Link adaptation of frequency hopping systems

Abstract

To provide a method for determining an optimal modulation and coding (MCS) when link adaptation is applied to frequency hopping transmission, a computer program, and a transceiver.SOLUTION: A transmission method including frequency hopping between channels includes adjusting a modulation and coding scheme of each set of channels for each frequency hop. A set of link adaptation algorithm is used for adjusting the modulation and coding scheme. A transceiver includes a transmitter, a receiver, and a controller for controlling operation of the transmitter and the receiver. The controller controls operation according to the method. A computer program includes instructions for causing the transceiver to perform the method.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present disclosure generally relates to a method for providing link adaptation to frequency hopping transmissions.

Background Art

[0002] Link adaptation (LA) is known to be beneficial for improving the performance of wireless systems when channel conditions vary significantly. Basically, the goal of LA is to use a modulation and coding scheme (MCS) that is optimal for the current channel conditions. Here, the optimal one may vary somewhat depending on the supported application, but generally, it is the MCS that achieves the highest data rate with a sufficiently low error probability.

[0003] LA is used in cellular systems such as 3G, 4G, 5G, etc. developed by 3GPP (registered trademark). It is also an important feature of the IEEE 802.11 standard generally called Wi-Fi. Which MCS to select in these systems may depend on the distance between the transmitter and the receiver, or on the interference level at the receiver, or on a combination of both. The variation of MCS can correspond to a receiver signal-to-interference-plus-noise ratio (SINR) in the range of 0 to 30 dB. In the case of 0 dB, it usually corresponds to the most robust modulation, and usually binary phase shift keying (BPSK) is used with a low-rate error correction code. On the other hand, 30 dB corresponds to the ability to transmit multiple streams in parallel using multiple-input multiple-output (MIMO), where each stream is modulated using a high-order modulation alphabet such as 256 quadrature amplitude modulation (QAM) and a relatively high-rate error correction code.

[0004] For LA to function as intended, the transmitter needs accurate information about the receiver's status to select the appropriate MCS. Such information may be obtained through explicit feedback from the receiver, or it may be obtained by the transmitter itself by monitoring the success or failure of transmissions using different MCSs. The former is usually preferred, but it incurs a small additional cost for the signal.

[0005] Another feature beneficial to almost all wireless systems is frequency diversity. In most cases, the wireless channel between the transmitter and receiver has different characteristics depending on the frequency. Today, many systems use channel bandwidths of at least 20 MHz, and sometimes exceeding 100 MHz. In this case, the channel varies significantly within the channel bandwidth. In this case, the channel is said to be frequency-selective. In effect, operating with frequency-selective channels requires equalizing the channel, thus making the receiver more complex. However, even if the channel at a particular frequency varies significantly, the average channel condition does not fluctuate as much, making performance more predictable. LA inherently offers the greatest advantage for a variety of channel conditions. For example, the average SINR of a 20 MHz channel may vary by only a few dB, while the SINR of each frequency within that 20 MHz channel can easily vary by 30 dB or more.

[0006] However, some wireless systems use relatively small channel bandwidths. One example is Bluetooth® Low Energy (BLE), which, depending on how bandwidth is defined, has a channel bandwidth of approximately 1 MHz. This means that in many typical BLE use cases, the wireless channel is essentially the same across the entire channel bandwidth; that is, the channel is modeled as a single complex number, and the received signal is the transmitted signal multiplied by this complex number plus some additive noise.

[0007] In this case, the channel is said to be frequency-flat, indicating that the entire channel bandwidth experiences the same channel conditions. This means that the signal is not subject to frequency diversity.

[0008] A frequency-flat channel means that receiver processing is simplified; for example, reception can be based on simple differential demodulation without having to perform channel estimation. The main drawback of a frequency-flat channel is that the entire channel can become very bad, a condition called (flat) fading. As mentioned above, channel variation can be 30 dB, which effectively means the system will experience flat fading of a 30 dB channel variation.

