TR-MAC: An Energy-E cient MAC Protocol for Wireless Sensor Networks exploiting Noise-based Transmitted Reference Modulation

Transcription

1 TR-MAC: An Energy-E cien MAC Proocol for Wireless Sensor Neworks exploiing Noise-based Transmied Reference Modulaion Sarwar Morshed and Geer Heijenk Universiy of Twene, The Neherlands {s.morshed, Absrac. Energy-consrained behavior of sensor nodes is one of he mos imporan crieria for successful deploymen of wireless sensor neworks. The medium access conrol (MAC) proocol deermines he ime a sensor node ransceiver spends lisening or ransmiing, and hence he energy consumpion of he overall node. Transmied reference (TR) modulaion as he underlying physical layer provides new opporuniies and challenges o be explored in he MAC layer. To uilize he advanages and overcome he challenges provided by he TR modulaion, a new energy-e cien MAC proocol TR-MAC ha uses noise-based carrier for wireless sensor neworks is proposed in his paper. TR-MAC realizes muliple access using individual frequency o ses for a pair of nodes, allows boh ransmier-driven and receiver-driven communicaion and is suiable for asynchronous low daa rae applicaion. TR- MAC enables energy-driven communicaion since nodes can adap heir duy cycle based on available energy, hus he proocol becomes energye cien. Keywords: TR modulaion, energy-e ciency, MAC proocol, TR-MAC 1 Inroducion and Moivaion The Medium Access Conrol (MAC) proocol is responsible for addressing and providing a channel access mechanism o enable various nodes wihin a nework o communicae wih each oher in a shared wireless communicaion medium. The physical layer underlying he MAC layer modulaes he daa o he reference signal in order o send i wih a specified frequency hrough he medium. As opposed o regular modulaion echniques, Transmied Reference (TR) modulaion [1] no only sends he modulaed signal, bu also sends he reference signal wih a known ime o se, as presened in Fig. 1 on he lef. Following his, a receiver can resore he original daa by correlaing he received signal wih a delayed version of iself wih he same ime o se since all muli-pah componens conain idenically disored pulses wih consisen muual delay. This ineresing propery of TR modulaion allows o use noise as informaion carrier ha is also easy o generae [2]. The receiver can resore he original signal wihou rake receiver or channel sae informaion or power-hungry sable oscillaors.

2 Consequenly, he signal acquisiion process becomes faser allowing for shorer synchronizaion ime, giving a poenial for reducing power consumpion. Furhermore, frequency o ses can be used in place of ime o ses, because he former are easier o implemen on a chip [2]. Moreover, muliple nodes can ransmi simulaneously by employing various frequency o ses wihou he need for muual iming coordinaion. Therefore, TR modulaion is suiable for asynchronous low daa rae communicaion o ering addiional flexibiliy o he upper MAC layer. However, TR modulaion consumes more power han a general modulaion echnique o ransmi individual bis since he reference signal is also sen. Transmier Receiver Pulse source T 1 LP Daa +Noise T 1 T 2 Daa T 2 Fig. 1. Transmied Reference modulaion In his paper we will invesigae how we can opimally exploi he characerisics of TR modulaion a he MAC layer in order o realize a wireless sensor nework echnique compaible wih energy harvesing. We inroduce a new MAC layer proocol, called TR-MAC, o exploi all he advanages provided by he TR modulaion echnique minimizing is drawbacks. Insead of sending long preambles o inform a receiver ha wakes up abou an upcoming daa packe, TR-MAC sends daa righ away wih a very shor preamble as daa packes in wireless sensor neworks are generally very small. Moreover, he ransmier lisens for acknowledgemen from receiver afer sending each daa burs. Thus he ransmier is able o reduce he lengh of he consecuive daa-lisen burss if i receives an acknowledgemen from he receiver for unsynchronized links. When he link beween a node pair becomes synchronized, hen communicaion in TR-MAC can be ransmier-driven or receiver-driven as boh he ransmier and receiver sore each oher s nex wake up ime. Finally, TR-MAC enables energy-driven communicaion by allowing he nodes o adap heir duy cycle based on he local energy availabiliy. The conribuions of his paper are as follows: (1) we inroduce a MAC proocol, TR-MAC, exploiing he characerisics of TR modulaion; (2) we provide

