Cooperative Spectrum Sensing
The Fig. 7 presents various performance metrics of Cognitive Radio Networks (CRN) plotted against Signal-to-Noise Ratio (SNR) in decibels (dB). The throughput (in bits per second) increases as SNR increases. At SNR = -10 dB, throughput is approximately 0.5 bps. At SNR = 0 dB, throughput increases to around 1 bps. At SNR = 10 dB, throughput reaches approximately 2 bps. Higher SNR leads to significantly improved throughput, indicating that better signal quality allows for higher data rates. The Latency (in seconds) decreases as SNR increases. At SNR = -10 dB, latency is around 0.008 seconds. At SNR = 0 dB, latency reduces to approximately 0.005 seconds. At SNR = 10 dB, latency further decreases to about 0.002 seconds. Improved SNR results in lower latency, suggesting that better signal conditions facilitate faster communication.
Spectrum utilization remains constant across all SNR levels. Spectrum utilization is approximately 10 for all measured SNR values. The system maintains consistent spectrum usage regardless of changes in SNR, indicating efficient spectrum management. PDR stays constant irrespective of changes in SNR. PDR is consistently around 1 (or 100%) for all SNR levels. The cognitive radio network exhibits robust delivery performance, ensuring high packet delivery rates regardless of signal quality. QoS remains stable across the SNR range. QoS hovers around 0.9 (90%) for the entire SNR range. This stable QoS indicates that the system effectively manages network performance even with varying SNR conditions. Energy efficiency (measured in bits per joule) increases with rising SNR. At SNR = -10 dB, energy efficiency is approximately 1 bit/J. At SNR = 0 dB, it rises to about 2 bits/J. At SNR = 10 dB, energy efficiency reaches around 5 bits/J. Better signal quality enhances energy efficiency, allowing for more effective energy use in data transmission. Cooperative Spectrum Sensing shows that higher SNR leads to better throughput, reduced latency, improved energy efficiency, and stable delivery and quality of service. The consistent performance metrics for spectrum utilization and PDR demonstrate the network's robustness and efficiency in resource management.
Task distribution among Users
The Fig. 8 presents various Task Distribution Performance Metrics in Cognitive Radio Networks (CRNs).
Task distribution among Users in spectrum sensing shows that Higher SNR leads to better throughput and energy efficiency while reducing latency. The consistent performance of spectrum utilization, PDR, and QoS indicates robust and efficient resource management in cognitive radio networks, ensuring reliable communication even in varying signal conditions.
Optimal Spectrum sharing
The Fig. 9 presents various Optimal Spectrum sharing in Cognitive Radio Networks (CRNs). It presents a comprehensive overview of the performance metrics for cognitive radio networks as a function of SNR. The trends show that higher SNR leads to better throughput and energy efficiency while reducing latency. The consistent performance of spectrum utilization, PDR, and QoS highlights the robustness of cognitive radio networks in maintaining reliable communication even in varying signal conditions. These results emphasize the importance of improving SNR in enhancing the overall performance of cognitive radio networks.
Energy Minimization
The Fig. 10 presents Energy Minimization in Cognitive Radio Networks.
The Fig. 10 clearly illustrates the effectiveness of energy minimization strategies in CRNs. The quantitative results demonstrate that, through dynamic spectrum access and optimized power allocation, it is possible to significantly enhance both energy efficiency and spectrum utilization. Future work should focus on real-world implementations and further optimizations in energy management strategies.
Performance Parameters:
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Throughput (T)
Throughput measures the rate of successful data transmission over the network. In CRNs, it is affected by spectrum sensing, channel switching, and the presence of primary users (PUs).
Throughput CRN= Number of Successfully Transmitted Bits/ Total Transmission Time – (1)
Throughput CRN = R × Utilization Factor × (1 − PPU)
Where:
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RRR is the data transmission rate (bits per second).
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Utilization Factor is the fraction of time the channel is used for data transmission.
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P PU is the probability of primary user activity.
