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RETRACTED ARTICLE: Enhancing throughput using channel access priorities in frequency hopping network using federated learning

This article was retracted on 14 May 2024

This article has been updated


The data are sent by the nodes taking part in frequency hopping communications (FHC) utilising carrier frequencies and time slots that are pseudo-randomly assigned. Because of this, a high degree of protection against eavesdropping and anti-interference capabilities is provided. When using FHC in an environment, sharing time and frequency resources, avoiding collisions, and differentiating services are all made more complex as a result of this. A protocol for FHC that is based on dispersed wireless networks is presented by the authors of this research. It is a mechanism for multiple access control, which is prioritised and distributed. The ratio of empty channels metric can be found in the previous sentence. It is possible to provide priority in channel access by assigning different preset ratios of empty channel thresholds to the various traffic classes. Frames from frequency spread segments that have a partial collision are included as well. An analytical model is simulated for the analysis in terms of collision probability, transmission probability, and frame service time in order to carry out a theoretical examination of the performance of FHC. The objective of this inquiry is to determine how well FHC works. The analytical model has been proven correct by the exhaustive simulations as well as the theoretical findings. Cloud platforms are often used in the instruction of the most cutting-edge machine learning techniques of today, such as deep neural networks. This is done in order to take advantage of the cloud's capacity to scale elastically. In order to satisfy the criteria of these sorts of applications, federated learning, has been proposed as a distributed machine learning solution. This is done in order to fulfil the requirements of these kinds of applications. In federated learning (FL), even though everyone who uses the system works together to train a model, nobody ever shares their data with anybody else. Each user trains a local model with their own data, and then communicates the updated models with a FL server so that the data can be aggregated and a global model can be constructed. This process ensures that each user's model is unique. This process is repeated until a global model has been developed. This kind of training not only reduces the amount of network overhead that is necessary to transfer data to a centralised server, but it also safeguards the personal information of the users. Within the framework of this work, we looked at the feasibility of using the FL technique of learning on the many devices that are part of the dispersed network. On a centralised server, we conduct an analysis of the performance of the FL model by comparing its accuracy and the amount of time it takes to train using a range of various parameter value combinations. Additionally, the accuracy of these federated models may be made to reach a level that is comparable to that of the accuracy of central models.

1 Introduction

In difficult communications environments, such those seen in the military, frequency hopping (FH) has been employed extensively [1, 2]. FH terminals are provided with what are widely believed to be pseudo-random (PN) time and frequency hopping sequences during conversations. The end result is a robust anti-interference capability and protection against eavesdropping on private talks. Time–frequency hopping, on the other hand, may be interpreted as a separate subchannel. Spreading provides a large number of sub-channels in the time–frequency domain, allowing several users to send and receive data at the same time without interfering with one another. If the stream travelling through an FH sub-channel has overlap with the streams flowing through other sub-channels, then the information contained in each individual stream may be retrieved using error correction coding. This is so because the lost data can be reconstructed. Because of this, the FH communications system may take use of the advantages of multiplexing [3,4,5] by supporting numerous, simultaneous streams.

Using a multiple access method in conjunction with hopping patterns is recommended for frame transmission and retransmission planning and collision avoidance. This is because the network can serve numerous users at once thanks to the multiple access mechanism. Second, there is the possibility of separating the various types of traffic flows, and these distinct types of traffic should be given priority when using the available channels. Third, it is possible to tell the several traffic streams apart. In order to make the most of the time–frequency channel's available resources, it is necessary to provide greater priority to the transmission of time-sensitive messages and real-time streams that must be sent in a timely manner [6]. Third, it is essential that the FH pattern construction and channel access coordination be executed in a completely omnidirectional method. Independent FH and contention-based channel access provide clear advantages over centralised methods. Some examples of these advantages include a scalable design, autonomous behaviour, and low maintenance requirements. The aforementioned benefits are lacking in centralised operations [7].

The technique for dynamically switching between two user interfaces was shown by the authors of [8]. Transmission was the primary function of the initial interface, which relied on fast hopping. The second interface, which relied on sluggish hopping, was designed primarily for data reception. Since wireless nodes may dynamically switch between channels, congestion could be avoided without the requirement for a dedicated control channel. It was speculated in [9, 10] with FH and it may be used for time division multiple access (TDMA) based multiple access control (MAC). It enhanced the providing of QoS in various ways, including better loss and delay performance. When applied to all users, the hopping sequences established by the authors of [11] allow for a high system throughput with low latency thanks to the difference set-based MAC they offer. All users were subjected to the jumping sequences to get this result. This was done so the system could handle a high volume of data with little delays [12]. The proposed method of interaction Based on the channel's current use and topological data, MAC may suggest an alternative channel. Depending on the condition of the channel, such suggestions may be offered. An analytical paradigm for collaborative MAC is proposed in [13].

