Energy Efficient MAC Protocol for Multimedia IoT devices

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Adaptive Duty Cycling based Multi-hop PSMP for

Internet of Multimedia Things

Bilal Afzal, Sheeraz A. Alvi, Ghalib A. ShahAl-Khawarizmi Institute of Computer Science, UET, Lahore 54000, Pakistan

Email contact:  {bilal.afzal, sheeraz.akhtar, ghalib}@kics.edu.pk 

 Abstract—In several use-cases of Internet of Things (IoT),IEEE 802.11 based WLANs are more favorable due to superiordata rate support even though their energy efficiency is notup to the mark. Particularly, wireless multimedia sensors basedWLANs demand higher energy resources. In this regard, variousIEEE 802.11 based power saving mechanisms are developed.IEEE 802.11n standard specifies Power Save Multiple Poll(PSMP) protocol. However, PSMP is infeasible for many IoTbased systems specifically in use-cases where multi-hop com-munication is required. Moreover, PSMP scheduling mechanismlacks the capability to adapt to the dynamic Quality of Service

(QoS) requirements in Internet of Multimedia Things (IoMT). Inthis paper, a QoS aware Multi-Hop PSMP (mPSMP) protocol isproposed to enable energy efficient multimedia communicationover IoT. The mPSMP incorporate a traffic scheduling modelto allocate channel resources in a time division multiple accessmanner. Therein, adaptive duty cycling is employed to minimizeenergy utilization, while assuring the required multimedia QoSfor each node. The proposed protocol is implemented in NetworkSimulator-2 (NS-2). Analytical analysis and simulation study sug-gests reduction in end-to-end delay and duty cycling along withsignificant improvement in energy efficiency of IoMT devices.

 Index Terms—Internet of Things, Multimedia sensors, PSMP,Energy efficiency, Multi-hop communication.

I. INTRODUCTION

Internet of Things (IoT) is characterized as the notion of inter-connected ‘things’ which are uniquely identifiable and

able to communicate with any device connected to the Internet

[1]. Recent escalation in the utilization of multimedia services

and applications such as video conferencing, telemedicine,

online-gaming, etc., incited an ostentatious growth of the band-

width hungry multimedia content. Moreover, the availabil-

ity of Complementary Metal Oxide Semiconductor (CMOS)

cameras and microphones has attracted lot of research on

the Wireless Multimedia Sensor Networks (WMSNs) [2],

[3], wherein resource constrained devices retrieve multimedia

content from the physical environment.

The ‘Internet of Multimedia Things’ (IoMT) is a novel

paradigm whose prime objective is to enable multimediastreaming as part of the realization of IoT. The IoMT

paradigm enables a wide range of applications in the areas of 

home/building security, smart cities, traffic monitoring, and en-

ergy management [4]. The wireless communication technology

proposed for IoT systems, i.e. ZigBee, is designed for sensor

network application requiring limited data rate of 250 Kbps.

This data rate is infeasible for multimedia applications and

particularly for real-time multimedia communication. There-

fore, IEEE 802.11 standard (Wi-Fi) is a potential alternative

for IoMT and has already been adopted for WMSNs due to

its higher data rate support [5], [6]. Nevertheless, the current

power saving mechanisms in IEEE 802.11 standard, i.e. Power

Save Mechanism (PSM), Power Save Multiple Poll (PSMP),

lack the capability to adapt to the dynamic Quality of Service

(QoS) requirements of IoMT systems.

In [7], it is suggested that the transmit power of energy con-

strained devices along multi-hop routes in dense wireless net-

works to be kept limited in order to conserve energy and avoid

interference. Consequently, power utilization is improved withthe increase in number of hops between source and destination

nodes. Likewise, IoT devices are mostly battery operated,

posses short range radios, and hence have limited transmis-

sion power capabilities. Thus, Low-power IoT devices may

benefit from multi-hop communication mechanism to reduce

the energy consumption. Existing IEEE 802.11 power saving

standards, however, only support single-hop communication.

Therefore, IEEE 802.11 power saving mechanisms need to be

optimized to enable energy efficient multi-hop communication

over IoMT while meeting the desired QoS requirements.

