In this paper,we study the advantages of cooperation in broadcasting systems from a geosynchronous earth orbit(GEO)satellite to mobile terminals(MTs),achieved through a terrestrial complementary ground station(CGS) wi...In this paper,we study the advantages of cooperation in broadcasting systems from a geosynchronous earth orbit(GEO)satellite to mobile terminals(MTs),achieved through a terrestrial complementary ground station(CGS) with fixed installment,which acts as a relay.Moreover and in the context of the digital video broadcasting-satellite-to-handheld(DVB-SH) standard,the performance improvements offered by the rotated constellations method are investigated,where prior transmission,a phase rotation of the transmitted symbols by a fixed angle is applied followed by a random component interleaver.Turbo codes with soft decision decoding and appropriate random channel interleavers are also considered.We present analytical expressions for the bit log-likelihood ratios(LLRs)that are needed for soft decision decoding at the MT turbo decoder,while the code combining technique is adapted to improve the end-to-end(E2E) performance.Then,we obtain through extensive computer simulations the average bit error probability(ABEP) of quadrature phase-shift keying(QPSK) signals received over pure land-mobile satellite(LMS)and pure CGS links for coding rates 1/3 and6/7.Moreover,the optimal rotation angles are obtained for both links.E2 E ABEP results are then presented assuming cooperation between GEO and CGS,while the power allocation issue is investigated under fixed total transmission power.Our performance evaluation results show that by using the constellation rotation technique,a performance gain can be achieved for high coding rates.展开更多
The research is designed to examine current teaching practices and perceptions of elementary and secondary school language teachers so as to inform the design of a large-scale project on AWE （Automated Writing Evalua...The research is designed to examine current teaching practices and perceptions of elementary and secondary school language teachers so as to inform the design of a large-scale project on AWE （Automated Writing Evaluation） application in the Chinese classroom. The data indicated that teachers were confident in their computer use and understood formative assessment notions and their role in technology-enhanced teaching and learning. However, concerns were raised on the writing rubrics interpretation, the pedagogy on integrating AWE into teaching, and the suitability of the whole English software to Chinese learners. Solutions and suggestions were discussed. Sample lesson plans, pedagogy training and technical support were considered necessary for the participating teachers.展开更多
基金Support to the SatNEx-Ⅲ Network of Experts (SatNEx-Ⅲ) CoO2,2011-2012
文摘In this paper,we study the advantages of cooperation in broadcasting systems from a geosynchronous earth orbit(GEO)satellite to mobile terminals(MTs),achieved through a terrestrial complementary ground station(CGS) with fixed installment,which acts as a relay.Moreover and in the context of the digital video broadcasting-satellite-to-handheld(DVB-SH) standard,the performance improvements offered by the rotated constellations method are investigated,where prior transmission,a phase rotation of the transmitted symbols by a fixed angle is applied followed by a random component interleaver.Turbo codes with soft decision decoding and appropriate random channel interleavers are also considered.We present analytical expressions for the bit log-likelihood ratios(LLRs)that are needed for soft decision decoding at the MT turbo decoder,while the code combining technique is adapted to improve the end-to-end(E2E) performance.Then,we obtain through extensive computer simulations the average bit error probability(ABEP) of quadrature phase-shift keying(QPSK) signals received over pure land-mobile satellite(LMS)and pure CGS links for coding rates 1/3 and6/7.Moreover,the optimal rotation angles are obtained for both links.E2 E ABEP results are then presented assuming cooperation between GEO and CGS,while the power allocation issue is investigated under fixed total transmission power.Our performance evaluation results show that by using the constellation rotation technique,a performance gain can be achieved for high coding rates.
基金funded by a key MoE project titled "Using Automated Writing Assessment in China EFL Classrooms"(Project number:GFA097005)
文摘The research is designed to examine current teaching practices and perceptions of elementary and secondary school language teachers so as to inform the design of a large-scale project on AWE （Automated Writing Evaluation） application in the Chinese classroom. The data indicated that teachers were confident in their computer use and understood formative assessment notions and their role in technology-enhanced teaching and learning. However, concerns were raised on the writing rubrics interpretation, the pedagogy on integrating AWE into teaching, and the suitability of the whole English software to Chinese learners. Solutions and suggestions were discussed. Sample lesson plans, pedagogy training and technical support were considered necessary for the participating teachers.
