Disclaimer:
The samples provided in this section are for educational purposes only. The recordings do not necessarily reflect the current or historical situation in a country or a city.


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LTE 800 MHz Digital Dividend

Terrestrial TV Broadcasting can be found in the UHF band (174 - 230 MHz) and in the VHF band (470 - 862 MHz). Many countries decided to switch-off Analogue TV (PAL, SECAM, NTSC) in favor of more efficient digital systems such as DVB-T, ISDB-T or ATSC (GE06 agreement). WRC07 opened up a part of the digital dividend to IMT mobile services (790 - 862 MHz).

Germany was one of the first countries in Europe to tender the DD 800 MHz band in 2010. As a result, the spectrogram recorded in Munich shows the DVB-T signals next to the new 4G LTE carriers. Both Vodafone D2 and Telefónica O2 launched a 10 MHz LTE service.

DVB-T tuners or set-top boxes may suffer from LTE interference and 4G low-pass filters are provided to the public e.g. by BNetzA in Germany or at800 in UK. Furthermore, Programme-Making and Special Events users (PMSE) may also need to move to avoid noise degradation.

Photo: Olympia Tower, Munich, 23 January 2013
Olympia Tower Munich

LTE 1800 MHz Refarming

The 1800 MHz band is allocated to cellular services. For years, GSM technology is deployed in this band but nowadays Mobile Network Operators (MNO) start refarming their 1800 MHz frequencies to launch 4G LTE.

T-Mobile Germany covers the rural areas with LTE800 and the populated areas with LTE1800. The spectrogram from Munich shows how T-Mobile refarmed their GSM frequencies and deploys a LTE network with a 20 MHz bandwidth.

Refarming the 1800 MHz band is not always an easy task. GSM traffic must be migrated to other bands or networks and the mobile operator must have sufficient spectrum available (at least 2x 10 MHz, but 2x 20 MHz is preferred). Hence Vodafone D2 and Telefónica O2 have a disadvantage compared to T-Mobile and e-plus.
 
T-Mobile LTE coverage 800 MHz (left) and 1800 MHz (right) in Munich (snap-shot of January 2013)

4G TD-LTE and 3G TD-SCDMA

For reasons, China has always been a strong promotor of TDD technology. Its main carrier China Mobile deploys TDD-networks for 3G and 4G services. The smaller operators China Unicom and China Telecom focus primarily on FDD.

The Chinese 1800 MHz band houses an interesting mix of GSM, UMTS and LTE signals in FDD and TDD mode. The Shenzhen recording of the subbband 1805 - 1880 MHz downlink (paired with 1710 - 1785 MHz uplink) shows two FDD LTE networks. Also some legacy GSM can be found.

The subband 1880 - 1920 MHz is dedicated to TDD. China Mobile uses this band for a 20 MHz TDD LTE service and the remaining 20 MHz for its 3G TD-SCDMA network. Since TDD and FDD signales are unlikely to co-exist adjacently, 1875 - 1880 MHz will probably be maintained as guard band. Hence, China Telecom's 4G service is limited to 15 MHz bandwidth only.

CDMA450 and CDMA800

Until 2014, Myanmar (Burma) has been served by a single, state-owned operator MPT. Mobile penetration is very low (< 10%) and people use tele centers instead. MPT operates four networks: CDMA450, CDMA800, GSM900 and UMTS2100. The 1800 MHz band has not been licensed thus far.

The upper spectrogram shows a 3.75 MHz wide CDMA450 signal captured in Yangon (Rangoon). Some sidelobes are visible which may indicate a faulty transmitter of the base station. Uplink signals have not been detected.

The 7.5 MHz wide CDMA800 carrier in the lower spectrogram seems not compliant with the license. It has an offset of at least 1MHz, probably aligned to 869 MHz. This case stresses once more the importance of spectrum monitoring and enforcement.

Photo: Outdoor Tele Center, Yangon, 17 July 2013

Smilde High Tower Collapse

On 15 July 2011 two broadcast towers in the Netherlands caught fire on the same day. The Lopik tower (367 meters) survived the fire, but the Smilde tower (294 meters) collapsed. Terrestrial Radio and TV broadcasts were interrupted in large parts of the country for about 1 year. A temporary mast (100 meters) was erected in nearby Assen city to repair some of the lost coverage.

The sequence of events on the day of the Smilde collapse is clearly visible in the spectrograms.

The Smilde tower has been rebuild. Despite strong rumors, the cause of the fires has not been determined to date.

Photo: Stills from TV Drenthe News Broadcast, 15 July 2011

iDEN Mobile Network

Integrated Digital Enhanced Network, or iDEN for short, is a Motorola proprietary 2G network that became famous with business users for its Push-To-Talk service (PTT). iDEN has been deployed in over 20 countries, primarily in the Americas.

In Mexico, the iDEN network is operated by Nextel (NII). It uses the 806 - 821 MHz band for uplink and 851 - 866 MHz for downlink, giving it a 45 MHz duplex gap. The channel spacing is 25 kHz. iDEN supports up to 6 active calls on 1 channel (TDMA).

