Wireless Communication - IE3050 PDF

Wireless Communication – IE3050 Uditha Dharmakeerthi Introduction to Wireless Communication Lecture 01 Learning Objectives ▪ To provide an in-depth coverage of existing and emerging wireless data communication networks technologie...

Wireless Communication – IE3050 Uditha Dharmakeerthi Introduction to Wireless Communication Lecture 01 Learning Objectives ▪ To provide an in-depth coverage of existing and emerging wireless data communication networks technologies. ▪ To study the technology components which form the infrastructure of the wireless data communication networks. ▪ Wireless Technologies ▪ Wireless standards and specifications ▪ Introduction to signals and systems Topics to cover Assessment breakdown Task Value % Mid Semester 1 20 percent Exam Skill Based 2 30 percent Assessment 3 Final -Exam 50 percent Wireless Data Network  Transmission quality (bandwidth, error rate, Wireless delay) Communication modulation, coding, interference media access, regulations Areas of interest for location dependent services Mobility Wireless Data location transparency quality of service Network support (delay, jitter, security) power consumption Portability limited computing power, sizes of display, usability  Wired vs. Wireless Wired Wireless 802.3 802.11 Frequency The rate of occurrence of a wave; the occurrence of something over time.  Radio waves Frequency (up/down) λ is one cycle 1cycle/sec = 1Hertz E is electric field H is magnetic field Hertz The standard unit of frequency in the International System of Units; one cycle per second.  Frequency Units Hertz Kilohertz Hz kHz (1 Hz) (1,000 Hz) Megahertz Gigahertz MHz GHz (1,000,000 Hz) (1,000,000,000 Hz) Electromagnetic Spectrum The wavelengths of all known electromagnetic radiations.  Electromagnetic Spectrum Frequency bands 2.4 GHz & 5 GHz 2.400 – 2.4835 GHz 5.150 – 5.250 GHz 5.250 – 5.350 GHz 5.470 – 5.725 GHz 5.725 – 5.825 GHz 5 GHz may expand Victor Blacus / CC-BY-SA-3.0 Channelization The division of a wide frequency band into narrow-band channels. Bandwidth The width of the smallest frequency band within which a desired signal can fit.  Bandwidth Channels Channel separation Non- overlapping Michael Gauthier / CC-BY-SA-3.0 Overlapping Phase A part of a sequence or cycle occurring over time.  Phase Θ is the phase shift Peppergrower / CC-BY-SA-3.0  Phase In phase Out of phase Wavelength The length of a single cycle of a wave, as distance measured between one peak or trough of a wave and the next.  λ is wavelength 2.4 GHz is 4.92 inches 5 GHz is 2.36 inches Needed for antennas E/H is amplitude Increase frequency Decrease wavelength Amplitude The absolute value of the vertical component of a wave. Amplitude increases Frequency constant Ezechia / CC-BY-SA-3.0  Power Units Watt Milliwatt W mW (1 W) (0.001 W)  Decibel (dB) uses logarithms to compare 𝑃2 Originally for sound 𝑑𝐵 = 10𝑙𝑜𝑔𝑙𝑙 ( ) Power values divided then converted 𝑃1 Another version uses subtraction dBm The power ratio in decibels (dB) of the measured power referenced to one milliwatt (mW). Effective Isotropic Radiated Power (EIRP) The actual power radiated from an antenna connected to a transmitter.  Effective Isotropic Radiated Power (EIRP) Transmitter Cable Antenna dBm – dB + dBi Power Loss Gain = (dBm) (dB) (dBi) EIRP Received Signal Strength Indication (RSSI) A measure of the observed energy received by an antenna of a signal. Sensitivity Level The dBm threshold at which a receiver distinguishes between intelligible and unintelligible signals. Noise Erroneous signals received on the same frequency as the receiving frequency.  Noise Sensitivity level Noise Floor The average dBm signal strength of received erroneous signals. Signal-to-noise Ratio The difference between the RSSI of an intended signal and the noise floor.  Noise floor Signal-to-noise ratio Carrier Signal A steady, predictable frequency by which modulation may be applied to transfer information. Modulation The process by which a carrier signal is changed to transfer information.  Carry information 𝑥𝑚(𝑡) = information 𝑥𝑐(𝑡) = carrier signal Modulation Wi-Fi = 1’s and 0’s Amplitude Ivan Akira / CC-BY-SA-3.0 Frequency Ivan Akira / CC-BY-SA-3.0 Phase Ivan Akira / CC-BY-SA-3.0 Spread Spectrum Wireless communications where the frequency is deliberately spread through a band to increase bandwidth while minimizing interference and noise.  