Wireless Communications Review 350 F24 PDF

Essay Question E Multiple Choice MC Problems P GUIDE TO WIRELESS COMMUNICATIONS, FOURTH EDITION, JORGE L. OLENEWA (ch1,2,3) Chapter One : RF Signals and Modulation Comparing Wired and Wireless Networks (E ) What does wireless network provide us as an advantage (E or MC) Signal...

Essay Question E Multiple Choice MC Problems P GUIDE TO WIRELESS COMMUNICATIONS, FOURTH EDITION, JORGE L. OLENEWA (ch1,2,3) Chapter One : RF Signals and Modulation Comparing Wired and Wireless Networks (E ) What does wireless network provide us as an advantage (E or MC) Signal in wireless travels as electric and magnetic fields travel along together and are always at right angles to each other Definition of frequency two main frequency ranges used for wireless LAN communication lies between 2.400 and 2.4835 GHz. This is usually called the 2.4-GHz band The other wireless LAN range is usually called the 5-GHz band because it lies between 5.150 and 5.825 GHz (MC) The actual frequency range needed for the transmitted signal is known as the signal bandwidth Relation between bandwidth and channel width RF signal properties o Phase o Frequency o Amplitude (Understand how changing their values affect the shape of the signal) Signal Power levels 𝑃 Comparing Power Levels Between Transmitters: 𝑑𝐵 = 10 𝑙𝑜𝑔10 (𝑃2 ) 1 Decibel and linear representation (Laws of 3 and 10s) (P) In wireless networks, the reference power level is usually 1 mW, so the units are designated by dBm (dB-milliwatt). (P) Antenna’s gain is measured by comparing its performance with that of a reference antenna, an isotropic antenna, so the gain is measured in dBi (dBisotropic). (Define, what is the isotropic antenna) Effective isotropic radiated power (EIRP): actual power level that will be radiated from the antenna  Calculating Received Signal Strength Over the Path of an RF Signal Receivers measure a signal’s power in dBm according to the received signal strength indicator (RSSI) scale. (what does it mean and its use in loss budget calculation E or P) Signal-to-noise ratio (SNR) (definition , use , calculation , what values are better higher or lower) Modulation ( What does it do, different types ) Spread Spectrum Categories : o Frequency-hopping spread spectrum (FHSS) {Main idea and shortcomings} o Direct-sequence spread spectrum (DSSS) { how and main components and their (functions o differential binary phase shift keying (DBPSK) and differential quadrature phase shift keying (DQPSK). modulation scheme. (main idea, calculate data rate ) o CCK can take 4 bits of data at a time and build out redundant information to create a unique 6-chip symbol. Two more bits are added to indicate the modulated phase orientation for the symbol, resulting in 8 chips total. o The chipping rate remains steady at 11 MHz, but each symbol contains 8 chips. o Symbol rate= chipping rate /number of chips per symbol o Bit rate= Symbol rate* number of bits per symbol o This results in a symbol rate of 1.375 MHz. Each symbol is based on 4 original data bits, so the effective data rate is 5.5 Mbps. o barker code, CCK, chipping rate , symbol rate o Symbol rate= chipping rate /number of chips per symbol o Bit rate= Symbol rate* number of bits per symbol  o o Orthogonal frequency-division multiplexing (OFDM) (Main idea, calculate data rate) o Ex: familiar BPSK modulation can be used along with two different coder ratios. In this case, OFDM still uses 48 subchannels or tones, with a reduced tone rate of 250 Kbps. OFDM with BPSK 1/2 results in a 6-Mbps data rate, whereas BPSK3/4 gives 9 Mbps. QPSK 1/2 and 3/4 can be used to increase the data rate to 12 and 18 Mbps, respectively. o o OFDM are named according to the fraction of symbols that are new or unique, and not repeated. For example, BPSK 1/2 designates that one half of the bits are new and one half are repeated. BPSK 3/4 uses a coder that presents three-fourths new data and repeats only one fourth Signal encoding techniques : Digital Modulation Reasons for Choosing