HetNets : Carrier WiFi muscles in !!

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The shift from wired to wireless is well underway and as mobile demand continues to skyrocket, capacity continues to shrink. According to Cisco, global mobile network data grew by 70% in 2012, amounting to 885 petabytes per month, up from 520 petabytes per month at the end of 2011. Total data volume in 2012 was a staggering 12 times more than the size of the entire global Internet in the year 2000. By 2017, monthly global traffic is expected to reach 11.2 exabytes, which is 1144% higher than in 2012, an average growth rate of 66% per year.

A recent survey revealed that tier-one mobile network operators expect 22 percent of all additional data capacity added during 2014 to come from Wi-Fi offload, according to the Wireless Broadband Alliance.By 2018, Wi-Fi offload is predicted to contribute 20 percent of additional mobile data capacity plus a further 21 percent will come from small cells with integrated Wi-Fi.These findings demonstrate how important data offload is to mobile network operators, accounting for an average of 20 percent of data traffic, up to 80 percent in densely populated areas such as transport hubs and cafes. Within homes and businesses offload levels are 50 to 60 percent.Telstra will spend more than $100 million to build a wi-fi network by next year involving around 8000 Telstra-built hot spots and a further 1.9 million wi-fi access points provided by its customers nationally.

The Cisco Visual Networking Index report that a laptop can consume up to 450 times more bandwidth than a simple phone and 30 times more than a smartphone. The estimated capacity consumption of an iPhone is estimated to be 30 times that of a simple phone.Even assuming some reduction in the rate of traffic growth over the next few years (expected by most data traffic forecasts), mobile operators still need to increase network capacity quickly and cost effectively, without relying solely on new spectrum availability. In this context, densification of the network infrastructure with both small cells and Wi-Fi is necessary for operators to keep up with demand without breaking the bank.

With traditional network design strategies, mobile service providers essentially have three primary capacity expansion tools, including:

■ Increase macro cell site density: Each cell split would require regulatory approval, new sites and civil work.

■ Technology upgrade to OFDMA-based 4G technologies WiMAX and LTE: To achieve a 3 to 4x increase in capacity.

■ Expand radio spectrum resources: Acquiring new spectrum can be expensive, limited by availability and subject to government regulatory timelines.In each case the backhaul transmission network may also need to be upgraded accordingly.

The HETNET can consist of different cell scales which range from macro to micro, pico and even femtocells, potentially sharing the same spectrum. Nodes can deploy different access technologies over both licensed and unlicensed bands. Co-channel femtocells can provide linear gains in air interface capacity with increasing number of femto-APs in a hybrid deployment.While the macro network provides coverage, small cells (pico and femto) are better suited for capacity infill and indoor coverage. Small cells require no tower infrastructure or low lease cost, therefore drastically cutting the operational and capital expenditures.

A large proportion of the world’s small cells have been deployed in Asia Pacific in Korea and Japan, with volumes picking up in China and India. In dense environments, mobile operators are deploying enterprise and residential small cells in indoor venues to add capacity locally, with the potential for a 1-to-4 ratio of macrocells to small cells.Outdoor picocells will most likely leverage a Cloud-RAN architecture and will roll out in 2017. Cloud-RAN deployments are now out of the proof of concept stage and are currently in trials. These cloud-based access points, which are also known as virtual base stations or C-RANs, will form the base of a 5G network architecture. They will handle not only the voice and data traffic for consumers, but will also support the M2M and IoT applications that form the ‘connected network’ of the future.The majority of small cells will be multi-mode, supporting both LTE and Wi-Fi in the 5GHz band, allowing operators to take advantage of cost savings due to leveraging unlicensed spectrum. By supporting the 5GHz band, mobile operators can also deploy LTE-LAA on the same small cell.

Despite the benefits HETNETS pose a new set of challenges for network planners including:

■ Cross tier interference: A dense femtocell deployment poses significant interference to macro cells. While interference to data can be addressed via intelligent use of Fractional Frequency Reuse (FFR), interference to control signals requires new mechanisms.

■ Mobility management: Handover across small cells at moderate to high speeds gobbles network resources, and can degrade user experience if not managed well.
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■ Self-Organizing Networks (SONs) are essential for consumer deployed nodes like femtocells, and are important for managing inter-tier deployment.

■ Security management between nodes of different ownership (consumer, enterprise, operators) and Service continuity, QoS management and delivery across multiple tiers are essential for high performance and high capacity heterogeneous networks.

In a HetNet scenario combining small cells with Wi-Fi and macrocells, mobile operators are rolling out a number of interference management techniques to ensure the network is optimized for capacity and coverage such as :

• Enhanced Inter-cell Interference Coordination (eICIC) works as the interference manager for small cells as part of a HetNet. It uses advanced time domain scheduling to reduce radio interference and increase the coordination between network cells to ensure a streamlined flow of information.
• Multiple Input and Multiple Output (MIMO) is an approach which serves to increase efficiency across the spectrum by leveraging smart antenna technology that analyzes how base stations, antennas and user equipment communicate.
• Coordinated Multi-Point (CoMP) is a technique that ensures that even greater performance is achieved at the edge of the network, by increasing coordination between small cells, and between small cells and macro cells.
• Relay Nodes are low-power base stations that reduce the site-to-site distance in the macro network. They were added to the LTE Release 10 specification.