2 Federated learning

In the recent past, there has been an increase in interest in the notion of learning from distributed data through edge devices [13]. This interest has continued to grow over the course of many years. The following variables have contributed significantly to the growth in popularity that has been seen. In order for the business to get off the ground, the massive volumes of data that are generated by mobile phones, wearables, and autonomous automobiles need to be handled. It is not always practical to upload all of one's data to a remote server located in the cloud [14]. One of the reasons for this is that these devices have a restricted network capacity, but another cause might be that high propagation delays lead to unbearable latency. Second, the sensitive nature of the data at stake, such as recorded phone calls and videos from a lifelogging app, creates a privacy risk when it is transferred to cloud servers [15]. This risk is compounded by the fact that cloud servers are not always secure. This is due to the fact that cloud servers are accessible to everyone who has a computer and an internet connection. Applications that deal with unstructured data, such as photo and video analytics, may put a strain on the backbone networks owing to the transmission of such enormous volumes of data to a cloud server for processing. This pressure may be caused by the fact that these applications deal with unstructured data. These are some of the reasons why machine learning applications are progressively shifting their data processing and model training tasks to the edge devices. Other reasons include advancements in the storage and computation capabilities of these edge devices. The reason for this shift is that services are increasingly being pushed to devices at the edge of the network rather than to servers located in the cloud. Because of this, federated learning (FL), which is at the intersection of the machine learning and edge computing domains, has grown more popular [16, 17].

Imagine a large number of user devices, such as mobile phones or self-driving cars, each of which has its own individual and distinct collection of photographs taken by the cameras that are located inside the device or on the vehicle itself. For example, a mobile phone. If all of the data that is kept on many different devices can be retrieved in one location, it is feasible to acquire a high-performance machine learning model that has been trained on a very large dataset [18]. This is made possible by having all of the data saved in one location. This opens the way for the acquisition of a model that has been trained on a model that has been trained on a huge dataset.

However, consumers should be made aware that releasing data is not encouraged owing to security concerns. This is something that should be communicated to customers. A type of decentralised machine learning known as FL [19] works very well with edge computing because of its natural match. Recently, it was suggested as a solution to processing needs such as these, and it is particularly well-suited for use in edge computing. The state of Florida ensures the confidentiality of any data held on mobile devices. In spite of the fact that they collaborate on the development of an advanced machine learning model by sharing information, these mobile devices keep their data to themselves. Every node in the network creates its own unique model independently, making use of just the information that is stored locally on that node. After then, the devices will notify a FL server of any modifications to their model parameters, such as changes to their model weights. The server will then use each of these changes in the process of developing a standardised global model. The FL server communicates the merged model to the mobile devices so that further training may take place. This process is continued for the required number of cycles until either the target degree of accuracy is achieved or the training budget is used up, whichever occurs first.

In recent years, FL has seen an increase in popularity due to the fact that its usefulness has been shown in a range of different application fields [20]. The growing popularity of FL may be attributed, in large part, to the many advantages that it provides in contrast to more conventional machine learning (ML) methods [21,22,23,24]. FL is able to accomplish its core computations by using the combined computing capacity of all of its edge devices. As a consequence of the fact that these calculations are carried out in close proximity to the user, the data do not need to leave the device, which results in greater user privacy. In addition, the device used by the user does not need to be unplugged in order for massive volumes of unstructured data, such as video and image files, to be sent [25]. As a direct result of this, the overhead of the network is reduced, and there is a chance that the network latency for applications that need quick decision making may become more acceptable.

Two different strategies for cutting down on communication expenses were offered by Konecny et al. [26]. Their methods include learning from a constrained space that is then parameterized by making use of a fewer number of variables and learning from a model that is more condensed. The FL protocol has been updated by others in order to cut down on the communication overheads. Wang et al. [27] made the suggestion that a feedback loop should be included in the FL process. The nodes get feedback information on the overall trend of model update at the conclusion of each cycle. Each node evaluates their own update to see whether or not it conforms to this overall trend and whether or not it is relevant enough to contribute to model improvement. Their method may significantly cut down on the amount of communication overhead required by ensuring that it does not upload any unnecessary changes to the server. As a result of the need to carry out ML operations on edge devices with limited resources while simultaneously exchanging the model parameters with the server, performance is a significant concern in this framework. Several studies [27,28,29,30,31,32,33] have been conducted to investigate the performance of federated operations.

Within the scope of this work, we suggested novel system architecture for distributed networks that make use of FH channels. The contributions of this paper are as follows:

  1. 1.

