Link adaptation of frequency hopping system

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 for frequency hopping transmissions. [Background technology]

[0002] Link Adaptation (LA) is known to be beneficial in improving the performance of wireless systems when channel conditions vary widely. Essentially, the goal of LA is to use the modulation and coding scheme (MCS) that is optimal for the current channel conditions. The optimal one here depends somewhat on the supported application, but is generally 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. It is also an important feature of the standard developed by IEEE 802.11, commonly called Wi-Fi. The choice of MCS 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 may correspond to a receiver signal-to-interference-and-noise ratio (SINR) ranging from 0 to 30 dB. The 0 dB case typically corresponds to the most robust modulation, typically binary phase shift keying (BPSK) 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 modulation alphabet such as 256 quadrature amplitude modulation (QAM) and a relatively high-rate error correction code.

[0004] For LA to work as intended, the transmitter needs to have accurate information about the receiver's conditions in order to select an appropriate MCS. Such information can be obtained either by explicit feedback from the receiver, or by the transmitter itself by monitoring the success or failure of transmissions using different MCS. The former is usually preferred, but comes at a small cost of additional signaling.

[0005] Another feature that is beneficial to almost all wireless systems is frequency diversity. In most cases, the wireless channel between the transmitter and the receiver has different characteristics depending on the frequency. Today, many systems use channel bandwidths of at least 20 MHz, and sometimes even more than 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 a frequency selective channel requires the receiver to be more complex, since the channel must be equalized. However, performance is also more predictable, since the average channel conditions do not vary as much even if the channel at a particular frequency varies significantly. LA inherently offers the greatest benefit for a variety of channel conditions. To give an example, the average SINR of a 20 MHz channel varies only by a few dB, but the SINR of each frequency within the 20 MHz channel can easily vary by 30 dB or more.

[0006] However, some wireless systems use a relatively small channel bandwidth. An example is Bluetooth Low Energy (BLE), which has a channel bandwidth of around 1 MHz, depending on how you define the bandwidth. This means that in many typical use cases of BLE, the wireless channel is essentially the same across the entire channel bandwidth, i.e., 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, meaning that the signals do not experience frequency diversity.

[0008] A frequency-flat channel means that the receiver processing is simplified, e.g. reception can be based on simple differential demodulation without the need to perform channel estimation. The main disadvantage of a frequency-flat channel is that the overall channel can be very bad, the channel is said to be (flat) fading. As mentioned above, the channel variation can be 30 dB, which effectively means that the system experiences a flat fading of 30 dB of channel variation.

[0009] To address the problem of signals not receiving frequency diversity, it is common to use frequency hopping (FH) to obtain frequency diversity. FH means that the frequency is changed so that the channel conditions experienced by the signal are different 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 the term used to indicate that the hopping rate was as fast as the rate of the channel coding symbols. Thus, a single symbol can be represented by transmitting information at multiple different frequencies, effectively achieving frequency diversity at the symbol level. As data rates become higher, the hopping rate is usually significantly lower than the symbol rate. In conventional Bluetooth systems, the frequency is changed after each packet (acknowledgements are also sent at the same frequency). This means that individual packets usually 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) will usually experience a completely different channel. FH can be seen as a means of averaging different channels so that the system experiences average (across the bandwidth) conditions rather than the worst channel conditions (without FH, the narrowband channel selected would be the worst channel in the bandwidth). In BLE, frequency hopping is utilized by changing channels at each connection event, which can be configured to occur at intervals ranging from 7.5 ms to 4 seconds. The hopping pattern is defined in the specification, and adaptive FH is used by blacklisting channels with poor signal strength or high interference.

[0010] Considering LA and FH, the former can be seen as a means to make optimal use of the channel, and the latter as a means to experience average channel conditions. Also, systems using FH typically use LA, which is intended to match average (over the bandwidth) channel conditions. Essentially, the MCS is chosen such that performance is good enough in the majority of channels used by FH systems.

