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Link/Network Layer: MIMO, Cognitive Radio; Energy Management of Radio Resource Control (RRC). Y. Richard Yang 11 /15/2012. Outline. Admin. and recap Improve mesh capacity Reduce L (infrastructure “ blackholes ” , mobility for delay tolerant networks) MIMO: Use multiple antennas - PowerPoint PPT Presentation
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Link/Network Layer:MIMO, Cognitive Radio; Energy Management of
Radio Resource Control (RRC)
Y. Richard Yang
11/15/2012
2
Outline
Admin. and recap Improve mesh capacity
Reduce L (infrastructure “blackholes”, mobility for delay tolerant networks)
MIMO: Use multiple antennas Cognitive radio: use more spectrum
Radio resource management for energy management of mobile devices
Admin.
Project meeting slots to be posted on classesv2
3
4
Recap: Constraints in Capacity Analysis
transmission successful if there
are no other transmitters within a
distance (1+)r of the receiver
Interference constraint a single half-duplex
transceiver at each node
Radio interface constraint
T
b
nWTbh
1 2)(
21
)(
1
2 16)(
WTr
T
b
bh
h
hb
receiver
sender
r(1+)r
5
Recap: Capacity Bound
n
ii
n
ii xnx
1
2
2
1
Note:
Let L be the average (direct-line) distance for all T end-to-end bits.
T
b
bh
h
hbrTL
1
)(
1
T
b
bh
h
hb
T
b
T
b
bh
h
hb rbhrTL
1
)(
1
2
11
)(
1
)()(
nWTWTWTn
TL
816
2 2
nW
L
8rate*distance capacity:
6
Improving Wireless Mesh Capacity
transmission successful if there
are no other transmitters within a
distance (1+)r of the receiver
Interference constraint a single half-duplex
transceiver at each node
Radio interface constraint
T
b
nWTbh
1 2)(
21
)(
1
2 16)(
WTr
T
b
bh
h
hb
nW
L
8
rate*distance capacity:
Reduce LIncrease
W
Approx.optimal
Multipletransceivers
Reduceinterf. area
7
Outline
Admin. and recap Improve mesh capacity
Reduce L (infrastructure “blackholes”, mobility for delay tolerant networks)
MIMO: Use multiple antennas
Multiple Input Multiple Output (MIMO)
4x4 MIMO http://www.quantenna.com/qac-2300rdk.html
LTE
Kindle Fire HD
8
MIMO Basics
9
1
2
1
2
2221122
2211111
xhxhy
xhxhy
11h
12h
21h
22h
Solve two variables from two equations.
Using MIMO for more Concurrency: Motivation
10
Assume tx1 is sending to rx1
Can tx2 transmit in 802.11 using carrier sensing?
No Transmission in current 802.11n
MIMO Benefit: Concurrency using Interference Nulling
tx2: for every symbol q,transmits q on first antenna and aq on second antenna.
11
11h 21h31h
interference at rx1:
qhh )( 3121
if tx2 picks 31
21
hh
NO interference at rx1.
Problem
- rx2 hears p from tx1
- Can rx2 decode?
12
11h 21h31h
Decoding at rx2: Observation
- for different symbols p from tx1, the received signal at rx2 moves along a 1-d vector
13
11h 21h31h
phph
hy tx1
13
12
1txh
- rx2 can estimate channels h12, h13 from preamble
Perp. Of tx1 space
Decoding at rx2: Removing tx1 signal by Projection
- rx2 projects received signal orthogonal to
14
11h 21h31h
phph
hy tx1
13
12
1txh
projection space
Decoding at rx2: Projection Details
- rx2 picks w2 and w3:
to compute
15
11h 21h31h
projection space
3322 ** ywyw
Decoding at rx2: Projection Details
16
11h 21h31h
=>
qhhw
hhw
ywyw
)](
)([
33233
32222
3322
Summary: MIMO allows concurrency w/ interference nulling.
Problem of Only Nulling
17
Assume both tx1 and tx2 are transmitting.
If only nulling, tx3 cannot
transmit
nulli
ng
Solution: MIMO using Interference Alignment
18
Assume both tx1 and tx2 are transmitting.
