Research Article MAC Protocol for Quality-Aware Real...

Research ArticleMAC Protocol for Quality-Aware Real-Time Voice Delivery inCognitive Radio-Enabled WSNs

Bosung Kim Gyu-min Lee and Byeong-hee Roh

Department of Computer Engineering Ajou University Suwon-si Gyeonggi-do 443-749 Republic of Korea

Correspondence should be addressed to Byeong-hee Roh bhrohajouackr

Received 17 April 2015 Accepted 28 July 2015

Academic Editor Shamik Sengupta

Copyright copy 2015 Bosung Kim et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

We propose a quality-aware media access control (MAC) protocol for real-time voice delivery in cognitive radio- (CR-) enabledwireless sensor networks (WSNs) The temporal structure of the system model is addressed by using periodic timeslots in order tomake more efficient use of the spectrum In our proposed temporal structure a bandwidth broker in such centralized CR networks(CCRNs) is selected as a central counterpart to synchronize with secondary users (SUs) and assign spectral resources to themWe develop an analytical model for SUs for the Call Admission Control (CAC) of voice traffic using the quality of service (QoS)requirements of delay bound and delay bound violation probability Ours is an approach that provides reliable data transmissionand reduces packet delay and packet delay jitter In addition to the aforementioned packet-level performancemetrics we calculateda call-level performance metric that is the number of acceptable SUs satisfying QoS requirements

1 Introduction

With the introduction of the Internet ofThings (IoT) wirelesssensor networks (WSNs) are expected to play an importantrole in future social technologiesMajor applications ofWSNshave traditionally involved the simple use of sensing andreporting [1] since the nodes in WSNs are constrained interms of storage resources computational capability com-munication bandwidth and power supply [2 3] WSNs usedfor applications such as emergency healthcare and disastersurveillance are required to support voice and low-rate videocapabilities These networks also have stricter quality ofservice (QoS) requirements such as low data latency andmaximum reliability than traditional WSNs [1]

Although the collective effort of all communicationprotocols is necessary for QoS provision the media accesscontrol (MAC) layer is particularly important because itsmedium sharing and influence on upper-layer protocols aredominant [1] The numerous QoS-aware MAC protocols thathave been proposed for WSNs [4ndash11] which we survey inSection 22 all assume the presence of only licensed usersthat is primary users (PUs) in the network

However WSNs mostly operate in license-free bandsand are expected to suffer heavy interference from other

wireless networks sharing the same spectrum [12] With theimposition of increasing demands on wireless networks bythe license-free spectrum it is difficult to guarantee QoS onlyfor WSNsTherefore the coexistence of multiple networks inthe same license-free spectrum becomes inevitable and raisesissues regarding improving spectral efficiency and providingQoS for real-time traffic [12]

A cognitive radio network (CRN) is a promising approachto providing real-time services in a WSN with strict QoSrequirements [13] According to their network architectureCRNs can be categorized into centralizedCRNs (CCRNs) anddistributedCRNs (DCRNs)TheCCRNhas a central networkentity such as a base station (BS) in cellular networks or anaccess point (AP) in wireless local area networks (WLANs)On the contrary an unlicensed user that is a secondary user(SU) in the DCRN can communicate with other SUs throughad hoc connections on unlicensed bands Thus the CCRN isa suitable network architecture for WSNs where each sensornode determines how to recognize available channels andwhich available channel to access [14]

The flux in the availability of licensed channels posessevere problems in guaranteeing acceptable QoS for voiceusers [15]When channel availability varies with the activities

Hindawi Publishing CorporationInternational Journal of Distributed Sensor NetworksVolume 2015 Article ID 952951 10 pageshttpdxdoiorg1011552015952951

2 International Journal of Distributed Sensor Networks

of PUs on licensed channels voice calls requested by SUsshould accordingly be regulated to ensure the satisfaction ofQoS requirements Thus unlike traditional QoS provisionwhich relies primarily on traffic statistics providing QoS forSUs should be implemented through spectrum sensing spec-trum access and the admission control across the relevantnetwork layers [14]

Some research has been conducted in recent years onmodeling CRNs with voice traffic [16ndash22] but this is insuffi-cient Furthermore from the viewpoint of network architec-turemost past research onCCRNshas been conducted underunrealistic assumptions which we detail in Section 23

In this paper we propose a quality-ware MAC protocolfor real-time voice delivery in CR-enabled WSNs For moreefficient Call Admission Control (CAC) for voice traffic wepropose a temporal structure with periodic timeslots forCR-enabledWSNsThe IEEE 80211 distributed coordinationfunction (DCF) [23] is applied to several SUs to avoid inter-ference with PUs in a timeslot Furthermore a bandwidthbroker (BB) is automatically determined by the proposedtemporal structure and operates as a central counterpart inthe network The BB is responsible for identifying availableresources in PU channels and assigning them to SUs Wethus develop an analytical model for the satisfaction of QoSrequirements by the CAC We used delay bound and itsviolation probability as QoS requirements and calculatedthe following packet-level and call-level performancemetricsusing ourmodel average packet delay packet delay jitter andthe number of acceptable SUs

The rest of this paper is organized as follows In Section 2we describe theQoS requirements for real-time voice deliveryas well as research in the area related to QoS-aware MACprotocols The system model and operation of our proposedscheme are described in Sections 3 and 4 respectivelyIn Section 5 we detail the analytical and simulation-basedresults obtained from the proposed scheme We offer ourconclusions in Section 6

2 Related Work

21 QoS Requirements for Real-Time Voice The pattern ofpacket arrivals closely follows that of speech generationthat is this source of traffic exhibits ldquointrinsic temporalbehaviorrdquo [24] and this patternmust be preserved for faithfulreproduction of the speech at the receiverrsquos end The packetnetwork will introduce delay fixed propagation delay aswell as queuing delay that can vary from packet to packetHence the network cannot serve such a source at arbitraryrates as in the case of elastic traffic In fact depending onthe adaptability of a stream source the network may needto reserve bandwidth and buffers in order to provide anadequate transport service to a stream source Applicationssuch as real-time voice and video conferencing are examplesof stream sources

The following are typical QoS requirements of streamsources

(i) Delay (Average and Variation (Jitter)) real-time inter-active traffic requires tight control of end-to-end

delays For example for voice packets the end-to-enddelay may need to be controlled for it to be shorterthan the delay bound with a violation probability ofless than 001

(ii) Packet Loss due to the high levels of redundancy inspeech and images a certain amount of packet lossis imperceptible For example in voice packets whereeach packet carries 20ms of speech and the receiverconducts lost packet interpolation 5 to 10 of thepackets can be lost without significant degradation ofspeech quality Due to delay constraints the accept-able packet loss target cannot be attained by firstlosing and then recovering the lost packets in otherwords stream traffic expects a specific ldquopacket lossratiordquo from the packet transport service

In this paper as well as the aforementioned packet-levelperformancemetrics that is average packet delay and packetdelay jitter we define the number of acceptable SUs that isthe number of voice calls in CR-enabled WSNs as a call-level performance metric We assume that no packet lossoccurs in the network because only SUs are accepted whenachieving QoS requirements and thus the relevant packetsare transmitted successfully

22 QoS-Aware MAC Protocols for WSNs The MAC layerof the architecture stack plays a key role in QoS provisionbecause the upper layers cannot be accessed without theassumption of a MAC protocol that solves the problemsof medium sharing and supports reliable communicationVarious MAC protocols for WSNs have been proposedfor decades but few consider QoS support The primarymotivation underlying almost all traditional MAC protocolsis energy awareness due to the characteristics of WSNssuch as severe resource constraints and harsh environmentalconditions However there is a rising need for efficientQoS-aware MAC protocols proportional to the increasingnumber of the fields of their applications such as health caresurveillance and process control

