# IEEE 802.15.4 - Asynchronous CSMA MAC

This example shows how to simulate the IEEE® 802.15.4™ asynchronous CSMA MAC [1] using the Communications Toolbox™ Library for ZigBee® and UWB.

### Background

The IEEE 802.15.4 standard specifies the MAC and PHY layers of Low-Rate Wireless Personal Area Networks (LR-WPANs) [1]. The IEEE 802.15.4 MAC and PHY layers provide the basis of other higher-layer standards, such as ZigBee, WirelessHart®, 6LoWPAN and MiWi. Such standards find application in home automation and sensor networking and are highly relevant to the Internet of Things (IoT) trend.

The IEEE 802.15.4 MAC [1] specifies two-basic MAC modes: (i) non-beacon-enabled, and (ii) beacon-enabled MAC. The non-beacon enabled MAC is an asynchronous carrier-sense multiple access (CSMA) MAC, which is very similar to the IEEE 802.11 MAC. The beacon-enabled MAC allows two different MAC periods: (i) a synchronized-CSMA MAC period, and (ii) a time-slotted, contention-free MAC period. This example provides an extensive simulation of the non-beacon-enabled, asynchronous, CSMA-based IEEE 802.15.4 MAC.

### Network Setup

An IEEE 802.15.4 PAN (personal area network) is set up by a standard process between end devices and PAN coordinators. First, devices that would like to join a network perform either active or passive scanning. Active scanning means that a device first transmits a Beacon Request and later on it performs passive scanning. Passive scanning means that the device sniffs to collect beacon frames from PAN coordinators (who may have received their Beacon Request in the case of active scanning). Upon the collection of beacons during passive scanning, the end device chooses the PAN with which it would like to associate. Then it transmits an Association Request to the coordinator of this PAN and the coordinator acknowledges it.

In contrast to IEEE 802.11, the coordinator does not follow the acknowledgment of an Association Request with an immediate transmission of an Association Response. Instead, the IEEE 802.15.4 coordinator first stores the Association Response locally; it is only transmitted when the end device sends a Data Request and the coordinator acknowledges it. The IEEE 802.15.4 standard uses the term indirect transmission to refer to this mechanism for transmitting frames. In general, this mechanism is very useful for battery-powered devices of low-traffic networks (such as sensor networks). Such devices may periodically activate their radios to check whether any frames are pending for them, instead of continuously using their radios to receive a frame immediately.

Once the Association response is received and acknowledged, the end device is associated with the PAN. At that time, data frames can be exchanged between the coordinator and the end device in any direction. The data frames may be acknowledged, depending on their Acknowledgment Request indication.

### Asynchronous Medium-Access Control (MAC)

The asynchronous CSMA IEEE 802.15.4 MAC is similar to the generic CSMA operation and the IEEE 802.11 MAC. In this MAC scheme, acknowledgment frames are transmitted immediately, without using the CSMA method. All other frames are transmitted using CSMA.

Specifically, once a device has a frame to transmit, it randomly chooses a backoff delay (number of backoff periods) in the range [0 ${2}^{\mathit{BE}}$-1], where BE is the backoff exponent. The duration of each backoff period is 20 symbols. For the OQPSK PHY in 2.4 GHz, this duration corresponds to 640 chips and 0.32 ms. Once the device has waited for the chosen number of backoff periods, it performs carrier sensing. If the medium is idle, the device begins transmission of its frame, until it is entirely transmitted.

If the medium is busy during carrier sense, then the backoff exponent increments by 1 and a new number of backoff periods is selected from the new [0 ${2}^{\mathit{BE}}$-1] range. When the backoff counter expires again, carrier sensing is performed. If the maximum number of backoff countdowns is reached without the medium being idle during any carrier sensing instance, then the device terminates its attempts to transmit the frame.

