A Real-Time Performance Evaluation of Tightly Coupled LTE Wi-Fi Radio Access Networks

A tight coupling of LTE and Wi-Fi interfaces can be achieved by integrating them at the radio protocol stack. LTE and Wi-Fi radio level integration with IPSec tunnel (LWIP) is standardized by 3GPP in Rel-13 for tighter level of LTE-Wi-Fi interworking at IP layer. This tighter level of interworking replaces the traditional way of cellular-Wi-Fi interworking through a packet gateway and it can react to the dynamic changes in the wireless link quality. In this paper, we present a new variant of LWIP prototype that works with commercial UE (Nexus 5). The developed LWIP prototype uses OpenAirInterface (OAI) for LTE network and Cisco Access Point (AP) as Wi-Fi AP. We also present the design and implementation of LWIP prototype and interesting results for tight interworking of LTE and Wi-Fi at IP level. We have evaluated the LWIP performance with different Link Aggregation Strategies (LAS) using both UDP and TCP. We have observed that, in a highly loaded Wi-Fi channel, when LWIP employs Wi-Fi only in Downlink (WoD) LAS, then sum of individual TCP flow throughput has improved by 28% as compared to LWIP operating with Flow Split (FS) LAS. We have enumerated the challenges which has to be addressed in LWIP to reap the maximum benefits. A Real-Time Performance Evaluation of Tightly Coupled LTE Wi-Fi Radio Access Networks | Request PDF. Available from: https://www.researchgate.net/publication/320416949_A_Real-Time_Performance_Evaluation_of_Tightly_Coupled_LTE_Wi-Fi_Radio_Access_Networks [accessed Jan 25 2018]

Traffic Steering in Radio Level Integration of LTE and Wi-Fi Networks

A smartphone generates approximately 1, 614 MB of data per month which is 48 times of the data generated by a typical basic-feature cell phone. Cisco forecasts that the mobile data traffic growth will remain to increase and reach 49 Exabytes per month by 2021. However, the telecommunication service providers/operators face many challenges in order to improve cellular network capacity to match these ever-increasing data demands due to low, almost flat Average Revenue Per User (ARPU) and low Return on Investment (RoI). Spectrum resource crunch and licensing requirement for operation in cellular bands further complicate the procedure to support and manage the network. In order to deal with the aforementioned challenges, one of the most vital solutions is to leverage the integration benefits of cellular networks with unlicensed operation of Wi-Fi networks. A closer level of cellular and Wi-Fi coupling/interworking improves Quality of Service (QoS) by unified connection management to user devices (UEs). It also offloads a significant portion of user traffic from cellular Base Station (BS) to Wi-Fi Access Point (AP). In this thesis, we have considered the cellular network to be Long Term Evolution (LTE) popularly known as 4G-LTE for interworking with Wi-Fi. Third Generation Partnership Project (3GPP) defined various LTE and Wi-Fi interworking architectures from Rel-8 to Rel-11. Because of the limitations in these legacy LTE Wi-Fi interworking solutions, 3GPP proposed Radio Level Integration (RLI) architectures to enhance flow mobility and to react fast to channel dynamics. RLI node encompasses link level connection between Small cell deployments, (ii) Meeting Guaranteed Bit Rate (GBR) requirements of the users including those experiencing poor Signal to Interference plus Noise Ratio (SINR), and (iii) Dynamic steering of the flows across LTE and Wi-Fi links to maximize the system throughput. The second important problem addressed is the uplink traffic steering. To enable efficient uplink traffic steering in LWIP system, in this thesis, Network Coordination Function (NCF) is proposed. NCF is realized at the LWIP node by implementing various uplink traffic steering algorithms. NCF encompasses four different uplink traffic steering algorithms for efficient utilization of Wi-Fi resources in LWIP system. NCF facilitates the network to take intelligent decisions rather than individual UEs deciding to steer the uplink traffic onto LTE link or Wi-Fi link. The NCF algorithms work by leveraging the availability of LTE as the anchor to improvise the channel utilization of Wi-Fi. The third most important problem is to enable packet level steering in LWIP. When data rates of LTE and Wi-Fi links are incomparable, steering packets across the links create problems for TCP traffic. When the packets are received Out-of-Order (OOO) at the TCP receiver due to variation in delay experienced on each link, it leads to the generation of DUPlicate ACKnowledgements (DUP-ACK). These unnecessary DUP-ACKs adversely affect the TCP congestion window growth and thereby lead to poor TCP performance. This thesis addresses this problem by proposing a virtual congestion control mechanism (VIrtual congeStion control wIth Boost acknowLedgEment -VISIBLE). The proposed mechanism not only improves the throughput of a flow by reducing the number of unnecessary DUPACKs delivered to the TCP sender but also sends Boost ACKs in order to rapidly grow the congestion window to reap in aggregation benefits of heterogeneous links. The fourth problem considered is the placement of LWIP nodes. In this thesis, we have addressed problems pertaining to the dense deployment of LWIP nodes. LWIP deployment can be realized in colocated and non-colocated fashion. The placement of LWIP nodes is done with the following objectives: (i) Minimizing the number of LWIP nodes deployed without any coverage holes, (ii) Maximizing SINR in every sub-region of a building, and (iii) Minimizing the energy spent by UEs and LWIP nodes. Finally, prototypes of RLI architectures are presented (i.e., LWIP and LWA testbeds). The prototypes are developed using open source LTE platform OpenAirInterface (OAI) and commercial-off-the-shelf hardware components. The developed LWIP prototype is made to work with commercial UE (Nexus 5). The LWA prototype requires modification at the UE protocol stack, hence it is realized using OAI-UE. The developed prototypes are coupled with the legacy multipath protocol such as MPTCP to investigate the coupling benefits