    The FHC was developed by including patterns into the design. Because of this, the procedure ends up being more effective. The data frames are then chopped up and arranged in matrices that are made up of frequency resource blocks. The ratio of empty channels is a measure that was established in order to offer an indicator of the resource utilisation in a matrix. It does this by counting the number of empty channels relative to the total number of channels. The transmissions of the active traffic flows that are now present in the network are what define the utilisation level of this resource. Only the flow in question will be permitted to send data if the percentage of vacant channels is below a certain threshold. If this does not take place, there will be a collision in the virtual world.

  2. 2.

    Differentiating the channel access priority may be accomplished by giving a higher-priority traffic class when ratio of empty channels threshold that is much higher than the others.

  3. 3.

    It is possible to combine the successfully received segments with the ones that were retransmitted in order to conduct decoding when a frame cannot be decoded due to an excessive number of its segments overlapping with those of other frames (also known as a “real collision”). A greater level of channel resource utilisation in FHC networks is achieved as a result of the reusing of portions of frames that have been corrupted.

  4. 4.

    An investigation is conducted to see how successful an analytical model for a decentralised network may be. All of these metrics—the frame service time, the throughput for individual users, the throughput for the network, and the overall throughput—were determined from our computations.

Even if the offered methods show promise for boosting the effectiveness of federated training, utilising them and fine-tuning FL's parameters both require knowledge of the effects that various settings have in order to be successful. This study analyses how different training criteria, such as the total number of training cycles, affect training duration as well as the degree to which federated models are correct. Specifically, the study looks at how training duration is affected by the total number of training cycles. We also investigate the impact that the customers had on the network in terms of the number of nodes that were involved, the magnitude of the difference that their data made, and the variations that were produced by the participation of the same or different groups of nodes throughout the course of multiple rounds of training. In none of the studies have the numerous effects that were shown to have been brought about by the participants in the earlier research been subjected to a comprehensive investigation.

3 Proposed model

Let us say that there are \(F\) carrier frequencies that are utilised for transmissions and that the time is broken up into slots that each last of a second. We organise \(T\) time for the purpose of channel resource scheduling slots together with the \(F\) carriers into a matrix that consists of \(F \times T\) time–frequency resource blocks. One unit of channel resource allocation is referred to as a block. After doing so, a coded data frame is then put into a resource matrix after being partitioned into \(S\) segments such that \(S \le T\). One frame segment utilises a resource block. In the context of operationally plausible configurations, a station might have a single radio frequency (RF) chain or many RF chains. That means you may send and receive the same amount of segments on different carriers at the same time, and then switch between them in the next time frame.

We take into consideration a distributed network that makes use of frequency hopping (FHC) communications in this study. In order to do the hopping in both the time and frequency domains, a pair of transceivers chooses two PN sequences that are common to both domains. Because there is no centralised controller, the spreading patterns that are used by the various pairs of stations are determined separately and at random.

3.1 Channel access plan for FHC networks: FL framework

In order to facilitate differentiated service delivery, we use a distributed and prioritised multiple access mechanism in FHC-based networks. A framework for distributed machine learning (ML) on edge devices is what we want to accomplish with FL. In the FL process, the two most important entities are the data owners, sometimes known as the client, and the server which is interpreted in terms of a network of nodes connected to a server.

Let's represent the set of \(N\) nodes as \(n = n_{1} , n_{2} , \ldots N\) where each node has a data \(D_{{{\text{frame}}}}\) saved on the network devices, such as their smartphones or computers. In traditional methods, every node transmits their data to the server, which then trains a standard model, model, in a centralised manner utilising all of the nodes data using the formula \(D_{{{\text{frame}}}} = \bigcup\nolimits_{i = 1}^{n} {D_{{{\text{frame}}}} \left( i \right)}\). However, as was said previously, this is not practical for all applications because of issues over users' privacy and the constraints imposed by the edge computing devices in terms of their network capacity. In FL, the nodes do not share their private data with the remote server; rather, they develop a local model by making use of their own data \(D_{{{\text{frame}}}} \left( i \right)\). Following this, judgements are made about the network, and the trained model's parameters are communicated with the FL server based on the information provided by this model. Because of this, the FL server is unable to obtain unauthorised access to the data stored on the nodes. The server is in charge of collecting all of the local model parameters and then integrating them into a federated model, which is a single global model consisting of all of the local model parameters combined together. The trained model is then sent to the customers so that they may make further improvements. This procedure is repeated for multiple rounds of training.

  • One of a neural network's hyper-parameters is its optimizer, often known as its learning rate. This is true for both regional and international models. This decision is taken at the same time that the framework for the model that all of the nodes will be training is established.

