Composition of Bluetooth LE Node

With Bluetooth^® Toolbox, you can create Bluetooth low energy (LE) nodes by using the bluetoothLENode object. This object enables you to simulate an LE piconet, LE audio, LE advertising, or a mesh network. For an LE piconet, LE audio, or LE advertising, these Bluetooth nodes contain a traffic manager and a protocol stack that comprises the link layer and physical (PHY) layers, as illustrated in this figure.

The protocol stack of a mesh node additionally includes transport and network layers. For more information on the structure of LE mesh nodes, see Protocol Stack for LE Mesh Nodes. This topic outlines the functionalities implemented by the bluetoothNode object for LE piconets, LE audio, LE advertising, and LE mesh networks.

To use the bluetoothNode object, you must download the Communications Toolbox Wireless Network Simulation Library. For more information on installing add-ons, see Get and Manage Add-Ons.

Traffic Manager

The traffic manager uses the networkTrafficOnOff traffic pattern object from the Communications Toolbox™ Wireless Network Simulation Library to model real-world data traffic. This object generates a traffic pattern with two states: on or off.

Link Layer

This section presents the link layer functionalities for LE piconet, LE audio, and LE advertising nodes:

LE Piconet

The link layer of an LE Piconet has these functionalities:

Connection events — During a connection event, both the Central and Peripheral devices alternate in sending and receiving data packets, adhering to the scheduled time slots determined by the connection interval. The connection interval defines the time between two consecutive data exchange events between a Central device and a Peripheral device.
Retransmission and acknowledgement — Marks packets for retransmission in the next connection event if they receive no acknowledgment or a failure acknowledgment.
Supervision timeout — Supports a connection supervision timeout. This supervision timeout represents the maximum amount of time that can elapse without receiving any valid packets before the connection is considered lost.
Adaptive frequency hopping (AFH) and channel selection — Uses the AFH technique when two devices connect. This changes the radio channel for packet communication at intervals. A channel selection algorithm determines the choice of channels. The link layer uses two channel selection algorithms: Channel Selection Algorithm 1 and Channel Selection Algorithm 2. For more information about these channel selection algorithms, see Volume 6, Part B, Sections 4.5.8.2 and 4.5.8.3 of the Bluetooth Core Specification v5.3.
Channel classification — Classifies a channel as used or unused, where used indicates the suitability for transmission and unused indicates an unsuitable channel for transmission.

Use bluetoothLEConnectionConfig to set the link layer connection configuration parameters of a Bluetooth LE Central or Peripheral node.

LE Connected Audio

The link layer for an LE connected audio has these functionalities.

Connected isochronous stream (CIS) events — Schedules transmission and reception time slots within a connected isochronous group (CIG) and for each CIS and facilitates synchronization between a CIS Central and a Peripheral. The time between two adjacent CIS anchor points, the ISO Interval, defines the precise moments when data transmission and reception should occur within each CIS. The term CIS anchor point refers to the start of the event.
Retransmission and acknowledgement — Sends same packets in successive sub-events within a CIS when the receiver has not acknowledged a transmission.
Flush timeout — Limits the number of CIS events and sub-events for retransmitting a payload.

Use the bluetoothLECISConfig object to specify the connected isochronous stream (CIS) configuration parameters of a Bluetooth LE node.

LE Broadcast Audio

The link layer for an LE broadcast audio has these functionalities.

Broadcast isochronous stream (BIS) events — Schedules transmission time slots within a broadcast isochronous group (BIG) and for each BIS, and facilitates synchronization between a receiver and a broadcaster. The time between two adjacent BIS anchor points, the ISO Interval, defines exact moments of data transmission and reception within each BIS.
Pre-transmission — Enables sub-events to carry data associated with future BIS events.
Repetition — Facilitates transmitting a payload multiple times within a single BIS event for reliability.

Use the bluetoothLEBIGConfig object to set the BIG configuration parameters between an isochronous broadcaster and a synchronized receiver.

