White Paper: "Ditching Your Network's Voicemail"

Contents

Introduction
Corporate Voicemail: The Situation Today
Benefits of Unifying Around The Corporate Voicemail Systems
Mobile MWI
Configuring the Mobile Phone for Corporate Voicemail
Setting up Diverts
Changing the Voicemail Access Number in the Mobile Phone
Configuring Asterisk for Mobile MWI
Other Considerations

 

Introduction

If you are operating voicemail services on your Asterisk servers then you will already have a good feel for the benefits of provisioning your own voice messaging instead of that available with a third-party's managed voicemail system.

In this paper we will address a solution to the particular problem of introducing mobile phones into the communications mix, namely the elimination of the mobile network's voicemail services in favour of adopting a more unified messaging approach based around your own Asterisk voicemail environment. The solution proposed serves as a complete replacement, gaining all the advantages of centralising the messaging onto the corporate voicemail server, whilst preserving the benefits of the mobile voicemail service. i.e. instant notification on the mobile handset through the MWI (Message Waiting Indicator).

Corporate Voicemail: The Situation Today

Typically companies will fall into one of the following use cases:

Benefits of Unifying Around the Corporate Voicemail System

Taking the mobile network's voicemail system out of the equation and instead unifying all voice messaging onto the corporate voicemail system presents several advantages not only for the mailbox user, but also the mailbox user's team colleagues, the person calling the mailbox, and for the comms manager.

Whilst the exact list of advantages are dependent on the feature-set of the mobile network's voicemail system and, reciprocally, the feature-set of the corporate voicemail system, we have attempted to provide a general feel based on the common limitations found with mobile voicemail systems, and the standard voicemail application supplied with Asterisk.

The advantages for the mailbox user are:

• Interacts through exact same user interface whether picking up messages left on mobile or on PBX.
• Common mailbox means no confusion or trying to remember where the message was left.
• Multiple folders for storing voicemails to (e.g. project / category specific).
• Web-based playback and management of voicemail.
• Email delivery of voicemails.
• Possibility to recover accidentally deleted voicemails.
• Integration into CRM systems for automatic retrieval of call history / client contact details.
• One or two button call-back of the person who left the voicemail.
• Messages do not get automatically deleted after a period determined by the network (as short as 7 days on many mobile networks).
• With the appropriate Asterisk add-ons, possibility to automatically set the voicemail / divert status based on either IM (Instant Messenger) status or Bluetooth proximity, or even the user's schedule from the Microsoft Exchange server.

The advantages for the mailbox user's team colleagues are:

• Group mailboxes / broadcast voicemail.
• Forwarding of voicemails to other extensions.
• Delegate access to another user's mailbox.

The advantages for the caller are:

• Can choose to be transferred to an operator / assistant before or after leaving a voicemail.
• Separate away and unavailable greetings.
• No need to leave two voicemails (one on the PBX, another on the mobile).

The advantages for the comms manager are:

• All voice messages stored on common servers.
• Backups of messages can be kept for the period required by company policy.
• Reduced call costs (no dialing-out from PBX to mobile voicemail).
• Can enforce own security policies on access restrictions and data storage.
• Emergency access to a user's mailbox possible without user's participation (in mobile network voicemail case would have been impossible without knowing user's PIN code).

Mobile MWI

Mobile networks typically notify users that a message is waiting by one of three methods:

• Calling them. One of the oldest methods used on mobile networks, it has to a greater degree now gone out of fashion in favour of less obtrusive methods. This is a reflection of the way mobile phone usage culture has shifted from one of "switching the phone off when in meetings" to a more popular trend of "switching the phone to silent alert when in meetings".
• SMS. A simple text message is delivered to the user to notify them that one or more voice messages are waiting in their mailbox. Messages are stored in their regular SMS inbox and must be deleted like any other message. The drawback to this approach is that it isn't fully synchronous with the voicemail system, i.e. if the user listens to their voicemails and then deletes them, the SMS delivered to their handset will stay in the inbox until it is separately deleted. The counter problem also exists, in that the SMS alert is not persistently held on the handset until the voicemail has been checked, that is to say a user could easily delete the SMS alert before they get around to checking their voicemail, leaving no indicator on their handset that voicemail is still waiting.
• MWI. The Message Waiting Indicator is an icon (typically resembling a tape / cassette) that is most commonly displayed in one of the top corners of the screen whenever an unlistened voicemail is in the system. The icon will normally remain on the screen until the point the voicemail has been played back, at which point the network will signal to the handset to extinguish this indicator. Some phones also have an LED that flashes when the MWI is set.

MWI is arguably the best mechanism available for voicemail notification on mobile phones. Surprisingly though whilst most handsets and networks support it, not all networks choose to utilise it. However the good news is that just because they don't utilise it on their own voicemail server, doesn't mean that the MWI can' t be set from a corporate voicemail system!

Bayham Systems' FastSMS module for Asterisk makes it possible to set and unset the mobile's MWI indicator with a simple command which can be called from within an Asterisk dialplan. With one command you can switch the MWI on (when a voicemail has been left) and with another you can turn it off again (e.g. when there aren't any messages pending).

