The 802.15.4 Model¶
Overview¶
IEEE 802.15.4 is a technical standard which defines the operation of low-rate wireless personal area networks (LR-WPANs). IEEE 802.15.4 was designed for data rates of 250 kbit/s or lower, in order to achieve long battery life (months or even years) and very low complexity. The standard specifies the physical layer and media access control.
IEEE 802.15.4 is the basis for the ZigBee, ISA100.11a, WirelessHART, MiWi, SNAP,and the Thread specifications, each of which further extends the standard by developing the upper layers which are not defined in IEEE 802.15.4. Alternatively, it can be used with 6LoWPAN, the technology used to deliver IPv6 over WPANs, to define the upper layers. (Thread is also 6LoWPAN-based.)
The INET Framework contains a basic implementation of IEEE 802.15.4 protocol.
Network Interfaces¶
There are two network interfaces that differ in the type of radio:
Ieee802154NarrowbandInterface is for use with narrowband radios
Ieee802154UwbIrInterface is for use with the UWB-IR radio
To create a wireless node with a 802.15.4 interface, use a node type
that has a wireless interface, and set the interface type to the
appropriate type. For example, WirelessHost is a node type which
is preconfigured to have one wireless interface, wlan[0].
wlan[0] is of parametric type, so if you build the network from
WirelessHost nodes, you can configure all of them to use 802.15.4
with the following line in the ini file:
**.wlan[0].typename = "Ieee802154NarrowbandInterface"
Physical Layer¶
The IEEE 802.15.4 standard defines several alternative PHYs. There are several narrowband radios at various frequency bands using various modulation schemes (DSSS, O-QPSK, MPSK, GFSK BPSK, etc.), a Direct Sequence ultra-wideband (UWB), and one using chirp spread spectrum (CSS).
INET provides the following radios:
Ieee802154NarrowbandScalarRadio is currently a partially parameterized version of the APSK radio. Before using this radio, one must check its parameters and make sure that they correspond to the specification of the 802.15.4 narrowband PHY to be simulated.
Ieee802154UwbIrRadio models the 802.14.5 UWB radio.
One must choose a matching medium model, for example Ieee802154UwbIrRadioMedium for Ieee802154UwbIrRadio, and Ieee802154NarrowbandScalarRadioMedium for Ieee802154NarrowbandScalarRadio.
MAC Protocol¶
The 802.15.4 MAC is based on collision avoidance via CSMA/CA. Important other features include real-time suitability by reservation of guaranteed time slots, and integrated support for secure communications. Devices also include power management functions such as link quality and energy detection.
The Ieee802154Mac type in INET is currently a parameterized version of a generic CSMA/CA protocol model with ACK support.
There is also a Ieee802154NarrowbandMac.