In this paper, an adaptive duty cycling based multi-hop

PSMP protocol is proposed which enables energy efficient

multi-hop communication in infrastructure based WLANs.The proposed mPSMP protocol extends the single-hop PSMP

protocol specified by IEEE 802.11n standard. The QoS re-

quirements of the multimedia traffic, particularly real-time

traffic, is considered by incorporating a traffic scheduling

model. The model allocates traffic opportunity to nodes in

a Time Division Multiple Access (TDMA) fashion to fulfill

the delay bound of packets per second in order to realize

multimedia communication over IoMT. Moreover, the energy

utilization and end-to-end delay of each node is minimized by

employing adaptive duty cycling at each network node which

then aggregate their generated packets while considering the

delay restriction to ensure required QoS.

The main contributions of this paper are as follows:

•   A multi-hop communication protocol is proposed for

multimedia communication over IoMT.

•   A QoS aware bandwidth allocation algorithm is designed

to support real-time multimedia traffic.

•   Adaptive duty cycling is incorporated and a traffic

scheduling model is designed for performance analysis.

•   Frame aggregation is utilized to minimize protocol over-

head and conserve energy consumption.

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I I . RELATED  W OR K

The design of low-power hardware modules and recent work 

in literature focused on reducing energy consumption along

with improving energy efficiency of IEEE 802.11 standard

made it a good candidate for IoT [6], [8], [9]. In [9], feasibility

of low-power Wi-Fi sensors for IoT is studied and energy

consumption results in different power states are compared

with 6LowPAN. Owing to higher data rates, low-power Wi-Firadios are proved to perform better when bigger data packets

are communicated, in multimedia streaming for example, since

packet fragmentation is avoided.

IEEE 802.11 standard based power saving schemes pro-

posed in [10], [11], and [12] curtail energy consumption by

regulating the number of nodes in awake mode and schedul-

ing beacons aperiodically to minimize duty cycling. In [12],

centralized PSM (C-PSM) is proposed in which Access Point

(AP) selects optimal values of beacon interval and reported

energy efficiency as much as 76% compared to standard PSM.

However, C-PSM lacks support for multi-hop communication.

Higher number of nodes in a network results in increased

interference and contention time; thus nodes stay awake for

longer durations. To mitigate these issues, authors in [13] sug-

gested to divide beacon interval into time slots and assigning

them to individual nodes in a TDMA like mechanism, allowing

them to only wake up at their scheduled time slots. In [14],

authors proposed a scheduling mechanism named NAPman

which controls the traffic destined for PSM-enabled stations

so that the other stations in the network do not starve.

The authors in [15] has proposed a Congestion Aware-

Delayed Frame Aggregation (CA-DFA) algorithm, wherein the

transmissions are intentionally delayed and only transmitted

utilizing frame aggregation when the congestion level drops to

a certain threshold. Similarly, another buffering scheme namedLow Energy Data-packet Aggregation Scheme (LEDAS) is

proposed in [16]. However, the LEDAS scheme does not

consider application specific delays induced by buffering

particularly for real-time multimedia traffic. These proposed

schemes lacks the support for multi-hop communication.

Recently, a multi-hop IEEE 802.11 PSM mechanism named

as MH-PSM is presented in [17] for multi-hop toy-to-toy

communication. The proposed traffic announcement scheme

enables nodes along multi-hop route to stay awake only if 

there is pending traffic for them and hence, reducing significant

associated cost with mandatory wake-ups at each beacon

intervals. However, in MH-PSM when multiple nodes contend

for the channel to transmit PS-Poll frames to retrieve theirpackets, the collision probability increases which results in

energy and bandwidth wastage.

In PSMP, AP schedule uplink (UL) and downlink (DL)

transmissions of nodes in a TDMA manner, and afterwards

they can go into sleep mode. Hence, energy and bandwidth

overhead is significantly reduced compared to other power

saving mechanisms. However, PSMP is infeasible for multi-

hop IoT scenarios and the scheduling mechanism does not

adapt to dynamic QoS requirements of IoMT systems.

III. PROPOSED M ULTI-H OP  PSMP PROTOCOL

 A. Problem Definition

Real-time multimedia communication in IoMT environment

necessitate stringent QoS traffic requirements in terms of 

bandwidth, delay, jitter, and reliability. In addition, the frame

aggregation threshold, already proven to be bandwidth and

energy efficient in prior research studies [15], is another

critical network metric. Moreover, frame aggregation is inturn dependent upon supported data rate and application

specific delay bounds corresponding to various multimedia

devices. Therefore, multimedia communication over multi-hop

networks requires an efficient energy saving algorithm which

is aware of the dynamic QoS requirements and also take into

account various interdependent parameters such as data rate,

frame rate, frame aggregation threshold and delay bounds

while reducing duty cycling of multimedia network devices.

