research article psfcs: robust emergency communications...

Research ArticlePSFCS Robust Emergency Communications Supporting HighMobility Based on WiMAX MMR Networks

Wen-Kang Jia12 Chia-Yao Chen2 and Yaw-Chung Chen2

1 Smart Network System Institute (SNSI) Institute for Information Industry (III) Taipei Taiwan2Department of Computer Science National Chiao Tung University (NCTU) 1001 University RoadHsinchu 300 Taiwan

Correspondence should be addressed to Chia-Yao Chen raycs96gnctuedutw

Received 2 October 2013 Revised 20 February 2014 Accepted 12 March 2014 Published 16 April 2014

Academic Editor Hai Vu

Copyright copy 2014 Wen-Kang Jia 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

Nowadays public safety networks are widely deployed to support highly reliable wireless communications in case of emergencyTheadoption of standardized systems such as WiMAX for emergency communications represents a significant advance in the off-the-shelf technologies for error detection and error correction Since it is difficult to fully eliminate the Doppler effect under high speedmoving environment we propose an enhanced CRC-based error correction scheme that carries as much extra segmented frameCheck Sequence (FCS) information as subblocks of emergency multicastbroadcast service (MBS) frame called progressive andselective frame check sequence (PSFCS) In a mobile multihop relay (MMR) environment a high-mobility mobile station mightreceive an emergencyMBS framemore than once so the PSFCS could be cross-referenced by duplicated frames receivedThereforethe PSFCS achieves a significant performance improvement over the legacy FCS scheme in terms of error detection and correctionof emergency MBS frames in a WiMAX MMR network operating in transparent mode The experimental results show that thegoodput and utilization of high-mobility mobile stations can be improved remarkably

1 Introduction

More and more natural disasters and anthropogenic hazardshave been causing great damage around the world [1ndash4] Oneoften cited use case for vehicular networks is applications thatrelate to vehicles emergency communications [3 5] Emer-gency communications are methods whereby local regionalor national authorities can contact masses to warn themof an impending emergency such as weather emergenciesgeological disasters industrial disasters radiological disas-ters medical emergencies and warfare or acts of terrorismToday emergency communication system is an importantconstitution part of traffic monitoring on modern express-way systems As soon as an emergency event occurs theadjacent communication infrastructure may be overloadeddegraded or destroyed Ensuring communication amongfirst responders especially during a crisis is amajor challengefor public safety agencies Since interoperability is critical

for success we need a versatile system which can rapidlybe deployed at every emergency scene For this reasonthe robust channel of emergency communication system isstudied To meet the actual condition of expressway systemsa so-called progressive and selective frame check sequence(PSFCS) for robust emergency communication based onWiMAX MMR networks is developed and the correspond-ing structure of hardware and software is depicted Thispaper focuses on the high mobility of WiMAX applicationwhich we call ldquoWiMAX Mobile Emergency CommunicationSystemrdquo

The rest of the paper is organized as followsTheWiMAXMMR-based emergency communications for expressway sys-tems are described in Section 2 In Section 3 we discuss theproposed scheme in detail In Section 4 the simulation andnumerical results are presented for evaluating the perfor-mance Section 5 concludes the work

Hindawi Publishing CorporationInternational Journal of Distributed Sensor NetworksVolume 2014 Article ID 254753 11 pageshttpdxdoiorg1011552014254753

2 International Journal of Distributed Sensor Networks

2 Emergency Communications for ExpresswaySystems and Problem Statements

21 Intelligent Traffic Systems (ITS) and Vehicle Ad HocNetworks (VANET) and Emergency Communications SystemsEmergency communication system could use wireless com-munication to warn other vehicle drivers or to preempt trafficlights Such an application can reduce accident risks duringemergency response trips and help save valuable time [3 5]We outline a comprehensive design of such an emergencyvehicle warning system that makes full use of intervehi-cle communication (aka vehicle-to-vehicle V2V) but alsoencompasses roadside wireless communication infrastruc-ture (aka vehicle-to-infrastructure V2I) In such systemsvehicle drivers are not simply warned of an approachingaccident location they also receive detailed route informa-tion Based on such emergency information timely andappropriate reaction of other vehicle drivers is possibleTherefore drivers can react early or correctly which may beuseful in responding to and recovering from emergencies

VANET is one of the representative emerging tech-nologies in telematics and intelligent traffic systems (ITS)Coordination of communications among vehicles (V2V)or between vehicles and road-side-units (V2I) can providevarious intelligent and telematics-related services The recentemergence of ubiquitous wireless connectivity such as dedi-cated short range communication (DSRC) and WiMAX hastriggered immense interest in the possibilities of connectivityamong moving vehicles Regarding the V2I communicationsof VANET orthogonal frequency division multiple access(OFDMA) has become a popular modulation technique forhigh speed wireless communications By using the multi-carrier modulation when transmitting signals through noisychannels OFDMA is able to mitigate the detrimental effectsof multipath fading using a simple one-tap equalizer Thereis a growing need to quickly transmit information wirelesslyand accurately and OFDMA is a suitable technique for highdata rate transmission with an appropriate error controlscheme over wireless channels and it has been developed intopopular wideband digital communication systems such asWiMAX which is already widely deployed inmany countriesand is igniting the mobile broadband revolution

Recently mobile stations in vehicles or trains have beengradually encountering some communication problems suchas intersymbol interference (ISI) intercarrier interference(ICI) and fading and Doppler effect This research willmainly focus on the Doppler effect of signals between atransmitter and a fast moving receiver The Doppler shiftnot only changed the frequency of the incoming signal butalso squeezed it into a slightly shorter time period As aresult the OFDMA receiver may be unable to recognize thetiming pulse in its expected time interval thus the incomingdata stream may become unreadable and that can seriouslyaffect the performance of mobile communications In suchcase effective error control schemes must be deployed toensure the reliability of OFDMA-based wireless networksTwo mechanisms are commonly deployed to accommodatethe error control automatic repeat request (ARQ) mecha-nism and the hybrid ARQ (HARQ) mechanism which are

implemented in the logical link control (LLC) sublayer of themedium access control (MAC) layer and the physical layer(PHY) respectively

22 Deploying Emergency Communications Systems UsingWiMAXMMR Technologies A plethora of potential applica-tions for high speed vehicle environments has been proposedin the areas of public safety traffic infrastructure manage-ment information notification and entertainment [3 4 6]Among them safety-related applications attract the mostattention through V2I wireless communications [1] Futureemergency communications for public safety will demanda mobile broadband service migrating from the currentlydominant voice-only mode to multimedia applications Theuse of common standard-based commercial technologiesas an alternative approach to conventional land wirelessnetwork infrastructures was introduced Many public safetyorganizations have used WiMAX systems to take advan-tage of the common access and minimal costs availablein the license-exempt spectrum bands Several shortfallsto using this method for public safety communicationswere also addressed [2] One of the major issues related toWiMAX is the limited range resulting from the maximummobility available coupled with the restrictions associatedwith the interference acceptance requirements This paperaddresses the emergency communications of high speedmobile WiMAX and suggests how to improve it as well asmake it a viable candidate for use by public safety agenciesThe enhanced multicastbroadcast service (E-MBS) feature ofthe mobile network is a promising technology for providingemergency services because it allows simultaneous deliveryof emergency messages to large-scale user communities ina cost effective manner Using E-MBS a certain part withineach superframe can be set aside for multicast-only orbroadcast-only data The entire frame can also be designatedas a downlink-only broadcast frame A major task of theE-MBS module is to provide a reliable sequence of E-MBS frames to multiple recipients simultaneously Thus theemergency message transfer might repeat until all data arereceived by all the receivers whether intended or unintendedIf the E-MBS feedback is enabled one or multiple cellswould receive the information about downlink multicastand broadcast service Typically the multicast and broadcastservice is a downlink-only transmission and has no uplinkmechanism to send feedback to the base station however ifa bidirectional RF carrier is aggregated with a downlink-onlyRF carrier the feedbackmay be sent through the bidirectionalRF carrier In this situation the mobile stations can usea common uplink channel to transmit E-MBS feedback Ifthe predefined feedback condition was satisfied an ACK orNACK is transmitted through this E-MBS feedback channel[7]

