Tagged Node Research Articles

Evaluation of the end-to-end response times in an energy harvesting wireless sensor network using a receiver-initiated MAC protocol

In this paper we propose an analytical model for the evaluation of the end-to-end response time in an energy-harvesting wireless sensor network where the nodes use a receiver-initiated MAC protocol. Each individual node is modeled by means of a finite capacity queue with repeated server vacations of different types. The available energy is modeled by means of an extra variable. The system occupancy in a tagged node together with the available energy are observed at inspection instants, leading to a discrete-time Markov Chain. We derive closed form formulas for the system occupancy distribution at inspection instants and at arbitrary time instants together with the mean response time in this tagged node. The model is applied for the evaluation of the end-to-end response time a packet experiences when crossing different nodes in an energy-harvesting wireless sensor network. The model allows to determine important system parameters, such as the time a node listens to the medium to receive a beacon, the frequency of the transmission of beacons.

Targeted Axillary Dissection after Chemotherapy: Feasibility Study with Clip and Carbon Dye Tattoo – Neotarget Trial

Background: Axillary staging in patients with complete response after neoadjuvant chemotherapy (NAC) is still controversial. Our objective was to test tattoo alone and subsequentially tattoo plus clip as markers in the targeted axillary dissection of ycN0 patients. Methods: Prospective cohort of cT1-T3, cN1 (proven histologically), M0 patients scheduled to receive NAC. Exclusion criteria were lobular histology, prior axillary surgery, and clinical N2/3. In cohort 1 this positive node (Neotarget node) was tattooed at diagnosis. If ycN0, a targeted axillary dissection was performed. After an interim analysis with negative results we changed the protocol in order to do a double marking procedure (Cohort 2): the positive node was clipped at diagnosis and after NAC a tattoo was done before surgery. Results: Thirteen patients in Cohort 1 and 18 patients in Cohort 2. Failure to identify the Neotarget node with multiple nodes retrieved in 9/13 (69%) of Cohort 1 patients. Also in 5/13 (38%) of Cohort 1 patients and 3/18 (17%) of Cohort 2 there was a failure to clearly identify tattooed nodes. In Cohort 2, clip identification by surgical specimen radiography allowed the identification of the tagged node in 17/18 (94,4%) of cases. The concordance between the clipped node and sentinel nodes was 16/18 (89%). Conclusions: The introduction of double marking by clipping the metastatic node and verifying their removal by surgical specimen radiography, using carbon ink as a tracer, allowed the identification of the metastatic node in 94% of cases, with a simple, reproducible, and easy-to-implement targeted axillary dissection procedure.

