This paper considers a millimeter-wave wideband point-to-point MIMO system with fully digital transceivers at the base station and the user equipment (UE), focusing on mobile UE scenarios. A main challenge when building a digital UE combining is the large volume of baseband samples to handle. To mitigate computational and hardware complexity, we propose a novel two-stage digital combining scheme at the UE. The first stage reduces the Nrreceived signals to Ncstreams before baseband processing, leveraging channel geometry for dimension reduction and updating at the beam coherence time, which is longer than the channel coherence time of the small-scale fading. By contrast, the second-stage combining is updated per fading realization. We develop a pilot-based channel estimation framework for this hardware setup based on maximum likelihood estimation in both uplink and downlink. Digital precoding and combining designs are proposed, and a spectral efficiency expression that incorporates imperfect channel knowledge is derived. The numerical results demonstrate that the proposed approach outperforms hybrid beamforming, showcasing the attractiveness of using two-stage fully digital transceivers in future systems.

Digital phased arrays have often been disregarded for millimeter-wave communications since the analog-to-digital converters (ADCs) are power-hungry. In this paper, we provide a different perspective on this matter by demonstrating analytically and numerically how the ADC resolution can be reduced when using digital phased arrays. We perform a theoretical analysis of the quantization noise characteristics for an OFDM signal received and processed by a digital phased array, using Gaussian approximation of the OFDM signal. In particular, we quantify the quantization noise suppression factor analytically and numerically. This factor describes how much the coherent combining reduces the quantization noise as a function of the number of antennas, which allows for reducing the ADC bit resolution. For instance in a 8–16 antenna digital phased array the ADC resolution can be reduced with 1–2 bits compared to the ADC required for an analog phased array.

In E-UTRAN multiple co-located carriers will typically be deployed requiring efficient inter-frequency (IF) handover procedures and algorithms for retaining service quality, better coverage and load balancing between the carriers. Five IF handover criteria using RSRP, RSRQ or combination thereof are investigated in synchronous and asynchronous E-UTRAN deployment scenarios. The results depict that an IF handover solely based on RSRP significantly increases number of handovers. Conversely the handover criterion based only on RSRQ reduces handovers but it slightly increases the packet loss rate. The overall best performance is achieved with the combined handover criterion, which uses both RSRP and RSRQ and thus guarantees that the received pilot strength as well as the signal quality stays within the desired limit after the handover.

An important feature of HSDPA (high speed downlink packet access) for WCDMA is to provide very high data rates, up to several Mb/s in the downlink. In order to achieve these high data rates, a good receiver design is needed. Further, from a terminal perspective, the receiver design needs to be efficient from a cost, current and size perspective. A direct conversion receiver fulfills these criteria. However, such a receiver design often suffers from DC-offset and I/Q gain and phase mismatch, degrading the receiver performance. In this paper we make an analysis of how such impairments affect the performance in HSDPA. It is furthermore shown in the paper that by doing a good receiver design the implementation losses due to direct conversion impairments can be made small providing a possibility to make cost efficient HSDPA terminals with good receiver performance.

We analyze how the sampling instant error affects the receiver performance in a raised-cosine filtered DS-CDMA systems. An expression is presented for the signal to inter chip interference (S/IC1) ratio as a function of the sampling error characteristics and raised-cosine roll-off factor. Finally, we use the analysis in the paper to derive the sufficient sampling resolution for the high performance WCDMA-HSDPA system.

This paper discusses the TPC detection performance in soft handover in WCDMA. A simple TPC commands combining method is evaluated and an improved TPC combining method is proposed. Results show that although the simple combining method fulfills the 3GPP requirements, it does not perform well from the system performance perspective. The proposed combining method significantly improves the system performance.

Direct conversion receivers are increasingly popular for use in mobile terminals. This is due to advantages over other architectures such as heterodyne receivers in terms of cost, electrical current, and physical size. However, a direct conversion receiver often generates a DC-offset that has to be taken care of either by suppressing the DC-offset in the radio-frequency part of the receiver, or by taking care of it during baseband processing. A theoretical analysis of the bit error rate (BER) performance in a direct conversion receiver with different levels of DC-offset suppression is presented. Explicit results are presented on how the BER depends on the signal-to-noise ratio (SNR), the signal-to-DC-level, and the choice of pilot symbols both with M-QAM and M-PSK in a slow, flat Rayleigh fading channel. A design rule, which applies to the design of DC-compensation in direct conversion receivers, is also presented.

The basic concept of EDGE (Enhanced Data rates for GSM and TDMA/136 evolution) is to provide higher data rate transmission, over 384 kbits/s, than in the GSM and TDMA/136 systems of today. In order to be able to reach such a high data rate within the GSM bandwidth a very good receiver design is required. Further, from a terminal perspective, the receiver design needs to be efficient from both a cost, current and size point of view. A direct conversion receiver fulfil these criteria. However, such an architecture gives rise to a DC offset that must be taken care of in order for good demodulation. A DC offset compensation algorithm based on joint estimation of the radio channel and the DC offset is presented, giving competitive receiver performance for the EDGE system.