Key idea: rx2 ignores interference from tx1 by projection. If tx3 aligns tx3 -> rx2 interference along the same direction as that oftx1 -> rx2, then rx2 can remove it too.
nulli
ng
MIMO with Nulling and Alignment
19
tx3 picks ’, ’, ’
rx2 sees:
1txh
Because rx2 projects to orthogonal to , nointerference from tx3 to rx2
20
Outline
Admin. and recap Improve mesh capacity
Reduce L (infrastructure “blackholes”, mobility for delay tolerant networks)
MIMO: Use multiple antennas Cognitive radio: use unlicensed spectrum
Spectrum Allocation Chart
21
Unlicensed Spectrum
Opportunity: unlicensed spectrum is large and has low utilization US unlicensed freq:
• 2.400-2.4835 G• 902-928 M• 5.800-5.925G• 5.15-5.25 G (200 mw)• 5.25-5.35 (1 w)• 5.725-5.825 (4w)
22
Problem of Using Unlicenced
Unlicensed spectrum may have occupants and is fragmented
Requirement: Coexistence with dynamic and unknown narrowband devices in the unlicensed spectrum
23
Zigbee 802.11a Others
UnlicensedSpectrum
Zigbee 802.11a Others
UnlicensedSpectrum
1. Operate below noise-level Limits range
Wideband
Existing Solutions
Zigbee 802.11a Others
UnlicensedSpectrum
1. Operate below noise-level Limits range
2. Pick a contiguous unoccupied band Limits throughput
Wideband
Existing Solutions
Zigbee 802.11a Others
UnlicensedSpectrum
1. Operate below noise-level Limits range
2. Pick a contiguous unoccupied band Limits throughput
Wideband
Sacrifice Throughput or Range!
Existing Solutions
Zigbee 802.11a Others
UnlicensedSpectrum
Cognition: Detect unoccupied bandsAggregation: Weave all unoccupied bands into one link
Wideband
Swift: Cognitive Aggregation
Research Issues
How to detect available frequency bands?
How to operate across chunks of non-contiguous frequencies?
How do sender and receiver establish communication when their perceived available frequency bands differ?
Aggregating Non-Contiguous Bands
Leverage OFDMDivides frequency band into multiple sub-bands that can be treated independently
Transmitter: Puts power and data only in OFDM bands not occupied by narrowband devicesReceiver: Extracts data only from OFDM bands used by transmitter
Frequency band
Cognition: How to detect occupied bands?
Unlicensed Can’t assume known narrowband devices Typical solution: Power threshold
Ideal ThresholdNarr
ow
ban
d
Pow
er
in d
Bm
Baseband Frequencies (MHz)
Faraway 802.11
Cognition: How to detect occupied bands?
Unlicensed Can’t assume known narrowband devices Typical solution: Power threshold
Ideal ThresholdNarr
ow
ban
d
Pow
er
in d
Bm
Baseband Frequencies (MHz)
Faraway 802.11
Problem: No Single Threshold Works Across All Locations
Ideal Threshold
Narr
ow
ban
d
Pow
er
in d
Bm
Baseband Frequencies (MHz)
Faraway 802.11
Nearby 802.11
Unlicensed Can’t assume known narrowband devices Typical solution: Power threshold
Cognition: How to detect occupied bands?
Adaptive Sensing
Intuitively: Poke the narrowband device, putting power in ambiguous bandsIf the narrowband device reacts, back away
Reasonable for unlicensed spectrum, which operates as best-effort
Unlicensed devices typically react to interferenceCarrier sense in 802.11, TCP backoff, etc.
Continuously sense the medium when not sending a packet
Detect appearance of narrowband device when narrowband power exceeds noise level
Detect reaction from changes in narrowband power profile
Adaptive Sensing: Alg
Narrowband Reaction
Detection Metric
Carrier Sense (e.g.,802.11): Will not transmit when sensing a SWIFT packet
Probability of narrowband power immediately after a SWIFT packet
Back-off (e.g., TCP, MAC): Will send less often
Inter-arrivals of narrowband power
Autorate: Will use lower modulation, increasing packet size
Duration of narrowband power
Look for statistically significant change in metric using standard tests (e.g. t-
test)
Adaptive Sensing in Action
Start with a conservative choice of bands
Keep tightening as long as narrowband is unaffected
ConservativeThreshold
Wideband
• Start with a conservative choice of bands• Keep tightening as long as narrowband is
unaffected
Adaptive Sensing in Action
Wideband
Metric
Estimate Normal Behavior
Adaptive Sensing in Action
Wideband
Metric
Tighten
Sense
Test: Same as Normal
Adaptive Sensing in Action
Wideband
Metric
Tighten
Sense
Test: Different from Normal
Adaptive Sensing in Action
Wideband
Metric
Loosen
Sense
Test: Same as Normal
Adaptive Sensing in Action
Wideband Throughput and Range
Baseline that operates below the noise of 802.11
Wideband Throughput and Range
Other Work
Cognitive Radios802.22, KNOWS, CORVUS, DIMSUMNet etc.