In fact FastSMS allows you to control four different message waiting indicators:

MWIVOICEMAIL This is the recommended MWI to set for voicemail. In addition to displaying an icon some phones will also pop-up an onscreen alert message, e.g. "You have received a voicemail. Press SEND to listen".		MWIFAX This notification could be triggered from a personal fax service to alert the user that an unread fax message is waiting.		MWIEMAIL Fairly obviously, MWIEMAIL is used to notify a user that there is an unread email message pending.		MWIOTHER Whilst this indicator is strictly speaking "reserved for future use", it is however already supported on most handsets and so it can be used as required. Possible uses include: a secondary voicemail indicator for when the user has two mailboxes; or an alert when a priority delivery has come in to the mailroom and needs to be collected and signed for.

(Note: actual graphical representation of these MWI's will differ from handset to handset and are down to the handset vendor's discretion. The examples shown are purely indicative.)

Whilst each MWI has a specific purpose (apart from MWIOTHER) the choice is of course entirely at the discretion of the administrator / developer as to how they are assigned to services (e.g. there's no reason why the MWIEMAIL indicator couldn't be used to notify the user about voicemails if that is desired).

Configuring the Mobile Phone for Corporate Voicemail

In order to create the best user experience for corporate voicemail on a mobile handset there are a couple of recommended steps that should be taken:

1. Set-up conditional diverts on the mobile to the corporate voicemail mailbox number.
2. Change the Voicemail Access number in the handset.

We will now describe these steps in greater detail.

Setting-up Diverts

Broadly speaking mobile networks support two types of divert: Conditional and Unconditional.

Conditional diverts will route a call to another number under certain conditions. The conditional diverts defined in the GSM standard are:

• No Answer. When the phone is switched on and in coverage, an incoming call will cause it to ring until it is either answered, rejected, or, if set, the No Answer divert kicks in. The length of ring time before the divert takes over can be adjusted in 5 second increments up to 30 seconds maximum.
• Unreachable. This divert will apply when the phone has either been switched off or is out of coverage.
• Busy. When the phone is either mid-call (and call waiting is not available) or the user rejects the incoming call, then the Busy divert will apply.

Unconditional diverts are used to route all inbound calls to another number. When this is active the phone will not ring (this feature is rarely used as most users prefer to take advantage of the conditional divert Unreachable which will automatically apply when the phone is switched off).

The GSM standard defines the following USSD codes for controlling diverts:

(*) Note: whilst supported on all GSM phones, diverts are a network rather than a handset function, therefore it is ultimately down to the network to support these diverts. It should be noted that some pre-paid / pay-as-you-go subscriptions will not allow diverts. Also some networks require you to call customer services to enable diverts as a service on your subscription. Additionally in some cases diverts are supported by non-standard USSD strings. The general rule here is if the above divert codes don't work as you would expect them to on your phone then you should check the user-guide that your network supplied with your phone or contact their customer services team.

Changing the Voicemail Access Number in the Mobile Phone

Most handsets can be configured with a voicemail access number. This number is then usually available as a single key dial (e.g. by holding down the "1" key for a second or more), and may also be invoked when pressing the SEND / CALL key if the phone displays a "New Voicemail. Listen now?" type popup when the MWI is set.

Changing the number from that configured by the network to the corporate access number is done through a menu option specific to your handset.

For instance on a Nokia 6310, it is set in Menu -> Messages -> Voice Messages -> Voice Mailbox Number

Check the user guide for your phone if you cannot immediately find where the menu option is.

Configuring Asterisk for Mobile MWI

Asterisk can easily be set-up to control the Mobile MWI. The prerequisites are that you must have installed the FastSMS module (either the C version or the Perl AGI version) and have created a FastSMS account. If you haven't carried out both of these steps then please visit the FastSMS homepage.

Mobile MWI activation and deactivation is carried out through dialplan commands. The FastSMS command is constructed like this:

FastSMS(destination|message_text[|sender_id])

Here's a couple of examples that show how this command can be used to send regular SMS text messages:

In order to use FastSMS to control the mobile's MWI, we simply substitute the message_text parameter with one of the following reserved MWI commands:

MWIVOICEMAILON
MWIVOICEMAILOFF
MWIFAXON
MWIFAXOFF
MWIEMAILON
MWIEMAILOFF
MWIOTHERON
MWIOTHEROFF

And some examples of this are:

Now to pull this together into a functional Asterisk dialplan. For this example, +44765123456 is the number of the mobile associated with the voice mailbox, and +44123456000 is the voicemail access number.

Here is the part of the dialplan that switches the MWI on when a new voicemail has been left:

And here is the part of the dialplan that switches the MWI off when there are no more unread voicemails:

Other Considerations

One of the main considerations with designing a unified voicemail solution that has not already been discussed here is the planning and configuration of the voicemail access extensions.

There are two principal use cases that need to be covered by this:

Whilst it is outside the scope here to have an extensive discussion about all the possible approaches that would support these use cases, the following table hopefully gives some starting indicators to support you in planning the best approach for your network: