HSFN (Hypersystem frame number)

Last updated on Apr 17, 2023

The Hypersystem Frame Number (HSFN) is a numbering system used in telecommunications networks to manage frame synchronization. In this article, we will explore the concept of HSFN, its importance in network synchronization, and how it is calculated.

Overview of Frame Synchronization

In digital communications, a frame is a fixed-length sequence of bits transmitted between two devices. The frames are transmitted at regular intervals, and the receiving device needs to synchronize with the transmitting device to correctly receive the frames.

Frame synchronization refers to the process of aligning the incoming data stream with the receiving device's clock. In a synchronized system, each frame starts and ends at a predictable point in time, allowing the receiver to accurately demodulate and decode the transmitted data.

To achieve frame synchronization, the transmitter and receiver must use a common clock reference. Typically, the transmitter sends a synchronization signal or a frame alignment signal (FAS) to the receiver to establish synchronization. The FAS is a special bit sequence inserted into the data stream that indicates the start of the frame. Once the receiver detects the FAS, it can start counting bits to correctly receive the frame.

However, frame synchronization can be lost due to transmission errors, network congestion, or equipment malfunctions. To maintain synchronization, networks use various techniques to ensure that the FAS is correctly detected by the receiver, even in noisy or congested environments.

Overview of HSFN

The Hypersystem Frame Number (HSFN) is a numbering system used to manage frame synchronization in telecommunication networks. HSFN is a unique identifier assigned to each frame transmitted in a network. The HSFN is used to synchronize the receiver's clock with the transmitter's clock, ensuring that the receiver correctly demodulates and decodes the transmitted data.

HSFN is typically used in synchronous digital hierarchy (SDH) networks, which are high-speed telecommunications networks used to transmit large volumes of data over long distances. In SDH networks, data is transmitted in fixed-length frames, with each frame consisting of multiple time slots. The HSFN is used to identify the start of each frame and ensure that the receiver is synchronized with the transmitter.

The HSFN is a 32-bit number that is incremented by one for each frame transmitted. The HSFN is transmitted in the overhead bytes of each frame, allowing the receiver to detect the start of each frame and synchronize its clock with the transmitter's clock.

The HSFN is also used to detect and correct errors in the data stream. In SDH networks, the HSFN is used in conjunction with other synchronization signals, such as the frame alignment signal (FAS) and the section and line synchronization signals, to ensure that the data is correctly transmitted and received.

Calculation of HSFN

The HSFN is calculated based on the frequency of the network's clock and the number of frames transmitted per second. The HSFN is typically calculated using the following formula:

HSFN = (N x f) / 2^32

Where:

N is the number of frames transmitted since the start of the network
f is the frequency of the network's clock

The formula divides the product of N and f by 2^32, which is the maximum value that can be represented by a 32-bit number. The result is a unique 32-bit number that identifies each frame transmitted in the network.

For example, suppose a network has a clock frequency of 155.52 MHz and transmits 8000 frames per second. The HSFN for the 100th frame transmitted would be calculated as follows:

N = 100 f = 155.52 MHz HSFN = (N x f) / 2^32 HSFN = (100 x 155.52 HSFN = (100 x 155.52) / 4294967296 HSFN = 0.0000036367

In this example, the HSFN for the 100th frame is 0.0000036367. This number is transmitted in the overhead bytes of the frame, allowing the receiver to identify the start of the frame and synchronize its clock with the transmitter's clock.

Importance of HSFN in Network Synchronization

HSFN is an important component of network synchronization in SDH networks. The HSFN provides a unique identifier for each frame transmitted in the network, allowing the receiver to accurately detect the start of each frame and synchronize its clock with the transmitter's clock.

HSFN is also used to detect and correct errors in the data stream. The HSFN is transmitted in the overhead bytes of each frame, allowing the receiver to detect errors and retransmit frames if necessary. This ensures that the data is correctly transmitted and received, even in noisy or congested environments.

HSFN is also used in conjunction with other synchronization signals, such as the frame alignment signal (FAS) and the section and line synchronization signals, to ensure that the data is correctly synchronized across the entire network. This is critical in high-speed telecommunications networks, where even small synchronization errors can result in significant data loss or corruption.

Conclusion

The Hypersystem Frame Number (HSFN) is a unique identifier assigned to each frame transmitted in a telecommunications network. HSFN is used to manage frame synchronization, ensuring that the receiver accurately demodulates and decodes the transmitted data.

HSFN is calculated based on the frequency of the network's clock and the number of frames transmitted per second. The HSFN is typically transmitted in the overhead bytes of each frame, allowing the receiver to detect the start of each frame and synchronize its clock with the transmitter's clock.

HSFN is an important component of network synchronization in SDH networks, where even small synchronization errors can result in significant data loss or corruption. The HSFN ensures that the data is correctly transmitted and received, even in noisy or congested environments, and is critical for the reliable operation of high-speed telecommunications networks.