QoS-aware MAC protocols for WSNs are categorizedinto two trends protocols with differentiated service [4ndash8] and application-specific protocols [9 10] The formerprovide service differentiation by varying contentionwindow(CW) size contention slot selection probability transmissionslot scheduling interframe space (IFS) duration the backoffexponent and adaptation coefficients The latter fulfills theQoS requirements of specific applications that performmulti-media transmission vehicular communication tactical com-munication and so forth They attempt to provide hardsoftQoS bounds by employing various mechanisms such asadaptation and learning data suppression and aggregationerror control and clustering

A system for quality-aware voice streaming (QVS) inWSNs has most recently been proposed [11] QVS comprisesseveral novel components including an empirical modelfor online voice quality evaluation and control dynamicvoice compressionduplication adaptation for lossy wirelesslinks and distributed stream admission control that exploitsnetwork capacity for rate allocation

International Journal of Distributed Sensor Networks 3

23 Real-Time Voice Services in CRNs With the developmentof CR technology voice services are considered very impor-tant and useful in CRNs However scant research has beenconducted on the mathematical modeling of CRNs whileconsidering voice traffic For mathematical verification [16ndash19] assumed a fixed number of secondary users [16ndash18] onlyone wireless channel [17] or an infinite backlog model [18]Moreover traffic analyses developed in [16ndash19] ignored theeffect of unreliable spectrum sensing

More importantly the Call Admission Control (CAC)scheme has not been considered in [16ndash18] to guaranteeQoS for voice services Hence [16ndash18] did not consider theadmission control scheme with the call-level dynamics of thesystem CAC schemes for multimedia streaming have beenproposed in [21 22] These schemes assume that PUs andSUs generate traffic modeled by a Poisson arrival process andconsider call blocking and dropping probabilities to be QoSrequirements of admission control In this paper we deploythe infinite backlog model for the voice packet generationof each SU in order to measure the number of concurrentconnections For this we define the number of acceptableSUs in the network to satisfy the followingQoS requirementsdelay bound and delay bound violation probabilityThese aredescribed in Section 21

We calculate average packet delay and packet delay jitterfor packet-level analysis and use the number of acceptableSUs as the call-level performance metric However [21 22]use fragmentary approaches using performance metric Onlycall-level analysis was conducted in [21] due to which thedelay was unknown Contrary to [21] with call-level perfor-mance metric while [22] compared the proposed schemewith complete sharing in terms of packet-level performancemetrics its results were unrestricted by such delay boundsand delay bound violation probabilities

It is further assumed in [21 22] that a channel is only usedfor an SU to deliver its packet This is an impractical assump-tion that can lead to inefficient spectrum use Thus givena condition that satisfies QoS requirements our proposedscheme makes multiple SUs occupy a channel and contendwith one another based on IEEE 80211 DCF [23] in order tojudiciously use the channel

Of [16ndash22] the majority of studies concerned CCRNsThe central entity in these networks is a secondary basestation (SBS) a sink node and so forth A few [18 19]consider the DCRNs where the channel access of eachSU is controlled by a distributed MAC protocol In [18]slottedALOHAand round robin protocols were usedwithoutconsidering the accompanying control signaling overheadincurred for executing the protocols There was a limitationin [19] whereby each channel can be accessed only by oneSU The greater the number of SUs the greater the controloverhead required Thus this kind of overhead should beconsidered as it affects network performance

3 System Model

We consider a CR-enabled WSN as shown in Figure 1 Thenetwork consists of four kinds of nodes primary users (PUs)

PU

PU

PUSU

SU

SU

BB

CSI

ad hoc connection

CSICSI

CSI

JOIN

JOIN

JOIN

PBS

Figure 1 A CR-enabled WSN scenario for the proposed scheme

a primary base station (PBS) secondary users (SUs) anda bandwidth broker (BB) The PUs represent legacy nodeswith a license for occupied channels All channels licensedby PUs are monitored continuously by the PBS which candetermine the status of a given channel by estimating theavailable bandwidth as detailed in Section 41 The availablebandwidth estimated by the PBS is then delivered by periodi-cally transmitting a beacon message The BB is automaticallydetermined among SUs through an algorithm and is operatedas a central counterpart that synchronizes with other SUsand assigns spectrum resources in the network as detailedin Section 42 The BB receives the beacon message fromthe PBS and thus knows the status of the relevant channelThe BB then transmits a beacon message including theestimated available bandwidth periodically to SUs to notifythem regarding channel availability at any given time An SUrepresents an unlicensed user communicating with anotherSU in ad hoc connection as shown in Figure 1 The SUsare interested in real-time voice with stringent QoS require-ments Once SUs receive the beacon message they inquirewith the BB regarding a channel to transmit a real-time voiceby exploiting a JOIN message based on channel availabilityThe BB that receives requests admits or rejects them usingthe Call Admission Control with strict QoS requirementsdetailed in Section 43 The SU admitted by the BB sendsits voice traffic by contending with the other SUs over anassigned channel Note that all control signaling exceptcontention-based data transmission over assigned channelsis performed in a control channel

Figure 2 shows the temporal structure for the QoS provi-sion for real-time voice traffic in CR-enabled WSNs where asingle control channel aswell as119873pu data channels licensed byPUs existThe control channel allows the SUs to synchronizenotify the channel availabilities to the other SUs and requestresources for voice calls It is assumed that each SU hastwo half-duplex transceivers a data transceiver to transmitand receive data over PU channels and a control transceiverto exchange control packets over the control channel Thisapproach is called a dedicated control channel [25 26] inwireless networks such as CRNs that allow all SUs tolisten to the control channel at all times even during data


Controlchannel

Datachannel

Idle Idle Busy

Idle Busy Idle

Busy Idle Idle

1

2

JOINLEAVE(N)ACKt

t

Sensing Contention Transmission

Npu

TPBS (PBS beaconing period)

TBB (BB beaconing period)

Tsens Tctrl Tdata

Ts

middot middot middot



Figure 2 Temporal structure for real-time voice delivery in CR-enabled WSNs

transmission It is well known that this approach is suitablefor hybrid protocols for CRNs [13 27 28]

We further assume that time in the PU channels is dividedinto timeslots each of which has a duration of 119879

119904 The

channels are implemented by the ONOFF source modelwhich has been widely used in numerous studies [13] Itis a probabilistic model to determine channel states at thebeginning of each timeslot The channel states remain inthe ON (busy) and OFF (idle) with probabilities 120572 and 120573respectively

In order to use a timeslot at any given time the state ofthe PU channel is sensed by SUs assigned to the channel bythe BB during the sensing period (119879sens) at the beginningof the timeslot On the basis of the sensing result the PUchannel is classified as busy or idle within timeslots in thePU channels Each timeslot used in the PU channels isdetermined through contention which is based on IEEE80211 DCF [23] Following the contention phase (119879ctrl) theremaining time (119879data) within the timeslot is used for thewinner SU to transmit data Therefore the length of thetimeslot should be

119879119904ge 119879sens +119879ctrl +119879data (1)

4 Quality-Aware MAC for CR-Enabled WSNs

41 Available Bandwidth Estimation Available bandwidthestimation (ABE) is one of the most critical functions inall QoS mechanisms applicable to CRNs [29] A numberof studies on estimating the available bandwidth in wirelessnetworks have been conducted However it remains a chal-lenging problem in CRNs because the radio environmentchanges momentarily due to the activities of PUs and hencethe wireless bandwidth needs to be shared among SUs toprevent interference in the PUs in the network

