ZigBee

Combined topologies

Mesh Topologies

In a mesh network, regular beacons are not allowed.

• Devices in a mesh network can only communicate with each other by peer-to- peer transmissions.

In a tree network, the coordinator and routers can announce beacons.

Device addressing

Two or more devices communicating on the same physical channel constitute a WPAN which includes at least one FFD (PAN coordinator).

Each independent PAN will select a unique PAN identifier.

All devices operating on a network shall have a unique 64-bit extended address (IEEE 802.15.4). This address can be used for direct communication in the PAN.

The network address can use a 16-bit short address, which is allocated to the child routers by the PAN coordinator when the device associates.

256 sub-addresses may be allocated for subunits.

Address assignment in a ZigBee network

In ZigBee, network addresses are assigned to devices by a distributed address assignment scheme.

The ZigBee coordinator determines three network parameters to set the allocations.

• the maximum number of children (Cm) of a ZigBee router.

• the maximum number of child routers (Rm) of a parent node.

• the depth of the network (Lm).

A parent device utilizes Cm , Rm , and Lm to compute a parameter called Cskip.

• which is used to compute the size of its children’s address pools.

If a parent node at depth d has an address Aparent,

• the nth child router is assigned to address
• the nth-child end device is assigned to address

Routing protocols

In a tree network.

• Utilize the address assignment to obtain the routing paths.

In a mesh network.

• Two options.

  • Reactive routing: if having routing capacity.

  • Use tree routing: if do not have routing capacity.

Note:

• ZigBee coordinators and routers are said to have routing capacity if they have routing table capacities and route discovery table capacities.

Summary of ZigBee network layer

Pros and cons of different kinds of ZigBee network topologies.

Application Level

ZigBee defined Objects (ZDO):

• provides common function for applications.

• initializes APS, NWK-Layer and Security Service Specification.

• offers services like device-/service-descovery, binding and security management.

• assembles information about the network.

• for ZBC/ZBR -> e.g. binding table.

Profiles

Definition of ZigBee-Profiles:

• describes a common language for exchanging data.

• defines the offered services.

• device interoperability across different manufacturers.

• standard profiles available from the ZigBee Alliance.

• profiles contain device descriptions.

• unique identifier (licensed by the ZigBee Alliance).