Most safety-related applications particularly for highspeed vehicles require fast and reliable emergency mes-sage dissemination through broadcast [6 8] However theconventional broadcast mechanism is neither efficient norreliable because it results in low network performance andhigh network deployment cost Therefore the relay station

International Journal of Distributed Sensor Networks 3

(RS) is an effective technology to achieve cost effectivedeployment that provides methods for high data rate deliverywith high correctness To achieve a more cost effectivesolution picocellfemtocell relay stations capable of decod-ing and forwarding the emergency messages from macro-cellmicrocell BS to MSs through radio interface would helpoperators achieve higher SINR in a cost effective mannerRelay stations do not need a wire-line backhaul and thedeployment cost of RSs is expected to bemuch lower than thecost of BSs The performance could be further improved byintelligent resource scheduling and cooperative transmissionin systems employing relays Deploying RS can improve theperformance of IEEE 80216m network in various aspectsFigure 1 illustrates an emergency communication system thatcan be established by deploying RS within an IEEE 80216mnetwork Nowadays mobile multihop relaying has becomeone of the most important subsystems for deploying newdistributed base stations

Due to the extreme fast mobility and unpredictableenvironmental aspects in a real road environment themajor challenges of the VANET are reducing number ofrebroadcasting and improving the robustness particularlyfor emergency message communications Little is knownabout the reliable emergency broadcasting performance ofsuch wireless technologies in real world VANET scenariosIn this paper evaluation of a V2I VANET using mobileWiMAX relay networks for the emergency communicationis performed and presented We first propose a novel CRC-based error correction schememdashprogressive and selectiveframe check sequence (PSFCS)mdashfor emergency broadcastingin highDoppler shift environments based on 80216mmobilemultihop relay (MMR) networks The scheme performsmultiple checks to ensure the accuracy of received datahence it reduces the frequency of retransmissions Ourmajorobjective is to fully utilize the OFDMA padding to extendthe original CRC information Besides the original framecheck sequence (FCS) we subdivide the entire payload ofemergency messages into several independent data blocksand calculate the FCS of each block These sub-FCS (s-FCS)blocks are then inserted into the original padding positionuntil the padding space is full In our approach if an erroroccurs in a received frame due to the Doppler effect acorrupted frame still contains correct subblocks that couldhelp the receiver combine two corrupted frames to derive acorrect frame based on the corresponding correct subblocks

23 Orthogonal Frequency DivisionMultiple Access (OFDMA)Systems and Their Drawbacks Considering the problem ofdata-burst grooming in OFDMA-based networks a databurst (aka data region) is a transmission unit in whichassembled frames have the same edge-node destination [9ndash11] it is a two-dimensional allocation of contiguous logicalsubchannels in a group of contiguous OFDMA symbols(or slots) Partial usage of subchannels (PUSC) or fullusage of subchannels (FUSC) allocates the subchannels onthe OFDMA downlink For downlink FUSC and downlinkoptional FUSC using the distributed subcarrier permutationone slot is a subchannel with one OFDMA symbol For

downlink PUSC using the distributed subcarrier permuta-tion one slot is a subchannel with twoOFDMA symbolsThisallocation may be visualized as a rectangle such as a 4 times 8

rectangle Using the corresponding algorithms MAC framescan be processed and mapped to an OFDMA data burst fordownlink and uplink transmission Based on the subchannelallocation method of OFDMA data bursts have a minimumlength Namely the data burst will contain a little surpluspadding space when MAC frames are added to the rectangle[9ndash11]

Further modulation and coding schemes (MCS) arecritical factors affecting the growth of the padding overheadIn an OFDMA-based system for both variable-length framesand fixed-length frames a padding overhead of data burstvaries according to factors such as the type of subframethe modulation and coding scheme the resource allocationscheme and the frame length distribution Generally thesmaller the number of OFDMA symbols in a burst is thelarger the padding overhead will be According to [12ndash14] theoverhead to payload ratio may be over 30 depending on theframe length distribution modulation rate coding rate andburst length

Several proposed methods can reduce the padding over-head in OFDMA-based systems [13 14] Unlike previousapproaches our method does not attempt to reduce thepadding overhead Instead it tries to fully exploit theoverhead to (1) develop a robust OFDMA-based errordetectioncorrection scheme and (2) construct a highly effi-cient OFDMA-based transmission system to support high-mobility emergency broadcasting environments

3 System Model

In this section we consider the behavior of the transmitter(ie base station) receiver (ie mobile station) and relaynode (ie relay station) under our proposed error correctionscheme

31 Base Station (BS) Based on the size of data burst wecan calculate the padding length 119885

119894of the frame in the 119894th

transmission Let Γ119894denote the burst size and let 119864

119894denote

the datagram size of the frame in the 119894th transmission thesize Γ119894of an OFDMA burst will be greater than or equal to 119864

119894

because the burst size includes the data size and the paddinglength 119885

119894can be calculated as follows [15]

119885119894=

Γ119894minus 119864119894 if Γ

119894gt 119864119894

0 if Γ119894= 119864119894

where Γ119894= ((120579 timesNs) times Sc times (119872 times Cr)

8)

(1)

In (1) 120579 denotes the number of data subcarriers Ns denotesthe number of symbols in a frame Sc denotes the numberof subcarriers 119872 is the M-QAM alphabet size and Cris the coding rate of the modulation Equation (4) showsthe padding length in different modulation orders whenthe packets in any length distribution (traffic pattern) areencapsulated in fitted OFDMbursts All types of frames must


1km 1km 1km 1km 2km 1km 1km 1km 1km

BS RS2 RS4RS3 RS1 RS6RS5RS7 RS8

90kmh 120 kmh150kmh

Figure 1 Proposed scenario considered in the simulations

contain variable-length padding and high order modula-tions will have more padding than low order modulationsThe average padding lengths in BPSKQPSK 16QAM and64QAM are 4sim8 bytes 8sim15 bytes and 15sim22 bytes respec-tively

Before a frame is transmitted the BS needs to decide thepadding length and padding content The padding length ofthe frame in 119894th transmission can be denoted as119885

119894 Unlike the

original padding method the s-FCSs are used as the paddingcontent Based on the average padding overhead a BS canchoose the padding content immediately and the averagepadding overhead 119901

119900in 119894th transmission can be calculated

through the following equation

119901119900= lfloor

119885119894

119903rfloor (2)

where 119903 denotes the length of the FCS Let 119874119896denote the

sequence ⟨1198740 1198741 1198742 119874

119875119900minus1

⟩ which is an integer indicat-ing the displacement of each s-FCS from the beginning of thepayload up to a given padding overhead size 119901

119900 The concept

of a distance is valid only if all elements of the s-FCS are withthe same size

119874119896

119896=012119901119900minus1

=

119896

2lfloorlog2119901119900rfloor

if 119896 lt 2120601

119896 minus 120601

2lceillog2119901119900rceil

if 119896 ge 2120601

where 120601 = 119901119900minus 2lceillog2119901119900rceil

(3)

