Document Actions
Deploying and Managing Femtocells in Today's Mobile Networks
Consumers have begun to demand ubiquitous voice and broadband data connectivity from their mobile networks, from inside buildings and from the convenience of their own homes. Operators can achieve this indoor coverage by deploying more towers with large base stations coupled with paid backhaul links to each tower; however, this approach is prohibitively expensive to deploy and operate. This situation is driving operators to explore alternative, cost-effective solutions for increasing wireless coverage indoors.
One option that has been considered is leveraging WiFi access points in combination with a cellular infrastructure to enable a cost-effective offload of data and voice services. While technically feasible, this model has presented challenges to operators, such as the lack of wide availability of handsets with WiFi radios. Additionally, operators find it difficult to ensure Quality of Service (QoS) over unlicensed and interference-prone WiFi connections, keep subscribers on the service provider's network, and effectively manage subscribers in a standardized way.
An alternate solution gaining momentum among both mobile operators and their customers is femtocells. Femtocells are miniature base stations, based on WiMAX or 3G technologies that are deployed within buildings or homes. This model enables lower-power, lower-cost base station designs similar to WiFi Access Points (WAPs). Backhaul traffic from femtocells can piggyback on existing broadband connectivity to the building or home, further reducing the cost and expense of deploying a wireless infrastructure. Linking the femtocells with macrocell base stations and other wireless infrastructure promises service providers a homogenous network infrastructure that can leverage uniform management, security, QoS, provisioning, and billing. This model also eliminates the need for an additional WiFi radio in the handset.
Despite these benefits, making the femtocell vision a reality requires tackling a number of technical hurdles. It is not simply a matter of building lower cost base stations. Operators must also provide the appropriate end-to-end architecture to ensure proper coordination between femtocells and macrocells, simplified provisioning, sufficient security, seamless handovers and reasonable overall cost of deployment and operation. Operators that want to take advantage of this market opportunity must address these challenges, and integrate the right tools and network intelligence to address them.
Management and Provisioning
Rather than hundreds of base stations in a given geographic region, the femtocell model calls for hundreds of thousands of smaller, cheaper base stations in a similar footprint. This introduces challenges to the traditional models for management and control of base stations. With the residential market, for example, femtocells need to be plug-and-play devices that connect automatically to the operator's network without a lot of complicated steps and procedures. Furthermore, terminating sessions from the vast number of femtocells will require high capacity access service gateways (e.g., WiMAX ASN Gateways). These devices will need to manage and control interactions between the femtocells and the wireless network infrastructure.
Security
Deploying femtocells within buildings and homes requires additional security to ensure integrity of the traffic. Since all voice and data traffic going to femtocells travels over public networks, this traffic needs to be secured using encryption. Authentication is also important to ensure rogue femtocells are not able to join the network and subscribers are properly identified and authorized to use the service. These requirements drive the need for centralized gateways that can support encryption and authentication on a large scale.
Spectral and Mobility Management
Since femtocells use an operator's limited licensed spectrum, effective sharing of spectrum among femtocells and between femtocells and macro base stations is essential. Carriers also want to ensure proper handoffs among femtocells and between femtocells and macrocells. Mobility management in the femtocell model is more challenging than mobility management between a WiFi network and a cellular network, as in the latter case, the handset has two radios that create two independent connections to the network core before handoff. Centralized intelligence and control in access service gateways enable carriers to manage the valuable spectral resource and ensure seamless handovers for real-time services such as voice or video.
Cost Efficiencies
Another critical factor for this model to work, is achieving very low cost femtocells. Some operators have indicated that femtocells need to cost less than $100 - a far cry from typical base stations that can cost tens of thousands of dollars. Meeting this price requires highly integrated base station chipsets and the elimination of complex base-station functionality that can be more efficiently handled by a centralized gateway solution.
Standards and Interoperability
Perhaps one of the biggest challenges for femtocells is the coordination of standards and interoperability. The Femto Forum was recently created to help drive this ecosystem and promote interoperability. Vendors with diverse technologies are attempting to work together to solve a common problem; yet, each brings its legacy perspective of interfaces, making it challenging to find a single solution. In some respects, the concept of standards-based, mass-consumer femtocells is at odds with the traditionally closed architectures that large telecom vendors have built over the last few decades. WiMAX may have an edge in this area, as this technology was born out of IEEE and IETF's IP protocol, both of which have a history of open standards, interoperability, and letting the market dictate which solutions are superior. Success with femtocells will require this new type of "open market" thinking. As they say, a rising tide will float all boats.
Bringing Order to Chaos
The femto model is very compelling, but the industry will need to overcome these challenges for femtocells to become a mainstream technology. A critical component of the solution will be an access service gateway, or ASN Gateway in WiMAX networks. This is an intelligent core platform that provides centralized coordination and management of hundreds or thousands of femtocell base stations. Such a solution can help offload cost and complexity within the femtocells and ensure optimal overall network performance.
Different solutions for the enterprise and the home will likely emerge. Within enterprises or large public buildings, such as airports or shopping malls, carriers will likely deploy small intelligent access service gateways that can manage several femtocells and ensure optimal performance. These networks will involve a higher number of inter-femto handovers and increased spectral coordination between femtocells. For residential deployments, the access service gateway will likely be deployed within the carrier's network and serve several subscribers. For these deployments, handovers and coordination will be between femtocells and macrocells.
The femtocell model is an exciting vision that can enable ubiquitous broadband wireless access. Before this vision becomes a reality, however, the industry will have to tackle several issues to provide the right cost points, manageability, and performance to enable broad adoption. A critical piece of this network will be centralized, intelligent control in the form of access service gateways - a solution that enables simpler, lower-cost femtocells and provides the necessary coordination to ensure optimal end-to-end network performance.
By: Eric Andrews
_____
tags:
