Operation in the DMD15/DMD15L, Reed-Solomon Code Rate

Operation	DMD15/DMD15L IBS/IDR Satellite Modem

5.Press <ENTER>. The modem has now copied the current Rx Settings to the Rx Channel/Timeslot display ).

Note: It is not mandatory to assign timeslots in sequential order, although the

lowest timeslot must be entered in the lowest channel. For example: timeslots may be assigned 1-2, 2-5, etc. but not 1-5, 2-2.

3.18 Reed-Solomon Codec (Refer to Figures 3-14, 3-15, and Table 3-1)

Utilizing a Reed-Solomon (RS) Outer Codec concatenated with a Convolutional Inner Codec is an effective way to produce very low error rates even for poor signal-to-noise ratios while requiring only a small increase in transmission bandwidth. Typically, concatenating an RS Codec requires an increase in transmission bandwidth of only 9 – 12% while producing a greater than 2 dB improvement in Eb/No. RS is a block Codec where K data bytes are fed into the encoder which adds 2t = (N – K) check bytes to produce an N byte RS block. The RS decoder can then correct up to “t” erred bytes in the block.

3.18.1 Operation in the DMD15/DMD15L

When the Reed-Solomon Codec is enabled, data is fed to the RS Encoding Section of the DMD15/DMD15L where it is scrambled, formed into blocks, RS encoded, and interleaved. Unique words are added so that the blocks can be reformed in the Receiving Modem (Refer to Figure 3-13). Data is then sent to the modulator where it is convolutionally encoded, modulated and transmitted to the satellite.

When the signal is received and demodulated by the Receiving Modem, it is fed to a Viterbi Decoder for the first layer of error correction. After error correction is performed by the Viterbi Decoder, the unique words are located and the data is deinterleaved and reformed into blocks. The RS Decoder then corrects the leftover errors in each block. The data is then descrambled and output from the RS Section.

3.18.2 Reed-Solomon Code Rate

The RS Code Rate is defined by (N, K) where N is the total RS block size in bytes - data + check bytes - and K is the number of data bytes input into the RS Encoder. The transmission rate expansion required by the RS Codec is then defined by N/K. The DMD15/DMD15L automatically sets the correct RS code rate for IDR/IBS open network operation in accordance with the data shown in Table 3-1. In Closed Net Mode, the DMD15/DMD15L allows any N or K setting up to N = 255, and K = 235 to allow tailoring of the code rate to meet system requirements.

3.18.3 Interleaving

The DMD15/DMD15L allows for interleaving depths of 4 or 8 RS Blocks. This allows burst errors to be spread over 4 or 8 RS blocks in order to enhance the error correcting performance of the RS Codec. For Open Network Modes, the DMD15/DMD15L automatically sets the interleaving depth to 4 for QPSK or BPSK or 8 for 8PSK. In Closed Network Mode, the interleaver depth can be manually set to 4 or 8.

Figure 3-14. Reed-Solomon Encoder Functional Block Diagram

3-20	TM051 – Rev. 5.8

DMD15, DMD15L specifications

The Paradyne DMD15L and DMD15 are advanced digital modems designed to enhance communication in a variety of networking environments. As part of Paradyne's robust portfolio of networking solutions, these devices are engineered to deliver reliable and efficient data transmission over both copper and fiber optic connections.

One of the main features of the DMD15L and DMD15 is their capability to support Multiple Protocol Data Units (MPDUs), which enables them to handle a diverse range of network protocols seamlessly. This flexibility makes them suitable for different applications, from industrial automation to telecommunications.

These modems utilize advanced modulation techniques, such as Quadrature Amplitude Modulation (QAM), to maximize data throughput while maintaining signal integrity. This ensures that users benefit from high-speed connections, even in challenging signal environments. Furthermore, the DMD15 series incorporates Error Correction Codes (ECC) that enhance data reliability, effectively reducing packet loss and ensuring data coherence during transmission.

The DMD15L is particularly notable for its long-range capabilities, making it a go-to solution for users requiring extended distances without compromising data quality. It features built-in Adaptive Equalization, which automatically adjusts signal levels to optimize performance over varying transmission distances. This technology is crucial in maintaining consistent high-speed connectivity, especially in environments with variable conditions.

Both models are equipped with user-friendly interfaces that facilitate configuration and management. They support SNMP (Simple Network Management Protocol) for real-time network monitoring, allowing administrators to track performance metrics and identify potential issues before they impact users. The devices also include LED indicators for quick status checks, ensuring that users have immediate visibility of operational conditions.

In terms of physical characteristics, the DMD15 and DMD15L are designed for durability and ease of installation. They come in a compact form factor, making them suitable for deployment in constrained spaces. Additionally, their robust casing is built to withstand harsh environmental conditions, making them suitable for both indoor and outdoor installations.

Overall, the Paradyne DMD15L and DMD15 are high-performance modems that combine versatile technologies, reliability, and user-friendly features. They are excellent choices for organizations looking to enhance their communication capabilities and ensure robust data transmission across diverse networks. With their advanced functionalities and adaptability, these modems stand out as key components in modern network infrastructure.

Paradyne DMD15 Reed-Solomon Codec Refer to Figures 3-14, 3-15, and Table, Reed-Solomon Code Rate

Models: DMD15 DMD15L

Operation