GB2547315A

GB2547315A - Indoor wireless positioning and navigation

Info

Publication number: GB2547315A
Application number: GB1621462.9A
Authority: GB
Inventors: Taha Samer; Alasad Ahmad; Smadi Mohammed
Original assignee: Waseela Int Holding Inc
Current assignee: Waseela Int Holding Inc
Priority date: 2015-12-16
Filing date: 2016-12-16
Publication date: 2017-08-16
Anticipated expiration: 2036-12-16
Also published as: GB201621462D0; GB201522166D0; GB2547315B

Abstract

An indoor wireless geographical location method employs a Wi-Fi network having a plurality of Access Points 1a-1c providing a coverage area, for example in a building such as an office or shopping mall. Also provided is a battery powered Wi-Fi beacon device 4 which provides additional coverage within the coverage area, transmitting signals but not acting as an Access Point. The beacon device cycles between a fully operative awake state, transmitting a beacon frame in accordance with IEEE 802.11 protocols, and a reduced power state, wherein for a predetermined time interval no transmission of data can take place. The battery may be replaceable and the reduced power state may be maintained for extended time periods according to a schedule, e.g. outside of expected office or shopping hours, in order to save battery power. The device may also include a microcontroller arranged to set parameters which may include timer means. There may also be a serial connection for setting up configurations using an external processor.

Description

Indoor Wireless Positioning and Navigation

Field of the Invention

The present invention relates to apparatus and method for indoor wireless geographical location techniques, such as positioning, navigation, geo-fencing, primarily for use with wireless enabled user devices such as smart phones and other handheld mobile stations, tablets, notepads, laptops and other computing devices.

Background Art

Indoor wireless positioning, geo-fencing and navigation solutions rely primarily on wireless beacons. At the same time, it is desired for economical and practical reasons to rely on standard wireless technologies that are supported by smart handhelds commonly available with users inside large buildings. Another constraint other than the need to limit wireless beacons to standard technologies supported by common smart handhelds is that it is not always convenient to provide power source to all wireless beacons at all locations inside mega buildings. Accordingly many techniques and solutions recently were adopted based on battery-powered Bluetooth beacons, and then emerged the very common approach of low-power Bluetooth beacons in order to ensure long-life cycle of the beacons without need for power source and without need for frequent replacement of batteries.

Bluetooth beacons though suffer from some shortcomings. The low transmission power means short transmission range which translates to unreasonably large number of beacons to achieve full coverage within a large building. Bluetooth signals can be effectively used for proximity detection but not for accurate positioning. . Since Bluetooth and Wi-Fi networks work on the same frequency band, large numbers of Bluetooth beacons lead to high levels of interference on both networks (Bluetooth and Wi-Fi). Lastly, users do not commonly prefer to keep Bluetooth modules enabled by default on their smart handhelds.

There are many indoor positioning and navigation solutions that rely on Wi-Fi signals, however the challenge being faced that it is costly to deploy and maintain full Wi-Fi coverage inside mega buildings. Indoor tracking and navigation systems prefer to use existing Wi-Fi data network infrastructure to minimise system installation cost and because of the vast availability of Wi-Fi technology on commercial smart handheld devices, i.e. smart phone, PDA, tablets and smart watches. However, Indoor location tracking and navigation requires that at least three

Access Points to be visible in order to get reliable position estimation. Infrastructure data Wi-Fi networks, usually, do not satisfy this requirement.

The current approach to solving the problem of the coverage gaps of infrastructure Wi-Fi networks depends on adding extra Access Points (AP) to fill the coverage gaps of the existing Wi-Fi network, re-designing the infrastructure Wi-Fi network, or, in case there is no pre-installed Wi-Fi network, designing the Wi-Fi network from scratch to satisfy indoor location tracking and navigation coverage requirements. All these solutions present an increase of the installation cost, extra wiring, oversized and overloaded network and a higher level of RF interference due to the large number of Access Points transmitting and receiving data at the same time in a small physical area.

