How to implement an IP telephony-enabled mobile infrastructure Published: 1 August 2007

Transcription

How to implement an IP telephony-enabled mobile
infrastructure
Published: 1 August 2007
© 2007 SAS Global Communications Limited. Reproduction of this publication in any form without express
permission is forbidden. The information contained herein has been obtained from sources believed to be reliable.
SAS does not accept liability for errors, omissions or inadequacies in the information or its interpretation. The
opinions expressed in this document are based on judgements at the date of publication and are subject to change
without notice. All Rights Reserved.
Table of contents
Introduction ............................................................................................................................... 3
Glossary ................................................................................................................................... 3
What you need to know about mobility ..................................................................................... 4
Autonomous access points ................................................................................................... 4
Lightweight access points ..................................................................................................... 4
Access point deployment – general considerations .............................................................. 5
Voice coverage .................................................................................................................. 5
Signal and bandwidth performance. .................................................................................. 5
Battery life ......................................................................................................................... 5
Integrating mobile users with the network ......................................................................... 5
Quality of service ............................................................................................................... 6
Technology comparisons ...................................................................................................... 8
Implementing a mobile infrastructure ........................................................................................ 9
RF audit and channel management ...................................................................................... 9
Security ............................................................................................................................. 9
Access point deployment................................................................................................. 10
Structured cabling; route planning ................................................................................... 10
Guest access................................................................................................................... 10
The MOS test .................................................................................................................. 11
How to monitor and manage the infrastructure ....................................................................... 13
Dead-zone coverage ........................................................................................................... 13
Roaming.............................................................................................................................. 13
Appliance location detection ............................................................................................... 14
Rogue device detection ...................................................................................................... 14
AP monitoring ..................................................................................................................... 15
Monitoring QoS ................................................................................................................... 16
Fixed mobile convergence - now and in the future ................................................................. 18
Conclusion .............................................................................................................................. 19
About SAS .............................................................................................................................. 20
List of Figures
Figure 1-1 WLAN ............................................................................................................................................... 4
Figure 1-2 Routers............................................................................................................................................. 6
Figure 1-3 Mobile infrastructure ......................................................................................................................... 7
Figure 1-4 Technology comparisons.................................................................................................................. 8
Figure 1-5 RF audit and channel management .................................................................................................. 9
Figure 1-6 Upgrading a data WLAN to a converged WLAN ............................................................................. 11
Figure 1-7 MOS test ........................................................................................................................................ 11
Figure 1-8 RF coverage and signal strength .................................................................................................... 13
Figure 1-9 Appliance location detection ........................................................................................................... 14
Figure 2-1 Rogue device detection .................................................................................................................. 14
Figure 2-2 AP monitoring ................................................................................................................................. 15
Figure 2-3 Monitoring QoS .............................................................................................................................. 16
Figure 2-4 Seamless connectivity between fixed and wireless networks ......................................................... 18
© SAS Global Communications Limited
Page 2 of 20
Introduction
Enterprises are becoming increasingly aware of the business benefits to be gained from
mobility; greater productivity, cost savings and flexible working.
Mobility projects, however, invariably raise concerns about reliability, security and support,
particularly when they herald the introduction of voice, video and other QoS-dependent
applications.
This white paper provides advice on avoiding the common pitfalls of mobility through following
a best-practice approach to planning, installing and integrating an IP telephony-enabled
mobile network. It also focuses on the main priorities for supporting a mobile infrastructure
and outlines proven techniques for proactive network management.
Glossary
FMC – Fixed/ mobile convergence
GPRS – General packet radio services
GSM – Global system for mobile communications
LWAPP – Lightweight access point protocol
MAC address – Media access control
Nanocell – Localised cell phone network
QoS/CoS - Quality of service/ class of service (AF/EF/standard)
RF – Radio frequency
rd
UMTS – Universal mobile telecommunications service is a 3 generation
VoIP - Voice over IP – analogue traffic converted to IP at the router.
VoWLAN – Voice over WLAN
WAP – Wireless access point
WiFi – Wireless fidelity
WiMAX – Worldwide interoperability for microwave access
WLAN – Wireless local area network
Page 3 of 20
What you need to know about mobility
Configuration of a wireless LAN requires deployment of specialised technology to deliver
wireless voice connectivity within any current IT infrastructure.
