Multipath Channels with Strong Doppler Effects

Authored by: Paulo Montezuma , Fabio Silva , Rui Dinis

Frequency-Domain Receiver Design for Doubly Selective Channels

Print publication date:  June  2017
Online publication date:  June  2017

Print ISBN: 9781138700925
eBook ISBN: 9781315169576
Adobe ISBN:

10.1201/9781315169576-7

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Abstract

In broadband mobile wireless systems the channel’s impulse response can be very long leading to very large blocks, with hundreds or even thousands of symbols. Under these conditions it can be difficult to ensure a stationary channel during the block duration, which is a crucial requirement of conventional SC-FDE receivers. In order to avoid significant performance degradation due to strong Doppler effects, wireless systems based on SC-FDE schemes employ frequency-domain receivers which require an invariant channel within the block duration. Hence, a significant performance degradation occurs if the channel changes within the block’s duration. SC-FDE detection is usually based on coherent receivers, therefore accurate channel estimates are mandatory. These channel estimates can be obtained based on training sequences and/or pilots [16]. Although the use of training sequences allows an efficient and accurate channel estimation, as seen in Chapter 5, these estimates are local and the channel should remain almost constant between training blocks, something that might not be realistic in fast-varying scenarios due to strong Doppler effects.

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