WO2003021886A2 - Adaptation de canaux dans un reseau de communication - Google Patents

Adaptation de canaux dans un reseau de communication Download PDF

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Publication number
WO2003021886A2
WO2003021886A2 PCT/GB2002/003929 GB0203929W WO03021886A2 WO 2003021886 A2 WO2003021886 A2 WO 2003021886A2 GB 0203929 W GB0203929 W GB 0203929W WO 03021886 A2 WO03021886 A2 WO 03021886A2
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WIPO (PCT)
Prior art keywords
channel
reselection
communication
quality information
devices
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PCT/GB2002/003929
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English (en)
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WO2003021886A3 (fr
Inventor
Michael Philip Fitton
Siew Chung Leong
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Toshiba Research Europe Limited
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Publication of WO2003021886A2 publication Critical patent/WO2003021886A2/fr
Publication of WO2003021886A3 publication Critical patent/WO2003021886A3/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/06—Reselecting a communication resource in the serving access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/24—Reselection being triggered by specific parameters
    • H04W36/30—Reselection being triggered by specific parameters by measured or perceived connection quality data
    • H04W36/302—Reselection being triggered by specific parameters by measured or perceived connection quality data due to low signal strength
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W24/00—Supervisory, monitoring or testing arrangements
    • H04W24/10—Scheduling measurement reports ; Arrangements for measurement reports
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W48/00—Access restriction; Network selection; Access point selection
    • H04W48/08—Access restriction or access information delivery, e.g. discovery data delivery
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/02—Selection of wireless resources by user or terminal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access
    • H04W74/04—Scheduled access
    • H04W74/06—Scheduled access using polling
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/18—Self-organising networks, e.g. ad-hoc networks or sensor networks

Definitions

  • the present invention relates to dynamic selection of channels for communication between devices, particularly for use in wireless personal area networks such as Bluetooth.
  • the current technology allows two or more such devices to form a wireless 'piconet', a short-range communication cell, to allow them to communicate with one another.
  • Such wireless devices currently employ a frequency hopping spread spectrum system to mitigate the effects of unknown and unpredictable interference, or 'noise'.
  • Some systems do employ fixed frequency links that can be switched in use to an alternative frequency on instruction from a fixed access point.
  • these systems are generally dictated by a single device and have crude and unreliable methods for assessing the relative quality of alternative channels.
  • a centralised topology such as this removes much of the flexibility of a distributed structure.
  • a communication device for communication with one or more other communication devices comprising: means for measuring the signal quality of a communication channel; comparison means for determining if the measured signal quality exceeds a predetermined value; channel reselection means responsive to said comparison means for generating a channel reselection signal to be transmitted to said one or more other communication devices and for determining a reselection channel for further communication based upon channel quality information; and switching means for switching communication to said reselection channel and for transmitting a signal, for reception by said one or more other communication devices, indicating the reselection channel.
  • Each device can initiate a channel reselection whether it is currently the master or not. Since there is no one specific master device which controls channel reselection and initial selection, use can be made of the distributed topology. Thus if the channel quality is poor in one part of the network area, a device in that area can initiate and complete channel reselection even if the original channel is acceptable everywhere else in the network area.
  • the device comprises update means for transmitting a signal indicating the reselection channel which is received by the other communication devices. They can then retune to the new channel as well.
  • the device can initiate the reselection without reference to any other device, reselection can be carried out rapidly without delays which may occur due to all the devices forming a consensus.
  • the channel quality information can be obtained from a channel scanning means for scanning some or all of the available channels. It is not necessary to scan all channels. For example, only one channel in a certain band may be scanned if it is likely that interference extends across such a band. Therefore, where interference of a certain bandwidth is known to be present, channels may be scanned at intervals corresponding to the interference bandwidth.
  • the channel scanning means may determine the channel quality information in response to said comparison means determining that the quality is insufficient or alternatively, it may rely on information already collected prior to determining that the quality is insufficient. This clearly reduces the time overhead of scanning channels after it has been detemiined to reselect the channel. Furthermore, the pre-existing information may be updated after reselection has been determined to be necessary.
