Transmission Opportunities Research Articles

Cultural transmission among hunter-gatherers

We examine from whom children learn in mobile hunter-gatherers, a way of life that characterized much of human history. Recent studies on the modes of transmission in hunter-gatherers are reviewed before presenting an analysis of five modes of transmission described by Cavalli-Sforza and Feldman [L. L. Cavalli-Sforza, M. W. Feldman, Cultural Transmission and Evolution: A Quantitative Approach (1981)] but not previously evaluated in hunter-gatherer research. We also present two modes of group transmission, conformist transmission, and concerted transmission, seldom mentioned in hunter-gatherer social learning research, and propose a unique mode of group transmission called cumulative transmission. The analysis of the additional modes of transmission indicated that cultural evolutionary signatures of vertical transmission, such as the conservation of cultural traits, have been underestimated because previous studies have seldom considered remote generations or distinguished intrafamilial from extrafamilial horizontal and oblique transmission. However, field data also indicate that hunter-gatherer children interacted with and learned from many nongenetically related individuals; about half of children's and adolescents' horizontal and oblique social learning came from nongenetically related individuals. Intimate living conditions of hunter-gatherers provide opportunities for group transmission, and ethnographic evidence presented demonstrates that at least three types of group transmission exist. All three forms of group transmission theoretically contribute to the conservation of culture, homogeneity of intracultural diversity, and high intercultural diversity. Analysis of additional modes of oblique and horizontal transmission and discussion of previous and unique modes of group transmission demonstrate the various mechanisms by which hunter-gatherer children learn and how cultures are conserved and contribute to cumulative culture.

Delay management for heterogeneous traffic in vehicular sensor networks using packet fragmentation of low priority data

AbstractVehicular sensor networks (VSNs) are expected to revolutionize the transportation systems through automated decision‐making. These networks function on the communication between vehicles, traffic infrastructure, and people. One of the major challenges of VSNs is to deal with heterogeneous traffic due to the diverse nature of information and data generated by different types of sensors and devices within the vehicular environment. To ensure an effective operation of the network, it is crucial to offer a differentiated quality of service to each traffic class. Media access control (MAC) protocols offer an opportunity to provide differentiated channel access to the traffic of different priorities. This work is focused on offering comparison of recent MAC schemes in terms of their performance for heterogeneous traffic generated by VSNs. Two protocols FROG‐MAC and UrgMAC have been selected: FROG‐MAC is developed using a simple concept of packet fragmentation, where the packets of lower priority are fragmented to offer an early transmission opportunity to urgent traffic; on the other hand, urgMAC is designed using advanced cross‐layer techniques of two‐tiered service differentiation mechanism, adaptive data rate adjustment mechanism, urgency‐based contention window size adaptation, traffic type adaptive duty cycle, and multimedia message passing. It has been found that the FROG‐MAC outperforms urgMAC in terms of delay, energy consumption and packet delivery ratio.

Regional variation in the landscape ecology of West Nile virus sentinel chicken seroconversion in Florida.

How landscape composition and configuration impact the distribution of multi-vector and multi-host mosquito vector-borne disease systems, such as West Nile virus (WNV), remains challenging because of complex habitat and resource requirements by hosts and vectors that affect transmission opportunities. We examined correlations between landscape composition and configuration and 2018 WNV sentinel chicken seroconversion in Florida, USA across the state and within five National Oceanic Atmospheric Administration (NOAA) bioclimatic regions to understand strength and variation of landscape effects during an elevated transmission year. Although few landscape studies have examined WNV in Florida, we expected higher percentages of residential or medium-developed landscapes and more fragmented landscapes would be positively correlated with WNV seroconversion owing to the main mosquito vector habitats and avian host distributions. However, we expected to find variation in the importance of forest, wetland, and agriculture landscapes across bioclimatic regions in the state. WNV seroconversion rates were calculated using Florida 2018 Department of Health WNV sentinel chicken seroconversion data from 187 flocks maintained by mosquito control programs. Percent land cover and edge density metrics were calculated for multiple land cover classes and within multiple buffer distances from chicken coops using 2019 National Land Cover Data. We used binomial generalized linear mixed effects models to calculate the importance of landscape metrics to WNV seroconversion. We found no statewide predictors of seroconversion, but as expected, the importance of landscape varied across regions. In the north-central part of the state, we found higher seroconversion in less populated suburban areas while higher seroconversion in south-central Florida was correlated with fragmented forested areas within 0.5 km of coops and intact woody wetland areas within 2 km of coops. This work corroborates previous findings that consistent landscape predictors of WNV are difficult to identify across broader geographic areas and sets the stage for additional work that incorporates climate and landscapes interactions for a greater understanding of WNV ecology in this geographic region.

