Guard Period Research Articles

Faster growth and larger size at crèche onset are associated with higher offspring survival in Adélie Penguins

Abstract We conducted the first assessment of Adélie Penguin (Pygoscelis adeliae) chick survival that accounts for imperfect resighting. We found that when chicks are larger in size when they enter the crèche stage (the period when both parents forage at the same time and chicks are left relatively unprotected), they have a higher probability of survival to fledging. We investigated the relationships between growth, crèche timing, and chick survival during one typical year and one year of reduced food availability. Chicks that hatched earlier in the season entered the crèche stage older, and chicks that both grew faster and crèched older entered the crèche at a larger size. These relationships were stronger in the year of reduced food availability. Thus, parents increased their chicks’ chance of fledging if they provided sufficient food for faster growth rates and/or extended the length of the brood-guarding period. Early nest initiation (i.e., early hatching) provided parents with the opportunity to extend the guard period and increase chick survival. However, to extend the guard stage successfully, they must provide larger meals and maintain higher chick growth rates, even if just one parent at a time is foraging, which previous work has shown is not possible for all individuals. We show that the factors governing tradeoffs in chick-rearing behavior of Adélie Penguin parents may vary in accord with environmental conditions, a result from which we can better understand species’ adaptations to environmental changes.

Underwater Acoustic Communication With Multicarrier Binary Frequency Shift Keying

This article describes a novel approach for robust and reliable underwater acoustic communication targeting low data rate applications in very challenging channels. The well-known binary frequency shift keying (BFSK) modulation is extended with multiple pair-wise BFSK subcarriers forming a multicarrier (MC) waveform referred to as MC-BFSK. Time offsets between neighboring subcarriers combined with windowing and guard periods are employed to increase the robustness against Doppler-induced frequency spread/shift and reverberation together with novel methods for synchronization, peak-to-average-power ratio reduction, and soft-value extraction. For the design of the parameters of the waveform, a heuristic approach is utilized. A noncoherent matched filter receiver with spatial diversity is adopted. The MC-BFSK transmission scheme is evaluated by means of computer simulations as well as sea-trial measurements. The obtained results are compared with competing modulation schemes where the proposed MC-BFSK shows better performance in challenging channels. In particular, we are able to decode frames in a sea-trial scenario where the direct path between the transmitter and the receiver is blocked by an island.

Intra- and inter-individual changes in little penguin diving and isotopic composition over the breeding season

Seabirds allocate different amounts of energy to reproduction throughout the breeding season, depending on the trade-off between their own needs and those of their chicks and/or changes in environmental conditions. Provisioning parents therefore modulate their foraging behaviour and diet accordingly. However, for diving seabirds, many studies have extrapolated from individuals monitored over a short period and then assumed the observed patterns were representative of the birds’ foraging activity over the entire breeding stage/season. To address this shortcoming, we monitored continuously the diving performance of ten male little penguins from incubation to chick fledging. Simultaneously, isotopic composition was examined using δ15N and δ13C values from whole blood samples collected every 3 weeks. Birds dived more frequently but performed shallower and shorter dives as the season progressed. The guard period was especially different, with birds spending a consistently smaller proportion of time at the bottom and performing fewer prey pursuits, compared to other periods. Isotopic composition varied less within the season, although there was a slight tendency for δ15N values to decrease through time. Finally, isotopic values were highly repeatable within individuals, suggesting that individuals specialized on different prey and in different areas. Diving was less repeatable within individuals but still explained a small but significant part of the variance in blood isotopic values. Our results suggest that it is important to take into account individual variability over the course of the breeding season, as well as timing of bio-logger deployment within a stage when designing bio-logging studies.

