An Overview of Channel Estimation Approaches for UWB impulse radio

Aside from being a very hot research topic from some time, Ultra Wideband (UWB) impulse radio is quickly becoming a reality due to the standardization efforts leading by the IEEE 802.15.3a working group for wireless personal area networks. However, the issue of increasing the receiver performance is still open due to the tough engineering challenges that face its design. Among all the problems that are present in receiver design, two arise as the most difficult to address with a moderate cost-complexity solution: synchronization and channel estimation using extremely narrow pulses in the order of nanoseconds. Timing requirements are rigorous because even small misalignments render symbol detection impossible. Also channel estimation becomes critical for coherent detection but the large number of parameters together with the formidable sample rates required, motivates the search for alternatives to the traditional methods developed for narrowband and spread-spectrum methods. This article focus on channel estimation and it intends to review what are the challenges and some of the approaches that have been proposed to tackle the issue. The work will be further complemented with a report of the topics covered by the NEWCOM summer school on Estimation theory for wireless communications to be held at the Ecole Nationale Supérieure des Télécommunications, Paris, France in October 2005.