SBT (Sense Before Transmit) Based LTE Licenced Assisted Access for 5 GHz Unlicensed Spectrum

Utilization of unlicensed spectrum under licensed assisted access ensuring fair co-existence with Wi-Fi networks is a good solution to address immense usage of mobile data. Radio communication operation of LTE in unlicensed frequency band is referred as LTE-unlicensed (LTE-U) or LTE-licensed assisted access. In this paper, we consider a HGNW in which coverage area of Wireless-Fidelity (Wi-Fi)’s Access Point is integrated within the LTE-U small base station’s cellular network coverage area. To overcome the disadvantages of existing LTE-U technics like carrier sense adaptive transmission and listen before talk, we proposed a new methodology i.e., sense before transmit in this paper by adopting a transmit power control mechanisms using reciprocity theorem based on the channel state information to assign the secondary carriers in the uplink as well as in the downlink directions in the unlicensed spectrum to carry the traffic. In our proposal, LTE-U users are allowed to use the unlicensed spectrum provided that the interference produced at Wi-Fi users due to LTE-U activities is remained below a certain threshold. We evaluated the performance of proposed network model in terms of outage probability and achievable throughputs.

     

DM-CSAT: a LTE-U/Wi-Fi coexistence solution based on reinforcement learning

Recent literature demonstrated promising results of Long-Term Evolution (LTE) deployments over unlicensed bands when coexisting with Wi-Fi networks via the Duty-Cycle (DC) approach. However, it is known that performance in coexistence is strongly dependent on traffic patterns and on the duty-cycle ON–OFF rate of LTE. Most DC solutions rely on static coexistence parameters configuration, hence real-life performance in dynamically varying scenarios might be affected. Advanced reinforcement learning techniques may be used to adjust DC parameters towards efficient coexistence, and we propose a Q-learning Carrier-Sensing Adaptive Transmission mechanism which adapts LTE duty-cycle ON–OFF time ratio to the transmitted data rate, aiming at maximizing the Wi-Fi and LTE-Unlicensed (LTE-U) aggregated throughput. The problem is formulated as a Markov decision process, and the Q-learning solution for finding the best LTE-U ON–OFF time ratio is based on the Bellman’s equation. We evaluate the performance of the proposed solution for different traffic load scenarios using the ns-3 simulator. Results demonstrate the benefits from the adaptability to changing circumstances of the proposed method in terms of Wi-Fi/LTE aggregated throughput, as well as achieving a fair coexistence.

     

非授权频段中LTE和Wi-Fi共存系统性能研究

为了应对移动数据日益增长的需求,3GPP(3rd Generation Partnership Project)对LTE(Long Term Evolution)扩展到非授权频段展开了相关讨论。LAA(Licensed-Assisted Access),亦称为LTE-U(Unlicensed LTE),与目前已经运行在5GHz非授权频段上的其他无线接入技术(如Wi-Fi)的共存问题,成为了研究的焦点。本文主要研究了在非授权频段上运行LTE和Wi-Fi系统共存的机制,设计实现了基于LAA和Wi-Fi共存场景的系统级仿真平台。仿真结果表明,在非授权频段上LAA能与Wi-Fi和谐共存。针对LAA系统设计一种合理的退避机制,能够同时提升LAA和Wi-Fi系统的吞吐量,提高资源分配的公平性和使用效率。     

Performance analysis of LTE-U coexistence network with WiFi using queueing model

The unforeseen mobile data explosion as well as the scarce of spectrum resource pose a major challenge to the performance of today's cellular networks which are in urgent need of novel solutions to handle such voluminous mobile data. Long term evolution-unlicensed (LTE-U), which extends the LTE standard operating on the unlicensed band, has been proposed to improve system throughput. In LTE-U system, arriving users will contend the unlicensed spectrum resource with wireless fidelity (WiFi) users to transmit data information. Nevertheless, there is no clear consensus as to the benefits of transmission using unlicensed bands for LTE users. To this end, in this paper an analytical model is presented based on a queue system to understand the performance achieved by unlicensed based LTE system taking quality of services (QoS) and LTE-U users' behaviors into account. To obtain the stead-state solutions of the queue system, a matrix geometric method is used to solve it. Then, the average delay and utilization of unlicensed band for the LTE-U users is derived by using the queuing model. The performance of LTE-U coexistence is evaluated with WiFi using the proposed model and provide some initial insights as to the advantage of LTE-U in practice.     