In this paper we propose a practical approach for theBB to periodically estimate the available bandwidth of PUchannels Here it is assumed that channel states are classifiedinto busy and idle The passive listening method [29] is used

to estimate bandwidth The PBS is capable of continuouslymonitoring changes in channel state thus listens to allchannels to determine channel status and computes the busytime for 119879PBS The busy time of the 119894th channel in the 119905th 119879PBSis then obtained by

119879119894

busy (119905) = 119873119894

busy (119905) sdot 119879119904 (2)

where 119873119894

busy(119905) denotes the number of busy states of the 119894thchannel in the 119905th 119879PBS 119879

119894

busy(119905) is divided by the observationperiod 119879PBS to calculate the busy ratio

119877119894

busy (119905) =

119879119894

busy (119905)

119879PBS (3)

Therefore the PU channel utilization measured by PBS iswritten as

120588 = lim119879rarrinfin

1119879

119879

sum

119905=1

119873pu

sum

119894=1119877119894

busy (119905) (4)

As shown in Figure 1 BB performs a role in a centralentity that synchronizes with other SUs and assigns availablechannels to them in a CR-enabled WSN To this end itreceives the beaconmessage from the PBS to synchronize andknow the channel availabilities estimated by the PBS for eachbeaconing period (119879PBS) The BB sends the beacon messageat the beginning of its beaconing period (119879BB) to synchronizewith other SUs and notify them of the available bandwidthThe remaining time excluding 119879PBS and 119879BB is used for theSUs to request resources for voice calls through JOINACKexchanges as detailed in Section 43

42 Bandwidth Broker Selection The available bandwidthcan be controlled independently by users or by agents withsome knowledge of the priorities and policies of the relevantorganization such that they can allocate bandwidth withrespect to these policies Independent labeling by users is


simple to implement but unlikely to be sufficient for pertinentresource allocation since it is unreasonable to expect all usersto know all of their organizationrsquos priorities and network usepolicies and to always mark their traffic accordingly

In this CR-enabled WSN an agent called the bandwidthbroker (BB) is required to perform admission control in orderto determine whether an incoming voice call request will beaccepted and to synchronize with the SUs

For the proposed scheme a BB is required to period-ically send beacon messages thereby allowing each SU tosynchronize with the others and share its available band-width information through the network The procedure forselecting the BB is as follows An SU joining the CR networkfirst attempts to receive beacon messages periodically sentby the BB If it does not listen to any beacon messages for119870 consecutive 119879BB it is concluded that this is the first SUin the network Therefore this SU becomes the BB in thenetwork and proceeds to periodically send beacon messagesincluding available bandwidth information

Moreover for seamless voice call management a backupBB is required when the BB no longer exists An SU thatneeds voice service sends a voice call request that is a JOINmessage to the BB If the BB receives the message for the firsttime it responds with beacon messages to the effect that therelevant SU has been selected as the backup BB Hence thebackup BB can substitute for this role even though there is noBB in the network

43 Voice Call Admission Control To guarantee the QoS ofvoice traffic it is crucial to apply a proper CAC mechanismCAC is responsible for accepting and rejecting new voicecalls based on the available bandwidth to satisfy the QoSrequirements of all admitted voice calls Let 119873av be theaverage number of idle PU channels (119873av = [0119873pu]) Then

119873av =

119873pu

sum

119894=1119894 sdot (

119873pu

119894) sdot (1minus120588)

119894

sdot 120588119873puminus119894 (5)

The probability that an SU takes the chance to occupy anavailable PU channel is given by

119875su = min(1119873av119899

) (6)

where 119899 is the number of accepted SUs (119899 = [1119873su]) where119873su denotes the number of existing SUs in the networkContrary to (6) the probability that an SU does not obtainany available PU channel is

1198751015840

su = 1minus119875su (7)

Moreover the probability that a channel state secured byan SU changes from idle to busy is as follows

119875su = 119875su times (1minus120572) (8)

In order to identify a packet that satisfies the delay boundand the delay bound violation probability we need to knowthe number of timeslots used to serve a packet that has

t

A packetarrival

1 2 kmiddot middot middot k + 1k ndash 1ith ch

Figure 3 Voice packet arrival and the corresponding timeslots overthe 119894th channel

arrived Figure 3 shows an instance of voice packet arrival andthe corresponding timeslots over the 119894th channel

Thus we obtain the probability that an SU sends its packetat the next 119896th timeslot [119896 = [1 +infin) see Figure 3] once itspacket has been generated with 119899 as follows

119891 (119896 119899) = 119875119896= (1198751015840

su +119875su)(119896minus1)

sdot 119875su sdot 120572 (9)

The number of timeslots denoted by 119909 from the firsttimeslot where a packet is generated to the 119896th timeslot towhich it is successfully transmitted such that it exceeds thedelay bound denoted by 120575 is first required as follows

119909 = argmax119896

(119864 [119863119896] gt 120575) (10)

where ldquoarg maxrdquo represents the argument of the maximumand 119864[119863

119896] is the delay from the time a packet is generated

at the SU to when it is successfully transmitted from theoriginator as described in Section 44

With (9) and (10) the probability that the delay time119864[119863119896] for a packet to be transmitted exceeds the delay bound

is the sum of the probability that a packet is successfullytransmitted at the 119896th [119896 gt 119909 see Figure 3] timeslot Thuswe obtain

119865 (119896 119899) asymp 119875 (119864 [119863119896] gt 120575) = sum

119896gt119909

119875119896 (11)

Thus we can attain the maximum number of acceptableSUs as the call-level performance metric in the presence ofa constraint on the delay bound violation probability 120576 asfollows

119873ac = argmax119899

(119865 (119896 119899) le 120576) asymp argmax119899

(sum

119896gt119909

119875119896le 120576)

for 119896 = [1 +infin) 119899 = [1 119873su]

(12)

where 119873ac is the number of acceptable SUs in the networkand the maximum value 119873ac may be calculated through (12)as 119899 increases

Algorithm 1 is the procedure for Call Admission Controlin the BB to accept or reject call requests by SUs in thenetwork using (12) The BB first receives a beacon messagefrom the PBS and updates 119873ac using (12) because its systemcan be sent the QoS requirements that is the delay bound 120575

and its violation probability 120576 through packet marking [30]If 119873ac lt 119899 the BB broadcasts a beacon message to notify

of the compulsory withdrawal of (119899 minus 119873ac) number of SUs inthe network to all the SUs The BB then checks the message


Input 120575 120576Update 119873ac using (12) at the end of the 119905th 119879PBS

(1) if (119873ac lt 119899) then(2) It broadcasts beacon to notify of the withdrawal of (119899 ndash 119873ac) SUs in the network to all the SUs(3) end if(4)(5) if (rcvd msg)(6) if (rcvd msg == JOIN) and (119873ac ge 119899 + 1) then(7) It sends ACK to accept the SU in the network(8) else (ie if 119873ac lt 119899 + 1)(9) It sends NACK to reject the SU for the network(10) end if(11)(12) if (rcvd msg == LEAVE)(13) It sends ACK to allow the SU to leave the network(14) end if(15) end if

Algorithm 1 Voice Call Admission Control by BB

(rcvd msg) received from the SUs to decide whether to admitthe SUrsquos request in the network If the received message isJOIN and the available bandwidth is enough to accept an SUrsquosvoice call request in the network that is 119873ac ge 119899 + 1 itsends the ACK message to the SU to admit it to the networkOtherwise the BB sends the NACK message to the SU todeny its call request An SU completing the voice servicecan request a withdrawal using the LEAVE message The BBsimply allows the SU to leave the network using the ACKmessage

