Chapter 8 Wireless Communications

 

8.1 Introduction

- LOS (line of sight) link: 40 mi = 40 ¡¿ 1.6094 km = 64 km

 

- Wireless Communication by Environment

     Ground fixed

     Ground mobile

     Marine

     Satellite

     Aerospace: deep space communication

     Military

     Underground: subway, mine

     IoT and sensor network

 

- Wireless Communication Technology Areas

     Source coding: data compression, error correction

     Modulation, waveform design, signal conditioning: spectrum efficiency, interference rejection, robustness against channel variations

     Channel coding: multipath fading, interference

     Transmitter: circuit, digital, SoC

     Antenna: base station, handheld device, smart antenna, MIMO

     Channel and propagation

     Receiver: circuit, digital, SoC

     Signal processing

     Wireless communication network

 

- Link between wireless and wired communications

 

- Online radio coverage tool

VE2DBE, www.ve2dbe.com

 

Nautel, http://support.nautel.com/login/

 

8.2 Friis Transmission Equation

 

 

 

 

8.3 Space Loss

8.4 Link Equation and Link Budget

8.5 Effective Isotropic Radiated Power and G/T Parameters

 

 

 

8.6 Radio/Microwave Links

 

 

 

1) Fading Channel Models

Small-scale fading: Rayleigh distribution, Rice distribution

Large-scale fading: Log-normal distribution

Fast fading

Flat fading

Frequency-selective fading

Delay spread

Doppler spread

Clarke's channel model

Jakes' channel model

Nakagami distribution

 

2) Path Loss Model

Hata model

COST 231 model

Stanford University interim channel model

ITU path loss model

 

3) AWGN (Additive White Gaussian Noise) model

- The only impairment to communication is a linear addition of wideband or white noise.

- A good model for many satellite and deep space communication links.

- It is not a good model for most terrestrial links because of multipath, terrain blocking, interference, etc.

- For terrestrial path modeling, AWGN is commonly used to simulate background noise of the channel under study

 


8.7 Satellite Communication Systems

1) Why SATCOM?

- In the middle of an ocean

- On Himalayan mountains

- On Sahara desert

- In Amazon jungles

- On aircrafts

- GNSS, navigation

- Scientific research

- Military communication and surveillance

 

2) Communication satellites

Figure: IS-34 C- and Ku-band comsat built by Space Systems/Loral for Intelsat

 

Figure: Satellite communication payloads. Left: Korea's Ariragn-5, Right: Korea's Chollian

 

3) Communication via satellites

Figure: Global SATCOM market share

 

Figure: Thuraya X5-Touch Android mobile/satcom phone

 

GEO (geosynchronous orbit): 36,000 - 42,000 km

LEO (low earth orbit): 500 - 2,000 km

MEO (medium earth orbit)

 

 

C-band: downlink 3.7-4.2 GHz, uplink 5.925-6.425 GHz

Ku-band: downlink 11.7-12.2GHz, uplink 14.0-14.5 GHz

 

 

 

Multiple access methods

FDMA

TDMA

 

8.8 Mobile Communication Systems

8.8.1 Cellular Communication

 

Frequency allocation

Multiple access method

Duplex method

Number of channels

Channel spacing

Modulation

Bit rate

 

 

8.8.2 History

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Figure: History of mobile communication technology

 

8.8.3 3G and 4G Mobile

1) 3G Mobile

- 3GPP (3rd Generation Partnership Project): 1998.12 stated, 3G mobile communication standardization, ETSI (À¯·´), ARIB (ÀϺ»), TTC (ÀϺ»), CCSA (Áß±¹), ATIS (¹Ì±¹), TTA (Çѱ¹)

     3GPP Release 98: pre-3G GSM network technology (1998)

     ...

     3GPP Release 10: LTE Advanced (2011)

- 3GPP2: ED-DO

- Mobile Wi-Max, Wi-Bro, Flash-OFDM, IEEE 802.20

 

2) 4G Mobile (IMT-Advanced)

- 3GPP: LTE-A

- WiMax: WiBro Evolution (IEEE 802.16m)

 

Table: LTE, LTE-A performance

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Table: LTE technical parameters

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8.8.4 5G Mobile

1) 5G Specifications

 

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Figure: 5G mobile communication performance

 

Table: 5G specifications by ITU

    

2) 5G Waveforms

- OFDM (orthogonal frequency division multiplexing)

- FBMC (filter bank multi-carrier)

- UFMC (universal filtered multi-carrier modulation)

- GFDM (generalized frequency division multiplexing)

- F-OFDM (filtered OFDM)

- CP-OFDM (cyclic-prefix OFDM)

- CP-DFT-s-OFDM (cyclic-prefix discrete Fourier transform spread OFDM)

- ZT-DFT-s-OFDM (zero-tail DFT-s-OFDM)

- UW-DFT-s-OFDM (unique word DFT-s-OFDM)

 

3) 5G Standards

- 3GPP: 5G, Standards to be completed in 2020. Release 14, 15, 16 (technical reports for 5G)

- ITU: IMT-2020, 5G usage scenario

     eMBB (enhanced mobile broadband)

     mMTC (massive machine type communication)

     URLLC (ultra-reliable and low latency communications)

 

 

8.9 Personal Communication Systems

PCS

LMDS

WLAN

Satellite personal communication systems