APT700 AN EFFECTIVE BAND FOR GLOBAL HARMONIZATION STRATEGIC WHITE PAPER Adoption of the 700MHz Asia-Pacific Telecommunity band plan (APT700) by a growing number of countries across the APAC and Latin America regions represents a major opportunity for global spectrum harmonization of LTE systems with the potential to serve over 4 billion people globally. This step paves the way for economies of scale for devices and network infrastructure, fosters improved roaming and provides additional capacity to support new mobile broadband services. This white paper offers background on the state of APT700 around the world, including the economic and technical benefits of the band plan. It also addresses technical considerations for implementing networks within this plan and provides an overview of the Alcatel-Lucent APT700 solution.
Transcript
APT700 – AN EFFECTIVE BAND FOR GLOBAL HARMONIZATIONSTRATEGIC WHITE PAPER
Adoption of the 700 MHz Asia-Pacific Telecommunity band plan (APT700)
by a growing number of countries across the APAC and Latin America regions
represents a major opportunity for global spectrum harmonization of LTE
systems with the potential to serve over 4 billion people globally. This step paves
the way for economies of scale for devices and network infrastructure, fosters
improved roaming and provides additional capacity to support new mobile
broadband services.
This white paper offers background on the state of APT700 around the world,
including the economic and technical benefits of the band plan. It also addresses
technical considerations for implementing networks within this plan and provides
an overview of the Alcatel-Lucent APT700 solution.
TABLE OF CONTENTS
1. Introduction / 1
2. APT700 around the world / 2
2.1 Creation of the digital dividend (ITU Regions 1, 2 and 3) / 2
2.2 Significance of APT700 / 2
2.3 Global harmonization / 3
2.4 Device availability / 5
3. Addressing spectrum efficiency / 5
3.1 The US digital dividend band plan / 5
3.2 The APT digital dividend band plan / 7
3.3 ITU Digital dividend band plans / 8
4. Technical considerations / 9
4.1 Interference / 9
4.2 Global roaming / 15
4.3 Dual duplexers in terminal equipment / 16
4.4 Antenna size / 16
5. Alcatel-Lucent APT700 solution / 17
5.1 Solution component overview / 17
5.2 Solution benefits / 17
6. Conclusion / 18
7. Acronyms / 18
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1. INTRODUCTIONMobile network operators face the challenge of meeting rising mobile broadband demand. The availability of new devices, applications and faster access technologies is leading to increases in subscriber usage. Using a conservative model, a Bell Labs analysis of operator networks worldwide forecast a tenfold increase in monthly per-subscriber usage — from roughly 0.5 GB per user each month in 2013 to 5.0 GB per user each month in 2017.
Operators have a number of ways to address this growth. Primarily, they plan to handle it through a mix of new spectrum, via increases in spectral ef!ciency delivered by newer technologies like LTE and through further spatial densi!cation of the network, for example, by using small cells.
Recognizing the importance of meeting broadband demand and its impact on stimulating economic growth, governments have been freeing so called “digital dividend” spectrum operating at sub-1 GHz. The excellent propagation characteristics of this spectrum enable better coverage and in-building penetration. However, its availability varies across countries, and different band plans have been adopted, as a result.
It is widely recognized that both developed and developing countries could gain from global harmonization. It would allow economies of scale and enable more cost-effective devices to become available, as vendors are assured of high volumes. It would also enable better roaming, because the same band plan could be used across countries.
As a result, many countries have either opted for the APT700 band plan already, or they are now considering such a plan. The APT700 band plan has been designed to enable the most ef!cient use of available spectrum. It divides the band into contiguous blocks of frequencies. For Frequency Division Duplex (FDD), the plan creates two 45 MHz blocks of spectrum, one for downlink and one for uplink. For Time Division Duplex (TDD), a single 100 MHz block of continuous spectrum is used.
This paper examines the state of APT700 around the world, addresses technical considerations for implementing networks within this band plan and includes an overview of the Alcatel-Lucent APT700 solution.
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2. APT700 AROUND THE WORLDA growing number of countries across the Asia Paci!c and China (APAC) and Latin America regions are adopting the APT700 band plan. This trend represents a major opportunity for global spectrum harmonization of LTE systems. Figure 1 provides a projection of the global population covered by digital dividend bands with the APT700 band plan showing the highest level of growth in the coming years.
2.1 Creation of the digital dividend (ITU Regions 1, 2 and 3) Digital dividend is the term commonly applied to spectrum that has been made available for alternative uses by the transition from analog to digital television broadcasting. The introduction of digital television (DTV) has reduced the amount of spectrum required to provide broadcast television services. This spectrum is in the UHF band and is highly attractive for cellular operations because of its propagation characteristics. The digital dividend varies by region, because the spectrum used for analog television was not identical. In ITU Regions 2 and 3 (the Americas and Asia-Paci!c), the !rst digital dividend is in the frequency band 698 MHz to 806 MHz, sometimes referred to as the 700 MHz band. (The digital dividend in ITU Region 1 [EMEA] is 790 MHz to 862 MHz and is not considered in this paper).