  • the devices preferably include polling means for transmitting a polling signal to be received by one or more other communication devices.
  • polling means for transmitting a polling signal to be received by one or more other communication devices.
  • the devices can provide channel information back to the original device. This allows any lack of homogeneity in the network to be compensated for by getting a picture of the channel status at different locations.
  • the information provided may be pre-existing information or collected in response to the polling. If pre-existing information is available at one device, this can avoid the need for the supervisor device which initiated the reselection to carry out a scan of the spectrum.
  • Channel information which has been collected from different devices and at different times may be less accurate that other information and so the information may be weighted to reduce the significance of less useful information, for example data which was collected some time ago.
  • Devices may keep a list of channels and their determined quality which is updated with new quality data periodically. This ensures that the device always has some estimate of the best channel available if reselection is to occur whether initiated by itself or another device.
  • the devices preferably include control means for receiving a polling signal from another communication device, producing local channel quality information and transmitting said local channel quality information for reception by said another communication device. This allows a device to act as a slave for providing information as well as a supervisor for carrying out reselection. In this way when a device is not in supervisor mode, it can still assist another device by providing local channel quality information in response to a polling signal.
  • the present invention provides both a device as indicated above for use in a network but also a collection of two or more devices forming a network.
  • the present invention provides a method for operating a device for use with a network and a method for operating a communication network comprising a plurality of communication devices, the method comprising in each device: monitoring the quality of a communication channel at a communication device, and determining if the quality is below a predetermined level and if so: producing channel quality information for a plurality of candidate channels; generating a channel reselection signal to be transmitted to one or more of said other communication devices; determining a reselection channel for communication based upon said channel quality information; transmitting a signal, for reception by other communication devices, indicating the reselection channel; and switching communication to the reselection channel.
  • Figure 1 shows a representation of a network to which the present invention can be applied
  • Figure 2 is a flow diagram showing how an embodiment of the present invention operates
  • Figure 3 shows an example of measurement frequencies used during channel evaluation
  • Figure 4 is a schematic diagram of a communication device according to the present invention.
  • the present invention relates to a system for enhancing the communication between devices operating in a network over a communication channel.
  • the following embodiment is described in relation to a piconet operating using a radio frequency communication link as part of a wireless personal area network (WPAN), e.g. Bluetooth.
  • WPAN wireless personal area network
  • a typical network includes a number of devices, which want to communicate with each other. Such an arrangement is shown in figure 1. These devices may be part of one or more networks with some devices connecting to more than one of these networks.
  • one network might include a laptop computer 10, a printer 11, a scanner 12 and a mobile phone 13.
  • Another network may be formed between the mobile phone 13 and a personal digital assistant 14 and a further network may be formed between the mobile phone 13 and another PC 15.
  • HR communication Whilst basic communication is carried using the LR piconet using a broadband system, HR communication is carried out using narrowband techniques. This allows for the higher data communication rate but is much more susceptible to narrowband fading, interference in the band and time dispersion.
  • the subnet 1 shown in figure 1 comprises four links A-D providing HR communications between the four devices.
  • data is transferred between the devices.
  • the channel may deteriorate for a number of reasons such as the devices have moved into a different environment, moved relative to each other, another interfering source has moved closer to the devices and so on. The result is that satisfactory communication on the current channel is no longer possible.
