What is a static channel allocation in computer networks?

In wireless networks, a channel can be allocated between source and destination. The communication path consists of multiple routers connected in a peer-to-peer manner, and the entire channel encompasses these network elements. Channel allocation schemes determine how available bandwidth is distributed among users.

Channel allocation is fundamental to network performance, as it directly affects how efficiently the available spectrum is utilized and how well the network can handle varying traffic demands.

Types of Channel Allocation

The different types of channel allocation schemes are as follows:

• Static channel allocation − Fixed allocation of bandwidth portions to users
• Dynamic channel allocation − Bandwidth allocated on-demand based on current needs
• Hybrid channel allocation − Combination of static and dynamic approaches

Static Channel Allocation

Static channel allocation is a method where the available bandwidth is divided into fixed portions, with each user assigned a dedicated channel. This approach uses predetermined allocation that remains constant regardless of actual traffic demand.

How Static Allocation Works

Step 1: If there are N users, the total bandwidth is divided into N equal-sized partitions, where each user receives one dedicated portion.

Step 2: When there is a small and constant number of users with heavy traffic loads, this division provides a simple and efficient allocation mechanism.

Step 3: A practical example is FM radio stations, where each station gets a portion of the FM band and uses it continuously to broadcast signals.

Performance Analysis

The performance of static allocation can be analyzed using queueing theory. For a single channel with capacity C bps, frame arrival rate ? frames/sec, and average frame length 1/? bits:

Mean delay: T = 1/(?C - ?)

For N subchannels with capacity C/N each:
TN = N/(?C - ?) = NT

Example: With C = 100 Mbps, mean frame length = 10,000 bits, and ? = 5000 frames/sec:

T = 1/(?C - ?) = 200 ?sec

Static Allocation Techniques

Disadvantages

• Spectrum waste − If fewer than N users are active, allocated but unused spectrum is wasted
• Blocking − When more than N users want to communicate, some are denied access despite idle channels
• Poor fit for bursty traffic − Computer data traffic often has peak-to-mean ratios of 1000:1, leaving most channels idle most of the time

Conclusion

Static channel allocation provides predictable, dedicated bandwidth to users through fixed partitioning schemes like TDMA and FDMA. While simple to implement, it suffers from inefficient spectrum utilization, especially with bursty data traffic patterns common in modern computer networks.