10
SPECTRUM FOR MOBILE TV SERVICES
All progress is precarious and the solution of one problem brings us face to face with another problem.
—Martin Luther King
All the wireless technologies are dependent on the use of the spectrum to deliver the content to the intended users. The use of spectrum has a long history dating back to the use of the radio waves for wireless communications and broadcasting.
The delivery of mobile TV over the airwaves requires the transmission of QCIF or QVGA content that has been appropriately coded using H.263, MPEG-4, WMV, or H.264/AVC standards. This presents the need to transmit or stream a data stream, which can vary from a bit rate of 64 to 384 kbps or even higher depending on the exact technology used and the resolution selected. The rapidly growing interest in bringing up networks that can deliver mobile TV has led to the search for appropriate spectrum to deliver these services in the shortest time frame.
Operators of services based on different technologies such as 3G, digital audio broadcasting (DAB), wireless networks (wireless LANs), and terrestrial digital TV (i.e., those offering DVB-T) have all adapted varying approaches to be able to find and deploy spectrum quickly, in coordination with the International Telecommunications Union (ITU) as well as their national frequency allocation bodies.
Allocation of spectrum for various services has always been an area of considerable attention from the service providers as well as the users. This is not surprising considering that the spectrum is a limited resource. The approach for allocation of spectrum is now globally harmonized with the ITU, through a consultative process allocating globally harmonized bands for various services while leaving country-specific allocations to the governments. The specific allocations vary from country to country with the underlying principle of optimizing the utilization of this resource, noninterference with other users, and development of new services. There is also a need to coordinate the use of spectrum beyond national borders, i.e., internationally. The allocation of spectrum goes hand in hand with the technical specifications for the services and intended usage. The international coordination of spectrum is done under the aegis of the ITU.
The challenge of spectrum allocation lies in the fact that there is need to cater to a range of continuously evolving new technologies: mobile phones, 3G, WCDMA, mobile broadcasting, wireless, digital TV, and others. Moreover the evolution of technologies continues to bring forth new requirements on the use of spectrum, which need to be coordinated and allocated.
The ITU-R (ITU–Radio Communication) is the body responsible for management of the radio frequency spectrum and a large number of services such as fixed services, mobile services, broadcasting, amateur radio, broadband, and GPS as well as a range of other services. ITU’s radio regulations serve as reference points for all regulators for allocation of spectrum.
Allocation of spectrum for varying services has always been a consultative process with all stakeholders from all countries meeting under the aegis of the WARC (World Administrative Radio Conference) and recommending spectrum use for various services. In addition to the WARC at the apex level there are regional radio communication conferences, which also focus on recommendations of allocation of spectrum on a regional basis. The individual countries are then responsible for making allocations within their own country based on criteria that they wish to adopt, such as auction or license or need-based allocation. Following ITU-based recommendations for internationally coordinated frequencies makes it possible to use the services uniformly in all countries. The use of GSM spectrum in the 800- and 1800-MHz bands is an example of such coordinated allocation which, makes roaming possible worldwide. There have been exceptions to such allocations being done globally due to historical reasons such as in the United States, where GSM networks operate in the 1900-MHz band (Fig. 10-1).
FIGURE 10-1 Technology-Based Use of Spectrum for Mobile TV
The WARC meets periodically, and gaps in between the meetings have been traditionally due to the consultative process involved. But this has not been ideally suited to services such as mobile TV and multimedia broadcasting, which are growing rapidly with ever-increasing need for spectrum, and country-based approaches to allocation for various services are common.
10.2 BACKGROUND OF SPECTRUM REQUIREMENTS FOR MOBILE TV SERVICES
10.2.1 Spectrum for 2G Services
The bands that have been recognized internationally (with country-specific exceptions) for 2/2.5 generation mobile services are given in Table 10-1.
10.2.2 IMT2000 Spectrum
The spectrum for multimedia services under the IMT2000 was finalized by the WARC in 1992 and in 2000. These bands as well as the frequency arrangements associated with them are important, as adherence to these arrangements facilitates roaming. WARC ’92 allocated the frequency bands of 1885 to 2025 and 2110 to 2200 MHz for IMT2000. WARC 2000 subsequently identified additional bands in which, based on country-specific policies, the IMT2000 spectrum could be provided (Table 10-2).
