Wonyong Yoon

An application-aware MAC scheme for IEEE 802.15.3 high-rate WPAN

The emerging high-rate wireless personal area network (WPAN) technology, currently being developed by IEEE 801.15.3 task group, provides a very high-speed short-range transmission capability with quality of service provisions. MPEG-4 bit stream is anticipated to occupy a large portion of the traffic in the WPAN, and its decoding depends on successful transmissions of frame data, which require a low JFR (job failure rate) and a Iow delay variance as well as a high throughput. In this paper, we propose a simple application-aware MAC scheme for the WPAN in order to achieve a high-quality video transmission of MPEG-4 stream: a device tells the piconet controller the maximum sizes of its frames along with the channel time requests, and then the controller allocates a channel time for the device according to the predefined MPEG frame sequence. Simulation results show that our scheme achieves significantly lower JFRs, lower delay variances, and higher throughputs than the standard scheduling scheme.

Enhanced Non-Seamless Offload for LTE and WLAN Networks

Non-seamless WLAN offload is a currently available approach to the data explosion issue in cellular networks without requiring new hardware and functional deployment on network sides. In this article, we propose two enhanced offloading methods that guarantee session continuity for non-seamless WLAN offload. We describe how the proposed methods manipulate multi-radio (LTE and WiFi) interfaces to maintain IP sessions in the dynamics of available radios. We present a performance analysis that studies the throughput and energy consumption of smart devices.

SDN-based resource allocation for heterogeneous LTE and WLAN multi-radio networks

To meet increasing bandwidth demand, cellular network operators have increasingly deployed wireless local area networks (WLANs) on top of their cellular networks [e.g., long term evolution (LTE)]. State-of-the-art smartphones can utilize such heterogeneous LTE and WLAN radio bandwidth by operating the multi-radio interfaces simultaneously. This paper investigates how such heterogeneous radio bandwidth should be controlled and allocated to multi-radio user devices. A software-defined networking (SDN)-based resource allocation framework is proposed that can properly orchestrate heterogeneous radio bandwidth in emerging LTE/WLAN multi-radio networks in a centralized and holistic manner. The proposed framework is implemented and evaluated in a computing environment that combines a real SDN controller with simulated network forwarding entities.

A combined group/tree approach for scalable many-to-many reliable multicast

We present the design, implementation, and performance analysis of group-aided multicast (GAM), a scalable many-to-many reliable multicast transport protocol. GAM achieves high quality ACK trees while keeping the tree maintenance overhead reasonably low in the presence of dynamic group membership and route changes. It is supported by a group configuration mechanism organizing the members in a multicast session into multiple small groups and a tree configuration mechanism maintaining logical trees according to the underlying multicast routing trees. With the two mechanisms, GAM builds a two-layer hierarchy of multi-level logical trees from which high-quality per-source ACK trees are generated. Simulation results show that the GAM protocol is more scalable than a NACK suppression protocol in terms of processing time for request/repair messages and recovery latency.

Routing Exploiting Multiple Heterogeneous Wireless Interfaces: A TCP Performance Study

This paper proposes a routing scheme that exploits multiple heterogeneous wireless interfaces: a primary 802.11a interface and a secondary 802.11b (or 802.11) interface. In normal conditions, a TCP flow uses a primary path over the 802.11a interface discovered by a reactive routing protocol. But in presence of route breakage due to node mobility, it resorts to its backup path over the 802.11b interface which is already maintained by a proactive routing protocol and is being used for delivery of other packets. The secondary interface exhibits different property than the primary interface (i.e., slower rate but larger transmission range), which helps keep TCP flows alive and preserve the TCP window size, thereby making them more robust to route breakage induced by mobility. ns-2 implementation and experiments reveal several potential benefits of the proposed routing scheme.

Price-based congestion control and local channel-link assignment for multi-radio wireless mesh networks

Display Omitted We extend a price-based approach to multi-radio wireless networks.We devise a closely coupled congestion control and local channel selection framework.We demonstrate the convergence of proportional fair rate allocation by the framework.We demonstrate the convergence of max-min fair rate allocation. In multi-radio multi-channel wireless mesh networks, engineering the network capacity requires a complex cross-layer design. In this paper, in order to make the complex problem implementable in a distributed manner, we make a decoupling approach that breaks down the entire design space into routing and initial channel assignment, and distributed congestion control and local channel reassignment. We propose a unified priced-based framework for distributed congestion control and localized channel-link assignment algorithms. We demonstrate the convergence of the proposed algorithms with respect to different fairness objectives (i.e., proportional fairness and max-min fairness) via simulation on both grid and random topologies. The proposed algorithms achieve faster convergence with less overhead in the control and forwarding plane than previous multi-path based algorithms.

