Femtocell Technology
Today’s mobile networks have been built on large cells (“macrocells”) each covering an area of a few square miles. Each cell serves hundreds of subscribers from a radio base station in a centrally located cell site. While such a macrocell architecture works well in covering large geographic areas, it falls short in providing consistent coverage, especially inside buildings where increasingly most usage occurs. As a result of low radio signal levels, mobile phone user experience inside buildings is significantly inferior to that of fixed-line telephony.
While voice coverage problems persist, mobile devices are undergoing perhaps their greatest transformation since the early days of cellular telephony. Feature phones are being replaced by smartphones, and use of data applications on these smartphones is rapidly growing. This is starting to expose another major limitation of the macrocell network: there is not enough spectrum to meet the needs of subscribers, whose monthly data usage is growing 2-3x annually. Further, sharing the total available data capacity of a macrocell base station by hundreds of subscribers in a single cell reduces the data throughput available to an individual subscriber, thus degrading their mobile broadband experience.
With widespread availability of broadband Internet access lines in most homes and businesses, it is now possible to circumvent these inherent limitations of cellular networks by creating very small indoor cells served by small access points – femtocells – that connect users to mobile operator networks via the Internet. Femtocells not only solve the long-standing in-building coverage problem, they also relieve the data strain on wireless networks by offloading in-building smartphone data traffic to fixed-line networks, essentially making the cost of delivering services to a mobile phone comparable to the cost of delivering fixed-line voice and Internet services. The small cells created by femtocells allow mobile operators to deliver the capacity of a single sector of a macrocell base station to a single household thus greatly improving the mobile broadband experience of individual users. Reusing the same spectrum in every home dramatically increases the spectral efficiency of the wireless network.
Realizing the enormous potential of femtocells, however, required advances in a number of technical areas:
Femtocells are intelligent cellular access points that support any 3G mobile device using standard cellular air interfaces, such as CDMA2000, UMTS and LTE. They are cellular radios that are tightly integrated with the existing macrocell radio network and thus create a seamless experience for mobile users as they move in and out of femtocell coverage, whether on an active call or in standby. Femtocells learn their radio frequency (RF) surroundings and use this information to self-optimize their operation. In particular, femtocells use their RF awareness to control interference between themselves and between femtocells and macrocells. This is achieved without requiring any modification to billions of mobile devices that are already in use. Femtocells also support access controls, whereby only users authorized by the femtocell owner are allowed to use it. The Femtocell Radio Technology section addresses these topics, and highlights some of the advanced radio solutions used in Airvana’s femtocell products.
Femtocell Network Architecture:
Connecting femtocells to operator networks requires unique architectures that address the security needs of operators and mobile users and support the deployment of scalable femtocell networks that can serve millions of subscribers. The femtocell network architecture is also designed to allow ordinary consumers to install them with plug-and-play simplicity. Significant adaptive and self-organizing capabilities built into this architecture support zero-touch service activation by the user. Network architecture is also critical in supporting emergency calling, which can now be delivered to mobile devices inside buildings with the same reliability and accuracy as fixed-line emergency calling. The Network Architecture section addresses these critical topics, presents alternative approaches that are used in femtocell products, and highlights some of the unique solutions used in Airvana femtocell products.
Standardization of Femtocells:
One of the key requirements for mass-market adoption of femtocells is standardization. With standardization, network operators can offer femtocell solutions from multiple vendors, thus driving competition and lowering prices. Airvana has been a strong advocate of rapid standardization of femtocells and holds a number of leadership positions in organizations such as the Femto Forum and 3GPP2 that are leading femtocell standardization. The Femtocell Standards section addresses this topic and provides the current status of the standardization of femtocell technology.
Femtozone Applications & Services:
Femtocells also offer a new opportunity to enable innovative mobile phone applications and services in homes and offices by taking advantage of the unique relationship between the femtocell, the mobile device and the home and office network. A number of unique applications and services will be enabled and these will further improve our digital lifestyles. The Femtozone Applications section gives examples of these applications.