Unacknowledged Mode Research Articles

On the Capability of QoE Improvement Based on the Adjustment of RLC Parameters.

The constant evolution in mobile communications networks have led operators to seek new techniques to optimize their mobile networks with the objective of satisfying the expectations of the users. In this way, traditional optimization techniques based on improving radio indicators, have given way to new techniques based on improving the quality of experience (QoE) perceived by users. This paper is focused on analyzing the impact of the adjustment of radio link control (RLC) layer configuration parameters on the QoE perceived by the users of two different types of services. Firstly, an evaluation of the QoE experienced by the user of a real-time video streaming service with respect to the transmission buffer size of the RLC layer in unacknowledged mode (UM) has been carried out. Secondly, the QoE perceived by the user of a file transfer service in relation to the variation of the configuration parameters of the RLC layer in acknowledged mode (AM) has been evaluated. The study, which has been carried out in a simulated cellular environment, has been performed for different system bandwidth values, thus proving the relationship between the QoE perceived by the users, the optimal RLC configuration parameters values and the available bandwidth.

Extreme Coverage in 5G Narrowband IoT: A LUT-Based Strategy to Optimize Shared Channels

One of the main challenges in IoT is providing communication support to an increasing number of connected devices. In recent years, narrowband radio technology has emerged to address this situation: Narrowband Internet of Things (NB-IoT), which is now part of 5G. Supporting massive connectivity becomes particularly demanding in extreme coverage scenarios such as underground or deep inside buildings sites. We propose a novel strategy for these situations focused on optimizing NB-IoT shared channels through the selection of link parameters: modulation and coding scheme, as well as the number of repetitions. These parameters are established by the base station (BS) for each block transmitted until reaching a target block error rate (BLER_t ). A wrong selection of these magnitudes leads to radio resource waste and a decrease in the number of possible concurrent connections. Specifically, our strategy is based on a look-up table (LUT) scheme which is used for rapidly delivering the optimal link parameters given a target QoS. To validate our proposal, we compare with alternative strategies using an open source NB-IoT uplink simulator. The experiments are based on transmitting blocks of 256 bits using an AWGN channel over the NPUSCH. Results show that, especially under extreme conditions, only a few options for link parameters are available, favoring robustness against measurement uncertainties. Our strategy minimizes resource usage in all scenarios of acknowledged mode and remarkably reduces losses in the unacknowledged mode, presenting also substantial gains in performance. We expect to influence future BS software design and implementation, favoring connection support under extreme environments.

Analytical modeling of RLC protocol of LTE using stochastic reward nets

SummaryRLC (radio link control) is a layer 2 protocol of LTE used for reliable transmission of data packets in communication networks. This protocol operates in three modes, namely, transparent mode (TM), unacknowledged mode (UM), and acknowledged mode (AM). In this paper, analytical models are developed to study the flow of data streams in all the three modes of the RLC protocol. Stochastic reward net (SRN) is adopted as a modeling technique as it easily captures various aspects of this protocol such as protocol data unit (PDU) transmission, assigning header with each PDU, requesting for status report, retransmission of PDU(s), management of PDU losses due to expiration of various timers (quick repeat timer, poll timer, status timer). Throughput, average delay and probability of PDU loss are evaluated as the performance measures using the SRN models. Based on these performance measures, a comparative study between the UM and AM is presented which depicts that the modes are performing their key functions decently. Analytical results are also validated via simulation.

A novel hybrid forwarding strategy for content delivery in wireless information-centric networks

Information-centric networking (ICN) is a promising solution for content delivery in multi-hop wireless networks. In these environments, the ICN forwarding strategies typically rely on broadcasting, which facilitates content distribution by taking advantage of the shared medium, but brings about undesirable side effects. To avoid the broadcast-related issues of packet redundancy and unreliability due its unacknowledged mode, a few recent proposals advocated unicasting as the communication mode to resort to, once the content provider has been discovered. However, unicasting may suffer from connectivity breakages due to node mobility and harsh propagation conditions, and, generally, limits the data sharing capability of the wireless medium.In this paper, we design a robust ICN-based forwarding strategy, called Ad Hoc Dynamic Unicast (ADU), that wisely harnesses unicast and broadcast primitives on top of IEEE 802.11-based wireless networks. ADU relies on unicasting for content dissemination after the provider discovery, and promptly falls back to broadcast to find a new content provider in case of a link failure notified by the Medium Access Control (MAC) layer. Extensive simulations in two different multi-hop wireless scenarios, i.e., mobile and vehicular ad hoc networks, under different load settings, assess the ADU performance against benchmark ICN forwarding schemes, representative of broadcast-based and unicast-based solutions. Results show that ADU outperforms them in all circumstances, proving its better responsiveness to link failures, which guarantees a shorter content retrieval delay and a lower message overhead and energy consumption.

Walking, Literature, and English Culture: The Origins and Uses of Peripatetic in the Nineteenth Century

Walking, Literature, and English Culture is a cultural history of walking in nineteenth-century England, assessing its importance in literature and in culture at large. Engaging with current debates about the relationship between industrialization and cultural production, and between technology and the picturesque, Anne Wallace examines the forces that transformed walking from an unwelcome fact of life to a celebrated activity for mind and body. Rereading Wordsworth in the context of contemporary changes in transport, agriculture, and aesthetics, she articulates a previously unacknowledged literary mode - peripatetic. Walking and its representation is set in terms of specific historical circumstances, for examples the rise of enclosure, which Wallace shows is partially undermined by the assertion of footpath rights. Her discussions move from eighteenth-century approaches to peripatetic through its varied uses in Victorian literature, notably in the work of Barrett Browning, Dickens, and Hardy. This is a major contribution to the study of rural English literature (and georgic), in which Anne Wallce demonstrates how a proper understanding of peripatetic significantly enriches our assessment of a text's relation to its culture. 'it provides an excellent survey of literary walkers and walkers in literature, and a most enticing bibliography. It is studded with unusual jewels.' Christina Hardyment, The Independent

An insightful analysis of the hybrid insulated-gate bipolar transistor

The shorted-anode or hybrid insulated-gate bipolar transistor (HIGBT) is examined theoretically (using a first-order analysis) and experimentally (using specially designed test structures) to give physical insight regarding the unique electrical properties of this power switching device. Basic differences between the HIGBT and the conventional lateral IGBT reflected by measurements of on-state conductance, transient turn-off time, and latchup current are explained and shown to be critically dependent on the structural geometry of the device. Also, a previously unacknowledged mode of operation of the HIGBT is demonstrated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>