Sewook Jung

BlueTorrent: Cooperative Content Sharing for Bluetooth Users

People wish to enjoy their everyday lives in various ways, among which entertainment plays a major role. In order to improve lifestyle with more ready access to entertainment content, we propose BlueTorrent, a P2P file sharing application based on ubiquitous Blue tooth-enabled devices such as PDAs, cellphones and smart phones. Using BlueTorrent, people can share audio/video contents as they move about shopping malls, airports, subway stations etc. BlueTorrent poses new challenges caused by limited bandwidth, short communications range, mobile users and variable population density. A key ingredient is efficient peer discovery. This paper approaches the problem by analyzing the Bluetooth periodic inquiry mode and by finding the optimum inquiry/connection time settings. At the application layer, the BlueTorrent index/block dissemination protocol is then designed and analyzed. The entire system is integrated and implemented both in simulation and in an experimental testbed. Simulation and measurement results are used to evaluate and validate the performance of BlueTorrent in content sharing scenarios

P2P Content Distribution to Mobile Bluetooth Users

The use of handheld devices, such as smart phones for personal entertainment, has become commonplace in todays lifestyle. Virtually all of these devices are equipped with Bluetooth technology, which can be used to distribute entertainment content, such as music and movie clips. Mobile users can download content from opportunistically available infrastructure (e.g., digital billboards) and direct peer-to-peer (P2P) collaboration, which significantly increases content availability/coverage. P2P content distribution protocol design is heavily influenced by the characteristics of Bluetooth, which is a main departure from Internet-based content distribution. However, little has been done to understand the performance of overall Bluetooth operations, ranging from peer discovery to data downloading, in dynamic environments with mobility, interference, and different Bluetooth versions/chipsets. In this paper, we perform an extensive measurement study and find that Bluetooth-based content distribution suffers from time/energy-consuming resource discovery and limited bandwidth, even with the enhanced features of the latest Bluetooth version. Given this, we discuss strategies that can effectively improve the performance of the resource-discovery and downloading phases.

Comparisons of ZigBee Personal Area Network (PAN) Interconnection Methods

ZigBees low power consumption, built-in security method and ratified specifications make it very suitable to be used with medical sensor devices. Medical sensors in a human body self organize in a ZigBee Personal Area Network (PAN). At a higher level, these PANs are interconnected in a Healthnet. To this end, a ZigBee PAN detects the existence of another PAN with beacon detection or active channel scan and selects proper target based on the peak energy (when energy detection channel scan is used). Different ZigBee interconnection schemes are then possible. PAN bridge method uses special bridge node that works for different PANs with time division method. PAN merge method changes PAN coordinators role as bridge node and merges two PANs. Peer-to-peer network can be used when all PANs use the same channel and operates as an ad-hoc network. In this paper, we perform extensive evaluations using NS-2 simulations to compare PAN interconnection methods. Results show that the PAN bridge is the most useful method because it is not affected by router/node ratio and is applicable to different channel and user scenarios.

Hop count based optimization of Bluetooth scatternets

In the past five years Bluetooth scatternets were one of the most promising wireless networking technologies for ad hoc networking. In such networks, mobility together with the fact that wireless network nodes may change their communication peers in time, generate permanently changing traffic flows. Thus, forming an optimal scatternet for a given traffic pattern may be not enough, rather a scatternet that best supports traffic flows as they vary in time is required. In this paper we study the optimization of scatternets through the reduction of communication path lengths. After demonstrating analytically that there is a strong relationship between the communication path length on one hand and throughput and power consumption on the other hand, we propose a novel heuristic algorithm suite capable of dynamically adapting the network topology to the existing traffic connections between the scatternet nodes. The periodic adaptation of the scatternet topology to the traffic connections enables the routing algorithms to identify shorter paths between communicating network nodes, thus allowing for more efficient communications. We evaluate our approach through simulations, in the presence of dynamic traffic flows and mobility.

Throughput, energy and path length tradeoffs in Bluetooth scatternets

In this work, we determine an analytical relationship between the average path length of traffic connections of a Bluetooth scatternet and the overall throughput and power consumption of the network. Results obtained implementing this analytical relationship to different scatternet topologies are presented and discussed. By reducing the hop count in a scatternet we can achieve better performance in terms of throughput and power consumption. Therefore, the issue of minimizing the hop count in the presence of mobility, changing traffic flows and varying interference receives an important role. In our analysis we also show the impact of the link quality on the overall throughput. The obtained results motivate the importance of heuristics aimed at reducing the communication path length in a scatternet.