Battery-powered wireless Access Points are available commercially. These Access Points are battery powered fully functional wireless Access Points with some performance limitations in order to save battery life. For example, to lengthen battery life, the manufacturers usually limit the transmission power so that the expected coverage is few tens of meters. However, these Access Points' batteries usually last only for few hours (8-10 hours). Therefore, using existing battery-powered Access Points is not practical for indoor tracking and navigation applications. This because of the low coverage area and the short battery life as these Access Points would need to be recharged every day at best. In addition, the battery is usually irremovable, thus, the whole Access Point has to be un-mounted and the system has to go offline during the recharging process. In other prior attempts, half-duplex wireless Access Points were proposed to further reduce the power consumption and thus lengthen the battery life, however wireless Access Points that are compliant to WiFi standards will continue to consume power at a relatively high rate even if they are not transmitting. This will still not enable the deployment of battery-powered WiFi beacons in a practical way, which is the objective of this invention. This is because any wireless Access Point using a WiFi standard compliant chipset will be operating in listening mode state when it is not transmitting, and this listening mode state contributes to a relatively high power consumption rate even if the wireless Access Point is used for transmission only. Other prior attempts, proposed increasing the beaconing interval to attempt reducing the power consumption of the wireless Access Point by reducing the beaconing frequency, in addition to the fact that in such methods the achieved reduction in power consumption is not significant, such methods do not work optimally with standard client WiFi devices. Standard client WiFi devices expect standard beaconing frequency and may completely miss the beacons coming from wireless Access Points that are transmitting beacons based on longer beaconing intervals. CN203342197U shows a the beacon that has been modified to include a label or tag indicating the location of the beacon, so that a mobile device can adopt the beacon's location or otherwise. However, this does not actually permit accurate location of the mobile device, rather it allows the mobile device to detect that beacon's location in an area that may otherwise not be covered. CN203342197U also includes means to update the location of the beacon (by updating a memory via a USB port). There are many drawbacks to using this method, including the inconvenience of setting a large number of beacons, and the inconvineince and inflexibility of potentially having to reset the beacons.

There are many services available over an 802.11 network that requires the use of location information (either of the AP or the non-AP station). Some of the sub-standards that leverage this include 802.llv and 802.11k. Examples of these instances in the 802.11 2012 standard include the location reference subelement, the location shape subelement, and the 2 and 3D point location shape values. However, it is more convenient if another method, which does not require the beacon transmission to be set or altered to transmit its location, can be provided.

It is an object of the invention to provide a low cost method and apparatus for use in a Wi-Fi system which implements indoor geographical location techniques.

Summary of the Invention

We have realised that the availability of low cost battery-powered Wi-Fi beacons that do not require power connection and do not require network cabling would accelerate the adoption and success of indoor wireless positioning and navigation solutions. So far, battery-powered Wi-Fi beacons are not available mainly because when standard Wi-Fi systems are powered by commercially available batteries the system cannot operate more than few hours. This is mainly due to the high power consumption of standard Wi-Fi system operation. For example, even if a high-capacity power bank of 10,000 mAh is used to power a simple low-power home-usage Wi-Fi Access Point, such battery capacity will not be enough to keep the Access Point running for two days.

However, we believe a battery-powered Wi-Fi-based beacon would provide a significant value to the solutions of indoor wireless positioning and navigation. This is mainly due to the longer-range capability of Wi-Fi technology, ability to achieve more accurate positioning based on Wi-Fi signals, and because it is more common for users to keep their WiFi modules enabled on their smart handhelds. Additionally, the availability of many frequency channels allow the deployment of Wi-Fi beacons while coexisting with other data Wi-Fi networks within same building.

Embodiments of the invention employ a practical battery-powered low-cost Wi-Fi-based beacon device that can facilitate the deployment and adoption of Wi-Fi-based indoor positioning and navigation solutions. Embodiments of the invention enable the production of low-cost Wi-Fi beacons that can operate per Wi-Fi standards, do not require the transmission of any unique or pre-defined labels including the beacon's location, but instead transmit standard beacon frames per standard beaconing intervals, and at the same time can run for at least one month while powered by a low-cost commercial battery.

An embodiment of the battery-powered beaconing device maintains high transmission power values and enters a reduced power state, switching from an awake state, after each successful 802.11 beacon frame transmission. The reduced power state and the fact that there is no transmission activity other than the beacon frame, enable our beaconing device to conserve power for about a month of operation per charge while providing a coverage area just like any other commercial AC powered Access Point. Additionally, embodiments of our beaconing device use a removable and easily accessible battery, which makes the re-charging process a lot easier and the system does not have to go offline for more than few seconds needed to replace the depleted battery with a fully charged one.

