GB2242296A - Base station controller and interface - Google Patents

Abstract

A communications bus (13) connects a radio base station controller (10) and interface units (11). The bus comprises first and second bidirectional patch lines, input and output audio lines and a serial control bus (19). Each interface unit (11) has means for connection to a peripheral communications unit (e.g. a base station) and switching means for selectively connecting the communications unit to the first and second patch lines, or the input and output audio lines. The switching means are controlled by packets of data on the serial control bus. <IMAGE>

Description

BASE STATION CONTROUtER AND INEREACE Background of the Invention This invention relates to a radio base station controller and a bus and interface for connecting base stations to such a controller.

Summary of the Prior Art The conventional method for connecting peripherals to a base station controller for multi-base station functions in a radio system uses dedicated lines for patch, unselect and multi-select functions to each base station. This leads to a complex system with a high hardware cost, and one which is not expandable beyond the capacity of the controller in terms of available inputs and outputs and switches therebetween.

Summary of the Invention According to the present invention, there is provided an interface unit for a communications bus, comprising first and second bidirectional patch lines, input and output audio lines, a serial control bus, means for connection to a peripheral communication unit, and switching means for selectively connecting the communication unit to the first and second patch lines, or the input and output audio lines, said switching means being controlled by packets of data on the serial control bus.

The communication unit may be a base station or other unit such as a modem.

The bidirectional patch lines enable the communication unit to be connected directly to another communications unit on the bus via another similar interface unit.

The interface unit is used in combination with a controller having a microphone and loudspeaker for connection to the input and output audio lines of the interface and control means for transmitting packets of data to the interface for control thereon.

The controller may have a further input, such as a telephone input for connection to the input and output audio lines or the first and second bidirectional patch lines.

Each data packet preferably comprises an indicator near the start thereof indicating the length of the packet.

In a particularly preferred embodiment, each interface is capable of generating packets of data requesting connection to the patch lines or audio lines of the bus. The controller comprises priority registers for registering the priority of each interface connected to the bus. The controller causes each interface to be connected to the bus in accordance with its priority. A higher priority interface is connected before a lower priority interface.

Each interface is capable of raising and lowering its priority. This feature allows for efficient use of the bus.

A further preferred feature is the ability of each interface unit to control other interfaces.

Brief Description of the Drawings Fig 1 shows a block diagram of the system of the preferred embodiment.

Fig 2 shows the switching circuitry connecting two interfaces together on the bus.

Fig 3 shows a data packet on the serial control bus.

Detailed Description of the Preferred Embodiment Referring to Fig 1, there is shown a control console 10 connected to two base station interfaces 11 and 12 via a bus 13.

The bus comprises a microphone audio line 14, first and second patch lines 15 and 16, a select audio line 17 an unselect audio line 18 and an RS-232 serial bus 19. The microphone audio line is unidirectional from the console 10 to the base station interfaces 11 and 12, while the select and unselect audio lines are unidirectional in the other direction. The patch lines 15 and 16 are bidirectional.

The interfaces have bidirectional connectors 20 and 21 for connection to base stations or other communication equipment, such as a modem, a paging terminal, a repeater etc. The console 10 has a microphone 22, first and second loudspeakers 23 and 24 and a telephone connector 25.

Referring to Fig 2, the connections between the base station interfaces 11 and 12 and the bus 13 are shown. The base station interface 11 comprises first and second double-pole switches 30 and 31 connecting the first and second patch busses 15 and 16 respectively to the base station transmit and receive lines of the base station connector 20. A switch 32 connects the base station transmit line to the microphone audio bus 14 and a two-way switch 33 connects the receive audio line of the base station connector 20 to either the select audio bus 17 or the unselect audio bus 18. The base station interface 12, of course, has the same structure. Each of the switches 30, 31, 32 and 33 is controlled by the serial data bus 19.

The operation of the system is as follows.

The bidirectional patch lines can connect any base station to any other base station by closing one half of each of switches 30 and 31. The microphone 22 can be connected to any base station by connection within the console 10 to the microphone audio bus and by closing switch 32 at the appropriate base station interface.

Likewise, a base station can be connected to the loudspeaker 23 at the console by connection of the respective receive audio line to the select audio bus 17. The select and unselect audio busses 17 and 18 are identical, except that the select audio bus is normally connected to the loudspeaker 23, whereas the unselect audio bus is not normally connected to the loudspeaker 23, but may be routed to another audio output, such as subsidiary loudspeaker 24. In other words, if the operator of the console requires that incoming audio is output through the loudspeaker at the console, this causes the relevant base station to be connected to the select audio bus. Other communication means, such as a telephone may be connected via the console 10 to either the patch buses or the microphone and select or unselect audio buses.

