Mayank Joshi, Deputy Director, Fixed Network Solutions, Huawei India

Telecom carriers in India are in a state of surprise. On the one hand, the data traffic growth has increased multifold and on the other, the backhaul capacity for carrying this huge traffic is not available. Moreover, everyone has a clear visibility of further enhancement in data traffic. Tele­com carriers will have to bear significant costs to build new fibre-based infrastructure to have any bandwidth at any site and to increase their site footprint to keep pace with ongoing market developments and trends.

Every telecom carrier focuses on reaching returns on investment as soon as possible, and this leads to it choosing microwave for 70-80 per cent of its mobile backhaul transport over fibre, compromising on bandwidth (300 Mbps without compression). Most of the intra-city microwave implementation undertaken so far has been in traditional microwave bands (6-42 GHz) and is regulated by the Wireless Planning Coordination wing in India. The traffic handling capacity of traditional microwave is limited owing to only 28 MHz of bandwidth. Therefore, the only solution to increase capacity is to enhance modulation or add hardware for cross-polarisation interference cancellation, which will again add to the carrier’s capex.

The introduction of 3G and, in some cases, 4G, has already made carriers evolve their networks from time division multiplexing to hybrid microwave. But now, data demand on a per site basis is increasing significantly. Going forward, LTE-Advanced and 4K video will demand bigger pipes for an uninterrupted and enhanced end-user experience, and this data growth will keep on increasing. Therefore, the network engineering and dimensioning done today should consider future technology evolution and high data demand to save telecom carriers pain at a later stage. More 3G and 4G sites will be required to ensure seamless connectivity and a rich user experience, which will call for a high amount of small cell implementation. This will lead to various challenges, including the following:

  • To save costs without compromising on quality, a company has to go for full outdoor implementation, involving C-RAN architecture, which, in turn, creates a demand for common public radio interface (CPRI).
  • New spots of microwave frequencies are required, preferably in another band, to avoid interlink interference, but this will lead to a higher annual spectrum fee.
  • A high capacity link has to be provided initially at the aggregation layer and later towards the edge of the network, demanding new technologies/products.
  • Full outdoor microwave capability is required to meet the outdoor implementation criteria.
  • The need for more spectrum implies a higher licence fee and increased opex.

Thus, a solution is required that will not only give higher bandwidth (1 Gbps and above) but will also entail reduced overall costs (capex, opex and spectrum fee).

Such a solution is possible with extended microwave bands in millimetre wave range, called E-Band. Against 6-42 GHz of traditional microwave frequency, E-Band is in the 80 GHz range, with the lowest bandwidth of 250 MHz. Due to this, the per link capacity increases from 300 Mbps to 1.25 Gbps. The design of E-Band products has also changed, from split mount microwave to full outdoor with all-weather working capability giving flexibility for faster implementation, and Wi-Fi-based login for faster commissioning and troubleshooting. An­other advantage of E-Band links is that they can be used not only for backhaul but also for front-haul applications in C-RAN architecture with 1.25 Gbps and 2.5 Gbps of CPRI. Due to the high frequency, the beam width is very low and gives better planning options in a high density urban area, enabling telecom carriers to implement more sites for better coverage.

There are various applications of E-Band:

  • Gigabit links: These can be used to complement fibre in the last mile in mobile backhaul or FTTx scenarios
  • Feeder links: At the aggregation location, these links are fed to a cluster of traditional microwave links at the edge.

Globally, there are more than 60 countries that have released E-Band spectrum for building high capacity mobile backhaul and front-haul links with either zero or very low spectrum fee. It is hoped that E-Band spectrum will be released in India as well, at a nominal licence fee to give an opex advantage to carriers and promote greater use of this solution, especially in high-traffic-generating geographic areas.