MODEL AND PERFORMANCE MEASUREMENTS
The communication access technology implementation is carried out in line with the proposed architecture in Figs. 5.2 and 5.3. It was modeled before carrying out the physical implementation in order to have satisfactory and seamless communication in the SG ecosystem. The simulation and modeling tool used here is the NetSim modeling software and well suited for network lab experimentation [158], [214]–[216].
COMMUNICATION 5.5.1 System Model
The received signal at the receiver of the access technologies to be implemented can be modeled as:
yi(t) =
p
Eshi(t)x(t) + ni(t) (5.10)
where yi(t) is the received signal, Es is the transmit signal power, x is the transmitted
symbol (signal), hi(t) is Nakagami-q fading channels impulse response (suitable channel
for harsh environmental condition of SG) i is in range of 1 to 2, i.e [1,2], is the ith number receiving antennas of fading channels for the multi-homed access links, ni(t) is the noise
with complex Gaussian distribution.
Also, the link feasibility at the receiver or the received signal power Pycan be deter-
mined by the expression:
Py= Px+ Ay+ Ax− Ly− Lx− Lp (5.11)
where Pyis the received signal power in dBm, Pxis the transmit power in dBm, Axand
Ayare the transmit antenna and receiver antenna gain respectively, in dBi, Lxand Ly are the losses in dB due to transmitting and receiving access devices respectively such as mismatch, access device kit and cable connectors, and Lpis the free space path loss in dB.
In free space without other impairment such as attenuation, obstruction and disturbances, the path loss propagation model can be expressed as:
Lp= 10 log µP x Py ¶ = −10 log · AxAy µ c 4πd f ¶2¸ (5.12) This expression can also be referred to as link budget Where c is the speed of light, d is the distance between transmitting and receiving access devices, and f is the operating frequency. The path loss models in an environment where there are obstructions, attenuation and disturbances include Hata- Okumura, Modified Erceg-SUI, COST231-Hata, WINNER II, ITU-R M.2135-1, and Log-Normal shadowing path loss, etc. NIST has recommended a large-scale outdoor path loss model for last-mile wireless communication in various segments of an SG (WAN, NAN, FAN, and AMI), and in the utilities [217]. This is due to the varying propagation conditions in a SG environment. However, the Log-Normal shadowing path loss model has been the most widely employed in SGs and in IoT-based SG [218]–[220]. Hence, the Log-Normal shadowing path loss (LN PL) can be expressed as:
LN PL= PL(d0) + 10n log
µ d d0
¶
+ Xσ (5.13)
where PL(d0) is the path loss initially present due to a reference distance (d0) of 1 m; n
is the path loss exponent which varies with the environmental conditions, and adjusts the rate at which the power degrades with distance and d is the entire covered distance of propagation path. The last term Xσ is the zero-mean Gaussian random distributed variable, which models the shadowing and multi-path environments, while the parameter
COMMUNICATION σdenotes the variation of the standard deviation of distribution around the mean.
Consequently, the Log Normal Shadowing path loss as shown in equation (5.13) is the SG factor to be considered as the key immunity compliance requirements in a CRSN deployment for SG.
The link feasibility can be estimated in the area of deployment of the wireless communica- tion for a SG, by considering the signal power and receiver sensitivity.
However, we can estimate the difference between the received signal power and the receiver sensitivity. This is called the fade margin, expressed as:
Fm= Py− ys (5.14)
where Fmis the fade margin in dB, ysis the receiver sensitivity in dBm. Hence, adequate received signal power will result in an appreciable fade margin. The fade margin will account for the impairment or losses caused by multi-path fading, shadowing, attenuation and other obstruction. Fade margin is maximized in order to get a desired received signal [221]. Based on field experience, and link budget analysis, it has been discovered that increasing the fade margin can lead to outage-free links [222]-[223]. Thus, is suggested that the fade margin should be increased to a level of at least twice the total antenna gain of the transceiver access devices in a CRSN based SG implementation. This is due to the fact that SG has harsh environmental conditions.
5.5.2 Network implementation setup
All the experiments were modeled with the same SG application configuration parameters alongside their respective device parameters. Eight nodes of the respective access devices are used. The nodes are placed in the varying distances with locations of (X, Y) coordinates; e.g., the location of UED and UEK in Fig. 5.6 are (115m,390m) and (890m,390m). Similarly, other access devices node placement follows the same trend of placements. In this thesis, since the investigation is of a prototype, 8 nodes are used with 1000m maximum horizontal range for the LTE Cat1/M1 and CDMA EVDO-1x access devices, and 400m maximum horizontal range for TVBD and Wifi (IEEE 802.11b) access devices.
However, this prototype is scalable, hence, larger scale deployment can be carried out based on the stipulated parameters with many nodes randomly placed at the various coordinates within long range. Regarding the transmission path, the dotted lines are the link path from the base station to each node. The green and pink lines are the paths for the transfer of SG application data to the nodes. Each SG application is transmitted independently using a unicast mode to differentiate each application transfer from the other.
5.5.3 Modeling LTE CAT1/M1
In this section, we modeled LTE CAT1/M1 and compare it with legacy cellular such as CDMA EV-DO which is 3G wireless technology and suited for data transmission. Table
COMMUNICATION
5.1 shows network parameters for LTE CAT1/M1 base station (eNB). Table 5.2 shows the network parameters used for modeling LTE CAT1 and LTE M1 user equipment modules respectively; while Fig. 5.6 depicts the simulation experimental testbed for LTE CAT1/M1. The experiment is modeled with six smart grid applications such as: Automatic Me- tering infrastructure (AMI), Demand Response Management (DRM), Distributed Energy Resources (DER), Home Energy Management System (HEMS), Wide Area Situational Awareness (WASA) and Distribution Automation (DA). The SG applications are generated from the SG application server with a packet size of 1460 bytes, which are then used by the LPWA communication access devices for various SG data services. Table 5.3 shows the SG application parameters.We also modeled legacy cellular such as CDMA EVDO to compare it with our LPWA (LTE CAT1/M1) model. Table 5.4 shows the EVDO base station and module parameters. Fig. 5.7 depicts the simulation experimental testbed.
5.5.4 Modeling TVBD
Since the communication access technologies is based on multi-homing, we modelled TVBD which is the other interface, that is responsible for making use of TVWS as well as a redundant link in case of primary link failure. Table 5.5 shows the TVBD configuration parameters, and the simulation experimental testbed is shown in Fig. 5.8.
We also modeled legacy Wi-Fi (802.11b) to compare it with our TVBD model.
Table 5.5 shows the Wi-Fi base station and module parameters. Fig. 5.9 depicts the simulation experimental testbed.
COMMUNICATION
Figure 5.6: LTE CAT1/M1 Simulation Experimental testbed