Coded modulation in UWB communications

Exploiting the abundant freedom of UWB signals can increase the Euclidean distance among codewords which will lead to an enhancement of the communication quality. In this paper, a coded modulation UWB system combining PPM, PAM and convolutional coding is proposed, which can significantly increase the power efficiency without degrading the data rate. The performance of this coded modulation system primarily depends on the free Euclidean distance and the number of corresponding error bits induced by the error paths. The code generator with maximal minimum free distance and minimum error bits is found to optimize the system. In order to avoid the difficulty of channel estimation and accurate time synchronization in rich multipath environments, a joint multiple symbol detector and decoder for the coded modulation system is presented which is able to approximate the performance of uncoded PPM system in AWGN channel under viable computational burden. Simulation results obtained from Nakagami multipath channel agree with our analysis.