Uplink Connections Research Articles

Network Optimization using Real Time Polling Service With and Without Relay Station in WiMAX Networks

IEEE 802.16 can be seen as a compelling replacement for conventional broadband technologies because its primary goal is to provide Broadband Wireless Access (BWA). The variable and uncertain nature of wireless networks makes it much more challenging to ensure QoS in this network. WiMAX Technology is used to support various quality of services which includes UGS, rtps, nrtps, ertps and Best Effort. This study employs an IEEE 802.16 network simulator, which offers adaptable and reliable features for assessing a particular QoS parameters for rtps. Achieving better internet performance in real time services is a challenge now a days, and it is also need of present scenario. This work emphasized on better internet service with good quality of service using rtps with Relay Station and Without Relay Station. In this work the CBR packet size, CBR data rate and data rate with rtps service are fine-tuned for achieving the better performance with good quality of service. When comparing uplink connections in rtps with and without relay station, it is found that the throughput in the uplink is 200% greater when using a relay station. The throughput and goodput are evaluated in uploading and downloading with single and multiple subscriber stations and observed that the multiple subscriber stations in downloading give better performance as compare to single subscriber stations. The throughput and goodput in single subscriber stations is better than multiple subscriber station in uploading. the Academic researchers and commercial developers can use this analysis to validate different WiMAX Network implementation mechanisms and parameters.

Artificial Intelligence-Empowered Doppler Weather Profile for Low-Earth-Orbit Satellites.

Low-Earth-orbit (LEO) satellites are widely acknowledged as a promising infrastructure solution for global Internet of Things (IoT) services. However, the Doppler effect presents a significant challenge in the context of long-range (LoRa) modulation uplink connectivity. This study comprehensively examines the operational efficiency of LEO satellites concerning the Doppler weather effect, with state-of-the-art artificial intelligence techniques. Two LEO satellite constellations-Globalstar and the International Space Station (ISS)-were detected and tracked using ground radars in Perth and Brisbane, Australia, for 24 h starting 1 January 2024. The study involves modelling the constellation, calculating latency, and frequency offset and designing a hybrid Iterative Input Selection-Long Short-Term Memory Network (IIS-LSTM) integrated model to predict the Doppler weather profile for LEO satellites. The IIS algorithm selects relevant input variables for the model, while the LSTM algorithm learns and predicts patterns. This model is compared with Convolutional Neural Network and Extreme Gradient Boosting (XGBoost) models. The results show that the packet delivery rate is above 91% for the sensitive spread factor 12 with a bandwidth of 11.5 MHz for Globalstar and 145.8 MHz for ISS NAUKA. The carrier frequency for ISS orbiting at 402.3 km is 631 MHz and 500 MHz for Globalstar at 1414 km altitude, aiding in combating packet losses. The ISS-LSTM model achieved an accuracy of 97.51% and a loss of 1.17% with signal-to-noise ratios (SNRs) ranging from 0-30 dB. The XGB model has the fastest testing time, attaining ≈0.0997 s for higher SNRs and an accuracy of 87%. However, in lower SNR, it proves to be computationally expensive. IIS-LSTM attains a better computation time for lower SNRs at ≈0.4651 s, followed by XGB at ≈0.5990 and CNN at ≈0.6120 s. The study calls for further research on LoRa Doppler analysis, considering atmospheric attenuation, and relevant space parameters for future work.

MABASR—A Robust Wireless Interface Selection Policy for Heterogeneous Vehicular Networks

Connectivity is rapidly becoming a core feature of modern vehicles to enable the provision of intelligent services that promote safer transport networks, real-time traffic infotainment systems and remote asset monitoring. As such, a reliable communications back-bone is required to connect vehicles that deliver real-time data to smart services deployed at cloud or edge architecture tiers. Hence, reliable uplink connectivity becomes a necessity. Next-generation vehicles will be equipped with multiple wireless interfaces, and require robust mechanisms for reliable and efficient management of such communication interfaces. In this context, the contribution of this article is a learning based approach for interface selection known as the Multi-Armed Bandit Adaptive Similarity-based Regressor (MABASR). MABASR takes advantage of the underlying linear relationship between channel quality parameters and uplink data rate to realise a robust interface selection policy. It is shown how this approach outperforms algorithms developed in prior work, achieving up to two orders of magnitude lower standard deviation of the obtained reward when trained on different data sets. Thus, higher reliability and less dependency on the structure of the training data are achieved. The approach is tested in mobile, static, and artificial static scenarios where severe network congestion is simulated. All data sets used for the evaluation are made publicly available.