Embodiments of the invention provide a Wi-Fi beacon transmission in accordance with the IEEE 802.11 standards. IEEE 802.11 is a set of Media Access Control (MAC) and physical layer (PHY) specifications for implementing wireless local area network (WLAN) computer communication, commonly known as Wi-Fi There is a family of 802.11 standards, each standard having a suffix a, b, g, n etc, so that each standard is designated 802.11<suffix>. A basic architecture of a Wi-Fi system based on IEEE 802.11 comprises one or more Access Points (AP) which communicate with Clients or Stations (STA), which may be smart phones, laptops, etc, which are within the range of an Access Point. The Access Points communicate with a wider network to give access to the Internet, email, etc... The 802.11 standards set out the procedures, mechanisms and protocols by which the Access Points and Clients inter-communicate. In particular, wireless communication is carried out by means of MAC frames, each of which comprises a string of fields, each field comprising one or more data bits and having a designated function. In particular, a beacon frame is defined in Section 8.3.3.2 of IEEE Std 802.11™-2012. The beacon frame is transmitted at periodic intervals by an Access Point, and enables stations to establish and maintain communications in an orderly fashion. . For the purposes of the present specification, the term "beacon frame" is intended to mean a frame, defined in accordance with 802.11 standards, or any frame intended to advertise the presence of an IEEE 802.11 Access Point in an area.

Embodiments of the invention include a Wi-Fi chip or module device, which is controlled through a microcontroller. A Wi-Fi chip or module is a radio device that implements the IEEE 802.11 protocol. A Wi-Fi module generally includes a processor (CPU), memory, and a radio transceiver that is configured to implement the 802.11 protocol. W-Fi modules are very well known, and are available from many manufacturers, such as Texas Instruments, Samsung, Gainspan.

Wi-Fi modules commonly incorporate a power management mechanism so that the module can operate in a number of states, namely a fully awake state in which all functions are enabled, and one or more power saving states, which are variously termed doze mode, sleep mode, deep sleep mode, etc.. A feature of these various modes is that the CPU of the module is switched off, and the radio is at least partially switched off, and in particular data transmission is disabled. It will be noted that, according to the IEEE 802.11 standards, an Access Point is invariably in an awake mode, which is fully operative. Client Stations STA may however enter power saving modes (PS), in accordance with the standards.

In embodiments, a microcontroller is configured to control the Wi-Fi module, so that the Wi-Fi module emits a series of beacon signals at periodic intervals. In the time period interval between each beacon signal, the microcontroller is arranged to switch the Wi-Fi module to a reduced power state in which the CPU of the module is switched off and the radio is at least partially switched off.

While in principle a WiFi chip may be controlled by a microprocessor or any form of computer processor, it is preferred to employ a microcontroller, for simplicity. A microcontroller is a standalone single-chip 1C that contains at least a CPU, memory, and interface connections. Usually, a microcontroller includes read-only memory to store the program, RAM to store variables used in the execution of the program, and various I/O buses to connect to the outside world such as SPI, I2C, UART and others. A microcontroller is programmed via an external interface to a PC. A microcontroller may require an external clock. However embodiments of the invention employ an internal clock. A large number of manufacturers produce microcontrollers, e.g. Atmel, Infineon, but we prefer to use a PIC microcontroller, as manufactured by Microchip Technology, on account of low cost, wide availability and serial programming capability. By serial programming is meant the capability of being programmed through a serial data interface when the microcontroller is installed within a control system. Embodiments of the invention employ a microcontroller having a serial input for programming from e.g. an external PC or other computer. Furthermore they employ a serial programming interface for coupling the microcontroller to the WiFi chip module for controlling the operation of the WiFi chip module.

For the purposes of the present specification "geographical location" is intended to cover all known and envisaged techniques for determining the physical location of a user device within a geographical area.

In a first aspect, the invention provides, at least in embodiments, a method of indoor wireless geographical location, employing a Wi-Fi network having a plurality of Access Points providing a wireless coverage area, comprising providing a Wi-Fi beacon device providing coverage within said coverage area, wherein said beacon device is battery powered, and wherein said beacon device is arranged for enabling, at least in part, the IEEE 802.11 protocol, and said beacon device has a first awake state wherein the beacon device is fully operative, and a second reduced power state in which data transmission is not possible, and the method comprising controlling said beacon device so that said beacon device transmits at periodic intervals a beacon frame , wherein as an iterative procedure, following a beacon frame transmission the beacon device enters said reduced power state for a predetermined time interval, wherein no transmission of data takes place, following which said beacon device enters said awake state in which a further beacon frame is transmitted, and then said beacon device re-enters said reduced power state for said predetermined time interval.

