Frame Structure Design and Analysis for Millimeter Wave Cellular Systems

The millimeter-wave (mmWave) frequencies have attracted considerable attention for fifth generation (5G) cellular communication as they offer orders of magnitude greater bandwidth than current cellular systems. However, the medium access control (MAC) layer may need to be significantly redesigned to support the highly directional transmissions, ultra-low latencies and high peak rates expected in mmWave communication. To address these challenges, we present a novel mmWave MAC layer frame structure with a number of enhancements including flexible, highly granular transmission times, dynamic control signal locations, extended messaging and ability to efficiently multiplex directional control signals. Analytic formulae are derived for the utilization and control overhead as a function of control periodicity, number of users, traffic statistics, signal-to-noise ratio and antenna gains. Importantly, the analysis can incorporate various front-end MIMO capability assumptions -- a critical feature of mmWave. Under realistic system and traffic assumptions, the analysis reveals that the proposed flexible frame structure design offers significant benefits over designs with fixed frame structures similar to current 4G long-term evolution (LTE). It is also shown that fully digital beamforming architectures offer significantly lower overhead compared to analog and hybrid beamforming under equivalent power budgets.Comment: Submitted to IEEE Transactions for Wireless Communication

Statistical QoS Analysis of Full Duplex and Half Duplex Heterogeneous Cellular Networks

In this paper, statistical Quality of Service provisioning in next generation heterogeneous mobile cellular networks is investigated. To this aim, any active entity of the cellular network is regarded as a queuing system, whose statistical QoS requirements depend on the specific application. In this context, by quantifying the performance in terms of effective capacity, we introduce a lower bound for the system performance that facilitates an efficient analysis. We exploit this analytical framework to give insights about the possible improvement of the statistical QoS experienced by the users if the current heterogeneous cellular network architecture migrates from a Half Duplex to a Full Duplex mode of operation. Numerical results and analysis are provided, where the network is modeled as a Mat\'ern point processes with a hard core distance. The results demonstrate the accuracy and computational efficiency of the proposed scheme, especially in large scale wireless systems

Enabling RAN Slicing Through Carrier Aggregation in mmWave Cellular Networks

The ever increasing number of connected devices and of new and heterogeneous mobile use cases implies that 5G cellular systems will face demanding technical challenges. For example, Ultra-Reliable Low-Latency Communication (URLLC) and enhanced Mobile Broadband (eMBB) scenarios present orthogonal Quality of Service (QoS) requirements that 5G aims to satisfy with a unified Radio Access Network (RAN) design. Network slicing and mmWave communications have been identified as possible enablers for 5G. They provide, respectively, the necessary scalability and flexibility to adapt the network to each specific use case environment, and low latency and multi-gigabit-per-second wireless links, which tap into a vast, currently unused portion of the spectrum. The optimization and integration of these technologies is still an open research challenge, which requires innovations at different layers of the protocol stack. This paper proposes to combine them in a RAN slicing framework for mmWaves, based on carrier aggregation. Notably, we introduce MilliSlice, a cross-carrier scheduling policy that exploits the diversity of the carriers and maximizes their utilization, thus simultaneously guaranteeing high throughput for the eMBB slices and low latency and high reliability for the URLLC flows.Comment: 8 pages, 8 figures. Proc. of the 18th Mediterranean Communication and Computer Networking Conference (MedComNet 2020), Arona, Italy, 202

EFFICIENT FINE-GRAINED 802.11AX BSR-BASED OFDMA RU ALLOCATION

Proposed herein are techniques that provide a simple Institute of Electrical and Electronics Engineers (IEEE) 802.11ax (WiFi6®) uplink (UL) orthogonal frequency-division multiple access (OFDMA) throughput improvement by exploiting existing standards and enterprise traffic patterns