The IMT2000 spectrum allocations were not done for any specific technology. Instead IMT2000 envisaged the use of five types of air interfaces, which could use the spectrum for providing the IMT2000 services. The air interfaces took into account the following interfaces:
International Allocations for 2/2.5G Mobile Services
• 3G GSM-evolved networks using the UMTS technology;
• 3G CDMA-evolved networks using the CDMA2000 and other evolved technologies;
• TDMA-evolved networks (UWC-136), primarily for the U.S. TDMA networks; and
• digital cordless networks (DECT or CorDECT) (Fig. 10-2).
The ITU also recommended paired frequency arrangements for specific services in order that the IMT2000 use could be globally harmonized.
IMT2000 Frequency Bands as Ratified by the ITU (M.1036)
WARC ’92 |
1885–2025MHz |
2110–2200MHz |
WARC 2000 |
806–960MHz |
1710–1885MHz |
2500–2690MHz |
FIGURE 10-2 IMT2000 Terrestrial Interfaces (ITU-R)
There have been developments since then, which have turned the spectrum allocators’ attention to the requirement of new allocations needed to permit the growth of mobile TV services. First, the 3G services themselves had been planned for the use of the Internet and multimedia. The 3G as originally envisioned provided for the use of 144 kbps multimedia services at higher speeds of travel, 384 kbps for outdoor use with pedestrian speeds, and 2 Mbps for use indoors in a stationary environment. The widespread use of mobile TV in unicast mode has created new requirements for additional resources and spectrum. In the case of CDMA2000 these are in the form of 1×EV-DO or a data-only carrier that can carry broadcast or unicast mobile TV services. In the case of UMTS the migration to new service modes such as HSUPA and MBMS is generating the requirement of additional spectrum.
However, with the realization that 3G networks were not the only ones best suited to provide live TV and also with the broadcasters moving in to have direct access to mobile handsets, bypassing the regular 3G spectrum, the need arose for additional bands, so far used for TV broadcast, to be allocated for the use of mobile TV services together with the air interfaces and approved modulation techniques.
The DVB-H technologies are a manifestation of this type of demand for which the spectrum earmarked for broadcast is now being allocated on a country-by-country basis.
Other services have relied on preallocated spectrum, e.g., the DMB services have used the allocations for DAB spectrum, the existing digital audio broadcast service. The FLO technologies in the United States use 700 MHz spectrum, which is owned by MediaFLO as a result of winning previous FCC auctions, although the use of the technology itself is not limited to this frequency or band.
The potential growth of mobile TV using either the IMT2000 or the terrestrial broadcast networks had never been anticipated to reach the dimensions being envisioned now. In fact, even the growth of mobile networks themselves has exceeded all expectations. The number of installed telephones in India in 1992, when the mobile GSM technologies were introduced, was 6.5 million, after over 50 years of growth. In 2006, the industry was adding close to 6 million users in a month, the number that had been added in 50 years of fixed-line development, leading to a frantic search for spectrum. The situation in most countries has been similar.
Terrestrial television transmission systems in the VHF and UHF bands are also being digitized by using different technologies such as DVB-T, ATSC (in North America and Korea), and ISDB-T (in Japan). This has led to the simulcasting of analog and digital TV programs and consequently no space in the UHF and VHF bands to allocate to the simulcasting of mobile TV as well. This has, in part, led to varied approaches in allocation of spectrum for mobile TV services. Examples are the use of the DAB spectrum, which was meant for the digital audio broadcast services (as replacements of FM transmissions), by modification of the standards to support mobile multimedia and TV. The DAB-IP service by BT Movio and the T-DMB services are examples of such implementations. In other countries, such as the United States, where the ATSC transmissions cannot be used to carry mobile TV transmissions by sharing the spectrum and transmission infrastructure, broadcasters have had to fall back on their own spectrum, won as a result of auctions. The launch of DVB-H services by Modeo in the 1670-MHz band and HiWire in the 700-MHz band is the result of the urgent need to bring forth mobile TV services without waiting for the lengthy consultation processes on the common use of spectrum for mobile TV, which may become available in the future.
