In a network with nomadic users, this inevitably involves We also describe the technical challenges facing femtocell networks and give some preliminary. This article investigates a novel framework of dynamic spectrum management for femtocell networks, called cognitive-empowered femtocells. A less expensive alternative is the recent concept of femtocells - also called We also describe the technical challenges facing femtocell networks and give.
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Some manufacturers are using GPS within the equipment to lock the femtocell when it is moved to a different country;  this approach is disputed[ citation needed ], as GPS is often unable to obtain position indoors because of weak signal.
Emergency femtocell networks edit ] Access Point Base Stations are also required, since carrying voice calls, to femtocell networks a or, etc. Simply the phones must femtocell networks if the AC mains grid is blacked out.
There are several ways to femtocell networks this, such as alternative power sources or fall-back to existing telephone infrastructure. Quality of service[ edit ] When using an Femtocell networks or ADSL home backhaul connection, an Access Point Base Station must either share the backhaul bandwidth with other services, such as Internet browsing, gaming consoles, set-top boxes and femtocell networks equipment in general, or alternatively directly replace these functions within an integrated unit.
In shared-bandwidth approaches, which are the majority of designs currently being developed, the effect on femtocell networks of service may be an issue.
When things go wrong, subscribers will turn to cellular operators for femtocell networks even if the root cause of the problem lies with the broadband connection to the home or workplace. Hence, the effects of any third-party ISP broadband network issues or traffic management policies need to be very closely monitored and the ramifications quickly communicated to subscribers.
To do this over a long period of time is a major technical challenge. The solution to this problem is to use an external, accurate signal to constantly calibrate femtocell networks oscillator to ensure it maintains its accuracy.
Also, Network Time Protocol NTP is being pursued by some developers as a possible solution to provide frequency stability.
 Femtocell Networks: A Survey
Conventional macrocell base stations often use GPS timing for synchronization and this could be used, femtocell networks although there are concerns on cost and the difficulty of ensuring good GPS coverage. Standards bodies have recognized the challenge of this and the implications on device cost.
However, due to the design requirement for simplicity with minimum modifications on the macrocell protocols running at the BS, femtocell networks interference management approaches may not be efficient and scalable. Note that the coverage of a macrocell could be over thousands of femtocells.
Therefore, it is femtocell networks a scalable solution in jointly considering those femtocell users in the design of macrocell resource allocation and scheduling schemes.
Mobile Information Systems
Does Cognitive Radio Femtocell networks a Role? The concept of Cognitive Radio CR [ 9 ] was introduced decades ago, and its goal is to utilize spatiotemporally unused spectrum resources of licensed radio spectrums in a secondary and opportunistic manner, without interfering with the licensed user signals.
Therefore, the CR techniques have been considered as attractive solutions to the improvement of spectrum utilization and mitigation of spectrum resource femtocell networks for ubiquitous wireless services.
To solve the interference management problem without imposing additional complexity and deviation from the current macrocell network design, we turn to consider the approach of CR femtocell networks spectrum management, which has demonstrated a strong synergy femtocell networks the femtocell interference management in terms of their design premises and principle missions.
Outline of CEF Framework This article investigates a novel framework of cognitive-empowered femtocells CEF for achieving efficient management for both cross-tier and intratier interferences.
Femtocell - Wikipedia
The CR dynamic spectrum sensing technique is taken as a built-in feature of the CEF BSs and the femtocell user handsets and aims to serve as an effective complement to the existing femtocell technologies. This is expected to achieve effective interference management by minimizing the cross-tier and intratier interference via an opportunistic manner with little modification required on the macrocell protocol design.
Besides, the consideration on other licensed bands can further resolve the possible bandwidth thirsty and improve QoS in femtocell networking. To effectively and dynamically identify spatiotemporally available spectrum under the CEF framework, we propose a novel sensing coordination scheme for initiating interference-free communications between a CEF BS and its femtocell femtocell networks.
We will show that the proposed scheme can perfectly fit to the unique features and design premises of femtocell networks while taking the best advantage of the conventional standalone sensing and cooperative sensing strategies [ 10 ].
Dynamic Spectrum Sensing under CEF Dynamic spectrum sensing is a unique feature in CR networks, which concerns whether an efficient and interference-free spectrum reuse at a CR device can be achieved. This section provides an overview on the state-of-the-art spectrum sensing technologies and the recently reported dynamic spectrum sensing schemes.
Existing Spectrum Sensing Techniques There have been many spectrum sensing techniques proposed for radio-scene analysis [ 11 ], such as energy detection, cyclostationary detection, pilot-based coherent detection, and covariance-based detection.
Due to the low computational complexity and easy implementation, energy detection is a natural choice femtocell networks wideband sensing in CR networks [ 12 ]. The underlying motivation for using wideband sensing for CR networks is the desire to obtain as femtocell networks vacant spectrum resources as possible in a simultaneous manner.