2.2 Significance of APT700 Because of its excellent propagation characteristics, the low-frequency sub-1 GHz spectrum is ideal for providing both outdoor and deep indoor coverage, in both rural and urban environments:
In rural areas: These bands are effective for helping to ensure mobile system coverage in a cost effective manner. By using this spectrum fewer sites are needed leading to reductions in the cost of network roll-out and the cost of providing services. In urban environment: The lower-frequency bands tend to refract better around corners and can pass more easily through walls. Therefore, low frequencies provide improved indoor coverage.
Figure 1. Digital dividend band plan coverage of the world population
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The sub-1 GHz spectrum is ideal for economically deploying mobile coverage relatively quickly in wide areas, as well as for in-building use. According to a GSMA study1 the low-frequency bands enable mobile operators to build low-cost networks capable of handling the explosion of data consumption. Deploying a network that uses higher-frequency capacity bands requires more base stations to cover the same area. Rolling out a 700 MHz–based network can save up to 30 percent of the cost of rolling out a 2100 MHz–based network, and this translates into greater access and a more affordable service for customers.
Figure 2. Relative number of sites and CAPEX for coverage
0
CAP
EX
3500 MHz
28
5
10
15
20
25
30
35
2600 MHz
9
2100 MHz
5
1800 MHz
4
900 MHz
1.1
800 MHz
1.0
700 MHz
1.0
1.0
Site need
1.0 1.2 4.6 5.6 10.8 35.6
CAPEX
2.3 Global harmonizationGovernments have a major role to play in the way mobile Internet unfolds. As economic activities become more dependent on the Internet, its availability and reliability are now topics ranking high on the countries’ political agendas. Governments around the world are realizing the added value that broadband access and information and communication technology (ICT) can potentially bring to any public service, in areas as different as education, health, security, entrepreneurship and social programs. As a result, they are interested in the radio spectrum as a means for effectively creating a new convergence of governmental and commercial traf!c over IP.
The APT700 plan also known also as the “2 x 45 MHz option,” offers the best chance to answer the governments’ goals while delivering the bene!ts of regional harmonization. The band is likely to be allocated for mobile broadband (MBB) services in both Asia Paci!c and Latin America, at different times during 2014 through 2017, which gives it the potential to become the most-used band for LTE worldwide, covering over 4 billion people.
The Asia Paci!c Telecommunity Wireless Group completed planning for the APT700 plan in late 2011. This plan was the result of careful study, debate and deliberation, which took into account existing deployed systems, band-edge sharing issues, !lter capabilities, the LTE (IMT Advanced) standard and current 3GPP work toward expanding the 850 MHz band. It therefore represents one of the most carefully crafted plans that takes into account the complex needs of a wide range of countries within and beyond Region 3.
The APT700 plan protects adjacent television broadcasting services by using a signi!cant guard band and de!ned emission limits, which are re#ected in the newly released 3GPP Band 28 Frequency Division Duplex standard.
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Beyond the technical deliberations, one of the most important factors in developing this plan was economies of scale for handset manufacturers. The administrations, vendors and carriers involved were well aware of the bene!ts to developing nations of Internet access using affordable handsets and tablets. It is perhaps this reason, more than others, that has encouraged many countries beyond ITU-R Region 3 to recently adopt the plan.
Additionally, in Region 1 (EMEA) the second digital dividend (694 MHz to 790MHz) was included at the WRC-2012, in the agenda of the next conference, which will be held in 2015 (Resolution 232 (WRC-12)). Under the A.I.1.2, the member states of Region 1 (EMEA) must examine the results of ITU-R studies on the use of the 694 MHz to 790 MHz frequency band by the mobile service, except aeronautical mobile, and take the appropriate measures. The debate is now focused on how to allocate this spectrum to achieve the best economies of scale and harmonization within the region and with the countries adopting the APT700 band plan.
Figure 3. Near global harmonization possible with APT700 (Band 28)
C
CITELATU
ASMG
CEPT
APTITU region 2
ITU region 1
ITU region 3
US Band Plan
Band 28 decisions/preference
Band 28 possible
Source: GSMA, Feb 2013
Lower 2 x 30 MHz for ITU region 1, 2 x 45 MHz for regions 2 and 3 (upper 30 MHz for Japan)
APT Asia Pacific TelecommunityASMG Arab Spectrum Management GroupATU African Telecommunications UnionCEPT Conférence Européenne des administrations des Postes et des TélécommunicationsCITEL Comisión Interamericana de Telecomunicaciones
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Alcatel-Lucent is aligned with the industry’s point of view, and we believe that, as mobile broadband becomes the main broadband delivery mechanism in the world, harmonization is playing an important role globally for the following reasons:
Absence of harmonization (within a given region or among regions) can lead to fragmented markets. This could result in signi!cant reductions in the take-up of any mobile service due to prohibitive handsets costs.Harmonization will allow mobile operators and manufacturers to address large markets more ef!ciently, by achieving economies of scale for equipment manufacturers that produce both network equipment and mobile terminals. The propagation characteristics of spectrum below 1 GHz make the 700 MHz UHF digital dividend band very suitable for wide coverage provision. This UHF spectrum is also very well suited to in-building coverage provision, for example, in urban areas.
