Methods, apparatuses and computer programs for inter-cluster connection in a wireless personal area network

[0001] The present invention relates to a wireless personal area network (WPAN).

DESCRIPTION OF THE FIELD OF THE INVENTION [0002] Recently, attempts have been made to increase the level of cooperation between home appliances. In line with this growing demand, a number of wireless technologies have been developed, including, for example, Bluetooth and similar technologies that generally allow communication within about 10 meters - in other words, with a very short range. These private short-range networks are commonly referred to as wireless personal networks (WPANs).

[0003] In the case of WPAN, the goal is to facilitate smooth operation between home and business devices and systems, and any device in the WPAN network will be able to connect to another device in the same WPAN, provided that they are within their mutual physical range . At home, WPANs provide wireless connections for alarms, home appliances, and entertainment systems.

[0004] An example of a suitable WPAN network protocol is the IEEE 802.15 standard, including for example the Bluetooth standard (IEEE 802.15.1), which is suitable for low-power digital radio devices such as wireless headphones connecting to cell phones using short-wave radio waves range. Another example is the ZigBee (IEEE 802.15.4) specification, which is focused on building automation. The ZigBee technology is intended to be simpler and cheaper than e.g. Bluetooth, and thus it should be oriented towards the use of radio frequency (RF) requiring low data transmission speed, longer battery life and safe network operation. The problem in the case of WPAN is, however, the fact that the current implementation of the network topology is in the form of non-cooperating networks based on slaves, each of which may potentially exist and operate on a channel with a different frequency, and thus communication between different networks will be more difficult.

[0005] Patent EP 1 528 717 attempts to solve this problem by providing improved cooperation between various wireless devices in a WPAN network. It provides a method of transmission that solves problems when the device recognizes at least two different WPANs communicating on the same channel frequency. Such a conflict is recognized and the coordinating device, i.e. the coordinator, transmits the coordinator reconciliation command to the devices, recommending changing the currently used channel to another. The reconciliation command contains information about the change in the synchronous signal data field, and a specific identification bit located in the reserved bit of the synchronous signal frame control field.

[0006] Even though the patent EP 1 528 717 proposes a partial solution to the problem with the conflict of WPAN networks communicating on the same channel frequency, it does not, however, take into account the initialization phase in which a number of coordinators are organized so that they communicate with each other, and a process that allows coordinators to switch to the optimal channel frequency.

Rather, EP 1 528 717 relies solely on topology of non-cooperating networks based on slave devices known in the art, which introduces additional network traffic due to delay problems.

[0007] Patent US 2007/076596 describes the implementation of a blind, smooth channel change (BSCC) that occurs when a series of wireless communication devices are stuck in the current communication channel. The first wireless communication device sends a BSCC message on the current communication channel to the second wireless communication device, which message contains information about a communication channel selected from a series of communication channels to which the first communication device then switches, and the period of time for which the first communication device will transmit on the selected communication channel. The first communication device switches to the selected communication channel. The second communication device receives the BSCC message and switches to the selected communication channel. The first and second wireless communication devices resume normal wireless communication.

BRIEF DESCRIPTION OF THE INVENTION [0008] There is a need for a WPAN network that takes into account the initialization phase when a number of coordinators are configured to communicate with each other, and which further provides less delay, increased bandwidth, and energy efficiency. The invention is defined by independent claims. The dependent claims define preferred embodiments.

[0009] According to an aspect of the invention, the above object is achieved by a method for a first coordinator working on a first channel frequency in a wireless personal network (WPAN), which WPAN also includes a second coordinator working on a second channel frequency, which method comprises transmission steps messages on a number of channel frequencies, including the second channel frequency, requesting from the second coordinator to change the second channel frequency to the first channel frequency and to communicate with the second coordinator using the first channel frequency.

