# User Association Performance Trade-Offs in Integrated RF/mmWave/THz Communications
## 6 Results  
MatlabTM software (version MatlabR2023b) is used to analyze the performance of our proposed model. Monte Carlo simulations are run to estimate the coverage probability for different SINR thresholds, and an analytical solution for coverage probability is also derived. Matlab simulation is performed to evaluate the performance of the proposed user association Algorithm 1. Table 2 lists the values we use in estimating the performance of the proposed method. Using 900 MHz to represent the sub-6 GHz RF band would be more appropriate than 2.4 GHz, given real-world deployments. Here are some details on Canadian spectrum allocations for RF:  
* In Canada and other countries, 900 MHz falls within the mainstream cellular allocations. Instead, 2.4 GHz is used mostly for unlicensed WiFi, so it does not represent the licensed cellular spectrum in the same way. * The 700 MHz band (698-806 MHz) was auctioned off for commercial use and is being deployed for LTE. * Cellular networks traditionally used the 800-900 MHz Extended Range CDMA (ERCDMA) block, now being reframed for LTE. * Bell Mobility and Telus operate terrestrial digital PCS networks in the 850-900 MHz bands. * The 900 MHz band (806-960 MHz) is allocated for cellular and PMR use. It is commonly used by GSM networks. The Microwave system models interference-limited coverage probability at a frequency of 900 MHz. Interferers are distributed according to a PPP. The user is interested in  
Figure 1: Scores illustration. achieving a target SINR threshold. Monte Carlo simulations are run to determine the coverage probability. ```
1:Initialize: numUsers, numBS, userProfiles, BSbands, blockageModels, userPositions, BSpositions, associations Categorize Users:
2: Categorize each user based on profile Calculate Time-Varying Band Metrics:
3: Calculate raw SINR. 4: Calculate blockage Prob. 5: Normalize SINR across bands Calculate Blockage Risk:
6: Calculate blockage risk per band Calculate User Scores:
7:for each user \(i\)do
8:for each BS \(j\)do
9: score[i][j] = normalizeSINR[i][j]/(blockageRisk[j] + profileWeight[i][j])
10:endfor
11:endfor
12:Reassociate Users:
13:for each batch of users do
14: Rank BSs for each user by score
15: Select BS weighted by scores
16: Maintain min. Users Per Band
17:endfor
18:Monitor Network:
19:Periodically track metrics
20:Update models and profiles Balance Loads:
21: Transfer users between overloaded/underloaded BSs
22: Repeat re-associations periodically
23:Output results
```  
**Algorithm 1** Multi-band user association algorithm. The interference power is modeled as a lognormal random variable, and the coverage probability is calculated analytically using the CDF of the interference power distribution. The results show which interference power distribution provides the closest match to the simulations. The millimeter wave system consists of base stations, interferers, and blockages (modeled as rectangles), which are distributed according to a PPP. In our blockage model, first \begin{table}
\begin{tabular}{l l} \hline \hline
**Parameter** & **Value** \\ \hline Absorption coefficient & 0.01 dB/km \\ Area Length & 2000 m \\ Ref Distance & 50 m \\ Density of interferers & 0.00005 /m\({}^{2}\) \\ Density of blockages & \(4\times 10^{6}\) /m\({}^{2}\) \\ blockage Len. & 500 m \\ User Power & 1 Wait \\ Transmitted power for RF & 40 dBm \\ Transmitted power for mmW & 30 dBm \\ Transmitted power for THz & 10 dBm \\ Freq. RF & 900 MHz \\ Freq. mmW & 28 GHz \\ Freq. THz & 1 THz \\ Number of Monte Carlo iterations & 50 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulation parameters. we define the expected length and width of blockages and the number of blockages in the network area. We generate random blockage coordinates, then we check if a link is blocked by any of the blockages. If a link is blocked, then the path loss exponent is set to \(PL_{NLOS}\), and the received signal strength is set to 0, modeling the complete blockage, and the interference from that interferer is also set to 0.