A Heuristic Approach for Optical Transceiver Placement to Optimize SNR and Illuminance Uniformities of an Optical Body Area Network

The bi-directional information transfer in optical body area networks (OBANs) is crucial at all the three tiers of communication, i.e., intra-, inter-, and beyond-BAN communication, which correspond to tier-I, tier-II, and tier-III, respectively. However, the provision of uninterrupted uplink (UL) and downlink (DL) connections at tier II (inter-BAN) are extremely critical, since these links serve as a bridge between tier-I (intra-BAN) and tier-III (beyond-BAN) communication. Any negligence at this level could be life-threatening; therefore, enabling quality-of-service (QoS) remains a fundamental design issue at tier-II. Consequently, to provide QoS, a key parameter is to ensure link reliability and communication quality by maintaining a nearly uniform signal-to-noise ratio () within the coverage area. Several studies have reported the effects of transceiver related parameters on OBAN link performance, nevertheless the implications of changing transmitter locations on the uniformity and communication quality have not been addressed. In this work, we undertake a DL scenario and analyze how the placement of light-emitting diode (LED) lamps can improve the uniformity, regardless of the receiver position. Subsequently, we show that using the principle of reciprocity (POR) and with transmitter-receiver positions switched, the analysis is also applicable to UL, provided that the optical channel remains linear. Moreover, we propose a generalized optimal placement scheme along with a heuristic design formula to achieve uniform and illuminance for DL using a fixed number of transmitters and compare it with an existing technique. The study reveals that the proposed placement technique reduces the fluctuations in by and improves the illuminance uniformity up to as compared to the traditional approach. Finally, we show that, for very low luminous intensity, the values remain sufficient to maintain a minimum bit error rate (BER) of with on-off keying non-return-to-zero (OOK-NRZ) modulation format.

Interference-aware Coordinated Access Control for Heterogeneous Cellular D2D Communication Networks

Device-to-Device (D2D) communications is expected to be a key technology of the forthcoming mobile communication networks because of its benefits in terms of spectral efficiency, energy efficiency, and system capacity. To mitigate frequency collisions as well as reduce the effects of co-channel interference between user's connections, we propose an interference-aware coordinated access control (IaCAC) mechanism for heterogeneous cellular D2D communication networks with dense device deployment of user equipment (UEs). In the proposed network setting, we consider the co-existence of both macro base stations (MBSs) and smallcell base stations (SBSs). In the proposed IaCAC mechanism, MBSs and SBSs are coordinated to perform access control to their UEs while MBSs allocate bandwidth parts dynamically to SBSs based on the interference levels measured at SBSs. Besides, to reduce D2D-to-cellular interference, device user equipments (DUEs) can perform power control autonomously. Simulation results show that the proposed IaCAC can provide higher system throughput and user throughput than those achieved by the network-assisted device-decided scheme proposed in [21]. Moreover, simulation results also reveal that the proposed IaCAC also significantly improve SINR of MUE’s and SUE’s uplink connections.

Fiber-Enabled Optical Wireless Communications With Full Beam Coverage

This work proposes a fiber-enabled optical wireless communication (FE-OWC) system for bidirectional communications between the base station (BS) and a number of mobile user terminals (UTs) via full beam coverage, aimed at facilitating ultra-high data rate communications. The FE-OWC system comprises optical antennas, optical chains, and baseband units at both BS and UTs. The innovative optical antenna consists of an array of fiber ports and a transceiver lens, which can form a number of transmit and receive optical beams and provide a full beam coverage for simultaneous downlink and uplink connections with a number of UTs, respectively. We present analysis to characterize downlink and uplink channel models and gains, including both optical and electrical parts, between the BS and UTs and conduct a complete link budget analysis. We further design downlink and uplink multiuser multiple-input multiple-output (MIMO) as well as massive MIMO transmission protocols and develop asymptotically optimal schemes for a large number of fiber ports. Numerical results illustrate that the FE-OWC system has the potential to support over 10 Gbps data rate per UT and Tbps system throughput required in future 6G mobile communication systems.

