It is no secret that we live in a mobile centric world. There’s been an explosion in the number of mobile devices running on operator’s networks, the majority of which have capabilities comparable and even greater than the PCs of five years ago.
Reports suggest global mobile subscriptions grew by approximately 8% year-on-year to Q1 2013. The number of mobile broadband subscriptions increased even more, rising by 45% to reach 1.7 billion worldwide in the same time frame.
As the world’s 6.4 billion mobile subscribers’ appetite for mobile data continues to grow, so too have their expectations of their mobile network. According to the majority (20%) of mobile subscribers from across Europe, Latin America and Asia, consistent network performance is the greatest driver of their loyalty to their mobile operator. This ranks considerably higher than value for money (16%) and even customer support (9%).
As data demand and customer expectations grow, the planning, optimising and management of networks has become paramount to operators’ long term success. In order to ensure ongoing, high-level network performance in a scalable environment, there are several technologies and physical cell site developments that can assist operators in ensuring they retain subscribers whilst the industry evolves.
Historically, each generation of mobile networks has been assigned a new frequency band and wider spectral bandwidth per frequency channel. But, as the 4G revolution continues to juggernaut, there is little room for new frequency bands or larger channel bandwidths.
Due to this spectrum scarcity, we see spectrum agility as playing a major role in future network evolution. That is, networks that can intelligently adapt to take advantage of free or lightly used spectrum, such as that currently reserved for military transmissions.
This is often labelled a ‘Self Optimising Network’ (SON). Within a SON, a software layer controls network hardware to actively switch transmission frequencies to the least crowded spectrum available. This allows operators to ensure that subscribers receive the fastest possible upload/download speeds, even in crowded urban environments.
MIMO (multiple-input, multiple-output) will also be a crucial tool in increasing spectral efficiency for cell sites in LTE networks and beyond. MIMO improves capacity and other aspects of network performance by using multiple antennas at both the cell site and the user’s handset.
One dual-polar array is commonly used as a base station antenna to provide two-way transmit and receive signals. Operators are currently examining the benefits of adding a second dual-polar array to enable four-way transmit and receive, or eight-way in the still longer term
MIMO offers significant increases in data throughput and link range without additional bandwidth or increased transmission power. Two different streams of information are transmitted over the same radio channel using two separate antennas, or two different polarisations of the same antenna, to achieve an array gain that improves the spectral efficiency (more bits per second per hertz of bandwidth).
The same technique can be used to improve link reliability by transmitting the same steam of information through two antennas, creating a diversity path to combat fading or other types of interference.
Remote radio head technology
First generation network architecture kept base station equipment in shelters, where they could be held in a protected environment. One major technology enhancement has been the development of remote radio head (RRH) technology. This allows the radio head to be separate from the base band and provides significant flexibility in deployment.
The RRH can be mounted in any number of ways. However, mounting close to the actual base station antenna reduces some losses in the system and can potentially improve signal strength. The trade off here is that the antenna is always the highest point of the site, so a closely mounted RRH inherently creates some new risks given the harsh environment and expense of site maintenance and repair at the tower top level.
A key industry trend of late has been the integration of the RRH and base station antenna into one physical implementation. This proximity reduces loss, yielding greater efficiency as well as power, space and wind load savings. However, despite the potential gains of deploying more flexible, integrated solutions, their maintenance requirements are often more complex.
This can increase the likelihood of longer network downtime in the event of a hardware failure. For example, if a radio in an integrated antenna fails, an operator must decouple the whole assembly from the tower to effect repairs. On a traditional tower, the operator could simply remove and repair
the radio, while leaving the
Signal to noise ratio
Through all of the technology evolution in mobile networks, one factor is likely to remain constant – the need for a high signal to noise ratio (SNR) to ensure a robust data service. This ratio has become increasingly important in the last decade, and the appetite for mobile data worldwide shows no signs of lessening.
Shannon’s law describes the limitation of any system to achieve its maximum theoretical capacity, due to the level of noise or interference in the system. Today’s latest radio technology for 3G, LTE and LTE Advanced are referred to as ‘noise limited systems’, as they could achieve this maximum capacity, were it not for the limitation of noise in the RF path.
In fact, this is such an important consideration that, in 2005, in one of the first widely distributed technical papers, Peter Rysavy of Rysavy Research summed it up very well: ‘The focus of future technology enhancements should be on improving system performance aspects that improve and maximise the experienced SNRs in the system.’
To this end, operators must focus on ensuring a clean RF path through new technologies, carefully sculpted transmission patterns and network optimisation. One thing we can be certain of is that the future holds more complexity for mobile networks and more crowded airspace, meaning that robust, expertly engineered infrastructure will be crucial to the success of the next ‘G’ and beyond.