Design and Evaluation of Multi-Hop Relaying in Emerging Radio Networks
Abstract
Cognitive radio networks have emerged to exploit optimally the scarcely-available
radio spectrum resources to enable evolving 5G wireless communication systems. In
these networks, dynamic spectrum access is considered spectrally more efficient than
networks using fixed spectral allocation. These networks are characterized by dynamically changing channel sets at each node. Multi- hop cognitive radio network is a
cooperative network in which cognitive users take help of their neighbors to forward
data to the destination. These networks tend to cater to the ever-increasing demands
of higher data rates, lower latencies and ubiquitous coverage. Adding buffers at each
relay node provides additional flexibility of storing the data and later transmitting when
conditions are favorable for transmission. Thus, the use of buffer-aided cooperative relaying, a cognitive radio network can enhance both, the spectral efficiency and the range of the network; although, this could incur additional end-to-end delays. To mitigate this possible limitation of the buffer-aided relaying in the underlay cognitive network, a buffer-aided multi-hop relay selection (BAMR) technique is proposed that integrates a virtual duplex multi-hop mechanism with the simple buffer-aided relaying in a CRN , which improves throughput and reduces end-to-end delays, while keeping the outage probability to a minimum as well. This scheme, simultaneously, takes into account the inter-relay interference and the interference to the primary network. The proposed scheme is modeled as a Markov chain, and Monte Carlo simulations under various scenarios are conducted to evaluate several key performance metrics; such as, throughput, outage probability, and average packet delay. The simulation results show that BAMR scheme outperforms all other contemporary schemes
After developing BAMR scheme the focus was shifted to enhancing the relaying selection process through Multi objective optimization. The relays are generally selected
on the basis of signal to interference and noise ratio (SINR) and throughput or delay
performance; however other factors such as power consumption and buffer capacity can also have a significant impact on relay selection. In this work, a multi-objective relay
pair selection scheme is proposed that simultaneously takes into consideration throughput and delay performance along with the battery power and buffer space at the relay nodes while maintaining the required SINR as well. The proposed scheme involves the formulation of four objective functions to respectively maximize throughput , minimize the delay, and takes into account battery power consumption and availability of buffer space for interim storage of packets, before transmission . A weighted sum approach is then used to combine these objective functions to form a single multi-objective optimization problem. A variety of application quality-of-service (QoS) requirement scenarios involving a mix of real-time (RT) traffic, non-real-time (RT) traffic along with power-consumption and buffer space limitations have been considered through assignment of weights and analyzed correspondingly. Genetic algorithm (GA) and particle swarm (PSO) based techniques were used to validate the results obtained by our weighted sum technique . Although GA required more iterations then PSO, but both methods yielded the same relay for these application scenarios. The analysis shows that the proposed scheme performs equally well in all aspects and enables to select the best relay pair for each of the application scenarios.
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