Wireless Networks: An Introduction
Master Universitario en Ingenierıa de Telecomunicacion
I. Santamarıa
Universidad de Cantabria
Introduction Cellular Networks WLAN WPAN Conclusions
Contents
Introduction
Cellular Networks
WLAN
WPAN
Conclusions
Wireless Networks: An Introduction 0/16
Introduction Cellular Networks WLAN WPAN Conclusions
Basic model
Data in
Channel
ChannelEncoder
I/Q Symbol Mapper
Basebandfilters
Interleaver Up-Conv.RF TX
NoiseFading
Interference
RF RXDown Conv.
I/Q demod
De-interleaver
ChannelDecoder
Symbol,Bit recovery Data out
Frequency, phase, symbol & timing recovery
I System resources: frequency, time, space (MIMO), codes(CDMA), power,...
I Figures of merit: BER, SER, FER, PER, SNR, SINR, QoS,...
Wireless Networks: An Introduction 1/16
Introduction Cellular Networks WLAN WPAN Conclusions
Fundamental Limits (AWGN)
5 10 15 20 25 30SNR dB
0
2
4
6
8
10
Cap
acity
(bp
s/H
z)64-QAM
16-QAM
4-QAM (QPSK)
Gaussian inputs log(1+SNR)
Shaping gain (1.53 dB)
Pe (symbol) = 10-6 (uncoded)
I Nowadays, the use of power channel encoders (e.g. LDPC orturbo codes) allows us to operate close to capacity in AWGNchannels
Wireless Networks: An Introduction 2/16
Introduction Cellular Networks WLAN WPAN Conclusions
Wireless Technologies
Wireless Networks: An Introduction 3/16
Introduction Cellular Networks WLAN WPAN Conclusions
1 Mbps
10 Mbps
100 Mbps
1 Gbps
1 m 10 m 100 m km
Communication range
Bluetooth/Zigbee
c802.11b
802.11a/g
802.11n
UWB
802.16WiMax
c3G (UMTS)
2.5 G2G (GSM)
4G (LTE, LTE-A)
Wireless Networks: An Introduction 4/16
Introduction Cellular Networks WLAN WPAN Conclusions
Cellular Networks
Wireless Networks: An Introduction 5/16
Introduction Cellular Networks WLAN WPAN Conclusions
Evolution1
HUAWEI TECHNOLOGIES CO., LTD. Huawei Proprietary - Restricted Distribution Page 2
1Reprinted from Huawei TechnologiesWireless Networks: An Introduction 6/16
Introduction Cellular Networks WLAN WPAN Conclusions
Radio Access TechnologiesI 2G-GSM
I Two frequency bands of 25 MHz each (890-915 MHz uplink,935-960 MHz downlink)
I Channel spacing 200 kHz, 124 channels per frequency bandI Modulation format: Gaussian Minimun Shift Keying (GMSK)I Multiple Access Technique: Time Division Multiple Access
(TDMA)
I 3G-UMTSI Frequency band: 1.8-2.4 GHzI Bandwidth: 1.25, 5 or 20 MHzI Modulation format: Spread Spectrum, chip rate: 3.84
Mchips/s, orthogonal variable spreading factor codes (OVSF),spreading factor 4-256
I Multiple Access Technique: Code Division Multiple Access(DS-CDMA),
I Duplexing (uplink/downlink): Frequency Division Duplex(FDD), Time Division Duplex (TDD)
Wireless Networks: An Introduction 7/16
Introduction Cellular Networks WLAN WPAN Conclusions
I 4G-LTEI Frequency band: 2-8 GHzI Bandwidth: up to 100 MHz via carrier aggregationI Modulation format: OFDMI Multiple Access Technique: Orthogonal Frequency Division
Multiple Access (OFDMA)
I 5G: technologies under discussionI New Waveforms (filtered OFDM, FBMC, GFDM, ...)I New spectrum sharing (NOMA or Non-Orthogonal Multiple
Access Techniques)I New radio frame design (e.g., Short TTI)I New L1/L2 control signaling design (Low latency HARQ,
decouple data TTI with control channel, fully dynamicresource assignment,...)
