|Topic:||Microwave for cost-effective mobile backhaul|
|Author:||Ram Prakash Tripathi|
|Title:||President & Managing Director|
Ram Prakash Tripathi is the President and Managing Director of Ceragon India; he has over 20 years of experience in the telecommunications industry. Prior to Ceragon he held managerial positions at several companies including Stratex and Reliance.
Ram Prakash Tripathi is a graduate Engineer with a BE in Electronics & Communication.
India has an enormous appetite for mobile backhaul network capacity. This demand comes from its 3G and 4G mobile networks, bandwidth-intensive data services and applications, smartphones that enable data-rich applications and extensive mobile use for home and office-based data services in lieu of absent fixed-line telephony. Optical fibre is expensive and time-consuming to deploy, so India uses microwave for its 2G and 3G bandwidth. The latest microwave technology delivers enough capacity to meet the ever-increasing gigabit-per-second requirements of mobile backhauling.
India’s mobile connectivity – gigantic and growing rapidly
Mobile telephony came to India in 1995 and has since undergone adoption at a breathtaking rate. Today, only 17 years later, with a subscriber base of more than 900 million, the mobile telecommunications system in India is the second largest in the world. It already dwarfs the national fixed-line population as more than 90 per cent of total telephone connections are wireless.
Smartphones are accelerators of heavy mobile backhaul use and India’s smartphone user population is growing briskly. Market share for smartphone shipments stood at 2.2 per cent in 2011 and should rise to 8.5 per cent by 2016 putting India among countries that will see the fastest growth in this segment. In urban areas, smartphone users constitute ten per cent of the entire mobile subscriber base and now number over 27 million. Enabling the sorts of applications that were once restricted to powerful computers, 3G and 4G enabled smartphones provide real-time television, rich movie and video downloads, shopping, web surfing, social networking and a wealth of other bandwidth-intensive, staying-connected services. In fact, social-media giant Facebook’s user base in India has grown from eight million in 2010 to over 60 million and the majority of these users access Facebook through their mobile phones.
“While for other countries it was the desktop which was first used to get into the portal, in the case of India, it was the mobile phone,” states Kirthiga Reddy, Facebook Director of Online Operations, India.
Contending with mobile backhaul strain
Backhaul networks are the pipes that connect cell towers to the mobile operator’s switching centre. All voice and data signals – conversations, SMSs, video downloads – travel through the backhaul network. As the number of subscribers and the intensity and volume of their usage increase, demand for capacity on the backhaul network escalates. Mobile operators have to contend with this growing demand to provide quality service to all of their subscribers.
Mobile operators have four media over which to deploy their backhaul networks. Each medium has advantages and disadvantages:
Copper – Decades ago, copper was the only game in town. Throughout the world, immense networks of copper cable connected base stations across countries. However, by today’s standards, cable deployment is expensive, labour-intensive and slow. Since copper wire’s capacity is quite limited and cannot keep up with today’s demands, it is being phased out.
Satellite – Orbiting above our planet are satellites that provide telecommunication services including mobile backhaul. However, as capacity is limited and the time to beam signals into space and back down again is relatively great, satellite backhaul is used only for remote cell sites that cannot be effectively serviced any other way.
Optical fibre – Optical fibre provides the greatest capacity for mobile backhaul and is widely used, however, it has some serious shortcomings. Deployment is time-consuming and very expensive; the costs for trenching and deploying fibre increase rapidly with distance. Right-of-way permits and the labour-intensiveness of trenching add significantly to the expense and time required. Furthermore, network operators are vulnerable to a sudden loss of capacity if a fibre breaks due to weather, construction (e.g., road work) or vandalism.
Microwave – Given the challenges involved in constructing mobile backhaul networks in India, all such networks use a combination of microwave and optical fibre. In fact, because of its cost-effectiveness and ability to provide the needed capacity, nearly 80 per cent of cell sites in India have a microwave-based backhaul link.