Spread Spectrum Types Orthogonal Frequency- Direct-sequence Frequency- hopping Spread Spread Spectrum division Spectrum Multiplexing (DSSS) (FHSS) (OFDM)  FHSS 79 channels Synchronized hops between 1MHz wide frequencies Too narrow, slow data rate Transmitter collisions (1-2 Mbps)  DSSS 14 channels Non-overlapping channels 22 MHz wide (1, 6, 11) Phase modulation More resilient (1-11Mbps)  OFDM 14 channels Non-overlapping channels 20 MHz wide (1, 6, 11) Multiple modulation Subchannels (6-54 Mbps) Simple reference model used here (TCP/IP) Application Application Transport Transport Network Network Network Network Data Link Data Link Data Link Data Link Physical Physical Physical Physical Radio Medium TCP/IP Layers LAYER INFLUENCE OF MOBILE COMMUNICATION TO THE LAYER MODEL service location APPLICATION multimedia adaptive applications congestion and flow control TRANSPORT quality of service addressing, routing, NETWORK device location hand-over authentication, media access DATA LINK Multiplexing media access control encryption, modulation, interference, attenuation, PHYSICAL frequency Overlay Networks - the global goal integration of heterogeneous fixed and mobile networks with varying transmission characteristics regional vertical handover metropolitan area campus-based horizontal handover in-house Electromagnetic Spectrum Frequencies for communication twisted pair coax cable optical transmission 1 Mm 10 km 100 m 1m 10 mm 100 m 1 m 300 Hz 30 kHz 3 MHz 300 MHz 30 GHz 3 THz 300 THz VLF LF MF HF VHF UHF SHF EHF infrared visible light UV VLF = Very Low Frequency UHF = Ultra High Frequency LF = Low Frequency SHF = Super High Frequency MF = Medium Frequency EHF = Extra High Frequency HF = High Frequency UV = Ultraviolet Light VHF = Very High Frequency Frequency and wavelength: λ = c/f wavelength λ, speed of light c ≅ 3x108m/s, frequency f  VHF-/UHF-ranges for mobile radio simple, small antenna for cars deterministic propagation characteristics, reliable connections SHF and higher for directed radio links, satellite Frequencies for communication small antenna, beam forming mobile large bandwidth available communication Wireless LANs use frequencies in UHF to SHF range some systems planned up to EHF limitations due to absorption by water and oxygen molecules (resonance frequencies) weather-dependent fading, signal loss caused by heavy rainfall etc.  IEEE 802.11 Set of media access control (MAC) and physical layer (PHY) specifications for implementing WLAN 802.11 LANs There are four major factors to consider before implementing a wireless network: High availability Scalability Manageability Open architecture  Wireless LANs are an “addictive” technology Strong commitment to Wireless LANs by technology Momentum is heavy-weights Cisco, IBM, Intel, Microsoft Building in Wireless LANs The embedded market is growing IoT Sensor networks The WLAN market is expanding  Industry has segmented: consumer vs. business “business-class” products: Security Business-Class Upgradeability Network management vs Consumer Advanced features WLAN Choice of antennas Highest throughput Scalability “consumer-class” products Ease of use Reliability  Mobility Scalability Flexibility Short- and long-term Benefits of cost saving WLANs Installation advantages Reliability in harsh environments Reduced installation time Wireless Technologies Wireless LAN Security WPA WEP Security must be turned on (part of the installation process) Employees will install WLAN equipment on their own (compromises security of your entire network) It takes just 3 seconds to extract a 104-bit Wired Equivalent Privacy (WEP) key from intercepted data using a 1.7GHz Pentium M processor. WPA (Wi-Fi Protected Access) is a wireless security protocol released in 2003 to address the growing vulnerabilities of its predecessor, WEP. The WPA Wi-Fi protocol is more secure than WEP, because it uses a 256-bit key for encryption Service set (802.11 network) In IEEE 802.11 wireless local area networking standards, a service set is a group of wireless network devices which share a service set identifier — typically the natural language label that users see as a network name Basic Service Set (BSS) Independent Basic Service Set (IBSS) Extended Service Set (ESS) and Distributed System (DS) In IEEE 802 LAN/MAN standards, the medium access control (MAC), also called media access control, is the layer that controls the hardware responsible for interaction with the wired (electrical or optical) or wireless transmission medium. MAC Architecture Before sending a frame, (Stations) STAs must get access to the medium. IEEE 802.11 MAC, carrier sense multiple access with collision avoidance (CSMA/CA), is called the Distributed Coordination Function (DCF) Point Coordination Function (PCF), creates contention-free (CF) access CSMA: Carrier-sense multiple access  Interframe Space (IFS) Values Shortest IFS Short IFS (SIFS) Used for immediate response actions Inter Frame Space (IFS) When a station finds the channel busy it senses the channel again, when the Mid-length IFS station finds a channel to be idle it waits Point coordination for a period of time called IFS time. IFS Used by centralised controller in PCF scheme function IFS (PIFS) when using polls can also be used to define the priority of a station or a frame. Higher the IFS lower is the priority. Distributed Longest IFS coordination Used as minimum delay of asynchronous function IFS (DIFS) frames contending for access Interframe Spaces THANK YOU Make tomorrow better.