Extended GFDM Framework: OTFS and GFDM Comparison

Orthogonal time frequency space modulation (OTFS) has been recently proposed to achieve time and frequency diversity, especially in linear time-variant (LTV) channels with large Doppler frequencies. The idea is based on the precoding of the data symbols using symplectic finite Fourier transform (SFFT) then transmitting them by mean of orthogonal frequency division multiplexing (OFDM) waveform. Consequently, the demodulator and channel equalization can be coupled in one processing step. As a distinguished feature, the demodulated data symbols have roughly equal gain independent of the channel selectivity. On the other hand, generalized frequency division multiplexing (GFDM) modulation also employs the spreading over the time and frequency domains using circular filtering. Accordingly, the data symbols are implicitly precoded in a similar way as applying SFFT in OTFS. In this paper, we present an extended representation of GFDM which shows that OTFS can be processed as a GFDM signal with simple permutation. Nevertheless, this permutation is the key factor behind the outstanding performance of OTFS in LTV channels, as demonstrated in this work. Furthermore, the representation of OTFS in the GFDM framework provides an efficient implementation, that has been intensively investigated for GFDM, and facilitates the understanding of the OTFS distinct features.Comment: Accepted in IEEE Global Communications Conference 9-13 December 2018 Abu Dhabi, UA

The value of verbal information

TO MAKE PROFITABLE INVESTMENT DECISIONS, INVESTORS NEED TO ASSESS THE FINANCIAL FUTURE OF FIRMS. DUE TO INVESTORS’ LACK OF INTERNAL INFORMATION ABOUT THE FIRMS’ FUTURE PROSPECTS, THEY OFTEN HAVE TO RELY ON MANAGERS’ VERBAL STATEMENTS FOR THIS TASK. HOWEVER, AS MANAGERS MIGHT HAVE AN INCENTIVE TO PRESENT POSITIVELY BIASED INFORMATION, THE VALUE OF THEIR STATEMENTS FOR INVESTORS IS NOT CLEAR. IN THIS REPORT, WE SHOW HOW TEXTUAL ANALYSIS TOOLS CAN BE USED TO ASSESS THE VALUE OF MANAGERS’ VERBAL STATEMENTS DURING EARNINGS CONFERENCE CALLS FOR INVESTORS. WE FIND THAT IN PARTICULAR MANAGERS’ NEGATIVE STATEMENTS SIGNI FICANTLY PREDICT LOWER FUTURE EARNINGS

On preambles with low out of band radiation for channel estimation

International audienceWe investigate preamble designs for channel estimation that jointly address the estimation efficiency and the out of band (OOB) radiation of the transmit preambles. Accordingly, we provide two novel techniques for obtaining preambles for a single carrier system. Furthermore, we give a juxtaposition based method to extend their application to multi-carrier systems. The obtained preambles have 10 dB to 35 dB lower OOB radiation than the existing preamble based estimation techniques in literature. We also bring out the fundamental trade-off that exists between the estimation efficiency and the OOB radiation power, and highlight that the improved OOB performance comes at a cost of increased estimation error. Finally, as a case study, we study the performance of the obtained preambles in a multiple input multiple output (MIMO) Generalized Frequency Division Multiplexing ( GFDM) system, aimed for transmit diversity

Mapping Market Structure Evolution

The paper develops a novel methodology for uncovering changes in firms’ competitive positions in evolving market structure maps

GFDM-Based Asynchronous Grant-Free Multiple-Access

For next-generation Internet-of-Things (IoT) networks, asynchronous instant transmission has attracted increasing research interest with the expectation of achieving near-zero latency without excessive initiation procedure. However, in an asynchronous multiple-access scenario, there exist significant inter-carrier interference between sub-carriers allocated to different users. To suppress out-of-band emission (OOBE) of each sub-carrier, a new generalized frequency division multiplexing (GFDM) has been proposed, which has lower OOBE than the conventional orthogonal frequency division multiplexing (OFDM). In this paper, by using GFDM, two types of receivers are proposed with the aim of reducing latency and improving throughput: a GFDM-based minimum mean square error (MMSE) receiver and a GFDM-based MMSE-successive interference cancellation (SIC) receiver. Then, we develop a lightweight scheme using an epsilon-conservative rate control with GFDM-based MMSE receivers and also invent a performance-focused scheme using an advanced rate control with GFDM-based MMSE-SIC receivers. In particular, the latter scheme provides higher throughput with limited increase in computational load of user equipments. Numerical results show that with a high successful transmission probability higher than 99 %, the performance-focused scheme and the lightweight scheme achieve up to 85 % and up to 70 % higher throughput compared to the conventional OFDM-based asynchronous multiple-access scheme, respectively. Furthermore, since our proposal does not require any centralized user scheduling or initiation procedure, it presents a significant reduction in latency compared to the existing low-latency technologies