(2) Energy Consumption (E)
Energy consumption in CRNs includes the energy used for data transmission, spectrum sensing, and channel switching. The total energy consumption can be represented as:
E CRN = E Transmission+ E Sensing+ E Switching - (2)
Where:
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E Transmission is the energy used for data transmission.
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E Sensing is the energy spent in spectrum sensing.
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E Switching is the energy used when switching channels.
To calculate these components:
E Transmission=P Transmit ×T Transmit
Where P Transmit is the transmission power, and T Transmit is the transmission time.
E Sensing=P Sensing × T Sensing
Where P Sensing is the power consumed during sensing, and T Sensing is the time spent on spectrum sensing.
Energy for Switching :
E Switching= P Switch × T Switch
Where P Switch is the power used during channel switching, and T Switch is the time for switching.
3. Spectral Efficiency (SE)
Spectral efficiency measures how efficiently the available spectrum is utilized. It is defined as the throughput per unit bandwidth and can be influenced by spectrum sensing accuracy, channel availability, and interference.
Spectral Efficiency CRN = (Throughput CRN/ Bandwidth) -(3)
In a dynamic environment, accounting for sensing accuracy and channel availability:
Spectral Efficiency CRN= ((R× Utilization Factor × (1 − PPU))/Bandwidth)
Where:
These equations reflect the unique characteristics of CRNs, including dynamic spectrum management, energy efficiency considerations, and adaptive spectrum usage.
4.Latency
In CRNs, latency includes additional delays due to spectrum sensing and channel switching. The total latency can be expressed as:
Latency CRN =Transmission Delay + Propagation Delay + Queuing Delay + Processing Delay + Sensing Delay + Switching Delay − (4)
5.Packet delivery ratio:
In CRNs, the PDR is affected by spectrum availability and interference from primary users (PUs). It can be expressed as:
PDR CRN = (Number of Packets Successfully Delivered/Number of Packets Sent) ×100% -(5)
Factors that can reduce PDR in CRNs include:
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Interference from PUs, which can cause packet loss.
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Frequent channel switching due to dynamic spectrum changes.
6.QOS
QoS in CRNs takes into account metrics like latency, PDR, spectrum availability, interference levels, and channel utilization. A comprehensive QoS score can be calculated by considering these parameters, typically using a weighted sum approach:
QoS CRN=w1(1/(Latency CRN)) + w2 (PDRCRN) + w3 (Spectrum Availability) − w4(Interference Level)
− (6)
Performance Parameters Table
Table 1 summarizing the performance parameters as the number of users varies from 1 to 200, with a total bandwidth of 100 MHz
Table 1
The performance parameters for 1 to 200 number of users and bandwidth of total bandwidth of 100 MHz.
Number of Users | Throughput (Mbps) | Energy Efficiency (bps/J) | Spectrum Utilization (%) | Latency (ms) | Packet Delivery ratio (%) | Quality of Service |
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1 | 1 | 0.5 | 1 | 0.01 | 95 | 0.8 |
10 | 10 | 0.8 | 10 | 0.1 | 94 | 0.85 |
50 | 50 | 1.2 | 50 | 0.5 | 92 | 0.9 |
100 | 100 | 1.5 | 100 | 1.0 | 90 | 0.95 |
150 | 150 | 1.1 | 150 | 1.5 | 88 | 0.9 |
200 | 200 | 0.9 | 200 | 2.0 | 85 | 0.87 |
Figure 11 (a): Energy Minimization in Cognitive Radio Networks for 1 to 200 number of users and bandwidth of total bandwidth of 100 MHz
Tables 1 and 2 summarizing the performance parameters as the number of users varies from 1 to 5000, with a total bandwidth of 100 MHz
Table 2
The performance parameters for 1 to 5000 number of users and bandwidth of total bandwidth of 100 MHz.