Architectural Challenges and Solutions for Collocated LWIP - A Network Layer Perspective

Achieving a tighter level of aggregation between LTE and Wi-Fi networks at the radio access network (a.k.a. LTE-Wi-Fi Aggregation or LWA) has become one of the most prominent solutions in the era of 5G to boost network capacit y and improve end user's quality of experience. LWA offers flexible resource scheduling decisions for steering user tr affic via LTE and Wi-Fi links. In this work, we propose a Collocated LTE/WLAN Radio Level Integration architecture at IP layer (C-LWIP), an enhancement over 3GPP non-collocated LWIP architecture. We have evaluated C-LWIP performance in vari ous link aggregation strategies (LASs). A C-LWIP node ( i.e. , the node having collocated, aggregated LTE eNodeB and Wi-Fi access point functionalities) is implemented in NS-3 which introd uces a traffic steering layer ( i.e. , Link Aggregation Layer) for efficient integration of LTE and Wi-Fi. Using extensive simulations, we verified the correctness of C-LWIP module in NS-3 and evaluat ed the aggregation benefits over standalone LTE and Wi-Fi netwo rks with respect to varying number of users and traffic types. We found that split bearer performs equivalently to switched b earer for UDP flows and switched bearer outperforms split bearer in the case of TCP flows. Also, we have enumerated the potential challenges to be addressed for unleashing C-LWIP capabilit ies. Our findings also include WoD-Link Aggregation Strategy whi ch is shown to improve system throughput by 50% as compared to Naive-LAS in a densely populated indoor stadium environmen t

VISIBLE: Virtual Congestion Control with Boost ACKs for Packet Level Steering in LWIP Networks

Tightly coupled LTE-Wi-Fi networks have emerged as a promising solution for improving capacity and coverage of wireless networks. Different architectures which realize this integration includes LTE-Wi-Fi radio level interworking with IPSec tunnel (LWIP) and LTE-Wi-Fi Aggregation (LWA). The major issue with these architectures is that they do not exhibit expected performance when TCP is employed, i.e., TCP throughput decreases compared to using either LTE or Wi-Fi for transmission. Also, Multipath TCP (MPTCP) is inefficient while aggregating LTE and Wi-Fi links, especially when the link rates are incomparable. In this paper, we propose VIrtual congeStion control wIth Boost acknowLdgEment (VISIBLE) algorithm for LWIP networks which encompasses an efficient packet level traffic steering technique for steering Downlink traffic across LTE and Wi-Fi links of LWIP node and Boost ACK technique to reduce the number of duplicate ACKs (DUP-ACKs) delivered to the TCP sender. Unlike MPTCP, VISIBLE+LWIP uses both LTE and Wi-Fi links efficiently even if their link rates are incomparable and reduces unnecessary DUP-ACKs. We have developed VISIBLE+LWIP framework in NS-3 and compared its performance with the state-of-the-art MPTCP algorithms. We could observe that the proposed VISIBLE algorithm has doubled the throughput of basic LWIP and outperformed throughput of MPTCP by 37%. Also, it has enhanced the throughput by 30% as compared to basic LWA