Increased pathogen exposure of a marine apex predator over three decades.

Environmental changes associated with global warming create new opportunities for pathogen and parasite transmission in Arctic wildlife. As an apex predator ranging over large, remote areas, changes in pathogens and parasites in polar bears are a useful indicator of changing transmission dynamics in Arctic ecosystems. We examined prevalence and risk factors associated with exposure to parasites and viral and bacterial pathogens in Chukchi Sea polar bears. Serum antibodies to six pathogens were detected and prevalence increased between 1987-1994 and 2008-2017 for five: Toxoplasma gondii, Neospora caninum, Francisella tularensis, Brucella abortus/suis, and canine distemper virus. Although bears have increased summer land use, this behavior was not associated with increased exposure. Higher prevalence of F. tularensis, Coxiella burnetii, and B. abortus/suis antibodies in females compared to males, however, could be associated with terrestrial denning. Exposure was related to diet for several pathogens indicating increased exposure in the food web. Elevated white blood cell counts suggest a possible immune response to some pathogens. Given that polar bears face multiple stressors in association with climate change and are a subsistence food, further work is warranted to screen for signs of disease.

An efficient beam sweeping scheme with backup paging occasions in NR-Unlicensed Spectrum

With the increasing demand of user applications and the shortage of cellular spectrum, New Radio (NR) access to Unlicensed Spectrum (NR-U) is getting significant attention. Listen Before Talk (LBT) procedure is used to sense unlicensed channel availability prior to transmission. The transmissions are subjected to LBT procedure failure, which brings extra delay as they are postponed to the next available transmission opportunity. This excess delay also affects time-critical procedures, such as paging. The directional communication in NR requires beamforming, which further complicates paging procedure as additional paging message transmissions are needed to cover all the beams. In this work, we propose an NR-U paging mechanism (called FF_BP) consisting of Full and Fast Paging Cycles with Backup Paging Occasions (POs). Full Paging uses a normal NR-U paging cycle and broadcasts a paging message on all the beams. On the other hand, Fast Paging, which targets delay-sensitive mobile users, uses a shorter paging cycle and broadcasts a paging message on selected beams only. The Backup POs deal with LBT procedure failure impairments while paging broadcast on selective beams reduces paging resource usage. We analyze FF_BP using a discrete-time semi-Markov chain model and validate the model by extensive simulations. The simulation results show that FF_BP outperforms several baseline mechanisms in terms of average paging delay and paging resource usage.

Variation in bacterial pathotype is consistent with the sit-and-wait hypothesis.

The sit-and-wait hypothesis predicts that bacteria can become more virulent when they survive and transmit outside of their hosts due to circumventing the costs of host mortality. While this hypothesis is largely supported theoretically and through comparative analysis, experimental validation is limited. Here we test this hypothesis in Streptococcus suis, an opportunistic zoonotic pig pathogen, where a pathogenic ecotype proliferated during the change to intensive pig farming that amplifies opportunities for fomite transmission. We show in an in vitro environmental survival experiment that pathogenic ecotypes survive for longer than commensal ecotypes, despite similar rates of decline. The presence of a polysaccharide capsule has no consistent effect on survival. Our findings suggest that extended survival in the food chain may augment the zoonotic capability of S. suis. Moreover, eliminating the long-term environmental survival of bacteria could be a strategy that will both enhance infection control and curtail the evolution of virulence.

Giving voice to educators: Primary school teachers explain how they promote values to their pupils