In a second aspect, the invention provides apparatus for use in a method of indoor wireless geographical location, employing a Wi-Fi network, comprising a Wi-Fi beacon device which is battery powered, and wherein said beacon device is arranged for enabling, at least in part, the IEEE 802.11 protocol, and said beacon device having a first awake state wherein the beacon device is fully operative, and a second reduced power state in which data transmission is not possible, and wherein said beacon device is arranged to transmit at periodic intervals a beacon frame, wherein as an iterative procedure, said beacon device is arranged, following a beacon frame transmission, to enter said reduced power state for a predetermined time interval, wherein no transmission of data takes place, following which said beacon device is arranged to enter said awake state in which a further beacon frame is transmitted, and then said beacon device re-enters said reduced power state for said predetermined time interval.

Brief Description of the Drawings

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, wherein:

Figure 1 is a schematic diagram of a prior art Wi-Fi network, illustrating the problem with which the present invention is concerned;

Figure 2 is a schematic diagram of a Wi-Fi network, which incorporates the solution according to the present invention;

Figure 3 is a block diagram of a Wi-Fi beacon according to an embodiment of the invention and including a Wi-Fi module and a PIC microcontroller;

Figure 4 is a flow chart, illustrating the method of operation of the embodiment of Figures 3 and 4; and

Figure 5 is a schematic block diagram of the Wi-Fi module of Figure 3.

Description of an Embodiment

An embodiment of the invention comprises a Wi-Fi beaconing device that transmits 802.11 beacon frames only and has a battery life of about a month per charge and coverage up to 300m line of sight to aid indoor tracking and navigation system. In embodiments, a concept of the invention is to provide a Wi-Fi beacon device which transmits 802.11 beacon frames only, but wherein other functions of the 802.11 standard, in particular data transmission are not enabled. Therefore, after the transmission of a beacon signal, the beacon device is switched to a reduced power state of operation, and stays in this reduced power state, until the beacon device is woken up in order to transmit a further beacon signal. A client station may pick up these beacon signals, and employ them, together with beacon signals from neighbouring Access Points, to perform triangulation, trilateration, or any other algorithmic procedures for geolocation. A client station cannot however communicate with the beacon device in order to transmit data.

The trilangulation or trilateration may rely on the RSS (received signal strength) of the beacon frame signal and that of the neighbouring Access Points. The location of the beacon may be retrieving from a database, either as an absolute position or relative to the neighbouring Access Points (whose positions may also be provided by the database), and this allows the mobile device to compute its position based on an intersection of the distance from each Access Point and the beacon. Other methods of determining the location of the beacon may also be used.

Referring to Figure 1, this shows the case where the infrastructure Wi-Fi networks fail to meet indoor tracking and navigation requirements. A Wi-Fi network is provided by Access Points la, lb, lc, which together provide a wireless coverage area of the network. In this case the smart phone 2, whose position to be estimated, is located within the coverage area at area 3 in which only two Wi-Fi Access Points la, lb, are visible, but not a third Access Point lc. Indoor location tracking and navigation requires that at least three Access Points to be visible in order to get reliable position estimation. The common practice to overcome this problem is to re-design the Access Points' la-c locations so that area 3 has at least three visible Access Points. Another common practice is to keep the network design as it is, and add a new Access Point to the network (not shown) so that area 3 has a three visible Access Points.

Figure 2 depicts the solution of this embodiment to the problem indicated in figure 1. A low cost battery-powered Wi-Fi-based beacon device 4 provides wireless coverage within a central region of the coverage area provided by Access Points la-lc. Beacon device 4 transmits only 802.11 beacon frames (without any data transmission). This creates a virtual further visible Access Point within area 3 without disturbing the data Wi-Fi network. Thus, the location tracking performances enhanced, without adding extra load and wiring to the existing data network or modifying the existing data network infrastructure.

It will be appreciated that other geographical configurations of Access Points and beacon device may be provided. For example two or more beacon devices may be provided within a Wi-Fi network, which cooperate with one or more Access Points in order to increase the total area where three virtual access points are visible. In some locations within a Wi-Fi network, it is possible that all visible access points are provided by beacon devices.

