ZigBee NET Frame Generation and Decoding

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This example shows how to use the Communications Toolbox™ to generate and decode NET frames of the ZigBee specification [ 1 ].

Background

The ZigBee standard specifies the network (NET or NWK) and application (APP or APL) layers for low-rate wireless personal area networks. These NET- and APP-layer specifications build upon the PHY and MAC specifications of IEEE® 802.15.4™ [ 2 ]. ZigBee devices find application in home automation and sensor networking and are highly relevant to the Internet of Things (IoT) trend.

Architecture

A zigbee.NETFrameConfig configuration object is used both in generating and decoding ZigBee NET frames. Such objects describe a NET-layer frame and specify its frame type and all applicable properties. The zigbee.NETFrameGenerator function accepts a zigbee.NETFrameConfig object describing the frame, and optionally a NET-layer payload (APP-layer frame) in bytes (two-characters), and outputs the NET frame in bytes. The zigbee.NETFrameDecoder function accepts a NET Protocol Data Unit (NPDU) in bytes and outputs a zigbee.NETFrameConfig object describing the frame and possibly a NET-layer frame in bytes. Clause 3.3 in [ 1 ] describes the NET frame formats.

Decoding NET Frames of Home Automation ZigBee Radios

This section decodes NET frames transmitted from a commercial ZigBee radio enabling home automation, and captured using a USRP® B200-mini radio and the Communications Toolbox Support Package for USRP® radio.

The zigbee.NETFrameDecoder function can decode NET-layer ZigBee data frames and the header of net-command frame types.

load zigbeeNETCaptures % netFrame

[netConfig,netPayload] = zigbee.NETFrameDecoder(netFrame);
netConfig

netConfig = 
  NETFrameConfig with properties:

                FrameType: 'Data'
          ProtocolVersion: 'ZigBee 2007'
           SequenceNumber: 212

   Addressing:
            SourceAddress: '0000'
       DestinationAddress: '35EA'
           IEEEAddressing: 'None'

   Security:
                 Security: 1
           DataEncryption: 0
                MICLength: 0
            KeyIdentifier: 'Network'
            ExtendedNonce: 1
             FrameCounter: 193458
    SecuritySourceAddress: '24FD5B00000014B6'
              KeySequence: 0

   Routing:
                   Radius: 30
            DiscoverRoute: 1
            SourceRouting: 1
               RelayIndex: 0
                RelayList: [0x4 char]

   Multicast:
                Multicast: 0

Note that NET-layer decoding indicates that the NET-layer payload is encrypted (Security = true). Security can be used either in the network or the application layer; this frame uses network-layer security. On the one hand, the DataEncryption field is false in the frame and the message integrity code (MIC) length is zero, which indicate that security level #0 is used and that the payload is not encrypted. However, according to the ZigBee standard (Clause 4.4.1.2 in [ 1 ]), these two fields are overwritten with values locally stored during network setup. In this case, this frame was secured with security level #5, which means that the NET-payload is encrypted and that the MIC length is 32 bits.

Generating NET Frames

The zigbee.NETFrameGenerator function can generate unsecure NET-layer ZigBee data frames. The configuration object can be further customized.

netConfig = zigbee.NETFrameConfig( ...
    'SequenceNumber',123, ...
    'DestinationAddress','E568');
numOctets = 50;
payload = dec2hex(randi([0 2^8-1],numOctets, 1),2);
netFrame = zigbee.NETFrameGenerator(netConfig,payload);

Further Exploration

The example uses these undocumented utilities. The API and functionality of undocumented utilities may change in the future. To view the source code of the utilities, use the edit function.

zigbee.NETFrameGenerator
zigbee.NETFrameDecoder
zigbee.NETFrameConfig

References

1 - ZigBee Alliance, ZigBee Specification Document 053474r17, 2007.

2 - IEEE 802.15.4-2011 - IEEE Standard for Local and Metropolitan Area Networks--Part 15.4: Low-Rate Wireless Personal Area Networks (LR-WPANs).