New results on the capacity of M-ary PPM ultra-wideband systems
Zhang, J.
Kennedy, R.A.
Abhayapala, T.D.
Dept. of Telecommun. Eng., Australian Nat. Univ., Canberra, ACT, Australia;
This paper appears in: Communications, 2003. ICC '03. IEEE International Conference on
Publication Date: 11-15 May 2003
Volume: 4,
On page(s): 2867- 2871 vol.4
ISBN: 0-7803-7802-4
INSPEC Accession Number: 7906098
Digital Object Identifier: 10.1109/ICC.2003.1204547
Current Version Published: 2003-06-11
Abstract
In this paper, some new results on the capacity of a typical M-ary pulse position modulation (M-PPM) time hopping (TH) ultra-wideband (UWB) systems are presented. Previous results using a "pure PPM model" are proven to exaggerate the real capacity of a UWB system. Based on an extended model containing correlator and soft decision decoding, the capacity is evaluated in the single-user case and in the case of a system with asynchronous multiple user interference (MUI) when the inputs are equiprobable. It is found that only when bit- signal-to-noise ratio (bit-SNR) is high enough, larger M leads to higher capacity; and for a specific M, the optimal values of PPM time offset parameter Td, which maximizes the capacity, are independent of bit-SNR. The influence of MUI on capacity is detrimental, especially in the case of high bit-SNR.
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