A foldable wheelchair includes a seat frame having a front side provided with a foot frame, a rear side provided with two push handles, and a bottom side provided with two wheel frames. A current source supplies a current to both the light-emitting device and an impedance. In the dynamic channelpower allocation method, a BS receives a feedback channel condition from an MS provided with a service of the BS and allocates a subchannel group with a high SINR to each MS in consideration of the fairness and the distance information of each MS. The first and second sloped sides include at least one body portion offset in opposite radial directions to form a cascaded winding pattern and providing increased cooling surface area for the winding.