Traditional Chinese medicine in the treatment of postpartum bell´s palsy

Introduction: Pregnant women have more risk for Bell´s palsy compared to non-pregnant women. The majority of cases occur in the third semester of the immediate period post-partum. In traditional Chinese medicine, Bell´s palsy occurs due to the invasion of the external pathogenic factor Wind-Cold attacking the face´s channel. The purpose of this study is to demonstrate why women in post-partum period had more propensity to Bell’s palsy and that the patient has chakras’ energy deficiencies that leads to propensity to develop this problem. Methods: through one case report, 36 years old women who had cesarean section in on November 14th 2020. She wakes up in the next day with the face completely deviated to the right side and cannot close her eyelid in the right eye. She searched for Western medicine physician that orientate her to intake corticosteroids. She went to the author´s clinic and told the doctor that she always turns on the fan on top of her because she was felling much hot in her body during the pregnancy and after the partum. The treatment consisted in Chinese dietary counseling, auricular and systemic acupuncture. It was orientated to restart to intake the homeopathies, crystal based medications that was recommended to her one year ago, and she stopped to intake during the pregnancy. Results: After the first acupuncture session, her face improved very well (50 percent) and she could smile and move the tongue, close her right eyelid better, and the deviation reduced completely using three acupuncture sessions. She also was orientated to avoid raw foods, cold water and walk barefoot and dry the hair after washing it and avoid to go outside her home during the guard period (for a period of 40 days). Conclusion: Women in the post-partum period has more propensity to develop Bell´s palsy because they lost very much Blood and other fluids during the child-birth and usually loose much energy in this process weakening the body and had more propensity to the invasion of Cold and Wind, generation in this form, Bell´s palsy symptoms.

Time-lapse camera photographs reveal arrival and breeding timing of short-tailed albatrosses Phoebastria albatrus

Monitoring the ecology of seabirds breeding on remote islands is often challenging. However, time-lapse cameras have enabled the surveillance of inaccessible sites. We examined arrival/departure movements and breeding timing of the endangered short-tailed albatrossPhoebastria albatruswith time-lapse cameras on Torishima, a remote and uninhabited island in the northwestern Pacific, from November 2016 to June 2017. The photographic images revealed that the first arrival of the albatrosses on the island was on 7 October 2016, and the number of birds reached a peak of 506 on 5 November. The white pairs arrived and began incubating approximately 1 wk earlier than the white/brownish pairs. From the end of January, the number of birds repeatedly increased and decreased within a short period of time. The birds’ movement out of the breeding colony often occurred synchronously with a rapid decline in the mean daily air pressure. Adult birds began to leave the colony in April. The number of chicks reached up to 200 at the beginning of May, but they all left the colony before 1 June. The processing of the photographic images taken during the incubation and early guard periods revealed that hatching failed in approximately 10% of the pairs. The validity of information collected by time-lapse cameras was confirmed by comparing it with the results of previous field studies. This study will contribute to the collection of essential information for monitoring and conserving seabirds breeding on remote islands where successive or frequent fieldwork is difficult.

On the Sensitivity of Zero-Tail DFT-Spread-OFDM to Small Bandwidth Allocations

The benefits of zero-tail discrete Fourier transform-spread-orthogonal frequency division multiplexing (ZT DFT-s-OFDM) in terms of spectral containment and link performance subsume that the internal guard period of the waveform has negligible power. However, the effective power of such guard period depends in practice on the bandwidth allocation and is still significant in case of small bands. In this letter, we characterize the residual energy of the ZT DFT-s-OFDM guard period and evaluate its impact on spectral containment, non-cyclic inter-symbol interference (ISI) and link performance when small transmission bands are used. Spectral containment is shown not to be affected thanks to the oscillating part of the guard period, which ensures the presence of low power samples in the transition between adjacent time symbols. Despite the larger tail power, link performance is shown to be only marginally affected. This is because small bandwidth configurations experience a nearly flat fading, and therefore minimum non-cyclic ISI over the next symbol.

Generalized DFT-s-OFDM Waveforms Without Cyclic Prefix

This paper deals with generalized discrete Fourier transform—spread—orthogonal frequency division multiplexing (G-DFT-s-OFDM) waveforms, which replace the cyclic prefix of traditional OFDM/DFT-s-OFDM with an internal guard period. Such waveforms feature significant benefits in terms of flexibility, spectral containment, and low peak-to-average power ratio. Aspects related to reference sequence design and mapping for channel estimation are thoroughly addressed, and a new estimator for the specific zero-tail DFT-s-OFDM case is proposed. Furthermore, we address the opportunity of exploiting the internal guard period at each symbol for frequent channel state information updates, thus enabling the possibility of tracking rapidly varying propagation conditions.

