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Identity Theft - As the name indicates it is a theft of identity, someone could use a mobile phone services and charge your account. Bill Avoidance - Anyone can use a femtocell be used to avoid paying for services provided.
Phone-Tapping - Anyone can use a femtocell solution to intercept your voice or data calls.
These are described in more detail below.
The Femtocells uses the similar confirmation/authentication scheme to prove the identity of the end user by a phone network around the world. This is basically same for both GSM and UMTS (3G) systems which are the most common.
A SIM card (Subscriber Identification Module) has a small electronic circuit with a secret code. When the mobile phone first registers itself with a mobile network a different set of numbers are used to query the SIM card and the response compared with a set of answers provided by the network operator's online database (the HLR or Home Location Register). The above mentioned number will change every time a registration is performed and the method to generate them is known only to the SIM card and HLR. The method is standardized for transporting the numbers and comparing them so as to create a algorithm and can be different for every SIM card. Hence intercepting the information transferred and would not provide a key which could be reused with other phones. Also, even if the key and algorithm was identified, this may not work with other batches of SIM cards or other operators. Up to now, the GSM SIM card security scheme has not been compromised, and even if it was broken for one operator or phone, this doesn't mean that it is unlocked for any other subscribers. It would also be possible for operators to upgrade to a more complex scheme in the future.
The Standard femtocells simply transfer these security messages from the mobile phone to the operator's network, and so are not otherwise involved in the authentication process. Therefore, there is no security loophole to exploit, even if the messages could be intercepted. For the SIP based architecture proposed as a future alternative, it may be necessary for the femtocell itself to perform the authentication.
This would involve comparing the two sets of numbers received from the mobile device and HLR. Whilst this may not allow easy breaking of the SIM code/algorithm, it could open up access into the operators network (e.g. access to the HLR) which they may not be comfortable with. Therefore, it would be expected that authentication continue to take place in the operator's network, and the femtocell rely on that before allowing even "free" voice or data calls through the system.
Bill avoiding falls in the same class as bypassing the electricity or gas meter so that services can be obtained for free. Where all calls or data traffic are controlled by and routed through the core network, it is difficult to see how billing and charging functions could be avoided.
However, if the femtocell itself becomes the controlling network element (ie the MSC or GSN function), then there is a risk that the femtocell could be compromised to achieve that purpose. We have seen considerable efforts to "hack" and unlock the iPhone, as well as re-engineering consumer boxes such as TiVo players, Xbox games machines etc. If it becomes possible to do this for a femtocell, then any core billing functions may be at risk. Vendors have proposed including a SIM card in the femtocell itself, in order to validate that the owner of the device is known, and thus stolen or compromised units can be disconnected from the network.
Phone tapping is a common concern of early mobile phone users that their conversations might be overheard. Older, analogue networks often did not use any encryption over the air, and thus could easily be listened to by anyone in range.
Digital networks, like GSM and UMTS, encode the voice and data messages sent from the mobile device to the basestation, effectively avoiding that problem. The other weak link is from the basestation to the operators central switching centres. Femtocells will typically encrypt their voice and data traffic using secure tunnels (IPsec) between the femtocell and the operators network. This is may be more secure than when using the mobile phone outdoors, where no encryption is used.
The FigureÂ below shows a Femtocell implementation. The figure shows a femtocell for local basestation operation in UMTS band one, as well as a monitor signals in the 850MHz, 900MHz, 1,800MHz, 1,900MHz and 2,100MHz bands. But on the transmit side the digital baseband signals is fed by a 12 bit parallel data stream to the AD9863 transceiver which will convert it to an analog baseband signal. The baseband signal is converted to RF (by an ADF4602) and amplified by the PA gain stages, and sent to a duplexer. A power detector monitors the RF output.
Figure 13:- Femtocell implementation 
One single-pole which is a six-throw (SP6T) switch which what to transmit or receive and the monitoring chain is connected to the single antenna. The above signal chain will provide 13dBm output power at the RF output connector, while meeting transmit ACLR specifications as defined in 3GPP standard TS25.104.
The receiver chain includes a surface acoustic wave (SAW) filters and SPDT switches for monitoring the main path. The matching blocks consist of a simple series/shunt inductor for each receive port. The RF signal is downconverted and filtered to a baseband I/Q signal. The baseband signal is sampled by the dual on-chip ADCs and converted to dual 12-bit parallel bit streams for the digital baseband. The femtocell requires an accurate reference clock (Â±0.1 ppm) to meet 3GPP specifications. To achieve this, several possibilities exist, including GSM macrocell synchronisation via the monitoring receivers, GPS synchronisation, and IEEE 1588 precision timing protocol. In some instances, a combination may be implemented.