Dual Connectivity in Decoupled Aerial HetNets With Reverse Frequency Allocation and Clustered Jamming

The extensive increase in the number of mobile devices and their data-rate requirements will lead to the scarcity of network resources. One of the promising solutions to keep up with the capacity and coverage demands of the 5th generation and beyond of cellular networks is to exploit the dual connectivity (DC) feature in heterogeneous networks (HetNets). In this work, a two-tier aerial HetNet with decoupled access and reverse frequency allocation strategy is considered and the DC feature for the network edge users is investigated. The analytical expressions of the coverage probability for the first and second uplink (UL) connections in DC are derived. Our proposed setup improves the coverage performance of the DC with decoupled access in relation to single connectivity (SC) with and without decoupled access. The results show a relative increase in the DC-based coverage performance of 10.6% and 82.6%, for a signal-to-interference-ratio (SIR) threshold of −20 dB, with respect to SC with and without decoupled access, respectively. Moreover, DC-based coverage in aerial HetNets is resilient to jamming interference. The results also show that if the wide-band jammers (WBJs) are present around a target-user equipment, the legitimate UL transmission is severely disrupted by the jamming interference. For instance, the percentage-decrease in the coverage performance of DC with decoupled access for the SIR threshold set to −20 dB is 4.9% and 10.6%, when the WBJs is set to 2 and 4, respectively. The coverage performance further decreases with an increase in the transmit powers of the WBJs and their number, whereas increases with an increase in the radius of the WBJs cluster.

Self-Adaptive Clustering and Load-Bandwidth Management for Uplink Enhancement in Heterogeneous Vehicular Networks

Due to the diversity of traffic scenes and high mobility of vehicles, the propagation environment between moving vehicles and road side access points can be highly dynamic, which causes unstable uplink connectivity and time-varying uplink data rates in vehicular networks. In this paper, we study the uplink performance of heterogenous vehicular networks, which integrate dedicated short-range communications (DSRCs) and Long Term Evolution vehicle-to-everything (LTE V2X) into a single vehicular network to provide high reliability, low latency, and wide area coverage. Here, we adopt a cluster-based approach, in which DSRC and LTE are utilized to provide vehicle-to-vehicle communications between vehicles within a cluster and vehicle-to-infrastructure communications between vehicles and access points, respectively. Specifically, a self-adaptive clustering method is proposed based on the iterative self-organizing data analysis technique algorithm, in which the number of clusters can automatically adjust to the optimal value according to the mobility information. Also, a joint load-bandwidth management scheme is proposed to distribute traffic load and bandwidth resources between DSRC and LTE. Simulation results show that the proposed algorithm outperforms the traditional section-based and ${K}$ -means clustering methods, and a tradeoff between average uplink data rate and signaling overhead can be achieved.

Spatiotemporal Stochastic Modeling of IoT Enabled Cellular Networks: Scalability and Stability Analysis

The Internet of Things (IoT) is large scale by nature, which is manifested by the massive number of connected devices as well as their vast spatial existence. Cellular networks, which provide ubiquitous, reliable, and efficient wireless access, will play fundamental rule in delivering the first-mile access for the data tsunami to be generated by the IoT. However, cellular networks may have scalability problems to provide uplink connectivity to massive numbers of connected things. To characterize the scalability of cellular uplink in the context of IoT networks, this paper develops a traffic-aware spatiotemporal mathematical model for IoT devices supported by cellular uplink connectivity. The developed model is based on stochastic geometry and queueing theory to account for the traffic requirement per IoT device, the different transmission strategies, and the mutual interference between the IoT devices. To this end, the developed model is utilized to characterize the extent to which cellular networks can accommodate IoT traffic as well as to assess and compare three different transmission strategies that incorporate a combination of transmission persistency, backoff, and power-ramping. The analysis and the results clearly illustrate the scalability problem imposed by IoT on cellular network and offer insights into effective scenarios for each transmission strategy.

