DW1000 User Manual
© Decawave Ltd 2017
Version 2.12
Page 209 of 242
9
Operational design choices when employing the DW1000
This chapter discusses some of the operational considerations to using the DW1000 in general RF transceiver
applications, with some additional focus on its use in real-time location systems, (RTLS).
9.1 Operating range
The operational range of the DW1000 depends on the frame data rate and the preamble length. In free-
space, line-of-sight (LOS), this may vary from 60 m at the 6.8 Mbps data rate to up to 250 m at the 110 kbps
data rate. In a typical indoor environment the LOS range is generally larger than the quoted free-space LOS
figure because multipath reflections give extra usable receive signal, e.g. the range at 850 kbps could be 40%
longer (and more) than that quoted for free-space LOS. In non-LOS conditions (NLOS), where there are
obstructions in the LOS path, the range will be reduced due to receive signal attenuation. The operating
range also varies depending on the channel centre frequency and channel bandwidth selected – a lower
centre frequency gets more range than a higher one, while the wider bandwidth channels channel 4 and
channel 6 have more range than the standard 500 MHz bandwidth channels as the wider channel allows
more energy to be sent at a given dBm / MHz regulatory limit.
9.2 Channel and Bandwidth selection
The choice of channel’s centre frequency is often dictated by regional regulations, e.g. USA and EUROPE
have different rules, albeit with some overlap, so channel choice in a product may depend on the target
market for that product. The choice of bandwidth may also depend on whether the resultant spectrum is
within the regional regulations. The IEEE 802.15.4 standard UWB PHY defines a number of channels, from 0
to 10 GHz, some with same centre frequency and different bandwidths, (e.g. channel 2 and channel 4 both
have 3993.6 MHz centre frequency, but have bandwidths of 499.2 and 1331.2 MHz respectively). Table 61 in
section
10.5 – UWB channels and preamble codes
lists the channels supported by the DW1000.
Operating at a wider bandwidth increases range but also increases power consumption. The DW1000 has
fine control of the TX pulse width allowing optimum control of transmitted spectrum bandwidth.
9.3 Choice of data rate, preamble length and PRF
For a given operating centre frequency and bandwidth the choice of data rate generally determines the
operating range. However, the length of the preamble sequence also has a bearing on range.
The preamble is a repeated sequence of pulses following a pattern defined in the IEEE 802.15.4 standard.
See section
10.3 – Synchronisation header modulation scheme
for details. On each numbered channel the
802.15.4 standard defines two preamble codes for the nominal 16 MHz PRF (pulse repetition frequency) and
four preamble codes for the nominal 64 MHz PRF. Table 61 in section
10.5 – UWB channels and preamble
lists the preamble codes allowed on each channel as defined in the IEEE 802.15.4 standard. These
codes are semi-orthogonal. This can allow devices on the same physical channel but using correctly chosen,
different, preamble codes to operate simultaneously under certain circumstances as if on separate
channels. Care should be exercised in the choice of preamble codes and the reader is referred to Decawave
Application Note APH010 on this topic. The preamble sequences’ property of perfect periodic auto-
correlation allows the receiver to accumulate the repeated preamble and ascertain an accurate model of the