### Network Simulation Capabilities

This example offers an implementation for the described network setup process and the CSMA method via the `lrwpan.MACFullFunctionDevice` and the `lrwpan.MACReducedFunctionDevice` classes. Specifically, the following capabilities are enabled:

• Active and passive scanning

• Association Request and Association Response exchange

• Indirect transmissions using Data Requests

• Frame acknowledgments and frame retransmissions if acknowledgments are not timely received

• Short and long interframe spacing (SIFS and LIFS)

• Binary exponential backoff

• Carrier sensing

### Network Simulation

In this section, we create an IEEE 802.15.4 network of 3 nodes: one PAN coordinator and two end devices. The network simulator is configured to process all devices at increments of a single backoff duration (20 symbols, 0.32 ms).

First, the following code illustrates the association of the first device with the network.

```symbolsPerStep = 20; chipsPerSymbol = 32; samplesPerChip = 4; symbolRate = 65.5e3; % symbols/sec time = 0; stopTime = 5; % sec % Create PAN Coordinator panCoordinator = lrwpan.MACFullFunctionDevice( ... 'PANCoordinator', true, ... 'SamplesPerChip', 4, .... 'PANIdentifier', '7777', ... 'ExtendedAddress', [repmat('0', 1, 8) repmat('7', 1, 8)], ... 'ShortAddress', '1234'); % Create first end-device endDevice1 = lrwpan.MACReducedFunctionDevice( ... 'SamplesPerChip',4, ... 'ShortAddress','0001', ... 'ExtendedAddress',[repmat('0', 1, 8) repmat('3', 1, 8)]);```
```0001: ********* Adding Beacon Request frame to the queue 0001: Passive scanning for 1584 steps ```
```% Initialize device inputs received1 = zeros(samplesPerChip * chipsPerSymbol * ... symbolsPerStep/2, 1); received2 = zeros(samplesPerChip * chipsPerSymbol * ... symbolsPerStep/2, 1); while time < stopTime % Pass the received signals to the nodes for processing. Also, % fetch what they have to transmit: transmitted1 = panCoordinator(received1); transmitted2 = endDevice1(received2); % Ideal wireless channel, where both nodes are within range: received1 = transmitted2; % half-duplex radios, none receiving % while transmitting received2 = transmitted1; time = time + symbolsPerStep/symbolRate; % update clock end```
```0001: Processing next frame from the queue 0001: Initializing transmission; backoff delay = 1 steps 0001: Backoff delay = 1 steps -> 0 steps 0001: Carrier sensing: Medium is idle. 0001: Clear to transmit 0001: Transmitting Beacon Request 0001: IFS offset = 0 samples 0001: Transmitting 1-1280 of 2050 ```
```Found preamble of OQPSK PHY. Found start-of-frame delimiter (SFD) of OQPSK PHY. ```
```0001: IFS offset = 0 samples 0001: Transmitting 1281-2050 of 2050 0001: Finished transmission 0001: Need to wait for SIFS (12) symbols. Offset = 12, next IFS = 4 0001: Entering passive scanning ```
```1234: PHY decoded IEEE 802.15.4 frame CRC check passed for the MAC frame. 1234: *********** Received frame type = MAC command 1234: *********** Received MAC Command type = Beacon request 1234: Need to wait for SIFS (12) symbols. Offset = 12, next IFS = 4 1234: ********* Adding Beacon frame to the queue 1234: next IFS = 4 1234: Processing next frame from the queue 1234: Initializing transmission; backoff delay = 7 steps 1234: Backoff delay = 7 steps -> 6 steps 1234: Backoff delay = 6 steps -> 5 steps 1234: Backoff delay = 5 steps -> 4 steps 1234: Backoff delay = 4 steps -> 3 steps 1234: Backoff delay = 3 steps -> 2 steps 1234: Backoff delay = 2 steps -> 1 steps 1234: Backoff delay = 1 steps -> 0 steps 1234: Carrier sensing: Medium is idle. 1234: Clear to transmit 1234: IFS offset = 256 samples 1234: Transmitting 1-1024 of 2562 1234: IFS offset = 0 samples 1234: Transmitting 1025-2304 of 2562 ```
