Transmit Power Efficiency of Multi-Hop Hybrid Selection/MRC Diversity for a DS-CDMA Virtual Cellular Network

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1 Trasmi ower Efficiecy of Muli-Hop Hybri Selecio/ Diversiy for a DS-CDMA Virual Cellular ework Imae DAOU, Eisuke KUDOH a Fumiyuki ADACHI Dep. of Elecrical a Commuicaio Egieerig, Grauae School of Egieerig, Tohoku Uiversiy Aza-Aoba, Aramaki, Aoba-ku, Seai, Japa {imae, kuoh}@mobile.ecei.ohoku.ac.p, aachi@ecei.ohoku.ac.p Absrac I a muli-hop virual cellular ework (VC) propose for high aa rae mobile commuicaios, he sigal rasmie from a mobile ermial is receive by he muliple wireless pors isribue i a virual cell a relaye o he ceral por ha acs as a gaeway o he core ework. Muli-hop maximal raio combiig () ca be use o reuce he oal rasmi power of he wireless pors alog a roue by combiig he sigals receive from all he previous pors. However, he receive sigals from far previous pors may be very weak a o effecive i iversiy combiig. I orer o reuce he umber of sigals o be combie, we apply he hybri selecio/ (H-S/) iversiy echique. We evaluae by compuer simulaio he power efficiecy of he muli-hop H-S/ a compare i wih ha of. Keywors- Muli-hop iversiy, Trasmi power corol, Wireless muli-hop. I. ITRODUCTIO The mobile commuicaio sysems services are shifig from voice coversaios o aa commuicaios hrough he iere. As he aa rasmissio rae becomes higher, he peak rasmi power icreases. To ecrease he peak rasmi power, a muli-hop virual cellular ework (VC) was recely propose []. I he muli-hop VC, as show i Fig, each virual cell (VC) has a ceral por, which is a gaeway o he ework, a may wireless pors isribue i each VC. A group of he wireless pors works as a virual base saio. If all he wireless pors commuicae irecly wih he ceral por, some wireless pors may ee sigificaly large rasmi powers ue o pah-loss, shaowig loss a muli-pah faig. To avoi his, wireless muli-hop echique is use. Ulike he so-calle wireless a-hoc ework []-[5], each saioary wireless por relays he sigal o he ex por. For uplik (owlik) aa rasmissios, may wireless pors ca be use o relay he sigal rasmie from a mobile ermial (he ceral por) o he ceral por (a mobile ermial). Rouig algorihm is a impora echical issue. Various rouig algorihms have bee propose for wireless muli-hop ework or a-hoc ework []-[5]. They ca be applie o he VC. To icrease he frequecy efficiecy of he VC, a power-efficie rouig algorihm ha miimizes he oal uplik rasmi power while limiig he umber of hops was irouce [6]. While relayig he aa alog a cosruce muli-hop roue, each wireless por alog he cosruce muli-hop roue receives o oly from is immeiaely previous por, bu also may receive from muliple previous pors ha have rasmie he same sigal o heir ex pors. The cocurre receive sigals rasmie from muliple previous pors ca be iversiy-combie [7]. By applyig TC wih muli-hop maximal raio combiig () iversiy, he rasmi power ca be ecrease. However, he receive sigals from far previous pors may be very weak a o effecive i iversiy combiig. I his paper, i orer o reuce he umber of sigals for iversiy combiig, we borrow he iea of he hybri selecio/ (H-S/) iversiy echique [8] a irouce he muli-hop H-S/ o he muli-hop VC. For muli-hop roue cosrucio, a corol chael is use a is carrier frequecy may be iffere from hose of aa chaels for aa relayig. Sice he faig correlaio bewee he corol chael a he aa chaels may o be, he muli-hop roue which miimizes he oal rasmi power eermie by usig he corol chael may o miimize he oal rasmi power of he aa commuicaios. I orer o miimize he rasmi power pealy ue o he faig correlaio, we apply he roue moificaio algorihm [7]. The res of he paper is orgaize as follows. Sec. II preses he muli-hop H-S/ iversiy a he rasmi power aalysis. I Sec. III, he power efficiecy of muli-hop H-S/ is evaluae by compuer simulaio. Sec. IV gives some coclusios. Core ework ework corol saio Wireless por Ceral por Fig. Virual cellular cocep. Virual cell /5/$. (c) 5 IEEE