[0011] Efficient LA is based on accurate knowledge of the communication channel, especially the receiver conditions. LA does not work well when used in situations where the receiver conditions vary widely. By design, FH-based systems ideally have a channel that varies with the frequency used for transmission, so standard LA generally does not work well when applied to FH systems.

[0012] Specifically, LA usually tries to select the MCS that gives the best overall results based on the average channel conditions. There are at least two main problems with applying standard LA to FH systems. The first problem is that the performance achieved is usually far from what is theoretically possible. In particular, MCSs that correspond to 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. Usually, the LA algorithm converges to an optimal MCS and updates slightly as channel conditions change. If the system is FH, the LA algorithm does not converge but constantly adjusts, so unless the LA algorithm is based on long-term averaging, the performance becomes almost completely unpredictable, which means that the algorithm reacts very slowly to channel changes.

[0013] The above information disclosed in this Background section is intended to enhance understanding of the background of the disclosure and, therefore, may include information that does not form part of prior art known to those skilled in the art. Summary of the Invention [Problem to be solved by the invention]

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

[0015] According to a first aspect, there is provided a method of transmission involving frequency hopping between channels, the method including adjusting a modulation and coding scheme for each set of channels for each frequency hop, a set of link adaptation algorithms being used to adjust the modulation and coding scheme, and multiple link adaptation algorithm instances being used simultaneously.

[0016] A channel set may include a single channel, or may include multiple channels that are contiguous in frequency.

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

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

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

[0020] The method may include determining whether the channel is noise-limited or interference-limited, and the adjustment of the modulation and coding scheme may be further based on the determination of the limitations of the channel.

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

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

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

[0024] The hopping sequence may be based on knowledge gained about the channels. The hopping sequence may be based on results of a scan of at least a subset of the channels. The hopping sequence may be determined at each hop. The hopping sequence may be determined at each scan.

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

[0026] According to a second aspect, there is provided a computer program comprising instructions which, when executed on a processor of a transceiver, cause the transceiver to perform a method according to the first aspect.

[0027] According to a third aspect, there is provided a transceiver comprising a transmitter, a receiver and a controller for controlling operation of the transmitter and receiver, the controller configured to control operation in accordance with the method according to the first aspect.

[0028] Since the LAs are separate for the different sets of channels, an appropriate MCS is selected for each set of channels used, and the data rates of the selected MCS usually vary significantly from one channel set to another. In particular, very high data rates can be achieved on channels with good conditions, thus greatly improving the spectral efficiency of the system.

[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 preferred embodiments of the present disclosure, with reference to the accompanying drawings. [Brief description of the drawings]

[0030] [Figure 1] 1 shows an example of how the SNR varies for different channels. [Diagram 2] 1 shows an example of how the symbol error rate varies for different channels. [Diagram 3] FIG. 1 shows an example of how the symbol error rate varies for different channels when the MCS is low. [Figure 4] FIG. 11 shows how the SNR varies with different channels according to another example. [Diagram 5] FIG. 4 illustrates how the symbol error rate varies for different channels according to another example. [Figure 6] FIG. 13 shows how the symbol error rate varies for different channels for low MCS according to another example. [Figure 7] 1 illustrates an overview of an initial packet exchange for measuring, selecting, and signaling an MCS, according to an example. [Figure 8] FIG. 13 illustrates an overview of an initial packet exchange for measuring, selecting, and signaling an MCS, according to another example. [Figure 9] 1 is a flow chart illustrating a method according to several embodiments. [Figure 10] 2 is a block diagram illustrating a transceiver according to one embodiment. [Figure 11] 1 is a schematic diagram illustrating a computer readable medium and a processing device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The proposed method is typically applied in systems where the carrier frequencies used are not expected to remain the same for more than a relatively short period of time, e.g., between 1 ms and 1 s, and the reason for using multiple carrier frequencies is to avoid situations where a large portion or the entire channel is in a deep fade.

[0032] To simplify the description of this disclosure, a system employing FH and operating in the 2.4 GHz Industrial, Scientific, and Medical (ISM) band will be described. Specifically, we will assume approximately the same communication parameters as those used in Bluetooth® systems, i.e., a channel bandwidth of 1 MHz, channels separated by 1 MHz, a total of 79 channels available, and FH is used. This disclosure may be equally applied to BLE with a slight increase in channel bandwidth and channels separated by 2 MHz, a total of 40 channels.

