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Mobile Communications(KECE425)
Lecture Note 103-03-2014
Prof. Young-Chai Ko
114년 3월 3일 월요일
Prof. Y. -C. Ko
Course Information
Instructor
Prof. Young-Chai Ko ([email protected], Tel: x3254, Room#416)
Textbook
Principles of mobile communications (by G. Stuber)
Wireless communications (by A. Goldsmith)
Grading
Midterm (40%), Final (45%), Homework (10%), Attendance (5%)
Office Hour: (1:00-2:00 PM on Mon. and Wed.)
TA
Young-Jun Kim and Sungkyung Jo (x3778)
214년 3월 3일 월요일
Prof. Y. -C. Ko
Summary
Introduction
Downlink and uplink channels
Half duplex division (HDD) and full duplex division (FDD)
TDD and FDD
Cellular concept
314년 3월 3일 월요일
Prof. Y. -C. Ko
Basic Mobile Communications
downlin
k (forw
ard) c
hanne
ldownlink (forward) channelup
link (r
everse
) chan
nel
uplink (reverse) channel
Base station (BS)Mobile station (MS) Mobile station (MS)
A direct link is not allowed yet between two communication parties !
414년 3월 3일 월요일
Prof. Y. -C. Ko
Half Duplex and Full Duplex
Half-duplex
Walkie-Talkie (push and talk)
X
Xor
Full-duplex
Full-duplex emulation
Time division duplex (TDD) or frequency division duplex (FDD)
514년 3월 3일 월요일
Prof. Y. -C. Ko
Frequency Band Allocation for Mobile Service Companies
Company Frequency band (MHz) Bandwidth Systems
SKT
824~834 (10) / 869~879 (10) 20 MHz 2G (CDMA)
SKT
834~839(5) / 879~884(5) 10 MHz 3G or LTE
SKT
1755~1765(10) / 1850~1860(10) 20 MHz 3G or LTE
SKT 1930~1940(10) / 2120~2130(10) 20 MHz 3G or LTESKT
1940~1960(20) / 2130~2150(20) 40 MHz 3G or LTE
SKT
2300~2327(27) 27 MHz WiBro
SKT
Total 137 MHz
KT
819~824(5) / 864~869(5) 10 MHz 3G or LTE
KT
905~915(10) / 950~960(10) 20 MHz 3G or LTE
KT1745~1755(10) / 1840~1850(10) 20 MHz 2G, 3G or LTE
KT1960~1980(20) / 2150~2170(20) 40 MHz 3G or LTE
KT
2331.5~2358.5(27) 27 MHz WiBro
KT
Total 117 MHz
LGU+
839~849(10) / 884~894(10) 20 MHz 3G or LTE
LGU+1779~1780(10) / 1860~1870(10) 20 MHz 2G, 3G or LTE
LGU+1920~1930(10) / 2110~2120(10) 20 MHz 3G or LTE
LGU+
Total 60 MHz
614년 3월 3일 월요일
Prof. Y. -C. Ko
FDD vs. TDD
DL (BS Tx, MS Rx)
UL (BS Rx, MS Tx)
time (ms) 5
Freq
uenc
y (M
Hz)
0
1940
1945
2130
21355 MHz
5 MHz
• FDD transmits and receives on two
frequency bands simultaneously.
‣ 2X5MHz so total bandwidth is
10MHz.
‣ For binary modulation, total data
transmitted is 5MbpsX5ms
‣Total data received is 5MbpsX5ms
• TDD transmits and receives on two
time slots simultaneously.
‣ Total bandwidth is 10MHz.
‣ Total data transmitted is
10MbpsX2.5ms
‣Total data received is 10MbpsX2.5ms
[FDD]
time (ms) 5
Freq
uenc
y (M
Hz)
0
2360
2370
DL(BS Tx, MS Rx)
UL (BS Rx, MS Tx) 10 MHz
[TDD]
714년 3월 3일 월요일
Prof. Y. -C. Ko
FDD vs. TDD
• In terms of data throughput, FDD and TDD are identical.