Performance of Differential-Phase OFDM Systems over Selective Multipath Fading Channels

This paper investigates the performance of differential-phase Orthogonal Frequency Division Multiplexing (OFDM) over frequency-selective multipath Nakagami-m radio fading channels. A closed form for the average signal to noise/interference ratio in the presence of the selective multipath fading channel and additive white Gaussian noise (AWGN) is derived. The results reveal that the system performance is impacted by the interference between the adjacent OFDM frames in two successive signaling intervals which is called Inter-Symbol-Interference (ISI). In addition, the system will possibly be distorted when the orthogonality between the adjacent subcarriers is ceased, creating Inter-Channel-Interference (ICI). This paper also studies the bit-error-rate (BER) performance of the differential-phase OFDM system over the Nakagami-m channel in the presence of AWGN, ISI, and ICI under different conditions and parameters. Moreover, the effect of adding the guard period and the number of subchannels on the probability of error is analyzed. The IEEE 802.11a standard parameters with 64 subcarriers and a decaying exponential power delay profile with root-mean-square value of 129 ns are used in this study. The system performance is also simulated at different guard intervals, number of OFDM subcarriers, Nakagami severity parameter values, and different numbers of possible differential phases.

Flexible DFT-S-OFDM: Solutions and Challenges

Discrete Fourier transform spread orthogonal DFT-S-OFDM, adopted in 3GPP LTE uplink, enables the synthesis of block-based single carrier waveforms with various bandwidths by changing the size of the DFT-spread block. Conceptually, it also allows a transition between block-based multicarrier and single-carrier schemes when multiple DFT-spread blocks are employed in the structure. Recently, it has been shown that DFT-S-OFDM can also accommodate an internal guard period that offers flexibility on the duration of the guard periods without affecting the symbol duration. In this article, we present further modifications of DFT-S-OFDM that offer improvements in flexibility and discuss the latest enabling techniques on this topic. Considering the flexibility introduced by DFTs-OFDM and its variations, the DFT-S-OFDM family also offers a set of promising waveforms for 5G networks, which will require a flexible physical layer.

Temporal variation in the diet of gentoo penguins at the Falkland Islands

Knowledge of diet is critical in interpreting the ecological roles of marine top predators and provides information towards their conservation and management. The Falkland Islands hold the largest number of breeding gentoo penguins. Yet knowledge of gentoo penguin diet at the Falklands is limited to either broad taxonomic divisions of prey items or dietary samples collected only on a single day. This study is the first to investigate gentoo penguin diet at Cow Bay, Falklands, to the species level, over repeated sampling intervals during the breeding period. Through stomach content analysis, we determined diet over a large temporal scale (2002/2003/2004–2011/2012/2013) and between the guard and creche periods of chick rearing. The principle prey item by reconstituted mass was rock cod fish Patagonotothen spp., for all periods (47–78 %) except that of the 2012/2013 creche period (19 %) when Falkland herring Sprattus fugensis made up the bulk of the diet (52 %). Of the cephalopods recovered, Patagonian squid Doryteuthis gahi was prominent (1–24 %), while crustaceans contributed negligibly to gentoo penguin diet. Our findings revealed that gentoo penguins breeding at the Falkland Islands were primarily demersal foragers with an ability for pelagic feeding. Diet choice appears to reflect prey availability.

Enhanced Common-Mode Noise Rejection Method Based on Impedance Mismatching Compensation for Wireless Capsule Endoscopy Systems

Common-mode noise (CMN) is an unresolved problem in wireless capsule endoscopy (WCE) systems. In a WCE system, CMN originates from various electric currents found within the human body or external interference sources and causes critical demodulation performance degradation. The differential operation, a typical method for the removal of CMN rejection, can remove CMN by subtracting two signals simultaneously received by two reception sensors attached to a human body. However, when there is impedance mismatching between the two reception sensors, the differential operation method cannot completely remove CMN. Therefore, to overcome this problem, we propose an enhanced CMN rejection method. The proposed method performs not only subtraction but also addition between two received signals. Then a CMN ratio can be estimated by sufficient accumulation of division operation outcomes between the subtraction and addition outputs during the guard period. Finally, we can reject the residual CMN by combining the subtraction and addition outputs.

BER Performance of OFDM with GI in SISO and MIMO System

overcome a multipath fading environment with low complexity and to achieve wireless broadband multimedia communication systems, orthogonal frequency division multiplexing (OFDM) transmission scheme is used. OFDM is one of the applications of a parallel data transmission scheme, which reduces the influence of multipath fading. The performance of OFDM can be improved further using concept of spatial diversity Multiple Input Multiple Output. The paper explains the performance of MIMO OFDM under the Rayleigh channel, also it uses different guard interval with modulation schemes as 4-QAM. It shows that by using OFDM with SISO and MIMO, remarkable performance is shown in terms of Bit Error Rate (BER). KeywordsMultiple Input Multiple Output (MIMO), orthogonal frequency division multiplexing (OFDM), Bit Error Rate (BER), Cyclic Prefix (CP), Guard Period, 4-QAM, Rayleigh channel.