[0009] To address the problem of signals not experiencing frequency diversity, frequency hopping (FH) is commonly used to achieve it. FH means that the frequency is changed so that the channel conditions experienced by the signal differ depending on the channel used. The hopping rate (how often the frequency is changed) can vary greatly from system to system. Historically, when FH was used for very low data rates, high-frequency hopping was a term used to indicate that the hopping rate was as fast as the rate of channel-coded symbols. Thus, a single symbol can be represented by transmitting information at multiple different frequencies, and frequency diversity can be effectively achieved at the symbol level. At higher data rates, the hopping rate is usually significantly lower than the symbol rate. In traditional Bluetooth® systems, the frequency is changed after each packet (acknowledgments are also transmitted at the same frequency). This means that individual packets typically experience very different channel conditions, so even if one packet experiences a bad channel, the next packet (which may be a retransmission of the previous packet) can typically experience a completely different channel. FH can be seen as a means of averaging different channels, so that the system experiences average (overall bandwidth) conditions rather than the worst channel conditions (without FH, a selected narrowband channel may become the worst channel within the bandwidth). In BLE, frequency hopping is used by changing channels with each connection event, which can be configured to occur at intervals ranging from 7.5 milliseconds to 4 seconds. Hopping patterns are defined in the specification, and adaptive FH is used by blacklisting channels with low signal strength or strong interference.

[0010] Considering LA and FH, the former can be seen as a means to optimize channel usage, while the latter can be seen as a means to experience average channel conditions. Furthermore, systems using FH typically use LA, which is intended to match average (overall bandwidth) channel conditions. Essentially, the MCS is selected so that it performs sufficiently well across the majority of channels used by the FH system.

[0011] Efficient signal regulating (LA) relies on precise knowledge of the communication channel, particularly the receiver's state. Using LA in situations where the receiver's state changes significantly will not work well. Since FH-based systems are ideally designed so that the channel changes depending on the frequency used for transmission, applying standard LA to FH systems generally does not work well.

[0012] Specifically, LAs typically attempt to select the MCS that yields the best overall results based on average channel conditions. Applying standard LAs to FH systems presents at least two major problems. The first problem is that the performance achieved is usually far from what is theoretically possible. In particular, MCSs that accommodate high data rates are not used because they do not work well with a relatively large number of channels. The second problem is the behavior of the LA algorithm itself. Normally, an LA algorithm converges to the optimal MCS and updates slightly as channel conditions change. When the system is FH, the LA algorithm constantly adjusts without converging, so unless the LA algorithm is based on long-term averaging, performance becomes almost completely unpredictable, which means the algorithm's response to channel changes is very slow.

[0013] The information disclosed in this background section is intended to enhance the understanding of the background of the disclosure and therefore may contain information that does not constitute prior art known to those skilled in the art. [Overview of the project] [Problems that the invention aims to solve]

[0014] This disclosure is based on the inventors' recognition that at least some of the problems described above can be mitigated by combining LA and FH, where different LA are performed on the various channels used for frequency hopping. In this way, the LA algorithms can converge to different MCSs on the various channels, thus achieving performance relatively close to the theoretical optimal value. Since an approach using many potentially independent LA algorithms means that each LA algorithm has less data available for training, it is proposed to build the LAs on explicit feedback. For example, the receiver of interest could explicitly suggest the optimal MCS, or the transmitter could derive a suitable MCS from the response from the receiver, or information about a suitable MCS could be derived from other measurements. [Means for solving the problem]

[0015] According to a first embodiment, a transmission method is provided which includes frequency hopping between channels. The method includes adjusting the modulation and coding scheme for each set of channels for each frequency hop, and a set of link adaptation algorithms is used for adjusting the modulation and coding scheme, and multiple instances of the link adaptation algorithms are used simultaneously.

[0016] A set of channels may include a single channel or multiple channels with adjacent frequencies.

[0017] The number of link adaptation algorithm instances in a set of link adaptation algorithms can be the same as the number of channels in a set of channels.

[0018] The channels belonging to each set of channels can be adapted during operation.

[0019] The adjustment of the modulation and coding scheme may include transmitting the first packet on a channel using the most robust and available modulation and coding scheme, receiving a response to the first packet, obtaining an appropriate modulation and coding scheme for the channel, and adjusting the modulation and coding scheme for the next packet based on the appropriate scheme. Obtaining an appropriate modulation and coding scheme may include receiving an indication of an appropriate modulation and coding scheme in the received response, or determining an appropriate modulation and coding scheme from the received response. The first packet may use the smallest modulation and coding scheme for the operating mode being used.

[0020] The method involves determining whether the channel is limited by noise or interference, and the adjustment of the modulation and coding scheme may further depend on the determination of channel limitation.

[0021] The method may include scanning at least a subset of the set of channels to determine the channel characteristics, and adjusting the modulation and coding scheme based on the knowledge gained about at least a subset of the set of channels.

