Mobile data traffic in the country has witnessed steady growth over the past year. According to Nokia Solutions and Networks’ (NSN) MBit Index, mobile data usage almost doubled in 2012 and was mainly driven by the growing uptake of 3G services. Moreover, a substantial amount of data is being consumed inside buildings in urban areas.

According to a joint study by ADC and Building Industry Consulting Service International (BICSI), over 70 per cent of the mobile data traffic comprising email, multimedia content, video clips and specialised applications is generated inside buildings. This requires better network coverage and capacity inside buildings.

In order to meet the increasing data demand, telecom operators have been focusing on in-building solutions (IBS) as a part of their overall heterogeneous network strategy.

 Options for IBS

According to the ADC-BICSI study, IBS can be deployed as:

Radio frequency (RF) source: This is required for all distributed antenna systems (DAS). It entails deploying an antenna or repeater to provide RF connectivity from the outdoor cellular network. The base transceiver station (BTS) installed by operators in this set-up provides dedicated RF connectivity.

Passive DAS: In this set-up, RF is distributed over coaxial cables to each antenna from an RF source (a repeater or a BTS). However, using coaxial cables reduces the effectiveness for higher frequency transmissions in large buildings.

Active DAS: This set-up deploys an optic fibre cable (OFC) backbone, which helps reduce transmission losses that occur in a coaxial cable-based system. This solution is largely deployed for providing IBS in medium- to large-sized buildings.

Distributed radios: This system consists of an internal cellular network made up of small cellular radios termed as picocells and femtocells. It is still an evolving technology, often used for deploying Wi-Fi hotspot solutions and can only be provided by telecom operators.

 IBS in India

So far, telecom operators in India have been largely deploying IBS through a shared DAS architecture. This set-up is well suited for large and very large buildings.

However, according to NSN, Wi-Fi hotspots and small cells are also being examined and implemented on a small-scale basis. These cells are expected to address the IBS requirements in the small to medium building space exclusively and complement DAS in large to very large buildings.

 Challenges in deploying IBS

•   According to NSN, the inadequate availability of WCDMA spectrum has been a major limiting factor for the adoption of small cell solutions. Moreover, there are challenges associated with interference management.

•   While DAS solutions are not expensive, deploying OFC and coaxial cables entails high upfront costs.

•   After initial deployment, a DAS may sometimes be insufficient to meet the increasing voice and data traffic. Moreover, operators are focusing on network densification instead of enhancing their capacity.

•   There is a lack of coordination between telecom operators and building owners on deployment considerations.

•   If deployed as a stand-alone device, microcells have limited capacity and can support a single carrier with up to two frequencies on a single technology (either GSM or UMTS or 3G/4G).

•   Picocells can support a few frequencies and only one wireless service provider per unit. They cost more than femtocells and involve elaborate installation and configuration processes. Like microcells, picocells are generally not interconnected to nodes within a DAS network. However, a single site may have multiple picocells to address capacity- or coverage-related issues.

•   Femtocells only support a single technology from one wireless service provider. This implies that separate units are required for 3G and 4G support, even from a single carrier. Femtocells can hand off an RF source to the macrocellular network but cannot hand in the RF signal from the macrocellular network to the femtocell. The technology functions as a one-way broadcasting medium and not a seamless part of the network.

•   Wi-Fi can be installed on the wired element of a DAS, creating hotspots that provide connectivity. However, the Wi-Fi RF coverage range from a shared antenna is smaller than voice services, and hence the antennas need to be installed close to each other to provide seamless Wi-Fi coverage. This translates into more antenna and reduced voice power to minimise the overlap.

 The way forward

Going forward, IBS will remain an area of interest for telecom operators. These solutions are expected to increase network coverage (for long-term evolution-time division duplex and WCDMA) and capacity. Technology-wise, with an increase in WCDMA data traffic, the demand for high capacity hotspots is expected to increase substantially between 2014 and 2016. All in all, IBS is witnessing rapid adoption in the country to accommodate the growing data traffic.