Driver Assistance Technical Report D Analytical Performance Considerations of p. Date:

Size: px

Start display at page:

Download "Driver Assistance Technical Report D Analytical Performance Considerations of p. Date:"

Marcia Martin
5 years ago
Views:

1 Driver Aiance Technical Repor D Analyical Performance Conideraion of 802.p Dae: Bernhard Kloiber, Thoma Srang, Fabian de Pone Müller

2 Table of conen Inroducion... 3 The freeway, a challenging reference cenario... 4 Simple hroughpu conideraion... 5 Communicaion overhead... 7 Mean channel occupancy... 8 Mean arrival rae and iner arrival ime... 9 Concluion... 0 Reference... 2 Seie 2 von 2

3 Inroducion Fuure driver aiance yem uch a Cooperaive Adapive Cruie Conrol (CACC) are baed on he periodic beaconing of Cooperaive Awarene Meage (CAM) from vehicle in he viciniy uing he IEEE 802.p communicaion echnology. 802.p provide everal 0 MHz channel locaed in he 5,9 GHz frequency band, which have o be hared among all communicaion paricipan. The mo imporan one i he conrol channel (CCH) which i ued for he beaconing of CAM. In high dene raffic cenario he number of communicaion paricipan migh be high enough o caue congeed channel, which lead o a dramaic decreae of he communicaion performance and he reliabiliy of he whole yem. Thi echnical repor um up ome analyical performance conideraion, baed on implified aumpion. We primarily addre Media Acce Conrol (MAC) layer iue a hey are paricularly challenged by a high number of fa mobile node. The main arge of hi preliminary analyi i o e he cope for a comprehenive imulaive performance analyi. Seie 3 von 2

The freeway, a challenging reference cenario Figure how a poible claificaion of differen cenario uing acciden aiic provided by he Saiiche Bundeam in Germany.

4 The freeway, a challenging reference cenario Figure how a poible claificaion of differen cenario uing acciden aiic provided by he Saiiche Bundeam in Germany. Figure : Claificaion of differen cenario We will inveigae a freeway cenario which eem o be he mo challenging one for he communicaion in Vehicular Ad-hoc NET (VANET) in erm of media acce. Thi freeway cenario i decribed by he following parameer and i he bae for he re of hi echnical repor: Number of lane l in each direcion: 6 Mean ime ahead diance AD (ee below) beween conecuive car: / 2 Communicaion range r: 000 m CAM ize m: 00 Bye / 250 Bye / 500 Bye CAM ranmiion frequency f: Hz / 2 Hz / 0 Hz Gro daa rae R: 6 Mbp (Defaul on CCH) Slo ime S : 3 μ Mean velociy v: 30 m/ By uing he mean ime ahead diance and he mean velociy, he mean diance d beween conecuive car can be calculaed: d vad m d m AD 2 m d 30 30m AD Seie 4 von 2

5 A we now know he mean diance, we can calculae he mean number n of car on he freeway wih l lane per direcion wihin he communicaion range r: r n2 l2 d n 408 n AD 2 AD 804 Simple hroughpu conideraion For ome fir hroughpu conideraion, we will neglec he overhead caued by MAC and PHY header. Furher inveigaion including he MAC/PHY overhead will be hown in he nex ecion. Uing he poible number of car wihin communicaion range, he differen CAM ranmiion frequencie and CAM packe ize, he ne hroughpu S can be calculaed by he following equaion: S nm f For a CAM packe ize of 00 Bye, hi reul in: S 40800ByeHz 40,8 0,3264 n408, f Hz S 40800Bye2Hz 8, 6 0, 6528 n408, f 2Hz S 40800Bye0Hz 408 3,264 n408, f 0 Hz S 80400ByeHz 80, 4 0, 6432 n804, f Hz S 80400Bye2Hz 60,8, 2864 n804, f 2Hz S 80400Bye0Hz 804 6, 432 n804, f 0Hz Seie 5 von 2