[0033] Originally, Bluetooth was based on Gaussian Frequency Shift Keying (GFSK) with a symbol rate of 1Msymbol / s. At the time, the highest data rate was 1Mb / s, and lower rates were possible using error-correcting codes. Later, Enhanced Data Rate (EDR) was introduced to increase the maximum data rate. EDR is based on Differential Phase Shift Keying (DPSK) and has two variants: Differential Quadrature Phase Shift Keying (DQPSK) and Differential Eight Phase Shift Keying (D8PSK). The former has a total data rate of 2Mb / s, and the latter has a total data rate of 3Mb / s, and are commonly referred to as EDR2 and EDR3.

[0034] For simplicity, we assume that no data rate dependent error correction code is used, so that the transmitter uses 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 give some figures, the simulation results provided use a non-coherent receiver for all modulation formats. It is well known that better results can be obtained by trying to generate some kind of phase reference, but this is not relevant to this disclosure. The disclosure is applicable regardless of the details of the demodulation.

[0036] First, we assume that the channel within the channel bandwidth (1 MHz) is flat, so 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 the three different modulations. The fact that the 2 Mb / s mode is better than the 1 Mb / s mode is due to the modulation used, but the result is of course that the 1 Mb / s mode is never used when EDR is supported. If the SNR is high enough, EDR3 in 3 Mb / s mode is used, otherwise EDR2 in 2 Mb / s mode is used. This shows a very simple link adaptation.

[0037] Now consider the fact that Bluetooth uses 79 FH channels, and different channels have different signal attenuation. An example of how the SNR varies across 79 channels is shown in Figure 1, where the 79 channels are numbered from -39 to 39, with 0 being the middle channel.

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

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

[0040] It is worth noting that EDR3 appears to be the preferred modulation for about half of the channels. For about 35% of the channels, EDR2 is recommended because EDR3 has too high a SER. Chan For the remaining 15% of channels, no modulation works. Now, let us not distinguish between the various channels and set the LA based on their overall performance. In this case, for example, we can consider whether EDR2 or EDR3 gives the highest total throughput by considering the product (probability of correct bit) * (number of transmitted bits / symbol). When this is done, we find that EDR3 is the best choice. However, if we need a smaller probability of error at the expense of a lower total throughput, 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 (assuming a noise figure of 7 dB and noting that the terminal noise of a 1 MHz channel is -114 dBm). A simple link budget analysis shows that the received power can be significantly higher in many typical use cases. Therefore, consider a scenario where the SNR increases from 20 dB to 40 dB. The corresponding SNR variation 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 is above 26 dB.

[0042] The reason for this performance is that the channel experiences a very deep fade at channel number -25, so that the amplitude and phase of the channel vary significantly within the 1 MHz channel, distorting the signal significantly. Specifically, the assumption that the channel is flat is not valid. In fact, the signal suffers from inter-symbol interference (ISI), i.e., symbols interfere with each other to some extent.

[0043] From the simulation results and the above discussion, we can learn a number of things. First, when using an FH system, the optimal MCS depends on the channel used. Some channels are relatively good, and for these channels we can use an MCS that allows for high data rates, while other channels are relatively bad, and for these channels we need to use a more robust MCS that supports lower data rates.

[0044] Second, when relatively simple receivers are used, where ISI may occur in some channel links, the SNR at the receiver alone cannot be used to judge the performance of the receiver, especially when the MCS achieves relatively high data rates, where ISI, not noise, may limit performance.

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

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

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

[0048] As another example, to reduce complexity, the number of LA algorithms running in parallel may be less than the number of channels used for FH. The number of LA algorithms running in parallel may be based on an estimate of how much the channel varies in frequency, i.e., how frequency selective the channel is. As an example, in 79 channels, if the behavior of 5 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 required for LA of the 79 channels.

