Electronic shelf label (ESL) systems have historically relied on proprietary protocols for wireless communication, presenting a barrier to global adoption. To address this challenge, leaders from the ESL industry teamed with the Bluetooth Special Interest Group (SIG) to create a scalable, ultra-low power, highly secure ESL wireless standard based on Bluetooth® technology.
This article highlights the benefits of ESL and outlines the features and specifications that will enable standardized Bluetooth ESL.
Electronic Shelf Labels
Electronic shelf labels (ESL) are devices that are attached to shelves in settings like large supermarkets. An ESL has a display used to show images that contain information such as the name, description, and the price of the product on the shelf.
ESLs often have LEDs for attracting attention and sensors for collecting data like the ambient temperature. Using wireless communication, a central device known as an access point (AP) can send commands for changing prices, enabling LEDs, or collecting sensor data, for example.
An AP is a wireless networking device that transmits and receives data over a wireless local area network (WLAN) and is typically integrated with relevant enterprise systems.
ESL use cases include:
- Changing the price of individual products or groups of products. Imagine discounting all freshly baked bread an hour before closing every day to ensure it is sold while at its best.
- Illuminating the red LED on a series of unrelated products to help a shop worker find and collect the items in a customer’s order.
- Monitoring the temperature of refrigerators.
The wireless communication system used with ESLs must support a large, one-to-many topology with a single AP able to communicate with thousands of ESLs. The communication capability must be bidirectional, with ESLs able to send responses to commands from the AP.
ESLs are usually powered by small batteries, which must last several years.
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Bluetooth® Core Specification Version 5.4 Technical Overview
This paper details new features and updates included in Bluetooth Core Specification Version 5.4.
The Bluetooth Logical Transports
Bluetooth® Low Energy (LE) supports several modes of operation known as logical transports.
Connection-oriented communication allows a single central device to communicate in a bidirectional fashion but with a relatively small number of simultaneously connected devices.
Connectionless communication, known as advertising, is available in several different forms and allows a device called a Broadcaster to communicate with very large numbers of receiver devices known as Observers. Before the latest release of the Bluetooth Core Specification, advertising supported unidirectional data communication only.
Historically, the ESL market has been hampered by a lack of standardization, especially concerning wireless communication, where proprietary 2.4 GHz solutions are common. This has led to considerable fragmentation, vendor lock-in, and market growth headwinds.
According to ABI Research, 2.4 billion ESL devices are estimated to be installed by 2027. The adoption of standards is expected to drive substantial growth in this market.
Periodic Advertising with Responses
Bluetooth Core Specification version 5.4 introduces a new logical transport called Periodic Advertising with Responses (PAwR). PAwR uses advertising and supports large one-to-many topologies. In contrast to other Bluetooth® advertising modes, it supports bidirectional application data communication.
The periodic part of the PAwR name refers to the broadcasting of packets by a central device like an access point, which takes place at precisely timed, regular intervals. Communication takes place in bursts of activity during periods of time called events. Events are divided into subevents.
Figure 2 – PAwR events and subevents
Subevents are further divided into time slots which are used for the transmission of one packet by the central Broadcaster device, followed by several time slots during which to receive responses from Observer devices.
PAwR defines procedures by which Observer devices can acquire the event and subevent schedule of the Broadcaster. Other procedures define how the Observer is allocated a specific subevent during which to listen and a response slot within that subevent to use for replies.
Assigning devices to specific subevents only means that they switch into receive mode infrequently, substantially increasing battery life.
PAwR is designed to accommodate data that changes at every transmission and is delivered to individual or groups of devices. Application logic ensures that data transmitted in each subevent is relevant to the devices listening at that time, so there is little wasted energy.
PAwR is essentially stateless, and this makes it very scalable. Bi-directional, one-to-many communication involving thousands of devices like ESLs is achievable using PAwR.
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Electronic Shelf Labels (ESL)
With the introduction of a wireless standard for the electronic shelf label (ESL) market, Bluetooth® technology will help unlock the next phase in retail digital transformation to deliver better retail outcomes for both stores and shoppers.
The Electronic Shelf Label Profile
The Electronic Shelf Label profile specification enables standardized, interoperable ESL products that use Bluetooth® LE to be created.
The profile specification includes an addressing scheme and a series of commands and parameters which an AP may transmit to one or more ESL devices in a single packet sent during a PAwR subevent.
ESLs are members of groups, of which there may be 128, each with a numeric ID. Each group may have 255 ESL devices, each with a numeric ID. The unique address of an individual ESL in the whole network is a combined Group ID and ESL ID, and, consequently, an ESL network can contain up to 32,640 electronic shelf labels, each of which can be controlled from a single access point.
Before a new ESL can be used, it has to go through a set-up procedure. This involves the AP connecting to the ESL, allocating it an address in the network, and, typically, transferring a series of images to it. PAwR event and subevent details are passed to the ESL over the same connection. The assigned ESL Group ID determines the subevent to be used, whereas response slots are allocated dynamically, using standardized message processing logic.
ESL commands and responses are encrypted and authenticated using the AES-CCM algorithm to secure communication between the AP and ESLs. This capability is made possible by another new Bluetooth LE feature called Encrypted Advertising Data.
ESL and PAwR in Action
Figure 2 shows an exchange between an access point and several ESL devices over several subevents.
Conclusion
ESL systems enable dynamic pricing automation, more efficient store operations, and, perhaps most importantly, an increase in shopper satisfaction. New Bluetooth® technology features, developed by ESL industry leaders and the Bluetooth SIG, herald the arrival of a new industry standard for the electronic shelf label market. An important next step is for ESL solution providers to migrate their systems to standards-based wireless technologies, making it possible to expand their total addressable market. With the introduction of a wireless standard for the electronic shelf label (ESL) market, Bluetooth technology is helping unlock the next phase in retail digital transformation to deliver better outcomes for both stores and shoppers.
FEATURED INNOVATION
Electronic Shelf Labels (ESL)
With the introduction of a wireless standard for the electronic shelf label (ESL) market, Bluetooth® technology will help unlock the next phase in retail digital transformation to deliver better retail outcomes for both stores and shoppers.
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