A SELF-OR GA NIZING MULTI-CHANNEL ME UM CC CONTROL MMC) F OR WIRELESS SENSOR WO Kae-Hsiang Kwong, Tsung-Ta W u , Craig Michie, Ivan Andonovic Institute f o r Communications a n d Signal Processing Department o f EEE, Royal College Building, 2 0 4 George Street, Glasgow,United Kingdom [kwong/ twu/c.michie/[email protected]] Abstract-This paper proposes a novel multi-channel medium access control (MAC) protocol designed f o r wireless sensor networks (WSN). Although multiple channel radio communication protocols are well understood in ad h oc wireless a n d other radio networks, most are not applicable i n WSN a s sensor nodes which a r e constrained by l o w cost a n d a primitive physical layer. T h e proposed MAC allows data transmissions take place o n multiple channels simultaneously within a single o r multiple overlapped radio zones. This MAC applies a light weight, two- tier handshaking algorithm permitting sensor nodes t o negotiate a non-occupied channel dynamically. Experimental results show that SMMAC c an improve t h e network performance compared with traditional single channel MAC. Keywords- WSN, medium access control, multiple channels, a n d MANET I . INTRODUCTION Wireless sensor networks have evolved from simple monitoring/data acquisition applications t o multi purpose data hungry applications. These n e w applications place higher demands on t h e networks; f o r example [ 1 ] h as proposed a n ew hybrid network structure which integrates WS N into a wired network. I n [2 ] t h e WSN design principle h a s migrated from l o w data volume t o information-rich data applications i n which data volume h a s increased sharply. T h e design issues o f such applications have been discussed i n other studies [3-4]. In general, a n e w trend c a n b e observed i n which applications i n WS N a r e evolving from traditional lo w data rate monitoring t o high data volume multi-purposes applications. This addresses t h e challenges associated with implementing a MA C a s t h e bandwidth demand of WSN evolves from conventional l o w data applications into data hungry sensor network applications (i.e. video surveillance i n battle field scenarios, o r multiple sensors installed into a node sharing single radio interface). A multiple channel MA C protocol, referred t o a s 'Self- organizing Multi-channel Medium Access Control (SMMAC)' is proposed. SMMAC increases network capacity, reduces packet loss a n d delay b y using a number o f radio channels simultaneously allowing information being transmitted i n parallel across th e network. T h e remainder of th e paper i s structured a s follows: Section 2 firstly reviews a f ew representative multi-channel MACs currently used i n wireless networks. A description o f SMMAC is provided i n Section 3 . Section 4 discusses th e experimentation results obtained from MICAz test bed. Finally t h e paper i s concluded i n Section 5 . I I . RELATED RESEARCH A significant body o f research h a s been reported [6-12] o n multiple channel protocols i n wireless networks. O ne noteworthy protocol i s th e 'Multi-channel MA C (MMAC)' [ 9 ] built o n t o p o f t h e IEEE 802.11 power-saving mechanism. MMAC i s a time-slotted protocol i n which bandwidth i s divided into time slots comprising beacon period, ATIM window a n d data window. Nodes a r e configured t o tune into a predefined signalling channel during t h e ATIM window, i n so doing informing a l l nodes about a ll future transmissions a n d their corresponding channel allocations. Hence a more informed decision regarding their o w n channel allocation c a n b e reached. MMAC requires network-wide temporal synchronization; although time synchronization i s achievable i n t h e WSN environment of ow specification sensors nodes, nonetheless, frequent synchronization introduces a n additional power overhead. T h e 'Dual Busy Tone Multiple Access (DBTMA)' protocol [8 ] equips each node with multiple radio interfaces a n d tw o extra bands o n t o p o f t h e data channel. These 'extra' channels a r e n o t used f o r data transmission b u t a r e primarily used f o r resolving RTS/CTS collisions.
