Microsoft Word CellBreathing

5.
 
Simulation Results 
The simulation is performed to study the effect of Group handover. The network is 
based on WCDMA and consists of two Node Bs (Node_B and Node_B_0), an RNC and 
the Core Network as shown in Figure 2. UEs are transmitting three traffic classes i.e. 
Conversational, Interactive, and Background. 
The Node_B provides service to 15 UEs while Node_B_0 is communicating with 
25 UEs as shown in Figure 2. The UEs connected to Node_B_0 form a logical sub 
network. This sub network can be considered as users travelling in a train or a bus 
following a straight line trajectory as shown by white line in Figure 2. 
Groups
H/O
expected
Codes
Av
ai
lable
?
Assign
Higher
SF
to
users
having
Conversational
or
Background
Traffic
Codes
Av
ai
lable
?
Assign
Higher
SF
to
users
having
Conversational
or
Background
Traffic
Codes
Av
ai
lable
?
Reject
H/O
Accept H/O
Yes
Yes
Yes
No
No
No

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Figure 2: Simulation Experiment Setup 
The users at the cell edge are in the soft handover state. As the UEs from Node_B_0 
enter the coverage of Node_B, the border users are disconnected from Node_B and only 
communicate with Node_B_0. This can be verified from Figure 3 as the Active Set for 
the UEs (shown for MN1 in Figure 2) changes from two to one. 
Figure 3 Active Set Cell Count of Border User (MN1) 
Figure 3 depicts that the border users that were in soft handover at the start of 
simulation are now disconnected from Node_B because coverage area of Node_B has 
shrunk due to Group Handover.
In the second scenario, it is assumed that Node_B informs Node_B_0 via RNC 
about the Group Handover and Node_B_0 assign longer SFs and thus decreases the data 
rates of the users using interactive and background traffic class and as a result 
disconnection of border users from Node_B_0 is avoided and the users remains 
connected to both the cells in the overlap region. This result can be observed from Active 
set cell count in Figure 4 for MN2. The Active Set remains 2 for the whole duration of 
the simulation which clearly indicate that Cell Breathing has not occurred and border 
user can remain in the state of software handover even after the Group Handover. 

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Figure 4: Active Set Cell Count of Border User (MN2)