[0010] According to the present invention, the coordinator should be understood as a wireless communication device capable of creating a WPAN network, e.g. in general, a controlled or controllable device, which is generally a stationary device connected to a power source. Thus, according to the present invention, two such devices are configured to form a "pair" during the initialization phase and the transition to the frequency of the coordinator channel which initiated the communication. On the contrary, according to prior art solutions, the first coordinator will adopt the channel frequency of the second coordinator, which leads to the problem of increased delays and to additional network traffic because the coordinators will have to switch between their preferred channel frequencies.

[0011] Furthermore, the expression "message" should be understood to mean a signal meaning at least in part containing specific content intended for a request from the second coordinator to switch to the frequency of the first coordinator. In addition, the message may be any type of message, e.g., a specific initialization message (or initialization signal), or it may be included in a generally transmitted message.

[0012] The benefits of the present invention include no need for a priority-based mechanism. This is due to the fact that the coordinator starting communication decides on the frequency of the channel used, i.e. each coordinator defining communication can order the coordinator from which he wants to establish communication to change the frequency on his own. Another advantage of the present invention is that it will allow easy transmission of the transmission message and implementation of the amplifier solution.

[0013] However, this method is not only useful during the initialization phase when a WPAN is being created, but it is also useful when more devices are connected to the WPAN. According to this statement, in the case where the WPAN network preferably includes an additional third coordinator, with the third coordinator working on the third channel frequency, each of the first and second coordinators is preferably adapted to independently implement the stages of sending a message on a series of channel frequencies, including the third channel frequency, with a request to change the third channel frequency by the third coordinator to the first channel frequency, and communication with the third coordinator using the first channel frequency. This means that each of the first and second coordinators can, independently of each other, ensure the transition of the third coordinator to the channel frequency of the first coordinator, thereby enabling communication on one channel frequency. As discussed above, this increases the available bandwidth and optimizes the WPAN's energy efficiency.

[0014] Furthermore, the method of the present invention is not limited to the first coordinator only. According to this statement, the respective method steps can therefore be implemented by a second (or third) coordinator present in the WPAN, the second coordinator working on the second channel frequency, and the WPAN further including the first coordinator working on the first channel frequency. From the perspective of the second (or third) coordinator, the method thus includes the steps of receiving a message from the first coordinator, receiving from the first coordinator a request to change the second channel frequency to the first channel frequency and communication with the first coordinator using the first channel frequency. These steps can of course be carried out by the first coordinator if, for example, the second coordinator initiates communication.

[0015] According to a preferred embodiment of the invention, the request to change to the first channel frequency is provided in the form of a separate message (or signal) when the first coordinator receives a response from the second coordinator.

[0016] According to a preferred embodiment of the invention, a request to change to the first channel frequency is included in the message. This means that preferably at least one of the messages is a packet type message including a header containing information about the frequency of the first coordinator channel, for example by including at least two bits specific to the channel frequency in the header. By using two channel frequency bits, you can communicate up to four different channel frequencies. However, channel frequency dedicated information may also include one or more than two bits. Thus, the header will be communicated (e.g., placed) a channel frequency favorable to the first coordinator, the header being preferably a network header, but it may be any type of header. Other types of commonly used headers are PHY headers, MAC headers, transport headers, etc.

[0017] The step of sending a message on a series of channel frequencies also preferably utilizes the use of frequency flexibility, commonly referred to as dynamic channel / frequency selection. Frequency flexibility or the use of the frequency flexibility mechanism that will be discussed in detail below includes periodic change of transmission frequency or a change within a series of predefined channel frequencies. The use of frequency flexibility is also used to avoid interference from a known disturbing factor or other signal source, for example causing a WPAN conflict in a given coordinator's environment. For example, at home it is likely that several types of wireless networks are fighting for the same frequency bands, and there are also unintentional interference from equipment. Thus, the ability to relocate within the spectrum will be an important determinant of network success.

