Downlink Radio Resource Management Research Articles

On the Multiplexing of Data and Metadata for Ultra-Reliable Low-Latency Communications in 5G

This paper addresses the problem of downlink radio resource management for ultra-reliable low-latency communications (URLLC) in fifth generation (5G) systems. To support low-latency communications, we study performance of two multiplexing schemes namely in-resource control signalling and joint encoding of data and metadata . In the former, the metadata and data are separately encoded and the metadata is sent at the beginning of transmission time prior to the data. Thus, it benefits from a low-complexity receiver structure to decode the data block. The latter takes advantages of transmitting a larger blocklength to enhance the reliability and improve spectrum efficiency by jointly encoding data and metadata as a single codeword. Dealing with small URLLC payloads, the overhead and error of sending metadata are not negligible and have a significant impact on the system performance in terms of resource usage the reliability of transmission. For each scheme, we derive expressions for the outage probability and resource usage by taking into account impacts of the finite blocklength payloads, overhead and error of sending metadata, and probability of error in uplink feedback channel. We propose a novel framework for joint data and metadata link adaptation to minimize the average number of allocated resources, while ensuring the stringent URLLC quality of service requirements. An optimization problem is formulated for each scheme that is mixed-integer non-convex problem, difficult to solve in polynomial time. Solutions based on successive convex optimization are proposed. Numerical evaluations show that the proposed algorithms perform close to the optimal solution and demonstrate remarkable gains of up to $\mathbf {27\%}$ improvement in resource usage. Finally, we present sensitivity analysis of the results for various network parameters.

Downlink Radio Resource Management Through CoMP and Carrier Aggregation for LTE-Advanced Network

Long Term Evolution-Advanced (LTE-A) offers several new technologies to improve the performance of the user. However, poor received signal and interference from adjacent cells in the cell-edge area can reduce the efficiency of using individual technology. Therefore, the cell-edge users have lower throughput compared to the other users in the cell and LTE-A standard. An efficient downlink radio resource management scheme is proposed in this paper by combining the coordinated multipoint transmission and reception technique along with carrier aggregation technique to achieve higher throughput for the cell-edge user and better overall performance. The proposed method jointly transmits multiple component carriers to the cell-edge user from different cells to increase the bandwidth, strengthen the received signal, and reduce the interference while it satisfies several constraints. Modified largest weighted delay first packet scheduling algorithm is deployed for resource allocation, which takes into account the delay parameters, the probability of packet loss, and data rates of the user. The obtained system-level simulation results show that the proposed method significantly enhances the throughput performances, spectral efficiency, and fairness index, compared with the existing conventional methods.

QoS‐aware downlink radio resource management in OFDMA‐based small cells networks

Interference management and supporting quality-of-service (QoS) requirements are the main challenges for the spectral resource allocation in orthogonal frequency division multiple access (OFDMA) small cells networks. In this study, the authors propose an algorithm for assigning physical resource block (PRB) with QoS constraints to eliminate interference among femtocells. They formulate the proposed resource allocation scheme as an optimisation problem where interference among femtocells is entirely avoided and multiple QoS for different services are supported. The proposed optimisation problem imposes the fairness among different femtocells and maximises the PRB efficiency. However, this problem is NP-complete, and thus, they offer a greedy algorithm for solving the problem. Simulation results show the throughput of their greedy algorithm is close to the optimal solution of the optimisation problem. Moreover, the proposed algorithm improves the network throughput by over 30–50% in different simulation scenarios with various femtocells densities in comparison to the previous methods. Furthermore, simulations illustrate the rejection ratio for all classes of services is lower than 3 % . Besides, the delays of different services are lower than the delay constraints.

Resource allocation in downlink OFDMA distributed multipoint systems with incoherent and coherent transmitters

Distributed multipoint systems (DMS) are important and timely for the move to future broadband wireless communication systems. Traditional studies on DMS have mainly focused on the issues with the spatial division multiple access such as precoding techniques, which only consider a narrowband case. This paper addresses the downlink radio resource management of the orthogonal frequency division multiple access DMS (OFDMA-DMS), including power allocation between users or subcarriers, and distributed antenna selection. Signal models with incoherent and coherent transmitters are built. To maximize the system throughput, for the incoherent transmitter case, a strategy based on the iterative water-filling power allocation is proposed to approach the optimality. As for the coherent case, where coherent additions of the signal could occur at the users, the problem is transformed into an integer programming which is solvable. Numerical results show that the gain from the coherent transmitter is promising. And to achieve a near-optimal solution, only part of the DA ports will be used, which have better channel conditions.

An overview of downlink radio resource management for UTRAN long-term evolution

Radio resource management algorithms ranging from bearer admission control to semi-persistent and dynamic packet scheduling, fast link adaptation, and transmission control of multi-antenna transmission modes are addressed in this article for UTRAN long-term evolution. First, a high-level system overview of LTE is given, with special emphasis on the important components related to RRM. The quality of service parameter framework is outlined, as one of the main objectives for the families of RRM algorithms is to maximize system capacity while serving all users according to their minimum QoS constraints. It is demonstrated how the collocation of the RRM algorithms at the base station with easy access to air interface measurements offers opportunities for efficient cross-functional optimization between layers 1, 2, and 3. Examples of performance results for different traffic mixes and antenna transmission schemes are also presented, and the article is concluded with recommendations on how to operate the various RRM options under different load and traffic conditions.