SMALL

CELLS-1

FEMTO

CELLS

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

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.

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.

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 :

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 :

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

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.

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

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.

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.

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.

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.

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.

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.

Femto Cells- Standard

3GPP release 8 and 9

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.

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)

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.

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

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.

Femto Cells- Architecture

CDMA

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

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.

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.

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.

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.

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

Femto Cells- Evolution

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.

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.

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.

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.

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)

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.

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.

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.

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

Femto Cells- Working

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 .

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

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.

Femto Cells- Handover

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.

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.

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.

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.

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.

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.

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.

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

Femto Cells- Packaging

Standalone

Integrated with existing DSL broadband modem

Cable Modem

TV Set-Top Box

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.

Reference: http://www.thinksmallcell.com

https://en.wikipedia.org/wiki/Small_cell

www.smallcellforum.org

www.radio-

electronics.com/info/.../femtocells/femto-

cells...basics.php

www.techrepublic.com/.../data-center/pros-and-

cons-of-using-femtocells

https://en.wikipedia.org/wiki/Femtocell

http://www.rfwireless-world.com

http://www.rfwireless-world.com/Tutorials/femtocell-

architecture.html