```Found preamble of OQPSK PHY. Found start-of-frame delimiter (SFD) of OQPSK PHY. ```
```1234: IFS offset = 0 samples 1234: Transmitting 2305-2562 of 2562 1234: Finished transmission 1234: Need to wait for LIFS (40) symbols. Offset = 4, next IFS = 24 1234: Decreased wait time by 20 symbols to 4 ```
```0001: PHY decoded IEEE 802.15.4 frame CRC check passed for the MAC frame. 0001: *********** Received frame type = Beacon 0001: Need to wait for SIFS (12) symbols. Offset = 4, next IFS = -4 0001: next IFS = 0 0001: Scanning finished 0001: ********* Adding Association request frame to the queue 0001: Processing next frame from the queue 0001: Initializing transmission; backoff delay = 0 steps 0001: Carrier sensing: Medium is idle. 0001: Clear to transmit 0001: IFS offset = 0 samples 0001: Transmitting 1-1280 of 3458 ```
```Found preamble of OQPSK PHY. Found start-of-frame delimiter (SFD) of OQPSK PHY. ```
```0001: IFS offset = 0 samples 0001: Transmitting 1281-2560 of 3458 0001: IFS offset = 0 samples 0001: Transmitting 2561-3458 of 3458 0001: Finished transmission 0001: will wait for ack for 54 symbols additional to IFS = 0 ```
```1234: PHY decoded IEEE 802.15.4 frame CRC check passed for the MAC frame. 1234: *********** Received frame type = MAC command 1234: *********** Received MAC Command type = Association request 1234: Need to wait for LIFS (40) symbols. Offset = 14, next IFS = 34 1234: ********** Directly transmitting acknowledgement frame (no CSMA/CA) 1234: ********* Adding Data response frame to the PENDING queue 1234: next IFS = 34 ```
```0001: Decreasing ack wait durations by 20 symbols to 34 ```
```1234: IFS offset = 896 samples 1234: Transmitting 1-384 of 1410 ```
```0001: Decreasing ack wait durations by 20 symbols to 14 ```
```1234: IFS offset = 0 samples 1234: Transmitting 385-1410 of 1410 1234: Finished transmission 1234: Need to wait for SIFS (12) symbols. Offset = 16, next IFS = 8 ```
```0001: Decreasing ack wait durations by 20 symbols to -6 Found preamble of OQPSK PHY. Found start-of-frame delimiter (SFD) of OQPSK PHY. 0001: PHY decoded IEEE 802.15.4 frame CRC check passed for the MAC frame. 0001: *********** Received frame type = Acknowledgment 0001: Need to wait for SIFS (12) symbols. Offset = 16, next IFS = 8 0001: *********** Adding Data request frame to the queue 0001: next IFS = 1920 0001: Decreased wait time by 20 symbols to 1900 0001: Decreased wait time by 20 symbols to 1880 0001: Decreased wait time by 20 symbols to 1860 0001: Decreased wait time by 20 symbols to 1840 0001: Decreased wait time by 20 symbols to 1820 0001: Decreased wait time by 20 symbols to 1800 0001: Decreased wait time by 20 symbols to 1780 0001: Decreased wait time by 20 symbols to 1760 0001: Decreased wait time by 20 symbols to 1740 0001: Decreased wait time by 20 symbols to 1720 0001: Decreased wait time by 20 symbols to 1700 0001: Decreased wait time by 20 symbols to 1680 0001: Decreased wait time by 20 symbols to 1660 0001: Decreased wait time by 20 symbols to 1640 0001: Decreased wait time by 20 symbols to 1620 0001: Decreased wait time by 20 symbols to 1600 0001: Decreased wait time by 20 symbols to 1580 0001: Decreased wait time by 20 symbols to 1560 0001: Decreased wait time by 20 symbols to 1540 0001: Decreased wait time