What are the best MCS optimization techniques for SATCOM in a jamming scenario?

1 MCS basics

MCS is a combination of two parameters: modulation and forward error correction (FEC) coding. Modulation is the process of varying the amplitude, frequency, or phase of the carrier wave to convey information. FEC coding is the process of adding redundancy to the data to enable error detection and correction at the receiver. The choice of MCS affects the data rate, bandwidth, and signal-to-noise ratio (SNR) of the SATCOM link. Generally, higher-order modulation and lower coding rate result in higher data rate and lower bandwidth, but also require higher SNR and are more susceptible to jamming. Conversely, lower-order modulation and higher coding rate result in lower data rate and higher bandwidth, but also require lower SNR and are more robust to jamming.

2 Adaptive coding and modulation (ACM)

ACM is a technique that dynamically adjusts the MCS according to the channel conditions and the quality of service (QoS) requirements. ACM enables the SATCOM link to achieve the maximum data rate possible under the current SNR, while maintaining a target bit error rate (BER) or packet error rate (PER). ACM requires feedback from the receiver to the transmitter, which can be done either by a dedicated channel or by piggybacking on the data packets. ACM can also be combined with other techniques, such as power control, beamforming, or frequency hopping, to further enhance the SATCOM link performance and resilience.

3 Spread spectrum modulation (SSM)

SSM is a technique that spreads the signal over a wider frequency band than the minimum required by the data rate. SSM reduces the power density and increases the bandwidth of the signal, making it more difficult for a jammer to detect and interfere with it. SSM can be either frequency hopping (FH) or direct sequence (DS). FH changes the frequency of the carrier wave according to a predetermined or random pattern, while DS adds a pseudo-random noise (PN) code to the data before modulation. Both FH and DS require synchronization between the transmitter and the receiver, and can be used with different modulation and coding schemes.

4 Differential modulation (DM)

DM is a technique that encodes the information in the phase difference between consecutive symbols, rather than in the absolute phase of each symbol. DM eliminates the need for phase reference at the receiver, which can be corrupted by jamming or fading. DM can be applied to various modulation schemes, such as phase shift keying (PSK) or quadrature amplitude modulation (QAM). DM can also be combined with FEC coding to improve the error performance of the SATCOM link.

5 Turbo codes (TC)

TC are a type of FEC coding that use two or more convolutional codes in parallel or serial, and an iterative decoding algorithm that exchanges soft information between the codes. TC can achieve near-optimal error performance at low SNR, and are widely used in SATCOM systems. TC can be used with different modulation schemes, and can be adapted to different channel conditions and QoS requirements. TC can also be combined with interleaving, which rearranges the data bits to reduce the effect of burst errors caused by jamming or fading.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?