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Small cells I : Femto cell


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Small cells are Low-powered radio access nodes, Operate in licensed and unlicensed spectrum, Short range mobile phone base stations, Range from very compact residential femto-cells of area 10 meters to larger equipment used inside commercial offices or outdoor public spaces of area 1 or 2 kilometers, "small" compared to a mobile macro cell, with range of a few tens of kilometers, Complements mobile phone service from larger macro cell towers, Offer excellent mobile phone coverage and data speeds at home, in the office and public areas for both voice and data, Developed for both 3G and the newer 4G/LTE radio technologies.
Femto cells are Initially designed for residential and small business use with a short range and a limited number of channels. Femtocell devices use licenced radio spectrum. Femto cells must be operated and controlled by a mobile phone company, One cell with one mobile phone operator. When in range, the mobile phone will detect cell and use it in preference to the larger macrocell sites. Calls are made and received in exactly the same way as macrocell. Except, the signals are sent encrypted from the small cell via the public or private broadband IP network to one of the mobile operators main switching centres.

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Small cells I : Femto cell

  2. 2. Small Cells TOPICS  Small Cell Types  Femto cell :  Introduction  Liscence  Power and Quality  Capacity  Security and Management  Compatibility  Standards  Architecture  Components and building blocks  System software  Evolution  Installation  Working  Handover  Location lock  Reparenting  Security  Timing and synchronization  Issues  Reference
  3. 3. Small Cells  Low-powered radio access nodes.  Operate in licensed and unlicensed spectrum.  Short range mobile phone base stations.  Range from very compact residential femto-cells of area 10 meters to larger equipment used inside commercial offices or outdoor public spaces of area 1 or 2 kilometers.  "small" compared to a mobile macro cell, with range of a few tens of kilometers.  Complements mobile phone service from larger macro cell towers.  Offer excellent mobile phone coverage and data speeds at home, in the office and public areas for both voice and data.  Developed for both 3G and the newer 4G/LTE radio technologies.
  4. 4. Small Cells TYPES :  Small cells may encompass femtocell, picocell and microcell.  Small cells provide a small radio footprint, ranging from 10 meters within urban and in-building locations to 2 km for a rural location.
  5. 5.  Picocells and microcells can also have a range of a few hundred meters to a few kilometers,  But they differ from femtocells in that they do not always have self-organising and self-management capabilities Small Cells TYPES :
  6. 6.  Small-cell networks can also be realized by  Distributed radio technology using centralized baseband units  Remote radio heads  Beam-forming technology  Feature central management by mobile network operators. Small Cells TYPES :
  7. 7. Femto Cells  The most common form of small cells.  Initially designed for residential and small business use with a short range and a limited number of channels.  Femtocells with increased range and capacity is frequently known by names like:  metrocells,  metro femtocells,  public access,  enterprise femtocells,  super femtos,  Class 3 femtos,  greater femtos  microcells
  8. 8. Femto Cells- Licence  Femtocell devices use licenced radio spectrum.  Must be operated and controlled by a mobile phone company.  One cell with one mobile phone operator.  When in range, the mobile phone will detect cell and use it in preference to the larger macrocell sites.  Calls are made and received in exactly the same way as macrocell.  Except, the signals are sent encrypted from the small cell via the public or private broadband IP network to one of the mobile operators main switching centres.
  9. 9.  Making and receiving calls uses the same procedures and telephone numbers as macro-cell.  All standard features- call divert, text messaging, web browsing are available in the same way.  Data services should operate more quickly and efficiently due to the short range involved. Femto Cells- Licence
  10. 10. Femto Cells- Power & Quality  Small cells operate at very low radio power levels.  Less than cordless phones, Wi-Fi or some other household equipment.  This substantially increases the battery life, both on standby and talk time.  In close vicinity to the handset or mobile device, hence..  call quality is excellent.  data devices can operate at full speed.
  11. 11. Femto Cells- Capacity  Most indoor products have standard capacity of 8.  The smallest femtocells can handle up to 4 simultaneous active calls from different users.  Larger small cell designs for business (enterprise) or public areas use can handle 16, 32 or more concurrent calls or data sessions.  A few of the latest multi-mode 3G and LTE small cells can cope with up to 64 3G and 128 LTE concurrent active sessions.  Restrictions can be applied on who can access a small cell.