Transcript
8/2/2019 A Self-Organizing Multi-Channel Medium Access Control (SMMAC) Protocol for Wireless Sensor Networks - 5
K a e - H s i a n g K w o n g , T s u n g - T a Wu, C r a i g M i c h i e , I v a n A n d o n o v i c
I n s t i t u t e f o r C o m m u n i c a t i o n s a n d S i g n a l P r o c e s s i n g
D e p a r t m e n t o f E E E , R o y a l C o l l e g e B u i l d i n g , 2 0 4 G e o r g e S t r e e t , G l a s g o w , U n i t e d K i n g d o m
[ k w o n g / t w u / c . m i c h i e / i . a n d o n o v i c @ e e e . s t r a t h . a c . u k ]
A b s t r a c t - T h i s p a p e r p r o p o s e s a n o v e l m u l t i - c h a n n e l mediuma c c e s s c o n t r o l (MAC) p r o t o c o l d e s i g n e d f o r w i r e l e s s s e n s o r
n e t w o r k s ( W S N ) . A l t h o u g h m u l t i p l e c h a n n e l r a d i o
c o m m u n i c a t i o n p r o t o c o l s a r e w e ll u n d e r s t o o d i n a d h oc w i r e l e s s
a n d o t h e r r a d i o n e t w o r k s , m o s t a r e n o t a p p l i c a b l e i n WSN a s
s e n s o r n o d e s w h i c h a r e c o n s t r a i n e d b y l o w c o s t a n d a p r i m i t i v e
p h y s i c a l l a y e r .
T h e p r o p o s e d MAC a l l o w s d a t a t r a n s m i s s i o n s t a k e p l a c e o n
m u l t i p l e c h a n n e l s s i m u l t a n e o u s l y w i t h i n a s i n g l e o r m u l t i p l e
o v e r l a p p e d r a d i o z o n e s . T h i s MAC a p p l i e s a l i g h t w e i g h t , t w o -
t i e r h a n d s h a k i n g a l g o r i t h m p e r m i t t i n g s e n s o r n o d e s t o n e g o t i a t ea n o n - o c c u p i e d c h a n n e l d y n a m i c a l l y . E x p e r i m e n t a l r e s u l t s showt h a t SMMAC c a n i m p r o v e t h e n e t w o r k p e r f o r m a n c e c o m p a r e d
w i t h t r a d i t i o n a l s i n g l e c h a n n e l MAC.
K e y w o r d s - WSN, medium a c c e s s c o n t r o l , m ul t ip l e c h a nn el s ,
a n d MANET
I . INTRODUCTION
W i r e l e s s s e n s o r n e t w o r k s h a v e e v o l v e d f r o m s i m p l em o n i t o r i n g / d a t a a c q u i s i t i o n a p p l i c a t i o n s t o m u l t i p u r p o s e d a t ah u n g r y a p p l i c a t i o n s . T h e s e new a p p l i c a t i o n s p l a c e h i g h e rd e m a n d s o n t h e n e t w o r k s ; f o r e x a m p l e [ 1 ] h a s p r o p o s e d a newh y b r i d n e t w o r k s t r u c t u r e w h i c h i n t e g r a t e s WSN i n t o a w i r e d
n e t w o r k . I n [ 2 ] t h e WSN d e s i g n p r i n c i p l e h a s m i g r a t e d f r o ml o w d a t a v o l u m e t o i n f o r m a t i o n - r i c h d a t a a p p l i c a t i o n s i n w h i c hd a t a v o l u m e h a s i n c r e a s e d s h a r p l y . T h e d e s i g n i s s u e s o f s u c h
a p p l i c a t i o n s h a v e b e e n d i s c u s s e d i n o t h e r s t u d i e s [ 3 - 4 ] . I n
g e n e r a l , a new t r e n d c a n b e o b s e r v e d i n w h i c h a p p l i c a t i o n s i nWSN a r e e v o l v i n g f r o m t r a d i t i o n a l l o w d a t a r a t e m o n i t o r i n g t oh i g h d a t a v o l u m e m u l t i - p u r p o s e s a p p l i c a t i o n s .
T h i s p a p e r a d d r e s s e s t h e c h a l l e n g e s a s s o c i a t e d w i t h
i m p l e m e n t i n g a MAC a s t h e b a n d w i d t h d e m a n d o f WSN
e v o l v e s f r o m c o n v e n t i o n a l l o w d a t a a p p l i c a t i o n s i n t o d a t ah u n g r y s e n s o r n e t w o r k a p p l i c a t i o n s ( i . e . v i d e o s u r v e i l l a n c e i nb a t t l e f i e l d s c e n a r i o s , o r m u l t i p l e s e n s o r s i n s t a l l e d i n t o a n o d e
s h a r i n g s i n g l e r a d i o i n t e r f a c e ) .
