DCF Protocol Research Articles

Animal-based welfare indicators for dairy cows and their validity and practicality: a systematic review of the existing literature.

Animal welfare is of increasing importance, with consumers preferring animal products made with ethical practices due to growing awareness. This shift highlights the need for reliable methods to evaluate welfare. This systematic review aims to assess the validity of current animal-based welfare indicators for dairy cows to aid farmers and agricultural professionals in evaluating and improving welfare amidst the lack of a clear legislative definition. The literature search spanned five databases: CAB Direct, PubMed, Scopus, Google Scholar and Livivo, covering publications in English and German from 2011 to 2021. Specific search terms were employed, and abstracts were screened for relevance. Publications were categorized based on exclusion criteria, with a final verification process conducted by three independent scientists. Research highlights correlations between welfare measures, farm characteristics and innovative indicators like hair cortisol concentration. Farming systems and housing methods significantly affect welfare, with pasture-based systems generally resulting in reduced lameness and improved behavior. Proper housing design and management practices are important, as they influence indicators like lameness and cleanliness. Heart rate variability and heart rate monitoring provide insights into dairy cow stress levels during milking and other stressors, making them valuable for welfare assessment. Biomarker research emphasizes the need to balance productivity and health in breeding strategies, as high milk production alone does not indicate good welfare. Behavioral studies and the human-animal relationship are key to understanding welfare. Precision Livestock Farming offers real-time assessment capabilities, although validation is needed. Stress physiology is complex, and while cortisol measurement methods are promising, further research is necessary. Assessment tools like the Animal Needs Index and routine herd data analysis are valuable for identifying welfare concerns. Key findings highlight the WQ® protocol's effectiveness and versatility, the challenge of its time demands, and the DCF protocol's promise for more practical and efficient welfare assessments. Commercial animal welfare audits should prioritize easily observable indicators and herd records due to logistical constraints in measuring biomarkers or heart rate variability. This focus on easily accessible indicators, such as body condition score, lameness, claw health, cleanliness, and somatic cell count allows effective welfare assessments, enabling prompt action to enhance wellbeing.

On a probabilistic backoff distribution for IEEE 802.11 DCF networks

For the DCF protocol model at the data link layer and in a saturated network, the self-similar structure of the probabilistic distribution of a data transmission time is studied, and both exact and approximate expressions for the distribution are obtained. A comparison with the simulation results is carried out.

A memory-oriented MAC-layer design for future IoT systems

The Internet of Things (IoT) paradigm envisions billions of interconnected things. This high density of things generates a huge amount of data, which results in communication delays and increases the amount of contention. Thus, it is necessary to have efficient Medium Access Control (MAC) protocols to coordinate channel access. In this paper, we consider a network throughput maximization problem in which a set of selfish nodes compete for transmission opportunities in the IoT scenario. To enhance cooperation among the nodes and to reduce the collision rate, we formulate a memory-one channel access game in which the nodes maximize their payoffs by optimizing their channel access probabilities, conditioned on their previous transmission state. A distributed learning algorithm is used by the nodes to solve the problem efficiently in order to overcome any coordination overhead. We investigate the impact of the network topology on the solution to the problem. Our simulation results show that the throughput achieved by the memory-one game outperforms the throughput achieved by other methods including IEEE 802.11 DCF protocol.

A Simplified Stochastic SMP Model on Beacon Message Dissemination

Beacon message dissemination presumes the top priority in the smart transportation network. The successful transmission of the sent messages without collision or loss in the DSRC medium needs to be modeled. This communication is attained by IEEE 802.11 DCF protocol. A semi Markov Processes model is proposed to attain the expected throughput in the broadcast of the beacon messages.

Efficacy of pegfilgrastim administration in patients with esophageal cancer treated with docetaxel, cisplatin, and 5-fluorouracil.