10.3 WHICH BANDS ARE MOST SUITABLE FOR MOBILE TV?
This is a difficult question to answer as there may not be much of a choice for a particular technology. Mobile TV is usually delivered on handsets, which are designed to operate in the 800-, 1800-, and 1900-MHz bands, having antennas built in for such reception. The use of other bands typically requires the use of additional antennas based on the frequency. Lower frequency bands require the use of larger antennas for effective reception. At the same time higher frequency bands are characterized by higher Doppler frequency shifts (proportional to the frequency) and higher losses (proportional to the square of the frequency). For the mobile environment, which is characterized by the handsets in motion at high speeds, the Doppler shift in frequency can be significant. The Doppler shift is given by the formula
Ds = (V × F/C) × cos(A)
where Ds is the Doppler shift, V is the velocity of the user, C is the speed of light, and A is the angle between the incoming signal and the direction of motion. The loss (L) is given by the equation
where D is the distance from transmitter, F is the frequency, and C is the speed of light (Fig. 10-3).
10.3.1 Path Loss
The second factor of importance is the operating frequency and the path loss. The path losses increase with the square of the frequency. Hence the path loss at 2 GHz (IMT2000 frequency band) is about 12dB higher than the UHF band at 0.5 GHz. This is compensated somewhat by the antenna size as the typical antenna in a handset at 2 GHz (with quarter wavelength) will have a gain of about 0 dBi, while an antenna at 0.5 GHz, where the wavelength is four times larger, will have a gain of – 10 dBi.
FIGURE 10-3 Doppler Shift and System Limits. Doppler-limited speeds for various systems are ATSC, 50 km/hour; UHF, 300 km/hour; and VHF, 500 km/hour
The third factor is the in-building penetration loss, which again increases with the frequency. The mobile TV-type applications also require a large bandwidth, which can be as high as 8 MHz for a DVB-H transmission. This has an impact on the transmitted power, which increases with the frequency.
10.3.2 Frequency Bands
The following are the characteristics of the frequency bands when viewed from the perspective of usage for mobile TV.
VHF band: The VHF band is used for T-DMB services in Korea. In this band the wavelengths are large (e.g., 50 cm) and hence antennas tend to be of larger size unless gain is to be compromised. However, the propagation loss is low and Doppler shift effects are insignificant.
UHF band: The UHF band implies the use of frequencies from 470 to 862 MHz and includes two bands, UHF IV and V. The upper UHF band is well suited from the antenna-length standpoint as mobile phones support antennas for the GSM 800 band. However, country-specific spectrum occupation for GSM 900 services may lead to these bands not being available. The Doppler shifts in the band are low enough to permit mobile reception at speeds of 300–500km/hour.
L-band: Spectrum in the L-band has been traditionally used for mobile satellite communications. Inmarsat has been using the L-band for maritime and land-based mobile communications. The L-band allocable slots include the 1450- to 1500- and the 1900-MHz bands. The propagation losses are very high in this band as is also the case for Doppler shift, limiting the receiver velocity to less than 150km/hour. The band is better suited to satellite-based delivery as the losses in this band are very high—rising with the distance from the transmitter. Hence, if used for terrestrial transmissions the range is quite limited due to higher losses at these frequencies.
S-band: The S-band is used for satellite-based DAB and DMB systems (e.g., S-DMB in the 2.5-GHz band). The signals are repeated by ground-based repeaters for delivery in cities and inside homes where the users may not have a direct view of the satellite. Owing to the high loss with distance, the usage is primarily for satellite-delivered transmissions and short-distance land-based repeaters such as within buildings and tunnels where satellite signals cannot reach.
Mobile TV services can be provided by a wide range of technologies and the spectrum used is dependent on the technology employed. Technologies such as the DVB-H are based on terrestrial transmission and can use the same spectrum as the DVB-T. The 3G technologies, which fall under the IMT2000, use spread spectrum techniques (i.e., WCDMA) and are based on the use of either the UMTS framework or the CDMA2000 framework. The IMT2000 has defined five types of radio interfaces that can be used to access the various bands. Broadly, the spectrum for mobile TV services falls into the following distinct areas based on the technology used:
• broadcast terrestrial TV spectrum as used for DVB-T and DVB-H services (UHF);
• broadcast spectrum used for DAB;
• broadcast television VHF spectrum (used for T-DMB services);
• 3G cellular mobile spectrum;
• UMTS;
• CDMA2000, CDMA2000 1×EV-DO, CDMA2000 3× and
• broadband wireless spectrum.