A m u l t i p l e c h a n n e l MAC p r o t o c o l , r e f e r r e d t o a s ' S e l f -o r g a n i z i n g M u l t i - c h a n n e l Medium A c c e s s C o n t r o l (SMMAC)'i s p r o p o s e d . SMMAC i n c r e a s e s n e t w o r k c a p a c i t y , r e d u c e s
p a c k e t l o s s a n d d e l a y b y u s i n g a n u m b e r o f r a d i o c h a n n e l ss i m u l t a n e o u s l y a l l o w i n g i n f o r m a t i o n b e i n g t r a n s m i t t e d i np a r a l l e l a c r o s s t h e n e t w o r k . T h e r e m ai nd er o f t h e p a p e r i ss t r u c t u r e d a s f o l l o w s : S e c t i o n 2 f i r s t l y r e v i e w s a f e wr e p r e s e n t a t i v e m u l t i - c h a n n e l MAC s c u r r e n t l y u s e d i n w i r e l e s sn e t w o r k s . A d e s c r i p t i o n o f SMMAC i s p r o v i d e d i n S e c t i o n 3 .S e c t i o n 4 d i s c u s s e s t h e e x p e r i m e n t a t i o n r e s u l t s o b t a i n e d f r o mMICAz t e s t b e d . F i n a l l y t h e p a p e r i s c o n c l u d e d i n S e c t i o n 5 .
I I . RELATED RESEARCH
A s i g n i f i c a n t b o d y o f r e s e a r c h h a s b e e n r e p o r t e d [ 6 - 1 2 ] o nm u l t i p l e c h a n n e l p r o t o c o l s i n w i r e l e s s n e t w o r k s . O n en o t e w o r t h y p r o t o c o l i s t h e ' M u l t i - c h a n n e l MAC (MMAC)' [ 9 ]b u i l t o n t o p o f t h e IEEE 8 0 2 . 1 1 p o w e r - s a v i n g m e c h a n i s m .
MMAC i s a t i m e - s l o t t e d p r o t o c o l i n w h i c h b a n d w i d t h i sd i v i d e d i n t o t i m e s l o t s c o m p r i s i n g b e a c o n p e r i o d , A T I Mw i n d o w a n d d a t a w i n d o w . N o d e s a r e c o n f i g u r e d t o t u n e i n t o a
p r e d e f i n e d s i g n a l l i n g c h a n n e l d u r i n g t h e A T I M w i n d o w , i n s od o i n g i n f o r m i n g a l l n o d e s a b o u t a l l f u t u r e t r a n s m i s s i o n s a n dt h e i r c o r r e s p o n d i n g c h a n n e l a l l o c a t i o n s . H e n c e a m o r ei n f o r m e d d e c i s i o n r e g a r d i n g t h e i r o wn c h a n n e l a l l o c a t i o n c a n
b e r e a c h e d . MMAC r e q u i r e s n e t w o r k - w i d e t e m p o r a ls y n c h r o n i z a t i o n ; a l t h o u g h t i m e s y n c h r o n i z a t i o n i s a c h i e v a b l e i nt h e WSN e n v i r o n m e n t o f l o w s p e c i f i c a t i o n s e n s o r s n o d e s ,n o n e t h e l e s s , f r e q u e n t s y n c h r o n i z a t i o n i n t r o d u c e s a n a d d i t i o n a lp o w e r o v e r h e a d .
T h e ' D u a l B u s y T o n e M u l t i p l e A c c e s s ( D B T M A ) ' p r o t o c o l[ 8 ] e q u i p s e a c h n o d e w i t h m u l t i p l e r a d i o i n t e r f a c e s a n d t w o
e x t r a b a n d s o n t o p o f t h e d a t a c h a n n e l . T h e s e ' e x t r a ' c h a n n e l sa r e n o t u s e d f o r d a t a t r a n s m i s s i o n b u t a r e p r i m a r i l y u s e d f o rr e s o l v i n g RTS/CTS c o l l i s i o n s .
8/2/2019 A Self-Organizing Multi-Channel Medium Access Control (SMMAC) Protocol for Wireless Sensor Networks - 5
I I I . T HE S E L F - O R G A N I Z I N G MULTI-CHANNEL M E D I U MACCESS C O N T R O L ( S M M A C ) P R O T O C O L
I n t h i s s e c t i o n , s i g n a l l i n g p a c k e t s i . e . R e q u e s t T u n e t oC h a n n e l ( R T C ) a n d C h a n n e l t o S e n d ( C T S ) a r e f i r s ti n t r o d u c e d . A d e t a i l e d d e s c r i p t i o n o f SMMAC i s t h e n f o l l o w e d
i n w h i c h a t w o - t i e r p r o c e d u r e i s d e f i n e d a l l o w i n g s e n d e r s a n d
r e c e i v e r s t o a g r e e o n a n o n - o c c u p i e d c h a n n e l f o r t r a n s m i s s i o ni n a p r o m p t l y m a n n e r .