44 Voice Packet Delay Analysis Quality of service is a majorissue in real-time voice traffic The fluctuation in the avail-ability of licensed channels poses severe problemswith regardto guaranteeing acceptable QoS for voice users [15] Whenchannel availability varies with the activities of the PU onlicensed channels voice calls requested by the SUs should beaccordingly regulated to ensure voice service satisfactionTheservice requirement for voice calls is characterized by averagepacket delay and delay variations (jitter) at the packet levelThe specified end-to-end packet delay requirement refers tothe absolute value of delay experienced by voice packets Inthis section we analyze the average packet delay and thepacket delay jitter as packet-level performance metrics to testthe reliability of our proposed scheme

Packet delay is the amount of time it takes for a packetto travel from end to end Let 119864(119863

119896) be the average delay of

successfully transmitted packets from the 119896th timeslot [seeFigure 3]The delay119863

119896is the sum of delay times experienced

by a packet at the 119896th timeslot after it has been generated [seeFigure 3] 119864[119863

119896] is calculated as follows

119864 [119863119896] = 119896 sdot 119879

119904+119879sens +119879ctrl +119879

119905119909 (13)

where 119879ctrl = 120590(119882 minus 1)2 [31 32] 119882 and 120590 being thecontentionwindow size and a slot time respectively119879

119905119909is the

time taken by a packet to be successfully transmitted Hence

we can calculate the average packet delay [31 32] using (9)and (13)

119864 [119863] =

infin

sum

119896=1(119864 [119863

119896] 119875119896) (14)

If the delay is short and constant voice quality is unaf-fected Voice quality is affected by considerable packet delayvariation (jitter) that is the fluctuation from packet topacket in the time taken from the generation of a packet atthe source to its arrival at the receiver Accordingly using (9)and (14) we compute 119864[119863

2

] as follows

119864 [1198632] =

infin

sum

119896=1(119864 [119863

119896])

2119875119896 (15)

From (13) and (15) we can compute the packet delay jitter119869 of the packet delays [31 32]

119869 = radic119864 [1198632] minus (119864 [119863])2 (16)

5 Performance Evaluation

For the analytical and simulation-based results we usedMATLAB as performance analyzer The parametersemployed in the proposed scheme are shown in Table 1Unless otherwise specified the following parameters wereused in the plots shown in this section The number ofcontrol and PU channels was set to one and five respectivelyThe PBS and the BB transmit beacon messages every secondover the control channel to synchronize with other SUs andshare the available bandwidth Considering the IEEE 80211b[23] as the physical medium 119879DIFS 119879SIFS and 119879slot were setto 50 120583s 10 120583s and 20 120583s respectively The default value of 119879

119904

was set to 10ms in consideration of (1) G729 was consideredthe voice codec but IPUDPRTP headers included in itformed a considerable portion of the overhead In order to


Table 1 Parameters of the proposed scheme

Symbol Description Value120575 Delay bound (s) 015120576 Delay bound violation probability 001119871DATA Voice packet size (bits) 224119873ctrl Number of control channels 1119873pu Number of PU channels 5119877 Data rate (bps) 1000000119879BB Length of BB beaconing period (s) 10119879DIFS Length of DIFS (s) 000005119879119904

Length of timeslot (s) 001119879sens Length of sensing period (s) 000002119879SIFS Length of SIFS (s) 000001119879slot Length of backoff window (s) 000002

05

101520253035404550

01 02 03 04 05 06 07 08 09

Num

ber o

f acc

epta

ble S

Us

PU channel utilization

Analysis (Npu = 5)Simulation (Npu = 5)Analysis (Npu = 10)

Simulation (Npu = 10)Analysis (Npu = 15)Simulation (Npu = 15)

Figure 4 Analytical and simulation-based results for the numberof acceptable secondary users plotted against the channel utilizationof primary users with 119873pu = 5 10 15

reduce overhead we used compressed RTP (cRTP) due towhich the 119871DATA was 224 bits including the physical layerconvergence protocol (PLCP) header and the preamble ForQoS requirements the delay bound and the delay boundviolation probability were set to 150ms and 001 respectivelyWe assumed that voice services are capable of satisfying theQoS requirements of the system through packet marking[30]

All our numerical results were validated by our simula-tion To show this Figure 4 shows the number of acceptableSUs versus PU channel utilization with 119873pu = 5 10 15 Weobserved that the number of acceptable SUs increased linearlyas (a) PU channel utilization decreased and (b) the number ofPU channels increased This was because as PU channel uti-lization decreased or the number of PU channels increaseda greater amount of the available spectrum resources wereutilized For instancemore than 15 SUswere acceptable when119873pu = 10 and 120588 le 05 and 119873pu = 15 and 120588 le 06 Howeverwhen 119873pu = 5 it needed to be the case that 120588 le 01

It is necessary to check whether the proposed schemecould stably perform for SUs allowed to join the networkFigure 5 plots the average packet delay against packet delayjitter for whether the proposed scheme is applied where119873pu = 5 Figure 5(a) shows that the permitted SUs couldtransmit packets within 31ms on averageWhen the proposedscheme was not applied as the PU channel utilization orthe number of SUs increased the average packet delayexponentially increased This was because all SUs had accessto the PU channels regardless of channel conditions Thepacket delay jitter was an indicator of voice quality as shownin Figure 5(b) The proposed scheme on average exhibitedvery low delay jitter (lt1ms) in packet delivery On thecontrary when the proposed scheme was not applied QoSfor voice packet delivery could not be guaranteed becausepacket delay jitter increased as PU channel utilization and thenumber of SUs increased A serrated line appears in Figure 5because the system cannot admit a fraction of a voice call

Figure 6 shows the analytical results for the number ofacceptable SUs plotted against PU channel utilization with(a) 119873pu from 1 to 9 with a gradation of 1 (b) 119879

119904from 5ms

to 45ms with a gradation of 5ms and (c) 120575 from 50ms to250ms with a gradation of 25ms In the plots of Figure 6a 3D representation is used in order to simultaneouslyvisualize the effect of (a) (b) and (c) Figures 6(a) 6(b)and 6(c) commonly show that the number of acceptable SUsincreased as PU channel utilization decreased As in Figure 4Figure 6(a) shows that the increase in the number of PUchannels has a positive effect on the number of acceptableSUs Figure 6(b) shows that a reduction in the length of thetimeslot has a positive effect on the number of acceptableSUs Figure 6(c) shows that an increase in the delay boundhasan impact on the number of acceptable SUs In other wordsthe more the stringent delay bound the fewer the number ofthe SUs accepted Therefore we conclude that the number ofacceptable SUs is affected by the number of PU channels thelength of the timeslot and the delay bound

6 Conclusion

In this paper we proposed a quality-aware MAC protocolfor real-time voice delivery in CR-enabled WSNs For QoSprovision in CR-enabledWSNs we first address the temporalstructure of the system model A bandwidth broker as acentral entity for such CCRNs is selected automatically in theproposed temporal structureThe BB then synchronizes withother SUs and allocates the remaining resources utilized byPUs based on the estimated available bandwidth We noticedthat with regard toQoS requirements that is the delay boundand the delay bound violation probability we developed ananalytical model for evaluating the number of acceptable SUsfor call-level analysis as well as average packet delay andpacket delay jitter for the packet-level analysis We showedthat the number of acceptable SUs varied according to thecomposition of the number of PU channels the durationof the timeslot and the delay bound With the calculatedaverage packet delay and the packet delay jitter we confirmedthat the proposed scheme can stably ensure reliable packetdelivery to accepted voice users In spite of these challenges


