Wireless Communication Systems

Wireless Communication – IE3050

• Introduction to Wireless Communication is the topic of Lecture 01.

Learning Objectives

• The lecture provides in-depth coverage of existing and emerging wireless data communication networks technologies.
• Technology components that form the infrastructure of wireless data communication networks are examined.
• Wireless technologies, standards, specifications, and introduction to signals and systems are covered.

Topics to Cover

• Week 01 introduces wireless communication systems and includes an introduction to signals and systems.
• The basics of wireless networks are covered in Lab 01.
• Wireless Communication Basics are discussed in Weeks 02 and 03, including signal propagation, Free Space Loss (FSL), and line of sight path (LoS).
• Signal Modulation techniques, FHSS, and DSSS are examined.
• Lab Session 02 involves setting up a basic WLAN using client adapters and wireless access points.
• Week 04 is about antennas - including introduction antennas, antenna theories, antenna variables, Directional and Omni directional antennas and Link engineering and RF path planning.
• Lab session 03 involves configuring WLAN using real world devices
• Weeks 05 and 06 cover Wireless Local Area Networks (WLAN) - which include IEEE and 802 community, network standardization, IEEE 802 architecture, IEEE 802.11 MAC layer, and IEEE 802.11 PHY layer.
• Cellular System Infrastructure and LAN security are examined in Week 07 and 08.
• Introduction to 2G networks, GSM network systems design, GSM operations, BTS configurations in mobile networks, speech coding methods and usage, mobile network planning and Link Budget calculations in mobile networks feature in the curriculum
• Configuring wireless LAN security using Medium Access Control (MAC) filtering is covered.
• Weeks 09 studies Networks after 2G (2.5 G, 3G, 4G and 5G) and covers 2.5G networks and GRPS network architecture.
• Quality of Service in 2.5G networks (GPRS), Universal Mobile Telecommunication System (UMTS) and 3G/4G/5G Architecture are examined.
• Wired Equivalent Privacy (WEP) is covered in Lab Session 08.
• Internet of Things is studied in Week 10, covering pillars of IoT and IoE, Mobile IP and bringing all together.
• Lightweight Extensible Authentication Protocol (LEAP) is used in Lab Session 09.
• Advance Topics in Networking (Week 11 and 12) and the introduction to Sensor systems (WSN) and WSN applications are covered.
• Managing IOS System Files and IOS Licensing are covered in Week 9.

Assessment breakdown

• The mid Semester Exam is worth 20 percent.
• Skill Based Assessment is worth 30 percent.
• The Final Exam is worth 50 percent.

Wireless Data Network

• The Wireless Data Network includes sectors such as Consumer & Home, Smart Infrastructure and Security & Surveillance.
• Health care, retail, industrial sectors and transportation also feature.

Areas of interest for Wireless Data Network

• Wireless Communication quality involves bandwidth, error rate, delay, modulation, coding and interference.
• Mobility includes location dependent services, location transparency, quality of service support, delay, jitter and security.
• Portability includes power consumption, limited computing power, sizes of display and usability.

Wired vs. Wireless

• Wired networks use 802.3
• Wireless networks use 802.11

Frequency

• Frequency pertains to the rate of occurence of a wave.

Radio waves

• Frequency is measured as up/down cycles.
• Lambda, λ, is one cycle.
• 1 cycle per second equals 1 Hertz.
• E represents electric field.
• H represents magnetic field.

Hertz

• Hertz is the standard unit of frequency.
• One cycle per second is measured as Hertz.

Frequency Units

• Hertz (Hz) equals 1 Hz.
• Kilohertz (kHz) equals 1,000 Hz.
• Megahertz (MHz) equals 1,000,000 Hz.
• Gigahertz (GHz) equals 1,000,000,000 Hz.

Electromagnetic Spectrum

• The spectrum is the wavelength of all known electromagnetic radiations.

Electromagnetic Spectrum: Frequency Bands

• Common wireless communication frequency bands include 2.4 GHz and 5 GHz.
• The frequency bands range from 2.400 – 2.4835 GHz to 5.725 – 5.825 GHz.
• The 5 GHz range may expand.

Channelization

• Channelization divides a wide frequency band into narrow-band channels.

Bandwidth

• Bandwidth is the width of the smallest frequency band within which a desired signal can fit.
• Channels are either overlapping, or non-overlapping.

