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Enhancing the throughput of multi-user (MU) massive multiple-input multiple-output (MIMO) networks is one of the biggest promises that the fifth generation (5G) networks are expected to deliver. In the Third Generation Partnership Project (3GPP) New Radio (NR) standardization efforts, downlink precoding designs that balance performance and uplink feedback overhead are being investigated. Most recently, a high-resolution precoder (Type-II codebook) was specified for downlink NR Release (Rel.) 15 wherein the channel state information (CSI) feedback is compressed in the spatial domain via exploiting a Discrete Fourier Transform (DFT)-based codebook structure. An extension of the Type-II codebook for NR Rel. 16 which also exploits frequency correlation to reduce CSI feedback overhead is currently under study. In this paper, an overview of some of the recent developments for Rel. 16 Type-II codebook is provided. In addition, a practical approach is proposed that uses multi-stage quantization of codebook parameters with variable quantization resolution, where the resolution is proportional to the coefficients' amplitude values. This approach helps provide better utilization of the CSI feedback, compared with the case with the same quantization resolution for all coefficients. System-level simulation results are provided which show that the proposed approach significantly reduces the CSI feedback overhead without notable impact on performance.

Multiple communication standards including 3GPP LTE and IEEE 802.11, employ codebooks of antenna precoders. For these standards, feedback from the receiver is used to optimize the antenna precoder selection performed at the base station. This optimization process implicitly assumes that the antenna precoders which have equal Euclidean norm are mapped to antenna patterns with equal transmit power. However, for coupled antennas, it can be shown that that if the precoders are implemented as a vector voltage source in a Thevenin source model or as a vector current source in a Norton source model, the equal power condition is not satisfied. The effect of transmission lines between the source and the antenna array are included in the analysis, as this affects the power delivered to the array, as does the use of matching networks. To illustrate, an example is considered using two half-wavelength dipoles for which the variation in transmit power can be in excess of 3 dB even when the Euclidean norm of the precoders is held constant. Given this problem, two methods are proposed which can be used to map equal norm antenna precoders to equal power antenna patterns. The first of these two methods requires signaling of scale factors to the receiver, while the second method can be implemented in a manner that is completely transparent to the receiver.

In this paper, we describe a CRC-based optimal Blind Transport format determination algorithm with application in UMTS uplink. A MAP detector is derived. Simulation results under both AWGN and fading channel are given.

In digital communication systems, variable-length Walsh codes, also called orthogonal variable spreading factor codes, are used to support simultaneous variable-rate data transmission. This paper describes algorithms for dynamic variable- length Walsh code assignment. Optimal assignment criterion is derived and an efficient data structure for maintaining variable- length Walsh codes is introduced. The benefits of code reallocation are also studied. Performance is evaluated via simulation.

We describe a CRC-based optimal blind transport format determination algorithm for UMTS uplink.

The paper addresses the problem of synchronous CDMA communications when, due to bandwidth limitations, signature waveforms have relatively large correlations. A receiver which uses the multiple received signals available from an antenna array is proposed and its performance analyzed. This receiver may be interpreted as a multichannel extension of the decorrelating detector and therefore shares its immunity to near-far effects. The receiver uses the discrimination afforded by the antenna array to effectively reduce the correlation between users' transmitted signals thereby avoiding the reduction in performance which occurs in the single channel decorrelator when signature correlations become significant. >