[0049] Since each of the different channels in an FH system is used only a small fraction of the time, an LA algorithm based on collecting a large amount of statistical data may not be appropriate. Based on this observation, a method for performing actual LA is also disclosed.

[0050] To find the optimal MCS to use, the following approach based on explicit feedback is disclosed: The first packet sent from the transmitter to the intended receiver has the primary purpose of allowing the receiver to determine the most appropriate MCS, and either carries no data or carries the least amount of data possible (i.e., the lowest data rate and Possible In this case, the optimal MCS is determined by the receiver and reported to the transmitter, which uses the proposed optimal MCS in the next transmission. In this way, the optimal MCS can be used in the second transmission on this channel. In the next transmission, where the channel is expected to change only at a relatively slow rate, the LA can be based on explicit feedback from the receiver or, alternatively, without explicit feedback, the transmitter can set the LA based on statistics of ACK / NACK reports.

[0051] Also, some of the embodiments may provide explicit feedback to the receiver to indicate whether the link is noise limited or inter-symbol interference limited.

[0052] Since different channels have very different performance, it is advantageous to use the best channels and especially to avoid the worst ones. According to this embodiment, a scan is performed before starting the actual transmission of data. As an example, if there are a total of 79 available channels, the transmitter transmits a packet on each of these channels and reports to the receiver, for example, what MCS can be used for each channel. to make By doing so, it can ask for information back about the quality of these different channels. For example, if the packet duration is 100 microseconds and the switching frequency time is 150 microseconds, then it can scan 4 channels in 1 millisecond, which means it can scan 79 channels in 20 milliseconds to find a suitable channel to use for the actual transmission.

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

[0054] If the FH system is such that the frequency is changed after each packet transmission, such as the original Bluetooth system, the FH sequence may be configured only with the frequency determined to be the highest data rate achievable, or the FH sequence may be configured with the two highest data rate achievable frequencies, and different MCSs may be used for different channels depending on the estimated channel quality, as shown in Figures 1-6.

[0055] A similar approach is used where instead the FH system uses one channel that is deemed good enough and only changes when this condition is not met, but the next frequency in the FH sequence is only used if the current frequency is found not to be good enough. This method of performing FH is similar to the approach used in BLE.

[0056] Channels are often slowly changing, but are usually not completely static. This means that even if one scans the entire bandwidth to determine the best channels to use at a given time, these channels may not have the desired characteristics when actually needed. In order to avoid hopping to channels that were previously classified as good, but that have changed to bad, the following approach is disclosed. This approach is primarily intended for situations where the channel is used as long as it is good, even though it could in principle also be used for situations where the channel changes with every transmission.

[0057] According to this embodiment, the transmitter maintains an updated list of suitable channels to change to if the channel currently used to transmit data becomes poor. The list may consist of a single channel or multiple channels used in sequence. To maintain this updated list, the transmitter uses a portion of the transmission to perform a scan on another frequency to determine if this frequency is a suitable frequency to change to if necessary. As an example, assume that the transmitter needs to maintain an average 1 Mb / s data stream to the receiver, which may correspond, for example, to some kind of streaming application. By using a suitable channel, it is possible to transmit at 4 Mb / s, so that 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 a probing packet every 100 milliseconds on a frequency other than the one used for data transmission to determine if the frequency is a suitable candidate to change to if the currently used channel starts to deteriorate. To maintain the list of suitable frequencies, the transmitter and receiver may, for example, agree on a list of 10 candidate frequencies to be probed according to a predefined order, such that all 10 candidate frequencies are probed every second. As a frequency to change to if necessary, the transmitter and receiver may agree to use the last scanned frequency that was found to be good enough.

[0058] In the specific case of a BLE system, an initial transmission on each connection event is used to transmit data on that particular channel. conditions Information regarding the above can be obtained.