3 basic models o analyze he energy consumpion of his MAC proocol and wo reference proocols; and (3) we evaluae he energy consumpion and show ha he inroduced MAC proocol in combinaion wih TR modulaion compares favorably o he reference proocols. This paper is organized in 6 secions. Relaed work in Secion 2 is followed by TR-MAC proocol design in Secion 3. Aferwards, Secion 4 describes he TR-MAC modeling and Secion 5 gives he resuls and analysis. Finally, Secion 6 provides our conclusions and fuure work. 2 Relaed Work In his secion, we will analyze exising MAC proocols from he perspecive of energy-e ciency. The proposed MAC proocols in he lieraure are classified ino hree caegories: reservaion-based, proocols wih common acive period, and asynchronous preamble sampling MAC proocols by [3]. Afer exensive analysis, he auhors of [3] claimed ha preamble sampling proocols are he mos energy e cien caegory of MAC layer proocols. The preamble sampling proocols allow he nodes o wake up and sleep independenly of he oher nodes, hus hey are ermed Low Power Lisening (LPL) proocols. However, he receiver has o wake up periodically o check for daa ransmission in he channel. The ransmier precedes he daa packe wih a preamble of maximum lengh equal o he receiver s sleep or check inerval whenever i wishes o send any daa. If he receiver deecs some aciviy in he channel during is periodic wake up ime, i coninues o lisen in order o receive he daa from he ransmier. Compared o he oher caegories, he preamble sampling proocols have a greaer energy saving capabiliy wih less need for nework-wide managemen, hus are very suiable for low daa rae asynchronous applicaions. The preamble sampling proocols can be realized in hree ways as menioned in [3], and he references herein. Firsly, he ransmier can replace he long preamble by shor preamble packe burss wih desinaion address o allow he arge receiver o wake up laer o receive daa, whereas a non-arge receiver can go back o sleep afer receiving a single burs. Alernaively, he ransmier can send preamble-lisen burss o shoren is preamble lengh by an acknowledgemen from he inended receiver if i wakes up. However, hese proocols do no adap preamble lengh for fuure ransmissions and do no send any acknowledgemen afer successful daa ransmission. Proocols like X-MAC [4], SpeckMAC-B [5], ConikiMAC [6] are examples of his caegory of MAC proocols. We ake X-MAC [4] as a reference proocol of his caegory. Secondly, he ransmier can adap is preamble lengh by remembering he receiver s wake up ime for forhcoming communicaions. However, hese receiver-driven proocols are unfavorable for broadcas ra c where one ransmier has o wake up muliple imes for is muliple neighbors. Furhermore, hese proocols have o send he longes possible lengh of preamble for he firs ime communicaion. WiseMAC [7], CSMA-MPS [8], TrawMAC [9], SyncWUF [10] falls ino his caegory. We ake WiseMAC [7] as a reference for his class of proocols. Finally,

4 here are some proocols where he sensor node can adap is duy cycle based on requess from he neighborhood, ra c load, or opology informaion. Neverheless, hese duy cycle adapable proocols are suiable only for applicaion specific scenarios, no for all scenarios; and hey have no mechanism o adap he communicaion based on energy availabiliy on individual nodes. 3 TR-MAC Proocol Design As inroduced in Secion 1, TR modulaion is characerized by fas synchronizaion, allowing for he use of very shor preambles; and inheren muliplexing, allowing for implici idenificaion of possibly simulaneous ransmissions. To exploi hese characerisics, and o miigae he ransmi power penaly of TR modulaion, a new energy-e cien proocol, TR-MAC, is proposed ha combines he bes characerisics from all hree caegories of preamble sampling proocols. TR-MAC allows he receiver o deec any ransmission in he channel wih a very shor preamble because of he inheren benefi provided by underlying TR modulaion. Moreover, small daa packe can be included in he preamble as he daa packes in wireless sensor neworks are generally very small, wihin a range of few byes. As he preamble is a par of he daa packe and TR-MAC sends daa righ away wih he preamble, herefore from now on preamble-daa will be referred as only daa in his paper. TR-MAC sends daa muliple imes o deal wih uncerainy regarding he receiver s wake up ime. Furhermore, jus one bi in he daa packe is enough o insruc he receiver o coninue lisening in case more large daa packes are following he iniial small ones. As ransmission is cosly for TR modulaion, herefore TR-MAC inroduces some lisen periods jus afer every daa packe where he ransmier lisens he medium for acknowledgemen from he receiver. Thus he ransmier minimizes he oal daa-lisen duraion based on he recepion of acknowledgemen from he receiver for firs ime communicaions. Afer firs ime communicaion, boh ransmier and receiver synchronize heir fuure communicaion by soring each oher s nex periodic wake up ime o reduce he daa-lisen duraion in order o save energy. Hence daa ransmission can be eiher ransmier-driven or receiver-driven when he link is synchronized beween a pair of nodes, hus giving a considerable flexibiliy o he upper layers. Moreover, he duy cycle of a sensor node can be adaped based on eiher he available energy on nodes or applicaion requiremen. Therefore he newly proposed TR-MAC proocol is energy-driven, hus energy-e cien. Muliple access is anoher criical issue o address for any wireless sensor neworks. Nodes following he radiional MAC proocols adap heir ransmi imes o deal wih muliple ransmiers aemping o access he channel simulaneously. However, he new TR-MAC proocol achieves muliple access using individual frequency o ses for a pair of nodes, a key advanage creaed by he underlying TR modulaion. Hence collision can be avoided as fuure communicaion will ake place in di eren virual channels by using di eren frequency o ses.