Considering these unique compulsions, we formulate an ILP

problem whose objective function is to minimize duty cycling

utility function,   U u(∂ i, γ i, Ψi), subject to the delay bound∂ i, supported data rate   γ i   and frame aggregation threshold

Ψi   constraints. Let   N u   =   {u1, u2,.....,un}   be the set of multi-hop nodes   ui   and let   Qu,i   =   { p1, p2, . . ,pm}, be theircorresponding set of queues. The problem is formulated as:

Minimize:

ui∈N u

U u(∂ i,γ i,ψi)   ∀ui ∈  N u   (1)

Subject to:

m

i=1

∂  p,i ≤  ∂ i,max   ∀ p ∈  Qu, ∀ui ∈  N u   (2)

ρ p,iψu,i

γ u,i ≤ ∂  p,1   ∀ p ∈  Qu,∀ui ∈  N u   (3)

n

i=1

nτ u,i ≤  1   ∀ui ∈  N u   (4)

The Constraint (2) in above formulation ensures that the delay

associated with any packet   pi   buffered at the queue   Qu   of 

station ui, should not exceed the maximum delay bound limit,

∂ i,max. In addition, the delay induced by buffering a packet

in queue is in turn dependent upon the frame aggregation

threshold and data rate; thus Constraint (3) mandates that

aggregated packets are transmitted within the limitation of 

delay bound of oldest packet in queue, (∂  p,1). While, the

Constraint (4) corresponds to the allocation of TransmissionOpportunity (TXOP)  τ u,i, and ensures that QoS requirements

specified by frame rate are met within one second. In real-

time multimedia streaming, the variation in QoS requirement

for every multi-hop away node is variable and hence affects

the duty cycling of a node as well as its child-nodes. Thus,

the solution to the given ILP problem is found out to be NP-

Complete and computationally expensive in terms of energy

requirement. However, the multimedia devices in an IoMT sys-

tem are inherently resource constrained for such computations.

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(a) Time-line of Multi-hop PSMP0 00 00 01 11 11 1

Internet of Things

STA 1 STA 3

STA 5

STA 4

STA 2

AP

(b) Topology

Fig. 1: mPSMP Operation for a 5 Node Network 

In this section, we provide the operational details of the

proposed multi-hop PSMP protocol, referred to as ‘mPSMP’.The mPSMP protocol enables multi-hop operations in PSMP

based WLANs while minimizing the utility function of duty

cycling. The protocol adaptively selects appropriate frame

aggregation threshold and the TXOP duration for each node

based on its uplink schedule time, data transmission rate, the

QoS specified minimum frame per seconds and application

specific delay bound with respect to the arrival time of the

oldest pending packet in queue. When a data packet is received

at the MAC layer, it is appended in the pending packets queue

maintained at each node. Based on Channel State Information

(CSI) received from the intended receiver node, the transmitter

node determines the highest supported data rate for the given

channel conditions. Higher data rate alleviates the need of longer PSMP Uplink Transmission Time (UTT) and Downlink 

Transmission Time (DTT) duration requirement, thus band-

width resources are conserved. The aggregated packets are

then transmitted as soon as the amount of data in the queue

exceeds the frame aggregation threshold or the delay for oldest

packet equals the maximum delay bound limit.

Once a transmitting node determines the aggregation thresh-

old and achievable data rate, it can ask AP (or parent node) for

the TXOP or more accurately PSMP-UTT service period. In

a PSMP sequence, AP (or parent node) shares its own TXOP

to provide PSMP enabled nodes to transmit uplink traffic

and/or receive downlink traffic. Moreover, as highlighted in

[16], another pertinent issue is the requirement for a node tostay awake for its allocated TXOP even if it has no more

traffic to send in current PSMP sequence. This results in

energy and bandwidth under utilization. This issue is resolved

in mPSMP protocol by incorporating adaptive duty cycling,

i.e. if a node has no more packets to be sent in its allocated

TXOP, it can sleep for the rest of its PSMP-UTT duration,

which helps in minimizing the duty cycling utility function.

Lastly, the traffic demand and associated parameters of delay

bound, frame aggregation, frame rate and data rate are being

fed to the traffic scheduling model explained in next section.

