No abstract

Multihop relay-based cellular networks are attracting much interest because of their throughput enhancement, coverage extension, and low infrastructure cost. In these networks, relay stations (RSs) between a base station (BS) and mobile stations (MSs) drastically increase the overall spectral efficiency, with improved channel quality for MSs located at the cell edge or in shadow areas, and enhanced throughput of MSs in hot spots. These relay-based networks require an advanced radio resource management scheme because the optimal amount of radio resource for a BS-to-RS link should be allocated according to the MS channel quality and distribution, considering the interference among RSs and neighbor BSs. In this paper, we propose optimal resource planning algorithms that maximize the overall utility of relay-based networks under a proportional fair scheduling policy. In the first phase, we determine an optimal scheduling policy for distributing BS-to-RS link resources to RSs. In the second phase, we determine the optimal amount of the BS-to-RS link resources using the results of the first phase. The proposed algorithms efficiently calculate the optimal amount of resource without exhaustive searches, and their accuracy is verified by comparison with simulation results, in which the algorithms show a perfect match with simulations.

Silybum marianum (L.) Gaertner. (also known as milk thistle) is a species of the Asteraceae family that it native to the Mediterranean area and has features similar to annual or biennial, self-fertile plants that grow wild throughout the region (Hetz et al. 1993, Leng-Peschlow 1996. Milk thistle is a serious weed in many countries (LeRoy et al. 1997). It grows preferentially in fertile soils, but it can also grow successfully in sandy soils and heavier clay soils (Khan et al. 2009, Karkanis et al. 2011. It tends to occupy areas and eliminate other plant species through competition (Berner et al. 2002). Silybum marianum contains silymarin, which has hepatoprotective effects.Silymarin is highly accumulated in the external cover of Silybum marianum seeds and is composed of flavonolignan isomers (silybin, isosilybin, silychristin, isosilychristin, and silydianin) (Deep et al. 2008, Valková et al. 2021. Silybin is the principal active compound (Saller et al. 2001). Silybum marianum is a troublesome weed, but it can also be cultivated as a medicinal plant because of its silymarin components.

In this paper, we propose a resource allocation scheme that guarantees transmission rate for each mobile stations by mitigating interference between a base station-to-mobile station link and a relay station-to-mobile station link. Specifically, we dynamically adjust the boundary between access zone and relay zone using signal to interference plus noise ratio. Moreover, we cluster the mobile stations under sever interference and manage the channel quality of these mobile stations by allocating additional radio resource. Our simulation results show that the proposed scheme can improve the efficiency of radio resources and ensure fairness among mobile stations.