On the Improved Memory Utilization in HARQ Pooling

Guest editorial IJSCN special issue on 3GPP NTN standards for future satellite communications

Hybrid automatic repeat request (HARQ) is a high-performance communication protocol, leading to the effective use of the wireless channel and the resources with only limited feedback about the channel state information (CSI) to the transmitter. In this paper, the throughput of HARQ with incremental redundancy (IR) and fixed transmission rate is studied in the presence of statistical queuing constraints imposed as limitations on buffer overflow probabilities. In particular, tools from the theory of renewal processes and stochastic network calculus are employed to characterize the maximum arrival rates that can be supported by the wireless channel when HARQ-IR is adopted. Effective capacity is employed as the throughput metric, and a closed-form expression for the effective capacity of HARQ-IR is determined for small values of the quality-of-service (QoS) exponent. The impact of the fixed transmission rate, queuing constraints, and hard-deadline limitations on the throughput is investigated, and comparisons with type-I HARQ and HARQ with Chase Combining are provided.

High speed downlink packet access (HSDPA) is specified in the 3GPP to cope with the increasing demand of high-speed Internet-based multimedia services. HSDPA is based on techniques such as base station scheduling, adaptive modulation and coding, hybrid automatic repeat request, and advanced receiver design. This work presents system-level simulation results on the HSDPA performance to reveal the effects of user equipment (UE) capabilities such as the maximum number of multicodes and receive diversity. The results show that a 15- and 10-multi-code UE and the receive diversity significantly improve the cell capacity. Experiments using the HSDPA test-beds are conducted to investigate the true HSDPA performance. Furthermore, TCP/IP-level simulation results show the application-level throughput, i.e. end-user throughput, in the HSDPA system. The results indicate that reduction of the round trip time, a higher uplink data rate, and low uplink block error rate are required to achieve the high TCP-level throughput.

In high speed downlink packet access (HSDPA)developed by 3GPP, adaptive modulation and coding (AMC)and hybrid ARQ (HARQ)are adopted to increase throughput of downlink packet transmission. To implement AMC and HARQ, the user equipment (UE)transmits downlink channel quality information and HARQ acknowledgement, respectively, on the uplink feedback channel (HS-DPCCH).In this paper, we propose an elegant uplink power control scheme to improve reliability of uplink feedback signalling on the HS-DPCCH when UE is in soft handoff region. Simulation results show that the proposed scheme significantly improves reliability of the feedback signalling.

The fifth-generation new radio technology (5G NR) introduces improved functions to the air interface. In addition, the 5G NR non-standalone (NSA) will operate with long-term evolution, enabling vehicle-to-everything communications (V2X) for improved infotainment services. V2X includes four main classes of communications: vehicle-to-vehicle, vehicle-to-infrastructure, vehicle-to-pedestrian devices, and vehicle-to-network. However, the stringent transmission frequency, latency, and throughput requirements of infotainment applications constrain the transmitting packets of 5G-V2X-based NSA in highway scenarios. In this paper, the latency is improved by preventing the physical layer of gNodeB and the user equipment (UE) from sending redundant packets for service in a highway scenario. The proposed approach adopts an adaptive neuro-fuzzy inference system (ANFIS), a powerful modeling technique based on artificial neural networks ,and a fuzzy inference system. The performance of ANFIS is compared with that of the traditional 5G V2X NSA architecture in a simulation study using Voice over Internet Protocol (VoIP) traffic. The delays, throughputs, and packet losses of both architectures are determined in radio link control (RLC) and VoIP applications. The switch-modes, signal-to-interference-noise ratios (SINRs), hybrid automatic repeat request (HARQ) error rate, channel quality indicators (CQIs), served blocks, and transmission-state of gNodeB are computed for the two architectures for device-to-device (D2D), uplink (UL) and downlink (DL) traffic directions. The simulation results show comparable SINRs, CQIs, served blocks ,andswitchmodes in both scenarios, but the presented ANFIS model significantly outperforms the traditional architecture in delay by 66% in D2D, 29% in UL, 25% in DL, and packet loss by 21% in UL in RLC, the HARQ error rate by 9% in D2D, 30% in UL, 95% in DL, transmission-state in gNodeB by 29%, and the delay by 4% for UEs, and frame loss by 90%for UE in VoIP.