[0022] The method may include omitting the use of a set of channels determined to have characteristics below a first threshold. The first threshold may correspond to the feasibility of using the minimum data rate modulation and coding scheme for the operating mode being used.

[0023] The method may include listing a set of channels that have characteristics that reach a second threshold. The second threshold may correspond to the feasibility of using the maximum data rate modulation and coding scheme for the operating mode used.

[0024] A hopping sequence can be obtained based on the knowledge obtained for a channel. A hopping sequence can be obtained based on the results of scanning at least a subset of channels. A hopping sequence can be determined at each hop. A hopping sequence can be determined at each scan.

[0025] The frequency hopping rate can be adjustable based on a decision to adjust the modulation and coding scheme. The frequency hopping rate can be determined at each hopping. The frequency hopping rate can be determined when obtaining new information regarding a set of channels. The frequency hopping rate can be determined by hopping to a new channel when the channel in use has characteristics below a third threshold. The third threshold can correspond to the feasibility of using the target modulation and coding scheme of the operating mode being used. The hopping rate and the hopping sequence can be determined such that the set of channels used satisfies a second threshold.

[0026] According to a second aspect, a computer program is provided that includes instructions that, when executed by a processor of a transceiver, cause the transceiver to execute the method according to the first aspect.

[0027] According to a third aspect, a transceiver is provided that includes a transmitter, a receiver, and a controller for controlling the operations of the transmitter and the receiver, and the controller is configured to control the operations according to the method according to the first aspect.

[0028] Since the LA is individual for various sets of channels, an appropriate MCS is selected for each of the channel sets used, and the data rate of the selected MCS is usually very different for each channel set. In particular, a very high data rate is achieved for channels in good conditions, so the spectral efficiency of the system is greatly improved.

[0029] The above and additional objects, features, and advantages of the present disclosure will be better understood through the following illustrative and non-limiting detailed description of the preferred embodiments of the present disclosure, with reference to the accompanying drawings.

Brief Description of the Drawings

[0030] [Figure 1] A diagram showing an example of how the SNR changes in different channels. [Figure 2] A diagram showing an example of how the symbol error rate changes in different channels. [Figure 3] A diagram showing an example of how the symbol error rate changes in different channels when the MCS is low. [Figure 4] A diagram showing an example of how the SNR changes in different channels according to another example. [Figure 5] A diagram showing an example of how the symbol error rate changes in different channels according to another example. [Figure 6] A diagram showing an example of how the symbol error rate changes in different channels when the MCS is low according to another example. [Figure 7] A diagram showing an overview of an initial packet exchange for measuring, selecting, and signaling the MCS according to an example. [Figure 8] A diagram showing an overview of an initial packet exchange for measuring, selecting, and signaling the MCS according to another example. [Figure 9] A flowchart showing a method according to multiple embodiments. [Figure 10] A block diagram showing a transceiver according to one embodiment. [Figure 11] A diagram schematically showing a computer-readable medium and a processing device.

Modes for Carrying Out the Invention

[0031] The proposed method is generally applicable to systems where the carrier frequency used is not expected to remain the same for a relatively short period of time, for example, between 1 ms and 1 s. The reason for using multiple carrier frequencies is to avoid situations where a large portion or the entire channel is in deep fading.

[0032] To simplify the explanation of this disclosure, we will describe a system that employs FH and operates in the 2.4 GHz Industrial Scientific and Medical (ISM) band. Specifically, we assume nearly the same communication parameters as those used in Bluetooth® systems, namely, a channel bandwidth of 1 MHz, channels separated by 1 MHz, a total of 79 channels available, and the use of FH. This disclosure may also be similarly applicable to BLE, where the channel bandwidth is slightly increased, channels are separated by 2 MHz, and a total of 40 channels are available.

[0033] Originally, Bluetooth® was based on Gaussian frequency-shift keying (GFSK) with a symbol rate of 1 M symbols / s. The highest data rate at the time was 1 Mb / s, and lower rates were possible by using error correction codes. Subsequently, Extended Data Rate (EDR) was introduced to increase the maximum data rate. EDR is based on differential phase-shift keying (DPSK) and comes in two types: differential 4-phase-shift keying (DQPSK) and differential 8-phase-shift keying (D8PSK). The former has a total data rate of 2 Mb / s, and the latter has a total data rate of 3 Mb / s, and are generally referred to as EDR2 and EDR3.