5 The newly proposed TR-MAC proocol has hree saes, as shown in Fig. 2, namely (1) firs ime communicaion; (2) unsynchronized link; and (3) synchronized link. In he firs sage for firs ime communicaion, a node does no have any informaion abou is neighbors. Thus one node ransmis daa-lisen burss in he defaul frequency o se if i wans o send any daa. The receiver periodically lisens o he defaul frequency o se o deec any daa ransmission, like oher preamble sampling proocols. When he inended receiver wakes up and receives a single he daa burs, hen i responds wih an acknowledgemen indicaing a successful ransmission. In his sage, he nodes perform he process of neighbor discovery, exchange he full MAC address, esablish a link idenifier and agree on he frequency o se o be used in he following communicaions. Firs ime communicaion Adap wake up cycle Neighbor discovery Exchange MAC address Esablish link idenifier (Frequency offse) Synchronized Link Remember wake up ime Unsynchronized Link Fig. 2. TR-MAC: Three saes Afer he firs ime communicaion, he proocol moves o he nex, unsynchronized link sage, as presened in Fig. 3. During his sage, he ransmier sends shor daa-lisen burss a he previously agreed upon frequency o se unil i receives an acknowledgemen from he receiver. The receiver lisens o he agreed frequency o se for any daa ransmission. If he receiver is able o deec any daa packe, hen i can derive he link idenifier from he lisening o se and preamble of he daa packe. A very small preamble is enough o deec any ransmission in he channel because of he TR modulaion. The receiver s nex wake up ime is specified in he acknowledgemen packe indicaing wheher he check inerval will be a normal one, or a half or double of he previous one based on ra c load or applicaion requiremen. Also a reques for he ransmier o acknowledge in is nex communicaion wheher he ransmier will follow i or no is indicaed. The ransmier menions wheher i agrees or no on he proposed ime in is nex ransmission. Hence he nodes decide wheher fuure communicaion will be ransmier-driven or receiver-driven. A his poin, he

6 Unsynchronized Link Synchronized Link X-MAC T P,X T A,X T D,X X-MAC T P,X T A,X TD,X A,X Tx T i,x Tx T i,x Rx T S,X T R,X T A,X T D,X Rx T S,X T R,X T A,X T D,X T i,x Overhearer T i,x WiseMAC T P,W T A,W T D,W WiseMAC T P,W T D,W T A,W Tx T i,w Tx Rx T R,W T A,W T D,W Rx T R,W T D,W T A,W T i,w Overhearer T i,w TR-MAC T PD,T T A,T TR-MAC T A,T T PD,T Tx T i,t Tx T i,t Rx T S,T T R,T T A,T Rx T S,T T R,T T A,T T i,t Overhearer T i,t Preamble Idle Preamble Receive Daa ACK wih daa ACK Sleep Lisen lisen Fig. 3. Comparison of MAC Proocols