  • After then, the server will send the model and its parameters out to all of the nodes. During the first round, the model that is transmitted does not have any training. The server will then broadcast the model that has been aggregated from all of the node’s local training in the subsequent rounds.

  • Participating nodes may grab the model and tweak its parameters to fit their local data if they so want throughout the training process. The objective of the local training approach for each node is to identify the ideal model parameters that, when applied to the node's own local data, will provide the least amount of model loss that is even remotely achievable. The ultimate objective is to determine which model parameters are optimal, and this objective will be achieved after ideal model parameters have been located.

  • After each node has completed its training, that node will share its trained model with the FL server and updates to the model's parameters.

  • The aggregation of models on a global scale will take place when nodes that are participating in the programme communicate their models with the server.

It is essential to keep in mind that the number of nodes that are actively participating in the training may fluctuate at various stages during the operation. It is conceivable that certain nodes may be unable to participate in the training procedure; for instance, their device may be turned off while the session is in progress. Because of this, the server only expects to receive model updates from a subset of all nodes throughout each cycle of the training process. This is because of the way the training process is designed.

Because the FL technique does not need nodes to report back to the server, those nodes do not do so. When nodes just communicate the parameters of their own particular local models with one another, the network overhead is dramatically reduced as compared to transferring the data across the network. The parameters of the model will be transmitted between the nodes and the server via the use of a standard FL protocol. The procedure will not have any modifications made to it, such as data compression (26), for example. After a client has finished uploading its local model to the server at the beginning of each round, another client will then begin receiving the round's aggregated model. Each time a new round begins, the nodes upload the local models they have been working on to the server. At each of these steps, the parameters are repeatedly changed and swapped with one another. Each and every one of the customers who take part in the campaign will not need to worry about this aspect of the experience. There is a one-to-one relationship between the number of clients, the number of rounds, and the size of the model in terms of the communication costs that are connected with each of these factors.

It is possible for many stations within a geographically scattered network to simultaneously deposit their frame segments into the resource matrix. It is possible that the stations will do this. Because every station makes its own independent choice about the frequency hopping (FH) sequences that it will broadcast, the spreading patterns that are produced can never be totally orthogonal. Because of this, it is conceivable that certain segments from a number of different senders will be placed in the same blocks, making it difficult to receive them in the correct sequence. As a result of this, channel coding is employed in order to efficiently rebuild a frame from the successfully received sections of that frame without any overlapping occurring. This is done in order to avoid any errors caused by the possibility of overlapping. If the non-overlapping sections are insufficient to decode the data in the right manner, however, the frame will have to be resent. When it comes to the FHC systems, it is to everyone's interest that the correctly received segments be put to use in the process of decoding rather than being thrown away, and this is because throwing away the segments would be a waste.

3.2 Linear randomisation

As a network coding strategy we assume an initial data frame, which we will refer to as \(D_{{{\text{frame}}}}\), is cut into \(S\) segments, as shown in the equation \(D_{{{\text{frame}}}} = \left[ {D_{1} , D_{2} , \ldots , D_{s} } \right]^{{\text{T}}}\), where the row vector \(D_{l} \left( {S = 1, 2, \ldots , s} \right)\) represents the sth segment of the data frame. The sender will first produce a random coefficient matrix (CM) with a size of \(S \times S\), which will be represented by the equation \(C = \left[ {c_{1} , c_{2} , \ldots , c_{s} } \right]^{{\text{T}}}\) is a \(1 \times S\) vector that is also known as the coefficient vector (CV). It is defined by the expression \(c_{s} = \left[ {c_{1} , c_{2} , \ldots , c_{s} } \right]\). After that, an original data frame is coded into \(S\) segments by using the matrix multiplication such that \(D_{{{\text{frame}}}}{\prime} = C { }D_{{{\text{frame}}}}\). The CM is not the only one that can code the original data, and that multiple CMs may do so. After the receiver has accumulated a sufficient number of \(s\) CPs, the CVs included may be arranged into a new CM.

If the CVs are linearly independent, as is quite likely given that the CVs are generated at random, then the rank of the newly merged CM will be \(s\). This is the case for as long as the CVs are linearly independent. This will continue to be the case for as long as there is a continuous flow of CVs being produced. \(C^{ - 1} { }D^{\prime}_{{{\text{frame}}}}\) needs to be applied in order to decode the initial data is referred to as \(D_{{{\text{frame}}}}\).

