This paper introduces a fully portable, lightweight exosuit-type device for shoulder and elbow assistance. The main motivation of this research was to design a portable upper limb exosuit capable to assist dynamic rehabilitation tasks where patient can involve trunk motions and overground movements (e.g., during pick-and-place tasks). The proposed system provides assistance for shoulder flexion and abduction, as well as for elbow flexion. The mechanism is driven by DC motors which are worn on the wearer's back, and the power is transferred from the actuators to the arm by means of cable-driven transmission. The unique features of the proposed exosuit are the absence of rigid links or joints around the arm, high compliance and portability. This paper describes operating principle and kinematic model of the proposed exosuit and provides force analysis and experimental evaluation of the manufactured device. As the result of this work, we performed a simulation of rehabilitation scenario with the developed wearable prototype.