Wireless Personal Area Networks & Wide Area Networks Patrick J. Stockreisser p.j.stockreisser@cs.cardiff.ac.uk
Lecture Outline In the lecture we will: Look at PAN s in more detail Look at example networks Look at specific technologies Bluetooth Infrared A quick look at advancements in home networks Look at wireless WAN s in more detail Overview of GSM and GPRS
Personal Area Network (PAN) A personal area network (PAN) is a computer network used for communication among computer devices (including telephones and personal digital assistants) close to one person. The devices may or may not belong to the person in question. The reach of a PAN is typically a few meters. PANs can be used for communication among the personal devices themselves (intrapersonal communication), or for connecting to a higher level network and the Internet (an uplink). Personal area networks may be wired with computer buses such as USB and FireWire. A wireless personal area network (WPAN) can also be made possible with network technologies such as IrDA and Bluetooth. WPANs address wireless networking of portable and mobile computing devices such as: PCs, Personal Digital Assistants (PDAs), peripherals, cell phones, pagers, and consumer electronics; allowing these devices to communicate and interoperate with one another.
Example Equipment for PANs
Local Area Network Standards
Bluetooth Bluetooth is an industrial specification for wireless personal area networks (PANs). Bluetooth provides a way to connect and exchange information between personal devices via a secure, globally unlicensed short-range radio frequency. In 1998 Ericsson, IBM, Toshiba, Nokia and Intel form Bluetooth Special Interest Group (SIG). Provides universal short-range wireless capability Uses 2.4-GHz band with a data rate of 1 Mbps Available globally for unlicensed users Devices within 10m can share up to 720 kbps of capacity Supports an open-ended list of applications
Bluetooth Applications Data and voice access points Real-time voice and data transmissions Cable replacement Eliminates need for numerous cable attachments for connection between devices of close proximity Ad hoc networking Device with Bluetooth radio can establish connection with another when in range
Classes of Transmitter Class Maximum Permitted Power (mw) Maximum Permitted Power (dbm) Range (approximate) Class 1 Still Available 100 mw 20 dbm ~100 meters Class 2 Most Common 2.5 mw 4 dbm ~10 meters Class 3 Rare 1 mw 0 dbm ~1 meter
Bluetooth Standards Documents Core specifications Details of various layers of Bluetooth protocol architecture Profile specifications Use of Bluetooth technology to support various applications
Bluetooth Protocol Stack
Usage Models
Piconet A piconet is an ad-hoc computer network of devices using Bluetooth technology protocols to allow one master device to interconnect with up to seven active slave devices Basic unit for Bluetooth networking One master and one to seven slave devices Master determines channel and phase
Scatternets A scatternet is set of piconets connected through sharing devices. A device in one piconet may exist as master or slave in another piconet. Allows many devices to share same area Makes efficient use of bandwidth
Examples
Physical Links between Masters and Slaves Synchronous Connection Oriented (SCO) Allocates fixed bandwidth between point-to-point connection of master and slave Master maintains link using reserved slots Master can support three simultaneous links Asynchronous ConnectionLess (ACL) Point-to-multipoint link between master and all slaves Only single ACL link can exist
IrDA The Infrared Data Association (IrDA) defines physical specifications communications protocol standards for the short range exchange of data over infrared light, for uses such as in PANs. IrDA is a very short-range example of free-space optical communication. IrDA interfaces are used in palmtop computers and mobile phones.