  • the devices When multiple devices are present, if the devices are outside the coherence distance in the environment then narrowband and wideband fading will be uncorrelated between the different links A-D. For example, the link D may be deeply faded but links A-C have good received signal power. Consequently not all the devices would determine that reselection was required. Therefore, several and possibly all of the devices in the subnet monitor the channel. If one of the devices determines that the signal quality of the channel falls below a certain level then it initiates reselection as a supervisor. Some or all of the devices may initiate reselection and if so they become the supervisor. Thus any one of such devices can begin the reselection process without having to use a decentralised system ,where a consensus must be reached by all the devices. This is also more convenient that having a permanent master device for controlling the channel because this restricts the operability of this type of network because it means that all devices must be able to communicate with the master. The master must always be available and cannot move away from the other devices or vice vers
  • this dynamic channel selection process can be applied to deal with a number problems which may restrict signal quality, including (i) interference in the band; (ii) narrowband fading; and (iii) time dispersion. These problems are somewhat linked. A high RMS delay spread is likely to be experienced when the instantaneous narrowband channel attenuation is large. Furthermore, deep fade in the band will exacerbate problems of interference. Preferably, averaging of the measurements would be carried out to remove the impact of fast fading on the interference measurement. In addition, because interference may not be homogenous throughout the piconet such that different interferers dominate in different parts of the piconet then several measurements can be taken for an optimal solution.
  • Figure 2 shows a flow chart representing the steps to be carried out for monitoring and reselecting a channel.
  • SI normal communication takes place.
  • a check is carried out to determine whether each of the devices have quality of service above a predetermined level.
  • the quality of service can be measured in a number of ways. However, the most favoured option is monitoring the segment failure or segment error rate whilst in the most robust mode available (BPSK mode in the case of Bluetooth).
  • the specific segment error rate required to trigger a reselection of the channel will be based on the required quality of service for the link.
  • Other parameters that may be used are the received signal strength (RSSI) and the carrier to interference ratio (C/I) or combinations of any of these.
  • the regularity at which the quality of service is monitored depends on a number of factors. The most important of these is the rate at which interferers join or leave the vicinity of the devices and the multipath fading (due to the wireless channel) which is experienced on the desired and interfering links. In most situations, the rate of change due to multipath fading (as characterised by the Doppler frequency) will dominate the birth/death process of interferers. This is not a problem where the measurement is taken and then immediately acted upon such that there is little time between the measurement being taken and being acted upon.
  • the measurements may be 'stale', i.e. out of date.
  • This can be avoided by taking the measurements at a rate that is faster than the rate of change of the environment (dominated by the Doppler frequency as described above). This can be determined by the device itself based upon examining the difference between subsequent measurements or broadcast across the subnet by one or the other or the devices. Alternatively less frequent measurements may be tolerated by classifying the measurements taken according to their age. Newer measurements can be allocated a higher weighting value that is decreased with time as they become increasingly out of date. The quantisation of these weighting values could be related to the number of frames/packets since the measurement was taken or otherwise. Then when the measurements are taken into account, those which are older can be arranged to have less weight than more recent measurements.
  • the initiating device is assigned temporary supervisor status.
  • a device initiating a new HR link is assigned temporary supervisor status. It then sends a dynamic channel selection request (DCS__Request) to the other devices in the subnet, step S3.
  • DCS__Request dynamic channel selection request
  • N there are N devices on the subnet and that the subnet is arranged such that M devices must accept a DCS_Request before it is accepted.
  • M N-1 meaning that all other devices on the subnet must accept the DCS_Request to ensure a robust implementation.
  • the process may be speeded up by allowing M to be less than N-l .
  • DCS_Accept the required M acceptances
  • S5 the maximum (N-M) number of explicit rejections
  • DCS_Reject the maximum number of explicit rejections
  • step S6 a check to see if the maximum time (T DCS ) has expired. If some of the devices have not responded within this time, then the process continues without their response and they are effectively assumed to have accepted the request for DCS. If the time has not yet expired then operation reverts to step S4 and so on.
  • the initiating device is established as the supervisor. As such, it is responsible for determining the new channel and for updating the other devices with the new channel information.
  • the simplest way of determining the new channel is for the supervisor to determine the status of the alternative channels itself and make the appropriate selection.
  • the supervisor may select a channel which appears to be satisfactory to the supervisor but which is not ideal for another device of the subnet. Therefore, the supervisor may additionally incorporate information from some of the other devices on the subnet or even from another source which is able to provide local channel information.
  • the settling time is likely to be of the order of 200 ⁇ s and a measurement time of 1 ⁇ s.