Number of Users | Throughput (Mbps) | Energy Efficiency (bps/J) | Spectrum Utilization (%) | Latency (ms) | Packet Delivery ratio (%) | Quality of Service |
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1 | 1.2 | 0.6 | 0.00012 | 0.05 | 97 | 0.85 |
100 | 120 | 1.5 | 0.012 | 0.30 | 95 | 0.88 |
500 | 500 | 2.0 | 0.05 | 0.50 | 93 | 0.90 |
1000 | 950 | 2.3 | 0.095 | 0.75 | 90 | 0.92 |
2500 | 2300 | 1.9 | 0.23 | 1.50 | 85 | 0.87 |
5000 | 4500 | 1.5 | 0.45 | 3.00 | 80 | 0.85 |
5.Analysis of Results
The throughput of the cognitive radio network exhibits a remarkable growth trend as the number of users increases, escalating from 1.2 Mbps for a single user to an impressive 4,500 Mbps when accommodating 5,000 users. This significant increase indicates that the network is adept at leveraging its resources to facilitate a high volume of data transmission. As more users connect, the cognitive radio network efficiently allocates available bandwidth, ensuring that each user experiences enhanced connectivity and speed. This capability is particularly important in an era where data demands are surging due to applications such as video streaming, online gaming, and cloud computing. The ability to maintain high throughput in a multi-user environment demonstrates the robustness of cognitive radio technologies in managing spectrum dynamically and effectively, making it a promising solution for meeting the growing demands of wireless communication.
The analysis of energy efficiency reveals an intriguing pattern: energy efficiency initially climbs with the increase in users, reaching a peak of 2.3 bps/J for 1,000 users before experiencing a decline to 1.5 bps/J for 5,000 users. This initial increase suggests that the cognitive radio network employs optimal strategies for power allocation, allowing it to handle user requests efficiently while conserving energy. However, the subsequent decrease in energy efficiency indicates that as the user base expands, the network may face challenges related to congestion and interference. Increased demand can lead to suboptimal resource allocation, necessitating higher energy consumption to maintain performance levels. This trade-off highlights the importance of developing adaptive energy management strategies that can sustain efficiency even as user demands rise, ultimately contributing to a more sustainable and cost-effective communication system.
The gradual increase in spectrum utilization, from 0.00012% with one user to 0.45% at the maximum user capacity, illustrates the effective deployment of spectrum resources within the cognitive radio network. This steady rise signifies that the network is optimizing the use of available spectrum bands as more users connect. Efficient spectrum utilization is crucial in cognitive radio networks, which are designed to dynamically access underutilized frequency bands to alleviate congestion in heavily loaded channels. By maximizing spectrum usage, the network not only enhances its capacity but also contributes to the overall goal of spectrum efficiency, thereby supporting diverse applications that require varying bandwidth levels.
The increase in latency from 0.05 ms for one user to 3.00 ms for 5,000 users reflects a critical aspect of network performance. As user numbers rise, the network's response time becomes progressively longer, which can lead to noticeable delays in data transmission. This increase in latency is a common challenge in multi-user environments, where shared resources can create bottlenecks. The implications of higher latency are particularly significant for applications requiring real-time communication, such as VoIP and online gaming, where delays can detract from the user experience. Understanding and managing latency is essential for maintaining user satisfaction, and future enhancements in the cognitive radio network may need to focus on minimizing delays, especially during peak usage times.
The packet delivery ratio reveals a concerning trend, decreasing from 97% with one user to 80% when the network is saturated with 5,000 users. This decline indicates potential difficulties in maintaining reliable communication as network congestion grows. A lower PDR can lead to increased packet loss, which adversely affects the quality of services provided. This finding underscores the necessity of implementing robust error correction and retransmission mechanisms to ensure that data packets reach their intended destinations even under high traffic conditions. Maintaining a high PDR is crucial for sustaining user trust and satisfaction in network services.
The analysis of QoS presents a nuanced view: it initially improves from 0.85 to 0.92 as the number of users rises to 1,000, suggesting that the network can effectively accommodate moderate user loads while delivering high-quality services. However, as user numbers swell to 5,000, the QoS slightly declines to 0.85. This fluctuation indicates that while the cognitive radio network excels in providing quality service at lower to moderate loads, it may struggle to uphold the same standards under maximum capacity. This finding highlights the importance of continuously monitoring QoS metrics and adapting strategies to enhance performance, particularly as demand continues to grow.