WO2013011263A1

WO2013011263A1 - Method for power saving in bio sensor when attaching to base station, system and bio sensor

Info

Publication number: WO2013011263A1
Application number: PCT/GB2012/050380
Authority: WO
Inventors: Damitha Wilwara Arachchige; Alan Wong
Original assignee: Toumaz Uk Limited
Priority date: 2011-07-15
Filing date: 2012-02-21
Publication date: 2013-01-24
Also published as: GB2492960B; GB2492960A; GB201112197D0

Abstract

A method of attaching a client device to one of a plurality of base stations each of which is transmitting on one of a plurality of channels, is disclosed. The method comprises the steps of: (i) setting a receiver of said client device to a first sensitivity and scanning said channels to detect a valid base station transmission; (ii) if a base station transmission is not detected by the scan, incrementally increasing the sensitivity of the receiver and re-scanning said channels for each increase until a valid base station transmission is detected; and (iii) upon detection of a valid base station transmission, attaching the client device to the base station transmitting said valid base station transmission. A system and client device for carrying out the above method is also described.

Description

METHOD FOR POWER SAVING IN BIO SENSOR WHEN ATTACHING TO

BASE STATION, SYSTEM AND BIO SENSOR

Field of the Invention

This invention relates to a wireless communication method and system and, more specifically, to a method of attaching a client device to one of a plurality of base stations. Other aspects of the invention relate to the client device for said communication system. A particular, non-limiting, application for such a system relates to medical diagnostics, monitoring, and treatment of patients through the tracking of client devices in a hospital or other location where healthcare services are provided.

Background to the Invention

The following discussion primarily addresses such medical applications, although it will be appreciated that the problems and solutions considered also have non-medical applications. More specifically, aspects of the present invention are advantageous in any application requiring low-power wireless periodic communications.

Biosensors that are either implantable or wearable on a patient's skin can provide substantially continuous monitoring of a given condition and offer the prospect of closed loop treatment systems, where treatment is applied in direct response to the monitored values, as well as giving feedback to users and clinicians. For example, proposals have been made and systems produced that inject insulin into a patient's system in response to the detection of a low blood sugar level. Both types of sensor, implantable and wearable, have their own distinct advantages, and will be used in different circumstances and to monitor and treat different conditions.

A number of factors are likely to be key to the successful development of commercially viable implantable and wearable biosensors. Chief amongst these is the need for low power consumption. Particularly in the case of implantable sensors, battery life must be extremely long, as surgical intervention would be required to replace a battery. In addition to minimising device power consumption levels, consideration has been given to powering devices using the electrochemical reaction of bodily substances, and even using electric and magnetic fields generated by the body (so-called energy scavenging techniques). In the case of wearable sensors that are likely to be disposable, low cost is also a priority. To provide substantially continuous monitoring of data from implantable and/or wearable sensors it is necessary to transmit data between the sensor (i.e. client device) and some monitoring and control system using some form of wireless transmission mechanism. As it is important to minimise the power consumption of such sensors, wireless transmission (e.g. via RF signals) must be at low power and therefore of limited range, and as such requires that the corresponding receiving equipment must be situated within close proximity to the transmitting sensor device. This can be achieved by the patient wearing or carrying a transceiver device, for example, in the form of a wireless PDA or smart phone, which can process and display the data received from the sensors and can retransmit this data, at higher powers, over a suitable access network to, for example, a central monitoring and processing computer system. Alternatively, this could be achieved through a network of numerous transceiver devices (or "base stations") distributed throughout a location where monitoring is of specific importance, such as a hospital, a care home or other facility, and with which the sensors communicate directly. The provision of such a network for receiving the sensor data transmissions removes the need for each individual to carry a transceiver device and provides a means for tracking the location of each sensor within the network. In order to successfully implement substantially continuous monitoring and tracking of sensors using a network of transceivers or "base stations", any system must incorporate a method of allowing each sensor to connect with a base station within close proximity and also allow each sensor to move throughout the network and be handed-off from one base station to another.

The applicants have developed one such suitable sensor device which is marketed under the name TELRAN. After power-on, the TELRAN device is configured to hunt for a base station, be configured over the air, and then communicate with any peripheral device (acting as a communications node or a sensor node), without the need for any external CPU or user device controlling it. The device may be employed in a closed network where it is configured to connect to a specific base station in order to acquire the relevant sensor template (even in a multi-base station environment). Alternatively, the device may be employed in an open network where it can connect to any base station in the network; in which case, it is important for the robustness of the network that the device connects with the base station associated with the strongest signal received by the device. In either case, a challenge for the device is to have all of this functionality and be ultra low power.