A . S i g n a l l i n g p a c k e t f o r m a t
T h e p a c k e t s t r u c t u r e s o f R T C a n d CT S a r e i l l u s t r a t e d i nF i g u r e 1 . T h e s e p a c k e t s f o r m a c r u c i a l p a r t o f SMMAC. T h e ya r e u s e d b y s e n d e r s a n d r e c e i v e r s d u r i n g t h e c h a n n e l
n e g o t i a t i o n p r o c e s s a n d t h e y a l s o e l i m i n a t e i s s u e s c a u s e d b yh i d d e n t e r m i n a l . T h e R T C p a c k e t i s r e l e a s e d b y a s e n d e r t o ar e c e i v e r i n i t i a l l i n g a n e w s e s s i o n o f p a c k e t t r a n s m i s s i o n s . T h eR T S p a c k e t b e s i d e s c o n t a i n i n g a s o u r c e a n d a d e s t i n a t i o na d d r e s s e s w h i c h i s u s e d t o i d e n t i f y t h e s e n d e r a n d t h e r e c e i v e r .CCL a n d F r a g C o u n t f i e l d s a l s o p r e s e n t . I n t h e CCL t h e s e n d e rd e s c r i b e s t h e c h a n n e l u s a g e a n d i n f o r m s t h e r e c e i v e r w h i c hc h a n n e l s a r e c u r r e n t l y f r e e . O n t h e o t h e r h a n d , t h e F r a g C o u n t i su s e d t o i n f o r m t h e r e c e i v e r t h e n u m b e r o f p a c k e t s w i l l b e
t r a n s m i t t e d .
T h e CT S p a c k e t i s g e n e r a t e d b y t h e r e c e i v e r i n r e s p o n s e t oa R T C . A CT S p a c k e t o n l y c o n t a i n s t h r e e f i e l d s : s o u r c ea d d r e s s , d e s t i n a t i o n a d d r e s s , a n d CCL f i e l d . T h e u s a g e o f
s o u r c e a n d d e s t i n a t i o n a d d r e s s e s i s a p p a r e n t . T h e CCL f i l e d i s
u s e t o n o t i f y t h e s e n d e r t h e n e w l y s e l e c t e d c h a n n e l f o rc o m m u n i c a t i o n .
CCL
S o u r c e a d d r e s s D e s t i n a t i o n 1 0 1 1 1 0 0 0 F r a g C o u n ta d d r e s s
2 b y t e s 2 b y t e s 1 b y t e 1 b y t e
( a )CCL
S o u r c e a d d r e s s D e s t i n a t i o n 0 0 1 0 0 0 0 0a d d r e s s
2 b y t e s 2 b y t e s
( b )
1 b y t e
F i g u r e 1 . ( a ) R T C p a c k e t f o r m a t ; ( b ) CT S p a c k e t f o r m a t .
B . C a n d i d a t e C h a n n e l L i s t
E a c h n o d e m a i n t a i n s a d a t a s t r u c t u r e c a l l e d t h e C a n d i d a t e
C h a n n e l L i s t( C C L )
i n d i c a t e s w h i c h d a t a c h a n n e l i sa v a i l a b l e .T h e CCL o f e a c h n o d e i s u p d a t e d i n a j u s t - i n - t i m e m a n n er . F o r
i n s t a n c e , when a s e n d e r w a n t s t o i n i t i a t e a c h a n n e l n e g o t i a t i o nprocess, i t w i l l s c a n t h r o u g h a l l d a t a c h a n n e l s a n d r e c o r d t h es t a t u s o f e a c h c h a n n e l . T h i s j u s t - i n - t i m e CCL u p d a t e n o t o n l ya l l o w s e a c h n o d e t o m a i n t a i n an a c c u r a t e C C L , i t c an a l s or e d u c e t h e p o w e r r e q u i r e d t o c o n s t a n t l y m o n i t o r t h e r a d i oc h a n n e l s . T h e p r e s e n t e d p r o t o c o l u s es b i n a r y s t a t e t o r e p r e s e n t
t h e c h a n n e l c o n d i t i o n . T h e d e s i g n a t i o n s " O " a n d " 1 " s i m p l y f o r
c o n v e n i e n c e r e p r e s e n t c h a n n e l " b u s y " a n d " f r e e " r e s p e c t i v e l y .F o r e x a m p l e , F i g u r e 1 s h o w s t h a t t h e s e n d e r h a s d e t e c t e d t h a tc h a n n e l 1 , 3 , 4 a n d 5 a r e f r e e a n d t h e r e c e i v e r h a s s e l e c t e dc h a n n e l 3 f o r t r a n s m i s s i o n .
