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Paper text:
ieee 802.15.4  @xcite specifies a _ physical _ ( phy ) and a _ medium access control _
( mac ) layer for use in _ low rate wireless personal area networks _
( lr - wpans ) .
802.15.4 itself is used as a stand - alone communication solution for resource - constrained wireless sensor nodes or as a basis for additional standards like wirelesshart or zigbee .
it facilitates the so - called _ wireless embedded internet _ and _ internet of things _ ( iot ) scenarios in combination with the ipv6 adaptation protocol 6lowpan  @xcite .
layers and interfaces of 802.15.4 are depicted in figure  [ fig : ieee802154_stack ] .
the phy is responsible for the transceiver management ( incl .
frequency selection ) , receiving and transmitting data , as well as _ energy detection _ ( ed ) and _ clear channel assessment _ ( cca ) operations , both required for the _ carrier sense multiple access collision avoidance _ ( csma - ca ) functionality of the mac layer .
the mac provides lr - wpan management operations , csma - ca , network beacon operations , security functions , a guaranteed time slot ( gts ) mechanism with a superframe structure , as well as the provision of a reliable link between mac instances .
both layers define header and frame structures and a number of command messages .
in addition , a _ service specific convergence sublayer _
( sscs ) is specified to adapt ieee 802.2 llc frames for use with the 802.15.4 mac .
additional descriptions are provided by @xcite .
802.15.4 simulation models are already included in the omnet`++`extension frameworks inetmanet , mixim and castalia .
our reasons to create a new implementation for inet _
2.x _ are manifold .
mixim s 802.15.4 implementation focuses on the phy layer , with an implementation of the 802.15.4a impulse radio ultra wide - band ( ir - uwb ) standard in addition to the narrow - band version .
the mac model only covers the csma - ca functionality of 802.15.4 ; other functions are not included .
castalia s implementation includes an extensive phy model and many mac functions .
castalia s main drawbacks are the lack of higher layer protocols for internet applications ( i.e. , ipv6 , tcp and udp for use in iot scenarios ) as well as support for beacon management and newer omnet`++`releases .
inetmanet includes a port of an older ieee 802.15.4 model  @xcite , originally developed for inet-2006/omnet`++`3.4 .
inetmanet s implementation is missing support for newer 802.15.4 revisions as well as several mac layer service primitives , channel scan operations , and various beacon and wpan management functions .
as the wireless embedded internet requires protocols from the tcp / ip family , we favor using the inet framework and implementing a new 802.15.4 simulation model from scratch , to enable feature completeness as well as further combinations with other iot standards like 6lowpan , coap and rpl .
the composition of implemented ( compound ) models is shown in figure  [ fig : ieee802154_host ] .
we modeled each layer , their connecting interfaces as well as the service primitives according to the standard specifications ( refer to figure  [ fig : ieee802154_stack ] and @xcite ) and general modeling guidelines for ieee 802.15.4 ( * ? ? ?
12.3 ) .
the 802.15.4 model itself consists of the following parts :    * ` ieee802154radio ` : this base class is an extension of inet s abstract _ radio class_. it includes the reception and the radio model with adjustments for 802.15.4 ( e.g. , _ energy detection _
( ed ) , _ clear channel assessment _ ( cca ) functions , link layer service primitives ) . * ` ieee802154phy ` : this class represents the phy layer .
message exchange between the mac layer and the radio interface is handled here and service primitives for cca and ed functions are generated in this class . * ` ieee802154mac ` : the mac layer completes the _ network interface card _
( nic ) of a ieee 802.15.4 host .
this layer manages mac functions such as csma - ca , gts , beacon and wpan management , amongst others . * ` sscs`/`stdllc ` : both modules connect applications to 802.15.4 s mac layer .
sscs is used for ieee 802.2-compatible _ logical link control _
( llc ) instances ( i.e. , applications ) , whereas the ` standardllc ` provides means for conversions of messages from non-802.2-compatible applications like inet s ` ipvxtrafgen ` .
