Chapter 20 summary of Advanced Electronic Communications Systems by Tomasi

1. JIA GENEROSA 1
1971
Bell Laboratories proposed AMPS (Advanced
Mobile Telephone System)
October 13, 1983
• AMPS was operational
• 2100 square mile cell coverage area
• low power 7-watt transmitters
• narrowband frequency modulation
• usable audio frequency 300 to 3kHz
• maximum frequency deviation ± 12 kHz at 100%
modulation
• Carson’s Approximation
𝐵𝑊 = 2(𝑓𝑚 + 𝛿)
• Requires minimum signal–to–interference ratio
(SIR) of 18 dB
• Smallest reuse factor = 7
• Frequency Allocation: 40 MHz frequency band
• Analog
• 666 channels
• 30 kHz spacing
• A Channels(1–333)
• B Channels(334-666)
*Mobile units
Channel 1: 825.03 MHz
Channel 666: 844.98 MHz
*Bast Station
Channel 1: 870.03 MHz
Channel 666: 889.98 MHz
*21 Control Channels
*312 Voice Channels
• Frequency Division Duplexing (FDD)
• Transmissions:
BS to MU – Forward Links (Downlink)
MU to BS – Reverse Links (Uplink)
• Rcvr operates at + 45 MHz above Tx frequency
1989
• FCC assigns additional 10 MHz to original 40
MHz
• Increased number of simplex channels by 166 to
a total of 832 (416 Full Duplex Channels).
• Additional Frequencies are called expanded
spectrum includes channels 667–799 and 991–
1023
*33 were added below the original frequency
spectrum
*133 were added above the original frequency
spectrum
MU’s Transmit Carrier Frequency in MHz
𝒇 𝒕𝒄 = 𝟎. 𝟎𝟑𝑵 + 𝟖𝟐𝟓
𝒇 𝒕𝒄 = 𝟎. 𝟎𝟑(𝑵 − 𝟏𝟎𝟐𝟑) + 𝟖𝟐𝟓
MU’s Receive Carrier Frequency in MHz
𝑓𝑟𝑐 = 𝑓𝑡𝑐 + 45 𝑀𝐻𝑧
• FCC authorizes companies to operate in Cellular
Geographic Service Areas (CGSA) that lies
within Standard Metropolitan Statistical Area
(SMSA)
• Transmissions are separated in the frequency
domain – each channel is allocated channel
frequency and channel bandwidth
• Mobile Identification Number (NIM)
*34–bit binary code
Digit
Area code Prefix Subscriber
• Electronic Serial Number (ESN)
*32–bit binary code permanently assigned to
each MU
• Four–Bit Station Class Mark (CSM)
*indicates if terminal has access to all 832
AMPS channels or 666 channels only.
• System Identifier (SID)
*15–bit binary code
• Local operating Companies assign two–bit digital
color code (DCC) and a Supervisory Audio Tone
(SAT)
*SAT frequencies: 5970 Hz, 6000 Hz, 6030 Hz
*DCC: 00 01 10 11
• For exchanging control information between MU
and BS
• 21 control channels in A and 21 control channels in
B formation
• Are used to enable mobile units to communicate
with the cellular network through BS without
interference with normal voice traffic.
• Used for call origination, call termination and to
obtain system information
• Digital and employ FSK.
• BS broadcast on the Forward Control Channel
(FCC)
• Also sometimes called Setup or Paging Channels
• Transmits a 10-kbps data using FSK
• Forward Control Channel consists of three
different channel streams
–Stream A [MIN = 0]
–Stream B [MIN = 1]
–Busy-Idle stream: indicate status of RCC
• Types of Messages transmitted over the FCC
–Mobile Station control Channel
–Overhead message train
Cellular Telephone Systems

2. JIA GENEROSA 2
• Developed by Motorola intended to increase
AMPS capacity
• Short term solution to traffic congestion
• Allows up to three mobile units to use a single
30 kHz cellular channel at the same time
• Maximum frequency deviation is reduced which
results to the reduction of required bandwidth
to 10 kHz.
• With narrower bandwidth: voice channels are
more vulnerable to interference.
• Compensated by the addition of an interference
avoidance scheme called Mobile Reported
Interference (MRI) which uses voice companding
to provide synthetic voice channel quieting
• Capable of using four types of handoffs:
1. Wide Channel to Wide Channel (30 kHz to 30
kHz)
2.Wide Channel to Narrow Channel (30 kHz to 10
kHz)
3.Narrow Channel to Narrow Channel (10 kHz to
10 kHz)
4.Narrow Channel to Wide Channel (10 kHz to 30
kHz)
• United Stated Digital Cellular (USDC) was
designed and developed with the intent of
supporting higher user density with a fixed
bandwidth frequency spectrum.