Modeling and performance analysis of unlicensed bands MAC strategy in multi-channel LTE-A networks with M2M/H2H coexistence

With the growing use of the machine-to-machine (M2M) communication and the unlicensed band by advanced long term evolution (LTE-A) networks, known as LTE unlicensed (LTE-U), demand for resource access strategy is rapidly increasing and has recently been attracting considerable attention of mobile operators. The requirement set by 3rd generation partnership project in the release 11 about LTE standards will allow LTE-U and other unlicensed band access technology to peacefully coexist and operate in the same unlicensed band. LTE-U supports not only the human-to-human (H2H) communication but also the M2M communication. In this paper, a new MAC protocol for LTE-U that allow friendly co-existence of H2H with M2M communications working in unlicensed bands is presented. The proposed MAC mechanisms is designed to ensure an efficient and fair channel access as well as enabling better H2H/M2M coexistence. The throughput performance of both H2H and M2M systems is evaluated analytically and by simulation. The impact of H2H/M2M transmissions periods and spectrum sensing time on the throughput performance of H2H and M2M systems are also studied.     

BiLSTM Based Reinforcement Learning for Resource Allocation and User Association in LTE-U Networks

LTE-unlicensed (LTE-U) technology is a promising innovation to extend the capacity of cellular networks. The primary challenge for LTE-U is the fair coexistence between LTE systems and the incumbent WiFi systems. In this paper, we aim to maximize the long-term average per-user LTE throughput with long-term fairness guarantee by jointly considering resource allocation and user association on the unlicensed spectrum within a prediction window. We first formulate the problem as an NP-hard combinatorial optimization problem, then reformulate it as a non-cooperative game by applying the penalty function method. To solve the game, a novel reinforcement learning approach based on Bi-directional LSTM neural network is proposed, which enables small base stations (SBSs) to predict a sequence of future actions over the next prediction window based on the historical network information. It is shown that the proposed approach can converge to a mixed-strategy Nash equilibrium of the studied game and ensure the long-term fair coexistence between different access technologies. Finally, the effectiveness of the proposed algorithm is demonstrated by numerical simulation.

     

基于Licensed Assisted Access技术的退避算法设计与优化

随着无线宽带网络的发展,移动数据业务疯狂增长,频谱资源紧缺,为了扩充LTE容量,提高频谱利用率,LAA(Licensed Assisted Access)技术,即在非授权频段部署LTE网络,与其他无线接入技术(如Wi-Fi技术)融合共存的问题,逐渐成为研究焦点。因此,竞争机制中退避算法的设计成为关键。本文主要针对Wi-Fi与LAA共存的场景,基于LBT(Listen Before Talk)竞争机制,设计了三种退避算法,并在ns-3仿真平台上实现仿真,对比纯Wi-Fi环境下的性能表现,对退避算法进行合理的优化。     

Quality of service-aware coexistence in unlicensed 5G new radio based on time-domain virtualization

The deployment of mobile systems is facing several challenges. Precisely, the lack of available licensed bands limits the network capacity, affecting the quality of service (QoS). Consequently, there has been significant interest in utilizing the unlicensed spectrum for mobile data traffic. 3GPP proposed and improved the coexistence of LTE and Wi-Fi in the unlicensed band starting in Release 13 and the following releases, such as LTE-LAA and 5G NR-U. This will cause significant interference and drastically affects the Wi-Fi users' QoS. To that end, we propose the use of time-domain virtualization between 5G NR-U and Wi-Fi systems. In particular, a scheduling algorithm is proposed, where the sharing mechanism is allocated in time slots rather than allocating a subband frequency for each technology. 5G use cases have different QoS requirements and our proposed solution aims at meeting these requirements. Accordingly, the performance is evaluated by studying the impact of resource virtualization and the coexistence configuration. Simulation results confirm that the minimum rate and maximum delay constraints are met. Moreover, it is shown that resource virtualization improves the throughput in both technologies. Furthermore, the delay performance is displayed for both 5G NR-U and Wi-Fi to show any impact of time-sharing coexistence.     

