1. Field of the Invention
The invention relates to signal transfer points (STPs) used in telecommunication networks and, more particularly, to cabinet designs for STPs.
2. Description of the Related Art
Advanced Intelligent Networks (AIN) are modern telephone networks that separate call control from the actual trunk that carries the voice or data transmission of a call. In general, AIN Networks include a system in which the network queries a database to determine how a call should be processed once a set of call digits have been received from a phone. AIN Network generally includes three basic elements. A signal control point (SCP) is a computer controlled database that is for storing customer""s specific information that is used by the network to determine how to route and/or process calls. A signal switching point (SSP) is a digital telephone switch that is operable to communicate with SCPs and to obtain the customer""s specific instructions for processing the call. A signal transfer point (STP) is a packet switch that shuttles messages between the SSPs and the SCPs. All three, namely the SCP, the SSP, and the STP communicate via what is known as out-of-band signaling. Out-of-band signaling generally refers to the signaling that is for controlling a call. In other words, out-of-band signaling does not include the actual call data or voice information. Typically, the three described systems utilize a signaling system No. 7 (SS7) protocol or a variant thereof.
When a call is dialed, the SSP creates a query to the database within the SCP to find out how a call should be processed. The query is passed via out-of-band signaling through at least one STP to the SCP. The SCP interprets the query based on criteria within its databases and based upon information provided by the SSP. Once the SCP retrieves and transmits a return message through the STPs to the SSPf SSP may properly process the call within the network.
The STP is, in essence, a router for the SS7 network. It relays messages through the network but does not originate them. It is similar to a voice switch except that it only routes control signals. STPs also serve as gateway devices that may convert messages that flow between dissimilar systems. For example, a STP within the US may provide conversions between ANSI SS7 and ITU-T SS7. STPs may also provide other functionality including various security functions and message filtering wherein messages of a non-conforming nature are not passed through from one point to another. Other STP functions include traffic monitoring for billing purposes and for developing usage statistics.
Compact PCI is an adaptation of the Peripheral Component Interconnect (PCI) specification for industrial and/or embedded applications requiring a more robust mechanism form factor than desktop PCI. Compact PCI uses industry standard mechanical components and high performance connector technologies to provide a system optimized for rugged applications. Compact PCI is electrically compatible with the PCI specification allowing low cost PCI chip sets to be used in a mechanical form factor suited for rugged environments. In general, Compact PCI is a rugged variation of the PCI bus that was designed by PC makers wanting to create industridi grade PCs. The motivations for the design were to put more PCI cards into one PC (eight instead of four) and to make the resulting PC more rugged, and better able to withstand shaking and rough environmental conditions.
The physical configuration of the hardware conforms to the Eurocard (VMR-style) standard. The cards are identical to VME cards in size but differ in that they use a high-density 2-millimeter pin and socket connector (contact space) for interfacing the card to a passive backplane. Typically, the Compact PCI comes in a rugged 3U or 6U Eurocard form factor and has either a 32 or 64 bit data bus with transfer rates of up to 528 megabits per second.
As mentioned before, Compact PCI typically includes a passive backplane. Each shelf on the front side of a Compact PCI system includes slots for eight cards. Traditionally, a controller goes into slot one leaving seven slots for other specialized peripheral cards. Accordingly, cabinets made to house Compact PCI equipment typically provides cooling only to a front portion of the cabinet. The xe2x80x9cfront portionxe2x80x9d is the portion that is in front of the backplane.
Traditionally, active cards go in the front side while passive circuitry goes on the backside. In a typical configuration, a Compact PCI card having active elements includes pin outs that are passed through the backplane to passive transition modules on the back side. The transition modules terminate the signals into connectors wherein that may readily be accessed from behind. Because the circuitry on the back side of the backplane is passive, there has been no need hereto before to provide cooling or thermal management for the back side of the Compact PCI cabinet in a telecommunications environment.
A current design goal for the present invention is to utilize Compact PCI in the design of modern telecommunication systems. As systems become more complex, however, Compact PCI systems are being pushed to the limit in terms of capacity. A typical cabinet for a Compact PCI system may have several shelves of cards all generating tremendous amounts of heat energy for a cabinet of that size. Accordingly, thermal management issues may become acute. As telecommunication networks continue to increase in sophistication, there will be an ever-increasing need to add more circuitry within the Compact PCI cabinets. Unfortunately, however, this also means that more space must be found to provide the additional card slots. Greater thermal management must be achieved to maintain temperatures at an acceptable level if new cards are added. What is needed, therefore, is a cabinet architecture that provides for greater circuit capacity and yet accommodates an efficient thermal management system therefor, preferably within the context of a Compact PCI-compliant equipment rack.
The Compact PCI cabinet includes an inlet port for receiving external air, a set of blowers for drawing the air into the cabinet and for expelling the air from an exhaust port of the cabinet after having cooled internal active circuits, and a plurality of louvers and openings that create thermal convection within a back portion of the Compact PCI cabinet to cool active components coupled to the back side of the backplane of the Compact PCI system. More specifically, a bottom panel, lining one wall of the chamber that receives the external air through the input port, includes a plurality of louvers that allow some of the air to be conducted into the back portion of the Compact PCI cabinet. Additionally, a plurality of perforated air openings located approximately at the bottom and back end of a side panel of the Compact PCI cabinet also is included to receive and conduct air from the external environment. Finally, the invention includes forming openings between a plurality of card guides located approximately at the top of the back side of the back portion of the Compact PCI cabinet wherein air may be conducted into the back portion of a Compact PCI cabinet or out of the back portion of the Compact PCI cabinet. The air is conducted here, from and into the exhaust from the blowers.
Because exhaust from the blowers is being partially directed into the back portion of the Compact PCI cabinet, that exhaust must be cooled before it is used to cool active components in the rear portion of the cabinet. Accordingly, a pin field is placed in the air path between the blowers and the openings through which the air may be conducted into the back portion of the Compact PCI cabinet. The pin field is coupled to a heat sink that is for extracting heat energy from the pins. Accordingly, heat is convected away from the exhaust into the pins and up into the heat sink where it is radiated outwardly from the cabinet.
Finally, the invention includes placing a thermistor in the exhaust path so that the fan speed of the blowers maybe adjusted according to the temperature of the exhaust after passing through the pin field. Thus, acoustic concerns are addressed by minimizing fan speed and associated noise levels so as to operate the blowers at nearly a minimal level required for maintaining the internal temperatures within the PCI cabinet at an acceptable level.
In another embodiment of the invention, the louvered panel at the bottom of the Compact PCI cabinet is installed at an angle relative to vertical so that a greater amount of the air received at the inlet port is conducted into the back portion of the Compact PCI cabinet and so that the louvers create lower amounts of air resistance to that air which is being conducted into the back portion of the Compact PCI cabinet.