Refreshing networks: the move towards the next G

Spectrum scarcity will necessitate spectrum agility, says Phil Sorsky, as he runs through the technical options networks have to achieve this new agility, and move their networks towards the next G.

Today’s subscribers have heightened expectations and will continue to demand a positive customer experience from their mobile operator. The more innovative and personalised the technology or service, the better the quality of service required. By planning, optimising and managing networks, operators can ensure a high-level of performance in a scalable environment for the long-term.

There are several technologies and physical cell site developments that can assist an operator in ensuring they retain subscribers as the wireless industry evolves.

Historically, each generation of mobile networks has been assigned a new frequency band and wider spectral bandwidth per frequency channel. However, following the 4G rollout, there is now little room for new frequency bands or larger channel bandwidths. Because of 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). A software layer would control network hardware to actively switch transmission frequencies to the least crowded spectrum available. This would allow operators to ensure that subscribers receive the fastest possible upload / download speeds, even in crowded urban environments.

MIMO (multiple-input, multiple-output) will 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.

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.

One trend in the industry is 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 antenna untouched.

Site acquisition has been a major problem for operators since the earliest days of mobile networks. This is likely to continue, given the limited space available in urban situations and on cell towers. ‘Small cells’ has become an often used and often misunderstood term in the industry. The rationale behind small cells is simple. Clearly network capacity demand will out strip current architectural limitations and require new approaches. Simply adding more cells reaches a point of saturation so new ideas are required. Therefore, we expect to see a continuing trend towards the components in cell sites being made smaller and more integrated, so that more revenue-generating equipment can be deployed.

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.

Phil Sorksy is VP of Wireless Sales, Europe, CommScope.

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