0

005

01

015

02

025

03

01 02 03 04 05 06 07 08 09

Aver

age p

acke

t del

ay (s

)


wo CAC (Nsu = 5)

wo CAC (Nsu = 10)Proposed

(a) Average packet delay

01 02 03 04 05 06 07 08 09

Pack

et d

elay

jitte

r (s)


1E minus 04

1E minus 03

1E minus 02

1E minus 01

1E + 00

wo CAC (Nsu = 5)


(b) Packet delay jitter

Figure 5 Average packet delay and packet delay jitter plotted against PU channel utilization for whether the proposed scheme is appliedwhere 119873pu = 5

02

46

810

002

0406

081

05

1015202530


Number of PU channels

Num

ber o

f acc

epta

ble S

Us

(a) 119873pu = 1 to 9 by 1

0001

002003

004005

002

0406

081

05

1015202530

Length of timeslot (s

)


Num

ber o

f acc

epta

ble S

Us

(b) 119879119904= 0005 to 0045 by 0005

00501

01502

025

002

0406

081

05

1015202530


Delay bound (s)

Num

ber o

f acc

epta

ble S

Us

(c) 120575 = 005 to 025 by 0025

Figure 6 Variation in the number of acceptable SUs plotted against the channel utilization of PUs with (a) 119873pu = 1 to 9 by 1 (b) 119879119904= 0005

to 0045 by 0005 (c) 120575 = 005 to 025 by 0025


it is necessary for the proposed scheme to calculate optimalparameters to guarantee voice delivery

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work was supported by the National Research Founda-tion of Korea (NRF) grant funded by the Korea Government(MSIP) (no NRF-2015R1A2A2A01005577)

References

[1] M A Yigitel O D Incel and C Ersoy ldquoQoS-aware MACprotocols for wireless sensor networks a surveyrdquo ComputerNetworks vol 55 no 8 pp 1982ndash2004 2011

[2] R V Kulkarni A Forster and G K Venayagamoorthy ldquoCom-putational intelligence in wireless sensor networks a surveyrdquoIEEE Communications Surveys amp Tutorials vol 13 no 1 pp 68ndash96 2011

[3] T Watteyne A Molinaro M G Richichi and M DohlerldquoFrom MANET To IETF ROLL standardization a paradigmshift inWSN routing protocolsrdquo IEEE Communications Surveysamp Tutorials vol 13 no 4 pp 688ndash707 2011

[4] N Saxena A Roy and J Shin ldquoDynamic duty cycle andadaptive contention window based QoS-MAC protocol forwireless multimedia sensor networksrdquo Computer Networks vol52 no 13 pp 2532ndash2542 2008

[5] H Kim and S-G Min ldquoPriority-based QoS MAC protocolfor wireless sensor networksrdquo in Proceedings of the IEEEInternational Symposium on Parallel amp Distributed Processing(IPDPS rsquo09) pp 1ndash8 May 2009

[6] B Yahya and J Ben-Othman ldquoEnergy efficient and QoSaware medium access control for wireless sensor networksrdquoConcurrency and Computation Practice and Experience vol 22no 10 pp 1252ndash1266 2010

[7] I Slama B Shrestha B Jouaber and D Zeghlache ldquoA hybridMAC with prioritization for wireless sensor networksrdquo inProceedings of the 33rd IEEE Conference on Local ComputerNetworks (LCN rsquo08) pp 274ndash281 October 2008

[8] MA Yigitel OD Incel andC Ersoy ldquoDiff-MAC aQoS-awareMAC protocol with differentiated services and hybrid prioriti-zation for wireless multimedia sensor networksrdquo in Proceedingsof the ACM Symposium on QoS and Security for Wireless andMobile Networks (Q2SWinet rsquo10) pp 62ndash69 October 2010

[9] U Baroudi ldquoEQoSA energy and QoS aware MAC for wirelesssensor networksrdquo in Proceedings of the 9th International Sympo-sium on Signal Processing and Its Applications (ISSPA rsquo07) pp1ndash4 IEEE Sharjah UAE Feburary 2007

[10] P Suriyachai U Roedig and A Scott ldquoImplementation of aMAC protocol for QoS support in wireless sensor networksrdquoin Proceedings of the IEEE International Conference on PervasiveComputing and Communications (PerCom rsquo09) pp 1ndash6 IEEEGalveston Tex USA March 2009

[11] L Li G Xing L Sun and Y Liu ldquoA quality-aware voice stream-ing system for wireless sensor networksrdquo ACM Transactions onSensor Networks vol 10 no 4 article 61 25 pages 2014

[12] Z Liang S Feng D Zhao and X S Shen ldquoDelay performanceanalysis for supporting real-time traffic in a cognitive radio sen-sor networkrdquo IEEE Transactions on Wireless Communicationsvol 10 no 1 pp 325ndash335 2011

[13] I F Akyildiz W Lee and K R Chowdhury ldquoCRAHNscognitive radio ad hoc networksrdquo Ad Hoc Networks vol 7 no5 pp 810ndash836 2009

[14] A Alshamrani X S Shen and L L Xie ldquoQoS provisioningfor heterogeneous services in cooperative cognitive radio net-worksrdquo IEEE Journal on Selected Areas in Communications vol29 no 4 pp 819ndash830 2011

[15] V Mishra L C Tong and C Syin ldquoQoS based spectrum deci-sion framework for cognitive radio networksrdquo in Proceedings ofthe 18th IEEE International Conference on Networks (ICON rsquo12)pp 18ndash23 December 2012

[16] H Lee and D-H Cho ldquoCapacity improvement and analysis ofVoIP service in a cognitive radio systemrdquo IEEE Transactions onVehicular Technology vol 59 no 4 pp 1646ndash1651 2010

[17] P Wang D Niyato and H Jiang ldquoVoice-service capacityanalysis for cognitive radio networksrdquo IEEE Transactions onVehicular Technology vol 59 no 4 pp 1779ndash1790 2010

[18] S Gunawardena and W Zhuang ldquoVoice capacity of cognitiveradio networks for both centralized and distributed channelaccess controlrdquo in Proceedings of the IEEE Global Communica-tion Conference (GLOBECOM rsquo10) pp 1ndash5 December 2010

[19] F Wang J Zhu J Huang and Y Zhao ldquoAdmission controland channel allocation for supporting real-time applicationsin cognitive radio networksrdquo in Proceedings of the IEEEGlobal Communications Conference (GLOBECOM rsquo10) pp 1ndash6December 2010

[20] S L Castellanos-Lopez F A Cruz-PerezM E Rivero-Angelesand G Hernandez-Valdez ldquoJoint connection level and packetlevel analysis of cognitive radio networkswith voip trafficrdquo IEEEJournal on Selected Areas in Communications vol 32 no 3 pp601ndash614 2014

[21] Y Y Mihov and B P Tsankov ldquoCognitive system with VoIPsecondary users over VoIP primary usersrdquo in Proceedings of the3rd International Conference on Advanced Cognitive Technolo-gies and Applications (COGNITIVE rsquo11) pp 30ndash35 September2011

[22] E S Hosseini V Esmaeelzadeh R Berangi and O B AkanldquoA correlation-based and spectrum-aware admission controlmechanism for multimedia streaming in cognitive radio sensornetworksrdquo International Journal of Communication Systems2015

[23] IEEE Standard 80211-2012 Wireless LAN Medium Access Con-trol (MAC) and Physical Layer (PHY) Specifications 2012

[24] A Kumar DManjunath and J KuriCommunication Network-ing An Analytical Approach Elsevier 1st edition 2004

[25] J Mo H-S So and J Walrand ldquoComparison of multichannelMAC protocolsrdquo IEEE Transactions on Mobile Computing vol7 no 1 pp 50ndash65 2008