The first area of consideration is enabling wireless network connectivity by use of access WiFi
point technology.
Figure 1-1 WLAN
WAN service
Carrier router
PSTN / BRI / PRI
Firewall
VPN
Voice gateway router
WAN router
Web server
Application server
SAN
Default gateway
Application server
Printer
Switch gateway
Email server
Switch
WiFi switch
Work station
WIP phone
UM server
Call control server
Switch gateway
IP phone
Laptop
Figure 1-1 shows a common configuration of local area network components found in most
office environments.
Wireless access points (note the WiFi switch highlighted) effectively perform the same task as
a standard LAN switch, connecting wireless devices into the core network.
Considerable versatility can be gained through utilisation of different types of access point
units: internal, external, and those that support directional aerials or antennae when booster
coverage is required. Most importantly, however, is the consideration that needs to be given
to the differences between autonomous and lightweight access points and how these
differences affect network capability and long-term management.
(WiMAX, also known as radio broadband, should not be confused with WiFi or WLAN access
points. This is the system for point-to-point connectivity over large distances, used mostly by
carriers and ISPs where a fixed-line broadband service is unavailable).
Autonomous access points
Autonomous access points proliferate at the lower end of the market, commonly in use in
domestic or standalone situations where the access point itself comprises the configuration
and control settings for wireless connectivity.
Lightweight access points
Lightweight access points, on the other hand, are centrally controlled and managed and, in
effect, create a single WLAN over multiple APs. Each AP works in tandem with other APs to
deliver a single hotspot. Lightweight access points are controlled by a central wireless LAN
controller, a separate switched device sitting on the network.
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When access points are used for voice traffic, or in large areas across multiple offices,
increased demands are placed upon their performance. Advanced usage requirements such
as voice and video militate in favour of lightweight intelligent access points, as opposed to
standalone autonomous access points.
Lightweight intelligent access points join together to form one wireless cell and enable users
to roam seamlessly between different access points whilst making voice calls. In addition, the
central controller adjusts the access point’s power up or down depending on utilisation and
coverage required. It also allows a level of intelligence whereby traffic can be switched
between access points; the controller enables connection to access points depending on the
aggregate level of traffic on the network rather than the proximity of the device to the
individual user. Autonomous access points will not work together in the same way.
Access point deployment – general considerations
Voice coverage
Access points provide a lower range of coverage for voice traffic than they do for data. When
deploying the protocols required for voice on an existing wireless network, it is frequently the
case that coverage is insufficient, even though it may have been faultless for data. In this
situation, further configuration may be required in the form of additional access points or
directional aerials to ensure the requisite coverage and create a seamless cell.
Signal and bandwidth performance.
Bandwidth performance suffers as the signal drops; the greater the distance from the access
point, the lower the amount of bandwidth available. This may not be of great concern, since
many applications, including IP telephony, require only a small amount of bandwidth, so users
encounter no problems since their service utilises the available bandwidth, even though it
may be minimised.
Battery life
Devices, such as PDAs or dual-mode devices, which use access points, consume more
battery life than traditional devices that connect through the GSM GPRS cellular network. It
may therefore be necessary to replace existing devices or upgrade their power supply to
maximise running time.
Integrating mobile users with the network
Mobile users, who sit outside the core internal network, will be connecting through other
security and communication gateways for remote access. Traffic going to any external mobile
users will pass through the LAN default gateway, where it is directed to the correct remote
access communication route.
Page 5 of 20
Figure 1-2 Routers
WAN service
Carrier router
PSTN / BRI / PRI
VPN
Firewall
WAN router
Voice gateway router
Web server
Application server
SAN
Switch gateway
Default gateway
Application server
Printer
Email server
Switch
WiFi switch
Work station
WIP phone
UM server
Call control server
Switch gateway
IP phone
Laptop
The wide area network router, shown on the left in Figure 1-2, takes traffic out through an
MPLS network to other sites on the WAN. These can be other company offices or home
offices.
Through deployment of lightweight access points, it is possible to configure a wireless
network to include additional access points in offices other than just the head office. These
can all be controlled and configured through a central wireless LAN (WLAN) controller to
create a standard WLAN across geographically diverse sites. This allows staff who move
between offices to use a standard wireless authentication configuration to gain access to the
corporate network and resources.
