Bluetooth, IEEE 802.11 & Cell Phone Systems --Arun Radhakrishnan --Thierry Fernaine --Vipul Gautam
Overview • What is Bluetooth? -- Vipul • Specifications and Protocols • What is 802.11? -- Arun • Specifications and Protocols • 802.11 vs. Bluetooth • Cellular Phone Systems -- Thierry • CDMA • TDMA • FDMA • Generations of cell phones (1G to 4G) • Experiments/Demonstrations • Summary and Future Plans
Schedule • Brainstorming the tasks involved in the project • 15th February, 2003 • Information on Bluetooth and 802.11 • 25th February, 2003 • Analyzing Bluetooth vs 802.11 • 28th April, 2003 • Obtaining materials on phone systems (CDMA, TDMA, FDMA) • 23rd April, 2003 • Information about 3G and 4G • 17th April, 2003 • Talking to a professor about doing an experiment on wireless • 10th March, 2003 • Observing the experiment performed by a TA • 2nd April, 2003
Bluetooth • Protocol for the efficient transmission of data • Designed for devices such as cell phones, printers, PDA’s, notebook computers, fax machines
Bluetooth • Low power link • Short time data transfers • Small indoor distances • Line of Sight is not required • Better than IR link
Bluetooth • Operates in the 2.4GHz band • Unlicensed band • Uses frequency hopping • 2.4 to 2.4385 GHz • 79 hopping frequencies separated by 1 MHz • Data rate 1Mbps
Frequency Hopping • Characterized by its system of fast frequency hops • 10 different types of hopping sequences are defined • 5 of the 79 MHz range/79 hop system and 5 for the 23 MHz range/23 hop system. • The different range system's hopping sequences differ in frequency range 79MHz / 23MHz, and segment length : 32 hops(79MHz system) / 16 hops(23MHz system).
Frequency Hopping • Assurance of high quality communication in large urban centers and high-capacity networks • The millisecond rhythm with which the change of frequency takes place enables interference to be eliminated and prevent fading effects. • Deployed primarily in the military sector as well as in diplomatic communications via radio due to its unique bug-proof characteristics.
Data Layer • Piconets are a collection of devices connected via BT technology in an ad hoc fashion. • Each may have as many as 8 connected devices. • One unit acts as the master and the others as slaves. • Devices create many overlapping networks called Scatternets. • Formed by multiple independent and non-synchronized piconets.
Data Layer • Master device- • Initiates an action or requests a service. • Clock and hopping sequences are used to synchronize all other devices in the piconet.
What is 802.11 Wireless standards that specify an interface between a wireless client and a central point of access and among wireless clients. The IEEE 802.11 specifications tailored to resolve compatibility issues between manufacturers of wireless LAN equipment. The original IEEE 802.11 specifications defined data rates of 1 Mbps and 2 Mbps via radio waves The IEEE 802.11 specifications continue to expand and new standards are being considered and ratified. The most commonly used wireless standard is IEEE 802.11b.
802.11 a-g 802.11a: designed to operate in the 5 GHz band. Achieves data transmission rates of 54Mbps. Not readily accepted overseas. 802.11b: "High Rate" standard, also known as Wi-Fi (for "wireless fidelity) The family of IEEE 802.11b specifications allows for a wireless data transmission rate of 11 Mbps as an unlicensed use of the 2.4-GHz radio frequency band. 802.11g: The latest wireless networking specification from IEEE based on 802.11b. will broaden 802.11b's data rates to 54 Mbps within the 2.4 GHz band using OFDM (Orthogonal Frequency Division Multiplexing) technology. IEEE 802.11g is backward compatible with IEEE 802.11b.
802.11 protocols contd.. Task Group "C" improving the MAC layer to improve bridging Task Group "D" modifying the Physical layer to meet regulatory requirements around the globe. Task Group "E" enhance the MAC layer to improve quality of service (QoS) for time-sensitive applications like real-time voice and video. Task Group "F" improve interoperability of access points from different vendors in a distribution system. Task Group "H" channel selection and transmit power issues to ensure that 802.11a is usable in Europe, similar to what "D" is doing for 802.11b. Some European countries currently do not allow 802.11a, favoring the European HiperLAN2 5 GHz wireless LAN standard instead. Task Group "I" recently spun-off from Task Group "E" to put more emphasis on improving the security and authentication mechanisms.
Motivation for 802.11 Increased flexibility: A conference with an ad-hoc network can be set up and dismantled in a short time. Increased mobility: Users can move around without restrictions and access LANs from anywhere. More economical: In old buildings it is more economical to put up some wireless stations than to break up walls. In factories, putting wires may not be feasible.
What is spread spectrum radio technology? Increase reliability Boost throughput Allow many unrelated products (e.g., microwave ovens) to share the spectrum with minimal interference. 2 spread spectrum techniques: Frequency hopping spread spectrum (FHSS) Direct sequence spread spectrum (DSSS)
FHSS: send a short burst of data shift frequencies (hop) send another short burst. DSSS: communicate by splitting each byte of data into several parts sending them concurrently on different frequencies FHSS: relatively simple radio design but limited to speeds of no higher than 2 Mbps leads to high amount of hopping. DSSS: uses a lot of the available bandwidth, about 22 megahertz (MHz) capable of much greater speed than FHSS since the devices can send a lot more data at the same time. What is spread spectrumradio technology?
