- Fundamentals
- What Makes UWB Unique?
- The I-UWB System Model
- The MC-UWB System Model
- Overview of the Book
- Bibliography
This chapter is from the book
This chapter is from the book
This chapter is from the book
1.4 The MC-UWB System Model
1.4.1 Overview of the MC-UWB System
In the past several years, MC-UWB (also called frequency domain UWB) has received a significant amount of attention. The transmit MC-UWB signal s(t) has the following complex baseband form
where N is the number of subcarriers,
)
is the symbol that is transmitted in the rth
transmission interval over the nth
subcarrier, and A is a constant that controls the transmitted power spectral density and determines the energy per bit. The fundamental frequency is
)
.
1.4.2 OFDM UWB
OFDM is a special case of multicarrier transmission that permits subcarriers to overlap in frequency without mutual interference and hence spectral efficiency is increased. Multiple users can be supported by allocating each user a group of sub-carriers. OFDM-UWB is a novel system that has been proposed as a physical layer for high bit rate, short-range communication networks. Reliable communication systems achieve high throughput by transmitting multiple data streams in parallel on separate carrier frequencies. Unlike narrowband OFDM, the OFDM-UWB spectrum can have gaps between subcarriers. OFDM-UWB is one proposed physical layer standard for 802.15.3a Wireless Personal Area Networks.
OFDM-UWB uses a frequency coded pulse train as a shaping signal. The frequency coded pulse train is defined by
where s (t) is an elementary pulse with unit energy and duration Ts < T, and p (t) has duration Tp
= NT. Each pulse is modulated with a frequency
)
where c (n) is a permutation of the integers {1, 2,...,N}. As shown in Chapter 6, the set
)
is orthogonal for k = 1, 2,...,N.