[26] A De Domenico E Calvanese Strinati and M-G DiBenedetto ldquoA survey on MAC strategies for cognitive radionetworksrdquo IEEE Communications Surveys amp Tutorials vol 14no 1 pp 21ndash44 2012

[27] S C Jha U Phuyal M M Rashid and V K Bhargava ldquoDesignof OMC-MAC an opportunistic multi-channel MACwith QoSprovisioning for distributed cognitive radio networksrdquo IEEETransactions on Wireless Communications vol 10 no 10 pp3414ndash3425 2011


[28] S Kwon B S Kim and B H Roh ldquoPreemptive opportunisticMAC protocol in distributed cognitive radio networksrdquo IEEECommunications Letters vol 18 no 7 pp 1155ndash1158 2014

[29] Y Peng Y Yu L Guo D Jiang and Q Gai ldquoAn efficient jointchannel assignment and QoS routing protocol for IEEE 80211multi-radio multi-channel wireless mesh networksrdquo Journal ofNetwork and Computer Applications vol 36 no 2 pp 843ndash8572013

[30] Traffic Classification CISCO WAN and Application Optimiza-tion Solution Guide Document Version 11 Cisco Systems Inc2008

[31] P Raptis V Vitsas P Chatzimisios and K Paparrizos ldquoDelayjitter analysis of 80211 DCFrdquo Electronics Letters vol 43 no 25pp 1472ndash1474 2007

[32] M Li M Claypool and R Kinicki ldquoPacket dispersion inIEEE 80211 wireless networksrdquo in Proceedings of the 31st IEEEConference on Local Computer Networks (LCN rsquo06) pp 721ndash729IEEE Tampa Fla USA November 2006

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Active and Passive Electronic Components

Control Scienceand Engineering

Journal of



RotatingMachinery


Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design



Shock and Vibration


Civil EngineeringAdvances in

Acoustics and VibrationAdvances in



Electrical and Computer Engineering

Journal of

Advances inOptoElectronics


Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of


Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014


Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation



DistributedSensor Networks



of PUs on licensed channels voice calls requested by SUsshould accordingly be regulated to ensure the satisfaction ofQoS requirements Thus unlike traditional QoS provisionwhich relies primarily on traffic statistics providing QoS forSUs should be implemented through spectrum sensing spec-trum access and the admission control across the relevantnetwork layers [14]

Some research has been conducted in recent years onmodeling CRNs with voice traffic [16ndash22] but this is insuffi-cient Furthermore from the viewpoint of network architec-turemost past research onCCRNshas been conducted underunrealistic assumptions which we detail in Section 23

In this paper we propose a quality-ware MAC protocolfor real-time voice delivery in CR-enabled WSNs For moreefficient Call Admission Control (CAC) for voice traffic wepropose a temporal structure with periodic timeslots forCR-enabledWSNsThe IEEE 80211 distributed coordinationfunction (DCF) [23] is applied to several SUs to avoid inter-ference with PUs in a timeslot Furthermore a bandwidthbroker (BB) is automatically determined by the proposedtemporal structure and operates as a central counterpart inthe network The BB is responsible for identifying availableresources in PU channels and assigning them to SUs Wethus develop an analytical model for the satisfaction of QoSrequirements by the CAC We used delay bound and itsviolation probability as QoS requirements and calculatedthe following packet-level and call-level performancemetricsusing ourmodel average packet delay packet delay jitter andthe number of acceptable SUs

The rest of this paper is organized as follows In Section 2we describe theQoS requirements for real-time voice deliveryas well as research in the area related to QoS-aware MACprotocols The system model and operation of our proposedscheme are described in Sections 3 and 4 respectivelyIn Section 5 we detail the analytical and simulation-basedresults obtained from the proposed scheme We offer ourconclusions in Section 6

2 Related Work

21 QoS Requirements for Real-Time Voice The pattern ofpacket arrivals closely follows that of speech generationthat is this source of traffic exhibits ldquointrinsic temporalbehaviorrdquo [24] and this patternmust be preserved for faithfulreproduction of the speech at the receiverrsquos end The packetnetwork will introduce delay fixed propagation delay aswell as queuing delay that can vary from packet to packetHence the network cannot serve such a source at arbitraryrates as in the case of elastic traffic In fact depending onthe adaptability of a stream source the network may needto reserve bandwidth and buffers in order to provide anadequate transport service to a stream source Applicationssuch as real-time voice and video conferencing are examplesof stream sources

The following are typical QoS requirements of streamsources

(i) Delay (Average and Variation (Jitter)) real-time inter-active traffic requires tight control of end-to-end

delays For example for voice packets the end-to-enddelay may need to be controlled for it to be shorterthan the delay bound with a violation probability ofless than 001

(ii) Packet Loss due to the high levels of redundancy inspeech and images a certain amount of packet lossis imperceptible For example in voice packets whereeach packet carries 20ms of speech and the receiverconducts lost packet interpolation 5 to 10 of thepackets can be lost without significant degradation ofspeech quality Due to delay constraints the accept-able packet loss target cannot be attained by firstlosing and then recovering the lost packets in otherwords stream traffic expects a specific ldquopacket lossratiordquo from the packet transport service

In this paper as well as the aforementioned packet-levelperformancemetrics that is average packet delay and packetdelay jitter we define the number of acceptable SUs that isthe number of voice calls in CR-enabled WSNs as a call-level performance metric We assume that no packet lossoccurs in the network because only SUs are accepted whenachieving QoS requirements and thus the relevant packetsare transmitted successfully

22 QoS-Aware MAC Protocols for WSNs The MAC layerof the architecture stack plays a key role in QoS provisionbecause the upper layers cannot be accessed without theassumption of a MAC protocol that solves the problemsof medium sharing and supports reliable communicationVarious MAC protocols for WSNs have been proposedfor decades but few consider QoS support The primarymotivation underlying almost all traditional MAC protocolsis energy awareness due to the characteristics of WSNssuch as severe resource constraints and harsh environmentalconditions However there is a rising need for efficientQoS-aware MAC protocols proportional to the increasingnumber of the fields of their applications such as health caresurveillance and process control

QoS-aware MAC protocols for WSNs are categorizedinto two trends protocols with differentiated service [4ndash8] and application-specific protocols [9 10] The formerprovide service differentiation by varying contentionwindow(CW) size contention slot selection probability transmissionslot scheduling interframe space (IFS) duration the backoffexponent and adaptation coefficients The latter fulfills theQoS requirements of specific applications that performmulti-media transmission vehicular communication tactical com-munication and so forth They attempt to provide hardsoftQoS bounds by employing various mechanisms such asadaptation and learning data suppression and aggregationerror control and clustering

A system for quality-aware voice streaming (QVS) inWSNs has most recently been proposed [11] QVS comprisesseveral novel components including an empirical modelfor online voice quality evaluation and control dynamicvoice compressionduplication adaptation for lossy wirelesslinks and distributed stream admission control that exploitsnetwork capacity for rate allocation







3 System Model


PU

PU

PUSU

SU

SU

BB

CSI

ad hoc connection

CSICSI

CSI

JOIN

JOIN

JOIN

PBS





Controlchannel

Datachannel

Idle Idle Busy

Idle Busy Idle

Busy Idle Idle

1

2

JOINLEAVE(N)ACKt

t


Npu



Tsens Tctrl Tdata

Ts







119904 The



119879119904ge 119879sens +119879ctrl +119879data (1)





119879119894

busy (119905) = 119873119894

busy (119905) sdot 119879119904 (2)

where 119873119894


119894


119877119894

busy (119905) =

119879119894

busy (119905)