In addition, mobile TV services can be provided through broadband wireless using technologies such as HSDPA.
We now take a brief look at the features related to spectrum for various broadcast technologies.
10.4.1 Broadcast Terrestrial Spectrum
The spectrum for TV broadcasting has been assigned to the VHF (bands 1, 2, and 3) and UHF (bands 4 and 5). The bands lie in the following frequency ranges (some of these bands may be country specific) (Fig. 10-4):
• VHF band 1, 54–72MHz;
• VHF band 2, 76–88MHz;
• VHF band 3, 174–214MHz;
• UHF band 4, 470–608MHz;
• UHF band 5, 614–806MHz.
FIGURE 10-4 VHF and UHF Band Allocations
The use is country specific, with the band being divided into a number of channels with either 6-MHz spacing (NTSC) or 7- to 8-MHz spacing (PAL). The broadcast bands provide a total bandwidth of around 400 MHz, which provides around 67 channels at 6MHz. At higher bandwidths, the number of channels is lower. Traditionally the terrestrial TV broadcast band has been used for analog broadcasts, with the changeover to digital happening now. The changeover is at various stages in different countries, with changeover to be completed within the years 2009 to 2012. The lower VHF bands are not suitable for mobile TV transmissions due to the large size of the antennas needed and consequent impact on the handsets. The higher UHF band (band V, 470–862 MHz) is better suited owing to its proximity to the cellular mobile bands and consequent antenna compatibility (Fig. 10-5).
Mobile operators have urged the industry associations (e.g., GSM Europe) to identify one national layer of 8 MHz for multimedia services.
FIGURE 10-5 Terrestrial DTV and DVB-H
The GSMA has also sought the broadbanding of spectrum use in the UHF for broadcast of multimedia services.
The digital carriers share the same band as analog TV and can use adjacent channels subject to control of adjacent channel interference. The digital TV standards are ATSC for the United States (and other countries that follow the NTSC standards) and DVB-T for Europe, Asia, etc. The data rate that can be handled in DVB-T varies depending on the modulation scheme used (QPSK, 16QAM, or 64QAM) and forward error correction (FEC) and can vary from 4.98 to 31.67 Mbps.
10.4.2 DVB-H Spectrum
The DVB-H is designed to use the same spectrum as DVB-T services. It can, however, also operate in other bands as well (e.g., UHF or L-band). The actual assignments would be subject to country-specific licensing as much of the spectrum is needed for the digitalization of TV transmissions from the existing analog systems. For digital TV, the ITU has issued its recommendations for 6-, 7-, or 8-MHz systems (ITU-R BT.798.1).
FIGURE 10-6 DVB-H Transmission
The key advantage of DVB-H is the sharing of spectrum as well as the infrastructure for digital TV, because of which the additional costs for the rollout of mobile TV services based on DVB-H standards are minimized. However, owing to the transmission characteristics and the small antenna size in the DVB-H, repeaters may still be required in the area of coverage of the existing transmitter network.
The parameters for DVB-H are different from those of DVB-T for better propagation characteristics. The modulation scheme used is COFDM with 4K carrier mode and the data rate possible is 5–11 Mbps depending on QPSK or 16QAM modulation. This can support 20 to 40 or more audio and video services in one 8-MHz slot (25–384 kbps per channel). This is against 5 or 6 channels in the DTT multiplex of 3–4 Mbps per channel (Fig. 10-6).
The implementation of DVB-H is based on the use of the same DVB-T MPEG-2 multiplex by the DVB-H transmission streams or it can be an independent DVB-H carrier depending on the implementation. In the former case, the MCPC carrier that is being transmitted by an existing DVB-T carrier may undergo little change.
10.4.3 Spectrum for T-DMB Services
T-DMB services constitute terrestrial broadcast of mobile TV, audio, and data channels and are based on extensions to the DAB standards (Eureka 147) by providing additional FEC. The physical layer is based on the DAB standards. One of the primary reasons T-DMB is considered attractive in many countries is the fact that the services are designed to use the DAB spectrum, which has been allocated in most countries based on the WARC and country-specific allocations. This implies that the contentious wait to have spectrum assigned in the 3G or UHF bands is not an immediate hindrance in moving ahead with the services.
