The telecommunications industry has seen a lot of drastic changes over the past few years. Numerous facets of the industry have been converging such as the internet to mobile devices and a lot more are being incorporated in today’s mobile computing.

And to enable all these technological advancements to be possible in our mobile life, telecom operators have been scrambling to find the ways and means to make sure that resources are available and can easily be incorporated in the current networks. In their search of resources, telecommunications associations with the support of its members, operators and vendors alike have agreed to tap the untapped resources,  or to simply put it, some of the idle resources that are capable and can support the current demands of the network operators are being utilized, including available spectrum.

Originally spectrum refarming is geared towards the 900mhz spectrum band. The GSM Association is one of the associations who believes and is continuously supporting the move for spectrum refarming because it believes that by utilizing the said spectrum it will allows operators to have more available spectrum and operators may be able to manage their voice and data traffic load to ensure there won’t be any dropped connection and eventually no loss in revenue.

This is a classic example wherein 3G services are being rolled out and utilizing 2G spectrums. However, as the demand for mobile data continues to explode, groups such as the GSMA are not limiting their options into the 900Mhz and 2100Mhz band. Other research organizations like Plum Consulting do believe that we must tap other frequencies and refarm them.

In their recent study done for Ericsson and Qualcomm, the company highlighted significant benefits of the 1400 mhz bands in the foray of spectrum. The main thing is that they believe and truly support is to tap into the 1452 to 1492Mhz band. It is noted on their report that by utilizing this spectrum, a network will be able to implement a supplemental downlink on their network.

What is the 1400Mhz band?

The band is variously called the 1.4 GHz/1.5 GHz/L-band in Europe. The band is currently allocated for use by digital audio broadcasting (DAB) services in most European countries – part of the band is for terrestrial networks and part is for satellite networks. None of these services have developed in the band.

Rather in all countries the satellite part of the band is unused and this is also the case in the terrestrial component in most countries. Although the study is best suitable for European countries, it is worth examining whether the untapped can also be used for other countries.

It was highlighted that best use for the 1.4Ghz band is for the supplemental downlink for the delivery of enhanced mobile multimedia and broadband services.

Supplemental Downlink

Supplemental downlink uses a wider channel for the downlink than for the uplink, by aggregating the usual downlink with a supplemental downlink channel. By using a wider downlink channel it enables faster download speeds for mobile or portable wireless devices and it supports a greater number of users, though this approach has not been implemented up until now in mobile networks since it requires new technology.

Supplemental downlink and carrier aggregation are now being enabled in the HSPA+ and LTE-Advanced standards. The technology allows the bonding of spectrum in different bands into a single wider downlink channel and it provides an efficient way of using spectrum because consumption of video and other data heavy applications over mobile broadband networks is asymmetric – there is much more traffic on the downlink as opposed to its uplink.

However, all these approaches are being considered not only in plans but also steps are being taken towards it. In fact, AT&T plans to use a supplemental downlink in its LTE network, thereby aggregating 700 MHz unpaired spectrum with other paired spectrum in which it will deploy LTE (outside of the 700 MHz band). The relevant standards work is under way in 3GPP in order to develop the detailed specifications for the technology that will be required by handset and other equipment manufacturers. And AT&T is expecting to deploy handsets and equipment using a supplemental downlink as early as 2014.

So where does 1400 mhz comes in on this approach? The use of the band in this approach is for future proof usage. Although the band is still in the basket of bands being tapped to deliver our multimedia services, the report highlighted that by tapping into it as early as now, it will most likely be the most reliable and capable band to deliver our rich content to our mobile devices in the future.

The report also shows that based on the Cisco study in Europe, mobile data traffic will increase from 6:1 to 10: periods covering 2010 to 2015. All spectrum currently used at present by mobile operators is paired but there is more capacity in the downlink because of the higher related transmission efficiency.

The ratio between DL and UL capacity is around 2:1, which implies there is a significant imbalance between DL/UL traffic ratio and DL/UL capacity ratio when relying solely on paired spectrum. A supplemental downlink provides only downlink capacity and would therefore help meet the likely growing demand in downlink traffic. Mobile traffic is growing rapidly and the growth rates are likely to continue. Thus, the need for additional licensed spectrum to support this traffic growth has been recognized in the draft RSPP which was voted on by the European Parliament on 11 May 2011. The draft proposes that at least 1200 MHz is allocated for mobile data services by 2015.

And to be able to achieve this target at least 300-500 MHz more licensed spectrum needs to be allocated to mobile services for harmonization. The 1.4 GHz band is one of the priority bands for harmonization for wireless broadband services called on by the European Parliament in the draft. Other bands mentioned are 700 MHz (694-790 MHz which is currently used for TV broadcasting) and the 2.3 GHz (2300-2400 MHz which is currently used for a variety of civil and military uses), neither of which is currently readily available for use. In addition, the value of releasing the 1.4 GHz band depends on whether other substitute spectrum may become available in the next 5 to 10 years. The 1.4 GHz band is intermediate between 800/900 MHz and 2.1 GHz, and as such its propagation characteristics are intermediate between the bands. Moving from 2.1 GHz to 800/900 MHz results in roughly a doubling of the propagation distance and hence a quadrupling of coverage areas from base stations.

The 1.4 GHz band would offer significant advantages in terms of coverage relative to say bands that could be made available above 2 GHz. These advantages could be even greater in this instance because the Maastricht Agreement allows transmission at a higher power than typical cellular networks, subject to cross border coordination. This means use of the 1.4 GHz band under current regulation is more akin to those at 800/900 MHz and so the band could be deployed in rural areas using existing infrastructure. In addition in urban areas more reliable in-building penetration could be possible, as compared with use of higher frequencies.

Currently all of these are being studied and planned whether the approach and even the spectrum in need for allocation are to be made available. It highlights various benefits, but given the capacity and capability of the 1400Mhz,

more likely than not it will tap into service for our future use. The mobile data upsurge will die down in the next 10 years, and all of our video and multimedia content will be streamed on handheld devices. As the report highlighted all else being equal, the band will surely rise up to the occasion for fully utilization.