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Real-World Experience with a Mobile Broadband Network
Dr. Jin YangVerizon Wireless
September 23, 2004IEEE Communications SocietyOakland-East Bay Chapter, CA
2JYang – IEEE Presentation
Outline
Introduction Overview of 1xEV-DO NetworkPerformance of SchedulerPerformance of Hybrid ARQ An Integrated cdma2000-1x and 1xEV-DO NetworkConclusions
3JYang – IEEE Presentation
Introduction
Applications drive architecture • Traditional wireless network: voice centric
• Low data rate• Low latency• Equal and stringent service quality
• Evolutional wireless network: versatile applications beyond voice• Very high data rate• Flexible latency• Flexible service quality
Mobile wireless data network is evolving to support broadband services• Large file transfer• Intranet and Internet• Multimedia
4JYang – IEEE Presentation
Wireless Broadband Technologies
cdma2000-1x Rev C/D
W-CDMARel. 4
HSDPARel. 5
1xEV-DO Rev A
cdma2000-1x1xRTT
1xEV-DO Rev 0
GSM/GPRS
EDGE
cdmaOneIS-95A/B
3GPP2 Standards
3GPP Standards
CDMA2000-1x Rev E
IEEE Standards
802.16d 802.16e
802.11b 802.11a 802.11gWiFi
802.20Flarion and others
HSUPA Rel. 6+
WiMax
802.11n
1xEV-DORev B
5JYang – IEEE Presentation
Data Rate vs. Coverage Distance
10 kbps
100 kbps
1 Mbps
100 Mbps
1m 100 m10 m 1,000 m 10,000 m
UWB
802.11b
802.11g
WCDMAcdma2000-1x
GSM/GPRS/EDGE
HSDPA1xEV-DO1xEV-DVBluetooth
Data Rate
Distance in meter
10 Mbps 802.11a
UWB*
802.16d
802.20Flarion
802.11n
ZigBee
Standards available, no commercial productsStandards and commercial products available Standards under development
6JYang – IEEE Presentation
TIA/EIA IS-856 1xEV-DO
1xEV-DO is an integral part of the cdma2000 family of standards developed by 3GPP2, and approved by ITU as IMT-2000 system for 3G to address MOBILE broadband access• Peak rate 2457.8 kbps on forward link for 1xEV-DO Rev 0
• 1xEV-DO Rev A supports peak rate 3072 kbps on forward link, 1843.2 kbps on reverse link
• Forward link throughput increased by • Full power transmission• Adaptive modulation and coding (AMC)• Hybrid Automatic Repeat reQuest (H-ARQ)• More efficient scheduling and multiple user diversity
• IP based packet data architecture
7JYang – IEEE Presentation
Overview of 1xEV-DO: AMC
1/31/31/31/31/31/31/31/31/51/51/51/5
Code Rate
16QAM8PSK
16QAMQPSK8PSKQPSKQPSKQPSKQPSKQPSKQPSKQPSK
Modulation Slots per Packet
Physical LayerData Rate (kbps)
12457.611843.221228.811228.82921.62614.41614.44307.22307.24153.6876.81638.4
Adaptive server selection, Adaptive Modulation and Coding (AMC)• The best server, modulation and coding schemes are adaptive to the
channel carrier-to-interference ratio (CIR) based on feedback from reverse link Data Rate Control (DRC) channel at 600 Hz rate
8JYang – IEEE Presentation
Overview of 1xEV-DO: Scheduler and H-ARQ
Fast Scheduler• Fast scheduler takes into account a-priori channel state information from DRC• Users are served when experiencing better than average channel Carrier-to-
Interference Ratio (CIR)• Aggregated sector throughput increases as number of users increases due to
scheduler taking advantage of multi-path fading diversity from users
Hybrid ARQ• Earlier termination (an ACKnowledgment received earlier) will increase the
effective throughputTransmitSlot 1
n n + 1 n + 2 n + 3 n + 4 n + 5 n + 6 n + 7 n + 9 n + 10 n + 11n + 8 n + 12
TransmitSlot 2
TransmitSlot 3
TransmitSlot 1
Slots
NAK‘1’
NAK‘1’
ACK‘0’
First slot for the next packet transmission
Effective throughput 204.8=(153.6 x 4/3)
Instead of 153.6 kbps
FL Transmissionwith 153.6 kbps(4 slots)
DRC Requesting 153.6 kbps
ACK ChannelTransmission
9JYang – IEEE Presentation
Overview of 1xEV-DO: Phy & App Throughput
The average physical and application layer throughput for ftp transmission over a trial network
0-2 0 2 4 6 8 10 12 14
Ave
rage
Thr
ough
put
(kbp
s)
0
500
1000
1500
2000
2500
-2 0 2 4 6 8 10 12 14Average Carrier-to-Interference Ratio (dB)
Physical Layer Throughput: Measured PredictedApplication Layer Throughput: Measured Predicted