3GPP standardization is evolving beyond 5G the New Radio air interface (NR-Uu) framework defined in 3GPP Release 15 (also known as 5G phase 1) to study the support of advanced vehicle to everything (V2X) services. The NR Sidelink (SL) being designed in 3GPP Release 16 (5G phase 2) to support advanced V2X services directly between vehicles and other road users is expected to finish by the end of 2019. The advanced V2X services primarily focuses on platooning, advanced driving, extended sensor and remote driving use-cases. Supporting an end-to-end latency of 3ms and high reliability up-to 99.999% requirement requires substantial improvements in the air-interface design. Long Term Evolution (4G LTE) V2X sidelink supports the delivery of Basic Safety Messages to nearby V2X User Equipments (UE, the mobile device), hence the sidelink physical layer and the higher protocol layers are designed to support only broadcast type traffic without Hybrid Automatic Repeat Request (HARQ) feedback. With the advanced V2X service requirement, NR sidelink design should study V2X message delivery for different cast types such as unicast, groupcast and broadcast type traffics that requires substantial changes starting in V2X Release 16 network architecture, physical and protocol layers. This paper provides insights on the current Release 16 NR sidelink design for V2X. The network architecture enhancement discusses supporting flow- based Quality of Service (QoS) model for NR sidelink and the newly introduced network entities such as Network Data Analytics Function (NWDAF) providing QoS analytic. The design of the NR sidelink physical layer based on the Cyclic- Prefix Orthogonal Frequency-Division Multiplexing (CPOFDM) waveform addresses the necessary improvements needed in the sidelink procedures for reliable packet transmissions in a certain communication range. The protocol layer introduces a new overlapping zone concept to study both about HARQ feedback in a communication range and the resource segregation.

5G New Radio (NR) is the 3rd Generation Partnership Project (3GPP) radio access technology for the next generation mobile communications network. A major evolution of 5G constitutes the integration of non-terrestrial networks including geostationary and low Earth orbit satellites. The seamless integration of satellites in the terrestrial mobile network requires significant adaptations within the radio access network and the development of new features in the core network to cope with the specific satellite channel characteristics. To date, the 5G control and data plane has been standardized to handle only continuous backhaul communication between the network components. However, a mobile satellite enabled next generation Node B (gNB) located in a vehicle or in a moving aerial platform needs to be able to handle frequent backhaul outages of various duration as well as longer signal delays as opposed to short terrestrial connections via fiber. In this paper, we report the results of an over-the-air (OTA) field trial comprising a mobile edge node connected to the 5G standalone core network components over a geostationary satellite. We analyze Transmission Control Protocol (TCP) acceleration and GPRS Tunneling Protocol (GTP)/TCP/Internet Protocol (IP) header compression features through the GTP. Moreover, the influence of short and long interruptions in the communication between the edge node and the central components on the entire system performance is investigated. The header compression and TCP acceleration modules were implemented on the satellite modems and are now part of the protocol stack of these devices. The results show up to 12% higher data rates for the 5G user equipment (UE), on a 1.5 MHz single carrier return link compared to deactivated TCP acceleration and header compression. We increased the data rate by 20% on the 4.5 MHz DVB-S2X forward link between the UE and 5G core. Moreover, our measurements reveal that even satellite-enabled gNB mobility is possible with the current Release 15 standard. After a short outage of the satellite connection due to shadowing, the UE can successfully re-establish the user plane connection to the core network. Our results will facilitate the full integration of satellite components in 5G through open and standard solutions.