Wideband systemsIntel, Chandrakasan et al., Mishra et al., Sodini et al.
45
Outline
Admin. and recap Improve mesh capacity Radio resource management for energy
management
46
Recall: GSM Logical Channels and Request
Many link layers use a hybrid approach Mobile device uses
random access to request radio resource
The device holds the radio resource during a session
BTSMS
RACH (request signaling channel)
AGCH (assign signaling channel)
SDCCH (request call setup)
SDCCH (assign TCH)
SDCCH message exchange
Communication
call setup from an MS
47
Radio Resource Control Setup for Data in 3G
RRC connection setup: ~ 1sec Radio Bearer Setup: ~ 1 sec+Figure source: HSDPA/HSUPA for UMTS: High Speed Radio Access for Mobile Communications. John Wiley and Sons, Inc., 2006.
Source: Erran Li.
48
RRC State Management in UMTS
Given the large overhead to set up radio resources, UMTS implements RRC state machine on mobile devices for data connection
Channel Radio Power
IDLE Not allocated
Almost zero
CELL_FACH
Shared, Low Speed
Low
CELL_DCH Dedicated, High
Speed
High
Courtesy: Erran Li.
49
RRC of a Large Commercial 3G Net
Promo Delay: 2 Sec
DCH Tail: 5 sec
FACH Tail: 12 sec
DCH: High Power State (high throughput and power consumption)FACH: Low Power State (low throughput and power consumption)IDLE: No radio resource allocated
Tail Time: waiting inactivity timers to expire
50
RRC Effects on Device/Network
FACH and DCH
Wasted Radio Energy 34%
Wasted Channel Occupation Time 33%
51
Case Study: Pandora Streaming
Problem: High resource overhead of periodic audience measurements (every 1 min)Recommendation: Delay transfers and batch them with delay-sensitive transfers
Problem: High resource overhead of periodic audience measurements (every 1 min)Recommendation: Delay transfers and batch them with delay-sensitive transfers
52
Case Study: Fox News
Problem: Scattered bursts due to scrollingRecommendation: Group transfers of small thumbnail
images in one burst
Problem: Scattered bursts due to scrollingRecommendation: Group transfers of small thumbnail
images in one burst
53
Case Study: BBC News
Scattered bursts of delayedFIN/RST Packets
Problem: Scattered bursts of delayed FIN/RST packetsRecommendation: Close a connection immediately if possible, or within tail time
Problem: Scattered bursts of delayed FIN/RST packetsRecommendation: Close a connection immediately if possible, or within tail time
54
Case Study: Google Search
Search three key words.ARO computes energy consumption for three phases
I: Input phase S: Search phase T: Tail Phase
UL PacketsDL Packets
Bursts
RRC States
Usr Input
Problem: High resource overhead of query suggestions and instant searchRecommendation: Balance between functionality and resource when
battery is low
Problem: High resource overhead of query suggestions and instant searchRecommendation: Balance between functionality and resource when
battery is low
55
RRC State Transitions in LTE
56
RRC State Transitions in LTE
RRC_IDLE
•No radio resource allocated•Low power state: 11.36mW average power•Promotion delay from RRC_IDLE to RRC_CONNECTED: 260ms
RRC state transitions in LTE
RRC_CONNECTED•Radio resource allocated
•Power state is a function of data rate:
•1060mW is the base power consumption•Up to 3300mW transmitting at full speed
57Cellular Networks and Mobile Computing (COMS
6998-11)Courtesy: Junxian Huang et al.
RRC state transitions in LTE
Continuous
ReceptionSend/receive a packet
Promote to RRC_CONNECTED
Send/receive a packetPromote to
RRC_CONNECTED
Reset Ttail
58Cellular Networks and Mobile Computing (COMS
6998-11)Courtesy: Junxian Huang et al.
RRC state transitions in LTE
Ttail stopsDemote to RRC_IDLE
DRX
Ttail
expiresTtail
expires
59Cellular Networks and Mobile Computing (COMS
6998-11)Courtesy: Junxian Huang et al.
60
Summary
App developers may not be aware of interactions with underlying network radio resource management
A good topic to think about as a part of your project