The sequence 119878119896shows that the size of a separate payload is

119878119896

119896=012119901119900minus1

=

1


if 119896 lt 2120601

1


if 119896 ge 2120601


(4)

For example given a payload length 119864119894 the BS can use the

deduced pair sequence (119874119896 119878119896) simultaneously to calculate

extra s-FCSs while constructing a frame The length of an s-FCS is identical to the length of the FCS

32 Mobile Station (MS) In a high speed MMR networkenvironment an MS will receive a multicast frame twiceWhen the firstmulticast frame arrives theMS checks the FCSand all s-FCSs simultaneously If the frame passes the FCScheck it means that there is no corruption in the receiveddata In case the FCS fails the check but all the s-FCSs pass

it then only the FCS is corrupted and the received data iscorrect In these two cases it is not necessary to wait forthe second frame However if both the FCS and any s-FCSfail the check the MS must record the correct data blocksthat already passed the s-FCS check and wait for the secondframe Algorithm 1 shows the pseudocode for the detailedprocedure at the receiver The check procedure is the samefor the second frame which is via an RS If any s-FCS failsthe check in the second frame the MS can use the ldquocorrectdata block informationrdquo of any two frames from either RS orBS to correct the received data Although the FCS and somes-FCSs may fail the check in the second frame the MS canstill obtain the correct data using the record of correct datablocks Figure 2 shows the flow diagram of error correctionprocedure in a MMR network

As its name implies our scheme proposes new strategiesfor the challenges in error correction techniques To reducethe transmission cost of existing error correction scheme wecouple the error detection and retransmission proceduresInstead of adding redundancy to the transmitted informationusing FEC scheme our algorithm progressively and selec-tively replaces subblocks with incorrect checksums of entiredata burst (frame) when necessaryWe refer to this strategy asprogressive and selective FCS However there is a small errorprobability in Algorithm 1 The retransmission procedureswill be resumed at next BSRS if necessary

33 Relay Station (RS) In the proposed scheme the RSsforward multicast frames in the same way as that in theoriginal relay network environment and these RSs performthe new error correction method that is like an MS attachedto the BS directly

4 Performance Evaluation

41 Simulation Scenarios The network parameters used toevaluate the performance of the proposed error correctionscheme are summarized in Table 1 [16ndash18] We assume thatthe BS RSs and MSs always use the higher modulation rateto achieve better performance Only one BS is used in thetransparent-mode relay networks and the cell coverage intransparent-mode relay networks is the same as the BS BPSKcoverage

We developed programs in EstiNet 70 (previouslyNCTU-ns) [19] simulator to compare our proposed schemewith the original scheme fromvarious viewpoints and param-eters The model is based on the Stanford University Interim(SUI) path lossmodel recommended by the 80216 task group[20] The BS is located in the middle of a straight highway


Input 119899 arrival of emergency packet 119885119899

Output emergency packet 119885 or send NACK

(1) if (crc(119885119899 FCS(119885

119899)) = 0) then

(2) countlarr 0(3) 119901

119900larr get s-FSC (119885

119899)

(4) if (119901119900≦ 0) then

(5) return NACK(6) else(7) for 119894 = 1 sdot sdot sdot 119901

119900

(8) if (∄119885119899minus1

(119894)) then(9) 119885

119899(119894) larr extract s-data (119885

119899 119894)

(10) s-FCS (119885119899(119894))larr extract s-FSC (119885

119899 119894)

(11) if (crc(119885119899(119894) s-FCS (119885

119899(119894))) = 0) then

(12) 119885119899minus1(119894) larr 119885

119899(119894)

(13) countlarr count + 1(14) else(15) 119885

119899minus1(119894) larr NULL

(16) endif(17) else(18) restore s-data (119885

119899 119885119899minus1(119894) 119894)

(19) countlarr count + 1(20) endif(21) endfor(22) if (count = 119901

119900) then

(23) return 119885

(24) else(25) return NACK(26) endif(27) endif(28) else(29) return 119885

(30) endif

Algorithm 1 Packet check

Zn(1)

Zn(1)

Zn(1)

middot middot middot



Zn(2)

Zn(2)

Zn(p0)

Zn(p0)Fail

Fail

BS RS

NACK

MS

Fail

Zn(3)

Zn(3)

(Znminus1(1) s-FCS (Znminus1(1))

nminus1(p0) s-FCS (Znminus1(p0)))

(Zn(1) s-FCS (Zn(1))(p0) s-FCS (Zn(p0)))

(Zn FCS(Z

n ))

ACK

(Znminus1 FCS (Z

nminus1))

(Zn

(Z

Figure 2 The error correction procedure in a WiMAXMMR network


Table 1 Parameters

Parameter ValueTransmission power of BS 30 dBmTransmission power of RS 24 dBmSubchannel bandwidth 20MHzChannel frequency 547GHzThermal noise minus100 97 dBmCRC type CRC-16Length of FCS 16 bitsOFDMA symbol duration 102857 120583s

that extends 10 kmThe deployment of RSs considered in thispaper is along the highway The distance between the BS andadjacent RS is 15 km and the distance between the RSs on theboundary is 1 kmThe simulation coverage of highway sectioncontains 1 BS and 8RSsThe proposed scenario considered inthe simulations is shown in Figure 1

42 Radio Propagation and Interference Model In a produc-tion network the signal quality may be attenuated due toseveral factors between the sender and the receiver includingthe shadowing fading and path loss which are criticalfeatures of any model in a wireless system In this section wedescribe the radio and interference models used in this work

First we consider attenuation caused by path loss dueto signal propagation over the distance The fading andshadowing effects are not considered In SUI path loss modelsome assumptions about the senderrsquos power and antennagains can be used to determine the power of the signalreceived at MS as well as the SNR The SNR at the receiveris calculated as follows

SNR[dB] = 10 times log

10(

119901MSBW times 119873

0

)

where 119901MS =119866BS times 119866MS times 119875BS

119871 (BSMS)

(5)

In (5) BW denotes the effective channel bandwidth in hertz1198730is the thermal noise density119875BS is the transmission power

of the BS 119866BS and 119866MS are the antenna gains at the BS andMS respectively and 119871(BSMS) is the path loss from the BSto MS Given the SNR of the MS the BS can determine theMCS based on Table 2 Specifically the BS will use the highestMCS whoseminimum required SNR is smaller than SNR

[dB]The SNR between the BS and the MS depends on the

signal power distance 119889 and the noise and can be calculatedas follows [16]

SNR[dB] = 119901

119905[dBm] minus 119873[dBm] minus (20 times log 4120587119889120582

) (6)

In (6) 120582 denotes the wavelength 119901119905denotes the transmission

power and 119873 denotes the noise Using (6) the SNR can beestimated when MS locates in different positions

Table 2 MSC and SNR threshold

MSC Threshold 120572 (dB)BPSK 12 6BPSK 34 916QAM 12 11516QAM 34 1564QAM 12 1764QAM 23 1964QAM 34 21

Second we consider the LOS propagation The effectivetransmitting power is reduced with Doppler effects and canbe derived as follows [21]

1199011015840

119905= 119901119905sinc2 (119891

119889119879)

where 119891119889=119906

120582

(7)

In (7) 119879 denotes the OFDMA symbol duration 119906 is therelative speed from the receiver to the transmitter From (6)and (7) the SNR becomes

