Adaptive Access Mechanism Research Articles

ADAM: An Adaptive Access Mechanism for NB-IoT Systems in the 5G Era

The technology of Narrow Band Internet of Things (NB-IoT) is expected to contribute towards the support of massive Machine Type Communications (mMTC), i.e., one of the fundamental performance objectives of 5G networks. However, that call for massiveness, requests a thorough revisit on the NB-IoT access procedure. Considering this, the performance of the NB-IoT access procedure is analysed under different network densities and for various combinations of the related configuration parameters. The analysis led to a useful reference table with 3GPP compliant configurations that maximize the access success probability in an NB-IoT system. The table enables an adaptive access mechanism, where the access parameters are adjusted according to the expected network density. The evaluation results quantify the gain that adaptiveness can provide to the performance of the access procedure.

A Temporal Adaptive Access Mechanism for Data Fusion in an IoT Environment.

Data fusion in the Internet of Things (IoT) environment demands collecting and processing a wide variety of data with mixed time characteristics, both real-time and non-real-time data. Most of the previous research on data fusion was about the data processing aspect; however, successful data transmission is a prerequisite for high-performance data fusion in IoT. On the other hand, research on data transmissions in IoT mainly focuses on networking without sufficiently considering the special requirements of the upper-layer applications, such as the data fusion process, that are consuming the transmitted data. In this paper, we tackle the problem of data transmission for data fusion in an IoT environment by proposing a distributed scheduling mechanism VD-CSMA in wireless sensor networks, which considers the values for data fusion, as well as the delay constraints of packets when determining their priority levels for transmission. Simulation results have shown that VD-CSMA may enhance both throughput and delay performance of data transmission as compared to the typical scheduling schemes used for data fusion in IoT.

Adaptive access mechanism with delta estimation algorithm of traffic loads for supporting weighted priority in IEEE 802.11e WLANs

Focusing on weighted throughput fairness that nodes get throughput proportions according to priority levels in IEEE 802.11e WLANs, we propose an adaptive and full-distributed access mechanism with delta estimation algorithm of traffic loads. We deduce a linear adjustment rule of Contention Window (CW) about traffic loads, which connects parameters of access mechanism with dynamic network conditions. To support weighted priority levels (WPLs) of throughput proportions, we introduce a priority index to restrict number of successful data transmission of nodes with different priority levels for accurate calculation of channel status information. And then, we give a delta estimation algorithm of traffic loads, which can reduce fluctuations of estimated results around true values. By setting different thresholds corresponding to the WPLs, each node can obtain suitable sizes of CW for better aggregated throughput even as the variations of traffic loads in networks. The selected sizes of CW determine the attempt probability of channel access, which guarantees the weighted fairness of throughput proportions corresponding to WPLs. The simulation results confirm the validity and good scalability of the proposed access mechanism with different ratios of node number between multiple priority levels.

Reliable and Efficient Access for Alarm-Initiated and Regular M2M Traffic in IEEE 802.11ah Systems

IEEE 802.11ah is a novel WiFi-based protocol, aiming to provide an access solution for the machine-to-machine (M2M) communications. In this paper, we propose an adaptive access mechanism that can be seamlessly incorporated into IEEE 802.11ah protocol operation and that supports all potential M2M reporting regimes, which are periodic, on-demand, and alarm reporting. The proposed access method is based on a periodically reoccurring pool of time slots, whose size is proactively determined on the basis of the reporting activity in the cell. We show that it is possible to both efficiently and reliably resolve all reporting stations in the cell, within the limits of the allowed deadlines. As a side result, we also provide a rationale for modeling the interarrival time in alarm events by using the Beta distribution, a model that is considered in the 3GPP standardization.

Adaptive Access Mechanism for WSNs of Eco-Environments

To solve the data transmission of eco-environment monitor by using WSNs, a new adaptive access mechanism is presented. The adaptive access mechanism senses the channel status information and the events of data transmissions, success or collision in the channel. Based on the measurement of idle slot intervals between two data transmission, nodes adjust parameters of access mechanism, which can adapt to the dynamic network configurations. The analysis and computer simulation demonstrate the validity and good scalability of the proposed access mechanism.

Performance Analyses of Adaptive Access Mechanism in IEEE 802.11 WLANs

The performance analyses of adaptive access mechanism have not been studied completely, especially in non-saturation conditions. By using feedback signal of channel, we propose an adaptive access mechanism, which adjusts parameters based on idle slot intervals between two data transmissions. Then, we analyze the network performance of throughput, media access delay and retransmission attempts of packets, which shows some main characteristics of adaptive access mechanism. The simulation results also demonstrate the validity and good scalability of the proposed access mechanism.

Adaptive Access Mechanism with Optimal Contention Window Based on Node Number Estimation Using Multiple Thresholds

How to improve the short-term fairness and increase the aggregated throughput simultaneously is a major problem in WLANs, yet has not been solved satisfactorily in previous work, especially in the situation that network loads vary significantly. To improve the performance in saturation state, we propose a novel access mechanism that sets an optimal Contention Window (CW) for all nodes in the network. By introducing a new parameter of CW Index (CWI), we present a linear CW adjustment rule based on the active node number and then develop an estimation algorithm of node number with three thresholds. Compared to previous algorithms, the new algorithm predicts the future node number based on the current network status, thus minimizes the fluctuating effect of idle slot intervals observed at each process. Moreover, it can identify the dense degree of idle slot intervals and track the changes of the accurate node number quickly. By selecting the optimal CWI adaptively, the maximum aggregated throughput keeps basically a constant despite the variation of the number of nodes. Meanwhile, by eliminating multiple transmission attempts of the same node, the short-term fairness is improved significantly. To evaluate the mechanism, we derive closed-form expressions for the network performance. The simulation results demonstrate the validity and good scalability of the proposed access mechanism.

Optimal callback with two-level adaptation for wireless data access

Strongly consistent callback cache mechanisms have been studied for data access in wireless networks. In cache access mechanisms, update information is extremely important since an updated data object in a remote server makes the corresponding data objects invalidated in mobile terminals (MTs), and the data object cache hit information in those MTs becomes almost useless. In this paper, we propose an adaptive access mechanism, called optimal callback with two-level adaptation. In the first-level adaptation, cache size in an MT is adaptively adjusted based on update-to-access-ratio (UAR), defined as the average number of updates per data object access. The range of the cache size is [O, M], where M is the maximum physical cache size of the MT. Two extreme cases are given as follows: 1) when the UAR is very large so that objects in the cache are always obsolete, the cache should not be used and, therefore, the cache size should be set to zero; 2) when the UAR is zero so that every object in the cache is valid, the cache size should be set to M. Under other situations, the cache size is dynamically changed between O and M. Define U-threshold of the UAR for any object, a particular important threshold, as a UAR value, beyond which the object should be not cached at all. The idea of the second-level adaptation is that if an object size is small, sending back the object may be a better choice than sending back an invalidation message when the object is updated. Therefore, when an object is updated at the server, it is sent directly to MTs if the object size is smaller than a threshold, called push threshold (T); otherwise, an invalidation message is sent to the MTs. We analytically model cost function for the proposed adaptive scheme as the total traffic involved between the server and an MT per data object access, and the optimal cache size and the optimal T value are obtained simultaneously to minimize the cost function. Furthermore, U-threshold is derived analytically. Both simulations and analytical results are used to study and compare the performance of the proposed scheme with several others under many different scenarios