Legacy Advertisement

The link layer offers these functionalities for legacy advertising:

Advertising — Broadcasts one or more advertising packets over the primary advertising channels during a specific interval. This interval defines the frequency at which the device broadcasts its packets over these designated physical channels for advertising purposes.
Scanning— Listens for advertising packets broadcast in the scanning interval. The scanning interval is the time duration between the beginnings of two consecutive scanning events.
Random advertisement — Randomly selects advertising channels for broadcasting advertising packets, instead of using the predetermined sequence of the primary advertising channels (37, 38, and 39).

Use the bluetoothLENode object to configure the legacy advertising parameters.

Periodic Advertisement

The link layer provides these functionalities specific to periodic advertising:

Periodic advertising train (PAT) — Enables an advertiser to broadcast advertising packets at regular intervals defined by the periodic advertising interval. The broadcaster transmits these packets on selected data channels, while the observer listens for these broadcasts on the same channels.
Channel classification and dynamic channel map update — Classifies channels as suitable or unsuitable for periodic advertisement. The link layer supports dynamic updates of the channel map for periodic advertising.

Use the bluetoothLEPeriodicAdvConfig object to specify the configuration parameters to simulate a Bluetooth LE periodic advertisement between a broadcaster and an observer.

PHY Layer

The Bluetooth LE node supports the full PHY processing. At the transmitter, the PHY layer involves these operations, as illustrated in this figure.

Generates a preamble.
Whitens the data.
Generates a frame that consists of the preamble and the whitened data payload.
Applies forward error correction to the frame.
Modulates the frame using Gaussian frequency shift keying (GFSK).
Adds channel impairments to the modulated data.

At the receiver, the PHY layer performs these operations, as shown in this figure.

Applies a low-pass anti-aliasing filter to the received signal.
Compensates for the frequency offset.
Performs timing synchronization.
Demodulate the signal.
Dewhitens the demodulated signal.
Checks for decode failures.

Protocol Stack for LE Mesh Nodes

A mesh network features a many-to-many topology, enabling each device to communicate with every other device in the mesh. Devices in a mesh network can relay messages to others, extending the end-to-end communication range well beyond the radio range of an individual range.

A Bluetooth mesh node incorporates the transport and network layers, in addition to the traffic, link, and PHY layers, as depicted in this figure. The traffic and PHY layer functionalities remain the same as those in the LE piconet, LE audio, and LE advertising networks.

Transport Layer

The transport layer of a Bluetooth mesh node has these functionalities.

Transports and receives data and control PDUs.
Supports a friend queue, which is a storage mechanism used by friend nodes to hold messages intended for low power nodes (LPNs). A Friend node efficiently manages message delivery to LPNs by releasing messages only when polled, in a relationship called Friendship.
Facilitates LPNs operating within a mesh network at significantly reduced receiver duty cycles, specifically in collaboration with a node that supports the Friend feature.

Network Layer

The network layer of a Bluetooth mesh node offers these functionalities.

Manages the network PDU transmission and reception over an advertising bearer and supports message repetition for reliability.
Supports relaying the network PDU over the advertising bearer.
Supports managed flooding, where Bluetooth mesh networking optimizes the flooding approach for reliability and efficiency. Key features include:
- Time to live (TTL) — Controls the maximum relay hops for Bluetooth mesh PDUs, conserving energy by limiting unnecessary relaying.
- Message cache — All nodes must implement a network message cache, which contains recently seen messages, enabling the node to discard duplicates efficiently.

Link Layer

The link layer of a Bluetooth mesh node in a mesh network has these key functionalities.

Link layer advertising bearer — Broadcasts or receives advertising packets over primary channels 37, 38, and 39.
Advertising and scanning — Uses advertising to broadcast messages to nearby devices, and employs scanning to listen for and act on these broadcasts. The link layer of an LE node in a mesh network also enables devices to switch roles between advertising and scanning. The node remains in the scanning state, except when transmitting data

To set mesh profile configuration parameters at an LE node, use the bluetoothMeshProfileConfig object, and to set the mesh friendship configuration between a Friend node and an LPN, use the bluetoothMeshFriendshipConfig object.