Uplink Decoupling Research Articles

Dynamic Channel Assignment for Downlink and Uplink Decoupling in Wireless Networks

The demand for wireless communication capacity continues to increase with the extensive usage of smartphones, tablets, and devices that are related to the Internet of Things (IoT). However, devices and base stations are diversified, and base stations of various sizes are mixed. In existing cellular networks, the transmission powers of the base stations are different. If the downlink received power from the base station that belongs to the device is maximum, the uplink received power from the device at the base station is not always the maximum. This study maximizes the power that is received from the device through downlink-uplink decoupling (DUDe). DUDe can improve the spectral efficiency by selecting the downlink base station and the uplink base station independently in a network with base stations with different transmission powers. This study focuses on two technologies, DUDe and the dynamic channel assignment (DCA). It proposes an association algorithm to solve the dynamic combinational optimization problem for uplink and downlink cellular networks separately using DUDe. When a user device arrives, it first connects to the base station that has the maximum capacity at that time. Subsequently, by using the base station assignment at that time as an individual, the proposed method performs a more optimal base station assignment with DCA by using a genetic algorithm. The computer simulations demonstrate that the proposed method can achieve up to a 140 % higher spectral efficiency than the existing DUDe in the fixed channel assignment (FCA).

X2-Based Signalling Mechanisms for Downlink Uplink Decoupling in Next Generation Communication Systems

Cell selection in cellular networks is an important aspect that impacts the quality of service. The traditional cell selection mechanism is based on downlink received power. Despite the dense deployment of macrocells, mobile network operators are still confronting the daunting challenge of providing capacity and coverage. Deployment of a large number of small cells has emerged as a promising solution towards addressing this problem. However, this success expands the heterogeneous cellular networks where there is a significant disparity in the transmit power of the different base station types. Downlink and Uplink Decoupling (DUDe) can improve efficiency by associating the downlink cell based on the downlink received power and the uplink based on the pathloss. While the higher layer signalling has not been proposed in detail for the DUDe mechanism yet, we aim to propose a solution for the problem. This work addresses four different signalling mechanisms to realise decoupled up/downlinks connections in the radio access network for the next-generation communication systems with handling mobility. Our proposed signalling mechanisms cover uplink decoupling, downlink coupling, downlink decoupling, and uplink coupling scenarios. We analyse the proposed signalling mechanisms using ns3 simulation and present the impact of applying the DUDe mechanism, which mainly shows improvements for the uplink. For the selected mobility scenario, delay and lost packets are reduced by 30% and 26%, respectively. Delay and lost packets are reduced by 36% and 27% for the fix location scenario, respectively. The improvements imply that it reaches particular demand considering next-generation communication systems, with a massive number of smart devices demanding high quality of service requirements.

Efficiency analysis of a K-tier clustered HCN using dual connectivity with DUDe access

The Heterogeneous Cellular Network (HCN) paradigm holds promise for increasing the coverage probabilities and date rates of its users. The concept of downlink and uplink decoupling (DUDe) has been extensively investigated to alleviate the load imbalance problem in HCNs. Furthermore, the dual connectivity (DC) access scheme, which allows user equipment (UE) to simultaneously connect with multiple base stations (BSs), has also been investigated for its bandwidth aggregation feature that can provide increased UE data rates. This work uses stochastic geometry to analyze the uplink spectral- and energy-efficiency gains provided in a K-tier HCN with clustered users by introducing DC jointly with DUDe access. The BSs in each tier are modeled by an independent, homogeneous Poisson point process, whereas the spatially clustered UEs are modeled by a Matern cluster process. The exact analytical expressions and the upper-bound on coverage probability, spectral and energy efficiencies of the typical user are derived. The main results demonstrate the relative advantage of using DC with DUDe relative to the cases of single connectivity (SC) with DUDe and SC with the conventional downlink reference received power-based association. Further, the results also show that clustering should be modeled with an MCP to analyze the performance of clustered-HCNs.

Performance analysis of downlink and uplink decoupled access in clustered heterogeneous cellular networks

The performance of heterogeneous cellular networks (HCNs) is typically analyzed with the assumption that the users connect with the same base station in uplink and downlink. However, recent investigations have shown that downlink–uplink decoupling (DUDe) can provide network performance gains relative to the conventional coupled access. Many authors have evaluated HCN performance while assuming that the network users are distributed according to a homogeneous Poisson point process (HPPP). However, the HPPP cannot accurately model the uplink interference when the users are clustered in urban hotspots such as shopping malls and sports stadiums. This work investigates DUDe access for an HCN with user-clustering modeled by the Matern cluster process. We derive analytical expressions of the coverage probability and average throughput for DUDe access as well as the conventional coupled access. The results show that DUDe outperforms the coupled access scheme in terms of coverage and throughput. The user-clustering is also shown to benefit the coverage and throughput performance relative to the case of HPPP distributed users. The derived results are validated by Monte Carlo simulations.

Decoupled Heterogeneous Networks With Millimeter Wave Small Cells

Deploying sub-6-GHz network together with millimeter wave (mm-wave) is a promising solution to simultaneously achieve sufficient coverage and high data rate. In heterogeneous networks, the traditional coupled access, i.e., users are constrained to be associated with the same base station in both downlink and uplink, is no longer optimal, and the concept of downlink and uplink decoupling (DUDe) has recently been proposed. In this paper, we analyze the coverage probability and area throughput for both the downlink and uplink of sub-6-GHz/mm-wave cellular networks with decoupled access. Compared with the existing works, we take uplink power control and mm-wave interference into account. Using the tools from stochastic geometry, the expressions of signal-to-interference-plus-noise ratio coverage probability, user-perceived rate coverage probability and the area throughput are derived. The impact of decoupled access and different small cells (SCells) is investigated. In particular, analytical results reveal that with decoupled access, UEs are more likely to be associated with SCells in uplink when the network is sparse, and the uplink traffic will be offloaded from sub-6-GHz SCells to mm-wave SCells when the network is dense. Moreover, the dense deployment of mm-wave SCells rather than sub-6-GHz SCells is more reasonable, and the DUDe is a key factor in improving the performance of dense cellular networks with multi-band.