SNR[dB] = 119901

119905[dBm] + 20 log (sinc (119891119889119879))

minus 1198731015840

[dBm] minus (20 times log 4120587119889120582

)

(8)

where1198731015840 denotes the total power of Gaussian noise and ICI

43 PERs versus Speeds The bit error probability (BEP) ofvarious types of modulation can be derived by using theSNR In the case of Multilevel-QAM the BEP 119875

119887can be

approximated as follows

119875119887cong

4

log2119872

[1 minus1

radic119872

]119876(radic[3

119872 minus 1]119864119887

1198730

) (9)

In (9)119872 denotes theM-QAMalphabet sizeThe packet errorrate (PER) of the 119905th transmission which uses the originalCRC scheme can be calculated as follows

PERori = (1 minus (1 minus 119875119887)119898+119903

)119905

(10)

In (10) 119898 represents the length of the transferred data 119903 isthe length of the FCS and (119898 + 119903) denotes the total lengthof the frame In our proposed scheme the double checkingprocedure can correct a corrupted FCS hence the PERnew ofthe 119905th transmission can be calculated as follows

PERnew = [(1 minus (1 minus 1198751198871)119898) times (1 minus (1 minus 119875

1198872)119898)

times (1 minus (1 minusmax (1198751198871 1198751198872))119898min(119901

11990011199011199002))]

119905

(11)

In (11) 1199011199001

and 1199011199002

are the average padding overheads offrames from the BS and RS respectively and 119901

1198871and 119901

1198872


Table 3 Actual coverage probabilities for confidence PERslowastlowast

PER

Coverage probabilitiesOriginal scheme Proposed scheme

90 kmhr 120 kmhr 150 kmhr 90 kmhr 120 kmhr 150 kmhr1st TXlowast 2nd TX 1st TX 2nd TX 1st TX 2nd TX 1st TX 2nd TX 1st TX 2nd TX 1st TX 2nd TX

0sim20 9619 100 6501 9602 5140 7395 100 100 8591 100 6636 906420sim50 381 0 3169 398 1522 2175 0 0 1409 0 2012 93650sim100 0 0 330 0 3338 43 0 0 0 0 1352 0lowast1st TX first transmission 2nd TX second transmissionlowastlowastPacket sizes = 128 bytes

are the bit error probabilities of frames from the BS and RSrespectively

In a general VANET BSRS coverage is always a key pointthat the industry must take into account when designinga robust emergency communication system For instancea macrocell base station with a greater coverage area iscommonly applicable to a less populated area in whichvehicles move fast Without loss of generality suppose thatprobability of successful transmission Pr(119883) follows thebinomial distribution with a random number of MSs 119899 andPERnew we write Pr(119883) sim 119861(119896 119899PERnew) The probabilityof getting exactly 119896 successful transmissions in number ofvehicles 119899 is given by the probability mass function

Pr (Χ) sim 119861 (119896 119899PERnew) = (119899

119896) (1 minus PERnew)

119896(PERnew)

119899minus119896

where 119899 =120588119889

119906 (

119899

119896) =

119899

119896 (119899 minus 119896)

(12)

where 120588 denotes the average traffic flows in a given period oftime the values are displayed in number of vehicles per hour(vhr) on the road 119906 denotes the average speed of vehiclesthe values are displayed in kilometer per hour (kmhr) And119889denotes the BSRS cell coverage along this stretch of the roadthe values are displayed in kilometers (km)

Figure 3 shows the PERs of the original error correctionscheme and proposed error correction scheme in variousdistances between BS and MS when the packet size is 128bytes Figure 3(a) shows that both schemes can achievegood communication with MS in low speed However theproposed scheme has better performance than the originalerror correction scheme The PER is lower than 20 for thewhole coverage Figure 3(b) shows that by using the originalscheme the PER is higher than 50 for some coverage Thismeans that the condition of communication is not quitesatisfactory and the MS may be temporarily disconnectedin some sections when the speed reaches 120 kmhr Onthe other hand the proposed error correction scheme caneffectively reduce PERThe PER is lower than 20 for 8951of the coverage and lower than 50 for all of the coverageWhen ARQ mechanism works the second transmission canalso reduce PER After second transmission there is only398 coverage in which PER is higher than 20 when

the speed of MS reaches 120 kmhr The proposed errorcorrection scheme with retransmission will achieve the besttransmission effect After retransmission the PER is lowerthan 20 for the whole coverage when the speed of MSreaches 120 kmhr But the retransmission will cause theadditional transmission latency which is a critical drawbackfor an emergency messaging system

With the increase in the speed of theMS the condition ofcommunication will become worse From Figure 3(c) whenthe MS uses the original scheme with speed reaching 150 kmthe PER is higher than 50 in 3338of the coverage For partof the coverage PER is even more than 90 However usingthe proposed scheme the coverage where the PER is higherthan 50 drops to 1352 Table 3 shows the actual coverageprobabilities for confidence PERs versus various speeds withtwo schemes

44 PERs versus Packet Sizes We also consider the packetsize 119864

119894of emergency messages that possibly caused high PER

because the packets transmitted over the air may introducebit errors Figure 4 shows the PERs of both original andproposed error correction schemes in various packet sizeswhen MS locates in different ldquozone typerdquo In all locations themodulation of RS is 64QAM When the distance betweenBS and MS is 11 km the modulation of BS is 64QAMWhen distance is 21 km the modulation of BS is 16QAMand the modulation of BS is BPSK when distance is 41 kmFigure 4(a) shows that both schemes can achieve goodcommunication with short packet size The PER is higherthan 50 when the packet size is longer than 1280 376and 120 bytes using original scheme and the speed of MSis 90 120 and 150 kmhr respectively If padding length ofa frame is 0 the proposed scheme has the same PER withthe original scheme (for example when the packet size is 323bytes) But when the frame has longer padding length thanthe original error correction scheme the proposed schemeachieves significant improvement When the packet size is236 bytes the padding length of 64QAM frame is 16 bytesThe PER is 07634 if MS uses the original scheme with speed150 kmhr But using the proposed scheme the PER can bereduced to 05757 Since the performance of our proposedscheme is depending on the padding length the PER curveof the proposed scheme is varying Figures 4(b) and 4(c)show the same result when MS locates in different positions


30

20

10

0

PER

()

Distance of BS and MS (km)0 25 5

Original scheme 1st TXOriginal scheme 2nd TX

Proposed scheme 1st TXProposed scheme 2nd TX

(a)

PER

()

Distance of BS and MS (km)0

0

20

40

60

25 5

Original schemeOriginal scheme

Proposed schemeProposed scheme

1st TX2nd TX

1st TX2nd TX

(b)

PER

()


0

20

40

60

80

100

25 5



1st TX2nd TX

1st TX2nd TX

(c)

Figure 3 PER of the original error correction scheme and proposed error correction scheme when packet size is 128 bytes and the speed ofMS is (a) 90 kmhr (b) 120 kmhr and (c) 150 kmhr

Table 4 shows the average PER reduction from Figure 4WhenMS is close to BS orMS is in low speed the average PERof the proposed scheme is reduced by 1sim5 only Converselywhen MS is far from BS or MS is in high speed the averagePER can be reduced by 6sim20 If a frame can carry asmany s-FCSs as possible by using the proposed scheme the MS canget the best performance improvement in poor connectioncondition

45 Actual Transmitted Data (Packet Delivery Ratio) Theactual transmitted data (ATD) is the size of the transmitteddata including the total frame and the retransmitted frameThe ATD will be no smaller than 119864