C . P r o t o c o l D e s c r i p t i o n o f S M M A C
T o a i d i n t h e u n d e r s t a n d i n g o f SM M AC , 4 n o d e s ( N o d e AD ) a n d 3 c h a n n e l s ( c h - 1 s i g n a l l i n g c h a n n e l , c h - 2 a n d c h - 3
d a t a c h a n n e l s ) a r e u s e d i n t h e f o l l o w i n g , s i m p l i f i e d e x a m p l e .P o w e r m a n a g e m e n t i s n o t c o n s i d e r e d ; a l l n o d e s a r e s e t t o b e
a l w a y s p o w e r e d o n . E v e n w h e n n o d e s a r e i d l e , t h e y w i l lc o n s t a n t l y m o n i t o r t h e s i g n a l l i n g c h a n n e l . N o d e A i s d e f i n e d a ss e n d e r a n d N o d e B , t h e r e c e i v e r . B o t h a r e r e q u i r e d t o n e g o t i a t ea new c h a n n e l f o r t r a n s m i s s i o n . N o d e C a n d D h a v e a n
e s t a b l i s h e d c o m m u n i c a t i o n i n c h - 2 . T h e n e t w o r k a r c h i t e c t u r e i s
i l l u s t r a t e d i n F i g u r e 2 w h e r e t w o r a d i o e f f e c t i v e z o n e s a r ep r e s e n t e d .
* N o d e A . N o d e B N o d e C N o d e D '
R T C [ c h - 2 , c h - 3 ]
C T S I c h - 3 ]A C K C o m m u n i c a t i o n s :
F i g u r e 2 . I l l u s t r a t i o n o f SMMAC p r o t o c o l .
T h e SMMAC a l g o r i t h m f o r n e g o t i a t i n g a new c h a n n e l i s a sf o l l o w s :
1 . N o d e A s c a n s t h r o u g h a l l a v a i l a b l e d a t a c h a n n e l s . FromN o d e A ' s p e r s p e c t i v e , a l l d a t a c h a n n e l s a r e a v a i l a b l e .H e n c e N o d e A w i l l g e n e r a t e a R T C i n d i c a t i n g t h a t b o t h
c h - 2 a n d c h - 3 a s f r e e c h a n n e l s . T h i s i s t h e n r e l e a s e d i n t h es i g n a l l i n g c h a n n e l . H e r e , i t i s a s s u m e d t h a t t h e R T C h a s
b e e n t r a n s m i t t e d s u c c e s s f u l l y .2 . O n c e N o d e B r e c e i v e s t h e R T C , i t k n o w s t h a t N o d e A i s
r e q u e s t i n g t o e s t a b l i s h a c o m m u n i c a t i o n c h a n n e l f r o m t h es o u r c e a n d d e s t i n a t i o n a d d r e s s i n t h e R T C . N o d e B w i l ls e l e c t c h - 3 t o b e d a t a c h a n n e l s i n c e c h - 2 i s o c c u p i e d . I t
w i l l g e n e r a t e a CT S s e l e c t i n g c h - 3 a n d r e p l y t o N o d e A i nt h e s i g n a l l i n g c h a n n e l .
8/2/2019 A Self-Organizing Multi-Channel Medium Access Control (SMMAC) Protocol for Wireless Sensor Networks - 5
3 . A f t e r r e c e i v i n g CT S r e l e a s e d b y N o d e B , N o d e A w i l lr e p l y N o d e B w i t h a n ACK a n d t h en s wi tc h i m m e d i a t e l y
t o c h - 3 a n d b e g i n t r a n s m i s s i o n .
4 . I f N o d e B r e c e i v e d a n ACK i n r e t u r n , i t m e a n s t h a t t h eCT S h a s b e e n r e c e i v e d b y N o d e A s u c c e s s f u l l y a n d i t w i l ls w i t c h t o c h - 3 a n d b e r e a dy t o r e c e i v e a p a c k e t f r o m N o d eA . O t h e r w i s e , a f t e r w a i t i n g f o r a p r e d e f i n e d t i m e p e r i o d , i t
d e t e r m i n e s t h a t t h e CT S i s l o s t o r h a s c o l l i d e d a n d i t w i l l
p e r f o r m a CT S r e t r a n s m i s s i o n .5 . B o t h N o d e A a n d B w i l l s w i t c h b a c k t o s i g n a l l i n g c h a n n e l
a s s o o n a s t h e c o m m u n i c a t i o n p r o c e s s i s c o m p l e t e d .