Connectivity would be provided to the mobile devices even though they are at remote
locations, routed through the wide area network and back to the central site. Regardless of
which office mobile users visit they would always enjoy the same functionality as staff with
fixed connectivity to the core internal network.
Quality of service
Even with the correct configuration and sufficient bandwidth to support all applications, when
voice is involved, quality of service must be maintained throughout the network. This will
entail the configuration of quality of service, by introducing parameters such as expedited
forwarding (EF) used for voice. Expedited forwarding ensures that voice quality is maintained
across every device that makes up the local area network and wide area network.
The voice gateway router, shown on the right in Figure 1-2, provides PSTN connectivity to the
outside world, including mobile devices.
The voice gateway router connects to the outside world through a PSTN dial network, using
an ISDN 30 (primary rate) or an ISDN 2 (basic rate) line.
At this point, as management of the call is handed off to the carrier PSTN network, so control
over quality of service is relinquished to the carrier. Carrier networks invariably ensure that
quality of service is maintained.
The mobile device, if outside the office environment, will be connected through the base
transceiver station system (BTS); the latter being the most likely route for mobile traffic. The
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BTS is the national network of mobile masts which house the antennae providing the cellular
network. The BTS identifies the GSM, GPRS or 3G device and ensures that the call is
delivered to the end node.
With some mobile devices using GSM/GPRS/3G and IP they are always connected to the
corporate network through the Internet or through a VPN rather than through the voice
gateway router that connects to the carrier PSTN network.
It is likely that, in the future, significant benefits will accrue from using a single carrier for both
Internet connectivity, or landline connectivity, and mobile GSM or GPRS services also known
as fixed mobile convergence (FMC).
This will be at the point when carriers are able to recognise exactly where devices are located
and the medium through which they are connected. This will also signify the arrival of
presence. Presence offers connection to the user regardless of location.
The network shown in Figure 1-3 shows office users connecting through an IP telephony
system, connected to the IP backbone. For internal calls the signal runs across the LAN and
is delivered to the user’s IP handset.
Figure 1-3 Mobile infrastructure
The head office user does not need to track down the number for the mobile device that a
remote user may happen to be using at any particular point in time. Simply by dialling the
extension number of the intended call recipient, presence will identify the best mode of
contact and, if the call recipient is not immediately available, will send a message to the
appropriate data device.
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Technology comparisons
Figure 1-4 Technology comparisons
Feature / benefit
GSM
GPRS
PSTN
ISDN 2
UMTS/3G
DSL
WiFi - 802.11a
WiFi - 802.11b
WiFi - 802.11g
WiFi - 802.11n
WiMAX - 802.16
Ethernet - Cat5e - 802.3 - 10BaseT
Ethernet - Fibre - 802.3 - 10BaseF
Speed
9kbps
56kbps
56kbps
64kps
385kbps
2mbps
54Mbps
11Mbps
54Mbps
100Mbps+
70Mbps
10/100/1000Mbps
1000Mbps+
Signal distance
Cell dependent
Cell dependent
33.5Km
33.5Km
Cell dependent
7.5Km
WAP dependent
WAP dependent
WAP dependent
WAP dependent
51.5Km
165Km
12Km
QoS enabled
No
No
No
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Figure 1-4 shows the different speed and signal distances available from each of the
communication technologies that can be used in creating a mobile network.
GSM is fairly restricted, at 9.6 kbps.
Whilst certain data applications are possible, they are limited to basic text. Data applications
have never been fully developed over GSM networks due to this speed restriction.
GPRS constitutes a significant improvement on GSM, increasing the bandwidth up to 56kbps.
This is the level at which the last generation of typical modems over PSTN analogue dial
networks were able to connect. 56K is adequate for delivery of email text messages, basic
screen shots and basic images. This bandwidth is insufficient, however, for feature-rich
Internet browsing experiences and use of online applications.
Moving further up the scale, in the UK, DSL capability now goes up to 8MB, with even higher
bandwidth services soon to be available.
WiFi currently offers three technologies: 802.11a, b and g. all of which offer point to multipoint connectivity.