Encoding Techniques (Different combinations( (E ) Signal Encoding Criteria ( relation between Signal-to-noise ratio, Data rate and Bandwidth) (MC) Factors Used to Compare Encoding Schemes (MC) Relationship between Data and Signal rate (P) Unipolar Scheme-NRZ (P) Differential Coding System (P) Bit rate, 𝑹𝒃 = 𝑴𝑹𝑺 Baud rate (P) 𝑳 = 𝟐𝑴 encoding M bits in each symbol element. Basic modulation Techniques (types ) (E/MC) Amplitude-Shift Keying Frequency Shift Keying (FSK) Phase Shift Keying (PSK) (Know their concept, illustrate with curves ) Two-level PSK (BPSK vs Differential PSK (DPSK) Four-level PSK (QPSK) (P) QAM is a combination of ASK and PSK PSK Constellation Diagrams (P) Examples (imp) Chapter 2: RF standards Why do we need regulatory bodies? (E)  What does ISM stand for and what are the bands for wireless? What are IEEE 802 Working Groups ( Ethernet and wireless) 802.11 Channel Use and Channels in the 2.4-GHz ISM Band, modulation (MC) 802.11 Channel Use Channels in the 5-GHz U-NII Bands, modulation (channel width and spacing) (MC) 802.11n o multiple-input, multiple-output (MIMO) system : described in the form T×R, where T is the number of transmitters and R is the number of receivers. (given a figure write its representation) o 802.11n features : Be able to state them and go through their operation) (E or Mc) o features that improve throughput: o Channel aggregation: that could operate on either a single 20-MHz channel or a single 40-MHz channel. By doubling the channel width to 40 MHz, the throughput is also doubled o o Spatial multiplexing (SM): , data can be multiplexed or distributed across two or more radio chains—all operating on the same channel o Remember that , a 3×3:2 MIMO device would have three transmitters, three receivers, and would support two unique spatial streams_(given figure express it) o Multipath (main concept) o MAC layer efficiency : o Block acknowledgment and Guard interval (to protect against is known as intersymbol interference (ISI)) o features that improve the reliability of the 802.11n RF signals: o Transmit beamforming (T×BF): a method to customize the transmitted signal to prefer one receiver over others by altering the phase of the signal as it is fed into each transmitting antenna so that the resulting signals will all arrive in phase at a specific receiver.  o 802.11ac: a set of capabilities known as very high throughput (VHT). (Identify their names and be able to discuss basic operation (E , MC) o Better channel aggregation—40-MHz bonded channels can be bonded again into channels that are 80 or 160 MHz wide. Because of the extensive use of channels, 802.11ac can be used only in the 5-GHz band. (RTS_CTS) o More dense modulation—256-QAM is used to modulate the RF signal in 256 different ways, taking more data at one time and boosting throughput. o MAC layer efficiency—More data can be aggregated with less overhead. o Explicit T×BF—To simplify and scale transmit beamforming, only a single feedback method is supported./ Null Data Packet (NDP o Scalable MIMO—Up to eight spatial streams can be used. o Multi-user MIMO (MU-MIMO)—An 802.11ac access point (AP) can send multiple frames to multiple receiving devices simultaneously. Chapter Three: RF signals in the Real world Interference: Neighboring and adjacent Channel Interference , Non-802.11 Interference (know their definition when do they happen and be able to identify them from figures) Free Space Path Loss (Define and be able to calculate ) The free space path loss (FSPL) in dB can be calculated according to the following equation: (Understand the relation between frequency, distance and  loss) FSPL (dB) = 20 log (𝑑) + 20 log (𝑓) + 32.44 10 10 where d is the distance from the transmitter in kilometers and f is the frequency in megahertz. Effective Range of 2.4-GHz and 5-GHz Transmitters: MC_T/F) free space path loss is greater in the 5-GHz band than it is in the 2.4-GHz band. range difference, where both transmitters have an effective isotropic radiated power (EIRP) of 14 dBm and the