[0034] For simplicity, we will assume that no data rate reliant on error correction codes is used, and as a result, the transmitter will use one of the following modulations: 1. GFSK-1Mb / s data rate 2. DQPSK-2Mb / s data rate 3. D8PSK-3Mb / s data rate

[0035] To provide some numerical values, the provided simulation results use a non-coherent receiver for all modulation formats. It is well known that better results can be obtained by attempting to generate some kind of phase reference, but this is not relevant to this disclosure. This disclosure is applicable regardless of demodulation details.

[0036] First, assuming the channel is flat within the channel bandwidth (1 MHz), it can be modeled as an additive white Gaussian noise (AWGN) channel. The required signal-to-noise ratio (SNR) can be assumed to be 16, 14, and 19 dB for three different modulations. The fact that the 2 Mb / s mode is superior to the 1 Mb / s mode is due to the modulation used, but the result is, of course, that the 1 Mb / s mode will never be used if EDR is supported. If the SNR is sufficiently high, EDR3 in 3 Mb / s mode is used, and otherwise EDR2 in 2 Mb / s mode is used. This demonstrates a very simple link adaptation.

[0037] Here, we consider the fact that Bluetooth® uses 79 channels of FH, and that signal attenuation differs for each channel. Figure 1 shows an example of how the SNR changes across 79 channels, with the 79 channels numbered from -39 to 39, where 0 is the middle channel.

[0038] In this simulation, the average SNR is 20 dB, and as can be seen from Figure 1, the SNR of various channels varies by approximately 20 dB, from 6 dB to 25 dB. Simulating the symbol error rate (SER) of 79 different channels using EDR3 (D8PSK) and EDR2 (DQPSK) yielded the results shown in Figures 2 and 3.

[0039] As you can see, the results are in very good agreement with the assumption that 14dB and 19dB are needed for EDR2 and EDR3, respectively.

[0040] It is noteworthy that EDR3 appears to be the preferred modulation for approximately half of the channels. For about 35% of the channels, EDR2 is recommended because EDR3 results in excessively high SER. Yane For the remaining 15%, no modulation works. Here, we will set the LA based on overall performance without distinguishing between different channels. In this case, for example, whether EDR2 or EDR3 gives the best total throughput can be considered by taking into account the product of (probability of correct bits) * (number of bits transmitted / symbol). When this is done, it is found that EDR3 is the best choice. However, if it is necessary to reduce the probability of errors at the expense of lower total throughput, then EDR2 is the preferred choice.

[0041] A received SNR of 20 dB corresponds to a receiver power of approximately -87 dBm in a Bluetooth® system with a bandwidth of 1 MHz (note that this assumes a noise figure of 7 dB and terminal noise on a 1 MHz channel is -114 dBm). A simple link budget analysis reveals that received power can be considerably higher in many typical use cases. Therefore, consider a scenario where the SNR increases from 20 dB to 40 dB. The corresponding SNR fluctuations and simulated SER are shown in Figures 4-6. Referring to Figures 5 and 6, errors occur around channel number -15 in both EDR2 and EDR3, even though the SNR exceeds 26 dB.

[0042] The reason for this performance is that the channel experiences a very deep fade at channel number -25, causing the channel's amplitude and phase to change significantly within the 1MHz channel, resulting in significant signal distortion. Specifically, the assumption that the channel is flat is not valid. In reality, the signal is affected by intersymbol interference (ISI), meaning that symbols interfere with each other to some extent.

[0043] Several things can be learned from the simulation results and the explanation above. Firstly, when using an FH system, the optimal MCS varies depending on the channel being used. Some channels are relatively good, and these channels can use an MCS that enables high data rates, but other channels are relatively poor, and these channels require a more robust MCS that can handle lower data rates.

[0044] Secondly, if a relatively simple receiver is used where ISI may occur on some channel links, the receiver's performance cannot be judged solely by the SNR at the receiver. In particular, when the MCS achieves relatively high data rates, ISI, rather than noise, can limit performance.

[0045] Based on the above discussion, the following embodiments and examples are disclosed to address the problem and achieve improved performance.

[0046] To address the fact that different channels in a frequency hopping system experience very different channel conditions, this embodiment covers an approach in which multiple instances of the link adaptation algorithm are used simultaneously. This approach is characterized in that multiple LA algorithms are updated (activated) one at a time, and which one is updated depends on which frequency channel is being used to transmit data.