Since the TELRAN device must be non-reliant on an external CPU, it must currently be able to find a base station in four different bands around the world (EU, US, China, Japan). This equates to possible operation in over 250 channels and so the device must scan through 250 frequencies as quickly as possible in order to establish communication with the base station. The present TELRAN device does this by spending less than 4ms on each channel to check if anything is transmitting on that channel and, if so, the device spends a little longer (e.g. 40ms) to check if the detected signal is that from a corresponding TELRAN base station. In this way the device can scan all channels in under a few seconds. However, this method does not work so well in a noisy environment where many channels are occupied by transmitters (i.e. false triggers) since the device will spend 40ms (as opposed to 4ms) on every noisy channel before deciding to skip to the next channel.

Once the device detects a base station it will exchange pairing keys and after which has been completed the device will join the base station's network. As a whole, this process is known as the initial connection process (ICP). It is important to note that searching for the correct communication channel requires the device (i.e. target sensor) to be receiving continuously but after the ICP the device will only be active during an allocated channel at a duty cycle of less than 1 %. Power consumption is therefore highest during ICP and, consequently, there is a need to minimise the connection time to save power.

It is therefore an aim of the present invention to provide a wireless communication method and system that addresses at least some of the aforementioned problems. Summary of the Invention

According to a first aspect of the present invention there is provided a method of attaching a client device to one of a plurality of base stations each of which is transmitting on one of a plurality of channels, the method comprising the steps of:

(i) setting a receiver of said client device to a first sensitivity and scanning said channels to detect a valid base station transmission; (ii) if a valid base station transmission is not detected by the scan, incrementally increasing the sensitivity of the receiver and re-scanning said channels for each increase until a valid base station transmission is detected; and

(iii) upon detection of a valid base station transmission, attaching the client device to the base station transmitting said valid base station transmission.

It will be understood that throughout this specification, a base station transmission will be considered a valid base station transmission if it is generated by a base station configured to communicate with the client device which detects the transmission.

It will be understood that the client device will attempt to attach to the base station identified as transmitting the first valid base station transmission received.

In a particular embodiment, the method may comprise the step of assessing the validity of a detected transmission by:

i) determining whether the detected transmission has been generated by the correct type of device (e.g. whether it came from an appropriate base station); and/or

ii) the client device attempting to exchange its pairing key with the base station in order to complete an initial connection process (ICP).

In a closed network, only a specific (or set of specific) unique client device pairing keys will be accepted by the base station for matching key exchange. In an open network, the base station may accept any client device key for matching key exchange. However, in both cases, only matching keys may complete the ICP.

Some benefits of embodiments of the invention rely on the assumption that a valid base station will be in close proximity to the client device when it begins the ICP and so the likelihood of the first detected transmission being from a valid base station to attach to is increased and hence the time to complete the ICP is minimised. Additional benefits of connecting to a valid device in close proximity are that to maintain a link the transmission power and client device (i.e. receiver) sensitivity can be reduced and consequently power consumption on the client device is minimised and link robustness is improved as a result of the close proximity. Embodiments of the present invention therefore provide a mechanism for low-power wireless devices (e.g. radio frequency nodes) to detect a valid base station and join its network. The method is particularly well suited to applications which require a client device to operate in a plurality (e.g. 100s) of different channels, connect to the correct source and to do this with minimum power consumption. More specifically, the method helps to ensure that the client device finds the base station quickly in order for the device to conserve battery power. In order to achieve this, the radio frequency sensitivity of the client is set to a first (low or minimum) level, in order to reduce the number of false triggers so that channel searching is quicker, and is increased gradually (if required). Accordingly, time to connection is reduced and power consumption during ICP is minimised.

It will be understood that the present method helps to ensure that the client has the best opportunity to connect with the closest base station since it is essentially configured to identify the strongest signal first. If the sensitivity were not set to a an initially low level, the client would be more likely to identify and test a large number of signals from incorrect sources, thus wasting time (and therefore power) before concluding that the signal is not the desired target signal and continuing to hunt through more frequencies.

It is noted that conventional thinking might lead a skilled person to actually increase the sensitivity of the client device so that it can ensure to detect the correct base station on a single pass of the frequency range. However, as this will also result in the client detecting and analysing more incorrect signals, the applicants have surprisingly found that the converse (i.e. reducing the sensitivity) is more effective as, due to the close proximity of the base station, there is an increased chance that any signal detected by the client will be the desired target signal.

In certain embodiments, the sensitivity may be incrementally increased in a gradual (e.g. step-wise) manner. This aspect of the invention allows for the correct base station to be further away from the client than initially expected although, as the sensitivity is increased, the likelihood of false triggers is also increased and therefore power consumption will deteriorate. The method may comprise the step of the client device entering a sleep mode if a valid base station transmission is not detected. Thus, the client device may be configured to give up hunting for a base station and to enter an ultra low power state to conserve energy until the chances of finding the base station may have changed. The method may comprise the step of the client device waking from its sleep mode and re-scanning the pre-defined frequency band for a valid base station transmission. The client device may be configured to waken after a pre-determined duration and/or on user intervention (e.g. by the pressing of a reset button).