119894 When the transmission

uses the original CRC scheme the ATDori can be defined asfollows

ATDori =119864119894

(1 minus 119875119887)119898+119903

(13)

Table 4 Average PER reduction in different speeds

SpeedAverage PER reduction ()

Distancebetween BS

and MS = 11 km

Distancebetween BS

and MS = 21 km

Distancebetween BS

and MS = 41 km90 kmhr 340 477 1453120 kmhr 352 661 2370150 kmhr 257 602 1780

Similarly when the proposed scheme is used for transmis-sion the ATDnew of the transmission can be calculated asfollows

ATDnew =119864119894

1 minus PERnew (14)


100

80

60

40

20

0

PER

()

Length of net data (bytes)64 424 784 1144 1500

90kmhr original scheme90kmhr proposed scheme120 kmhr original scheme

120 kmhr proposed scheme150kmhr original scheme150kmhr proposed scheme

(a)

100

80

60

40

20

0

PER

()




(b)

100

80

60

40

20

0

PER

()




(c)

Figure 4 PER of the original error correction scheme and proposed error correction scheme in various packet sizes when the distancebetween BS and MS is (a) 11 km (b) 21 km and (c) 41 km

Table 5 Goodput integral in different speed

SpeedGoodput integral (CDF)

Enhancement ()Originalscheme

Proposedscheme

90 kmhr 4561 486 656120 kmhr 4141 4631 1183150 kmhr 3422 4137 2089

The goodput is the size of the total amount of correctlyreceived data divided byATDWhen the value of the goodputequals 1 it means that all data transmissions are successfulin the first time and no retransmission is required Table 5

shows the goodput integral (ie CDF) with the distancebetweenBS andMS from0 to 5 kmWhenusing the proposedscheme goodput at different speeds is significantly improvedcomparing with the original scheme In particular with MSat speed 150 kmhr it shows a more than 20 improvementin goodput integral

5 Concluding Remarks

Understanding the constraints imposed by public safetyapplications and usage scenarios is a key in establish-ing deploying and operating public safety communica-tion networks It is challenging to provide a highly reli-able mission-critical emergency communications system for


a high-mobility environment Based on the characteristicsof emergency communications the adoption of the WiMAXwith mobile multihop relaying for emergency communica-tions represents a significant advance in the technologiesavailable for error detection and error correction operations

We presented a novel frameworkmdashPSFCSmdashfor reliableemergency communications in WiMAX MMR networksoperating under the transparent mode In a high-mobilityenvironment if an MS receives the same frame from theBS and an RS the error subblocks can be corrected duringthe two repeated transmissions Clearly our approach canimprove the throughput of WiMAX-based emergency com-munications systems

In HARQ the original data is encoded with a forwarderror correction (FEC) code such as turbo code By increasingthe code rate the error correction capability of FEC can beenhanced However with the expansion of code rate thedecoding time and the amount of data transmission are alsoincreasing Unlike HARQ the proposed scheme uses thepadding space to carry s-FCS and needs no extra bandwidthto transfer redundancy bits ldquoHARQ with soft combiningrdquois used at the MAC and PHY layer The MAC is used forsignaling control messages such as ACKNACK while PHYlayer is used for retention of transmission blocks and softcombining [22] The proposed scheme is used at MAC layerand can be used with ldquoHARQ with soft combiningrdquo togetherto achieve better error correction capability

The simulation results show that the PER is improvedsignificantly in a highway where the mobile stations havehigh packet error rates Even if the moving speed of an MSreaches 150 kmhr our approach still achieves a superior errorcorrection performance for all types of modulation andorcoding rates Therefore the scheme would be also usefulin environments with extremely poor radio conditions Inaddition the schemersquos error detection capacity is slightlybetter than that of the original CRC scheme Moreover theproposed scheme is also expected to achieve high energyefficiency because the number of retransmissions could bereduced

Conflict of Interests

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

References

[1] T Meireles and J A Fonseca ldquoSafety services in infrastructurebased vehicular communicationsrdquo in Proceedings of the IEEE16th Conference on Emerging Technologies and Factory Automa-tion (ETFA rsquo11) pp 1ndash4 September 2011

[2] J M Peha ldquoProtecting public safety with better communica-tions systemsrdquo IEEE Communications Magazine vol 43 no 3pp 10ndash11 2005

[3] W Y Lin YC Chen R Y Chang S H Chen and C L LeeldquoRapid WiMAX network deployment for emergency servicesrdquoin Proceedings 7th International Symposium on Wireless andPervasive Computing (ISWPC rsquo12) pp 1ndash5 2012

[4] P Neves P Simoes A Gomes et al ldquoWiMAX for emergencyservices an empirical evaluationrdquo in Proceedings The Interna-tional Conference on Next Generation Mobile Applications Ser-vices and Technologies (NGMAST rsquo07) pp 340ndash345 September2007

[5] A Buchenscheit F Schaub F Kargl andMWeber ldquoA VANET-based emergency vehicle warning systemrdquo in Proceedings ofthe IEEE Vehicular Networking Conference (VNC rsquo09) pp 1ndash8October 2009

[6] F Bai T Elbatt G Hollan H Krishnan and N SadekarldquoTowards characterizing and classifying communication basedautomotive applications from a wireless networking perspec-tiverdquo in Proceedings of 1st IEEE Workshop on AutomotiveNetworking and Applications (AutoNet rsquo06) 2006

[7] S Ahmadi ldquoThe IEEE 80216m Physical Layer (Part II)rdquo inMobile WiMAX A Systems Approach to Understanding IEEE80216mRadio Access Technology pp 489ndash624 Academic Press2010

[8] A Bohm and M Jonsson ldquoReal-time communication supportfor cooperative infrastructure-based traffic safety applicationsrdquoInternational Journal of Vehicular Technology vol 2011 ArticleID 541903 17 pages 2011

[9] ldquoIEEE Standard for Local and metropolitan area networks Part16 Air Interface for Fixed and Mobile Broadband WirelessAccess Systems Amendment for Physical and Medium AccessControl Layers for Combined Fixed and Mobile Operation inLicensed Bandsrdquo IEEE Std 80216e-2005 2005

[10] ldquoIEEE 80216-2004 Part 16 Air Interface for Fixed BroadbandWireless Access Systemsrdquo IEEE Std 80216-2004 2004

[11] ldquoIEEE Standard for Local and metropolitan area networksPart 16 Air Interface for Broadband Wireless Access SystemsAmendment 3 Advanced Air Interfacerdquo IEEE Std 80216m-2010 2010

[12] I C Msadaa and F Filali ldquoOn the performance bounds ofOFDM-based 80216 broadband Wireless networksrdquo in Pro-ceedings of the IEEE Wireless Communications and NetworkingConference (WCNC rsquo08) pp 1459ndash1464 April 2008

[13] C Hoymann M Puttner and I Forkel ldquoThe HIPERMANstandard-a performance analysisrdquo in Proceedings of IST Mobileand Wireless Communication Summit pp 827ndash831 2003

[14] C Hoymann M Puttner and I Forkel ldquoInitial performanceevaluation and analysis of the global OFDM metropolitanarea network standard IEEE 80216rdquo in Proceedings EuropeanWireless Conference 2004(EW rsquo04) pp 228ndash234 2004

[15] C Y Chen W K Jia and Y C Chen ldquoAn energy-efficient andreliable multicasting for WiMAX multi-hop relay networksrdquoIET Communications vol 6 no 14 pp 2169ndash2177 2012

[16] C Hoymann ldquoAnalysis and performance evaluation of theOFDM-based metropolitan area network IEEE 80216rdquo Com-puter Networks vol 49 no 3 pp 341ndash363 2005

[17] V Genc S Murphy J Murphy and A Nafaa ldquoSystem-levelperformance evaluation of multi-cell transparent mode relay80216j systemsrdquo inProceedings of the IEEEGlobal Telecommuni-cations Conference (GLOBECOM rsquo09) pp 1ndash7 December 2009

[18] J G Andrews A Ghosh and R Muhamed Fundamentalsof WiMAX Understanding Broadband Wireless NetworkingPrentice Hall 2007

[19] EstiNet 70 httpwwwestinetcom[20] IEEE 80216 BroadbandWireless AccessWorkingGroup Channel

Models for Fixed Wireless Applications 2003


[21] Y Li and L Cimini ldquoBounds on the interchannel interferenceof OFDM in time-varying impairmentsrdquo IEEE Transactions onCommunications vol 49 pp 401ndash404 2001

[22] D T Wong P Y Kong Y C Liang and K C Chua WirelessBroadband Networks Wiley 2009

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



2 Emergency Communications for ExpresswaySystems and Problem Statements

21 Intelligent Traffic Systems (ITS) and Vehicle Ad HocNetworks (VANET) and Emergency Communications SystemsEmergency communication system could use wireless com-munication to warn other vehicle drivers or to preempt trafficlights Such an application can reduce accident risks duringemergency response trips and help save valuable time [3 5]We outline a comprehensive design of such an emergencyvehicle warning system that makes full use of intervehi-cle communication (aka vehicle-to-vehicle V2V) but alsoencompasses roadside wireless communication infrastruc-ture (aka vehicle-to-infrastructure V2I) In such systemsvehicle drivers are not simply warned of an approachingaccident location they also receive detailed route informa-tion Based on such emergency information timely andappropriate reaction of other vehicle drivers is possibleTherefore drivers can react early or correctly which may beuseful in responding to and recovering from emergencies

VANET is one of the representative emerging tech-nologies in telematics and intelligent traffic systems (ITS)Coordination of communications among vehicles (V2V)or between vehicles and road-side-units (V2I) can providevarious intelligent and telematics-related services The recentemergence of ubiquitous wireless connectivity such as dedi-cated short range communication (DSRC) and WiMAX hastriggered immense interest in the possibilities of connectivityamong moving vehicles Regarding the V2I communicationsof VANET orthogonal frequency division multiple access(OFDMA) has become a popular modulation technique forhigh speed wireless communications By using the multi-carrier modulation when transmitting signals through noisychannels OFDMA is able to mitigate the detrimental effectsof multipath fading using a simple one-tap equalizer Thereis a growing need to quickly transmit information wirelesslyand accurately and OFDMA is a suitable technique for highdata rate transmission with an appropriate error controlscheme over wireless channels and it has been developed intopopular wideband digital communication systems such asWiMAX which is already widely deployed inmany countriesand is igniting the mobile broadband revolution

Recently mobile stations in vehicles or trains have beengradually encountering some communication problems suchas intersymbol interference (ISI) intercarrier interference(ICI) and fading and Doppler effect This research willmainly focus on the Doppler effect of signals between atransmitter and a fast moving receiver The Doppler shiftnot only changed the frequency of the incoming signal butalso squeezed it into a slightly shorter time period As aresult the OFDMA receiver may be unable to recognize thetiming pulse in its expected time interval thus the incomingdata stream may become unreadable and that can seriouslyaffect the performance of mobile communications In suchcase effective error control schemes must be deployed toensure the reliability of OFDMA-based wireless networksTwo mechanisms are commonly deployed to accommodatethe error control automatic repeat request (ARQ) mecha-nism and the hybrid ARQ (HARQ) mechanism which are

implemented in the logical link control (LLC) sublayer of themedium access control (MAC) layer and the physical layer(PHY) respectively

22 Deploying Emergency Communications Systems UsingWiMAXMMR Technologies A plethora of potential applica-tions for high speed vehicle environments has been proposedin the areas of public safety traffic infrastructure manage-ment information notification and entertainment [3 4 6]Among them safety-related applications attract the mostattention through V2I wireless communications [1] Futureemergency communications for public safety will demanda mobile broadband service migrating from the currentlydominant voice-only mode to multimedia applications Theuse of common standard-based commercial technologiesas an alternative approach to conventional land wirelessnetwork infrastructures was introduced Many public safetyorganizations have used WiMAX systems to take advan-tage of the common access and minimal costs availablein the license-exempt spectrum bands Several shortfallsto using this method for public safety communicationswere also addressed [2] One of the major issues related toWiMAX is the limited range resulting from the maximummobility available coupled with the restrictions associatedwith the interference acceptance requirements This paperaddresses the emergency communications of high speedmobile WiMAX and suggests how to improve it as well asmake it a viable candidate for use by public safety agenciesThe enhanced multicastbroadcast service (E-MBS) feature ofthe mobile network is a promising technology for providingemergency services because it allows simultaneous deliveryof emergency messages to large-scale user communities ina cost effective manner Using E-MBS a certain part withineach superframe can be set aside for multicast-only orbroadcast-only data The entire frame can also be designatedas a downlink-only broadcast frame A major task of theE-MBS module is to provide a reliable sequence of E-MBS frames to multiple recipients simultaneously Thus theemergency message transfer might repeat until all data arereceived by all the receivers whether intended or unintendedIf the E-MBS feedback is enabled one or multiple cellswould receive the information about downlink multicastand broadcast service Typically the multicast and broadcastservice is a downlink-only transmission and has no uplinkmechanism to send feedback to the base station however ifa bidirectional RF carrier is aggregated with a downlink-onlyRF carrier the feedbackmay be sent through the bidirectionalRF carrier In this situation the mobile stations can usea common uplink channel to transmit E-MBS feedback Ifthe predefined feedback condition was satisfied an ACK orNACK is transmitted through this E-MBS feedback channel[7]

Most safety-related applications particularly for highspeed vehicles require fast and reliable emergency mes-sage dissemination through broadcast [6 8] However theconventional broadcast mechanism is neither efficient norreliable because it results in low network performance andhigh network deployment cost Therefore the relay station









3 System Model





119894denote


119894



119885119894=

Γ119894minus 119864119894 if Γ

119894gt 119864119894

0 if Γ119894= 119864119894


8)

(1)





90kmh 120 kmh150kmh




119894 Unlike the




119901119900= lfloor

119885119894

119903rfloor (2)


sequence ⟨1198740 1198741 1198742 119874

119875119900minus1


119900 The concept


119874119896

119896=012119901119900minus1

=

119896


if 119896 lt 2120601

119896 minus 120601


if 119896 ge 2120601


(3)


119878119896

119896=012119901119900minus1

=

1


if 119896 lt 2120601

1


if 119896 ge 2120601


(4)














(1) if (crc(119885119899 FCS(119885

119899)) = 0) then

(2) countlarr 0(3) 119901

119900larr get s-FSC (119885

119899)

(4) if (119901119900≦ 0) then


119900

(8) if (∄119885119899minus1

(119894)) then(9) 119885


119899 119894)


119899 119894)

(11) if (crc(119885119899(119894) s-FCS (119885

119899(119894))) = 0) then

(12) 119885119899minus1(119894) larr 119885

119899(119894)




119899 119885119899minus1(119894) 119894)


119900) then

(23) return 119885


(30) endif


Zn(1)

Zn(1)

Zn(1)




Zn(2)

Zn(2)