10JYang – IEEE Presentation
Scheduler
Scheduler determines slot assignment for each user• Advanced scheduling scheme improves the spectrum efficiency
Proportional fairness algorithm• Scheduling based on channel condition, time allocation history and user
data on the pipe• Serving the user at better than average channel conditions and achieving
multiple user diversity gain• User throughput optimized to the maximum achieve level regardless of
other user RF conditionsFairness versus throughput efficiency tradeoff• Gives higher priority and longer time allocation to good RF condition
could increase aggregated sector throughput at the cost of poor RF condition user
• Absolutely equal throughput for all users will sacrifice network efficiency Scheduler based on class of service requirement• Higher priority on time allocation can be used to differentiate services,
support delay-sensitive or rate-sensitive applications
11JYang – IEEE Presentation
Scheduler: Time Allocation Per User
The proportional fairness scheduler provides fair chance for every user who needs to transmit data• Users under poor,
average and good RF conditions share similar CDF of time allocations
• The average percentage of time allocation for each user is around 25% when 4 users are active in the system
• The good RF condition user in a mixed RF scenario did not dominate radio resources on time basis
Percentage of Time Allocation Per Second
CD
F
00.10.20.30.40.50.60.70.80.9
1
0 75% 100%0
0.10.20.30.40.50.60.70.80.9
1
0 25% 50%
Edge Middle NearPercentage of Time Allocation Per Second
CD
F
00.10.20.30.40.50.60.70.80.9
1
0 75% 100%0
0.10.20.30.40.50.60.70.80.9
1
0 25% 50%
Edge Middle Near
CD
F
00.10.20.30.40.50.60.70.80.91
-2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14Carrier-to-Interference Ratio (dB)
Edge Middle Near
CD
F
00.10.20.30.40.50.60.70.80.91
0.10.20.30.40.50.60.70.80.91
-2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14Carrier-to-Interference Ratio (dB)
Edge Middle Near
12JYang – IEEE Presentation
Scheduler: Throughput Performance
The sector throughput increases as number of users increases. The user throughput increases as the radio condition improves
• The multiple users gain is particularly strong under poor RF conditions• Aggregated throughput of 4 and 16 users could increase to 2 and 3.4 times that of
a single user throughput, respectively• The throughput will be saturated as the number of users increases to more than 4
under good RF conditions
0
500
1000
1500
2000
2500
1 2 4 8 160
500
1000
1500
2000
2500
1 2 4 8 16Number of Active Users
Measured: CIR=0.4 dB CIR=5.9 dB CIR=10.3 dBTheoretical: CIR=0.4 dB CIR=5.9 dB CIR=10.3 dB
0
500
1000
1500
2000
2500
1 2 4 8 160
500
1000
1500
2000
2500
1 2 4 8 16Number of Active Users
0
500
1000
1500
2000
2500
1 2 4 8 160
500
1000
1500
2000
2500
1 2 4 8 16Number of Active Users
Theoretical: CIR=0.4 dB CIR=5.9 dB CIR=10.3 dBTheoretical: CIR=0.4 dB CIR=5.9 dB CIR=10.3 dB
0
500
1000
1500
2000
2500
1 2 4 8 160
500
1000
1500
2000
2500
1 2 4 8 16Number of Active Users
Sec
tor T
hrou
ghpu
t (kb
ps)
0
500
1000
1500
2000
2500
1 2 4 8 160
500
1000
1500
2000
2500
1 2 4 8 16Number of Active Users
Measured: CIR=0.4 dB CIR=5.9 dB CIR=10.3 dBTheoretical: CIR=0.4 dB CIR=5.9 dB CIR=10.3 dBMeasured: CIR=0.4 dB CIR=5.9 dB CIR=10.3 dB
Theoretical: CIR=0.4 dB CIR=5.9 dB CIR=10.3 dB
0
500
1000
1500
2000
2500
1 2 4 8 160
500
1000
1500
2000
2500
1 2 4 8 16Number of Active Users
0
500
1000
1500
2000
2500
1 2 4 8 160
500
1000
1500
2000
2500
1 2 4 8 16Number of Active Users
Theoretical: CIR=0.4 dB CIR=5.9 dB CIR=10.3 dBTheoretical: CIR=0.4 dB CIR=5.9 dB CIR=10.3 dB
0
500
1000
1500
2000
2500
1 2 4 8 160
500
1000
1500
2000
2500
1 2 4 8 16Number of Active Users
Sec
tor T
hrou
ghpu
t (kb
ps)
13JYang – IEEE Presentation
Hybrid ARQ
Hybrid ARQ provides further control mechanism to improve the data rate under adverse radio conditions • Hybrid ARQ enables early-termination of multi-slot transmission on physical
