Insun Jang

QoE-enhanced adaptation algorithm over DASH for multimedia streaming

In dynamic adaptive streaming over HTTP (DASH), a client consecutively estimates the available network bandwidth and decides the transmission rate for the forthcoming video chunks to be downloaded. Even though several enhancements to DASH have been reported in the literature, they do not well-investigate the current buffer status to cope with fluctuating network conditions and thus do not achieve seamless video streaming. In this paper, we propose a novel rate adaptation algorithm called quality of experience (QoE)-enhanced adaptation algorithm over DASH (QAAD), which preserves the minimum buffer length to avoid interruption and minimizes the video quality changes during the playback. We implemented a DASH testbed and conducted extensive experiments. Experimental results demonstrate that under fluctuating network conditions, QAAD provides seamless streaming with stabilized video quality while the previous buffer-aware algorithm (i.e., QoE-aware DASH) frequently changes the video quality and undergoes the interruption.

Minimizing content download time in mobile collaborative community

Mobile collaborative community (MCC) is an emerging technology where multiple mobile nodes (MNs) conduct a job (e.g., large content download) in a cooperative manner. In this paper, we consider a scenario in which multiple MNs form MCC for content download through wireless wide area network (WWAN) and share of the downloaded content through wireless local area network (WLAN). In the collaborative content download for MCC, the content chunk size assigned to an MN and the sharing order of the received chunk should be carefully determined to reduce the content download time. Therefore, we formulate an optimization problem that jointly considers the chunk size and the sharing order to minimize the content download time. Specifically, the optimization problem is formulated as a mixed integer non-linear programming (MINLP) problem that is known as NP-hard. The original optimization problem is relaxed into a linear programming (LP) problem and a heuristic algorithm minimizing the content download time and operating in a polynomial time is proposed based on the 2-opt algorithm. Simulation results demonstrate that the proposed algorithm can achieve near-optimal performance to the MINLP optimal solution and can reduce the content download time compared with other algorithms by choosing proper chunk size and sharing order.

FW-DAS: Fast Wireless Data Access Scheme in Mobile Networks

In wireless data access applications, reduction of both the access latency and the wireless traffic volume is essential. In this paper, we propose a fast wireless data access scheme (FW-DAS) for wireless data access applications in which data objects are frequently updated and fast access to data objects is indispensable. In FW-DAS, different operation modes are defined depending on the data object popularity, and only popular data objects are proactively pushed to the access point/base station to minimize the access latency while mitigating the traffic load over the wireless link. An analytical model for the access latency is developed and an operation mode selection algorithm is introduced to reduce the access latency. Extensive simulation results show the effects of access-to-update ratio, data popularity, cache size, data object size, and wireless bandwidth. Analytical and simulation results demonstrate that FW-DAS can reduce the access latency with reasonable traffic load compared with poll-each-read (PER)/callback (CB) and their combinations.

Optimal network resource utilization in service function chaining

Service function chaining (SFC) refers to as an order set composed of multiple service functions (SFs) that specific flows should be processed. In this paper, we formulate an optimization problem to efficiently utilize the network resource in SFC-enabled networks by determining the amount of flows assigned to each link and SF instance. Simulation results demonstrate that the proposed optimal solution can reduce the network resource usage and thus accommodate more flows compared with non-optimal solutions.

Design and analysis of cooperative wireless data access algorithms in multi-radio wireless networks

In the future, most mobile nodes will have multiple radio interfaces, and this feature can be exploited to reduce the transmission cost in wireless data access applications. In this work, we propose cooperative poll-each-read (CoopPER) and cooperative callback (CoopCB) wireless data access algorithms with strong consistency in multi-radio wireless networks. In addition, we investigate CoopPER and CoopCB in heterogeneous wireless networks where CoopPER and CoopCB nodes are mixed. Extensive simulations are done to show the effects of access-to-update ratio, data access pattern, cache size, and cooperation range. Simulation results demonstrate that CoopPER and CoopCB can significantly reduce the expensive transmission cost over wireless links.

Fast wireless data access scheme in wireless networks

For wireless data access applications where objects are frequently updated and fast access to objects is required, we propose a fast wireless data access scheme (FW - DAS), which extends the callback (CB) scheme to minimize the access latency and combines it with the poll each read (PER) scheme to mitigate the traffic load over the wireless link. Extensive simulations are carried out to show the effects of operation mode, access-to-update ratio, data popularity, and cache size. Simulation results show that FW-DAS can reduce the access latency with reasonable traffic load compared with PER/CB and their combinations.

The Software-Defined Vehicular Cloud: A New Level of Sharing the Road

A vehicular cloud (VC) is a type of mobile ad hoc cloud in which multiple vehicles share their resources and perform collaborative jobs. In this article, we propose a software-defined (SD) VC (SDVC) architecture to achieve flexible VC control and efficient resource utilization in a centralized manner.

Optimal middlebox function placement in virtualized evolved packet core systems

Current evolved packet core (EPC) systems in LTE/LTE-A networks suffer from the exponentially increased mobile traffic and thus research on new EPC architectures is ongoing. In this paper, we introduce a virtualized EPC (vEPC) system where middlebox functions of the existing EPC systems are implemented in virtualized software modules and the virtualized software modules operate over selected physical service nodes. To minimize the impact of the increased transmission cost in vEPC, the optimal placement of middlebox functions is also investigated. Numerical results demonstrate that the proposed scheme can achieve lower packet transmission cost than the conventional one.

Cooperative neighbor disco very for consumer devices in mmWave ad-hoc Networks

To reduce the neighbor discovery time in mmWave ad-hoc networks, we propose a cooperative neighbor discovery (CoopND) scheme exploiting the 2.4 GHz band with wider omni-range for management procedures and the 60 GHz band with directional beamforming-range for data transmissions. Simulation results demonstrate that CoopND can reduce the average neighbor discovery time significantly, especially when the directional antenna beam is narrow and the number of devices is large.

SDN-based distributed mobility management for 5G

Distributed mobility management (DMM) is an attractive approach to address the mobile traffic explosion problem, and thus it is perceived as a promising technology for mobility management in 5G. In this paper, we propose a software-defined networking (SDN) approach for DMM (denoted by SDN-DMM). Unlike the existing approaches for DMM (i.e., network-based or terminal-based), SDN-DMM implements the location and handover management functions at the centralized SDN controller while the packet forwarding function is fully distributed at access routers. Therefore, SDN-DMM can achieve the packet forwarding path optimization and provide significant benefits in terms of network and traffic management.