Telephonic communications – Plural exchange network or interconnection – With interexchange network routing
Reexamination Certificate
2000-12-11
2004-05-04
Deane, Jr., William J. (Department: 2642)
Telephonic communications
Plural exchange network or interconnection
With interexchange network routing
C379S221030
Reexamination Certificate
active
06731739
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention pertains to telecommunications, and particularly to the balancing of loads on links in a telecommunications network.
2. Related Art and Other Considerations
In a typical cellular radio system, mobile user equipment units (UEs) communicate via a radio access network (RAN) to one or more core networks. The user equipment units (UEs) can be mobile stations such as mobile telephones (“cellular” telephones) and laptops with mobile termination, and thus can be, for example, portable, pocket, hand-held, computer-included, or car-mounted mobile devices which communicate voice and/or data with radio access network.
The radio access network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a base station. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by a unique identity, which is broadcast in the cell. The base stations communicate over the air interface (e.g., radio frequencies) with the user equipment units (UE) within range of the base stations. In the radio access network, several base stations are typically connected (e.g., by landlines or microwave) to a radio network controller (RNC). The radio network controller, also sometimes termed a base station controller (BSC), supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
One example of a radio access network is the Universal Mobile Telecommunications (UMTS) Terrestrial Radio Access Network (UTRAN). The UTRAN is a third generation system which in some respects builds upon the radio access technology known as Global System for Mobile communications (GSM) developed in Europe. UTRAN is essentially a wideband code division multiple access (W-CDMA) system.
As those skilled in the art appreciate, in W-CDMA technology a common frequency band allows simultaneous communication between a user equipment unit (UE) and plural base stations. Signals occupying the common frequency band are discriminated at the receiving station through spread spectrum CDMA waveform properties based on the use of a high speed, pseudo-noise (PN) code. These high speed PN codes are used to modulate signals transmitted from the base stations and the user equipment units (UEs). Transmitter stations using different PN codes (or a PN code offset in time) produce signals that can be separately demodulated at a receiving station. In a phenomena know as diversity, the high speed PN modulation also allows the receiving station to advantageously generate a received signal from a single transmitting station by combining several distinct propagation paths or “legs” of the transmitted signal. In CDMA, therefore, a user equipment unit (UE) need not switch frequency when handoff of a connection is made from one cell to another. As a result, a destination cell can support a connection to a user equipment unit (UE) at the same time the origination cell continues to service the connection. Since the user equipment unit (UE) is always communicating through at least one cell during handover, there is no disruption to the call. Hence, the term “soft handover.” In contrast to hard handover, soft handover is a “make-before-break” switching operation.
There are several interfaces of interest in the UTRAN. The interface between the radio network controllers (RNCs) and the core network(s) is termed the “Iu” interface. The interface between a radio network controller (RNC) and its base stations (BSs) is termed the “Iub” interface. The interface between the user equipment unit (UE) and the base stations is known as the “air interface” or the “radio interface” or “Uu interface”. An interface between radio network controllers (e.g., between a Serving RNC [SRNC] and a Drift RNC [DRNC]) is termed the “Iur” interface.
Thus, a network such as a W-CDMA system has numerous nodes which are interconnected, for example numerous radio network controller (RNC) nodes which are connected by inter-RNC links. Typically, one radio network controller node (RNC), denominated as the serving RNC or SRNC, is assigned to control a connection. The connection is between a first party, which is a mobile party (e.g., mobile station or user equipment unit), and another party (which may either be a mobile party or a fixed party [e.g., in the PLMN]). The connection can have plural legs involving different base stations in view of the diversity capabilities mentioned above. Moreover, the connection (with its possibly plural legs) may be routed to its SRNC over one or more inter-RNC links and through several radio network controller nodes, some of which may function as drift RNCs (DRNCs).
When a new connection is requested in a network, the system typically tries to set up the connection through the shortest path, thus making the closest network node an anchor (e.g., SRNC) for the connection. However, if the shortest path results in a congested path due to the new connection, the connection request will usually be rejected.
Thus, heavily utilized networks can become overloaded when attempting to admit a new connection. One or more of the links necessary for the new connection may become congested if the new connection is actually admitted. Undesirably, the network may be forced to reject the new connection. It would be preferably to make room in the network to accommodate admission rather than refusal of the new connection. But unless the load in the network is optimally balanced upon approaching an overload situation, it is essentially impossible to reconfigure the connections to afford accommodation of the new connection. And realistically, it is unlikely for a network to be optimally balanced in any event.
What is needed therefore, and an object of the present invention, is a technique for resolving potential network overload situations to facilitate admission of new connections.
BRIEF SUMMARY OF THE INVENTION
A telecommunications network has a unit and technique to alleviate congestion on a congested link as can occur, e.g., when a new connection seeks admission to the network. The congestion avoidance technique/unit ascertains, from a set of candidate connections, a best candidate to route in order to avoid the congestion. Further, the congestion avoidance technique/unit determines a best candidate path to which the best candidate connection is to be routed. The best candidate connection and the best candidate path are determined so that, after routing the best candidate connection to the best candidate path, a load of the weakest link in the network is as low as possible.
The telecommunications network has plural nodes including a common node. The telecommunications network carries a plurality of connections, each of the plurality of connections being carried over one of plural paths of the network. Each path of the network includes at least one link (each link connecting two of the plural nodes). Each of the plural paths is connected to the common node by one of the plural links. The plural nodes include radio network controller (RNC) nodes of a radio access network (RAN). In differing embodiments, the common node is a core network node or a control node of the radio access network. The congestion avoidance unit which performs the congestion avoidance unit technique can be situated at the common node or one of the other nodes.
The congestion avoidance technique of the invention develops, for each candidate connection, a network topology candidate connection subtraction load scenario (e.g., graph). The candidate connection subtraction load scenario for a candidate connection has a load for the corresponding candidate connection subtracted therefrom. For each candidate connection subtraction load scenario the congestion avoidance technique next determines a weakest link, so that for each candidate connection there is a weakest link of its connection subtract
Riihinen Wesa
Söderberg Johan
Deane, Jr. William J.
Nixon & Vanderhye P.C.
Telefonaktiebolaget LM Ericsson (publ)
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