Link Success Probability Research Articles

Stochastic Models for the Fading Channel Success Rate of Sub-6G UWB Systems

This paper presents different stochastic models for entangled UWB fading channels. Closed-form canonical expressions are derived for the statistical distribution of the fading power difference of interfering independent and dependent mixture of flat-fading Rayleigh and Rician channels. The link success probability is derived in terms of the cumulative distribution function of the channel fading power differences. An alternative metric for link success rate (LSR) is developed in terms of the statistical distribution of the ratio of the diffuse powers. Under this alternative formulation, and for the case of 2 independent Rayleigh paths, the LSR statistical distribution was consistent with the heavy-tail Lomax distribution. The scope of future research includes the validation of theoretical and simulated models with real measurements on actual multi-user massive multiple-input-multiple-output (MU-mMIMO) beam-forming sub-6G physical systems.

Performance of Next-Generation Cellular Networks Guarded With Frequency Reuse Distance

In this paper, we lay an analytic framework for computing the downlink success probability of cellular networks, taking into account a frequency reuse distance as an interference mitigation scheme. We model the frequency reuse distance using tools from stochastic geometry, namely, we utilize the Matern hard-core (MHC) point process to capture the effect of interference protection zones created around base stations. To model the overall cellular network, we introduce a new point process composed of $N$ superimposed MHC processes, where each individual MHC process corresponds to a co-channel base station group; this new point process is called the union-MHC (UMHC) process. We further investigate the resulting performance of the UMHC process and present the link success probability in integral form. The success probability can be evaluated for an arbitrary fading model and an arbitrary number of orthogonal resource groups. We test the newly proposed model against the practical data sets from a network operator and observe a good match of the results.

The Cognitive Internet of Things: A Unified Perspective

In this article, we present a unified perspective on the cognitive internet of things (CIoT). It is noted that within the CIoT design we observe the convergence of energy harvesting, cognitive spectrum access and mobile cloud computing technologies. We unify these distinct technologies into a CIoT architecture which provides a flexible, dynamic, scalable and robust network design road-map for large scale IoT deployment. Since the prime objective of the CIoT network is to ensure connectivity between things, we identify key metrics which characterize the network design space. We revisit the definition of cognition in the context of IoT networks and argue that both the energy efficiency and the spectrum efficiency are key design constraints. To this end, we define a new performance metric called the ‘overall link success probability’ which encapsulates these constraints. The overall link success probability is characterized by both the self-sustainablitiy of the link through energy harvesting and the availability of spectrum for transmissions. With the help of a reference scenario, we demonstrate that well-known tools from stochastic geometry can be employed to investigate both the node and the network level performance. In particular, the reference scenario considers a large scale deployment of a CIoT network empowered by solar energy harvesting deployed along with the centralized CIoT device coordinators. It is assumed that CIoT network is underlaid with a cellular network, i.e., CIoT nodes share spectrum with mobile users subject to a certain co-existence constraint. Considering the dynamics of both energy harvesting and spectrum sharing, the overall link success probability is then quantified. It is shown that both the self-sustainability of the link, and the availability of transmission opportunites, are coupled through a common parameter, i.e., the node level transmit power. Furthermore, provided the co-existence constraint is satisfied, the link level success in the presence of both the inter-network and intra-network interference is an increasing function of the transmit power. We demonstrate that the overall link level success probability can be maximized by employing a certain optimal transmit power. Characterization of such an optimal operational point is presented. Finally, we highlight some of the future directions which can benefit from the analytical framework developed in this paper.

Dual-Branch MRC Receivers Under Spatial Interference Correlation and Nakagami Fading

Despite being ubiquitous in practice, the performance of maximal-ratio combining (MRC) in the presence of interference is not well understood. Because the interference received at each antenna originates from the same set of interferers, but partially de-correlates over the fading channel, it possesses a complex correlation structure. This work develops a realistic analytic model that accurately accounts for the interference correlation using stochastic geometry. Modeling interference by a Poisson shot noise process with independent Nakagami fading, we derive the link success probability for dual-branch interference-aware MRC. Using this result, we show that the common assumption that all receive antennas experience equal interference power underestimates the true performance, although this gap rapidly decays with increasing the Nakagami parameter $m_{\text{I}}$ of the interfering links. In contrast, ignoring interference correlation leads to a highly optimistic performance estimate for MRC, especially for large $m_{\text{I}}$. In the low outage probability regime, our success probability expression can be considerably simplified. Observations following from the analysis include: (i) for small path loss exponents, MRC and minimum mean square error combining exhibit similar performance, and (ii) the gains of MRC over selection combining are smaller in the interference-limited case than in the well-studied noise-limited case.

Enhanced IEEE 802.15.3 MAC Protocol for Efficient Support of Multiple Simultaneously Operating Piconets

The IEEE 802.15.3 medium access control (MAC) protocol is designed to support high-data-rate wireless personal area networks (WPANs). This protocol operates on a time-division multiple-access (TDMA) basis within a piconet, which guarantees interference-free connections. However, it is found that the protocol is not efficient for simultaneously operating piconets (SOPs). In the current protocol, SOPs can be linked by a parent/child (P/C) or parent/neighbor (P/N) configuration for interference mitigation. However, the throughput is limited because the same superframe is shared by the P/C and P/N piconets. In this paper, an adaptive channel time allocation (CTA) is proposed, including public and normal CTAs, to adaptively manage the interpiconet interference in SOPs. In a mobile environment, the public and normal CTAs can also be adaptively allocated based on the link status in the SOPs, thereby reducing interference and improving the efficiency of channel time usage. The proposed scheme is able to achieve a greater throughput than the P/C and P/N configurations. In addition, the link success probability can also be kept at a high value. Based on the SOPs of the direct-sequence ultrawideband (DS-UWB) system, the simulation results demonstrate that the proposed scheme effectively supports the coexistence of SOPs. Furthermore, it not only significantly improves the throughput of the SOPs but also maintains a high link success probability.

Efficient Management of Multiple Piconets in an MC-CDMA-Based UWB System

With multiple overlapped piconets, the IEEE 802.15.3 Medium Access Control (MAC) protocol uses a Parent/Child (P/C) or Parent/Neighbor (P/N) configuration to avoid inter-piconet interference. However, the throughput of a P/N or P/C configuration cannot exceed that of a single piconet. In the present paper we propose an efficient means of managing multiple piconets to cooperate with a Multi-Carrier Code Division Multiple Access (MC-CDMA) based UWB system. The proposed management approach uses an Intermediate Device (IDEV) to connect Piconet Coordinators (PNCs). A senior PNC adaptively arranges two simultaneous data transmission links with the proposed spreading matrices in each Channel Time Allocation (CTA) instead of a P/C or P/N configuration, which supports only a single link in each CTA. Simulation results demonstrate the proposed scheme can achieve a higher throughput with an acceptable compromise of link success probability in multiple overlapped piconets.

Interference Information Based Power Control for Cognitive Radio with Multi-Hop Cooperative Sensing

Reliable detection of other radio systems is crucial for systems that share the same frequency band. In wireless communication channels, there is uncertainty in the received signal level due to multipath fading and shadowing. Cooperative sensing techniques in which radio stations share their sensing information can improve the detection probability of other systems. In this paper, a new cooperative sensing scheme that reduces the false detection probability while maintaining the outage probability of other systems is investigated. In the proposed system, sensing information is collected using multi-hop transmission from all sensing stations that detect other systems, and transmission decisions are based on the received sensing information. The proposed system also controls the transmit power based on the received CINRs from the sensing stations. Simulation results reveal that the proposed system can reduce the outage probability of other systems, or improve its link success probability.