The circuitry allows simultaneous transmission (multi-select) to more than one base station at a time.

Control of the interfaces is via the RS-232 bus 19, which provides full modem control and adaptive polling, which will be described in detail below.

The console 10 and each base station interface 11, 12 is allocated a unique address. The console 10 sends data out to the control bus 19 in a packet which starts with the address of the relevant interface or interfaces. Such a packet is shown in Fig 3.

The packet comprises a preamble 40, which is divided into a 4-bit address 41 and a 4-bit-data length code 42 and from 0 to 15 command and data bytes 43. Finally, a one byte check sum is provided 44.

The whole command or response packet is from 3 to 18 bytes long, as required by the specific data transfer. The use of the a variable length packet minimises the loading on the microprocessor of the console.

Whenever the console or a base station interface detects its address on the control bus 19, this enables a tri-state driver allowing that unit to transmit any data it may have in its output buffer on to the control bus 19.

The console 10 maintains a priority register for each base station interface. The normal value of the priority byte is set to one, signifying that the peripheral will be polled next after a 48 milliseconds interval. When the console needs to poll a peripheral immediately, either from the requirements of the commands being sent, or because the last response packet from the peripheral calls for an immediate poll, then the priority byte for that peripheral is set to 0. A software driver of the communications bus interprets a 0 priority byte as requesting a poll to that peripheral on the next available time slot - i.e. after 12 milliseconds.

If a peripheral has been sent a command, such as an MDC data transmission, requiring an acknowledgement from a mobile, this will not cause a peripheral response for some time (in the example given, the mobile acknowledgement cannot be received until a minimum time of 2 MDC packets plus 2 pre-times). In this case, the priority byte is set to a higher value.

A value of 2 means a poll after 2 time slots, that is after 96 milliseconds. A value of 3 means polling after 3 time slots etc. This amounts to empty time slots and reduces the loading on the console microprocessor. A priority 0 poll will, of course, take over any empty time slot.

If 2 or more peripherals are at a priority 0, then they are polled in the normal order, but before any lower priority unit.

After each poll, depending on the command sent, or the response received, the priority byte is set accordingly. Thus the polling interval is always kept to the optimum for each peripheral.

The control unit 10 has a keyboard (not shown) which allows control of the base stations. Such control includes channel selection, modulation type, power, signalling and similar functions.

The system described optimises both the information data packet links and the polling intervals, so as to minimise the controller microprocessor loading and maximise the bus data transfer rate.

Claims (9)

1. An interface unit for a communications bus, comprising: first and second bidirectional patch lines, input and output audio lines, a serial control bus, means for connection to a peripheral communications unit, and switching means for selectively connecting the communications unit to the first and second patch lines, or the input and output audio lines, said switching means being controlled by packets of data on the serial control bus.

2. An interface unit according to claim 1, further comprising means for identifying a packet length indicator near the start of a data packet on the control bus and for controlling the receipt of a complete packet of data of variable length in response to the packet length indicator.

3. An interface according to claim 1 or 2, further comprising means for generating packets of data of variable length for control of other interfaces connected to the communications bus, and means for generating a packet length indicator near the start of each packet, indicating the length of the packet.

4. A communications system comprising an interface unit according to any one of the preceding claims, in combination with a control unit and a communications bus therebetween, wherein the control unit comprises a priority register corresponding to the interface unit and means for transmitting a packet of data identifying that interface unit, the timing of transmission of said packet relative to packets identifying other interface units connected to the bus being controlled by the priority register.

5. A system according to claim 4, wherein the interface unit has means for raising or lowering its priority in the priority register of the control unit by transmitting a data packet on the control bus.

6. A system according to claim 4, further comprising an input at the control unit for connection to a telephone and means for connecting the telephone to the input and output audio lines or to the first and second patch lines.

7. A system according to any one of claims 4 to 6 further comprising a keyboard at the control unit, a radio base station connected to the interface unit and means for control of the base station from the keyboard.

8. A system according to any one of claims 4 to 7, further comprising an unselect audio line substantially similar to the first mentioned audio line, and a loudspeaker at the control unit, wherein the interface unit is normally connected to the first mentioned audio line and loudspeaker and is temporarily connectable to the unselect audio line and subsidiary loudspeaker.

9. An interface unit or communications system substantially as hereinbefore described with reference to the accompanying drawings.

Pubbshed 1991 as The Patent Office. Concept House Cardiff Road. Newport Gvwent NP9 1RH Further copies may be obtained from Sates Branch. Unit 6. Nine Mik Point. Cumfeltnfach Cross Keys. Nevwport. NPI OHZ Printed by Multiplex techniques hd. St Mary Cray. Kent