WO1997034432A1

WO1997034432A1 - Base station

Info

Publication number: WO1997034432A1
Application number: PCT/EP1996/001089
Authority: WO
Inventors: Mervyn White; Neill Roderick Butcher; Thomas Paul Groves
Original assignee: Motorola Limited
Priority date: 1995-03-07
Filing date: 1996-03-14
Publication date: 1997-09-18
Also published as: GB9504591D0; GB2298995A

Abstract

A base station for use in a communications system including a plurality of modules each vertically housed in a chassis, a first heat sink integral with a first side wall of each chassis for naturally dissipating heat from the housed module, and an input/output base for services and input/output to the modules disposed at the bottom of the chassis and accessing the modules through apertures at the bottom of the chassis. The base station may further include a heat pump disposed along the first heat sink of at least one chassis or a heat pump disposed along the first heat sink of each chassis.

Description

BASE STATION

Field of the Invention

This invention relates in general to communications systems, and more particularly to a base station in a communications system.

Background to the Invention

There is continuous pressure in the communications system market to reduce the size of communications equipment. There is also a growing requirement of communications systems operators to install communications equipment, particularly, base stations wherever the need may be including outdoors in densely populated areas and on the side of buildings.

In cellular communications systems, radio coverage in a defined geographical area is known as a cell and is handled by a base station which uses an adjoining antenna system to transmit and receive radio signals. The base station consists of a digital controller for site management, transceiver for RF modulation/demodulation, communications equipment for back hauling the data to a network controller and a power supply.

In standard operation a mobile station (MS) identifies the best candidate base station and locks on to the network via that base station. When a call is to be made the MS requests the allocation of a dedicated communications resource or channel to meet the nature of the call. Once a channel has been established signalling and traffic information can be exchanged between the network and the MS until the call is cleared. The availability of a communications resource is determined by the bandwidth available, the efficiency of the speech coding algorithm and the frequency reuse. As capacity demands increase the most common method to address the capacity requirement is to reduce the cell size and have greater frequency reuse. Smaller cell sizes imply a larger number of base stations, some of which will be of small capacity such as is the case with microcellular base stations. The electronics in a cell site is housed in a cabinet specified to meet the environmental conditions prevailing in the location selected for installation. Often the location is outdoors and as such an integrated solution which meets the climatic, structural and EMC requirements has to be considered. Most commonly, prior art incorporates the electronics, communications equipment, power supply and heat management system (HMS) in a single cabinet or multiple cabinets. The large size of the cabinet is dictated by the degree of integration of electronics and the heat dissipation which may require a heat exchanger to keep the internal temperature within acceptable limits defined by the rating of the electronic components. Typical base stations can be, as an example, a GSM Base Transceiver

Station (BTS) within an integrated cabinet that also accommodates all the ancillary equipment. Power would be fed to the cabinet by means of underground cables bearing ac mains. In the cabinet, a power supply module converts the mains to the dc voltages required to drive the electronics. The HMS is normally a heat exchanger that consists of internal and external air circuits. The air paths, created by fans, traverse a heat exchanging matrix commonly known as a recuperator. The power to the fans can be either at ac mains voltage driven or at dc voltage driven. Where ambient temperatures are too high to allow heat transfer driven by the available temperature gradient over a matrix, a heat pump mechanism is used. In this case, work is done to transfer heat against a temperature gradient. Such systems using vapor compression include a number of large mechanical components and thus require quite large and bulky housing. Such base stations are then not suitable for mounting on an outside wall of a building.

From a physical design perspective it is important to reduce size and power of the existing base stations. The greater level of integration made possible by ASICs and the use of lower voltage devices drive down the power to such an extent that it becomes feasible to use natural conduction and natural convection in the cooling of a system even in outdoor environments. This trend is applicable to both analogue and digital cellular base station systems. Smaller cabinets decrease the cost incurred by the operator by reducing the area leased by the operator.

The difficulties of outdoor base stations are providing a suitable environment for the electronic components including cooling. Cooling implies the use of moving parts, such as, expensive heat exchangers, air conditioners or fans. Such moving parts reduce the reliability of the base station equipment and can require specialist maintenance procedures.

Thus there is a desire to have a compact base station located outdoors in a safe and suitable operating environment by decreasing the overall cost and complexity of the base station equipment.

Summary of the Invention

According to the present invention, there is provided base station for use in a communications system including a plurality of modules each vertically housed in a chassis, a first heat sink integral with a first side wall of each chassis for naturally dissipating heat from the housed module, and an input output base for services and input/output to the modules disposed at the bottom of the chassis and accessing the modules through apertures at the bottom of the chassis. The base station may further include a heat pump disposed along the first heat sink of at least one chassis or a heat pump disposed along the first heat sink of each chassis.

