Joint Multislot Scheduling and Precoding for Unicast and Multicast Scenarios in Multiuser MISO Systems

in IEEE Transactions on Wireless Communications (2022), 21(7), 5004-5018

This paper studies the joint multislot design of user scheduling and precoding to minimize the time needed to serve all the users for unicast and multicast transmission in single-cell multiuser MISO ... [more ▼]

This paper studies the joint multislot design of user scheduling and precoding to minimize the time needed to serve all the users for unicast and multicast transmission in single-cell multiuser MISO downlink systems. In the literature, the joint design of scheduling and precoding is typically undertaken based on feedback from previous slots. In a system with time-varying channels and QoS requirements, joint multislot designs can achieve better performance since they have the flexibility to schedule users over multiple slots and also can split users across slots efficiently. Further, a joint multislot design can provide a feasible solution even when the sequential design fails. In this paper, scheduling is represented by a binary matrix where the rows represent users, columns represent slots and entries represent scheduling of users in the slots. Noticing that the users may not be permuted across slots for time-varying channels, service time needed for scheduling is rendered as the highest column index corresponding to non-zero columns. With the help of binary scheduling matrix, service time minimization is formulated as a structured mixed-Boolean fractional programming. Further, by exploiting the hidden convex-concave structure in the problem, a convex-concave procedure-based iterative algorithm is proposed. Finally, we vindicate the necessity and illustrate the superiority in performance of joint multislot design over the sequential solution through Monte-Carlo simulations. [less ▲]

JOINT DESIGN OF USER SCHEDULING AND PRECODING IN WIRELESS NETWORKS: A DC PROGRAMMING APPROACH

Doctoral thesis (2020)

These scenarios are of relevance and are already being considered in current and upcoming standards including 4G and 5G. This thesis begins by presenting the necessity of the joint design of scheduling ... [more ▼]

These scenarios are of relevance and are already being considered in current and upcoming standards including 4G and 5G. This thesis begins by presenting the necessity of the joint design of scheduling and precoding for the aforementioned scenario in detail in chapter 1. Further, the coupled nature of scheduling and precoding that prevails in many other designs is discussed. Following this, a detailed survey of the literature dealing with the joint design is presented. In chapter 2, the joint design of scheduling and precoding in the unicast scenario for multiuser MISO downlink channels for network functionality optimization considering sum-rate, Max-min SINR, and power. Thereafter, different challenges in terms of the problem formulation and subsequent reformulations for different metrics are discussed. Different algorithms, each focusing on optimizing the corresponding metric, are proposed and their performance is evaluated through numerical results. In chapter 3, the joint design of user grouping, group scheduling, user scheduling, and precoding is considered for MGMC. Differently to chapter 2, the optimization of a novel metric called multicast energy efficiency (MEE) is considered. This new paradigm for joint design in MGMC poses several additional challenges that can not be dealt with by the design in chapter 2. Therefore, towards addressing these additional challenges, a novel algorithm is proposed for MEE maximization and its efficacy is presented through simulations. In chapters 2 and 3, the joint design is considered within a given transmit slot and temporal design is not considered. In chapter 4, the joint design scheduling and precoding are considered over a block of multiple time slots for a unicast scenario. Differently to single slot design, the multi-slot joint design facilitates to address users' latency directly in terms of time slots. Noticing this, joint design across multiple slots is considered with the objective of minimizing the number of slots to serve all the users subject to users' QoS and latency constraints. Further, this multi-slot joint design problem is modeled as a structured group sparsity problem. Finally, by rendering the problem as a DC, high-quality stationary points are obtained through an efficient CCP based algorithm. In chapter 5, the joint scheduling and precoding schemes proposed in previous chapters are applied to satellite systems. Finally, The thesis concludes with the main research findings and the identification of new research challenges in chapter 6. [less ▲]

A RAN Resource Slicing Mechanism for Multiplexing of eMBB and URLLC Services in OFDMA based 5G Wireless Networks

in IEEE Access (2020)

Enhanced mobile broadband (eMBB) and ultra-reliable and low-latency communications (URLLC) are the two main expected services in the next generation of wireless networks. Accommodation of these two ... [more ▼]

Enhanced mobile broadband (eMBB) and ultra-reliable and low-latency communications (URLLC) are the two main expected services in the next generation of wireless networks. Accommodation of these two services on the same wireless infrastructure leads to a challenging resource allocation problem due to their heterogeneous specifications. To address this problem, slicing has emerged as an architecture that enables a logical network with specific radio access functionality to each of the supported services on the same network infrastructure. The allocation of radio resources to each slice according to their requirements is a fundamental part of the network slicing that is usually executed at the radio access network (RAN). In this work, we formulate the RAN resource allocation problem as a sum-rate maximization problem subject to the orthogonality constraint (i.e., service isolation), latency-related constraint and minimum rate constraint while maintaining the reliability constraint with the incorporation of adaptive modulation and coding (AMC). However, the formulated problem is not mathematically tractable due to the presence of a step-wise function associated with the AMC and a binary assignment variable. Therefore, to solve the proposed optimization problem, first, we relax the mathematical intractability of AMC by using an approximation of the non-linear AMC achievable throughput, and next, the binary constraint is relaxed to a box constraint by using the penalized reformulation of the problem. The result of the above two-step procedure provides a close-to-optimal solution to the original optimization problem. Furthermore, to ease the complexity of the optimization-based scheduling algorithm, a low-complexity heuristic scheduling scheme is proposed for the efficient multiplexing of URLLC and eMBB services. Finally, the effectiveness of the proposed optimization and heuristic schemes is illustrated through extensive numerical simulations. [less ▲]

Joint Scheduling and Precoding for Frame-Based Multigroup Multicasting in Satellite Communications

in Bandi, Ashok; Shankar, Bhavani; Chatzinotas, Symeon (Eds.) et al Joint Scheduling and Precoding for Frame-Based Multigroup Multicasting in Satellite Communications (2019, December 09)

Recent satellite standards enforce the coding of multiple users’ data in a frame. This transmission strategy mimics the well-known physical layer multigroup multicasting (MGMC). However, typical beam ... [more ▼]

Recent satellite standards enforce the coding of multiple users’ data in a frame. This transmission strategy mimics the well-known physical layer multigroup multicasting (MGMC). However, typical beam coverage with a large number of users and limited frame length lead to the scheduling of only a few users. Moreover, in emerging aggressive frequency reuse systems, scheduling is coupled with precoding. This is addressed in this work, through the joint design of scheduling and precoding for frame-based MGMC satellite systems. This aim is formulated as the maximization of the sum-rate under per beam power constraint and minimum SINR requirement of scheduled users. Further, a framework is proposed to transform the non-smooth SR objective with integer scheduling and nonconvex SINR constraints as a difference-of-convex problem that facilitates the joint update of scheduling and precoding. Therein, an efficient convex-concave procedure based algorithm is proposed. Finally, the gains (up to 50%) obtained by the jointed design over state-of-the-art methods is shown through Monte-Carlo simulations. [less ▲]

A Joint Solution for Scheduling and Precoding in Multiuser MISO Downlink Channels

in IEEE Transactions on Wireless Communications (2019)

Sparsity-Aided Low-Implementation cost based On-Board beamforming Design for High Throughput Satellite Systems

in Bandi, Ashok; Joroughi, Vahid; Shankar, Bhavani (Eds.) et al 9th Advanced Satellite Multimedia Systems Conference (ASMS) and 15th Signal Processing for Space Communications Workshop (SPSC),Berlin, Sept. 10-12, 2018 (2018, September 10)