Multiplex communications – Channel assignment techniques – Adaptive selection of channel assignment technique
Reexamination Certificate
1998-11-06
2002-02-12
Kizou, Hassan (Department: 2662)
Multiplex communications
Channel assignment techniques
Adaptive selection of channel assignment technique
C370S235000, C370S238000, C370S328000, C370S329000, C370S352000, C370S431000, C370S441000, C370S464000, C370S465000, C709S226000
Reexamination Certificate
active
06347091
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to mobile communications, and in particular, to dynamically adapting a data communication connection to an optimal state.
BACKGROUND AND SUMMARY OF THE INVENTION
In current and future mobile radio communication systems, a variety of different services either are or will be provided. While mobile telephone systems have traditionally provided voice services, packet data services are also becoming increasingly important. Example packet data services include e-mail, file transfers, and information retrieval using the Internet. Because packet data services often utilize system resources in a manner that varies over the course of a packet data session, the flow of packets is often characterized as “bursty.”
FIG. 1
is a graph that illustrates packet bursts communicated over time and interspersed over periods where no packets are transmitted. In general, the “density” of packets is high for short time periods and often very low for long periods.
Mobile communication systems must be able to accommodate both circuit-switched services well suited for applications like voice as well as packet-switched services well suited for bursty data applications like e-mail, and at the same time, those services must efficiently use the limited radio bandwidth. In the context of these different types of services, mobile communication systems should provide different types of channels and different schemes for keeping track of the mobile location hereafter referred to as “mobility management.”
The Global System for Mobile communications (GSM) offers two categories of services including circuit-switched services via a Mobile Switching Center (MSC) node and packet-switched services via a General Packet Radio Service (GPRS) node. For circuit-switched, guaranteed service, e.g., High Speed Circuit-Switched Data (HSCSD), statically-dedicated traffic channels are employed. For packet-based, best effort service, another set of packet data channels are allocated from a pool of resources on a per packet basis using a media access control protocol or scheduling policy. Mobile communication systems in North America based on IS-95 standard offer packet data services by supporting variable rate transmission on an established, dedicated channel.
There are significant drawbacks with these current approaches which statically map a connection-oriented or a connectionless-oriented service onto a specific channel type. Inevitably, such static mapping results in a non-optimal use of system resources. Packet-switched services, in particular, require variable bandwidths and delays. A high-bandwidth, short-delay packet service like packet-switched audio and video benefits from using a dedicated channel reserved during the connection. But other packet services like messaging and e-mail do not require high bandwidth or short delay. In fact, the bursty nature of e-mail and messaging services underutilize a continuously reserved channel. The present invention overcomes these drawbacks and achieves optimal use of system resources by dynamically determining and allocating a best connection state depending on the packet data to be currently transmitted. In one embodiment, the connection state may specify the type of radio channel. In other embodiments, the connection state may specify additional characteristics. For example, an optimal channel type and a mobility management scheme best suited for that particular channel type may be dynamically allocated.
In a mobile communications system, a connection is established between a mobile station and a radio access network. A “connection” refers to a service provided by the radio access network to permit communication of information over a radio interface between the mobile station and the radio access network in both uplink (from the mobile) and downlink (to the mobile) directions. Such a connection may be established in response to the mobile station or by a core network connected to the radio access network. A connection may remain established even though the mobile station changes geographic cells/areas, i.e., a handover. The state of the connection specifies one of plural different types of radio channels to carry or bear the connection over the radio interface. The connection state preferably may also specify other characteristics such as one of plural, different mobility management schemes tailored to the selected channel type, channel bit rate(s), etc.
The connection is dynamically adapted to an optimal state based on one or more conditions relating to the connection. For example, one or more traffic parameters are determined for the connection and used to predict a future parameter value. Based on a predicted parameter value, an optimal connection state is determined and implemented. If the traffic parameter value changes later in the connection, another channel type may be dynamically selected that is better suited for the newly predicted parameter. Example traffic parameters are the amount of data to be sent in the future over the mobile data packet connection, packet arrival time, and packet density. A connection state may specify a radio channel type. Example channel types include a dedicated radio channel carrying data packets associated with only one mobile station and a shared radio channel carrying data packets associated with more than one mobile station. In addition, the shared radio channel type includes a temporary dedicated radio channel, a random access channel, and a paging channel. Taking the current amount of data in queue as an example traffic parameter, if the amount of data in the queue exceeds a threshold, it may be optimal to employ a dedicated channel to carry that high volume of data. Otherwise, it may be optimal to employ a shared channel.
In a preferred example embodiment based on the amount of data in queue for a packet data connection with a mobile station over a radio access network, if the determined amount of data in queue exceeds the threshold, it is also determined whether the packet data connection is temporarily disconnected or interrupted. If the packet data connection is temporarily disconnected or interrupted, no channel type decision or transfer is made. Otherwise, the packet data connection is established on or transferred to a dedicated radio channel. If the determined amount of packet data in queue is less than a threshold, a shared radio channel may be selected, or one or more other parameters may be considered in deciding what type of radio channel should bear the packet data connection. Preferably, such one or more other parameters relates to a flow of packets over the data packet connection. If the packet flow parameter exceeds a flow threshold, the packet data connection is allocated to a dedicated radio channel. If the packet flow parameter is less than or equal to a flow threshold, the packet data connection is allocated to a shared radio channel. An example flow parameter is the time interval between packets. When the determined time intervals between packets on the connection are similar, the packet data connection is assigned to a dedicated radio channel.
Such an example embodiment may be implemented in the downlink direction from the network to the mobile, although it may be used in the uplink direction as well. A network packet buffer is provided to store packets to be sent to the mobile station. A network packet router provides packets to the packet buffer. When the amount of packets currently stored in the packet buffer exceeds a predetermined percentage of the buffer size, the packet buffer generates a “back pressure” signal used to instruct the packet router to temporarily halt transmission of packets from the router to the packet buffer. The presence or absence of a back pressure signal may be employed in determining what type of radio channel should be allocated to bear the packet data connection.
In another example embodiment, the selected connection state may also specify one of plural mobility management (MM) schemes. In a first MM scheme, the mobile st
Bark Per O. G.
Hansson Ulf A.
Lindskog Leif P.
Rimhagen Thomas
Vilander Harri
Kizou Hassan
Logsdon Joe
Nixon & Vanderhye P.C.
Telefonaktiebolaget LM Ericsson (publ)
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