we combined above described layers and modules into a so - called ` ieee802154host ` , similar to inet s ` standardhost ` .        the following classes / headers are not included in fig .  [ fig : ieee802154_host ] , yet they are crucial for the simulation model s functionality :    * ` ieee802154enum ` : header that describes 802.15.4 s command , frame and timer types , amongst other enumerations from the standard specification . *
` ieee802154fields ` : header that defines _ structs _ for complex 802.15.4 data structures like the pan descriptor or the superframe specification . * ` macaddressext ` : extends inet s ` macaddress ` class with support for eui-64 ( 64-bit _ extended unique identifier _ ) mac addresses and 16-bit ( ieee 802.15.4 ) short addresses . * ` macframecontrolfield ` : class that generates the mac frame control field ( refer to ( * ? ? ?
7.2.1.1 ) ) .
* ` macpib ` / ` phypib ` : classes that represent mac and phy pan information bases ( pib )  databases that hold attributes required for the layer management .
the modules are initialized according to inet s multi - stage initialization procedure .
parameters are set to their default or user - specified values ( via ` omnetpp.ini ` ) .
necessary timers for the mac and phy layer ( i.e. , the radio module ) are started and the 802.15.4 node goes into receive state if nothing else is specified and no traffic generator is started .
packet reception and transmission is modeled with the use of according service primitives as specified in the standard .
packets and command frames are transferred over their corresponding interfaces .
different use cases ( e.g. , direct data transfer , indirect data transfer , gts handling ) are modeled and available as example configurations in the ` omnetpp.ini ` .
we are currently in the process of adapting the 802.15.4 model to the latest inet version and update its specifics to recent revisions of the 802.15.4 standard . at this stage , the model is used and developed as a standalone project .
we plan to integrate it completely into inet , thus simplifying the use of 802.15.4 in inet - based simulations .
for this , we plan to add ` ilivecycle ` support and integrate the 802.15.4 modules in inet s layer structure and its ` standardhost ` . providing an integration in omnet`++\:/\:`inet s project feature dialog is also outstanding work .    certain modulation schemes ( e.g. , ask and qpsk ) are not used in the 802.15.4 model nor provided in inet yet .
we need to tackle this issue along with the parametrization , inclusion of newer phys ( from current 802.15.4 revisions ) and the practical validation of the 802.15.4 model against real - life sensor nodes .
choosing phy and energy consumption parameters is another open question , as 802.15.4 hardware platforms from different vendors provide different characteristic numbers .
last but not least , we plan to combine and integrate the 802.15.4 model with our 6lowpan simulation model  @xcite for inet to expand the use of omnet`++\:/\:`inetin the area of sensor networks and iot simulation .          f.  chen and f.  dressler , `` a simulation model of ieee 802.15.4 in omnet++ , '' in _ 6 .
gi / itg kuvs fachgespraech drahtlose sensornetze , poster session _ , aachen , germany , july 2007 , pp
[ online ] .
available : http://www7.informatik.uni-erlangen.de/~dressler/publications/fg-sensornetze-2005.pdf      m.  kirsche and j.  hartwig , `` a 6lowpan model for omnet++ , '' in _ proc .
of the 6th omnet++ workshop , co - located with the 6th icst conference on simulation tools and techniques ( simutools 2013 ) _ , march 2013 .
[ online ] .
available : http://www.omnet-workshop.org/2013/general/technicalprogram
this paper introduces a new ieee 802.15.4 simulation model for omnet`++\:/\:`inet . 
 802.15.4 is an important underlying standard for wireless sensor networks and internet of things scenarios . 
 the presented implementation is designed to be compatible with omnet`++`__4.x _ _ and inet _ 2.x _ and laid - out to be expandable for newer revisions of the 802.15.4 standard .    
 ieee 802.15.4 , simulation model , omnet`++ `