[0047] For example, in a frequency hopping system, the number of simultaneous LA algorithms can be the same as the number of different frequencies used for FH. For instance, if 79 channels are used for FH, the number of LA algorithm instances running in parallel will be 79.

[0048] As another example, to reduce complexity, the number of parallel LA algorithms can be less than the number of channels used for FH. The number of parallel LA algorithms can be based on an estimate of how much the channel frequencies are changing, i.e., the frequency selectivity of the channels. For example, with 79 channels, if the operation of five adjacent channels is determined to be similar, the same LA algorithm can be used for them, and a total of 16 LA algorithms would be needed for 79 channels.

[0049] Since each of the different channels in the FH system is used for only a very short time, LA algorithms based on the collection of large amounts of statistical data may not be suitable. Based on this observation, we also disclose a method for actually performing LA.

[0050] To find the optimal MCS for use, the following approach based on explicit feedback is disclosed. The first packet sent from the transmitter to the target receiver has the primary purpose of allowing the receiver to determine the most appropriate MCS, and either transmits no data or the smallest possible amount of data (i.e., the lowest data rate and possible (By using the shortest packet length). The optimal MCS determined by the receiver is reported to the transmitter, which uses this proposed optimal MCS for the next transmission. In this way, the optimal MCS may be used for the second transmission on this channel. For the next transmission, it is expected that the channel will only change at a relatively slow rate, and LA will be performed based on or without explicit feedback from the receiver, and the transmitter may set LA based on statistics from ACK / NACK reports.

[0051] Furthermore, in some embodiments of this model, the receiver may indicate through explicit feedback whether the link is limited by noise or by intersymbol interference.

[0052] Because performance varies greatly depending on the channel, it is advantageous to use the best channel and especially avoid the worst one. According to this embodiment, a scan is performed before the actual transmission of data begins. For example, if there are 79 available channels in total, the transmitter sends packets on each of these channels and reports to the receiver, for example, which MCS is available on each channel. Let This allows us to request that information about the quality of these different channels be sent back. For example, if the packet duration is 100 microseconds and the switching frequency duration is 150 microseconds, we can scan 4 channels in 1 millisecond. This means we can scan 79 channels in 20 milliseconds and find the appropriate channel to use for actual transmission.

[0053] Adaptive FH is a method used in Bluetooth® primarily to avoid interference from Wi-Fi. The idea is that frequencies interfered with by Wi-Fi are not used, and the frequency hopping pattern is adjusted so that these frequencies are not used. Typically, this means that the hopping pattern is updated so that, for example, 20 consecutive channels corresponding to locations where Wi-Fi interference is detected are not used. However, FH adaptation can also be applied to individual frequencies. According to this embodiment, AFH is based on channel quality at different frequencies, for example, as described in Embodiment 3.

[0054] If the FH system is like the original Bluetooth® system, where the frequency changes after each packet transmission, the FH sequence may consist only of frequencies determined to be achievable at the highest data rate. Alternatively, the FH sequence may consist of two frequencies that are achievable at the highest data rates, with different MCSs used for different channels depending on the estimated channel quality, as shown in Figures 1 to 6.

[0055] Alternatively, a similar approach is used if the FH system uses one channel that is considered sufficiently good, and only changes when this condition is not met, but the next frequency in the FH sequence is only used if it is determined that the current frequency is not sufficiently good. This way of performing FH is similar to the approach used in BLE.

[0056] In many cases, channels change slowly, but are not always completely static. This means that even if you scan the entire bandwidth to determine the best channel to use at a given time, those channels may not have the desirable characteristics when you actually need them. To avoid hopping to channels that were previously classified as good but have changed to bad, the following approach is disclosed. This approach is primarily intended for situations where channels are used as long as they are good, although it can also be used in principle for situations where channels change with each transmission.

[0057] According to this embodiment, the transmitter maintains an updated list of suitable channels to switch to if the channel currently used to transmit data deteriorates. The list consists of a single channel or multiple channels used in sequence. To maintain this updated list, the transmitter uses a portion of its transmission to perform scans on other frequencies to determine if these frequencies are suitable to switch to as needed. As an example, suppose the transmitter needs to maintain an average data stream of 1 Mb / s to the receiver. This corresponds to, for example, certain streaming applications. By using a suitable channel, it is possible to transmit at 4 Mb / s, so only 25% of the total capacity needs to be used. The transmitter and receiver may then agree to perform sensing on a given frequency at a specific time. The transmitter may, for example, send probing packets every 100 milliseconds on a frequency other than the one used for data transmission to determine if the frequency is a suitable candidate to switch to when the currently used channel begins to deteriorate. The transmitter and receiver may, for example, agree on a list of 10 candidate frequencies to be probed in a predetermined order so that all 10 candidate frequencies are probed every second, in order to maintain a list of suitable frequencies. As for frequencies to be changed if necessary, the transmitter and receiver may agree to use the last scanned frequency that proved to be sufficiently good.

