Indoor Communications Rex Chen Rex Chen [email protected] Ubiquitous Computing - Winter Ubiquitous Computing - Winter 2007 2007
Dec 21, 2015
Indoor Communications
Rex ChenRex [email protected]
Ubiquitous Computing - Winter 2007Ubiquitous Computing - Winter 2007
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
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
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
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)
Indoor Communication Tools – specifically for IEEE 802.11 Access Point Detection
NetStumbler, Kismet
Wireless Packet Data Capture OmniPeek (aka, Ethereal)
Network Topology Management Ekahau
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 (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