On convergence and coexistence of LTE and Wi-Fi networks

The proliferation and penetration of smart phones and IoT devices is having profound impact on world economy. In order to support billions of wirelessly connected devices, and tackle exponentially increasing traffic demands and ever-increasing Quality of Experience and energy efficiency requirements of diverse services and applications being carried over communication network infrastructure, convergence and coexistence of various radio access technologies (RATs) is required. In this work, we present various architectures and traffic steering mechanisms for efficient interworking of LTE and Wi-Fi networks and evaluate their performance for carrying TCP traffic which is sensitive to out-of-order delivery of packets at the receiver. Unlike interworking which requires simultaneous usage of both LTE and Wi-Fi radios at user equipment (UE), mobile operators are considering deployment of LTE-U/LAA in unlicensed bands so that only one radio is used at UE. However, to use unlicensed bands LTE-U/LAA needs to fairly co-exist with Wi-Fi. To address this inter-RAT hidden terminal problem, we present novel solutions that either rely on a central inter-RAT controller or work without any such controller in a distributed manner

AMPS: Application aware multipath flow routing using machine learning in SDN

This paper proposes an application-aware multipath flow routing framework that integrates Machine Learning Techniques (MLT) in Software Defined Networks (SDN). Applications generated by the devices are diverse in nature, for each application bandwidth and delay requirements vary. The flows in the network compete for a constrained resource such as bandwidth or low latency path, an intelligent flow routing algorithm becomes a natural demand. Better overall network performance could be achieved only if the network is capable of prioritizing the flows and assign resources based on their application specific requirement. Our proposed, AMPS controller is capable of prioritizing each of the flow using MLT, and assign a path based on its classified priority. AMPS controller supports routing flows through different path even if the flows are between the same pair of nodes. The path finding algorithm employs Yen-K-shortest path algorithm, also it supports scalable flow routing for a large volume of flows. We have implemented the flow routing algorithm in OpenvSwitch as a proof of concept. A significant improvement is observed in comparison to SDN with traditional routing techniques involving a large number of flows. The proposed flow routing algorithm ensures high availability of an unloaded path for high priority flows even in a heavily loaded network

Network Coordination Function for Uplink Traffic Steering in Tightly Coupled LTE Wi-Fi Networks

Tight coupling of LTE and Wi-Fi networks is accomplished by binding their protocol stacks. LTE Wi-Fi radio level integration with IPSec tunnel (LWIP) corresponds to realizing this binding at IP layer. A collocated deployment of LWIP enables greater flexibility in utilizing the channel efficiently. With the advent of bandwidth-hungry smartphone Apps and IoT applications, the cellular uplink resources become highly demanding. This enforces Wi-Fi to support efficient uplink transmissions since the uplink transmissions through Wi-Fi suffers high contention because of distributed nature of Wi-Fi MAC. In order to improve Wi-Fi channel utilization by leveraging the potential of LWIP in controlling and coordinating the transmissions through LTE and Wi-Fi links, we introduce Network Coordination Function (NCF) in LWIP. The proposed NCF focuses on coordinating the uplink transmissions through Wi-Fi in a network with high load. NCF enhances the channel utilization of Wi-Fi network by regulating the packet arrival rate to the Wi-Fi link and also by revamping medium access techniques at the Wi-Fi interface of users associated with LWIP node. NCF is composed of four different uplink traffic steering algorithms with diverse objectives which improve Wi-Fi channel utilization by (i) minimizing collisions among LWIP users, (ii) increasing transmission opportunities for Wi-Fi users that are connected to legacy Wi-Fi APs operating on the same channel, and (iii) ensuring fairness for both LWIP and Wi-Fi users. Interestingly, NCF has not only improved the throughput of LWIP users but also the throughput of Wi-Fi users. Simulation experiments reveal that NCF has reduced collisions in the Wi-Fi uplink by 13-53% and improved throughput by 10-37% as compared to Wi-Fi offloading and Distributed Coordination Function (DCF)

On Efficient Scheduling of H2H Traffic and Reducing Signaling Overhead due to Uplink Small Data M2M Traffic in LTE-A Networks