[0058] In certain cases of BLE systems, the initial transmission in each connection event is used to determine the channel for that particular channel. conditions Information can be obtained.

[0059] The initial transmission of an event, always sent by the master device, may contain a flag indicating that the packet is intended to probe the channel. This packet is transmitted using a baseline data rate of 1 Mb / s. Alternatively, if an enhanced data rate mode is used, the baseline data rate may correspond to the lowest data rate supported by that enhanced mode. The slave device then responds to the packet with an acknowledgment, allowing the master device to perform channel quality measurements in its transmission and select an appropriate MCS for subsequent transmissions throughout the connection event. The selected MCS is indicated to the slave device in the next packet.

[0060] Assuming that the additional information needed to transmit the measurement fits within two octets and a basic 1 MBPS PHY is being used, this initial transaction to acquire the measurement, select the MCS to use, and signal would complete in 834 μs and be used to transmit data at a higher rate for the remainder of the current connection event.

[0061] Figure 7 shows an overview of the initial packet exchange, where (1) is the initial transmission of the connection event, (2) is the acknowledgment from the slave, (3) is the MCS indication packet, and (4) is the final acknowledgment from the slave. Optionally, (2) is the channel acquired by the slave device by performing the measurement in (1). conditions It includes information related to MCS selection and provides the master device with additional information for MCS selection.

[0062] If a higher data rate transmission mode is designed so that the receiver can decode any rate without prior knowledge of the rate being used, the initial packet exchange can be further shortened. In that case, packets (3) and (4) in Figure 7 may be omitted. Alternatively, the above approach based on explicit feedback can be used, i.e., receiverThe system determines the optimal MCS and can send this information to the master in a response packet. Figure 8 illustrates this short exchange, in which MCS information can be obtained in just 342 μs.

[0063] As mentioned above, the BLE frequency changes with each new connection event. Since the quality of different frequencies is expected to vary considerably, a good channel is necessary. conditions The channel is not a very good channel. conditions It is advantageous to be able to use more channels than the available ones. One approach already mentioned is to use AFH and simply avoid poor channels. However, in an environment where channels are changing, which channels are good and which are bad changes over time, and AFH may simply be too slow to function as intended. To achieve better channel use, i.e., to use more good channels, the following approach is disclosed, which follows the BLE FH approach with minor modifications. The FH sequence, as with BLE, is agreed upon before actual data transmission begins. However, the length of the connection interval is not fixed and can be changed for each connection event. Specifically, if a channel is found to be bad, the channel event can be terminated and a new connection event can be started at the next frequency in the FH sequence. On the other hand, if a connection event is using a good channel, the connection event can be extended to stay at this frequency as long as the channel is considered good enough.

[0064] A change in frequency, i.e., the termination of a connection event, can be initiated by any device and indicates that the channel is deteriorating.

[0065] Figure 9 is a flowchart illustrating the method according to different embodiments. Various options are available and are shown as dashed boxes. The central function is to adjust the modulation and coding scheme of each set of channels at each frequency hop (904), and a set of link adaptation algorithms is used for this adjustment. Essentially, the link adaptation algorithm is used for a single channel or a set of channels with correlated characteristics, such as adjacent frequencies. For other channels or sets of channels, different link adaptation algorithms are used. As mentioned above, this improves the matching and tracking of each channel.

[0066] MCS adjustment (904) can be obtained based on explicit feedback as described above. This involves sending the first packet on the channel to obtain a response, and when the channel is first used, the response will determine the appropriate MCS to use, i.e., the starting point for link adaptation. This can be done by receiving information about the appropriate MCS, or by determining the appropriate MCS based on the reception. The latter depends on the cross-channel. In this way, knowledge about the channel is obtained.

[0067] According to one option, Yane The channels are scanned (900). A subset of the available channels, or all available channels, are scanned. In this way, knowledge about the channel characteristics is obtained.

[0068] Based on the collected knowledge about the channels, some channels are considered defective and, for example, have characteristics that fall below the threshold corresponding to operation in the lowest MCS of the operating mode used, i.e., the most robust available MCS. Such channels may be ignored for further use, at least for a certain period of time (901).

