ZigBee Research Highlight Yu-Chee Tseng topics : multicast, covergecast, orphan problem, long-thin network.

ZigBee Research HighlightZigBee Research Highlight

Yu-Chee TsengYu-Chee Tseng

topics : multicast, covergecast, orphan topics : multicast, covergecast, orphan problem, long-thin networkproblem, long-thin network

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Outline

Network FormationData CollectionQuery and Reply

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Network Formation

Network Formation: Orphan Node Problem

In ZigBee, when forming a network, devices are said to join the network if it can receive a network address network address = 16 bitsA device has to associate with a coordinator or

a routerA coordinator/router will decide whether to

accept a request according to its capacityThe capacity is determined by 3 parameters and its

current status.

What Happens in Real Network Formation?

An ZigBee Address Assignment Example

Cm = 5Rm = 3Lm = 2

ZigBee coordinator ZigBee router

ZigBee router-capable deviceZigBee end device

Tree link Communication link

Addr = 0Cskip = 6

CE

BD

A

Addr = 1Cskip = 1

Addr = 2

Addr = 3Addr = 5

Addr = 8

Addr = 7Cskip = 1

Addr = 9Addr = 10

Addr = 19

Addr = 15 Addr = 13Cskip = 1

Addr = 14

Addr = 17

Addr = 18

Addr = 11

Addr = 12

0 1 7 13

Cskip=6 Total:21

19For coord.

7node B

20

A becomes an orphan node !!

Simulation Results on Large-Scale Networks

Results: Orphan Problem

The first work to model the orphan problem, which has two subproblems at the router side: Bounded-Degree-and-Depth Tree

Formation (BDDTF) problem at the end-device side: Maximum-Matching (EDMM)

problem Prove the BDDTF problem is NP-complete Propose an efficient network formation algorithm,

with better address pool utilization

Ref: MSWiM 2007 and to appear in IEEE TMC.

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ConvergeCast

Data Collection: Convergecast

Convergecast is a fundamental operation in WSN. sensors periodically report sensed data to a sink

Goal: low latency supporting low-power mode

sink

sensor

Convergecast + Beacon Scheduling

According to ZigBee standard, beacons are scheduled in the first active portion (slot).

Superframe structure of IEEE 802.15.4

A superframe can contain 2BO-SO active portions (slots), with duty cycle up to 2-12.

Beacon interval = u × 2BO

1

Active portion = u × 2SO

2 3 2BO-SO

u=aBaseSuperframeDuration

Network Scenario

In a tree network, routers can send regular beacons to support low duty cycle operations

Active Active

data from end devices

data from end devices

AB C

A

B

C

Sink

ZigBee router ZigBee end device

A’s beacon sche:

A wakes up to hear C’s beacon and report data

To C To C

Zzz .. Zzz ….

Zzz ..

Active Active

C’s beacon sche:

ZigBee coordinator

Results: Convergecast

Define a minimum delay beacon scheduling (MDBS) problem for ZigBee tree-based WSNs

Prove MDBS problem is NP-complete Propose ZigBee-compliant centralized and

distributed algorithms

Ref: ComCom

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Query and Reply

Query and Reply: Spatial and Temporal Correlation

spatial and temporal correlation of sensing data spatial correlation

temporal correlation

Data Compression: Multi-Resolution Coding

multi-resolution query and response shallower query: when

only a summary is needed

deeper query: when more details are needed

Ref: IEEE Trans. on Computer

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生命探測儀(Electromagnetic Life Detector)

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生命探測儀日製生命探測器是長約三公尺之六節伸縮鋁棍，可以伸進建築物內搜尋生命體。鋁 棍前端內附針孔攝影機，微型燈泡和高感度麥克風與微型喇叭。使用時是透過伸縮桿將 攝影機等伸入瓦礫堆中，此時攝影機可以在微型燈泡射下，清楚地將瓦礫堆中景像傳送 到另一端的監視螢幕，由救難人員也可以判斷有無生還者；而高感度麥克風也可以接收 瓦礫堆中的輕微聲音，包括生還者的呼吸聲，呼叫聲，敲擊聲，救難者也可以經由喇叭 將外界訊息傳給生還待援者，讓其安心配合待救。 生命探測器也有死角，受困東星大樓倒塌殘垣中長達 130 小時，奇蹟式獲救兄弟二人， 生命探測器卻未能偵測到其生命跡象。

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聲納式

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影像式生命定位系統，是一種先進的技術搜尋和救援設備，迅速找准受害者的位置以及受害者所處地理結構以便作出救援。 該系統結合了高分辨率的彩色攝像機，高靈敏麥克風，揚聲器，光源，遠程控制，伸縮探頭。屏幕上的圖形系統狀態保証了使用者可以監視系統或者進行搜索任務。

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生命侦测仪的组成

生命侦测仪移动探测系统由以下主要部件组成的传感器一个发送超宽频信号的发送器 一个侦测接收返回信号的接收器 一台用于读入接收器的信号并进行处理的电脑

传感器包含了可编程的固件。传感器产生的信号通过无线传输传送给掌上电脑（ PDA控制器）进行显示。

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生命侦测仪的工作原理生命侦测仪实际上是一个呼吸和运动探测器。雷达

信号发送器连续发射电磁信号，对一定空间进行扫描。，接收器不断接收反射信号并对返回信号进行算法处理。如果被探测者保持静止，返回信号是相同的。如果目标在动，则信号有差异。

生命侦测仪是通过测试被探测者的呼吸运动或者移动来工作的。由于呼吸的频率较低，一般每秒 1 到2 次，就可以把呼吸运动和其他较高频率的运动区分开来。测移动的原理也大致是这样。