Jun 12, 2014 - TV Distribution over Cellular Network ... VoD services: Netflix, BBC iplayer, SVT play, HBO go, etc. 20.5% ..... for 'long-tail'/VoD content trend ...
KTH ROYAL INSTITUTE OF TECHNOLOGY
Efficient Spectrum Utilization of UHF Broadcast Band PhD Candidate: Lei Shi Advisor: Prof. Jens Zander Co-advisor: Dr. Ki Won Sung
Opponent: Prof. Linda Doyle Committee: Prof. Mikael Skoglund Prof. Tommy Svensson Dr. Joachim Sachs
Stockholm, Sweden, June 12th, 2014
Overview • Background • Research Question & Scope • Summary of Thesis Contribution • Secondary Access in TV White Space • TV Distribution over Cellular Network
• Conclusion & Discussion
STOCKHOLM, SWEDEN, JUNE 12, 2014
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Overview • Background • Research Question & Scope • Summary of Thesis Contribution • Secondary Access in TV White Space • TV Distribution over Cellular Network
• Conclusion & Discussion
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4
Background What is UHF broadcast band?
CHAPTER 1. INTRODUCTIO
Spectrum allocation in the UHF broadcast band Second Digital Dividend (to be confirmed in WRC-15)
DVB-T1/T2
490 MHz 470 MHz
698 MHz
First Digital Dividend (completed by 2012)
790 MHz
862 MHz
(a) European Union
First Digital Dividend (Completed by 2009)
ATSC
490 MHz 470 MHz
698 MHz
Reallocated to Analog Mobile Telephony (1983)
806 MHz
890 MHz
(b) U.S.
Figure 1.1: Spectrum allocation in the UHF broadcast band [1] [2] STOCKHOLM, SWEDEN, JUNE 12, 2014
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Background Incumbents in UHF broadcast band • Program Making for Special Event PMSE • Digital Terrestrial Television (DTT) for Broadcasting Linear TV
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Background DTT has been a success in Europe Share of fixed TV distribution platforms (%)
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Background TV? What is TV? Distribution of TV time by age group Source: Verizon Digital Media Study, 3/14 24% 17% 59%
35~64
44% VoD DVR Live TV
15% 41% 16~34
• Linear TV remain popular among older generation • Video-on-Demand (VoD) is taking over – DTT’s primary offering losing its appeal to younger generation STOCKHOLM, SWEDEN, JUNE 12, 2014
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Background “Tablet is just a smarter TV screen” • VoD services: Netflix, BBC iplayer, SVT play, HBO go, etc Mobile & Tablets
20.5% 55.8%
Computer
2012 2014
Connected TV Games Consoles
VoD request on BBC iPlayer by device Source: BBC
• Mobile platform gaining greater share of VoD consumption STOCKHOLM, SWEDEN, JUNE 12, 2014
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Background Video is driving the growth of mobile data
Over 50% traffic is video Mobile data traffic growth forecast in Exabytes per month (Source: Ericsson Mobility Report 2014)
• New user behavior + higher resolution = more video traffic • More capacity to sustain traffic growth = more spectrum STOCKHOLM, SWEDEN, JUNE 12, 2014
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Background Already running out of capacity…
• Background • Research Question & Scope • Summary of Thesis Contribution • Secondary Access in TV White Space • TV Distribution over Cellular network
• Conclusion & Discussion
STOCKHOLM, SWEDEN, JUNE 12, 2014
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Background Where can we find more spectrum? Smartphones = Daily of screen minutes across countries2014 (mins) Mostdistribution Viewed / Used Medium in Many Countries, (Source: Milward Brown AdReaction 2014(Mins) Daily Distribution of Screen Minutes Across Countries Indonesia Phillipines China Brazil Vietnam USA Nigeria Colombia Thailand Saudi South Africa Czech Russia Argentina UK Kenya Australia Spain Turkey Mexico India Poland South Korea Germany Canada Slovakia Hungary Japan France Italy
Screen Minutes 0
181 174 170 149 168 151 193 165
117 143 161 146
132 99 89 113 69 147 131 114 78 102 115 111 98 104 148 132 125 124 111 93 96 98 127 129 104 95 98 125 134 89
160 103 80 123
110 115 59 66 69 43 39 35
167
96 99 126 122 158 114 97
50%
300
400
TV Laptop + PC Smartphone Tablet
500
600
• Less time on TV vs more time on smartphones & tablet • Reconsider DTT’s exclusive access to UHF broadcast band Source: Milward Brown AdReaction, 2014. Note: Survey asked respondents “Roughly how long did you spend yesterday...watching television (not online) / using the internet on a laptop or PC / on a smartphone or tablet?” Survey respondents were age 16-44 across 30 countries who owned or had access to a TV and a smartphone and/or tablet. The population of the 30 countries surveyed in the study collectively represent ~70% of the world population.