  • the time taken for an entire sweep is around 16ms.
  • An HR device could scan at 4MHz and so perform the same measurement in 4ms. Whilst these figures are pessimistic (times of approximately 50% may be more realistic) they do not include additional time for averaging of channel variations which may be required.
  • the supervisor can obtain channel data from other sources as well as or even in place of its own measurements (e.g. because it is unable to make a measurement in the time available or measurement would put undue demands on the power requirements of the device).
  • Obtaining information from other capable devices helps to ensure that the lack of homogeneity across the subnet is accounted for.
  • the supervisor collates measurement reports from capable devices.
  • the reports contain a list of the most suitable and/or the least suitable channels.
  • the supervisor can then combine the gathered information to determine the suitability of each channel as a candidate for the new channel.
  • the significance of the data from each device or within a single report can be weighted according to various factors such as accuracy or to rank the frequencies in order of suitability.
  • the informationiused may be collated in advance. If information is already available then this reducesfthe delay in developing the measurement information during the dynamic channel selection process. For example, if an LR and an HR net is coordinated and the LR piconet reports on current channel conditions, then this information may be used.
  • one or more of the devices in the HR subnet may be designated as monitoring devices and regularly rescan the entire band to maintain an up to date set of channel status data. This could be done when the device is idle. In this way when a device is idle, it can update its channel status information.
  • the ideal situation is where every device on the piconet would have its own model of the channel, interference and environment. Therefore, the combination of the information from such devices would be able to provide a comprehensive picture of the overall parameters and status of the band.
  • the supervisor will have sufficient pre-measured information available to determine the new channel. However, if this is not the case then again the supervisor may utilise one or more other devices to carry out measurements for it. Such units are referred to as designated monitoring units. Such units may be in active, sniff or park modes. Ideally devices in park mode are used since the scanning operation does not affect their performance. Where they are in active mode, such scanning operation may prevent normal operation, which is undesirable. Obviously, power consumption needs to be considered, particularly in portable devices, as it is undesirable to have excessive power consumption due to scanning activities when the device is in park mode, i.e. not carrying out its normal functions.
  • the supervisor When the decision to begin dynamic channel selection is made, the supervisor is generally in one of three positions: full knowledge of the channels (e.g. through pre- measurement); not in possession of full channel information but with sufficient time and capability to measure channels; and unable to measure channels.
  • the selection of the algorithm for determining the channel depends upon which of these positions apply.
  • the channels can be scanned randomly.
  • subsequent channel measurements can be performed separated by this bandwidth or greater. In this way the possibility of wasting time scanning several channels which are all adversely affected by the same interferer is avoided, hence improving the scanning rate. For example, if the likely interferer has a 20MHz bandwidth (e.g. 802.1 lb wireless LAN) it should be ensured that the next channel scanned is more than 20 MHz away.
  • the calculation is based on a joint optimisation of carrier and interference power, then it is desirable to ensure that the gap between subsequent channels scanned exceeds the coherence bandwidth.
  • a random selection pattern can be implemented.
  • the number of measurements that can be carried out will be determined by the latency permitted by the logical channel(s) quality of service requirements. The worst case and hence the fastest is where a random channel is selected without prior measurement.
  • One further option is to return to the best hop frequency in the set or remain at the last one measured.
  • the number of times that channel reselection is initiated can be used to control the switch back to LR mode. In this way, if re-selection is continually taking place, for example because the entire band is poor a return to LR is initiated.
  • the channels need to be compared based on one or more parameters as a guide to their likely quality of service.
  • Interference Signal strength indicator (ISSI) is the main factor in assessing each channel, although it does not reflect the degree of fading the desired channel(s) will experience and therefore the resulting quality.
  • Other parameters are the carrier to interference ratio (C/I). This requires probing the band with a transmitted signal.
  • C/I can be calculated by looking at the deviation of the known sequence from desired values or by taking separate measurements of received signal strength during reception and ISSI during guard intervals or gaps in transmission. Due to the significant processing and hence power consumption, C/I indication is preferable for a small number of devices such as a single link between two devices.