2.4 Device availability The device ecosystem for the APT700 band (Band Class 28) is still evolving. Key speci!cs concerning the Band Class 28 application-speci!c integrated circuit (ASIC) solution include the following points:
Today Qualcomm is the only chipset vendor that has enabled an LTE Band Class 28 chipset to support LTE multimode devices for different form factors. Data solutions include USB dongles, indoor and outdoor CPEs and Mi-Fi hot spots; and high-end devices including smartphones and tablets. Several other ASIC vendors are currently developing the APT700 band and plan to commercialize this band in the 2014 timeframe. Tier 1 ASIC vendors include Intel, Renesas and Samsung. Tier 2 vendors include Altair, Broadcom, GCT and Sequans. The lack of chipset solutions for the APT700 band is attributed to the lack of carrier LTE deployments globally in this band. Main deployments are anticipated to start in the second half of 2014 with commercial launches in 2015.
Device availability for the APT700 will be driven by chipset availability and carrier commitments within the Latin America and APAC regions.
The current indication is that test devices for the APT700 band will be available from selected Tier 2 original equipment manufacturers (OEMs), including Bandrich, BEC Technologies, Franklin Wireless, Gemtek, and Quanta, in early 2014, with commercial devices targeted for end of Q1/early Q2 2014 timeframe. High-end solutions (including smartphone and tablets) from Tier1 OEMs are currently targeted for 2Q/3Q 2014. These solutions will be driven strictly by LTE deployment timelines and volume commitments from key carriers (within Latin America and APAC regions) that are deploying this band.
3. ADDRESSING SPECTRUM EFFICIENCYThe strong adoption of the APT700 band plan paves the way for economies of scale for devices and network infrastructure, fosters improved spectrum ef!ciency and roaming, and enables additional capacity to support new mobile broadband services.
3.1 The US digital dividend band plan Given the advantages of this spectrum, the United States moved aggressively to develop a plan for the band, with auctions taking place in 2008 and commercial launch of networks in 2010 and 2011.
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At !rst glance, the US band plan seems to be the most obvious plan with which to encourage alignment. However, the US band plan has its own de!ciencies, which include:
Interference between DTV Channel 51 and lower 700 MHz cellular systems (See interference scenarios 1 and 2 in Figure 4.) Interference between lower 700 MHz D Block and lower 700 MHz cellular systems (See interference scenarios 3 and 4 in Figure 4.)Interference between public safety narrowband (PSNB) and upper 700 MHz cellular systems (See interference scenarios 7 and 8 in Figure 4.)High-power, downlink-only broadcasts in E Block into A Block downlink (See scenario 5 in Figure 4.) Limited block sizes not conducive to 20 MHz channel LTE Speci!c carve-outs for public safety
In Figure 4, interference scenarios 1, 3 and 7 are related to base station–to–base station (BS-to-BS) interference. Since base stations have high antennas and could have line of sight, the coupling loss from one BS to another BS could be much less than the coupling loss between a BS and user equipment (UE). Therefore the impact of BS to BS interference could be signi!cant.
The BS-to-BS interference could be mitigated by implementing various techniques, such as appropriate guard bands, BS transmitter emission mask improvements, receiver selectivity enhancements and so forth. It should be noted that there is a trade-off among the guard band, spectrum ef!ciency and !lter insertion loss, roll-off, cost, size, weight and waveform quality.
Interference scenarios 2, 4 and 8 in Figure 4 are related to UE-to-UE interference. Since the UE-to-UE separation could be small in public transportation, such as trains and subways, or hot spots such as airports and shopping malls, the coupling loss from UE to UE could be much less than the coupling loss between BS and UE. Therefore the impact of UE-to-UE interference could be signi!cant. UE duplex transmit (Tx) and receive (Rx) !lters typically have a passband covering the whole band class (that is, multiple blocks), and UE has size and cost limitations. As a result, UE may not provide sharp roll-off to prevent interference with other UE receivers in other bands.
Figure 4. Potential interference among US 700 MHz broadcast, public safety and cellular systems
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The UE-to-UE interference issue could be alleviated using various techniques, such as appropriate guard bands, UE transmitter emission mask improvements, receiver selectivity enhancements, limiting the UE transmit bandwidth at the maximum power, over-provisioning of Physical Uplink Control Channel (PUCCH) and additional maximum power reduction (AMPR).
A substantial guard band may be required to minimize interference from UE-to-UE interference. Potentially, this could be more than the guard band needed for BS-to-BS interference mitigation.
The shortcomings of this US 700 MHz band plan can be summarized as follows:Only up to 10 MHz channel bandwidth is supported by the 700 MHz LTE UE standard to prevent UE self desensitization.It is not possible to allocate larger carrier blocks in LTE, such as 20 MHz, because the plan is too fragmented due to the guard band required to mitigate inter-system interference. However, larger carrier blocks are essential for providing the highest spectral ef!ciencies and highest throughputs per user. The cost-per-delivered-megabit per second is higher, since optimal capacity-per-megahertz cannot be achieved.The cost, size and weight of cellular BS and UE Tx and Rx !lters are increased in order to alleviate BS-to-BS interference, UE-to-UE interference and interference between broadcast and cellular downlinks. The uplink LTE coverage, throughput or both could be reduced with AMPR. The LTE uplink peak data rate could be reduced through over-provisioned PUCCH.
In Asia Paci!c, the Asia-Paci!c Telecommunity Wireless Group (now the APT Wireless Forum or AWF), began considering how to make the best use of the digital dividend. Given the “front runner” status of the US band plan, there was some impetus within the Asia Paci!c region to adopt the US band plan. However, after due consideration of the issues described in this paper, there was no consensus to adopt the plan. The regional group developed and adopted two consensus band plans that offered greater spectrum usage and larger spectrum blocks, one FDD arrangement and one TDD arrangement.
