The present invention relates in general to mobile communications, and in particular, to flexibly providing a wide variety of mobile communications services and efficiently allocating resources to support those services.
Mobile communications have developed from first generation, analog-based mobile radio systems to second generation digital systems, such as the European Global System for Mobile communications (GSM). Current developments for a third generation of mobile radio communication include the Universal Mobile Telephone communications System (UMTS) and the IMT 2000 system. For simplicity, third generation systems are referred to simply as UMTS. In simple terms, UMTS is xe2x80x9ccommunication to everyone, everywhere,xe2x80x9d where communication also includes the provision of information using different types of media, i.e., multimedia communications.
From the user""s perspective, there should be no distinction in service capability between mobile or fixed network access. Because of the widespread success of the existing GSM platform, i.e., a global xe2x80x9cGSM footprint,xe2x80x9d as well as the inherent upgradability and modularity of the GSM platform, there is a strong impetus to base UMTS on an xe2x80x9cevolvedxe2x80x9d GSM platform. In fact, the present invention describes a UMTS based on an evolved GSM platform and therefore uses GSM terminology. Of course, those skilled in the art will recognize that the principles of the present invention are not limited to a GSM platform/terminology and may be implemented using other appropriate platforms.
Current mobile/cellular telecommunications networks are typically designed to connect and function with Public Switched Telephone Networks (PSTNs) and Integrated Services Digital Networks (ISDNs). Both of these networks are circuit-switched networks (rather than packet-switched) and handle relatively narrow bandwidth traffic. However, packet-switched networks, such as the Internet, are very much in demand and handle much wider bandwidth traffic than circuit-switched networks. While wireline communication terminals, e.g., personal computers, are capable of utilizing the wider packet-switched network bandwidth, wireless mobile radio terminals are at a considerable disadvantage because of the limited bandwidth of the radio/air interface that separates the mobile terminals from packet-switched networks.
Mobile terminals are currently limited in the data rates for data communications services such as facsimile, electronic mail, and Internet. While it is feasible perhaps to provide some slow-scan video and picture transfer at this limited rate over the radio air interface at this limited rate, as long as demands on quality are not too high, the expectations regarding real time use of the Internet are a more difficult challenge. The demand is growing for higher data transfer speeds in order the xe2x80x9csurf the netxe2x80x9d using mobile terminals with fast access to text, images, and sound. This multimedia application demands high peak bit rates in short bursts while the information is downloaded to the mobile terminal. Another challenging multimedia, mobile terminal application is simultaneous voice and data, e.g., PC application sharing or shared whiteboard. Although this latter type of multimedia application does not require particularly high bit rates, it does require real time, continuous operation because of the voice content. A demanding circuit-switched application (rather than packet-switched as in the Internet application) requiring relatively high bit rates is video conferencing. In order for mobile video conferencing to become practical, the amount of user bandwidth required must be reduced to a minimum without sacrificing image quality.
GSM already meets some of the requirements for UMTS. For example, two new service classes are under development for GSM to expand the current user data rate: High Speed Circuit Switched Data (HSCSD) and General Packet Radio Service (GPRS). Both services are designed to integrate with the current GSM system. HSCSD bearer services bundle up eight Time Division Multiple Access (TDMA) time slots within a 200 kHz GSM carrier to create a higher bandwidth channel. In other words, a 64 kbps circuit switched bearer channel uses all available TDMA slots. HSCSD is also being developed to provide bandwidth on demand at variable data rates. GPRS is a packet switching technique that employs reduced channel coding to achieve a net bit rate of 14.4 kbps per time slot providing a maximum throughput rate of 115 kbps. It is more suited to handling xe2x80x9cburstyxe2x80x9d traffic such as the infrequent transmission of e-mail messages, Internet information, and other data. Because GPRS is a packet switching service, it only requires a channel when data is being sent thereby enabling the frequency spectrum to be more efficiently allocated across voice and data calls and allowing channels to be shared between several users simultaneously.
However, one area of weakness for GSM is narrowband radio access. A UMTS Wideband-Code Division Multiple Access (WCDMA) radio access network provides wireless access at very high data rates and supports enhanced bearer services not realistically attainable with the first and second generation mobile communication systems. WCDMA currently supports 5 MHz-15 MHz, and in the future, promises an even greater bandwidth. In addition to wide bandwidth, WCDMA also improves the quality of service by providing robust operation in fading environments and transparent (xe2x80x9csoftxe2x80x9d) handoffs between base stations. Multiplath fading is used to advantage to enhance quality, i.e., using a RAKE receiver and improved signal processing techniques, contrasted in narrowband systems where fading substantially degrades signal quality.