by 20 symbols to 1520 0001: Decreased wait time by 20 symbols to 1500 0001: Decreased wait time by 20 symbols to 1480 0001: Decreased wait time by 20 symbols to 1460 0001: Decreased wait time by 20 symbols to 1440 0001: Decreased wait time by 20 symbols to 1420 0001: Decreased wait time by 20 symbols to 1400 0001: Decreased wait time by 20 symbols to 1380 0001: Decreased wait time by 20 symbols to 1360 0001: Decreased wait time by 20 symbols to 1340 0001: Decreased wait time by 20 symbols to 1320 0001: Decreased wait time by 20 symbols to 1300 0001: Decreased wait time by 20 symbols to 1280 0001: Decreased wait time by 20 symbols to 1260 0001: Decreased wait time by 20 symbols to 1240 0001: Decreased wait time by 20 symbols to 1220 0001: Decreased wait time by 20 symbols to 1200 0001: Decreased wait time by 20 symbols to 1180 0001: Decreased wait time by 20 symbols to 1160 0001: Decreased wait time by 20 symbols to 1140 0001: Decreased wait time by 20 symbols to 1120 0001: Decreased wait time by 20 symbols to 1100 0001: Decreased wait time by 20 symbols to 1080 0001: Decreased wait time by 20 symbols to 1060 0001: Decreased wait time by 20 symbols to 1040 0001: Decreased wait time by 20 symbols to 1020 0001: Decreased wait time by 20 symbols to 1000 0001: Decreased wait time by 20 symbols to 980 0001: Decreased wait time by 20 symbols to 960 0001: Decreased wait time by 20 symbols to 940 0001: Decreased wait time by 20 symbols to 920 0001: Decreased wait time by 20 symbols to 900 0001: Decreased wait time by 20 symbols to 880 0001: Decreased wait time by 20 symbols to 860 0001: Decreased wait time by 20 symbols to 840 0001: Decreased wait time by 20 symbols to 820 0001: Decreased wait time by 20 symbols to 800 0001: Decreased wait time by 20 symbols to 780 0001: Decreased wait time by 20 symbols to 760 0001: Decreased wait time by 20 symbols to 740 0001: Decreased wait time by 20 symbols to 720 0001: Decreased wait time by 20 symbols to 700 0001: Decreased wait time by 20 symbols to 680 0001: Decreased wait time by 20 symbols to 660 0001: Decreased wait time by 20 symbols to 640 0001: Decreased wait time by 20 symbols to 620 0001: Decreased wait time by 20 symbols to 600 0001: Decreased wait time by 20 symbols to 580 0001: Decreased wait time by 20 symbols to 560 0001: Decreased wait time by 20 symbols to 540 0001: Decreased wait time by 20 symbols to 520 0001: Decreased wait time by 20 symbols to 500 0001: Decreased wait time by 20 symbols to 480 0001: Decreased wait time by 20 symbols to 460 0001: Decreased wait time by 20 symbols to 440 0001: Decreased wait time by 20 symbols to 420 0001: Decreased wait time by 20 symbols to 400 0001: Decreased wait time by 20 symbols to 380 0001: Decreased wait time by 20 symbols to 360 0001: Decreased wait time by 20 symbols to 340 0001: Decreased wait time by 20 symbols to 320 0001: Decreased wait time by 20 symbols to 300 0001: Decreased wait time by 20 symbols to 280 0001: Decreased wait time by 20 symbols to 260 0001: Decreased wait time by 20 symbols to 240 0001: Decreased wait time by 20 symbols to 220 0001: Decreased wait time by 20 symbols to 200 0001: Decreased wait time by 20 symbols to 180 0001: Decreased wait time by 20 symbols to 160 0001: Decreased wait time by 20 symbols to 140 0001: Decreased wait time by 20 symbols to 120 0001: Decreased wait time by 20 symbols to 100 0001: Decreased wait time by 20 symbols to 80 0001: Decreased wait time by 20 symbols to 60 0001: Decreased wait time by 20 symbols to 40 0001: Decreased wait time by 20 symbols to 20 0001: Decreased wait time by 20 symbols to 0 0001: Processing next frame from the queue 0001: Initializing transmission; backoff delay = 2 steps 0001: Backoff delay = 2 steps -> 1 steps 0001: Backoff delay = 1 steps -> 0 steps 0001: Carrier sensing: Medium is idle. 0001: Clear to transmit 0001: IFS offset = 0 samples 0001: Transmitting 1-1280 of 3074 ```
