Upper-Bound Performance of a Wide-Band Adaptive Modem

Adaptive modulation is applied in conjunction with a decision-feedback equalizer (DFE) in order to mitigate the effects of the slowly varying wide-band multipath Rayleigh fading channel in a noise-limited environment. An upper-bound mean bit-error rate and bits per symbol performance is introduced for this scheme by utilizing the pseudo signal-to-noise ratio at the output of the DFE in order to switch the modulation schemes on a burst-by-burst basis. Index Terms—AQAM, QAM, quadrature amplitude modulation, wide-band adaptive modulation

Turbo-Coded Adaptive Modulation Versus Space-Time Trellis Codes for Transmission over Dispersive Channels

Decision feedback equalizer (DFE)-aided turbocoded wideband adaptive quadrature amplitude modulation (AQAM) is proposed, which is capable of combating the temporal channel quality variation of fading channels. A procedure is suggested for determining the AQAM switching thresholds and the specific turbo-coding rates capable of maintaining the target bit-error rate while aiming for achieving a highly effective bits per symbol throughput. As a design alternative, we also employ multiple-input/multiple-output DFE-aided space–time trellis codes, which benefit from transmit diversity and hence reduce the temporal channel quality fluctuations. The performance of both systems is characterized and compared when communicating over the COST 207 typical urban wideband fading channel. It was found that the turbo-coded AQAM scheme outperforms the two-transmitter space–time trellis coded system employing two receivers; although, its performance is inferior to the space–time trellis coded arrangement employing three receivers. Index Terms—Coded adaptive modulation, dispersive channels, space–time trellis codes

Embracing noise to improve cross-batch prediction accuracy

10.1186/1752-0509-6-S2-S3BMC Systems Biology6SUPPL.2

Burst-by-Burst Adaptive Decision Feedback Equalized TCM, TTCM, BICM and BICM-ID

Decision Feedback Equalizer (DFE) aided wideband Burst-by-Burst (BbB) Adaptive Trellis Coded Modulation (TCM), Turbo Trellis Coded Modulation (TTCM), Bit-Interleaved Coded Modulation (BICM) and BICM with Iterative Decoding (BICM-ID) are proposed and characterised in performance terms over the COST 207 Typical Urban (TU) wideband fading channel. These schemes are evaluated using a practical modem mode switching regime. System I represents schemes without channel interleaving, while System II invokes channel interleaving over four transmission bursts. A substantially improved Bit Per Symbol (BPS) and Bit Error Rate (BER) performance was achieved by System II in comparison to System I. BbB-adaptive TTCM was found to give the best performance, when aiming for a target BER of below 0.01%

Burst-by-Burst Adaptive Wireless Video Telephony over Dispersive Channels

The video performance benefits of burst-by-burst adaptive modulation are studied, employing a higher order modulation mode, when the channel is favourable, in order to increase the system's bits per symbol throughput and conversely, invoking a more robust, lower order modulation mode, when the channel exhibits inferior channel quality. It is shown that due to the proposed adaptive modem mode switching regime a seamless video-quality versus channel quality relationship can be established, resulting in error-free video quality right across the operating channel Signal-to-Noise Ratio (SNR) range

Interval oscillation theorems for asecond-order linear differential equation

AbstractInterval oscillation criteria are given for the forced second-order linear differential equation Ly(t) = (p(t)y′)′ + q(t)y = ƒ(t), tε (0, ∞), where p, q, ƒ are locally integrable functions and p(t) > 0, for t > 0. No restriction is imposed on ƒ(t) to be the second derivative of an oscillatory function as assumed by Kartsatos [1). Our results also allow both q and f to change sign in the neighborhood at infinity. In particular, we show that all solutions of y″ + c(sin t)y = tβ cos t with β ≥ 0 are oscillatory, for c ≥ 1.3448. This improves an estimate given by Nasr [2] for the linear equation

Network optimisation - A statistical physics perspective

Inference and optimisation of real-value edge variables in sparse graphs are studied using the tree based Bethe approximation optimisation algorithms. Equilibrium states of general energy functions involving a large set of real edge-variables that interact at the network nodes are obtained for networks in various cases. These include different cost functions, connectivity values, constraints on the edge bandwidth and the case of multiclass optimisation

Experiences of COVID-19 among Chinese-speaking lesbian, gay and bisexual people in Hong Kong: an inductive thematic analysis of survey response data

As social inequalities during the COVID-19 pandemic have been recognised, emerging research showed that lesbian, gay and bisexual (LGB) people may be additionally affected during the pandemic. This paper adds to the understanding of the experiences of LGB people during the pandemic with a focus on Hong Kong, where issues of space significantly influence LGB people’s lives in this city with high population density. As part of a larger community study of LGB lives in Hong Kong, COVID-19-related impact on 434 Chinese-speaking LGB people was explored. Data collection was conducted from 20 May to 30 June 2020. Inductive thematic analysis of the open-text response survey data found that the LGB participants described both negative and positive impacts brought by COVID-19. Such impacts could be dimensionalised into those related to personal space and privacy, romantic and sexual space, and community space. It was also found that the experiences of COVID-19 among LGB people in Hong Kong were intersectional, along the lines of living arrangement and relationship status. Such findings make unique contributions to the emerging literature. First, there needs to be a more nuanced understanding of sexual minority individuals’ experiences during COVID-19 across cultural contexts. Second, COVID-19 was described as having brought positive impact in addition to its widely known negative impact