Indoor Communications

Rex ChenRex Chenrex@ics.uci.edu

Ubiquitous Computing - Winter 2007Ubiquitous Computing - Winter 2007

Outline

Overview Technologies Challenges Paper Discussion Research Progress Conclusion

Overview of Indoor Communication Lots of electronic gadgets Need for connectivity Usually in proximity

e.g. 1 to 30 meters Characteristics

Residential Homes Corporate Offices Public Facilities

Wired vs. Wireless Indoor Communications?

Indoor Wireless Communication Technologies IEEE 802.11a/b/g Bluetooth IrDA ZigBee Powerline

Electronic Gadgets

A Closer look at 802.11 WLAN

Actual vs. theoretical bandwidth a major gap CSMA/CA overhead (contention-based access)

Spectrum Regulations 2.4 to 2.5 GHz unlicensed spectrum for open usage Interferences with microwave and cordless telephony

Protocol Frequency Data Rate (typical) Date Rate (Max) Range (Indoor)802.11a 5.15-5.35, 5.72-5.85 GHz 25 Mbits/sec 54 Mbits/sec ~30 meters802.11b 2.4-2.5 GHz 6.5 Mbis/sec 11 Mbits/sec ~30 meters802.11g 2.4-2.5 GHz 25 Mbits/sec 54 Mbits/sec ~30 meters

802.11 Logistics Standardization

IEEE 802.11 Specification Many revisions

Involve multiple parties Companies, governments

Wi-Fi Alliance 260+ member companies

802.11 Technicalities

Signal Strength Depend on signal-to-noise ratio Receive power ~ to 1/d2 (distance square)

Handoff Decision RSSI indicator

Bluetooth

Characteristics Short-range, 2.4 GHz RF Peak rates up to 1 Mbit/sec Line-of-sight not required Low power, cost, size

Applications Personal Computers

Keyboard, mouse, printer Communication Devices

Cell phone and wireless headset

Bluetooth Topology Piconet Formation

Comprise of master, slave (active), parked (ready), and stand-by nodes

Synchronization of hopping pattern required

Bluetooth Transmission Scatternet – joining of multiple piconets

Frequency Selection

IrDA

Characteristics Short-range communications with infrared light Requires line-of-sight Low power, cost, size Getting replaced by Bluetooth

ZigBee

Characteristics Low data rate, very low power consumption Cheaper than Bluetooth ($1 transceiver) Device Types:

ZigBee coordinator(ZC) ZigBee Router (ZR) ZigBee End Device (ZED)

Organized nodes in ad-hoc networks

ZigBee in Home Automation

Power line communications Characteristics

Use electrical power wiring as transmission medium Power plugs are ubiquitous Several competing standards Not widely adopted Interference with outside signals

Applications Home lighting and appliances

The Challenge for Indoor Wireless Communications

Lack of standard or regulation No protection against signal interferences Interoperability issue in power line communications

Network planning problems in 802.11 WLAN Dynamic building configurations Physical object obstruction (e.g. walls, windows) Dead spots

The Challenge for Indoor Wireless Communications (2) Security Problems

Encryption turn off in many access points WEP failure, can be cracked within a few days

Detecting unintended signals Unauthorized network access

e.g. Using neighbor wireless access point while surfing for child porn

Intensive data traffic download of “pirated” data using P2P applications (e.g. music, software)

Usability Setting up the wireless links can be difficult

Seidel – On Path Loss Prediction Models for Indoor Communication Goal

Understand implications of indoor wireless communication with respect to physical surroundings

Measurement Sample Grocery store, retail store, two office buildings

Model Mean path loss increases exponentially with

distance Path Loss (d) ~ (d/d0)n (solve for n)

Seidel – Mean path loss exponent and standard deviation

Seidel - Analysis

Indoor Communication Tools – specifically for IEEE 802.11 Access Point Detection

NetStumbler, Kismet

Wireless Packet Data Capture OmniPeek (aka, Ethereal)

Network Topology Management Ekahau

Indoor Comm Tools - NetStumbler Demo

Indoor Comm Tools – Ekahau

Indoor Comm Tools – Ekahau (2)

Indoor Comm Tools – Ekahau (3)

Relevant Projects withIndoor Communications

Ambient Networks Integration of device communications

e.g. PDA-> (IrDA) -> Laptop-> (Bluetooth) -> Mobile -> (GPS) -> Mobile phone network

PlaceLab Indoor location positioning

802.11 access point using beacon frames

The Future of Indoor Communications Everything Wi-Fi enabled?

The Future of Indoor Communications (2) Extending coverage reach

Wi-Fi interface with WiMAX Mesh routing

Higher throughput 802.11n, 10x more bandwidth than 802.11a/g Market Demand?

Multi-networked gaming Wireless IPTV streaming

Concluding Remarks

Many interested parties on indoor communications Telephony and Cellular carriers

Dual-mode Wi-Fi and 3G handset Wireless Internet Service Providers (WISP)

Inter-network from outdoor to indoor communication Cable Operators

Set-top boxes streaming video contents to multiple indoor clients

The FONERA Movement http://www.fon.com

Open Discussion