In the near future 802.11n is expected to be the next specification ratified for WiFi, with a
significant jump up to 100Mbps+.
Some access points currently enable the combined use of 802.11a and 802.11g, providing
108 kbps throughput by using both specifications.
WiMAX offers high capability at 70Mbps over a very large distance, 5l.5 kilometres.
This is purely for node-to-node connectivity; access to data services for a rural community
location, for example, or a location not connected to the current DSL infrastructure.
Structured cabling, in particular fibre, still provides significant bandwidth improvements over
all other scenarios in a local office point-to-point environment.
Page 8 of 20
Implementing a mobile infrastructure
RF audit and channel management
The first step in implementing a mobile infrastructure is to undertake an RF (radio frequency)
audit of the building or site.
Figure 1-5 RF audit and channel management
Coverage assessment
Figure 1-5 shows a CAD image of one floor of a multiple tenancy office building, overlaid with
the results of the RF audit for the floor.
At the top end of the building there is no coverage whilst at the bottom there is a high range of
cover.
This information is invaluable in itself when implementing a mobile infrastructure, but RF
audits can be used for more than simply revealing the building’s coverage.
Security
Understanding the arrangements that need to be made for security is one of the prime
benefits of an RF audit.
On the right in Figure 1-5 is a table of different access points in use on the site.
An apparent anomaly is highlighted in the number of channels in use, focussing particularly
on the number of devices using channel 6. In all WiFi protocols there are a limited number of
channels available for use. This means that in multiple tenancy buildings there can be WLAN
availability issues as WLANs from each floor compete for the limited channels available. In
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this example 18 APs are using channel 6. The impact of this will be that users will experience
loss of the WLAN as the APs compete for the same channel.
In a shared office environment, or a busy urban area, a number of access points will be in use
and it is necessary for a company to determine which access points are its own and which
relate to other businesses. This then facilitates access point configuration on a separate
channel that is both available and secure from other users. It may be that in office
environments tenants will have to agree a combined channel usage strategy to ensure that all
their WLANs operate without conflict.
Investigation of such anomalies leads to greater precision in access point deployment and
eradication of any potential security and WLAN availability issues.
Access points can then be fine-tuned to ensure minimum bleed into other tenant areas where
coverage is not required; achieved by use of directional aerials and LWAPP controllers to
direct access points internally into the building.
Access point deployment
Fundamentally, an RF audit is essential from a practical perspective; providing an essential
appreciation of where and how access points should be deployed.
These audits are cheap and cost-effective and will often recoup their investment by reducing
the number of access points required for deployment or, perhaps, reducing the need for
additional wireless LAN controllers. This in itself would be a cost benefit, not least because
the process results in good documentation of exactly what coverage is available, and where
(see Figure 1-5).
Structured cabling; route planning
As well as helping to decide upon optimum locations for access points, the RF audit, through
the CAD image and the details of the office building, facilitates route planning for the
structured cabling that serves them. Delivering power to the access points is another
consideration. If power sockets are not available then a decision might be taken to use power
over Ethernet switches to inject power into the structured cabling to keep the devices
configured. This allows for a much cleaner and simpler WLAN deployment, quicker moves,
adds and changes of APs, as well as providing business continuity options such as enabling
the WLAN to be available during power outages.
Guest access
In terms of providing Internet access for guest users, the options are to give blanket coverage
to an entire office area, through an open or password protected WLAN that both staff and
guests use (not advised), or as a better option, to provide a secondary password protected
network for guests, in the reception area or selected meeting rooms. This second network can
be delivered either through additional separate access points, a completely separate WLAN
secure from the corporate WLAN, or simply through using the existing corporate WLAN, and
using VLANs to create a separate password protected guest network.
An RF audit makes it possible to fine-tune and adjust the devices within a network to deliver
services down to users. It also assists in the introduction of VoWLAN where existing data
WLANs need to be reviewed to assess their suitability to carry voice traffic.
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Figure 1-6 Upgrading a data WLAN to a converged WLAN
In Figure 1-6, the left side shows how four access points were initially deployed to provide
access point coverage or WiFi access coverage throughout a building. The shading shows
the strength of signal that was found in each of the offices at the initial audit. On the right it
can be seen that the number of access points has been reduced to three. By using directional
aerials and re-tuning the configuration, significantly better coverage and significantly higher
bandwidth have been provided throughout the building.
