Applying WLANs in Warehouses

By Jim Geier

March 08, 2004

Wireless LANs have tremendous benefits in warehouses. Learn what applications and issues to consider when deploying these types of systems.

There are many opportunities for deploying wireless LANs in warehouses. In many cases, a company will implement a wireless LAN for one function, such as on the receiving dock to log incoming supplies, but eventually there will be wireless applications running everywhere throughout the warehouse.

Let's take a closer look at the types of applications in warehouses that make the most sense to implement and what issues you should consider.

Start at Receiving

Most businesses, no matter what they do, have some sort of receiving function. Manufacturers have a never-ending flow of incoming raw materials and components that will become parts of finished products, hospitals receive daily shipments of drugs and supplies for patients, and retail stores periodically obtain products to replenish empty shelves. In these cases, a company must monitor incoming goods to update inventory databases and accounting records, alert the correct person that the item has arrived, and initiate the payment for the received items.

A wireless bar code system provides significant advantages over paper-based methods when performing receiving functions. As an item is taken off a truck, for example, a clerk can perform receiving as follows:

  1. A warehouse clerk scans the item's bar code, which identifies the part number).
  2. The bar code data is sent over the wireless network to a database, which marks the item as received and updates other applicable databases.
  3. The bar code system, through a handheld scanner/printer, prints any pertinent data on a label that the clerk can affix to the item.

The use of a wireless bar code scanner for this function, similar to other applications, increases the mobility of the users and enables them to perform the receiving actions immediately when unloading the truck.

Inventory Management

Periodically, companies must perform the laborious task of inventorying items they have in warehouses, equipment rooms, and store shelves. The time savings and accuracy of using wireless bar code scanners for inventory management is significant. Think about, for example, performing the task of inventorying items in a large department store containing hundreds of thousands of items. The use of paper on a clipboard for this function is extremely inefficient and inaccurate.

Without a bar code system, the clerk would have to read the part number or stock number of the item and mark the item's presence on a clipboard. This approach is much more time consuming and prone to errors than using a bar code system. Many companies can realize 200-300 percent time savings when using wireless bar code-based systems over manual paper-based systems when performing inventories.

With a wireless network, a clerk scans an item's bin bar code or shelf label and either scans each item within the bin or counts the items by hand in order to record the number of items present. This wireless form of inventory management is much easier to perform and nearly eliminates human error. Also it's possible to quickly generate inventory reports that indicate the number of items on hand and any discrepancies noted.

Order Fulfillment

Before shipping items from a warehouse to a customer, a warehouse clerk must locate and collect the item. This process is known as picking.

The use of a wireless network for picking considerably enhances the efficiency and accuracy of the picking operation. These benefits are evident because a wireless handheld data collector can guide the clerk (through instructions on the display) to the item's correct storage location and enable the clerk to account for actually picking the item after scanning the bar code.

Some wireless systems even automatically generate an optimally ordered pick list based on the clerk's position in the warehouse. The use of this sort of location-based service significantly reduces the route and length of time to pick the items.

Shipping Orders Quicker

Companies must account for items they ship from their facilities. As an example, consider a retail distributor that ships 20,000 items each day to hundreds of customers located in all parts of the World. This volume of shipments would be very difficult to perform if using paper and pencil-based processes, requiring clerks to write down product codes and serial numbers as the items are packed in trucks.

The use of a wireless network makes the job much easier, enabling the clerk to record the shipment of the item by simply scanning the item's bar code. After the clerk scans the bar code on the item, the system can generate and print a shipping label that complies with the requirements of the customer. The system can also identify route information for the carrier to use when loading specific delivery trucks.

Consider Coverage Issues

When deploying a wireless LAN within a warehouse, you'll likely run into RF coverage problems. Metal racks and other obstacles attenuate radio signals and cause irregular propagation patterns. As a result, additional access points may be necessary to fully cover all areas of the warehouse.

In order to ensure coverage continually meets the needs of users, perform frequent RF monitoring of the coverage areas. Be sure to actually take measurements where users may operate their scanners, such as near the bottom shelf of a storage rack. Also, question users from time-to-time to identify where they may be having troubles using the system.

The problem you'll see is that the coverage changes as clerks change the configuration of storage racks. More or less items on the shelves will impact the radio signals differently, causing coverage holes to move about the facility over time. The resulting sporadic loss of connectivity causes frustration to users.

Bar code systems are generally transaction-oriented, and the loss of connectivity in the middle of a transaction can cause errors. This is especially common if the wireless handhelds are interfacing with a warehouse management system that had been written to support only wired terminals. In this case, the programmers would likely have not thought of wireless issues, such as sporadic connectivity, being present. In order to counter this issue, strongly consider using wireless middleware with wireless warehouse systems.

Jim Geier provides independent consulting services to companies developing and deploying wireless network solutions. He is the author of the book, Wireless LANs and offers training focusing on wireless LANs.



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