NASA SBIR 2005 Solicitation


SUBTOPIC TITLE:Coding, Modulation, and Compression
PROPOSAL TITLE:Near Shannon Limit Low Peak Mean To Envelope Power Ratio (PMEPR) Turbo Block Coded OFDM for Space Communications

SMALL BUSINESS CONCERN (Firm Name, Mail Address, City/State/Zip, Phone)
Doradus Technologies, Inc.
2181 Camino De Los Robles
Menlo Park ,CA 94025 - 6531
(408) 954 - 1400

PRINCIPAL INVESTIGATOR/PROJECT MANAGER (Name, E-mail, Mail Address, City/State/Zip, Phone)
Sam    Heidari
2181 Camino De Los Robles
Menlo Park, CA  94025 -6531
(408) 954 - 1400

It is proposed to study and develop an innovative Turbo-block coded modulation scheme suitable for Orthogonal Frequency Division Modulation (OFDM) system. The new approach not only is capable of reaching the Shannon limit capacity, but it can also reduce the peak to envelope power ratio (PMEPR) of the OFDM symbols. This approach is unique since the design of high performance capacity achieving codes where all the OFDM signals produced by the codewords with low peak to average power ratio remains an extremely important, albeit a very difficult problem to solve, because a physical layer based on such codes can significantly reduce the cost of base stations. Typically, about 45% of the total cost of OFDM base stations corresponds to that of power amplifiers. This is due to the large linear region requirement of power amplifiers in these systems. OFDM transmission requires a large power amplifier linear region because of its relatively high peak to average power ratio signals. Thus OFDM power amplifiers are particularly expensive. Furthermore, reduction of PMEPR will reduce cost and power consumption for mobile units, enabling wider deployments and longer battery life.

Future space operations require reliable modulation and transmission schemes that are capable of supporting 3 bits or even higher spectral efficiencies. Furthermore, future NASA space operations include LEO/MEO satellites along with high altitude airborne platforms such as drones and aircrafts. Such mobile devices require design of robust and reliable modulation schemes with high spectral efficiencies. Since many of these devices are moving at high speed, the channel condition can change rapidly and an adaptive coding and modulation scheme is very appropriate to design power efficient techniques that can adapt to channel variations. OFDM is a bandwidth efficient scheme capable of transmission of hundreds of Mbps. However, there are many practical issues related to the implementation of this multicarrier modulation scheme such as PMEPR. We will address all these issues in this proposal.

Common obstacles to wide acceptance of a given application three-folds as: 1) Cost, 2) power consumption, and 3) performance. OFDM systems have already demonstrated a higher performance through efficient utilization of the spectrum. Enabling solutions at lower cost and power consumption will further this acceptance and will enable applications which would have not been realizable otherwise. For example, higher data rate mobile systems where without reduction in power consumption are not deployable. Another example is automation applications similar to 802.15 where cost and power are obstacles to acceptance, and higher performance will enable a new dimension of applications such as multimedia exchange.

NASA's technology taxonomy has been developed by the SBIR-STTR program to disseminate awareness of proposed and awarded R/R&D in the agency. It is a listing of over 100 technologies, sorted into broad categories, of interest to NASA.

Architectures and Networks

Form Printed on 09-19-05 13:12