Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1997-07-01
2001-08-28
Trost, William (Department: 2683)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S452200, C455S453000, C455S454000, C455S466000, C370S329000, C370S468000
Reexamination Certificate
active
06282424
ABSTRACT:
FIELD OF THE INVENTION
The field of this invention pertains to telecommunications, including a telecommunications network that uses a primary circuit switched service in conjunction with other services.
DESCRIPTION OF THE TECHNOLOGY
In an ideal telephone switch system, arriving connection requests, i.e, calls, are immediately allocated a telephone line. That is, arriving connection requests are immediately served when a “server,” i.e., a connection path, is available; otherwise, the connection request is denied.
The utilization of a telephone switch system can be driven arbitrarily close to one-hundred percent (i.e., an ideal telephone switch system) when the rate at which connection requests are placed with the switch is equal to or greater than the duration of any one connection in progress at the switch. At first glance, this appears desirable, as the system is maintained full with revenue-bearing traffic. However, the penalty paid for such a scenario is that the associated “call blocking rate,” i.e., the connection request denial rate, can become unacceptably high. This can occur because, in order that a high utilization of the available server capacity is achieved, the service provider only provides enough connection resources to satisfy the average or lowest rate of call requests, thereby ensuring that upon termination of a call connection that is currently in progress, a new connection request is available to utilize the now available connection resource. The service time, however, is usually significantly longer than the “inter-arrival time,” i.e., the time between connection request arrivals at the switch. This high utilization situation is intrinsically unacceptable from a system user's perspective, as the high utilization means a correspondingly higher blocking rate, since if the inter-arrival time is greater than or equal to the service time, service requests will not be immediately serviced, resulting in the now all-to-familiar “all circuits are busy, please try your call again later” message. Generally, to ensure satisfactory customer service, service providers provide excess connection resources so that the worst case chance of a connection becoming denied is low, typically on the order of one-tenth of one percent to one percent. For an exemplary twenty-five server system, this corresponds to an average utilization of the available system capacity that ranges between forty to sixty percent, depending on the service time of the system's traffic.
The observation that the average utilization of the available system capacity lies between forty to sixty percent for small server systems has provided motivation to seek methods of utilizing the “unused;” i.e., available, system capacity. This, in turn, has resulted in the introduction of a secondary packet data service that shares the same switch/router with the primary, i.e., circuit switched, service.
The introduction of a secondary service is based on the notion that this secondary service has a significantly shorter service time than that of the primary service and, in addition, the secondary service time is comparable to or shorter than the arrival rates of the primary service connection requests. Under these conditions, the secondary service should appear transparent to the users of the primary service because, although the unused system capacity is utilized by the secondary service, the connection resources used by the secondary service should be used and released before a blocking event, i.e., a primary service connection request denial, occurs. However, in reality, this is only true in a few highly optimized scenarios and, in general, the introduction of a secondary service may cause the primary service blocking rate to increase.
In an effort to reduce high blocking rates for the primary service, service providers have held primary service connection requests for a short period of time until a server becomes available to which they may be allocated, the short period of time preferably comparable to the time to service a secondary connection in progress. However, this solution is only completely successful if the average service time of the secondary service is sufficiently short that a primary service user will not perceive the waiting period required for a server to become available. Yet, if the maximum permitted waiting time for a dial tone for the primary service is less than the generally preferred maximum waiting time of a quarter of a second, the constraints upon the secondary service times become unduly severe, necessitating very short secondary service data packets.
Thus, while the introduction of a secondary service may increase system utilization, it may also significantly increase the chance that a primary service connection request will be blocked. This undesirable characteristic may be inherent in the system even if the primary service connection requests are handled in a preferential manner.
Thus, it would be advantageous to provide a telecommunications system with high utilization that handled both primary and secondary services while maintaining a low primary service blocking rate below the secondary service blocking rate.
SUMMARY OF THE INVENTIONS
The present inventions provide a telecommunication system with a high utilization percentage and that handles a primary service and other services while maintaining a low primary service connection request blocking rate. The inventions comprise apparatus and methods for employing a controller in a network switch or router that enables the network to support a primary service and other services while minimizing the blocking rate of its primary service connection requests.
In a preferred embodiment, a controller gives priority to the primary service connection requests, allocating each pending primary service connection request to an idle server before it allocates a secondary service connection request to an idle server. When the controller determines to process a secondary service connection request, it first checks if the allocation of a server to the secondary service connection request will reduce a threshold of servers reserved for use by the primary service. The threshold of reserved servers is a number of servers maintained for the primary service's use. If the server allocation to the secondary service connection request will not reduce the threshold of reserved servers, the controller allocates an idle server to the secondary service connection request. If, however, the server allocation to the secondary service connection request will reduce the threshold of reserved servers, the controller denies a server allocation to the secondary service connection request, thereby blocking the secondary service connection request.
Thus, a general object of the present inventions is to support a low primary service blocking rate on a network that handles both a primary and a secondary service. Other and further objects, features, aspects and advantages of the present inventions will become better understood with the following detailed description of the accompanying drawings.
REFERENCES:
patent: 5355616 (1994-10-01), Herold et al.
patent: 5363427 (1994-11-01), Ekstrom et al.
patent: 5579372 (1996-11-01), Astrom
patent: 5802456 (1998-09-01), Hulsebosch
Mansfield Carl
Newton Helen R.
Wright Andrew S.
Opuswave Networks, Inc.
Sobutka Philip J.
Trost William
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