STOCKHOLM, SWEDEN, JUNE 12, 2014
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Background Why UHF broadcast band? UHF band is premium for mobile reception - - -
Propagation condition and device size 200-300MHz potentially available SpectrumUHF bandsband below 700MHz could be assigned for m EC considering possibilities to re-farm The 700MHz spectrum band: market drivers and harmonisation challenges worldwide
highly unlikely Figure 32: The correlation between device size and spectrum band [Source: Analysys Mason, 2012]
The opportunity to extend m below 700MHz is limited bec
the UHF band spans a wi (470–862MHz in total) an exhibit different propagati
in particular, body loss va of RF noise, which affects indoor penetration becaus signal-to-noise ratio
it becomes increasingly d 700MHz for mobile servic antennas to account for g
Consequently, spectrum bel mobile services, but it is verg some countries, such as Bra 450MHz band) is used for fix applications.
Radio frequency spectrum Lower frequencies
Higher frequencies
From a commercial and regu band is perhaps the last sub be assigned for mobile use.
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STOCKHOLM, SWEDEN, JUNE 12, 2014 © Analysys Mason Limited 2012
Overview • Background
• Research Question & Scope • Summary of Thesis Contribution • Secondary Access in TV White Space • TV Distribution over Cellular network
• Conclusion & Discussion
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Problem definition RQ: How much extra capacity can be provided for wireless broadband service by allowing it to access the UHF broadcast band? On-Demand TV Hybrid TV
Anytime, anywhere
Chromcast Amazon TV
Convergence with Cellular System
In-home viewing DVB-T/T2 Coexistence with Secondary System Status Quo
On-the-move viewing DVB-H Dyle Mobile TV broadcasting
Linear TV STOCKHOLM, SWEDEN, JUNE 12, 2014
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Problem definition 1. Coexistence between DTT and wireless broadband— secondary access in TVWS • Does the existing regulation policy ensure reliable primary protection without being overly restrictive? • Is TVWS suitable for massive deployment of short range secondary systems?