[0018] Preferably, communication between the control unit and the device is provided by means of radio frequency (RF) communication, and most preferably it is RF communication based on at least one of the IEEE 802.15.3 and IEEE 802.15.4 standards. In general, when implementing WPAN networks in the IEEE 802.15.3 or IEEE 802.15.4 standard, the basic network topology will be in the form of a basic star, and the WPAN network may consist of connected stars. Also, depending on the network technology used, a different number of channel frequencies are available. For example, when using IEEE 802.15.4, a total of 16 channel frequencies are available in the United States, but for the purposes of frequency flexibility only a subset of these channels will be available, otherwise the delays will become too great for network capabilities. Thus, the practical number of channel frequencies for use in IEEE 802.15.4 technology is three or four.

[0019] According to a further aspect of the present invention, there is provided a first coordinator for use in a WPAN network, the first coordinator working on a first channel frequency and having solutions that ensure sending a message on a series of channel frequencies, including a second channel frequency, a solution requesting from the second coordinator changing the second channel frequency to the first channel frequency, and a solution communicating with the second coordinator using the first channel frequency.

[0020] This aspect of the invention provides similar advantages to the method discussed above, including, e.g., the fact that it does not need to use a priority-based mechanism, and that any coordinator determining communication can cause a change in the frequency used by the coordinator with which he wants to communicate. Another advantage of the present invention is the ability to easily send a transmission message and the implementation of an amplifier solution.

[0021] The coordinator is preferably a consumer electronic device (CED) such as at least one television receiver (TV), DVD player (DVD), home theater system (HTS) and wireless remote control (RC).

[0022] Furthermore, the mentioned and other objects of the present invention can be achieved by means of a computer program adapted to work on a coordinator (e.g., first, second or third coordinator) according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS [0023] These and other aspects of the present invention will now be described in more detail with reference to the accompanying drawings showing currently preferred embodiments of the invention in which:

Fig. 1 shows a WPAN network comprising a number of coordinators working according to a known network topology configuration;

Fig. 2 is a WPAN similar to the network shown in Fig. 1, operating according to the network topology configuration of the present invention; and

Fig. 3 is a time diagram illustrating an example of a stepwise transition to a single / optimal channel frequency according to the present invention.

DETAILED DESCRIPTION OF CURRENTLY PREFERRED EMBODIMENTS OF THE INVENTION [0024] The present invention will now be described in more detail with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. The invention may, however, be made in many other forms and should not be construed as limited to the embodiments shown in the text; the embodiments shown are rather intended to provide a full overview of the invention and they completely convey the scope of the invention to an addressee with the appropriate skills.

[0025] Referring now in particular to the drawings and figure 1, a prior art WPAN 100 network is shown comprising a series of coordinators or devices that can act as coordinators 102, 104 and 106, each of which has a separate WPAN identifier (or other suitable network coordinator) and configured to communicate on a separate channel frequency, e.g. first f1, second f2 and third frequency of channel f3, where coordinators 102, 104 and 106 are configured as a non-cooperating network based on slaves.

[0026] As discussed above, the coordinators are preferably consumer electronic devices (CEDs), such as, for example, a television receiver (TV), DVD player (DVD) and home theater system (HTS). According to the prior art WPAN 100 technique shown in Figure 1, a device capable of acting as a coordinator starting communication will use the WPAN identifier and channel frequency of the device with which it wants to communicate, instead of its own WPAN identifier and its own channel frequency, and thus if one of the coordinators 102, 104 or 106 wants to control one or more devices, it will have to switch from one channel frequency to the next.

[0027] If the coordinator 102 of the WPAN 100 known in the art wants to establish communication with the coordinator 104 during operation, he will have to switch to the frequency of the coordinator channel 14, i.e. he must complete the transition from the first frequency of the channel f1 to the second frequency of the channel f2. At this time, the coordinator 106 cannot communicate with the coordinator 102 because for some time the coordinator 102 will not be able to receive communication from the coordinator 106. This means that the coordinator 102 will be more or less "deaf" to communication from the coordinator 106. Because of the non-cooperative network topology based on slave devices used by the art network 100 known in the art, the frequency flexibility mechanism will be more often addressed, increasing delay and leading to additional flow data on the network. Similarly, if the coordinator 102 wants to communicate with the coordinator 106, he will have to switch to the frequency of the coordinator channel 106 (i.e., the third frequency of channel f3) and he will not be able to simultaneously communicate with the coordinator 104, i.e. the coordinator 102 will be similar "deaf" way of communication from the coordinator 104.