On the right side of the iDEN frequencies the 850 MHz band can be found (869 - 894 MHz). Originally home to Digital AMPS and cdma2000, it is now also used for GSM850 and UMTS850. Telcel (America Movil) deploys only UMTS850, while Movistar (Telefónica) operates both GSM850 and UMTS850 in Mexico city region.

Photo: Telmex public phone, Mexico City, 26 April 2014

ISM Band 2400 - 2483,5 MHz

Microwave ovens typically use 2.4 GHz frequency to heat up food and beverages. These signals could interfere with professional radio services and as such co-existence will not be possible. Therefore, the 2.4 GHz band is allocated world wide to ISM (Industrial-Scientific-Medical).

The most popular application is WiFi, but all sorts of SRD exist. The spectrogram shows signals from a microwave oven and a WiFi access point.

Photo: City WiFi, Luxembourg, 10 April 2010

OIRT Band 65,8 - 74,0 MHz

FM sound broadcasting in the Eastern Europe region was originally allocated in the OIRT band 65,8 - 74,0 MHz (OIRT = Organisation Internationale de Radiodiffusion et de Télévision). These countries nowadays deploy the standard FM broadcast band 87,5 - 108,0 MHz. In Russia however, the old OIRT band is still in use anno 2012.

The sample spectrogram above shows a recording from a monitoring site in Moscow. The time is between 9.30PM and 8.30AM. Nine radio stations were identified. Most of them are broadcasted from the Moscow Ostankino TV tower. Three stations cease their transmission during night hours.

A lot of interference can be seen in this spectrogram. The source was not identified, but is most likely of local origin.

Photo: Ostankino TV Tower, Moscow, 11 November 2012

3G 2100 UMTS Deployment over time

The market consolidation in the Netherlands resulted in three main players: KPN, Vodafone and T-Mobile. Telfort was bought by KPN and Orange was bought by T-Mobile. However, the merger of the UMTS licences caused some regulatory difficulties. KPN had to return to Telfort licence and T-Mobile was forced to fulfill the individual Orange licence conditions.

Together with the 3G UMTS traffic uptake, the spectrograms over the past years show an interesting development in the 2100 MHz band. UMTS carriers were switched on or off because of regulatory or traffic demand.

In-Band-On-Channel Digital Radio Broadcasting

While the migration from terrestrial Analogue TV (PAL/SECAM/NTSC) to Digital TV (DVB/ISDB/ATSC) runs very smooth, how different it is for Analogue Sound Broadcasting (FM/AM). The industry is strongly divided into 3 groups: do nothing, build up a new digital infrastructure (DAB/DRM) or upgrade the existing FM-networks. The latter is known as In-Band-On-Channel (IBOC), but no open standard is available to date.

The USA currently favours IBOC and two proprietary solutions can be found on air. The top left plot shows the HD Radio solution by iBiquity Digital Corporation. The recording was made in San Francisco at 94.9 MHz (30kW ERP / 357m HAAT). The HD Radio OFDM carriers are placed on either side of the analogue FM-carrier at ±130-200kHz distance. The neighbouring station at 95.7 MHz also has enabled HD Radio. The top right plot shows the analogue baseband (MPX) signal after demodulation which is not affected by the HD Radio technology.

The 2nd proprietary IBOC solution is FMeXtra by Digital Radio Express and is shown in the bottom two plots. The signal was captured in San Francisco at 88.5 MHz (110kW ERP / 387m HAAT). The FMeXtra technology places the OFDM carriers in the baseband (SCA), thus before FM modulation. Digital Radio Express claims that the modulation power will increase only little due to FMeXtra.

Non-licensed FM Broadcasting

Pirate radio stations are a common phenomenon in the northeastern part of the Netherlands. In the past these illegal broadcasters used self-build low-power transmitters, nowadays more and more professional high-power equipment is being deployed. Dipole antennas mounted on poles of 80 meters and higher are no exception anymore.

The spectrogram dated from 2005 shows that the pirate radio stations are mainly active between 94.0 MHz and 98.0 MHz. Illegal FM-transmitters can be identified easily from their irregular operating times as well as from their spectrum masks. Some pirate FM stations broadcast a few hours per day and sometimes only at night.

Operators of non-licensed broadcasting in the Netherlands risk high penalties.

Photo: Non-licensed FM-transmitter, the Netherlands, 21 April 2010

Big Small Cells


Photo left: Singapore, 1 June 2013
This antenna is mounted on a lamp post and pointing into the direction of a large appartment building. The basestation is probably intended to provide indoor coverage to a VIP subscriber.

Photo right: Mexico City, 5 July 2014
This full base station configuration is installed on a very low pole behind a bus stop. Its purpose becomes not clear directly, but most likely the neighbourhood did not agree on a higher position.

Photo left: Stockholm Sweden, 24 June 2015
To protect the city's historic profile, the properties facing the Stockholm harbour cannot have antennas on top of them. Basestations are thus build on low beach-houses at the boulevard, like this one here.

Photo right: Hong Kong, 1 August 2015
The combination of macro cells and small cells can become dififcult to manage if not setup properly. This example shows how both layers have a line-of-sight path resulting in too much interference.