A new CM is produced at random for each retransmission of a frame and is used for linear coding in the same manner as described in [9]. The advantages will be discussed in the following paragraphs. Since the hopping sequences of the stations do not change, the locations of the successfully received segments in the resource matrix will remain the same even if the same stations conflict again in the retransmissions. This ensures that the locations of the segments remain the same. However, the CMs used in this transmission are different from those used in the broadcasts that came before it. As a consequence of this, it is possible that the segments that have been correctly received will still need to be linked with the segments that have been received in the past in order to decode the message. As a result, the network coding technique includes random dispersion in the time and frequency domains in addition to randomisation in the coding domain. This improves both the ability to reduce collisions and the efficiency with which resources are used.

3.3 Ratio of empty channels

In this paper, we propose ratio of empty channels \(\left( {R_{{{\text{EC}}}} } \right)\) to denote the activities carried out by stations inside a resource matrix. The \(R_{{{\text{EC}}}}\) is defined as,

$$R_{{{\text{EC}}}} = \frac{{B_{t} }}{FT}$$

when there is a total of \(B_{t}\) blocks that are filled by the segments that are being broadcast from the stations that are transmitting data at the moment. In a configuration that is representative of the actual world, a station may have a single RF chain or multiple chains, depending on the configuration of the system. As a consequence of this, it is able to determine whether or not there are signals present inside a resource matrix. It is possible to create an approximation using \(R_{{{\text{EC}}}}\) based on the number of empty resource blocks in a matrix because the segments are distributed in a consistent manner throughout the matrix. This is possible due to the fact that the matrix as a whole contains no empty resource blocks.

3.4 Prioritised channel access

Traffic may be separated into access categories with varying priority according to the quality of service needs. In order to differentiate the services that are offered, various ratio of empty channels levels have been assigned to the different access mechanisms. The greater an access mechanisms priority, the more attention it receives.

In most cases, it is associated with a larger \(R_{{{\text{EC}}}}\) value. If the \(R_{{{\text{EC}}}}\) is lower than the threshold that has been set for the flow's priority, it is feasible to send out the frames of a waiting flow. This is only the case if the flow's priority has been set. This indicates that the flow's segments will be deposited into the subsequent resource matrix in the same order as their respective FH sequences are in. On the other hand, if the \(R_{{{\text{EC}}}}\) value at the moment is higher than the threshold, the station will carry out exponential backoff.

Note that varied \(R_{{{\text{EC}}}}\) threshold is used to provide prioritised channel access. This is important information to keep in mind. When there is a low volume of traffic in the network, low-priority frames may be sent since the \(R_{{{\text{EC}}}}\) is regularly low enough to fall below the needed thresholds. This allows for the transmission of lower-priority frames. However, when the volume of traffic increases, the scheduling scheme will start to reject lower-priority frames since the \(R_{{{\text{EC}}}}\) will be more than their thresholds. This will allow the scheme to conserve resources for higher-priority flows, which will assure quality of service. The \(R_{{{\text{EC}}}}\) will then reduce since there will be less high-priority traffic to transport, and the channel resources will be available to be used by low-priority flows. This allows high-priority flows to get transmission chances even when the network is congested. Low-priority flows, on the other hand, may only broadcast during periods of low demand for time and frequency because of the \(R_{{{\text{EC}}}}\) thresholds.

3.5 Methods for avoiding collisions and retransmitting

We will be able to get a full-rank CM and correctly decode a frame so long as the \(s\) coded elements of the frame are received in the correct manner. In the event that this does not take place, the frame gearbox will fail, which will ultimately lead to a collision in the real world. Under these conditions, the recipient will not send an acknowledgement of receipt back to the sender before the expiration of the allotted amount of time. Instead, for the purpose of collision avoidance and retransmission, making use of the exact same procedure as for the virtual collision. At the receiver, the chance of successfully decoding a frame is increased by combining the various sections of the frame that have been collected through several unsuccessful transmission attempts. This is done in order to reduce the amount of time spent trying to decode a frame.

4 The frequency hopping communication (FHC) model

In this section, we are going to work on constructing an analytical model so that we can quantify the performance of the FHC model. The method known as mean value analysis is the one that we will be applying in this study. This method, which is grounded on the renewal reward theory [34], may be used to describe the station's macroscopic behaviour. When the station is participating in a frame service cycle, this technique is used. Once steady state has been reached, it is possible to get the average statistics of the performance measures. As part of this study, an analytical model of a fully loaded, single-hop network was created. Even while the work that is going to be presented may be generalised to apply to a number of other access mechanisms, we are only going to concentrate our first study on one access mechanism. This helps us avoid unnecessary formulation and makes the model simpler to grasp.

