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In this paper, we investigate the performance of hard switching‐based radio frequency/visible light communication (RF/VLC) downlink system, for indoor wireless communication system. The proposed system exploits the advantages of VLC and RF system, ie, high data rate transmission by VLC and pervasive coverage by RF. The indoor RF link is considered to be Nakagami‐m fading channel while the VLC links are subjected to statistical channel model based on the uniformly distributed end user position. In this paper, we study the performance of hybrid RF/VLC system in terms of outage probability, average bit error rate, ergodic capacity, packet error rate, and throughput. Furthermore, we compare the results of proposed RF/VLC system with stand‐alone VLC system to prove its effectiveness. The results prove that, for lower values of average signal‐to‐noise ratio, the proposed system outperforms the stand‐alone VLC system.

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In this paper, a relay selection-based amplify-and-forward (AF) with mixed radio frequency/free space optical (RF/FSO) system is proposed. We have considered two relay selection schemes namely max-select, distributed switch and stay (DSS) and compared their performance when all relays are active. The AF-based relay employs (1) full-channel state information relaying (amplification gain dependent on instantaneous signal-to-noise ratio of source-relay link) (2) semi-blind relaying (fixed amplification gain) for the amplification purpose. The selected AF relay converts the received RF signal into an optical signal using the subcarrier intensity modulation scheme. The RF link is subject to a generalised Á distribution, while the channel for free space optical link is modelled as gamma-gamma distributed along with pointing errors. Novel analytical expressions for the probability density function, cumulative distribution function and the moment generating function of the equivalent signal-to-noise ratio is derived. Capitalising on these channel statistics, we provide the closed form expressions of the outage probability for different relay selection schemes.

Energy efficiency is a major concern in the emerging mobile cellular wireless networks since massive connectivity is to be expected with high energy requirements from the network operators. Non-orthogonal multiple access (NOMA) being the frontier multiple access scheme for 5G, there exists numerous research attempts on enhancing the energy efficiency of NOMA enabled wireless networks while maintaining its outstanding performance metrics such as high throughput, data rates and capacity maximized optimally.The concept of green NOMA is introduced in a generalized manner to identify the energy efficient NOMA schemes. These schemes will result in an optimal scenario in which the energy generated for communication is managed sustainably. Hence, the effect on the environment, economy, living beings, etc is minimized. The recent research developments are classified for a better understanding of areas which are lacking attention and needs further improvement. Also, the performance comparison of energy efficient, NOMA schemes against conventional NOMA is presented. Finally, challenges and emerging research trends, for energy efficient NOMA are discussed.

The complexities of sensemaking suggest that collaboration should be difficult, requiring a rich ecology of collaboration support. This can be a problem for handoff sensemaking, where one person must continue where another has left off, sometimes with only material artifacts as the basis of the handoff. A detailed analysis of essential attributes of sensemaking tasks, and elements identified in the computer supported collaborative work literature were combined to yield insight into handoff sensemaking and guide empirical work. A lab-study showed that handoffs relying only on artifacts from previous sensemaking could be successful. The lab studies also indicated timing and quality affects on the sensemaking handoffs, with different quality materials used differently, and early efforts possibly being particularly difficult to hand off. Design of support for sensemaking handoffs will have to take such effects into account. IntroductionSensemaking is often done collaboratively. While this collaboration can take place in many modes, the research focus here is on handoffs. Handoffs are a form of serial-asynchronous collaboration where provider's unfinished worked is picked up and completed by a recipient.The goal of our research has been to understand the unique nature of sensemaking and the various factors that affect sensemaking handoffs. The ultimate intent is to use this understanding to provide implications for design of sensemaking handoff support systems.We have employed a sequence of approaches, which we sketch in this paper. First, an examination of sensemaking theories and scenarios helped to identify several critical attributes of sensemaking. These were then further examined in the light of general research on collaboration to suggest how the unique nature of sensemaking would impact its collaborative handoff. This framing then led to several empirical studies beginning with an exploratory field study of sensemaking handoffs in computer support helpdesks. This was followed by lab studies focusing on specific aspects of sensemaking handoffs including some temporal characteristics and aspects of handoff-material. The two lab studies are detailed in this paper which focused on the handoff artifact usage during sensemaking handoffs. Essential Attributes of Sensemaking TasksThe first step in understanding sensemaking handoffs was to understand the unique nature of sensemaking in general and how this would impact sensemaking handoffs. We were interested in studying activities that exhibit serious amounts of difficult sensemaking and hence might require support. Consideration of theories and examples provided us attributes for identifying such activities. We used the sensemaking theories of Russell et al (1993), Weick (1996) and Dervin (1998) and examined prototypical sensemaking scenarios like the diagnosis of 1999 West Nile Virus (WNV) outbreak in Queens, NY, as well as tasks used in the sensemaking literature. The result was a detailed set of attributes, falling into two groups, that has been useful for concep...