With the proliferation of smartphones and next-generation technologies such as high speed packet access (HSPA) and long term evolution (LTE), there has been a significant increase in the adoption of data services. The growing use of over-the-top applications has resulted in a huge surge in data traffic on the networks of telecom operators; however, the volume of data traffic varies across locations. Given this scenario, operators are struggling to meet the rising demand for high bandwidth, especially in urban clusters, as the existing networks are reaching their capacity limits.

In mature telecom markets, additional demand for bandwidth is arising due to the increasing traction of machine-to-machine applications, cloud computing solutions and the concept of connected devices, which puts a greater onus on telecom operators to provide higher capacity. According to Ericsson, the global data traffic on telecom networks is expected to increase tenfold between 2013 and 2019, which will require a considerable upgradation of backhaul networks to ensure optimum user experience.

Traditionally, telecom operators have set up several macro cell sites to support voice and data traffic on the network. The majority of these cell sites were initially backhauled by copper cable networks as most of the traffic was generated by voice services. However, with the rise in the share of data services, operators are migrating to fibre networks. Microwave solutions are also being implemented to provide backhaul connectivity to tower sites in several areas where wired connectivity is not cost effective. Operators started deploying fibre cables to augment their network capacity so as to support bandwidth-intensive applications. However, due to cost constraints and right-of-way issues, fibre has not managed to become the dominant technology for backhaul networks, especially in urban areas.

Fibre or microwave

While fibre technology has been favoured by most telecom operators as the primary technology for backhaul connectivity due to its scalability benefits, microwave has also witnessed significant adoption on account of its ease of deployment and lower total ownership costs. In mature markets such as the US and Japan, fibre technology has gained significant market share as many operators have upgraded their networks to HSPA and LTE technologies. However, operators in the majority of the developing regions are yet to fully migrate to LTE and therefore, most tower sites are not fibrised. Ericsson predicts that regions such as the Middle East, Sub-Saharan Africa and Southeast Asia will witness a slow transition to fibre technology as compared to the Western Europe and Latin American markets.

The debate over technological choice is gaining further momentum, especially with the deployment of small cells as well as macro cell sites to form a heterogeneous network. Most operators are increasingly deploying small cell sites to offer higher capacity and better data network coverage in high density areas. However, the deployment of small cells involves several backhaul issues. Given that small cell sites are scattered, providing backhaul to each of them through the fibre network would be costly and financially unviable. In fact, so far, only service providers in Japan and South Korea have used the fibre cable network for providing backhaul to small cell sites. In other countries, operators have used wireless backhaul solutions for small cell sites, including unlicensed spectrum in the 5 GHz and 60 GHz bands. For instance, T-Mobile US has recently signed an agreement with Nokia Networks to set up small cell sites using unlicensed spectrum in the 5 GHz band through LTE-unlicensed small cell solutions or licence assisted access-LTE. While the spectrum band is currently used for Wi-Fi services in the US, Huawei and NTT DOCOMO conducted a trial test using the frequency band, which highlighted that LTE networks performed better than Wi-Fi networks in terms of both coverage and capacity. In fact, several equipment vendors such as Qualcomm and Ericsson have also launched products that support unlicensed 5 GHz LTE networks. Further, US-based Fastback Networks offers non-line-of-sight (NLOS) technology that operates in the 5 GHz band and offers speeds of up to 500 Mbps.

Further, a few industry stakeholders are of the view that licensed spectrum can also be used for providing backhaul connectivity to small cells. In this regard, spectrum in the 2600 MHz band is being explored as an alternative frequency band for microwave backhaul connectivity, though in a few countries this spectrum is already sold to telecom operators for offering 4G services and, therefore, cannot be used for backhaul purposes. Meanwhile, lightly licensed spectrum in the 3.65 GHz band is also being considered to provide NLOS connectivity, which can be highly useful for small cells located in densely populated urban areas.

Copper still an option

While fibre technology is being projected as the ideal solution for wired backhaul connectivity, copper cable is regaining relevance as a backhaul solution. Equipment vendors reckon that copper cable along with bonding technologies can act as a good substitute to fibre-based backhaul, at least in the near future. In copper bonding, a pair of copper cables is twisted to form a thick pipe that can provide speeds as high as 150 Mbps over 1.5 km. This has emerged as a good alternative for operators that do not intend to incur the high costs associated with fibre networks while continuing to support higher bandwidth demands. For instance, Turk Telecom, in collaboration with Alcatel-Lucent, has deployed a copper cable network along with VDSL 2 (very high speed digital subscriber line 2) bonding technology as a backhaul connectivity solution. Copper cable networks can also act as a good solution for small cells sites, which have lower bandwidth requirements. This would also be an easy option from the deployment perspective as the majority of areas already have copper connectivity.

SON and NFV

While operators are required to make huge investments in upgrading networks to support the growing data traffic, many of them are looking at solutions such as self-organising networks and network function virtualisation (NFV) to optimise bandwidth utilisation so as to reduce their capex. For instance, NTT DOCOMO is planning to begin the commercial deployment of NFV by March 2016. DOCOMO is currently working with vendors such as Ericsson, Fujistu and NEC to integrate NFV into its telecom networks. While Ericsson will be responsible for installing the system that controls the virtualised hardware, Fujitsu and NEC will provide virtualised Evolved Packet Core software.

Future outlook

With data services gaining traction and data traffic growing at a significant pace, operators will have to ultimately deploy fibre cable networks to ensure an optimum data experience, which becomes essential with applications such as video services. However, in the near term, operators can implement relatively more cost-effective solutions such as unlicensed and licensed spectrum as well as copper cable networks to ensure adequate backhaul connectivity between cell sites.