WO2001091490A1

WO2001091490A1 - Picocell base station arrangement

Info

Publication number: WO2001091490A1
Application number: PCT/EP2001/005577
Authority: WO
Inventors: John Steven Cundall; Michael Kevin Hook; Lawrence William Conroy
Original assignee: Roke Manor Research Limited
Priority date: 2000-05-25
Filing date: 2001-05-15
Publication date: 2001-11-29
Also published as: GB2362781A; GB0012606D0

Abstract

A picocell base station (100) is provided for communication, in the radio frequency for example, with a wired portion of a data network infrastructure (120). To facilitate implementation, the picocell base station (100), is arranged on a low-power fluorescent light bulb (102) which is coupled to a mains power cabling (110). The picocell base station (100) includes a wireless network interface unit (112) and a wired network interface unit (106) which are housed in the base portion (108) of the light bulb (102). An antenna unit having multiple antennas (104) is provided on, and supported by, the envelope portion (118) of the light bulb. The wireless network interface unit (112) can drive signals on the antenna unit, thus transmitting onto the wireless network (130), and receive signals from the wireless network (130) via the antenna unit. The wired network interface unit (106) interfaces with the wired network (120) using either a power-line communications system or a dedicated cable network disposed in the light bulb socket.

Description

PICOCELL BASE STATION ARRANGEMENT

The present invention relates to a picocell base station arrangement. More particularly, the picocell base station is provided for a picocell within a wireless network. The picocell base station is hosted on an appliance, for example a low-power fluorescent light bulb, which couples with a wired network through an attachment node.

In short range radio telecommunications, for instance within a building or factory, a plurality of short range base station units cooperate to provide a wireless network. The area covered by each short range base station unit is called a "picocell". Each picocell base station unit provides any mobile stations in the corresponding picocell with access to a fixed, wired network. The term 'mobile station' includes: mobile telephones; computers and personal digital assistants (PDAs) with radio access equipment; and pager devices.

As the use of computers in the workplace and at home increases, the amount of wiring required to support computer data networks in office buildings increases apace. A reduction in wiring can be achieved by implementing a wired, fixed network using mains electricity cabling. In addition to providing power to networked devices, existing power- line communication systems enable the transfer of network communications over conventional mains electricity cabling alone. Wireless networks are becoming increasingly popular as they reduce the amount of wiring yet further. Rather than physically connecting computing devices and peripherals to a fixed, wired network via wires, for example shielded twisted-pair Category 5 cable, a wireless network enabled computer or printer can be arranged to communicate with the fixed, wired network via a wireless link.

Network infrastructures implemented within buildings use picocell base station units to support wireless communications and to act as interfaces between wireless portions and wired, fixed portions of the network infrastructure. Wireless communications are commonly implemented in radio frequency (RF) according to a communications standard, for example, Digital Enhanced Cordless Telecommunications (DECT), HomeRF or Bluetooth. Since the range required of each picocell base station unit is limited, the operational power consumption can be kept low, in the order of 500mW. Each picocell base station unit has an antenna, a receiver and a transmitter. RF signals arriving at the antenna are detected at the receiver. The received signal is then passed via an interface unit to the fixed, wired network. Likewise wired network signals from the fixed, wired network are passed via the interface unit to the transmitter. The transmitter in turn drives the antenna with the wired network signals to generate a new RF signal.

Signals are never free of error or interference in the real world. One approach to this problem has been to provide a plurality of antennas rather than a single antenna. Associated with each antenna there is a corresponding receiver and a corresponding transmitter. When the signals received and transmitted by the plurality of antennas is signal processed by a conventional active signal processor, sources of interference can be excluded, for instance using a 'null steering' technique and spurious signals can be rejected, using Rake antenna processing, for example. In order to implement a robust network infrastructure with both wired and wireless portions, a plurality of picocell base stations are coupled to a wired network at respective attachment nodes.

When the wired network is implemented using network specific cabling, additional apparatus is required to provide appropriate attachment nodes and appropriate attachment nodes are relatively rare.

