Performance Analysis of Impulse Radio Ultra-Wideband Differential Detection Schemes for Body Area Networks Igor Dotli´ c * and Ryuji Kohno * * Medical ICT Institute, National Institute for Information and Communications Technology 3-4, Hikarino-oka, Yokosuka, 239-0847, Japan Email: {dotlic, kohno}@nict.go.jp Abstract—In this work differentially coherent communication schemes for Impulse Radio Ultra-Wideband (IR-UWB) that transmit single uninterrupted package of energy per symbol, expected to be included in the IR-UWB IEEE 802.15.6 wireless Body Area Networks (BAN) standard are considered. Models for two receiver architectures, suitable for such communication schemes and feasible to implement in current CMOS technology - duty-cycled sampling receiver and chirp receiver are derived. After that, two differential detection techniques for employed receiver architectures - ordinary DPSK and Sample-wise DPSK (S-DPSK) are described. Theoretical analysis of probability of error for S-DPSK is also provided. Performances of the sampling and the chirp receiver architectures with DPSK and S-DPSK detection methods employed are analyzed under narrowband and Frequency-Modulated UWB (FM-UWB) types of interference. I. I NTRODUCTION Since its Effective Isotropic Radiated Power (EIRP) levels are limited by regulations to be very low, application of un- licensed UWB radio is limited to short-range communication systems, such as Personal Area Networks (PAN) or BAN. IR- UWB is a class of UWB devices suitable for low to medium data rate communications in which transmitted symbols con- sist of pulses of energy. Thanks to the fact that IR-UWB data rates are typically low compared to the bandwidths used, duty cycle of IR-UWB communication schemes can be relatively low. This fact gives an opportunity to a IR-UWB devices to employ duty-cycling to its Radio Frequency (RF) front-end. Since transceiver’s RF front-end is typically responsible for a large portion of its overall power consumption, employing RF front-end duty-cycling, i.e. turning off RF front-end for significant percentage of communication time gives a potential for significant power consumption savings. Thus, IR-UWB is attractive for BAN, where power consumption and battery life are critical in many applications, and it is currently being standardized as one of wireless BAN radio interfaces [1]. Classic and widespread IR-UWB communication scheme of using isolated short pulses as chips [2], although inherently having a low duty cycle, is not particularly convenient for duty-cycling of transceiver’s RF front-end; it requires turning RF front-end on and off for each chip transfered and, depend- ing on a data rate, there can be many chips per symbol. In contrast, communication scheme employed by IEEE 802.15.4a IR-UWB standard [3] of transmitting single uninterrupted package of energy (short-pulse burst) as symbol is much more convenient for the duty-cycling of transceiver’s RF front end, since it requires only a single on-off cycle per symbol. When coherence of a IR-UWB communication scheme is considered, we can state that it is true that non-coherent, energy-detection IR-UWB systems are easier to design and have lower power consumption than (differentially) coherent. However, their sensitivity to different kinds of interference is high. This, together with the fact that number of UWB channels of 500 MHz bandwidth available worldwide is only 3 [1] limits their usage in significant number of applications such as medical BAN in which many networks can be co- located. Thus, our attention is directed towards coherent and particularly differentially coherent systems. Differential phase modulation enables both fully coherent detection and differential detection. Some modalities of differ- ential detection allow gathering of a significant portion, if not all, of multipath energy available in the channel without chan- nel estimation. For this reason, differential detection schemes have been studied in IR-UWB, where channel estimation is not trivial and can significantly increase receiver’s complexity. However, all of IR-UWB differential communication schemes studied in available literature are based on isolated short-pulse chips 1 . As mentioned above, it is very likely for a IR-UWB system to operate in the presence of interference and for many appli- cations, such as medical BAN, performance under interference can be critical. Some differential detection methods, especially if no channel estimation is employed, are more sensitive to interference compared to the fully coherent detection methods. Therefore, it is of interest to evaluate how well IR-UWB differential detection schemes perform under interference. In this work we develop a model of differential detection for differential communication schemes, included in the draft of IR-UWB IEEE 802.15.6 wireless BAN standard, that for a sake of efficient duty cycling of transceiver’s RF front-end use single uninterrupted package of energy per symbol. Receiver architectures that are considered are the sampling receiver [5], however, with RF front-end duty-cycling employed and 1 Fairly complete list of references can be found in [4].