According to a second aspect of the present invention there is provided a wireless communication system comprising:

a plurality of base stations, each of which is configured to transmit on a plurality of channels; and

a client device having a receiver, said client device being configured to:

(i) set the receiver to a first sensitivity and scan said channels to detect a valid base station transmission;

(ii) if a valid base station transmission is not detected by the scan, incrementally increase the sensitivity of the receiver and re-scan said channels for each increase until a valid base station transmission is detected; and

(iii) upon detection of a valid base station transmission, attach the client device to the base station transmitting said valid base station transmission.

According to a third aspect of the present invention there is provided a client device for a wireless communication system comprising a plurality of base stations, each of which is configured to transmit on a plurality of channels, the client device having a receiver and being configured to:

(iii) upon detection of a valid base station transmission, attach the client device to the base station transmitting said valid base station transmission. The client device may be configured to enter a sleep mode if a valid base station transmission is not detected. Thus, the client device may be configured to give up hunting for a base station and to enter an ultra low power state to conserve energy until the chances of finding the base station may have changed. The client device may be configured to wake from its sleep mode and re-scan the pre-defined frequency band for a valid base station transmission. The client device may be configured to waken after a pre-determined duration and/or on user intervention (e.g. by the pressing of a reset button). Brief Description of the Drawings

Embodiments of the present invention will now be described with reference to the accompanying drawings in which:

Figure 1 illustrates a wireless communications system according to an embodiment of the present invention; and

Figure 2 illustrates a method of attaching a client device to one of a plurality of base stations, in accordance with an embodiment of the present invention.

Detailed Description of Certain Embodiments

In an embodiment of the invention, there is provided a wireless communications system 10, as illustrated in Figure 1 , in which a first base station (1 ) 12 and a second base station (2) 22 are configured for wireless TDMA communication with three client devices A, B, C. Other embodiments of the invention may be applied to other types of wireless communication systems having more or less base stations and/or client devices.

The base stations 12, 22 each comprise a wireless transceiver (or receiver) 14 and a master clock 16. Similarly, each client A, B, C is provided with a wireless transceiver 18 and a local clock 20. Figure 2 illustrates a method of method of attaching a client device A, B, C to one of the base stations 12, 22, each of which is transmitting on one of a plurality of channels, in accordance with an embodiment of the present invention. The method comprises a step 30 of setting a receiver of said client device A, B, C to a first sensitivity and scanning said channels to detect a valid base station transmission. The method also comprises a step 32 of incrementally increasing the sensitivity of the receiver and re- scanning said channels for each increase until a valid base station transmission is detected, if a valid base station transmission is not detected by the scan. In addition, the method comprises a step 34 of attaching the client device A, B, C to the first base station 12/22 detected which is transmitting a valid base station transmission.

Thus, in accordance with an embodiment of the present invention, the sensitivity of each transceiver/receiver 14 is initially set to a first (e.g. low or minimum) level to reduce background noise while still enabling the detection of a strong local signal from a base station 12/22. It will be noted that in the example illustrated, the device A is closer to base station (1 ) 12 than base station (2) 22 and so it will detect a valid base station transmission from base station 12 before its sensitivity is increased to enable it to also detect a valid base station transmission from base station 22. Conversely, the device C is closer to base station (2) 22 than base station (1 ) 12 and so it will detect a valid base station transmission from base station 22 before its sensitivity is increased to enable it to also detect a valid base station transmission from base station 12. Accordingly, the client devices A, B, C are able to quickly scan through a range of (e.g. 250) frequencies, spending only a short time (e.g. 4ms) on each channel, looking for a base station transmission. If a base station transmission is detected, the device A, B, C will spend a longer duration (e.g. 40ms) analysing the signal to determine if it is a valid base station transmission. Consequently, embodiments of the present invention can reduce the power consumption of the client device A, B, C during the ICP.

Although not illustrated in Figure 2, if no valid base station transmission is detected with the sensitivity set to the pre-determined (maximum) level, the client device A, B, C will enter a sleep mode to conserve power until the chances of finding the base station may have changed. Accordingly, the client device A, B, C is configured to wake from its sleep mode after a 5, 10 or 30 minute interval and to re-scan the channels for the transmission. This procedure is then repeated until a connection has been made with a base station 12, 22.

