Satellite Communication

Satellite Communication (SATCOM), in telecommunications, is the use of satellites to provide communication links between various points on Earth. It facilitates wide-area telecommunications by receiving radio signals from Earth, amplifying them, and relaying them back down to terrestrial receivers.

Satellite communications plays a vital role in the global telecommunications systems.

STUAM has experience in developing SATCOM related products as per the customer requirements.

Digital Video Broadcasting-S2

Digital Video Broadcasting - Satellite - Second Generation is a digital television broadcast standard that has been designed as a successor for the popular DVB-S system[1]. DVB-S2 is designed for broadcast services including High Definition Television (HDTV), interactive services including internet access, and (professional) data content distribution. DVB-S2 offers performance gain in terms of available bit-rate of around 30% compared to DVB-S at the same satellite transponder bandwidth and transmit power.

Transmitter

Receiver

Features

As per ETSI EN 302 307 v 1.2.1 [2]
Modulation Schemes include QPSK, 8PSK, 16 APSK and 32 APSK which are based on one or more PSK like rings around the constellation origin. This sort of modulation has lower PAPR compared to QAM and is more well-behaved in presence of nonlinear distortion introduced by high-power amplifiers in the signal path
Inner LDPC coding and outer BCH coding offer near Shannon-limit performance (0.7 to 1.2 dB away from Shannon limit) in terms of spectral efficiency achievable at a given SNR. The outer code avoids error-floors at low bit-error-rates
Flexible bandwidth up to 36 MHz [3] and symbol rate up to 30 Msps

Square root raised cosine filtering at transmitter and receiver. Improved roll-off factors of 0.20 and 0.25 in addition to the roll-off factor of DVB-S (0.35)
Adaptive modulation and coding (ACM) to allow flexibly adapting transmission parameters to the reception conditions of terminals, e.g. switching to a lower code rate during fading
Several code rates for flexible configuration of transmission parameters : 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, 6/7, 8/9 and 9/10. Code rates 1/4, 1/3 and 2/5 have been introduced for exceptionally poor reception conditions in combination with QPSK modulation
Optional input stream synchronization to provide a constant end-to-end delay
Normal (64800 bits) and short (16200 bits) frames

Specifications

Constellation	QPSK
Usage of Pilots	Enabled
FEC Frame	Normal (64800 bits)
Roll off factor	0.2
Symbol Rate	30 Msps
FEC rate	3/4
Gross Data Rate	60 Mbps
Net (final) data rate	43.54 Mbps
Satellite bandwidth	30 MHz
Occupied bandwidth	36 MHz
Input Interface	Multiple transport stream and generic stream encapsulation
Modes	Variable coding & modulation and adaptive coding and modulation
FEC	LDPC + BCH (1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, 6/7, 8/9, 9/10)
Modulation	QPSK, 8PSK, 16-APSK, 32-APSK
Interleaving	Bit interleaving
Pilots	with or without pilot symbols - 36 pilot symbols per 16 slots of 90 symbols each
Spectral efficiency	0.7 to 1.2 dB away from Shannon limit
RF Frequency	Ku band, i.e. 12-18 GHz (IF output of the baseband unit is at L-band)
Frequency Source and Stability	1) GPS disciplined oscillators with < 5 ppb stability 2) Reference OCXO with equivalent stability including aging plus or minus 5 X10^-8 / year (in the absence of GPS)

Digital Video Broadcasting-RCS

DVB-RCS (Return Channel via Satellite) is a specification for an interactive on-demand multimedia satellite communication system formulated in 1999 by the DVB Consortium [1]. It has highly efficient bandwidth management, making it a cost efficient alternative solution for many users. It also provides an established foundation for further satellite communications research. DVB-RCS was designed initially for video, but was quickly adopted worldwide for 2-way high-capacity IP based communications perfect for Everything over IP. It is the backbone of many tactical military systems like the US Department of Defense Global Broadcast System and for mission critical Civilian Agency Internal networks.

Transmitter

Receiver

Features

As per ETSI 301.790 v1.4.1 [2]
Reed Solomon outer coding with convolutional inner coding or alternatively Turbo codes using a double binary Circular Recursive Systematic Convolutional (CRSC) code
QPSK Modulation
Prior to modulation, the I & Q signals are square root raised cosine filtered. The roll-off factor is 0.35

The Reverse Channel via Satellite Terminal (RCST) is capable of adjusting the transmit EIRP in steps of nominally 0.5 dB over the operating range
The satellite access scheme is Multi-Frequency Time Division Multiple Access (MF-TDMA). MF-TDMA allows a group of RCSTs to communicate with a gateway using a set of carrier frequencies, each of which is divided into time-slots. The Network Control Center (NCC) allocates to each active RCST a series of bursts, each defined by a frequency, a bandwidth, a start time and a duration. MF-TDMA may be either fixed-slot (fixed MF-TDMA) or dynamic slot (dynamic MF-TDMA, which is optional)

Specifications

Modulation	QPSK
FEC	Seven code rates are defined for the Turbo mode. R = 1/3, 2/5, 1/2, 2/3, 3/4, 4/5, 6/7. For the non-Turbo mode, a Reed Solomon RS (N-B,K-B,T) shortened code derived from the original RS(255,239,8) code shortened by B bytes, can be applied along with convolutional inner code, with rates 1/2, 2/3, 3/4, 5/6 and 7/8
Filtering	square root raised cosine filtering with roll-off of 0.35
Multiple access	MF-TDMA based
Symbol clock accuracy	Symbol clock accuracy is within 20 ppm from the nominal symbol rate in the Timeslot Composition Table (TCT)
Carrier frequency accuracy	Normalized carrier frequency accuracy is better than 10^-8 (root mean square)
RF Frequency	Ku band, i.e. 12-18 GHz (IF output of the baseband unit is at L-band)
Frequency Source and Stability	1) GPS disciplined oscillators with < 5 ppb stability [3] 2) Reference OCXO with equivalent stability including aging plus or minus 5 X10^-8 / year (in the absence of GPS)

Digital Video Broadcasting-SH

DVB-SH (Digital Video Broadcasting - Satellite services to Handhelds)[1] is a physical layer standard for delivering IP based media content and data to handheld terminals such as mobile phones or PDAs based on a hybrid satellite/terrestrial downlink and (for example) a GPRS uplink. The DVB-SH system is designed for frequencies below 3 GHz, supporting UHF band, L band and S band. Depending on the transmitted signal modulation we can find two kinds of architectures: SH-A and SH-B. In SH-A architecture both terrestrial and satellite physical layers use OFDM which is robust against multipath. In SH-B architecture the terrestrial component uses OFDM but satellite uses Time Division Multiplexing (TDM).

Transmitter

Receiver

Features

Based on ETSI EN 302 583 v 1.2.1 [2]
There are two modulation possibilities for the satellite path: an OFDM mode based on DVB-T standard and a TDM mode, partly derived from DVB-S2
FEC using 3GPP2 Turbo code [3]
Interleaver diversity is largely provided by a common channel bit interleaver. An additional symbol interleaver is specified for OFDM

Modulation: OFDM - QPSK and 16-QAM (uniform, non-uniform) TDM - QPSK, 8PSK and 16 APSK
In OFDM 4 FFT modes are defined : 1K, 2K, 4K and 8K with the number of active carriers as 853, 1705, 3409 and 6817 respectively

Specifications

OFDM and TDM modes
FEC using turbo codes
Modulation	QPSK, uniform 16-QAM, non-uniform 16 QAM for OFDM and QPSK, 8PSK, 16 APSK for TDM
4 FFT sizes in OFDM	1k, 2k, 4k and 8k