According to the Belgian small-cell base station specialist Accelleran, operators worldwide are wasting $130 billion of spectrum assets by neglecting LTE TDD
The wireless industry needs to take better advantage of TDD and its favourable economics by using wasted spectrum and from the efficiency of TDD for asymmetric data traffic, argues Accelleran.
The anomaly here is the concern over the shortage of spectrum, and the huge sums spent on it.
Operators have paid $25 billion for spectrum that is not being exploited.
This colossal waste is significant enough just in its purchase price, but the missed opportunities to the operator and the wider economy are even larger at $130 billion, estimates Accelleran.
What is more, at a time when LTE roaming is a challenge many of these bands are usable globally, representing another waste.
The importance of TDD technology and its capacity advantage over FDD for small cells is because it better reflects the asymmetry of data transfer.
However, despite these efficiency advantages, billions of dollars worth of unpaired spectrum remains unused or underused years after it was allocated.
More than a decade ago, European operators paid over $160 billion in the UMTS 2.1GHz auctions held across Europe. Part of that UMTS spectrum, being unpaired, was intended for use with UMTS TDD technology.
A simple proportional calculation of the price for that TDD spectrum is almost $25 billion. This unused resource is in European Band 33, a subset of the more successful Chinese B39.
But that does not consider the real value for society and the digital economy lost over time for neglecting a very scarce resource. Using data from studies on the general economic value of mobile services in Europe (Europe Economics, Analysys Mason, Plum), the extrapolated lost economic value of this spectrum in Europe between 2002 and 2014 would total $130 billion.
Above 3 GHz, the spectrum situation differs regionally. Much of the spectrum and deployments were initially allocated for fixed wireless access, initially used for WiMAX, and would be ideally suited to LTE TDD. In Europe, we seem to have finally agreed to harmonize 3400-3600 MHz spectrum towards a “TDD preferred” allocation and 3600-3800 MHz spectrum towards a TDD allocation.
The extrapolated economic value of this spectrum in Europe for a decade between 2005 and 2015 would be more than $2500 billion. In some cases this spectrum is in use, but mainly for fixed wireless applications, which at the best case yields a fraction of the economic value mobile services would generate.
This is especially important as Japan is gearing up to the allocation of 3.5GHz spectrum during 2015. In the US, the 3.5GHz situation seems to be gaining real momentum (FCC organised an important 3.5GHz Spectrum Access System workshop last 14th January). This US 3.5GHz spectrum, for which small cells are key, will eventually use a spectrum shared access system based on geolocation databases and a tiering model. Europe is developing similar proposals for shared access, but for the 2300-2400 MHz spectrum.
South Korea was unusual in its widespread use of TDD for WiBro and WiMAX in the 2300-2400 MHz band. Korea is one of the most advanced markets for LTE FDD, pushing the boundaries of the LTE-Advanced features to the limit - and yet still neglecting the use of the LTE TDD mode and the potential LTE FDD/TDD combined synergies and economies of scale.
To summarize, things are slowly moving on the regulatory front in different regions towards embracing the advantages, the economies of scale and global roaming potential of LTE TDD in certain spectrum bands. However, the overall costs of unused spectrum resources, regulatory delays and lack of harmonization are very costly to society as a whole and are putting a brake on the development of the digital economy and generation of economic value in the different regions.
“At Accelleran we are very aware that one of the key requirements for operators is to have a small cell platform that is flexible enough to accommodate the evolution of the LTE TDD spectrum in different bands such as 3.5GHz, 2.6GHz, 2.3 GHz or 1.9/2.1GHz.”, says Accelleran's Jeff Land, "that is why we designed the M101 small cell platform to allow operators to take advantage of this otherwise wasted spectrum.”
M101 is a small cell designed for LTE and LTE-Advanced with the specific additional support for 3.5GHz and 1.9/2.1GHz TDD bands.
With 73 LTE TDD networks launched, in deployment or firmly planned worldwide, 304 devices supporting LTE TDD (GSA, Jan 2014) and global roaming potential of LTE TDD spectrum, interest in LTE TDD is huge – but until now there has been no optimised, small form factor LTE TDD small cell.