Joint resource allocation over licensed and unlicensed spectrum in U-LTE networks

Wireless Networks - By sharing unlicensed spectrum with Wi-Fi networks, unlicensed LTE (U-LTE) is one of the promising approaches to further improve LTE network throughput. However, the problem of...     

LTE-U技术及其部署策略研究

本文先从LTE-U技术原理、产业发展情况以及与Wi-Fi共存的技术挑战等方面分析,然后与LWA、ANDSF等非授权频谱利用技术进行比较,再结合频谱政策等因素提出了对运营商部署LTE-U的策略建议.     

LTE-U关键技术与网络规划策略

LTE-U是一种在非授权频谱上部署LTE技术以提供电信级移动通信服务的无线接入技术.本文首先研究了LTE-U关键技术,然后从频率使用、载波聚合方案、网络部署策略、干扰规避等方面分析了LTE-U引入对网络规划的影响,针对性的提出了以提升中国移动LTE网络质量与建设效率为目标的LTE-U网络规划策略,为中国移动未来LTE-U部署提供参考.     

Hybrid Channel Access Mechanism Based on Coexistence Scenario of NR-Unlicensed

With the rapid development of 5G NR(New Radio),the explosive increment of traffic amount is calling the utilization of unlicensed band.3GPP has proposed LAA(Licensed Assisted Access)to use LTE in unlicensed band and pointed out that NR-U(NR-Unlicensed)can reuse most designs of it.However,the existing channel access mechanism of LAA is conservative under the coexistence scenario of NR-U,which leads to the waste of time resource.To address the problem this paper proposes a hybrid channel access mechanism to take advantage of the LBT(Listen-Before-Talk)mechanism of LAA when channel is quite busy and transmit directly with reduced power when it is relatively idle.The channel busy degree is judged by a series of periodically updated adaptive thresholds.System-level simulation verifies that under the coexistence scenario of NR-U the proposed mechanism can achieve higher UPT(User Perceived Throughput)and lower delay than other channel access mechanisms.     

5G非授权频段组网技术

随着移动通信业务需求的不断增长，授权频段的短缺日益明显，5G网络亦开始考虑在非授权频段的部署，即使用NR协议在非授权频段提供接入服务。5G非授权频段组网的主要挑战是在5G新技术特性下支持LBT机制，保障同已有非授权全频段系统（WLAN、LTE LAA等）的公平性，合理共享频谱。从LBT机制的演进入手，分析了LBT对5G非授权频段组网的影响，归纳了相关的标准化进展及挑战，并针对突出的关键技术问题提出可行的创新解决方案，保障5G非授权频段组网性能，最小化LBT失败带来的影响。     

通信技术将向网络融合技术发展

2G、3G、LTE、Wi-Fi等在内的多种网络将在一定时间内共存发展,而多网融合将成为推动技术发展的重点。多网融合从部署上将呈现异网建设、基于覆盖的共存、多网协同融合等阶段。通过在核心网、接入网和终端3个层面发展多网融合技术,将为无线网络带来巨大发展空间。     

Coexistence algorithms for LTE and WiFi networks in unlicensed spectrum: performance optimization and comparison

Wireless Networks - Facing the challenges brought by the surge in the demand for mobile data traffic, many coexistence algorithms for long-term evolution (LTE) and WiFi networks in the unlicensed...     

Analysis of resource splitting scheme with cognitive based admission control for femto-WiFi wireless networks

The coexistence of femtocell and WiFi networks in a heterogeneous spectrum environment with licensed and unlicensed bands will support multi-mode femtocell users (FUs) to simultaneously transmit on both licensed and unlicensed bands. The efficient integration of both femtocell and WiFi technologies is seen as crucial for supporting the offloading of femtocell traffic to WiFi networks. To successfully deploy these integrated technologies, the overall licensed and unlicensed spectrum usage must be efficiently managed. Thus, we propose a new cognitive-based connection-level admission control with access retrial for a femtocell network that operates under a mixed spectrum of unlicensed and licensed bands. By deploying cognitive radio concepts, the FUs will utilize the unused spectrum of the existing unlicensed spectrum of the WiFi network in an opportunistic manner in addition to using the licensed spectrum. By using the retrial phenomenon policy, the blocked FUs can retry the access, which can reduce their loss probability. An analytical model using a three-dimensional continuous time Markov chain with a level-dependent quasi birth-and-death structure was developed to evaluate and study the performance of the proposed scheme. The matrix analytic method was used to obtain the steady state probability and performance measures. The result shows that the performance of FUs for integrated femtocell-WiFi networks using the proposed scheme significantly improved in terms of FUs throughput and loss probability. The results also show that the retrial phenomenon of FUs enhances their performance.     