layer and increases the user data rate. The chart illustrates the scheduled and final served data rate for a user moving at the edge of a sector• Hybrid ARQ results in a new set of derived packet types with increased rate
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
38.4 68.26 76.8 87.77 102.4 153.6 204.8 307.2 409.6 614.4 921.6 1228.8 1843.2 2457.6
Data Rate (kbps)
Perc
enta
ge o
f Rat
es
Scheduled Rate Served Rate
14JYang – IEEE Presentation
Hybrid ARQ: Throughput Gain
Hrbrid ARQ supports up to 1 dB throughput gain across network• The hybrid ARQ gain is significantly higher when mobile is at edge of the cell
with vehicular speed, where a-priori channel estimate is not accurate due to highly unpredictable channel conditions and interference patterns
• The gain is minimal when the user is near the cell with good a-priori channel state information
Hybrid ARQ combined with AMC and scheduler results in high average sector throughput across various RF environments
0.0
0.2
0.4
0.6
0.8
1.0
Hyb
rid A
RQ
Gai
n (d
B)
0 2 4 6 8 10 12Carrier-to-Interference Ratio (dB)
Pedestrian Vehicular Stationary
15JYang – IEEE Presentation
An Integrated Network Solution
1xEV-DO is an integral part of the cdma2000 family of standards• The same 1.2288 MHz frequency bandwidth• The similar reverse link budget enables one-to-one overlay of 1xEV-DO
on existing cdma2000-1x network • Hybrid mode supports smooth seamless hand-off between 1xEV-DO and
cdma2000-1x• cdma2000-1x voice calls are successfully terminated and originated during
1xEV-DO active data session using the trial network
A highly integrated network architecture provides a spectrum efficient way for both delay sensitive voice and delay tolerant data services• The integrated network can share packet data network elements, such as
Packet Data Serving Node (PDSN), Foreign Agent (FA), Authentications, Authorization and Accounting (AAA), and Home Agent (HA)
• Only Radio Network Controller (RNC) and dedicated 1xEV-DO base station modem cards are needed to upgrade the existing cdma2000-1x network
16JYang – IEEE Presentation
VisitedAAA
HomeAAA
PDSN/FA HA
An Integrated Network: Architecture
HomeNetwork
R-P
IP Network
VisitedNetwork
HLRIOS
PSTN
BSC(cdma2000-1x)
RNC(1xEV-DO)
Multi-mode BTSMSC/VLR
AbbreviationsAAA Authentications, Authorization and AccountingHA Home AgentFA Foreign AgentIOS Interoperability StandardR-P Radio Packet InterfaceRNC Radio Network ControllerPDSN Packet Data Serving Node New network elements required for 1xEV-DO
1x
1xEV-DO
Shared network elements with cdma2000-1x
SS7Network
InternetGateway
17JYang – IEEE Presentation
An Integrated Network: Link Budgets
Reverse link budgets for 1xEV-DO and cdma2000-1x• The link budget of a 1xEV-DO system is similar to that of cdma2000-1x
under serving rate of 38.4 kbps
cdma2000-1x 1xEV-DOData Rate (kbps) 38.4 38.4Portable Tx ERP Power (dBm) 23 23Base Rx Antenna Gain (dB) 17 17Base Rx Cable Loss (dB) 3 3Receiver Sensitivity (dBm) -120.64 -120.80
Thermal Noise (dBm/Hz) -169.98 -169.98Noise Figure (dB) 4 4
Data Rate (dB -Hz) 45.84 45.84Eb/No Req. @ PER 3% (dB) 3.5 3.34
Total Link Margin (dB) 25.17 25.17 System Loading (75%) (dB) 6.02 6.02
Log-normal Std. Dev. (dB) 8.00 8.00 Fading Allowance (dB) 10.25 10.25
Soft Hand -off Gain (dB) 4.1 4.1Body Loss (dB) 3 3
Building/Vehicle Penetration Loss(dB) 10 10
Maximum Path Loss (dB) 132.46 132.62
18JYang – IEEE Presentation
Conclusions
The 1xEV-DO has achieved high data throughput and high spectral efficiency through a combination of adaptive modulation and coding, fast scheduler and hybrid ARQ The aggregated sector throughputs increases as the number of users increasesThe proportional fairness scheduler provides fair chance for each user to share radio resources in a timely manner with an efficient network throughputAn integrated 1xEV-DO and cdma2000-1x network can support both delay sensitive voice and delay tolerant data services