Heterogeneous network (HetNet) comprises multiple radio access technologies (RATs) allowing a user to associate with a specific RAT and steer to other RATs in a seamless manner. To cope up with the unprecedented growth of data traffic, mobile data can be offloaded to wireless fidelity (WiFi) in a long term evolution (LTE) based HetNet. In this paper, an optimal RAT selection problem is considered to maximize the total system throughput in an LTE-WiFi system with offload capability. Another formulation is also developed where maximizing the total system throughput is subject to a constraint on the voice user blocking probability. It is proved that the optimal policies for the association and offloading of voice/data users contain threshold structures. As a policy search over the entire policy space may become computationally inefficient, we propose computationally efficient algorithms based on the threshold structures for the association and offloading of users in LTE-WiFi HetNet. Simulation results are presented to demonstrate the voice user blocking probability and the total system throughput performance of the proposed algorithms in comparison with other benchmark algorithms.

Optimal Radio Access Technology Selection Algorithm for LTE-WiFi Network

As a part of Fourth Generation (4G) wireless communication system, a user can associate with any radio access technology (RAT) when there are multiple RATs available and can move seamlessly among them. To handle the explosive growth of traffic in cellular network, the idea of mobile data traffic offloading to Wireless Fidelity (WiFi) has been proposed. In this paper, we focus on mobile data offload assisted optimal association problem in a heterogeneous network. The problem has been formulated under the framework of constrained Markov decision process (CMDP). Value iteration and gradient descent algorithm has been used to determine the optimal policy. We aim to maximize the expected average per-user throughput of the system subject to a constraint on blocking probability of voice users. In our model, we consider the possibility of mobile data user offload from one RAT to another during association or departure of a user. Optimal policy has been found to follow a threshold structure. Numerical results are presented to show how the average per-user throughput of the system varies under different load conditions.

Optimal radio access technology selection policy for LTE-WiFi network

The fully accomplished standardization of the new mobile generation has led to the deployment of fifth-generation (5G) wireless networks to gratify enormous traffic volume for Internet services. The current centralized mobility system could not be sufficient to manage an explosive increase in data volume and is considered a steadily rising issue in modern wireless communication. A new technique that can affluently handle traffic problems and completely avoid network breakdown chances is indispensable. Recently, distributed mobility management (DMM) was introduced to overcome the inevitable obstacles that destructively impact the existing networks. Specifically, a novel design based on the deployment of distributed mobility anchors, closer to the terminal points, was introduced. Several works have been proposed to build DMM solutions with different focuses for 5G-and-beyond networks (B5G), which are also referred to as sixth-generation solutions (6G). In this paper, we present the potential and benefits of flat network design for efficient and fast routing of traffic and furnish the effectiveness of the scheme toward mobility management in B5G by delineating recent research works. We also present the current limitations, challenges, and future research directions for seamless mobility to achieve the desired objectives in the current 5G and upcoming 6G cellular communications. 

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Mobility Management Issues and Solutions in 5G-and-Beyond Networks: A Comprehensive Review

Currently, there are ongoing research and development efforts directed to data offloading. Data offloading allows load distribution by suitably allocating data communication traffic to other systems, such as wireless LANs or vehicle-to-vehicle communication systems. Especially, there is also ongoing research into traffic offloading using vehicle-to-vehicle communication. In traffic offloading using vehicle-to-vehicle communication, generally, while effectively utilizing mobile phone communication (V2I communication), vehicle-to-vehicle communication (V2V communication), in which content is shared among neighboring vehicles, is additionally used. In V2V communication, since the amount of data that can be transmitted at one time is not so large, and the opportunities for exchanging content are limited due to movement of vehicles, it is not easy to efficiently share relevant content within a certain period of time. Accordingly, we have designed an efficient content-delivery controlling algorithm for use in a situation where vehicles generate content in real time. The algorithm utilizes route prediction information in order to efficiently share content among the vehicles by way of V2X communication (i.e., V2I communication and V2V communication used in combination). This paper proposes the algorithm and reports its effectiveness demonstrated through simulated performance evaluation.

Contents Delivery Method Using Route Prediction in Traffic Offloading by V2X

To support the tremendously increasing data traffic volume in cellular networks, novel network architectures are getting evolved. Heterogeneous Network (HetNet) architecture is one such approach, where the serving nodes belonging to different Radio Access Technologies (RATs) coexist with the existing macro cell network, as an overlay. To leverage the full capacity of HetNet, efficient traffic handling schemes are required. With this consideration, we study and propose network based traffic offloading scheme and compare their performances on ns-3 simulator, for the Long Term Evolution (LTE) and Wireless Local Area Network (WLAN) RATs scenario in HetNet.