SummaryFor the first time, 3GPP considered in Release‐17 the introduction of mobile satellite service (MSS) frequency bands for 3GPP user equipment (UE) direct connectivity with satellites and had to consider the coexistence in adjacent bands with terrestrial networks (TNs). This paper will further explain the most challenging and the main surprising outcomes of this work, which opened new market opportunities for both terrestrial and nonterrestrial stakeholders. 5G New Radio nonterrestrial networks (NTNs) for satellite communications are representing a major breakthrough in the history of telecommunication for the capability of reuniting two different types of services, that is, terrestrial and nonterrestrial, by reusing the same waveform and potentially the same type of terminal. One of the major conclusions of the 5G NR NTN 3GPP work in Release‐17 was that NTN UE could reuse the current requirements of the TN UE. For this reason, the same terminal can connect to both TNs and to nonterrestrial satellite constellations. Consequently, the market is not fragmented and therefore there will be a real opportunity for both terrestrial and satellite operators to increase the coverage and the quality of the service all over the world. This is one of the most important breakthroughs that 3GPP Release‐17 work was able to justify because it clearly shows that satellite connectivity using 5G NR technology is not only for dedicated satellite 5G NR UE with a higher power class. On the other hand, the 3GPP work also shows that the satellite connectivity does not require a dedicated satellite waveform, because 5G NR waveform based on CP‐OFDM (for downlink) and DFT‐s‐OFDM (for uplink) is sufficient. Another important finding is that TN can coexist with NTN on adjacent channels with relaxed ACIR requirements for the tested simulation scenarios. In fact, the satellite 5G NR requirements are lower when compared with terrestrial base station (BS) requirements from previous 3GPP releases. The satellite ecosystem tremendously changed after these findings, and both satellite and terrestrial stakeholders now see a potential market opportunity.

Purpose of software-defined radio (SDR) network positioning technology design is substantiation and experimental validation of new technical solutions for user equipment (UE) location estimation improvement, using infrastructure of existing 4G Long-Term Evolution (LTE) and emerging 5G New Radio (NR) networks, which is highly relevant in Global Navigation Satellite System (GNSS) denied urban environments. Approach for experimental validation is prototyping of eNodeB (eNB) reference signals transmission and UE reception procedures using SDR testbed with Universal Software Radio Peripheral (USRP) hardware and Matlab software. Generation and transmission of reference signals, performed by eNB on the physical layer, is defined by 3GPP technical specification 36.211, and receiver processing procedures, performed by UE, and strongly affecting the accuracy of primary measurements, can be designed as a proprietary solution. Findings of current research include formalization, software realization and results of experimental validation of a sequence of procedures for receiving and processing LTE reference signals in order to collect primary range-difference measurements on the UE side for observed time difference of arrival (OTDOA) positioning with developed SDR testbed. Research and development campaign on the current stage has limitation of SDR testbed validation only in laboratory conditions. Practical implications of developed UE SDR testbed allow to proceed campaign to the field conditions and test proposed technical solution with ambient LTE signals.

The recommended bit rate (RBR) is assigned by gNodeB to the user equipment (UE) using MAC control element (CE) entity to provide bit rate information in 5G New Radio (NR). At the UE, the bit rate information is passed on to the upper layers; i.e., transport or application, for a specific logical channel either in uplink or downlink. However, based on specific application rate of target, UE does not know how to efficiently utilize and distribute RBR/throughput in lower and upper layer, respectively considering the specific logical channel. To address these problems, we propose a cross layer rate adaptation (CLRA) mechanism for UE. CLRA consists of two parts. In the first part, CLRA utilizes RBR received from gNodeB to compute throughput at lower layer. In the second part, CLRA distributes the throughput in upper layer received from lower layer based on specific applications rate of target. CLRA provides an intelligent mechanism to distribute throughput among foreground/ background applications and voice over internet protocol (VoIP) application considering a learning based codec adaptation. We conduct experiments with Samsung Galaxy S8 device and simulations to validate CLRA mechanism for applications in 5G NR.

Broadcast and multicast will be an important feature supported in 5G New Radio. In this paper a new transmission method is proposed to improve the receiver side User Equipment (UE) resource efficiency by using redundant multicast channels at the transmitting Base Station (BS). Transmission is tailored for UEs with different channel characteristics. A sub-grouping algorithm is designed to fast allocate UEs of a multicast group to their most suitable channels. Numeric sample calculation proves the validity of the proposed method.