• Cellular telephone systems that use digital
modulation – Digital Cellular
• Utilizes AMPS frequency allocation scheme
• Complies with IS–54 which specifies Dual–Mode
operation and backward compatibility with
standard AMPS.
• Also known as Digital Amps (D–Amps or
DAMPS)
• Has an additional frequency band in the 1.9 GHz
range = not compatible with AMPS.
• Individual channel bandwidth is 30 kHz
• Divides total radio–frequency spectrum into
individual 30 kHz cellular channels
• USDC–TDMA transmission frame consists of 6
equal duration time slots enabling each 30 kHz
AMPS channel to support three full–rate users
or 6 half–rate users.
• Random Access Channel (RACH)
–unidirectional channel specified for transmission
from MU to BS only
–short message service (SMS)
–capable of operating in dual–mode using
contention resolution similar to voice channels
–can operate in reservation mode
• SMS Point–to–point, Paging and Access
Response Channel (SPACH)
–used to transmit information from BS to
specific MS
–3 subchannels: SMS point–to–point messages,
paging messages and access response
messages
1. Paging Channel (PCH)
–transmits paging messages, message
waiting messages and user–alerting
messages
2. Access Response Channel (ARCH)
–carry assignments to another
resource
3. SMS Channel (SMSCH)
–used to deliver ptp messages to a
specific MS
–200 characters of text limitation
• Broadcast Control Channel (BCCH)
–unidirectional BS to MU transmission shared
by all units
1. F-BCCH
–broadcasts digital control channel
(DCC) structure parameters
2. E–BCCH
–carries less critical information than
F–BCCH
• Shared Channel Feedback Channel (SCF)
–supports random access channel operation
• 40 ms TDMA frame = 6 time slots containing
324 bits each
• 6.67 ms (Bursts)
• USDC voice channel frame = 4 data channels (3
for control and one for digitized voice and user
data)
• Digital Traffic Channel carries digitized voice info
• Reverse Traffic Channel carries a forward digital
traffic channel (FDTC)
1. Coded Digital Verification Color Code
(CDVCC)
–provides co–channel identification
similar to SAT signal transmitted in the
AMPS system
–8–bit digital voice color code number
between 1–255 appended with 4 coding
bits derived from shortened hamming
code
2. Slow Associated Control Channel
(SACCH)
–12 coded bits per TDMA burst and is
transmitted in every time slot
–provides signalling channel in parallel
with digitized speech information
3. Fast Associated Control Channel
(FCCH)
–blank and burst type of transmission
–for control and specialized supervision
and traffic messages b/n BS and MU

3. JIA GENEROSA 3
• IS 54
1990 – Electronics Industries Association and
Telecommunications Industry Association
(EIA/TIA) standardized dual–mode (able to
operate in either analog AMPS or the digital
USDC)
–voice channel (analog & Digital)
–Control Channel (Digital)
1. AMPS – 42 Primary Control Channel
(FSK)
2. USDC – 42 Primary Control Channel
(PSK)
–42 Secondary Control Channel
(PSK) 10 kbps
–Mobile units use AMPS forward and reverse
control channels
–When mobile unit transmits access request
this indicates it is capable of operating in digital
mode then BS allocates digital voice channel.
