High peak-to-average-power ratio (PAPR) is an inevitable challenge in orthogonal frequency-division multiplexing (OFDM) based networks, known to be particularly harmful to efficient utilization of practical power amplifiers (PAs). To preserve the waveform quality, PA back-off can be introduced which, however, directly limits the potential uplink (UL) coverage. This paper proposes a novel PAPR reduction method, by transmitting a peak-cancellation signal (PCS) spatially-precoded to the frequency resources within the operating channel, without introducing any overheads or receiver side interference. The proposed approach can be applied to codebook-based and non-codebook-based transmissions, while also allows for extending the PCS frequency allocation towards neighboring physical resource blocks (PRBs) without interference to other users. Extensive numerical results are provided, conforming with the 3GPP 5G NR transmitter requirements, while also incorporating realistic uplink PA models. The obtained numerical results at FR1 reveals up to 2.6 dB net gain in the effective uplink link budget via using the novel PCS, compared to the plain legacy OFDM signal. Such link budget gains translate to substantial uplink coverage improvements, which can be one major asset in future network deployments towards the 6G era.

In this paper, a novel binary waveform with low peak-to-average power-ratio (PAPR) and low out-of-band (OOB) emissions is presented, targeting at extreme uplink coverage solutions towards the 6G era. It uses the discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) signal model, as the baseline, togetherwith quadrature phase-shift keying (QPSK) modulation symbols, similar to the widely considered $\pi / 2$ binary phase-shift keying ($\pi / 2$-BPSK). The proposed approach further incorporates trellis-coding in a way which avoids sharp phase transitions in the generated signal, resulting in greatly reduced PAPR and OOB emissions. Additionally, while linear filtering based spectrum shaping has been widely considered in recent low-PAPR waveform studies, we propose to use phase interpolation to increase the sampling rate. This is nonlinear operation, but it helps to significantly reduce the PAPR compared to linear spectrum shaping. This can be achieved both with and without bandwidth extension. Further enhancement to the spectrum localization is achieved by improving the phase continuity of the generated signal, avoiding excessive phase transitions between consecutive transform-precoded OFDM symbols and between each main symbol and its cyclic prefix (CP).

This paper investigates the potential to leverage existing 5G NR signals for network-side integrated sensing and communications (ISAC). In general, the synchronization signal block (SSB) is a suitable candidate for always-on downlink sensing, due to its frequent periodical availability and because of its beam-sweeping nature. However, as this work demonstrates, using only the SSB has challenges related to radar ambiguity while being also limited in both distance and velocity resolution due to limited bandwidth and per-beam time duration, respectively. A novel solution is then introduced by combining SSB with downlink control information (DCI) and system information block 1 (SIB1) symbols. The corresponding implications and variants how SIB1 is optimized and configured are discussed, covering both 5G evolution and potential 6G solutions. The performance of the proposed approach is also assessed through realistic numerical evaluations at both 3.5 GHz and 28 GHz network deployments, and shown to yield up to 25 dB suppression in radar peak sidelobe level (PSL) compared to SSB-only based range-velocity profile. Also considerable improvements in the sensing resolution in the order of 120–190% are demonstrated.

5G New Radio (NR) has been a great success story since its introduction. It offers high reliability, low communication latency, flexibility, and efficiency that further enable 5G networks to be used for mission critical applications. Currently, there are specialized networks serving industry verticals that would benefit from the NR properties. Key use cases include communications for critical infrastructure such as railways, public safety, and smart energy and infrastructure. These networks often use dedicated spectrum allocations that are narrower than the original minimum operating bandwidth of NR. In this paper, we describe how new flexibility is being introduced into the NR design to allow operation with bandwidths between about 3 and 5 MHz. As a use case study, we focus on railway communications, and study the co-existence of the Global System for Mobile Communications–Railway (GSM-R) and Future Railway Mobile Communication System (FRMCS) based on NR during the decade-long migration period. We discuss the changes required for the NR control channels and signaling and study the effect of the changes on the system performance.

The use of lattice reduction (LR) has been shown to be a very effective method for signal detection in multiple antenna systems. In this paper, the performance of the sub-optimal soft-output maximum a posteriori (MAP) detector with lattice reduction is studied. We propose a polynomial-time method to generate the desired size candidate list in the reduced lattice. This sub-optimal soft-output MAP detector provides a near-optimal performance in uncorrelated MIMO systems, but with significantly reduced computational complexity.