2. Convergence between broadcast and broadband—cellular TV distribution • Is it feasible to provide terrestrial TV service in UHF broadcast band using cellular network infrastructure and technology? • What is the gain of CellTV in real environments with mixed morphologies and evolving video consumption trends? STOCKHOLM, SWEDEN, JUNE 12, 2014
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CHAPTER 2. RESEARCH METHODOLOGY Thesis Scope Utilization of UHF Band
Near Future
Scenarios
Long-Term Future
Secondary Access in TVWS
TV Service Requirement
Converged CellTV platorm
User Demand Distribution
Secondary Interference Management
Regulation Policy
SFN/Unicast Resource Management
Spectrum Opportunity Assessment
Qualitative Comparison
Spectrum Saving Evaluation
Figure 2.1: Overall research approach of the thesis. STOCKHOLM, SWEDEN, JUNE 12, 2014
of details of the results we are interested in. In certain cases, compromises are
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Overview • Background • Research Question & Scope • Summary of Thesis Contribution
o Secondary Access in TV White Space o TV Distribution over Cellular Network
• Conclusion & Discussion
STOCKHOLM, SWEDEN, JUNE 12, 2014
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Secondary Access in TV White Spaces Previous work Geolocation Database TV signal
WSD Adjacent-Channel Interference
Co-Channel Interference WSD
WSD
WSD
WSD
WSD
TV Coverage
WSD
• Mostly focused on cellular-like secondary system->limited availability • We instead focus on short range system (e.g. ‘Super Wi-Fi’) – Modeling of the effect of adjacent channel interference – Control aggregate secondary interference – Scalability assessment STOCKHOLM, SWEDEN, JUNE 12, 2014
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Secondary Access in TV White Spaces Cumulative effect of multi-ch interference 3.2. PROTECTION OF PRIMARY SYSTEM • Proposed Model
TV signal level =−78dBm, N=Channel 27 (522MHz)
•
the interference received on adjacent channel k. • a measure for – TV receiver filter quality – Out-of-band emission of the interference signal
• Verified against measurements in both lab and 2 real apartments
Maximum tolerable interference power (dBm)
−40 −42 −44
Ch. N−1 (Measurements) Ch. N+1 (Measurements) Ch. N+1 (Theoretical) Ch. N−1 (Theoretical)
−46 −48 −50 −52 −54 −56 −58 −60
1 2 3 5 Number of simultaneously used adjacent channels (1 WSD per adjacent channel )
Maximuminterference interference power a given adjacent channelchannel vs Figure 3.2: Maximum powerlevel levelonthat a certain adjacent vs. the number WSDsofsimultaneously in TVWS [6] theofnumber simultaneously transmitting interfered adjacent channels
the TV reception, which can clearly be seen in Fig.3.3 [7]. we37propose t 19/ STOCKHOLM, SWEDEN, JUNE 12, 2014 To avoid this overestimation of spectrum opportunity, arate the effect of TV signal outage and secondary interference violati conditional probability. Letting Z denote Ptv ≠ (P min + Itv ), (2.4) c
ting [5, 6].
Secondary Access in TV White Spaces
Primary Protection Framework
34 CHAPTER 3. SECONDARY ACCESS IN TV WH protection framework e the protection of thePrimary primary system, we have first developed an anapproach for estimating the maximum permissible transmit power of secondary user. This approach is based on the regulatory framework 60 ed in [21]:
Estimate permissible Tx power + Itv + “su ( f ) GPsu } Ø q1 ≠
q,
58
Permissible SU transmit power (dBm)
= Pr{Ptv Ø
min Ptv
56
(2.4)
TV signal Sensitivitytransmit TV Int. power Secondary is the secondary andInt. “su ( f )95% is the1% same 54 protecefined in (2.2) with a frequency offset of f between the interference
su
Monte Carlo simulation
• Pro: accurate • Con: computationally prohibitive
Analytical solution • Regulatory approach inaccurate
52 50 48 46 44
42 0.9
– 10dB over-estimation
~10dB
SE43 Approach Proposed Approach Monte Carlo Simulation Lower Bound [5]
0.91
0.92
0.93
0.94
0.95 q
0.96
0.97
0.98
0.99
1
1
Permissible Tx power for SU at 50km away from victim TV Rx • Propose alternative approach Figure 3.3: Permissible transmit power for WSD located at 50 km away fro with different TV qsignal strength receiver with different q1 (q2 = – Match closely with simulation 1 ≠ 0.01, ‡S = 8dB, ‡G = 10dB. The references are defined in [7]). approach included in ECC report 186) (Proposed – Little added complexity STOCKHOLM, SWEDEN, JUNE 12, 2014
expressed as follows:
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Secondary Access in TV White Space Control Aggregate Secondary Interference
Regulatory approach 36 • Reference geometry for worst-case ACI • Fixed margin for multiple SUs
CHAPTER 3. SECONDARY ACCESS IN TV WH
Permissible Tx power on adjacent channel
• Mobile/portable • High density
40
Propose statistical model • Poisson distribution • Obtain permissible transmit power analytically • Estimate higher avaiablity
Permissible SU transmit power (dBm)
Too pessimistic for short range SUs
50 Ref Geo @ N+1 Proposed Approach @ N+1 Simulation @ N+1 Ref Geo @ N+5 Proposed Approach @ N+5 Simulation @ N+5
30
Secondary Mobile Device
20 10 0 −10 Secondary
Secondary Mobile Device
Mobile Device −20 −30
0 Secondary Mobile Device
Dominant Interference Region 200
400
600
800
1000
1200
1400
1600
2
SU density per km
Figure 3.4: Permissible transmit power with different WSD densities ⁄. q1 = 21/37 STOCKHOLM, SWEDEN, JUNE 12, 20140.95 [8].
