The aim of this chapter is to demonstrate the ability of broadband multi-beam satellite systems to operate in aggressive frequency reuse modes, enabled by advanced signal processing methods, namely precoding, when practical constraints affects the implementation of signal processing techniques. To accomplish the objective, a specific hardware infrastructure composed by properly interconnected software-defined radios (SDRs) has been built. The infrastructure is able to emulate a satellite forward (FWD) link transmission using a GW emulator and a multi-beam satellite channel emulator, which includes, on top of the satellite impairments, the multiple-input-multiple-output (MIMO) user link channel and a set of independent UTs radio frequency (RF) impairments emulators. To enable real-time precoding implementation, a feedback channel from UTs to the GW is emulated accordingly. The general infrastructure includes a various number of SDR development platforms called universal software radio peripherals (USRPs), each of them connected to a central hub used for selecting the sub-infrastructure required for the specific test, while also providing control and monitoring functionalities. Each board is itself a single-antenna/multi-antenna system equipped with a RF module, digital-to-analog (DAC) and analog-to-digital converters (ADC) and a high performance FPGA for user-defined digital processing. The central hub is also supported by a high computational capabilities workstation equipped with a set of FPGAs, used for the centralized processing.

Chapter Contents:

• 9.1 Introduction on precoding
• 9.1.1 Recent projects on precoding
• 9.1.2 Related literature on precoding for SATCOMs
• 9.2 Analysis of the practical constraints for precoding and possible solutions
• 9.2.1 System model
• 9.2.2 Differential phase distortion for precoded waveforms
• 9.2.3 Timing misalignment on precoded waveforms
• 9.2.3.1 Analysis on the impact of timing misaligned waveform in precoded systems
• 9.2.3.2 Impact of time misalignment of bundled frames on channel estimation
• 9.2.4 Numerical results on the quality of CSI with timing pre-compensated waveforms
• 9.2.4.1 Precoded symbols analysis
• 9.2.5 Numerical results on precoding degradations with timing misaligned waveforms
• 9.3 Description of the precoding implementation
• 9.3.1 Precoding technique
• 9.3.2 Non-negative least squares algorithm
• 9.3.3 Impact of proposed SLP on constellation
• 9.4 In-lab validation of the precoding techniques
• 9.4.1 Experimental validation of a 2 x 2 sub-system
• 9.4.2 Symbol-level optimized precoding evaluation
• 9.4.3 Un-coded bit error performance of NNLS-SLP
• 9.5 Conclusions and future works
• References

Inspec keywords: frequency allocation; satellite links; satellite antennas; MIMO communication; broadband networks; antenna arrays; software radio; precoding

Other keywords: RF module; satellite forward link transmission; ADC; single-antenna-multiantenna system; feedback channel; advanced signal processing methods; MIMO user link channel; universal software radio peripherals; specific hardware infrastructure; GW emulator; analog-to-digital converters; monitoring functionalities; broadband multibeam satellite systems; RF impairments emulators; software-defined radios; independent UTs radio frequency impairment emulators; high performance FPGA; SDR development platforms; centralized processing; USRPs; user-defined digital processing; digital-to-analog converters; multibeam satellite channel emulator; aggressive frequency reuse modes; satellite multibeam precoding software-defined radio demonstrator; satellite impairments; central hub

Subjects: Antenna arrays; Satellite communication systems