I V . E X P E R I M E N T A T I O N
I n t h e f o l l o w i n g e x p e r i m e n t s 3 0 MICAz n o d e s [ 1 4 ] ( 1 5s e n d e r - r e c e i v e r p a i r s ) w e r e u s e d . T h e s e n o d e s w e r e p l a c e dw i t h i n t r a n s m i s s i o n r a n g e o f e ac h o t h e r a n d f o r m e d a s i n g l er a d i o e f f e c t i v e z o n e . T h e d a t a p a c k e t s i z e w a s s e t t o b e 1 1 0b y t e s a n d a P o i s s o n d i s t r i b u t i o n u s e d t o g e n e r a t e d a t a s t r e a m .T h e r e c e i v e r s u t i l i s e d a c o u n t e r t o r e c o r d t h e n u m b e r o f p a c k e t ss u c c e s s f u l l y r e c e i v e d . A t t h e e n d o f t h e e x p e r i m e n t , t h er e c e i v e r s r e p o r t e d o n t h e c o u n t e r v a l u e t o a b a s e s t a t i o n .
T h e r e s u l t s o b t a i n e d f r o m t h e e x p e r i m e n t s a r e s h o w n i n t h ef o l l o w i n g d i a g r a m s . I n t h e l e g e n d o f t h e s e d i a g r a m s , 'BMAC'i s u s e d t o d e n o t e t h e r e s u l t o f s i n g l e c h a n n e l B-MAC p r o t o c o l[ 5 ] . W h e r e a s , ' S M M A C - C H x - F r a g y ' i n d i c a t e s t h e r e s u l t s o f
SMMAC p r o t o c o l ; x r e p r e s e n t s t h e n u m b e r o f d a t a c h a n n e l su s e d i n t h e e x p e r i m e n t a n d y s h o w s t h e n u m b e r o f p a c k e t sb e i n g r e l e a s e d b y t h e s e n d e r i n e a c h t r a n s m i s s i o n s e s s i o n .
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b e t w e e n B-MAC a n d SMMAC w i t h d i f f e r e n t n u m b e r o f
a v a i l a b l e d a t a c h a n n e l s . T h e x - a x i s d i s p l a y s t h e o f f e r e d d a t at r a f f i c l o a d w h i c h i s t h e a g g r e g a t e d t r a f f i c l o a d f r o m a l l 1 5s e n d e r s . I n t h e s e e x p e r i m e n t s , B-MAC h a s s a t u r a t e d w h e no f f e r e d l o a d r e a c h e s 1 5 8 K b p s a n d t h e n e t w o r k t h r o u g h p u ts t a r t s d e g r a d i n g b e y o n d t h i s p o i n t a s h i g h c o l l i s i o n r a t e h a sd e f e r r e d t h e s e n d e r s f r o m s e n d i n g . T h e r e s u l t s o f S M M A Ch a v e c l e a r l y s h o w n t h a t n e t w o r k t h r o u g h p u t i s , i n g e n e r a l ,i m p r o v e d a s t h e t o t a l n e t w o r k c a p a c i t y i s m u l t i p l i e d b yi n t r o d u c i n g e x t r a d a t a c h a n n e l s . T h e e x p e r i m e n t s a l s o i n d i c a t et h a t r e s u l t s o b t a i n e d f r o m 4 - d a t a c h a n n e l SMMAC a r e c l o s e t o2 - d a t a c h a n n e l SMMAC w h e n o n l y o n e p a c k e t i s t r a n s m i t t e db y t h e s e n d e r s a f t e r e a c h RTC/CTS e x c h a n g e . B o t h o f t h e s es y s t e m s b e c o m e s a t u r a t e d w h e n o f f e r e d t r a f f i c l o a d r e a c h e s2 5 0 K b p s . T h i s i s a n i n t e r e s t i n g f i n d i n g a s 4 - d a t a c h a n n e l
SMMAC i s e x p e c t e d t o h a v e a f a r b e t t e r p e r f o r m a n c e g i v e n t h ef a c t t h a t i t s t o t a l n e t w o r k c a p a c i t y i s 5 0 0 K b p s m o r e t h a t 2 - d a t ac h a n n e l SMMAC. T h i s p h e n o m e n o n i s c a u s e d b y c o n g e s t i o ni n t h e s i g n a l l i n g c h a n n e l . W h e n t h e o f f e r e d t r a f f i c l o a di n c r e a s e s t h e a m o u n t o f RTC/CTS g e n e r a t e d b y s e n d e r s a n dr e c e i v e r s w i l l i n c r e a s e l i n e a r l y a n d a l l o f t h e s e p a c k e t s a r et r a n s m i t t e d i n t h e s i g n a l l i n g c h a n n e l .