  12. 12. Femto Cells- Security & Management  Small cells encrypt all voice and data sent and received.  Ensures a high level of protection from sniffing or snooping.  In order to reduce operational and installation costs,  these units are self –installing  sense which frequency to transmit on and power level to use.  Unlike large outdoor mobile phone base stations they –  don't require specialists to design, calibrate or configure themselves.  minimise the on-going cost of maintaining them.  They have remote management from the network operator to upgrade the configuration and software as required.
  13. 13. Femto Cells- Compatibility  Compatible with 3G and 4G mobile phones.  No additional software required.  Same interface for radio to mobile phone and to core network.  Compatible with existing mobile phone networks, phones and services.  3G UMTS- Small cell subsystem connects into operator's core network using IU interface same as traditional outdoor cell sites.  LTE- Standard S1 interface to the core is used, conforming to standard radio transmission frequencies and protocols of today.
  14. 14. Femto Cells- Compatibility  MSC and data switch (SGSN) communicate with the small cell controller same way as other mobile calls.  Services like phone numbers, call diversion, voicemail operate in exactly the same way and appear the same to the end user.  The small cell appears to the standard 3G or LTE phone as just another cell-site from the host mobile operator,  Can be used by any phone including roamers from abroad.
  15. 15. Femto Cells- Interface-Standards  The connection between the small cell and controller/gateway is the Iu-h interface.  It uses a secure IP encryption (IPsec) to avoid interception.  LTE uses the standard S1 interface protected by IPsec.  Authentication of the small cell ensures valid access point.  Each small cell connects with a small cell gateway over broadband IP.  Gateway consolidates hundreds of thousands of small cells into a single IU or S1 interface.  Carries thousands of concurrent calls and data sessions.
  16. 16. Femto Cells- Standard  3GPP release 8 and 9
  17. 17. Femto Cells- Architecture  Complete working of a mobile phone base station is inside femtocell .  Additional functions like RNC (Radio Network Controller) processing also included.  May have Core network element to manage data sessions locally.  The extra capabilities demand it to be self-installing and self-configuring.  Requires S/W to scan environment continuously for frequencies, power level , scrambling codes.  Femtocell gateways aggregate large numbers of femtocell connections (typically 100,000 to 300,000).  These are first securely connected through high capacity IP security firewalls.
  18. 18. Femto Cells- System Architecture  Industry has standardised on common solutions published by the 3GPP standards committees.  There are three architectures, one for each of the three main different radio technologies-  UMTS - the most common and used for today's 3G UMTS phones  CDMA- applies to 3G CDMA femtocells compatible with 3G CMDA phones  LTE- the 4G standard uses a different approach, having incorporated small cells into the system from the outset. 3GPP (3rd generation partnership project) UMTS(Universal Mobile Telecommunication System) CDMA(Code Division Multiple Access) LTE(Long Term Evolution)
  19. 19. Femto Cells- Architecture  3GPP HNB femtocell network architecture:  Home NodeB (HNB): 3G UMTS terminology for femtocell access point within the home, or other location.  Incorporates the capabilities of a standard Node B as well as the radio resource management functions found within a Radio Network Controller, RNC.
  20. 20. Femto Cells- Architecture  HNB Gateway (HNB-GW): Entry point to the core network.  The link into the core network is provided over Iu-cs and Iu-ps interface.  Already used for links from Radio Network Controllers to the remaining core network.  Functions:  Provides authentication and certification to allow only data to and from authorised HNBs.  Aggregates traffic from a large number of HNBs and provides an entry point into the operator core network.  Provides a mechanism to support enhanced features such as clock sync distribution, other IP based synchronisation
  21. 21. Femto Cells- Architecture  Iu-h Interface: Used to provide the link or interface that connects the HNB with the HNB-GW.  Includes a new HNB Application Protocol, HNBAP that provides the high level of scalability required for the HNB deployment in ad-hoc fashion.