Values are the trans-situational goals guiding human attitudes and behavior (Schwartz, 1992). As early socialization agents, teachers have a responsibility to promote democratic values of citizenship to create an inclusive, fair, and sustainable society, necessary for individual and collective well-being (OECD, 2019). By facilitating social and cognitive development through social interactions, the school setting helps spark curiosity, leading to reflection and adaptation. Across the curriculum, teachers use strategies like imitation, modelling, priming, and discussion to help children make sense of the world (Makarova et al., 2024; Oeschger et al., 2022). Yet little empirical evidence exists to support how teachers achieve this. The present study gives voice to educators through the personal experiences of ten UK primary school teachers. Semi-structured interviews were conducted, lasting between 50 and 90 min. Data was analyzed in two stages: First, a deductive structuring content analysis identified how values of self-transcendence versus self-enhancement and openness to change versus conservation, as defined in Schwartz’s (1992) model, were reflected in the interview data. Second, an inductive thematic analysis yielded the following themes: mechanisms of value transmission; implicit vs explicit instruction of values; values that are most difficult to teach; value transmission through taught lessons; the role of collective worship and cultural days; opportunities for value transmission in the wider school environment; and the role that a school culture and ethos play in the transmission of values. This study supports the view that values are promoted through a variety of methods and across all areas of the school environment.

An optimized and intelligent metaverse intrusion detection system based on rough sets

The convergence of the Internet of Things (IoT) and the Metaverse is revolutionizing the digital world by providing immersive, interactive environments as well as new data transmission opportunities. However, this rapid integration raises complex security issues, including an increased risk of unlawful access and data breaches. Strong cybersecurity measures are required to identify and prevent these attacks, preserving the security and confidentiality of users. Finding significant features for recognizing malicious attacks and enhancing the accuracy of network intrusion detection in general, and particularly in the virtual environment, are some of the significant research needs. This paper introduces an intelligent intrusion detection system (IIDS) based on rough set-based electric eel foraging optimization (RSEEFO) in conjunction with the AdaBoost-based classification algorithm. The main objective of this system is to detect and recognize different types of attacks on the interaction and connectivity between the IoT and the metaverse. The proposed IIDS-RSEEFO consists of three phases, which are data pre-processing, multi-IoT attack classification, and evaluation. The main problems associated with the adopted dataset are handled in data pre-processing. Then, in the second phase, a one-versus-all approach is employed along with RSEEFO and AdaBoost to handle the multi-class classification problem. Finally, several evaluation metrics are employed to assess the reliability and robustness of the proposed IIDS-RSEEFO. The proposed IIDS was tested on CIC-IoT-2023 and validated on UNSWNB-15. It achieved high accuracy across all attack types of CIC-IoT-2023, with accuracies of 99.7 %, 100 %, 100 %, 99.8 %, 100 %, 100 %, 99.8 %, and 100 % for benign traffic, DDoS, brute force, spoofing, DoS, Mirai, recon, and web-Based respectively, accompanied by robust sensitivity, F1-Score, Specificity, G-Mean, and crossover-error rate metrics demonstrating its effectiveness in accurately predicting each attack type. Additionally, it obtained high accuracy for all attack types of UNSWNB-15, with accuracies of 96.48 %, 99.12 %, 99.24 %, 93.78 %, 92.55 %, 92.55 %, 92.55 %, 94.73 %, 94.73 %, 98.09 %, 98.39 %, 99.50 %, and 99.95 % for analysis, backdoor, DoS, exploits, fuzzers, generic, normal, reconnaissance, shellcode, and worms, respectively. In addition, the results evaluated that the proposed model is superior compared to the existing intrusion detection systems.

ALTERNATIVE ROUTE OF TRANSMISSION AND HOST SPECIFICITY OF CYRTOSOMUM PENNERI IN FLORIDA'S INVASIVE LIZARDS.

The atractid nematode Cyrtosomum penneri is an autoinfective parasite of several lizard species. Intraspecific transmission between hosts appears to occur exclusively through sexual copulation, yet it is unclear how worms are transferred between different host species. Our research aims to test the possibility of oral transmission of C. penneri using experimental infections. The lizards Anolis sagrei, Leiocephalus carinatus, Hemidactylus mabouia, and Agama picticauda were experimentally exposed to C. penneri in 1 of these groups: (1) oral infection using a feces and saline slurry to approximate host coprophagy, (2) oral infection with a large meal to approximate host predation, and (3) venereal infection using a pipette to confirm sexual transmission. Experimental infections to test venereal transmission were successful in A. sagrei, A. picticauda, and H. mabouia, but were unable to establish infections in L. carinatus. In the predation exposures, A. picticauda, A. sagrei, and H. mabouia hosted infections, whereas L. carinatus were uninfected. Finally, coprophagy experimental infections did not result in infections for any species of host. Our study corroborates venereal transmission of C. penneri in multiple species of lizards and establishes predation as an alternative route of infection. Predation as an oral route of transmission may provide C. penneri an opportunity for interspecific transmission that would otherwise be unlikely during host copulation.