Figure 3 shows a block diagram of the functional elements of the low cost, battery powered Wi-Fi beaconing device 4. On board Dual Band Wi-Fi module 9 is responsible for transmitting the 802.11 beacon frames. The Wi-Fi module includes a Command Line Interface SPI (Serial Peripheral Interface) that supports serial data control through which a PIC microcontroller 7 configures, controls, and monitors the Wi-Fi module 9. PIC microcontroller 7 is the main controller of the system; it includes a timer and carries out the timing and controlling functionalities of the beacon frame transmission of Wi-Fi module 9 (switching between operating mode and reduced power mode). Furthermore, configuration parameters such as SSID, Transmission power, default beacon interval values (usually set at 100ms, but is configurable) are set via the PIC microcontroller over the SPI interface. A PC 11 is needed at the initial setup stage only to set the Wi-Fi module parameters and timing schedule through custom software installed on PC 11, and is connected to microcontroller 7 via a serial USB connection. PIC microcontroller 7 receives commands from the custom software over UART (universal asynchronous receiver/transmitter) interface; therefore, a UART to USB converter 8 is introduced. Rechargeable battery 6 supplies the required voltage to both micro controller and Wi-Fi module (in this example 3.6V), and optional dc power is supplied at the required dc voltage through a regulator 5 (in this example a 3.6V regulator). Battery 6 is replaceable and is mounted in a holder 6H, from which it may easily be removed.

Figure 4 shows a flow chart illustrating the timing and controlling logic through which the PIC microcontroller 7 controls the switching between the operating and reduced power mode of the Wi-Fi module 9. The process starts with controller 7 checking "Operating Mode", that is whether the local time is within operating or inoperative hours (operating hours such as a commercial malls' working hours, company working hours etc.). If the time is within inoperative times of a schedule then the Wi-Fi module 9 is forced to remain in reduced power state and the PIC microcontroller keeps repetitively checking for the time the beacon device is set to start working (operating mode activation). Once operating mode is activated the PIC microcontroller 7 triggers the Wi-Fi module 9 to enter its awake state, to wake up and start transmitting a beacon frame. Once a successful beacon frame transmission is detected, the PIC microcontroller 7 triggers the Wi-Fi module to switch back from the awake state to reduced power state to conserve power. Then the PIC microcontroller 7 initialises a timer for the next beacon frame (beacon interval). In this example, the beacon interval is 100 ms, and the timer increments in 1ms increments. At the end of the beacon interval timer, the above steps are repeated, starting from the "Operating Mode" check. This continues until the local time goes from operating hours to inoperative hours, whereupon the module remains in the reduced power state.

Referring to Figure 5, this is a block schematic of the Wi-Fi module 9 of Figure 4. It comprises radio transceiver 20 configured to implement the 802.11 protocol, a CPU 22, a RAM memory 24, a flash memory 26 and a power management mechanism or unit 28. Unit 28 defines the awake state and power reduced states of the module. A control interface 30 is provided, which includes an SPI link and a UART link, together with Ethernet, JTAC and GPIO connections.

Our invention enters reduced power state after each successful 802.11 beacon frame transmission in which it differs from commercially available battery-powered Access Points that switch to data receiving/transmitting mode that drains the battery fast. Additionally, the reduced power mode is customisable so that our invention could be programmed to enter reduced power mode at certain periods over day or night to reduce battery consumption when indoor tracking and navigation is not active i.e. shopping mall closed hours, company off business hours ...etc. Reduced power mode settings and schedule are set through the custom software installed on PC Hand sent to PIC microcontroller 7 via USB to UART converter 8 shown in Figure 3.

Another aspect in which our invention differs from commercial battery powered Access Points is that the battery is easily removable and swappable. This ensures that the system remains online while the batteries are being re-charged and provide the ability to supply our invention with custom size batteries to extend or double battery life for not easily accessible beacons.

Inventive aspects of the invention are as follows: 1. Prior work on indoor tracking and navigation applications always focuses on exploiting existing Wi-Fi networks. Therefore, any lacking of indoor tracking and navigation requirements is usually compensated by modifying the existing Wi-Fi network instead of considering adding new supporting elements. 2. The obvious failure of using commercially available battery powered Wi-Fi Access Points discouraged further research on the possibility of using battery powered Wi-Fi based beacons. 3. The vast commercial availability of AC powered Access Points makes it easier to buy an off-the-shelf Access Points instead of investing time and money to design a battery-powered Wi-Fi beaconing device with battery life of up to 1 month. 4. Power-saving modes under the 802.11 technology standards are defined and elaborated for the Wi-Fi Client mode and not for the Wi-Fi Access Point mode, which prevents a low-power Wi-Fi AP mode of operation through usage of standard complying Wi-Fi chipsets.

