Physical layer

Physical layer

In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer. It deals with the connection between devices.

This layer is important because it handles how data moves through wires, cables, or other media.

The physical layer provides an electrical, mechanical, and procedural interface to the transmission medium. It decides the shapes of electrical connectors, the frequencies to transmit on, the line code to use, and other details needed for communication.

At the electrical layer, the physical layer is often implemented in a special chip called a PHY chip. In electronic design automation, it is created using a design block. In mobile computing, many devices use the MIPI Alliance *-PHY family of interconnect protocols.

Role

The physical layer is the first part of a network that helps devices connect. It decides how to send information as signals over wires or other paths. This layer changes data into signals that can travel between devices.

It includes the electronic parts that make this happen and works with the next level of the network to send and receive these signals. The physical layer supports higher levels that put data into packages for sending.

Physical signaling sublayer

In a network using the Open Systems Interconnection (OSI) architecture, the physical signaling sublayer is part of the physical layer. It works with the data link layer's medium access control (MAC) sublayer. It helps with sending and receiving data and decoding the information. It also keeps electrical parts separated.

Relation to the Internet protocol suite

The Internet protocol suite is a set of rules for the Internet and other networks. It tells us how data travels but does not explain the wires or cables that connect devices.

Services

The physical layer helps devices send data, one piece at a time, over a connection. It decides how connectors and cables should look and work, including things like cable length and signal strength. It makes sure signals don’t get mixed up and helps manage how data moves between devices.

It also decides how to change data into electrical signals and helps devices share the connection. To make sure data arrives correctly, it can use special ways to fix mistakes. Other topics include how fast data can travel, how devices are arranged, and how they talk to each other.

PHY

"PHY" redirects here. For other uses, see PHY (disambiguation).

A PHY, short for physical layer, is an electronic circuit. It helps devices connect to each other. It works with the first layer of the OSI model.

A PHY connects a device that manages data to a physical medium like an optical fiber or a copper cable. It helps send data over the medium.

Ethernet physical transceiver

The Ethernet PHY works with the physical layer of the OSI network model. It helps send and receive Ethernet signals. It connects analog signals to the digital parts of a system. It usually works with a special interface called media-independent interface.

Common Ethernet connections use fiber or several copper wires. Newer types like Single Pair Ethernet can work with just one pair of wires. Examples include chips from companies like Texas Instruments and Marvell.

Other applications

• Wireless LAN or Wi-Fi: The PHY part handles radio signals for wireless connections.
• Universal Serial Bus (USB): Most USB devices include a PHY chip.
• IrDA: The Infrared Data Association has a specification called IrPHY.
• Serial ATA (SATA): Controllers for SATA use a PHY.
• PCI Express (PCIe): Controllers for PCIe use a PHY.

Technologies

The physical layer connects devices using different technologies. Some of these technologies include:

• 1-Wire
• ARINC 818 Avionics Digital Video Bus
• Bluetooth physical layer
• CAN bus (controller area network) physical layer
• DSL
• EIA RS-232, EIA-422, EIA-423, RS-449, RS-485
• Etherloop
• Ethernet physical layer Including 10BASE-T, 10BASE2, 10BASE5, 100BASE-TX, 100BASE-FX, 1000BASE-T, 1000BASE-SX and other varieties
• G.hn/G.9960 physical layer
• GSM Um air interface physical layer
• UMTS air interface physical layer
• LTE air interface physical layer
• 5G air interface physical layer
• Communications satellite technologies physical layers
• IEEE 802.15.4 physical layers
• IEEE 1394 interface
• IRDA physical layer
• ISDN
• ITU Recommendations: see ITU-T
• I²C, I²S
• LoRa
• Low-voltage differential signaling
• Mobile Industry Processor Interface physical layer
• Modulated ultrasound
• Optical Transport Network (OTN)
• SMB
• SONET/SDH
• SPI
• T1 and other T-carrier links, and E1 and other E-carrier links
• Telephone network modems — ITU-T V.92
• TransferJet physical layer
• USB physical layer
• PCI Express physical layer
• 802.11 Wi-Fi physical layer
• Visible light communication co-ordinated under IEEE 802.15.7
• X10