119879PBS (3)



1119879

119879

sum

119905=1

119873pu

sum

119894=1119877119894

busy (119905) (4)









119873av =

119873pu

sum

119894=1119894 sdot (

119873pu

119894) sdot (1minus120588)

119894

sdot 120588119873puminus119894 (5)


119875su = min(1119873av119899

) (6)


1198751015840

su = 1minus119875su (7)


119875su = 119875su times (1minus120572) (8)


t

A packetarrival





119891 (119896 119899) = 119875119896= (1198751015840

su +119875su)(119896minus1)

sdot 119875su sdot 120572 (9)


119909 = argmax119896

(119864 [119863119896] gt 120575) (10)






119865 (119896 119899) asymp 119875 (119864 [119863119896] gt 120575) = sum

119896gt119909

119875119896 (11)


119873ac = argmax119899

(119865 (119896 119899) le 120576) asymp argmax119899

(sum

119896gt119909

119875119896le 120576)

for 119896 = [1 +infin) 119899 = [1 119873su]

(12)

















119864 [119863119896] = 119896 sdot 119879

119904+119879sens +119879ctrl +119879

119905119909 (13)


119905119909is the



119864 [119863] =

infin

sum

119896=1(119864 [119863

119896] 119875119896) (14)


2

] as follows

119864 [1198632] =

infin

sum

119896=1(119864 [119863

119896])

2119875119896 (15)


119869 = radic119864 [1198632] minus (119864 [119863])2 (16)



119904






05

101520253035404550

01 02 03 04 05 06 07 08 09

Num

ber o

f acc

epta

ble S

Us









119904from 5ms


6 Conclusion



0

005

01

015

02

025

03

01 02 03 04 05 06 07 08 09

Aver

age p

acke

t del

ay (s

)


wo CAC (Nsu = 5)



01 02 03 04 05 06 07 08 09

Pack

et d

elay

jitte

r (s)


1E minus 04

1E minus 03

1E minus 02

1E minus 01

1E + 00

wo CAC (Nsu = 5)




02

46

810

002

0406

081

05

1015202530



Num

ber o

f acc

epta

ble S

Us

(a) 119873pu = 1 to 9 by 1

0001

002003

004005

002

0406

081

05

1015202530


)


Num

ber o

f acc

epta

ble S

Us

(b) 119879119904= 0005 to 0045 by 0005

00501

01502

025

002

0406

081

05

1015202530


Delay bound (s)

Num

ber o

f acc

epta

ble S

Us

(c) 120575 = 005 to 025 by 0025


to 0045 by 0005 (c) 120575 = 005 to 025 by 0025





Acknowledgment


References




































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation















3 System Model


PU

PU

PUSU

SU

SU

BB

CSI

ad hoc connection

CSICSI

CSI

JOIN

JOIN

JOIN

PBS





Controlchannel

Datachannel

Idle Idle Busy

Idle Busy Idle

Busy Idle Idle

1

2

JOINLEAVE(N)ACKt

t


Npu



Tsens Tctrl Tdata

Ts







119904 The



119879119904ge 119879sens +119879ctrl +119879data (1)





119879119894

busy (119905) = 119873119894

busy (119905) sdot 119879119904 (2)

where 119873119894


119894


119877119894

busy (119905) =

119879119894

busy (119905)

119879PBS (3)



1119879

119879

sum

119905=1

119873pu

sum

119894=1119877119894

busy (119905) (4)









119873av =

119873pu

sum

119894=1119894 sdot (

119873pu

119894) sdot (1minus120588)

119894

sdot 120588119873puminus119894 (5)


119875su = min(1119873av119899

) (6)


1198751015840

su = 1minus119875su (7)


119875su = 119875su times (1minus120572) (8)


t

A packetarrival





119891 (119896 119899) = 119875119896= (1198751015840

su +119875su)(119896minus1)

sdot 119875su sdot 120572 (9)


119909 = argmax119896

(119864 [119863119896] gt 120575) (10)






119865 (119896 119899) asymp 119875 (119864 [119863119896] gt 120575) = sum

119896gt119909

119875119896 (11)


119873ac = argmax119899

(119865 (119896 119899) le 120576) asymp argmax119899

(sum

119896gt119909

119875119896le 120576)

for 119896 = [1 +infin) 119899 = [1 119873su]

(12)

















119864 [119863119896] = 119896 sdot 119879

119904+119879sens +119879ctrl +119879

119905119909 (13)


119905119909is the



119864 [119863] =

infin

sum

119896=1(119864 [119863

119896] 119875119896) (14)


2

] as follows

119864 [1198632] =

infin

sum

119896=1(119864 [119863

119896])

2119875119896 (15)


119869 = radic119864 [1198632] minus (119864 [119863])2 (16)



119904






05

101520253035404550

01 02 03 04 05 06 07 08 09

Num

ber o

f acc

epta

ble S

Us









119904from 5ms


6 Conclusion



0

005

01

015

02

025

03

01 02 03 04 05 06 07 08 09

Aver

age p

acke

t del

ay (s

)


wo CAC (Nsu = 5)



01 02 03 04 05 06 07 08 09

Pack

et d

elay

jitte

r (s)


1E minus 04

1E minus 03

1E minus 02

1E minus 01

1E + 00

wo CAC (Nsu = 5)




02

46

810

002

0406

081

05

1015202530



Num

ber o

f acc

epta

ble S

Us

(a) 119873pu = 1 to 9 by 1

0001

002003

004005

002

0406

081

05

1015202530


)


Num

ber o

f acc

epta

ble S

Us

(b) 119879119904= 0005 to 0045 by 0005

00501

01502

025

002

0406

081

05

1015202530


Delay bound (s)

Num

ber o

f acc

epta

ble S

Us

(c) 120575 = 005 to 025 by 0025


to 0045 by 0005 (c) 120575 = 005 to 025 by 0025





Acknowledgment


References




































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Controlchannel

Datachannel

Idle Idle Busy

Idle Busy Idle

Busy Idle Idle

1

2

JOINLEAVE(N)ACKt

t


Npu



Tsens Tctrl Tdata

Ts







119904 The



119879119904ge 119879sens +119879ctrl +119879data (1)





119879119894

busy (119905) = 119873119894

busy (119905) sdot 119879119904 (2)

where 119873119894


119894


119877119894

busy (119905) =

119879119894

busy (119905)

119879PBS (3)



1119879

119879

sum

119905=1

119873pu

sum

119894=1119877119894

busy (119905) (4)









119873av =

119873pu

sum

119894=1119894 sdot (

119873pu

119894) sdot (1minus120588)

119894

sdot 120588119873puminus119894 (5)


119875su = min(1119873av119899

) (6)


1198751015840

su = 1minus119875su (7)


119875su = 119875su times (1minus120572) (8)


t

A packetarrival





119891 (119896 119899) = 119875119896= (1198751015840

su +119875su)(119896minus1)

sdot 119875su sdot 120572 (9)


119909 = argmax119896

(119864 [119863119896] gt 120575) (10)






119865 (119896 119899) asymp 119875 (119864 [119863119896] gt 120575) = sum

119896gt119909

119875119896 (11)


119873ac = argmax119899

(119865 (119896 119899) le 120576) asymp argmax119899

(sum

119896gt119909

119875119896le 120576)

for 119896 = [1 +infin) 119899 = [1 119873su]

(12)

















119864 [119863119896] = 119896 sdot 119879

119904+119879sens +119879ctrl +119879

119905119909 (13)


119905119909is the



119864 [119863] =

infin

sum

119896=1(119864 [119863

119896] 119875119896) (14)


2

] as follows

119864 [1198632] =

infin

sum

119896=1(119864 [119863

119896])