This means that all devices 102, 104 and 106 will communicate with each other on different channel frequencies.

[0028] Thus, the prior art network topology used by the WPAN 100 network will not provide any mechanism for migrating to one channel frequency, and the coordinator 102 may rely on including energy detection (ED) scanning and potentially abnormal checksum information (CRC) ) to activate the channel frequency change. In addition, transmission messages will not be possible and / or useful, and the implementation of the amplifier (i.e. device having the function of an amplifier) ​​will not work in the non-cooperating network discussed above.

[0029] According to the present invention, an exemplary implementation thereof is shown in figure 2, which shows a WPAN 200 similar to the WPAN 100 shown in figure 1. However, in addition to the three coordinators 202, 204 and 206, the WPAN 200 in Figure 2 includes a multi-functional wireless remote control (M_RC) 208, provided to control the functions of different coordinators, with the wireless remote control generally not having the coordinator function, but it is possible having a multi-functional remote control with the function of a coordinator. A device unable to act as a coordinator will operate according to a solution known in the art. As discussed above, the coordinators are preferably consumer electronic devices (CEDs), such as a television receiver (TV), DVD player (DVD) and home theater system (HTS), or any other similar device used in the home environment. It should be understood, however, that with respect to the present invention any other devices currently used and intended for use in connection with the WPAN network can be considered.

[0030] Similar to WPAN 100, each of the coordinators 202, 204 and 206 (e.g., the first, second and third coordinators respectively) have separate WPAN identifiers, thus each of them is on a separate frequency channel e.g. on first f1, second f2 and third frequency of channel f3, respectively. Also similar to the WPAN network shown in Figure 1, if a coordinator, e.g., first coordinator 202, wants to communicate with another coordinator, e.g., with the second coordinator 204, the first coordinator 202 will use the frequency flexibility mechanism to find the coordinator 204 (e.g., using subsequent scanning of different channel frequencies (such as first f1, second f2 and third channel frequency f3). When the first coordinator 202 finds the second coordinator 204, it communicates the frequency of the channel on which it works, and after receiving this message the coordinator 204 sends confirmation on the channel on which the message was received, and then switches to the frequency channel of the coordinator that initiated the communication (i.e. the coordinator 202). However, the benefit of the present invention is also greater when additional coordinators are provided for their mutual communication.

[0031] For example, as has just been discussed, if the first coordinator 202 wants to communicate with the second coordinator 204, he will request the second coordinator 204 to switch to the preferred channel frequency of the coordinator 202, i.e. to the first channel frequency f1. If then the first coordinator wants to establish communication with the third coordinator 206, it will cause the coordinator 206 to move to the frequency of the coordinator 202, i.e. transition from the third frequency of channel f3 to the first frequency of channel f1. Similarly, if the multi-functional wireless remote control 208 communicates with different coordinators 202, 204 and 206, the multi-functional wireless remote control 208 will switch to the frequency of the coordinator channel that initiated the initial communication, which in this case will be the first coordinator 202. This means that all devices 202, 204 , 206 and 208 will communicate on the channel frequency (i.e. first frequency of channel f1) of the first coordinator 202.

[0032] However, if a source of interference were introduced in the immediate vicinity of WPAN 200 and a violation of the currently operating channel frequency occurs, any of the coordinators 202, 204 and 206 may individually decide to switch to a different channel frequency without informing the other coordinators. Since the coordinators are expected to work in close proximity, it would be expected that all other coordinators will also detect the source of interference and that they will switch individually. If some devices switch and some devices do not, then the same mechanism as described above will be used to facilitate communication between devices that can and cannot perform the function of coordinator. Another way would be to transmit the channel change message when the channel is changed.

