The rising demand for broadband data services has recently been spilling over more and more into the sector of mobile networks as well. Operators of these networks and network outfitters find themselves confronted by a major challenge: they must provide efficient network solutions which make high transmission rates available at a commercially reasonable price to the places where they are required. The cooperation between networks and their elements can lead to a reduction in infrastructure costs, turning it into a component of an efficient network solution.

The demand for mobile data services is rising steadily. More and more mobile network customers are coming to expect the same transmission quality while on the go that they enjoy at home and in the office. Bandwidths of 2 to 50 Mbit/s are available in homes, and rates of 100 Mbit/s are no longer a rarity in offices.  

In the past, wireless communications systems have improved continuously as the exploitation of radio resources has been constantly furthered by an increase in spectral efficiency. Spectral efficiency describes the capacity (bit/s) which a system can provide for each spectral resource (Hz) and transmitter (site). This factor came to about 0.17 bit/s/Hz/site for GSM (2G) while the current HSPA standard (3G) offers 0.45 bit/s/Hz/site. Future systems like LTE will increase efficiency by as much as a factor of five. But the increase in efficiency is no longer enough to satisfy the demands made on modern broadband systems. In other words: more spectrum will be necessary for the operation of these systems so that the expected standards for data transmission can be met. 

Spectrum remains a scarce commodity even after WRC '07  

Radio spectrum is absolutely essential for the provision of mobile services, making it a coveted commodity. Spectrum assignments are generally subject to regulation by national and international bodies. On a global scale, the ITU (International Telecommunication Union) regulates the distribution of spectrum by means of recommendations which serve as a basis for the frequency assignments by national regulatory authorities.

But spectrum is not infinite and freely available; it is assigned to the various application sectors such as television, military, or mobile telecommunications by national and international organizations. The World Radiocommunication Conference 2007 (WRC '07) of the ITU promptly responded to the rising needs of mobile data communications and identified new spectrum for so-called IMT (International Mobile Telecommunication) services. However, this newly identified spectrum is not sufficient to satisfy the demands made by users on mobile data communication.

While preparing for the WRC '07, a number of initiatives in which both manufacturers and operators participated calculated the spectrum requirements for future data services. The spectrum requirements for the year 2020 were estimated at 1280 to 1720 MHz, i.e., an additional 530 to 1160 MHz of spectrum, depending on the region, must be made available. Figure 1 shows the results of the WRC '07. Despite intensive lobbying, only 136 MHz were identified as standard availability worldwide. An additional 392 MHz are available in many regions. No additional negotiations of the spectrum for mobile and wireless data communication are on the agenda for the next WRC so that additional spectral resources will not be identified for at least 6-8 years.
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