Subband Full Duplex (SBFD) is an innovative duplexing method for advanced 5G/6G cellular communication that enhances uplink coverage and minimizes communication latency compared to TDD. SBFD allows a base station to transmit and receive simultaneously in distinct downlink and uplink sub bands within the channel bandwidth of a TDD carrier. To maximize the advantages of SBFD communications, it's crucial to mitigate self-interference and cross-link interference between nodes. This paper initially discusses the enablers for interference mitigation in SBFD deployment, followed by an evaluation analysis and field measurement results of SBFD duplex technology for a 5G massive-MIMO macro network in the 5G band.

Time-division duplex (TDD) and frequency-division duplex (FDD) are mainly used in commercial new radio (NR) deployments, where the time- or frequency-domain resources are split between downlink (DL) and uplink (UL). Full duplex (FD) will enable 5G-advanced and 6G systems to go beyond TDD and FDD operation into a new duplexing mode that leverages the benefits of both TDD/FDD deployments. It achieves higher throughput and lower latency while enabling flexible UL/DL scheduling. However, there are several challenges that need to be overcome to enable FD operation in large-scale system deployment, including intranode and internode [user equipment (UE) and next-generation node B (5G base station)] interference along with intercarrier interference. In this article, we present solutions to mitigate self-interference (SI) and cross-link interference (CLI) in 5G-advanced/6G systems, provide system-level evaluations, and discuss the outcome of Third Generation Partnership Project (3GPP) study item on duplexing evolution. We introduce the concept of subband FD (SBFD) as an effective solution for a macro network to achieve the key features of FD, such as latency reduction and UL link budget improvement. Finally, we present the field test results for the performance of world-first SBFD prototype of high transmit power massive-multi-input-multioutput (MIMO) macro network.

We present our study results on the neural network based approaches to the transmitter/receiver design over nonlinear channel. In the first part, we discuss the transmitter design for the peak-to-average power (PAPR) reduction. The algorithm unrolling is applied to a well-known PAPR reduction algorithm. The learning-based approach achieves the performance on par with the classical approach, but at the smaller computational complexity. The second part discusses the joint transmitter/receiver design for the mitigation of the transmitter nonlinearity. It is shown that by combining the neural network with the unfolded algorithm for PAPR reduction at the transmitter and employing the receiver neural network, sizable gain is achieved when the emission criterion is relaxed.

In this paper, we discuss UE power saving (PS) techniques for eXtended Reality (XR) applications in 5G NR system. XR traffic is characterized by pseudo periodic packet arrival, high bit rate, and low latency requirement. It is challenging to support such traffic in a small device form factor with limited battery size, e.g., head-mounted display (HMD) or XR glasses. Therefore, it is desired for 5G NR to support effective UE PS techniques. We first discuss a few PS techniques defined in 5G NR specifications Release 15 and 16. Then, we introduce new PS techniques that are evaluated via system level simulations with the UE power consumption model defined in a 3GPP. Evaluation results show that UE power consumption can be substantially reduced by the new PS techniques, up to 40%.

We present system-level evaluation results to characterize the performance of eXtended Reality (XR) applications over a 5G NR system. A split-rendering framework is assumed, where the XR device uses 5G to offload computation associated with rendering and encoding of video frames to an edge server. The XR traffic model includes rendered video frames on the downlink and user pose and control updates on the uplink. We present results for both sub-6 GHz (FR1) and millimeter-wave (FR2) bands. Additionally, we also discuss potential enhancements to further improve user experience for XR applications over 5G.

Tactile internet is defined as a network that offers a response to a physical process or an object in perceived real time. The development of new radio (NR) and long-term evolution (LTE) technologies with tailored high-reliability and low-latency design is expected to reliably transmit data in milliseconds, leading to the promising realization of tactile internet with applications in areas such as factory automation, education, gaming, and healthcare. In this paper, from a physical layer and medium-access control (PHY/MAC) perspective, we discuss the systems design of ultrareliable and low-latency communications (URLLC) in NR and LTE technologies, both belonging to the fifth-generation (5G) wireless technologies. Motivated by the safety and privacy requirements of tactile internet, we also outline the 5G security landscape, major categories of attackers, and potential countermeasures. Finally, we provide a case study of factory automation as an example of the proposed 5G-based tactile internet.

Among the three 5G scenarios identified by ITU-R, massive MTC poses very challenging uplink design target which requires the simultaneous support of enhanced coverage, long battery life and massive connection density. During the 5G Release 14 study phase in 3GPP, the working group studied the Non-Orthogonal Multiple Access (NOMA) scheme which can improve link budget and increase user density with the cost of complex user detection scheme. Among all the candidates, Resource Spread Multiple Access (RSMA) scheme shows promising performance gain without introducing too much complexity on the receiver design. In this paper, we briefly review the RSMA scheme. For the link level performance analysis, we firstly analyze and compare the link budget among RSMA, TDMA, and FDMA to find where the gain for RSMA comes from. Meanwhile, we provide preliminary results to justify the gains compared with OMA scheme. On system design, we review the whole procedure and propose to use user centric mobility and grant free to improve the system efficiency along with NOMA.