The Femtocells can be packaged in a many different physical formats. The following are the main ones :
This type of format is an original concept. It has a unit with two wired connections they are:
one for power through an external main adaptor,
one for data through an Ethernet RJ45 to your broadband modem.
There can also be a few indicator lights but very little is needed to install and make use of the product. During the very early days of product evolution, the capacity to focus on the new system will ignore any external issues and quickly evolve new versions is important.
But it has support issues and longer term cost. Many home users may not be talented in connecting wired devices to their router but there is no knowing what the router model is and how it is configured. This can lead to the result of femtocell not working at all, or worse, not working well. For example, if voice traffic is not given priority then calls may dropout during heavy data usage on laptops or computers in the same house.
To integrate the Femtocell into an existing DSL broadband modem design is the next step. No additional or external connections are needed, the modem will already have the power and data connectivity, and usually a lot of other standard features too. The femtocell module is basically hardwired into the modem and can be given priority for voice calls to ensure improved performance. The overall cost of the combined unit is much less than two separate boxes, it is the ease of installation and remote management which benefits this option. If the additional cost of a combined modem/femtocell is acceptable, then this could be shipped to customers as part of a package.
More and more households in the USA receive their broadband internet service from their cable TV supplier other than from the phone company as is the more common situation in Europe and elsewhere. The modem can be separate from the TV Set-top box or a combined unit.
In US the large TV companies such as Comcast had previous agreements to resell the mobile services on a sprint network but this is now gradually decreasing. Although Cable TV companies do own some spectrum (via the Spectrum Co) business, and so could legally start and operate a network using this, their investments seem to be more based around WiMax rather than traditional mobile phone technology at present.
TV Set-Top Box
These days many customers are becoming used to a set-top box to watch additional TV channels, record/playback programs and play games. The femtocell must serve the whole house, rather than just the room with computers in, it can make more sense for it to be located near the TV.
The typical examples of set top boxes include the following:
A cable TV decoders, which can include the following:
PVR (Tivo-like) ability to record programs to hard disk for later viewing
IPTV ability to download or stream video programs from the internet
A satellite TV decoders with similar capabilities. For example, in the UK, SKY+ a combined satellite receiver/decoder and PVR is extremely popular.
Games consoles, such as Nintendo Wii, Sony PSP etc. Some of these products are now also capable of handling IPTV services such as the BBC's iPlayer.
Those Operators who want to take the major part of the household spend will want to control of as many of these functions as possible. Several of these options are being offered by Cable, Satellite, telephone and some Internet Service Provider companies in many countries.
6.2.Benefits of Femtocell Technology:-
The major benefit of femtocell technology is that it will not increase the coverage and call quality of mobile phones within a residential area or small business environment. However, there are also additional benefits of this technology which may enhance its appeal to someone who is weighing the options of whether or not to invest in a base station for the home. Some of those additional benefits include:
â€¢Â Reduced costs on calls:- This factor varies on the situation that the phone is going through and also the calling plan but also they have capability of reducing the calling rates when we use this Femtocell technology in order to improve the calls This feature is increasing as more companies start to look at creating femtocell technology solutions for their consumers. The cost to the cell phone operator is actually lower in terms of both initial expense and ongoing expense when femtocell technology is used. As it sees more widespread use, it is likely to see these phone operators reducing costs accordingly.
â€¢Â Increased call capacity:- Most phone companies are mainly interested in developing femtocell technology because it allows them to reduce the exhaust on their own networks and offer increased calling capacity to consumers. With more and more people taking an interest in capacity-draining services such as mobile broadband, it is becoming necessary for technology to be developed that supports this kind of use.
â€¢Â New services:- The Femtocell technology has the prospective to offer new services to mobile phone users. This new technology is still being developed and improved upon so the options are very minimum at the moment but there is always a future scope. Some of those services, such as increased mobile broadband options, are related to the increased call capacity that femtocell technology offers. Others are related to the type of network that is created and include things like easily sharing data between your home computer and your mobile phone.
â€¢Â Early alternative to Fixed Mobile Convergence (FMC) possibilities:- This is one of the areas of mobile phone technology that developers are currently working hard so to make the idea of fixed mobile convergence a reality. This refers to a flawless change from the users between wired and wireless communication devices.
When it becomes a reality it would be possible to use one phone to switch between different networks and calling plans. Until this technology becomes a reality, femtocell technology provides an in-home opportunity that mobile phone users can take advantage of.
Femtocells offer a number of important benefits to both consumers and operators. For consumers, they will provide improved mobile coverage (better signal strength) in their homes, and high performance mobile data providing faster access to mobile services and multimedia content. Mobile operators may also offer attractive service bundles for femtocell users.
Some other benefits provided by this technology includes better coverage (signal strength) at home, improved quality and personal 'bandwidth' for dedicated access to services such as mobile TV and music. Femtocells also make it easier for families to track their bills.