The emergence of next-generation network technologies and high-bandwidth devices has led to an exponential increase in data traffic, calling for an urgent transformation of operators' backhaul networks.

An increasing demand for backhaul connections and capacity is expected as operators expand their 3G network rollout to tier-II and tier-III cities and deploy long-term evolution-time division duplex (LTE-TDD) access infrastructure. Bandwidth-hungry applications such as mobile TV and multimedia content streaming are anticipated to require a sharp increase in capacity for cell sites and the operators need to optimize their existing transport networks.

Time division multiplexing (TDM) backhaul has dominated backhaul deployments since the inception of wireless communication. Leasing the backhaul access for every cell site incurs large operating expenses, particularly for providers who do not own the last mile. The present-day 3G/4G cellular technologies have spurred a major change in backhaul network, bringing in the transition from TDM to packet backhaul. Like their global counterparts, operators in India are looking for an IP transition to support NGN mobile technologies. Femtocells and high-speed packet access points are also being considered to reduce backhaul congestion in markets, where xDSL is widely deployed. The existing microwave backhaul infrastructure needs significant upgradation to cater to data traffic growth and to manage the increasing subscriber base, variations in the type of traffic transported across the network, and the demand for quality of service.

Synchronization is playing a central role in packet-based networks. Current applications rely on a transport network that can preserve stringent timing information. Given the cost point of these technologies, network expansion has become CapEx sensitive. Market trends indicate that the demand for non-real-time delay-sensitive high-peak bandwidth and low duty cycle traffic is increasing consistently. This has prompted service providers to deploy packet-switched networks (PSN).

Market Dynamics

The Indian market for transmission equipment was estimated at `4372 crore in 2011-12. Alcatel Lucent, Ericsson, Huawei, ECI Telecom, ZTE, and Nokia Siemens Networks are the major vendors in the transmission and backhaul industry. Fibcom, Commscope, Juniper Networks, Radwin and Tejas Networks are other aggressive players in the market.

Bharti Airtel has selected Alcatel Lucent to create CEN-based IP access network, which will enable Airtel to deliver faster mobile broadband speeds to its customers. This IP network will allow the operator to meet the surging bandwidth requirements of customers while accessing data, video, and Internet services on an array of devices, such as smartphones, tablets, and laptops. The key elements of the Bharti Airtel mobile backhaul network are Alcatel-Lucent's 7750 Service Router, 7705 Service Aggregation Router (SAR), and 5620 Service Aware Manager.

With ever-growing data demand for both personal and enterprise broadband services set to soar further, Bharti Airtel's CEN (carrier-grade Ethernet)-based IP access network will help the company offer its customers various services such as video streaming, high speed data, social-network-based applications, online gaming, video conferencing, and online collaboration. Additionally, this network would also be catering to the DSL broadband as well as 2G/3G/4G voice and data traffic, making it a true converged network.

Airtel has selected NSN to build and operate its LTE-TDD network in Maharashtra. NSN will roll out the LTE-TDD network for Airtel, and supply end-user data devices that can provide data speeds of up to 100 Mbps. Further, NSN will provide its LTE-TDD 6 pipes radio solution and use its global network solutions center, located at Noida, to provide remote service delivery for efficient network performance.

The operator has awarded a 4G contract with ZTE in the Kolkata circle. Under the contract, Airtel will source its LTE-TDD equipment from ZTE during the first phase of deployment.

Airtel has also renewed its managed services contract with NSN in eight of its circles, viz., Bihar and Jharkhand; Kolkata, Gujarat, Maharashtra, and Goa; Madhya Pradesh and Chhattisgarh; and Mumbai, Orissa, and West Bengal. NSN will continue managing the operator's 2G and 3G networks in these circles for the next five years.

This development follows the operator's renewal of its managed services contract with Ericsson India. Under the five-year contract, Ericsson will manage and maintain Bharti Airtel's mobile networks in 15 circles.