  22. 22. Femto Cells- Architecture  CDMA
  23. 23. Femto Cells- Architecture E-UTRA: Evolved UMTS Terrestrial Radio Access UE: User Equipment Uu: Unique user HeNB: Home e-node B GW: Gateway MME: Mobility Management Entity CSG: Closed Subscriber Group HSS: Home Subscriber Server SGW: Serving Gateway PGW: Packet data n/w Gateway PCRF: Policy and Charging Rule Function IMS: IP Multimedia Subsystem
  24. 24. Femto Cells- Architecture  LTE femtocell architecture:  Required to take account of the LTE SAE, System Architecture Evolution requirements.  Provides a much flatter overall network architecture.  This has many advantages in terms of network simplification.  Key element in enabling much lower levels of latency - a key requirement for LTE.  Allows maximum flexibility and scalability to ensure that the deployment can be easily incorporated into the existing structures.  Deployment of femtocells is achieved on an ad-hoc basis, this forms a large requirement for the system.
  25. 25. Femto Cells- Enterprise Small Cells  The same technology and architecture used.  Small cells have higher capacity and slightly higher RF power to give a larger range.  Small cells may co-operate in clusters to provide seamless service.  For larger enterprises, a small cell controller may be used to provide additional local services including direct connection to the enterprise network.
  26. 26. Femto Cells- Urban and Rural Small Cells  Public areas use specially designed urban small cells (metro-cells) which are also based on the same architecture.  Take advantage of Femto-cell gateway, sharing its use between residential, enterprise and urban installations.  Requirement:  weather proof and vandal proof.  Operating in harsh unsupervised environments with wide temperature fluctuations.  Urban small cells are installed by the network operator.  Broadband IP connection back to the regional switching centre (backhaul) is also required.
  27. 27. Femto Cells- Components and Building Blocks  RF Front-End connects to the antenna-  converts the digital signals to and from radio transmissions  Baseband processing –  analyse and decode the complex transmissions into meaningful data  Control processing runs the software –  to communicate with handsets and the femtocell gateway.  Memory chips, read/write chip for transient data (RAM)  Read only chip which holds the program (ROM)  Crystal frequency oscillator , provides a very accurate clock-  important for synchronising the timing of signals to handsets.
  28. 28. Femto Cells- Application Software  Software controls overall operation of femtocell:-  what the femtocell does on startup and how quickly it is ready to make/receive a call  how it searches out and determines the correct frequency/scrambling codes to transmit on  how quickly it responds to a changing environment (e.g. someone opening a window)  What handover options are available when entering/leaving the home  what features are provided specifically for enterprise/business users  what self-service management features are included, such as setting up a list of barred/enabled phones  what diagnostic features are incorporated to reduce the cost of remote diagnostic/maintenance and customer care
  29. 29. Femto Cells- Evolution
  30. 30. Femto Cells- Installation  Femtocells require no radio planning.  Reduced impact on the outdoor macrocellular network, ( low power, no wall penetration.  No negotiation for site acquisition.  No ongoing running costs per site for site rental, power or backhaul transmission .  Femtocells are “self configuring”. (directly connected to RNC for configuration).  Can be managed on rental basis, like TV or Set Top Box.  Standards needed for enforcing interoperability.  Device can be used around the world.  Drastically reduced cost from mass production.
  31. 31. Femto Cells- Installation  Indicators are required to show:  Broadband signal connection active and online.  Connection into the operator’s network active and online.  If a mobile phone is “camped” on the femtocell.  When a voice or data call is active.  “camped” – only determined by mobile when an active call is made / received.  Mobile network only aware of “location area” of each phone.  Phone sends location update message, when changes cell, to network for broadcast to all cellsites in the paging area.
  32. 32. Femto Cells- Installation  Each femtocell may be configured as an individual paging area.  ensures femtocell knows when the mobile phone enters the home zone.  impacts on the sizing capacity of the MSC and SGSN which initiate the paging messages  potential for increased numbers of location update messages to the network.