3.2 The APT digital dividend band planFDD frequency arrangementThe Asia-Paci!c region developed its band plan by taking into consideration the capabilities of existing !lter technology and aiming to maximize the amount of FDD spectrum. An FDD plan with a 2 x 45 MHz FDD structure with a 10 MHz center-band gap was chosen.
A “conventional duplex direction” — with the lower block (703 MHz to 748 MHz) allocated for mobile “uplink” transmissions — was adopted. This approach recognizes the proliferation of Radio Navigation Satellite Service (RNSS) receivers in pedestrian and vehicular environments and the risk of harmonic interference from user device emissions in the 779 MHz to 805 MHz segment. Figure 5 shows the overall structure of the harmonized FDD arrangement for the 698 MHz to 806 MHz band.
The dual-duplexer arrangement is needed to facilitate mobile terminal implementation, while the overlap offers #exibility to administrations as they plan national spectrum. (This topic is explained in greater detail in later sections of this paper.)
45 MHz
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It should be noted that in many Asia-Paci!c countries the broadcast spectrum will be cleared down to 694 MHz, due to the size of the TV channel rasters. So there will be a guard band of up to 9 MHz on the bottom end.
TDD frequency arrangement
The TDD band plan also calls for a minimum internal guard band of 5 MHz at the lower edge (698 MHz) and 3 MHz at the upper edge (806 MHz), in addition to the external 4 MHz guard band (694 MHz to 698 MHz).
3.3 ITU Digital dividend band plansRecommendation ITU-R M.1036 recommends frequency arrangements for IMT-2000. This document has been revised to include the three new band plans for the spectrum 698 MHz to 806 MHz. Table 1 contains these recommended 700 MHz band plans, which are Band Plans A4, A5 and A6.
Table 1. Paired frequency arrangements in the 698 MHz to 960 MHz band
Frequency arrangements
Paired arrangements Unpaired arrangements (e.g., for TDD) (MHz)
Mobile station transmitter (MHz)
Center gap (MHz)
Base station transmitter (MHz)
Duplex separation
(MHz)
A1 824–849 20 869-894 45 None
A2 880–915 10 925-960 45 None
A3 832–862 11 791-821 41 None
A4 698–716 776–793
12 13
728-746 746-763
30 30
716-728
A5 703–748 10 758-803 55 None
A6 None None None 698-806
Figure 5. APT harmonized FDD arrangement for 698 MHz to 806 MHz
DTTV694MHz
698MHz
5MHz
10 MHzcenter gap
3 MHz
45 MHz 806MHz
PPDR/LMR45 MHz
Figure 6. APT harmonized TDD arrangement for 698 MHz to 806 MHz
806MHz
PPDR/LMRDTTV694MHz
698MHz
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4. TECHNICAL CONSIDERATIONS As previously discussed, the APT700 band plan offers both economic and technical bene!ts by helping to achieve global harmonization and economies of scale. The following sections address the technical considerations involved when implementing networks within this band plan.
4.1 InterferenceDespite the APT700 band plan’s obvious improvement over the US plan, some challenges associated with the Asia-Paci!c FDD plan still remain, including:
Critical interference scenario from LTE UE transmitter to a DTV receiver (especially for countries with 6 MHz TV rasters up to 698 MHz)Critical interference scenario from land mobile radio (LMR) mobile transmitter to a LTE UE receiver Potential third-order passive intermodulation (PIM) with 850 MHz systems
One way that the Asia-Paci!c plan addresses these challenges is through guard bands and the use of dual duplexers. However, the arrangement of the dual duplexers still needs to be !nalized. Sub-band size and overlap will determine the various sub-band allocations that administrations can allocate. For example, Figure 7 shows a 5 MHz overlap, with some options for sub-band allocation following a 5 MHz raster. The smaller 20 MHz duplexer B is the higher band, which helps relax requirements on the UE !lters for protection of self-desensitization across the 10 MHz center band gap. It also helps the base transceiver station (BTS) !lter for the sharp roll-off required for protection of any adjacent Public Protection and Disaster Relief (PPDR).
Figure 7. Sub-band allocation options with APT 698 MHz to 806 MHz band plan
APT UHF (2x45 MHz, Conventional FDD)
Sub-band allocation options
698MHz 703 728 748 758 783 788 803
806733
45 MHz 10 MHz5 MHz 3 MHz
45 MHz
A10 MHz
A10 MHz
A10 MHz
B10 MHz
B5 MHz
A20 MHz
B20 MHz
A5 MHz
A15 MHz
A15 MHz
B15 MHz
A5 MHz
A15 MHz
A10 MHz
B15 MHz
A5 MHz
A20 MHz
B10 MHz
B10 MHz
A10 MHz
A10 MHz
A10 MHz
B10 MHz
B5 MHz
A20 MHz
B20 MHz
A5 MHz
A15 MHz
A15 MHz
B15 MHz
A5 MHz
A15 MHz
A10 MHz
B15 MHz
A5 MHz
A20 MHz
B10 MHz
B10 MHz
Duplex B -Uplink 20 MHz
Duplex B -Downlink 20 MHz PPDR
UplinkDuplex A -Uplink 30 MHz
Duplex A -Downlink 30 MHz
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4.1.1 Digital TVThere are three digital terrestrial television broadcasting (DTTB) systems in the world. They include Digital Television (DTV), developed in the United States; Digital Video Broadcasting – Terrestrial (DVB-T), developed in Europe; and Integrated Services Digital Broadcasting-Terrestrial (ISDB-T), developed in Japan. This section considers interference of APT700 with DVB-T and ISDB-T.