A Realistic Uplink–Downlink Coupled and Decoupled User Association Technique for K-tier 5G HetNets

Cell association policies in present-day heterogeneous networks (HetNets) cannot promise fairness and high capacity to all network users. To optimize this cell association, concept of downlink (DL)–uplink (UL) decoupling (DUDe) has been introduced where uplink and downlink channels can be associated with two different base stations (BSs) instead of existing policy of being associated with same BS. For this decoupled access, a number of theoretical uplink or downlink analysis frameworks have been proposed. However, these frameworks do not fully take into account the practical realization aspects. In these preceding works, all network users are assumed to employ decoupled access despite the fact that it is not preferred by all users. These models also ignore noise to get simplified solutions which can result into practical inaccuracies. In this paper, we propose a realistic user association technique in which both coupled access and decoupled access are permissible to users, depending upon their location and benefits. Therefore, the goal of the present paper is to present K-tier uplink analysis framework for network devices that prefer decoupled access. Simple closed-form solutions without ignoring noise are presented, which relate user performance to number of HetNet tiers, base-station densities and power levels. Moreover, derived distributions are also employed to compare performance of DUDe case with existing process of coupled access. Finally, decoupling impacts on K-tier network design have been presented. Based on conducted analysis, it can be concluded that decoupling is beneficial and can be easily realized in 5G K-tier HetNets.

Downlink and Uplink Decoupling in Heterogeneous Networks for 5G and Beyond

To meet the explosively increased data traffic demand from 5G and beyond, one of the most promising technologies is densified heterogeneous networks (HetNets). In HetNets, base stations (BSs) are brought closer and closer to users by densifying small BSs, which results in considerable high spectral efficiency and energy efficiency for cellular systems. However, HetNet topology challenges the traditional cellular systems. One of the most important challenges is user association. Aiming to avoid the drawback brought by coupled access (CA) in user association of HetNets, a decoupled access (DA) approach has emerged recently. By allowing access points in uplink (UL) and downlink (DL) association to be different, DA significantly improves UL performance of HetNets. This article focuses on recent works in DA. First, typical scenarios of HetNets for DA are described, which is followed by presenting two major decoupled association policies under typical scenarios. Then, DA shows its superiority over CA under different scenarios and decoupled association policies via various performance metrics. Finally, future work on DA in HetNets is discussed.

Analysis of K-tier 5G heterogeneous cellular network with dual-connectivity and uplink–downlink decoupled access

Smallcells deployment in heterogeneous networks (HetNets) introduce uplink (UL) downlink (DL) asymmetry, backhaul bottleneck, cell load imbalances, increased core network signaling, interference and mobility management problems. In order to address these issues, concept of dual connectivity has been introduced in 3rd generation partnership project (3GPP) release 12. In dual connectivity, a given user equipment can consume radio resources of at least two different network points connected through non-ideal backhaul for spectrum aggregation and cooperative access mechanisms in dense 5G HetNets. Alternatively, another concept of downlink and uplink decoupling (DUDe) has also been recently introduced in 3GPP to improve uplink performance, load balancing and cell capacity. In order to take advantage of the strengths of these latest developments, this paper significantly advances prior work by analyzing K-tier 5G HetNets having dual connectivity and decoupled access (joint DUDe dual-connectivity) for spectrum aggregation in UL and DL. In the preceding works, K-tiers as per present-day heterogeneity, uplink power control and receiver noise have not been considered for joint DUDe dual-connectivity. With the use of stochastic geometry, we have developed closed form solutions for association, coverage and outage probabilities along with average throughput for joint DUDe dual-connectivity by considering uplink power control, receiver noise and K-tiers of HetNets. The resultant performance metrics are evaluated in terms of achieved gains over conventional downlink received power access policies. Results show that cell association technique based on joint DUDe dual-connectivity can significantly improve load balancing, mobility management and UL performance for forthcoming 5G HetNets.

Downlink and Uplink Decoupling in Two-Tier Heterogeneous Networks With Multi- Antenna Base Stations

In order to improve the uplink performance of future cellular networks, the idea to decouple the downlink (DL) and uplink (UL) association has recently been shown to provide significant gain in terms of both coverage and rate performance. However, all the works are limited to a single input single output (SISO) network. Therefore, to study the gain provided by the DL and UL decoupling in multi-antenna base stations (BSs) setup, we study a two tier heterogeneous network consisting of multi-antenna BSs, and single antenna user equipments (UEs). We use maximal ratio combining (MRC) as a linear receiver at the BSs and tools from stochastic geometry, and we derive tractable expressions for both signal-to-interference ratio (SIR) coverage probability and rate coverage probability. We observe that as the disparity in the beamforming gain of both tiers increases, the gain in terms of SIR coverage probability provided by the decoupled association over non-decoupled association decreases. We further observe that when there is asymmetry in the number of antennas of both tiers, then we need further biasing toward femto-tier on the top of decoupled association to balance the load and get optimal rate coverage probability.