By adapting base stations for coupling to wired networks using power-line communication systems, mains electricity sockets, including lighting sockets, can be used as attachment nodes for a base station wireless network. Mains electricity sockets are certainly not rare in most homes and offices.

Ideally, a building is supplied with a number of appropriate attachment nodes at which to install picocell base station units for a wireless network and the number is sufficient to span a given area with the minimum of additional apparatus.

In accordance with the present invention, there is provided a picocell base station including an antenna unit, a wireless network interface unit and a wired network interface unit; the wireless network interface unit having transmitter means and receiver means and communicating with a wireless portion of a network infrastructure and the wired network interface unit interfaces between the wireless network interface unit and a wired portion of the network infrastructure at an attachment node.

Advantageously, the attachment node is a fitting for a light bulb and the base station is formed upon the light bulb that has a base portion and an envelope portion.

The wired and wireless network interface units may be housed within the base portion of the light bulb. The antenna unit is preferably arranged on an outer surface of the envelope portion. i Alternatively the antenna unit may be arranged on an inner surface of the envelope portion. The antenna unit may also be embedded within the material of the envelope portion.

Construction of the antennas on the envelope portion of the light bulb and housing the network interface units in the base portion of the light bulb allows ready access to supply power and to potentially ubiquitous fixed, wired network attachment nodes with limited corresponding manufacturing difficulty.

The light bulb is preferably a low-power fluorescent light bulb. The light bulb may however be an incandescent light bulb.

Advantageously, the wired network interface unit and the wireless network interface unit are provided as a single network interface unit.

Preferably, the antenna unit has a plurality of antennas, the receiver means has a plurality of receivers and the transmitter means has a plurality of transmitters and each antenna is associated with a corresponding transmitter and a corresponding receiver. In a high radio frequency regime, for instance the frequency band for picocell RF signals, a single antenna and receiver/transmitter element would have to operate at relatively high powers, thus requiring the use of specially manufactured semiconductor components. In contrast, distributing the operation amongst a plurality of antennas permits the use of low power off-the-shelf CMOS (conductor-metal oxide-semiconductor) transmitter and receiver components. Furthermore, the picocell base station will continue to operate in the face of failures of individual transmitters, receivers or antennas. A single failure or manufacturing fault will not lead to a complete failure of the whole base station but rather to a 'graceful degradation' of service.

With multiple antennas, the wireless network interface means preferably includes a passive combiner, each of the inputs of the plurality of transmitters are connected together electrically and each of the outputs of the plurality of receivers are connected together via the passive combiner.

Alternatively, the wireless network interface means further includes an active signal processor, the transmitters are driven individually by the active signal processor and the outputs of the receivers are combined by the active signal processor.

A null steering technique may be used to avoid sources of interference and Rake antenna processing may be used to improve rej ection of spurious signals .

In a further alternative, each transmitter may drive a separate signal on the corresponding antenna and each receiver receive a separate signal from the corresponding antenna, to allow the picocell base station to handle multiple signals concurrently. One method of providing a whole building with an adequate wireless network, is to provide sufficient short range base stations to cover the whole building. The provision of a plurality of picocell base stations on light bulbs is advantageous since light bulb sockets are generally numerous in, and substantially evenly spaced throughout, the rooms of buildings and since any one light bulb socket can be used as an appropriate node to the wired infrastructure of the building. As a consequence of the ubiquity of light bulb sockets, a wireless network can be implemented without requiring the RF transmission power to be great whilst the whole building can be adequately provided with base stations.

Low-power fluorescent light bulbs have certain features which make them particularly appropriate hosts for picocell base stations. Each fluorescent light bulb has a base portion and an envelope portion made, for example, of glass, which isolates a fluorescing plasma from the air. The base portion includes light bulb driver electronics. The envelope portion is formed into loops. The plurality of antennas can be disposed on the surface of the loops. The construction of base stations on light bulbs adds little additional manufacturing difficulty. Firstly, the antennas can be disposed on the surface of the light bulb envelope using conventional plating techniques, the envelope to which the antennas are fixed providing structural support. Plating the antennas on the outer surface of the light bulb glass envelope requires little change to the normal light bulb envelope production process. On the other hand, placing the antennas on the inside of the glass envelope requires additional processing to deal with heat sealing the glass envelope, but conveys better protection from physical damage during working life. Secondly, base station interface electronics and light bulb driver electronics can be combined in the manufacture of the light bulb so no separate unit is required.

