Wireless data networks: issues beyond the link layer

Multiple access methods in a wireless network allow multiple nodes to share a set of available channels for data transmission. The nodes can either compete or cooperate with each other to access the channel(s) so that either an individual or a group objective can be achieved. Game theory, which is a mathematical tool developed to understand the interaction among rational entities, can be applied to model and to analyze individual or group behaviour of nodes for multiple access in wireless networks. Game theory also enables us to model the selfish/malicious behaviour of nodes, and subsequently design the punishment or defense mechanisms for robust multiple access in wireless networks. In addition, game models can provide distributed solutions to the multiple access problems, which are based on solid theoretical foundations. In this survey, we provide a comprehensive review of the game models (e.g., noncooperative/cooperative, static/dynamic, and complete/incomplete information) developed for different multiple access schemes (i.e., contention-free and contention-based random channel access) in wireless networks. We consider time-division multiple access (TDMA), frequency-division multiple access (FDMA), and code-division multiple access (CDMA), ALOHA, and carrier sense multiple access (CSMA)-based wireless networks. In addition, game models for multiple access in dynamic spectrum access-based cognitive radio networks are reviewed. The major findings from the game models used for these different access schemes are highlighted. To this end, several of the key open research directions are outlined.

The gateways are the performance bottleneck of wireless mesh access networks and thus alleviating stress on them is essential to making such wireless networks robust and scalable. Using proxy servers or wireless peer-to-peer streaming techniques can help reduce the gateway load. However, these techniques, because they are data caching methods, do not save wireless resources. We instead consider a communication-sharing approach in this paper. Traditional stream sharing solutions depend on cooperation with the video server. However, in the wireless access network it is difficult to cooperate with online video sites. To address this problem in wireless mesh access networks, we propose a distributed video sharing technique called Dynamic Stream Merging (DSM). DSM is able to improve the robustness of the access network without cooperation from the online video site or the users and has the intelligence to handle sudden spikes in demand for certain videos due to specific events, thereby preventing adverse effects to other daily wireless traffic. The technique can also leverage the 80:20 data access pattern, common for many video applications, to substantially increase the service throughput. We explain the DSM technique, present the system prototype, and discuss the experimental results.

Energy Efficient Scheduling on Hybrid Multiple Access at Backend of FiWi

We consider a mobile network consisting of both the wireless access network and the backhaul network. All base stations in the access network and gateways in the backhaul network are equipped with caches, so that routing costs for serving content requests can be reduced by caching the requested content items closer to the users. In this case, user association in the wireless access network must be aware of both the quality of wireless channels and the content caching strategy. In this paper, we propose a framework that jointly optimizes wireless user association and content caching in both access and backhaul networks. The resulting problem is NP-hard. We propose a polynomial-time algorithm based on convex approximation and pipage rounding that produces a solution within a constant factor of 1 − 1/e from the optimal. Simulation results show that the proposed joint algorithm outperforms schemes that combine cache-independent user association methods with traditional caching strategies (e.g. LRU) in terms of minimizing the aggregate routing cost and backhaul traffic while achieving a high data sum rate in the access network.

5G-Flow: A unified Multi-RAT RAN architecture for beyond 5G networks

Commoditization and virtualization of wireless networks are changing the economics of mobile networks to help network providers, e.g. Mobile Network Operators (MNOs), Mobile Virtual Network Operator (MVNO), move from proprietary and bespoke hardware and software platforms to an open, cost-efficient and flexible cellular ecosystem. In addition, rich and innovation local services can be efficiently materialized through cloudification by leveraging the existing infrastructure. The future communication architecture for mobile cloud services - Mobile Cloud Networking (MCN) is a EU FP7 large-scale integrating project (IP) funded by the European Commission that is focusing on how cloud computing and network function virtualization concepts are applied to achieve virtualization of cellular networks. It aims at the development of a fully cloud-based mobile communication and application platform, or more specifically, it aims to investigate, implement and evaluate the technological foundations for the mobile communication system of long-term evolution (LTE), based on mobile network with decentralized computing and smart storage offered as one atomic service: on-demand, elastic and pay-as-you-go. MCN will investigate, implement and evaluate the technological foundations for that system to meet real-time performance and support efficient and elastic use and sharing of radio access and mobile core network resources between operators. Mobile network functionalities-such as baseband unit processing, mobility management and quality of service (QoS) control-will run on the enhanced mobile cloud platform leveraging commodity hardware, which requires extensions toward higher decentralization and enhancing them to elastically scale up and down based on load. The end-to-end control and management orchestrates infrastructure and services across several technological domains: wireless, mobile core and data centres, providing guaranteed multiple end-to-end service, mobility through the Follow-Me Cloud concept. In this chapter, we present three enabling components of such a future MCN architecture: Radio Access Network as a Service (RANaaS), Information-Centric Networking as a Service (ICNaaS) and Mobility Prediction as a Service (MOBaaS).

The proliferation of mobile demands and increasingly multifarious services pose challenges to both the radio access networks (RANs) and the core network (CN). Unfortunately, the traditional networks can hardly meet the increasing requirements. Software-defined network (SDN) and network virtualization (NV) are considered as innovative paradigms to stress these problems. By extending SDN to wireless networks, software-defined wireless network (SDWN) consisting of both RANs and CN can be obtained. In this paper, the RANs and CN of SDWN are virtualized to virtual access points (VAPs) and network slices respectively based on NV technology. Considering the system scenario that a SDWN consists of overlapping RANs, an optimal joint VAP and network slice selection scheme is proposed. To characterize the complicated transmission performance of VAPs and network slices, the concepts of utility function and network calculus are introduced, and the joint utility of VAPs and network slices is formulated based on which the optimal VAP and network slice combination corresponding to the maximal joint utility can be selected. The simulation results demonstrate the efficiency of the proposed scheme.