7 proocol advances o is final synchronized link sage where he link beween a pair of node is synchronized, as shown in Fig.3. During his sage, he nodes already know he frequency o se and he specific ime o wake up o reach a paricular node, hereby opimally minimizing he daa-lisen burs lengh o as minimum as possible. Moreover, in his final sage, he nodes can adap heir duy cycles o mee he requiremens of he nework or anoher node having less energy o increase nework lifeime. A new node joining he nework someimes can move o synchronized sage skipping he unsynchronized sage if he link idenifier can be finalized beween a pair of nodes. The use of boh ransmier-driven and receiver-driven duy cycling provides some ineresing opporuniies o realize energy-e cien muli-hop communicaions a he nework level. For insance, TR-MAC is able o creae a ripple e ec while broadcasing sill mainaining is energy e ciency. The ransmier can insruc is firs hop neighbors o follow is lead and hose can in urn insruc heir respecive neighbors o follow hem in order o broadcas more e cienly: saving boh energy and ime. Finally, a sysem of Green Waves [11] can be creaed o deliver packes o heir desinaions wih limied delay. 4 Modeling In his secion, we presen a mahemaical represenaion of TR-MAC for unsynchronized links in erms of energy consumpion o send or receive a packe and for periodic lisening. We also derived he analyical models for X-MAC and WiseMAC for he previously menioned scenarios and compared wih ha of TR-MAC. The comparison resuls are presened in Secion 5. In he symbols below, we use he comma separaed subscrip T, X, W o denoe a symbol specific for TR-MAC, X-MAC and WiseMAC respecively. If he subscrip is omied, he symbol applies o muliple or all hree MAC proocols. To model he energy consumpion o send or receive a packe, les consider P Tx, P Rx and P S o represen power o send, receive and sleep having values 1 mw, 1 mw and 15 µw respecively. TR-MAC sends boh reference and modulaed signals, hus is power level P Tx,T is 2 mw. The daa rae is considered as 25 kbps and a single daa packe duraion is considered wih 32 bis having duraion 1.28 ms. T W represens he periodic check inerval ha is a summaion of sleep duraion, T S, and periodic lisen duraion, T i. The power consumpion and ime for swiching from sending o receiving and vice-versa are much smaller compared o he oher values, and are negleced in our modeling. The TR-MAC daa packe, T PD,T, consiss of 8 bis of preamble, T P,T, 16 bis of header, T H, followed by 32 bis of daa, T Daa, hus having 56 bis wih duraion 2.24 ms. We also consider he preamble duraion, T P,T, is enough for he receiver o deec any ransmission in he channel because of he inheren advanage provided by he TR modulaion. The acknowledgemen packe, T A,T, consiss of 8 bis preamble, T P,T, and 16 bis header, T H, in oal 24 bis having duraion.96 ms. The daa packes of X-MAC and WiseMAC, T D,X and T D,W respecively, includes 16 bis header, T H, and 32 bis daa, T Daa, hus have 48 bis wih dura-

8 ion 1.92 ms. The symbols and values for TR-MAC, X-MAC and WiseMAC are given in Table 1. The values used for TR-MAC reflec he main characerisics of TR-MAC, i.e., is very shor preamble a he cos of increased ransmission power. Table 1. Sysem parameers Parameers TR-MAC X-MAC [4] WiseMAC [7] Preamble duraion, T P 8bis(.32ms) 65bis(2.6ms) T W ACK duraion, T A 24 bis (.96 ms) 65 bis (2.6 ms) 80 bis (3.2 ms) Header duraion, T H 16 bis (.64 ms) 16 bis (.64 ms) 16 bis (.64 ms) Daa duraion, T Daa 32 bis (1.28 ms) 32 bis (1.28 ms) 32 bis (1.28 ms) Daa+header duraion, T D 56 bis (2.24 ms) 48 bis (1.92 ms) 48 bis (1.92 ms) Power o send, P Tx 2mW 1mW 1mW Power o receive, P Rx 1mW 1mW 1mW All hese preamble sampling proocols have he periodic lisen as heir background energy consumpion, E PL, given by Eq. 1. Here he periodic lisen of TR-MAC, X-MAC and WiseMAC are T i,t, T i,x and T i,w respecively and he sleep duraion are T S,T, T S,X and T S,W respecively. E PL = P RxT i + P S T S T S + T i (1) TR-MAC periodic lisen duraion, T i,t, has o be greaer han or equal o he duraion of he acknowledgemen duraion, T A,T, plus wo imes preamble duraion, T P,T, in order o deec a daa ransmission in he medium given by T i,t T A,T +2T P,T. (2) We ake he minimum duraion for he periodic lisen of TR-MAC in our calculaion o minimize power consumpion because ha is enough o deec a ransmission. Similarly he condiion for periodic lisen X-MAC is given by Eq. 3 and we ake he minimum value of T i,x for calculaion. T i,x T A,X +2T P,X (3) For WiseMAC, he minimum lisen duraion, T i,w, is aken as he minimum preamble duraion, T P,T, because he receiver keeps lisening in case i deecs any ransmission in he channel. Therefore, he periodic lisen for TR-MAC is aken as 40 bis wih duraion 1.6 ms, for X-MAC is aken as 195 bis wih duraion 7.8 ms and for WiseMAC is aken as he minimum duraion o deec any ransmission, ha is 8 bis wih duraion.32 ms, respecively.