The MOS test
Quality of service is critical to delivery of voice over a wireless network or VoWLAN.
The most effective way to determine the quality of service availability on a network is through
a testing system known as mean opinion score (the MOS test) covering all aspects of the
network infrastructure, not just individual devices or components or the wireless network. The
MOS test monitors the delay, jitter and packet loss across any path, whether a structured
network, wireless network or a hybrid. A MOS test will test each network segment to assess
its ability to support QoS and identify any device along the intended voice path which may not
be fit for the purpose.
Figure 1-7 MOS test
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The rankings range from 5 for ‘excellent’ to 1 for ‘bad’; these are used to judge voice quality.
4.34 is judged to be ‘carrier quality’ and users are always very satisfied with this level of
service. 3.6 is judged to be ‘business quality’ but some users might be dissatisfied with this
quality. 3.1 is where users are really dissatisfied.
Figure 1-7 details the results from a MOS test report for a company with six offices, each of
which has an IP address, shown on the left, which represents the wide area network router
and the local area network core switch.
In this test, the overall network was let down by the IP address, 10.8.1.240, second from
bottom, as the jitter and data loss were unacceptable.
Due to that one address, the whole network failed the test (although 10.8.1.253 also showed
considerable loss but this was owing to the 10.8.1.240).
In this instance there were two issues affecting the network, the WAN router being set to half
duplex instead of full duplex and an incorrect QoS setting on the carrier network.
Important to remember is that the MOS test is not specific to the network devices (e.g. access
points or to individual mobile devices), it tests each network segment to see if it can support
voice traffic. In effect it covers the voice path (i.e. the route a voice call would travel over the
WAN and LAN) across every segment of the network; across local area network switches,
into the IP telephony device and through the routers.
If traffic is to be routed across a wide area network, the quality of service requested must be
consistent to maintain the quality of the call and support the optimum number of calls being
made.
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How to monitor and manage the infrastructure
A number of parameters are taken into account when monitoring and managing the
infrastructure. These range from RF coverage and signal strength, through to monitoring
bandwidth and application performance and QoS.
Dead-zone coverage
Close infrastructure monitoring provides the best guarantee of availability for access points
connecting to the network, particularly when WLANs are supporting business critical
applications or voice services.
Figure 1-8 RF coverage and signal strength
Figure 1-8 represents the network map of a live infrastructure and shows access points
deployed in an office. It also shows how data can be displayed by channel, power level, MAC
address or users connected. A large amount of data can be collected from a WLAN for
precise management. By virtue of the deployment of lightweight access points there are many
benefits. One of the main benefits is that a fault-tolerant WLAN is created. For example, when
one access point fails or is not available for maintenance purposes, the other access points
located within its vicinity can increase their signal strength to compensate for the dead zone.
Roaming
It is also important to ensure continuity of service when staff are moving between APs –
particularly when using voice applications such as IPT. Should a user walk around the
building he or she needs to be able to move from cell to cell without interruption or loss of the
call.
In the case of data applications, in an autonomous scenario where wireless LAN controllers
are not deployed, there will be a small jump in the data as it passes from one access point to
another while the data or the connection is re-configured. With most applications the jump
may be indiscernible or may take the form of a small pause. Such a jump would not be
acceptable on a voice call. This is another major benefit of LWAPP controllers – the hand-off
of the voice call between APs.
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Appliance location detection
Appliance location detection is a monitoring parameter which facilitates not only precise
identification of the location of the access points but also the location of the individual users
connected to the network.
Figure 1-9 Appliance location detection
Overlaid on the same network map as shown in Figure 1-8 are the devices, within the
network, which utilise the access point configuration.
In a lightweight access point system, the system will re-configure itself to spread additional
user connections across access points, should a cluster of users access one particular
access point; their demand on the WLAN can be load-balanced.
Users will not be accommodated simply by the nearest available access point with the
strongest signal. The network will be spread to deliver services via a number of access points
available in the area.
Appliance location detection also enables the identification of rogue devices.