Tree-based reliable multicast in combined fixed/mobile IP networks

This paper proposes a solution to delivering multicast data reliably not only to/from fired hosts but also to/from mobile hosts in combined fixed/mobile IP networks, particularly with regard to the per-source shortest path multicast routing protocol and remote subscription option in the IETF mobile IP multicast standard. We propose exploiting tree-based error recovery, well-established concept for reliable multicast in fixed networks, where a hierarchical logical tree of a source and receivers is constructed over which the responsibility of error recovery is distributed. We introduce a new entity named ARMM (Agent for Reliable Mobile Multicast) located at each cell of the wireless/mobile networks. Each ARMM participates in a logical tree as a parent of mobile hosts in the corresponding cell. It is responsible for retransmission and requesting for retransmission on behalf of the mobile hosts. With aid of ARMM, the proposed scheme features (1) adaptive reconstruction of logical trees due to host mobility, (2) retransmission to mobile hosts via optimal routes, (3) abstracting a group of mobile hosts into a single ARMM (and thus reducing logical tree maintenance overhead), (4) efficient use of wireless bandwidth for retransmission, and (5) low processing burden on mobile hosts themselves. The experimental results show that the proposed scheme provides higher scalability than a scheme applying a generalized tree-based reliable multicast in mobile environments.

Fair rate control for cognitive multi-channel wireless ad hoc networks

Multi-channel wireless ad hoc networks enhance network capacity with the use of available channels in parallel but should strike a balance between maintaining network connectivity and maximizing utilization of different channels. Also, a promising wireless multi-channel ad hoc network should be cognitive to interference from various wireless devices operating on industrial, scientific, and medical bands effectively by scavenging less loaded channels dynamically using periodic spectrum sensing and distributed channel selection algorithm. In this paper, we study cross-layer fair rate control problems for hybrid channel assignment-based multi-channel ad hoc networks in the cognitive context. We first identify two inherent constraints which are specific to multi-channel multi-radio wireless ad hoc networks and primary user interference. We then formulate a fair rate control problem by exploiting the network utility maximization framework and propose a price-based distributed solution. We investigate in detail the convergence property of the distributed solution via simulation on a grid topology. We also show its convergence in adaptation to the change in primary user interference in the cognitive context. We present a performance comparison study with a generic class of existing works in the literature.

Adaptive tree-based recovery for scalable reliable multicast

As the scale of a network becomes larger in terms of both the number of users and geographic span, reliable multicast protocols suffer more severely from acknowledgement implosion and exposure to retransmissions. In this paper, we propose a scalable, efficient recovery scheme for a tree-based reliable multicast transport protocol. The scheme first constructs a logical tree of receivers as close to a multicast routing tree as possible by using error bitmap information. This ensures that the receivers residing at a higher level in a multicast routing tree than ones requesting retransmissions be appointed as parents in a corresponding logical tree. In our scheme, the logical tree is adaptively reconfigured as the session membership or the multicast route changes. Our scheme also forms local groups with separate multicast addresses in the tree for efficient recovery. We compare our scheme with a static tree-based reliable multicast protocol. Results of the simulation show that our adaptive tree-based recovery scheme outperforms the compared protocol in terms of the implosion and exposure as the session size increases.

Application-awareness support for QoS-aware routing protocols in wireless ad-hoc networks

In order to support QoS in wireless ad-hoc networks, each node needs to monitor the network status and to determine whether the current network status satisfies the requirements of an application or not. Since the network requirements on an intermediate node are usually different from those on the end nodes, there is a need to convert the application requirement into a hop-by-hop network requirement. This paper induces link validation formulas for each node to determine if a link can satisfy the requirement of a specific application. The simulation results show the effectiveness of application-awareness on discovering appropriate routes for a specific application type in wireless ad-hoc networks.