I Full Duplex TransceiversI Massive MIMO data transmission
Wireless Networks: An Introduction 8/16
Introduction Cellular Networks WLAN WPAN Conclusions
LTE Frame Structure
I Generic frame used in FDD for both Downlink and Uplink
I LTE frame are 10 ms in duration
I They are divided in 10 subframes (Transmission Time Interval:shortest decodable transmission)
I Each subframe is further divided in two slots
I Slots consist of either 6 or 7 OFDM symbols
Wireless Networks: An Introduction 9/16
Introduction Cellular Networks WLAN WPAN Conclusions
Available Downlink Bandwidth is Divided into Physical Resource Blocks
LTE Reference Signals are Interspersed Among Resource Elements
[source: 3GPP TR 25.814]
Wireless Networks: An Introduction 10/16
Introduction Cellular Networks WLAN WPAN Conclusions
LTE
I OFDM modulation parameters (BW = 20 MHz)
Total Subcarriers (NFFT ) 2048
Payload subcarriers 1200
Subcarrier spacing ∆f 15 kHz
Sampling frequency (fs) 30.72 MHz (∆f ∗ NFFT )
OFDM Symbol duration Ts 66.7 µs
Normal cyclic prefix (TGn) 4.7 µs
Extended cyclic prefix (TGe) 16.7 µs
Occupied Bandwidth 18 MHz
Wireless Networks: An Introduction 11/16
Introduction Cellular Networks WLAN WPAN Conclusions
WiFi Networks
I IEEE 802.11 denotes a set of WLAN standards developed bythe Working Group 11 of the IEEE LAN/MAN Committee
Parameter 802.11a/g 802.11n 802.11acAir rate 54 Mbps 200+ Mbps 500+ MbpsRange 30 m 50 m 50 m
Frequency 5 GHz 2.4/5 GHz 5 GHzBandwidth 20 MHz 20/40 MHz 80/160 MHzModulation OFDM OFDM+MIMO OFDM+MIMO
Spatial streams 1 1,2,3,4 up to 8
I WiGig: Multi-Gigabit per second transmissions over theunlicensed 60 GHz band (also OFDM based)
Wireless Networks: An Introduction 12/16
Introduction Cellular Networks WLAN WPAN Conclusions
802.11a
I OFDM modulation parameters
Total Subcarriers (NFFT ) 64
Payload subcarriers 48
Subcarrier spacing ∆f 312.5 kHz
Sampling frequency (fs) 20 MHz (∆f ∗ NFFT )
Pilot subcarriers 4
OFDM Symbol duration Ts 4 µs
Cyclic prefix (TG ) 800 ns
Occupied Bandwidth 16.56 MHz
GI Signal
0.8+3.2=4μs
GI Data 1
0.8+3.2=4μs
GI Data n
0.8+3.2=4μs
GI2 LT1 LT2
2x0.8+2x3.2=8μs
t1 t2 t3 t4 t5 t6 t7 t8 t9 t0
10x0.8=8μs
Short Training Symbols:Frame detect, AGC,
Time and coarse Freq. Sync.
Long Training Symbols:Channel Estimation
Frequency offset correction
DATA Field:SERVICE + PSDU + TAIL + PAD
Signal Field:rate + length
Wireless Networks: An Introduction 13/16
Introduction Cellular Networks WLAN WPAN Conclusions
Modulation and Coding Scheme (MCS)
I 802.11a provides 8 PHY layer modes with differentmodulation schemes and different convolutional coding rates
Mode Modulation Channel Coding Data rate1 BPSK 1/2 6 Mbps2 BPSK 3/4 9 Mbps3 QPSK 1/2 12 Mbps4 QPSK 3/4 18 Mbps5 16-QAM 1/2 24 Mbps6 16-QAM 3/4 36 Mbps7 64-QAM 2/3 48 Mbps8 64-QAM 3/4 54 Mbps
Wireless Networks: An Introduction 14/16
Introduction Cellular Networks WLAN WPAN Conclusions
Wireless Personal Area Networks
I IEEE 802.15 wireless personal area standarsI Bluetooth (802.15.1)
I Communications between multiple electronic devices within10m each other
I 2.4 GHz frequency bandI Frequency Hopping- Spread Spectrum (FHSS)I Rate: 1 - 3 MbpsI Nodes/Master 7
I ZigBee(802.15.4)I Range 70-300 mI Intended for Wireless Sensor Networks (thousands of devices)I Low cost/low power consumptionI 868 MHz band/ 915 MHz bandI Rate: 250 kbps, 40 kbps, 20 kpbsI Modulation format: Offset quadrature phase-shift
keying(OQPSK)and DSSS (Direct Sequence Spread Spectrum)
Wireless Networks: An Introduction 15/16
Introduction Cellular Networks WLAN WPAN Conclusions
Conclusions
I Range, coverage and mobility are key aspects defining thevarious types of wireless networks
I Cellular Networks: 2G (GSM), 3G (UMTS, GPRS, EDGE,HSDPA,...), 4G (LTE, LTE-A), and 5G soon
I WLAN networks: 802.11 standards
I WPAN networks: Bluetooth, ZigBee
Wireless Networks: An Introduction 16/16
Top Related