Rogue device detection
Figure 2-1 Rogue device detection
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The device indicated in Figure 2-1 is transmitting on the WiFi network, and has been
introduced outside the scope of the internal corporate network.
Identifying rogue devices is important for a number of reasons:
 Through this process, access points can be traced that may have been configured in
the office area without approval as well as staff members using their laptops to share
the corporate WLAN.
 As an example, there was a hotel chain which had a central agreement with a carrier
for deployment of hot spots at each location. The management team was aware that
individual hotels had in the past signed up to different agreements with different
carriers on an individual basis. For consistency of presentation to customers and
guests it was important for the management team to ascertain if the group was
offering more than one scenario or more than one access point configuration so that
the standalone hot spots could be identified and removed.
 Whilst offering a uniform message to a selected target audience is important to
companies operating within certain sectors, there is one area of rogue device
detection of concern to all businesses and organisations: security. In the corporate
environment potential security risks, posed by rogue devices, have to be investigated.
It may simply be a case of a device on another floor in the building over which the
company or organisation has no jurisdiction that may be affecting WLAN availability.
A company needs to be able to locate the access point and identify who is
responsible for the AP in order to reach a resolution. Companies in multiple-tenancy
buildings will need to discuss a channel management strategy with other tenants to
ensure that all their respective WLANs operate without issue.
AP monitoring
Figure 2-2 AP monitoring
Access point monitoring is not only an invaluable trouble-shooting mechanism, identifying
problems and opportunities as dealt with in this section, but can also provide input for trending
and capacity planning. It can help identify the need for office relocation, expansion,
contraction or simply employee relocation, whilst, at the same time, enabling an organisation
to assess the impact of such adjustments.
Page 15 of 20
Access point monitoring can also help ensure a level of change control and policy
enforcement, particularly concerning lightweight access points.
Whilst this will be coordinated through the wireless LAN controller it can also accommodate
changes such as software upgrades to ensure consistent levels of service, offering seamless
levels of connectivity, regardless of which access point users connect into.
Understanding the utilisation levels of different devices is an additional benefit that comes
from the process of monitoring the access points and ensures adequate end user
performance.
Although the fundamental logic of access point deployment may initially have been sound,
organisations and users are dynamic, and usage patterns change over time.
Redeployment of access points is necessitated most commonly by office refurbishments, staff
changes or application changes. It is a common occurrence that some access points are then
under-utilised whilst others are stretched.
Monitoring QoS
The prime objective of monitoring quality of service is to ensure that it is maintained long-term
and understand the average as well as peak QoS demands.
Figure 2-3 Monitoring QoS
The test shown in Figure 2-3 was conducted to monitor the quality of service across an
international wide area network infrastructure over a three-day period (from 27 April). At the
start of the period, the system failed, dropping below the acceptable threshold for quality of
service delivery
At the top, in blue, is the overall MOS test result. Peaks and troughs are in evidence
throughout at any period of time. The quality of service is varied and as the peak shown on
the far top right-hand side shows where quality of service reached the threshold beyond
which voice quality is affected. The MOS test shows the average utilisation and performance
as well as peak demand and shows that both were being accommodated within the QoS
parameters on the WAN and LAN..
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Configuration changes were made through the first day, with demonstrable improvements;
packet loss, jitter and delay were all reduced and an acceptable level of service was
established. In this example, these issues were caused by incorrect router configuration, i.e.
where some legacy routers did not support QoS and incorrect WAN configuration.
Nonetheless there were still peaks, outside the threshold parameters. On the afternoon of the
28th there was a spike, a peak in the delay, above and beyond the threshold. Again, in this
example, the peaks were caused by testing that was being undertaken on the video
conference units in order to set the correct QoS parameters.
By monitoring such occurrences longer term, user’s expectations can be managed; interim
adjustments can be made to correct problem issues before the overall quality of service is lost
on the network. Ongoing monitoring also permits time-stamped remedial investigations if
users complain of voice quality problems after implementation and any changes to the voice
path on any segment of the corporate network.
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Fixed mobile convergence - now and in the future
Figure 2-4 Seamless connectivity between fixed and wireless networks
Fixed mobile convergence (FMC) is the phrase used to describe seamless connectivity
between the fixed and wireless network. This is now a dominant trend within the
telecommunications industry. FMC takes place when a mobile device can access corporate
data or applications irrespective of whether it is connected via a fixed or wireless network
within or outside the office premises.
