Abstract
In this paper, a coded M-ary pulse position modulation (PPM) scheme for transmitted reference ultra-wideband (TR-UWB) systems is proposed. In conventional M-ary PPM TR-UWB scheme, modulation level M is defined only with a number of possible pulse positions Z. So, Z radio frequency (RF) wideband delay lines are required in order to map data bits into the proper pulse position, which makes such system very impractical to implement when the current CMOS technology is used. In the proposed scheme the number of required delay lines is reduced by mapping data bits in both, pulse position and K different orthogonal codes on frame level of the signal, producing a modulation level of M = KZ. To evaluate the performances of the proposed coded M-ary PPM scheme, the analytical model for realistic IEEE standard UWB channel models is developed. The performances of the proposed scheme are compared with these of the conventional M-ary PPM scheme for the same modulation level M. The results show that the proposed coded M-ary PPM scheme achieves approximately the same bit error probability (BEP), higher data rate and higher bandwidth efficiency, while the hardware complexity is lower in terms of number of required RF delay lines. However, by increasing the number of used orthogonal codes the minimum number of frames per one information symbol rises and consequently the maximum achievable data rate is limited. Thus the trade-off between the number of orthogonal codes and target data rate should be made. DOI: http://dx.doi.org/10.5755/j01.eee.20.10.6797
Highlights
There are many challenges that emerge in development of the short range, high speed communication systems
UWB enables the usage of various modulation types, including on-of keying (OOK) [1], pulse amplitude modulation (PAM) [2], bi-phase shift keying (BPSK) [3], pulse position modulation (PPM) [4], pulse interval modulation (PIM) [5] as well as different hybrid modulation schemes which improves system performances [6], [7]
The proposed scheme requires K times less radio frequency (RF) wide-band delay lines needed to map the data bits in the proper position compared to the conventional Mary PPM scheme
Summary
There are many challenges that emerge in development of the short range, high speed communication systems. At the Rake receiver, the channel estimation is required in order to demodulate the received signal This is a very difficult and hardware demanding task. The scheme proposed in [11] eliminates IPI by using a pair of matched-filters, which allows smaller time delays (less than Tmds) between the reference and the data pulse and the data rate is increased. In this paper the coded M-ary TR PPM scheme is proposed, in which the number of required delay lines is reduced by mapping data bits in both, pulse position and K different orthogonal codes on frame level of the signal. By using the proposed scheme the data rate is increased by reducing the number of RF wideband delay lines (shorter frame time), which increases the bandwidth efficiency when comparing to the conventional M-ary TR PPM system.
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