PNP-MAC: Preemptive slot allocation and Non

Preemptive transmission for Providing QoS in

Body Area NetworksPublished in IEEE CCNC 2010.

Author:

June S. Yoon,

Gahng-Seop Ahn,

Seong-Soon Joo,

Myung J. Lee

Department of Electrical Engineering,

The City University of New York.

Electronics and Telecommunications Research Institute.

Presented by:

Iffat Anjum (Roll: 16)

Nazia Alam (Roll: 28)

Date: 30th May, 2012.

Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Contents

Contribution.

Problem Definition.

Overview of PNP-MAC.

Features of PNP-MAC.

Priority Classification.

Fast, Preemptive DTS allocation.

Non-Preemptive transmission.

Prioritized CCA in ETS.

Prioritized random back-off in CAP.

Performance Evaluation.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Contributions

Proposes a PNP-MAC protocol that can flexibly handle variety of

applications with diverse requirements through,

Fast, preemptive slot allocation,

Non-preemptive transmission in the allocated slots ,and

Flexible super-frame adjustments.

This PNP-MAC protocol can satisfy diverse delay and throughput

requirements of various applications such as,

Continuous streaming,

Routine periodic monitoring, and

Time-critical emergency alarm.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Slide 4 Problem Definition

The BAN applications have diverse QoS requirements in terms of

throughput, latency, and reliability.

Most of the physiological data monitoring applications are periodic

and low rate.

But emergency alarm, the most time-critical data in BAN, requires

instantaneous delivery with the highest reliability.

A BAN should be able to cope with the diverse requirements

simultaneously even when those applications are used together at

the same time.

4Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Overview of PNP-MAC In order to reflect all design considerations, PNP MAC exploits a

hybrid approach that uses both contention based and time

division-based schemes.

BAN super-frame shows how the two schemes are integrated.

Figure 1: BAN Superframe structure.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Overview of PNP-MAC The advertisement informs newly joining nodes and member

nodes of basic information of the BAN coordinator and super-

frame such as,

BAN identifier,

Advertisement interval, and

The length of CAP periods.

Initially the BAN coordinator begins BAN super-frame without

DTS until DTS allocation request is received during CAP.

Then it collects DTS requests embedding the priority of nodes’

data and then allocates DTS slots based on the priorities.

Then announces allocation status through beacon broadcasting.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Overview of PNP-MAC

TDMA data transmit period is a contention-free period for time-

critical continuous and periodic data.

It consists of data transmit slot (DTS) and Emergency Data

Transmit slot (ETS).

It allocates time-critical data to DTS.

If all DTSs are exhausted, the BAN coordinator can allocate

time critical data to ETSs.

Emergency Data Transmit Slot (ETS) is a contention access

slot reserved for urgent delivery of unpredictable emergency

data.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Features of PNP-MAC PNP-MAC provides QoS in accordance with the priority of

traffics.

Back-off in CAP, CCA (Clear Channel assessment) in ETS, and

DTS allocation, all are performed depending on priority.

Priority is determined by the degree of importance and the types

of data.

Generally emergency alarm has the highest priority and medical

data has next highest priority.

The order of importance for data types is:

continuous data, periodic data, and then non-periodic data.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Priority Classification

Features of PNP-MAC

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Table 1: Priority and Back-off class.

Priority Classification

Features of PNP-MAC

A BAN device requests DTS allocation during CAP after it

recognizes the existence of the BAN coordinator from the

advertisement.

Then, the BAN coordinator allocates DTS and notifies it through

the beacon.

And then the devices transmit data in its designated slot.

If the allocation fails due to the lack of remaining DTSs or the

loss of the request packet, the allocation of the slot is not

announced.

The device that has requested DTS allocation can find out the

failure after receiving the beacon, then the device requests DTS

allocation again.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Fast, Preemptive DTS allocation

Features of PNP-MAC

Unlike 802.15.4, all the stated processes are done in sequence

and within the same superframe interval in PNP-MAC.

Figure 2: Allocation delay comparison.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Fast, Preemptive DTS allocation

Features of PNP-MAC

Higher priority data is served first in any case even in heavy

contention.

The BAN coordinator sorts all the requests and allocates higher

priority first from the first available slot.

Figure 3: Priority based DTS allocation.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Fast, Preemptive DTS allocation

Features of PNP-MAC

If remaining DTSs are insufficient to admit all requests, higher

priority data preempts lower priority data.

Figure 4: Priority based DTS allocation.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Fast, Preemptive DTS allocation

Features of PNP-MAC

Emergency alarms are transmitted using both CAP and ETS

whichever comes first to reduce delay.

The number of ETSs is configurable and ETSs are distributed

within data transmission period (DTP) .

Unlike DTS, preemption of ETS is not allowed.

As emergency alarms rarely occur, dedicating ETS slots may not

be justifiable in view of efficient use of resources.

So, we allow non-emergency alarm data to use ETSs using

prioritized CCA.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Non-Preemptive transmission

Features of PNP-MAC

ETS can be assigned to non-emergency data only when available

DTSs are not enough to meet demands from sensor nodes.

The assignee to the ETS must perform CCA first for the

duration specified in Equation below, to avoid collision.

CCA Duration of slot assignee = unitCCAduration × N

N is the number of mini slot for CCA.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Prioritized CCA in ETS

Features of PNP-MAC

For the prevention of collision among emergency alarms, they

also need to confirm the availability of the ETS before

transmission.

Emergency alarms also perform CCA for the duration

specified in Equation below,

CCA Duration of alarm = [0, unitCCAdurtion × (N-1)]

The winner is the one who chooses the smallest duration.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Prioritized CCA in ETS

Features of PNP-MAC

The figure below is an example of prioritized CCA when N=3.

Figure 4: Prioritized CCA in ETS.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Prioritized CCA in ETS

Features of PNP-MAC

Prioritized random back-off is applied during CAP.

All nodes intending to transmit during CAP perform random

backoffs and CCAs.

In Table 1,mentioned before, three back-off classes were listed

based on the priority.

The back-off time is randomly chosen in,

[0, 2BE (Class+1)-1],

where BE denotes the back-off exponent.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Prioritized random back-off in CAP

Performance Evaluation

Here star topology has been used, where a BAN coordinator is

centered and sensor devices are placed around it.

The superframe size of PNP-MAC is selected for performance

evaluation is the same as the beacon interval of IEEE 802.15.4

with superframe parameters ,

Beacon Order ,BO=6,

Superframe Order, SO=3,

slot size=7.68ms, and

CAP size=8 slots.

Total number of slots in a BAN superframe of PNP-MAC is 128

slots.

Channel capacity is 250Kb/sec.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Performance Evaluation

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Figure 5: Allocation delay comparison using one node.

Performance Evaluation

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Figure 6: Emergency alarm delays.

Performance Evaluation

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Figure 7: Prioritized back-off delays.

Performance Evaluation

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Figure 8: Allocation delay comparison using seven nodes.

Green Networking Research

Dept. of Computer Science and Engineering,

University of Dhaka

Thank You

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