Cellular Phones as
Embedded Systems
EEL 6935 - Embedded Systems
Dept. of Electrical and Computer Engineering
University of Florida
Liza Rodriguez
Aurelio Morales
Outline
• Introduction
• Today’s Cellular Phone
• Architecture Challenges for Wireless Access
• Memory, OS, and Power Challenges
• Conclusions
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Outline
• Introduction
• Today’s Cellular Phone
• Architecture Challenges for Wireless Access
• Memory, OS, and Power Challenges
• Conclusions
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Cellular Generations
o Analog Cellular Technology (1G)
 Early 1980’s
 NMT, AMPS (FDMA)
 Susceptible to noise and interference. No protection.
o Digital Mobile Communication (2G, 2.5G)
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Early 1990’s
GSM (TDMA), IS-95 (CDMA), IS-136 (D-AMPS, TDMA), PDC (TDMA)
Data services: SMS
Digital encryption of conversations. Enhanced privacy.
o Wide Band Mobile Communication (3G, 3.5G)




Early 2000’s
EDGE (TDMA), CDMA 2000, UMTS (CDMA)
Data transfer rates >= 2 Mbit/s
Data & Voice convergence, Internet access.
o Broadband Mobile Communication (4G)
 LTE Advanced, IEEE 802.16 (WiMAX)
 Data transfer rates >= 100 Mbits/s
 Mobile IPTV, Wireless VoIP.
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Introduction (cont.)
Evolution of Radio Systems, Mobility, Data Rates
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Introduction (cont.)
Digital Convergence
• Convergence enables people to create, share and
consume digital content, using interoperable devices
• Cellular phones evolve from traditional cost-optimized
handhelds to multifunctional terminals
• Cellular phones: key platform for mobile convergence
applications (web browsing, video streaming, etc.)
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Agenda
• Introduction
• Today’s Cellular Phone
• Architecture Challenges for Wireless Access
• Memory, OS, and Power Challenges
• Conclusions
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Today’s Cellular Phone
• Extremely complex embedded system
• Functional blocks are custom-made for mobility
• Chips are either proprietary designs or based
on available chips.
• Miniaturization and functionality
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Block diagram of triple-band cellular phone
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Example: Blackberry Bold
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Example: Blackberry Bold
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Example: Blackberry Bold
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Example: Blackberry Bold
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Example: Nokia N95
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Example: Nokia N95
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Example: Nokia N95
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Example: Nokia N95
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Agenda
• Introduction
• Today’s Cellular Phone
• Architecture Challenges for Wireless Access
• Memory, OS, and Power Challenges
• Conclusions
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Development of Cellular phones
• Miniaturization
• Functionality
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Baseband and RF domains challenges
Challenge
Possible solution
New Challenges
Baseband ASICs are
limited in performance by
computational power, onchip communication and
clock distribution
Decentralized architectures:
small distributed controller
processors running at lower
frequencies
Management of processing
power resources
Baseband flexibility and
support for multiple radio
systems
Use configurable logic,
configurable processors, or
processor generators
Design methodology,
verification and testability
RF Cost and size of
BiCMOS chips
RF on digital CMOS
technology
Substrate-coupling effects,
device models
RF design portability
RF on digital CMOS
technology
New RF circuits and
architectures based on fast
sampling and time-discrete
signal processing needed
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RF challenges: Multiradio
o Wide variety of radio
systems
o Combination of systems at
reasonable cost and size
o Interference
o Miniaturization challenges
 Antennas
 Filters
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Outline
• Introduction
• Today’s Cellular Phone
• Architecture Challenges for Wireless Access
• Memory, OS, and Power Challenges
• Conclusions
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Memory Challenge
• Total memory requirement is increasing rapidly
• Mass Memories – interactive games, high
quality video
• Large memories are required to support data
downloading and local storage
• Supported by external memory cards: MMC or SD
• Small Memories – processing and small
applications
• Memory chips and their interconnections consume large
areas on PCBs and are accessed frequently
• New types of NVRAM may challenge memory chips to
provide smaller and more cost effective memory solutions
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NVRAM – Alternatives to Flash Memory
• Ferroelectric RAM (FeRAM)
• DRAM cell with ferroelectric dielectric in the storage capacitor
• Advantages: low power, faster reads and writes (single word vs. entire
block erase), greater number of write-erase cycles (1016 vs. 106)
• Disadvantages: lower storage density, higher cost
• Phase Change Memory
• Glass cells that become crystalline
or amorphous by cooling
• Advantages: faster reads and writes,
greater number of write-erase cycles
(108 vs. 106), longer hold times
• Disadvantages: temp sensitivity,
no pre-programming
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Application Platform
• Mobile internet – web browsing, video
calls and high bit rate streaming
• Java ME – provides flexible user
interfaces, built in network protocols,
multimedia support
• Fact: 2.1 Billion mobile phones use
Java platforms
• 3rd Party Mobile Applications – if
developed in Java, are portable
enough to run on almost all cell phones
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Java – Hardware or Software?
• Hardware – an additional small processor dedicated for
running Java
• Improves performance, minimizes memory requirements
• Software becomes dependent on inflexible hardware
implementation
• Software – Java is run on
baseband processor
• Virtual machine – Java commands
are interpreted as equivalent
microprocessor commands -- slow!
• Just In Time – compiler that would
translate Java classes into processor
instructions --- fast!
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Power Challenge
• Recent evolution of communication and application
functions have substantially increased power
consumption
• Constant annual growth of 10% in battery capacity has
enabled battery volume shrinkage while having mAh
level constant
• However, when 3G or WLAN communication is run
simultaneously with multimedia applications, power
consumption must be reduced
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Power consumption and Battery Capacity
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Solutions to Power Gap
• 10% increase in battery capacity will continue forever
• Reduce power hungry components:
• Antennas – Bluetooth, Wi-Fi, RF
• Digital displays
• Dynamic voltage and frequency scaling (DVFS)
• Reconfigurable RF components to reduce the number
of ICs.
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Outline
• Introduction
• Today’s Cellular Phone
• Architecture Challenges for Wireless Access
• Memory, OS, and Power Challenges
• Conclusions
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Conclusions
• Cellular phones have come a long way from analog
communication devices to digital mobile computers.
• Today, a cellular phone is a paradigm of an embedded
system having highly optimized cost, size, efficiency
and performance.
• Challenges in RF circuits, implementation architecture,
memory, and power consumption are still affecting the
development and growth of mobile devices.
• New technologies such as decentralized architectures,
reconfigurable circuits, advanced memories, and low
power designs will help overcome challenges.
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References
• http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1332581
• http://en.wikipedia.org/wiki/Mobile_phone
• http://www.portioresearch.com/resources.html
• http://www.phonewreck.com/wiki/index.php?title=BlackBerry_Bold
• http://www.phonewreck.com/wiki/index.php?title=Nokia_N95
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Questions?
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