DAB or Eureka-147 spectrum consists of 1.744-MHz slots in the L-band (1452 to 1492 MHz) or the VHF band (233 to 230 MHz) as per international allocations (ITU-R BO.1114). (However it is important to note that many of the spectrum allocations and channel plans in the band remain country specific.) Most of the available commercial DAB receivers are available so as to be able to work in the VHF I, II, and III and L-bands (Fig. 10-7).
Commercial T-DMB services were launched in Korea in December 2005 for mobile TV and multimedia broadcast. The spectrum for the services was allocated in the VHF band III comprising VHF channels 7–13 in the frequency band 174–213 MHz. Initially two channels (of nominally 6 MHz each) were used for T-DMB transmissions, with each being further subdivided into three carriers of 1.54 MHz each. Thus two 6-MHz slots that were made available could be used by six operators.
FIGURE 10-7 DAB L-Band Allocations (DAB Allocations and Assignments Are Country Specific)
T-DMB services have also begun in Germany based on the technology developed in T-DMB Korea (Fig. 10-8). The T-DMB operation in Germany is in the 1.4-GHz L-band, which is the satellite allocation for DAB services. It is noteworthy that Germany already uses channel 12 in VHF for countrywide DAB broadcasting.
10.4.4 Spectrum for Satellite-Based Multimedia Services (S-Band)
As per the ITU allocations in the S-band, some frequencies have been reserved for satellite-based DAB or multimedia transmissions. These bands include (RSAC Paper 5/2005):
• 2310–2360 MHz (USA, India, Mexico) and
• 2535–2655 MHz (Korea, India, Japan, Pakistan, Thailand).
These bands are further subject to country-specific allocations.
The S-DMB systems are designed to use these bands for delivery of multimedia services directly to handsets as well as through ground-based repeaters.
FIGURE 10-8 T-DMB VHF Band Mobile TV Services (Korea)
10.4.5 Spectrum for 3G Services
UMTS has been adapted as the standard in Europe, with UMTS Terrestrial Radio Access (UTRA) being the access standard. Other countries such as Japan and the United States will also follow the same standard in selected networks. This uniform standard will permit roaming access as well in 3G networks. UTRA provides data access up to 2 Mbps, which makes possible broadband Internet or video services. The spectrum allocations for UMTS in Europe and as a part of the ITU recommendations of UMTS are as follows.
The spectrum for UMTS consists of 155 MHz of total spectrum of which 120 MHz comprises paired spectrum (60 × 2 MHz) and 35MHz comprises unpaired spectrum in the 2-GHz band. The paired spectrum use is mandated for WCDMA while the unpaired spectrum will be used by TD-CDMA. The following are the allocations that were made by WARC ’98:
The 1920- to 1980- and 2110- to 2170-MHz bands are used as paired spectrum for uplink and downlink, respectively, for UMTS (FDD, WCDMA). These bands are for terrestrial use. The bands are of 60MHz each and can be subdivided into 5-MHz FDD carriers. The carriers can be allocated to one or more operators based on traffic requirement.
The bands 1900–1920 and 2010–2025 MHz are for the use of terrestrial UMTS with TD-CDMA. The transmission in TD-CDMA is bidirectional and paired bands are not required.
The bands 1980–2010 and 2170–2200MHz are allocated for satellite-based UMTS using the FDD-CDMA technology. The bands are paired and the transmissions in this band (from or to satellite) follow the same interface as for terrestrial transmissions (3GPP UTRA FDD-CDMA) (Fig. 10-9).
10.4.6 Process of Allocation of Spectrum
Different countries have followed different approaches for the allocation of spectrum, the most common method being its auction. The alternative method is to allocate spectrum to service providers based on the license for providing such services. European countries went in for the auction of spectrum quite early and the bids for the slots for 3G were very high, placing considerable strain on the companies that had bid for the spectrum. In other countries, including India, the spectrum for 2G services is allocated based on subscriber base and a percentage of revenue share.
FIGURE 10-9 European Frequency Allocations—IMT2000
10.5 COUNTRY-SPECIFIC ALLOCATION AND POLICIES
In Europe most countries adopted a uniform method for allocation of spectrum by auctioning the 60-MHz band divided in 5-MHz blocks. Twelve slots of 5 MHz each were thus available for the operators who won them in auctions (Fig. 10-10).
10.5.1 UMTS Allocation Summary for Europe
• TD-CDMA 1900–1920 and 2010–2025 MHz time division duplex, TD-CDMA unpaired, channel spacing is 5 MHz (raster is 200 kHz).