DVB-TInterference can occur when IMT services (based on LTE) co-exist with digital TV systems (based on DVB-T) adjacent to the lower end of the band. This can happen with either a 5 MHz or a 9 MHz guard band in the APT700 band plan. The potential interference scenarios include:
Scenario 1: Interference from LTE UE transmitter to DTV receiver Scenario 2: Interference from DTV station transmitter to LTE base station
Alcatel-Lucent conducted system-level probabilistic simulations, following the methodology of TR36.942, with deviations for certain parameters agreed on by the AWG Correspondence Group.2
The scenario we considered was for interference from LTE UE transmitters to 8 MHz DVB-T receivers for Sub-Case b in a suburban area. That is, an outdoor LTE UE Tx is interfering with DTV Rx with an outdoor rooftop antenna at a minimum distance of 10 meters.Worst case assumptions were used for the LTE UE OOB emissions, power control implementation and UE scheduling.An adjacent channel interference ratio (ACIR) approach was used. However the LTE UE adjacent channel leakage ratio (ACLR) (OOB emissions) levels dominated ACIR impact.
We observed that the 9 MHz guard band with 5 MHz LTE UE transmission bandwidth case had negligible impact on 8 MHz DVB-T receive quality. In addition, in a realistic LTE deployment, the number of simultaneously transmitting LTE user devices would not exceed 25, and the transmit bandwidth at the coverage edge would not exceed 5 MHz (25 RBs). Therefore, we considered the corresponding UE OOB maximum emissions from this scenario, which were –21 dBm/8 MHz, as an appropriate limit for protection of adjacent DVB-T reception for all band scenarios. To account for other DVB-T system bandwidths in the region, this level would translate to –21.4 dBm/7MHz and –22 dBm/6MHz.
2 AWG-11/INP-17
Figure 8. Potential interference among APT700 broadcast and cellular systems
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To maintain this limit for all LTE channels (up to 20 MHz), additional !lter attenuation of at least 13 dB would be required in the DVB-T receive band.
ISDB-TA recent analysis conducted by the government of Japan examined interference between a digital ISDB-T and IMT (uplink and downlink) in the 700 MHz band. The study con-sidered protection ratios and overload threshold values for ISDB-T as noted in Table 2. A comparison of these parameter values with those of DVB-T in the ITU-R Joint Task Group 4-5-6-7/126 revealed that the parameter values for DVB-T are similar to those for ISDB-T3. As a result, the sharing and compatibility studies based on DVB-T can also be applicable to ISDB-T.
Table 2. Findings of a study examining protection ratios and overload threshold values for ISDB-T
Interferer offset N/(MHz)
LTE base station LTE user equipment
PR (dB) Oth (dBm) PR (dB) Oth (dBm)
Co-channel (AWGN) 20.2 - 20.2 -
Co-channel (LTE) 20 - 19.5 -
1/(9 MHz) -22.5 -12 -4.2 -20
2/(15 MHz) -34.9 -10 -9.8 -17.5
4/(27 MHz) -36.2 -8 -32.5 -16
6/(39 MHz) -37.2 0 -50.1 -15.5
18/(111 MHz) -38.9 0 -46.9 -6
19/(117 MHz) -38.9 0 -45.8 -7
Note: PR and Oth values for a 6 MHz ISDB-T 64-QAM with code rate 7/8 signal interfered with by a 10 MHz LTE base station or user equipment signal in a Gaussian channel environment for all tuners and traf!c loadings
4.1.2 LMR PPDRStudies conducted in AWG during the development of the APT digital dividend band plan focused on interference issues with the existing narrowband public safety systems above 806 MHz. Those studies found that “Using the study from ECC Report 131 as a basis, it appears feasible for the 806 MHz to 894 MHz frequency to be used for mobile broadband services including for PPDR applications.”4
4.1.3 Cross-border (US band and APT band)Along the US-Mexican border, inconsistencies between the US and APT700 FDD band plans will cause interference requiring carefully coordinated radio planning to mitigate. The dif!culties are evident in the comparative band plan shown in Figure 9. It illustrates the US band plan with 3GPP bands 12, 13, 14 and 17 on the top. The APT700 FDD Band 28 plan appears below. Between them, the frequency regions of particular interference concerns are shown as arrow where the US downlink is on the same frequencies Mexico uses for uplink (between 716 MHz and 748 MHz). So existing US base stations transmit directly on frequencies the Mexican base stations will otherwise use for uplink reception. The spectrum from 776 MHz to 803 MHz has Mexican base stations potentially injecting co-channel interference into base station receivers on the US side of the border, as
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well as into some public safety !xed receivers. These regions of spectrum require close coordination of base station placement and antenna orientation to reduce the incidence of interference. At a minimum, some “buffer zone” is needed where the operator in one nation’s system would be overly desensitized by co-channel interference from base stations across the border. Negotiation between operators can bene!t everyone, because the harm is reciprocal. Judicious down-tilting of antennas near the border would be helpful, as would placing antennas near the border but directed toward the serving areas, probably with fewer sectors than normal, as shown in Figure 10. The !gure (which is not to scale) illustrates two-sectored towers near the border and conventional three-sectored antennas far from the border. Operators may also place smaller cells near the border, and indoor cells may be located particularly close to the border. In this case, the building-penetration loss contributes helpfully to the antenna isolation needed to obtain an agreed-upon desensitization level.