[0069] Based on the collected knowledge about the channels, some channels are considered good and possess characteristics that reach a threshold corresponding to operation at the target MCS or the maximum MCS of the operating mode used. Such channels are listed (902) for further use, at least for a certain period of time.

[0070] The collected knowledge about the channel can also be used to determine whether the channel is limited by noise or interference (903). Such knowledge about channel limitations can also be used to adjust the channel's MCS by frequency hopping.

[0071] Frequency hopping itself can also be adjusted. For example, the hopping sequence, i.e., which channels to switch to when performing frequency hopping, is adapted (905) based on knowledge gained about the channels. For example, known good channels are preferred, and known bad channels are avoided. Timing aspects of frequency hopping can be adapted (906) additionally or alternatively. The operation involves staying in good, i.e., good and persistent characteristics for longer periods, while channels with changing characteristics are used for shorter periods. In the context of frequency hopping, the term “hopping rate” is referred to, meaning a predetermined pace for performing frequency hopping. However, in this disclosure, the term “hopping rate” should be interpreted in a broader sense and should be considered a matter of variable and adjustable timing.

[0072] Figure 10 is a block diagram showing a transceiver 1000 according to one embodiment. The transceiver 1000 comprises an antenna configuration 1002, a receiver 1004 connected to the antenna configuration 1002, a transmitter 1006 connected to the antenna configuration 1002, a controller which is preferably a processing element 1008 including one or more circuits, one or more input interfaces 1010, and one or more output interfaces 1012. Interfaces 1010 and 1012 are user input toughThe faces and / or electrical or optical signal interfaces may be used. Transceiver 1000 is configured to operate in a cellular communication network. In particular, transceiver 1000 can combine frequency hopping and link adaptation, as the processing element 1008 is configured to perform the embodiments shown with reference to Figures 1 to 9. The processing element 1008 can also fulfill a number of tasks ranging from signal processing that enables reception and transmission because the processing element 1008 is connected to receiver 1004 and transmitter 1006, to application execution, control of interfaces 1010, 1012, and so on.

[0073] The method according to this disclosure is particularly suitable for implementation using processing means such as a computer and / or processor, when the processing element 1008 described above comprises a processor that processes frequency hopping and link adaptation. Accordingly, a computer program is provided which includes instructions configured to cause the processing means, processor, or computer to perform any step of the method according to any embodiment described with reference to Figures 1 to 6. The computer program preferably includes program code stored in a computer-readable medium 1100, as shown in Figure 11, and is loaded and executed by the processing means, processor, or computer 1102 to perform each of the methods according to embodiments of this disclosure, preferably the embodiments described with reference to Figures 1 to 6. The computer 1102 and the computer program product 1100 are configured to execute the program code sequentially, so that any action of the method is performed stepwise or on a real-time basis. The processing means, processor, or computer 1102 may preferably be what is commonly called an embedded system. Therefore, the computer-readable medium 1100 and computer 1102 shown in Figure 11 are for illustrative purposes only to provide an understanding of the principle and should not be interpreted as direct examples of the elements.

[0074] This disclosure can be summarized in the following points:

[0075] 1. A transmission method including frequency hopping between channels, This includes adjusting the modulation and coding scheme for each set of channels for each frequency hopping, A method in which a set of link adaptation algorithms is used for adjusting modulation and encoding schemes.

[0076] 2. A method according to item 1, wherein the set of channels includes a single channel.

[0077] 3. A method according to item 1, wherein the set of channels includes multiple channels of adjacent frequencies.

[0078] 4. A method according to any one of items 1 to 3, wherein the number of link adaptation algorithms in the set of link adaptation algorithms is the same as the number of channels in the set of channels.

[0079] 5. A method according to any one of items 1 to 4, wherein the channels belonging to each set of channels are adapted during operation.

[0080] 6. A method according to any one of items 1 to 5, wherein the modulation and encoding schemes are adjusted. The first packet is transmitted over a single channel using the lowest modulation and coding scheme, Receiving a response to the first packet, To obtain an appropriate modulation and encoding scheme for the channel, A method comprising adjusting the modulation and coding scheme of the following packets based on an appropriate modulation and coding scheme.

[0081] 7. A method relating to item 6, wherein obtaining a suitable modulation and coding scheme includes receiving an indication of a suitable modulation and coding scheme in a received response.