Zn(p0)

Zn(p0)Fail

Fail

BS RS

NACK

MS

Fail

Zn(3)

Zn(3)




(Zn FCS(Z

n ))

ACK

(Znminus1 FCS (Z

nminus1))

(Zn

(Z



Table 1 Parameters






10(

119901MSBW times 119873

0

)


119871 (BSMS)

(5)





SNR[dB] = 119901


) (6)






1199011015840

119905= 119901119905sinc2 (119891

119889119879)

where 119891119889=119906

120582

(7)


SNR[dB] = 119901

119905[dBm] + 20 log (sinc (119891119889119879))

minus 1198731015840


)

(8)



119887can be


119875119887cong

4

log2119872

[1 minus1

radic119872

]119876(radic[3

119872 minus 1]119864119887

1198730

) (9)



)119905

(10)



1198872)119898)


11990011199011199002))]

119905

(11)

In (11) 1199011199001

and 1199011199002


1198871and 119901

1198872



PER






Pr (Χ) sim 119861 (119896 119899PERnew) = (119899


119896(PERnew)

119899minus119896

where 119899 =120588119889

119906 (

119899

119896) =

119899

119896 (119899 minus 119896)

(12)









30

20

10

0

PER

()




(a)

PER

()


0

20

40

60

25 5



1st TX2nd TX

1st TX2nd TX

(b)

PER

()


0

20

40

60

80

100

25 5



1st TX2nd TX

1st TX2nd TX

(c)






ATDori =119864119894

(1 minus 119875119887)119898+119903

(13)



Distancebetween BS

and MS = 11 km

Distancebetween BS

and MS = 21 km

Distancebetween BS



ATDnew =119864119894

1 minus PERnew (14)


100

80

60

40

20

0

PER

()




(a)

100

80

60

40

20

0

PER

()




(b)

100

80

60

40

20

0

PER

()




(c)





Proposedscheme

90 kmhr 4561 486 656120 kmhr 4141 4631 1183150 kmhr 3422 4137 2089












References


























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation

















3 System Model





119894denote


119894



119885119894=

Γ119894minus 119864119894 if Γ

119894gt 119864119894

0 if Γ119894= 119864119894


8)

(1)





90kmh 120 kmh150kmh




119894 Unlike the




119901119900= lfloor

119885119894

119903rfloor (2)


sequence ⟨1198740 1198741 1198742 119874

119875119900minus1


119900 The concept


119874119896

119896=012119901119900minus1

=

119896


if 119896 lt 2120601

119896 minus 120601


if 119896 ge 2120601


(3)


119878119896

119896=012119901119900minus1

=

1


if 119896 lt 2120601

1


if 119896 ge 2120601


(4)














(1) if (crc(119885119899 FCS(119885

119899)) = 0) then

(2) countlarr 0(3) 119901

119900larr get s-FSC (119885

119899)

(4) if (119901119900≦ 0) then


119900

(8) if (∄119885119899minus1

(119894)) then(9) 119885


119899 119894)


119899 119894)

(11) if (crc(119885119899(119894) s-FCS (119885

119899(119894))) = 0) then

(12) 119885119899minus1(119894) larr 119885

119899(119894)




119899 119885119899minus1(119894) 119894)


119900) then

(23) return 119885


(30) endif


Zn(1)

Zn(1)

Zn(1)




Zn(2)

Zn(2)

Zn(p0)

Zn(p0)Fail

Fail

BS RS

NACK

MS

Fail

Zn(3)

Zn(3)




(Zn FCS(Z

n ))

ACK

(Znminus1 FCS (Z

nminus1))

(Zn

(Z



Table 1 Parameters






10(

119901MSBW times 119873

0

)


119871 (BSMS)

(5)





SNR[dB] = 119901


) (6)






1199011015840

119905= 119901119905sinc2 (119891

119889119879)

where 119891119889=119906

120582

(7)


SNR[dB] = 119901

119905[dBm] + 20 log (sinc (119891119889119879))

minus 1198731015840


)

(8)



119887can be


119875119887cong

4

log2119872

[1 minus1

radic119872

]119876(radic[3

119872 minus 1]119864119887

1198730

) (9)



)119905

(10)



1198872)119898)


11990011199011199002))]

119905

(11)

In (11) 1199011199001

and 1199011199002


1198871and 119901

1198872



PER






Pr (Χ) sim 119861 (119896 119899PERnew) = (119899


119896(PERnew)

119899minus119896

where 119899 =120588119889

119906 (

119899

119896) =

119899

119896 (119899 minus 119896)

(12)









30

20

10

0

PER

()




(a)

PER

()


0

20

40

60

25 5



1st TX2nd TX

1st TX2nd TX

(b)

PER

()


0

20

40

60

80

100

25 5



1st TX2nd TX

1st TX2nd TX

(c)






ATDori =119864119894

(1 minus 119875119887)119898+119903

(13)



Distancebetween BS

and MS = 11 km

Distancebetween BS

and MS = 21 km

Distancebetween BS



ATDnew =119864119894

1 minus PERnew (14)


100

80

60

40

20

0

PER

()




(a)

100

80

60

40

20

0

PER

()




(b)

100

80

60

40

20

0

PER

()




(c)





Proposedscheme

90 kmhr 4561 486 656120 kmhr 4141 4631 1183150 kmhr 3422 4137 2089












References


























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation












90kmh 120 kmh150kmh




119894 Unlike the




119901119900= lfloor

119885119894

119903rfloor (2)


sequence ⟨1198740 1198741 1198742 119874

119875119900minus1


119900 The concept


119874119896

119896=012119901119900minus1

=

119896


if 119896 lt 2120601

119896 minus 120601


if 119896 ge 2120601


(3)


119878119896

119896=012119901119900minus1

=

1


if 119896 lt 2120601

1


if 119896 ge 2120601


(4)














(1) if (crc(119885119899 FCS(119885

119899)) = 0) then

(2) countlarr 0(3) 119901

119900larr get s-FSC (119885

119899)

(4) if (119901119900≦ 0) then


119900

(8) if (∄119885119899minus1

(119894)) then(9) 119885


119899 119894)


119899 119894)

(11) if (crc(119885119899(119894) s-FCS (119885

119899(119894))) = 0) then

(12) 119885119899minus1(119894) larr 119885

119899(119894)




119899 119885119899minus1(119894) 119894)


119900) then

(23) return 119885


(30) endif


Zn(1)

Zn(1)

Zn(1)




Zn(2)

Zn(2)

Zn(p0)

Zn(p0)Fail

Fail

BS RS

NACK

MS

Fail

Zn(3)

Zn(3)




(Zn FCS(Z

n ))

ACK

(Znminus1 FCS (Z

nminus1))

(Zn

(Z



Table 1 Parameters






10(

119901MSBW times 119873

0

)


119871 (BSMS)

(5)





SNR[dB] = 119901


) (6)






1199011015840

119905= 119901119905sinc2 (119891

119889119879)

where 119891119889=119906

120582

(7)


SNR[dB] = 119901

119905[dBm] + 20 log (sinc (119891119889119879))

minus 1198731015840


)

(8)



119887can be


119875119887cong

4

log2119872

[1 minus1

radic119872

]119876(radic[3

119872 minus 1]119864119887

1198730

) (9)



)119905

(10)



1198872)119898)


11990011199011199002))]

119905

(11)

In (11) 1199011199001

and 1199011199002


1198871and 119901

1198872



PER






Pr (Χ) sim 119861 (119896 119899PERnew) = (119899


119896(PERnew)