Thirdly, the casing of the lamp can be used to dissipate heat from the electronics, for instance the 'Edison Screw' electrical contact can be used as a 'heat sink'.

Fourthly, the low power requirement allows simple CMOS manufacturing techniques to be adopted as opposed to more exotic semiconductor manufacturing processes, using for example gallium arsenide or gallium carbide. CMOS transmitter and receiver elements are small and light weight. Furthermore CMOS elements are capable of manufacture as integrated circuit electronics at low cost.

Arranging a picocell base station on a light bulb confers a further advantage: the single act of switching a light off will also result in the picocell base station being switched off, thus saving power. Base stations in unlit, and presumably unoccupied, sections of a building are thus switched off.

The wired portion is preferably provided by cabling that also provides electrical power.

Preferably, the wired network interface unit uses a power-line communications system to transfer data over the wired portion of the network infrastructure.

Providing the communications over electricity cables, whether mains power or locally generated, is advantageous since buildings invariably have provision for light bulbs that are interconnected by at least electricity cabling. There are buildings which provide light sockets with systems control cabling in addition to electricity cabling, for instance to remotely cut power to lights in a portion of a building. The present invention takes advantage of electricity cabling which is already in-place to provide the fixed portion of the network infrastructure.

The wired portion of the network infrastructure may further include a separate network cable whereby the wired network interface unit is capable of transferring data over the separate network cabling. Even when the supply power cables are not used for the wired network, having base stations arranged upon light bulbs is advantageous since separate network cables can be carried along ducts already used to carry the power wiring for light fixtures.

For a better understanding of the present invention, reference will now be made, by way of example only, to the accompanying drawings in which Figure 1 shows a picocell base station according to the present invention.

Referring to Figure 1, a picocell base station 100 is provided for communication with a wired data network 120 via mains power cabling 110, using the Powerline Communications system from Siemens Information and Communication Networks Inc. The picocell base station 100, having a plurality of antennas 104, an RF interface unit 112 and a wired network interface unit 106, is arranged on a light bulb 102. The antennas 104 are disposed upon the envelope portion 118 of the light bulb: the RF interface unit 112 and the wired interface unit 106 are housed in the light bulb base portion 108. In the present embodiment, the antennas 104 are formed on the outer surface of the envelope. Alternatively, the antennas 104 can be formed on the inner surface of the envelope portion 118 or even embedded within the material of the envelope portion 118. Communication between computers using the picocell base station 100 is achieved by bringing a wireless network enabled computer within range of the picocell base station 100. The picocell base station 100 provides an interface between the wireless network enabled computer and the fixed, wired part of the network 120. There are three potential configurations which can be imposed on a picocell base station having multiple antennas: the basic configuration; the improved signal performance configuration; and the multiple (concurrent) communication support configuration. The basic configuration allows redundant connection. In the basic configuration, each of the inputs of the transmitters are connected together electrically and each of the outputs of the receivers are connected together via a simple passive combiner. In the enhanced signal processing configuration, the outputs (and inputs) of the individual transmitter/receiver/antenna components can be combined to improve signal coverage and to reject interference. In this case, the transistors are driven individually from a common active signal processor. Similarly, the outputs of the receivers are combined by the active signal processor, resulting in a single measurement. Thus, the enhanced signal processing configuration allows, for example, 'null steering' to avoid sources of interference, and/or Rake antenna processing to improve rejection of spurious signals.

