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  MINIATURE SATELLITE TERMINALS

The SC2001 ASTRA and the SC3001 DIRAC ICs provide the full digital baseband transceiver resp. receiver functionality for CDMA-based satcom terminals. Application examples include 'little LEO' and 'big LEO' terminals for voice, data, messaging and geolocation. 

An example of a ‘little LEO’ application in which the SC2001 ASTRA is used, is the LLMS (Little LEO Messaging System), also called IRIS (Intercontinental Retrieval of Information by Satellite) from SAIT Systems. This network allows worldwide bi-directional communications to between small terminals and a number of satellites, which demodulate and store incoming data streams, and forward them when designated ground stations are in the footprint. In the terminals, the SC2001 ASTRA is the key component for the CDMA/spread spectrum processing of up- and downlink streams of a few kbps, with a processing gain of over 20 dB. The on-chip decimating filter and SRRC filter, together with the sufficiently long PN sequence length allow proper data recovery in the heavily interference-polluted VHF ‘little LEO’ band.

NAVIGATION TERMINALS

Navigation is one of the best known spread spectrum applications. Sirius Communications’ IC’s and CDMA technology are applied in various ways in the architecture of navigation terminals.

The SC2001 ASTRA can be applied in combination with a GPS or a GPS/GLONASS OEM module, providing a bi-directional communications channel, complementary to the receiver of the navigation channel.The SC2001 ASTRA can be configured as the baseband PHY layer of specialty GPS and GPS/GLONASS receivers.

Sirius Communications’ NAVICOMTM patented baseband IC architecture providing solutions for GPS and GLONASS codes, as well as the GNSS-1 EGNOS codes and the WAAS augmentation codes. Low power, small size and low cost are the key advantages of this novel approach.

Sirius Communications’ CDMA technology is also adopted for alternative (non-GPS based) navigation systems. Read the Wireless Design and Development article on a custom designed ASIC for 2-way paging and geolocation using a LEO bentpipe constellation, exploiting both pseudorange and Doppler information to obtain an accurate position fix.

Sirius Communications is developing chip sets for use in the future GNSS-2 satellite navigation system. 

High-precision RTK receiver baseband chips, exploiting both GPS and GLONASS reception, are designed on request, through Sirius Communications’ CDMA ASIC Design Service.

VSAT TERMINALS AND HUBSTATIONS

CDMA/Spread Spectrum gets an increasing attention as the technology of choice for VSAT (Very Small Aperture Terminal) applications. The SC2001 ASTRA is present in several commercial products and products under development. Feedback from the market confirms the following benefits of an SC2001 ASTRA-based CDMA VSAT implementation:

CDMA cdma ASIC Low psd (power spectral density) of the transmitted signal;
CDMA cdma ASIC Robustness against adjacent channel and in-channel interference, through processing gains over 30 dB, if required. This allows operation in bands suffering from interference, or using the CDMA/Spread Spectrum channel as an overlay simultaneously with other, non-CDMA applications. An example of this is the implementation of a D-SNG (Digital Satellite News Gathering) channel on a DVB transponder in use;
CDMA cdma ASIC Versatility in the assignment of number of channels per user;
CDMA cdma ASIC User data rate can be traded off for robustness, occupying the same bandwidth;
CDMA cdma ASIC Proprietary codes can be used (downloadable in on-chip RAMs of the SC2001 ASTRA), supporting any custom framing and clock frequency planning for the terminal;
CDMA cdma ASIC LPD/LPI for secure communications through the support of any custom PN code sequences and the possibility for dynamic PN code allocation;
CDMA cdma ASIC On-chip module for the support of QS-CDMA (Quasi-Synchronous CDMA), which provides a superior bandwidth efficiency (capacity) for star networks. The dual receiver architecture provides parallel demodulation of a Pilot and a Traffic channel;
CDMA cdma ASIC In the hub, several (tens of) SC2001 ASTRA chips can be put in a Master-Slave configuration (symbol clock and oversampled chip clock) for the processing of many simultaneous channels.

70 MHz Intermediate Frequency up/down converters are available, which plug in directly on the SC2002 ASTRA Development Board. 