Secondary Access in TV White Spaces Scalability of short range secondary access
Maximize admitted SU number • Combined ACI and CCI constraint • 1000+ SU/km2 except TV coverage border @30dBm Tx power
Primary Protection • Against CCI only is insufficient • Against ACI only is near optimal • ACI is the limiting factor for short range secondary access in TVWS Resulting TV reception violation (location probability >94%)
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Secondary Access in TV White Spaces Capacity of ‘WiFi’ like secondary system 38
CHAPTER 3. SECONDARY ACCESS IN TV WH
Optimize secondary Tx power
Findings • Comparable performance with ISM band given similar bandwidth • Higher throughput per user if more unoccupied TV channels • Except in rural with weak TV signal
Maximum average throughput per user (Mbps)
• Protect TV reception • Minimize SU collisions (CSMA/CA) • Maximize the throughput
200
TVWS in Ptv=−65dbm Rural area TVWS in Ptv=−71dbm Rural area TVWS in Ptv=−65dbm Urban area TVWS in Ptv=−71dbm Urban area ISM band in Rural area ISM band in Urban area
175
150
125
Urban
100
Rural
75
50
4
8
12 16 20 24 Unoccupied TV channel number
28
32
– Only case when capacity limited Average Throughput vs number of unoccupied channelnumb Figure 3.6: Maximum average throughput vs. unoccupied TVTVchannel by primary protection
ent TV signal Ptv . ⁄ = 100 WSDs/km2 in rural, 3000 WSDs/km2 in urban, w aggregation [10].
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mit power P opt is chosen by an exhaustive search in the simulation su
Overview • Background • Research Question & Scope • Summary of Thesis Contribution o Secondary Access in TV White Space
o TV Distribution over Cellular Network • Conclusion & Discussion
STOCKHOLM, SWEDEN, JUNE 12, 2014
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1.2. SPECTRUM ACCESS IN UHF BAND
TV distribution over cellular network Previous study SFN Unicast link B Broadcast Links
Unicast link A
Cellular BS B Cell B Unicast Coverage
Cellular BS A
Broadcast
Unicast
Unicast
A
B
Spectrum Saving
Cell A Unicast Coverage
UHF band
• Substantial studies on mobile TV provision (with MBMS) Cellular content distribution network. environment • FocusedFigure on the1.5: implementation issue in homogeneous • We instead focus on replacing DTT for fixed reception (stricter QoS) – Feasibility study from the spectrum perspective – Resource management for unicast/SFN in areas with mixed morphologies STOCKHOLM, SWEDEN, JUNE 12, 2014
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TV distribution over cellular network 30 CHAPTER 2. RESEA Feasibility Analysis
Assumptions for Case study of Sweden 2020 • Increasing number of HD programs – 24HD + 36SD – Differentiated channel popularity
• Use existing cellular infrastructure – eMBMS+unicast
• OTA view demand correlated to population density and environments • ‘Worst-case’ scenarios
80 k
m
