What are Femtocells and what are their advantages and disadvantages
A Femtocell is a mini base station consisting of a mini radio unit like that of a cell tower for a mobile operators network. It is designed to provide short range coverage – in and around an apartment, for example. It is small, and customers can install them by themselves. An ethernet connection allows the Femtocell to use the DSL or cable internet connection to back-haul voice and data calls to the cellular operator through internet but directly to the cellular core network, thus by-passing the cellular macro cells deployed in that area. So, the cellular coverage is extended into the homes of the subscribers by using their internet connection.
Advantages and applications of Femtocells:
¤ A Femtocell is used for compensating poor cellular coverage inside the homes – in some places.
¤ A Femtocell can also give lower call charges while the caller calling from home, using the Femtocell as it directly connects to the core network through the internet.
¤ Some vendors are also planning to incorporate all the three features – Wi-Fi, cellular and DSL into the same box to achieve maximum functionality.
¤ The voice calls/data calls through the Femtocells are encrypted and the cell phones automatically switches over to the Femtocells when they come in their range – eg. in homes, where they are installed.
¤ Femtocell units can handle up to three or four simultaneous calls, from the same operator, depending on the model. They can operate with normal cellphones, without any enhancements.
¤ Femtocell units can help related cellular services like 3G by offering a better speed and data rate when inside buildings, where the coverage and data rate is generally lesser than outside.
¤ Generally, the cell towers are back-hauled by using lines with bandwidth of around 2 Mbps (in some places) and hence when newer services like 3G are introduced, these lines may not be sufficient and hence may require a upgrade. But with Femtocells, since the subscribers internet connection is used, there may not be an issue with existing infrastructure if Femtocells are adopted in a large scale.
¤ Femtocells can not only extend the cellular macro network but can also become the primary network if enough Femtocells are adopted in an area. So, all future upgrades etc. can be done by the Femtocells itself, reducing the number of macro base stations required to cover an area – but this is a long shot, based on the current situation and the problems described below.
Dis-advantages of Femtocells:
¤ Some internet data plans today, charge on the basis of bandwidth used. So, asking the subscriber to pay additional data charges for internet back-end connectivity for the core cellular network may not be easily accepted.
¤ Femtocells can support both open and closed usage. That is neighbouring subscribers may or may not be allowed to connect to them. If they are, then the access control list needs to be managed by the cellular network. There will also be a question on the ownership and the location of placement, in case of shared ownerships. If they are not, then the individual subscriber may have to pay the full price (if they are not subsidised by the vendor or operator) for the femtocells.
¤ If the Femtocells are used to their full capacity, it may require around 500 Kbps – which is available in broadband networks – but not for all plans. Similarly, there might be reduction in call quality/ internet browsing if huge files are being downloaded from the internet simultaneously.
¤ The determination of location of the Femtocells becomes critical as the RF channel in which they need to transmit would be determined by their location and the RF channels used by nearby Femtocells. But normally, a particular operator may have licenses for different channels in adjacent geographic areas so there should not be any overlapping which would result in reduction of quality of communications. Also, they should not interfere with the RF channel used by the overlapping macro cell network. For all these things, the determination of accurate location is very important – and it is not clear as to how the operators are planning to address this.
¤ At least initially, the Femtocells would work for only a particular cellular operator. So, every one at home may require to change to the same operator.
¤ Not all cellular operators are on IP Multimedia Subsystem (IMS), which might become the interface for the Femtocells.
¤ Cellular only service providers are dependant on the broadband services which are beyond their control. So, trouble shooting may become an issue.
Wi-Fi and Femtocells:
Many homes have Wi-Fi coverage for accessing the internet. This technology has been standardised and matured over the years. Now Wi-Fi supports voice, data and video over the internet. There are two aspects of Wi-Fi which pose a challenge to the Femtocells.
Dual mode handsets with Cell/Wi-Fi features supporting VOIP may become the de-facto standard for calling in the future. This uses internet connectivity directly, and hence is supported over the Wi-Fi connected to internet.
Wi-Fi standards can support Fixed Mobile Convergence (for details click the link) for the convergence and handover of calls between Wi-Fi and cellular networks. So, this can basically do what Femtocells are doing, if VOIP picks up for local calling as well. But Wi-Fi deployment this way could also face similar challenges like Femtocells. Probably as femtocells are integrating Wi-Fi, DSL and Cellular capablities in a single device – it could be the right way to go, provided the existing challenges are addressed.
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