[0082] 8. A method relating to item 6, wherein obtaining a suitable modulation and coding scheme comprises determining a suitable modulation and coding scheme from a received response.

[0083] 9. A method according to any one of items 1 to 8, comprising determining whether the channel limitation is due to noise or interference, and further adjusting the modulation and coding scheme based on the determination of the channel limitation.

[0084] 10. A method according to any one of items 6 to 9, wherein the first packet uses the least modulation and coding scheme for the operating mode used.

[0085] 11. A method according to any one of items 1 to 5, This involves scanning at least a subset of the set of channels to determine the channel properties. A method for adjusting modulation and coding schemes, which includes adjusting based on knowledge gained about at least a subset of the set of channels.

[0086] 12. A method according to any one of items 1 through 11, comprising not using a set of channels that are determined to have properties below a first threshold.

[0087] 13. A method relating to item 12, wherein the first threshold corresponds to the feasibility of using the smallest modulation and coding scheme for the operating mode used.

[0088] 14. A method according to any one of items 1 to 13, comprising listing a set of channels having properties that reach a second threshold.

[0089] 15. A method according to item 14, wherein the second threshold corresponds to the feasibility of using the maximum modulation and encoding scheme for the operating mode used.

[0090] 16. A method relating to any one of items 1 through 15, wherein the hopping sequence is based on the results of scanning at least a subset of channels.

[0091] 17. A method relating to item 16, wherein the hopping sequence is determined at each hop.

[0092] 18. A method according to item 16, wherein the hopping sequence is determined in each scan.

[0093] 19. A method according to any one of items 1 to 18, wherein the frequency hopping rate is adjustable based on a decision to adjust the modulation and coding scheme.

[0094] 20. A method according to item 19, wherein the frequency hopping rate is determined for each hop.

[0095] 21. A method relating to item 19, wherein the frequency hopping rate is determined when acquiring new information about a set of channels.

[0096] 22. A method according to item 19, wherein the frequency hopping rate is determined by hopping to a new channel when the channel in use has properties below a third threshold.

[0097] 23. A method relating to item 22, wherein the third threshold corresponds to the feasibility of using the target modulation and coding scheme for the operating mode used.

[0098] 24. A method according to item 15, 17, 21, 22, or 23, wherein the hopping rate and hopping sequence are determined such that the set of channels used satisfies a second threshold.

[0099] 25. A computer program that, when executed on the transceiver's processor, contains instructions that cause the transceiver to perform any one of the methods described in items 1 through 24.

[0100] 26. A transceiver comprising a transmitter, a receiver, and a controller for controlling the operation of the transmitter and receiver, wherein the controller is configured to control the operation in accordance with the method described in any one of items 1 to 24.

Claims

1. A method for adjusting a modulation and coding scheme for transmission, including frequency hopping between channels, The first packet is transmitted over a single channel using the most robust and available modulation and encoding scheme, Receiving a response to the aforementioned first packet, Determining whether the channel is limited by noise or interference, Based on the appropriate modulation and coding scheme for the received response, the modulation and coding scheme for the next packet transmitted on the same channel is adjusted. Includes, Adjusting the modulation and encoding scheme is further a method based on the determination of the channel limitation.

2. The method according to claim 1, The appropriate modulation and coding scheme is a method based on an indication of the appropriate modulation and coding scheme in the received response.

3. The method according to claim 1, The method for determining the appropriate modulation and coding scheme is based on determining an appropriate modulation and coding scheme from the received response.

4. A method according to any one of claims 1 to 3, A method comprising not using a set of channels that have been determined to have characteristics below a first threshold.

5. The method according to claim 4, A method wherein the first threshold is determined so that a minimum data rate modulation and coding scheme can be used when the characteristic is greater than or equal to the first threshold.

6. A method according to any one of claims 1 to 5, A method comprising listing a set of channels having characteristics that reach a second threshold for future use of the set of channels.

7. The method according to claim 6, A method wherein the second threshold is determined so that the maximum data rate modulation and coding scheme can be used when the characteristic is greater than or equal to the second threshold.

8. A computer program, when executed on the processor of a transceiver, includes instructions causing the transceiver to perform the method according to any one of claims 1 to 7.

9. A transceiver comprising a transmitter, a receiver, and a controller for controlling the operation of the transmitter and the receiver, wherein the controller is configured to adjust the modulation and coding scheme according to the method of any one of claims 1 to 7.

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