Internal and external drivers interact to create highly dynamic mosquito blood-feeding behaviour.

Blood-feeding, which is necessary for most female mosquitoes to reproduce, provides an opportunity for pathogen transmission. Blood-feeding is influenced by external factors such as light, temperature, humidity and intra- and inter-specific interactions. Physiologically, blood-feeding cycles are linked to nutritional conditions and governed by conserved hormonal signalling pathways that prepare mosquito sensory systems to locate and evaluate hosts. Human activities also alter mosquito blood-feeding behaviour through selection pressures such as insecticide usage, habitat and ecosystem alterations, and climate change. Notably, blood-feeding behaviour changes within a mosquito's lifespan, an underexplored phenomenon from an epidemiological standpoint. A review of the literature indicates that our understanding of mosquito biology and blood-feeding behaviour is predominantly based on studies of a handful of primarily tropical species. This focus likely skews our comprehension of the diversity of critical drivers of blood-feeding behaviour, especially under constraints imposed by harsh conditions. We found evidence of remarkable adaptability in blood-feeding and significant knowledge gaps regarding the determinants of host use. Specifically, epidemiological analyses assume host use is modified by external factors, while neglecting internal physiology. Integrating all significant factors is essential for developing effective models of mosquito-borne disease transmission in a rapidly changing world.

Serosurvey for Canine Influenza in Coyotes (Canis latrans) in Illinois, USA, 2000-23.

Coyotes (Canis latrans) share urban habitats with domestic dogs (Canis lupus familiaris), providing opportunities for pathogen transmission. In Chicago, Illinois, USA, canine influenza virus (CIV) is prevalent in dogs. Serologic investigation for exposure in 101 coyote samples collected 2000-23 did not detect any antibodies against CIV H3N2 and H3N8.

Invisible invaders: range expansion of feral Neocaridina davidi offers new opportunities for generalist intracellular parasites

The release of ornamental pets and associated pathogens outside their native range might directly or indirectly impact the recipient community. In temperate regions, e.g., central Europe, feral freshwater species of tropical and sub-tropical origins are mainly constrained to thermally polluted waters and thermal springs. However, species with high environmental plasticity and reproduction rates, such as the shrimp Neocaridina davidi, may adapt to colder water regimes over time. A widening thermal niche may eventually overcome thermal barriers, further expanding the range and enhancing transmission opportunities for host generalist parasites. This study assesses the observed (field observations) and theoretical (species distribution models) range expansion of N. davidi and associated parasites in Europe. We report three newly established N. davidi populations from thermally polluted waters in central Europe (Germany, Hungary, and Slovakia) and provide further evidence of its range expansion into colder environments. Species distribution models predict thermally suitable habitats in the Mediterranean and a foreseeable expansion into Western Europe and the Balkans by 2050. We confirm the presence of the microsporidian parasite Ecytonucleospora hepatopenaei in feral N. davidi populations across Europe and expand the list of microsporidians found in this host from two to four. Furthermore, we provide the first evidence of parasite spillover from/to the invasive crayfish Procambarus clarkii, suggesting that parasite exchange with native biota might be possible. Such possibility, coupled with an ongoing range expansion of N. davidi bolstered by human-mediated introductions and climate change, will likely exacerbate the impact on native biota.

Learning-Based Autonomous Channel Access in the Presence of Hidden Terminals

We consider the problem of autonomous channel access (AutoCA), where a group of terminals tries to discover a communication strategy with an access point (AP) via a common wireless channel in a distributed fashion. Due to the irregular topology and the limited communication range of terminals, a practical challenge for AutoCA is the hidden terminal problem, which is notorious in wireless networks for deteriorating throughput and delay performances. To meet the challenge, this paper presents a new multi-agent deep reinforcement learning paradigm, dubbed MADRL-HT, tailored for AutoCA in the presence of hidden terminals. MADRL-HT exploits topological insights and transforms the observation space of each terminal into a scalable form independent of the number of terminals. To compensate for the partial observability, we put forth a look-back mechanism such that the terminals can infer behaviors of their hidden terminals from the carrier-sensed channel states as well as feedback from the AP. A window-based global reward function is proposed, whereby the terminals are instructed to maximize the system throughput while balancing the terminals' transmission opportunities over the course of learning. Considering short-packet machine-type communications, extensive numerical experiments verified the superior performance of our solution benchmarked against the legacy carrier-sense multiple access with collision avoidance (CSMA/CA) protocol.