Iterative Group Splitting Algorithm for Opportunistic Scheduling Systems

An efficient feedback algorithm for opportunistic scheduling systems based on iterative group splitting is proposed in this paper. Similar to the opportunistic splitting algorithm, the proposed algorithm adjusts (or lowers) the feedback threshold during a guard period if no user sends a feedback. However, when a feedback collision occurs at any point of time, the proposed algorithm no longer updates the threshold but narrows down the user search space by dividing the users into multiple groups iteratively, whereas the opportunistic splitting algorithm keeps adjusting the threshold until a single user is found. Since the threshold is only updated when no user sends a feedback, it is shown that the proposed algorithm significantly alleviates the signaling overhead for the threshold distribution to the users by the scheduler. More importantly, the proposed algorithm requires a less number of mini-slots than the opportunistic splitting algorithm to make a user selection with a given level of scheduling outage probability or provides a higher ergodic capacity given a certain number of mini-slots.

Effects of carrier frequency offset on the average effective SNR and the average BER for asynchronous MC‐CDMA uplink systems with a guard period

AbstractThis paper presents an analysis of asynchronous multicarrier‐code division multiple access (MC‐CDMA) systems over frequency‐selective multipath fading channels when the carrier frequency offsets (CFOs) of all users are random variables and the frequency offset for the desired user is compensated. The effect of residual CFO on the average bit error rate (BER) is evaluated by the semi‐analytical method, then the approximated BER performance is obtained as a closed‐form expression. Moreover, the signal‐to‐noise ratio (SNR) loss caused by residual CFO is evaluated. Derived results show that the performance degradation due to residual frequency offset is negligible if the estimation error of CFO for the desired user is less than the normalized value of 10−1. Copyright © 2011 John Wiley & Sons, Ltd.

Hybrid STT/ERT and SC-FDE technique for single carrier transmission with a guard period

This paper proposes a hybrid shortened transmission/expanding reception technique and single carrier modulation with a zero forcing frequency domain equalizer when a single carrier modulation with a guard period is transmitted. Regarding single carrier transmission data as shortened OFDM transmission data allows an expanding reception technique and a maximum ratio to be combined in the receiver, and a parallel single carrier modulation with a frequency domain equalizer is used as a secondary receiver. The proposed hybrid scheme does not have channel codec but simulation results show it has better performances in comparison with the coded OFDM algorithm at the expense of algebraic calculations and FFT executions.

Generation of Filter Bank-Based Multicarrier Waveform Using Partial Synthesis and Time Domain Interpolation

Recently, multirate filter banks have been recognized as high performance signal processing tools that could significantly enhance the efficiency and flexibility of future wireless communications. Filter bank-based multicarrier (FBMC) modulation allows increasing the spectral efficiency of high data rate transmission, both through the lack of time domain guard periods and the reduced frequency domain guard bands. Further, the inherent frequency selectivity is regarded as a vital characteristic, which enables high quality radio scene analysis, necessary for successful deployment of dynamic spectrum access in the context of cognitive radio technology. When applied to multicarrier communications, the filter banks are operated in the so-called transmultiplexer configuration where typically equal-size synthesis and analysis filter banks are utilized at the transmitter and receiver, respectively. This paper presents a new approach to generate an FBMC signal waveform. We focus on contiguous narrowband subcarrier allocation, which is often encountered in uplink transmission. Instead of using a full-size M-subchannel synthesis filter bank, the proposed scheme relies on a cascade of a P-subchannel synthesis bank (P ≪ M), time domain interpolation, and a user-specific frequency shift. This method allows constructing a transmitter-receiver pair using synthesis and analysis filter banks of different sizes. The presented approach is shown to provide notable computational complexity savings over a wide range of practical user bandwidth allocations, when compared to the conventional implementation consisting of equally sized filter banks. Therefore, this novel scheme provides flexible and low-complexity synthesis of spectrally well-localized FBMC uplink waveforms, which show strong potential for future broadband mobile communications.