In this paper we consider a heterogeneous LTE network where femto cells are randomly deployed in a macro network. Femto cells are modeled as closed cells, namely only group member UEs can be associated with the femto cells. We demonstrate that inter-cell interference may prevent reliable operations for non-member UEs that are in proximity of a closed cell, which thus experience outage. We show how some of the novel features introduced in the Rel-10 specifications of the LTE standard can be leveraged by a suitable inter-cell interference coordination scheme (ICIC), which relies upon resource partitioning among different nodes to reduce the inter-cell interference problem. Additional significant improvements can be achieved when the proposed ICIC scheme is associated to a simple yet effective autonomous power control algorithm, described in detail in the paper, and further gains are demonstrated for UEs employing interference cancellation of broadcast interfering signals. We finally propose an enhanced ICIC method, based on a tighter coordination between macro and femto nodes, whose significant performance improvements advocate for suitable updates to the future LTE specifications.

In this paper we consider a heterogeneous LTE network where femto cells are randomly deployed in a macro network according to the two models described in [1], namely dual-strip and NxN. Femto cells are modeled as closed cells, namely only group member UEs can be associated with the femto cells. Therefore, dominant interference may be experienced by non-member UEs that are in proximity of a closed cell and leave these UEs in outage. We show geometry performance in a practical deployment, and discuss an autonomous power control method, which allows to dramatically reduce the outage probability, and we evaluate a resource partitioning method between macro and femto cells that further improves the performance of macro users.

We consider wireless femtocell networks where scheduling of transmissions is coordinated across multiple cells to mitigate interference and deliver fairness and quality of service (QoS). Coordination across multiple cells entails (i) exchange of (serving and interfering) channel information and traffic priority (which is a function of packet delays, average rate, queue length), and (ii) signalling of transmission powers over pilots so that neighboring cells can determine the expected SINR to pick the right modulation and coding scheme. Such an exchange entails delay in coordination, resulting in scheduling decisions being made on the basis of stale information received from other cells. In this paper, we study aspects of practical signalling and algorithm design to account for such coordination delay and study its impact. When the coordination across cells is done over a high latency backhaul, we design a hybrid signalling mechanism where minimal amount of additional over-the-air (OTA) signalling enhancement can lead to tremendous performance improvement. We numerically demonstrate the benefits of our approach via comparison to a centralized scheduler and reuse one scheme using system simulations based on 3GPP evaluation methodology.

Next generation wireless communications rely on large bandwidths and orthogonal frequency division multiple access (OFDMA) techniques to achieve high data rates. In an OFDMA-based cellular network, interference management is key to system performance characteristics, such as capacity, coverage and stability. Conventional cellular systems typically employ frequency reuse, such as 1/3, or 1/7 frequency reuse, to reduce inter-cell interference, resulting in low bandwidth efficiency. This study introduces a frequency resource and interference management scheme for use in an OFDMA cellular communication system, referred to as dynamic frequency resource allocation, in which the network divides frequency band into multiple partitions with various inter-sector interference blocking capabilities. In addition, an interference identification scheme that allows the network to acquire a terminal's interference properties is also proposed. Therefore the terminals under different inter-sector interference can be dynamically assigned with the most efficient frequency resources depending on the interference sources, enabling the network to optimise both bandwidth usage and cell edge performance with increased flexibility and accuracy.

Embedding pico/femto base-stations and relay nodes in a macro-cellular network is a promising method for achieving substantial gains in coverage and capacity compared to macro-only networks. These new types of base-stations can operate on the same wireless channel as the macro-cellular network, providing higher spatial reuse via cell splitting. However, these base-stations are deployed in an unplanned manner, can have very different transmit powers, and may not have traffic aggregation among many users. This could potentially result in much higher interference magnitude and variability. Hence, such deployments require the use of innovative cell association and inter-cell interference coordination techniques in order to realize the promised capacity and coverage gains. In this paper, we describe new paradigms for design and operation of such heterogeneous cellular networks. Specifically, we focus on cell splitting, range expansion, semi-static resource negotiation on third-party backhaul connections, and fast dynamic interference management for QoS via over-the-air signaling. Notably, our methodologies and algorithms are simple, lightweight, and incur extremely low overhead. Numerical studies show that they provide large gains over currently used methods for cellular networks.