Genomic epidemiology of Mycobacterium abscessus at an adult cystic fibrosis programme reveals low potential for healthcare-associated transmission.

Nontuberculous mycobacteria (NTM) has been reported to be transmitted between people with cystic fibrosis (CF) attending CF centres. A suspected Mycobacterium abscessus outbreak was investigated at the University of Texas Southwestern (UTSW) Adult CF Program using a combination of pathogen genomic sequencing and epidemiologic methods. The objectives of the present study were to apply the Healthcare-Associated Links in Transmission of NTM (HALT NTM) study to investigate the occurrence of potential healthcare-associated transmission and/or acquisition of NTM among people with CF infected with genetically similar NTM isolates. Whole-genome sequencing of respiratory M. abscessus isolates from 50 people with CF receiving care at UTSW was performed to identify genetically similar isolates. Epidemiologic investigation, comparison of respiratory and environmental isolates, and home residence watershed mapping were studied. Whole-genome sequencing analysis demonstrated seven clusters of genetically similar M. abscessus (four ssp. abscessus and three ssp. massiliense). Epidemiologic investigation revealed potential opportunities for healthcare-associated transmission within three of these clusters. Healthcare environmental sampling did not recover M. abscessus, but did recover four human disease-causing species of NTM. No subjects having clustered infections lived in the same home residence watershed. Some subjects were infected with more than one M. abscessus genotype, both within and outside of the dominant circulating clones. Healthcare-associated person-to-person transmission of M. abscessus appears to be rare at this centre. However, polyclonal infections of M. abscessus species and subspecies, not originating from the endemic hospital environment, suggest multiple shared modes of acquisition outside the healthcare setting.

Genetic infrapopulation sizes in blood parasites: a pilot quantification of the bottleneck in louse fly vectors

IntroductionBottleneck events are crucial for the strength of genetic drift, selection and speed of evolution. They are believed to play a particularly prominent role for parasitic infrapopulations, inhabiting single host individuals, which are often established by very few parasite individuals during transmission. In vector-borne pathogens, the bottlenecking effects can even be serialized through repeated filtering of parasitic stages at different tissues and organs of the vector. Using qPCR we aimed to quantify the number of potentially transmittable sporozoites of the hemosporidian blood parasite Haemoproteus columbae in the specialized vector louse flies Pseudolynchia canariensis which transmit these parasites between house pigeon hosts Columba livia.ResultsBased on qPCR measurements of organ-derived DNA of individual louse flies, we estimate that the midgut of these vectors contains on average 20 parasites, the hindgut and other intestines ca. 50 parasites and the salivary glands ca. 5 parasite cells. Nearly one third of all vector individuals appeared to lack parasite DNA, despite having only infected hosts as blood meal sources. The magnitude of parasite numbers in midgut and salivary glands tended to correlate positively.DiscussionOur results indicate, potential severe bottlenecking of parasite populations during individual transmission events and a probable effect of individual vector immunity on this variable. However, this may be partly alleviated by the coloniality of house pigeons, the frequency of louse flies and their daily feeding events in most populations, leading to repeated transmission opportunities, decreased quasi-vertical transmission between parents and offspring and probable panmixia of Haemoproteus columbae lineages. Many of these mechanisms might not apply in other host-vector systems. We propose several additional molecular and microscopical tools to improve the accuracy of estimating parasite population sizes in vectors and call for more estimations in different vector species to better understand the co-evolution between malaria-like blood parasites and their avian and insect hosts.

Proportional Fairness for Long-Term Evolution-Licensed Assisted Access (LTE-LAA) with Wi-Fi Coexistence in Unlicensed Spectrum