• WCDMA 1920–1980 and 2110–2170MHz frequency division duplex (FDD, WCDMA), paired uplink and downlink, channel spacing is 5 MHz. (raster is 200 kHz).
FIGURE 10-10 UMTS Spectrum Allocation in Europe.
An operator needs three or four channels (2 × 15 or 2 × 20 MHz) to be able to build a high-speed, high-capacity network (Fig. 10-11).
10.5.2 Spectrum Allocations in the United States
2G and 3G mobile spectrum: Spectrum allocations in the United States can be categorized broadly in two bands called the “cellular” (850 MHz) and the “PCS” (1850–1990 MHz) bands. The growth of AMPS-based cellular mobile networks in the 1980s led to full utilization of the 850-MHz band, where the FCC had allocated as many as 862 frequencies of 30 kHz each. The spectrum for the AMPS services extended into the UHF band as well. The AMPS services evolved into D-AMPS in the same frequency bands. At the same time the FCC also permitted new technology-based personal communication services (PCS) in the 1850–1990 MHz as well. FCC gave freedom to the PCS operators to choose technology, i.e., CDMA, TDMA, or GSM. The PCS spectrum in the band of 1850–1990 MHz (i.e., total of 140 MHz) was allocated in six bands termed A to F (Table 10-3).
FIGURE 10-11 Worldwide IMT2000 Allocations
Allocation of PCS Band in the United States
Allocation |
1850–1990 MHz |
PCS A |
30 MHz |
PCS B |
30 MHz |
PCS C |
30 MHz |
PCS D |
10 MHz |
PCS E |
10 MHz |
PCS F |
10 MHz |
SMR |
10 MHz |
Total |
130 MHz |
As the operators had the freedom to select the technology, the cellular and PCS bands in the United States presents a mixture of GSM, CDMA, 3G, and other technologies. So far as the usage for IMT2000 is concerned these frequency bands along with the 800/850-MHz bands stand fully utilized, which has made it difficult for the FCC to allocate frequencies for the IMT2000 technologies in the 2-GHz band as per harmonized global allocations (as is the case in Europe and elsewhere). This has led the FCC to explore alternative bands that can be used for the 3G services and still have compatibility with other networks in use globally, which was the primary objective of the UMT2000 initiative.
IMT2000 spectrum in the United States: The UMTS spectrum bands as recommended by WARC 2000 and the ITU are already in use in the United States for existing cellular/PCS operators. Hence the 3G services have come up with sharing the 1900-MHz band with the 2G services. Cingular Wireless has launched UMTS services in the 1900-MHz band in the United States. There is a future plan for freeing up the spectrum in the UMTS band by the FCC. Until then the roaming and interoperability of the European/Asian systems with those in the United States will not be possible.
Operators having access to the 1900-MHz band (PCS band) and 850-MHz band have started using these bands for providing 3GPP WCDMA-based UMTS services. This includes T-Mobile (1900-MHz band), Cingular (1900- and 850-MHz bands), etc.
3GPP2 operators having CDMA-based systems are also moving to 3G (CDMA2000 and 1×EV-DO) based on the existing spectrum. Sprint operates its CDMA network in the 1900-MHz band.
At present both the cellular and the PCS bands have a variety of systems and air interfaces in use, which include:
• IS95A (CDMA),
• IS95B (CDMA with packet data),
• CDMA1×RTT,
• 1×EV-DO,
• GSM,
• EDGE,
• UMTS (3G), and
• HSDPA.
Advanced wireless services (AWS) spectrum auctions in the United States: In order to provide additional spectrum and enable the growth of advanced wireless services, including mobile TV, the FCC had auctioned spectrum in the 2 GHz band (1710–1755 MHz and 2110–2155 MHz). The auction of this band was completed in September 2006 and a total of 1087 licenses were issued to 104 bidders. This additional 90 MHz of spectrum now licensed will enable growth of 3G services, mobile data services and wireless extensions for cable TV services amongst other uses.