9 The expeced energy o send a single packe for TR-MAC, E Tx,T, is given by Eq. 4 and is derived as follows. The energy required for a single cycle of sending a packe of preamble and daa, followed by lisening for an acknowledgemen (regardless of is receip) is given by P Tx,T T PD,T + P Rx T A,T. Always a leas one such cycle is needed for sending he daa, hence he +1. Exra cycles migh be needed depending on when he receiver wakes up. If we assume ha he firs cycle of sending a packe will sar a an arbirary momen beween he sar of wo consecuive lisen periods wih duraion T i,t + T S,T, we can derive he expeced number of exra cycles. If he packe sars wihin he firs T i,t T P,T seconds of he lisen period of he receiver, no exra cycles are needed as he receiver will receive he complee preamble from which i can derive ha i needs o say awake for he res of he packe. If he packe ransmission sars laer, wih probabiliy (TS,T+TP,T) /(T i,t+t S,T), exra cycles will be ransmied unil he nex lisen period of he receiver. On average, he number of exra cycles will be 1 2 (TS,T+TP,T) /(T PD,T+T A,T). The energy needed o send a packe is hus given by! E Tx,T = 1 2. (T S,T + T P,T ) 2 (T i,t + T S,T )(T PD,T + T A,T ) +1 (P Tx,T T PD,T + P Rx T A,T ). (4) In addiion o he periodic lisen energy, he receiver has o spend exra energy o receive a packe. To calculae his addiional energy, he periodic lisen duraion, T i,t, has o be subraced from he expeced exended lisening duraion, T R,T, for he recepion of he daa packe. Furhermore, he energy o send an acknowledgemen has o be added. The addiional energy o receive a packe E Rx,T is given by E Rx,T = P Rx T R,T T i,t + P Tx,T T A,T. (5) The receiver lisen duraion has o be a leas he duraion of a daa packe, and i can be exended up o he acknowledgemen packe duraion plus wo imes daa packe duraion depending on he random wake up ime of he receiver. I is given by T A,T +2T PD,T >T R,T T PD,T. (6) Given ha he wake-up ime of he receiver is uniform by disribued over he inerval, he expeced exended lisening duraion, T R,T, is given by T R,T = T A,T+2T PD,T =T PD,T P (T R,T = )d = 1 2 T A,T T PD,T, (7) which is aken as 96 bis wih duraion 3.84 ms for calculaion.