Chemotherapy is among the standard treatments for esophageal cancer. The docetaxel, 5-fluorouracil, and cisplatin (DCF) protocol yields a better response rate than 5-fluorouracil plus cisplatin. However, the incidence of side effects, such as febrile neutropenia and hematologic toxicity, is also significantly high with the DCF protocol. The granulocyte colony-stimulating factor and pegfilgrastim are prophylactically administered to prevent febrile neutropenia. This retrospective study evaluated the efficacy and safety of pegfilgrastim in patients receiving DCF therapy. Of the 65 patients who were administered DCF therapy in our hospital from 2011 through 2016, 21 received pegfilgrastim 24 hours or more after the end of chemotherapy. The protocol comprised 70 mg/m2 each of docetaxel and cisplatin on day 1 and 700 mg/m2 5-fluorouracil on days 1 to 5 via intravenous injection in a 3-week cycle. The primary endpoint was the rate of grade 3-4 neutropenia and febrile neutropenia. The mean patient age was 66.4 years. The incidence of grade 3 and 4 neutropenia was 14.2 % and 11.4 %, respectively, in the pegfilgrastim group and 31.9 % and 37.8 %, respectively, in the non-pegfilgrastim group. The incidence of febrile neutropenia in the pegfilgrastim group and non-pegfilgrastim group was 11.4 % and 40.3 %, respectively. Statistical analysis showed that the incidence of neutropenia and febrile neutropenia was significantly different (p<0.05) between the two groups. Pegfilgrastim prevents severe neutropenia and febrile neutropenia in patients with esophageal cancer who are treated according to the DCF protocol.

The analysis of IEEE 802.11 DCF protocol based on LEO satellite Wi-Fi network

Aiming at the problems of traditional IEEE 802.11 DCF protocol applied to LEO satellite Wi-Fi network, the influence of propagation delay, hidden terminal and user collision on the throughput of MAC layer is fully analysed, and a specific scheme is proposed to adjust the ACK Timeout and the minimum contention window value. The improved two-dimensional Markov model has been used to analyse the DCF protocol throughput theoretically. By using MATLAB simulation, it is verified that the throughput performance is directly related to the transmission probability, and throughput performance is negative correlated with the number of nodes and transmission distance.

Design and Modeling of Self‐Adapting MAC (SaMAC) Protocol with Inconstant Contention Loss Probabilities

Networks based on IEEE 802.11 standard are one of the main options for deployment in industrial environment. Degradation of throughput in congested networks and short‐term unfairness are well‐known drawbacks of 802.11 DCF and similar MAC protocols. Those shortcomings represent significant limitation in forecasted growth of wireless usage. This is especially important in industrial wireless networks (IWN) where the scalability of wireless MAC is one of the main requirements. In this paper, a novel self‐adapting MAC protocol (SaMAC) is defined and mathematically modeled. SaMAC employs constrained countdown freezing enhanced with shifted window mechanism. As a result, the protocol outperforms 802.11 DCF standard as well as shifted contention window (SCW) and constrained countdown freezing (CPCF) protocols in achieved throughput, fairness, and jitter, while keeping simple implementation. Despite protocol’s simple design, it is shown that its mathematical model is extremely complex. For proposed protocol, the assumption of constant contention loss probability, which is normally used for modeling of MAC schemes, does not hold. In the presented multidimensional Markov chain model, a unique iterative method for determining contention loss probability is developed as well as a method for throughput calculation based on such a chain. Accuracy of the presented model is verified in several network scenarios. Considering the performance of the proposed protocol, authors believe that it could be of benefit to deploy it in heavily loaded wireless networks with timing constraints, such as IWNs.

The analysis of IEEE 802.11 PCF protocol based on LEO satellite Wi-Fi

In view of the problem of long propagation delay, hidden terminals and serious user conflicts in LEO satellite Wi-Fi scenario, this paper analysis the incompatibility of 802.11 DCF protocol briefly. A scheme of PCF polling mechanism based on priority is proposed and the frame format is adaptively modified. Through MATLAB simulation, the system throughput of the original scheme and the improvement scheme over the different transmission distance and nodes are analysed. The simulation results show that the improved PCF protocol can improve the throughput under the multi-user over long distances.

Throughput-Delay Evaluation of a Hybrid-MAC Protocol for M2M Communications

This paper proposes a robust hybrid-MAC protocol for direct communication among M2M devices with gateway coordination. The proposed protocol combines the benefits of both contention-based and reservation-based MAC schemes. The authors assume that the contention and reservation portion of M2M devices is a frame structure, which is comprised of two sections: Contention Interval (CI) and Transmission Interval (TI). The CI is based on p-persistent CSMA mechanism, which allows M2M devices to compete for the transmission slots with equal priorities. After contention, only those devices, which have won time-slots, are allowed to transmit data packets during TI. In the authors' proposed MAC scheme, the TI is basically a TDMA frame and each M2M device is 802.11 enabled. Each M2M transmitter device and its corresponding one-hop distant receiver communicate using IEEE 802.11 DCF protocol within each TDMA slot to overcome the limitations of TDMA mechanism. The simulation results demonstrate the effectiveness of the proposed hybrid-MAC protocol.