Phase

• Phase is a part of a sequence or cycle occurring over time.
• Theta, Θ, is the phase shift

Phase

• Waves can either be in phase or out of phase.

Wavelength

• Wavelength is the length of a single cycle of a wave.
• It is measured between one peak or trough of a wave and the next.

Wavelength

• Lambda, λ represents wavelength.
• 2.4 GHz is 4.92 inches.
• 5 GHz is 2.36 inches.
• Wavelength is needed for antennas.
• E/H defines amplitude.

Wavelength

• Frequency and wavelength are inversely proportional, as one increases the other decreases

Amplitude

• Amplitude is the absolute value of the vertical component of a wave.
• Amplitude increases, frequency remains constant.

Power Units

• Watt (W) is equal to 1 W.
• Milliwatt (mW) is equal to 0.001 W.

Decibel (dB)

• Decibel (dB) uses logarithms to compare values.
• It was originally created for sound.
• Power values are divided then converted.
• Another version uses subtraction.

dBm

• dBm is the power ratio in decibels (dB) of the measured power referenced to one milliwatt (mW).

Effective Isotropic Radiated Power (EIRP)

• Effective Isotropic Radiated Power (EIRP) pertains to the actual power radiated from an antenna connected to a transmitter.
• EIRP is equal to dBm - dB + dBi

Received Signal Strength Indication (RSSI)

• This is a measure of the observed energy received by an antenna of a signal.

Sensitivity Level

• Sensitivity Level measures the dBm threshold at which a receiver distinguishes between intelligible and unintelligible signals.

Noise

• Noise measures erroneous signals received on the same frequency as the receiving frequency.

Noise Floor

• The noise floor is the average dBm signal strength of received erroneous signals.

Signal-to-noise Ratio

• This is the difference between the RSSI of an intended signal and the noise floor.

Carrier Signal

• A steady, predictable frequency is used by which modulation may be applied to transfer information.

Modulation

• This describes the process by which a carrier signal is changed to transfer information.

Modulation

• Carry information and modulation are the same as Wi-Fi.
• Wi-Fi comprises 1's and 0's.
• Xm(t) is equal to information.
• Xc(t) is equal to the carrier signal.

Types of Modulation

• Amplitude
• Frequency
• Phase

Spread Spectrum

• Spread Spectrum is a wireless communication type where the frequency is deliberately spread through a band to increase bandwidth while minimizing interference and noise.

Spread Spectrum Types

• Frequency-hopping Spread Spectrum (FHSS)
• Direct-sequence Spread Spectrum (DSSS)
• Orthogonal Frequency-division Multiplexing (OFDM)

FHSS

• FHSS has 79 channels, and a range of 1MHz wide.
• Transmissions use synchronized hops between frequencies.
• The data rate is slow, at 1-2 Mbps.
• Transmitter collisions are possible.

DSSS

• DSSS has 14 channels, with 22 MHz wide.
• Channels 1, 6 and 11 are non-overlapping.
• Uses Phase modulation (1-11 Mbps).
• DSSS is more resilient.

OFDM

• OFDM has 14 channels, at 20 MHz wide.
• Channels 1, 6 and 11 are non-overlapping.
• It uses Multiple modulation (6-54 Mbps).
• OFDM utlizes subchannels for data.

Simple Reference Model

• The TCP/IP reference model is simple model for network communication.
• The layers are Physical, Data Link, Network, Transport, and Application.

TCP/IP Layers

• The Application layer is influenced by service location, multimedia, and adaptive applications.
• Transport congestion & flow control, as well as quality of service are factors.
• Network layers are influenced by addressing, routing, device location, and hand-over.
• Data Link layer is affected by authentication, media access, multiplexing, and media access control.
• Encryption, modulation, interference, attenuation, and frequency are influenced by the physical layer.

Overlay Networks

• Overlay Networks integrate heterogeneous fixed and mobile networks with varying transmission characteristics for hand over.

Electromagnetic Spectrum

• VHF stands for Very High Frequency.
• UHF stands for Ultra High Frequency.
• SHF stands for Super High Frequency.
• EHF stands for Extra High Frequency.