2 II. MULTI-HO H- S/ DIVERSITY Wih muli-hop relay alog he miimum rasmi power roue, he rasmi power of each wireless por ca be sigificaly reuce; however he iroucio of muli-hop iversiy may furher reuce he rasmi power. I muli-hop relay as illusrae i Fig. (a), each wireless por relays he sigal o is ex por. Bu, he same sigal may be receive by muliple pors alog he roue. A. riciple of muli-hop H-S/ iversiy Fig. (b) explais he cocep of muli-hop H-S/ wih J selece receive sigals. We assume ha he receive sigal from he immeiaely previous por is always selece i muli-hop H-S/. We cosier a -hop relay from he mobile ermial o he ceral por; por # is he mobile ermial a por # is he ceral por, whereas pors # (-) are iermeiae pors. or # receives o oly he sigal rasmie from he por #(-), bu also he same sigal from pors #, #,, #(-). Therefore, he (J-) sroges receive sigals are selece amog he receive sigals from pors #, #,, #(-), a are -combie ogeher wih he oe receive from immeiaely previous por #(-). iversiy is a special case of muli-hop H-S/ wih J equal o he umber of he previous pors. Durig he relayig process, a wireless por may also receive he sigals rasmie from is ex pors. However, hose sigals from he ex pors will be receive afer havig se he sigal a herefore, ca o coribue o muli-hop iversiy combiig. The rasmi power wih muli-hop H-S/ is iscusse below. Time Mobile ermial # # # #3 #4 Mobile ermial Trasmi sigal Wireless por (a) Muli-hop relay. Selecio Ceral por Selecio # # # #3 Wireless por Selecio of oe sigal (b) Muli-hop H-S/ relay. Ceral por #4 Selecio of oe sigal Fig. Muli-hop H-S/ iversiy relay for J. B. Toal rasmi power We assume he ieal TC base o he sigal-o-oise power raio (SR) measureme a he ieal rake combiig. We assume a L-pah faig chael. The receive sigal power r () of por # from he mobile ermial # is expresse as () () r η, L α,,( l), () where () is he mobile ermial rasmi power, α is he pah-loss expoe a,m, η,m a,m (l) are respecively he isace, he log-ormally isribue shaowig loss (i B) wih he saar eviaio of σ a he l-h pah complex pah gai bewee wireless pors # a #m. Therefore, he mobile ermial rasmi power () wih ieal TC is give by () req η, L α,, ( l), () where req is he require receive sigal power. For pors #, he receive sigal power r () a por # is he sum of he receive powers from he selece previous wireless pors a is give by r J ( ) ( ) s s, s, ηs, L, (3) where s is he selece wireless por iex a (s, s,, s J- ) (,,,, -). The receive sigal from he immeiaely previous wireless por is always selece, i.e., s J- -. Sice r () req wih TC a assumig ha he por # has receive more ha J sigals, he rasmi power (-) of he por #(-) is give by ( ) req J, s, L ( s ) s, s, η, L η,. (4) The oal rasmi power oal is give by he sum of he por rasmi powers alog he roue: ( ). (5) oal C. Roue moificaio algorihm If he sum of he receive sigal powers a he por # from he pors #s #s J-, excep from he immeiaely previous por #(-), is larger ha he require receive power, he immeiaely previous por #(-) ca be remove from he cosruce roue; he por # re-selecs he (J-) sroges receive sigals from he previous pors excluig he por #(-). This is calle he roue moificaio algorihm [7]. The rasmi power (-) of he por #(-) is give by Eq. (4)

3 wih replacig (-) by (-). This roue moificaio algorihm ecreases he umber of hops a cosequely, he relay ime. III. COMUTER SIMULATIO Mobile ermials a wireless pors are raomly locae i each VC. The average oal rasmi power alog he roue from a mobile ermial o he ceral por is evaluae by compuer simulaio. I orer o limi he relay ime, he maximum umber of hops is limie o. We iscuss he impacs of he umber J of selece receive sigals, he raio propagaio parameers (pah-loss expoe α, he shaowig saar eviaio σ, he umber L of propagaio pahs a also he faig correlaio ρ bewee he corol chael a aa chaels) a he umber K of wireless pors per VC. A. ormalize rasmi power of muli-hop H-S/ The ormalize average rasmi power orm is efie as he average oal rasmi power alog he roue wih he muli-hop H-S/ iversiy ormalize by ha of he sigle-hop case, i.e., orm E[ oal ]/E[ sigle-hop ], where oal a sigle-hop are give by Eq. (5) a Eq. (), respecively. orm becomes orm E[ E[ E oal ] sigle-hop ] E ( s ) ηs, + J L, + s req η, L,,, η, L, s,. (6) The rasmi power (s ) is give by Eq. () for por #s a by Eq. (4) for pors #s (,,, -) wih replacig #(-) by s. (s ) is obaie recursively from Eq. (6). Sice () req, i ca be easily uersoo ha (s )/ req is o a fucio of req. As a cosequece, orm oes o epe o req. Fig. 3 plos he ormalize average rasmi power as a fucio of he maximum umber of allowable hops wih J as a parameer for α3.5, σ7b, L, a K5. J is he case of o iversiy. iversiy is a special case of muli-hop H-S/ wih J. I is see ha as J icreases, he oal rasmi power ecreases, a J () gives he miimum power. However, wih J5, he power icrease from he case of is oly % for ρ a % for ρ whe. If % of he power icrease is allowe, he umber J of selece receive sigals for muli-hop H-S/ ca be limie o 5. ormalize ower orm.. L α 3.5 σ7b K 5 ρ ρ o iversiy J J3 J4 J5 J6 J7 J Fig.3 Effec of H-S/ o he ormalize average rasmi power alog he roue. B. Impacs of various propagaio parameers Fig. 4 plos he ormalize average rasmi power as a fucio of wih ρ as a parameer. We assume J5, K5, α3.5, σ7b, L a ρ, oherwise sae. I is see ha he rasmi power ecreases as ρ icreases for boh a muli-hop H-S/. Muli-hop H-S/ requires slighly larger rasmi power ha ; his is because he umber of sigals o be combie is limie o J. The power pealy of muli-hop H-S/ is more sigifica for larger values of. This is because, as icreases, he umber of receive sigals ha are o selece i H-S/ icreases, a cosequely, he sum of uselece receive sigal powers icreases also; resulig i he icrease rasmi power pealy. Figs. 5 a 6 plo he ormalize average rasmi power as a fucio of wih α a σ as a parameer, respecively. I is see ha he rasmi power ecreases as α a σ icrease for boh a H-S/. Fig. 7 plos he ormalize rasmi power as a fucio of wih L as a parameer. The rasmi power almos oes o epe o L. However, muli-hop H-S/ requires slighly larger rasmi power ha. The power pealy of muli-hop H-S/ is isesiive o he values of α, σ a L, bu i is more sigifica for larger values of. The power pealy is arou % for. C. Impac of K Fig. 8 plos he ormalize average rasmi power as a fucio of wih K as a parameer. The rasmi power ecreases as K icreases for boh a H-S/. The power pealy of muli-hop H-S/ is isesiive o he values of K, bu i is more sigifica for larger values of. The power pealy is arou % for.