Multiple-input multiple-output (MIMO) communications based on multiple transmit and receive antennae will be applied to enhance the data rates of the third generation (3G) cellular systems or wideband code division multiple access (WCDMA) and in particular, their high speed downlink packet access (HSDPA) services. This causes both spatial multiplexing interference (SMI) and downlink multiple access interference (MAI). In this paper, we derive an improved linear minimum mean square error (LMMSE) detector approximation suitable for MIMO-WCDMA systems. We also propose a new two-stage receiver architecture to suppress the effects of both MAI and SMI in HSDPA communications. SMI often dominates MAI, since it does not benefit from spreading gain. Therefore, a spatial maximum a posteriori (MAP) detector is used to suppress SMI, and a LMMSE based channel equalizer is applied as its front- end. The performance of the resulting LMMSE-MAP receiver structure is studied via Monte Carlo computer simulations with assumptions very realistically mimicking those of the HSDPA specification. The results show that it clearly outperforms the rake receiver or the improved LMMSE equalizer approximation, which, on the other hand, is also shown to be superior to the more conventional LMMSE equalizers.

Flexible spectrum use (FSU) within a radio access network (RAN) offers a flexible way to adapt the network capacity to the spatial and diurnal variations on the user distributions over the cell and network areas. In this paper, FSU is applied to the downlink of a radio access network (RAN) that utilises both wideband (WB) and narrowband (NB) carriers. Intra-RAN FSU is used to provide flexibility in the spectrum use between the WB and NB carriers. The considered network is assumed to offer multiple real-time and non-real-time services. The focus of the paper is to determine performance of the considered spectrum use scenarios against the average distance of active users to their nearest basestation. The obtained results indicate that although the WB carrier is able to provide high peak data rates, its performance is highly dependent on the average distance of active users and substantial improvement on downlink performance of the network can be obtained by fragmenting spectrum according to the average distance of active users

The use of lattice reduction (LR) has been shown to be a very effective method for signal detection in multiple antenna systems. In this paper, the performance of the sub-optimal soft-output maximum a posteriori (MAP) detector with lattice reduction is studied in multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system. We propose two polynomial-time methods to generate the desired size candidate list in the reduced lattice. The sub-optimal soft-output MAP detector with these list generation methods provides a near-optimal performance in uncorrelated MIMO-OFDM systems, but with significantly reduced computational complexity

The use of lattice reduction (LR) has been shown to be a very effective method for signal detection in multiple antenna systems. In this letter, the performance of the suboptimal soft-output maximum a posteriori (MAP) detector with lattice reduction is studied. We propose two polynomial-time methods for flat fading channels to generate the desired size candidate list in the reduced lattice. The suboptimal soft-output MAP detector with these list generation methods provides a near-optimal performance in uncorrelated multiple-input multiple-output systems but with significantly reduced computational complexity.

Receivers based on channel equalization have proven to be one of the most promising candidates for terminal receivers in wideband code-division multiple-access (WCDMA) downlink. The channel equalizers provide multiple access interference (MAI) suppression, and thus ensure adequate receiver performance even with a high number of active users. However, the performance improvement provided by the equalizers in conjunction with a powerful forward error control (FEC) coding has been unclear. The performance of adaptive equalizers is numerically evaluated with 1/3-rate turbo coding, and compared to the performance of the conventional RAKE receiver. The numerical results show significant performance improvement over the conventional RAKE receiver in a Rayleigh fading multipath channel.

Receivers based on channel equalization have proven to be one of the most promising candidates for terminal receivers in wideband code-division multiple-access (WCDMA) downlink. The channel equalizers provide multiple access interference (MAI) suppression, and thus ensure adequate receiver performance even with a high number of active users. However, the suitability of the equalizers to soft handover has been unclear. In this paper, adaptive equalizer structures for soft handover are introduced, and their performance is numerically evaluated. The results show a significant performance gain over the conventional RAKE receiver.

The most important 3rd generation 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 the despreading, thus restoring the orthogonality of users and resulting in multiple access interference (MAI) suppression. In this paper four adaptive versions of chip-level channel equalizers are studied and their performance is evaluated in a Rayleigh fading multipath channel. The numerical results show a significant performance improvement over the conventional RAKE receiver with a large number of active users.