Performance Enhancement of IEEE 802.11AX in Ultra-Dense Wireless Networks

IEEE 802.11ax, which is one emerging WLAN standard, aims at providing highly efficient communication in ultra-dense wireless networks. However, due to a large number of stations (STAs) in dense deployment scenarios and diverse services to be supported, there are many technical challenges to be overcome. Firstly, the potential high packet collision rate significantly degrades the network efficiency of WLAN. In this thesis, we propose an adaptive station (STA) grouping scheme to overcome this challenge in IEEE 802.11ax using Uplink OFDMA Random Access (UORA). In order to achieve optimal utilization efficiency of resource units (RUs), we first analyze the relationship between group size and RU efficiency. Based on this result, an adaptive STA grouping algorithm is proposed to cope with the performance fluctuation of 802.11ax due to remainder stations after grouping. The analysis and simulation results demonstrate that our adaptive grouping algorithm dramatically improves the performance of both the overall system and each STA in the ultra-dense wireless network. Meanwhile, due to the limited RU efficiency of UORA, we adopt the proposed grouping scheme in the Buffer State Report (BSR) based two-stage mechanism (BTM) to enhance the Uplink (UL) Multi-user (MU) access in 802.11ax. Then we propose an adaptive BTM grouping scheme. The analysis results of average RU for each STA, average throughput of the whole system and each STA are derived. The numerical results show that the proposed adaptive grouping scheme provides 2.55, 413.02 and 3712.04 times gains in throughput compared with the UORA grouping, conventional BTM, and conventional UORA, respectively. Furthermore, in order to provide better QoS experience in the ultra-dense network with diverse IoT services, we propose a Hybrid BTM Grouping algorithm to guarantee the QoS requirement from high priority STAs. The concept of ``QoS Utility is introduced to evaluate the satisfaction of transmission. The numerical results demonstrate that the proposed Hybrid BTM grouping scheme has better performance in BSR delivery rate as well as QoS utility than the conventional BTM grouping

Performance evaluation of TCP-based traffic over direct communications in LTE-Advanced

Direct (or device-to-device, D2D) communications are being investigated in the framework of LTE-Advanced. They allow one-to-one communications between two endpoints, under the control of the eNodeB, which allocates resources for the d2d flow, but does not act as a relay for its traffic. The direct link can also be used for file transfer or proximity-based browsing, i.e. applications running on TCP. In this paper, we evaluate the performance of TCP-based traffic transported through the direct link, in several scenarios. We show and explain non-intuitive results, which arise from the interplay of TCP and LTE-A protocol mechanisms, and compare the existing TCP versions in a dynamic environment, where mode switches between the direct and the infrastructure link may induce periodic losses

Predictive resource allocation in the LTE uplink for event based M2M applications

For certain event based M2M applications, it is possible to predict when devices will or may need to send data on the LTE uplink. For example, in a wireless sensor network, the fact that one sensor has triggered may increase the probability that other sensors in the vicinity may also trigger in quick succession. The existing reactive LTE uplink access protocol, in which a device with pending data sends a scheduling request to the eNodeB at its next scheduled opportunity, and the eNodeB responds with an uplink grant, can lead to high latencies. This is particularly the case when the system utilizes a high scheduling request period (of up to 80ms) to support a large number of devices in a cell, which is characteristic of M2M deployments. In this paper, we introduce, analyze and simulate a new predictive/proactive resource allocation scheme for the LTE uplink for use with event based M2M applications. In this scheme, when one device in a group sends a scheduling request, the eNodeB identifies neighbor devices in the same group which may benefit from a predictive resource allocation in lieu of waiting for those neighbors to send a scheduling request at their next scheduled opportunity. We demonstrate how the minimum uplink latency can be reduced from 6ms to 5ms and how the mean uplink latency can be reduced by greater than 50% (in certain scenarios) using this method

QUALITY OF SERVICE IMPROVEMENTS IN IEEE 802.11AX WI-FI

IEEE 802.11ax is the latest high rate Wi-Fi technology (also known as high efficiency Wireless) introduces some new features like OFDMA, Uplink multi-user MIMO (UL MU-MIMO) to deliver benefits in reliability, capacity, and speed. 802.11ax is better suited to some new use cases, such as live video streaming and IoT than previous versions of Wi-Fi (802.11n/ac). In this article, we study the Quality of Service (QoS) mechanism to guarantee certain levels of service to various traffic flows with the help of weighted fair queuing (WFQ) hierarchical scheduler. The multi-user mode of enhanced distributed channel access (MU mode EDCA) illustrates the controlling aspects, issues, and possible solutions of EDCA for the 802.11ax standard to satisfy QoS requirements in dense deployment scenarios