The GEMMA project concerns the design, development and demonstration of innovative gateway and user terminal prototypes able to support and provide M2M services in either geostationary or non-geostationary scenarios characterized by user mobility and high Doppler and exploiting the aid of an ad-hoc Forward Link.
The main objectives of the proposed activity are:
The main challenge of the project is to efficiently support bi-directional M2M services via low-cost user terminals (i.e. with low EIRP, low quality oscillators and low complexity) in a difficult environment like the satellite communications one, characterized by huge distances and huge Doppler (for LEO scenarios).
A further challenge is coming from the mobile nature of the main target applications to be supported as mobility brings with itself potentially strong fading to deal with.
Space Engineering and MBI are strategic partners and have a strong heritage in the development of ground solutions for M2M applications based on E-SSA (Enhanced Spread Spectrum Aloha) random access, being among the inventors of the technology. Such know-how was gained from both ESA studies (including the precursor Artes 5.1 AO6830) and commercial projects.
E-SSA technology proved to be the most suitable to manage a large and uncoordinated population of inexpensive terminals and ESA has largely supported the development of E-SSA in the past.
The main advantages of the proposed solution are its efficiency and the high flexibility in terms of supported system scenarios, channelization and terminal characteristics.
Furthermore, the following benefits apply:
The proposed solution is bi-directional and can support a variety of services also exploiting the ad-hoc forward link designed for the scope. The E-SSA-based return link is completely asynchronous and can operate in different environments and with different bandwidth constraints (e.g. from 50KHz to several MHz). It supports operation with terminals having very low EIRP (e.g. -16 dBW). Bitrates per terminal in the order of 200 bit/s can be provided on the return link, with an aggregated spectral efficiency higher than 1 bit/s/Hz. The great versatility of the E-SSA technology makes it suitable for implementation with extremely simple terminals, asynchronous and low-power without any limitation of band and satellite system.
The forward link allows on one side to enable applications based on outbound communication and on the other side to efficiently support the inbound communication, enhancing the return link management and helping in minimizing the terminals’ cost.
The system designed, developed and demonstrated in the project is a testbed consisting in three main components:
The gateway is the heart of the system and implements both a E-SSA-based rx chain (return link) in charge of receiving messages from the population of terminals and a tx chain able to send messages to terminals through the ad-hoc forward link air interface.
The traffic generator is essential in reproducing the traffic coming from a huge population of terminals, thus allowing tests in realistic traffic conditions.
The user terminal prototype implements a simple tx chain for asynchronous transmission and a rx chain allowing to test and demonstrate the designed forward link air interface performance.
The project duration is 18 months.
The first phase deals with the scenarios and requirements definition as well as the state-of-art analysis and lasts four months (ending with the SRR milestone).
The second phase deals with target system design and ends after 8 months (CDR milestone).
The third phase regards the testbed implementation and ends after 16 months (TRR milestone).
The last project phase is the validation and demonstration of the implemented testbed (ending with the FR milestone after 18 months).
The project has been kicked-off and the activities related to the first phase have recently started.