In a preferred embodiment the plurality of chassis include a first chassis for housing a first RF module, a second chassis for housing a first controller module and being disposed at a front side of the first chassis, and a third chassis for housing a micro base site controller module and being disposed at a back side of the first chassis.

The base station may further comprising a power supply box disposed at a front side of the second chassis.

Brief Description of the Drawing

FIG. 1 shows a back side view of a base station according to an embodiment of the present invention.

FIG. 2 shows a front side perspective view of a base station according to a further embodiment of the present invention.

FIG. 3 shows a front side perspective view of a base station according to a further embodiment of the present invention.

FIG. 4 shows a cross-sectional view of the base station of FIG. 1 with an added heat pump. FIG. 5 shows a cross-sectional view of the base station of FIG. 2 with added heat pumps. FIG. 6 shows a cross-sectional view of a heat pump.

FIG. 7 shows a printed circuit board with printed circuit board tracks.

Detailed Description of the Preferred Embodiment FIG. 1 shows a back side view of a base station 1 for use in a communications system including a plurality of modules 2, 4, 5 each vertically housed in an aluminium chassis 10, 12, 19 where each chassis has a first side wall, a second side wall, a front side, a back side, a top and a bottom. Each chassis encases a respective module. For example, as shown a first chassis 10 has a first side wall 41, a second side wall 43, a front side 45, a back side 47, a top 49 and a bottom 51.

A first heat sink 53 is integral with the first side wall 41 of the chassis 10 for naturally dissipating heat from the housed module 2. In FIG. 1, heat sinks are shown as integral with at least a first side wall of each chassis. The heat sinks are passive heat sinks including aluminium fins perpendicularly disposed to the side walls of the modules for passively dissipating heat from the modules.

An input output base 16 for housing services and inputs outputs to the modules is disposed at the bottom 51 of the chassis 10 and accesses the module 2 through apertures at the bottom of the chassis 10.

The first chassis 10 completely encases or houses a first controller module 2. A second chassis 12 houses a first RF module or RF printed circuit board 4 where the second chassis 10 is disposed at the back side 47 of the first chassis 10. A third chassis 19 houses a micro base site controller module 5 and is disposed at the front side 45 of the first chassis 10.

The micro base controller module 5 provides the controls for the base station and controls the base station transceiver equipment. The micro base controller module 5 communicates with the mobile switching center. The controller module 2 provides digital controls for the transceiver equipment. The base station transceiver equipment is provided by the RF module 4. The input/output base 16 for housing services and providing inputs/outputs to the modules (as explained above) is also disposed at the bottoms 48, 50 of the second and third chassis 12, 19 and accesses the respective modules 4, 5 through apertures at the bottom of each chassis 12, 19. A power supply box 18 for housing a power supply is disposed at the back side 33 of the second chassis 12.

A one carrier base station 1 may simply have the first controller module 2 housed in the first chassis 10, the first RF module 4 housed in the second chassis 12, the micro base site controller module 5 housed in the third chassis 19, the input/output base 16 and the power supply box 19 all covered by a plastic or similar shroud (not shown).

A one carrier base station may also be simply expanded to a two carrier base station 2 as shown in FIG. 2. FIG. 2 shows a front side view of a two carrier version of the base station of FIG. 1. The two carrier version is achieved by adding a second controller module 6 housed in a fourth chassis 20 and a second RF module 8 housed in a fifth chassis 22 disposed at the back side 37 of the fourth chassis 20 and where the fourth chassis 20 and the fifth chassis 22 are attached to the second side wall 43 of the first chassis 10 and second side wall 35 of the second chassis 12.

The first and second chassis 10, 12 of FIG. 2 are shown staggered behind the fourth and fifth chassis 20, 22 and as a matter of design choice do not have to be directly behind the fourth and fifth modules or lined up to them. Only one micro base site controller module (housed within the third chassis 19) is needed for the two RF modules and two controller modules. The input/output base 16 has connections to the second controller module 6 and the second RF module 8 through apertures at the bottom of the respective chassis 20, 22 similar to the first controller and RF modules. The plurality of chassis may be oriented in any manner as long as the input/output base has access to their respective modules.

In an alternative embodiment, the base station of the present invention further includes a modular heat pump disposed along the integral heat sink of each chassis as shown in FIG. 3. For example, heat pumps 26, 27. 8, 29, 24 are disposed along or attached to the heat sinks 55, 53, 54, 57, 56 of each chassis 12,10, 19, 22, 24, respectively. The modular heat pumps are attachable to each chassis as needed, thus any number of heat pumps may be added.

FIG. 4 shows a cross-sectional view of the base station of FIG. 1 with added heat pump 26 on the second chassis 12. Furthermore, a one carrier version of the base station may include heat pumps along the heat sinks 53, third chassis 19. Depending on the modules and the ambient temperature a heat pump is disposed along the integral or first heat sink of each chassis.