 B. mPSMP Protocol Operation

The operation of proposed mPSMP protocol is described as

follows; and a sample operation for a five node network topol-

ogy Fig. 1b is shown in Fig. 1a. For detailed understanding

of PSMP operation, reader is referred to [18].

•   Firstly, AP advertise its service set identifier (SSID) peri-

odically using Beacon frame which has Timestamp sub-

type containing value of stations synchronization timer at

the time the frame was transmitted.

•   This enables synchronization between AP and stations

and accordingly, AP assign them association IDs (AIDs)

starting from AID 1. After this, AP send PSMP Action

frame, indicating if there is any traffic buffered for nodesin Traffic Indication Map (TIM) field.

•   The PSMP frame’s STA Info field notifies the TXOP for

each node including their PSMP-DTT and PSMP-UTT

Duration, and PSMP-DTT and PSMP-UTT Start Offset.

•   Correspondingly, each one-hop node knows what state it

should be in at particular times. The schedule is assigned

in the order of Association IDs (AIDs) of one-hop away

nodes, i.e. STA 1’s schedule leads STA 2’s, and so on.

Hence, only a single node stays awake for the time

duration specified for it in the STA Info field.

•   In this way, each one-hop away node wakes up as per the

order given in TIM bit of PSMP Action frame, receives

its DL transmission from AP in PSMP-DTT and upon itscompletion fell asleep for the remaining duration of DL

traffic transmission of other nodes.

•   The PSMP-DTT is followed by PSMP-UTT, therein each

one-hop away node wakes up on its turn and sends

its buffered UL traffic towards AP and then fell asleep

when its PSMP-UTT duration expires. In the first PSMP

sequence, all one-hop away nodes are served by AP.

•   In subsequent PSMP sequences, two-hop away nodes get

their traffic schedule by their respective one-hop parents.

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The parent nodes initiate PSMP sequences based on their

AIDs, i.e. PSMP sequence initiated by STA 1 leads that

of STA 2, and so on. Similarly, each one-hop away node

will act as an AP for its child-nodes.

•   To specify a single wake up interval for child-nodes,

all PSMP sequences are set apart to the maximum

PSMP sequence duration specified in standard [18], i.e.

8.184msecs. Therefore, even if the previous PSMP se-

quence DTT and UTT durations change, still the PSMP

sequence interval of others is not disturbed. This enables

efficient duty cycling, as shown in Fig. 1a.

•   The parent nodes need to wake up for the PSMP-frame

and their PSMP-DTT and PSMP-UTT durations. In ad-

dition, they have to stay awake in the PSMP sequence

which they are providing to their child-nodes. Rest of 

the time they can sleep to conserve energy.

•   Likewise, the child-nodes which are not supporting other

nodes, are required to receive the PSMP frame from their

respective parents and only stay awake for their PSMP-

DTT and PSMP-UTT durations.

•

  In the subsequent PSMP sequence durations, the samepattern is repeated iteratively for three hop away nodes,

and so on, until the traffic demand of all the nodes is

served. After these PSMP sequences, the AP starts the

contention period till the next phase of PSMP sequences

as specified in standard [18].

Although, the algorithm outlined above is implemented and

optimized considering an infrastructure based network sce-

nario, however, the mPSMP protocol can also be adapted in

an ad hoc network scenario. The only major difference will

be that in current implementation, the AP is kept awake all

the time as it is considered to have a power line. While in

ad hoc mode, the node which starts the first PSMP sequence

will go into sleep state upon completion of its PSMP sequenceduration; and afterwards the child-nodes of next hop will be

served in subsequent PSMP sequence durations.

IV. PERFORMANCE  A NALYSIS

In this Section, a traffic scheduling model is presented con-

sidering the QoS traffic requirements of IoMT based systems.

Let the time spent in transmission is denoted by  T tx and power

consumed in transmission state by  P tx. Similarly, let the time

spent in sleep mode is denoted by T sl  and power consumed by

node in sleep state by  P sl. Let  λ  represents frame rate that is

number of frames to be transmitted by a node in one second in

order to support the QoS requirements. Ensuring frame rate is

important to support smooth streaming of multimedia content.It is essential to be considered in order to keep the jitter level

within some pre-defined bound to provide satisfactory Quality

of Experience (QoE).