Idea has a 3G network presence run on IP radio technology and by the end of 2012, the company will have a minimum of 25 Mbps backhaul capacity in at least 10 cities. The operator has deployed a dense wavelength division multiplexing (DWDM) product portfolio in its network. The DWDM technology enables multiplexing of bands (typically 40-80 channels) spaced at 100 GHz or 50 GHz, which enhances the capacity and reduces the overall networking costs. The operator has extended its managed services agreement with Ericsson India from one circle to five circles, namely Mumbai, Jammu and Kashmir, Himachal Pradesh, the Northeast, and Assam. Under the three-year agreement, Ericsson will be responsible for managing Idea's network and field operations, maintenance activities for its 2G and 3G sites network design and planning, and improving network performance for the operator's infrastructure.

Reliance Communications (RCom) owns and operates an extensive NGN-IP-enabled connectivity infrastructure, comprising over 277,000 km of optic fiber cable systems. RCom has a fiber-based backhaul, which supports high bandwidth and provides one of the lowest latencies in the industry. All its 3G sites are connected through IP backhaul to provide maximum download speeds.

Tata Teleservices Limited (TTL) has been expanding its network for both coverage and capacity in mobility and enterprise business segments. Since this requires backhaul for both TDM and IP traffic, TTSL has deployed Japan-based NEC's iPASOLINK platform to upgrade its backhaul mobile transport network. The platform is designed to support the transition from hybrid TDM and Ethernet backhaul to full IP transport.

Bharat Sanchar Nigam Limited (BSNL) has one of the largest backhaul networks in the country with a 50,430 route km microwave network and over 600,000 km of optic fiber. This low-cost backhaul fiber network provides BSNL an edge over its competitors, particularly in rural areas. The company is aware of the inherent TDM limitations with respect to NGN technologies and has been transforming its networks to packet-based category. The company is focusing on procuring equipment that can manage voice, data, and video traffic across a single core and backhaul infrastructure for current and future mobile network expansion.

Power Grid Corporation of India has partnered with ZTE to provide fixed-network transmission services across the country. As part of the agreement, ZTE will deploy more than 385 DWDMs, 1025 SDHs, and several PTN devices to enhance PGCIL's network coverage and service quality.

In FY12, Centre for Development of Telematics (C-DOT) has designed and developed GPON technology, which offers speed up to 1 Gbps and is ideal for rural and urban areas. The technology is meant for fiber expansion in the country to meet the requirements of major national programs such as NOFN (National Optical Fiber Network), SWAN (State Wide Area Network), broadband connectivity in rural, northeast, and tribal areas, as well as expansion of defense and railway networks, and many other strategic networks.

In this direction, C-DOT has transferred Gigabit Passive Optical Network (GPON) technology to seven public and private manufacturers - ITI; Bharat Electronics (BEL); Electronics Corporation of India (ECIL); VMC, Hyderabad; Sai Information Systems, Ahmedabad; SM Creative, Gurgaon; and Tejas Networks, Bengaluru.

Ethernet-over-SDH Technology

With mobile data traffic showcasing exponential growth, mobile backhaul networks will prove to be a lucrative segment for attracting a significant amount of investments. Government-driven pan-India initiatives, including the National Knowledge Network (NKN), Network for Spectrum (NFS), and rural broadband, will act as primary growth drivers for the transmission equipment segment. The industry is witnessing first-rate HDTV prospects, which will crave the requirement for high-bandwidth services and will add required thrust to the market.

Ethernet-over-SDH technology is being adopted by most of the equipment vendors. These standards enable the inter-working of TDM payloads over SDH. With the availability of next-generation SDH equipment, various Ethernet-based services are possible directly through Layer 1 and Layer 2 Ethernet interfaces of SDH that were earlier realized through external hubs and switches, with limited bandwidths. These networks support not only circuit-switched interfaces, but also packet-switched interfaces.

The paradigm shift has come in transport, SDH, and technology to support bandwidth-hungry Ethernet-based applications. Although IP-based applications are the hype in the market, they have not been cleared on quality grounds. Both primary multiplexers and next-generation SDH equipment are based on TDM technology. Hence, it is crystal clear that TDM is here to stay.

Mobile Backhual Gaining Ground

Backhaul of TDM trunks is one of the major challenges encountered by carriers, mainly in terms of OpEx and CapEx. Traditionally, service providers chose either wireline or licensed band wireless (microwave) solutions as the way to go. To meet the growing demand for bandwidth while minimizing costs, service providers are continually seeking new methods for backhauling.