Abstract P4-02-17: Targeted axillary dissection after neoadjuvant chemotherapy

Abstract Background: Although neoadjuvant chemotherapy (PST) in early breast cancer patients is preferentially indicated according to the biological type of the disease, information about the involvement of the axillary lymph nodes (LNN.) is still required as prognostic factor, as response marker in PST, and to indicate adjuvant radiotherapy. Therefore, baseline clinically and ultrasound-guided examination of the axilla is mandatory; suspicious axillary LNN. should further be examined by core needle biopsy (CNB) und marked with a tagging clip before initiating PST. After PST, targeted axillary dissection (TAD), defined by resection of both sentinel lymph node and tagged node, can be performed to reduce the extent of the axillary intervention. The aim of the study was to evaluate the retrieval of the tagged LNN in a prospective manner after PST. In addition, we want to evaluate the axillary response rate after PST. Methods: In 50 patients with suspicious axillary LNN who started PST between July 2016 and April 2019, ultrasound-guided core needle biopsy of the most prominent lymph node was performed in local anesthesia, and a tagging clip was inserted into the node (BIP-O-Twist-Marker, BIP biomedical instruments & products, Germany, Tuerkenfeld). After PST, the axilla was again evaluated by ultrasound and TAD was performed. Four patients with primarily histologically negative nodes underwent sentinel excision, only. In 10 patients, for persistent bulky nodes axillary dissection was performed. In 36 patients, the sentinel node, the tagged node and surrounding LNN. were removed. Prior to surgery, the clip-marked lymph node was localized by ultrasound, and a hook- wire for better retrieval was inserted. Results: The evaluation includes 36 patients who started PST between July 2016 and April 2019 (Table 1). Prior to PST, four patients had no evidence of tumor in the CNB of the suspicious lymph node, confirmed by TAD after PST (median: 2 LNN; range 1-3). In 32 patients, lymph node tumor infiltration was found by the initial CNB. Thirteen of these patients had TAD (median: 5 LNN: range 4-10) and pathologic complete axillary response was described. In 19 patients, node-positive disease after PST was observed. TAD only was performed in five patients. Ten patients with clinically suspicious LNN underwent TAD and axillary dissection. Four patients underwent excision of the tagged node only (no sentinel) and axillary dissection. The median number of excised LNN was 11 (range 4 - 21), the median number of tumor-infiltrated LNN was 3 (range 1 - 10). In summary, in all patients the clip-tagged LNN was detected supported by hook-wire-marking before surgery, corresponding to a 100% retrieval rate. In 13 patients (41%) of 32 patients with tumor-infiltrated nodes before PST no residual tumor was found after PST. In patients with an axillary complete response after PST, less LNN were removed than in patients without an axillary complete response. To date, no locoregional recurrence was observed. Conclusion: Technically, TAD is feasible and can be performed with a high retrieval rate. Particularly in patients with low tumor load in the axilla and clinically complete response, TAD may aid to reduce the extent of axillary dissection. Results of TAD after PST in relation to the initial lymph node status. Initial lymph node statusClinically suspect, CNB negative (N=4)Tumor-infiltration (CNB positive) (N=32)Lymph node infiltration after PSTNo infiltrationComplete remission (N=13)Residual disease (N=19)Retrieved lymph nodes (by TAD)41319Excised LNN. [median (range)]2 (1-3)5 (4-10)11 (4-21)Tumor-infiltrated LNN [median (range)]003 (1-10) Citation Format: Susanne Steer, Regina Große, Holger Zentgraf, Christoph Thomssen. Targeted axillary dissection after neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-02-17.

Modeling the Impact of Heterogeneous Transmission Powers on the Throughput of IEEE 802.11 Multi-Hop Ad Hoc Networks

Transmission power control (TPC) leads to heterogeneous transmission power levels of the nodes in multi-hop wireless ad hoc networks. This eventually results in a quite complicated collision scenario due to hidden and exposed terminal problems, and brings a big challenge for analyzing the saturation throughput of the flows. This paper presents a saturation throughput model for IEEE 802.11 multi-hop ad hoc networks with heterogeneous transmission powers. In the model, one tagged node goes through with three processes, i.e., backoff, freezing and transmission, and each of which is composed of a certain number of continuous fixed length time slots. We put forward a four-dimensional Markov chain model for the behavior of the tagged node in each fixed-length time slot. Under the condition of heterogeneous transmission powers, we consider two types of collisions, i.e., the instantaneous and persistent collisions. Their probabilities are characterized by the one-step transition probability matrix of the Markov chain. The per-flow saturation throughput of the flow is eventually derived through an iterative way. Finally, the accuracy of our model is validated by comparing the analytical values and the simulation results, and the impact of the heterogeneous power levels on the performance of the wireless multi-hop ad hoc networks is effectively analyzed.

Cross Layer Analysis of P2MP Hybrid FSO/RF Network

This paper presents and analyzes a point-tomultipoint (P2MP) network that uses a number of freespace optical (FSO) links for data transmission from the central node to the different remote nodes of the network. A common backup radio frequency (RF) link can be used by the central node for data transmission to any remote node in case any one of the FSO links fails. Each remote node is assigned a transmit buffer at the central node. Considering the transmission link from the central node to a tagged remote node, we study various performance metrics. Specifically,we study the throughput from the central node to the tagged node, the average transmit buffer size, the symbol queuing delay in the transmit buffer, the efficiency of the queuing system, the symbol loss probability, and the RF link utilization. Numerical examples are presented to compare the performance of the proposed P2MP hybrid FSO/RF network with that of a P2MP FSO-only network and show that the P2MP hybrid FSO/RF network achieves considerable performance improvement over the P2MP FSO-only network.

