I. Introduction
Parkinson's Disease(PD) is one of the most common neurodegenerative disorders. It is caused by the loss of dopaminergic and other sub-cortex neurons. One of PD symptoms is freezing, which may occur during gait, speaking or a repetitive movement such as handwriting. Freezing of Gait (FoG) can be defined as “a brief, episodic reduction of forward progression of the feet despite the intention to walk”, and is often described by patients as if their feet are glued to the floor for a short period of time [1]. FoG is one of the most common disturbing and least understood symptoms in advanced stages of PD. This disabling symptom often results in falls [2] and consequent injuries impairing quality of life. Its unpredictable occurrence and sensitivity to external factors such as medication, environmental triggers, or cues make it hard to detect FoG in a clinic or research laboratory [3]. The incidence of occurrence of PD has been reported as 1% of the population over the age of 50, and 10% of occurrence over the age of 65 [4]. It has been shown that 80% of PD patients suffer from movement disorders, 10% with wild symptoms while 80% of those severely affected experience freezing. Over half of patients with PD eventually develop freezing of gait (FoG)[5]. FoG occurs more frequently in men than in women, especially those who report tremor symptoms [6]. Accurate detection and rating of both the severity and impact of FoG is therefore important [7], [8]. Although, detection of FoG phenomenon has taken an apparent area of interest in research, a golden standard measure of FoG is currently unavailable. Designing a system that is able to detect patient's FoG episodes accurately, would lead to the knowledge of the necessary actions that can be taken to overcome and correct each FoG episode. Therefore, careful observation and gait pattern analysis may lead to a successful management of PD patients with FoG.