T h i s p r o b l e m c a n b e r e s o l v e d b y a l l o w i n g t h e s e n d e r s t ot r a n s m i t m o r e t h a n o n e p a c k e t i n e a c h s e s s i o n . I n t h e S M M A Cp r o t o c o l , t h e s e n d e r n e e d s t o i n f o r m t h e r e c e i v e r t h e a m o u n t o f
p a c k e t s w i l l b e t r a n s m i t t e d d u r i n g RTC/CTS e x c h a n g e , t o d os o , t h e s e n d e r n e e d s t o f i l l i n t h e n u m b e r o f p a c k e t s f o rt r a n s m i s s i o n i n F r a g C o u n t .
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a v a i l a b l e d a t a c h a n n e l s i n h i g h o f f e r e d t r a f f i c l o a d .
F i g u r e 5 s h o w s t h e a m o u n t o f p a c k e t l o s s o f a b o v e
e x p e r i m e n t s . O n c e a g a i n , f o r t h e SMMAC s y s t e m s , w h e n o n l yo n e p a c k e t i s t r a n s m i t t e d i n e a c h s e s s i o n , t h e n e t w o r k i s l i m i t e db y c o n g e s t i o n i n t h e s i g n a l l i n g c h a n n e l c a u s i n g s u b s t a n t i a ll o s s e s . T h e f i g u r e a l s o s h o w s t h a t t h e p a c k e t l o s s c a n b e
r e d u c e d b y a l l o w i n g m o r e t h a n o n e p a c k e t b e i n g t r a n s m i t t e d i ne a c h s e s s i o n .
F i g u r e 6 s h o w s t h e r e s u l t s o f SMAAC w i t h 2 , 4 , a n d 6 d a t ac h a n n e l s . I n t h e s e e x p e r i m e n t s , 5 p a c k e t s a r e t r a n s m i t t e d b ys e n d e r s i n e a c h s u c c e s s f u l e x c h a n g e o f R T C / C T S . T h e r e s u l t s
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i n d i c a t e t h a t SMMAC w i t h i t s l i g h t - w e i g h t p r o t o c o l c a n b e
s c a l e d u p t o s u p p o r t 6 d a t a c h a n n e l s or even more.
V. C O N C L U S I O N S
A S e l f - O r g a n i z i n g M u l t i - C h a n n e l MAC (SMMAC) i sp r o p o s e d , a n d f u r t h e r d e v e l o p e d a n d t e s t e d on MICAzh a r d w a r e p l a t f o r m . T i n y o s was s e l e c t e d a n d u s e d f o r s o f t w a r ed e ve l op m en t . E x p er i m e nt a l r e s u l t s h a v e s h o w n t h e p o t e n t i a l o f
t h i s l i g h t - w e i g h t p r o t o c o l t o b e o n e o f t h e t o p c a n d i d a t e s f o rm i g r a t i n g WSN i n t o f u t u r i s t i c i n f o r m a t i o n r i c h a p p l i c a t i o n s .
T h e n e x t s t e p s o f t h i s r e s e a r c h w i l l i n c l u d e e n h a n c e d
SMMAC w i t h m o b i l i t y s u p p o r t , a n d i n d e p t h s t u d i e s o f
SMMAC p e r f o r m a n c e i n a m u l t i - h o p r e l a y e n v i r o n m e n t . T h e s e
f u t u r e s t u d i e s w i l l b r i n g t h e R&D o f WSN c l o s e r t oi m p l e m e n t i n g a h i g h d a t a r a t e a d h oc n et wo r k on t o p o f l o wc o s t / s p e c i f i c a t i o n h a r d w a r e p l a t f o r m .
R E F E R E N C E S
[ 1 ] R u i T e n g , " R B R : A R e g i on - B as e d R ou t i ng P r o t o c o l f o r M o b i l e N o d e si n H y b r i d Ad Hoc N e t w o r k s " , IEEE C o m m u n i c a t i o n s M a g a z i n e , V o l . 4 4 ,
N o . 1 1 , N ov 2 0 0 6 .
[ 2 ] Y o n g h e L i u , S a j a l K . D a s , " I n f o r m a t i o n - i n t e n s i v e W i r e l e s s S e n s o rN e t w o r k s : P o t e n t i a l a n d C h a l l e n g e s " , IEEE C o m m u n i c a t i o n s M a g a z i n e ,
V o l . 4 4 , N o . 1 1 , N ov 2 0 0 6 .
