Jour na l of Southeast U niversity (Eng lis h Edition) V o.l 22,N o .1,pp .21-25M ar .2006 I SSN 1003 7985
Physical layer design of wireless sensor net work nodes
Z hong Z iguo
Hu A iqun W ang D an
(D epart m ent o f R adio Eng ineer i ng ,So ut heast U n i ve rsit y,N an jing 210096,Ch i na )
Abstract :M ajor consi der ation di m ensi ons fo r the phy sical l ayer design of w irel ess sensor net w ork (W SN )
nodes is analyzed by co m paring differe nt w ireless co mm unication approaches ,di verse m ature sta ndar ds ,i m po rtant radi o frequency (RF )para m eters and various m icr ocontr o ller unit (M CU )so lutions .An i m p l e m entation of theW SN node is presente d w ith experi m ental r esults and a novel one processo rw o r ki ng at t w o frequenc i es energy sav i ng strategy .The lifeti m e esti m ation issue is anal yzed w ith consi derati on to t he peri odical listen required by co mm onW SN m edi a access contro l (M AC )a l gorith m s .It can be concluded that the startup ti m e of t he RF which deter m ines the best sleep ti m e rati o and t he shortest backoff sl o t ti m e ofM AC,the RF frequency and m odulati on m ethods w hic h deter m i nate the RX and TX curren,t and the overall energy consu m pti on of t he dual fr equency M CU SOC (syste m on chi p)are them o st essential factors for theW SN node phy si ca l layer design .K ey words :w ir e l ess senso r net w ork node ;phy si cal layer ;radi o f r equency ;e nergy consu m pti on ;node lifeti m e
Recei ved 2005-06-30.
F oundati on ite m:Th e National H i gh T echnology Res earc h and D eve -l opm en t Progra m of Ch i na (863Program )(No.2003AA 143040).B i ographi es :Z hong Z i guo (1981 ),m ale ,g raduat e ;H u A iqun (corres -pond i ng aut hor),m ale ,doct or ,profess or ,aqhu @s eu .edu .cn .
The w ireless senso r net w o r k (W SN )has been show n to be a prom isi n g prospect in vari o us applica -ti o ns .I n itia l researc h on W SN w as m a i n l y m o ti v ated
by m ilitary app lications :e .g .s m art dust [1]
funded by t h e D efense Advanced Research Pr o j e cts A gency (DARPA ).W ith the exp l o sive developm ent o f m i c ro electro -m echanica l syste m s (M E M S ),integ rated cir -cuits and w ire l e ss co mm un ications ,low co s,t l o w pow er consu m pti o n and ti n y size com ponen ts are off t h e shelf now.W SN has becom e m ore available in civ il applica -ti o ns :e .g .an i m a l obser va ti o n [2],g lacier m on ito ri n g [2],
nuclear pow er plantm on ito ri n g [3]
,etc .
The design of W SN nodes presents a big cha-l
lenge because o f the li m ited resources o f each node .A l o t of w ork has been done i n this area ,such as the M o te s fa m ily i n the s m art dust pro ject i n B er keley ,t h e P i c o Radio pro jec,t also i n B erke ley ,t h e i B adge in UCLA,M I T s PushPi n ,and W ise Ne t i n Sw itzerland .M assi v e deploy m ent o f the nodes requires the co st of each node to be as l o w as po ssible ;the i n conven ience of rep lac i n g the ba tteries and the re l a ti v e ly sl o w ly i m -proved battery techno logy advoca te m ini m al pow er consu m pti o n o r energy ex tracti n g techniques ;s m a ll size is a l w ay s a good advantage during deploy m en.t In the W SN,the co mm unication data ra te is usua lly no t an es -sentia l factor since W SN is deployed usua ll y no t fo r
da ta trans m issi o n but fo r event detecti n g .
I n this paper ,W SN node physica l layer desi g n consi d erati o ns are d iscussed in de tail and an i m ple m en -tation is presented fo ll o w ed by test results and analy sis o f the node s lifeti m e esti m ation.
1 D esign Consideration D i m ensions
W ithout doub,t a good W SN node desi g n needs no t only consi d er t h e physical l a yer ,but a lso other op -ti m ized design spaces [2]such as the opti m ized MAC layer a l g o rithm,the s m art r o ute strategy ,and t h e eff-i
c ient so ft w are sy ste m,etc .In this section ,w e w ill con -centrate on som e basic consideration
d i m ensions fo r th
e desi g n o
f the phy sica l layer .M assive m anufacture can settle the co st pr ob l e m;here energy is t h e m a j o r facto r .1 1 A rchitecture o f the node
Fig .1show s the syste m architecture o f a generic W SN node .
Fig .1 W S N node a rchitecture
The basic parts are com po sed o f fo ur entiti e s .The pow er supp l y and m anage m ent m ode,l usua ll y som e kind o f battery ,prov ides the nodes e lectrical ener g y .
