2012.10.24
Koo
1

• There will be three main types of power management techniques.
1.
DVFS (Dynamic Voltage & Frequency Scaling)
2.
DMS (Dynamic Modulation Scaling)
3.
Network Coding
2

Contents
• Part I. Introduction of Practical Real-Time systems
• Part II. Energy-aware Real-time scheduling (DVFS)
• Part III. Introduction of Network Coding
3

Contents
1.
Block diagram
2.
Function applications
3.
Case study by worse case
4.
Power consumption by L-04A (NTT DoCoMo)
5.
Conclusion
4

RF ICs
[LTE, WCDMA,
GSM, GPS, etc.]
Application processor with modem
Memory
(DRAM, eMMC)
I/O devices
PMIC
5

e.g. Qualcomm RTR8600
SP
6T
GSM PA
WCDMA dual PA
RX SAW
TX SAW
TX SAW
RF IC
GSM
WCDMA
LTE
GPS
* PA : Power Amplifier
* SAW : Surface Acoustic Wave
* RX: Receiving
* TX : Transmitting
* SP6T: Single Pole 6 Throws
 There are various types of RF ICs such as
Blue Tooth, WLAN, and RFID.
6

1. Block Diagram (Baseband
; e.g. Qualcomm MSM8960
)
Application processor with modem
I/O devices
LCD
Camera
Speaker
USB
Memory
(DRAM, MMC)
LPDDR2
SDRAM eMMC
PMIC
Keypad
Vibrator
Battery
Adapter
*LPDDR : Low Power Double Data Rate
* eMMC : embedded Multi Media Card
7

(LCD operation)
MSM 8960
MDP
(Mobile Display Processor)
HDMI
(High Definition
Multimedia Interface)
MIPI
(Mobile Industry
Processor Interface)
PMIC LED backlight
LCD
Camera
 When a LCD module operates, it needs a LED backlight. A LCD module displays an image by LED backlighting. The backlight is one of major power
consumptions in a cell phone . Its amount depend on brightness of LCD.
8

9
2. Function application
( wireless communication )
Wireless communications
GSM, WCDMA, HSPA, LTE
Bluetooth
GPS
RFID
Wireless LAN
IrDA (Infrared Data Association)
Modes of power amplifier
Stand-by mode
Low mode
Middle mode
High mode  Max. power owing to lack of connectivity

10
Example(from previous slide)
• A brief flow chart of power scheduling
Three types of call modes
Power-on Start-up
Idle mode
High freq. & low vtg.
Communication off / on
High power mode
Sleep mode
Low freq. & low vtg.
Active mode
High freq. & high vtg.
Computation System(off-line operation)
*For DVS, there are low & high frequency clocks
. DC converter and LDO provide various types of voltages.
Medium power mode
Low power mode
Communication System (on-line operation)
*Low /medium/high power mode is decided by antenna condition.

• Video call & high power mode on WCDMA
: This case needs a LCD and a camera with the max. power of power amplifier at WCDMA communication
.
Memory
(DRAM, MMC)
WCDMA dual PA
TX SAW
RFIC
WCDMA
Camera
Application processor with modem
LCD
PMICs
LED backlight
11

4. Power consumption by L-04A (NTT DoCoMo)
• The most power consumption 5 & 5
No.
1
2
3
4
5
Condition1
Camera
Camera
MP3
MP3
Stand-by
Condition 2 Current consumption [Vin= 3.8V]
VGA
CAMERA
250mA
2M CAMERA 213mA
Speaker
Ear-mic
92mA
57.5mA
1mA
No.
1
2
3
4
5
Condition1
W2100
W800
W800
W2100
W800
Condition 2
VT
VT
Talk
VT
VT
TX power
23 dBm
23 dBm
23 dBm
12 dBm
12 dBm
Current consumption
[Vin= 3.8V]
732mA
721mA
520mA
487mA
480mA
12

• Multimedia parts (ARM core, power regulators,
LCD, camera, etc.) are the major part of power consumption when a wireless embedded system does not work for communication.
• RX power amplifier, RF module will also critical when the system work for wireless communication.
13

Contents
1.
PMIC
2.
System Block Diagram
3.
Case Study (DVFS)
4.
General methods of Power Management
5.
Future Works
14

• Why do we need PMIC?
-. From a single battery to various types of inside modules and I/O devices, PMIC controls their power.
• What are its main tasks?
-. Input power (battery, charger, USB)
-. Output power (SMPS, LDO, charge pump)
-. IC interface (PA control, GPIO)
-. General housekeeping by internal CLKs
-. User Interface (LED, LCD, Vibrator, Headset, Speaker)
15

• RF(Radio Frequency) vs. BB (Baseband)
I/O devices
RF ICs
[LTE, WCDMA,
GSM, GPS, etc.]
Application processor with modem
PMIC
Memory
(DRAM, MMC)
16

17
• According various scenarios, it needs a good algorithm for PM.
Task A Task B
Game State : Running
Save context
State : Blocked
Interrupt Vector Table
Interrupt
Interrupt Service
Routine
Context
Switch
State : Ready
State : Running
Message
Waiting
State : Ready
Message

(Dynamic Voltage and Frequency Scaling)
• DVFS
18
-. According to scheduled modes, PMIC provides processors’ core with different types of power by scaling voltage and frequency.

