Short-Range Wireless Communication Fundamentals

What Defines Short-Range Connectivity?

In terms of electronics, range is defined by the maximum amount of space in which communication can occur between two antennas in a wireless network. Short-range wireless technology has been a useful adoption in industrial equipment, household appliances, and medical environments. Determining which short-range wireless protocol that’s appropriate for your device design is a matter of its intended use case(s). The following are factors to consider when determining the wireless communications protocol for your device design:

• What frequency does your device’s incorporated antenna use? What is its impedance?
• Are there physical obstacles the communications solution will encounter? Some wireless standards work best through line of site; barriers like walls, terrain, and/or appliances can affect range capabilities.
• Will the level of noise in the area of transmission interfere with wireless communications?

Bluetooth Low Energy®

Based on the 802.15.1 IEEE standard, Bluetooth is a widely adopted wireless sensor technology that is used in transceivers, basebands, protocol stacks, and more. According to Bluetooth’s annual market update, “By 2025, annual Bluetooth enabled device shipments will exceed six billion.” Bluetooth’s popularity makes it a widely accessible choice as a wireless communications protocol. While there are many variants of Bluetooth technology, Bluetooth Low-Energy (BLE) is an effective short-range communications method because it is optimized for power, cost, and size constrained projects.

Among other things, BLE enabled devices differ from Bluetooth Classic (Figure 1) in application scenarios. Classic Bluetooth is commonly used for wireless speakers, telephone, and headphone connections. BLE technology is mainly seen in wearables, smart IoT, and battery powered-accessories because of its inherent low power consumption.

Key Features and Specifications of Bluetooth Low Energy (BLE):

• Ultra-low peak, average, standby mode power consumption
• Cost efficient
• Compatible with Android, iOS, and other popular vendors
• Enhanced transmission range and receiver sensitivity
• Extremely power efficient. BLE enabled-devices can operate for years using standard, coin-cell batteries

Figure 1: Bluetooth Comparison

Source: Nordic Semiconductors 

Ultra Wide-Band (UWB)

As a high-performance communications protocol, ultra-wideband (UWB) is an optimal solution for interference in wireless transmissions. UWB is innately low power and cost efficient. Its high bandwidth allows for precise tracking and enhanced data collection/communication of >500 MHz. UWB is an effective short-range wireless solution with common applications in data communications, radar, sensing, localization, identification.

Key Features and Specifications of Ultra-Wideband (UWB) Technology:

• Inherently low power, operating at 0.5 mW / -41.3 dBm/MHz.
• Offers 10-30 cm precision location accuracy
• High-level security
• Protection from multipath and interference

802.15.4 Based Zigbee, Z-Wave, and Thread Wireless Based Protocol:

Thread, Zigbee, and Z-Wave technologies are based off IEEE 802.15.4 and support the access layer for low-rate wireless personal area networks (WPAN). These types of technologies are commonly used in smart home environments and are renowned for their low power consumption and data rates. Managed by the Z-Wave Alliance, Z-Wave separates itself from Thread and Zigbee technologies by operating on unlicensed frequency bands in the 908Mhz range to avoid interference with other types of wireless technologies.

Zigbee Key Features and Specifications:

• Low latency
• Operating range of 35 ft.
• Supports a maximum of 65,000 nodes
• Zigbee’s inherent low power consumption provides durable battery life
• Supports mesh topology, but is also able to supports star topology
• Supports multiple network topologies

Z-Wave Key Features and Specifications:

• Operating range of 100 ft.
• Connects a maximum of 232 connections
• 9.6-100 kbps data rate
• Operates on 908/916 Mhz frequency

Thread Key Features and Specifications:

• Operating range of 100 ft.
• Generally supports mesh topology, but is also able to supports star topology
• 250-300 maximum number of connections
• Maximum data rate of 250 kbps
• Operates on 2.4 GHz frequency

Radio Frequency Identification (RFID):

RFID technology is based on Automatic Identification and Data Capture (AIDC) and is an essential tool in supply chain tracking. Consisting of three components, a smart label, a reader, and an antenna, RFID methods identify and collect data about objects. One of the biggest advantages of RFID is that the technology does not require line of site. Primarily used in asset tracking, RFID technology can track multiple tags at one time. RFID readers can eliminate human error in their ability to automatically retrieve data. RFID tags are commonly used in short-range wireless asset tracking, and come in three frequency ranges (Figure 2):

• Low Frequency (LF RFID) supports frequencies from 30 KHz to 300 KHz and provides a tracking range of 10cm. LF RFID applications include livestock tracking and access control.
• High Frequency (HF RFID) supports frequencies from 3 to 20 MHz and provides a tracking range of 10cm to 1m. HF RFID applications include transfers, ticketing, and payment tracking.
• Ultra-High Frequency (UHF RFID) supports frequencies of 300 MHz to 3 GHz and provides a tracking range of up to 12m. UHF RFID applications include inventory tracking, wireless communications, and methods surrounding pharmaceutical anti-counterfeiting.

Figure 2: LF, HF, and UHF RFID comparison

Source: Impinj.com

Wi-Fi Location Tracking:

While many variants of Wi-Fi exist, the Wi-Fi that we commonly use for video streaming and large data transfers is based on 802.11 IEEE standards. Wi-Fi is used for internet access and connecting local area devices. While Wi-Fi positioning systems are more expensive to implement than RFID technology, they can be advantageous in the fact that they operate on existing Wi-Fi infrastructure. Wi-Fi location tracking systems use techniques like time difference of arrival (TDOA) measurements in conjunction with bandwidth to provide a tracking range from 3 to 5m.

Resources

• Long Range vs. Short Range Wireless Communications: What’s Best for Your Project?
• Things You Should Know About Bluetooth Range
• Technology of short-distance wireless communication and its application based on equipment support
• Zigbee, Z-Wave, Thread, and WeMo: What’s the Difference?
• Wireless Connectivity Options for IoT Applications – Technology Comparison
• Wi-Fi Location Tracking & Positioning