–Specifies 48.6 kbps rate per 30 kHz channel
divided among 3 simultaneous users (each user
is allocated 13 kbps, 9.6 kbps is used for timing
and control overhead)
–disadvantage: gradual changeover from AMPS
to USDC results in increase in interference and
dropped calls
• IS 136.2
–USDC offers twice as many control channels
(42 primary CC + 42 secondary CC)
–provides twice the capacity for control traffic
–USDC cellular systems use same signalling
techniques and modulation scheme (FSK) to
maintain compatibility with AMPS
–formerly IS 54 Rev. C = replaces FSK with π/4
DQPSK modulation for digital mobile to operate
in digital domain
–often called North American – Time Division
Multiple Accessing (NA–TDMA)
–provides PSK instead of FSK to increase
control data rates and provide specialized
services – Paging and SMS (up to 239
characters)
–provides additional sleep mode (conserves
power)
–not compatible with IS 54 (FSK CC are not
supported)
–3 channels
1. Analog Control Channels
2. Analog Voice Channels
3. 10 kbps binary FSK digital Control Channel
(DCCH)
*IS 136 Rev. C = provides same three channels +
a fourth (digital control channel with a data rate
of 48.6 kbps on USDC–only Control Channels)
–meant to replace analog CC
*IS 136 Version 0 = more features (SMS,
display phone number of incoming call, sleep mode)
*IS 136 Rev. A = add newer features and uses
vocoder
• IS 95
1984
–Qualcomm Inc. proposed a new standard based
on spread spectrum technology and increased
capacity
–based on Code–Division Multiple Accessing
(CDMA)
–MU to BS compatibility standard for dual–
mode wideband spread spectrum communications
–allows users to differentiate using a unique
code rather than a frequency or time
assignment
–designed to be compatible with analog cellular
telephone systems (AMPS freq. band)
Specifications:
–OQPSK (uplink) & QPSK (downlink)
–800 MHz (45 MHz separation for R and F)
50 MHz spectral allocation
–1900 MHz band (90 MHz separation)
120 MHz spectral allocation
–2.46 MHz total BW
1.23 MHz(Rev) & 1.23 MHz (For)
–Direct sequence CDMA accessing
–8 kHz voice BW
–64 total channels / CDMA BW
55 voice channes / CDMA BW
• Groupe Special Mobile (1982)
–responsibility was transferred to European
Telecommunications Standard Institute (ETSI)
• Backward compatible with any existing analog
cellular telephone system
1981
–began service in Germany
1983
–36 GSM networks in 22 countries
• GSM 900(phase 1) operates in the 900 MHz
for voice only
• GSM phase 2 (1995) included facsimile, video
and data transmission
• GSM 1800 and GSM 1900 were introduced
after implementation of PCS frequencies
• Radio channel bandwidth limitations and cost
prohibit GSM to operate at the 64 kbps data
rate.
• Classified into 3 categories:
1. Bearer Service
2. Teleservices
3. Supplementary Services
• Analog speech signals are digitally encoded and
then transmitted as digital data stream
• Users can send and receive up to 9600 bps to
subscriber in POTS(Plain old Telephone Service),
ISDN Networks, Circuit Switched Pubic Data
Networks (CSPDN) using various access
methods and protocols

4. JIA GENEROSA 4
• Modem is not required between user and GSM
network
• Offers SMS (bi–directional service for sending
alphanumeric messages up to 160 bytes)
• Base Station Subsystems (BSS)
–also known as radio subsystem
–provides and manages rad–frequency
transmission paths b/n MU and BS
• Network Switching Subsystems (NSS)
–manages switching functions
–allows MSCs to communicate with other
Telephone Networks
• Operational Support Subsystems (OSS)
–supports operation and maintenance of the
system
• Designed for 200 full duplex channels/ cell with
900 MHz transmitting frequency
• Later allocated at 1800 MHz
• Uses 2 25 MHz frequency for system use
• 890 MHz – 915 MHz used for BS to MU
(forward transmission)
• Uses FDMA and a combination of TDMA & FDMA
techniques for simultaneous access to multiple
MU
• Forward and Reverse Freq. bands are subdivided
into 200 kHz called Absolute Radio–Frequency
Channel numbers (ARFCN)
• 45 MHz channel separation
• Radio transmission both ways: 270.833 kbps
• Effective channel transmission rate of 33.833
kbps
Parameters:
–Gaussian MSK
– 50 MHz BW
890 MHz – 915 MHz (Reverse)
935 MHz – 960 MHz (Forward)
–FDMA/TDMA
–8 25 kHz / 200 kHz traffic channel
–200 kHz traffic channel
–992 full duplex channels
–Supplementary services
• Mobile Satellite Systems (MSS) provides the
vehicle for PCSS
• Are repeaters in essence
• PCSS uses LEO (Low–Earth Orbit) and MEO
(Medium–Earth Orbit) that communicate with
small, low power mobile telephone units
• PCSS’s intention is to provide same features
and services offered by traditional, terrestrial
cellular providers while being able to receive or
make calls anywhere in the world.
• Advantages:
1. Provides global coverage
2. Host of integrated services
3. Fills vacancies between land based cellular
and PCS telephone systems and provides
wide–area coverage
• Disadvantages:
1. High risk associated with high cost of
designing, building and launching satellites.
2. High cost of terrestrial based networking
and interface infrastructure maintenance
• Transparent interfaces and features sets
among network providers of mobile and wireline
telephone services
• Capable of operating with both American National
Standard International (ANSI) and CCITT (now
known as ITU) network constraints
• Must be able to operate in Dual Mode with
protocols (TDMA, FDMA or CDMA)
• Should provide unique MSS features and
characteristics