New bluetooth interconnection methods: Overlaid Bluetooth Piconets (OBP) and Temporary Scatternets (TS)

In a large scale Bluetooth network, the permanent Scatternet is regarded as the only method to interconnect Piconets. But, many Bluetooth devices do not support Scatternet. When they support it, features are limited. Moreover, in high mobility situations, the permanent Scatternet is not useful because of the extremely high overhead caused by frequent disconnections and reconnections. We propose Overlaid Bluetooth Piconets (OBP) and Temporary Scatternets (TS) to interconnect Piconets and form a virtual Scatternet. In OBP, every Piconet continuously changes its stages and collects metadata from Piconets within communication range. If metadata shows the existence of useful data to transfer, an inter-piconet connection is made and data is transferred. TS can be used instead of using permanent Scatternet to interconnect Piconets when needed. TS does not require large Scatternet formations and complex maintenance schemes. Moreover, it does not keep routing information. In this paper, we introduce and illustrate the OBP and TS concepts. We then compare throughput and efficiency of OBP and TS with respect to Scatternet.

Decentralized optimization of dynamic Bluetooth scatternets

Previous work analytically showed that communication path length reduction is an efficient way for improving the performance of Bluetooth scatternets. Maintaining short communication paths is mainly important in dynamic scatternets with changing traffic flows, mobile nodes and in the presence of interference, when the network topology changes continuously. In this work we aim at demonstrating through simulations that in such dynamic scatternets by periodically reducing the path length (i.e. hop count) between the communicating nodes, the overall throughput supported by the network can be significantly increased and the available energy of nodes can be consumed more efficiently. For this purpose, we present a distributed technique for repeatedly re-configuring the scatternet topology such that to support the current traffic flows between all of the communicating peers with a small number of hops.

Peer to peer video streaming in Bluetooth overlays

As Bluetooth is available in most personal and portable terminals (eg, cellular phone, PDA, videocamera, laptop, etc) Peer-to-peer video streaming through Bluetooth networks is now a reality. Camera equipped Bluetooth phones capture video and broadcast it to other Bluetooth devices and to the infrastructure. Tra ditionally, large scale Bluetooth networks were designed using scatternet concepts. However, many Bluetooth devices do not support Scatternet connections and, even if they support it, they provide only very limited features suitable mostly for static environments. In high mobility situations, a traditional Scatternet design is not useful because of frequent disconnections and reconnections. To overcome these problems, we propose overlaid Bluetooth Piconets (OBP) and simplified overlaid Bluetooth Piconets (SOBP) that interconnect Piconets forming virtual Scatternets. In OBP, every Piconet dynamically reconfigures to collect metadata from neighboring Piconets. If metadata shows the existence of useful data to transfer, an inter-Piconet connection is made to carry out the transfer. SOBP can be used instead of OBP once neighbor Piconets have already discovered each other. In this paper, we compare via analysis and simulation the throughput and efficiency of OBP, SOBP and Scatternet for video applications. We demonstrate the feasibility of video over OBP and SOBP for a representative application.

Comparison of Bluetooth Interconnection Methods using BlueProbe

Many Bluetooth researches are targeted to form efficient scatternets. However, scatternets do not have much popularity in general because many Bluetooth devices do not support scatternet capabilities and high mobility makes it difficult to keep the connectivity. Instead we choose temporary interconnection of piconets to reduce scatternet formation overhead. To compare several interconnection methods, we propose BlueProbe. BlueProbe finds out the allocated time slots size, which makes it apt for Bluetooth style TDMA capacity measurement. BlueProbe is applicable to both piconet and scatternet whether a cross traffic exists or not. Results based on our real testbed measurements show that the interconnection method is more important than the hop length and the number of simultaneous flows, whereas previous researches based on simulations concentrate on these two factors. Based on these results, we show efficient interconnection methods among Bluetooth Piconets.

Performance comparison of overlaid bluetooth piconets (OBP) and bluetooth scatternet

In a large scale Bluetooth network, scatternet is regarded as the only interconnection method among piconets. But, most Bluetooth devices do not support scatternet connection. Moreover, in high mobility situations, scatternet is not useful because of frequent disconnections and reconnections. We propose overlaid Bluetooth piconets (OBP) to interconnect piconets and form a virtual scatternet. Every piconet continuously changes its stages and collects metadata of piconets in the communication range. If metadata shows existence of data to transfer, an inter-piconet connection is made and data is transferred. We compared throughput and efficiency of OBP with those of scatternet. Results show the feasibility of OBP usage instead of scatternet