In the present invention, a UMTS Terrestrial Radio Access Network (UTRAN) responds to radio access bearer service requests with flexible and efficient allocation of resources needed to support a communication with a mobile radio. The UTRAN includes plural base stations for communicating with mobile radios over a radio air interface using radio channel resources allocated by a radio network controller connected to the base stations. External network service nodes that interface with external networks communicate with mobiles via the UTRAN. When one of the service nodes requires communication with a mobile radio, the service node requests a radio access bearer from the UTRAN rather than a specific radio channel resource. A radio access bearer is a logical connection with the mobile station through the UTRAN and over the radio air interface and corresponds to a single data stream. For example, one radio access bearer may support a speech connection, another bearer may support a video connection, and a third bearer may support a data packet connection. Each radio access bearer is associated with quality of service (QoS) parameters describing how the UTRAN should handle the data stream. Examples of quality of service parameters include data rate, variability of data rate, amount and variability of delay, guaranteed vs. best effort delivery, error rate, etc.
The radio access bearers are dynamically assigned to UTRAN transport and radio channel resources by the UTRAN. The radio access bearer service and the UTRAN isolate the details of transport and radio resource allocation handling as well as details of radio control, e.g., soft handoff. The UTRAN approach is different from traditional approaches where an external network and/or an external network service node is involved in the details of requesting, allocating, and controlling specific radio connections to and from the mobile radio. Instead, the external network service node only needs to request a radio access bearer service over a RAN interface to the UTRAN along with a specific quality of service for a communication to a specific mobile radio. The UTRAN provides the requested service at the requested quality of service (if possible).
Plural radio access bearers may be established and released independently to one mobile radio including bearers from different networks. Moreover, plural radio access bearers, e.g., one carrying circuit-switched information and another carrying packet-switched information, intended for the specific mobile radio may be multiplexed onto the same CDMA channel. Each bearer may have its own Asynchronous Transfer Mode (ATM) transport connection through the UTRAN, or it may be multiplexed with other bearers onto one ATM transport connection.
To initiate a radio access bearer service, a request is transmitted to the UTRAN for communication with a mobile radio. One or more parameters accompany the radio access bearer service request. When establishing each bearer, the UTRAN flexibly xe2x80x9cmapsxe2x80x9d or allocates the radio access bearer to physical transport and radio channel resources through the UTRAN and over the radio air interface, respectively. The transport connection between nodes in the UTRAN in a preferred example embodiment is an ATM type connection. A radio channel over the air interface includes one or more CDMA spreading codes.
The mapping is based on the one or more parameters associated with the radio access bearer service request. In addition to quality of service parameters, the parameters may also include one or more traffic condition parameters like a congestion level on a common channel, an interference level in the geographic location area in which the mobile radio is currently operating, a distance between the mobile radio and the base station, radio transmit power, the availability of dedicated channel resources, the existence of a dedicated channel to a mobile station, and other traffic parameters or conditions.
In the example embodiment, two different types of radio channels are provided. A dedicated type of channel delivers frames of information as received without substantial delay. A common or shared type of channel delivers packets of information in a scheduled manner. When the quality of service parameter(s) requested is (are) relatively high, e.g., for a speech or a synchronized communication, soft/softer handover, etc., the dedicated channel may for example be selected. When the quality of service requested is relatively low, e.g., for an e-mail message, the common channel may for example be selected.
As mentioned above, the channel type selection may also take into account traffic parameters like the interference level in the geographic location area in which the mobile radio is currently operating. If that interference level is high, a dedicated radio channel may for example be selected which typically includes mobile transmit power control to help reduce the interference level. When the interference level is low, the shared radio channel may for example be selected to available more dedicated channel resources for other connections. Indeed, if the availability of dedicated channels is low, the dedicated radio channel may be selected. Although, the channel type selection may be based on one parameter, e.g., one quality of service parameter, it is preferably based on plural quality of service parameters associated with the connection, or on a quality of service parameter associated with a connection and a current traffic condition, like the interference level in the mobile""s geographic location area.
On the other hand, if dedicated channel already exists between the UTRAN and the mobile radio, a new logical connection is mapped to the already-existing dedicated channel since the UTRAN can multiplex different logical connections associated with the mobile station onto the single dedicated channel. Similarly, control signaling associated with the logical connection, while generally transferred on the common channel, is transferred on a dedicated channel if one exists to the mobile station.
In addition to initially selecting one of plural radio channel types when a connection associated with a radio access request is initially established by the UTRAN, one or more parameter values relating to quality of service, traffic conditions, etc. is monitored during the lifetime of the connection. If the monitored parameter(s) changes enough from what was initially determined when the channel type for the connection was selected, the connection may be switched to another type of radio channel. For example, if a common radio channel is established for the connection based on an initial quality of service value, and the quality of service associated with that connection subsequently increases (preferably by a certain threshold amount over the initial quality of service value), the connection may be switched to a dedicated radio channel. Alternatively, if the quality of service associated with the connection subsequently decreases when a dedicated channel was initially established, the connection may be switched to the common radio channel. In another example, even though the common radio channel was initially established for a connection, the interference level in the cell may subsequently may have increased such that it warrants switching the connection to a dedicated radio channel in order to decrease the interference level in the cell.