10 Similarly, he expeced energy o send a packe for X-MAC, E Tx,X,isderived like TR-MAC and given by Eq. 8 wih he excepion ha X-MAC needs o send he daa packe separaely.! E Tx,X = 1 2. (T S,X + T P,X ) 2 (T i,x + T S,X )(T P,X + T A,X ) +1 (P Tx,X T P,X + P Rx T A,X ) + P Tx,X T D,X (8) And he addiional energy o receive a packe for X-MAC does no have he energy o receive a preamble because ha is already calculaed wihin he periodic lisen energy. Therefore only he energy o send an acknowledgemen and he energy o receive he daa packe is presen in he expression o calculae he addiional energy o receive a packe, E Rx,X, given by E Rx,X = P Tx,X T A,X + P Rx T D,X. (9) Finally, he expeced energy o send a packe for WiseMAC, E Tx,W,includes he energy o send a preamble, hen o send he daa and laer o receive he acknowledgemen, E Tx,W = P Tx,W T P,W + P Tx,W T D,W + P Rx T A,W. (10) The receiver has o spend addiional energy E Rx,W o lisen for he preamble, hen o lisen for he daa packe, a las o send he acknowledgemen. So, E Rx,W = P Rx T R,W T i,w + P Rx T D,W + P Tx,W T A,W, (11) where he average receiver lisen duraion is T R,W = TW 2. 5 Resuls and Analysis We compue he analyical models of TR-MAC, X-MAC and WiseMAC for unsynchronized links in Malab in order o compare heir energy consumpion o send or receive a packe and for background energy in periodic lisening. We vary he check inerval duraion, T W, for hese proocols and measured he energy consumpion. The symbols and corresponding values are given in Secion 4 and Table 1. Fig. 4 depics he energy o send a packe. I can be observed ha TR- MAC consumes less energy han WiseMAC even hough TR-MAC needs more power o ransmi a single packe. The reason is ha TR-MAC adaps is oal daa-lisen duraion based on acknowledgemen from receiver whereas WiseMAC sends a full preamble of lengh equal o he check inerval duraion T W. However, X-MAC has less energy consumpion han TR-MAC because of he underlying

11 TR modulaion echnique ha needs more power o ransmi boh reference signal and he modulaed signal. Neverheless, we expec o have advanage over X-MAC because unlike X-MAC, TR-MAC has defined synchronized links where he ransmier is able o adap he sar of he daa-lisen sequence o an opimized value based on he receiver s nex wake up ime. Energy per packe (J) Energy o send a packe TR MAC X MAC WiseMAC Check inerval duraion (s) Fig. 4. Energy o send a packe The oal energy spen a he receiver side can be divided in wo pars: periodic lisen and addiional energy o receive a packe, presened consecuively in Fig. 5 and Fig. 6. The periodic lisen energy in Fig. 5 shows ha TR-MAC is beer han X-MAC as TR-MAC is capable of deecing ransmission wih a smaller preamble, hus he lisen duraion can be smaller. Also he smaller acknowledgemen duraion in TR-MAC allows o have smaller periodic lisen duraion. Neverheless, WiseMAC seems beer han TR-MAC having small periodic lisen duraion. However, WiseMAC overhearers will spend much energy for receiving a packe since hey have o lisen he whole preamble duraion if hey deec any communicaion in he channel in order o receive he daa aferwards. For each packe sen, an overhearer spends he addiional energy shown in Fig. 6. However, a TR-MAC overhearer can go back o sleep jus afer receiving a single daa burs. So no exra energy is spen by overhearers in TR- MAC besides he energy consumpion shown in Fig. 5. Thus TR-MAC will spend much less energy in he long run hough WiseMAC has beer performance for background energy consumpion due o periodic lisen. Fig. 6 represens he addiional energy consumpion of he proocols o receive a packe where he curves for TR-MAC and X-MAC overlap and show very small energy consumpion, bu

12 Energy per second (W) x Periodic lisen energy TR MAC X MAC WiseMAC Check inerval duraion (s) Fig. 5. Periodic lisen energy x 10 4 Addiional energy o receive a packe TR MAC X MAC WiseMAC Energy per packe (J) Check inerval duraion (s) Fig. 6. Addiional energy o receive a packe