Figure 10. Mitigating co-channel interference along the border through careful RF planning
Border
There are ranges of frequency where the uplink-downlink orientation will be the same on both sides of the border, as shown in Figure 9 (703 MHz to 716 MHz for uplink and the US public safety downlink blocks). This is not helpful to the US C Block operator, but the Mexican operator in the lower 13 MHz of the spectrum will bene!t. Some co-channel interference will still occur, approximately the same degree of interference that arises near any service area boundary. In these cases, operator coordination of power-#ux density, at ground level near the border region, can be agreed upon and controlled through antenna orientation. Unfortunately, because the channelization is not exactly
Figure 9. Potential interference between US and APT700 band plans
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the same, and bands are different, one country’s UE may drag a call into the neighboring country without intersystem handoffs to return the terminal to the lowest transmit power levels.
Adjacent channel interference can arise across the border, as shown in Figure 11.
Through careful analysis of these adjacent channel interference (ACI) cases, we have found that the standard Adjacent Channel Leakage Ratios (ACLR) and Adjacent Channel Selectivity (ACS) are such that the buffer regions needed to protect against ACI are smaller than the buffer region needed to protect against co-channel interference considered earlier. In addition, the restrictions on the channels that are “in accord” limit the bandwidth of operation to 10 MHz uplink in !lter 1 (703 MHz to 713 MHz) and, provides an additional guard band, protecting against adjacent channel leakage into the other country’s system.
Currently, these co-channel interference scenarios are not insigni!cant, and negotiations are made more dif!cult by the substantial existing deployment of systems on the US side. However, the reciprocity of the interference should motivate negotiations as the Mexican spectrum is put to use, and coordination of the radio network planning can proceed among the operators. The increasing availability of small cells (Alcatel-Lucent metro cells and indoor cells) provides new and very useful tools for radio planning and should help mitigate the size of the exclusion zones near the border.
Alcatel-Lucent’s use of frequency selective scheduling (FSS) tends to mitigate interference by scheduling physical resource blocks (PRBs) that are somewhat “orthogonal” to those of an interfering source that may overlap the channel. Some important interference mitigations have used “over provisioned PUCCH” to reduce ACLR in bands with particularly onerous emission leakage regulations.
In addition, Alcatel-Lucent has spearheaded research in interference rejection combining (IRC) to greatly reduce interference in the uplink, by making use of multiple receiver diversity branches. The direction of arrival (DOA) of noise (or more generally the spatial noise covariance among antenna columns) is used to solve the minimum mean squared error (MMSE) criterion to derive the complex weights on the multiple antenna columns, essentially steering nulls toward interfering sources. This method helps optimize the signal to interference plus noise ratio (SINR) by reducing the interference, “I,” as well as increasing the signal, “S.” It is distinct from the Maximum Ratio Combiner which optimizes the SNR only.
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There may be other cases where FDD and TDD versions of the APT700 bands are used in adjacent countries. However, the economics have favored FDD systems, reducing the number of instances of this discrepancy, for example, to regions along the Chinese borders.
Troublesome cross-border interference issues may be dealt with using the tools and methods just discussed to ef!ciently minimize the buffer zones with the acceptable performance penalties.
4.1.4 GPSAs mentioned in section 3.2.2, the APT700 FDD band plan places the downlink in the spectrum from 758 MHz to 803 MHz. Harmonics from these powerful downlink signals can be a concern for operations in the lower L band (second harmonic) and the SDARs band (third harmonic) where Sirius-XM have international operations. The second harmonic is of particular concern for signals in the upper !lter 2 duplexer region, because it includes the GPS Radio Navigation Satellite Services (RNSS). These sensitive receivers are tuned to listen to very weak satellite signals centered at 1575.42 MHz and with substantial bandwidths of many megahertz. Moreover, these receivers are often used in close proximity to mobile handsets and may even be built inside the same smartphones.
This is a design challenge for the upper C Block terminals used in the United States. However, with care and by sampling the GPS receiver during those time slots when the UE is not transmitting, adequate performance can be obtained. The larger power levels used in the base stations tend to generate correspondingly larger harmonic products, if care is not taken in the connection and installation of base station radios and their antennas. Passive harmonic generation from poor connectors, water ingress or even “rusty bolts” on the antenna mounts and structure have been found to generate deleterious harmonic products. Provided that good installation practices are followed, however, this should not be a problem, particularly for conventional macro cells with antennas that are some distance from the GPS receivers. Metro cells and other small cells must be considered carefully, so that they are not mounted too close to locations where GPS receivers may need to operate.