Resource management for symmetrical applications over heterogeneous services in IEEE 802.16

Symmetrical applications are multimedia applications that require both uplink and downlink connectivity. The demands of symmetrical applications are expected to grow rapidly in the future but there is still no resource management that can efficiently support symmetrical applications over heterogeneous services in IEEE 802.16 system. In this paper, we propose a resource management scheme that can support symmetrical applications along with heterogeneous services. The proposed scheme comprises of a joint uplink and downlink allocation, dynamic control system and bandwidth recycling framework. Simulation studies show that the proposed scheme outperforms asymmetrical scheme in terms of throughput, delay and packet loss. The proposed scheme also achieves similar performance gains in more complex environment.

A Downlink and Uplink Alignment Scheme for Power Saving in IEEE 802.16 Protocol

This study shows the problem of power saving mechanism (PSM) that sleep intervals of uplink (UL) connections do not synchronize with sleep intervals of downlink (DL) connections. That is, the energy of a mobile station (MS) is not really saved if the DL connections are in the sleep mode while the UL connections are in normal mode, and vice versa. To avoid the asynchronism of power saving (PS) between UL and DL connections, we invent a mechanism of DL connections regulating UL connections, called DL and UL Alignment (DUAL) scheme, to improve the energy efficiency for PS. Considering that the buffer size of MS is limited, DUAL uses the mean packet arrival rate of UL λ u and a relatively safe threshold of buffer size Q T as the parameters to estimate the maximum allowable waiting time to align the UL with the DL connections. To analyze the performance of DUAL, a system model of PS is proposed to evaluate the performance of DUAL under different conditions. The correctness of performance analysis of DUAL is validated by using simulation with realistic parameters. Numerical experiments show that DUAL improves the energy conservation significantly when UL traffic is greater than DL traffic.

Multi-Hop Connectivity Probability in Infrastructure-Based Vehicular Networks

Infrastructure-based vehicular networks (consisting of a group of Base Stations (BSs) along the road) will be widely deployed to support Wireless Access in Vehicular Environment (WAVE) and a series of safety and non-safety related applications and services for vehicles on the road. As an important measure of user satisfaction level, uplink connectivity probability is defined as the probability that messages from vehicles can be received by the infrastructure (i.e., BSs) through multi-hop paths. While on the system side, downlink connectivity probability is defined as the probability that messages can be broadcasted from BSs to all vehicles through multi-hop paths, which indicates service coverage performance of a vehicular network. This paper proposes an analytical model to predict both uplink and downlink connectivity probabilities. Our analytical results, validated by simulations and experiments, reveal the trade-off between these two key performance metrics and the important system parameters, such as BS and vehicle densities, radio coverage (or transmission power), and maximum number of hops. This insightful knowledge enables vehicular network engineers and operators to effectively achieve high user satisfaction and good service coverage, with necessary deployment of BSs along the road according to traffic density, user requirements and service types.

Providing QoS support through scheduling in WiMAX systems

The WiMAX system outlines support for quality of service (QoS) through several service classes differentiation. However, no specific scheduling has been defined to carry the task. In this paper, we propose a simple and standard-compliant scheduling algorithm for downlink and uplink connections. The proposed algorithm calculates and grants the needed resources in terms of slots based on the QoS requirements and the priority of the service classes. The simulation results show that the scheduling algorithm has fulfilled the QoS provisions of all service classes of WiMAX system in terms of delay and throughput requirements.