```Found preamble of OQPSK PHY. Found start-of-frame delimiter (SFD) of OQPSK PHY. ```
```0001: IFS offset = 0 samples 0001: Transmitting 1281-2560 of 3074 0001: IFS offset = 0 samples 0001: Transmitting 2561-3074 of 3074 0001: Finished transmission 0001: will wait for ack for 54 symbols additional to IFS = 0 ```
```1234: PHY decoded IEEE 802.15.4 frame CRC check passed for the MAC frame. 1234: *********** Received frame type = MAC command 1234: *********** Received MAC Command type = Data request 1234: Need to wait for SIFS (12) symbols. Offset = 8, next IFS = 0 1234: ********** Directly transmitting acknowledgement frame (no CSMA/CA) 1234: Moving frame for 0000000033333333 from pending queue to the transmission queue 1234: next IFS = 0 1234: IFS offset = 0 samples 1234: Transmitting 1-1280 of 1410 ```
```0001: Decreasing ack wait durations by 20 symbols to 34 ```
```1234: IFS offset = 0 samples 1234: Transmitting 1281-1410 of 1410 1234: Finished transmission 1234: Need to wait for SIFS (12) symbols. Offset = 2, next IFS = -6 ```
```Found preamble of OQPSK PHY. Found start-of-frame delimiter (SFD) of OQPSK PHY. 0001: Decreasing ack wait durations by 20 symbols to 14 ```
```1234: Processing next frame from the queue 1234: Initializing transmission; backoff delay = 5 steps 1234: Backoff delay = 5 steps -> 4 steps ```
```0001: PHY decoded IEEE 802.15.4 frame CRC check passed for the MAC frame. 0001: *********** Received frame type = Acknowledgment 0001: Need to wait for SIFS (12) symbols. Offset = 2, next IFS = -6 0001: next IFS = 0 ```
```1234: Backoff delay = 4 steps -> 3 steps 1234: Backoff delay = 3 steps -> 2 steps 1234: Backoff delay = 2 steps -> 1 steps 1234: Backoff delay = 1 steps -> 0 steps 1234: Carrier sensing: Medium is idle. 1234: Clear to transmit 1234: IFS offset = 0 samples 1234: Transmitting 1-1280 of 4226 1234: IFS offset = 0 samples 1234: Transmitting 1281-2560 of 4226 ```
```Found preamble of OQPSK PHY. Found start-of-frame delimiter (SFD) of OQPSK PHY. ```
```1234: IFS offset = 0 samples 1234: Transmitting 2561-3840 of 4226 1234: IFS offset = 0 samples 1234: Transmitting 3841-4226 of 4226 1234: Finished transmission 1234: will wait for ack for 54 symbols additional to IFS = 0 1234: Decreasing ack wait durations by 20 symbols to 34 ```
```0001: PHY decoded IEEE 802.15.4 frame CRC check passed for the MAC frame. 0001: *********** Received frame type = MAC command 0001: *********** Received MAC Command type = Association response 0001: Need to wait for LIFS (40) symbols. Offset = 6, next IFS = 26 0001: *********** Association successful, changing short address to = 8CEC 8CEC: *********** Association successful, associated to PAN = 7777 8CEC: ********** Directly transmitting acknowledgement frame (no CSMA/CA) 8CEC: next IFS = 26 ```
```1234: Decreasing ack wait durations by 20 symbols to 14 ```
```8CEC: IFS offset = 384 samples 8CEC: Transmitting 1-896 of 1410 ```
```Found preamble of OQPSK PHY. Found start-of-frame delimiter (SFD) of OQPSK PHY. 1234: Decreasing ack wait durations by 20 symbols to -6 ```
