Electronic Design

Low-Power Wi-Fi Breakthrough Offers Active RFID And Location Services

Radio-frequency identification (RFID) is one of the fastest growing wireless technologies. It brings the benefits of both barcode and wireless technology to asset management, product tracking, shipping and transportation ID, inventory control, and location detection.

According to G2 Microsystems' marketing data, based on estimates from of the major market research firms, the market for asset tracking by RFID is expected to grow from a little over $100 million in 2006 to about $900 million in 2011. The major applications categories are transportation, government/Department of Defense, automotive, enterprise, hospital and pharma, and chemical.

Most RFID uses passive tags that get their power via RF from their readers. This setup makes for a small and cheap tag, but it limits reading range and data storage. Active tags with a battery can provide longer-range reading and reliability, yet they're larger and more expensive.

Designers contemplating an RFID solution often pay less attention to the total cost of ownership (TCO) than they should. In almost every case, a new network system must be built and installed to deal with the blizzard of data created by RFID. Regardless of the RFID technology involved, it still is an extra cost over the already existing networking infrastructure, which 99 times out of 100 is an Ethernet network with Wi-Fi extensions. If only the tags used Wi-Fi.

Now, designers can use a Wi-Fi active RFID tag chip from G2 Microsystems. The G2C501 works directly with existing wireless access points on the network, meaning no new network installation is required. The tags are programmed with a URL, so designers can track them through an existing 802.11 wireless local-area network (WLAN) and the Internet.

Wi-Fi isn't known for its low power consumption. To the contrary, most Wi-Fi chips are power hogs. But who cares when they're used in ac-powered routers, gateways, PCs, and laptops? Still, battery-powered Wi-Fi radios must be able to operate for years to make it in the RFID space. The G2C501 is up to the task.

The G2C501 draws just 10 µA in sleep mode. Current draw is very low during actual usage, which is periodic anyway. Most transmission duty cycles are very low, making it possible for batteries to last for years. A pair of AA cells and a 40-s report rate yield a five-year battery life. This low power consumption makes all of the chip's features possible.

The chip's standard 2.4-GHz 802.11b transceiver is fully Wi-Fi compatible and acceptable worldwide (Fig. 1). It talks directly to existing access points, hotspots, or new transceivers. Using existing networks eliminates the need for new infrastructure. Leveraging the existing network can reduce the cost of an RFID system to less than 25% of the cost of a RFID system with its own readers/ interrogators and network wiring.

The G2C501 also has two other RFID technologies built in—the standard electronic product code (EPC) 915-MHz radio and a standard 125-kHz magnetic radio. Powered internally, they don't need the reader's RF to turn on. With these two additional radios, the chip can talk to other existing RFID systems in their neighborhood.

The chip's location technology permits the system to determine the physical location of the tagged item. Using the receive signal strength indicator (RSSI) feature on the transceiver, the chip can be programmed to make three RSSI measurements from three different access points. It then can perform a triangulation calculation to determine the location within about 15 ft.

The G2C501 supports the ISO 24370 (ANSI 371.1) standard time delay of arrival (TDOA) location system, which can locate a tag within about 6 ft. The G2C501's interfaces can attach to any typical GPS receiver chip for additional location capability.

Its 32-bit programmable CPU offers 64k of RAM and 384k of ROM. Interfaces are provided for external flash or other memory. The CPU has a TCP/IP stack, and it runs the highly compact eCos operating system. GPIO, UART, and serial peripheral interfaces are available on-chip. A security accelerator covers AES and RC4 encryption as well as MD5 and SHA1 hashing functions.

The chip even features a sensor interface. In tracking applications, getting a read on the environment is essential. Temperature is particularly key, especially in food and pharmaceutical tracking. The interface can handle temperature, pressure, moisture, motion, shock, flow, and battery condition sensor inputs. A current loop and analog-to-digital converter (ADC) are provided for interfacing. Alarms can be set to trigger a transmission if a critical point is detected.

The chip targets the mobile resource management market, specifically organizations deploying real-time location systems (RTLS). These include hospital, automotive/trucking, transportation, pharmaceutical, oil and gas, and distribution companies. It's good for tracking major assets like skids, crates, trailers, and even people. While it's not a good match for passive tag applications like pill bottles or product packages, it may be a sleeper for low power 802.11b applications or wireless mesh sensor networks.

The G2C501 comes in a 72-pin, 10-by 10-mm quad flat no-lead package. Samples as well as a software development and evaluation board will be available later in the third quarter (Fig. 2). Production quantities are expected in the third quarter this year. Price is $12 in large quantities.

G2 Microsystems Inc.

TAGS: Automotive
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