4.1 Distribution of the ratio of empty channels and probability

We take into consideration a distributed network of \({\mathbb{K}}\) stations, all of which are within each other's range of coverage. The \(R_{{{\text{EC}}}}\) is an extremely important parameter since it is the one that decides whether a frame may be delivered or if a virtual collision will take place. Assume for the sake of argument that during a resource matrix, \({\mathbb{K}}\) stations will continue to actively broadcast, meaning that they will deposit their parts in the matrix, and that a total of \(B_{{\mathbb{K}}}\) resource blocks inside the matrix are now being used. As a result of the segments overlapping one another, \(B_{{\mathbb{K}}}\) is a random variable, and \(S \le B_{{\mathbb{K}}} \le \min \left\{ {{\mathbb{K}}S, FT} \right\}\). The following derivation will show you how to find \(B_{{\mathbb{K}}}\) distribution.

When the \({\Bbbk }\)th station \(\left( {{\Bbbk } = 1, 2, \ldots , {\mathbb{K}}} \right)\) deposits \(S\) segments into the matrix, \({\Bbbk }\) segments are placed into the blocks that are currently empty, and \(S_{{\mathbb{K}}}\) segments are placed into the blocks that are currently occupied (overlapping with segments that are already there). To phrase it another way, the number of blocks that are occupied has grown by \({\mathbb{K}}\). As a result, we obtain \(B_{{\mathbb{K}}} = \sum\nolimits_{{{\Bbbk } = 1}}^{{\mathbb{K}}} {S_{{\mathbb{K}}} , S_{1} = S^{\prime}.}\)

The function of the joint probabilities of the RVs \(S_{{\mathbb{K}}}\) for \({\Bbbk } = 1, 2, \ldots , {\mathbb{K}}\) leads to the conclusion that the probability of \(B_{{\mathbb{K}}}\) thereby increases the probability that \(R_{{{\text{EC}}}}\) is larger than a threshold \(\tau_{{{\text{th}}}}\) by assuming that \({\mathbb{K}}\) stations are sending out signals, we may calculate the likelihood of a virtual collision., is

$$p_{{{\text{virtual}}}} = \Pr \left\{ {\tau > \tau_{{{\text{th}}}} } \right\} = 1 - \Pr \left\{ {B_{{\mathbb{K}}} \le FT\tau_{{{\text{th}}}} } \right\}$$
$$p_{{{\text{virtual}}}} = 1 - {\text{CDF}}\left( {FT\tau_{{{\text{th}}}} } \right)$$

\({\text{CDF}}\left( . \right)\) is the cumulative distribution function of the normal distribution.

4.2 The actual probability of collision

If \(S\) or more of the frame's segments are received in an exact manner, it may be possible to successfully decode the frame. In this scenario, there is going to be an actual collision. The actual probability of a frame colliding with another, denoted by the symbol \(p_{{{\text{real}}}}\), is the probability that there will be fewer segments without overlapping \(S\). This probability increases as the number of segments without overlapping S decreases.

According to the concept that was just presented, the \(R_{{{\text{EC}}}}\) is equal to \(\tau_{{\Bbbk }}\) when there are \({\Bbbk }\) stations that have inserted segments in a matrix. When one segment is deposited into the matrix by the \({\Bbbk }\)th station in a random and uniform fashion, the likelihood that the segment will be placed in a resource block that is already occupied (i.e., will have overlapping with segments that are already there) is \(\tau_{{\Bbbk }}\). This means that the probability of the segment being placed in a resource block that is already occupied is equal to the probability that the segment will be placed in a resource block that is already occupied.

As a result, the expectation for the number of segments that will be put into an idle resource block is denoted by the symbol \(B_{{\mathbb{K}}}\), is given by the formula

$$E \left[ {B_{{\mathbb{K}}} \left] { = E } \right[S \left( {1 - \tau_{{\Bbbk }} } \right)} \right]$$

The formula for calculating the expected \({R}_{\mathrm{EC}}\) for \({\mathbb{k}}\) stations is as follows:

$$E \left[ {\tau_{{\Bbbk }} } \right] = \frac{{E \left[ {B_{{\mathbb{K}}} } \right] + E \left[ {S_{{\Bbbk }} } \right]}}{FT}$$

where \(E \left[ {S_{{\Bbbk }} } \right]\) represents the \(R_{{{\text{EC}}}}\) when just a single station puts a frame in a matrix. It can be said with absolute certainty that \(E \left[ {B_{{\mathbb{K}}} } \right] = \frac{S}{FT}\).

