Uplink Control Channel Research Articles

Towards the use of Unsupervised Causal Learning in Wireless Networks Operation

The current paradigm in Mobile Wireless Networks (MWNs) operation is being defied by the increasing importance of Machine Learning (ML) and Artificial Intelligence (AI). Nevertheless, another paradigm shift is rising with recent developments in causal inference and causal discovery, which, although having the potential to be applied to MWNs, have been relatively unexplored. This paper aims to develop a data-driven methodology using unsupervised ML and Conditional Independence Tests (CITs), typically used in causal discovery tasks, to identify distinct network performance patterns and pinpoint causal factors to explain them. The proposed methodology was first evaluated with crowdsourcing data from User Equipments (UEs). Afterwards, a dataset from a Long-Term Evolution (LTE) network, composed of a set of arbitrary performance indicators and configuration parameters, was considered. The crowdsourcing dataset, containing multiple network speed tests, revealed that the measured uplink throughput contributed the most to the observed performance patterns due to the used Radio Access Technologies (RATs). Furthermore, the LTE dataset revealed a causal relationship between the number of reserved signalling resources in the Physical Uplink Control Channel (PUCCH) and the UE uplink throughput. Notwithstanding, the key contribution of this paper is the consideration of causal-based concepts and methods for network operations enhancement.

Constructions of Non-Contiguous Complementary Sequence Sets and Their Applications

Due to their beautiful aperiodic correlation properties and low peak-to-average power ratio (PAPR), Golay complementary pairs (GCPs) and complementary sequence sets (CSSs) have been well studied. However, conventional GCPs and CSSs can only adapt to contiguous spectral resource allocation in wireless communication systems, and it is difficult for them to be compatible with non-contiguous resource allocation. Inspired by recent constructions of non-contiguous GCPs given by Şahin and Yang, we propose a new construction of non-contiguous GCPs, which can be regarded as an extension of Turyn’s construction. Besides, we then propose some constructions of non-contiguous CSSs, which can adapt to flexible resource allocation, having more flexible lengths, and lower time domain cross correlation than non-contiguous GCPs. Finally, we propose a CSS-based physical uplink control channels (PUCCH) scheme for up to 2 uplink control information (UCI) bits. Simulations show that its performance is similar to the GCP-based PUCCH scheme.

Enhanced Reliability and Capacity with Multi-TRP Transmission

In this article, we discuss the evolution of multi-TRP transmission, which consists of several MIMO features of the 5G New Radio standardization. First, we describe the Rel-16 basic multi-TRP fea-ture that mainly targets downlink data channel enhancements and consists of two different frame-works to address both ideal and non-ideal back-haul scenarios. Next, we describe some of the Rel-17 enhancements such as reliability enhancements for downlink control channel, reliability enhancements for uplink data and uplink control channels, beam management enhancements for multi-TRP, and enhancements that address high-speed train deployment with single-frequency network (SFN) transmission. We also briefly describe other multi-TRP related enhancements in Rel-17 such as inter-cell multi-TRP transmission and joint channel state information for multi-TRP schemes.

Bringing AI to the edge: A formal M&S specification to deploy effective IoT architectures