Digital audio broadcasting in the United States: Digital audio broadcasting is possible via two technologies, S-DAB (satellite DAB) and T-DAB (terrestrial DAB). The spectrum for DAB has been allocated by the ITU (WARC ’92) in the L-band of 1452–1492MHz (40MHz) for international use. This is for both S-DAB and T-DAB services to be used on a complementary basis. As per ITU Resolution 528, only the upper 25MHz can be used for S-DAB services. Further, as per the 2002 Maastricht arrangement in Europe, the band 1450–1479.5 is to be used for T-DAB and the balance 1479.5 to 1492 MHz is to be used for S-DMB services.
In the United States, the FCC has allocated the S-band (2320–2345MHz) for satellite radio services, which are being provided by Sirius and XM Radio (DARS). This allocation of 25 MHz permits 12.5 MHz to be used by each operator. The United States has developed the IBOC (in band on channel) standard for digital audio broadcasting. The standard has an ITU approval for DAB services. It uses the existing FM band of 88–108 MHz by using the sidebands of the existing FM carriers for additional digital carriers.
Spectrum for time division multiplexed television (TDtv) services: TDtv has been conceived to use the unpaired part of the 3G spectrum reserved for use with TDMA technologies. TDtv is a broadcast technology based on the use of technologies such as MBMS (3GPP release 6 defines the MBMS), which can be broadcast to an unlimited number of users. 3 UK, Telefonica, and Vodafone have already announced the launch of a technical trial of TDtv. The trial is based on the use of 3GPP MBMS and uses the UMTS TD-CDMA (unpaired spectrum) as the air interface.
Spectrum for MediaFLO services: Even in the 700-MHz band the FCC allowed some existing broadcasters to continue to use the spectrum for a limited period. This concession, which was valid until 2006, has now been extended until February 2009. Some of the existing operators such as Verizon Wireless are planning to use the 700-MHz band (6 MHz) using MediaFLO technology.
The MediaFLO services in the United States would operate in the 700-MHz frequency band, although there is no technology-specific limitation on the band of use.
MediaFLO is a subsidiary of Qualcomm and owns the 700-MHz spectrum as a result of winning it in spectrum auctions. The spectrum would involve the use of UHF channel 55 with 6-MHz capacity. The FLO network would function as a shared resource for U.S. CDMA2000 and WCDMA (UMTS) cellular operators to enable them to deliver mobile interactive multimedia to subscribers without incurring the cost of deployment and operation of a dedicated multimedia network. This implies that existing operators having CDMA 1×, 1×EV-DO, and WCDMA would be able to ride on the FLO network on a shared basis without their having to acquire any further spectrum, etc., on their own.
With respect to other countries, they would be able to use the same technology if the frequency bands comprising UHF channels 54, 55, and 56 are vacant or can be reserved for MediaFLO services.
Spectrum for DVB-H services—United States (Modeo): Modeo is planning to use the L-band at 1670 MHz with 5 MHz of bandwidth for its DVB-H services. Modeo has spectrum available at this frequency across the United States as a result of winning the spectrum auction in 2005.
10.5.3 Korea
In Korea the broadcasting system used is ATSC with 6-MHz bandwidth spacing in the UHF and VHF bands. For terrestrial mobile TV transmissions the Korean government has allocated channels 8 and 12 in the VHF band, corresponding to the frequencies corresponding to 180–186 and 204–210 MHz. The relatively low frequencies assigned allow larger areas of coverage and better mobility but the mobile phones are required to use a relatively large antenna. In the S-band, the S-DMB service of TuMedia operates in the band of 2630–2655MHz.
For mobile services, the spectrum in Korea is allotted on a fixed-fee basis rather than through auctions. Apart from the internationally harmonized bands Korea uses the 1700-MHz band for PCS in a manner somewhat akin to that for the 1900-MHz PCS band in the United States. The 1700-MHz PCS band is a paired band with 1750–1780MHz being the mobile-to-base station frequencies and 1840–1870 MHz being used in the reverse direction. Following are the operators in Korea:
• 2100-MHz band, KTF and SKT;
• 1700-MHz PCS band (Korean), LG and KTF; and
• 800-MHz band, SKT.
10.5.4 India
In India the digital terrestrial broadcasting services have not yet been opened up for private operators and the state-owned Doordarshan remains the sole terrestrial operator. All terrestrial transmissions are analog, with a few exceptions in the metro areas where DVB-T transmissions have commenced as free-to-air transmissions. Trials have been conducted for DVB-H services using the DVB-T platform in New Delhi and proved successful. Spectrum for terrestrial broadcasting has been provided in both the VHF and the UHF bands, but only a fraction of the available capacity is used for terrestrial broadcast services. It is expected that the DVB-H services will be launched on a commercial basis by the state-owned operator.