  • a further parameter is to measure the packet error rate for the associated LR piconet.
  • the above parameters may be combined or used in isolation depending upon the arrangement, environment, etc.
  • FIG. 4 A schematic representation of an exemplary communication device 40 of the present invention is shown in figure 4.
  • the device comprises an antenna 41 connected to a receiver/transmitter 42 for allowing communication with other terminals.
  • the quality of service calculator 43 monitors the quality of service of the received signal to determine if it exceeds the predetermined threshold. If the quality of service drops below this level then dynamic channel reselection must be carried out and a signal is sent to the channel quality information requestor 44 and the channel quality calculator 45.
  • the channel quality information requestor 44 sends out signals to the other devices in the piconet to indicate that DCS is taking place and that it is temporarily assuming the role of supervisor for the piconet.
  • the channel quality calculator 45 begins analysing the channels to determine the local channel properties. If required, the channel quality information receiver 46 receives channel quality information from the other devices of the piconet which have been polled by the signal from the channel equality information requester 44. The channel quality information from the channel quality calculator 45 and/or the channel quality information receiver 46 is sent to the alternative channel selector 47 which determines the best channel for further communication based upon the received channel information and/or on stored information. The determined channel is then used to adjust the receiver/transmitter 42 for future transmission and also to send a signal to the other devices on the piconet for similar channel reassignment.
  • the measurement of carrier power in a slave-master link is done in Bluetooth 1 mode, in this construction. This is achieved by scanning through the band and measuring corresponding carrier power values at each defined channel following the hopping pattern of the master.
  • the slave determines the carrier power (C) at each channel utilising the received signal strength indication (RSSI) functionality of the receiver.
  • the measurement is done during all 1-slot packets (and first slot of multiple slot frames) from master-to-slave slots.
  • the measured absolute received signal strengths are stored on the condition that the known access code (used for synchronization and addressing in Bluetooth 1 mode) has been found, i.e. the correlation threshold level has been exceeded. These measured C values can be averaged for each 1MHz channel.
  • transmitter power control it is necessary for the master to ensure sure that the transmit power of the transmitting slave is known, for example by giving powerUp commands untiLJhe, transmission power (TxP) of the slave is in at its maximum (MaxTxP).
  • TxP transmission power
  • MaxTxP maximum transmission power
  • the measurement of carrier power in a slave-slave link can also be carried out to allow the path loss between slaves to be measured. This is potentially required as there is slave-to-slave communication in high-rate, which does not occur in low rate.
  • transmitter power control the master makes sure that the transmit power of the transmitting slave is known, for example by giving powerUp commands until the TxP of the slave is at MaxTxP.
  • the low rate master commands slave A to measure slave-to-slave path loss.
  • the master transmits to slave B and slave B responds on the return slot.
  • the slave A makes a measurement during the slave B transmission.
  • the measurement by slave A now determines the receive power of the transmission from slave B (as well as all inter piconet interference). It may be necessary to repeat the measurement a number of times to ensure sufficient averaging.
  • slave A reports its measurements (receive power levels) to the master, who already knows the transmit power of the slave B, hence the path loss can be estimated.
  • Determination of the interference level, in the frequency band is one of the most important measures used in DCS, and therefore in the selection of the best channel on which to position the HR subnet. This measurement can be performed in low-rate mode for channel selection. Two methods for performing the interference plus noise are described here:
  • the interference power is measured during slave-to-master slots. Again, it might be beneficial to average multiple measurements per channel. In order to avoid measuring the slave-to-master transmission itself or its spectral leakages, an appropriate frequency offset between the slave-to-master frequency channel and the frequency channel to be measured needs to be used. This frequency offset value has to be high enough so that the transmitted power leaking to the adjacent channel does not affect the measurement results (see figure 3).
  • the interference power is measured during the guard period between transmissions. Either the retune to the new frequency is delayed, and the receiver measures the interference (using RSSI) at the current frequency, or the receiver is retuned to the new frequency and the measurement is performed there.