ABSTRACT Internet of Things applications are based on ubiquitous networks of multiple distributed devices, with limited computing resources and power, capable of collecting and storing data from heterogeneous sources in real-time. To avoid network saturation and delays, new architectures are needed to provide real-time Big Data and data analytics capabilities at the edge of the network, where energy efficiency needs to be considered to ensure a sustainable and effective deployment in areas of human activity. In this research, we present an IoT model based on the principles of Model-Based Systems Engineering. It covers the description of the entire architecture, from IoT devices to the processing units in edge data centres, and includes the location-awareness of user equipment, network, and computing infrastructures to optimise federated resource management in terms of delay and power consumption. We present a framework to assist the dimensioning and the dynamic operation of IoT data stream analytics applications. Abbreviations : ADAS Advanced Driver Assistance System. 20, 21, 24AI Artificial Intelligence. 2, 24ANN Artificial Neural Network. 2, 21AP Access Point. 5, 10, 11, 12, 13, 17, 18, 19, 20CNF Core Network Function. 5DEVS Discrete Event System Specification. 3, 5, 6, 7, 9, 10, 11, 12, 15, 16, 17, 18, 20, 21, 24, 27, 28EDC Edge Data Centre. 2, 3, 5, 6, 9, 10, 12, 13, 20, 21, 22, 23, 25FaaS Function-as-a-Service. 3, 4, 5, 6FDD Frequency Division Duplexing. 11, 18, 19FSPL Free-Space Path Loss. 20GPU Graphics Processing Unit. 2, 21IoT Internet of Things. 2, 3, 4, 5, 6, 14, 19, 23, 24ISP Internet Service Provider. 5, 10M&S Modelling and Simulation. 3, 24M&S&O Modelling, Simulation, and Optimisation. 21MBSE Model-Based Systems Engineering. 3, 4, 5, 24MCS Modulation and Codification Scheme. 12MDC Micro Data Centre. 2ML Machine Learning. 2, 20, 24, 25NR 5G New Radio. 12P2P Point-to-Point. 5, 10PBCH Physical Broadcast Channel. 19PDCCH Physical Downlink Control Channel. 19PDSCH Physical Downlink Shared Channel. 19PSS Primary Synchronisation Signal. 11, 14PU Processing Unit. 7, 9, 21, 22, 23, 24, 25PUCCH Physical Uplink Control Channel. 19PUSCH Physical Uplink Shared Channel. 19QoS Quality of Service. 2, 4, 5, 6, 12, 24RAN Radio Access Network. 5, 10, 13, 16, 17, 20SDN Software-Defined Network. 5, 10SNR Signal-to-Noise Ratio. 11, 12, 14, 17UE User Equipment. 4, 5, 6, 10, 11, 12, 13, 14, 16, 17, 18, 19, 21, 22, 23, 24, 25WSN Wireless Sensor Network. 4

An Overview of Physical Layer Design for Ultra-Reliable Low-Latency Communications in 3GPP Releases 15, 16, and 17

Ultra-reliable low-latency communication (URLLC) has been introduced in 5G new radio for new applications that have strict reliability and latency requirements such as augmented/virtual reality, industrial automation and autonomous vehicles. The first full set of the physical layer design of 5G release, Release 15, was finalized in December 2017. It provided a foundation for URLLC with new features such as flexible sub-carrier spacing, a sub-slot-based transmission scheme, new channel quality indicator, new modulation and coding scheme tables, and configured-grant transmission with automatic repetitions. The second 5G release, Release 16, was finalized in December 2019 and allows achieving improved metrics for latency and reliability to support new use cases of URLLC. A number of new features such as enhanced physical downlink (DL) control channel monitoring capability, new DL control information format, sub-slot physical uplink (UL) control channel transmission, sub-slot-based physical UL shared channel repetition, enhanced mobile broadband and URLLC inter-user-equipment multiplexing with cancellation indication and enhanced power control were standardized. This article provides a detailed overview of the URLLC features from 5G Release 15 to Release 16 by describing how these features allow meeting URLLC target requirements in 5G networks. The ongoing Release 17 targets further enhanced URLLC operation by improving mechanisms such as feedback, intra-user-equipment multiplexing and prioritization of traffic with different priority, support of time synchronization and new quality of service related parameters. In addition, a fundamental feature targeted in URLLC Release 17 is to enable URLLC operation over shared unlicensed spectrum. The potential directions of URLLC research in unlicensed spectrum in Release 17 are presented to serve as a bridge from URLLC in licensed spectrum in Release 16 to URLLC in unlicensed spectrum in Release 17.