  33. 33. Femto Cells- Installation  A straightforward installation is connecting the box to the broadband DSL line and power.  If GPS equipped, it needs to be located near to a window.  Femtocells including WiFi and/or PC connections, onboard configuration website required.  DHCP should be enabled for all wired and wifi connections.  WPA should be enabled for wifi requiring reconfiguring the WPA clients on each laptop.  Benefits of using mobile broadband than WiFi -more automatic security setup.
  34. 34. Femto Cells- Two stage registration process:  The femtocell has standard, common software installed in the factory  On first powerup, it connects to the vendor’s website, sending its serial number.  The vendor’s website downloads any firmware and security updates to the device  Vendor’s website uses serial number to identify the mobile, redirects femtocell to contact mobile operator’s servers.  Femtocell registers with the mobile operator’s network and receives operator specific configuration (operating frequency, max power level, cell id, paging area)
  35. 35. Femto Cells- Two stage registration process:  The mobile operator network also downloads the list of phones allowed to use the femtocell  indication can be given to the customer before a call to show applied billing rates.  To restrict use of femtocell to authorised phones where the customer requests it.  The femtocell is authorised to transmit by the mobile operator’s network and becomes part of the live operation.  The customer can make or receive calls using the femtocell.
  36. 36. Femto Cells- Outdoor cellsite installation  Complex radio planning tools are used to analyse the area to be covered.  Using topology of the area , simulation run to identify best locations for cellsites.  Operators’ targets for their plans:  coverage (able to use phone in any part of the country, inside buildings, cars, moving trains etc)  capacity ( ensuring enough traffic channels for everyone in an area to make and receive calls).  Radio parameters are computed - maximum transmission power, frequency hopping (for 2G), coding sequence (for 3G), angle of the transmission antenna , list of neighbour cellsites to handover to/from.
  37. 37. Femto Cells- Outdoor cellsite installation  Transmission network connects cellsite to core network of the operator via leased lines, microwave links or high capacity SDH fibre owned by the operator  These are concentrated into an RNC (Radio Network Controller for 3G) or BSC (Base Station Controller for 2G).  The transmission planners will allocate capacity from the cellsite to the central switching centre.  Includs port mappings for each input and output across every transmission hub.  Actively configured at the appropriate point in the cellsite rollout.  All basestations and RNCs are managed by a central Network Management System.  Radio configuration parameters periodically downloaded into basestations via NMS for synchronization.
  38. 38. Femto Cells- Outdoor cellsite installation  Fault management systems used-  to capture, collate and analyse alarms and fault indications from the network equipment.  Performance management systems used –  to monitor the capacity and overall throughput of the systems.  to ensure maximum utilisation of the network.  to identify additional capacity or coverage required
  39. 39. Femto Cells- Working
  40. 40. Femto Cells- Handover  Handover/handoff - process by which:-  a mobile phone switches between different cellsites during a phone call  continues with seamless audio in both directions.  Femtocell users need this capability when entering or leaving their home .
  41. 41. Handover in Mobile phone Mobile phone  As we move around when on a call, mobile phone continuously measures the signal level and quality from nearby cellsites.  Current active basestation determines when and where to initiate a handover sequence.  Complex algorithms uses all available capacity whilst reducing call dropping during a handover.  3G systems and CDMA are complex as mobile may be actively connected to more than one cellsite at the same time.  Called soft handover- same signal transmitted by a mobile phone to be picked up by multiple cellsites
  42. 42. Femto Cells- Handover  In Femto cell  Do not implement soft handover.  All calls switched instantly to or from femtocell and the external outdoor cellular network.  This is known as “hard handover” .  Not audible or noticeable to the caller.  Handover between 2G and 3G can occur-GSM and UMTS.  3G systems more common because of higher traffic capacity and lower costs.
  43. 43. Femto Cells- Handover 
  44. 44. Femto Cells- Handover effects  Usability  User unaware whether using 2G or 3G mode.  Calls originating using 2G continues until completion, even entering the femtocell.  No automatic handover into the femtocell zone.  Billing Implications  Charges based on where the call originated.  i.e. inside or outside the femtocell coverage.  Irrespective of discounts offered inside/outside femtocell.  Clarity of the billing mechanism.  No large loophole for revenue loss to exploit.  Forced handovers are possible.