For each frame,  ψ   number of packets are aggregated based

on the achievable data rate and QoS requirement of a node. As

specified earlier, it is critical to keep the delay bound of the

queued packets in consideration while adaptively selecting the

frame aggregation at each node. Thus, the number of packets

needs to be sent by a node in one second are  λ × ψ. Let the

size of a single packet is   ρ   bits. Correspondingly, required

amount of throughput  Γ  per second can be given as:

Γ =  λ × ψ × ρ bits per sec   (5)

Similarly, given the data rate of  γ  Mbps, the time  τ  required

by each node to transmit this data while satisfying the QoS

requirement of  λ  frames per second can be given as:

τ  = Γ

γ   =  λ × ψ × ρ

γ    secs   (6)

Thus,   τ   is the cumulative PSMP UTT duration required

to send  Γ  amount of data by a single node in one second inorder to satisfy the delay bound. However, since the maximum

duration of PSMP sequence is 8.184   msecs, therefore this

cumulative time is scheduled in multiple PSMP sequences.

Within a single PSMP sequence, the Downlink transmission

time (i.e.   DLt) and Uplink transmission time (i.e.   U Lt) are

allocated depending upon the number of child-nodes to be

scheduled in single PSMP-sequence belonging to each parent

node, at a specific hop level. If there are    number of nodes

required to be scheduled in single PSMP sequence, then

the possible per node allocated transmission time for bothDownlink and Uplink traffic can be calculated as:

DLt + U Lt  = 8.184

  msecs   (7)

Considering PSMP-DTT and PSMP-UTT durations to be

equal, DLt   =  U Lt   =  T t, implies

2 × T t  =  DLt + U Lt   (8)

T t  = 8.184

2 ×   msecs   (9)

Here  T t   is the transmission time.In a single-hop scenario, back-to-back PSMP sequences

can be initiated (PSMP bursts). However, to enable multi-hop

communication and to provide access to nodes located outsidethe transmission range of AP, each single-hop away node needs

to carry its child-nodes traffic towards AP along with its own

traffic. Hence, assuming the traffic demand of every child-

node is same as their peers belonging to other single-hop away

node; if every  i  node has  j   number of child-nodes, then after

determining the required amount of transmission time for node

i i.e.  T t,i, the updated required number of PSMP sequences Λfor the node   i  within one second can be calculated as:

Λi,j  =  τ  ×  j

T t,i,   0 ≤  i, j  ≤     (10)

This essentially means that multiple PSMP sequences are

scheduled in one second to facilitate the traffic demand of every child-node. Moreover, the time after which a specific

PSMP sequence is scheduled again to allocate TXOP for the

child-nodes is referred as PSMP interval. Based on the value of 

Λi,j , we can now determine the value of PSMP interval  δ , afterwhich TXOP is assigned again to a node (this is uniformly

distributed over one second):

δ  =  1

j=1

Λi−1,j

(11)

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Fig. 2: Energy consumption: TDMA vs mPSMP

Therefore,   T t   can now be calculated by adding the total

TXOPs allocated to all the nodes within one second. Using

equation 9 and 10 we calculate  T aw,i, which is the total time

a node   i  stays in awake state in one second duration:

T aw,i  =

i=1,j=1

Λi,j(2××T t,i+3×T sifs+T  pf +T wait)   (12)

Here T sifs  represents the number of SIFS intervals in each

PSMP sequence,  T wait   is the additional short time spend for

each node to stay awake before sending a lost TXOP request

towards AP, and   T  pf    is the time spent in sending PSMP

frames. Likewise, the total sleep time of a node   i   denoted

by  T sl,i  can be given as:

T sl,i = 1 − T aw,i   (13)

Each node  i  fell sleep between the time duration of any of 

its two TXOPs as described in proposed algorithm. However,

if a node is also acting as the parent of any next hop child-

node, then it has to stay awake till the time duration itcommunicate with and exchange frames to its child-nodes.