• FDD uses half the bandwidth for twice the time compared to TDD, so overall data transmitted
is the same whether TDD or FDD is used.
Tx/Rx switch
PA
LNA
Tx
Rx
Filter(Tx)
Filter(Rx)
PA
LNA
Tx
Rx
[TDD RF front end] [FDD RF front end]
PA: Power amplifier
LNA: Low noise amplifier
814년 3월 3일 월요일
Prof. Y. -C. Ko
“Real” Full-Duplex
time (ms) 5
Freq
uenc
y (M
Hz)
0
2360
2370
DL(BS Tx, MS Rx)
UL (BS Rx, MS Tx)
Co-time and co-frequency transmission/reception will be
“real” implementation of full-duplex!
914년 3월 3일 월요일
Prof. Y. -C. Ko
Frequency Allocation per Frequency Band
[Ref: 한국전파진흥협회, http://www.rapa.or.kr]
1014년 3월 3일 월요일
Prof. Y. -C. Ko
[Ref: 한국전파진흥협회, http://www.rapa.or.kr]
1114년 3월 3일 월요일
Prof. Y. -C. Ko
Omni-Directional and Directional Antennas
rPomni Pdire
Pdire
=2⇡
✓dPomni
r
✓d rad/s
[Omni-directional antennas] [Directional antennas]
1214년 3월 3일 월요일
Prof. Y. -C. Ko
Path loss
Pt
Pr
rPr ⇠ Pt
r2
Pr = kPt
r2
or
where k is a constant.
1314년 3월 3일 월요일
Prof. Y. -C. Ko
Signal-to-Noise Ratio
In digital communications, we study that the bit-error-rate (BER) or
symbol-error-rate (SER) is a function of only the signal-to-noise ratio.
For example, BER of BPSK is
Pb = Q⇣p
2�⌘
where � is the received signal-to-noise ratio (SNR) defined as
� =Pr
N0W• Pr: received signal power
• N0: one-sided noise power spectral density
• W : signal’s bandwidth
1414년 3월 3일 월요일
Prof. Y. -C. Ko
BER of BPSK versus Distance
• Then we can easily show that �(d)dB = 10 log10
⇣0.52
d2
⌘+ 16
• Let �(0.5km)dB = 10 log10
⇣Pr(0.5)N0W
⌘= 16 [dB] at 500 m distance long.
- where Pr(d) is the received power at the distance d.
or �(d) = 10
�(d)dB/10in linear scale.
1514년 3월 3일 월요일
Prof. Y. -C. Ko
0.5 1 1.5 210−8
10−7
10−6
10−5
10−4
10−3
10−2
10−1
d [km]
BER
BER of BPSK versus the distance [km]
Quality of service requirement for voice communications
1614년 3월 3일 월요일
Prof. Y. -C. Ko
SER of M-QAM
Pe = 4
✓1� 1p
M
◆Q
r3
M � 1
EavN0
!
�4
✓1� 1p
M
◆2
Q2
r3
M � 1
EavN0
!
• For a given time T , as M increases, the spectral e�ciency gets higher.
- which means we can transmit more data (bits) given a certain time
duration.
• M -QAM transmits log2 M bits for the time symbol interval T .
• Symbol error rate
1714년 3월 3일 월요일
Prof. Y. -C. Ko
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 210−8
10−7
10−6
10−5
10−4
10−3
10−2
10−1
100
d [km]
SER
BER of M-QAM versus the distance [km]
M = 4M = 16
M = 64
1814년 3월 3일 월요일
Prof. Y. -C. Ko
Cellular Systems
�f1 +�f2 +�f3 = �fTotal bandwidth
�f1�f2
�f3
1914년 3월 3일 월요일
Prof. Y. -C. Ko
Cellular Concept
Key idea of cellular system: frequency reuse
�f1
�f1
�f2
�f2
�f3
�f3
�f3
�f1
�f2
. . .. . .
�f1 +�f2 +�f3 = �fTotal bandwidth
. . .
. . .
2014년 3월 3일 월요일