Thus, the real collision probability is equal to the possibility that fewer than \(S\) segments will be put in idle resource blocks when a frame is deposited into a matrix by the \({\Bbbk }\)th station. This probability is also known as the real collision probability \(\left( {p_{{{\text{real}}}} } \right)\) such that,

$$p_{{{\text{real}}}} = \mathop \sum \limits_{s = 0}^{S - 1} C_{s} \left[ {\left( {1 - \frac{S}{FT}} \right)^{{{\Bbbk } - 1}} } \right]^{s} \left[ {1 - \left( {1 - \frac{S}{FT}} \right)^{{{\Bbbk } - 1}} } \right]^{s - 1}$$

4.3 Collision probability

The entire collision probability for a frame transmission, designated as \({p}_{\mathrm{collision}}\), may be stated as

$$p_{{{\text{collision}}}} = p_{{{\text{virtual}}}} + p_{{{\text{real}}}}$$

This takes into account both the virtual and actual collisions.

4.4 The throughput

It is possible for a frame to be successfully decoded as it is being sent, and it is also possible for more than \(S\) segments to be received in the right format (for the sake of ease of analysis, accumulative decoding is ignored here).

Therefore, the probability of successful transmission, given by the symbol \({p}_{\mathrm{success}}\), may be computed using

$$p_{{{\text{success}}}} = p_{{{\text{trans}}}} \left( {1 - p_{{{\text{collision}}}} } \right)$$

The per-user throughput \(\left( {\eta_{{{\text{user}}}} } \right)\) is thus expressed as

$$\eta_{{{\text{user}}}} = \frac{{p_{{{\text{success}}}} L_{{{\text{payload}}}} }}{\delta K}$$

where \(L_{{{\text{payload}}}}\) is the payload length of a frame measured in bits.

The formula for calculating the network throughput \(\left( {\eta_{{{\text{network}}}} } \right)\) is as follows:

$$\eta_{{{\text{network}}}} = K.\eta_{{{\text{user}}}}$$

where a total of K stations is present in the network.

4.5 The typical duration of frame service

A frame's service time is the time it takes from competing to be put into a resource matrix through delivery or rejection due to the retry limit. A frame, on average, requires \(E \left[ {B_{{\mathbb{K}}} } \right]\) and \(E \left[ {\tau_{{\mathbb{K}}} } \right]\) matrices for transmission trials The duration of a matrix is denoted by the symbol \(T\); hence, the mean service time may be calculated as follows:

$$T_{{{\text{mean}}}} = \delta K\left( {E \left[ {B_{{\mathbb{K}}} } \right] + E \left[ {\tau_{{\mathbb{K}}} } \right]} \right)$$

5 Simulation results

Extensive simulations utilising an event driven simulator have been carried out so that the analytical model can be validated and the performance of the FHC that has been suggested can be assessed. Since the network can be reached with just one hop, no hidden terminals exist. Each station is overwhelmed with an excessive amount of traffic.

The collision probabilities, for a varying number of station counts are shown in Fig. 1.

Fig. 1
figure 1

Collision probability versus number of stations

There is a range of sizes available for the time–frequency resource matrix, denoted by the number of frequency points. First, the suggested analytical model has been validated due to the consistency between the findings of the analysis and those of the simulation. Second, it is clear that the number of users contributes to an increase in the likelihood of a collision occurring. The collision probability is at its highest when \({\mathbb{K}}\) is equal to 10, and it is at its lowest when \({\mathbb{K}}\) is 15. These findings are to be anticipated on account of the fact that the \(R_{{{\text{EC}}}}\) rises either when the traffic load is raised, i.e., the number of resource allocation units is decreased. Therefore, there is less of a potential for transmission, and there are also fewer segments in a matrix that do not overlap with one another. As a direct result of this, the likelihood of both virtual and actual collisions has increased.

The transmission probability, of a station throughout is shown in Fig. 2. When there are more people using the system, or when there are less people using the system, the transmission probability goes down. This is due to the fact that the \(R_{{{\text{EC}}}}\) is larger on average, which results in a station having a lower likelihood of transmitting. In the meanwhile, a higher \(R_{{{\text{EC}}}}\) leads to a greater increase in the true collision probability. This results in a lower transmission probability and the lengthened waiting period.

Fig. 2
figure 2

Transmission probability versus number of stations

The per-user throughout is shown in Fig. 3. Because of the increasing \(R_{{{\text{EC}}}}\) and collision probability, per-user throughout fall at an alarmingly rapid rate as the number of users continues to rise. It is an interesting observation to make that when the number of users is low (the traffic load), the per-user throughput achieves the maximum value, although the values achieved using the other two resource matrices are identical. Because the planning of additional data frames may be accomplished in the same amount of time, this paves the way for the delivery of additional frames. This is a possibility due to the fact that frames can be stored in a matrix without coming into contact with one another. When there is a high demand on the network, the \(R_{{{\text{EC}}}}\) is still unacceptable high in a tiny resource matrix, which increases the risk of collisions occurring. A greater value for \({\mathbb{K}}\) enhances channel resource utilisation, which ultimately results in a larger throughput in this particular scenario.