```8CEC: IFS offset = 0 samples 8CEC: Transmitting 897-1410 of 1410 8CEC: Finished transmission 8CEC: Need to wait for SIFS (12) symbols. Offset = 8, next IFS = 0 ```
```1234: PHY decoded IEEE 802.15.4 frame CRC check passed for the MAC frame. 1234: *********** Received frame type = Acknowledgment 1234: Need to wait for SIFS (12) symbols. Offset = 8, next IFS = 0 1234: next IFS = 0 ```
```8CEC: ********* (t=4.079360) Injecting data frame to the queue. From: 8CEC -> To: 1234 8CEC: Processing next frame from the queue 8CEC: Initializing transmission; backoff delay = 6 steps 8CEC: Backoff delay = 6 steps -> 5 steps 8CEC: Backoff delay = 5 steps -> 4 steps 8CEC: Backoff delay = 4 steps -> 3 steps 8CEC: Backoff delay = 3 steps -> 2 steps 8CEC: Backoff delay = 2 steps -> 1 steps 8CEC: Backoff delay = 1 steps -> 0 steps 8CEC: Carrier sensing: Medium is idle. 8CEC: Clear to transmit 8CEC: IFS offset = 0 samples 8CEC: Transmitting 1-1280 of 8578 ```
```Found preamble of OQPSK PHY. Found start-of-frame delimiter (SFD) of OQPSK PHY. ```
```8CEC: IFS offset = 0 samples 8CEC: Transmitting 1281-2560 of 8578 8CEC: IFS offset = 0 samples 8CEC: Transmitting 2561-3840 of 8578 8CEC: IFS offset = 0 samples 8CEC: Transmitting 3841-5120 of 8578 8CEC: IFS offset = 0 samples 8CEC: Transmitting 5121-6400 of 8578 8CEC: IFS offset = 0 samples 8CEC: Transmitting 6401-7680 of 8578 8CEC: IFS offset = 0 samples 8CEC: Transmitting 7681-8578 of 8578 8CEC: Finished transmission 8CEC: will wait for ack for 54 symbols additional to IFS = 0 ```
```1234: PHY decoded IEEE 802.15.4 frame CRC check passed for the MAC frame. 1234: *********** Received frame type = Data 1234: Need to wait for SIFS (12) symbols. Offset = 14, next IFS = 6 1234: ********** Directly transmitting acknowledgement frame (no CSMA/CA) 1234: next IFS = 6 1234: IFS offset = 384 samples 1234: Transmitting 1-896 of 1410 ```
```8CEC: Decreasing ack wait durations by 20 symbols to 34 ```
```1234: IFS offset = 0 samples 1234: Transmitting 897-1410 of 1410 1234: Finished transmission 1234: Need to wait for SIFS (12) symbols. Offset = 8, next IFS = 0 ```
```Found preamble of OQPSK PHY. Found start-of-frame delimiter (SFD) of OQPSK PHY. 8CEC: Decreasing ack wait durations by 20 symbols to 14 8CEC: PHY decoded IEEE 802.15.4 frame CRC check passed for the MAC frame. 8CEC: *********** Received frame type = Acknowledgment 8CEC: Need to wait for LIFS (40) symbols. Offset = 8, next IFS = 28 8CEC: next IFS = 28 8CEC: Decreased wait time by 20 symbols to 8 8CEC: ********* (t=4.795200) Injecting data frame to the queue. From: 8CEC -> To: 1234 8CEC: Processing next frame from the queue 8CEC: Initializing transmission; backoff delay = 6 steps 8CEC: Backoff delay = 6 steps -> 5 steps 8CEC: Backoff delay = 5 steps -> 4 steps 8CEC: Backoff delay = 4 steps -> 3 steps 8CEC: Backoff delay = 3 steps -> 2 steps 8CEC: Backoff delay = 2 steps -> 1 steps 8CEC: Backoff delay = 1 steps -> 0 steps 8CEC: Carrier sensing: Medium is idle. 8CEC: Clear to transmit 8CEC: IFS offset = 512 samples 8CEC: Transmitting 1-768 of 8578 ```
```Found preamble of OQPSK PHY. ```
```8CEC: IFS offset = 0 samples 8CEC: Transmitting 769-2048 of 8578 ```
```Found preamble of OQPSK PHY. Found start-of-frame delimiter (SFD) of OQPSK PHY. ```
```8CEC: IFS offset = 0 samples 8CEC: Transmitting 2049-3328 of 8578 8CEC: IFS offset = 0 samples 8CEC: Transmitting 3329-4608 of 8578 8CEC: IFS offset = 0 samples 8CEC: Transmitting 4609-5888 of 8578 8CEC: IFS offset = 0 samples 8CEC: Transmitting 5889-7168 of 8578 8CEC: IFS offset = 0 samples 8CEC: Transmitting 7169-8448 of 8578 8CEC: IFS offset = 0 samples 8CEC: Transmitting 8449-8578 of 8578 8CEC: Finished transmission 8CEC: will wait for ack for 54 symbols additional to IFS = 0 ```