[0059] The first transmission of an event, always sent by the master device, may include a flag indicating that the packet is intended to probe the channel. This packet is sent using a baseline data rate of 1 Mb / s. Alternatively, if the extended data rate mode is being used, the baseline data rate may correspond to the lowest possible data rate supported in this extended mode. The slave device then responds to the packet with an acknowledgement, allowing the master device to perform channel quality measurements on that transmission and to 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 the additional information required to convey the measurement fits within two octets and that a basic 1 MBPS PHY is being used, this initial transaction to obtain the measurement and select and signal the MCS to be used is completed in 834 μs and is used to transmit data at the 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 first transmission of a connection event, (2) is the acknowledgement from the slave, (3) is the MCS indication packet, and (4) is the final acknowledgement from the slave. Optionally, (2) is the channel indication acquired by the slave device by performing the measurements in (1). conditions This includes information about the MCS and provides the master device with additional information for MCS selection.

[0062] The initial packet exchange can be made even shorter if the higher data rate transmission mode is constructed such that the receiver can decode any rate without prior knowledge of the rate used. In that case, packets (3) and (4) in Figure 7 can be omitted. Alternatively, the above approach based on explicit feedback can be used, i.e. Receivercan determine the optimal MCS and send this information to the master in the response packet. Figure 8 shows this short exchange, where the MCS information can be obtained in just 342 μs.

[0063] As mentioned above, the BLE frequency is changed for each new connection event. The quality of different frequencies is expected to vary considerably, so it is important to select a good channel. conditions of channels are not very good channels conditions It would be advantageous if more than one channel could be used. One approach already mentioned uses AFH and simply avoids poor channels. However, in an environment with changing channels, which channels are good and which are bad may change over time and AFH may simply be too slow to work as intended. To achieve a better use of the channels, i.e. to use more of the good channels, the following approach is disclosed, which follows the BLE FH approach with minor modifications. The FH sequence is agreed upon before the actual data transmission starts, just like in BLE. However, the length of the connection interval is not fixed and can change for each connection event. In particular, if the channel is found to be bad, the channel event can be terminated and a new connection event can be started on the next frequency in the FH sequence. On the other hand, if the connection event uses a good channel, the connection event can be extended to stay on this frequency as long as the channel is considered good enough.

[0064] A frequency change, and thus a termination of the connection event, can be initiated by either device and indicates that the channel is getting worse and worse.

[0065] Figure 9 is a flow chart showing a method according to different embodiments. Various options are available and are shown as dashed boxes. The central function is to adjust (904) the modulation and coding scheme of each set of channels for each frequency hop, and a set of link adaptation algorithms are used to adjust the modulation and coding scheme. Essentially, a 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, other link adaptation algorithms are used. As mentioned before, this allows for better matching and tracking of the respective channels.

[0066] The adjustment of the MCS (904) can be based on explicit feedback as described above. This involves sending an initial packet on the channel to get a response, from which the appropriate MCS to use when first using the channel is obtained, i.e. a starting point for link adaptation. This can be done by receiving information about the appropriate MCS, or by determining the appropriate MCS based on reception, the latter depending on the reciprocal channel. In this way, knowledge of the channel is obtained.

[0067] According to one option, Chan The channels are scanned (900). Either a subset of the available channels or all available channels are scanned. In this manner, knowledge about the channel characteristics is gained.

[0068] Based on the collected knowledge about the channels, some channels are deemed bad, e.g., have characteristics below a threshold corresponding to operation at the lowest MCS of the operating mode used, i.e., the most robust available MCS, and such channels may be ignored (901) for further use, at least for some period of time.

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

[0070] From the collected knowledge about the channel, it can also be determined whether the channel is noise-limited or interference-limited (903). Such knowledge about the channel limitations can also be used to adjust the MCS of the channel with frequency hopping.

[0071] The frequency hopping itself can also be adjusted. For example, the hopping sequence, i.e., which channel to change 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. The timing aspects of the frequency hopping can additionally or alternatively be adapted (906). Operation involves staying on good, i.e., good and persistent characteristics, for a long time, while channels with changing characteristics are used for a shorter time. In the context of frequency hopping, reference is made to a "hopping rate" which means a predetermined pace for performing frequency hopping. However, in this disclosure, the term "hopping rate" should be interpreted in a broader sense and considered as a variable and adjustable timing issue.

