What is Half Duplex Communication
Data transmission via half-duplex communication allows devices to send and receive information, but only one device can send at a time. It is a bi-directional system, which means that although data can move in both ways, it does so sequentially as opposed to simultaneously. In contrast, full-duplex communication allows data to travel in both directions at the same time, while simplex communication only allows data to flow in one direction.
You can also read UHF Connectors, UMCC Connector & K Connectors in Network
How Half-Duplex Communication Works
Devices in a half-duplex system send and receive data over a single communication channel. As a result, they have to alternate sending and receiving information. There is frequently a “turnaround time” before the other device may start delivering a response after the first device has completed sending its data. A physical device, such a “push-to-talk” button, or a protocol may be used to control this operation.
The vulnerability of half-duplex to collisions is a crucial feature. A collision will happen if two or more devices try to send data on the same channel at the same time, which could result in data loss, garbled messages, or transmission failures. The Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol is used in systems such as Ethernet to control media access and avoid collisions.
Key Characteristics and Features
Bidirectional, Sequential Data Flow: Sequential, bidirectional data flow allows data to flow in both directions, but not simultaneously.
CSMA/CD Protocol: To control media access and avoid collisions, half-duplex Ethernet uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD). A collision will happen if two or more devices try to transmit at the same time.
Single Communication Channel: Sending and receiving are usually done over the same channel.
Collision Potential: Data collisions occur when numerous devices transmit data simultaneously.
Collision Domains: As is the case with hubs, where all connected ports are part of the same domain, half-duplex communication frequently shares a collision domain.
Efficiency: Compared to full-duplex Ethernet, half-duplex Ethernet is less efficient. For instance, because of overhead and collision handling, a 100BASE-T network operating half-duplex usually only reaches 30% to 40% of its maximum 100 Mbps capacity. The effective throughput of even 10 Mbps Ethernet in half-duplex mode is constrained.
Turnaround Time: Before the other device can begin delivering data, the channel must “turn around” once the first device has finished transmitting.
You can also read How To Set Up A LAN Network Devices Connection Guidelines
Examples of Half-Duplex Communication
Common real-world examples include:
- Users of walkie-talkies or CB radios press a button to speak and release it to listen; the “over” symbol is frequently used to indicate the conclusion of a transmission.
- Half-duplexes are comparable to one-lane road with two-way traffic, where vehicles can move in either direction but not simultaneously without colliding.
In embedded systems and networks, half-duplex is found in:
- Older Ethernet networks, including 10Base-2 and 10Base-5, especially those that use hubs and coaxial cable systems.
- The I2C protocol is half-duplex by nature. Bidirectional, but not simultaneous, communication occurs between the slave and master devices; the slave reacts when addressed, while the master initiates and regulates communication.
- Certain variants of the SPI protocol, such as Dual and Quad SPI
- Wireless systems that are unable to use the same frequency for simultaneous transmission and reception.
- Time-division duplexing (TDD) systems, such as 2-wire or hubbed Ethernet, Wireless Local Area Networks (WLANs), and Bluetooth, can be considered as half-duplex packet-switched networks based on carrier-sense multiple access.
Advantages and Disadvantages of Half-Duplex Communication
Advantages:
Resource Efficiency: By using a single channel for both transmission and reception, fewer resources are used.
Lower Cost: The implementation of half-duplex systems is frequently less costly.
Disadvantages:
Lower Throughput: Due to the impossibility of simultaneous connections, data transmission speeds are constrained, resulting in a decreased total data capacity.
Increased Latency: Communication lag increases as a result of devices having to wait for their turn to communicate.
Coordination Needed: In order to prevent collisions or missing messages, participants or protocols must coordinate turns, which slows down communication.
Duplex Mismatch
Duplex mismatches, which happen when one end of an Ethernet link operates in full-duplex and the other in half-duplex, are a frequent problem in switched networks. This results in severe performance deterioration, needless frame discards, and retransmissions because of collisions, but it does not cause the link to fail. If one end is manually set to a particular duplex configuration, the other end must be manually set to match to avoid this. The device attempting autonegotiation will identify the speed and switch to half-duplex if it is 10 Mbps or 100 Mbps, provided that one device has disabled autonegotiation.
You can also read Triax Cable Connector, SMP Connector, Twinax Cable Connector