  • This approach has the advantage that it is unlikely to require additional hardware as simultaneous operation and measurement are not required.
  • guardjperiod > synth_settling + interference_measurement + ramping_interval
  • step S13 the supervisor determines the new frequency channel. This may be with information obtained from other devices by following the optional steps S8-S12. In these steps, the supervisor issues a request to other devices. Capable devices return their reports on the channel's status. When all the reports have been returned or after a predetermined time, TDcsmeasurement, the process continues to step SI 3 where the supervisor determines the new channel. The supervisor broadcasts the new channel to the other devices. If an acknowledgement is required then it is necessary to wait for all the devices to acknowledge the change of channel (S15-S17). If all the devices have not acknowledged the change of channel within a predetermined period of time, T DCS _A CK , then the supervisor resends the change of channel command. This is repeated a number of times (SI 9) after which the change of channel is aborted and the system returns to 'Normal operation'. Once all the devices have acknowledged, all devices switch to the new channel.
  • SI 9 number of times
  • the LR master is updated with the new HR channel so that new devices can be directed to the right frequency and so that devices which have lost track and have dropped down to LR mode can return to HR mode.
  • a device initiating the high rate subnet would perform initial channel selection but according to the present invention other of the devices of the piconet maybe able to carry out channel reselection.
  • the high-rate RF channel is based on 4 MHz wide channels in the 2.45 GHz ISM band.
  • a Bluetooth FH piconet Before a high-rate channel can be established, a Bluetooth FH piconet must exist. Units in the FH piconet can negotiate for the high-rate channel.
  • the location of the high-rate RF channel in the spectrum is adaptive and responsive to occupation by other ISM users.
  • 77 overlapping channels are defined.
  • the carrier spacing is chosen to be 1 MHz to obtain the highest resolution for positioning the RF channel in the ISM spectrum.
  • DCS dynamic channel selection
  • the participating units carry out measurements in the entire ISM band. Based on these measurements, the most appropriate part of the spectrum is selected to position the high-rate channel. Sufficient averaging can be applied to cancel short-term interference (e.g. other devices carrying out frequency hopping cannot be avoided but their influence can be averaged out).
  • an ordered list of channel quality can be formed, describing the most suitable carriers that can be used for the high rate link.
  • the first carrier on the list is the one believed to give the best transmission result, the second one is the carrier believed to give the second best result and so on.
  • the ordered list is preferably distributed before the devices enter the HR mode, and the best carrier is used as the initial channel of the HR subnet.
  • the first part of the link adaptation consists of using all available measurement information to create an ordered list of the 77 possible carriers that can be used for the high rate link. As described below, this ordered list can be used in dynamic channel reselection.
  • the ordered channel quality list is formed.
  • the low rate master that is setting up the HR subnet collates all the measurement reports.
  • the overall ordered list is then formed by summing together all available measurement reports. At this stage it is possible to scale each measurement report if required, to indicate the quality of the estimate.
  • the minimum baseline requirement for performing initial channel selection when setting up a high rate subnet is based upon interference power measurements.
  • the test strategy is designed assuming that this method is employed, if a more primitive (and insufficient) technique is used to select the new HR channel, it will fail the specified tests.
  • the interference signal strength measurement can be performed by a proxy depending on the implementation.
  • the ordered channel quality list is formed from a set of measurements performed at a single point in the prospective HR subnet. For example, if the quality indication for each channel is 0 to 3, 0 corresponds to negligible observed interference, 3 to very high interference levels. Suitable averaging can be applied. The purpose of this approach is to ensure that the HR subnet is placed on a channel which has sufficiently low interference contribution.
  • a slightly extended version of the interference only measurement system described previously uses carrier and interference power measurements for initial channel selection.
  • the measurement point the low rate master or proxy
  • This device performs carrier power measurements on one or more links to other devices that will also be participating in the HR subnet.
  • the quality indicator for each channel will be based on the ratio between carrier and interferer
  • a further method may be implemented which utilises interference measurements from multiple participating HR devices. This method more accurately reflects that devices in different locations within the subnet will experience different interference levels.
