Two of the original usage models for Bluetooth involve voice over Bluetooth. The two models are “Three-in-one phone” and “headset” usage models. The three-in-one phone usage model describes how a mobile phone with Bluetooth can be used in three different scenarios:
1. As cordless telephone with Bluetooth interface together with a home base station,
2. as Intercom with Bluetooth interface, peer to peer communication with no network.
3. and as traditional mobile phone over the GSM network.
The headset usage model describes a wireless portable handsfree solution. The latter usage model has already found its way into several products and will not be discussed further here. The “three-in-one phone” seams quite obvious, but it has not been implemented in any product yet. The reason is the negative reception the usage model has received from mobile operators.
As a counter reaction Ericsson has come up with a new usage model for GSM/GPRS over Bluetooth. The usage model is supported by a candidate profile called Mobile Services Profile.
This document describes the three usage models for voice over Bluetooth and supporting profiles. That is Cordless Telephone Profile (CTP), Intercom Profile (ICP) and Mobile Services Profile (MSP).
Fixed mobile conversion (FMC) i.e. the use of mobile phone over the fixed network, is the goal for this usage model. A home cordless base station will connect the mobile phone to the ISDN/PSTN network in order to reduce cost of calls and to remove the need for dedicated home wireless terminals as DECT phones.
The mobile phone will have both GSM and Bluetooth radio interfaces active when it is within radio range of the home cordless base station. Incoming calls to GSM-number will go over the GSM interface, while outgoing calls will go over the fixed network via the ISDN/PSTN interface. Incoming calls to the fixed network number will also be routed over the Bluetooth interface to the mobile phone. See also figure below. Roaming between cordless base stations are not supported, nor are handover between Bluetooth and GSM. In fact no coordination between the GSM and Bluetooth interfaces is specified.
Bluetooth GSM Mobile Network Fixed Network Blue Box ISDN / PSTN Bluetooth GSM Mobile Network Fixed Network Base Station
The user will need a mobile phone with Bluetooth and Cordless Telephone Profile.
There are no mobile phones that support this profile today; however there are indications that this will change, and that at least one mobile phone vendor will support CTP from 2003. In addition several access point vendors supports CTP with dedicated terminals and other vendors has stated that they will support CTP as soon mobile phones become available. For more information on supported products see http://www.bluetooth.com/tech/products.asp
The Intercom usage model and Intercom profile describes a peer-to-peer communication solution where two mobile phones can communicate directly without any network. This is a “walkie-talkie” scheme for short-range communication. The usage model has limited value and no services for operators are foreseen.
The Mobile Services Profile is not only a voice solution; it is a way to support all GSM/GPRS services over Bluetooth. The figure below shows how Bluetooth is fitted into the GSM infrastructure. The Bluetooth specific part of the solution consist of a mobile phone with MSP support, a Home Base Station (HBS) connected to a Home Base Station Controller (HBSC) over the fixed network. The Home Base Station Controller is linked to the GSM backbone via the MSC. Each home would need a Home Base Station to offer GSM/GPRS over Bluetooth.
Bluetooth offers an alternative radio access with higher capacity and shorter range than the regular GSM radio access. Thus services can be supported which requires high bandwidth. The capacity of one Home Base Station is equivalent to one UMTS cell.
The main advantages of MSP are listed below:
The main disadvantage
of the MSP is the fact that it is not an approved Bluetooth Profile nor is it a
draft profile. Plus it is only supported by one vendor (Ericsson /
Sonyericsson). Even if it is a great technical concept it is unlikely that we
will see products with MSP.
One possible alternative solution is that the MSP is replaced with the combination of CTP and SIM Access Profile (SAP). (The SIM Access Profile is developed for car phones to take over the identity of a portable mobile phone. Thus user can used the same SIM card for his or hers portable mobile phone and the integrated car phone.) A Home Base Station can register with the GSM network as a mobile phone over the fixed network via a modified HBSC, and the CTP can be used to communicate between the HBS and the mobile phone. The advantage of this solution is that it is based on standardised profile. The disadvantage is the lack of roaming support.