Performance Evaluation of Secondary Users Operating on a Heterogeneous Spectrum Environment

Radio spectrum is a limited natural resource and with the increasing number of wireless devices, an efficient spectrum management concept to make a better utilization of this resource is essential. Opportunistic spectrum access (OSA) concept is a solution to increase the spectrum capacity and thus reducing the data collision for wireless ad hoc networks. Cognitive radio (CR) technology is developed to realize OSA. Based on CR, the secondary users access opportunistically the spectrum owned by primary users. However, the consequence appearance of primary users affects greatly the performance of secondary users within OSA. Thus, a new spectrum management scheme is a must to reduce such effect. In this paper, a new spectrum management scheme over a heterogeneous spectrum environment is proposed. The proposed scheme is based on using channels from both licensed and unlicensed bands as spectrum environment for ad hoc networks. An analytical model based on Markov chains is developed to evaluate the proposed scheme.     

认知 mesh 网络服务区分的动态频谱接入策略

动态频谱接入策略是实现认知无线电网络高效利用频谱的关键。与传统认知无线电网络不同,认知mesh网络中不同QoS需求的多类型业务共同接入,为适应这一特点,提出服务区分的动态频谱接入策略。策略依据业务的QoS需求确立优先级,针对不同优先级业务采取不同的信道接入方案,实时业务依据最优传输延迟期望选择接入信道集合,在减小传输延迟的同时降低数据传输过程授权用户出现的概率,普通业务选择最优理想传输成功概率的信道,降低信道切换概率。理论与实验结果表明,与传统的认知网络频谱接入策略相比,提出的策略能提供不同业务的服务区分,满足实时业务的低延迟需求,降低数据传输的中断率,同时在授权信道空闲率与网络负载较大时吞吐量性能较优。     

On utilization efficiency of backbone bandwidth for a heterogeneous wireless network operator

To provide a comprehensive network access service to wireless users, a network operator may operate different types of wireless networks (such as GPRS, Wi-Fi, HSDPA, UMTS, WiMAX and 3GPP LTE) simultaneously to become a heterogeneous wireless network operator, such as Vodafone and T-Mobile. With convenience of accessing wireless networks, ubiquitous services would stimulate the bandwidth expenditure in the network backbone. Lots of various demanded traffic from heterogeneous access networks may converge toward Internet through the common backbone in the operator. Efficiently utilizing the common backbone can offer a better quality of service to users and maximize the revenues for the operator. To our best knowledge, few studies had ever been made in such a contemporary wireless network environment in the past. In this study, we propose solutions to efficiently allocate the bandwidth for user requests and fully utilize the unused bandwidth in the network backbone owned by the heterogeneous wireless network operator. Our simulation results show that our scheme can increase the utilization of the backbone bandwidth, shorten the request completion time for users and generate more revenue for the operator.     

Improving QoS Performance in IEEE 802.11e Under Heavy Traffic Loads

IEEE 802.11e standard is a concrete attempt to QoS challenge, but when the volume of traffic flows increases, this approach is not sufficient. Several techniques have been developed to improve WLAN QoS performance, mainly introducing a trade-off between performance and standard compatibility. This work describes the techniques used to enhance EDCA efficiency by suitably regulating standard’s parameters and it introduces an innovative algorithm, named Dynamic TXOP (DTXOP), capable of enhancing fairness between upstream and downstream resource allocation in Wi-Fi networks. Finally, after a brief review of admission control algorithms for QoS support under heavy traffic loads, a suitable admission control scheme is integrated with DTXOP as a possible solution for facing QoS degradation of active sources due to an excessive network load. The benefits obtained by integrating DTXOP and the proposed admission control policy are shown in terms of QoS enhancement and efficiency in resource allocation.