Fig. 3
figure 3

Throughput (per user) versus number of stations

The typical duration of frame service is shown in Fig. 4. The number of users contributes to a rise in the value of since it is mostly associated with the collision. A high volume of traffic leads to a lower \(R_{{{\text{EC}}}}\), which in turn results in a reduced collision probability.

Fig. 4
figure 4

Frame service time versus number of stations

Figure 5 illustrates how the network performance changes depending on the number of stations. We are able to see that network throughput has a spike initially and then a decline after that. There is a consistent pattern that emerges across all of the varying number of stations. The maximum throughput appears roughly with the stations \(K = 15\), respectively.

Fig. 5
figure 5

Network throughput (Mbps) versus number of stations

The research indicates that it is feasible to attain maximum network performance with optimal traffic load. During times of low network traffic, performance degrades as a result of insufficient exploitation of the time–frequency resources that are readily available. When there is an excessive amount of traffic load, there is also a higher probability of collisions, which leads to a higher \(R_{{{\text{EC}}}}\) value. This causes the throughput to decrease. This occurs when there is an excessive number of people visiting the site. The number of resources that are utilised falls to a lower level as a direct result of this scenario. When there is a lot of traffic, reducing the \(R_{{{\text{EC}}}}\) as much as possible makes it possible to be more successful in allocating resources and preventing accidents.

In order to complete our investigation, we have been putting our federated learning model through its paces. The FL model's test and training accuracy are shown in Figs. 6 and 7, respectively. An iterative technique was used during the training of the FL model. There is a possibility that the accuracy of the training as well as the length of time necessary to train the federated model will be affected by the number of rounds that the exercise consists of. We do several experiments with altering the number of training cycles in order to examine how each round from five to one hundred, noting both the accuracy and the total number of the measurements of the time spent training. We train a federated deep learning network so that we may achieve this goal. During the whole of this project, we will be providing training for both a centralised and a federated approach to the main network. We employ the same network topology and hyper-parameters for both of our models, federated and central, so that we can make it easier to compare the two types of models. This structure, as well as the responsibility of allocating it to each node, is the responsibility of the FL server. The results of a comparison of the test accuracy for fixed nodes, variable nodes, federated models, and central models are shown in Fig. 8. A comparison of the amount of time required for training with fixed nodes, variable nodes, federated models, and central models is shown in Fig. 9. Because the FL model saves data locally on the network devices, we are unable to train a central model because we do not have access to all of the data that is required. Instead, we are going to build the central model by merging all of the local models, which will result in an accuracy that is just somewhat worse. The degree to which the FL model loses its accuracy may be minimised, as was previously noted, either by increasing the number of nodes who participate or by lengthening the number of training sessions. Both of these options are available.

Fig. 6
figure 6

Test accuracy (%) versus epochs

Fig. 7
figure 7

Training accuracy (%) versus epochs

Fig. 8
figure 8

Test accuracy comparison

Fig. 9
figure 9

Training time comparison

6 Conclusion

We have suggested a multiple access system for FHC in distributed networks using federated learning. This approach is able to make full use of the multichannel resources, prevent collisions, and give channel access priority in a distributed way. The results of the simulation have not only shown that the analytical model is accurate but also shown to achieve maximum network performance is possible. FL makes it possible for individuals in different places to work together on the training of a model without any of them having to disclose any of their personal information. This not only makes the user's privacy more secure but also reduces the amount of overhead caused by communication. Using a federated data format, we built a deep learning model for this study. Following that, we investigated how the federated parameters affect the amount of time required for the model's training as well as its accuracy. In this article, we explain the importance of basing your choices on these considerations so that you may make an informed choice. We show that despite FL's ability to improve privacy and reduce the amount of communication overhead, it is still capable of achieving an accuracy that is comparable to that of a central model. In order to broaden the scope of our proposed work in the future by using additional models and taking into account the variety of nodes that are already present in the network.

Availability of data and materials

No data available.

Change history



Frequency hopping communications


Multiple access control


Federated learning


Frequency hopping




Time division multiple access


Quality of service


Machine learning


Coefficient matrix


Coefficient vector


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YH conceptualised this research and co-wrote the first version of the paper; XZ took part in the formal analysis of the data and helped validate the findings.

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Han, Y., Zhu, X. RETRACTED ARTICLE: Enhancing throughput using channel access priorities in frequency hopping network using federated learning. J Wireless Com Network 2023, 101 (2023).

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