Serial Transmission vs Parallel Transmission: Detailed Comparison

The data between two computers is exchanged in either of the two transmission modes – serial or parallel. Although most of us use computers, laptops, and several network devices,we are largely unaware of these data transmission types.

These data transmission methods are similar and dissimilar in many ways. Comparing parallel and serial transmission: Parallel transmission uses multiple links to send data bits simultaneously, whereas serial transmission uses a single communication link to transfer data sequentially from one end to the other. This post introduces you to these types and also compares them to help you understand their differences.

What is Serial Data Transmission?

Serial data transmission is a method of transferring data one bit at a time over a single communication channel. This type of data transmission typically uses two lines - one for sending data (Tx) and another for receiving data (Rx). The communication protocols for some systems may also include synchronization signals as well as control signals.

Types of Serial Transmission

1. Asynchronous Serial Transmission: In asynchronous serial transmission, the data is sent in a start-stop fashion, with each character or byte preceded by a start bit and followed by a stop bit. This allows the receiver to synchronize with the sender even if there are gaps between characters. It is typically used for low-speed data transmission, such as in serial communication between a computer and a modem.
2. Synchronous Serial transmission: In synchronous serial transmission, the data is sent in a continuous stream of bits, with a clock signal that is sent along with the data to synchronize the sender and receiver. The clock signal tells the receiver when to expect each bit. It is typically used for high-speed data transmission, such as in Ethernet networks.

What is Parallel Data Transmission?

Parallel data transmission is a method of sending multiple bits of data simultaneously across multiple wires or channels. Parallel data transmission allows the transmission of eight bits simultaneously, but it operates in a half-duplex transmission mode. Each wire or channel carries a single bit of data, allowing faster data transfer. There are two modes of transmission: synchronous, in which data is transmitted at fixed intervals, and asynchronous, in which data is transmitted on demand.

Serial vs. Parallel Transmission: A Few Important Factors Compared

Is parallel communication effective or serial communication? The following pointers will help you make the decision.

• Speed: As said before, the parallel communication channel may comprise multiple electrical conductors at the physical layer to send eight bits or bytes. When compared with serial transmission at the same speed, the parallel transmission will be eight times faster.
• Disturbances: In serial transmission, multiple bits are simultaneously sent in one clock pulse, which produces noise and leaves scope for error. However, in serial transmission one bit is sent at a time, so there is no crowding and hence minimal chances of error and noise. This means electromagnetic interference is negligible or zero in case of serial transmission.
• Transmission Distance: Parallel communication may witness electromagnetic interference in long distance transmission, which is why they are used in short distance transmission. Against this, serial transmission is ideal for long distance data transmission. Most computer networks use serial communication.
• Converters: Serial transmission utilizes converters that enable data conversion from parallel to serial type, while parallel transmission requires no such data converters
• Transmission Modes: In parallel data communication, although eight bits can be sent at a time, it has a half-duplex transmission mode. This is because the data can be either sent or received at a time. However, in serial transmission, the sender can receive and send the data simultaneously. Thus, it has a full-duplex transmission mode.
• Affordability: Parallel communication has been used for integrated circuits as well as RAM and peripheral buses. However, serial communication is used in computer networks. By closely observing these examples, the integrity and complexity of different applications can be easily made out. On comparison, it can be rightly said that serial communication is cheaper compared to parallel communication.
• Complexity of Connections: A parallel connection may require several devices and cables, which adds to its complexity. Against this, a serial connection requires fewer cables for interconnection, and requires less space, too. Its small footprint enables better isolation of the system from its surroundings.
• Clock Skew: This is also known as timing skew, and it is a phenomenon in computers and other digital circuit systems where the same clock signal will report to different components with certain time differences. The difference between the clock readings is known as a skew. In parallel communication, the clock skew between different channels can be an issue, while in serial communication, this is not an issue.
• Cable Lengths: The serial communication cables are longer, thinner, and economical when compared to parallel communication cables, and they run to several kilometers.

Serial Vs Parallel Communication Summary:

Advantages of Parallel Data Transmission

• Faster data transfer: Since multiple bits are sent at once, parallel data transmission is faster than serial transmission.
• Simpler hardware: Parallel data transmission requires fewer complex electronic components than serial transmission.

Disadvantages of Parellel Data Transmission

• Limited distance: Parallel data transmission is limited by the distance covered by the wires or channels used to transmit data. This distance is typically shorter than serial transmission.
• Synchronization issues: In synchronous transmission, the sender and receiver must be synchronized in terms of timing, which can be challenging to achieve and maintain. Transmissions that occur asynchronously may have start-stop bits that add overhead.

Advantages of Serial Data Transmission

• Longer distance : Serial transmission can cover longer distances than parallel data transmission because it requires fewer wires or channels to transmit data.
• Lower cost: Serial transmission requires fewer wires or channels and simpler hardware, making it a lower-cost option than parallel data transmission.

Disadvantages of Serial Data Transmission

• Slower data transfer: Because data is sent one bit at a time, serial transmission is slower than parallel transmission for transferring large amounts of data.
• Limited error detection and correction: In serial transmission, errors can occur during transmission, and there may be limited ability to detect or correct these errors.

Knowing the similarities and differences between serial communication and parallel communication may not serve the purpose. You must use quality devices that enable conversion from serial-to-parallel or vice versa. VERSITRON provides serial to fiber converters, which serve as converters for serial RS-422, RS-485, RS-232, RS-530, and V.35 protocols. These modems can support a multidrop, a redundant ring, and a point-to-point link.