```1234: PHY decoded IEEE 802.15.4 frame CRC check passed for the MAC frame. 1234: *********** Received frame type = Data 1234: Need to wait for SIFS (12) symbols. Offset = 2, next IFS = -6 1234: ********** Directly transmitting acknowledgement frame (no CSMA/CA) 1234: next IFS = 0 1234: IFS offset = 0 samples 1234: Transmitting 1-1280 of 1410 ```
```8CEC: Decreasing ack wait durations by 20 symbols to 34 ```
```1234: IFS offset = 0 samples 1234: Transmitting 1281-1410 of 1410 1234: Finished transmission 1234: Need to wait for SIFS (12) symbols. Offset = 2, next IFS = -6 ```
```Found preamble of OQPSK PHY. Found start-of-frame delimiter (SFD) of OQPSK PHY. 8CEC: Decreasing ack wait durations by 20 symbols to 14 8CEC: PHY decoded IEEE 802.15.4 frame CRC check passed for the MAC frame. 8CEC: *********** Received frame type = Acknowledgment 8CEC: Need to wait for LIFS (40) symbols. Offset = 2, next IFS = 22 8CEC: next IFS = 22 8CEC: Decreased wait time by 20 symbols to 2 ```
```1234: ********* (t=5.001280) Injecting data frame to the queue. From: 1234 -> To: 8CEC 1234: Processing next frame from the queue 1234: Initializing transmission; backoff delay = 1 steps 1234: Backoff delay = 1 steps -> 0 steps 1234: Carrier sensing: Medium is idle. 1234: Clear to transmit 1234: IFS offset = 0 samples 1234: Transmitting 1-1280 of 8578 1234: IFS offset = 0 samples 1234: Transmitting 1281-2560 of 8578 ```
```Found preamble of OQPSK PHY. Found start-of-frame delimiter (SFD) of OQPSK PHY. ```
```1234: IFS offset = 0 samples 1234: Transmitting 2561-3840 of 8578 1234: IFS offset = 0 samples 1234: Transmitting 3841-5120 of 8578 1234: IFS offset = 0 samples 1234: Transmitting 5121-6400 of 8578 1234: IFS offset = 0 samples 1234: Transmitting 6401-7680 of 8578 1234: IFS offset = 0 samples 1234: Transmitting 7681-8578 of 8578 1234: Finished transmission 1234: will wait for ack for 54 symbols additional to IFS = 0 1234: Decreasing ack wait durations by 20 symbols to 34 ```
```8CEC: PHY decoded IEEE 802.15.4 frame CRC check passed for the MAC frame. 8CEC: *********** Received frame type = Data 8CEC: Need to wait for SIFS (12) symbols. Offset = 14, next IFS = 6 8CEC: ********** Directly transmitting acknowledgement frame (no CSMA/CA) 8CEC: next IFS = 6 8CEC: IFS offset = 384 samples 8CEC: Transmitting 1-896 of 1410 ```
```Found preamble of OQPSK PHY. Found start-of-frame delimiter (SFD) of OQPSK PHY. 1234: Decreasing ack wait durations by 20 symbols to 14 ```
```8CEC: IFS offset = 0 samples 8CEC: Transmitting 897-1410 of 1410 8CEC: Finished transmission 8CEC: Need to wait for SIFS (12) symbols. Offset = 8, next IFS = 0 ```
```1234: PHY decoded IEEE 802.15.4 frame CRC check passed for the MAC frame. 1234: *********** Received frame type = Acknowledgment 1234: Need to wait for LIFS (40) symbols. Offset = 8, next IFS = 28 1234: next IFS = 28 1234: Decreased wait time by 20 symbols to 8 ```

Once the 1st end device has been associated, data frames are randomly injected into the link between the end device and the PAN Coordinator.

Next, a third device joins the PAN and data frames are subsequently exchanged between the coordinator and both end devices, in a star topology fashion (end devices must only transmit frames to coordinators). In this case, the output is suppressed.

