The most important third generation (3G) cellular communications standard is based on wideband CDMA (WCDMA). Receivers based on TDMA style channel equalization at the chip level have been proposed for a WCDMA downlink employing long spreading sequences to ensure adequate performance even with a high number of active users. These receivers equalize the channel prior to despreading, thus restoring the orthogonality of users and resulting in multiple-access interference (MAI) suppression. In this paper, an overview of chip-level channel equalizers is delivered with special attention to adaptation methods suitable for the WCDMA downlink. Numerical examples on the equalizers′ performance are given in Rayleigh fading frequency-selective channels
Abstract-Inter-operator spectrum sharing in a widearea broadband network is considered in this paper. A packet-based cellular model is developed, emphasizing the shift in the telecommunications industry towards IP-based services. In the framework of this architecture, we show the ideal maximum load that the network can handle without excessive delays, and present our main result: that even with sharing, this operating point is rarely achieved. This is the consequence of geographical and physical layer constraints, which limit the gains achievable by spectrum sharing. Using a physical layer cellular model with idealistic resource management, we quantify the achievable sharing gains. We further analyze these gains in the context of variable data rates, quality of service guarantees, and number of operators.
The 3rd generation cellular communications standard will be based on wideband CDMA (WCDMA). To obtain adequate performance multiuser receivers, such as LMMSE receivers, can be used. Unfortunately, previously suggested LMMSE receivers cannot be applied in WCDMA systems employing long scrambling codes. In this paper, linear receivers suitable also for downlink with long scrambling codes are studied. These receivers equalize the channel prior to the despreading, thus restoring the orthogonality of users and suppressing multiple access interference (MAI). The numerical results show that chip equalizer based receivers can offer significant performance improvement in comparison to the conventional RAKE receiver.
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