Unsaturated Throughput Analysis of IEEE 802.11 DCF Under η − μ Fading Channel

This letter investigates the throughput performance of the IEEE 802.11 DCF protocol in unsaturated traffic conditions, taking into account the signal capture with incoherent addition of interfering signals, and channel fading following the η-μ model. A set of numerical results on the performance of the protocol is presented. The results show the adjustment flexibility of the proposed channel model and establishes the parameter μ as the one responsible for the coarse adjustment of the channel, while the parameter η defines the fine adjustment.

Efficient Cooperative MAC and Routing in Wireless Networks

Cooperative communication refers to the collaborative processing and retransmission of the overheard information at those stations surrounding the source. It exhibits various forms at different protocol layers and introduces many opportunities for cross layer design and optimization. To fully reap the benefits of cooperative communications in wireless networks, the entire protocol stack - physical, MAC, and routing protocols - should be carefully redesigned or reengineered. In this paper, we first propose a cooperative MAC protocol by enhancing IEEE 802.11 DCF with minimal modifications to maximize the benefit of cooperative diversity. Its performance is compared to that of an existing cooperative MAC and legacy 802.11 DCF protocols and shown to be superior. We also propose a cluster based cooperative routing protocol which has minimal control overhead and time consumed in establishing the cooperative paths. Through extensive simulations, the performance of the proposed protocols are evaluated and compared to other combinations of MAC and routing protocols.

利用訊號變化與遮蔽效應之802.11 MAC碰撞避免協定

IEEE 802.11 DCF is widely used and able to avoid the collisions of the hidden terminal problem in a wireless network. However, there may be collisions existing in the DCF MAC protocol. That is, when a node in NAV state does not receive any control signal, a collision may occur after the node ends the NAV period. In this paper, to solve this collision problem, a detailed analysis about the problem is given. Afterwards, according to the analysis, we utilize the “masking effect” and the detection of signal variation to design the MAC collision avoidance protocol. With the received signal strength and the variation of received signal strength of a node, the node can determine whether there are other transmissions occurring in the transmission range. Therefore, a node can determine whether the period of NAV state can be extended to avoid collisions. Simulation results show that our proposed MAC protocol can efficiently reduce 60% and 41% collisions than the IEEE 802.11 DCF protocol and OCS-MD. In addition, our proposed MAC protocol also shows shorter transmission delay and lower retransmissions than the 802.11 DCF and OCS-MD to have better network throughput.

Backoff Design for IEEE 802.11 DCF Networks: Fundamental Tradeoff and Design Criterion

Binary Exponential Backoff (BEB) is a key component of the IEEE 802.11 DCF protocol. It has been shown that BEB can achieve the theoretical limit of throughput as long as the initial backoff window size is properly selected. It, however, suffers from significant delay degradation when the network becomes saturated. It is thus of special interest for us to further design backoff schemes for IEEE 802.11 DCF networks that can achieve comparable throughput as BEB, but provide better delay performance. This paper presents a systematic study on the effect of backoff schemes on throughput and delay performance of saturated IEEE 802.11 DCF networks. In particular, a backoff scheme is defined as a sequence of backoff window sizes $\{W_{i}\}$ . The analysis shows that a saturated IEEE 802.11 DCF network has a single steady-state operating point as long as $\{W_{i}\}$ is a monotonic increasing sequence. The maximum throughput is found to be independent of $\{W_{i}\}$ , yet the growth rate of $\{W_{i}\}$ determines a fundamental tradeoff between throughput and delay performance. For illustration, Polynomial Backoff is proposed, and the effect of polynomial power $x$ on the network performance is characterized. It is demonstrated that Polynomial Backoff with a larger $x$ is more robust against the fluctuation of the network size, but in the meanwhile suffers from a larger second moment of access delay. Quadratic Backoff (QB), i.e., Polynomial Backoff with $x=2$ , stands out to be a favorable option as it strikes a good balance between throughput and delay performance. The comparative study between QB and BEB confirms that QB well preserves the robust nature of BEB and achieves much better queueing performance than BEB.