Video is expected to be the dominant application by traffic volume over mobile networks in the near future. Mobile network operators are deploying video optimization techniques to enhance the user experience and network utilization for video delivery. Video optimization is typically “out-of-network” and includes techniques such as transcoding, transrating, time shifting and pacing that are implemented outside of mobile radio access and core networks. However, such techniques cannot easily exploit information about real time cell congestion and radio conditions for the video terminals because it is difficult to obtain such information from the radio access network. We propose a novel “in-network” video optimization technique, named Adaptive Guaranteed Bit Rate (AGBR), for HTTP-based Adaptive Streaming (HAS) video. This optimization technique is implemented at the base station and can thus exploit knowledge of the radio and congestion conditions. With only limited knowledge of the video stream properties or content, AGBR works by adjusting the throughput delivered to the different HAS clients that in turn adjust the video quality they request. The optimization algorithm maximizes aggregate quality across multiple video flows served by the base station without starving data clients, thereby improving the overall quality of experience. We demonstrate through extensive analytical modeling and simulations that AGBR can adapt to changing network conditions to support more video sessions at an acceptable quality than alternative algorithms, while enforcing fairness among all users competing for resources within a sector.

A bandwidth and effective hit optimal cache scheme for wireless data access networks with client injected updates

Guest editorial IJSCN special issue on 3GPP NTN standards for future satellite communications

Effective support of real‐time multimedia applications in wireless access networks, viz. cellular networks and wireless LANs, requires a dynamic bandwidth adaptation framework where the bandwidth of an ongoing call is continuously monitored and adjusted. Since bandwidth is a scarce resource in wireless networking, it needs to be carefully allocated amidst competing connections with different Quality of Service (QoS) requirements. In this paper, we propose a new framework called QoS‐adaptive multimedia wireless access (QoS‐AMWA) for supporting heterogeneous traffic with different QoS requirements in wireless cellular networks. The QoS‐AMWA framework combines the following components: (i) a threshold‐based bandwidth allocation policy that gives priority to handoff calls over new calls and prioritizes between different classes of handoff calls by assigning a threshold to each class, (ii) an efficient threshold‐type connection admission control algorithm, and (iii) a bandwidth adaptation algorithm that dynamically adjusts the bandwidth of an ongoing multimedia call to minimize the number of calls receiving lower bandwidth than the requested. The framework can be modeled as a multi‐dimensional Markov chain, and therefore, a product‐form solution is provided. The QoS metrics—new call blocking probability (NCBP), handoff call dropping probability (HCDB), and degradation probability (DP)—are derived. The analytical results are supported by simulation and show that this work improves the service quality by minimizing the handoff call dropping probability and maintaining the bandwidth utilization efficiently. Copyright © 2006 John Wiley & Sons, Ltd.

Modelling and optimization of power consumption in wireless access networks

The complementary characteristics of wireless cellular networks and wireless local area networks (WLANs) make them suitable to jointly offer seamless wireless access services to mobile users. In an integrated cellular/WLAN system, the quality-of-service (QoS) requirements for different services (e.g., voice, real-time video) require admission control to limit the number of connections in each access network. In this paper, we first develop an analytical model to facilitate the evaluation of different admission control policies in a multiservice integrated cellular/WLAN system. We then formulate two different revenue-maximization problems. Each problem takes different QoS requirements into account. By solving the equivalent cost-minimization problems, we evaluate the system performance when different combinations of cutoff priority and fractional guard channel admission control policies are being used. Results show that using a cutoff priority policy in both wireless access networks can achieve the optimal solution for the two optimization problems under a wide range of network conditions.

Multicasting multiple video streams over wireless broadband access networks enables the delivery of multimedia content to large-scale user communities in a cost-efficient manner. Three dimensional (3D) videos are the next natural step in the evolution of digital media technologies. In order to provide 3D perception, 3D video streams contain one or more views that greatly increase their bandwidth requirements. Due to the limited channel capacity and variable bit rate of the videos, multicasting multiple 3D videos over wireless broadband networks is a challenging problem. In this article, we consider a 4G wireless access network in which a number of 3D videos represented in two-view plus depth format and encoded using scalable video coders are multicast. We formulate the optimal 3D video multicasting problem to maximize the quality of rendered virtual views on the receivers' displays. We show that this problem is NP-complete and present a polynomial time approximation algorithm to solve it. We then extend the proposed algorithm to efficiently schedule the transmission of the chosen substreams from each video in order to maximize the power saving on the mobile receivers. Our simulation-based experimental results show that our algorithm provides solutions that are within 0.3 dB of the optimal solutions while satisfying real-time requirements of multicast systems. In addition, our algorithm results in an average power consumption reduction of 86%.

In this paper we described advanced photonic devices used for optical networking. We also summarized our recent works on optical frame switches, broadband optical access networks, and dense wavelength division multiplexing (DWDM) backbone networks for wireless application and access networks. Photonic integrated circuits will play a key role in modern communications and help to realize the vision of high bandwidth pervasive connectivity.