This is increasingly being achieved through dual-mode (GSM and IP) mobile handsets. Dualmode is now commonly advertised as a feature of PDA devices and mobile phones; meaning
they are capable of GSM, GPRS 3G and WiFi connectivity and can hop from one network to
another.
The ultimate goal of fixed mobile convergence is to optimise transmission of all voice, video,
and standard data communications, across any device or location, and over any available
network.
It is likely that, in the very near future, devices will appear on the market that can connect and
be switched between wired and wireless networks without any user intervention. Such
devices will not only make life easier for mobile workers and people generally on the move
but they will also facilitate the use of presence.
Presence is where the systems can not only determine the multiple ways in which a user is
able to communicate, but will also work out the best mode of communication with another
user by assessing the communication status of the other user.
If a user is not in the office when another user dials their extension number, the telephone
system will automatically recognise that they are not available at that time and select the best
contact medium, which may be a call to their mobile or home phone or an email.
Presence assesses a user’s availability from data entered in their ‘diary’ to determine the best
method by which to communicate with them at any given point in time. The user may pick up
a telephone to make the call but the core system will automatically recognise that the person
being called is not available and determine the best method to communicate with them in the
quickest possible form, that most likely to elicit a response.
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Conclusion
Currently, there is no single technology solution designed to facilitate mobility in every
scenario. The market is characterised by combinations of different technologies being used to
produce combined solutions. Seamless connectivity in different mobile scenarios is thus
available and deployable. The decision whether or not to implement an IPT-enabled mobile
infrastructure should be informed by a number of well-considered steps:







Review business drivers and demands for IP telephony-enabled mobility; identifying
what is really driving the need for mobility to be connected through the internal IP
telephony system.
Identify and test solution components and their interdependencies. It is important to
assess the entire network infrastructure for quality of service and not simply the
individual mobility solution, whether that is the wireless LAN, a PDA or connectivity
through a GPRS device. The MOS test is the perfect benchmarking assessment for
network readiness for mobile voice.
Conduct user group trials to test and develop the solution before it is finally deployed.
Set limited expectations for the deliverables from fixed mobile convergence. Whilst
perfect anywhere-anytime connectivity will be available in the near future, being the
goal of the industry, it is yet to arrive and expectations should be managed
accordingly.
Ascertain whether or not the existing carrier used by the company is able to support
fixed mobile convergence and gain an understanding of the road map to which they
are working. It will become increasingly important to work with a single carrier who
can support the many demands that may be put upon a converged network
infrastructure. From wireless hot spots, to the Internet, and onto the cellular dial
network, the ability to provide seamless connectivity will militate strongly in favour of
single carrier agreements.
Understand the current carrier hardware and application limitations. With a wide
variety of connectivity options comes a huge variation in bandwidth and signal
distancing.
Ensure ease of use. Currently the solution is not easy to use and this could create a
barrier to adoption amongst intended users. The launch of the Blackberry created
immense excitement since users could simply turn on the device and receive emails
instantly. They would send an email and it would go just as instantly, with no need to
invoke a third party package or try to synchronise or connect to another system such
as a VPN, before they could actually use the system. Ease of use means instant
adoption and this could be the deciding success factor when an IPT enabled mobile
infrastructure is implemented. This is very, very important to remember.
Page 19 of 20
About SAS
SAS Global Communications is a major provider of managed and professional network
services. The company provides consultancy and implementation services to design, build
and manage converged IP networks for enterprises of all sizes. Since its inception in 1989,
the company has successfully delivered more than 2000 highly commended solutions, to a
broad spectrum of clients including many renowned brands, such as Coca Cola Enterprises,
The Body Shop International and Millennium and Copthorne Hotels.
For more information contact:
SAS Global Communications Limited
SAS House
Blackhouse Road
Colgate, Horsham
West Sussex RH13 6HS
Tel: +44 (0) 1293 851951
Fax: +44 (0) 1293 852200
Email: [email protected]
www.sas.co.uk
Page 20 of 20

How to implement an IP telephony-enabled mobile infrastructure Published: 1 August 2007

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