[0072] 10 is a block diagram illustrating 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. The interfaces 1010, 1012 are for user input. toughThe transceiver 1000 may be a cellular interface, a cellular radio interface, and / or an electrical or optical signal interface. The transceiver 1000 is configured to operate in a cellular communication network. In particular, the processing element 1008 is configured to perform the embodiments shown in reference to Figures 1 to 9, such that the transceiver 1000 can combine frequency hopping and link adaptation. The processing element 1008 can also fulfill a number of tasks ranging from signal processing to enable reception and transmission, since the processing element 1008 is connected to the receiver 1004 and the transmitter 1006, to running applications, controlling the interfaces 1010, 1012, etc.

[0073] The method according to the present disclosure is suitable for implementation using a processing means such as a computer and / or a processor, especially when the processing element 1008 shown above comprises a processor for processing frequency hopping and link adaptation. Thus, a computer program is provided that includes instructions configured to cause a processing means, processor or computer to perform any of the steps of the method according to any of the embodiments described with reference to Figs. 1 to 6. The computer program preferably includes a program code stored on a computer readable medium 1100 as shown in Fig. 11, and can be loaded and executed by a processing means, processor or computer 1102 to perform the method according to the embodiments of the present disclosure, preferably each of the embodiments described with reference to Figs. 1 to 6. The computer 1102 and the computer program product 1100 are configured to execute the program code sequentially, such that any of the actions of the method are performed step by step or on a real-time basis. The processing means, processor or computer 1102 can preferably be what is usually referred to as an embedded system. Thus, the computer-readable medium 1100 and computer 1102 shown in FIG. 11 are merely illustrative to provide an understanding of the principles and should not be construed as direct illustrations of elements.

[0074] This disclosure may be summarized in the following sections.

[0075] 1. A transmission method including frequency hopping between channels, comprising: adjusting the modulation and coding scheme of each set of channels for each frequency hop; A method in which a set of link adaptation algorithms is used for adjustment of the modulation and coding scheme.

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

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

[0078] 4. The 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. The 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. The method according to any one of items 1 to 5, wherein adjusting the modulation and coding scheme comprises: transmitting a first packet on one channel using a lowest modulation and coding scheme; receiving a response to the first packet; Obtaining a modulation and coding scheme appropriate for the channel; and adjusting the modulation and coding scheme of the next packet based on the appropriate modulation and coding scheme.

[0081] 7. The method according to claim 6, wherein obtaining the appropriate modulation and coding scheme includes receiving an indication regarding the appropriate modulation and coding scheme in the received response.

[0082] 8. The method according to item 6, wherein obtaining the appropriate modulation and coding scheme includes determining the appropriate modulation and coding scheme from the received response.

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

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

[0085] 11. The method according to any one of items 1 to 5, scanning at least a subset of the set of channels to determine channel properties; A method, wherein adjusting the modulation and coding scheme includes adjusting based on knowledge obtained for at least a subset of the set of channels.

[0086] 12. The method of any one of items 1 to 11, comprising not using the set of channels determined to have properties below a first threshold.

[0087] 13. The method according to item 12, wherein the first threshold corresponds to the feasibility of using a minimum modulation and coding scheme for the operating mode used.

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

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

[0090] 16. The method according to any one of items 1 to 15, wherein the hopping sequence is based on the results of a scan of at least a subset of the channels.

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

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

[0093] 19. The 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. The method according to item 19, wherein a frequency hopping rate is determined at each hop.

[0095] 21. The method of claim 19, wherein the frequency hopping rate is determined upon acquiring new information regarding the set of channels.

[0096] 22. The method of claim 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. The method according to item 22, wherein the third threshold corresponds to the feasibility of using a target modulation and coding scheme for the operating mode used.

[0098] 24. The method according to any one of claims 15, 17, 21, 22 and 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 comprising instructions which, when executed on a processor of a transceiver, cause the transceiver to carry out a method according to any one of items 1 to 24.

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

Claims

1. 1. A method of transmission including frequency hopping between channels, comprising: adjusting the modulation and coding scheme of each set of channels for each frequency hop; A method in which a set of link adaptation algorithms is used to adjust the modulation and coding scheme, and multiple link adaptation algorithm instances are used simultaneously.

