32 research outputs found
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
LWIR: LTE-WLAN Integration at RLC Layer with Integrated LTE-WLAN Scheduler for Efficient Aggregation
Abstract
Mobile data tra
ffi
c has seen an exponential growth in the past few years with the similar trend
expected to continue. Long Term Evolution (LTE) as a standalone cellular networking technology
will not be able to keep pace with the increasing tra
ffi
c demands. In the meanwhile, Wireless
LAN (WLAN) has proven itself as an economical wireless access technology. 3GPP has thus been
encouraged to standardize the integration of WLAN with LTE. LTE-WLAN integration at Radio
Access Network (RAN) level o
ff
ers tighter link level aggregation with enhanced system performance
compared to other WLAN inter-working and o
ffl
oading mechanisms. Having LTE as the anchor
for both networks, it provides uni
fi
ed control over both networks without any changes in LTE Core
Network (CN)
LWIR: LTE-WLAN Integration at RLC Layer with Integrated LTE-WLAN Scheduler for Efficient Aggregation
Abstract
Mobile data tra
ffi
c has seen an exponential growth in the past few years with the similar trend
expected to continue. Long Term Evolution (LTE) as a standalone cellular networking technology
will not be able to keep pace with the increasing tra
ffi
c demands. In the meanwhile, Wireless
LAN (WLAN) has proven itself as an economical wireless access technology. 3GPP has thus been
encouraged to standardize the integration of WLAN with LTE. LTE-WLAN integration at Radio
Access Network (RAN) level o
ff
ers tighter link level aggregation with enhanced system performance
compared to other WLAN inter-working and o
ffl
oading mechanisms. Having LTE as the anchor
for both networks, it provides uni
fi
ed control over both networks without any changes in LTE Core
Network (CN)
Multipath streaming: fundamental limits and efficient algorithms
We investigate streaming over multiple links. A file is split into small
units called chunks that may be requested on the various links according to
some policy, and received after some random delay. After a start-up time called
pre-buffering time, received chunks are played at a fixed speed. There is
starvation if the chunk to be played has not yet arrived. We provide lower
bounds (fundamental limits) on the starvation probability of any policy. We
further propose simple, order-optimal policies that require no feedback. For
general delay distributions, we provide tractable upper bounds for the
starvation probability of the proposed policies, allowing to select the
pre-buffering time appropriately. We specialize our results to: (i) links that
employ CSMA or opportunistic scheduling at the packet level, (ii) links shared
with a primary user (iii) links that use fair rate sharing at the flow level.
We consider a generic model so that our results give insight into the design
and performance of media streaming over (a) wired networks with several paths
between the source and destination, (b) wireless networks featuring spectrum
aggregation and (c) multi-homed wireless networks.Comment: 24 page
Intelligent Resource Allocation in 5G Multi-Radio Heterogeneous Networks
The fast-moving evolution of wireless networks, which started less than three decades ago, has resulted in worldwide connectivity and influenced the development of a global market in all related areas. However, in recent years, the growing user traffic demands have led to the saturation of licensed and unlicensed frequency bands regarding capacity and load-over-time. On the physical layer the used spectrum efficiency is already close to Shannon’s limit; however the traffic demand continues to grow, forcing mobile network operators and equipment manufacturers to evaluate more effective strategies of the wireless medium access.One of these strategies, called cell densification, implies there are a growing number of serving entities, with the appropriate reduction of the per-cell coverage area. However, if implemented blindly, this approach will lead to a significant growth in the average interference level and overhead control signaling, which are both required to allow sufficient user mobility. Furthermore, the interference is also affected by the increasing variety of radio access technologies (RATs) and applications, often deployed without the necessary level of cooperation with technologies that are already in place.To overcome these problems today’s telecommunication standardization groups are trying to collaborate. That is why the recent agenda of the fifth generation wireless networks (5G) includes not only the development schedules for the particular technologies but also implies there should be an expansion of the appropriate interconnection techniques. In