ENERGY EFFICIENCY IN IEEE 802.11 STANDARD WLAN THROUGH MWTDP

The main goal of this work is to achieve the energy efficiency in 802.11 WLAN through minimizing the econsumption in the network. In this proposed study, we introduced a mo dification in DCF for enhancing the performance of WLAN and it is achieved by giving a new definition for the DCF function of transmission. Generally, in DCF the way AP transmit s for the various nodes is one-way during the process of polling. The proposed function modification for DCF enhances the IEEE 80 2.11 standard DCF Multi-Way Transmission DCF Protocol (MWTDP) with an improved version MWTDP it g ives a low-complexity mechanism by which the active and non-active stations in the BSS save energy during the process of polling. With the inception of MWTDP transmissions are taken place in multi-way the acce ss to the WLAN channel for mobile nodes in the list generated for polling with the SIFS interval whenever the transmission in rece iving data packet from AP.

Proportional fair resource allocation in vehicle-to-infrastructure networks for drive-thru Internet applications

IEEE 802.11p, also known as wireless access in vehicular environment (WAVE), defines amendments to IEEE 802.11 to support Intelligent Transportation Systems applications. In a vehicle-to-infrastructure (V2I) network, the same road side unit (RSU) will be shared by more than one vehicle. When vehicles within the coverage of the same RSU use distinct data rates for transmission, an unfairness problem occurs among them, popularly known as performance anomaly. Essentially, the vehicle with the lowest data rate slows all other vehicles down to its rate, resulting in poor use of the wireless medium and reduced performance for all vehicles. This problem is caused by the 802.11 DCF protocol which provides unfair channel time allocation for vehicles with different data rates. In addition to the performance anomaly caused by the multiple data rates, vehicles in a multi-lane network (where lane i is being used by vehicles of mean velocity μvi), suffer from an access unfairness problem as well, due to the fact that vehicles having different mean velocities get unequal chances for channel access. Both these unfairness problems can significantly degrade the network performance. In this paper, we investigate the use of proportional fairness (PF) as the basis of resource allocation in a multi-rate multi-lane V2I network for drive-thru Internet applications. In this case, RSU is shared by vehicles that transmit at distinct data rates and moving with different mean velocities. We use the notion of PF resource allocation to resolve the unfairness problems and to improve the aggregate data transferred in the network. We find analytical expressions for the optimal setting of CWmin values to ensure proportional fair allocation in both single-lane as well as multi-lane multi-rate V2I networks. Through analytical and simulation results, we establish that the notion of proportional fair utility criterion can improve the aggregate data transferred as compared to the default CWmin setting.

CRP-CMAC: A Priority-Differentiated Cooperative MAC Protocol with Contention Resolution for Multihop Wireless Networks

To improve the cooperative efficiency of node cooperation and multiple access performance for multihop wireless networks, a priority-differentiated cooperative medium access control protocol with contention resolution (CRP-CMAC) is proposed. In the protocol, the helper selection process is divided into the priority differentiation phase and the contention resolution phase for the helpers with the same priority. A higher priority helper can choose an earlier minislot in the priority differentiation phase to send a busy tone. As a result, the protocol promptly selects all the highest priority helpers. The contention resolution phase of the same priority helpers consists of k round contention resolution procedures. The helpers that had sent the first busy tone and are now sending the longest busy tone can continue to the next round, and then the other helpers that sense the busy tone withdraw from the contention. Therefore, it can select the unique best helper from the highest priority helpers with high probability. A packet piggyback mechanism is also adopted to make the high data rate helper with packet to send transmit its data packets to its recipient without reservation. It can significantly decrease the reservation overhead and effectively improve the cooperation efficiency and channel utilization. Simulation results show that the maximum throughput of CRP-CMAC is 74%, 36.1% and 15% higher than those of the 802.11 DCF, CoopMACA and 2rcMAC protocols in a wireless local area network (WLAN) environment, and 82.6%, 37.6% and 46.3% higher in an ad hoc network environment, respectively.

Performance Analysis of Network Coding Based Two-Way Relay Wireless Networks Deploying IEEE 802.11

In this paper, we investigate the performance analysis of the IEEE 802.11 DCF protocol at the data link layer. We analyze the impact of network coding in saturated and non-saturated traffic conditions. The cross-layer analytical framework is presented in analyzing the performance of the encode-and-forward (EF) relaying wireless networks. This situation is employed at the physical layer under the conditions of non-saturated traffic and finite-length queue at the data link layer. First, a model of a two-hop EF relaying wireless channel is proposed as an equivalent extend multi-dimensional Markovian state transition model in queuing analysis. Then, the performance in terms of queuing delay, throughput and packet loss rate are derived. We provide closed-form expressions for the delay and throughput of two-hop unbalanced bidirectional traffic cases both with and without network coding. We consider the buffers on nodes are unsaturated. The analytical results are mainly derived by solving queuing systems for the buffer behavior at the relay node. To overcome the hidden node problem in multi hop wireless networks, we develop a useful mathematical model. Both models have been evaluated through simulations and simulation results show good agreement with the analytical results.

