Low‐complexity channel estimation and turbo equalisation for high frequency channels

Pilot‐assisted linear turbo equaliser over doubly selective channels

“…N( j) denotes the set of neighbouring variable nodes for check node j and N( j)\i is the set N( j) except the ith variable node. Then the messages for variable nodes from their neighbour check nodes are updated, calculated as (16) where M(i) is the set of neighbouring check nodes for the variable node i and M(i)\j is the set M(i) except the check node j.…”

“…It infers that channel estimation must be conducted first in practice, which makes the performance strongly dependent on the quality of channel estimator. In [14][15][16], adaptive equalisation algorithm, which can track the channel variations, is used to replace maximum a posteriori (MAP) algorithm.…”

Complementary M ‐ary orthogonal spreading OFDM architecture for HF communication link

“…As a powerful complementary or alternative technology to satellite communications, HF communication may possess lower cost and larger flexibility [1]. However, communications in HF band are not considered to be reliable, due to large variations and highly dispersive characteristics of the HF channel, such as multi-path delay, Doppler spread, noise and interferences [2][3][4]. In order to decrease the effects of HF fading channel, direct sequence spread spectrum (DSSS) technique with M-ary orthogonal modulation was employed in HF communications [5], where K data bits were mapped into one of M = 2 K spreading sequences.…”