User Access Delay Research Articles

Cooperative Caching Strategy Based on Two-Layer Caching Model for Remote Sensing Satellite Networks

In Information Centric Networking (ICN) where content is the object of exchange, in-network caching is a unique functional feature with the ability to handle data storage and distribution in remote sensing satellite networks. Setting up cache space at any node enables users to access data nearby, thus relieving the processing pressure on the servers. However, the existing caching strategies still suffer from the lack of global planning of cache contents and low utilization of cache resources due to the lack of fine-grained division of cache contents. To address the issues mentioned, a cooperative caching strategy (CSTL) for remote sensing satellite networks based on a two-layer caching model is proposed. The two-layer caching model is constructed by setting up separate cache spaces in the satellite network and the ground station. Probabilistic caching of popular contents in the region at the ground station to reduce the access delay of users. A content classification method based on hierarchical division is proposed in the satellite network, and differential probabilistic caching is employed for different levels of content. The cached content is also dynamically adjusted by analyzing the subsequent changes in the popularity of the cached content. In the two-layer caching model, ground stations and satellite networks collaboratively cache to achieve global planning of cache contents, rationalize the utilization of cache resources, and reduce the propagation delay of remote sensing data. Simulation results show that the CSTL strategy not only has a high cache hit ratio compared with other caching strategies but also effectively reduces user request delay and server load, which satisfies the timeliness requirement of remote sensing data transmission.

Distributed Q-Learning-Enabled Multi-Dimensional Spectrum Sharing Security Scheme for 6G Wireless Communication

In 6G wireless communication scenarios, the ultra-dense network (UDN) scenario has received extensive attention, as it is an inevitable case of 6G networks. How to keep users safe while providing universal service to a number of users is becoming a crucial topic of UDN. To battle this issue, we propose a distributed Q-learning-enabled multi-dimensional spectrum sharing security scheme for the millimeter-wave frequency band. With this scheme, a fine-grained spectrum sharing security framework based on spatial multiplexing is established, which balances UDN performance and security. Aiming at the multi-dimensional spectrum sharing security and optimal allocation problem, non-cooperative game theory is used for modeling and analysis. To prove the validity of this scheme, we used numerical simulations to verify the performance of the proposed distributed Q-learning algorithm for solving the spectrum sharing optimization problem in the UDN scenario. The results show that the proposed multi-dimensional spectrum sharing security scheme can significantly reduce the access delay of users, increase the number of unauthorized users that can be accommodated, and improve throughput, while achieving good security performance of the network.

Integrating the device-to-device communication technology into edge computing: A case study

The increasing demand on internet traffic makes the network operator face a dilemma: How to improve users’ quality of experience (QoE) with limited spectrum resources? In this study, we try to alleviate operators’ pressure by exploiting the merits of edge computing and device-to-device (D2D) communication technology. Offloading data or task to the edge can reduce the access delay of users, and the D2D communication technology helps to employ the unlicensed spectrum to transmit data. Furthermore, the information exchange can be completed without the network infrastructure. Considering these facts, we build an edge computing platform, in which devices can automatically switch the transmission pattern based on the communication distance or the strength of signals. We test the transmission performance of two D2D links, Wi-Fi Direct and Bluetooth, and that of the cellular link, and use the flower identification as a case study to verify the effectiveness of the platform. The experimental results validate that with the assistance of D2D communication technology, the response time is greatly improved compared with using the cellular link.

Backoff-Based Coded Random Access for Intelligent Connected Vehicles

The rapid growth in the scale of the intelligent connected vehicles (ICVs) brings about the need for novel random access schemes that realize collision avoidance and reliable communication. The coded random access (CRA) scheme utilizes successive interference cancellation (SIC) across slots to enable the extraction of multiple users' packets from the collision slots and proves to be an efficient solution to collision resolution. In this paper, we propose a random backoff-based CRA scheme to achieve a tradeoff between the access success probability and access delay for CRA. Specifically, we partition the traditional CRA frame into subframes, so that the user access delay is reduced to the same scale of the subframe length. In addition, the backoff operation among subframes is introduced so that access failures originated from the subframe length limit can be reduced with the retransmission in subsequent subframes. In particular, we consider practical Nakagami-m fading channel in the CRA performance analysis and take into account the capture effect in the iterative interference cancellation process. Simulation results show that backoff-based CRA can significantly reduce the average access delay without severe negative effect on the access success probability for moderate system load compared with traditional CRA. Comparisons with the state-of-the-art non-orthogonal random access (NORA) scheme proposed for 5G indicates that backoff-based CRA provides a feasible solution for random access of large-scale ICVs.

Cache Replacement Schemes Based on Adaptive Time Window for Video on Demand Services in Femtocell Networks

The cache replacement policy is a crucial phase in caching-based systems that deal with the process of selecting applicable cache contents. In this paper, we propose two novel cache replacement algorithms based on the dataset obtained from a typical wireless femto network. In the first algorithm, called Weighted Least Frequently used with an Adaptive Time Window (WLF-ATW), we aim to make a balance between the network's traffic and the recognition of popular contents. The WLF-ATW algorithm takes the frequency and the recency information of files into account to ascertain the popularity of contents. We suggest another new cache replacement policy namely Fairness Scheduling-based with an Adaptive Time Window (FS-ATW) that is based on fairness scheduling in order to minimize the user's access delay. The novelty of our proposed FS-ATW lies in ranking clients according to their last situations that lead to a further user's experience. The effectiveness of these new algorithms is evaluated from the cache hit ratio, transferred byte volume, user's access delay, user's experience, and load balance. A comprehensive numerical evaluation shows that the performance of the proposed WLF-ATW and FS-ATW algorithms is significantly better than some existing cache replacement strategies.

Replication Strategy for Spatiotemporal Data Based on Distributed Caching System.

The replica strategy in distributed cache can effectively reduce user access delay and improve system performance. However, developing a replica strategy suitable for varied application scenarios is still quite challenging, owing to differences in user access behavior and preferences. In this paper, a replication strategy for spatiotemporal data (RSSD) based on a distributed caching system is proposed. By taking advantage of the spatiotemporal locality and correlation of user access, RSSD mines high popularity and associated files from historical user access information, and then generates replicas and selects appropriate cache node for placement. Experimental results show that the RSSD algorithm is simple and efficient, and succeeds in significantly reducing user access delay.

Analysis of power saving and its impact on web traffic in cellular networks with continuous connectivity

In this work, we analyze the power saving and its impact on web traffic performance when customers adopt the continuous connectivity paradigm. To this end, we provide a model for packet transmission and cost. We model each mobile user’s traffic with a realistic web traffic profile, and study the aggregate behavior of the users attached to a base station by means of a processor-shared queueing system. In particular, we evaluate user access delay, download time and expected economy of energy in the cell. Our study shows that dramatic energy saving can be achieved by mobile devices and base stations, e.g., as much as 70%–90% of the energy cost in cells with realistic traffic load and the considered parameter settings.