Buffer Status Reports Research Articles

An Overview of MAC Scheduling techniques in 5G-NR

The advent of 5G technology has brought about a paradigm shift in wireless communication, enabling unprecedented data rates, ultra-low latency, and massive connectivity. At the heart of this technological revolution lies the 5G New Radio (5G-NR) standard, a key component that facilitates the seamless interaction between devices and networks. Within the 5G-NR architecture, the Medium Access Control (MAC) layer plays a pivotal role in optimizing the utilization of radio resources and ensuring efficient data transmission. This comprehensive overview delves into the intricate realm of MAC scheduling techniques within the context of 5G-NR. Scheduling, a fundamental aspect of wireless communication, is the process through which resources are allocated to different user devices to enable simultaneous and efficient data transmission. NR is essentially a scheduled system where the scheduler in the gNB controls downlink and uplink transmissions. This paper describes the details around dynamic scheduling, including associated functionality such as buffer-status report and power-headroom reports.

Will OFDMA Improve the Performance of 802.11 Wifi Networks?

WiFi 6 based on the IEEE 802.11ax amendment is intended to improve spectral efficiency and area throughput operations in high density environments. This is achieved (among other methods) by the introduction of Orthogonal Frequency Division Multiple Access (OFDMA) and enhanced multi-user Multiple Input Multiple Output (MU-MIMO) features. In this work, we explore the performance of downlink and uplink OFDMA in 802.11ax via extensive simulation based evaluation (latency, throughput, range) compared to conventional single user (SU) transmissions. Based on our results, we conclude that OFDMA can reduce the median latency from ~5 ms to less than 1 ms in non-saturation conditions. When used in conjunction with efficient multi-user buffer status report and restricted EDCA mechanisms, OFDMA can increase the saturation throughput by more than 10 percent. Moreover, UL OFDMA also improves aggregate throughput at longer ranges due to the narrower sub-channels (equivalently increased transmit power spectral density); four stations achieve an aggregate throughput 35 percent higher than a station transmitting SU frames and located at a range 1.5 times closer to the access point.

Multi-Dimensional Busy-Tone Arbitration for OFDMA Random Access in IEEE 802.11ax

IEEE 802.11ax has adopted orthogonal frequency division multiple access (OFDMA) to support multi-user (MU) transmissions. There exist two uplink MU OFDMA access methods in IEEE 802.11ax. The first one is uplink OFDMA random access (UORA) in which stations randomly select resource units (RUs) to send physical protocol data units (PPDUs), so its access efficiency is low. The second one is uplink OFDMA nonrandom access (UONRA) in which the access point (AP) schedules MU transmissions based on buffer status reports (BSR) from stations. However, stations usually rely on UORA to send BSRs, so the low efficiency of UORA can be a bottleneck of UONRA. Thus, UORA needs to be renovated to improve the performance of itself and UONRA. To this end, a multi-dimensional busy-tone arbitration (MBTA) mechanism is developed in this paper to reduce collisions among stations contending the same RU. Since there lacks an algorithm in IEEE 802.11ax to support coexistence of UORA and UONRA, a dynamic access-method selection (DAMS) algorithm is designed for the AP and stations to choose an optimal access method. Both MBTA and DAMS are analyzed rigorously and are further validated via simulations. The analytical and simulation results show that: 1) The MBTA dramatically improves the access efficiency of UORA; 2) DAMS always achieves a higher throughput than both UORA and UONRA.

Full-duplex MAC protocol using buffer status reports during unused uplink periods in WLAN

Full-duplex radio is a promising technique for next-generation wireless local area networks, because it can greatly increase the throughput by transmitting and receiving signals simultaneously within the same frequency band. Since conventional medium access control (MAC) protocols have been designed for half-duplex radio, they are not suitable for full-duplex radio. Therefore, we propose a novel MAC protocol to fully utilize full-duplex radio. The proposed MAC protocol consists of two periods: contention and scheduling. In the contention period, stations compete for channel access and report their buffer status information (BSI) and hidden stations to the access point (AP). Then, in the scheduling period, the AP provides transmission opportunities to stations without contention. One of the salient features of the proposed MAC protocol is that it utilizes unused uplink periods. Consequently, stations can report their BSI and hidden stations to the AP without time overhead. To evaluate the performance of the proposed MAC protocol, we performed an analytical evaluation and simulations. The evaluation results show that the proposed MAC protocol outperforms existing full-duplex MAC protocols.

