between positive and negative. Alternate Mark Inversion (AMI) - A neutral zero voltage represents binary 0. Binary 1's are represented by alternating positive and negative voltages. Pseudoternary - Bit 1 is encoded as a zero voltage and the bit 0 is encoded as alternating positive and negative voltages i.e., opposite of AMI scheme. Example: Data = 010010.  Advantages & Disadvantages of Unipolar Line Coding Advantages: Simple receiver circuit: The receiver circuit for unipolar line coding is simple, as it only needs to detect the presence or absence of a voltage. Low DC component: The unipolar line coding scheme has a low DC component, which is desirable for some communication systems. Low cost: Unipolar line coding scheme uses only a single voltage level, so it is easy to implement and requires fewer components, making it a cost-effective solution. Disadvantages: Poor noise immunity: The unipolar line coding scheme has poor noise immunity and is susceptible to errors, as it does not have a differential signal. Limited dynamic range: The unipolar line coding scheme has a limited dynamic range, as it only uses positive voltage levels. Advantages & Disadvantages of Polar Line Coding Advantages: High noise immunity: The polar line coding scheme has a high noise immunity, as it uses a differential signal. Error resistance: The polar line coding scheme is less susceptible to errors, as it uses a differential signal. Disadvantages: Complex receiver circuit: The receiver circuit for polar line coding is complex, as it needs to detect the positive and negative voltage levels. Limited data rate: The polar line coding scheme has a limited data rate, as it requires a larger number of bits to represent the same information as the unipolar or bipolar line coding schemes. Advantages & Disadvantages of Bipolar Line Coding Advantages: High data rate: The bipolar line coding scheme has a high data rate, as it uses positive and negative voltage levels to represent the digital signal. Differential signal: The bipolar line coding scheme uses a differential signal, which improves noise immunity and error resistance.