Scanning the frequencies for a valid base station transmission preferably involves the transceiver/receiver 14 monitoring, at each of the channels to be scanned, for a base station transmission. This may, for example, comprise monitoring a receive signal strength indicator (RSSI) signal. If there is a transmission on the channel then the RSSI flag is 1 if there is no transmission on the channel then the RSSI flag is 0. As discussed above, if there is no base station transmission on the channel then the client device scans the next unscanned channels until it detects a base station transmission or enters sleep mode if no base station transmission is detected with the sensitivity set to the predetermined (maximum) level. This step of scanning for a base station transmission is estimated to take less than 5ms.

As described above, if a base station transmission is detected then the signal received from the base station is analysed. Preferably, analysing the signal comprises at least two stages, first, the client device decoding a sync word downloaded from a transmitter and second validating pairing keys between the base station and the client device A, B, C.

The step of decoding a sync word enables the client device to determine that they are communicating with a base station in the system and not any transmitter. If no sync word is detected by the client device then the base station is not the correct type of base station or does not form part of the system the client device is to communicate with. In this instance the client device will recommence scanning the channels for a base station transmission. If a sync word is detected then the client device and base station exchange pairing keys allocated to them to determine whether the client device is communicating with the correct base station and vice versa. If the keys are validated then a connection is set up between the client device and base station. If no keys are validated then the client device moves to the next channel and begins to look for a valid base station transmission. As will be understood by one skilled in the art, the invention may be implemented using any suitable method of validation. For example, the client device may connect to the base station upon detecting a sync word without requiring an exchange of keys. Alternatively, the client device may attempt to validate keys with the base station without detecting a sync word.

It will be appreciated by persons skilled in the art that various modifications may be made to the above embodiments without departing from the scope of the present invention.

Claims

CLAIMS:

1 . A method of attaching a client device to one of a plurality of base stations each of which is transmitting on one of a plurality of channels, the method comprising the steps of:

(i) setting a receiver of said client device to a first sensitivity and scanning said channels to detect a base station transmission and, if a base station transmission is detected by the scan, assessing whether the detected base station transmission is a valid base station transmission by: determining whether the detected transmission has been generated by a correct type of device; and/or the client device attempting to exchange its pairing key with the base station in order to complete an initial connection process (ICP);

(ii) if a valid base station transmission is not detected by the scan, incrementally increasing the sensitivity of the receiver and re-scanning said channels for each increase until a valid base station transmission is detected; and

2. The communication method according to claim 1 wherein a base station transmission is considered a valid base station transmission if it is generated by a base station configured to communicate with the client device which detects the transmission.

3. The communication method according to claim 1 or claim 2 wherein the client device attempts to attach to the base station identified as transmitting the first valid base station transmission received.

4. The communication method according to any preceding claim wherein only a specific (or set of specific) unique client device pairing keys will be accepted by each base station for matching key exchange.

5. The communication method according to claim 1 wherein each base station may accept any client device key for matching key exchange.

6. The communication method according to any preceding claim further comprising the client device entering a sleep mode if a valid base station transmission is not detected.

7. The communication method according to claim 6 further comprising the client device waking from its sleep mode and re-scanning the pre-defined frequency band for a valid base station transmission.

8. The communication method according to claim 7 wherein the client device wakens after a pre-determined duration and/or on user intervention.

9. A wireless communication system comprising:

a client device having a receiver, said client device being configured to:

(i) set the receiver to a first sensitivity and scan said channels to detect a base station transmission and, if a base station transmission is detected, assessing whether the detected base station transmission is a valid base station transmission by: determining whether the detected transmission has been generated by a correct type of device; and/or the client device attempting to exchange its pairing key with the base station in order to complete an initial connection process (ICP);

10. A client device for a wireless communication system comprising a plurality of base stations, each of which is configured to transmit on a plurality of channels, the client device having a receiver and being configured to:

(i) set the receiver to a first sensitivity and scan said channels to detect a base station transmission and, if a base station transmission is detected by the scan, assess whether the detected base station transmission is a valid base station transmission by: determining whether the detected transmission has been generated by a correct type of device; and/or the client device attempting to exchange its pairing key with the base station in order to complete an initial connection process (ICP);

1 1 . The system of claim 9 or the device of claim 10 wherein the client device is configured to enter a sleep mode if a valid base station transmission is not detected.

12. The system of claim 9 or the device of claim 1 1 wherein the client device is configured to wake from its sleep mode and re-scan the pre-defined frequency band for a base station transmission.

13. The system of claim 9 or the device of claim 12 wherein the client device is configured to waken after a pre-determined duration and/or on user intervention.

14. A method of attaching a client device to one of a plurality of base stations, the method being substantially as hereinbefore described with reference to the accompanying drawings.

15. A wireless communication system substantially as hereinbefore described with reference to the accompanying drawings.

16. A client device for a wireless communication system substantially as hereinbefore described with reference to the accompanying drawings.