Security SSID: Each access point is associated with a SSID (service set identifier) To access the network a client computer should be configured with the correct SSID MAC: Each client computer has a unique MAC (Media Access Control) address. Each access point is programmed with a list of MAC addresses so it allows only those to associate with the AP. WEP: Wireless transmissions are easier to intercept than transmissions over wired networks. WEP (Wired equivalent privacy) employs the symmetric key encryption algorithm, Ron’s Code 4 Pseudo Random Number Generator (RC4 PRNG).
802.11 vs. Bluetooth Technology: Bluetooth uses FHSS (Frequency Hopping Spread Spectrum ) 802.11 used FHSS and DSSS. Currently 802.11b uses only DSSS for higher data transfer capability. 802.11a and 802.11g use a Orthogonal Frequency Division Multiplexing (OFDM) scheme in the 5 and 2.4-GHz frequency range, respectively Coverage: Bluetooth covers a personal area (PAN) – the space of a room (up to 30 feet). 802.11specifications provide coverage for local area networks (LANs) – an office building or parts of a campus using multiple access points (APs). Each AP has a range of up to 300 feet.
Cellular Phone Systems • TDMA • FDMA • CDMA • Cell Phones Generations • Specifications • Improvements • Future Plans
Frequency Division Multiple Access(FDMA) Frequency Each user is assigned one frequency to transmit. Example: AMPS W Hz User 4 User 3 User 2 User 1 Time T sec
Time Division Multiple Access(TDMA) Frequency W Hz Time User 1 User 2 User 3 User 4 T sec Several users transmit at the same frequency but in different time slots. Example: GSM and IS-136 Used by AT&T and T-Mobile
Code Division Multiple Access(CDMA) • Each user transmits all the time over all the frequency band, but has a different “spreading code”. • The base station differentiates users based on their codes. • Example: IS-95 (cdmaOne) • Used by Sprint and Verizon Code 1 Code 2 Code 3 Code 4
CDMA Pros & Cons Advantages: • Interference rejection • Provides security / privacy • Simple to add users to system • Greater coverage with fewer cell sites Disadvantages: • Near-Far Problem • Solution ?
Frequency Reuse FDMA & TDMA Need frequency planning Adjacent cells Different Frequencies CDMA NO need for frequency planning Adjacent cells Same freq. Separated by code channels
The “Near-Far Problem” • Nearby mobiles strong signal • Far away mobiles weak signals
Power Control in CDMA • Mobiles adjust power at which they transmit. • Base station receives all signals at the appropriate power. • The CDMA network independently controls the power at which each mobile transmits. • Extra advantage: Extended battery life
Generations of Cell Phones AMPS: 1983 GSM: 1992 IS-95: 1993 IS-136: 1996 cdma2000: 2002 WCDMA: 2002 Higher data rates for integration of mobile multimedia services
Generations of Cell Phones • 1G: • Phones are only capable of making and receiving voice calls. • 2G: • Phones can receive and send pieces of data: • E-mails, Web pages, etc… • Updated versions of TDMA and CDMA allow features like caller ID and SMS (short message service) • 3G: • Phones can receive and send both voice and data, but at speeds of about 144kbps, which is similar to what a broadband Internet connection offers PC users. • Current applications under development include geo-location capabilities using Global Positioning Systems (GPS), audio and video streaming, and other types of entertainment.
Goals of 3G • Rates • 2 Mbps in fixed applications • Up to 384 Kbps when a device is moving at pedestrian speed • 128 Kbps in a car Offer services like: • Increased Bandwidth • Wireless voice • Video • Email • Web browsing • Videoconferencing
Goals of 4G Enable mobile phones to be a combined: • Camera • Video camera • Computer • Stereo • Radio
CDMA Experiment • Equipment: • PN Code Generator • Carrier Frequency • Oscilloscope • Antennas (Transmitter & Receiver) • Signal source • Computers with LAWN software • Objectives: • Understand concept of CDMA • Understand how PN code generator works • Demonstrate jamming / interference
Summary • Future for Bluetooth and 802.11 • Can they coexist? • 802.11 Mobile LAN access • Long term: Bluetooth will be built in. • Currently: User has to choose between the two technologies. • Bluetooth is cheap!!! • 802.11e may have been designed to combat with Bluetooth. • Frequency hopping
Summary • Cellular Phone Systems • CDMA wider bandwidth, power efficient, interference rejection, security, more users. BUT … Near-Far Problem ! Solution: Power Control • TDMA Mostly used in Europe, partially in the US (AT&T and T-Mobile) • FDMA Previously used by AMPS (1G) • Generations of cell phones (1G to 4G) • Higher data rates, more multimedia features available • Experiment • PN Code generator, Frequency Jamming
References • a, b, e, and g--What 802.11 means to me (and you, too), David Coursey, Executive Editor, AnchorDesk • L.M. Correia and R. Prasad, “An Overview of Wireless Broadband Communication”, IEEE Communication Magazine, Jan. 1997, pp.28-33 • Naveen Chandran and Matthew C. Valenti, “Three generations of cellular wireless systems” • http://www.qualcomm.com/ • http://www-2.cs.cmu.edu/~dpwu/books/EE • Bluetooth versus 802.11, Nick Hunn, TDK Systems, www.cellular.co.za • http://www.palowireless.com • www.10meters.com/blue_802.html maintained by Karen E. Peterson and Caroline Scarborough • http://www.hoti.org/hoti9_tutorial.html, lecture by Pravin Bhagwat, ReefEdge Inc. • http://grouper.ieee.org/groups/802/11/main.html • http://www.utexas.edu/its/wireless/faqs/#80211 • http://www.oreillynet.com/pub/a/wireless/