A dispersive channel in the DS-CDMA downlink destroys the orthogonality of the synchronous users' spreading sequences. In this paper, we aim to re-establish this orthogonality blindly by means of a common chip-level equaliser. The adaptation algorithm is based on a constant modulus criterion forcing the various user symbols onto a constant modulus, for which a stochastic gradient descent algorithm is derived. This algorithm is structurally similar to a multiple error filtered-X LMS type approach, whereby the equaliser input CM update is replaced by a spreading code filtered version. Various simulations demonstrating the algorithm's convergence and noise performance are presented.
The purpose of this study was to investigate the effect of heel construction on ankle joint mechanics during the early stance phase of running. Kinematic and kinetic parameters (ankle joint angles, angular velocities and joint moments, lever arms of ground reaction force, triceps surae muscle tendon unit lengths, and rates of muscle tendon unit length change) were calculated from 19 male subjects running at 3.3 m/s in shoes with different heel constructions. Increasing heel height and posterior wedging amplified initial plantar flexion velocity and range. The potential for a muscle to control the movement of a joint depends upon its ability to produce joint moments. Runners in this study showed decreased external eversion moments and an increase in eversion range. Maximum eversion angles were not significantly affected by shoe conditions. Without considerable tendon prestretch, joint moment generation potentials of triceps surae and deep plantar flexors might be inhibited due to rapid plantar flexion based on the force–velocity relationship. It could be speculated that increasing ankle inversion at heel strike could be a strategy to keep maximum eversion angles inside an adequate range, if joint moment generation potentials of deep plantar flexors are inhibited due to rapid plantar flexion.
This paper focusses on the problem of the switching threshold between multicast and unicast transmission in the downlink of an OFDM based air interface. In general, unicast transmission can benefit from high rate channel state information and is flexible in downlink rate adaptation, but the number of required resources scales with the number of users. Multicell multicast, which is in discussion for the 3GPP Long Term Evolution standard, is more economic in terms of resource allocation and can benefit from multi-site simulcasting. However, for multicasting channel feedback information may not be available and the downlink transmission cannot be adapted individually. We evaluate the cost of setting up a multicast by analyzing the downlink throughput and resource allocation based on radio network simulations and provide switching thresholds indicating which cell user density is required to make multicasting beneficial compared to unicasting.
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