A Novel Delay Model for IEEE 802.11

With the popularity of the IEEE 802.11 standards, many analytical delay studies for the Distributed Coordination Function (DCF) have been reported. In this paper, we analyze the additional idle durations that a tagged node needs to wait due to other nodes transmissions. Separating the distributed inter-frame space (DIFS) and extended inter-frame space (EIFS) durations from the full time of a successful transmission, we provide a correct function analysis of the DIFS and EIFS durations and build a more accurate delay model for the IEEE 802.11 DCF. The theoretical analysis and simulation results prove that the proposed delay model is coincident with the real performance when the node number increases.

Packet Scheduling Algorithm in MAC of Smart Antenna System

Head of Line (HOL) blocking and deaf node problem are the main challenges in the smart antenna system in wireless ad hoc networks. To resolve these difficulties, we propose a novel packet scheduling algorithm based on the Directional Network Allocation Vector (DNAV). In the new algorithm, we divide the surrounding space of a tagged node into interference regions and free regions, and then transmit packets selected in turn from the data queue if there is an appropriately free region. The proposed algorithm can eliminate the deaf node problem and resolve the HOL blocking efficiently. Higher throughput and lower network delay are obtained by adapting to the dynamic network topology than other methods. The simulation results confirm the validity of the proposed algorithm.

Basic theorems on the backoff process in 802.11

Since its introduction, the performance of IEEE 802.11 has attracted a lot of research attention and the center of the attention has been the throughput. For throughput analysis, in the seminal paper by Kumar et al. [8], they axiomized several remarkable observations based on a fixed point equation (FPE). Above all, one of the key findings of [8] is that the full interference model, also called the single-cell model [8], in 802.11 networks leads to the backoff synchrony property which implies the backoff process can be completely separated and analyzed through the FPE technique. To date, however, only the uniqueness of the fixed point has been proven to hold under some mild assumptions [8, Theorem 5.1], and we still need an answer to the following fundamental question: Q1:“Exactly under which conditions the fixed point equation technique is valid?” (to be answered in Theorem 1) An intriguing notion, called short-term fairness, has been introduced in some recent works [2,4]. It can be easily seen that this notion pertains to a purely backoff-related argument also owing to the backoff synchrony property in the full interference model [8]. The two papers [2,4] considered the same situation where only two wireless nodes contend for the medium. The former [2] claimed and conjectured through simulations that the summation of the backoff values generated per a packet, denoted by Ω, is uniformly distributed because the initial backoff is uniformly distributed while the latter [4] conjectured based on their experiments that Ω is exponentially distributed in the sense that its coefficient of variation (CV) is one. This left room for misunderstandings about the backoff distribution: Q2:“One of the two works is incorrect?” (to be answered in Theorem 2) In addition, the two works [2,4] defined P[z|ζ] as the probability that other nodes transmits z packets while a tagged node is transmitting ζ packets and acquired the expression of P[z|ζ] valid only for the two node case. It is natural to ask the following pertinent questions: Q3:“Can we develop an analytical model for short-term fairness?” (to be answered in Theorem 3) Q4:“When does the short-term fairness undergo a dramatic