Overcoming unexpected interference is another hindrance for service providers. Meeting this challenge requires a robust wireless system with built-in mechanisms capable of addressing the interference issue. This is important especially when transmitting TDM traffic, since TDM is relatively intolerant of network performance degradation.

As networks are becoming complex with multiple technologies coexisting, planning and deployment of traffic protection mechanisms becomes intricate. Network growth is governed by business plans in tandem with market requirements. Currently, the next-generation networks are in the phase of justifying their deployment from cost economics and maintenance perspective. As the complexity of networks increases and the end-user bandwidth grows, technological platforms like automatic switched optical network (ASON) and automatic switched transport network (ASTN) will find their place in dedicated networks of the future. E-services like e-health, e-education, and e-security will offer requisite momentum to the growth graph. MSTP-based deployments, next-generation PTN deployments, and RPR-based technologies are some of the key concepts, which need to be looked out for around the corner.

Under converged services environment, various services and technologies have evolved including IMS, mobile Internet, IPTV, and cloud computing. In order to provide flexible and converged solution, multi-service operators need an integrated IP broadband transport network to provide high network bandwidth, simplified OAM, and low TCO. The advanced IP transport integrated device, a new-generation intelligent metro WDM/OTN device together with integrated service network gateway system can flexibly help the user build 3G/LTE backhaul transport and FMC metro-integrated transport solutions.

The rapid growth of 3G and 4G LTE technologies in India is driving the need for integrated broadband backhaul network solution. To address the all-IP trend of telecom services, IPTN solution based on all-packet core integrated with MPLS-TP and IP/MPLS technologies could be used to provide unified multi-media broadband services and end-to-end solution helping operators achieve smooth network evolution and rapid service development thus reducing TCO. In the current scenario of economic meltdown and cut-throat competition, telecom operators need to provide next-generation revenue services over their networks to address the problem of falling ARPU. IP-based next-generation converged network can serve this compelling requirement with a wide range of services efficiently.

Next generation network (NGN) is the system based on the emerging packetization technology of IP, which is leading to convergence of networks, services, and markets, thereby enhancing efficiency and flexibility. It offers service providers a converged, efficient, and flexible IP-based platform, which can evolve in a modular and flexible manner to create, deploy, and manage innovative unified application services.

Several operators are realizing NGN as the future panacea and are evolving toward it. The incumbent operators are also going for NGN and replacing their existing networks to IP-based in a time-bound manner. Most wireline operators are taking an incremental path to IMS, with their focus on applications such as residential VoIP, corporate IP centrex, or video conferencing.

There is a push toward converging the entire gamut of services like mobile, broadband, and enterprise into one network. This network also needs to have sophisticated packet-processing capabilities and transport features like MPLS-TP, OAM, and synchronization. While the share of data in total traffic is increasing, TDM services still have to be supported due to the presence of legacy equipment in the network. Another important requirement is migrating the network from TDM to data in a seamless manner over a period of time.

On impact of 3G and 4G rollouts

3G services launched by service providers in the last 18-24 months are capable of providing speeds up to 21 Mbps over HSPA+ and of up to 100 Mbps per user over 4G/LTE networks. This creates a huge demand for backhaul network which, therefore, needs to be overhauled. This overhaul can happen at different levels. First, a lot of India's mobile backhaul are built over TDM microwave links. With the advent of new data services, one needs a way to optimize these links to fit data traffic into similar links without having to throw away the existing investments.

Network expansion must happen in penetration of fiber deeper into the network. In the long term, only fiber can handle this kind of traffic growth in the network. In addition, technologies like DWDM, OTN, and PTN are required to get the best value out of the investments in laying fiber network.

On key technology trends

In terms of technology, the industry is seeing two key trends. One is a move toward packet transport technologies like PTN and a demand for features like MPLS-TP. MPLS-TP provides transport-style, deterministic, provisioned paths for traffic through a network and helps in better management of packet traffic. The second trend is a move toward OTN in the optical layer. OTN is gaining ground due to its superior reach through Enhanced FEC (EFEC) and better traffic management due to ODU0 level grooming and support for multi-protocol clients. These, along with DWDM and packet transport features like OAM, are providing the technology base for next-generation networks of the future.