Finally, in the multiple communication configuration, the transmitter/receiver/antenna components are driven with separate signals and their inputs are taken separately. Each transmitter/receiver/antenna component handles communication with a different set of mobile stations. The base station will then be able to handle multiple channels of RF signals concurrently. In further embodiments of the multiple communication configuration, combinations of transmitter/receiver/antenna components, usually pairs on opposite sides of the envelope, communicate with individual sets of mobile stations. Pairs of antennas are used separately to provide sectoral coverage. It will be understood that although the preceding description and

Figure 1 are in terms of an fluorescent light bulb, the invention is also applicable to light bulbs of other types. Other suitable types of light bulb include incandescent light bulbs (e.g. halogen light bulbs and tungsten filament light bulbs) and discharge tubes.

In alternative embodiments of the picocell base station on a light bulb, the operation of the picocell base station is independent of whether the light bulb is lit or even burnt out.

Wired networks can be implemented in many other ways, using, for example: existing telephone and fax cables or a central control network for air-conditioning, metering or clock systems.

Further embodiments of the invention build picocell base stations onto common appliances other than light bulbs, including: networked air-conditioning, metering or central heating devices; telephones; centrally controlled clocks and plug attachments.

Claims

CLAIMS:

1. A picocell base station including an antenna unit, a wireless network interface unit and a wired network interface unit, the wireless network interface unit having transmitter means and receiver means and communicating with a wireless portion of a network infrastructure and the wired network interface unit interfaces between the wireless network interface unit and a wired portion of the network infrastructure at an attachment node.

2. A picocell base station as claimed in Claim 1 , wherein the attachment node is a fitting for a light bulb and the picocell base station is formed upon a light bulb, which has a base portion and an envelope portion.

3. A picocell base station as claimed in Claim 2, the wired and wireless network interface units being housed within the base portion of the light bulb.

4. A picocell base station as claimed in Claims 2 or 3 , the antenna unit being arranged on an outer surface of the envelope portion.

5. A picocell base station as claimed in Claims 2 or 3, the antenna unit being arranged on an inner surface of the envelope portion.

6. A picocell base station as claimed in Claims 2 or 3, the antenna unit being embedded within the material of the envelope portion.

7. A picocell base station as claimed in any one of the preceding claims, wherein the light bulb is a fluorescent light bulb.

8. A picocell base station as claimed in any one of Claims 1 to 7, wherein the light bulb is an incandescent light bulb.

9. A picocell base station as claimed in any one of the preceding claims, wherein the wired network interface unit and the wireless network interface unit are provided as a single network interface unit.

10. A picocell base station as claimed in any one of the preceding claims, wherein the antenna unit has a plurality of antennas, the receiver means has a plurality of receivers and the transmitter means has a plurality of transmitters, each antenna being associated with a corresponding transmitter and a corresponding receiver.

11. A picocell base station as claimed in Claim 10, wherein the wireless network interface means further includes a passive combiner, each of the inputs of the plurality of transmitters are connected together electrically and each of the outputs of the plurality of receivers are connected together via the passive combiner.

12. A picocell base station as claimed in Claim 10, wherein the wireless network interface means further includes an active signal processor, the transmitters are driven individually by the active signal processor and the outputs of the receivers are combined by the active signal processor.

13. A picocell base station as claimed in Claim 12, wherein a null steering technique is used to avoid sources of interference.

14. A picocell base station as claimed in Claims 12 or 13, wherein Rake antenna processing is used to improve rejection of spurious signals.

15. A picocell base station as claimed in any one of Claims 10 to 14, wherein each transmitter drives a separate signal on the corresponding antenna and each receiver receives a separate signal from the corresponding antenna, to allow the picocell base station to handle multiple signals concurrently.

16. A picocell base station as claimed in any one of the preceding claims, wherein the wired portion is provided by cabling that also provides electrical power.

17. A picocell base station as claimed in Claim 10, wherein the wired network interface unit uses a power-line communications system to transfer data over the wired portion of the network infrastructure.

18. A picocell base station as claimed in any one of the preceding claims, wherein the wired portion of the network infrastructure includes a separate network cable and the wired network interface unit is capable of transferring data over the separate network cabling.

19. A picocell base station substantially as hereinbefore described with reference to the accompanying drawing.