– Urban Stockholm: highest viewer density – Somewhere in the north: lowest BS density
Figure 2.6: Studied area in the Greater Stockholm
STOCKHOLM, SWEDEN, JUNE 12, 2014
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TV distribution over cellular network
4.2. NETWORK CELLTV DEPLOYMENT IN INHOMOGENEOUS ENVIRONMENTS CHAPTER 4. CELLULAR CONTENT DISTRIBUTION IN A RE-FARMED UHF BAND
Feasibility Analysis
180
350
160
Rural Unicast with 4x1 legacy Rx antenna, 0.1% blocking Rural Unicast with 4x1 legacy Rx antenna, 5% blocking Rural Unicast with 4x4 MIMO, 0.1% blocking Rural Unicast with 4x4 MIMO, 5% blocking
BW required by current DVB−T deployment: 320 MHz
140 Required Bandwidth (MHz)
Required Bandwidth (MHz)
300
250 Urban Broadcast 4*1 legacy Rx antenna Urban Broadcast 4*4 diversity Urban Broadcast 8*8 diversity
200
150
120 100 80 60 40
100
20 50
0 0
500 1000 Inter Site Distance (m)
1500
4
6
8 10 12 Inter Site Distance (Km)
14
16
Requirement forCellTV hybrid CellTV unicast- in a rural Spectrum Requirement for CellTV broadcast inFigure Urban 4.2: Spectrum requirement for hybrid unicast-broadcast gure 4.1: Spectrum requirement for CellTV broadcast in a urban environment [11]. Spectrum
ment (The legends specify different broadcast in ruralreceiver antenna configurations for unicast lin
Spectrum requirement for CellTV
The unicast SINR of an arbitrary viewer at location ri is expressed as
• ~80 MHz in dense urban thanks to high SFN gain from small ISD spectrum saving of up to 250 MHz can be achieved by broadcasting all P¯ /q0 (ri ) SIN (ri , X) MHz = qm in rural with MIMO (4.3)over channels SFN (see Fig.4.1), thanks tochannels the densely deployed base statio • Runi~120 and unicasting ‘long-tail’ ¯ l=1 Xl P /ql (ri ) + N0 Õ
In sparsely populated areas, broadcasting over SFN is no longer as efficient
where X is the interference collision vector conditioned on the network in the load urban area due to the diminishing SFN gain in areas with large inter-s Õ x and m is the number STOCKHOLM, of interfering base stations (sites allocated with the are 27/ 37broadcast SWEDEN, JUNE 12, 2014distances. Therefore, only a few most popular TV channels same spectrum for unicast). The network load x in the system is obtained by the rest of the channels to the few viewers achieves the best res Unicasting solving the fixed point equation with around 200-150 MHz spectrum saving (see Fig.4.2). More spectr
TV distribution over cellular network
28
CHAPTER 2. RESEARCH METHODOLOG Realistic environments with mixed morphologies Urban
Suburban
Rural
UHF BC Band
Cellular sites
Ex Area
SFN1 MBB
Ex Area
Unicast
MBB SFN2
Ex Area
MBB
• BroadcastFigure efficient urban; unicast efficient in rural 2.5: in Illustration of the CellTV concept. • Seamless coverage require smooth transition in-between - Where to switch from broadcast to unicast? 2.2.1- What CellTV is theConcept impact on overall spectrum requirement?