Large coverage and global connectivity makes cellular networks as preferred choice for internet of things (IoT). Machine-to-machine (M2M) communications deal with communication and networking aspects of IoT. Since, cellular networks are optimized to support human-to-human (H2H) communication (e.g., Voice calls, Internet), incorporating M2M communication may affect the QoS of the former. Also, the large number of M2M devices incur significant signaling overhead on both core network (CN) and radio access network (RAN). In LTE-A networks, EPS bearer establishment procedure to connect a device to the PDN gateway involves several signaling messages exchange between the device and the network. M2M devices mostly generate traffic of low volume and less frequent, in nature. So, it is very uneconomical to have rigorous signaling messages exchange to send few bytes of data. In this paper, we first studied class based dynamic priority (CBDP) algorithm Giluka et al. (in: Proceedings of IEEE WF-IoT, 2014), which is a delay aware radio resource scheduling algorithm to support uplink M2M traffic with minimal effect on QoS of uplink H2H traffic. Further, we modeled the optimal behavior of the CBDP algorithm and compared with its behavior in practical scenarios. Apart from this, we propose a lightweight EPS bearer establishment procedure to be followed by M2M devices sending small data, in which M2M small data is piggybacked with control message. Further, in the same procedure, redundant signaling messages for small data transmission (SDT) are carefully removed preserving the security aspects of the system. To ensure security for the small data transmitted, a new insightful technique of replacing authentication with confidentiality is conceived. With this, we propose an enhanced version of CBDP algorithm, named as Non-SDT-CBDP algorithm or NSDT-CBDP algorithm, which schedules resources only to H2H and NSDT-M2M flows while SDT-M2M flows are piggybacked with Message 3 (MSG-3) of lightweight EPS bearer establishment procedure. The simulation results show performance gain of NSDT-CBDP over CBDP, specially for class-3 M2M and class-4 H2H. The NSDT-CBDP algorithm show percentage reduction in packet loss ratio by 25% for class-3 M2M, percentage reduction in end-to-end delay by 11 and 19% for class-4 H2H and class-3 M2M, percentage gain in throughput by 27 and 19% for class-4 H2H and class-3 M2M. Apart from this, NSDT-CBDP algorithm is able to allocate 12% more RBs to H2H devices in comparison to CBDP algorithm

Enhanced class based dynamic priority scheduling to support uplink IoT traffic in LTE-A networks

Internet of Things (IoT) has now become a common term in technological communities. Machine-to-machine communications (M2M) is one of the components of IoT which deals with communication of devices to device and device to the network aspects. LTE-A networks have emerged as one of the preferred underlying communication networks to support IoT or M2M traffic. However, the uplink packet scheduling to optimize the QoS (quality of service) of M2M traffic without affecting or least affecting the QoS of Human-to-human (H2H) traffic (traffic generated by regular users (also called as H2H users) such as smartphone traffic, Internet traffic, voice traffic, etc.) is one of the main challenges in LTE-A networks. As a solution, we propose an uplink packet scheduling mechanism, called as enhanced class based dynamic priority (E-CBDP) algorithm, which ensures the QoS of H2H traffic by giving it priority over M2M traffic but, optimizes the QoS of M2M traffic by pushing the scheduling of H2H traffic to their delay boundaries. Further, a dynamic M2M traffic control threshold is defined to enable the operator for proactive regulation of the huge M2M traffic to avoid network congestion as well as to minimise the impact on H2H traffic. We characterize the proposed scheduling algorithm via a mathematical analysis of metrics such as average length of the H2H queue, average length of the M2M queue, average waiting time of H2H packets, and average waiting time of M2M packets. We compare the performance of E-CBDP algorithm with some recent solutions in terms of average delay, percentage of packets dropped, aggregate throughput, fairness, and energy consumption. Simulation results show that E-CBDP algorithm demonstrates excellent performance in terms of packet drop rate and fairness while provides satisfactory performance in terms of delay, throughput, and energy consumption

INCARNATE: An interference aware spatial scheme for tightly coupled LTE-Wi-Fi networks

Stochastic geometry has been used in the literature to develop amenable models to delineate and apprehend the performance of wireless networks. In this paper, we develop a tractable and flexible model for heterogeneous wireless networks consisting of tightly coupled long-term evolution (LTE) Small cell eNodeBs (SeNBs) and wireless fidelity (Wi-Fi) access points (APs). We leverage stochastic geometry to characterize the key performance metrics of LTE-Wi-Fi Aggregation (LWA) system. The positions for SeNBs and APs are modeled as two independent homogeneous Poisson Point Processes (PPPs) in a non co-located LWA scenario. Enabling LWA operation with arbitrary number of Wi-Fi APs in a given region may not ensure maximum rate and coverage. Hence we propose a scheme, InterfereNCe Aware matéRN hArd-core poinT procEss (INCARNATE) to increase the performance of LWA system by allowing LWA operation with a chosen set of Wi-Fi APs. We derive Signal-to-Interference-plus-Noise Ratio (SINR) distribution of UE which is associated to SeNB, AP or LWA. INCARNATE is modelled as a modified Matérn Hard-Core Point Process (MHCPP). This further helps to find joint coverage probability and average data rate over the network. We then verify the accuracy of the analytical results with empirical outcomes. INCARNATE scheme outperforms the traditional MHCPP scheme by 73% and 17% in terms of data rate and coverage probability, respectively. Similarly, LWA with INCARNATE scheme excels by 51% and 6.23% as compared to regular LWA in terms of data rate and coverage probability, respectively