VTVT Bradley Department of Computer Engineering, VA 24061, 'J.1£lLC;i1U��U, wochung 1, .�bstrtlct -�al'gE' ad hoc and sensor networks impose stringent constramts on cost and energy efficiency. Impulse based ultra wideband (I-UWB) is an atiractivf' ramo technology, and we have df'Veloped fonr medium access (MAC) protocols to support 1-1JWB radios in such nf'IM.,, ·k,, _ The fOlll' MAC protocols are multichannel ALOHA (M-ALOHA): mn1tic�DDE'1 sense multiple access (M-PSMA), PS� wlih COIliSIOIl (PSMAlCA), and busy signal mnltiple access (BSMA). These MAC protocols pe1'lmt random, disttibnted medium IIccess with no central point of failDre. Thi,,; paper chllraciel'izes the energy efficiency, throughput, and delay oft h e The results suggest appropriate application :;; c, enarios each of the protocols. Index Terms -Ad hot and sensor networks, busv medimn access contl'Ol" pulse sense, ultra wideband • L ThTROIJUCTION Ad hoc and sensor netwotks demand low cost and dlslllp-atI,cm, and the radio and medium access control pnJtoCOJl h!�avIly influence cost and For ad hoc and sensor networks, UWB of IEEE 802.15.4a attractive due to its resilience to harmful nnlltipat:h trallSlID s:sicm power. I-UWB systems that have a width picoSe�COltlds and a bandwidth on repetition interval (pRI) is the width. We have low-cost I-UWB llensotnetworks [1]-[4]. for I -UWB are well target cellular and small area networks. Central coordination increases colmple:x:ity and overhead in large and it also leads of failure. Instead of centralized Of()toll ds witb an Otherwise, the source node waits a random period of time to retransmit the dsta. ALOHA well under traffi c but In narro Vlrbmld conclllT ent transmissions do not nel:: essall 1v int,erfier e with each other. Even with the I-UWB contain a large amount of between at moderate pulse rates. The dead tinle allows several concurrent transmissions to be time-intel"leaved_ The timeinterleaved trains occupy diffe rent channels, Hence, in an I-UWB ALOHA acts as a multichannel MAC Our multichann el ALOHA \ IV_L-.t-'1-L\Jl:1Lr1./ Dl"()to,:ol increases as to because concurren t transltnillSilJnS differ,ent channe ls do not collide_ the method of the cOlnp]texityand decrease s the sub-channel data rate. Code intmduces baseband and decreases the sub-chann el data rate the fadot. Frll quenc:y division adds front-end cOllI1Plexity the data rate by the Time centralized control and decreases the sub the nun'lher of time slots. In contrast neithe...