Performance evaluation of a DVB‐S2 system with a digital optical feeder link

Abstract

We investigate the physical layer performance of a DVB-S2 system with a digital optical feeder link. We consider three scenarios depending on how the DVB-S2 modulator functionalities are distributed between the optical gateway and the satellite. Our main objective is to specify the residual bit error rate of the optical channel error correction scheme in order to ensure a quasierror free link to the users. To that end, we provide theoretical models and/or simulations results. In two scenarios, our results show that a residual bit error rate of 10 −4 (assuming equally distributed errors) gives end-to-end physical layer performance compliant with the DVB-S2 standard. This specification is much higher than typical values in practical systems. K E Y W O R D S digital optical feeder link, digital video broadcasting (DVB), performance evaluation 1 | INTRODUCTION Satellite communications systems require to reduce the overall cost per bit in order to remain competitive with terrestrial solutions and to offer affordable high-speed Internet services. Increasing the total capacity is a logical way to reach these objectives. To that end, high and very high throughput satellite (HTS/VHTS) systems are mainly looking for more bandwidth. 1-3 The multibeam concept using narrow beams combined with frequency reuse enables to maximize the available user link bandwidth. In addition, the satellite operation frequencies are moving from the Ku-band to the Ka-band and beyond (Q/V band). However, HTS and VHTS systems face important challenges such as bandwidth scarcity and ground network size. 3 To tackle these issues, an alternative is to replace the radiofrequency (RF) feeder link by an optical link using the 1550-nm wavelength as depicted in Figure 1. 3-5 Optical technologies benefit from large available bandwidths and less interference issues (due to very narrow beams). We investigate the physical layer performance of a DVB-S2 1 system with a digital optical feeder link. An important matter is how the DVB-S2 modulator features 6 are distributed between the optical ground station (OGS) and the satellite as illustrated in Figure 2. This choice has strong consequences on the design and performance of the system. Our work focuses on three scenarios called regenerative, semiregenerative, and (digital) transparent. All the DVB-S2 modulator functionalities are done on-board in the regenerative case. At the opposite, the optical gateway handles everything in the (digital) transparent scheme. In the semiregenerative scenario, the OGS realizes the DVB-S2 forward error correction (FEC) encoding while the satellite manages the remaining features. The bitstream coming out the DVB-S2 modulator 1/2 serves to modulate the optical signal with a digital waveform such as OOK or DPSK. We assume that an FEC scheme protects the bits transmitted on the optical link. This scheme consists in an error-correcting code associated with an interleaver 7 in order to cope with the optical channel perturbations due to atmospheric phenomena (turbulence, 8 molecular ab...

Coherent optical feeder links for very high throughput satellite systems

“…Considering a DVB-S2 system with a digital optical feeder link, we set the required BER post-FEC on the optical feeder uplink to be lower than 10 −10 as in [15]. This is considered "error-free decoding" and ensures end-to-end performance in agreement with the standard specification while assuming any end-to-end digital architecture possible (i.e., fully regenerative or transparent).…”