Frequency Sharing Mechanism Using Pilot Sensing in OFDMA-Based Cognitive Radio Networks

Mobile operators need to migrate from 2G to 3G networks in a cost-effective manner. Cognitive radio systems are currently being investigated as a promising solution to achieve spectrum efficiency by allowing coexistence of unlicensed (secondary) networks and licensed (primary) networks. However, conventional mechanisms to operate these systems incur additional complexity and fail to maximize network performance. In this paper, we propose a pilot sensing and frequency selection method with low complexity for OFDMA-based cognitive radio systems. Subject to the interference constraints imposed by the primary network, capacity maximization problems involving both up-link and down-link connections are considered for overall network performance improvement. The throughput and outage probability of the proposed method are evaluated by simulations. Our proposed method shows outstanding performance if the channel varies frequently in the primary network and the frequency reuse factor of the primary network is high.

TCP-aware bidirectional bandwidth allocation in IEEE 802.16 networks

In this paper, we propose a bidirectional bandwidth-allocation mechanism to improve TCP performance in the IEEE 802.16 broadband wireless access networks. By coupling the bandwidth allocation for uplink and downlink connections, the proposed mechanism increases the throughput of the downlink TCP flow and it enhances the efficiency of uplink bandwidth allocation for the TCP acknowledgment (ACK). According to the IEEE 802.16 standard, when serving a downlink TCP flow, the transmission of the uplink ACK, which is performed over a separate unidirectional connection, incurs additional bandwidth-request/allocation delay. Thus, it increases the round trip time of the downlink TCP flow and results in the decrease of throughput accordingly. First, we derive an analytical model to investigate the effect of the uplink bandwidth-request/allocation delay on the downlink TCP throughput. Second, we propose a simple, yet effective, bidirectional bandwidth-allocation scheme that combines proactive bandwidth allocation with piggyback bandwidth request. The proposed scheme reduces unnecessary bandwidth-request delay and the relevant signaling overhead due to proactive allocation; meanwhile, it maintains high efficiency of uplink bandwidth usage by using piggyback request. Moreover, our proposed scheme is quite simple and practical; it can be simply implemented in the base station without requiring any modification in the subscriber stations or resorting to any cross-layer signaling mechanisms. The simulation results ascertain that the proposed approach significantly increases the downlink TCP throughput and the uplink bandwidth efficiency.

Analysis of GSM/GPRS Cell with Multiple Data Service Classes

This paper is concerned with the performance modelling and evaluation of a General Packet Radio Service (GPRS) for a wireless Global System for Mobile telecommunication (GSM) cell involving both voice and multiple class data services under a complete partitioning scheme (CPS). The GPRS is modelled as a system of access and transfer queues in tandem having an external multiple class compound Poisson bursty traffic with geometrically distributed batches under first-come-first-served (FCFS) and generalised processor-sharing (PS) scheduling disciplines, respectively. The proposed queueing model is valid for both uplink and downlink connections and provides multiple class data services with different arrival rates, interarrival-time squared coefficients of variation (SCVs), file (burst) sizes and different PS discrimination service levels. Based on the principle of maximum entropy (ME), a product form approximation is characterised for the two queues in tandem, subject to queueing theoretic mean value constraints. The ME solution implies a decomposition of the system into individual single server building block queues, each of which can be analysed in isolation. Consequently, ME closed form expressions and simulation results for the aggregate state probability together with the marginal mean queue length and blocking probability are divised to assess the credibility of the ME solution and also to study the effect of external GPRS bursty traffic upon the performance of the wireless cell.

Polling- and contention-based schemes for TDMA-TDD access to wireless ATM networks

The design of an efficient MAC protocol is of paramount interest for the definition of a wireless ATM (WATM) access. In the case of TDMA-TDD WATM access, the current trend in the standardization bodies is to adopt frames of fixed duration, whose slots are shared among uplink and downlink connections under the control of a MAC scheduler located in the base station. In this paper, we first compare polling and contention techniques, in order to identify the best access scheme to serve ATM connections. Then, since the knowledge of the queue status of the portable terminals can be used by the centralized scheduler to increase the efficiency of the slot assignment procedure, we propose different algorithms to code the buffer occupancy status. Moreover, we compare their performance by considering two different scenarios; the first loaded with ON-OFF sources served by nrt-VBR ATM connections, and the second with TCP/IP sources served by UBR ATM connections. The results show the superiority of the contention access and the advantages of the buffer status notification for the scheduler at the base station.