In sum, when compared with the US plan, the APT700 plan:Signi!cantly reduces the DTV interference concernImproves the interference scenario with PPDRManages the harmonic interference issue with GPS receiversOffers larger bandwidth to facilitate LTE deployment up to 20 MHz FDD or TDD channelsPotentially delivers respectable economies of scale, especially if Japan also manages to clear the 698 MHz to 806 MHz rangeMitigates self-desensitization by employing the dual duplex band plan to increase the duplex gap
The APT700 plan does not completely eliminate the challenges described here. However, it does signi!cantly reduce their impact. Careful consideration and planning must, as always, be used when deploying systems according to this plan.
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4.2 Global roamingTo take into account the needs of African and Arab states, the recent World Radio Conference (WRC-12) extended the Region One (Europe, Africa and the Arab States) mobile allocation to allow for IMT (790 MHz to 862 MHz). Essentially the conference expanded the Region One allocation to include the Region Three (Asia Paci!c - APT) allocation (698 MHz to 804 MHz).
Since the WRC-12 decision, many European operators and administrations have been arguing that the APT700 plan for Region Three should now be modi!ed to take into account the two Region One mobile allocations. Figure 12 shows one suggested arrangement.
Figure 12. Suggested modification to the two band plans
703 733 758 788
718 748 773736 791 803
791 821 832 862
APT ‘A’ - lower APT ‘A’ - upper
APT ‘B’ - lower APT ‘B’ - upper
CEPT - lower CEPT - upper
Harmonization of the APT700 band plan within the Caribbean and Latin America (CALA) region is essential for intra-region roaming purposes. In Mexico, most visitors and roamers are from the United States, but in other countries, the bulk of visitors and roamers come from within CALA and from Europe, as shown in Table 3.
Table 3. Visitors and roamers’ origin for CALA’s five largest countries
Percent of Visitors and Roamers
Brazil Mexico Colombia Argentina Peru
CALA 34% 2% 56% 55.5% 38%
NAR 15% 83% 27% 16.0% 19%
EU 32% 14% 17% 14.0% 32%
APAC 1% 1% 0% 1.5% 6%
Others 18% 0% 0% 13.0% 5%
Total 100% 100% 100% 100% 100%
There are then three different cases to support roaming into the CALA region:Roamers from the United States and Canada will use the US band plan.Roamers from APAC will use the APAC band plan.Roamers from Europe will use the 800 MHz band.
It will be challenging to have terminals supporting all the different band plans for the lower LTE frequencies. At some point, terminals will probably support both the US and the APAC700 band plans, but this will increase terminal complexity and cost.
Based on the data in Table 3, APAC roamers into CALA are limited, so roaming is not a major driver of the band-selection decision. However, adoption of the APT700 band plan
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within CALA would clearly help cut down on device costs, offer operators more spectrum and limit the interference issues that may arise with the US band plan.
Most of inter-regional roaming will not be achieved through the use of terminals supporting two or three different band plans for the lower frequencies, but rather through other bands, such as the AWS band for roamers from the United States and Canada and the 1.8 GHz and 2.6 GHz band for roamers from other countries. The 1.8 GHz and 2.6 GHz band will surely play a major role for international roaming and should be supported by most devices.
4.3 Dual duplexers in terminal equipmentDuplex !lters are needed to isolate the transmit and receive signals, saving the sensitive low-noise receive ampli!er (LNA) from being overloaded or desensitized by the strong transmit signal. They also help reduce out-of-band emissions from the transmit chain to meet regulatory requirements reducing interference with other products in other bands. Ideally, the duplex !lter’s receive side would pass the entire 45 MHz receive band and the corresponding 45 MHz transmit band as is done in the base station.
Unfortunately, among the current !lter technologies appropriate for handsets and tablets, duplexers are limited to operating over no more bandwidth than about 3.5 percent to 4.2 percent of the operating frequency.5 This corresponds to bandwidth no greater than about 26 MHz to 30 MHz, due to the material limitations of modern Surface Acoustic Wave (SAW) and Film Bulk Acoustic Resonators (FBAR) !lters. Because of these limitations, UEs will implement Band 28 with two sub-bands corresponding to the two overlapping !lters shown in Figure 7.
The sub-bands also make the duplex gap easier for the !lters in the UE to handle. So, instead of a 10 MHz duplex gap, each of the two duplexers has an easier transition of 25 MHz (758 MHz to 733 MHz). As a result, the !lter is smaller and somewhat lower in cost than those needed in the US band plan. This approach promotes the goal of having all Band 28 UEs equipped with both duplexers and supporting the entire APT700 band, thus providing for global roaming, including roaming among operators, and UE versatility. This larger ecosystem of dual-duplexer RF front-end modules (FEMs) helps to reduce costs further. (Doubling the quantity of units of the same model tends to reduce costs by about 18 percent.6)
4.4 Antenna sizeLike !lters, antennas are limited in their usable fractional bandwidths. If handset antennas are made to operate over a fractional bandwidth in excess of about 10 percent to 12 percent, then ef!ciency drops substantially. Some modern handset antennas compensate for this somewhat by often using a different feed point for transmit and receive bands. More recently, some tuning networks load the antenna differently for different channels of operation to essentially “retune” the antenna for whatever part of the band is in use. In these ways, the entire 700 MHz band can be served with a single antenna structure for each of the two diversity paths required of LTE terminals. For receive diversity, the handset uses two of the antennas, which are roughly about l/4 in size (for a quarter-wave monopole.) This is about 100 mm in length, which !ts nicely on the two sides of a mobile phone.