Backhaul is needed to connect the small cells to the core network, internet and other services. Mobile operators consider this more challenging than macrocell backhaul because small cells are typically in hard-to-reach near street level rather than in the clear above rooftops and carrier grade connectivity must be provided at much lower cost per bit In one survey, 55% operators listed backhaul as one of their biggest challenge for small cell rollout.Many different wireless and wired technologies have been proposed as solutions, and it is agreed that a ‘toolbox’ of these will be needed to address a range of deployment scenarios. An industry consensus view of how the different solution characteristics match with requirements is published by the Small Cell Forum.

Adding Wi-Fi to a small-cell enclosure does not increase its price significantly – and equipment typically accounts for a small part of the capex. The higher backhaul requirements may lead to an increase in equipment cost, but that is unlikely if operators use fiber or high-capacity wireless backhaul.Injecting Wi-Fi to cellular small cells not only gives the small cells a capacity boost, it substantially lowers the TCO for the combined cellular and Wi-Fi deployment, because the marginal cost is low.The same is true in the reverse: adding cellular radios to operator-owned Wi-Fi deployments likewise lowers TCO, because the marginal cost of adding LTE to a Wi-Fi hotspot with sufficient backhaul capacity is low.Furthermore, combining Wi-Fi with 3G small cells makes it more attractive for operators to have initial 3G and Wi-Fi small-cell deployments, in networks without LTE or without any need yet for additional 4G capacity, but with severe 3G congestion.

Equipment installation and operating costs remain the same when adding Wi-Fi to a cellular small cell, because the siting, installation and operating requirements are the same.As Wi-Fi and cellular become integrated in the same small-cell enclosure because of the TCO savings, a decision between Wi-Fi and LTE is no longer needed, because both get deployed throughout the small-cell footprint.Deploying a small cell with an integrated Wi-Fi solution is part of an overall strategy that operators will find maximizes the investment return from small cells. These additions leverage the investment of small cell deployments and require an incremental CapEx to add Wi-Fi into the solution mix.

China Mobile and AT&T are among those incorporating Wi-Fi into their heterogeneous network architectures and expect more operators to follow suit. Hotspot 2.0, or Passpoint, is also gaining traction – Time Warner Cable recently announced a national deployment of the technology for users of its Wi-Fi network, which means that users only have to log into the Passpoint network once and are automatically authenticated whenever they are in range thereafter.For outdoor cells, the main issue now appears to be the ability to acquire the sites where the mini base stations should be deployed – such as lamp posts and bus shelters – rather than with any technical issue. Some Pundits recommend the “crowd-sourcing” model, while operators say they are open to working with aggregators and the cities themselves.

When planning for a capacity expansion, the use of operator-owned carrier Wi-Fi networks will reduce the cellular capacity requirements. When planning for a small-cell sublayer, operators have to carefully select locations both for Wi-Fi and for cellular small cells where the subscriber density is highest. An even or peaked distribution of subscribers within the macro footprint, the choice between indoor and outdoor coverage, and the area topology have a great impact on the capacity gain that Wi-Fi and cellular small cells contribute.There is no doubt that Heterogeneous networks will enable the cost effective deployment of high performance networks in order to bring wireless broadband to every corner of the globe.

In future one expects client clustering and P2P communication to transmit/receive information over multiple paths between the base station and client. This creates the potential for improvement in throughput, capacity and reliability without increased infrastructure cost.The adoption of HetNet RAN architecture has a big impact on network management. In particular in order to manage the interworking and interoperability between macro e micro layers, it’s fundamental to adopt a solution called SON (Self Organizing Network).The main aim of the SON suite is to perform the optimization tasks, routines and activities, usually manually carried-out by engineers, in an automated, continuous, autonomous and closed-loop way, applying pre-defined optimization policies and rules.

TIM Brasil, a pioneer of Wifi SIM authentication, started the process of rolling out a large-scale carrier-class WiFi network to offload 3G and to reach previously underserved communities in the cities of Rio de Janeiro and Sao Paolo. TIM Brazil’s solution offers automatic EAP-SIM authentication to smartphones and SIM-enabled tablets, working joined with mobile network in order to manage the traffic bundle of the customer.WiFi was also installed in Airports and Stadiums; in April 2014 during the match between Botafogo and Union Espanhola, with 44.000 people watching in the Maracanà, around 28GB of traffic were managed by TIM WiFi network.In all the World Cup’s matches the WiFi offload was always between 20% and 45%, helping mobile network to provide good performance to the supporters.

by Sadiq Malik ( Telco Strategist )

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