India had over 115 million mobile users by the middle of 2006, a majority of them being on the GSM networks. India uses the international GSM bands for the 2G networks. CDMA networks are also extensive in India, operated by Reliance Infocom and Tata Teleservices in addition to the state-owned operator BSNL. The CDMA networks use the 800-MHz band. Table 10-4 gives the spectrum used for the Indian mobile cellular services.
Spectrum Allocations in India for Cellular Services
The bands for allocation of 3G spectrum have also been finalized by the TRAI with auction as a mechanism for allocation. The 3G spectrum has been identified for both the 3G-GSM services and the 3G-CDMA services (such as EV-DO). The following are the highlights of the 3G spectrum allocation recommendations:
• 2 × 25 MHz of spectrum in the 2.1-GHz IMT2000 band to be allocated to five operators, each being given 2 × 5 MHz for 3G-GSM services;
• 2 × 10 MHz of spectrum in the 1900-MHz PCS band to be considered for allocation to 3G-CDMA operators after interference studies;
• capacity of the 800-MHz CDMA band to be increased by new channelization plan that permits accommodation of 2 × 2.5MHz carriers for EV-DO services;
• capacity in the 450-MHz band to be provided to CDMA and EV-DO operations (2 × 5 MHz);
• other ITU-recommended bands for 3G to be considered for future allocation.
10.6 SPECTRUM ALLOCATION FOR WIRELESS BROADBAND SERVICES
An important area emerging in the field of mobile multimedia delivery is that of technologies such as WiMAX. WiMAX can be characterized as fixed WiMAX (IEEE 802.16d) or mobile WiMAX (IEEE 802.16e). In Korea the Korean mobile WiMAX service based on IEEE 802.16e operates in the 2.3-GHz spectrum. The process of allocation of spectrum is continuing for the WiMAX services in various countries. Similarly, Sprint Nextel in the United States has commenced operation of its mobile WiMAX network through spectrum available to it through its earlier licenses in MMDS and its PCS network across the country. Owing to the high potential of WiMAX for mobile multimedia delivery the allocation of spectrum to it is engaging the attention of all countries.
There are a number of bands that have been proposed for WiMAX allocations by the WiMAX forum. These fall into the categories of fixed WiMAX and mobile WiMAX services (Table 10-5, Fig. 10-12).
WiMAX Spectrum Allocations
FIGURE 10-12 WiMAX Frequency Allocations (Not All Country Allocations Shown)
Korea was an early pioneer in using the WiMAX services after 100MHz in the 2300- to 2400-MHz band was allocated for WiMAX services. In the United Kingdom, the radio agency has awarded licenses in the 3.4-GHz band and Ofcom is planning additional spectrum in the 4.2-GHz band. In the United States, the FCC has opened the 3650- to 3700-MHz band for unlicensed WiMAX coverage. In Singapore and Hong Kong the 3.4-Hz band has been allocated for WiMAX services.
10.7 WILL MOBILE TV BE SPECTRUM CONSTRAINED?
The projections for mobile subscribers that had been made by the ITU as well as those of the services that would be provided on these networks fell far short of the actual growth. The growth in mobile customers has been almost exponential in many countries (e.g., India and China), thus placing constraints on the use of spectrum even for existing voice services. The 3G spectrum in the harmonized bands has also fallen short for distribution among various operators as well as for its utilization for large-scale mobile TV services.
The scenario is similar for broadcast-based technologies such as DVB-H, in that the UHF spectrum in most countries stands used for terrestrial broadcast TV or other services.
The WARC is set to review the allocations and make further recommendations for globally harmonized growth of 3G and broadcast network based services in its meeting in 2007. The matters that have already been set for examination include:
• future development of IMT systems and systems beyond IMT2000;
• the need for harmonized frequency bands below the currently prescribed bands, including those being used for various services;
• UHF and VHF spectrum allocations by regional radio conferences.
Spectrum is certainly one of the foremost issues governing the plans of operators in selection of technology as well as the plans for rollout of mobile TV networks. Urgent deliberations are on in various countries to find an early and harmonized allocation for growth of mobile TV services.