Techniques of Transmitting Beamforming to Control the Generated Weights

In this paper, we consider the limited feedback Transmitting Beamforming for MISO systems. In conventional techniques, all vectors of a large codebook (CB), used for the feedback of the quantized channel state information (CSI), are broadcasted to all users, in a guard period which is followed by data burst periods. Instead of transmitting a high number of codevectors, we thought to divide the CB into several sub-codebooks (SC) and the broadcast would be based on the switch between them. Accordingly, a good performance can be provided while minimizing the required feedback channel capacity applying some proposed techniques such as “the switched Sub Codebook (SSC)” and “the Fairness SSC (FSSC)”. To minimize the quantization error, we propose two other techniques. The first is based on making Transmit SSC vectors controlled by a rotation weight (RW) to obtain almost a zero correlation between the SSC vectors used for the selected spatial channels. The second is based on introducing “the Schmidt algorithm” to construct an orthonormal weights using the generated weights. These two proposed techniques increase the probability of the selection of the worst case user on his best codevector to make zero the angle between his couple codevector and channel response. To analyze and validate the performance of these proposed techniques, simulation results are presented.

Performance evaluation for asynchronous MC‐CDMA systems with a symbol timing offset

AbstractThis paper models a symbol timing offset (STO) with respect to the guard period and the maximum access delay time for asynchronous multicarrier‐code division multiple access systems over frequency‐selective multipath fading channels. Analytical derivation shows that STO causes desired signal power degradation and generates self‐interferences. This effect of the STO on the average bit error rate (BER) and the effective signal‐to‐noise ratio (SNR) is evaluated using the semi‐analytical method, and the approximated BER and the SNR loss caused by STO are then obtained as closed‐form expressions. The tightness between the semi‐analytical result and the approximated one is verified for the different STOs and SNRs. Furthermore, the derived analytical results are verified via Monte Carlo simulations. Copyright © 2008 John Wiley & Sons, Ltd.

Blood fatty acids indicate inter- and intra-annual variation in the diet of Adélie penguins: Comparison with stomach content and stable isotope analysis

Adélie penguin ( Pygoscelis adeliae) diet is an important indicator of prevailing environmental conditions and resource availability. In this study, dietary variation within and between years was studied with fatty acid signature analysis (FASA), stomach content analysis (SCA) and stable isotope analysis (SIA). We profiled the fatty acid (FA) composition of whole blood collected from adult penguins throughout the breeding season, and from chicks during the crèche period, in 2001 and 2002. Differences were detected in FA profiles between years, breeding stage and age (adults vs. chicks). These patterns broadly corresponded to those observed from SCA and SIA, with a mix of krill and fish consumed in the early part of the breeding season in both years, krill dominating the diet during the chick-rearing periods in 2001, and fish in 2002. Different metabolic and physiological demands between stages, and ages, may also influence FA profiles but warrants further investigation. In-situ calibrations of adult FA blood profiles were made using corresponding stomach samples to quantify diet composition. Using linear discriminate function analysis, we classified adult FA profiles into 3 meal-types: krill, fish or mixed. A higher proportion of adults had fish-like profiles during the arrival and guard periods. Krill-like profiles dominated during the incubation and crèche periods, although there were a relatively high proportion of fish-like and mixed profiles as well. These patterns corresponded to results from SCA and SIA. This study demonstrates that FASA has the potential to be integrated with other dietary tools to enhance diet monitoring studies, which are currently integral to ecosystem management and conservation measures. The in-situ calibration method used offers a simple and effective alternative to more rigorous calibration techniques developed elsewhere.

Bandwidth Sharing Schemes for Multimedia Traffic in the IEEE 802.11e Contention-Based WLANs

Bandwidth allocation schemes have been well studied for mobile cellular networks. However, there is no study about this aspect reported for IEEE 802.11 contention-based distributed wireless LANs. In cellular networks, bandwidth is deterministic in terms of the number of channels by frequency division, time division, or code division. On the contrary, bandwidth allocation in contention- based distributed wireless LANs is extremely challenging due to its contention-based nature, packet-based network, and the most important aspect: only one channel is available, competed for by an unknown number of stations. As a consequence, guaranteeing bandwidth and allocating bandwidth are both challenging issues. In this paper, we address these difficult issues. We propose and study nine bandwidth allocation schemes, called sharing schemes, with guaranteed Quality of Service (QoS) for integrated voice/video/data traffic in IEEE 802.11e contention-based distributed wireless LANs. A guard period is proposed to prevent bandwidth allocation from overprovisioning and is for best-effort data traffic. Our study and analysis show that the guard period is a key concept for QoS guarantees in a contention-based channel. The proposed schemes are compared and evaluated via extensive simulations.