```% Create second end-device endDevice2 = lrwpan.MACReducedFunctionDevice( ... 'SamplesPerChip', 4, ... 'ShortAddress', '0002', ... 'ExtendedAddress', [repmat('0', 1, 8) repmat('4', 1, 8)], ... 'Verbosity', false); % Suppress detailed output endDevice1.Verbosity = false; panCoordinator.Verbosity = false; % Initialize input received3 = zeros(samplesPerChip * chipsPerSymbol * ... symbolsPerStep/2, 1); stopTime = 10; % sec while time < stopTime % Pass the received signals to the nodes for processing. Also, % fetch what they have to transmit transmitted1 = panCoordinator(received1); transmitted2 = endDevice1(received2); transmitted3 = endDevice2(received3); % Ideal wireless channel, where all nodes are within range: received1 = transmitted2 + transmitted3; % half-duplex radios % none receiving while % transmitting received2 = transmitted1 + transmitted3; received3 = transmitted1 + transmitted2; time = time + symbolsPerStep/symbolRate; % update clock end```

More nodes can be added to the network, as long as the channel relationship is established accordingly (for example, the received signals as a function of the transmitted signals).

### Further Exploration

The Communications Toolbox Library for ZigBee and UWB add-on contains the following generator and decoding functions and configuration object:

• lrwpan.MACFullFunctionDevice

• lrwpan.MACReducedFunctionDevice

• lrwpan.MACDevice

These utilities are undocumented and their API or functionality may change in the future. To view the source code for any of these utilities, use the `edit` function. For example, enter:

` edit lrwpan.MACFullFunctionDevice`

at the MATLAB® command line to open `lrwpan.MACFullFunctionDevice`.

### Selected Bibliography

1 - "IEEE Standard for Local and Metropolitan Area Networks – Part 15.4: Low-Rate Wireless Personal Area Networks (LR-WPANs)," in IEEE Std 802.15.4-2011 (Revision of IEEE Std 802.15.4-2006) , vol., no., pp.1-314, 5 Sept. 2011, doi: 10.1109/IEEESTD.2011.6012487.