  • all devices intending to join the new subnet have the option to send an interference measurement to the low rate master.
  • a standardized "scoring" scheme for exchanging this data is used, for example 0 to 3 with 0 being the highest quality and 3 being the worst.
  • This method would at least reflect the potentially non-homogeneous nature of interference.
  • an ordered list of the suitability of all available channels is formed during initial channel selection. This system can then be employed during dynamic channel reselection if the quality of the current channel degrades.
  • the ordered channel quality list is kept as up to date as possible in order to serve its purpose, as described below. This is achieved using one of a number of methods. For example one or more units on the BT2 link also are active on the BT1 link, so that measurements can be performed for the entire band. If the ordered channel quality list is updated, then the previous values can be incorporated into the new calculation as described above, using a suitable weighting to provide some memory of channel quality. The quality for the used carrier is of course monitored on a packet by packet basis. If the ordered channel quality list is updated, this information should be communicated over the HR link (on a network configuration interval, see [bt-bb]).
  • the supervisor will broadcast a message indicating when a change in channel will occur (and to which channel). However, it is possible that the broadcast message may not be received by all devices. Therefore, the units need to know when the new carrier will be used.
  • the network synchronisation slot or a priority slot on the HR link serve this purpose. If no network activity is observed during a certain predetermined time (e.g. a network synchronisation slot is missed), both the transmitter and the receiver change to the next carrier at the next priority slot. If the change of carrier is successful, the fact that a change of carrier has taken place is then communicated to the low rate master (if the master is not already aware of this).
  • Dynamic channel selection should be initiated based upon the segment error rate (SER) of a particular packet or sequence of packets failing predetermined quality of service parameters.
  • SER segment error rate
  • the segment error rate that causes dynamic channel selection can be varied for different links, reflecting different quality requirements.
  • the level may be associated with a particular modulation scheme.
  • an application may set the required SER to be 10% with QPSK, as the throughput in BPSK mode is insufficient. Consequently, if the SER is poorer than this level, dynamic channel reselection is initiated rather than link adaption to DBPSK mode.
  • the present invention has been described above in relation to a WPAN such as Bluetooth.
  • this invention can be applied to any kind of network where a distributed topology is used, to allow decentralised control for allocation and switching of a communication channel.
  • This allows devices to move freely in and out of a network coverage area as no device is necessary to the operation, i.e. as a master, of the network.
  • any device can join a network and reselect the channel if the current channel is not providing sufficient quality.
  • Other advantages include the ability to obtain a picture of the channel environment across the network area when selecting a new channel rather than simply selecting a channel which is of good quality in the vicinity of the master or supervisor.

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  • Radio Relay Systems (AREA)

Abstract

L'invention concerne un système à topologie distribuée, décentralisée, destiné à un réseau local d'entreprise ou analogue. Des dispositifs contenus dans le système contrôlent la qualité de canal. Si la qualité de canal se révèle insuffisante, une réévaluation du canal est effectuée dans le but d'identifier un meilleur canal. Ce nouveau canal est ensuite communiqué à d'autres dispositifs du réseau, de sorte que tous les dispositifs peuvent communiquer sur ce nouveau canal.