4 . Muli-hop H-S/ wih J5. Muli-hop H-S/ wih J5 ormalize power orm. ρ ρ. ρ.3 ρ.5 ρ.8 ρ L, α3.5, σ7b, K Fig.4 Impac of ρ. ormalize power orm. α3.5, σ7b, ρ, K 5 L 3 L 4 L Fig. 7 Impac of L... Muli-hop H-S/ wih J5 Muli-hop H-S/ wih J5 ormalize ower orm... α4.5 α3.5 α.5 L, σ7b, ρ K ormalize ower orm.. L, α 3.5, σ7b, ρ K3 K4 K Fig. 5 Impac of α. Fig. 8 Impac of K.. ormalize ower orm... σ6 σ7 σ8 Muli-hop H-S/ wih J5 L, α 3.5, K5, ρ Fig. 6 Impac of σ. IV. COCLUSIOS The muli-hop iversiy ca be use o reuce he oal rasmi power of wireless pors alog a roue i he muli-hop VC; bu he receive sigals from far previous pors i each wireless por alog he roue may be very weak a o effecive i iversiy combiig. I his paper, he muli-hop H-S/ iversiy was irouce o limi he umber of sigals o be combie. The power efficiecy of muli-hop H-S/ was evaluae by compuer simulaio. The impac of he umber J of selece receive sigals o he rasmi power was iscusse. I was show ha as J ecreases, he rasmi power icreases, bu he power pealy of muli-hop H-S/ compare o is oly % (%) for ρ () whe J5 a. The rasmi power pealy is more sigifica for larger values of, however, i is isesiive o he values of α, σ, L a K.

5 REFERECES [] E. Kuoh a F. Aachi, ower a frequecy efficie wireless muli-hop virual cellular cocep, IEICE Tras. Commu., Vol. E88-B, o. 4, pp.63-6, Apr. 5. [] E. M. Royer a C. K. Toh. A review of curre rouig proocols for ahoc mobile wireless eworks, IEEE ersoal Commu., Vol. 6, o., pp.46-55, April 999. [3] T. Mukai, H. Muraa a S. Yoshia, Suy o chael selecio algorihm a umber of esablishe roues of mulihop auoomous isribue raio ework, (i Japaese) IEICE Tras. Commu., Vol. J85-B, o., pp. 8-86, Dec.. [4] C. E. erkis, E. M. Belig-Royer, a S. Das, A hoc o ema isace vecor (AODV) rouig, IETF RFC 356, July 3. [5] A. Fuiwara, S. Takea, H. Yoshio, T. Osu a Y. Yamao, Capaciy improveme wih a mulihop access scheme i broaba CDMA cellular sysem, (i Japaese) IEICE. Tras. Commu. Vol. J85-B, o., pp.73-79, Dec.. [6] E. Kuoh a F. Aachi, Trasmi power efficiecy of a mulihop virual cellular sysem, roc. IEEE VTC 3 Fall, Orlao, Floria, USA, Oc. 3. [7] I. Daou, E. Kuoh a F. Aachi, Trasmi power efficiecy of muli-hop iversiy for a virual cellular ework, o appear i IEICE Tras. Commu., Vol. E88-B, Oc. 5. [8] M. Z. Wi a J. H. Wiers, Aalysis of hybri selecio/maximal raio combiig of iversiy braches wih uequal SR i Rayleigh faig, roc. 49 h Au. I. VTC., Vol., pp. 6-, Vacouver, Caaa, Jue 999.