RFID in the warehouse

What is RFID (Radio-Frequency Identification)?

RFID, or Radio-Frequency Identification, is a technology for the automatic and contactless identification of objects using radio waves. At its core, RFID is a system that always consists of three components:

1. RFID transponder (tag): The "label". It consists of a microchip that stores data (e.g. a unique serial number, the Electronic Product Code - EPC), and an antenna that sends and receives signals.
2. Reader: The brain of the operation. It emits a radio signal that "activates" the transponder (in the case of passive tags) and receives and decodes the tag's response.
3. Backend system (middleware/WMS): The received data (e.g. "Day 123 is now at gate 4") must be interpreted and translated into a business-relevant context (e.g. "pallet 456 has been booked as 'shipped'"). This is usually done through middleware that serves as an intermediary to the actual warehouse management system (WMS) or ERP system.

For logistics, RFID is the successor to the barcode, which not only reads, but also "sees" and "communicates" without the need for visual contact.

Passive vs. Active Tags: A Question of Energy and Range

The functionality and thus the application in logistics depends fundamentally on the type of transponder. A distinction is primarily made between passive and active tags.

Passive RFID tags: They do not have their own power source (battery). They draw all their operating energy from the electromagnetic field emitted by the reader.

• Function: The reader sends a strong signal; the antenna of the passive tag captures this energy, "wakes up" the chip, and the chip uses the energy to "reflect" its stored information back to the reader.
• Range: Depending on the frequency (see below) from a few centimeters to approx. 10-15 meters.
• Logistics focus: This is the dominant type in warehouse logistics (warehousing, retail). Why? They are extremely cost-effective (sometimes less than 5-10 cents per label), small and maintenance-free.

Active RFID Tags: They have their own built-in battery.

• Function: They actively "send" their signal at fixed intervals. You don't have to be "woken up" by a reader.
• Range: Significantly higher, often 100 meters and more.
• Logistics focus: Due to the higher cost (€20 to over €100 per day) and limited battery life, they are not used to label individual items. Their area of application is asset tracking (containers, valuable reusable containers) or the location (RTLS - Real-Time Locating Systems) of vehicles (e.g. forklifts) on the company premises.

The frequency is decisive: LF, HF and UHF in practice

The frequency at which RFID operates largely determines the range and susceptibility to interference – and thus the location of use in the logistics property.

• LF (Low Frequency, ~125 kHz): Very short range (a few centimeters). Less susceptible to failure to metal and liquids. Often used in animal identification or immobilizers, less often in logistics.
• HF (High Frequency, 13.56 MHz): Short range (up to approx. 1 meter). Known through NFC (Near Field Communication) in the smartphone. In logistics, this is relevant for precise identification on workpiece carriers or during picking at the place (pick-by tag).
• UHF (Ultra High Frequency, 860–960 MHz): The frequency band for warehouse and contract logistics. It offers the highest range (up to 15 meters) and, above all, the highest reading speed. Only UHF enables "bulk reading".

The challenge with UHF is that this band is susceptible to interference from liquids (which absorb waves) and metals (which reflect waves).

RFID vs. Barcode: Why the Comparison Is Limping

RFID is often referred to as a "better barcode", but this underestimates the technology. It is a fundamentally different process.

The biggest lever for logistics is bulk detection. A forklift doesn't have to stop, the driver doesn't have to get off and scan 100 boxes one by one. It passes the pallet through an RFID gate, and all 100 tags are captured in <1 second.

Application in logistics: Tracking processes instead of just objects

In warehouse and contract logistics, RFID optimizes not only individual steps, but entire process chains by decoupling data collection from physical work.

Incoming and outgoing goods: This  is the "sweet spot" for RFID. Fixed RFID gates (gates with multiple antennas) are installed on the sectional doors of the hall.

• Process: A truck is unloaded. The forklift driver drives the pallet through the gate. The system immediately records all EPCs on the pallet, compares them with the ASN and automatically posts the goods into the WMS – including the time stamp.
• Benefit: Drastic reduction of throughput time in incoming goods. Immediate error detection (wrong goods, short quantities). 100% loading control in the outgoing goods area (ensure that the right pallet ends up on the right truck).

Inventory and inventory management: RFID enables "permanent inventory" and eliminates operational downtime for the cut-off date inventory.

• Process: RFID readers are mounted on forklifts or sent through the aisles as drones/robots. During normal operation, they constantly scan the stocks on the shelf.
• Benefit: Inventory reliability of >99.5% (compared to 70-80% for manual processes). Reduction of safety stock (working capital).
• Contract logistics: This is an enormous added value for 3PL service providers, as they can provide their clients (customers) with accurate inventory data in real time at any time.

Picking and Value-Added Services (VAS): RFID reduces incorrect picks and documents VAS processes (e.g. set formation, packaging) seamlessly by integrating HF or UHF readers at the VAS workstations.

Requirements for the logistics property: The RFID-enabled warehouse

RFID is not a technology that you can "just turn on". It places specific structural and infrastructural requirements on the logistics property (hall).

1. Hardware integration: RFID gates at the gates require a stable power supply and network connection (often PoE - Power over Ethernet). The installation of the antennas must be planned precisely in order to optimally define the detection area.
2. Sources of interference (metal and water): A modern logistics hall is made of steel (shelving systems, steel girders, metal facades). These reflect UHF signals uncontrollably, which can lead to misreadings (e.g. a day before the gate is  read in the gate).
3. Shielding: Gates often have to be structurally "enclosed" or supplemented by special shielding materials (e.g. in the walls) to prevent "signal bleeding" (the crosstalk of antennas, e.g. from gate 1 to gate 2).
4. Conveyor technology: If goods are to be detected on conveyor belts, RFID tunnels or bridges must be integrated directly into the system, which influences the space requirements and the planning of the system.
5. Data infrastructure: An RFID system generates floods of data. A hall that uses RFID requires an extremely powerful IT infrastructure (WLAN coverage, LAN ports) and server capacities (or cloud connection) to process this data through the middleware.

Making a logistics property "RFID-ready" is an investment that goes beyond just buying hardware and often requires structural adjustments.

Q&A: Frequently Asked Questions about RFID in Logistics

Question: Is the investment (ROI) in RFID really worth it?

Answer: ROI is rarely achieved by saving on label costs (barcode is cheaper). The business case is based on process costs and error reduction. Typical ROI drivers are: 1. Reduced working time in incoming and outgoing goods (bulk recording instead of individual scans). 2. Elimination of expensive cut-off date inventory (no shutdown). 3. Reduced capital commitment due to exact stocks (less collateral stock). 4. Avoidance of expensive incorrect deliveries (penalties). An ROI of 12-24 months is realistic in high-volume warehouses.

Question: What to do with metal containers (KLTs) or liquids (beverage logistics)?

Answer: This is the biggest challenge for UHF. Standard labels fail here. The solution is special transponders:

• On-metal tags (OMT): These tags are specially designed (often with a foam spacer layer) to work on metal. They even use the metal surface to some extent as an extension of their own antenna.
• Flag tags: For liquids (e.g. beverage crates), "flag" labels (flag tags) are often used, which protrude from the object like a flag to avoid direct contact with the absorbent liquid.

Question: Do I need a completely new warehouse management system (WMS)?

Answer: Not necessarily, but the WMS must be "RFID-capable". A reader creates "data garbage" (e.g. "Day 123 seen, day 123 seen... 500x"). An RFID middleware is essential. It filters this raw data, interprets it (e.g. "500 readings from day 123 to antenna 4 means: 'Pallet ABC has left the warehouse'") and passes only this clean business event to the WMS.