Multi-Hop Collaborative Relay Networks with Consideration of Contention Overhead of Relay Nodes in IEEE 802.11 DCF

In a WLAN setting, the system throughput may be heavily affected by a small number of low data rate clients due to the packet-fairness property provided by IEEE 802.11 DCF. This is regarded as the performance anomaly problem. Client relay is a technology widely adopted to solve this problem. An important issue of client relay is to decide when a client's traffic should be relayed and who relays it. However, the existing protocols fail to consider the overhead introduced by DCF contentions, resulting in an inaccurate performance analysis and lead to wrong decisions for client relay. In this paper, we focus on the performance analysis for multi-hop relay networks with consideration of contention overhead of relay nodes in IEEE 802.11 DCF protocols. The main work of this paper includes: we consider the contention overhead in the performance analytical model of collaborative relay networks. This model is more accurate than the existing models. We present a throughput analytical model that considers different traffic demands of clients for the traffic pattern of relay networks. Extensive simulations have been done in NS-2. The simulation results show that our algorithm is more accurate and achieves higher relay performance, compared with existing methods.

The safety and efficacy of fluorouracil, leucovorin, oxaliplatin, and docetaxel (FLOT) combination in the front-line treatment for patients with advanced gastric or gastroesophageal adenocarcinoma: phase II trial

Combination therapy with docetaxel, cisplatin, and 5-FU has been shown to increase time to progression (TTP) and overall survival (OS) for patients with advanced gastric cancer; this regimen is limited by significant toxicity, including complicated neutropenia. This study was designed to incorporate docetaxel into a tolerable biweekly (once every 2 weeks) oxaliplatin-based chemotherapy regimen. Patients with measurable advanced and metastatic gastric or gastroesophageal cancer, aged >18 years, and with ECOG two or less, received oxaliplatin 85 mg/m(2), docetaxel 50 mg/m(2) on day 1, leucovorin 200 mg/m(2) on days 1 and 2, and 5-FU 1,200 mg/m(2) 24-h infusion on days 1 and 2 of every 2-week cycle. Toxic effects were graded according to NCI-CTC version 3. Responses were classified according to World Health Organization criteria. Fifty patients were included, 47 assessed for efficacy and toxicity. Median age was 55 years. The majority had metastatic disease (72 %). The over all response was observed in 55.3 % patients. Median TTP and OS were 6 and 10 months, respectively. Grade 3 or 4 hematological toxic effects were included neutropenia, leukopenia, and thrombocytopenia observed in 21 (44.7 %), 12 (25.5 %), and 1 (2.1 %) patients, respectively. Non-hematological were diarrhea (14.9 %), fatigue (12.7 %), and peripheral neuropathy (8.5 %). Complicated neutropenia (febrile neutropenia associated with infection) was observed in one (2.1 %) patient only. Biweekly FLOT regimen has tolerable toxicity, and efficacy in line with that of DCF protocol. The FLOT regimen needs more evaluation to be considered as alternative to DCF.

An interference avoidance MAC protocol design in mobile ad hoc networks

The multi-rate IEEE 802.11 DCF MAC protocol can transmit control signals at a basic transmission rate and data signals at various transmission rates. When the transmission rates of the control signals and the data signals differ, the transmission range of the lower transmission rate is larger than the transmission range of the higher transmission rate. Since a lower transmission rate increases the transmission range, it also increases the nodes in the Network Allocation Vector (NAV) status and decreases the network throughput. However, if a neighbor receiving the control signal of the ongoing communication pair communicates with another node, it may occur signal interference. This study proposes a Space Overlapping MAC (SO-MAC) protocol to increase the communication pairs and avoid interferences in single radio for multi-rate wireless network. The SO-MAC protocol uses a channel division mechanism to avoid interference between the data and control signals. This study also proposes a bandwidth allocation strategy for the sub-channels to maximize the utilization of the bandwidth of the divided sub-channels. To solve the interference between the data signals, SO-MAC allows a neighbor of the sender and the receiver to use the received signal strength to determine whether it can send or receive the data signal to increase the communication pairs. Simulation results show that, compared to the IEEE 802.11 DCF protocol and DCA protocol, the proposed SO-MAC protocol with the bandwidth allocation strategy can increase the communication pairs, achieve better throughput, reduce the number of handshake failures, and decrease the delay of transmitting a packet.