Process for pilot-aided carrier phase synchronisation
|492 - Abstract of the offer:|
|The European Space Agency (ESA) offers new carrier synchronization techniques for companies working in Radio Frequency digital transmission. Such novel algorithms are advantageous if operating with high level phase noise of transmitter/receiver oscillator. This is typical of consumers’ market where low quality components are chosen to reduce costs, as happens for common digital TV broadcast receivers. The novel pilot aided carrier technique provides an increase of data rates in the order of 30%.|
Description of the offer:
A correct coherent signal demodulation requires a fairly precise estimate of the phase of the received signal carrier. This task is performed by a carrier recovery unit at the receiver side. In broadband satellite transmissions, the phase of the carrier is usually affected by a number of (linear) distortions which comprise: i) static channel phase rotations due to delay and/or the presence of transmit (TX) and receive (RX) conditioning filters, ii) slowly varying phase rotations due to channel fading and iii) TX and RX oscillator phase and phase noise.
A number of algorithms are available in literature to address the issue of carrier phase recovery for different modulation schemes. However, due to the recent findings in channel coding theory and the use of higher carrier frequencies, the need to study novel and more efficient carrier phase estimate techniques has received a new boost. In fact, since the introduction of Turbo codes, the operating signal-to-noise ratios (SNR’s) at which the synchronizers have to be able to work have considerably lowered, thus stressing their jitter performance. Also, the carrier frequency is constantly moving upwards, due to the increasing demand of bandwidth by new services and the consequent congestion at more traditional frequencies. For example, in satellite systems, as the Ku band is becoming crowded, new systems are being developed to work at Ka and Q bands, which are to date still relatively unused. However, as the carrier frequency increases, the contribution of the oscillators phase noise to the total carrier phase distortion becomes much higher thus requiring new and faster carrier phase tracking schemes. In some cases the use of Pilot-Aided (PA) schemes is the only viable solution to the problem. In these schemes, a certain amount of pilot (known) symbols are interleaved with the data streams, in order to help the RX demodulation process. Pilot symbols are then discarded before the decoder.
The present innovation focuses on the analysis of PA algorithms and its performance in terms of residual phase jitter RMS and cycle slips is higher if compared to other types of solutions. This innovation is devoted particularly to DVB-S2-like applications, i.e. next generation satellite broadcast and unicast transmissions. However, the algorithms here implemented can easily be applied to other wireless or wireline applications where the issue of oscillators phase noise is particularly important.
Advanced coding schemes approaching the Shannon capacity bound are considered when setting the transmission operative SNR, and a set of modulation schemes with spectral efficiency between 1 and 4 bit/s/Hz will be analyzed. In particular, QPSK, 8PSK 16QAM and the more recent and non-linearity-friendly 4+12 APSK is analysed. The sensitivity study to residual carrier frequency errors was also be carried out and an overall carrier (phase and frequency) recovery scheme is proposed and tested.
Innovations and advantages:
The invented technique allows synchronizing the carrier phase of a digital communication system in the presence of strong oscillator phase noise with a relatively low complexity system. To this end it makes use of a set of known pilot symbols interspersed within the data symbols. The performance/complexity of known systems in this scenario is not satisfactory.
Domain of Application:
Its practical applications are DVB-S2 (new generation DVB-S systems) but also all the wireline and wireless transmissions not in baseband where the problem of phase noise is particularly important.
- Data Communications
- Data communication components
- Communications processors/network
Last update: 16 January 2013