Bearer services provide the capability for information transfer between access points and involve only low layer functions. These functions are sometimes referred as low layer capabilities (in reference to OSI layers). The user may choose any set of high layer protocols for his communication and the PLMN does not ascertain compatibility at these layers between users. In the general case a communication link between access points provides a general service for information transport. The communication link may span over different networks such as Internet, Intranets, LANs and ATM based transit networks, having network specific means for bearer control. Each network contributes to the end-to-end QoS perceived by the end-user. PS and CS domains provide a specific set of bearer capabilities. The Circuit bearer services are described in TS 22.002. The packet services (GPRS) is described in TS 22.060. Following chapters describe the overall requirements for both the CS and PS domain bearers and also for the bearers used by teleservices.

Bearer services are characterised by a set of end-to-end characteristics with requirements on QoS. The characteristics and requirements shall cover major network scenarios, i.e. the cases when the terminating network is PSTN, ISDN, IP networks/LANs, X.25 and a PLMN. Quality of Service is the quality of a requested service (Teleservice or Bearer Service or any other service, e.g. customer care) as perceived by the customer (ITU-T Recommendation E.800 [18]). QoS is always meant end-to-end. Network Performance of several network elements of the originating and terminating network(s) contribute to the QoS as perceived by the customer including terminals and terminal attachments. In order to offer the customer a certain QoS the serving network need to take into account network performance components of their network, reflect the performance of the terminal and ad sufficient margin for the terminating networks in case network performance requirements cannot be negotiated. As far as the QoS to the subscriber is concerned network elements have to provide sufficient performance (reflecting possible performance constraints in terminating networks) so that the PLMN cannot be considered as a bottleneck. This section outlines the requirements on bearer services in two main groups;

• Requirements on information transfer, which characterise the networks transfer capabilities for transferring user data between two or more access points.
• Information quality characteristics, which describe the quality of the user information transferred between two or more access points.

It shall be possible to negotiate / re negotiate the characteristics of a bearer service at session / connection establishment and during an on going session / connection. It shall be possible to allocate a particular QoS to any specific service of the user. The association between services and QoS can be handled either network based or UE based. In the case of a UE based association it shall be possible to be programmed by the Home Environment operator into the ME or the USIM. If the association exists in the UE the specific QoS for the invoked service shall be requested at session / connection establishment.

It shall be possible for one application to specify its traffic requirements to the network by requesting a bearer service with any of the specified traffic type, traffic characteristics, maximum transfer delay, delay variation, bit error ratios & data rates. It shall be possible for the network to satisfy these requirements without wasting resources on the radio and network interfaces due to granularity limitations in bit rates. It shall be possible for one mobile termination to have several active bearer services simultaneously, each of which could be connection oriented or connectionless. The only limiting factor for satisfying application requirements shall be the cumulative bit rate per mobile termination at a given instant (i.e. when summing the bit rates of one mobile termination's simultaneous connection oriented and connectionless traffic, irrespective of the traffic being real time or non real time) in each radio environment:

• At least 144 kbits/s in satellite radio environment (Note 1).
• At least 144 kbits/s in rural outdoor radio environment.
• At least 384 kbits/s in urban/suburban outdoor radio environments.
• Greater than 2 Mbits/s in urban/suburban outdoor radio environments (Note 2 and 3).
• At least 2048 kbits/s in indoor/low range outdoor radio environment. (Note 2)
• Greater than 2 Mbits/s in indoor/low range outdoor radio environment (Note 2 and 3).

It shall be possible for one application to specify its QoS requirements to the network by requesting a bearer service with any of the specified traffic type, traffic characteristics maximum transfer delay, delay variation, bit error ratios & data rates. The following table indicates the range of values that shall be supported. These requirements are valid for both connection and connectionless traffic. It shall be possible for the network to satisfy these requirements without wasting resources on the radio and network interfaces due to granularity limitations in QoS.

This section outlines the QoS requirements that shall be provided to the end user / applications and describes them as requirements between communicating entities (i.e. end to end). The QoS values in the Tables represent end to end performance, including mobile to mobile calls and satellite components. Delay values represent one -way delay (i.e. from originating entity to terminating entity). The values included in the following Tables are commonly accepted values from an end-user viewpoint [12]. The delay contribution within the mobile network should be kept to minimum since there may be additional delay contributions from external networks. Figure 5.5-1 below summarises the major groups of application in terms of QoS requirements. Applications and new applications may be applicable to one more groups. However, there is no strict one-to-one mapping between the groups of application/service defined in this TS and the traffic classes as defined in TS 23.107. For instance, an Interactive application/service can very well use a bearer of the Conversational traffic class if the application/service or the user has tight requirements on delay.

The following Tables further elaborate end user / application QoS requirements.

 

 

The following requirements shall lead the radio interface optimisation process;

• support of high bit rate (around the Peak Bit Rate), bursty, asymmetric, non-real time bearer capabilities;
• support of high bit rate (around the Peak Bit Rate), bursty, asymmetric, real time bearer capabilities;
• the ability to extend or reduce the bandwidth associated with a bearer capability in order to adapt to bit rate or radio condition variations, and to add or drop service components.

However, the services provided by existing systems (speech in particular) shall be supported in a spectrally efficient manner (at least as efficiently as included in GSM specifications) for the same quality of service. In order to allow the support of flexible, bandwidth on demand services, bearer services should be provided with the finest possible granularity that can be efficiently supported.

Many IP based services and applications will negotiate the resources required in an end to end manner on the application level. It is essential for the PLMN to provide the capability of ensuring that the resources provided and charged for shall be in line with that authorized by the service and subscription. The PLMN

• shall be able to dynamically allocate QoS according to service needs and subscription information.
• shall be able to give differentiated policing for the traffic within an APN. That is, the policing shall be on a per service flow basis (i.e. on the basis of specific flows of IP packets identified by the service).
• shall control the requested QoS parameters based on the invoked service needs and subscription information.
• shall facilitate service-flow level charging.

Any solution:

• shall support roaming users
• should minimise UE dependencies and optimize usage of network resources

In order to have efficient use of radio resources shared amongst terminals, it shall be possible for a PLMN to apply a limit to the cumulative bit rate per subscriber at a given instant for non-real time services (i.e. when summing the bit rates of one subscriber's simultaneous non-real time traffic).

The PLMN shall support both IPv4 and IPv6 connectivity. IPv4 only, IPv6 only and dual mode (IPv4/IPv6) terminals should be supported. Interworking between terminals, servers and access systems supporting different versions of IP shall be possible. Mobility between access systems supporting different IP versions shall be supported with minimal network/terminal impacts. The PLMN shall support simultaneous IPv4 and IPv6 usage for a single bearer connecting to the same PDN through the same APN. The operator shall be able to control whether or not an IPv4 only terminal is allowed access to the network. Service continuity of subscriber IP sessions shall be supported during UE handovers from one IP access network to another IP access network, regardless of whether the new IP access network supports the same version of IP as the old IP access network. The PLMN shall be able to handle user-to-server traffic, user-to-user traffic and user-to-group traffic. The PLMN shall be able to handle different types of IP traffic, such as real-time (e.g. VoIP), non-real time traffic (e.g. Web browsing), and mission critical traffic (e.g. M-Commerce).

The PLMN shall have the ability to support both private and public IPv4 and IPv6 addresses. User device IP addresses should normally be allocated dynamically by the network operator and managed without user intervention. For business critical applications, and for firewall configuration simplification purposes, it shall be possible for a user to be allocated a static IP address; the static address shall be assigned by the network operator. Details of an assigned static IP address shall be maintained with the subscriber's records in the HLR/HSS.