An Uplink Control Channel Design With Complementary Sequences for Unlicensed Bands

In this paper, two modulation schemes based on complementary sequences (CSs) are proposed for uplink control channels in unlicensed bands. These schemes address high peak-to-average-power ratio (PAPR) under non-contiguous resource allocation in the frequency domain and reduce the maximum PAPR to 3 dB. The first scheme allows the users to transmit a small amount of uplink control information (UCI) such as acknowledgment signals and does not introduce a trade-off between PAPR and co-channel interference (CCI). The second scheme, which enables up to 21 UCI bits for a single user or 11 UCI bits for three users in an interlace, is based on a new theorem introduced in this paper. This theorem leads distinct CSs compatible with a wide variety of resource allocations while capturing the inherent relationship between CSs and Reed-Muller (RM) codes, which makes CSs more useful for practical systems. The numerical results show that the proposed schemes maintain the low-PAPR benefits without increasing the error rate for non-contiguous resource allocations in the frequency domain.

CRC-Aided Logarithmic Stack Decoding of Polar Codes for Ultra Reliable Low Latency Communication in 3GPP New Radio

This paper provides a detailed tutorial on the Cyclic Redundancy Check (CRC)-aided logarithmic successive cancellation stack (Log-SCS) algorithm. We apply these algorithms for the ultrareliable decoding of polar codes, which has relevance for the control channels of the ultra-reliable low latency communication version of the third generation partnership project (3GPP) New Radio (NR). During the exploitation of the CRC codes to improve the error correction performance, we propose a novel technique which limits the number of CRC checks performed, in order to maintain a consistent error detection performance. In addition, we propose a pair of techniques for further improving the performance of the Log-SCS polar decoder. We demonstrate that the proposed S = 128 Improved Log-SCS decoder achieves a similar error correction capability as a logarithmic successive cancellation list (Log-SCL) decoder having a list size of L = 128 across the full range of block lengths supported by the 3GPP NR physical uplink control channel. This is achieved without increasing its memory requirement, while dramatically reducing its complexity, which becomes up to seven times lower than that of a L = 8 Log-SCL decoder.

Analysis of 5G New Radio Uplink Signals on an Analogue-RoF System Based on DSP-Assisted Channel Aggregation

The 3rd Generation Partnership Project (3GPP) is in the process of developing 5th generation (5G) radio access technology, the so-called new radio (NR). The aim is to achieve the performance requirements forIMT-2020 radio interface technology. In this paper, we focus on the analysis of the transmission of 5G NR uplink physical channels, such as physical uplink shared channel (PUSCH) and physical uplink control channel (PUCCH), dedicated for data and control channels, respectively, as specified in the 3GPP standard, using digital signal processing (DSP)-assisted frequency division multiple access (FDMA) and time division multiple access (TDMA) channel aggregation techniques on an analogue radio-over-fiber (A-RoF) architecture. We verified that there is ~34% spectral efficiency gain and lower error vector magnitude (EVM) achieved using the TDMA technique.

Realization of LTE physical layer baseband processing architecture for narrowband IOT

The 3GPP Long Term Evolution represents the major innovation in cellular technology. NB-IoT is the 3GPP standard for machine to machine communication finalized within LTE Release13. NB-IoT technology occupies frequency band of 180 kHz bandwidth which corresponds to one resource block in LTE transmission. The Long Term Evolution (LTE) supports higher data rates, higher bandwidth, Low latency, good Quality of Service whereas objective of Narrow Band Internet of Things (NB - IOT) is to achieve extended coverage, to support massive number of smart devices and have multi - year long battery life. So the main focus is linking LTE with IOT. The objective of this paper proposes transmitter architecture of PUCCH (Physical Uplink Control Channel) and PUSCH(Physical uplink Shared Channel) in SISO and SIMO configurations for physical uplink channels of LTE. The physical uplink and downlink channel processing involves scrambling, modulation, layer mapping, transform precoding, and resource element mapping at the transmitter and the receiver block to have demapping from the resource elements and detection of data. At present, the data for on-off control has been worked and the whole framework has been simulated using Modelsim and implemented in Spartan 6.

Analysis of the Influence of PCI Planning on the Physical Uplink Control Channel in LTE

In Long Term Evolution (LTE) systems, the physical cell identity (PCI) assigned to a cell during network planning determines the set of sequences used by subscribers as de-modulation reference signals (DM RS) in the uplink (UL). A proper assignment of PCIs must prevent neighbor cells from using the same DM RS to avoid interference problems, thus ensuring adequate performance both in control and user data channels in the uplink. In this paper, a comprehensive analysis is carried out to quantify the impact of PCI planning on the performance of physical uplink control channel (PUCCH) in LTE. First, a novel analytical model that reflects the influence of PCI planning on interference and outage probability due to DM RS collisions in PUCCH is presented. Based on this model, PUCCH performance with several classical PCI planning schemes is evaluated with a static system-level simulator implementing a real network scenario. Simulated cases cover different PUCCH frame formats, different UL power control (PC) schemes and both regular and irregular traffic scenarios. Results show that a PCI plan constructed solely based on avoiding PCI collision/confusion and reference signals collisions in the downlink achieves near-optimal performance in terms of DM RS collisions in PUCCH, but, however, in extreme cases, DM RS collisions caused by neighbor cells sharing the same sequence might degrade PUCCH performance significantly.

Traffic-Aware Joint Allocation of Uplink Control and Communication Channels in Multicast Systems

In multicast wireless access systems such as a trunked mobile radio system, channel allocation is performed based on multicast groups instead of radio units. Thus, in these systems, the call source units are these groups, which we also call the users . In a practical system, these users are finite in number, and each user or group may consist of many radio units. In this paper, we discuss the coupling of uplink control and communication segments (layers) of such finite source systems, in which the performance of one layer directly affects that of the other. The conventional studies model these system segments separately and, thus, are unable to capture the coupling issues in networks with the finite sources' constraint. We first propose a novel model that incorporates this coupling by jointly quantifying both the collision loss at the control layer and congestion loss at the communication layer. Under our proposed framework, we further optimize the number of uplink control and communication channels to minimize the joint total loss rate given a constraint on the total number of available channels. In addition, we demonstrate the capability of our proposed model in estimating the invisible actual traffic load and provide guidelines for developing an algorithm for the traffic-aware allocation of channels, based on the proposed model.

Improved Carrier Frequency Offset Estimation Algorithms for PUCCH Format 1 in LTE-Advanced

Physical Uplink Control Channel (PUCCH) is an important narrow-band channel in LTE-Advanced system, which carries the uplink control information, such as acknowledge/non-acknowledge (ACK/NACK) bits, downlink channel quality indicator (CQI), HARQ-ACK feedback information, and it requires much higher transmission quality than the other channels. With the aid of orthogonal CDMA, multiple users share the same time-frequency resource, the multiuser interference has been the main factor that limits the transmission quality of the control information [1]. In the high-speed mobile scenario, there exists a large Doppler frequency shift, which leads to loss of code orthogonality and also introduces inter-carrier interference (ICI) within a single SCFDMA symbol. Besides, the multiuser interference in high-speed mobile environment is severe. In this paper, the carrier frequency offset estimation algorithms are analyzed, and a double-iteration carrier frequency offset (CFO) estimation algorithm is proved to perform the best for PUCCH Format 1 in high-speed mobile scenario. The estimation process is achieved by coarse estimation and fine estimation, which enlarges the estimation range and improves the estimation accuracy.

Multiplexing SRS with Periodic CSI on Shortened PUCCH Format 2/2a/2b

In order to avoid dropping the SRS report frequently in case of collision between SRS and a periodic CSI report in LTE-Advanced system, this paper gives shortened PUCCH (Physical Uplink Control Channel) format 2/2a/2b for multiplexing SRS (Sounding Reference Signal) with periodic CSI (Channel State Information). The result of simulation shows that the shortened PUCCH format 2/2a/2b can effectively support simultaneous transmission periodic CSI and SRS. What’s more, on shortened PUCCH format 2/2a/2b with the first and last two encoded bits punctured, periodic CSI and HARQ-ACK feedback have the same performance as on PUCCH format 2/2a/2b without multiplexing SRS. Hence through the shortened PUCCH format 2/2a/2b, we can not only enhance simultaneous transmission of periodic CSI and SRS, but also guarantee the similar performance of periodic CSI and HARQ-ACK feedback as transmitting them on PUCCH format 2/2a/2b without multiplexing SRS.

Enhancing the security of LTE networks against jamming attacks

The long-term evolution (LTE) is the newly adopted technology to offer enhanced capacity and coverage for current mobility networks, which experience a constant traffic increase and skyrocketing bandwidth demands. This new cellular communication system, built upon a redesigned physical layer and based on an orthogonal frequency division multiple access (OFDMA) modulation, features robust performance in challenging multipath environments and substantially improves the performance of the wireless channel in terms of bits per second per Hertz (bps/Hz). Nevertheless, as all wireless systems, LTE is vulnerable to radio jamming attacks. Such threats have security implications especially in the case of next-generation emergency response communication systems based on LTE technologies. This proof of concept paper overviews a series of new effective attacks (smart jamming) that extend the range and effectiveness of basic radio jamming. Based on these new threats, a series of new potential security research directions are introduced, aiming to enhance the resiliency of LTE networks against such attacks. A spread-spectrum modulation of the main downlink broadcast channels is combined with a scrambling of the radio resource allocation of the uplink control channels and an advanced system information message encryption scheme. Despite the challenging implementation on commercial networks, which would require inclusion of these solutions in future releases of the LTE standard, the security solutions could strongly enhance the security of LTE-based national emergency response communication systems.

A Multi-user Receiver for Inter-Cell Interference Reduction in LTE PUCCH Signaling

In 3rd generation partnership project (3GPP) long term evolution (LTE) systems, when no resources has been assigned in the uplink to a given user equipment (UE), the control information associated with layers 1 and 2 in the protocol stack is conveyed back to the base station through the so-called physical uplink control channel (PUCCH). In PUCCH, the data streams transmitted by multiple UEs are multiplexed in the time-domain and in the frequency-domain with the aid of spreading codes. Although the spreading codes associated with UEs within the same cell can be assumed to be orthogonal, the presence of inter-cell interference (ICI) in multi-cell scenarios severely limits receiver performance. In particular, the Format 1 of PUCCH, which is associated with the transmission of hybrid automatic repeat request acknowledgements (ACK/NACK) and scheduling requests, has a major impact on system performance, since an incorrectly decoded ACK/NACK message may introduce significant delay in data transmission. In this contribution, we propose a new multi-user receiver for ICI reduction in PUCCH LTE that operates both in cooperative and non-cooperative multi-cell architectures. The proposed receiver relies on a constrained tensor modeling of the received signal in PUCCH signaling, and affords an iterative joint channel estimation and symbol detection by simultaneously exploiting the energy of the data symbols and the pilot tones present in PUCCH. The formulation of the proposed algebraic receiver model incorporates symbol-basis hopping and slot-basis hopping signaling schemes, which are interference randomization techniques existing in the 3GPP specifications of LTE system. Computer simulation results show the remarkable performance gains of the proposed receiver compared to the conventional time-frequency decorrelator based receiver.

Multiuser Receiver Scheme with SIC for PUCCH in High Speed Train Environment

A multiuser receiver scheme with successive interference cancellation (SIC) is proposed to suppress multiuser interference for physical uplink control channel (PUCCH) in high speed train (HST) environment. In the proposed algorithm, each user’s signal is detected iteratively in a descending order according to the signal strength at eNB. During each iteration, the strongest signal of all users’ is detected and regenerated, and then is subtracted from the composite signal before decoding the next user. Simulation results show that the proposed scheme obtains remarkable gains, e.g. 2 dB for PUCCH format 2 with 3 users in HST scenario 1. The improvement is more pronounced in the case of increasing number of users, e.g. 3.3 dB with 6 users.