this thesis, we describe and evaluate the concept of heterogeneous networks (HetNets), which involve the cooperation between several RATs.In the introductory part, we discuss the set of the problems, related to HetNets, and review the HetNet development process. Moreover, we show the evolution of existing and potential segments of the multi-RAT 5G network, together with the most promising applications, which could be used in future HetNets.Further, in the thesis, we describe the set of key representative scenarios, including three-tier WiFi-LTE multi-RAT deployment, MTC-enabled LTE, and the mmWave-based network. For each of these scenarios, we define a set of unsolved issues and appropriate solutions. For the WiFi-LTE multi-RAT scenario, we develop the framework, enabling intelligent and flexible resource allocation between the involved RATs. For MTC-enabled LTE, we study the effect of massive MTC deployments on the performance of LTE random access procedure and propose some basic methods to improve its efficiency. Finally, for the mmWave scenario, we study the effects of connectivity strategies, human body blockage and antenna array configuration on the overall network performance. Next, we develop a set of validated analytical and simulation-based techniques which allow us to evaluate the performance of proposed solutions. At the end of the introductory part a set of HetNet-related demo activities is demonstrated
On three use cases of multi-connectivity paradigm in emerging wireless networks
As envisioned by global network operators, the increasing trend of data traffic demand is expected to continue with exponential growth in the coming years. To cope with this rapid increase, significant efforts from the research community, industry and even regulators have been focused towards improving two main aspects of the wireless spectrum: (i) spectrum capacity and (ii) spectral efficiency. Concerning the spectrum capacity enhancement, the multi-connectivity paradigm has been seen to be fundamentally important to solve the capacity problem in the next generation networks. Multi-connectivity is a feature that allows wireless devices to establish and maintain multiple simultaneous connections across homogeneous or heterogeneous technologies. In this thesis, we focus on identifying the core issues in applying the multi-connectivity paradigm for different use cases and propose novel solutions to address them.
Specifically, this thesis studies three use cases of the multi-connectivity paradigm. First, we study the uplink/downlink decoupling problem in 4G networks. More specifically, we focus on the user association problem in the decoupling context, which is considered challenging due to the conflicting objectives of different entities (e.g., mobile users and base stations) in the system. We use a combination of matching theory and stochastic geometry to reconcile competing objectives between users in the uplink/downlink directions and also from the perspective of base stations.
Second, we tackle the spectrum aggregation problem for wireless backhauling links in unlicensed opportunistic shared spectrum bands, specifically, TV White Space (TVWS) spectrum. In relation to this, we present a DIY mobile network deployment model to accelerate the roll-out of high-end mobile services in rural and developing regions. As part of this model, we highlight the importance of low-cost and high-capacity backhaul infrastructure for which TVWS spectrum can be exploited. Building on that, we conduct a thorough analytical study to identify the characteristics of TVWS in rural areas. Our study sheds light on the nature of TVWS spectrum fragmentation for the backhauling use case, which in turn poses requirements for the design of spectrum aggregation systems for TVWS backhaul. Motivated by these findings, we design and implement WhiteHaul, a flexible platform for spectrum aggregation in TVWS. Three challenges have been tackled in this work. First, TVWS spectrum is fragmented in that the spectrum is available in non-contiguous manner. To fully utilize the available spectrum, multiple radios should be enabled to work simultaneously. However, all the radios have to share only a single antenna. The key challenge is to design a system architecture that is capable of achieving different aggregation configurations while avoiding the interference. Second, the heterogeneous nature of the available spectrum (i.e., in terms of bandwidth and link characteristics) requires a design of efficient traffic distribution algorithm that takes into account these factors. Third, TVWS is unlicensed opportunistic shared spectrum. Thus, the coordination mechanism between the two nodes of backhauling link is essential to enable seamless channel switching.