PCT/GB2002/003929 2001-08-28 2002-08-28 Adaptation de canaux dans un reseau de communication WO2003021886A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0120837.0 2001-08-28
GB0120837A GB2379358A (en) 2001-08-28 2001-08-28 Channel selection based on quality of signal

Publications (2)

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WO2003021886A2 true WO2003021886A2 (fr) 2003-03-13
WO2003021886A3 WO2003021886A3 (fr) 2003-04-24

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GB (1) GB2379358A (fr)
WO (1) WO2003021886A2 (fr)

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EP1598998A1 (fr) * 2004-05-18 2005-11-23 Alcatel Procédé et dispositif de prédiction d'une interruption de lien dans un réseau de communications ad hoc à protocole de routage de type manet
WO2006016330A1 (fr) * 2004-08-10 2006-02-16 Koninklijke Philips Electronics N.V. Procede et appareil pour reutilisation de frequence dynamique
WO2006024420A1 (fr) * 2004-08-31 2006-03-09 Telefonaktiebolaget Lm Ericsson Procede permettant d'apporter de la resistance a des canaux radioelectriques avec evanouissements
EP1879410A1 (fr) * 2006-07-11 2008-01-16 British Telecommunications Public Limited Company Sélection de canal dans un réseau ad-hoc sans fil
US7483674B2 (en) 2004-08-31 2009-01-27 Telefonaktiebolaget L M Ericsson (Publ) Providing robustness in fading radio channels
US7664120B2 (en) 2005-09-27 2010-02-16 Raytheon Company Multiple-transceiver distributed dynamic channel selection in a communication network
CN103596228A (zh) * 2013-11-19 2014-02-19 福建星网锐捷网络有限公司 一种无线信道切换方法及装置
CN113170406A (zh) * 2018-11-12 2021-07-23 亚德诺半导体国际无限责任公司 无线网络中的传输配置的优化

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FR2855005A1 (fr) * 2003-05-16 2004-11-19 Bouygues Telecom Sa Procede d'evaluation de la qualite video
US7414982B2 (en) 2003-06-24 2008-08-19 Raytheon Company Distributed dynamic channel selection in a communication network
WO2005011203A1 (fr) * 2003-06-24 2005-02-03 Raytheon Company Selection dynamique repartie des canaux dans un reseau de communication
KR101050037B1 (ko) * 2003-06-24 2011-07-19 레이티언 캄파니 통신 네트워크에서의 분산형 동적 채널 선택
WO2005011211A1 (fr) * 2003-07-24 2005-02-03 Qualcomm Incorporated Procede et appareil pour fournir un indicateur de seuil de service dans un systeme de communication sans fil
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FR2870657A1 (fr) * 2004-05-18 2005-11-25 Alcatel Sa Procede et dispositif de pridiction d'une interruption de lien dans un reseau de communication ad hoc a protocole de routage de type manet
EP1598998A1 (fr) * 2004-05-18 2005-11-23 Alcatel Procédé et dispositif de prédiction d'une interruption de lien dans un réseau de communications ad hoc à protocole de routage de type manet
WO2006016330A1 (fr) * 2004-08-10 2006-02-16 Koninklijke Philips Electronics N.V. Procede et appareil pour reutilisation de frequence dynamique
WO2006024420A1 (fr) * 2004-08-31 2006-03-09 Telefonaktiebolaget Lm Ericsson Procede permettant d'apporter de la resistance a des canaux radioelectriques avec evanouissements
US7483674B2 (en) 2004-08-31 2009-01-27 Telefonaktiebolaget L M Ericsson (Publ) Providing robustness in fading radio channels
US7664120B2 (en) 2005-09-27 2010-02-16 Raytheon Company Multiple-transceiver distributed dynamic channel selection in a communication network
EP1879410A1 (fr) * 2006-07-11 2008-01-16 British Telecommunications Public Limited Company Sélection de canal dans un réseau ad-hoc sans fil
WO2008007070A1 (fr) * 2006-07-11 2008-01-17 British Telecommunications Public Limited Company Sélection de canaux dans un réseau sans fil ad hoc
US8428012B2 (en) 2006-07-11 2013-04-23 British Telecommunications Public Limited Company Channel selection in ad hoc wireless network
CN103596228A (zh) * 2013-11-19 2014-02-19 福建星网锐捷网络有限公司 一种无线信道切换方法及装置
CN103596228B (zh) * 2013-11-19 2016-12-07 福建星网锐捷网络有限公司 一种无线信道切换方法及装置
CN113170406A (zh) * 2018-11-12 2021-07-23 亚德诺半导体国际无限责任公司 无线网络中的传输配置的优化

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WO2003021886A3 (fr) 2003-04-24
GB0120837D0 (en) 2001-10-17

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