5 IWPC Mobile RF Filter Group !ling of Don Brown, November 27, 2012, FCC ¿OLQJ in Docket No. 12-268, http://apps.fcc.gov/ecfs/document/view?id=7022066310
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5. ALCATEL-LUCENT APT700 SOLUTION As a global leader in LTE, Alcatel-Lucent is developing solutions that take full advantage of the APT700 band plan.
5.1 Solution component overviewAlcatel-Lucent has built the world’s largest and busiest LTE networks in record time and has the experience to get operators to market fast. Our wireless IP solutions and lightRadio™ Network portfolio has enabled operators to deliver an ultra-broadband experience with the capacity and dedicated performance needed now and into the future. Our global leadership in wireless and wireline technologies such as IP backhaul and transport solutions, small cells and LTE allow operators to stay ahead at every step, and our services ensure fast, right-the-!rst-time deployments.
Alcatel-Lucent is committed to the APT700 band plan with products supporting this band becoming commercially available in 2014. The Alcatel-Lucent LTE solution includes a full range of products supporting macro cells, metro cells, enterprise cells and residential cells, with the aim of providing capacity and coverage while achieving higher spectrum utilization and an improved user experience.
To ensure early availability of an end-to-end LTE solution, including the network and associated devices, Alcatel-Lucent has developed strategic partnerships with multiple device solution partners, including ASIC vendors and device OEMs. These partnerships will help enable LTE multimode devices (FDD and TDD) for global carriers.
To enable a wider device ecosystem for the APT700 band, Alcatel-Lucent will perform the required interoperability of the vendor ASIC platform with the Alcatel-Lucent infrastructure as chipsets become available. Alcatel-Lucent will execute testing, as required by the carrier for the customer’s preferred devices, to ensure interoperability testing (IOT) compliance and availability of an end-to-end LTE solution for the APT700 band.
5.2 Solution benefitsAlcatel-Lucent is at the forefront of macro cell and small cell innovation. In anticipation of the APT700 band plan, new radios will support operators that choose to deploy in this spectrum. These radios leverage unique capabilities speci!c to this band plan. For instance, the Remote Radio Head (RRH) !lter has a unique ability to address the full band (45 MHz) in a single radio. As a result, it avoids the space requirements and costs associated with multiple radios that can only satisfy part of the spectrum band. For example, three carriers of 15 MHz can be implemented on a single radio.
The radios also provide four receive branch diversity to enable better coverage and lower total cost of ownership. In addition, by avoiding interference through the use of new !lters, the radios enable co-existence with other bands, including GPS, Wi-Fi, Band 26 and other high-band radios, allowing for #exible deployments. As with other RRHs, the compact size enables deployments closer to the antennas, which reduces signal loss and requires less power. An innovative design also allows the new platform to evolve to support other bands, like 800EDD or future European bands making use of common assets. It can also support other form factors, that is, transmit receive duplexer unit (TRDU), higher power ampli!ers and evolution to LTE TDD, making the solution quite #exible for different deployment scenarios.
6. CONCLUSION The strong interest in and adoption of the APT700 band plan has demonstrated a desire for global harmonization. The unique characteristics of a low-frequency, sub-1 GHz spectrum make it ideal for providing both outdoor and indoor coverage, because of its excellent propagation characteristics, in both rural and urban environments. Of the three sub-1 GHz band plans, the APT700 plan is expected to show the highest growth in the coming years.
The APT700 band plan paves the way for economies of scale for devices and network infrastructure. It also delivers improved spectrum ef!ciency and roaming, and it enables additional capacity to support new mobile broadband services. The band plan also offers many economic and technical advantages.
The deployment of APT700 band networks will be dependent on the timing of frequency auctions and the availability of UE to support this band. Band Class 28 commercial devices (data solutions) are currently expected to be available by mid-2014. High-end devices, including smartphones and tablets, will start rolling out in the late 2014/early 2015 timeframe. With this anticipated timeline for the Band Class 28 device ecosystem, LTE carriers are likely to start deploying APT700 networks in the second half of 2014 with commercial launches expected in 2015.
As a leader in LTE, Alcatel-Lucent is developing solutions that take full advantage of the APT700 band plan. The Alcatel-Lucent LTE solution includes a full range of products supporting macro cells, metro cells, enterprise cells and residential cells that collectively provide capacity and coverage while achieving higher spectrum utilization and an improved user experience.
7. ACRONYMSACLR Adjacent Channel Leakage Ratio
AMPR Additional Maximum Power Reduction
APAC Asia Pacific and China
APT Asia Pacific Telecommunity
ASIC Application Specific Integrated Circuit
AWG Asia Pacific Telecommunity Wireless Group
BC Band Class
BS Base Station
CALA Caribbean and Latin America
CPE Customer Premise Equipment
DTTB Digital Terrestrial Television Broadcasting
DTV Digital Television
DVB-T Digital Video Broadcasting - Terrestrial
EDD European Digital Dividend
EMEA Europe, Middle East and Africa
FDD Frequency Division Duplex
TDD Time Division Duplex
GB Gigabyte
GHz Gigahertz
GPS Global Positioning System
GSMA Global System for Mobile Communications Association
ISDB-T Integrated Service Digital Broadcasting – Terrestrial