In this paper, we investigate link adaptation and incremental redundancy (IR) retransmission schemes over correlated wireless channels. While computer simulations have been used to study the performance of these techniques, a numerically tractable analytical approach is more desirable to analyze generic protocols, and to reveal insights into the performance tradeoffs. An error-recursion approach is developed in this paper to mathematically analyze the throughput, delay, and energy efficiency of rate-adaptation techniques over fading channels with arbitrary correlations between retransmissions. Using Reed-Solomon codes as an example, we quantitatively predict the performance tradeoff of throughput and latency for IR schemes and the performance dependency on the channel correlation. Numerical results also show that reactive rate-adaptation schemes with IR retransmission outperform proactive rate-adaptive schemes, even with perfect channel side information, in terms of throughput and energy efficiency.

A network coexistence methodology is investigated for robust coexistence of an arbitrary set of non-collaborative networks. It is shown that maximizing the energy efficiency of each node is the key to the capacity maximization for the coexisting networks. Unlike existing pairwise coexisting schemes, a two level distributed algorithm is proposed without resorting to any knowledge of the physical layer and MAC layer protocols of interfering networks. The coexistence scheme is formulated as an N-person noncooperative power-controlled coexistence game (NPCG) whose convergence and optimality properties are discussed from a game theory view point. One interesting property of the game is that the Nash equilibrium of the game is on the Pareto frontier, i.e., a social optimal of the distributed networks.

A generalized blocking model is derived for a switch access system that was investigated by Doshi, Dravida, Jeske, Murti and Samadi ( 1998) by relaxing the assumption that the line unit is a cross bar switch. The need for this arises from the fact that in some switch access architectures, the number of servers in a server group is smaller than the number of timeslots in the bus connecting the line units to the server groups. Lower and upper bounds on the blocking probability are derived to incorporate the architecture changes. The bounds are then applied to practical switch access systems and shown to be tight and useful.

Modified ARQ (automatic-repeat-request) techniques based on turbo coding are investigated for asynchronous DS-CDMA (direct-sequence code-division multiple-access) data networks under shadowing and frequency selective fading channel conditions. The throughput, delay, and energy efficiency performance of standard ARQ, metric combining, and RCPT (rate compatible punctured turbo) coded ARQ schemes are compared via simulations. The RCPT/ARQ schemes are shown to outperform the other two schemes in terms of both throughput and energy efficiency at the cost of larger delay and complexity. In addition, maximum network throughput is investigated for different ARQ schemes under energy constraints.

Summary form only given. A hybrid trellis-tree search algorithm, the H-PTCQ, which has the same storage requirement as PTCQ and, is presented. We assume 2 survivor paths are kept at each state. It is straightforward to extend the algorithm to the cases where n/spl ges/2. Simulation is conducted over 20-second speech samples using DPCM, PTCQ and H-PTCQ. The data sequence is truncated into blocks of 1024 samples. The optimal codebooks for a memoryless Laplacian source are used. Predictor coefficients for the 1st-order and 2nd-order predictors are {0.8456} and {1.3435, -0.5888}, respectively. Simulation results indicate that both PTCQ and H-PTCQ have about 3 dB gain over DPCM. H-PTCQ with 8-state convolutional code has about 0.2 to 0.3 db gain over PTCQ for the same trellis size; H-PTCQ with 256-state convolutional code has 0.05 to 0.1 dB gain over the PTCQ counterpart. Compared with a 2M-state PTCQ, the M-state H-PTCQ has the same computational complexity and uses half of the path memory. Since the performance improvement of an an 8-state PTCQ over a 4-state PTCQ is about 0.4 dB for a similar set of data, the 0.2 to 0.3 dB gain obtained by using H-PTCQ is quite remarkable. Notice that H-PTQ enables a transmitter to adapt performance according to the resource constraints without changing PTCQ receivers. It is also interesting to observe that the 0.1 dB gain of an 8-state TCQ against a 4-state TCQ plus the 0.3 dB gain of H-PTCQ is about the gain of an 8-state PTCQ over a 4-state PTCQ. The results for 256-state quantization also agree with this observation. Therefore, we conclude that most of the gain of a 2M- over M-state PTCQ comes from the better internal TCQ quantizer, and mostly from the better prediction by keeping more paths.

The concept of a general nonlinear parity-check equation was first proposed by Pietrobon et al. who used them to construct rotationally invariant trellis codes for two dimensional signal sets. This paper applies this technique to trellis-coded modulation (TCM) codes with multidimensional MPSK and MQAM constellations to construct nonlinear phase rotationally invariant multi-D codes. Based on this construction technique, a series of the best fully phase rotationally invariant multi-D trellis codes for a variety of signal constellations is obtained through a systematic code search program. The code search results show that most codes achieve the same asymptotic coding gain as the best linear, but nonphase rotationally invariant codes found by Pietrobon et al.