Today’s microwave technology provides impressive capacity. Where links were previously circuit-oriented and limited to a few STM-1s [Synchronous Transport Module level-1 fibre optic with a bit rate of 155.52 Mbit/s], they now carry capacities measured in gigabits and are geared toward efficient all-packet technology. Innovative technologies like dual-core radios, MIMO [multiple input/multiple output], advanced modulation and multi-channel bandwidth control empower operators to provide fibre-like capacity on wireless backhaul routes. Today’s microwave systems provide abundant capacity far in excess of India’s current and predicted demand for numerous backhaul deployments.
Microwave links are significantly less expensive and speedier to deploy than fibre; they avoid right-of-way issues and expensive trenching. Complete microwave networks can be deployed economically in short order reducing the operator’s time-to-revenue and lowering the total cost of ownership. Unlike fibre, microwave deployment costs do not increase with distance; long-distance hops of 20, 50 or even more than 100 km are practical to implement.
In the days of TDM circuit-switched networks, microwave network planners had to work around availability problems. Since TDM links do not degrade gracefully, but either function or fail, network planners had to design all sorts of topologies and backup schemes to achieve high availability. This necessitated heavy expenses for extra deployments, more equipment, complex fail-over scenarios and a nightmare for operations and maintenance personnel. These days are over.
Where inclement weather and other types of interference used to be mitigating factors in microwave link availability, today, leading microwave equipment vendors are able to maintain availability even in transient fading conditions. For example, innovative microwave systems monitor the quality of the transmission link and can automatically decrease the modulation technique in case of degraded signal quality. So, if a microwave transmission is humming along at maximum capacity and suddenly encounters fading, the microwave system automatically steps down the modulation to lower levels until the transmission network achieves the requisite level of availability. The traffic is distributed over all carriers using such technologies as Multi-carrier Adaptive Bandwidth Control (ABC), so, when one carrier is affected by reduced modulation, traffic is distributed to the remaining carriers. As the transient problems disappear, the resilient microwave system automatically re-applies more efficient modulation techniques to regain full capacity. All of this occurs automatically without human intervention.
Adaptive coding and modulation
The most advanced of these microwave networks provide service awareness; this means that operators can specify which subscriber services will get priority when conditions are and are not optimal.
Today’s microwave systems provide reliable support for TDM links and a field-implementable upgrade path to take advantage of much more efficient packet-switching architectures. They can support both technologies simultaneously, enabling network operators to evolve their networks according to plan.
Maintenance and operations
Unlike fibre, which is prone to breakage and loss of service, microwave is highly reliable. With a microwave site in one secure location booming traffic over the air to another site tens or even hundreds of kilometres away, operators need not suffer the maintenance problems associated with a long fibre cable snaking through remote or difficult terrain and its numerous connections along the way. The mean time between failures (MTBF) of leading microwave systems is now in excess of 100 years!
Advanced microwave systems consume far less power today than in the past. For example, the most innovative equipment vendors are coming to the market with small form-factor, all-outdoor configurations that do not require cooling units, significantly reducing the electrical supply needed to power them. With passive cooling and power consumption that can even be supplied by solar or wind power, the new microwave configurations suit India’s ecosystem perfectly.
Once placed in the ground, fibre is static while microwave is flexible. If a transmission route becomes redundant, microwave equipment can be moved quickly to a new route. One leading international microwave vendor has just introduced a new level of flexibility with zero-touch provisioning whereby already-deployed microwave equipment is re-configured remotely to change capacity, radio signal strength and other characteristics to meet dynamic backhaul requirements.
All of these microwave advantages add up to lower operating expenses and easier maintenance for network operators.
Leading microwave vendors today offer advanced all-packet backhaul solutions that make the most efficient use of limited spectrum and switching equipment. While India’s mobile network operators provide 2G (GSM and CDMA) and 3G mobile capabilities today, 4G/LTE is right around the corner. Further encouraging the use of data-rich applications by subscribers with faster and more powerful mobile handsets, 4G will boost demand for capacity from the backhaul network.
LTE also provides a plethora of new backhaul scenarios to accommodate the growing demand for capacity. Enabling new concepts such as small cells, C-RAN, super-size macro cells and distributed macro cells, 4G provides numerous new options for meeting the capacity challenge. For these new 4G backhauling scenarios, high capacity, small form-factor in all-outdoor configurations, low power consumption, powerful radios and flexibility make microwave the perfect cost-effective backhaul technology.