119899minus119896

where 119899 =120588119889

119906 (

119899

119896) =

119899

119896 (119899 minus 119896)

(12)









30

20

10

0

PER

()




(a)

PER

()


0

20

40

60

25 5



1st TX2nd TX

1st TX2nd TX

(b)

PER

()


0

20

40

60

80

100

25 5



1st TX2nd TX

1st TX2nd TX

(c)






ATDori =119864119894

(1 minus 119875119887)119898+119903

(13)



Distancebetween BS

and MS = 11 km

Distancebetween BS

and MS = 21 km

Distancebetween BS



ATDnew =119864119894

1 minus PERnew (14)


100

80

60

40

20

0

PER

()




(a)

100

80

60

40

20

0

PER

()




(b)

100

80

60

40

20

0

PER

()




(c)





Proposedscheme

90 kmhr 4561 486 656120 kmhr 4141 4631 1183150 kmhr 3422 4137 2089












References


























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation












(1) if (crc(119885119899 FCS(119885

119899)) = 0) then

(2) countlarr 0(3) 119901

119900larr get s-FSC (119885

119899)

(4) if (119901119900≦ 0) then


119900

(8) if (∄119885119899minus1

(119894)) then(9) 119885


119899 119894)


119899 119894)

(11) if (crc(119885119899(119894) s-FCS (119885

119899(119894))) = 0) then

(12) 119885119899minus1(119894) larr 119885

119899(119894)




119899 119885119899minus1(119894) 119894)


119900) then

(23) return 119885


(30) endif


Zn(1)

Zn(1)

Zn(1)




Zn(2)

Zn(2)

Zn(p0)

Zn(p0)Fail

Fail

BS RS

NACK

MS

Fail

Zn(3)

Zn(3)




(Zn FCS(Z

n ))

ACK

(Znminus1 FCS (Z

nminus1))

(Zn

(Z



Table 1 Parameters






10(

119901MSBW times 119873

0

)


119871 (BSMS)

(5)





SNR[dB] = 119901


) (6)






1199011015840

119905= 119901119905sinc2 (119891

119889119879)

where 119891119889=119906

120582

(7)


SNR[dB] = 119901

119905[dBm] + 20 log (sinc (119891119889119879))

minus 1198731015840


)

(8)



119887can be


119875119887cong

4

log2119872

[1 minus1

radic119872

]119876(radic[3

119872 minus 1]119864119887

1198730

) (9)



)119905

(10)



1198872)119898)


11990011199011199002))]

119905

(11)

In (11) 1199011199001

and 1199011199002


1198871and 119901

1198872



PER






Pr (Χ) sim 119861 (119896 119899PERnew) = (119899


119896(PERnew)

119899minus119896

where 119899 =120588119889

119906 (

119899

119896) =

119899

119896 (119899 minus 119896)

(12)









30

20

10

0

PER

()




(a)

PER

()


0

20

40

60

25 5



1st TX2nd TX

1st TX2nd TX

(b)

PER

()


0

20

40

60

80

100

25 5



1st TX2nd TX

1st TX2nd TX

(c)






ATDori =119864119894

(1 minus 119875119887)119898+119903

(13)



Distancebetween BS

and MS = 11 km

Distancebetween BS

and MS = 21 km

Distancebetween BS



ATDnew =119864119894

1 minus PERnew (14)


100

80

60

40

20

0

PER

()




(a)

100

80

60

40

20

0

PER

()




(b)

100

80

60

40

20

0

PER

()




(c)





Proposedscheme

90 kmhr 4561 486 656120 kmhr 4141 4631 1183150 kmhr 3422 4137 2089












References


























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Table 1 Parameters






10(

119901MSBW times 119873

0

)


119871 (BSMS)

(5)





SNR[dB] = 119901


) (6)






1199011015840

119905= 119901119905sinc2 (119891

119889119879)

where 119891119889=119906

120582

(7)


SNR[dB] = 119901

119905[dBm] + 20 log (sinc (119891119889119879))

minus 1198731015840


)

(8)



119887can be


119875119887cong

4

log2119872

[1 minus1

radic119872

]119876(radic[3

119872 minus 1]119864119887

1198730

) (9)



)119905

(10)



1198872)119898)


11990011199011199002))]

119905

(11)

In (11) 1199011199001

and 1199011199002


1198871and 119901

1198872



PER






Pr (Χ) sim 119861 (119896 119899PERnew) = (119899


119896(PERnew)

119899minus119896

where 119899 =120588119889

119906 (

119899

119896) =

119899

119896 (119899 minus 119896)

(12)









30

20

10

0

PER

()




(a)

PER

()


0

20

40

60

25 5



1st TX2nd TX

1st TX2nd TX

(b)

PER

()


0

20

40

60

80

100

25 5



1st TX2nd TX

1st TX2nd TX

(c)






ATDori =119864119894

(1 minus 119875119887)119898+119903

(13)



Distancebetween BS

and MS = 11 km

Distancebetween BS

and MS = 21 km

Distancebetween BS



ATDnew =119864119894

1 minus PERnew (14)


100

80

60

40

20

0

PER

()




(a)

100

80

60

40

20

0

PER

()




(b)

100

80

60

40

20

0

PER

()




(c)





Proposedscheme

90 kmhr 4561 486 656120 kmhr 4141 4631 1183150 kmhr 3422 4137 2089












References


























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











PER






Pr (Χ) sim 119861 (119896 119899PERnew) = (119899


119896(PERnew)

119899minus119896

where 119899 =120588119889

119906 (

119899

119896) =

119899

119896 (119899 minus 119896)

(12)









30

20

10

0

PER

()




(a)

PER

()


0

20

40

60

25 5



1st TX2nd TX

1st TX2nd TX

(b)

PER

()


0

20

40

60

80

100

25 5



1st TX2nd TX

1st TX2nd TX

(c)






ATDori =119864119894

(1 minus 119875119887)119898+119903

(13)



Distancebetween BS

and MS = 11 km

Distancebetween BS

and MS = 21 km

Distancebetween BS



ATDnew =119864119894

1 minus PERnew (14)


100

80

60

40

20

0

PER

()




(a)

100

80

60

40

20

0

PER

()




(b)

100

80

60

40

20

0

PER

()




(c)





Proposedscheme

90 kmhr 4561 486 656120 kmhr 4141 4631 1183150 kmhr 3422 4137 2089












References


























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










30

20

10

0

PER

()




(a)

PER

()


0

20

40

60

25 5



1st TX2nd TX

1st TX2nd TX

(b)

PER

()


0

20

40

60

80

100

25 5



1st TX2nd TX

1st TX2nd TX

(c)






ATDori =119864119894

(1 minus 119875119887)119898+119903

(13)



Distancebetween BS

and MS = 11 km

Distancebetween BS

and MS = 21 km

Distancebetween BS



ATDnew =119864119894

1 minus PERnew (14)


100

80

60

40

20

0

PER

()




(a)

100

80

60

40

20

0

PER

()




(b)

100

80

60

40

20

0

PER

()




(c)





Proposedscheme

90 kmhr 4561 486 656120 kmhr 4141 4631 1183150 kmhr 3422 4137 2089












References


























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










100

80

60

40

20

0

PER

()




(a)

100

80

60

40

20

0

PER

()




(b)

100

80

60

40

20

0

PER

()




(c)





Proposedscheme

90 kmhr 4561 486 656120 kmhr 4141 4631 1183150 kmhr 3422 4137 2089












References


























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation
















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 psfcs: robust emergency communications...

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