Frequencies for Communication

• VLF stands for Very Low Frequency -LF stands for Low Frequency -MF stands for Medium Frequency -HF stands for High Frequency -VHF stands for Very High Frequency -UHF stands for Ultra High Frequency -SHF stands for Super High Frequency -EHF stands for Extra High Frequency
• UV stands for ultraviolet light
• The formula depicting Frequency and wavelength is λ = c/f

Frequencies for mobile communication

• VHF-/UHF-ranges are utilized for mobile radio due to simple, small antenna for cars and deterministic propagation characteristics for reliable connections.
• Directed radio links and satellite communication leverages SHF and frequencies higher because small antennas, beam forming and large bandwidths are available.
• Wireless LANs use frequencies in the UHF to SHF range. Some systems are planned up to EHF.
• Wireless LANs have limitations due to absorption of water and oxygen molecules (resonance frequencies) and are subjected to weather-dependent fading with signal loss caused by heavy rainfall.

802.11 LANS

• IEEE 802.11 features media access control (MAC) and physical layer (PHY) specifications for implementing WLAN
• Four major factors for implementing a wireless network is considering High availability, Scalability, Manageability and Open architecture

Wireless LAN

• Wireless LANs are considered an addictive technology, and have strong backing from tech heavyweights like Cisco, IBM, Intel and Microsoft.
• The embedded market in Wireless LANs is growing thru loT and Sensor networks, and the WLAN market is expanding.

Business-Class vs Consumer WLAN

• The wireless LAN industry can is segmented into consumer vs. business.
• Business-class products generally have better security, upgradeability, network management, advanced features, choice of antennas, higher throughput and are moire scalable. Ease of use and Reliability feature on the consumer segments.

Benefits of WLANS

• Mobility, scalability, flexibility and savings can be realized.
• Installation advantages and time and and reliability in harsh environments are also listed.

Wireless Technologies

• Wireless technologies span a range of Bandwidth and Range Capabilities.

Wireless LAN Security

• Security must be turned on as part of the installation process.
• Employees who install WLAN equipment on their own are a risk.
• Extracting a 104-bit Wired Equivalent Privacy (WEP) key can be completed in moments.
• WPA (Wi-Fi Protected Access) released in 2003 is more secure than WEP due to the fact it uses a 256-bit key for encryption

Service set (802.11 network)

In IEEE 802.11 wireless, a service set is a group of wireless network devices sharing a service set identifier, or natural language label visible as a network name.

Basic Service Set (BSS)

• A Basic Service Set comprises one client connected to an access point which provides a connection to a Wired Network.

Independent Basic Service Set (IBSS)

• An Independent Basic Service Set comprises of client to client wireless connections.

Extended Service Set (ESS)

• An Extended Service Set (ESS) and Distributed System (DS) has multiple access points connected a to Wired Network.

MAC Architecture

• In IEEE 802 LAN/MAN standards, the medium access control (MAC) layer, or media access control layer, controls the hardware to interact with transmission medium, either wired (electrical or optical) or wireless.
• STAs must get access to the medium.
• IEEE 802.11 MAC carrier sense multiple access with collision avoidance (CSMA/CA), is the Distributed Coordination Function (DCF)
• Point Coordination Function (PCF) creates contention-free (CF) access.

CSMA

• CSMA, or Carrier-sense Multiple Access, involves a sending and receiving station interacting as shown, via Request to Send (RTS), ,Clear to Send (CTS), DATA and finally ACK.

Interframe Space (IFS)

When a station finds the channel busy it senses the channel again, when the station finds a channel to be idle it waits for a period of time called IFS time. IFS can also be used to define the priority of a station or a frame. Higher the IFS lower is the priority.

Interframe Space (IFS) Values

– There are three Interframe Space (IFS) Values: Short IFS (SIFS), Point coordination function IFS (PIFS) and Distributed coordination function IFS (DIFS)

• The functions are as follows: -Short IFS(SIFS) – Shortest IFS, Used for immediate response actions – Point coordination function IFS (PIFS) Mid-length IFS, Used by centralised controller in PCF scheme when using polls
• Distributed coordination function IFS (DIFS) Longest IFS, Used as minimum delay of asynchronous frames contending for access

Interframe Spaces

• The immediate access when medium is free is >= DIFS.
• Other values are DIFS, PIFS, and SIFS.
• Other factors involve busy medium, contention window, backoff window, slot time and next frame.
• Select slot and decrement backoff as long as medium is idle until deference is achieved.