13 WiseMAC consumes much energy as a receiver and a poenial overhearer has o lisen on average half of he check inerval duraion in order o receive a packe. 6 Conclusions and Fuure Work The TR-MAC wih noise-based TR modulaion underneah is an energy-e cien MAC proocol suiable for shor-range, low daa rae applicaions ha uilizes all he usefulness of TR modulaion while minimizing is drawbacks. TR-MAC has many aracive characerisics. A ransmier using TR modulaion can use noise as informaion carrier and a receiver can save energy by faser synchronizaion ime wihou power hungry sable oscillaors. In addiion, TR-MAC is capable of sending daa righ away wihou long preambles and receivers can deec ransmission by lisening o he specified o se wih he link idenifier. Moreover, nodes can adap heir duy cycle based on available energy, hus he proocol is oally energy-driven. Furhermore, TR-MAC can be boh ransmier-driven and receiver-driven based on he applicaion requiremen, hus gives much opporuniies for energy-e cien rouing in he nework layer. We modeled and compared he unsynchronized links sage of TR-MAC wih X-MAC and WiseMAC. I urns ou ha TR-MAC has a very low energy consumpion for periodic lisening, which is no a eced by overhearing ransmission for oher receivers, as in he case of WiseMAC. Furhermore, similar o X-MAC bu conrary o WiseMAC, TR-MAC needs very lile energy o receive a packe. Finally, ransmiing a packe is more cosly han in X-MAC, bu his can be compensaed by choosing a shorer check inerval. Overall, TR-MAC is very promising for energy-e cien communicaions in noisy environmens, where only a limied amoun of daa is ransmied beween a single pair of nodes. As our fuure work, we will model he synchronized link sage for TR-MAC and compare wih X-MAC and WiseMAC. We expec o have beer performance for synchronized link sage as TR-MAC has ineresing feaures for ha. In addiion, we will compare TR-MAC wih some oher proocols ha send daa insead of preamble. We will also evaluae TR-MAC wih ra c adapiviy in muli-hop neworks. Finally, energy harvesing will be incorporaed in fuure by leing ransmiers and receivers adap heir duy cycle based on locally available energy. Acknowledgemen This research is suppored by he Duch Technology Foundaion STW, which is par of he Neherlands Organisaion for Scienific Research (NWO), and parly funded by he Minisry of Economic A airs. I is done in he conex of STW projec Walnu: Hard o Crack - Wireless Ad-hoc Links using robus Noise-based Ulra-wideband Transmission. Also Arjan Meijerink is acknowledged for ediorial assisance.

14 References 1. Hocor, R., Tomlinson, H.: Delay-hopped Transmied-Reference RF Communicaions. In: IEEE Conference on Ulra Wideband Sysems and Technologies, pp (2002) 2. Meijerink, A., Coon, S.L., Benum, M.J., Scanlon, W.G.: Noise-based Frequency O se Modulaion in Wideband Frequency-selecive Fading Channels. In: Proceedings of he 16h Symposium on Communicaions and Vehicular Technology in he Benelux, Louvain-la-Neuve, Belgium (2009) 3. Cano, C., Bellala, B., Sfairopoulou, A., Oliver, M.: Low Energy Operaion in WSNs: A Survey of Preamble Sampling MAC Proocols. In: Elsevier Compuer Neworks, Vol: 55, Issue: 15, pp (2011). 4. Buener, M., Yee, G., Anderson, E., Han R.: X-MAC: A Shor Preamble MAC Proocol for Duy-cycled Wireless Sensor Neworks. In: Proceedings of he 4h Inernaional Conference on Embedded Neworked Sensor Sysems, pp Colorado, USA (2006) 5. Wong, K., Arvind, D.: SpeckMAC: Low-power decenralised MAC proocols for low daa rae ransmissions in specknes. In: Proceedings of he 2nd Inernaional Workshop on Muli-hop Ad hoc Neworks: from Theory o Realiy, pp New York, USA (2006) 6. Dunkels, A.: The ConikiMAC Radio Duy Cycling Proocol. Swedish Insiue of Compuer Science, Tech. Rep. T2011:13 (2011) 7. El-Hoiydi, A., Decoignie, J.: WiseMAC: An Ulra Low Power MAC Proocol for Muli-hop Wireless Sensor Neworks. In: Algorihmic Aspecs of Wireless Sensor Neworks, pp: Turku, Finland (2004) 8. Mahlknech, S., Bock, M.: CSMA-MPS: A minimum preamble sampling MAC proocol for low power wireless sensor neworks. In: Proceedings of he IEEE Inernaional Workshop on Facory Communicaion Sysems, pp (2004) 9. Zhang, X., Ansari, J., Mähönen, P.: Tra c aware medium access conrol proocol for wireless sensor neworks. In: Proceedings of he 7h ACM Inernaional Symposium on Mobiliy Managemen and Wireless Access MobiWAC 09, p. 140 (2009) 10. Shi, X., Sromberg, G.: SyncWUF: an ulra low-power MAC proocol for wireless sensor neworks. In: IEEE Transacions on Mobile Compuing vol. 6, issue. 1, pp (2007) 11. Guha, S., Chau, C., Basu, P.: Green Wave: Laency and Capaciy-e cien Sleep Scheduling for Wireless Neworks. In: Proceedings of 29h IEEE Inernaional Conference on Compuer Communicaions INFOCOM, pp San Diego, CA (2010)