With the growing demand for mobile data, cellular service operators are increasingly turning to small cells -- picocells, microcells, metrocells and femtocells -- to deal with the capacity crunch in dense urban areas and to add coverage in areas with low or zero cellular signal levels, such as indoors and in remote rural locations.
But the capacity of small cells, which use licensed spectrum, is dependent on the availability of that limited spectrum, can be degraded by interference between small cells, and requires significant planning. To cope, some service providers are looking to use Wi-Fi to augment their investment in small cells.
A number of vendors, including BelAir Networks (acquired by Ericsson), Ruckus Wireless and IP.Access, have announced Wi-Fi integrated LTE and HSPA picocells. At Mobile World Congress 2012, a number of announcements concerned Wi-Fi integrated small cell technology. Alcatel-Lucent, for example, announced a secure Wi-Fi gateway for small cells and an integrated Wi-Fi option for its existing femtocell and picocell products. Cisco also rolled out a small cell gateway to help operators integrate Wi-Fi into small cells, while Airspan Networks announced the integration of carrier Wi-Fi to its LTE small cell solution.
Integrating the Wi-Fi radio in a small cell will open a host of opportunities and benefits to cellular carriers, including:
* Cost-effective additional capacity: Integrating Wi-Fi radios into small cells provides cost-effective capacity and additional coverage for small cells, particularly for those cells that are targeted for public usage, like picocells, over and above their available cellular capacity. This additional boost will further help small cells deliver seamless data services in dense urban sites reeling under the capacity crunch, and will also enable a small cell site to gracefully handle peak capacity hours.
* Service extension to non-cellular devices: Since Wi-Fi support has become ubiquitous on everything from laptops to tablets and cameras, integrating Wi-Fi into small cells will allow carriers to extend data services to non-cellular devices, adding an additional source of revenue.
* Smart and intelligent data offload schemes: With Wi-Fi integration, smart data offload schemes will enable service providers to selectively allow voice and other carrier-managed value added services to be served through the carrier's core network (via cellular connection), while offloading Internet traffic to Wi-Fi. These offload schemes can provide mobile users the best of both worlds, cellular connectivity for voice and value added carrier services, and Wi-Fi connectivity for cost-effective data services. This would also enable carriers to launch cost-effective plans. [Also see: "Wi-Fi's promise for cell carriers running out of options"]
* Wi-Fi on-load: Wi-Fi, when part of a small cell, can be easily linked to the core network over the same backhaul link, allowing carriers to provide end-to-end quality of service guarantees and cellular-like security for Wi-Fi traffic. This essentially means that all carrier services, including the voice, value added and data services can be effectively and efficiently provisioned on the Wi-Fi radio itself. In fact, carriers will be able to roll out Wi-Fi only, cost-effective plans featuring full-fledged access to all sorts of carrier services -- talking, surfing, messaging, etc. The concept of Wi-Fi on-load is being aggressively targeted by service providers, such as Republic Wireless.
* Seamless cellular Wi-Fi handovers: Integration of cellular and Wi-Fi radios in a small cell also allows for seamless handover of traffic from cellular to Wi-Fi radio and vice versa as requirements shift due to, say, excessive interference, battery drain or overload conditions on either the cellular or Wi-Fi radio. Seamless handovers assures the continuity and quality of traffic for a mobile user regardless of radio access technology.
* Local breakout: This function essentially allows users to connect their mobile devices to the local home, office, or campus network without traversing the operator's core or any other outside network. Local breakout capability can be easily achieved with a small cell that has integrated Wi-Fi.
* Benefits of Wi-Fi radio virtualization: Wi-Fi radios can be virtualized into multiple exclusive Wi-Fi networks, leading to many benefits. That makes it possible, for example, to multiplex Wi-Fi offload and Wi-Fi on-load functions together over the same physical Wi-Fi radio. Similarly, other services such as business promotions and advertising can be easily multiplexed over a virtualized Wi-Fi radio along with regular services. Such multiplexing allows more flexibility for the carrier to cash in on various differentiated services over the same small cell site without extra capex/opex. Virtualization also helps carriers to share/resale part of Wi-Fi capacity cleanly.
* Wi-Fi backhaul: The presence of a Wi-Fi radio in a small cell also makes it possible for carriers to use Wi-Fi as an effective wireless backhaul link for cellular traffic when wired options are scarce. Moreover, Wi-Fi radios in multiple small cells can be arranged in a mesh for high availability and reliable backhaul. [Also see: "LTE performance will hinge on picocell backhaul"]
* Newer business models: With integrated Wi-Fi, a small cell can be leveraged into newer business models, such as managed/hosted Wi-Fi services for venues, enterprises, etc., which is not possible with the cellular-only capability of small cells. Moreover, these business models will allow carriers to further leverage their licensed spectrum via the cellular radio of the cell. Built-in Wi-Fi also presents the unique opportunity of selling/sharing the whole or partial Wi-Fi capacity (via virtualized Wi-Fi radio) to third parties, such as hotspot aggregators, MVNOs, etc.
* Low cost of ownership: Without Wi-Fi integration, carriers need to separately plan and spend for capex and opex to pursue both small cell and Wi-Fi strategies, which can result in a considerably higher cost of combined ownership. However, with integration at the site, carriers can reap the benefits of both strategies quickly and with lower cost of ownership, as integration allows sharing of resources between the two, saving on extra site rental and additional equipment, backhaul and other costs. Carriers can also save on separate OAM, gateway or provisioning modules, required for both strategies via integration, which otherwise might be required in a non-integrated scenario.
While in the past traditional small cell and Wi-Fi technology were considered competitors, it is now understood the technologies can complement each other well. Co-existence of both technologies in a single box at a particular site will ensure the use of the right technology at all locations and at all times, providing a seamless mobile experience that is completely agnostic to the type of radio access technology used.
Gupta is presently working as team lead at Wesley Clover Communications Solutions. He has been in the field of Wi-Fi access and security for more than seven years and is a frequent contributor to leading magazines and blogs on wireless topics.
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