Long-Term Evaluation-Licensed Assisted Access (LTE-LAA) has good potential for fair coexistence with Wi-Fi in an unlicensed spectrum. Though the LTE-LAA utilizes the same listen before-talk technique as the distributed coordination function in IEEE 802.11, it utilizes completely different parameters and transmission durations. For this reason, a fair coexistence between LTE-LAA and Wi-Fi leaves an open question on how the LTE-LAA network should choose its parameters. To tackle this issue, an analytical framework considering the effects of varying important parameters, which are the different initial back-off window sizes, the numbers of sensing durations, the maximum back-off stages, the number of retransmissions and the transmission opportunities for LTE-LAA and Wi-Fi nodes on their performances has been developed. The node and network airtime performances are evaluated by using the current standard parameters setting to see how this setting affects the node and network airtime performances. From there, optimal settings of the initial backoff window size and number of sensing durations are applied by using the obtained node airtime equation that is derived from the Markov renewal process and evaluated as functions of system parameters. The optimum initial backoff window size and number of sensing durations of LTE-LAA are evaluated and verified by the calculation and simulation using MATLAB software. The analysis shows that LTE-LAA maintained unfair coexistence with Wi-Fi by using the current standard parameter setting as its initial back off window size or sensing duration. But in contrast, using the optimum initial backoff window size and number of sensing durations of LTE-LAA shows that they can maintain proportional fairness. It is unconcealed that the initial backoff window size tuning of LTE-LAA carries a high possibility of achieving fairness because it needs less system data and achieves a higher exactness result.

Age of information for remote sensing with uncoordinated finite-horizon access

We analyze a remote sensing system in the Internet of things, where uncoordinated nodes send status updates to a common receiver to achieve information freshness, quantified through age of information. We consider a finite horizon scheduling over a random multiple access channel, where colliding messages are lost. We show that nodes must adopt a further randomization to deviate from identical schedules and escape collision deadlocks. Moreover, we discuss the impact of feedback availability if, due to, e.g., energy expenditure, it decreases the number of transmission opportunities.

Plant-pollinator network architecture does not impact intraspecific microbiome variability.

Variation in how individuals interact with food resources can directly impact, and be affected by, their microbial interactions due to the potential for transmission. The degree to which this transmission occurs, however, may depend on the structure of forager networks, which determine the community-scale transmission opportunities. In particular, how the community-scale opportunity for transfer balances individual-scale barriers to transmission is unclear. Examining the bee-flower and bee-microbial interactions of over 1000 individual bees, we tested (1) the degree to which individual floral visits predicted microbiome composition and (2) whether plant-bee networks with increased opportunity for microbial transmission homogenized the microbiomes of bees within that network. The pollen community composition carried by bees was associated with microbiome composition at some sites, suggesting that microbial transmission at flowers occurred. Contrary to our predictions, however, microbiome variability did not differ based on transfer opportunity: bee microbiomes in asymmetric networks with high opportunity for microbial transfer were similarly variable compared to microbiomes in networks with more evenly distributed links. These findings suggest that microbial transmission at flowers is frequent enough to be observed at the community level, but that community network structure did not substantially change the dynamics of this transmission, perhaps due to filtering processes in host guts.

The effect of host population heterogeneity on epidemic outbreaks

In the first part of this paper, we review old and new results about the influence of host population heterogeneity on (various characteristics of) epidemic outbreaks. In the second part we highlight a modelling issue that so far has received little attention: how do contact patterns, and hence transmission opportunities, depend on the size and the composition of the host population? Without any claim on completeness, we offer a range of potential (quasi-mechanistic) submodels. The overall aim of the paper is to describe the state-of-the-art and to catalyse new work.

On multiple handoff blocking‐then‐reaccess for opportunistic spectrum access

AbstractOpportunistic spectrum access (OSA), a promising technology to resolve radio spectrum scarcity, is still faced with some challenges, of which one is potentially frequent channel handoff (CH) even handoff blocking (HB) for secondary user (SU) to avoid primary user (PU). Reaccess is a direct way to resolve HB. However, multiple handoff blocking‐then‐reaccess (H‐BTR) are time consuming. Whether it is worthwhile to make multiple H‐BTR, is an interesting but hardly mentioned issue. To this end, the multiple H‐BTR‐based OSA are focused on here. Three key indices, the average transmission probability, handoff delay, and average reaccess times of SU in the H‐BTR‐based OSA, are deduced as close form first. Then, the effects of H‐BTR frequency and service traffic rate of SU on OSA are discussed. Finally, the H‐BTR‐based OSA is compared to two other schemes, the handoff without BTR (HWBTR)‐based OSA and the stop‐and‐waiting (SW)‐based OSA. Theoretical and simulated results show that the H‐BTR‐based OSA performs best among three schemes. Making H‐BTR in moderate frequency according to service traffic rate can increase transmission opportunity while additional delay of SU is tolerable, thus the performance of OSA can be well improved.