POWERLINE MODEMS

The SC2001 ASTRA is successfully applied for powerline communications by taking advantage of the following features:

CDMA cdma ASICBandwidth and band position can be accurately tuned in accordance with the local regulations, by exploiting the programmability of the user data rates, PN code lengths, digital up- and downconversion frequencies;
CDMA cdma ASICDifferent types of powerline communications can be mixed by selecting different PN code lengths for different QoS (Quality of Service), and hence different BERs (Bit Error Rates);

An efficient burst communication protocol is available as part of the SC2002 ASTRA Development Board software.
   

UMTS APPLICATIONS

UMTS has an enormous potential for the upcoming third generation (3G) mobile telecommunication systems. Code Division Multiple Access (CDMA) plays an important role in these developments. Also it is acknowledged that satellite communications business in relation to its integration in UMTS will become very important too. 

Taking into account this vast potential, Sirius Communications, as an industry innovator, has already established collaboration and started W-CDMA developments with major telecommunication partners in 1997, 1998 and 1999 and offers its W-CDMA ASIC design skills to other interested companies. 

Later in 1999, Sirius Communications will announce more information on its W-CDMA solutions in the Sirius Communications'  line of products.

CATV UPSTREAM MODEMS

Spread Spectrum/CDMA has many advantages over PSK-based solutions for CATV upstream modems. The SC2001 ASTRA provides the following features:

CDMA cdma ASICIngress noise is effectively cancelled through processing gain;
CDMA cdma ASICHigh aggregate data rates are obtained through efficient CDMA/FDMA multiplexing;
CDMA cdma ASICThe SC2001 ASTRA can be configured for different data rates and different processing gains, depending on the application (data transfer, Internet communication) by run-time programming the data rate, PN code and code length and the number of channels per user. 

The SC9002 ASAP Development Board provides an optimal balance between network capacity and interference rejection.

TERRESTRIAL WIRELESS TERMINALS

Terrestrial wireless communications have been boosted by the (almost) worldwide allocation of the license-free ISM (Industrial, Scientific and Medical) bands, such as the 902-928 MHz band in the US, and the 2.4-2.4835 GHz band worldide available. These bands offer at the same time an opportunity and a challenge:

CDMA cdma ASICAs a user license is not required, rapid development and deployment is possible, taking into account the FCC part 15.247 (US) or ETS 300 328 (Europe) regulations;
CDMA cdma ASICThe bands are per definition to be shared with other applications, which means that the interference levels are unpredictable, both in space and in time. In order to guarantee a future-proof robust link, sufficient processing gain is required, together with the possibility of trading off user data rate for PN code length, preserving the same bandwidth occupation.

The SC2001 ASTRA and SC3001 DIRAC ICs satisfy the above requirements. This chip is used both in the terminals and in the central stations (base stations). Depending on the data rates, duty cycles and aggregate throughput requirements of the application at hand, the communication can be organized through polling, through random Aloha-type access or using QS-CDMA.

Important features which make the Sirius Communications products the right choice for use in medium- and long-range terrestrial networks (for voice and data communication), SCADA (Supervisory Control And Data Acquisition) networks, remote monitoring, remote control, surveillance applications are the following: 

CDMA cdma ASIC High-end components: implementation loss <0.1dB;
CDMA cdma ASIC High-speed data communications with SC9002 ASAP Development Board
CDMA cdma ASIC On-chip filters and up/down converters to/from IF;
CDMA cdma ASIC 4 parallel BPSK/CDMA or 2 parallel (O)QPSK/DMA communication channels for transmission and reception per chip (SC2001 ASTRA);
CDMA cdma ASIC Integrated 32-bit RISC ARM6 processor (SC3001 DIRAC);
CDMA cdma ASIC High robustness: programmable codes with lengths up till 1,023 give over 30dB of Processing Gain, providing a high immunity to interference and multipath fading (reflections);
CDMA cdma ASIC 9.6 kbaud, 19.2 kbaud or higher data rates are possible;
CDMA cdma ASIC Development boards are equipped with RS-232 interfaces;
CDMA cdma ASIC The SC3001 DIRAC IC has on-chip UART VL16C550 from VLSI Technologies, Inc.;
CDMA cdma ASIC Low power consumption;
CDMA cdma ASIC License-free operation when combined with 902-928 MHz frontend (USA) or 2.4 GHz Frontend (Europe, Japan);
CDMA cdma ASIC Pilot channel and on-chip synchronization functions allow for QS-CDMA (Quasi Synchronous CDMA) networks and Dynamic Multiple Access.

           
 
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