effective range ends where a receiver’s received signal strength Indicator (RSSI) equals –67 dBm. dynamic rate shifting (DRS): (Important to understand its idea and be able to express it and know other names (E, MC) 802.11 devices have a clever way to adjust their modulation and coding schemes based on the current RSSI and SNR conditions. If the conditions are favourable for good signal quality and higher data rates, a complex modulation and coding scheme is used DRS is also known as link adaptation, adaptive modulation and coding (AMC), rate adaptation Express what happens in this figure while the user is moving outward Effects of Physical Objects (name them , understand basic idea and be able to identify them from figures or scenario ) Reflection (Multipath Transmissions) Absorption  Scattering Refraction Diffraction Fresnel Zones (Line-of-Sight Wireless Signal) LOSS BUDGET CALCULATION Chapter four: Understanding Antennas One type of antenna cannot fit every application Radiation Patterns (know that name) A plot that shows the relative signal strength around an antenna MC,E H plane or the horizontal plane, and usually shows a top-down view of the radiation pattern through the centre of the antenna. The plane at the right is known as the E plane or elevation plane, and shows a side view of the same radiation pattern. the gain of an antenna is a measure of how effectively it can focus RF energy in a certain direction (know the definition ) MC ,E Beamwidth: measure of the antenna’s focus (know definition and difference with gain , how is it calculated on radiation pattern) Polarization: (what types of polarization, what does mismatch do?) two basic types of antennas, omnidirectional and directional, Omnidirectional Antennas: (know their radiation patterns and applications) o Dipole - monopole antennas- Integrated omnidirectional (study their radiation pattern 3 and 2 D, commercial shape) (MC) Directional Antennas: study their radiation pattern, and applications)  o Patch antennas-Yagi Antenna-Parabolic Dish Antenna study their radiation pattern 3 and 2 D, commercial shape) (MC) Notice that the beamwidth is the largest for omnidirectional antennas, and then begins to narrow through the progression of directional antennas. MC_T/F opposite is true of the gain—omnidirectional antennas have the lowest gain, whereas directional antennas increase gain as their beamwidth narrows. MC_T/F Adding Antenna Accessories (amplifier- attenuator-lightning arrestor) (Mc-E) Chapter Five (Types of Wireless Networks) Know different types and range (Be able to place their names on figure , Know abbreviations ) E Unidirectional Communication and bidirectional (define and identify on TX_RX figure ) Half Duplex / Full Duplex( define and identify on TX_RX figure) Is 802.11 full duplex? Basic Service Set : (what does it consist of ) At the heart of every BSS is a wireless access point (AP) operates in infrastructure mode, What does this mean BSS is bounded by the area where the AP’s signal is usable known as the basic service area (BSA) or cell (Define , shape , traffic flow ) BSS identifier (BSSID and a service set identifier (SSID), (define MC) Association and becoming a client, or an 802.11 station (STA)( know what they mean MC) Be able to fill out a similar table distribution system (DS) for the wireless BSS (the upstream wired Ethernet) AP is a translational bridge, where frames from two dissimilar media (wireless and wired (MC) Supporting Multiple SSIDs on One AP : AP must be connected to the switch by a trunk link that carries the VLANs  AP then appears as multiple logical APs—one per BSS—with a unique BSSID for each (T/F, MC) Extended Service Set ESS (why do we need , figure ) Independent Basic Service Set/ an ad hoc wireless network (why do we need , figure) Other Wireless Topologies(why do we need , figures, given a certain situation which Ap mode would you need ) o Repeater o workgroup bridge (WGB) o Outdoor Bridge (point-to-point o Outdoor Bridge(Point-to-Multipoint) o Mesh Network