FIG. 5 shows a two carrier base station with added heat pumps 24, 26 on a plurality of chassis. A second heat pump 24 is shown connected to the integral heat sink 56 of the fourth chassis. A heat pump may also be preferably added along the integral heat sink of the fifth chassis as shown in FIG. 3.

The base stations of FIGs. 4 and 5 are shown connectable to a wall or side of a building 28 with an expandable shroud (or covering) 30 or larger shroud 31 for the two carrier heat pump embodiment.

A sectional view through a first heat pump 26 is shown in FIG. 6. The heat pump 26 is shown as added onto tile integral heat sink 55 of the second chassis 12. The heat pump 26 includes at least one peltier device 65 and a second heat sink 70. In fact, the heat pump may include a gasket 63 disposed across the fins of the first heat sink 55 and cold plate 61 disposed on top of the gasket 63. Then a spacer 67 is disposed on the cold plate 61 to create a small amount of space between the cold plate 61 and the peltier devices 65. On top of the peltier devices 65 is placed a second heat sink 70. Each module may comprise of at least one printed circuit board having an integral resistive heating element 70 as shown in FIG. 7.

Conventional printed circuit board tracks 70 may be used to implement the integral resistive heating element in the printed circuit boards. For example, conventional printed circuit board tracks may be constructed so that their dimensions provide a required resistance and hence power dissipation for a particular voltage rail that they are to be powered from. The modules are then disposed within their respective chassis.

For equipment required to operate over a wide temperature range a thermostat may be coupled on the printed circuit boards and thus employed to switch the heating element off above a preset temperature. This retains the components upper operating temperature Umit and can also save power if the components within the design are self-heating when operating. If components are likely to be damaged by being switched on below their operating temperature range, a second thermostat may be employed to inhibit switching on the system components until they are within their operating range. The advantages of incorporating integral heating elements in the modules over a conventional heater that warms circulating air or the chassis of the equipment are that the overall assembly size is significantly reduced and the cost of the integral heating elements is essentially zero. Furthermore less power is required to heat the modules because the modules are being heated directly from within themselves thus less heat is lost through the equipment chassis or surrounding air. The tracks may also be distributed on a pcb in order to provide even and efficient heating.

The present invention provides a compact base station that is able to operate in a wide temperature range. The modularity of the design allows the capacity of the base station to be easily increased without having to redesign the base station.

The present invention departs from traditional outdoor base station designs which require that active electronics modules are packaged together in a protective box. The present invention allows the box to be "opened" and simplified to the level of a shroud. The modules are better protected by the design of the present invention because they are protected individually or in small groups in individual protective chassis. This approach eliminates the requirement for heat exchange across an enclosure boundary and allows a higher power density to be passively cooled.

When there is insufficient temperature gradient for cooling the present invention allows for the addition of heat pumps. The present invention also allows for individual heat pumps to be applied for each of the modules on their respective chassis. Thus, a one carrier base station variant does not have to carry the overhead of a system designed for a two carrier variant.

The present invention provides a modular approach to designing base station that allows for both the heating and cooling advantages of individual modules as needed.

Claims

1. A base station for use in a communications system comprising: a plurality of modules each vertically housed in a chassis where each chassis has a first side wall, a second side wall, a front side, a back side, a top and a bottom; a first heat sink integral with the first side wall of each chassis for naturally dissipating heat from the housed module; and an input/output base for services and input/output to the modules disposed at the bottom of the chassis and accessing the modules through apertures at the bottom of the chassis.

2. The base station of claim 1 further comprising: a heat pump disposed along the first heat sink of at least one chassis.

3. The base station of claim 1 further comprising: a heat pump disposed along the first heat sink of each chassis.

4. The base station of claims 2 and 3 wherein the heat pump comprises at least one peltier device and a second heat sink.

5. Any of the preceding claims wherein the chassis comprise: a first chassis for housing a first controller module; a second chassis for housing a first RF module and being disposed at the back side of the first chassis; and a third chassis for housing a micro base site controller module and being disposed at the front side of the first chassis.

6. The base station of claim 5 further comprising a power supply box disposed at the front side of the second chassis.

7. The base station of claims 5 and 6 further comprising: a second controller module housed in a fourth chassis; a second RF module housed in a fifth chassis disposed at the front side or back side of the fourth chassis and where the fourth chassis and the fifth chassis are attached to the second side wall of the first chassis and the second chassis.

8. The base station of any of the preceding claims wherein the chassis is an aluminium chassis.

9. The base station of any of the preceding claims wherein the modules comprise printed circuit boards having an integral resistive heating element.

10. The base station of claim 9 wherein the integral resistive heating element comprises conventional printed circuit board tracks.

11. A base station substantially described herein with reference to FIG. 1 of the drawing.