The entire methodology adapted for this mathematical model

works in a TDMA like fashion while fulfilling the traffic

demand of each node. Finally, the energy consumed by a node

in various states can be calculated as follows:

E  =  T sl × P sl + T aw × P tx   (14)

E sl =  T sl × P sl = (1 − T aw) × P sl   (15)

E energysaving  =  E sl

E   (16)

EnergyEfficiency(%) =  E total − E 

E total× 100%   (17)

Here   E ,   E sl, and   E total, represent the energy consumption

in active state, in sleep state and the total energy consumed,

respectively. Let E  represents the energy consumption without

applying mPSMP protocol, then the energy efficiency can be

given as:

η =  E 

E   (18)

Fig. 3: Energy efficiency: PSMP vs mPSMP

V. PERFORMANCE E VALUATION

In this Section, we present the simulation model to evaluate

the performance of mPSMP protocol. The simulations consist

of an infrastructure based IoT network Fig. 1b, with an AP

and 5 stations (STAs) each generating constant bit rate (CBR)

traffic. The carrier sensing range of STAs is set such that the

connectivity between any two stations is ensured. We vary

the packet size from 128 to 2048 bytes and packet interval

from 0.01 to 0.1 secs with uniform distribution. Moreover,

the following values are considered for the energy model; Tx

Power = 660mW, Rx Power = 395mW, Idle Power = 35mW,

Sleep Power = 1mW, Initial Energy = 1000J.

Simulation results are averaged for multiple flows of several

distinct topologies and each simulation runs for 100 secs

duration. Unless specified, we used the packet size of 512

bytes, packet interval of 0.05 secs and frame rate of 25 frames

per second. We investigate the aggregate energy consumption,

by keeping the packet interval fixed at 0.05 secs while varying

the packet size from 128 to 2048 Bytes. The simulation model

also validates the traffic scheduling model of Section IV.The analytical results computed from traffic scheduling

model are compared with that of simulation results are shown

in Fig. 2. Evidently, the increase in packet size results in more

energy consumption due to the effective increase in throughput

at each station as more time is consumed in awake state to

meet the QoS requirement of 25 frames per second. However,

as depicted in Fig. 3, mPSMP significantly elevates the aggre-

gate energy efficiency (24% on average) and the increase in

packet size has only marginal effect on the energy efficiency

(4% cut) of multi-hop stations employing our mPSMP protocol

compared to the detrimental effect (20% cut) of packet size

variation (increase) in the absence of mPSMP mechanism.

Similarly, Fig. 2 also provides a comparison of mPSMP withthe traditional TDMA approach of IEEE 802.11 standard

without duty cycling and shows significant performance gains

in terms of energy consumption by employing mPSMP.

In standard PSMP protocol a station is not the TXOP holder

which essentially means that it stays awake for its allocated

TXOP even if there are no packets buffered in its queue.

mPSMP employs adaptive duty cycling which enables a station

to sleep dynamically after sending its pending traffic. The

impact of adaptive duty cycling on energy consumption for

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Fig. 4: Energy efficiency gain due to adaptive duty cycling (*)

multi-hop stations across the flow (STA-5→STA-4→STA-2)can be visualized in Fig. 4. This impact is enhanced with

increase in packet interval particularly for stations along multi-

hop route from AP. Thus, additional energy is conserved which

indicates the benefits of adaptive duty cycling in reducing

idle listening time, especially for multi-hop network topologies

where traffic generation rate varies over the period of time.

The average end-to-end delay results are shown in Fig. 4.As expected, end-to-end delay increases with an increase in

packet size. It is incremented proportionally with the increase

in number of hops; however thanks to the mPSMP protocol,

the maximum average end-to-end delay for 3 hop away nodes

is 20ms which is very much lower compared to the vari-

ous implementations of existing power saving mechanisms.

Moreover, while some packets are delayed and forwarded over

multi-hops in more than one PSMP Sequence; but QoS will be

guaranteed by the traffic scheduling model according to given

frame rate. It also ensures that the end-to-end delay for frames

at a given station is kept within per second delay bound.

VI . CONCLUSION AND F UTURE  W OR K

The existing IEEE 802.11 based energy saving mechanisms

do not meet the multi-hop communication and dynamic QoS

requirements. In this paper, mPSMP protocol is proposed

to enable multi-hop communication in IEEE 802.11 IoMT

systems. Moreover, a traffic scheduling model incorporating

adaptive duty cycling is designed to meet the QoS require-

ments of resource constrained multimedia devices. Simulation

results indicate reduction in duty cycling and end-to-end delay

along with significant improvement in energy efficiency of 

multi-hop nodes. In future, we aspire to make our protocol

more adaptive by relaxing the assumption of uniform traffic

distribution for stations by separately selecting QoS parameters

in accordance to distinct traffic classes; and in addition, to meet

the unique QoS specifications for various use-cases of IoMT.

ACKNOWLEDGEMENT

This work is supported by the National ICT R&D Fund,

Gov. of Pakistan under Grant no. ICTRDF/TR&D/2013/04.

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