[0033] We will now present figure 3, showing a time diagram of coordinators 202, 204 and 206 and pilot 208, passing from individual channel frequencies, i.e. first f1, second f2 and third channel frequency f3, to optimized single channel frequency to ensure communication between devices 202, 204, 206 and 208.

[0034] In the case of a time scheme, the process starts with the first coordinator 202, e.g. TV, initiating communication with the second coordinator 204, e.g. DVD. TV 202 uses frequency flexibility to find DVD 204. First, second and third positions 302, 304 and 306 denote moments when TV 202 successively transmits on first f1, second f2 and third frequency f3 to find DVD 204.

[0035] At position 308, TV 202 finds DVD 204 and communicates its operating (or preferred) channel frequency, i.e., first channel frequency f1, and DVD 204 switches to TV 202, i.e., first channel frequency f1. In a similar manner, the multi-functional remote control 208 uses frequency flexibility to find DVD 204 (as indicated by positions 310, 312 and 314). Then, remote control 208 adopts at position 316 the frequency of the TV channel 202, i.e. the first channel frequency f1 because DVD 204 inherited the channel frequency (i.e., channel frequency f1) of TV 202.

[0037] At position 318, DVD 204 initiates communication with a third coordinator, such as HTS 206, for example. Again, DVD 204 uses frequency flexibility to find HTS 206 (as indicated by positions 318, 320 and 322). HTS 206 adopts, at position 324, the frequency of the DVD channel 204 and switches to the first frequency of the channel f1.

[0038] At position 326, TV 202 initiates communication with HTS 206. Again, TV 202 uses frequency flexibility to find HTS 206 (as indicated by positions 326, 328 and 330). When TV 02 finds HTS 206, it communicates its channel frequency, i.e., first channel frequency f1 HTS 206 at position 332, and then HTS 206 switches to TV channel frequency 202, i.e., first channel frequency f1. In this example, HTS is already working on f1 TV as a result of the steps described in the previous paragraph. Therefore, it is not necessary to use this particular sequence.

[0039] In addition, at position 334, multi-functional pilot 208 attempts to communicate with HTS 206. Similarly, multi-functional pilot 208 will use a frequency flexibility mechanism to determine (as indicated by positions 334, 336 and 338) on which channel frequency HTS 206 is communicating. The multifunction pilot 208 will then adopt, at position 340, the first frequency of channel f1 for communication with HTS 206. Thus, at this point, all devices 202, 204, 206 and 208 have switched to the frequency of the TV channel 202 (i.e., to the first frequency of the channel f1), so that the optimized single transmission frequency will be used for communication between the devices. In fact, the pilot will start to communicate on the channel frequency on which HTS was originally operating. The pilot will need to use the mechanism to re-acquire frequency flexibility to find HTS and to appropriately adopt the new frequency. This applies only to devices that cannot be used as coordinators, such as remote controls.

[0040] Furthermore, the person having the appropriate skills realizes that the present invention is in no way limited to the preferred embodiments described above. On the contrary, an addressee with relevant skills in this field understands that many modifications and changes are possible within the scope of the appended claims. For example, the number of coordinators and devices other than coordinators is variable and can be reduced or increased as necessary. In addition, the frequency flexibility mechanism can be made more efficient by writing an RF channel on which another device should work. When a device wants to communicate with another device, it first checks the stored information and tries to communicate with the other device on that expected channel. If this attempt fails, the full channel frequency flexibility mechanism can be used.

[0041] In conclusion, according to the present invention, it is possible to provide a new method for a first coordinator working on a first channel frequency in a WPAN network, wherein the WPAN network also has a second coordinator working on a second channel frequency, and the method includes the steps of transmitting a message on a series of channel frequencies , including the second channel frequency, by requesting the second coordinator to change from the second channel frequency to the first channel frequency and to communicate with the second coordinator using the first channel frequency. According to the above discussion, the benefits of the present invention include the fact that there is no need for a priority-based mechanism, which results from the fact that the initiator (e.g. initiating) communication decides on the frequency used. In addition, each coordinator can provide a change in the frequency of the coordinator with whom he wants to communicate on the frequency of his choice.