Step 1) Analyze target task/application
: min./max. power requirement
Step 2) Seek leakage/unnecessary power e.g.) pending task after interrupt
Step 3) Make up specific algorithm with possible scenarios e.g.) DVFS, FSM, etc.
Step 4) Verify a side effect after a new PM algorithm
19

Contents
1.
Abstract of COPE architecture
2.
COPE: basic idea
3.
Three main parts of COPE
4.
COPE: Opportunistic Coding Protocol
5.
COPE implementation
20

21

XOR
Relay
=
Alice
Alice’s packet
Bob’s packet
Bob
Bob’s packet
Alice’s packet
3 transmissions instead of 4
 Saves bandwidth & power
 33% throughput increase
22

• Opportunistic Listening
 COPE tries to listen all packets by analyzing the headers.
• Opportunistic Coding
 By XOR, COPE performs network coding based upon next-hop basic.
• Learning Neighbor State
 In order to encode a packet, COPE needs know what packets a neighboring node needs, and the packets the node has received so fat.
23

24

4. COPE: Opportunistic Coding Protocol
Alice Bob
Bob Charlie
Charlie Alice
Charlie
Charlie’s packet
Alice’s packet
Bob’s packet
XOR XOR = Relay
Alice
Alice’s packet
Bob’s packet
Charlie’s packet
Bob’s packet
Charlie’s packet
Alice’s packet
Bob
25

20-node wireless testbed
There are two floors which have 10 node each; it runs on 802.11a with a bit-rate of 6Mb/s.

Software
• Nodes in the testbed run Linux; COPE is implemented using “Click Modular Router” toolkit like the under.
• The implementation sends and receives raw
802.111 frames from the wireless device using a lipcap-like inteface

MIT’s Click
• “ Push-Pull ” semantics
• Single-threaded
• Network element database: 200+ elements
• Tight integration with Linux
During Push
(forwarding)
During Pull
(backwarding)

Router
• [Routing protocol] Srcr (source-routes data packets); a state-of-the art routing protocol for wireless mesh network.
• [Algorithm] the protocol use Djikstra;s shortest path algorithm on a database of link weights based on
ETT expected transmission time) metric.
• The router output queue is bounded at 100 packets.

Srcr ( Roofnet: An 802.11b Mesh Network)
• Srcr: DSR(Dynamic Source Routing) like protocol.
-. Each link has metric.
-. Data packets contain full source routes (robust aganist loops; metric may be dynamics.)
-. Nodes keep database of link metrics.
-. Run Dijkstra’s algorithm over data to compute source routes.

Hardware
• Each node in the testbed is a PC equipted with an 802.11 wireless card attached to an omnidirectional antenna.
(The card are based on the NETGEAR 2.4 &
% GHz 802.11 a/g chipset.)
• They transmit at 15 dBm power and operate in the 802.11 ad hoc mode with RTS/CTS disabled as in the default MAC.

Traffic model
• They use an utility called “ updgen ” to generate
UDP (User Datagram Protocol) traffic and
“ ttcp ” to generate TCP (Transmission Control
Protocol) traffic.

• Please give me a question which you are interested in or not clear.
• Thank you.
33

• Qinglong Liu, and Gang Feng “Optimization Based Queue
Management for Opportunistic Network Coding” , 2011 6th
International ICST Conference on Communications and Networking in China ,2011, pp 1159-1164
• S. Katti, H. Rahul, W. Hu, D. Katabi, M. M. Medard and J.
Crowcroft, “XORs in the Air”: Practical Wireless Network Coding,” in Proc. of ACM SIGCOMM’06, Pisa, Italy, Sept. 2006.
• R. Ahlswede, N. Cai, S. Y. R. Li, and R. W. Yeung, “Network
Information Flow”, IEEE Transactions on Information Theory, vol.
46, no. 4, July 2000, pp.1204-1216.
• P. Glatz, J. Loinig, C. Steger, and R. Weiss, “A first step towards energy management for network coding in wireless sensor networks,” in 9th IEEE Malaysia International Con-ference on
Communications, dec. 2009, pp. 905 – 910.