IrOBEX Protocol IrDA developed OBEX (Infrared Object Exchange to exchange data objects over an infrared link Enables the exchange of arbitrary data objects (e.g. vcard, vcalendar or even applications) between infrared devices. It lies on top of the Tiny TP protocol, so Tiny TP is mandatory for IrOBEX to work. OBEX provides a session layer service for applications such as synchronization and file transfer (see slide Usage Models ) OBEX can use either the TCP/IP stack or go directly to RFCOMM interface (see slide Bluetooth Protocol Stack )
IrDA versus Bluetooth IrDA-Data Bluetooth Physical Media Infrared RF (2.4 GHz) Communications Range Up to at least 1m 10cm to 100m Connection Type, Direction Point-to-Point, Narrow Angle (30 degrees) Multipoint, Omni-directional Maximum Data Rate 4Mbps (16Mbps on the way) 1Mbps (aggregate) Security Physical limitations offer some builtin protection Authentication, encryption, spread spectrum
Home Networks Allow appliances to communicate with one another: with a central controller with an external entity Standards groups: CEBus Industry Council (CEBus) HomePlug Powerline Alliance homerf Working Group (homerf) Home Phoneline Networking Alliance (homepna) Open Services Gateway Initiative (OSGi)
ZigBee The ZigBee Alliance is an association of companies working together to enable reliable, cost-effective, low-power, wirelessly networked, monitoring and control products based on an open global standard. ZigBee is a specification set of high level communication protocols designed to use small, low power digital radios based on the IEEE 802.15.4 standard for wireless personal area networks (WPANs) This technology is designed to be simpler and cheaper than other WPANs (such as Bluetooth)
Home Networks CONTROL Enjoy flexible management of lighting, heating and cooling systems from anywhere in your home Automate control of multiple home systems to improve conservation, convenience and safety CONSERVATION Capture highly detailed electric, water and gas utility usage data Embed intelligence to optimize consumption of natural resource CONVENIENCE Install, upgrade and network home control system without wires Configure and run multiple systems from a single remote control SAFETY Easily install wireless sensors to monitor a wide variety of conditions Receive automatic notification upon detection of unusual events
Example HomePlug Network
Wireless Wide Area Networks Patrick J. Stockreisser p.j.stockreisser@cs.cardiff.ac.uk
Wireless WAN s Wireless WAN cover a much more extensive area than wireless LANs. For example, it can bridge branch offices of a company, facilitate connectivity for mobile users such as the travelling businessman. In general they allow users to maintain access to work-related applications and information while away from their office. In wireless WANs, communication occurs predominantly through the use of radio signals over analog, digital cellular, or PCS networks, Today, most wireless data communication takes place across 2G cellular systems such as TDMA, CDMA, PDC, and GSM, or through packet-data technology over old analog systems such as CDPD overlay on AMPS. Although traditional analog networks, having been designed for voice rather than data transfer, have some inherent problems, some 2G (second generation) and new 3G (third generation) digital cellular networks are fully integrated for data/voice transmission. With the advent of 3G networks, transfer speeds should also increase greatly.
WWAN A WWAN differs from a WLAN because it uses cellular network technologies such as GPRS, CDM, GSM or CDPD to transfer data. It can use also LMDS and Wi-Fi to connect to the Internet. These cellular technologies are offered regionally, nationwide, or even globally and are provided by a wireless service provider. Various computers now have integrated WWAN capabilities. This means that the system has a cellular radio (GSM/CDMA) built in, which allows the user to send and receive data. There are two basic means that a mobile network may use to transfer data 1. Packet-switched Data Networks (GPRS/CDPD) 2. Circuit-switched dial-up connections.
Example Portable devices receive communications as the connected wireless modems and wireless networks interact via radio waves. The modem directly interfaces with radio towers, which carry the signal to a mobile switching center, where the signal is passed on to the appropriate public or private network link (i.e., telephone, other high speed line, or even the Internet)
Example GPRS/GSM Network
General Packet Radio Service GPRS is a mobile data service available to users of GSM mobile phones GSM - The Global System for Mobile Communications GPRS data transfer is typically charged per megabyte of transferred data, while data communication via traditional circuit switching is billed per minute of connection time, independently of if the user actually has transferred data or been in an idle state. GPRS can be utilised for services such as WAP access, SMS and MMS, but also for Internet communication services such as email and web access. In the future, it is expected that low cost voice over IP will be made available in mobile phones. CDPD (Cellular Digital Packet Data) is an older, slower alternative to GPRS that has lost the battle.
Lecture Summary In this lecture we have: Looked at PAN s in more detail Looked at example networks Looked at specific technologies Bluetooth Infrared Drawn a comparison between the two technologies Briefly looked at advancements in home networks ZigBee example Looked at wireless WAN s in more detail Looked at a brief overview of GSM and GPRS