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A novel scheme for data retransmission for wireless unicast communication is presented. The scheme is based on a transmitter and receiver structure and bit-level data processing using a combination of channel coding and network coding that allows retransmissions to contain the previously incorrectly received information and new information, both destined to the same receiver. Results show that, for the chosen forward error codes, up to 68.75% retransmission throughput gains are achieved compared to HARQ with Chase combining., QC 20120312. © 2011 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. QC 20111201

In this paper, the MIMO framework within WINNER for fourth generation radio systems is further developed and assessed for various deployment scenarios. The emphasis is on radio network system aspects of multi-antenna techniques where preferred configurations for three basic deployment scenarios are given. In the wide area scenario which aims to provide ubiquitous coverage for rural, suburban and urban areas, the scheme selection depends on the user density of spatially separated users. It ranges from grid of fixed beams (GoB) (TDMA based) in case of few users to SDMA with a fixed linear precoding codebook, and finally to adaptive beams with SDMA for highly dense system. In the metropolitan area scenario which is targeting system deployments in large urban environments, multi-user (MU) MIMO precoding performs very well for slow moving users. For higher velocities, per antenna rate control (PARC) or adaptive linear dispersion codes (LDCs) are better choices. In the local area scenario which is characterized by isolated sites, the combination of SDMA and spatial multiplexing achieved by MU-MIMO precoding provides high spectral efficiency., QC 20110712

A Fixed Beam (FB) system that uses a beam specific Secondary-Common PIlot CHannel (S-CPICH) as a phase reference for channel estimation and demodulation in WCDMA is evaluated in a dynamic radio network simulator. The impact of the angular spread on the DownLink (DL) system performance is analyzed. Furthermore, various scrambling code allocation strategies and an adaptive load-dependent power tuning algorithm of the common channels are proposed and evaluated. Extensive simulation results have verified that increasing the number of FB from 1 to 2 or 4 beams per sector in a typical urban radio channel yields significant DL capacity gains., QC 20110217

In this paper, Simulated Annealing is used for designing a fixed multi-beam antenna array (AA) in a multi-user radio WCDMA system. The method can be used dynamically in a real system and/or in a radio planning tool. The proposed method is applied on a linear array by designing the Antenna Element (AE) pattern, the number of fixed beams, the AE spacing, and the AA transmit weights. The proposed method leads to a substantial BS power reduction which can be used to increase the system capacity or data throughput in a WCDMA system., QC 20110217

In this paper, single carrier frequency domain equalization with space time transmit diversity was implemented and evaluated in real-time using a DSP-based wireless MIMO test-bed. A new pilot structure for joint carrier frequency offset (CFO) and channel estimation is proposed and evaluated, to address the adverse inter-symbol interference and the severe CFO due to hardware impairments. The channel estimation method is done in the frequency domain using a non-parametric interpolation method. The new pilot scheme results in significant reduction of the required overhead signalling compared to previous schemes., QC 20110217

A comprehensive study is given of smart antennas for wide-band code-division multiple access (WCDMA). It analyzes, evaluates, and presents methods and ideas for the deployment of smart antennas in WCDMA third-generation wireless systems and for future generations. Three major implementations are evaluated and analyzed in a dynamic system simulator: higher order sectorization (HOS), fixed beams (FBs) with secondary common pilot channel (S-CPICH), and FBs with primary common pilot channel (P-CPICH) as a phase reference. The system modeling integrates antenna and wave propagation modeling to evaluate and design smart antennas in wireless communications. Furthermore, this paper analyzes the impact of angular spread of various antenna configurations, the interaction and impact of radio resource management as power tuning of the common channel, scrambling code (SCO) allocation technique, and soft and softer handover algorithm. Moreover, an SCO allocation strategy and an adaptive load-dependent power-tuning algorithm of the P-CPICH are proposed. Furthermore, a signal-to-(interference plus noise) ratio derivation is given. Extensive simulation studies are carried out to evaluate the capacity gains of HOS and FB. The 12-sector sites yield the best system downlink capacity gain compared to three-sector sites equipped with a single antenna, slightly more than three-sector sites equipped with four FBs each. The six-sector sites equipped with two FBs each reduce the gap between HOS and FB systems to 10%., QC 20111108

This paper analyzes higher order sectorization (HOS) in WCDMA. Sectorization is achieved by splitting the sites into smaller sectors using highly directional antennas. The impact of angular spread on the system throughput is evaluated using a dynamic radio network simulator. Increasing the number of sectors per site from 3 to 6 and 12 in a typical urban radio channel yields a downlink system capacity gain of 80% and 200% respectively. Simulations have shown that the increase in the ratio of users in soft and softer handover per sector is negligible and the impact of angular spread on the system performance of a 6 and 12 sector sites is minor and negligible for the 3 sector sites., QC 20111115

In this paper, single carrier frequency domain equalization with space time transmit diversity was implemented and evaluated in real-time using a DSP-based wireless MIMO test-bed. The implemented schemes supported a large set of modulations, from BPSK up to QAM64. Zero padding is introduced to mitigate inter-block interference. Robust time and frequency synchronization together with channel estimation based on Kalman filtering is used to address the adverse intersymbol interference and the severe carrier frequency offset due to hardware impairments., QC 20111107

The system capacity of speech users in WCDMA system is investigated using a number of different downlink transmit modes. A single antenna sectorized system, a two fixed-beam antenna array, a closed-loop (mode I) and an open-loop space time transmit diversity methods are compared in a dynamic radio network simulator. Frequency selective and flat fading channels are considered. The results show that the diversity gain in flat fading channels is substantial. In frequency selective fading, the benefits of fixed-beam systems are encouraging, whereas the performance of transmit diversity methods (especially the open-loop scheme) are rather unsatisfactory., QC 20111118