Third, we study the integration of multiple radio access technologies (RATs) in the context of 4G/5G networks. More specifically, we study the potential gain of enabling the Multi-RAT integration at the Packet Data Convergence Protocol (PDCP) layer compared with doing it at the transport layer. In this work, we consider ultra-reliable low-latency communication (URLLC) as one of the motivating services. This work tackles the different challenges that arise from enabling the Multi-RAT integration at the PDCP layer, including, packet reordering and traffic scheduling
Advanced Technologies Enabling Unlicensed Spectrum Utilization in Cellular Networks
As the rapid progress and pleasant experience of Internet-based services, there is an increasing demand for high data rate in wireless communications systems. Unlicensed spectrum utilization in Long Term Evolution (LTE) networks is a promising technique to meet the massive traffic
demand. There are two effective methods to use unlicensed bands for delivering LTE traffic. One is offloading LTE traffic toWi-Fi. An alternative method is LTE-unlicensed (LTE-U), which aims to directly use LTE protocols and infrastructures over the unlicensed spectrum. It has also
been pointed out that addressing the above two methods simultaneously could further improve the system performance.
However, how to avoid severe performance degradation of the Wi-Fi network is a challenging issue of utilizing unlicensed spectrum in LTE networks. Specifically, first, the inter-system spectrum sharing, or, more specifically, the coexistence of LTE andWi-Fi in the same unlicensed
spectrum is the major challenge of implementing LTE-U. Second, to use the LTE and Wi-Fi integration approach, mobile operators have to manage two disparate networks in licensed and unlicensed spectrum. Third, optimization for joint data offloading to Wi-Fi and LTE-U in multi-
cell scenarios poses more challenges because inter-cell interference must be addressed.
This thesis focuses on solving problems related to these challenges. First, the effect of bursty traffic in an LTE and Wi-Fi aggregation (LWA)-enabled network has been investigated. To enhance resource efficiency, the Wi-Fi access point (AP) is designed to operate in both the native
mode and the LWA mode simultaneously. Specifically, the LWA-modeWi-Fi AP cooperates with the LTE base station (BS) to transmit bearers to the LWA user, which aggregates packets from both LTE and Wi-Fi. The native-mode Wi-Fi AP transmits Wi-Fi packets to those native Wi-Fi users that are not with LWA capability. This thesis proposes a priority-based Wi-Fi transmission scheme with congestion control and studied the throughput of the native Wi-Fi network, as well as the LWA user delay when the native Wi-Fi user is under heavy traffic conditions. The results
provide fundamental insights in the throughput and delay behavior of the considered network. Second, the above work has been extended to larger topologies. A stochastic geometry model has been used to model and analyze the performance of an MPTCP Proxy-based LWA network with intra-tier and cross-tier dependence. Under the considered network model and the activation conditions of LWA-mode Wi-Fi, this thesis has obtained three approximations for the density of active LWA-mode Wi-Fi APs through different approaches. Tractable analysis is provided for the downlink (DL) performance evaluation of large-scale LWA networks. The impact of different parameters on the network performance have been analyzed, validating the significant gain of using LWA in terms of boosted data rate and improved spectrum reuse. Third, this thesis also takes a significant step of analyzing joint multi-cell LTE-U and Wi-Fi network, while taking into account different LTE-U and Wi-Fi inter-working schemes. In particular, two technologies enabling data offloading from LTE to Wi-Fi are considered, including LWA and Wi-Fi offloading in the context of the power gain-based user offloading scheme. The LTE cells in this work are subject to load-coupling due to inter-cell interference. New system frameworks for maximizing the demand scaling factor for all users in both Wi-Fi and multi-cell LTE networks have been proposed. The potential of networks is explored in achieving optimal capacity with arbitrary topologies, accounting for both resource limits and inter-cell interference. Theoretical analyses have been proposed for the proposed optimization problems, resulting in algorithms that achieve global optimality. Numerical results show the algorithms’ effectiveness and benefits of joint use of data offloading and the direct use of LTE over the unlicensed band. All the derived results in this thesis have been validated by Monte Carlo simulations in Matlab, and the conclusions observed from the results can provide guidelines for the future unlicensed spectrum utilization in LTE networks