Bandwidth Parts (BWPs) is a 5G New Radio (NR) Release 15 feature introduced for dynamically adapting the carrier bandwidth and numerology in which a User Equipment (UE) operates. In 4G/LTE, UEs support the maximum possible bandwidth of 20MHz. In 5G, the operating bandwidth can be as high as 800MHz per carrier. Each UE cannot support such a high bandwidth without high-power consumption. Therefore, a 5G UE has to communicate on a bandwidth smaller than the cell’s channel bandwidth. The smaller part is referred to as BWP. BWP enables higher spectrum flexibility with reduced baseband processing and power savings. BWP selection (or BWP switching) can be performed through several different methods. bwp-InactivityTimer is one of the methods or techniques to switch BWP. BWP switching is always associated with switch delay. Frequent BWP switching directly impacts latency and system throughput. In NR, new gap patterns with larger gap lengths of 40 ms and 66 ms features are implemented for accurate positioning measurements. The effect of bwp-InactivityTimer during larger measurement gaps and associated delays have not been studied and understood thoroughly for bursty traffic. Trade-offs must be carefully considered between energy efficiency and other performance aspects such as latency, throughput, and so on. In this paper, we propose an Efficient BWP Switch Method (EBSM) novel algorithm to handle bwp-InactivityTimer to reduce latency and thereby increase the system throughput during larger gap lengths configured for accurate positioning measurements. Simulation results show that the proposed EBSM algorithm is on average 29.8% more efficient in shortening latency and around 15-52% more efficient in avoiding unnecessary BWP switching in comparison with the specification-defined current legacy method.

LTE-Advanced offers significantly higher data rates than the legacy system. The carrier aggregation (CA) technology allows scalable expansion of effective bandwidth provided to user equipment (UE) through simultaneous utilization of radio resources across multi-component carriers. In this paper we propose a new packet scheduling (PS) criterion algorithm that satisfies the fairness among the different kinds of UEs by designing a weighting factor to proportional fair (PF) packet scheduling (PS) algorithms, while enhancing their throughput performance. The proposed PS algorithm is implemented and validated in a PS module for LTE/LTE-Advanced via system level simulations. Results show that PS-enhanced algorithm achieve higher throughput for both LTE and LTE-Advanced UEs.

The 3rd generation partnership project (3GPP) has recently specified the non-standalone 5G New Radio (NR), in which the dual connectivity (DC) feature plays an essential role. A User Equipment (UE) with DC is able to concurrently connect to an evolved NodeB (eNB) (e.g., using LTE in a macro cell) and a next generation NodeB (gNB) (e.g., using 5G NR in a small cell) aiming to satisfy the 5G's required Key Performance Indicators (KPIs). In this work, we focus on the issue of concurrent transmissions on the 5G small cell, which potentially exploit the benefits of DC. With DC, an application is able to spread its traffic over different two paths (via eNB and gNB) between the UE and the LTE core network. The traffic over diverse paths may experience different delay since the conditions are generally different (e.g., due to wireless channel, background traffic). Therefore, one of the most important problems in efficient operation with DC is minimizing the end-to-end delay considering all the connections. To address that problem, we adopt the deterministic network calculus to first characterize the delay experienced by each connection; then to model the overall end-to- end delay in the 5G small cell. We then formulate an optimization problem that attempts to find the optimal traffic splitting over the connections while minimizing the delay. We derive the solution for the problem, as well as, present the numerical results.

This paper proposes an evaluation of the performance of 5G communication between a user equipment (UE), which can be a car, and a 5G base station (gNB), under the influence of different numbers of UEs connected to that base station. There are two approaches to this communication evaluation: i) simulated mode, using Simu5G, which is a simulator for 5G New Radio (NR) networks; ii) a practical way using a hardware setup defined on the basis of a SIM8200EA-M2 module in order to test a real-life scenario. Various performance indicators are tracked and also compared, such as Signal-to-interference-plus-noise ratio (SINR), Channel Quality Indicator (CQI), and End-to-End (E2E) Delay in order to analyze the effect of network load on 5G communication between the UE and gNB.