一般的配送中心內大致包含儲備區，訂單揀貨區，進出貨停車區，退貨區，物料搬運設備，辦公區，電池更換區，以及保養區。相較於儲備區(Reserve Area)揀貨，物品存放在前置區（Forward Picking Area, FPA）時的訂單揀貨移動時間較短，故會產生揀貨節省。為達到訂單揀貨區的效率性，應該令該區域越小越好；因為越小的區域驅使運輸距離越短，也因此揀貨時間將更短。然而FPA的空間是有限的，換言之，週期性的經由儲備區補貨是必然的。既有研究前置─儲備倉儲系統的論文大多是討論哪些物品應該要放置在前置區，以及已經放置於前置區的物品個別應儲存多少數量，才能減少總成本：從儲備區補貨到前置區的成本與運輸成本。
本論文則是從另外一個角度探討前置─儲備倉儲系統。於研究中將探討的倉儲系統視為一個服務站，並且將等候理論套用到該系統，藉由理論方法計算各項績效指標，例如：平均每位顧客訂單待在系統中的時間(W)、平均每位服務員的利用率(ρ)。研究中建立一套評估系統績效的模型，透過這些指標分析系統中各項因素(例如：前置區域的大小、系統的服務員人數、物品種類與數量…)，同時建構模擬系統驗證所推導的績效評估模型的完整性。業者可於一定成本、有限資源與各項指標的不同考量下，確保顧客訂單花較少的時間停留在系統內以及提高系統整體利用率等。

Order picking is a major process of warehouse operations. To facilitate the time-consuming operation, one procedure is to locate fast-moving items in a compact forward area and slow-moving items in a reserve area, because the forward picking time is much less than the reserve picking time. However, the restricted forward area size requires periodical internal replenishment from the reserve area.
This research investigates the influence of the assignment and allocation of items in the forward area by developing queuing models to estimate the system performance based on the design factors, e.g. forward area sizes, numbers of forward items, allocated quantities of forward items, etc. Simulation models are constructed to verify the correctness of proposed theoretical models. Numerical experiments are performed to analyze the effect of design factors and properties of the forward reserve problem. According to the design and decision factors, the system performance estimation from the queuing models can provide an ideal solution to maximize the system utilization or minimize the system waiting time.

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