6 Conidering a CAM packe ize of 250 Bye, he reul are he following: S ByeHz 02 0,86 n408, f Hz S Bye2Hz 204, 632 n408, f 2Hz S Bye0Hz 020 8,60 n408, f 0 Hz S ByeHz 20, 608 n804, f Hz S Bye2Hz 402 3, 26 n804, f 2Hz S Bye0Hz 200 6, 080 n804, f 0Hz Finally, wih a CAM ize of 500 Bye we ge: S ByeHz 204, 632 n408, f Hz S Bye2Hz 408 3, 264 n408, f 2Hz S Bye0Hz ,320 n408, f 0 Hz S ByeHz 402 3, 26 n804, f Hz S Bye2Hz 804 6, 432 n804, f 2Hz S Bye0Hz ,60 n804, f 0Hz Seie 6 von 2

7 Communicaion overhead A already menioned he hroughpu conideraion o far do no include any communicaion overhead caued by addiional MAC and PHY header or railer, arbiraion and conenion procedure. In Figure 2 he complee MAC frame forma i hown. The differen header field um up o a lengh of 32 Bye, he railer conain he 4 Bye frame check equence. Thi make a oal of 36 Bye MAC overhead. Figure 2: MAC frame forma [] The PHY frame forma i depiced in Figure 3. I ar wih 0 hor and 2 long preamble ymbol, which have in oal a duraion of 32 μ. The preamble i hen followed by one 8 μ OFDM ymbol. Addiional 2 Bye for ervice are par of he PHY header a well. For he PHY railer we have 6 ail bi and ome pad bi (which we aumed o be 2 bi), o ha hi reul in Bye for he railer. Alogeher he PHY overhead coni of fixed 40 μ plu 3 Bye ranmied wih he choen daa rae (6 Mbp in our cae). Figure 3: PHY frame forma [] For arbiraion we aume ha CAM are ranmied uing he highe AC (Acce Caegory), i.e. hey are queued ino he AC[VO] (AC VOice) queue. The duraion of he AIFS (Arbiraion InerFrame Space) for voice raffic (AIFS[VO]) i calculaed according o [] by he following formula: AIFS[ VO] SIFS AIFSN[ VO] S The minimum conenion window ize CW min for AC[VO] i 4. Becaue CAM are broadca meage, he binary exponenial backoff mechanim doen work, i.e. he conenion window ize Seie 7 von 2

8 ay 4. The backoff couner i randomly choen ou of he inerval [0; CW min - ], conequenly he mean backoff couner ize i,5. Thi reul in a mean conenion duraion C of C S Auming ha here i alway conenion in high dene cenario, each node i pending AIFS[ VO] C 589,5 77,5 per packe for arbiraion and conenion in average. Mean channel occupancy Wih he addiional knowledge abou he communicaion overhead i i hen poible o calculae he mean channel occupancy occ for each meage by he following equaion: occ AIFS[ VO] C PHY _ preamble PHY _3 Mbp PHY _6Mbp MAC CAM Uing all he aumpion above, we ge for he differen CAM packe ize: 3Bye 36Bye 00Bye occ 58µ 9,5µ 32µ 8µ 302,8 m00bye Mbi Mbi Mbi µ Bye 36Bye 250Bye occ 58µ 9,5µ 32µ 8µ m250bye Mbi Mbi 502,8µ 6 6 Mbi 6 3Bye 36Bye 500Bye occ 58µ 9,5µ 32µ 8µ 836, 2 m500bye Mbi Mbi Mbi µ Auming each meage occupie he channel for he duraion calculaed above and he meage arrive in a manner ha no colliion occur, hen he mean number of poible meage ranmiion c per econd can be calculaed by he equaion: c occ For he differen CAM meage ize we ge a mean number of poible meage ranmiion: c c c m00bye m250bye m500bye ,8µ ,8µ ,2µ Seie 8 von 2