2119875119896 (15)


119869 = radic119864 [1198632] minus (119864 [119863])2 (16)



119904






05

101520253035404550

01 02 03 04 05 06 07 08 09

Num

ber o

f acc

epta

ble S

Us









119904from 5ms


6 Conclusion



0

005

01

015

02

025

03

01 02 03 04 05 06 07 08 09

Aver

age p

acke

t del

ay (s

)


wo CAC (Nsu = 5)



01 02 03 04 05 06 07 08 09

Pack

et d

elay

jitte

r (s)


1E minus 04

1E minus 03

1E minus 02

1E minus 01

1E + 00

wo CAC (Nsu = 5)




02

46

810

002

0406

081

05

1015202530



Num

ber o

f acc

epta

ble S

Us

(a) 119873pu = 1 to 9 by 1

0001

002003

004005

002

0406

081

05

1015202530


)


Num

ber o

f acc

epta

ble S

Us

(b) 119879119904= 0005 to 0045 by 0005

00501

01502

025

002

0406

081

05

1015202530


Delay bound (s)

Num

ber o

f acc

epta

ble S

Us

(c) 120575 = 005 to 025 by 0025


to 0045 by 0005 (c) 120575 = 005 to 025 by 0025





Acknowledgment


References




































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation















119873av =

119873pu

sum

119894=1119894 sdot (

119873pu

119894) sdot (1minus120588)

119894

sdot 120588119873puminus119894 (5)


119875su = min(1119873av119899

) (6)


1198751015840

su = 1minus119875su (7)


119875su = 119875su times (1minus120572) (8)


t

A packetarrival





119891 (119896 119899) = 119875119896= (1198751015840

su +119875su)(119896minus1)

sdot 119875su sdot 120572 (9)


119909 = argmax119896

(119864 [119863119896] gt 120575) (10)






119865 (119896 119899) asymp 119875 (119864 [119863119896] gt 120575) = sum

119896gt119909

119875119896 (11)


119873ac = argmax119899

(119865 (119896 119899) le 120576) asymp argmax119899

(sum

119896gt119909

119875119896le 120576)

for 119896 = [1 +infin) 119899 = [1 119873su]

(12)

















119864 [119863119896] = 119896 sdot 119879

119904+119879sens +119879ctrl +119879

119905119909 (13)


119905119909is the



119864 [119863] =

infin

sum

119896=1(119864 [119863

119896] 119875119896) (14)


2

] as follows

119864 [1198632] =

infin

sum

119896=1(119864 [119863

119896])

2119875119896 (15)


119869 = radic119864 [1198632] minus (119864 [119863])2 (16)



119904






05

101520253035404550

01 02 03 04 05 06 07 08 09

Num

ber o

f acc

epta

ble S

Us









119904from 5ms


6 Conclusion



0

005

01

015

02

025

03

01 02 03 04 05 06 07 08 09

Aver

age p

acke

t del

ay (s

)


wo CAC (Nsu = 5)



01 02 03 04 05 06 07 08 09

Pack

et d

elay

jitte

r (s)


1E minus 04

1E minus 03

1E minus 02

1E minus 01

1E + 00

wo CAC (Nsu = 5)




02

46

810

002

0406

081

05

1015202530



Num

ber o

f acc

epta

ble S

Us

(a) 119873pu = 1 to 9 by 1

0001

002003

004005

002

0406

081

05

1015202530


)


Num

ber o

f acc

epta

ble S

Us

(b) 119879119904= 0005 to 0045 by 0005

00501

01502

025

002

0406

081

05

1015202530


Delay bound (s)

Num

ber o

f acc

epta

ble S

Us

(c) 120575 = 005 to 025 by 0025


to 0045 by 0005 (c) 120575 = 005 to 025 by 0025





Acknowledgment


References




































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation





















119864 [119863119896] = 119896 sdot 119879

119904+119879sens +119879ctrl +119879

119905119909 (13)


119905119909is the



119864 [119863] =

infin

sum

119896=1(119864 [119863

119896] 119875119896) (14)


2

] as follows

119864 [1198632] =

infin

sum

119896=1(119864 [119863

119896])

2119875119896 (15)


119869 = radic119864 [1198632] minus (119864 [119863])2 (16)



119904






05

101520253035404550

01 02 03 04 05 06 07 08 09

Num

ber o

f acc

epta

ble S

Us









119904from 5ms


6 Conclusion



0

005

01

015

02

025

03

01 02 03 04 05 06 07 08 09

Aver

age p

acke

t del

ay (s

)


wo CAC (Nsu = 5)



01 02 03 04 05 06 07 08 09

Pack

et d

elay

jitte

r (s)


1E minus 04

1E minus 03

1E minus 02

1E minus 01

1E + 00

wo CAC (Nsu = 5)




02

46

810

002

0406

081

05

1015202530



Num

ber o

f acc

epta

ble S

Us

(a) 119873pu = 1 to 9 by 1

0001

002003

004005

002

0406

081

05

1015202530


)


Num

ber o

f acc

epta

ble S

Us

(b) 119879119904= 0005 to 0045 by 0005

00501

01502

025

002

0406

081

05

1015202530


Delay bound (s)

Num

ber o

f acc

epta

ble S

Us

(c) 120575 = 005 to 025 by 0025


to 0045 by 0005 (c) 120575 = 005 to 025 by 0025





Acknowledgment


References




































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation













05

101520253035404550

01 02 03 04 05 06 07 08 09

Num

ber o

f acc

epta

ble S

Us









119904from 5ms


6 Conclusion



0

005

01

015

02

025

03

01 02 03 04 05 06 07 08 09

Aver

age p

acke

t del

ay (s

)


wo CAC (Nsu = 5)



01 02 03 04 05 06 07 08 09

Pack

et d

elay

jitte

r (s)


1E minus 04

1E minus 03

1E minus 02

1E minus 01

1E + 00

wo CAC (Nsu = 5)




02

46

810

002

0406

081

05

1015202530



Num

ber o

f acc

epta

ble S

Us

(a) 119873pu = 1 to 9 by 1

0001

002003

004005

002

0406

081

05

1015202530


)


Num

ber o

f acc

epta

ble S

Us

(b) 119879119904= 0005 to 0045 by 0005

00501

01502

025

002

0406

081

05

1015202530


Delay bound (s)

Num

ber o

f acc

epta

ble S

Us

(c) 120575 = 005 to 025 by 0025


to 0045 by 0005 (c) 120575 = 005 to 025 by 0025





Acknowledgment


References




































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










0

005

01

015

02

025

03

01 02 03 04 05 06 07 08 09

Aver

age p

acke

t del

ay (s

)


wo CAC (Nsu = 5)



01 02 03 04 05 06 07 08 09

Pack

et d

elay

jitte

r (s)


1E minus 04

1E minus 03

1E minus 02

1E minus 01

1E + 00

wo CAC (Nsu = 5)




02

46

810

002

0406

081

05

1015202530



Num

ber o

f acc

epta

ble S

Us

(a) 119873pu = 1 to 9 by 1

0001

002003

004005

002

0406

081

05

1015202530


)


Num

ber o

f acc

epta

ble S

Us

(b) 119879119904= 0005 to 0045 by 0005

00501

01502

025

002

0406

081

05

1015202530


Delay bound (s)

Num

ber o

f acc

epta

ble S

Us

(c) 120575 = 005 to 025 by 0025


to 0045 by 0005 (c) 120575 = 005 to 025 by 0025





Acknowledgment


References




































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation













Acknowledgment


References




































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation

















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









Research Article MAC Protocol for Quality-Aware Real...

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