[ 3 ] P . M . R u i z , F . J . R o s , a n d A . G . S k a r m e t a , " I n t e r n e t C o n n e c t i v i t y f o rM o b i l e Ad Hoc N e t w o r k s : S o l u t i o n s a n d C h a l l e n g e s " IEEE Commun.M a g . , O c t . 2 0 0 5 .
[ 4 ] Y . S u n , E . M . B . R o y e r , a n d C . P e r k i n s . " I n t e r n e t C o n n e c t i v i t y f o r AdHoc M o b i l e N e t w o r k s , " I n t ' l . J . W i r e l e s s I n f o . N e t w o r k s , v o l . 9 , A p r .
2 0 0 2 .
[ 5 ] J . P o l a s t r e , J . H i l l , D . C u l l e r : V e r s a t i l e L o w P o w e r M e d i a A c c e s s f o rW i r e l e s s S e n s o r N e t w o r k s . ACM S e n S y s , 2 0 0 4
[ 6 ] J u n g m i n S o , N i t i n V a i d y a , " M u l t i - c h an n e l MAC f o r Ad Hoc N e t w o r k s :
H a n d l i n g M u l t i - C h a n n e l H i d d e n T e r m i n a l s U s i n g A s i n g l e T r a n s c e i v e r " ,MobiHoc 2 0 0 4 .
[ 7 ] Dong Z h en g, J un sh an Z h a n g, " P r o t o c o l D e si gn a nd T h r ou g h p ut
A n a l y s i s o f F r e q ue n c y -A g il e M u l t i -C h a n n e l Medium A c c e s s C o n t r o l " ,IEEE T r a n s a c t i o n s o n W i r e l e s s C o m m u n i c a t i o n s , V O L . 5 , N O . 1 0 , O c t
2 0 0 6 .
[ 8 ] J i n g p u S h i , T h e o d o r o s S a l o n i d i s , E d w a r d W. K n i g h t l y " S t a r v a t i o nM i t i g a t i o n T h r o u g h p u t M u l t i - C h a n n e l C o o r d i n a t i o n i n CSMA M u l t i - h o p
W i r e l e s s N e t w o r k s " , D e p t . o f E l e c t r i c a l a n d C o m p u t e r E n g i n e e r i n g ,R i c e U n i v e r s i t y H o u s t o n .
[ 9 ] R i t e s h M a h e s h w a r i , H i m a n s h u G u pt a a nd S a m i r R . D a s , " M u l t i - c h an n e l
MAC P r o t o c o l s f o r W i r e l e s s N e t w o r k s " , D e p t . o f C o m p u t e r S c i e n c e ,S t o n y B r o o k U n i v e r s i t y .
[ 1 0 ] J a e h y u k C h o i , J o on Y oo , S u n g h y u n C h o i , C h o n g k w o n K i m , " E B A : AnE n h a n c e m e n t o f t h e IEEE 8 0 2 . 1 1 D CF v i a D i s t r i b u t e d R e s e r v a t i o n " ,IEEE T r a n s a c t i o n s o n M o b i l e C o m p ut i n g , V o l . 4 , N o . 4 , J u l / A u g 2 0 0 5 .
[ 1 1 ] Z y g m u n t J . H a a s , J i n g D e n g , " D u a l B u s y T o n e M u l t i p l e A c c e s s
(DBTMA) A M u l t i p l e A c c e s s C o n t r o l S c h e m e f o r Ad Hoc N e t w o r k s " ,IEEE T r a n s a c t i o n s o f C o m m u n i c a t i o n s V o l . 5 0 , N o . 6 , J u n 2 0 0 2 .
[ 1 2 ] G a n g Z h o u , C h e n g d u H u an g , T in g Y an , T ia n H e , J o h n A . S t a n k o v i c ,T a r e k F . A b d e l z a h e r "MMSN: M u l t i - F r e q u e n c y M e d i a A c c e s s C o n t r o lf o r W i r e l e s s S e n s o r N e t w o r k s " , D e p t . o f C o m p u t e r S c i e n c e , U n i v e r s i t yo f V i r g i n i a .
[ 1 3 ] T i n y O S w e b s i t e , h t t p : / / w w w . t i n y o s . n e t
[ 1 4 ] C r o s s b o w T e c h n o l o g y I n c . , h t t p : / / w w w . x b o w . c o m