CellTV denotes the concept of using cellular infrastructure and the UHF broad• Formulate resource management as optimization problem cast - band to distribute audio-visual content and replace themorphologies traditional terresApply to the Greater Stockholm region with diverse trial TV broadcasting services. The network is based on mobile infrastructure withSTOCKHOLM, Multimedia Broadcast Multicast Services (MBMS) capability. The 28/37 SWEDEN, JUNE 12, 2014 TV content can be distributed either via a unicast data link or broadcast over
TV distribution over cellular network
CHAPTER 4. CELLULAR CONTENT DISTRIBUTION NET Realistic environments with mixed morphologies RE-FARMED 44
• • •
All channels broadcasted in urban and most of the suburban areas Popular channel also broadcasted in rural areas, but with lower modulation order Niche channels unicasted in rural areas
Consequence: • • •
450
Urban Suburban
Rural
400 Spectrum requirement per cell (MHz)
Optimal resource allocation minimize average spectrum requirement
350 300 250
Total local spectrum requirement Spectrum occupied by assisting cells
200 150 100
Niche CH SFN1
Niche CH Unicast
50
POP CH SFN1 POP CH SFN2 Low spectrum requirement in urban 0 0 10 20 30 40 50 60 70 80 High in populated rural Distance from urban center (km) Highest in suburban due to switch Localspectrum spectrum requirement in Greater Region Figure 4.3: Local requirementforofCellTV CellTV in the Stockholm Greater Stockholm between SFN to unicast or another SFN
ciency of the whole network. The discrepancy between the resource all 29/37 efficie STOCKHOLM, SWEDEN, JUNE 12, 2014in different locations will inevitably reduce the overall spectrum the CellTV network. Thus, we have developed a framework that optimi frequency allocation, the transmission method of each TV channel, a
TV distribution over cellular network
CHAPTER 4. CELLULAR CONTENT DISTRIBUTION NETWORK IN A 4.2. CELLTV DEPLOYMENT IN INHOMOGENEOUS ENVIRONMENTS RE-FARMEDwith UHF BAND Realistic environments mixed morphologies Switching condition between unicast and SFN (MCC = 6dB)
4
10
4
Unicast all channels Broadcast Popular CHs only Broadcast all CHs Stockholm Statisitcs
Population Density per Km
2
Urban 3
10
2
10
Suburban 1
10
Rural
0
10
BW Req = 200 MHz BW Req = 160 MHz BW Req = 120 MHz BW Req = 80 MHz BW Req = 40 MHz BW Req = 20 MHz Stockholm Statistics
Urban Population Density per Km2
10
3
10
2
10
Suburban 1
10
Rural
0
1000
2000
3000
4000 ISD (m)
5000
6000
7000
CellTV transmission modes in mixed morphologies
10
1000
2000
3000
4000 ISD (m)
5000
6000
7000
CellTV spectrum requirement in mixed morphologies
re 4.5: Optimal transmission modes for TV content delivery inFigure heterogeneous envi- requirement of CellTV in heterogeneous environments 4.4: Spectrum • Broadcast all in urban, unicast niche in rural, mixed in suburban ments [13].
t (MHz)
400
350
• Urban: more spectrum saving, sensitive to ISD able spectral efficiency is achieved at the SFN border. The spectrum saving in rural areas is density limited due to the relatively the hig • Rural: less spectrum saving, sensitive to population New linear TV channels New VoD channels DVB−T2 (3 SFNs 256QAM 5/6 coding) STOCKHOLM, SWEDEN, JUNE 12, 2014
number of households per BS and a higher reliance on over-the-air TV rec tion. Reducing the inter-site interference through advanced multi-cell coor nation could potentially alleviate the “spectrum bottleneck”30/ and 37make unic in rural areas more efficient [12], To gain a deeper insight into the impact of the heterogeneous environm
1000
2000
3000
4000 ISD (m)
5000
6000
400
7000
600
800 1000 Inter Site Distance (m)
1200
1400
TV distribution unicast over cellular network in urban environment.
e 4.5: Optimal transmission modes for TV content delivery in heterogeneous enviFig. 8: Spectrum requirement for hybrid CellTV broadcas ents [13].
Adaptation to evolving video consumption pattern 250
350
New linear TV channels New VoD channels DVB−T2 (3 SFNs 256QAM 5/6 coding)
300
Spectrum Savings
250
150
100