Dynamic group-based scheduling of machine-to-machine communication for uplink traffic in LTE networks

In wireless machine-to-machine communication, the signalling load and radio resource allocation are critical to successful service because the technology features a large number of connected devices that introduce significant connection- and resource-related signalling overheads to eNodeB. This paper proposes an uplink scheduling scheme to minimise signalling overhead and maximise system throughput in machine-type communication devices (MTCDs) in long-term evolution networks. The proposed scheme dynamically adjusts group members by considering channel conditions and quality of service and applies the allocation-before-request (AbR) concept to allocate the residual bandwidth and realise the above objectives. Exhaustive simulations were conducted to examine the performance of the proposed scheme. The simulation results showed that the proposed scheme achieves not only better system throughput but also decreased buffer status report (BSR) signalling when compared with the static group-based scheme.

Happy Bits Based BSR Mechanism in 5G Networks

Being an important part of uplink dynamic scheduling, Buffer Status Report (BSR) has theoretical and practical significance for improving the resource utilization ratio of Long Term Evolution (LTE) system. Because uplink scheduler in base station is not directly aware of the UEs buffer content, the performance of its resource allocation strategy heavily relies on the accuracy of BSR feedback. However, the currently adopted non-uniform quantization mechanism for BSR, will inevitably cause considerable quantization error, thereby lead to an enormous waste of radio resources when large buffer size is taken into account. Therefore, this paper presents a revised BSR mechanism to improve the accuracy of BSR by fully utilizing two reserved bits, so called “Happy bits”, in MAC BSR control element’s sub-headers. Besides, this paper also proposes criteria to set those Happy bits. Simulation results show that, this new mechanism tremendously improve radio resource utilization ratio without introducing additional signalling overhead.

Dynamic Group-based Scheduling of Machine-to-Machine Communication for Uplink Traffic in LTE Networks

In wireless machine-to-machine communication, the signalling load and radio resource allocation are critical to successful service because the technology features a large number of connected devices that introduce significant connection- and resource-related signalling overheads to eNodeB. This paper proposes an uplink scheduling scheme to minimise signalling overhead and maximise system throughput in machine-type communication devices (MTCDs) in long-term evolution networks. The proposed scheme dynamically adjusts group members by considering channel conditions and quality of service and applies the allocation-before-request (AbR) concept to allocate the residual bandwidth and realise the above objectives. Exhaustive simulations were conducted to examine the performance of the proposed scheme. The simulation results showed that the proposed scheme achieves not only better system throughput but also decreased buffer status report (BSR) signalling when compared with the static group-based scheme.

Uplink QoS Scheduling Algorithm with Delay Estimation for LTE Systems

In this paper, we propose a quality of service (QoS) uplink scheduling algorithm for long term evolution (LTE) that collaborates with delay estimation. Unlike downlink scheduling, uplink scheduling cannot incorporate packet delay information due to specification constraints of LTE. The limited information results in difficulty ensuring QoS when conventional scheduling algorithms are employed. To overcome the limitation in QoS scheduling, we estimate delays taking into account buffer status reports (BSRs) of LTE and propose an uplink QoS scheduling scheme with delay estimation. For given system parameters, such as BSR period, an optimal parameter for estimation is also proposed and analyzed. Via simulations, we show that the proposed QoS scheduling scheme can reduce the number of unsatisfied QoS services by half, even with a simple estimation.

Low-overhead buffer level signalling using weighted prioritisation

A novel modification of weighted fair queuing is proposed that enables significant savings in the number of signalling bits required for the mobile terminals to indicate the status of their data buffers to the scheduling node. Results based on practical voice-over-IP system simulations, particularly applicable to UMTS/LTE, demonstrate that it is possible to achieve the same performance with single-bit buffer status reports (BSRs) as with full BSRs, provided that a buffer occupancy threshold and weighting factor are jointly adapted.