Enhancing an existing Wi-Fi network to satisfy indoor tracking and navigation requirements using our low cost, cabling free, Wi-Fi based beacon would cost 80% less than using commercial Access Points to upgrade the same Wi-Fi network.

The coverage area of our Wi-Fi based beacon is 300m line of sight while standard Bluetooth beacon device can reach up to 50m line of sight. Flence, when our invention is used instead of Bluetooth beacons the number of Wi-Fi beacons required will be 1/3 the number of Bluetooth beacons. Additionally, installation cost can drop by 54% and the interference level will be improved by lOdBm.

Claims

Claims:

1. A method of indoor wireless geographical location, employing a Wi-Fi network having a plurality of Access Points (la-lc) providing a wireless coverage area, comprising providing a Wi-Fi beacon device (4) providing coverage within said coverage area, wherein said beacon device is battery powered (6), and wherein said beacon device is arranged for enabling, at least in part, the IEEE 802.11 protocol, and said beacon device has a first awake state wherein the beacon device is fully operative, and a second reduced power state in which data transmission is not possible, and the method comprising controlling (7) said beacon device so that said beacon device transmits at periodic intervals a beacon frame, wherein as an iterative procedure, following a beacon frame transmission the beacon device enters said reduced power state for a predetermined time interval, wherein no transmission of data takes place, following which said beacon device enters said awake state in which a further beacon frame is transmitted, and then said beacon device re-enters said reduced power state for said predetermined time interval.

2. A method according to claim 1, wherein said beacon device includes a module (9) for enabling the IEEE 802.11 protocol, said module having said first awake state and said second reduced power state, and wherein said beacon device includes controller means (7) which controls said module in a timed manner to produce said iterative procedure.

3. A method according to claim 2,wherein said module includes a radio means (20) configured to operate in accordance with the IEEE 802.11 protocol, a processor means (22), and memory means (24, 26), and wherein in said reduced power state, the processor means is switched off, and the radio means is at least partially switched off.

4. A method according to any preceding claim, including controlling said beacon device to remain in a reduced power state according to a predetermined schedule, wherein the time of day is repetitively checked, and if the time of day is within scheduled inoperative periods, then the beacon device remains in said power reduced state.

5. Apparatus for use in a method of indoor wireless geographical location, employing a Wi-Fi network, comprising a Wi-Fi beacon device (4) which is battery powered (6), and wherein said beacon device is arranged for enabling, at least in part, the IEEE 802.11 protocol, and said beacon device having a first awake state wherein the beacon device is fully operative, and a second reduced power state in which data transmission is not possible, and wherein said beacon device is arranged to transmit at periodic intervals a beacon frame, wherein as an iterative procedure, said beacon device is arranged, following a beacon frame transmission, to enter said reduced power state for a predetermined time interval, wherein no transmission of data takes place, following which said beacon device is arranged to enter said awake state in which a further beacon frame is transmitted, and then said beacon device re-enters said reduced power state for said predetermined time interval.

6. Apparatus according to claim 5, wherein said beacon device includes a module (9) for enabling the IEEE 802.11 protocol, said module having said first awake state and said second power reduced state, and wherein said beacon device includes controller means (7) for controlling said module to produce said iterative procedure.

7. Apparatus according to claim 6, wherein said module includes a radio means configured to operate in accordance with the IEEE 802.11 protocol, a processor means, and memory means, and wherein in said reduced power state, the processor means is switched off, and the radio means is at least partially switched off.

8. Apparatus according to claim 7 or 8, wherein said controller means comprises a microcontroller, which includes timer means and which is coupled to said module via a serial command line interface.

9. Apparatus according to claim 8, wherein said microcontroller is arranged to set configuration parameters of said module, including at least one of SSID, transmission power.

10. Apparatus according to claim 8 or 9, wherein said microcontroller has a serial connection (8) for receiving initial set up configurations from an external processor.

11. Apparatus according to any of claims 5 to 10, including a replaceable battery, which is mounted within a holder (6H).

12. Apparatus according to any of claims 5 to 11, wherein said controller means is arranged to check repetitively the local time against a predetermined operating schedule, and maintains said module in said power reduced state if the local time corresponds to inoperative periods of said schedule