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Difference between Fixed Channel Allocations and Dynamic Channel Allocations.
Channel allocation techniques are used in radio resource management for wireless and cellular networks to distribute bandwidth and communication channels to base stations, access points, and terminal devices.
The objective of channel allocation is to maximize system spectral efficiency in bits/s/Hz/site through frequency reuse while maintaining a high level of service by minimizing co-channel and neighboring channel interference among neighboring cells or networks that share the bandwidth.
Channel allocation techniques can be grouped into two categories: Fixed Channel Allocation and Dynamic Channel Allocation.
Read through this article to find out how these two channel allocation techniques are different from each other.
What is Fixed Channel Allocation?
Fixed Channel Allocation (FCA) is a technique in which cells are assigned a certain number of channels or voice channels. The channels cannot be altered after they have been assigned to certain cells. In FCA, channels are assigned in such a way that Frequency reuse is maximized. If a user makes a call and the cell is occupied, then the call is blocked. Borrowing the channels from other cells is a solution to this problem.
Fixed channel allocation scheme is preferred in situations where there are a small number of fixed users having a steady flow of uniform network traffic. The allocation technique is simple and so it can avoid the overhead of complex algorithms. In addition, there is no interference between the users since each user is assigned a fixed channel which is not shared with others.
What is Dynamic Channel Allocation?
Dynamic Channel Allocation is a channel allocation technique in which channels are not assigned to cells indefinitely. When a user requests a call, the Base Station (BS) sends the request to the Mobile Station Center (MSC) for channel or voice channel allocation. This reduces the chances of calls being blocked. As the volume of traffic grows, additional channels are assigned, and vice-versa.
DCA adjusts the bandwidth allotment as per the traffic volume and hence it is particularly suitable for bursty traffic. However, DCA schemes increase the computational as well as storage load on the system.
Difference between Fixed Channel Allocation and Dynamic Channel Allocation
The following table highlights the major differences between FCA and DCA.
| Key | Fixed Channel Allocation(FCA) | Dynamic Channel Allocation (DCA) |
|---|---|---|
| Channel Allocation | Cells are given a fixed number of channels or voice channels. | Cells are not given a fixed number of channels. The number of channels to be allotted to each cells is not fixed initially. |
| Blockage | If all the channels are occupied, then user call is blocked. | If all the channels are blocked, then the Base Station (BS) requests more channels from the Mobile Station Center (MSC). |
| Frequency Usage | Since the cellular channels are separated by the shortest possible distance, frequency reuse is maximized. | Frequency reuse is not maximum because of random channel allocation. |
| Algorithm | Complex algorithms are not utilized in FCA. | To determine which accessible channel is the most efficient, DCA uses complex and sophisticated algorithms. |
| Cost | FCA is less expensive than DCA. | DCA is costly as it requires real-time computation. |
| Cell Allocation | Once a call is finished in FCA, the cell retains the assigned channels. | When a call is concluded in DCA, the channel or voice channel is returned to the MSC. |
| MSC | The Mobile Station Center has less burden to handle in case of FCA. | The Mobile Station Center in case of DCA has high signal load, and has more responsibilities. |
Conclusion
In dynamic channel allocation, channels are allotted to users dynamically as per their requirements, from a central pool. Frequency channels are not permanently allotted to any user. The available channels are kept in a pool, which are distributed among the contending users based on the network requirements and the traffic load.
DCA helps in the optimum utilization of network resources and reduces the chances of denial of services, call blocking, and transmission interference to a great extent, which is why it is a better channel allocation technique than fixed channel allocation.
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