3G spectrum

3G Spectrum

When you read about radio spectrum this means a range of radio frequencies. The bandwidth of a radio signal is defined as being the difference between the upper and lower frequencies of the signal. For example, in the case of a voice signal having a minimum frequency of 300 hertz (Hz) and a maximum frequency of 3,300 Hz, the bandwidth is 3,000 Hz (3 KHz).
The amount of bandwidth needed for 3G services could be as much as 15-20 MHz. Compare this with the bandwidth of 30-200 KHz used for current 2G communication and you can see that there is as much as a 500-fold increase in the amount of bandwidth required. Now you can appreciate why radio spectrum has become such a precious and scarce resource in the information age - everybody from television broadcasters to the military wants spectrum, and it is in short supply. Michael Powell, the chairman of the U.S. Federal Communications Commission (FCC), has suggested that spectrum demand "is going to forever outstrip supply". The telecoms operators have had to buy 3G spectrum from governments around the world, and those governments - realising that they own a precious, valuable resource - have sought to sell that spectrum at the highest possible price.
Radio spectrum is often organised (and sold) as paired spectrum - a bit of spectrum in a lower frequency band, and a bit of spectrum in an upper frequency band (see the section on 3G Technology for an explanation of paired spectrum). Paired spectrum is often specified in a form like "2x15MHz" meaning 15MHz in a lower band and 15MHz in an upper band. This technique of two users talking to each other on two separate frequencies is called Frequency Division Duplex, or FDD (see the section on 3G Technology for an explanation of FDD). W-CDMA is an FDD technique (i.e., it requires paired spectrum) whereas TD-CDMA is a TDD technique (i.e., it can use unpaired spectrum).

Europe

CDMA2000 1X is very flexible in its spectrum requirements being designed to operate on all existing allocated spectrum for wireless communications. Unfortunately, the same cannot be said for UMTS which is quite specific about its spectrum requirements (this has resulted in the recent European bidding wars for UMTS spectrum). It has been suggested that choosing the rigid spectrum requirement for UMTS was a political move, aimed at creating a new export engine for Europe. CDMA2000's spectrum flexibility is one reason why the operational 3G systems have so far used CDMA2000 1X (also because CDMA2000 systems are being implemented on existing CDMA (CDMAone) networks).
UMTS specifies the bands 1900-2025 MHz and 2110-2200 MHz for 3G transmission. The satellite service uses the bands 1980-2010 MHz (uplink), and 2170-2200 MHz (downlink). This leaves the 1900-1980 MHz, 2010-2025 MHz, and 2110-2170 MHz bands for terrestrial UMTS (see the diagram below):



Diagram based on UK Official Licence Auction Site: Information Memorandum (3G Mobile Appendix)
As can be seen from the diagram, UMTS FDD is designed to operate in paired frequency bands, with uplink in the 1920-1980 MHz band, and downlink in the 2110-2170 MHz band. UMTS TDD is left with the unpaired frequency bands 1900-1920 MHz, and 2010-2025 MHz.
The UK Government auctioned five licences in these UMTS bands (for details, see the official UK licence auction site). After 150 rounds of bidding, the licences were sold for extraordinary sums (let's just say the "Buy-2-Get-1-Free" offer did not prove popular ...):

Licence Name	Frequencies	Winner	Final Amount Bid
Licence A (reserved for a new entrant to the industry)	2x15 MHz paired spectrum plus 5 MHz unpaired spectrum	Hutchison 3G	£4,384,700,000
Licence B	2x15 MHz paired spectrum	Vodafone	£5,964,000,000
Licence C	2x10 MHz paired spectrum plus 5 MHz unpaired spectrum	BT	£4,030,100,000
Licence D	2x10 MHz paired spectrum plus 5 MHz unpaired spectrum	One2One	£4,003,600,000
Licence E	2x10 MHz paired spectrum plus 5 MHz unpaired spectrum	Orange	£4,095,000,000

It is possible to show the position of these licences (A, B, C, D, and E) in the paired spectrum diagram (you can see that some licences were for 10 MHz and some licences were for 15 MHz):



Why did these licences go for so much money? One answer is that the auction was very cleverly structured. Read about Professor Ken Binmore and his game theory. Professor Binmore explains how Sotheby's mistakenly auctioned American satellite transponders in sequential fashion, as if they were selling paintings. As a result, the transponders went for wildly different prices. This is clearly not ideal if you want to raise the maximum total amount of money at your auction. By using many rounds of bidding, Professor Binmore's auction design ensured that the final winning bids were quite close in value - pulling in loadsamoney for the UK Government.

USA

As has just been explained, in Europe and Asia the choice of frequency band for implementing UMTS was clear. However, these frequency bands were not available in the U.S., so at the World Radio Conference (WRC-2000) in Instanbul, Turkey in May 2000, three frequency bands were suggested for implementing UMTS in the United States. The bands suggested were:

• the 806-890 MHz band (now being used for cellular and other mobile services),
• the 1710-1885 MHz band (largely used by the U.S. Department of Defense),
• the 2500-2690 MHz band (used by commercial users for instructional TV and wireless data providers).

As you can see, the problem for the U.S. was that all of the suggested bands were currently being used for other purposes. This was a worry for the U.S. - would this prove to be a major hindrance for the adoption of 3G in the U.S., thus allowing Europe and Asia to take the lead? As a result, on October 13th, 2000, President Clinton issued a Presidential Memorandum which initiated a study into the availability of extra spectrum in the USA.
On March 30th, 2001, the FCC produced their final report into the possibility of using the 2500-2690 MHz band for 3G transmission (for more details, see the FCC 3G site). Basically, they thought that the TV industry was very heavily entrenched in this band and it would take between $10.2 billion and $30.4 billion to relocate the incumbent users.
The NTIA (National Communications and Information Administration) was given the task of evaluating the 1755-1850 MHz band for possible 3G transmission (for more details, see the NTIA 3G site). The NTIA reported that the U.S. Army and Navy have refused to move their communications to another frequency band. As a result of the September 11th attacks, there was considerable resistance to any further reduction in military spectrum.
A new plan, known as the "3G Viability Assessment", was proposed to consider the availability of the 1710-1770 MHz band, and the 2110-2170 MHz band. The result of that assessment is that 45MHz of space in the 1710-1755 MHz band and 45 Mhz of space in the 2110-2170 band is to be made available for 3G services.