Network based offloading in LTE-WLAN Heterogeneous Networks

The increasing use of smartphones and content-rich and data-hungry applications has resulted in significant growth in demand for mobile data services in recent years. To meet this requirement, one of the widely-used approaches is to offload cellular data traffic to Wireless LAN as it operates in unlicensed bands. Offloading decisions are typically based on signal quality. In this paper, we propose an integrated offloading approach which takes both signal quality and network load into consideration. We focus on solutions that do not require significant changes to current network implementations and standards. We investigate the performance of this approach for different scenarios via extensive simulations and observe improved system and user performance in terms of throughput. The evaluation adheres to the methodology laid down by the global standards body 3GPP for such comparisons.

User-based integrated offloading approach for 3GPP LTE-WLAN network

IAB is a feasible and economical solution to deploy ultra-dense cells in the 5G networks, where access and wireless backhaul links share the same spectrum. IAB eliminates the need to connect ultra-dense cells to the core network through the wired backhaul. However, mmWave backhauling and multihop topology imposes new constraints on the 5G IAB network that become a hindrance to its effective performance. In this paper, we elaborate on cell selection and present a few cell selection policies designed explicitly for IAB networks. Unlike the popular RSRP based policy that may lead to load unbalance in the IAB network, the proposed policies are devised after considering the backhaul constraints and end-to-end performance requirements. The performance of these policies is investigated using system-level simulations. These policies have shown tremendous improvement in achieving cell-edge throughput while maintaining comparable average UE throughput. The policies provide better load balancing and topology in the IAB network than the RSRP based policy.

Backhaul-Aware Cell Selection Policies in 5G IAB Networks

As the Internet usage on mobile networks is increasing at an alarming rate, operators need techniques to provide more capacity and bandwidth. One solution proposed by the 3rd Generation Partnership Project (3GPP) is to offload data to other access networks. The 3GPP architecture is designed to work along with non 3GPP access networks like Wireless Local Area Networks (WLANs). IP Flow Mobility (IFOM) is one method standardized, that enables offloading of data to these alternate accesses. IFOM enabled User Equipment (UEs) have multiple interfaces which allows them to connect to different access networks such as Long Term Evolution (LTE) and WLANs simultaneously. Thus concurrent flows with different traffic types can exist over these networks, and selective and seamless switching of an IP flow from one access network to the other is feasible. Our objective in this paper, is to investigate the benefits of IFOM on UE throughput in Heterogeneous Networks (HetNets) for different traffic types and latencies under diverse network environments, loads and fading conditions. We have carried out extensive ns-3 simulations. Our simulation results show that the IFOM enabled UEs experience high throughput at latencies below 18 ms for Voice over Internet Protocol (VoIP) and 50 ms for video and higher throughput with lower latencies in the proximity of WLANs. We further propose an algorithm to switch traffic flows for IFOM enabled UEs so that, the average per UE throughput is maximized, to provide a better Quality of service (QoS). We carry out simulations with the same and achieve a significant 14% to 30% increase in the average per UE throughput under varying load conditions.

Performance evaluation and viability of IFOM in heterogeneous LTE — WLAN network

Multihop relaying with mobility support is a long due necessity in a cellular network. Researchers have made proposals to enable multihop relaying in the LTE network, but it garnered a little interest from the industry as these proposals require significant modifications in the standard network elements and signaling procedures. With the advent of 5G, the multihop relaying has become essential. This work proposes a novel architecture that supports multihop relay communications in 3GPP LTE and 5G networks. We introduce two new nodes into the network, namely Relay Node and Proxy-eNB (ProxygNB, resp.), that constitute radio and core stack of an eNB (gNB, resp.). These nodes are connected via LTE (5G, resp.) IP network and in conjunction provide eNB (gNB, resp.) functionality to the UE connected to a relay node. The architecture does not need modifications to any standard network element, and control and user data plane procedures. Further, the new nodes reuse the existing standard interfaces to communicate either on the radio or to the core network. We also provide handover procedures due to UE and/or relay mobility.

A Novel Architecture for Multihop Relaying in 3GPP LTE and 5G Networks

Integration of IEEE 802.11 wireless local area networks with the 3GPP based cellular networks has attracted significant interest in recent releases of 3GPP. But the current scanning procedures used for the discovery of WLANs, implemented in most smartphones, is very inefficient due to unnecessary scan operations. In this paper, we have proposed modified scanning algorithms to reduce the amount of undesirable scans. In the proposed schemes, the UE schedules its scanning operations with assistance from the cellular network on the operator deployed WLAN network and offload policies. The simulation results in ns-3, with additional modules implemented for ANDSF and IEEE 802.11u for 3GPP-WLAN interworking, have shown significant improvement in energy consumption along with better association time for the users.

Shashi Ranjan

Papers

User-based integrated offloading approach for 3GPP LTE-WLAN network

Backhaul-Aware Cell Selection Policies in 5G IAB Networks

Performance evaluation and viability of IFOM in heterogeneous LTE — WLAN network

A Novel Architecture for Multihop Relaying in 3GPP LTE and 5G Networks

Energy efficient IEEE 802.11 WLAN discovery for heterogeneous 3GPP LTE network