Downlink and Uplink Physical Channels in Long Term Evolution

Long Term Evolution (LTE) defines a number of physical channels to carry information blocks received from the MAC and higher layers. This paper presents two types of Physical channels: the first type is downlink physical channels which consist of Physical Broadcast Channel (PBCH), Physical Downlink Shared Channel (PDSCH), Physical Multicast Channel (PMCH), Physical Downlink Control Channel (PDCCH), Physical Control Format Indicator Channel (PCFICH) and Physical Hybrid ARQ Indicator Channel (PHICH). The second type of Physical channels is uplink physical channels which consist of Physical Uplink Shared Channel (PUSCH), Physical Uplink Control Channel (PUCCH) and Physical Random Access Channel (PRACH). This paper also highlights the structure of PDSCH and PUSCH, discuss the algorithms of the two types of physical channel and each of its features. The aim of this paper is to discuss the well-designed PHY Channels which provide high cell-edge performance with specific features, such as dynamic bandwidth allocation to users, the design of reference signals and control channels. These channels take into account a more challenging path loss and interference environment at the cell edge.

Efficient Receiver Scheme for LTE PUCCH

In 3rd. Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, physical uplink control channel (PUCCH) incorporate Reference Signals (RSs) for eNodeB to perform channel estimation. However the RSs in PUCCH formats 2a/2b are related to the transmitted 10th symbol in UE. As a result, the receivers can not have a priori knowledge about the transmitted RSs and perform channel estimation aided by all of the RSs directly. In this work, an efficient low complexity receiver is proposed for PUCCH formats 2a/2b. What's more, it is also practical for other PUCCH formats with all priori-known RSs. As will be shown in our simulation results, remarkable performance gains are obtained for all PUCCH formats.

Performance Evaluation of Joint MLD with Channel Coding Information for Control Signals Using Cyclic Shift CDMA and Block Spread CDMA

This paper presents joint maximum likelihood detection (MLD) using channel coding information for orthogonal code division multiple access (CDMA) to decrease the required average received signal-to-noise power ratio (SNR) satisfying the target block error rate (BLER), and investigates the effect of joint MLD from the conventional coherent detection associated with channel coding. In the paper, we assume the physical uplink control channel (PUCCH) as specified in Release 8 Long-Term Evolution (LTE) by the 3rd Generation Partnership Project (3GPP) as the radio interface for the uplink control channel. First, we clarify the best scheme for combining correlation signals in two frequency-hopped slots and in two receiver diversity branches for joint MLD. Then, we show that the joint MLD without channel estimation, in which correlation signals are combined in squared form, decreases the required average received SNR compared to that for joint MLD with coherent combining of the correlation signals using channel estimation. Second, we show the effectiveness of joint MLD in terms of the decrease in the required average received SNR compared to the conventional coherent detection in various delay spread channels. Third, we present a comparison of the average BLER performance levels between cyclic shift (CS)-CDMA and block spread (BS)-CDMA using joint MLD. We show that when using joint MLD, BS-CDMA is superior to CS-CDMA due to a lower required received SNR in short delay spread environments and that in contrast, CS-CDMA provides a lower required received SNR compared to BS-CDMA in long delay spread environments.

Realization of Physical Hybrid ARQ Indicator Channel for LTE using FPGA

Realization of transmitter and receiver architecture for LTE is the major research work being carried out by implementation experts. There are four Control channels available in LTE for both uplink and downlink. The uplink control channel is PUCCH. The downlink control channels are PDCCH, PCFICH and PHICH. The Physical Hybrid Automatic Repeat Request (ARQ) Indicator Channel(PHICH) is the control channel which carries the acknowledgement (ACK/NACK), denoted as Hybrid ARQ Indicator(HI).These control channels play a key role in the correct decoding of the payload information. The HI is used to indicate the ACK for data sent using Physical Uplink Shared Channel (PUSCH), and is important for the system performance. In this paper, the realization of architecture for the PHICH are done using FPGA, where the main aim is to estimate the HI correctly in the receiver side. The simulations are done using Modelsim and are implemented in Xilinx Spartan 3E kit.