9 Mean arrival rae and iner arrival ime Knowing he mean number of car wihin he communicaion range and he CAM ranmiion frequency, he mean arrival rae can be calculaed by he following equaion: n f Uing he poible number of car wihin communicaion range and he differen CAM ranmiion frequencie we ge: CAM 408Hz 408 n408, f Hz CAM 4082Hz 86 n408, f 2Hz CAM 4080Hz 4080 n408, f 0 Hz CAM 804Hz 804 n804, f Hz CAM 8042Hz 608 n804, f 2Hz CAM 8040Hz 8040 n804, f 0Hz The arrival rae calculaion above lead u o he mean iner arrival ime arrival wihin he communicaion range beween conecuive meage: arrival arrival n408, f Hz arrival n408, f 2Hz arrival n408, f 0Hz arrival n804, f Hz arrival n804, f 2Hz 2,45m CAM 408,225m CAM 86 0,245m CAM 4080,244m CAM 804 0,622m CAM , 0 0,24 CAM 8040 arrival n f Hz m Seie 9 von 2

10 Concluion Thi echnical repor repreen imple performance conideraion for IEEE 802.p by analyical calculaion under implifying aumpion. The main purpoe of he analyi wa o ge a e of indicaor o e he cope for a imulaive comprehenive analyi he performance of he MAC layer in IEEE 802.p baed VANET. Conidering our freeway reference cenario we calculaed he neceary ne hroughpu of he communicaion channel. We eimaed ne and gro hroughpu limi, i.e. wih and wihou he overhead caued by MAC/PHY header, arbiraion and conenion procedure. The ne reul how pure neceary hroughpu for perfecly equenially arriving CAM. Compared wih he gro daa rae provided by each 802.p channel i became obviou, ha high dene raffic cenario can produce uch high amoun of daa raffic ha he channel capaciy i exceeded. The mean channel occupancy per meage how he amoun of ime each meage occupie he communicaion channel in average, including alo he communicaion overhead, i.e. MAC/PHY header and arbiraion and conenion procedure. Uing hi informaion he oal amoun of CAM ranmiion per econd can be eimaed. The mean arrival rae and iner arrival ime of CAM, dependen on he repecive communicaion cenario, have been calculaed a well. In comparion wih he mean channel occupancy for high daa raffic cenario, he mean iner arrival ime i horer han he mean channel occupancy of he meage hemelve. Our analyi ha hown ha a imulaion environmen for high dene raffic cenario hall be able o uppor around 400 vehicle in recepion range of abou 000m for a ypical peed dependen pacing beween he vehicle. Each node in he nework hall be able o proce abou 200 CAM meage of a ypical ize of 500 bye (igned CAM). Depending on oher facor uch a increaed beaconing frequency, he imulaion parameer migh be even more challenging. Seie 0 von 2

11 Li of Acronym AC AIFS CACC CAM FCS MAC NET OFDM PHY PLCP QoS SIFS VO Acce Caegory Arbiraion InerFrame Space Cooperaive Adapive Cruie Conrol Cooperaive Awarene Meage Frame Check Sequence Media Acce Conrol NETwork Orhogonal Frequency Diviion Muliplexing PHYical Phyical Layer Convergence Procedure Qualiy of Service Shor InerFrame Space Voice Seie von 2

12 Reference [] IEEE Compuer Sociey, IEEE Sd Par : Wirele LAN Medium Acce Conrol (MAC) and Phyical Layer (PHY) Specificaion, June 2007 Seie 2 von 2

Performance optimization of a MAC protocol with multiple. contention slots in MIMO ad hoc networks

Performance optimization of a MAC protocol with multiple. contention slots in MIMO ad hoc networks Performance opimizaion of a MAC proocol wih muliple conenion lo in MIMO ad hoc nework Qiang Gao *, Li Fei, Jun Zhang, Xiao-Hong Peng 2 School of Elecronic and Informaion Engineering Beihang Univeriy, Beijing