Fairness Analysis of IEEE 802.11 Multirate Wireless LANs

This paper investigates the issue of fairness in IEEE 802.11-based multirate wireless local area networks (WLANs). Distributed coordination function, which is the medium-access control (MAC) protocol used in 802.11 WLANs, provides equal long-term channel access probability to competing stations, irrespective of the time required in sending a frame. When equal-sized frames are used and channel conditions are similar, each station, regardless of its data rate, achieves the same throughput. Furthermore, the aggregate throughput is reduced to a level much closer to what one gets when all stations are of lower rate. This anomaly in the performance is a result of unfair channel time allocation for stations when they use multiple data rates. We consider provisioning of time-based fairness in which each station receives an equal share of the wireless channel occupancy time. We demonstrate that under time-based fairness, the throughput that a tagged node achieves in a multirate WLAN with nodes is identical to what it would achieve in a single-rate WLAN with nodes all at the same data rate as the tagged node. Furthermore, we show that under time-based fairness scheme, the ratio of throughputs per station corresponding to two different bit rates is directly proportional to the ratio of their bit rates. We analyze different mechanisms in achieving time-based fairness by using an analytical model. Using Jain's fairness index, optimal MAC parameters required in achieving maximum fairness between slow and fast stations are obtained. The impacts of these mechanisms on throughput of slow and fast stations are explored. We also consider the notion of proportional fairness in a multirate scenario and prove that it is equivalent to fair channel time allocation. Last, our investigation of an alternative fairness criterion also leads us to propose that the IEEE 802.11 MAC protocol should be redesigned with temporal fairness as a design objective in avoiding inefficiencies related to the performance anomaly.

A stochastic reward net model for performance analysis of prioritized DQDB MAN

The performance of prioritized distributed queue dual bus (DQDB) metropolitan area network (MAN) under bursty traffic environment is studied in this article. The tagged node model is adopted to simplify the analysis. The processes of the packet arrivals to the tagged node, the empty-slot pattern from the upstream, and the request pattern from the downstream are assumed to be Markov Modulated Poisson Processes, a more general and appropriate model to capture the bursty characteristics existing in the traffic flows in high-speed networks. A stochastic reward nets model for the prioritized DQDB MAN is presented. With the help of the stochastic petri net package developed in Duke University, the steady state and as well as the transient behavior of packet loss ratio of tagged node are investigated. The influence of the burstiness of the empty-slot pattern, packet arrival and request pattern on the tagged node’s performance are examined.

Determination of Physiological Maturity in Oat1

AbstractIn studying various ecological and physiological factors affecting the yield of the several small grains, it is important to be able to define the length of the grain fill period, that is the period from anthesis to physiological maturity. Unfortunately, the various small grain crops do not develop a readily recognizable indicator, such as the ‘black layer’ in corn, Zea mays L., and tested methods to evaluate physiological maturity in small grains seem to be lacking. Our objective was to evaluate several techniques for determining when physiological maturity occurs in spring oat, Avena sativa L. In this study, five methods of determining physiological maturity were evaluated. Field grown plants of ‘Astro,’ ‘Noble,’ and ‘Otee’ spring oat were tagged when the spikelets at the second node from the base of the panicle were at anthesis. Plants were grown on a Murrill fine silty loam (a mixed, mesic Typic Hapludults.). Beginning 15 days after anthesis for each cultivar, spikelets at the tagged node were sampled daily, and an evaluation made of color changes in certain panicle parts, the uptake of a red, water‐soluble dye, and the uptake of14C‐sucrose. The groats were then weighed, freeze‐dried, and reweighed to secure dry weight and fresh moisture content. Lack of dry weight changes significant at p ⩽ 0.05 was used as the standard method to define physiological maturity and the other techniques compared to this. When half of the glume tips no longer took up the red dye and approximately 75% of the glume surface was yellow it provided a useful, nondestructive estimation of physiological maturity as defined by the dry weight method. Small amounts of 14C‐sucrose were taken up for a few additional days, but dry weight changes were not significant at p ⩽ 0.05. Groat and grain moisture content did not satisfactorily indicate physiological maturity. Observations of color changes in the glumes and cessation of dye uptake, either alone or in combination, provide a method of comparing the length of the oat fill period under various cultural and environmental conditions and for various genotypes.