Advanced Mathematics and Numerical Modeling of IoT

Create beacon bitmap

(depending on SD index)

Transmit beacon Beacon reception

Add the device ID to my

neighbor table

Select my SD index

(based on beacon

bitmap)

Tr a n s m i t

allocation allocation notification

message

Receive

SD index

collision?

Transmit collision

notification

notification

Ye s

Receive collision

notification?

Join with

network

No

Remove my SD index

and

wait for the next

beacon

Ye s

Active device (already joined) Prospective device

Figure 2: Flowchart of the IEEE 802.15.4e DSME beacon scheduling algorithm.

4.1. Experiment Environment.We implemented beacon
scheduling for IEEE 802.15.4 DSME based on the LR-WPAN
module of ns-3 [ 17 ]. For a channel model, a single model
spectrum channel was used and a communication channel
was constructed based on a long distance propagation loss
error model. Specific primitives and frames for DSME are
involved in the LR-WPAN media access control (MAC)
layer and additional PAN information base (PIB) attributes
and constants are defined in the MAC header. In addition,
instead of a superframe structure used in the original IEEE
802.15.4, a multisuperframe structure (a specific feature of
DSME) is used.

4.2. Pure DSME

4.2.1. DSME Beacon Scheduling Review.This subsection pre-
sents the DSME beacon scheduling algorithm in terms of
implementation.Figure 2shows a concrete flow chart of
a DSME beacon scheduling algorithm. The algorithm is
divided into two stages: the active node stage and the prospec-
tive node stage. First, an active node generates a beacon
bitmap based on its own SD index and the SD index infor-
mation of its neighboring nodes. This SDBitmap information
is contained in a beacon frame broadcasted periodically. All
nodes update their neighboring SD index table whenever

they receive a beacon frame containing an SDBitmap field.

Inparticular,ifaprospectivenodereceivesabeaconframe,it

adds the sender ID to the SD index table entry and updates SD

index information based on the SDBitmap contained in the

received beacon. Then, a prospective node selects an available

(vacant) slot and broadcasts a beacon allocation notification

message. All the nodes that receive the allocation notification

message check whether the notified slot is already used. If

the slot is available, the SD index table is updated by adding

the designated slot. However, if the slot is already used, the

node that receives the notification message sends a collision

notification message to the originator to prevent overlapped

SD slot usage. As soon as the prospective node, which sent

notification of its new SD index, receives a collision notifi-

cationmessage,itclearstheSDindexandthenwaitsuntil

the next beacon reception. After broadcasting the allocation

notification message, if a collision notification message is not

received by the end of the contention access period (CAP)

of the present superframe duration, the prospective node

becomes an active node with the allocated SD index, and it

can send its periodic beacon in the allocated SD index slot.

4.2.2. IEEE 802.15.4e DSME SD Slot Selection.If a prospective

node receives a beacon, a superframe slot of the node can

be allocated by selecting a vacant slot. The allocated slots are