  45. 45. Femto Cells- Handover optimization  Adding femtocells to the neighbour lists of the outdoor macrocells.  Adding some smarts into the mobile phone.  Making the femtocell as clever as possible.
  46. 46. Femto Cells- Location Lock  Location lock prevents a femtocell from changing its location without network operator’s awareness and permission.  Emergency Call Location: Operators report the location of emergency calls.  Femtocell only operates at the specified location.  Any moves to a new address are properly registered and tracked.  Spectrum Use: Femtocells must be used at the correct frequencies for the area they are located.  Disabled when away from licenced territories. (e.g. abroad on trip).  Commercial: Operators can charge additional fee to process a femtocell relocation.  Includs updating the registered operating address.
  47. 47. Femto Cells- Location Lock implementation  Femtocells are connected via broadband IP and are associated with an IP address.  If wired broadband and femtocell have same provider, IP address may associate with registered physical address.  But domestic customers allocated dynamic IPv4 addresses-  restrict identification to area served by pool of IP addresses.  Sniffing external 2G and 3G cellsites: Femtocells can detect and remember the cellsite IDs, which shouldn’t change frequently.  GPS: Although indoors, femtocells can have low power and sensitive GPS receiver for:  Location and look-up for licenced frequencies.  long term frequency clock accuracy.
  48. 48. Femto Cells- Re-Parenting/Re-homing  Network management operation- cellsite is switched across to a different controller (BSC or RNC).  Managed task under the planning and direction of the network planning and operations department.  Organic Network Growth: As networks grow, new controller is installed and some cellsites swapped across to balance the load.  Swanky New Products: Several controllers can be replaced by single, larger product with increased capacity /more cost effective technology.  Grooming: Existing transmission and location of controllers may be organised to be more efficient.  Commercial changes: For changing commercial agreements.
  49. 49. Femto Cells- Security  Identity Theft - No security loophole to exploit.  Authentication take place in the operator’s network before allowing voice or data calls through the system.  Phone-Tapping – Femtocells encrypt their voice and data traffic using secure tunnels (IPsec) between the femtocell and operators network.  More secure than mobile phone outdoors with no encryption is used.  Bill Avoidance – It is proposed to include a SIM card in the femtocell to validate the owner of the device.  Stolen or compromised units can be disconnected from the network.
  50. 50. Femto Cells- Security  Use of IPsec: In order to ensure femtocell security IPsec or IP security is used.  Defined by the Internet Engineering Task Force (IETF).  Femtocell Secure Authentication: Femtocell security procedures using SIM cards authentication or X.509 are used.  Wireless link security: To ensure that unauthorised users do not connect or take over the femtocell Techniques include femtocll coverage area not exceeding the physical area where the femtocell is to be used.  EAP, Extensible Authentication Protocol: for providing femtocell security.
  51. 51. Femto Cells- Timing and synchronisation  GPS: Provides very accurate frequency and phase alignment but little extra hardware.  Can also determine the location of the device.  NTP (Network Timing Protocol): Operates across domestic quality broadband Internet, low cost but potentially long time to acquire and lock-on to frequency  Network sniffing: Nearby macrocells used as an alternative clock source.  Synchronization needed for  Supply frequency information to handsets to synchronize to base stations.  Ensure reliable handover  Interference reduction  Ensures femtocell to be aware of adjacent cell sites
  52. 52. Femto Cells- Packaging  Standalone  Integrated with existing DSL broadband modem  Cable Modem  TV Set-Top Box
  53. 53. Femto Cells- Issues  Interference issues : Femtocells operate within spectrum shared with other cellular base stations.  3G and 4G are able to tolerate interference and single channel working.  Spectrum issues: Spectrum is scare resource, especially when large amounts of data are required.  Careful planning required.  Regulatory issues: Femtocells need regulatory approval to operate in licensed or regulated spectrum in each country.  International agreement may also be required,as private individuals take femtocells from one country to the next.  Health issues: RF radiation issue with health and safety.  Power levels emitted by femtocells are small - no greater than most Wi-Fi access points ,common in very many homes.  As per industry, no health issues of any concern.
  54. 54. Reference:     cells...basics.php  cons-of-using-femtocells    architecture.html