2. 2. The method of claim 1 , The method, wherein the set of channels comprises a single channel.

3. 2. The method of claim 1 , A method, wherein the set of channels includes a plurality of channels of contiguous frequencies.

4. 4. The method according to claim 1 , further comprising: A method, wherein a number of the plurality of link adaptation algorithm instances in the set of link adaptation algorithms is the same as a number of channels in the set of channels.

5. 5. The method according to claim 1 , further comprising: A method, wherein the channels belonging to each set of channels are adapted during operation.

6. 6. The method according to any one of claims 1 to 5, Adjusting the modulation and coding scheme comprises: Transmitting a first packet on one channel using the most robust available modulation and coding scheme; receiving a response to the first packet; obtaining a modulation and coding scheme appropriate for said channel; adjusting the modulation and coding scheme of a next packet based on the appropriate modulation and coding scheme; The method includes:

7. 7. The method of claim 6, The method, wherein obtaining the appropriate modulation and coding scheme includes receiving an indication regarding the appropriate modulation and coding scheme in the received response.

8. 7. The method of claim 6, The method, wherein obtaining the appropriate modulation and coding scheme includes determining an appropriate modulation and coding scheme from the received response.

9. 9. The method according to any one of claims 1 to 8, 11. A method comprising determining whether a channel is noise-limited or interference-limited, and wherein adjusting the modulation and coding scheme is further based on determining the limitations of the channel.

10. 10. The method according to any one of claims 6 to 9, The method of claim 1, wherein the first packet uses the most robust modulation and coding scheme available for the mode of operation being used.

11. 6. The method according to any one of claims 1 to 5, scanning at least a subset of said set of channels to determine channel characteristics; A method, wherein adjusting the modulation and coding scheme comprises adjusting based on knowledge obtained for at least the subset of the set of channels.

12. 12. The method according to any one of claims 1 to 11, The method includes not using a set of channels determined to have characteristics below a first threshold.

13. 13. The method of claim 12, A method according to claim 1, wherein the first threshold corresponds to the feasibility of using a minimum data rate modulation and coding scheme for the mode of operation being used.

14. 14. The method according to any one of claims 1 to 13, The method includes listing a set of channels having a characteristic that reaches a second threshold.

15. 15. The method of claim 14, A method according to claim 1, wherein the second threshold corresponds to the feasibility of using a maximum data rate modulation and coding scheme for the mode of operation being used.

16. 16. The method according to any one of claims 1 to 15, A method, wherein a hopping sequence is based on results of the scanning of the at least a subset of the channels.

17. 17. The method of claim 16, A method according to claim 1, wherein the hopping sequence is determined for each hop.

18. 17. The method of claim 16, A method wherein the hopping sequence is determined at each scan.

19. 19. The method of any one of claims 1 to 18, comprising: The method, wherein the frequency hopping rate is adjustable based on the determination of an adjustment to the modulation and coding scheme.

20. 20. The method of claim 19, A method according to claim 1, wherein the frequency hopping rate is determined for each hop.

21. 20. The method of claim 19, A method, wherein the frequency hopping rate is determined upon acquiring new information regarding the set of channels.

22. 20. The method of claim 19, The method of claim 1, wherein the frequency hopping rate is determined by hopping to a new channel when an in-use channel has a characteristic below a third threshold.

23. 23. The method of claim 22, A method according to claim 1, wherein the third threshold corresponds to the feasibility of using a target modulation and coding scheme for the mode of operation being used.

24. 24. The method of claim 15, 17, 21, 22 or 23, comprising: A method in which the hopping rate and hopping sequence are determined such that the set of channels used satisfies the second threshold.

25. A computer program comprising instructions which, when executed by a processor of a transceiver, cause said transceiver to perform a method according to any one of claims 1 to 24.

26. 25. A transceiver comprising a transmitter, a receiver and a controller for controlling operation of the transmitter and receiver, the controller being configured to control operation in accordance with a method according to any one of claims 1 to 24.

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