PHY physical layer, frame structure, parameters, data, energy, modulation, frame, format

1. What are the main functions of the PHY layer?

Activation and shutdown of radio transceiver

Energy detection (ED) in the current channel

Link quality indication (LQI) of received data packets

Idle channel evaluation (CCA) for carrier listening multiple access/conflict avoidance (CSMA-CA)

Channel frequency selection

Data transmission and reception

2. Physical parameters

868/915 MHz DSSS (direct sequence spread spectrum) adopts BPSK (binary phase shift keying) modulation

868/915 MHz DSSS (direct sequence spread spectrum) adopts O-QPSK modulation

868/915 MHz PSSS (parallel sequence spread spectrum) adopts BPSK and ASK (amplitude shift keying) modulation

2450 MHz DSSS (direct sequence spread spectrum) adopts O-QPSK modulation

3. PHY frame format

SHR: Synchronization header (including Preamble and SFD), allowing a receiving device to synchronize and lock to each stream at the same time.

PHR: PHY frame header (including Frame length and Reserved), the length information of the frame.

PHY Payload: A variable-length payload that carries the data frame of the MAC sublayer.

Among them, the SHR field: Preamble, which is used by the radio transceiver to obtain the chip and synchronization identification from the received data information. The length of the Preamble field is determined by the physical parameters as shown in the figure below.：

SFD, indicating the end of the SHR and the beginning of the packet, different physical parameters have different lengths as shown in the figure below：

The advantage of FTTR technology lies in its fast transmission speed and low latency.As a transmission medium, optical fiber has extremely high bandwidth and transmission speed, which can meet the needs of users for high-speed networks.Compared with traditional network connection methods, FTTR technology can provide a more stable and faster network connection, and users can easily carry out high-bandwidth activities such as online videos, online games, and high-definition downloads.

In addition, FTTR technology also has better network coverage and signal quality.Due to the long transmission distance of optical fiber, every room in the room can obtain stable signal coverage, avoiding the problem of weak or unstable network signals caused by long distances or signal interference in traditional wiring methods.This means that users can enjoy the same high-quality Internet connection no matter which room they are in.

In addition, FTTR technology can also provide higher security.The network signal transmitted by optical fiber is not susceptible to external interference, making the user's network connection more secure and reliable.Especially for some places with high security requirements, such as banks, hospitals and enterprises, FTTR technology can meet their requirements for network security.

In general, FTTR technology transmits the Internet connection directly to each room through optical fiber, providing users with a high-speed and stable network connection.Compared with traditional network connection methods, FTTR technology has faster transmission speed, better network coverage and signal quality, and higher security.With the continuous development of science and technology, FTTR technology will be widely used in various fields.

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